Combating Greenhouse Effects through Biomass Gasification: A Focus on Kinetic Modeling of Combustion and Gasification Zones

*Sunday J. Ojolo and Musbau G. Sobamowo*

## **Abstract**

The prevalent challenges of global warming, food security, food production, crop production systems, environment control called for consideration and better utilization of green energy system such as biomass. The advanced thermo-chemical conversion of the renewable energy source which is aimed at production of optimal yield of energy has not been well understood. In order to have better physical insights into the detailed structure of the biomass burning process inside a solid bed, the kinetics of the biomass combustion and gasification must be properly analyzed. Consequently, improved kinetic models of the combustion and gasification zones in the thermochemical conversion system are very required. Therefore, the present study focuses on the development of improved kinetic modeling of the combustion and gasification zones in the biomass gasification system. The performance of the biomass gasifier system is evaluated through the equivalence ratio, the syngas composition, cold gas efficiency and lower heating value. Also, the effects of the equivalent ratio on gas compositions, the gasifier performance and the low heating value of the biomass are analyzed. From the analysis, it is established that the concentration of CO, H2 and CH4 in the gasifier decrease as the equivalence ratio increases. However, CO2 concentration increases with an increase in the equivalence ratio. The cold efficiency and LHV decreases as the equivalence ratio increases while the gas yield increases with an increase in the equivalence ratio. The quantity of gas produced increases as the amount of oxygen consumed increases. Also, the ratio of CO/CO2 decreases as the temperature of the reduction zone increases. Such analysis as presented in this work, is very useful as a time-saving and cost-effective tool for designing and optimizing the biomass gasifier. Therefore, it is evident that this work will play a significant role in the system design including analysis of the distribution of products and ash deposit in the downdraft gasifiers.

**Keywords:** Kinetic models, Combustion Zone, Gasification Zone, Downdraft Biomass Gasifier

## **1. Introduction**

In the past few decades, the increasing concerns of global warming and fuel prices have aroused the development of new technologies in alternative energy. However, meeting the future demands for electricity, heat, cooling, fuels, and materials with highly limited and fluctuating resources, requires careful planning and allocation of the available resources with highly flexible systems. One of the few renewable resources that is capable of supplying the needs is biomass energy. Biomass as a source of renewable energy and as an organic material from plants and animals can be biochemically and thermochemically converted to produce heat, electricity and fuels. Among all the biomass conversion processes, gasification is one of the most promising [1]. Biomass gasification allows an environmentally friendly energy production. In such a thermochemical conversion process of solid fuel, the most important properties relating to the thermal and biological conversions are moisture content, ash content, volatile matter, and energy density. Therefore, an assessment of the use of biomass as a fuel requires a basic understanding of their composition, characteristics, and performance. The performance of the renewable energy sources in the combustion and gasification systems is ultimate determined by it specific properties [2]. Since biomass materials exhibit a wide range of moisture contents which affect their low and high heating values as a fuel source, it is very important to establish the moisture content of the biomass materials. High or excessive moisture content could defeat the main purpose of the biomass gasification process [3]. Also, the amount of the inorganic component (ash content) in biomass is very important to be determined especially for temperature gasification as melted ash may cause problems in the reactor [2]. The effects of moisture and ash contents on the low heating value (LHV) of some types of biomass are shown in **Table 1**.

grid-connected power net, and, on a larger scale, contribution to air pollution control and global warming reduction are the reasons for the increasing utilization

*Combating Greenhouse Effects through Biomass Gasification: A Focus on Kinetic Modeling of…*

Indisputably, the optimal yield of synthetic gases from gasifiers has been the main focus of the thermochemical conversion technologies. Based on the method of air introduction, solid fuel usage in the gasification zone and the direction of the syngas leaving the gasifier, there are four types of gasifiers, namely, updraft or countercurrent gasifiers; downdraft or co-current gasifiers; crossdraft gasifiers; and fluidized-bed gasifiers. These four types of gasifiers can be broadly classified as fixed and fluidized bed gasifiers. Yang et al. [4] reported that fixed bed gasification is the most common technology for the energy use of biomass and solid municipal wastes. They are relatively easy to design and operate but have limited capacity. Therefore, fixed bed gasifiers are preferred for small to medium scale applications with thermal requirements up to 1 MW [5, 6]. Fixed bed gasifiers include updraft and downdraft gasifiers The updraft gasifier comes with simple design,, high charcoal burn-out and internal heat exchange. Such reactor has low gas exit temperatures and. However, in such reactor, there is possibility of "channeling" in the equipment, which can lead to oxygen break-through and explosion. The requirement of installing automatic moving grates coupled with the problems associated with the disposal of the tar-containing condensates that result from the gas cleaning operations are also some of the major setbacks in the wide applications of the type of gasifier. **Table 2** shows the Typical Characteristics of Fixed-Bed and Fluidized-

Downdraft gasification is a comparatively cheap method of gasification that can yield producer gas with very low tar content. The downdraft gasifier has a simple and stable design, making it effective for small and modular applications if it is well designed. However, downdraft gasifiers cannot be used in some unprocessed fuels. Such gasifier produces higher ash content fuels (slagging) than updraft gasifiers. Also, fluffy, low-density materials give rise to flow problems and excessive pressure drop, and the solid fuel must be pelletized or briquetted before use. As compared to updraft gasifier, downdraft gasifier has lower efficiency due to the lack of internal heat exchange and the lower heating value of the gas. Also, it can only be used in a power range of less than 1 MW due to the necessity of maintaining uniform high temperatures over a given cross-sectional area. The operation of the fixed bed

**Characteristics Fixed-bed downdraft Fluidized-bed gasifier**

) < 0.5 < 1.5

) 4.5–5.0 1.0

Fuel size(mm) 10–200 0–20 Ash content (%wt) < 6 < 25 Moisture content > 10, < 25 > 30 Operating temperature (°C) 800–1400 750–950 Control Simple Average Turndown ratio 4 3 Capacity (MW) < 2.5 < 1–50 Hot gas efficiency (full load %) 85–90 — Cold gas efficiency (full load %) 65–75 —

of the biomass gasification technologies.

*DOI: http://dx.doi.org/10.5772/intechopen.97331*

Bed Gasifiers.

Tar content (g/Nm3

**Table 2.**

**133**

Low Heating Value (kJ/Nm<sup>3</sup>

*Typical characteristics of fixed-bed and fluidized-bed gasifiers.*

The thermal conversion process which involves incomplete combustion of biomass due to insufficient amounts of oxygen from the available supply of air, produces synthetic gases (syngas). Although, the actual biomass syngas composition depends on the gasification process, the feedstock composition and the gasifying agent, a typical syngas by weight from gasification of wood contains approximately 15–21% hydrogen (H2), 10–20% carbon monoxide (CO), 11–13% carbon dioxide, and 1–5% of methane which are combustible gases. The nitrogen gas (N2) involved in the gasification process is not combustible but it dilutes the syngas as it enters and burns in an engine. Compared to biomass combustion, biomass gasification has a lower environmental impact due to less greenhouse gas emission. Therefore, biomass gasification has been beneficial in decreasing greenhouse gases emissions. The reduction of fossil fuels dependence for energy supply, the decrease of land use and soil contamination for waste disposal, the higher efficiency and reliability of a


#### **Table 1.** *Effects of moisture and ash contents on LHV of some types of biomass.*

#### *Combating Greenhouse Effects through Biomass Gasification: A Focus on Kinetic Modeling of… DOI: http://dx.doi.org/10.5772/intechopen.97331*

grid-connected power net, and, on a larger scale, contribution to air pollution control and global warming reduction are the reasons for the increasing utilization of the biomass gasification technologies.

Indisputably, the optimal yield of synthetic gases from gasifiers has been the main focus of the thermochemical conversion technologies. Based on the method of air introduction, solid fuel usage in the gasification zone and the direction of the syngas leaving the gasifier, there are four types of gasifiers, namely, updraft or countercurrent gasifiers; downdraft or co-current gasifiers; crossdraft gasifiers; and fluidized-bed gasifiers. These four types of gasifiers can be broadly classified as fixed and fluidized bed gasifiers. Yang et al. [4] reported that fixed bed gasification is the most common technology for the energy use of biomass and solid municipal wastes. They are relatively easy to design and operate but have limited capacity. Therefore, fixed bed gasifiers are preferred for small to medium scale applications with thermal requirements up to 1 MW [5, 6]. Fixed bed gasifiers include updraft and downdraft gasifiers The updraft gasifier comes with simple design,, high charcoal burn-out and internal heat exchange. Such reactor has low gas exit temperatures and. However, in such reactor, there is possibility of "channeling" in the equipment, which can lead to oxygen break-through and explosion. The requirement of installing automatic moving grates coupled with the problems associated with the disposal of the tar-containing condensates that result from the gas cleaning operations are also some of the major setbacks in the wide applications of the type of gasifier. **Table 2** shows the Typical Characteristics of Fixed-Bed and Fluidized-Bed Gasifiers.

Downdraft gasification is a comparatively cheap method of gasification that can yield producer gas with very low tar content. The downdraft gasifier has a simple and stable design, making it effective for small and modular applications if it is well designed. However, downdraft gasifiers cannot be used in some unprocessed fuels. Such gasifier produces higher ash content fuels (slagging) than updraft gasifiers. Also, fluffy, low-density materials give rise to flow problems and excessive pressure drop, and the solid fuel must be pelletized or briquetted before use. As compared to updraft gasifier, downdraft gasifier has lower efficiency due to the lack of internal heat exchange and the lower heating value of the gas. Also, it can only be used in a power range of less than 1 MW due to the necessity of maintaining uniform high temperatures over a given cross-sectional area. The operation of the fixed bed


#### **Table 2.**

*Typical characteristics of fixed-bed and fluidized-bed gasifiers.*

**1. Introduction**

*Next-Generation Greenhouses for Food Security*

**Table 1**.

*Source: Quaak* et al*. [2].*

*Effects of moisture and ash contents on LHV of some types of biomass.*

**Table 1.**

**132**

In the past few decades, the increasing concerns of global warming and fuel prices have aroused the development of new technologies in alternative energy. However, meeting the future demands for electricity, heat, cooling, fuels, and materials with highly limited and fluctuating resources, requires careful planning and allocation of the available resources with highly flexible systems. One of the few renewable resources that is capable of supplying the needs is biomass energy. Biomass as a source of renewable energy and as an organic material from plants and animals can be biochemically and thermochemically converted to produce heat, electricity and fuels. Among all the biomass conversion processes, gasification is one of the most promising [1]. Biomass gasification allows an environmentally friendly energy production. In such a thermochemical conversion process of solid fuel, the most important properties relating to the thermal and biological conversions are moisture content, ash content, volatile matter, and energy density. Therefore, an assessment of the use of biomass as a fuel requires a basic understanding of their composition, characteristics, and performance. The performance of the renewable energy sources in the combustion and gasification systems is ultimate determined by it specific properties [2]. Since biomass materials exhibit a wide range of moisture contents which affect their low and high heating values as a fuel source, it is very important to establish the moisture content of the biomass materials. High or excessive moisture content could defeat the main purpose of the biomass gasification process [3]. Also, the amount of the inorganic component (ash content) in biomass is very important to be determined especially for temperature gasification as melted ash may cause problems in the reactor [2]. The effects of moisture and ash contents on the low heating value (LHV) of some types of biomass are shown in

The thermal conversion process which involves incomplete combustion of biomass due to insufficient amounts of oxygen from the available supply of air, produces synthetic gases (syngas). Although, the actual biomass syngas composition depends on the gasification process, the feedstock composition and the gasifying agent, a typical syngas by weight from gasification of wood contains approximately 15–21% hydrogen (H2), 10–20% carbon monoxide (CO), 11–13% carbon dioxide, and 1–5% of methane which are combustible gases. The nitrogen gas (N2) involved in the gasification process is not combustible but it dilutes the syngas as it enters and burns in an engine. Compared to biomass combustion, biomass gasification has a lower environmental impact due to less greenhouse gas emission. Therefore, biomass gasification has been beneficial in decreasing greenhouse gases emissions. The reduction of fossil fuels dependence for energy supply, the decrease of land use and soil contamination for waste disposal, the higher efficiency and reliability of a

**Biomass type (%) Moisture content (%) Ash content (dry) (kJ/kg) Lower heat value** Wood 10–60 0.25–1.70 8,400-17,000 Bagasse 40–60 1.70–3.80 7,700-8,000 Stalk 10–20 0.10 16,000 Rice husks 9 19.00 14.000 Gin trash 9 12.00 14,000

gasifiers is influenced by the morphological, physical and chemical properties of the fuel. In such reactors, there are technical problems such as lack of bunker flow, slagging and extreme pressure drop over the gasifier.

modeling and simulation study of downdraft gasifier. With the aid of computational fluid dynamics techniques, Hamzehei et al. [19] adopted multi-fluid Eulerian modeling while incorporating the kinetic theory for solid particles to simulate the unsteady-state behavior of two-dimensional non-reactive gas–solid fluidized bed reactor. The CFD tool was utilized by Tingwen et al. [20] to present detailed highresolution simulations of coal injection in a gasifier applying. In the following year, the hydrodynamic behaviors of an internally interconnected fluidized beds (IIFB) which is a novel, self-heating biomass fast pyrolysis reactor was studied by Zhang et al. [21] using the computational tool. The hydrodynamic behavior in a circulating fluidized bed (CFB) riser was studied by Peng et al. [22] with the help of the CFD model. Chen et al. [23] analyzed a three-dimensional simulation of gas–solid flow in biomass circulating fluidized bed gasifier's riser. Considering the conditions of highly preheated air and steam, Wu et al. [24] showed the a two-dimensional CFD simulation of biomass gasification in a downdraft fixed-bed gasifier. Luo [25] and Liu et al. [26] submitted a three-dimensional CFD model to simulate the full-loop of a dual fluidized-bed biomass gasification system consisting of a gasifier, a combustor, a cyclone separator, and a loop-seal. In the recent year, Lu et al. [27] used CFD model to analyze an updraft gasifier that uses carbonized woody briquette as fuel while in the same year, Kumar et al. [28] investigated the thermochemical conversion of biomass in a downdraft gasifier with a volatile break-up approach. Yang et al. [4] carried out a Eulerian–Lagrangian simulation of air–steam biomass gasifi-

*Combating Greenhouse Effects through Biomass Gasification: A Focus on Kinetic Modeling of…*

*DOI: http://dx.doi.org/10.5772/intechopen.97331*

The predictions of the temperature and pressure distributions and histories of a biomass particle in a downdraft gasifier are major determinants of a detailed characterization study of thermochemical conversions of biomass. Such predictions are heavily dependent on the kinetic modeling of the reaction process in the biomass gasification system [29, 30]. Consequently, improved kinetic models in the combustion and gasification zones in the thermochemical system are very needed. Therefore, the present study focuses on the developing improved kinetic models of the combustion and gasification zones in the biomass gasification system [31, 32]. The performance of the biomass gasifier system is evaluated through the equivalence ratio, the syngas composition, cold gas efficiency and lower heating value (LHV). Also, the effects of the equivalent ratio on gas compositions, the gasifier performance and the low heating value of the biomass are analyzed and presented.

Downdraft gasifier has four distinct zones which are drying, pyrolysis, oxidation/combustion, and reduction/gasification zones from top to bottom of the gasifier, respectively. In this type of gasifier, air or oxygen is usually admitted or drawn to the fuel bed in the drying zone through intake nozzles from the throat attached to

In the **drying zone**, biomass fuel descends into the gasifier and its moisture is removed by evaporation using heat generated in the zones below. The reaction

! *DryBiomass CHαOβ*ð Þ *w* � *y H*2*O* þ *m O*ð Þ <sup>2</sup> þ 3*:*76*N*<sup>2</sup>

After the evaporation of free surface water from the biomass as shown in Eq. (1), the dried biomass fuel descends to the pyrolysis **zone** where irreversible

<sup>þ</sup> *zH*2*<sup>O</sup>*

(1)

cation in a three-dimensional bubbling fluidized gasifier.

**2. The description of downdraft biomass gasifier**

the combustion zone of the gasifier as shown in **Figure 1a**.

*WetBiomass CHαOβ*ð Þ *w* � *y* þ *z H*2*O* þ *m O*ð Þ <sup>2</sup> þ 3*:*76*N*<sup>2</sup>

model is shown in Eq. (1) and **Figure 2**.

**135**

In order to combat these problems, a fluidized bed gasifier was developed. The fluidized-bed gasifiers are able to handle a wide range of biomass with high throughput. However, the fluidized bed design presents several flaws such as particle fracture due to collision with the walls of the vessel, propeller blades, and adjacent particles that render the packing ineffective and useless. Maintenance costs associated with the moving parts increase the overhead needed to repair the damage. These flaws make the immobilized packed design (fixed bed design) a more attractive and practical alternative since it eliminates the moving parts and their inherent problems, and also, allows for packing or media to be simply regenerated once it becomes saturated with contaminants. Instability of the reaction bed, feeding problems and fly-ash sintering in the gas channels can occur in fluidized bed. Additionally, the fluidized bed gasifier produces high tar content of the product gas (up to 500 mg/m<sup>3</sup> gas) with incomplete carbon burn-out, and poor response to load changes. A solution to the problem of tar entrainment in the gas stream is provided by the utilizations of downdraft gasifiers. In fact, the downdraft gasifiers have the possibility of producing a tar-free gas suitable for engine applications. Because of the lower level of organic components in the condensate, downdraft gasifiers suffer less from environmental objections than updraft and fluidized gasifiers.

The understanding of the interactions between chemical and physical mechanisms occurring in the gasifier is of fundamental importance for the optimal design of the reactor. This therefore, provokes the simulations of the thermochemical processes in the gasifiers. The increased computer efficacy and advanced numerical techniques as possessed in various numerical simulation techniques such as CFD tools have offered an effective means of simulating the physical and chemical processes in the biomass thermo-chemical reactors (such as fluidized beds, fixed beds, combustion furnaces, firing boilers, rotating cones and rotary kilns) under various operating conditions in different virtual environments. The CFD simulates the fluid flow behavior, heat and mass transfer, chemical reactions, phase changes and mechanical movement. CFD model results are capable of predicting both qualitative and quantitative information. The results of accurate simulations with the aid of CFD tools can help to optimize the system design and operations and understand the dynamic processes inside the reactors. Also, the use of CFD software for the flow visualization in a fixed bed gasifier has resulted in saving stresses and time engages in using other modeling and simulation methods. Additionally, the predictions made by the use of CFD software can help in the design of the fixed bed gasifier. Consequently, Fletcher et al. [7] simulated the flow and reaction in an entrained flow biomass gasifier using the CFX package. With the aid of CFD model, Gerun et al. [8] presented a two-dimensional heat and mass transfer for the oxidation zone in a two-stage downdraft gasifier. Meanwhile, Zhou et al. [9] adopted a CFD model to simulate the optimal conditions for the production of hydrogen-rich gas in a fluidized bed biomass gasifier. A further study was presented by Papadikis and Gu [10]. The authors presented CFD modeling of the fast pyrolysis of biomass in fluidized bed reactors. In the same year, Wang and Yan [11] carried out an overview of different CFD studies on thermo-chemical biomass conversions such as gasification and combustion processes in fixed beds, furnaces, and fluidized beds.

In some specific studies, Yimlaz, et al. [12] and Cornejo and Farias [13] adopted the multiphase model in FLUENT while Paes [14], Watanabe and Otaka [15], Huang and Ramaswamy [16] and with the aid of mathematical user-defined functions, Cuoci, et al. [17] presented the mathematical model of the thermochemical processes. Focusing on using oil-palm fronds, Atnaw and Sulaiman [18] submitted a

#### *Combating Greenhouse Effects through Biomass Gasification: A Focus on Kinetic Modeling of… DOI: http://dx.doi.org/10.5772/intechopen.97331*

modeling and simulation study of downdraft gasifier. With the aid of computational fluid dynamics techniques, Hamzehei et al. [19] adopted multi-fluid Eulerian modeling while incorporating the kinetic theory for solid particles to simulate the unsteady-state behavior of two-dimensional non-reactive gas–solid fluidized bed reactor. The CFD tool was utilized by Tingwen et al. [20] to present detailed highresolution simulations of coal injection in a gasifier applying. In the following year, the hydrodynamic behaviors of an internally interconnected fluidized beds (IIFB) which is a novel, self-heating biomass fast pyrolysis reactor was studied by Zhang et al. [21] using the computational tool. The hydrodynamic behavior in a circulating fluidized bed (CFB) riser was studied by Peng et al. [22] with the help of the CFD model. Chen et al. [23] analyzed a three-dimensional simulation of gas–solid flow in biomass circulating fluidized bed gasifier's riser. Considering the conditions of highly preheated air and steam, Wu et al. [24] showed the a two-dimensional CFD simulation of biomass gasification in a downdraft fixed-bed gasifier. Luo [25] and Liu et al. [26] submitted a three-dimensional CFD model to simulate the full-loop of a dual fluidized-bed biomass gasification system consisting of a gasifier, a combustor, a cyclone separator, and a loop-seal. In the recent year, Lu et al. [27] used CFD model to analyze an updraft gasifier that uses carbonized woody briquette as fuel while in the same year, Kumar et al. [28] investigated the thermochemical conversion of biomass in a downdraft gasifier with a volatile break-up approach. Yang et al. [4] carried out a Eulerian–Lagrangian simulation of air–steam biomass gasification in a three-dimensional bubbling fluidized gasifier.

The predictions of the temperature and pressure distributions and histories of a biomass particle in a downdraft gasifier are major determinants of a detailed characterization study of thermochemical conversions of biomass. Such predictions are heavily dependent on the kinetic modeling of the reaction process in the biomass gasification system [29, 30]. Consequently, improved kinetic models in the combustion and gasification zones in the thermochemical system are very needed. Therefore, the present study focuses on the developing improved kinetic models of the combustion and gasification zones in the biomass gasification system [31, 32]. The performance of the biomass gasifier system is evaluated through the equivalence ratio, the syngas composition, cold gas efficiency and lower heating value (LHV). Also, the effects of the equivalent ratio on gas compositions, the gasifier performance and the low heating value of the biomass are analyzed and presented.

### **2. The description of downdraft biomass gasifier**

Downdraft gasifier has four distinct zones which are drying, pyrolysis, oxidation/combustion, and reduction/gasification zones from top to bottom of the gasifier, respectively. In this type of gasifier, air or oxygen is usually admitted or drawn to the fuel bed in the drying zone through intake nozzles from the throat attached to the combustion zone of the gasifier as shown in **Figure 1a**.

In the **drying zone**, biomass fuel descends into the gasifier and its moisture is removed by evaporation using heat generated in the zones below. The reaction model is shown in Eq. (1) and **Figure 2**.

$$\begin{aligned} \text{WetBiomass} \left\{ \text{CH}\_{a}\text{O}\_{\beta}(w-y+z)\text{H}\_{2}\text{O}+m(\text{O}\_{2}+\text{3.76N}\_{2}) \right\} \\ \rightarrow \text{DryBiomass} \left\{ \text{CH}\_{a}\text{O}\_{\beta}(w-y)\text{H}\_{2}\text{O}+m(\text{O}\_{2}+\text{3.76N}\_{2}) \right\} + \text{zH}\_{2}\text{O} \end{aligned} \tag{1}$$

After the evaporation of free surface water from the biomass as shown in Eq. (1), the dried biomass fuel descends to the pyrolysis **zone** where irreversible

gasifiers is influenced by the morphological, physical and chemical properties of the fuel. In such reactors, there are technical problems such as lack of bunker flow,

In order to combat these problems, a fluidized bed gasifier was developed. The

fluidized-bed gasifiers are able to handle a wide range of biomass with high throughput. However, the fluidized bed design presents several flaws such as particle fracture due to collision with the walls of the vessel, propeller blades, and adjacent particles that render the packing ineffective and useless. Maintenance costs associated with the moving parts increase the overhead needed to repair the damage. These flaws make the immobilized packed design (fixed bed design) a more attractive and practical alternative since it eliminates the moving parts and their inherent problems, and also, allows for packing or media to be simply regenerated once it becomes saturated with contaminants. Instability of the reaction bed, feeding problems and fly-ash sintering in the gas channels can occur in fluidized bed. Additionally, the fluidized bed gasifier produces high tar content of the product gas (up to 500 mg/m<sup>3</sup> gas) with incomplete carbon burn-out, and poor response to load changes. A solution to the problem of tar entrainment in the gas stream is provided by the utilizations of downdraft gasifiers. In fact, the downdraft gasifiers have the possibility of producing a tar-free gas suitable for engine applications. Because of the lower level of organic components in the condensate, downdraft gasifiers suffer

less from environmental objections than updraft and fluidized gasifiers.

The understanding of the interactions between chemical and physical mechanisms occurring in the gasifier is of fundamental importance for the optimal design of the reactor. This therefore, provokes the simulations of the thermochemical processes in the gasifiers. The increased computer efficacy and advanced numerical techniques as possessed in various numerical simulation techniques such as CFD tools have offered an effective means of simulating the physical and chemical processes in the biomass thermo-chemical reactors (such as fluidized beds, fixed beds, combustion furnaces, firing boilers, rotating cones and rotary kilns) under various operating conditions in different virtual environments. The CFD simulates the fluid flow behavior, heat and mass transfer, chemical reactions, phase changes and mechanical movement. CFD model results are capable of predicting both qualitative and quantitative information. The results of accurate simulations with the aid of CFD tools can help to optimize the system design and operations and understand the dynamic processes inside the reactors. Also, the use of CFD software for the flow visualization in a fixed bed gasifier has resulted in saving stresses and time engages in using other modeling and simulation methods. Additionally, the predictions made by the use of CFD software can help in the design of the fixed bed gasifier. Consequently, Fletcher et al. [7] simulated the flow and reaction in an entrained flow biomass gasifier using the CFX package. With the aid of CFD model, Gerun et al. [8] presented a two-dimensional heat and mass transfer for the oxidation zone in a two-stage downdraft gasifier. Meanwhile, Zhou et al. [9] adopted a CFD model to simulate the optimal conditions for the production of hydrogen-rich gas in a fluidized bed biomass gasifier. A further study was presented by Papadikis and Gu [10]. The authors presented CFD modeling of the fast pyrolysis of biomass in fluidized bed reactors. In the same year, Wang and Yan [11] carried out an overview of different CFD studies on thermo-chemical biomass conversions such as gasification and combustion processes in fixed beds, furnaces, and fluidized beds. In some specific studies, Yimlaz, et al. [12] and Cornejo and Farias [13] adopted

the multiphase model in FLUENT while Paes [14], Watanabe and Otaka [15], Huang and Ramaswamy [16] and with the aid of mathematical user-defined functions, Cuoci, et al. [17] presented the mathematical model of the thermochemical processes. Focusing on using oil-palm fronds, Atnaw and Sulaiman [18] submitted a

**134**

slagging and extreme pressure drop over the gasifier.

*Next-Generation Greenhouses for Food Security*

*Tar C<sup>α</sup>*0*H<sup>β</sup>*0*O<sup>γ</sup>*<sup>0</sup> *w*<sup>0</sup> � *y*<sup>0</sup> ð Þ*H*2*O* þ *z*<sup>0</sup>

<sup>2</sup>*CO*<sup>2</sup> þ *x*<sup>0</sup>

*DOI: http://dx.doi.org/10.5772/intechopen.97331*

! *x*<sup>0</sup>

**Figure 3.**

**137**

<sup>1</sup>*CO* þ *x*<sup>0</sup>

� �

<sup>3</sup>*H*<sup>2</sup> þ *x*<sup>0</sup>

generated is used to drive the gasification reactions.

*Char CH* f g *aOb* þ *yO*<sup>2</sup> ! 2 � 2*y* � *b* þ

ð Þ *O*<sup>2</sup> þ 3*:*76*N*<sup>2</sup>

*Combating Greenhouse Effects through Biomass Gasification: A Focus on Kinetic Modeling of…*

<sup>5</sup>*CH*<sup>4</sup> þ *x*<sup>0</sup>

In the **oxidation/combustion zone**, the volatile products and the char produced during pyrolysis are partially oxidized (Eqs. (4)–(8)) in the exothermic reactions resulting in a rapid rise of temperature up to 1200°C in the throat region. The heat

> *a* 2 � �*CO* <sup>þ</sup> <sup>2</sup>*<sup>y</sup>* <sup>þ</sup> *<sup>b</sup>* � *<sup>a</sup>*

It should be stated that the combustion zone determines the temperatures in the gasifier and the reactions in the other zones and is therefore pivotal in the gasification process. **Figure 3** depicts the combustion reactions in the downdraft gasifier. The last zone in the downdraft gasifier is the **reduction zone** often refers to as the gasification zone as shown in **Figure 4**. In this zone, the char produced during pyrolysis is converted to the producer gas by reacting with the hot gases from the upper zones. The gases are reduced to form a greater proportion of H2, CO and CH4. While leaving the gasifier at the temperature between 200°C and 300°C, the produced gases carry over some dust, pyrolytic products (tar), and water vapor and

6

<sup>X</sup>*C<sup>λ</sup>*0*H<sup>ϑ</sup>*<sup>0</sup> <sup>þ</sup> <sup>3</sup>*:*76*N*<sup>2</sup> <sup>þ</sup> *<sup>x</sup>*<sup>0</sup>

*O*<sup>2</sup> ! *H*2*O* (4)

*O*<sup>2</sup> ! *CO*<sup>2</sup> (5)

*a*0 <sup>2</sup> � *<sup>b</sup>*<sup>0</sup>

*a*0 <sup>2</sup> � *<sup>b</sup>*<sup>0</sup>

*H*2*O* þ

� �*H*<sup>2</sup> (9)

� �*H*<sup>2</sup> (10)

<sup>2</sup> � <sup>1</sup> � �*CO*<sup>2</sup> <sup>þ</sup>

*CH*<sup>4</sup> þ 2*O*<sup>2</sup> ! *CO*<sup>2</sup> þ 2*H*2*O* (6)

*CnH*2*n*þ<sup>2</sup> þ ð Þ 2*n* þ 1 *O*<sup>2</sup> ! *nCO* þ ð Þ *n* þ 1 *H*2*O* (8)

<sup>7</sup>*Char* (3)

*a* 2 *H*2*O* (7)

<sup>4</sup>*H*2*O* þ *x*<sup>0</sup>

*H*<sup>2</sup> þ 1 2

*CO* þ 1 2

these are removed by scrubber and electrostatic precipitator.

*Char CHa*0*Ob* f g0 þ *CO*<sup>2</sup> ! 2*CO* þ *b*<sup>0</sup>

*Reactions at the combustion zone in the downdraft biomass gasifier [33].*

*Char CHa*0*Ob* f g0 þ ð Þ 1 � *b H*2*O* ! *CO* þ 1 þ

The Tar is given as *C*6*:*407*H*11*:*454*O*3*:*<sup>482</sup> while the Char is *CH*0*:*2526*O*0*:*0237.

**Figure 1.**

*(a) Downdraft biomass gasification plant. (b) Downdraft biomass gasifier.*

#### **Figure 2.**

*Reactions at the drying and pyrolysis zones in the downdraft biomass gasifier.*

thermal degradation takes place (Eq. (2)). The drying process is achieved by using the released heat energy released from the partial oxidation of the pyrolysis products. When the producer gas flows downwards through the reactor, it enables the pyrolysis gases to pass through hot bed of char which is around 1100°C. Thus, it will crack most of the tars into light chain hydrocarbon and water vapors as shown in Eq. (3) and **Figure 2**.

## **Primary Pyrolysis**

$$\{\text{Biomass} \rightarrow (1 - \gamma - \Psi)\text{Gases} + \Psi T ar + \gamma \text{Char}\}$$

$$\begin{aligned} \left\{ \text{DryBiomass} \left\{ \text{CH}\_{4}\text{O}\_{\theta}(w-y)\text{H}\_{2}\text{O} + \text{x}(\text{O}\_{2} + \text{3.76N}\_{2}) \right\} \right\} \\ \left\{ \text{D} \rightarrow \text{x}\_{1}\text{CO} + \text{x}\_{2}\text{CO}\_{2} + \text{x}\_{3}\text{H}\_{2} + \text{x}\_{4}\text{H}\_{2}\text{O} + \text{x}\_{5}\text{CH}\_{4} + \text{x}\_{6} \sum \text{C}\_{i}\text{H}\_{\theta} + \text{3.76N}\_{2} + \text{x}\_{7}\text{Char} + \text{x}\_{8}\text{Trav} \right\} \end{aligned} \tag{2}$$

## **Secondary Pyrolysis**

$$\{\Psi T ar \to \lambda Gases + (\Psi - \lambda)Char\},$$

*Combating Greenhouse Effects through Biomass Gasification: A Focus on Kinetic Modeling of… DOI: http://dx.doi.org/10.5772/intechopen.97331*

$$\begin{aligned} &\text{Tar}\left\{\text{C}\_{d}\text{H}\_{\beta'}\text{O}\_{\forall}(\text{w}^{\prime}-\text{y}^{\prime})\text{H}\_{2}\text{O}+\text{z}^{\prime}(\text{O}\_{2}+\text{3.76N}\_{2})\right\} \\ &\rightarrow \mathbf{x}\_{1}^{\prime}\text{CO}+\mathbf{x}\_{2}^{\prime}\text{CO}\_{2}+\mathbf{x}\_{3}^{\prime}\text{H}\_{2}+\mathbf{x}\_{4}^{\prime}\text{H}\_{2}\text{O}+\mathbf{x}\_{5}^{\prime}\text{CH}\_{4}+\mathbf{x}\_{6}^{\prime}\sum\text{C}\_{\lambda'}\text{H}\_{\vartheta'}+\mathbf{3.76N}\_{2}+\mathbf{x}\_{7}^{\prime}\text{Char} \\ &\tag{3} \end{aligned} \tag{3}$$

The Tar is given as *C*6*:*407*H*11*:*454*O*3*:*<sup>482</sup> while the Char is *CH*0*:*2526*O*0*:*0237.

In the **oxidation/combustion zone**, the volatile products and the char produced during pyrolysis are partially oxidized (Eqs. (4)–(8)) in the exothermic reactions resulting in a rapid rise of temperature up to 1200°C in the throat region. The heat generated is used to drive the gasification reactions.

$$H\_2 + \frac{1}{2}O\_2 \rightarrow H\_2O\tag{4}$$

$$\text{CO} + \frac{1}{2}\text{O}\_2 \rightarrow \text{CO}\_2\tag{5}$$

$$\text{CH}\_4 + \text{2O}\_2 \rightarrow \text{CO}\_2 + \text{2H}\_2\text{O} \tag{6}$$

$$\text{Char}\{\text{CH}\_{a}\text{O}\_{b}\} + y\text{O}\_{2} \rightarrow \left(2 - 2y - b + \frac{a}{2}\right)\text{CO} + \left(2y + b - \frac{a}{2} - 1\right)\text{CO}\_{2} + \frac{a}{2}\text{H}\_{2}\text{O}\tag{7}$$

$$\rm C\_nH\_{2n+2} + (2n+1)O\_2 \to nCO + (n+1)H\_2O \tag{8}$$

It should be stated that the combustion zone determines the temperatures in the gasifier and the reactions in the other zones and is therefore pivotal in the gasification process. **Figure 3** depicts the combustion reactions in the downdraft gasifier.

The last zone in the downdraft gasifier is the **reduction zone** often refers to as the gasification zone as shown in **Figure 4**. In this zone, the char produced during pyrolysis is converted to the producer gas by reacting with the hot gases from the upper zones. The gases are reduced to form a greater proportion of H2, CO and CH4. While leaving the gasifier at the temperature between 200°C and 300°C, the produced gases carry over some dust, pyrolytic products (tar), and water vapor and these are removed by scrubber and electrostatic precipitator.

$$\text{Char}\{\text{CH}\_{d'}\text{O}\_{b'}\} + (1 - b)\text{H}\_2\text{O} \rightarrow \text{CO} + \left(1 + \frac{d'}{2} - b'\right)\text{H}\_2\tag{9}$$

$$\text{Char}\{\text{CH}\_{a'}\text{O}\_{b'}\} + \text{CO}\_2 \rightarrow 2\text{CO} + b'H\_2\text{O} + \left(\frac{a'}{2} - b'\right)H\_2\tag{10}$$

**Figure 3.** *Reactions at the combustion zone in the downdraft biomass gasifier [33].*

thermal degradation takes place (Eq. (2)). The drying process is achieved by using the released heat energy released from the partial oxidation of the pyrolysis products. When the producer gas flows downwards through the reactor, it enables the pyrolysis gases to pass through hot bed of char which is around 1100°C. Thus, it will crack most of the tars into light chain hydrocarbon and water vapors as shown in

f g *Biomass* ! ð Þ 1 � *γ* � Ψ *Gases* þ Ψ*Tar* þ *γChar*

f g Ψ*Tar* ! *λGases* þ ð Þ Ψ � *λ Char*

<sup>X</sup>*CλH<sup>ϑ</sup>* <sup>þ</sup> <sup>3</sup>*:*76*N*<sup>2</sup> <sup>þ</sup> *<sup>x</sup>*7*Char* <sup>þ</sup> *<sup>x</sup>*8*Tar*

(2)

Eq. (3) and **Figure 2**. **Primary Pyrolysis**

**Figure 1.**

**Figure 2.**

**136**

**Secondary Pyrolysis**

*DryBiomass CHαOβ*ð Þ *w* � *y H*2*O* þ *z O*ð Þ <sup>2</sup> þ 3*:*76*N*<sup>2</sup>

! *x*1*CO* þ *x*2*CO*<sup>2</sup> þ *x*3*H*<sup>2</sup> þ *x*4*H*2*O* þ *x*5*CH*<sup>4</sup> þ *x*<sup>6</sup>

� �

*Reactions at the drying and pyrolysis zones in the downdraft biomass gasifier.*

*(a) Downdraft biomass gasification plant. (b) Downdraft biomass gasifier.*

*Next-Generation Greenhouses for Food Security*

#### **Figure 4.** *Reactions at the reduction zone in the downdraft gasifier.*

$$\text{Char}\{\text{CH}\_{a'}O\_{b'}\} + \left(2 - \frac{a'}{2} + b'\right) \text{H}\_2 \rightarrow \text{CH}\_4 + \left(b'H\_2O\right) \tag{11}$$

$$\text{Hydrocarbon} \left\{ \text{CH}\_{n}\text{O}\_{2n+2} \right\} + n\text{H}\_{2}\text{O} \rightarrow n\text{CO} + (2n+1)\text{H}\_{2} \tag{12}$$

$$\text{CO} + \text{H}\_2\text{O} \rightarrow \text{CO}\_2 + \text{H}\_2\tag{13}$$

**3.3 Methane combustion**

*<sup>e</sup> :* exp �*ECH*<sup>4</sup> *RTe* � �*CCH*4*CO*<sup>2</sup> � �, *CmixρCH*<sup>4</sup>

*DOI: http://dx.doi.org/10.5772/intechopen.97331*

*rchar*�*O*<sup>2</sup> ¼

*<sup>ε</sup>CnH*2*n*þ<sup>2</sup>*ACnH*2*n*þ<sup>2</sup>*TeP*<sup>0</sup>*:*<sup>3</sup>

*CmixρCnH*2*n*þ<sup>2</sup>

**3.6 Char reaction with water vapor**

**3.7 Char reaction with carbon dioxide**

*Rchar*�*H*2*<sup>O</sup>* ¼

*Rchar*�*CO*<sup>2</sup> ¼

<sup>150</sup>*DCH*<sup>4</sup> <sup>1</sup> � *<sup>ε</sup>CH*<sup>4</sup> ð Þ<sup>2</sup>*=*<sup>3</sup> *l* 2 *<sup>p</sup>εCH*<sup>4</sup>

> *Mchar* 1�*χ* 2þ*<sup>a</sup>* <sup>2</sup>�*<sup>b</sup>* ð Þ<sup>2</sup> *MO*<sup>2</sup> � �

" # " !

ð Þ *A=V charεO*2*CO*<sup>2</sup>

*Combating Greenhouse Effects through Biomass Gasification: A Focus on Kinetic Modeling of…*

*kk* <sup>¼</sup> *Achar* exp �*Echar*

*RTe* � �*C*<sup>0</sup>*:*<sup>5</sup>

*Te* ¼ *ΩTg* þ ð Þ 1 � *Ω Ts Tg* ≤*Ts*

*Te* ¼ *Tg Tg* ≤*Ts*

*<sup>Ω</sup> is a weighing  factor*

ð Þ *A=V charε<sup>H</sup>*2*OCH*2*<sup>O</sup>*

*kk* <sup>¼</sup> *AH*2*OTchar* exp �*Echar*

*kk* <sup>¼</sup> *ACO*2*Tchar* exp �*Echar*

ð Þ *A=V charCCO*<sup>2</sup>

1 *kd* <sup>þ</sup> <sup>1</sup> *kr*

1 *kd* <sup>þ</sup> <sup>1</sup>

*CnH*2*n*þ<sup>2</sup> exp �*EH*<sup>2</sup>

� �,

<sup>150</sup>*DCnH*2*n*þ<sup>2</sup> <sup>1</sup> � *<sup>ε</sup>CnHn*þ<sup>12</sup> � �<sup>2</sup>*=*<sup>3</sup> *l* 2 *<sup>p</sup>εCnH*2*n*þ<sup>2</sup>

1 *kd* <sup>þ</sup> <sup>1</sup> *kk*

*RTs*

*CnH*2*n*þ<sup>2</sup> *CO*<sup>2</sup>

1*:*75*uCnH*<sup>2</sup>þ<sup>2</sup> 1 � *εCnH*2*n*þ<sup>2</sup>

*MChar* ð Þ 1�*b MH*2*<sup>O</sup>* h i

*RTchar* � � (21)

*RTchar* � � (23)

*kr*

*MChar MCO*<sup>2</sup> h i

" # "

*lpε<sup>C</sup>*2*H*2*n*þ<sup>2</sup>

þ

<sup>þ</sup> <sup>1</sup>*:*75*uCH*<sup>4</sup> <sup>1</sup> � *<sup>ε</sup>CH*<sup>4</sup> ð Þ<sup>1</sup>*=*<sup>3</sup> *lpεCH*<sup>4</sup>

� � (18)

� �<sup>1</sup>*=*<sup>3</sup>

min *Cfuel Sfuel* , *CO*<sup>2</sup> *SO*<sup>2</sup>

min *Cfuel Sfuel* , *CO*<sup>2</sup> *SO*<sup>2</sup>

(16)

(17)

1

CCCCCA

(19)

(19a)

(20)

(22)

*rCH*4�*O*<sup>2</sup> <sup>¼</sup> min *<sup>ε</sup>CH*4*ACH*<sup>4</sup> *<sup>T</sup>*�<sup>1</sup>

**3.4 Char combustion**

**3.5 Hydrocarbon combustion**

0

BBBBB@

where

*rCnH*2*n*þ2�*O*<sup>2</sup> ¼ min

where

where

where

**139**

*where a = 0.2526 and b = 0.0237.*

## **3. Kinetic reactions models for the combustion and the gasification processes**

The combustion of CO2, CO, H2, CH4 and Hydrocarbon as well as the char combustion and gasification chemical-reactions are determined through improved chemical models. The models involve both homogeneous and heterogeneous reactions. The heterogeneous reaction-rates were determined by combining an Arrhenius kinetic-rate and a diffusion rate using the kinetics/diffusion surface reaction model. Homogeneous reaction-rates were described by a turbulent mixing rate using the eddy dissipation model.

The kinetic reaction rates in the gas phase and of the char are given as.

#### **3.1 Hydrogen combustion**

$$r\_{H\_2-O\_2} = \min\left( \left\{ 2\eta\_{H\_2} A\_{H\_2} \cdot T\_s^{-1, 3} \cdot \exp\left(\frac{-\mathcal{E}\eta\_2}{RT\_s}\right) \mathbf{C}\_{H\_2}^{\mathrm{cl}} \mathbf{C}\_{O\_2} \right\}, \begin{aligned} &\left( \mathrm{-E}\eta\_2 \right) \mathbf{C}\_{H\_2} \left[ \frac{150 D\_{H\_2} \left(1 - \varepsilon\_{H\_2}\right)^{2/3}}{\mathbf{I}\_p \varepsilon\_{H\_2}} + \frac{1.75 u\_{H\_2} \left(1 - \varepsilon\_{H\_2}\right)^{1/3}}{\mathbf{I}\_p \varepsilon\_{H\_2}} \min\left[ \frac{\mathbf{C}\_{\mathrm{fnd}}}{\mathbf{S}\_{\mathrm{fnd}}}, \frac{\mathbf{C}\_{O\_2}}{\mathbf{S}\_{O\_2}} \right] \right] \end{aligned} \tag{14}$$

#### **3.2 Carbon monoxide combustion**

$$r\_{\rm CO-O\_2} = \min\left( \left\{ \epsilon\_{\rm CO} \; A\_{\rm CO} \exp\left(\frac{-E\_{\rm Ht}}{RT\_s}\right) \mathbf{C}\_{\rm CO} \mathbf{C}\_{\rm CO}^{\rm O,3} \mathbf{C}\_{\rm HtO}^{\rm O,3} \right\}, \; \mathbf{C}\_{\rm NH} \rho\_{\rm CO} \left[ \frac{150 D\_{\rm CO} (1 - x\_{\rm CO})^{2/3}}{l\_p^2 \epsilon\_{\rm CO}} + \frac{1.75 u\_{\rm CO} (1 - x\_{\rm CO})^{1/3}}{l\_p x\_{\rm CO}} \min\left[ \frac{\mathbf{C}\_{\rm Ht}}{\mathbf{S}\_{\rm Ht}}, \frac{\mathbf{C}\_{\rm O,3}}{\mathbf{S}\_{\rm O,3}} \right] \right], \tag{15}$$

*Combating Greenhouse Effects through Biomass Gasification: A Focus on Kinetic Modeling of… DOI: http://dx.doi.org/10.5772/intechopen.97331*

### **3.3 Methane combustion**

$$\sigma\_{\rm GL\_{i}-O\_{2}} = \min\left( \left\{ \sigma\_{\rm GL\_{i}} A\_{\rm GL\_{i}} \, T\_{s}^{-1} \,. \, \exp\left(\frac{-E\_{\rm GL\_{i}}}{RT\_{s}}\right) C\_{\rm GL\_{i}} C\_{\rm O\_{2}} \right\}, \quad C\_{\rm mid} \rho\_{\rm GL\_{i}} \left[ \frac{150 D\_{\rm GL\_{i}} (1 - e\_{\rm GL\_{i}})^{2/3}}{l\_{p}^{2} c\_{\rm GL\_{i}}} + \frac{1.75 a\_{\rm GL\_{i}} (1 - e\_{\rm GL\_{i}})^{1/3}}{l\_{p} e\_{\rm GL\_{i}}} \min\left[ \frac{C\_{\rm fuel}}{S\_{\rm fuel}}, \frac{C\_{\rm O\_{2}}}{S\_{\rm O\_{2}}} \right] \right), \tag{116}$$

#### **3.4 Char combustion**

$$r\_{char-O\_2} = \frac{(A/V)\_{char} \varepsilon\_{O\_2} C\_{O\_2} \left[\frac{M\_{char}}{\left(1 - \frac{x}{2} + \frac{a}{2} - \frac{b}{2}\right) M\_{O\_2}}\right]}{\frac{1}{k\_d} + \frac{1}{k\_k}}\tag{17}$$

where

*Char CHa*0*Ob* f g0 <sup>þ</sup> <sup>2</sup> � *<sup>a</sup>*<sup>0</sup>

*where a = 0.2526 and b = 0.0237.*

*Reactions at the reduction zone in the downdraft gasifier.*

*Next-Generation Greenhouses for Food Security*

using the eddy dissipation model.

**3.1 Hydrogen combustion**

*rH*2�*O*<sup>2</sup> <sup>¼</sup> min 2*ε<sup>H</sup>*<sup>2</sup> *AH*<sup>2</sup> *<sup>T</sup>*�1*:*<sup>5</sup> *<sup>e</sup> :* exp �*EH*<sup>2</sup>

*rCO*�*O*<sup>2</sup> <sup>¼</sup> min *<sup>ε</sup>CO ACO* exp �*EH*<sup>2</sup>

**138**

**3.2 Carbon monoxide combustion**

*RTe* � � *C*<sup>1</sup>*:*<sup>5</sup> *H*<sup>2</sup> *CO*<sup>2</sup>

> *CCOC*<sup>0</sup>*:*<sup>25</sup> *<sup>O</sup>*<sup>2</sup> *C*<sup>0</sup>*:*<sup>5</sup> *H*2*O*

� �

*RTe* � �

� �

**processes**

**Figure 4.**

<sup>2</sup> <sup>þ</sup> *<sup>b</sup>*<sup>0</sup> � �

**3. Kinetic reactions models for the combustion and the gasification**

The kinetic reaction rates in the gas phase and of the char are given as.

, *Cmixρ<sup>H</sup>*<sup>2</sup>

, *CmixρCO*

<sup>150</sup>*DH*<sup>2</sup> <sup>1</sup> � *<sup>ε</sup><sup>H</sup>*<sup>2</sup> ð Þ<sup>2</sup>*=*<sup>3</sup> *l* 2 *<sup>p</sup>ε<sup>H</sup>*<sup>2</sup>

<sup>150</sup>*DCO*ð Þ <sup>1</sup> � *<sup>ε</sup>CO* <sup>2</sup>*=*<sup>3</sup> *l* 2 *<sup>p</sup>εCO*

" # " !

" # " !

<sup>þ</sup> <sup>1</sup>*:*75*uH*<sup>2</sup> <sup>1</sup> � *<sup>ε</sup><sup>H</sup>*<sup>2</sup> ð Þ<sup>1</sup>*=*<sup>3</sup> *lpε<sup>H</sup>*<sup>2</sup>

<sup>þ</sup> <sup>1</sup>*:*75*uCO*ð Þ <sup>1</sup> � *<sup>ε</sup>CO* <sup>1</sup>*=*<sup>3</sup> *lpεCO*

min *Cfuel Sfuel* , *CO*<sup>2</sup> *SO*<sup>2</sup>

min *Cfuel Sfuel* , *CO*<sup>2</sup> *SO*<sup>2</sup>

(14)

(15)

The combustion of CO2, CO, H2, CH4 and Hydrocarbon as well as the char combustion and gasification chemical-reactions are determined through improved chemical models. The models involve both homogeneous and heterogeneous reactions. The heterogeneous reaction-rates were determined by combining an Arrhenius kinetic-rate and a diffusion rate using the kinetics/diffusion surface reaction model. Homogeneous reaction-rates were described by a turbulent mixing rate

*Hydrocarbon CH* f g *nO*2*n*þ<sup>2</sup> þ *nH*2*O* ! *nCO* þ ð Þ 2*n* þ 1 *H*<sup>2</sup> (12)

*H*<sup>2</sup> ! *CH*<sup>4</sup> þ *b*<sup>0</sup>

*CO* þ *H*2*O* ! *CO*<sup>2</sup> þ *H*<sup>2</sup> (13)

*H*2*O* � � (11)

$$k\_k = A\_{char} \exp\left(\frac{-E\_{char}}{RT\_s}\right) \tag{18}$$

#### **3.5 Hydrocarbon combustion**

$$r\_{\mathbb{C},H\_{2s+2}-O\_{2}} = \min\left(\begin{cases} \left\{e\_{\mathbb{C},H\_{2s+2}} A\_{\mathbb{C},H\_{2s+2}} T\_t F\_{\mathbb{C},H\_{2s+2}}^{0,3} \exp\left(\frac{-E\_{\mathbb{H}\_2}}{RT\_t}\right) \mathbf{C}\_{\mathbb{C},H\_{2s+2}}^{0,5} \mathbf{C}\_{\mathbb{O}\_2} \right\}, \\\\ \mathbf{C}\_{\text{mix}\mathbb{P}\_{\mathbb{C}},H\_{2s+2}} \left[\frac{150 D\_{\mathbb{C},H\_{2s+2}} \left(1 - e\_{\mathbb{C},H\_{2s+2}}\right)^{2/3}}{l\_p^2 e\_{\mathbb{C},H\_{2s+2}}} + \frac{1.75 u\_{\mathbb{C},H\_{2s+2}} \left(1 - e\_{\mathbb{C},H\_{2s+2}}\right)^{1/3}}{l\_p e\_{\mathbb{C},H\_{2s+2}}} \min\left[\frac{\mathbf{C}\_{\text{far}}}{S\_{\text{fnd}}}, \frac{\mathbf{C}\_{\text{O}\_2}}{S\_{\text{O}\_2}}\right] \right\}, \end{cases} \tag{19}$$

where

$$T\_{\mathfrak{e}} = \mathfrak{Q}T\_{\mathfrak{g}} + (\mathfrak{1} - \mathfrak{Q})T\_{\mathfrak{s}} \quad T\_{\mathfrak{g}} \le T\_{\mathfrak{s}} \tag{19a}$$

$$T\_{\mathfrak{e}} = T\_{\mathfrak{g}} \tag{19a} \qquad \qquad \qquad T\_{\mathfrak{g}} \le T\_{\mathfrak{s}} \tag{19a}$$

*<sup>Ω</sup> is a weighing  factor*

#### **3.6 Char reaction with water vapor**

$$R\_{char-H\_2O} = \frac{(A/V)\_{char} \varepsilon\_{H\_2O} C\_{H\_2O} \left[\frac{M\_{char}}{(1-b)M\_{H\_2O}}\right]}{\frac{1}{k\_d} + \varepsilon\_{\frac{1}{k\_r}}} \tag{20}$$

where

$$k\_k = A\_{H\_2O} T\_{char} \exp\left(\frac{-E\_{char}}{RT\_{char}}\right) \tag{21}$$

#### **3.7 Char reaction with carbon dioxide**

$$R\_{char-CO\_2} = \frac{(A/V)\_{char}C\_{CO\_2}\left[\frac{M\_{char}}{M\_{CO\_2}}\right]}{\frac{1}{k\_d} + \frac{1}{k\_r}}\tag{22}$$

where

$$k\_k = A\_{CO\_2} T\_{char} \exp\left(\frac{-E\_{char}}{RT\_{char}}\right) \tag{23}$$

*Next-Generation Greenhouses for Food Security*

### **3.8 Char reaction with hydrogen gas**

$$R\_{char-H\_2} = \frac{(A/V)\_{char} \mathbf{C}\_{H\_2} \left[ \frac{M\_{char}}{(2+b-\frac{\rho}{2})M\_{H\_2}} \right]}{\frac{1}{k\_d} + \dots + \frac{1}{k\_r}} \tag{24}$$

where

$$k\_k = A\_{H\_2} \exp\left(\frac{-E\_{char}}{RT\_{char}}\right) \tag{25}$$

**4. Results and discussion**

*DOI: http://dx.doi.org/10.5772/intechopen.97331*

increase in the equivalence ratio.

the equivalence ratio increases.

**Figure 5.**

**141**

*Effects of equivalent ratio on the percentage gas composition.*

The developed models are solved numerically and parametric studies are carried out. The variations of gas compositions with equivalence ratio in the gasification zone are shown in **Figure 5**. The result depicts a slight decrease in the percentage composition of CH4 with an increase in the equivalence ratio. The decrease is simply attributed to increased moles of air intake into the gasifier. It could be observed that the variation of H2 concentration as the equivalence ratio increases follows an inverse trend. This is because higher availability of O2 first consumes H2, which is also reflected in an increasing concentration of H2O. The same trend was also observed in the variation of CO with the equivalence ratio. The decrease in CO concentration as the equivalent ratio increases is due to oxidation of CO at higher equivalence ratio, which is further validated by the increasing trend of CO2 concentration with equivalence ratio. It could therefore be stated that the compositions and distributions of CO, H2 and CH4 in the gasifier decrease as the equivalence ratio increases. However, the temperature distribution in the reactor increases with an

*Combating Greenhouse Effects through Biomass Gasification: A Focus on Kinetic Modeling of…*

In this work, the performance of the biomass gasifier system is evaluated through the equivalence ratio, the syngas composition, cold gas efficiency and lower heating value (LHV). **Figure 6** presents the variation of gasifier performance parameters i.e., cold gas efficiency, gas yield and LHV of gas with equivalence ratio. As it could be seen in the figure that the cold efficiency and LHV decrease as the equivalence ratio increases while the gas yield increases with an increase in the equivalence ratio. The increased gas yield is due to higher air intake as the equivalence ratio increases while the decrease in cold gas efficiency and LHV of gas may be attributed to the consumption of combustible gas due to more availability of air as

**Figure 7** shows the impact of oxygen consumed on gas produced while **Figure 8** depicts the influence of gasification zone temperature on the CO/CO2 ratio in the gasification zone. From the **Figure 7**, it is shown that the quantity of gas produced

#### **3.9 Water-gas shift**

$$R\_{CO-H\_2O} = \varepsilon\_{CO} k\_{WGS} \left( C\_{CO} C\_{H\_2O} - \frac{C\_{CO\_2} C\_{H\_2}}{k\_E} \right) \tag{26}$$

where

$$k\_{\rm WGS} = A\_{\rm WGS} \exp\left(\frac{-E\_{\rm WGS}}{RT\_{\rm CO}}\right), k\_E = A\_E \exp\left(\frac{-E\_E}{RT\_{\rm CO}}\right) \tag{27}$$

#### **3.10 Steam reforming of hydrocarbon**

$$R\_{CH\_{\pi}O\_{2n+2}} = A\_{\pi}T^{b+1} \exp\left(\frac{-E\_{\pi}}{RT}\right) \text{ } \text{ } C\_{CH\_{\pi}O\_{2n+2}} \text{ } \text{ } C\_{H\_2O} \tag{28}$$

where

$$k\_d = \begin{pmatrix} \frac{D\_\text{g} \left(0.644 \text{ Re}^{0.5} \text{Sc}^{0.433}\right)}{d\_p}, & \text{Rectangular} - \text{shaped particles} \\\\ \frac{D\_\text{g} \left(2 + 1.1 \text{Re}^{0.6} \text{Sc}^{1/3}\right)}{d\_p} & \text{Cylindrical} - \text{shaped particles} \\\\ \frac{D\_\text{g} \left(1.05 + 0.6 \text{Re}^{0.6} \text{Sc}^{1/3}\right)}{d\_p} & \text{Spherical} - \text{shaped particles} \end{pmatrix} \tag{29}$$

Where at a low Reynold number

$$k\_d = \frac{D\_{H\_2}\left\{W\_0(\text{Re})\text{Sc}^{0.33} + W\_1(\text{Re})\right\}}{d\_p} \tag{30}$$

$$W\_o = \begin{bmatrix} 0.4627 \exp\left(1.01633 \left(\log\_{10}(\text{Re})\right) + 0.05121 \left(\log\_{10}(\text{Re})\right)^2 & 10^{-2} \le \text{Re} \le 3.14\\ 0.597 \left(\frac{\text{Re}}{\ln \left(\frac{1}{\text{Re}}\right)^{\frac{1}{2}}}\right) & \text{Re} < 10^{-2} \end{bmatrix} \tag{31}$$
 
$$W\_1 = \begin{bmatrix} 0.10666 \exp\left(0.41285 \left(\log\_{10}(\text{Re})\right) + 0.43847 \left(\log\_{10}(\text{Re})\right)^2 + 0.1915 \left(\log\_{10}(\text{Re})\right)^3\right) \\ + 0.01802 \left(\log\_{10}(\text{Re})\right)^4 - 0.00325 \left(\log\_{10}(\text{Re})\right)^5 \\ 0.0917 \end{bmatrix} \tag{32}$$
 
$$\text{Re} < 10^{-2} \tag{33}$$

*Combating Greenhouse Effects through Biomass Gasification: A Focus on Kinetic Modeling of… DOI: http://dx.doi.org/10.5772/intechopen.97331*

## **4. Results and discussion**

**3.8 Char reaction with hydrogen gas**

*Next-Generation Greenhouses for Food Security*

where

where

where

0

BBBBBBBBBBBBB@

*kd* ¼

*Wo* ¼

*W*<sup>1</sup> ¼

**140**

2 6 4

**3.9 Water-gas shift**

*Rchar*�*H*<sup>2</sup> ¼

*kWGS* <sup>¼</sup> *AWGS* exp �*EWGS*

*RCHnO*2*n*þ<sup>2</sup> <sup>¼</sup> *AsrT<sup>b</sup>*þ<sup>1</sup> exp �*Esr*

**3.10 Steam reforming of hydrocarbon**

*Dg* 0*:*644 Re <sup>0</sup>*:*<sup>5</sup>

*Sc*<sup>0</sup>*:*<sup>433</sup> � � *dp*

*Dg* <sup>2</sup> <sup>þ</sup> <sup>1</sup>*:*1 Re <sup>0</sup>*:*<sup>6</sup>*Sc*<sup>1</sup>*=*<sup>3</sup> � � *dp*

*Dg* <sup>1</sup>*:*<sup>05</sup> <sup>þ</sup> <sup>0</sup>*:*6 Re <sup>0</sup>*:*<sup>6</sup>*Sc*<sup>1</sup>*=*<sup>3</sup> � � *dp*

1

<sup>þ</sup>0*:*01802 log <sup>10</sup>ð Þ Re � �<sup>4</sup> � <sup>0</sup>*:*005225 log <sup>10</sup>ð Þ Re � �<sup>5</sup>

Where at a low Reynold number

<sup>0</sup>*:*<sup>597</sup> Re *In* <sup>1</sup> Re � �<sup>1</sup> 3

0 @ ð Þ *A=V charCH*<sup>2</sup>

1

*kk* <sup>¼</sup> *AH*<sup>2</sup> exp �*Echar*

*RCO*�*H*2*<sup>O</sup>* <sup>¼</sup> *<sup>ε</sup>COkWGS CCOCH*2*<sup>O</sup>* � *CCO*2*CH*<sup>2</sup>

*RTCO* � �

> *RT* � �

*kd* <sup>¼</sup> *DH*<sup>2</sup> *<sup>W</sup>*0ð Þ Re *Sc*<sup>0</sup>*:*<sup>33</sup> <sup>þ</sup> *<sup>W</sup>*1ð Þ Re � � *dp*

<sup>0</sup>*:*4627 exp <sup>ð</sup>1*:*01633 log <sup>10</sup>ð Þ Re � � <sup>þ</sup> <sup>0</sup>*:*05121ðlog <sup>10</sup>ð Þ Re <sup>2</sup> <sup>10</sup>�<sup>2</sup> <sup>≤</sup> Re <sup>≤</sup>3*:*<sup>14</sup>

0*:*0917 *Re* <10�<sup>2</sup>

<sup>0</sup>*:*10666 exp 0*:*41285 log <sup>10</sup>ð Þ Re � � <sup>þ</sup> <sup>0</sup>*:*43847 log <sup>10</sup>ð Þ Re � �<sup>2</sup> <sup>þ</sup> <sup>0</sup>*:*1915 log <sup>10</sup>ð Þ Re � �<sup>3</sup> �

<sup>A</sup> Re <sup>&</sup>lt;10�<sup>2</sup>

*kd* <sup>þ</sup> <sup>1</sup>

*RTchar* � �

� �

, *kE* <sup>¼</sup> *AE* exp �*EE*

, *Rectangular* � shaped  particles

*Cylindrical* � shaped  particles

*Spherical* � shaped  particles

*MChar* <sup>2</sup>þ*b*�*<sup>a</sup>* ð Þ<sup>2</sup> *MH*<sup>2</sup> � �

(24)

(25)

(26)

(27)

1

CCCCCCCCCCCCCA

(29)

(30)

(31)

(32)

10�<sup>2</sup> ≤ Re ≤3*:*14

3 7 5

*kr*

*kE*

*RTCO* � �

*CCHnO*2*n*þ<sup>2</sup> *CH*2*<sup>O</sup>* (28)

The developed models are solved numerically and parametric studies are carried out. The variations of gas compositions with equivalence ratio in the gasification zone are shown in **Figure 5**. The result depicts a slight decrease in the percentage composition of CH4 with an increase in the equivalence ratio. The decrease is simply attributed to increased moles of air intake into the gasifier. It could be observed that the variation of H2 concentration as the equivalence ratio increases follows an inverse trend. This is because higher availability of O2 first consumes H2, which is also reflected in an increasing concentration of H2O. The same trend was also observed in the variation of CO with the equivalence ratio. The decrease in CO concentration as the equivalent ratio increases is due to oxidation of CO at higher equivalence ratio, which is further validated by the increasing trend of CO2 concentration with equivalence ratio. It could therefore be stated that the compositions and distributions of CO, H2 and CH4 in the gasifier decrease as the equivalence ratio increases. However, the temperature distribution in the reactor increases with an increase in the equivalence ratio.

In this work, the performance of the biomass gasifier system is evaluated through the equivalence ratio, the syngas composition, cold gas efficiency and lower heating value (LHV). **Figure 6** presents the variation of gasifier performance parameters i.e., cold gas efficiency, gas yield and LHV of gas with equivalence ratio. As it could be seen in the figure that the cold efficiency and LHV decrease as the equivalence ratio increases while the gas yield increases with an increase in the equivalence ratio. The increased gas yield is due to higher air intake as the equivalence ratio increases while the decrease in cold gas efficiency and LHV of gas may be attributed to the consumption of combustible gas due to more availability of air as the equivalence ratio increases.

**Figure 7** shows the impact of oxygen consumed on gas produced while **Figure 8** depicts the influence of gasification zone temperature on the CO/CO2 ratio in the gasification zone. From the **Figure 7**, it is shown that the quantity of gas produced

**Figure 5.** *Effects of equivalent ratio on the percentage gas composition.*

increases as the amount of oxygen consumed increases. This is due to increasing in the rate of combustion of the products of pyrolysis as more oxygen is consumed in the combustion process or oxidation reactions, more gases are produced from the reactor. It is also shown in **Figure 8** that the ratio of CO/CO2 decreases as the temperature of the reduction zone increases.

The validation of the computational fluid dynamic simulations is very necessary. The comparison of the computational fluid dynamic simulations with the results of the experiment [33, 34] as shown in **Figure 9**. The results showed good agreements with the results of the measurement.

**Figure 6.** *Effects of char particle diameter on the char combustion rate.*

**5. Conclusion**

*Comparison of the results.*

**Figure 9.**

**143**

**Figure 8.**

*Effects of temperature on CO/CO2 ratio in the gasification zone.*

*DOI: http://dx.doi.org/10.5772/intechopen.97331*

*Combating Greenhouse Effects through Biomass Gasification: A Focus on Kinetic Modeling of…*

ratio increases.

In this work, improved kinetic models for the combustion and gasification zones in the thermochemical system have been developed. The performance of the biomass gasifier system was evaluated through the equivalence ratio, the syngas composition, cold gas efficiency and lower heating value. Also, the effects of the equivalent ratio on gas compositions, the gasifier performance and the low heating value of the biomass were investigated. From the analysis, it is established that

i. the concentration of CO, H2 and CH4 in the gasifier decrease as equivalence

ii. the CO2 concentration increases with increase in the equivalence ratio.

**Figure 7.** *Effects of oxygen consumed on gas produced.*

*Combating Greenhouse Effects through Biomass Gasification: A Focus on Kinetic Modeling of… DOI: http://dx.doi.org/10.5772/intechopen.97331*

**Figure 8.** *Effects of temperature on CO/CO2 ratio in the gasification zone.*

**Figure 9.** *Comparison of the results.*

## **5. Conclusion**

increases as the amount of oxygen consumed increases. This is due to increasing in the rate of combustion of the products of pyrolysis as more oxygen is consumed in the combustion process or oxidation reactions, more gases are produced from the reactor. It is also shown in **Figure 8** that the ratio of CO/CO2 decreases as the

The validation of the computational fluid dynamic simulations is very necessary. The comparison of the computational fluid dynamic simulations with the results of the experiment [33, 34] as shown in **Figure 9**. The results showed good agreements

temperature of the reduction zone increases.

*Next-Generation Greenhouses for Food Security*

*Effects of char particle diameter on the char combustion rate.*

with the results of the measurement.

**Figure 7.**

**142**

**Figure 6.**

*Effects of oxygen consumed on gas produced.*

In this work, improved kinetic models for the combustion and gasification zones in the thermochemical system have been developed. The performance of the biomass gasifier system was evaluated through the equivalence ratio, the syngas composition, cold gas efficiency and lower heating value. Also, the effects of the equivalent ratio on gas compositions, the gasifier performance and the low heating value of the biomass were investigated. From the analysis, it is established that


iii. the cold efficiency and LHV decreases as the equivalence ratio increases while the gas yield increases with increase in the equivalence ratio.

**References**

1999.

2002.

1383 – 1393.

**145**

[1] L. Devi, K. J. Ptasinski, F. J. J. G. Jenssen. A review of the primary measures for tar elimination in biomass

*DOI: http://dx.doi.org/10.5772/intechopen.97331*

fluidized bed biomass gasifier for hydrogen rich gas. Chinese Journal of

[10] K. Papadikis, A. V. Bidgwater and S. Gu. CFD modelling of the fast pyrolysis of biomass in fluidized bed reactors", Part A: Eulerian computation of momentum transport in bubbling fluidized beds", Chemical Engineering

[11] Y. Wang and L. Yan. CFD studies on biomass thermo chemical conversion", Int J Mol Sci, 9, 1108 – 1130, 2008

[12] H. Yilmaz, S. Perumalsamy, G. Oeljeklaus, K. Gorner, T. Klasen, A. C. Benim. CFD Analysis of a Large Scale Entrained-Flow Gasifier for IGCC Power Plants. 7th International Conference on Multiphase Flow.

Tampa, FL: ICMF, 2010.

[13] P. Cornejo and O. Farias. Mathematical Modeling of Coal Gasification in a Fluidized Bed Reactor Using a Eulerian Granular Description. International Journal of Chemical Reactor Engineering, 9(1)(2011), 1-30.

[14] T. Paes. Modeling for control of a biomass gasifier. Eidhoven: Technische

Universiteit Eindhoven, 2005.

[15] H. Watanabe and M. Otaka. Numerical simulation of coal gasification in entrained flow coal gasifier. Fuel, 85(12-13). 2006, 1935-

[16] H. J. Huang and S. Ramaswamy. Modeling Biomass Gasification Using Thermodynamic Equilibrium Approach. Applied Biomechical Biotechnology, 154

(1-3) (2009), 193-204

[17] A. Cuoci, T. Garavelli, A, Frassoldati., R. Grana, S. Pierucci, E. Ranzi and S. Sommariva. Mathematical

modeling of gasification and

1943.

Chemical Physics, 19, 2006.

*Combating Greenhouse Effects through Biomass Gasification: A Focus on Kinetic Modeling of…*

Science, 63, 4218 - 4227, 2008.

[2] P. Quaak, H. Knoef and H. Stassen. Energy from Biomass: A Review of Combustion and Gasification Technologies. Energy Series World Bank Technica'l Paper NO. 422, I44,

[3] D. L. Klass. Biomass for Renewable

Academic Press, San Diego, 1998, 1-651.

[4] S.Yang., H. Wang, Y. Wei, J. Hu and J. W. Chew. Eulerian-Lagrangian simula tion of air-steam biomass gasification in a three-dimensional bubbling fluidized gasifier," Energy, Elsevier, 181(C),

[5] A. Klein. Gasification: An Alternative Process for Energy Recovery and Disposal of Municipal Solid Wastes,

[6] A. Klein and N. J. Themelis. Energy Recovery from Municipal Solid Wastes by Gasification. North American Waste to Energy Conference (NAWTEC 11)11 Proceedings, ASME International, Tampa FL (April 2003), 241-252, 2003

[7] D. F. Fletcher, D. F. Haynes, B. S. Christo, F. C. Joseph, S. D. A CFD based combustion model of an entrained flow biomass gasifier. Applied Mathematical Modelling, 24(3)(2000), 165- 182.

[8] L. Gerun, M. Paraschiv, R. Vijeu, J. Bellettre, M. Tazerout, B. Gøbel, U. Henriksen. Numerical investigation of the partial oxidation in a two-stage downdraft gasifier. Fuel, 87(2008),

[9] M. Zhou, L. Yan, Q. Guo. Non premixed combustion model of

Energy, Fuels, and Chemicals.

(2019), 1075-1093.

gasification processes. Biomass Bioenergy, 24(2003), 125–140.


The analysis is far less costly and time consuming than the experimental approach. Such analysis is useful as a time saving and cost effective tool for designing and optimizing the biomass gasifier.

## **Author details**

Sunday J. Ojolo\* and Musbau G. Sobamowo Department of Mechanical Engineering, University of Lagos, Nigeria

\*Address all correspondence to: sojolo@unilag.edu.ng

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Combating Greenhouse Effects through Biomass Gasification: A Focus on Kinetic Modeling of… DOI: http://dx.doi.org/10.5772/intechopen.97331*

## **References**

iii. the cold efficiency and LHV decreases as the equivalence ratio increases while the gas yield increases with increase in the equivalence ratio.

iv. the quantity of gas produced increases as the amount of oxygen consumed

v. the ratio of CO/CO2 decreases as the temperature of the reduction zone increases. The developed model is validated with the experimental results.

The analysis is far less costly and time consuming than the experimental approach. Such analysis is useful as a time saving and cost effective tool for

increases.

**Author details**

**144**

Sunday J. Ojolo\* and Musbau G. Sobamowo

provided the original work is properly cited.

\*Address all correspondence to: sojolo@unilag.edu.ng

Department of Mechanical Engineering, University of Lagos, Nigeria

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

designing and optimizing the biomass gasifier.

*Next-Generation Greenhouses for Food Security*

[1] L. Devi, K. J. Ptasinski, F. J. J. G. Jenssen. A review of the primary measures for tar elimination in biomass gasification processes. Biomass Bioenergy, 24(2003), 125–140.

[2] P. Quaak, H. Knoef and H. Stassen. Energy from Biomass: A Review of Combustion and Gasification Technologies. Energy Series World Bank Technica'l Paper NO. 422, I44, 1999.

[3] D. L. Klass. Biomass for Renewable Energy, Fuels, and Chemicals. Academic Press, San Diego, 1998, 1-651.

[4] S.Yang., H. Wang, Y. Wei, J. Hu and J. W. Chew. Eulerian-Lagrangian simula tion of air-steam biomass gasification in a three-dimensional bubbling fluidized gasifier," Energy, Elsevier, 181(C), (2019), 1075-1093.

[5] A. Klein. Gasification: An Alternative Process for Energy Recovery and Disposal of Municipal Solid Wastes, 2002.

[6] A. Klein and N. J. Themelis. Energy Recovery from Municipal Solid Wastes by Gasification. North American Waste to Energy Conference (NAWTEC 11)11 Proceedings, ASME International, Tampa FL (April 2003), 241-252, 2003

[7] D. F. Fletcher, D. F. Haynes, B. S. Christo, F. C. Joseph, S. D. A CFD based combustion model of an entrained flow biomass gasifier. Applied Mathematical Modelling, 24(3)(2000), 165- 182.

[8] L. Gerun, M. Paraschiv, R. Vijeu, J. Bellettre, M. Tazerout, B. Gøbel, U. Henriksen. Numerical investigation of the partial oxidation in a two-stage downdraft gasifier. Fuel, 87(2008), 1383 – 1393.

[9] M. Zhou, L. Yan, Q. Guo. Non premixed combustion model of

fluidized bed biomass gasifier for hydrogen rich gas. Chinese Journal of Chemical Physics, 19, 2006.

[10] K. Papadikis, A. V. Bidgwater and S. Gu. CFD modelling of the fast pyrolysis of biomass in fluidized bed reactors", Part A: Eulerian computation of momentum transport in bubbling fluidized beds", Chemical Engineering Science, 63, 4218 - 4227, 2008.

[11] Y. Wang and L. Yan. CFD studies on biomass thermo chemical conversion", Int J Mol Sci, 9, 1108 – 1130, 2008

[12] H. Yilmaz, S. Perumalsamy, G. Oeljeklaus, K. Gorner, T. Klasen, A. C. Benim. CFD Analysis of a Large Scale Entrained-Flow Gasifier for IGCC Power Plants. 7th International Conference on Multiphase Flow. Tampa, FL: ICMF, 2010.

[13] P. Cornejo and O. Farias. Mathematical Modeling of Coal Gasification in a Fluidized Bed Reactor Using a Eulerian Granular Description. International Journal of Chemical Reactor Engineering, 9(1)(2011), 1-30.

[14] T. Paes. Modeling for control of a biomass gasifier. Eidhoven: Technische Universiteit Eindhoven, 2005.

[15] H. Watanabe and M. Otaka. Numerical simulation of coal gasification in entrained flow coal gasifier. Fuel, 85(12-13). 2006, 1935- 1943.

[16] H. J. Huang and S. Ramaswamy. Modeling Biomass Gasification Using Thermodynamic Equilibrium Approach. Applied Biomechical Biotechnology, 154 (1-3) (2009), 193-204

[17] A. Cuoci, T. Garavelli, A, Frassoldati., R. Grana, S. Pierucci, E. Ranzi and S. Sommariva. Mathematical modeling of gasification and

combustion of solid fuels and wastes. Chemical Engineering Transactions, 18 (2009), 989-994.

[18] S. M. Atnaw and S. A. Sulaiman. Modeling and simulation study of downdraft gasifier using oil-palm fronds. Conference: 3rd International Conference on Energy and Environment. ICEE 2009.

[19] M. Hamzehei, H. Rahimzadeh, G. Ahmadi. Studies of gas velocity and particles size effects on fluidized bed hydrodynamics with CFD modeling and experimental investigation. Journal of Mechanics; 26(3), 2010.

[20] L. Tingwen, G. Aytekin, S. Madhava. High-Resolution simulations of coal injection in a gasifier. Ind. Eng. Chem. Res., 49(2010), 10767–10779.

[21] H. Zhang, S. Shao, R. Xiao, Q. Pan, R. Chen, J. Zhang. Numerical study on the hydrodynamics of a self-heating biomass fast pyrolysis reactor" Energy Fuels, 25(2011), 4077 – 4084, 2011.

[22] B. Peng, J. Zhu and C. Zhang. A new approach to specify the inlet boundary conditions for computational fluid dynamics (CFD) modeling of hydrodynamic behavior of a circulating fluidized bed (CFB) riser. Ind. Eng. Chem. Res., 51(2012), 2152 – 2165.

[23] W. Chen, X. Liu, X. Fan, L. Chu, Y. Yang, W. Liu. Three-Dimensional Simulation of Gas-Solid Flow in the Biomass Circulating Fluidized Bed Gasifier's Riser, Advanced Materials Research, 383-390(2012),6537-6542.

[24] Y. Wu, Q. Zhang, W. Yang, and W. Blasiak, Two-Dimensional Computational Fluid Dynamics Simulation of Biomass Gasification in a Downdraft Fixed-Bed Gasifier with Highly Preheated Air and Steam. Energy & Fuels, 27(6) (2013), 3274-3282.

[25] H. Luo, W. Lin, W. Song, S. Li, D-J. Songgeng, H. Wu. Three-dimensional

full-loop CFD simulation of hydrodynamics in a pilot-scale dual fluidized-bed system for biomass gasification. Fuel Processing Technolog y, 195(2019), 106146.

investigation of a downdraft biomass gasifier. Biomass and Bioenergy 23(4)

*DOI: http://dx.doi.org/10.5772/intechopen.97331*

*Combating Greenhouse Effects through Biomass Gasification: A Focus on Kinetic Modeling of…*

[34] Z. A. Zainal, R. Aliu, C. H. Lean and

K. N. Seetharamu. Prediction of performance of a downdraft gasifier using equilibrium modeling for different biomass material. Energy Conversion and Management 42(12)

(2002), 283-289.

(2001):1499-1515.

**147**

[26] H. Liu, R. J. Cattolica, R. Seiser, C. Liao. Three-dimensional full-loop simulation of a dual fluidized-bed biomass gasifier. Applied Energy, 160 (2015), 489-501

[27] D. Lu, K. Yoshikawa, T. M. Ismail and M. A. El-Salam. Computational Fluid Dynamics Model on Updraft Gasifier using Carbonized Woody Briquette as Fuel. 9th International Conference on Applied Energy, ICAE2017, 21-24 August 2017, Cardiff, UK

[28] U. Kumar, A. M. Salem, M. C. Paul. Investigating the thermochemical conversion of biomass in a downdraft gasifier with a volatile break-up approach. 9th International Conference on Applied Energy, ICAE2017, 21-24 August 2017, Cardiff, UK

[29] K. G. Santos, V. V. Murata and M. A. S. Barrozo. Three-dimensional computational fluid dynamics modelling of spouted bed. The Canadian Journal of Chemical Engineering. 87, 211-219, 2009.

[30] J. K. Kone, X. Zhang, Y. Yan, G. Hu, and G. Ahmadi. Three-dimensional multiphase flow computational fluid dynamics models for proton exchange membrane fuel cell: A theoretical development. The Journal of Computational Multiphase Flows, 9(1 (2017), 3–25

[31] Biomass Engineering Limited, Newton-le-Willows, Warrington, UK

[32] Jain, Ankur Scientific, Baroda, Indian March 2006 and Senior Capstone Design, Villanova University, 2006.

[33] Z. A. Zainal, A. Rafiu, G. A. Quadir and K. N. Seetharamu. Experimental

*Combating Greenhouse Effects through Biomass Gasification: A Focus on Kinetic Modeling of… DOI: http://dx.doi.org/10.5772/intechopen.97331*

investigation of a downdraft biomass gasifier. Biomass and Bioenergy 23(4) (2002), 283-289.

combustion of solid fuels and wastes. Chemical Engineering Transactions, 18

*Next-Generation Greenhouses for Food Security*

full-loop CFD simulation of

y, 195(2019), 106146.

(2015), 489-501

Cardiff, UK

2009.

(2017), 3–25

hydrodynamics in a pilot-scale dual fluidized-bed system for biomass gasification. Fuel Processing Technolog

[26] H. Liu, R. J. Cattolica, R. Seiser, C. Liao. Three-dimensional full-loop simulation of a dual fluidized-bed biomass gasifier. Applied Energy, 160

[27] D. Lu, K. Yoshikawa, T. M. Ismail and M. A. El-Salam. Computational Fluid Dynamics Model on Updraft Gasifier using Carbonized Woody Briquette as Fuel. 9th International Conference on Applied Energy, ICAE2017, 21-24 August 2017,

[28] U. Kumar, A. M. Salem, M. C. Paul. Investigating the thermochemical conversion of biomass in a downdraft gasifier with a volatile break-up

approach. 9th International Conference on Applied Energy, ICAE2017, 21-24

[29] K. G. Santos, V. V. Murata and M. A.

computational fluid dynamics modelling of spouted bed. The Canadian Journal of Chemical Engineering. 87, 211-219,

[30] J. K. Kone, X. Zhang, Y. Yan, G. Hu, and G. Ahmadi. Three-dimensional multiphase flow computational fluid dynamics models for proton exchange membrane fuel cell: A theoretical development. The Journal of

Computational Multiphase Flows, 9(1

[31] Biomass Engineering Limited, Newton-le-Willows, Warrington, UK

[32] Jain, Ankur Scientific, Baroda, Indian March 2006 and Senior Capstone Design, Villanova University, 2006.

[33] Z. A. Zainal, A. Rafiu, G. A. Quadir and K. N. Seetharamu. Experimental

August 2017, Cardiff, UK

S. Barrozo. Three-dimensional

[18] S. M. Atnaw and S. A. Sulaiman. Modeling and simulation study of downdraft gasifier using oil-palm fronds. Conference: 3rd International

[19] M. Hamzehei, H. Rahimzadeh, G. Ahmadi. Studies of gas velocity and particles size effects on fluidized bed hydrodynamics with CFD modeling and experimental investigation. Journal of

Conference on Energy and Environment. ICEE 2009.

Mechanics; 26(3), 2010.

[20] L. Tingwen, G. Aytekin, S.

Madhava. High-Resolution simulations of coal injection in a gasifier. Ind. Eng. Chem. Res., 49(2010), 10767–10779.

[21] H. Zhang, S. Shao, R. Xiao, Q. Pan, R. Chen, J. Zhang. Numerical study on the hydrodynamics of a self-heating biomass fast pyrolysis reactor" Energy Fuels, 25(2011), 4077 – 4084, 2011.

[22] B. Peng, J. Zhu and C. Zhang. A new approach to specify the inlet boundary conditions for computational fluid dynamics (CFD) modeling of

hydrodynamic behavior of a circulating fluidized bed (CFB) riser. Ind. Eng. Chem. Res., 51(2012), 2152 – 2165.

[23] W. Chen, X. Liu, X. Fan, L. Chu, Y. Yang, W. Liu. Three-Dimensional Simulation of Gas-Solid Flow in the Biomass Circulating Fluidized Bed Gasifier's Riser, Advanced Materials Research, 383-390(2012),6537-6542.

[24] Y. Wu, Q. Zhang, W. Yang, and W.

Simulation of Biomass Gasification in a Downdraft Fixed-Bed Gasifier with Highly Preheated Air and Steam. Energy & Fuels, 27(6) (2013), 3274-3282.

[25] H. Luo, W. Lin, W. Song, S. Li, D-J. Songgeng, H. Wu. Three-dimensional

Blasiak, Two-Dimensional Computational Fluid Dynamics

**146**

(2009), 989-994.

[34] Z. A. Zainal, R. Aliu, C. H. Lean and K. N. Seetharamu. Prediction of performance of a downdraft gasifier using equilibrium modeling for different biomass material. Energy Conversion and Management 42(12) (2001):1499-1515.

**149**

**Chapter 8**

**Abstract**

Design and Evaluation of an

Automated Monitoring and

*Arasu Sivagami, Michael Angelo Kandavalli* 

Crop Production

*and Bhaskarrao Yakkala*

Control System for Greenhouse

An embedded system integrated with sensors based on nanomaterial is proposed for closely monitoring and control microclimate parameters 24 hours a day to maximise production over the whole crop growth season by introducing greenhouse for the cultivation of plants or specific plant species. The system will also eliminate errors in human intervention to optimise production of crops. This system consists of sensors and actuators, an Analogue to Digital Converter (ADC) and a Raspberry Pi. The system will determine whether a defined threshold is passed by any climate parameter and systematically changes via the controller. The current work reduces human input through automated irrigation to optimally utilize a scarce resource, namely water. Climatic parameters for plant growth such as, moisture, humidity, temperature, water pressure in drip pipe, soil salinity etc. are monitored and optimized. Furthermore, work was extended to include GSM to control the entire farm remotely. For its success, it is very important to choose a greenhouse location. For instance, the problems are quite different when choosing an adjoining greenhouse, for instance a sunroom or greenhouse. The greenhouse location should be chosen for sunlight, proximity to power and water sources, wind, drain and freeze pockets, and the proximity of the garden and house. The intention behind accomplishment and devise of GSM based Fertigation System is to construct and evaluate the requirement of water in the yield as farming is the major resource of production which habitually depends on the water accessibility. Irrigation of water is usually done by manual method. To ease the work of the farmer GSM based automatic Fertigation (includes chemigation too) system can be implemented so that water wastage can be reduced and also the fertilizer can be added accordingly. Also the Soil Salinity can be checked and reduced if exceeds certain limit. By using GSM, only GSM command via GSM mobile can control the start and stop action of a motor that feeds the field with the water. GSM is used for controlling the entire process and the entire system backbone. It can be used from any distance to control irrigation. The results are assessed by electronic simulator PROTEUS using the desired optimised parameters, the design of this automated greenhouse system with PIC controller. As the inputs to the microcontroller and as an LCD screen record the respective outputs, the model produces a soil moisture sensor, light sensor and temperature sensor. The system

## **Chapter 8**
