Preface

The interest in biofuel production and application is governed by two main factors: the possible depletion of fossil fuel resources on a global scale and the more threatening pollution of the atmosphere because of the extensive emissions of greenhouse gases, such as carbon dioxide and methane that the present global vegetation cannot cope with. This trend became more threatening with the increased use of fossil fuels such as oil, coal, and natural gas because the atmosphere was shock-loaded by carbon emissions collected underground for millions of years. A remedy against the last problem is the use of biomass presently grown as a source for biofuel. Hence the carbon dioxide emissions in air can be processed by the present vegetation, thus closing the current carbon cycle. Such biofuels are biogas, bioethanol, biodiesel, etc.

On the other hand, fossils have been extensively used in the 20th century by mankind as feedstock for various chemical manufacturing, starting with nitrogen-containing fertilizers and ending with production of organic products such as plastics, synthetic rubber, dyestuffs, pharmaceuticals, etc. In this direction biofuels can be further utilized as substrates for organic syntheses for bulk chemical products, such as alcohols, biodegradable polymers, organic acids, etc.

These two options reveal different prospects for development of new biomassbased industries, although currently on a modest scale. This approach is known as the biorefinery concept as an analogue to the oil-based refineries producing fuels and chemical commodities.

Although attractive, the biorefinery approach must be evaluated by its secondary effects on economy, on the competitive use of vegetation and animal feedstocks for other purposes, on the unexpected impacts to the environment and biodiversity, etc. For example, biodiesel production leads to an inevitable release of large amounts of waste glycerol with limited demand, thus opening a new challenge for its treatment and removal. It has even been mentioned that it will be a "glycerol-based economy"!

On the other hand, the inevitable release of carbon dioxide when biofuels are used could be remediated after its conversion into chemicals (e.g. synthetics gas, methanol, formic acid) and to fuel, such as methane by chemical, electrochemical, or biotechnological processes. There are many efforts to recycle carbon dioxide in flue gases by lipid-containing algae. These lipids are further converted into biodiesel and so forth.

The present book offers some examples and new ideas for the broader applications of biofuels and the resulting raw materials for energy and chemical production as alternatives to the traditional fossil fuels.

> **Venko Beschkov** Institute of Chemical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria

**1**

Section 1

General

Section 1 General

**3**

**Chapter 1**

**Abstract**

high-boiling liquids

**1. Introduction**

Biorefinery Safety: A Case Study

*Roberto Lauri and Biancamaria Pietrangeli*

and therefore of its vapor pressure on evaporation rate.

Focused on Bioethanol Production

With reference to the framework for energy and climate, the European Union (EU) has stated that at least a 32% share of renewable energy consumption has to be achieved within 2030. This context generates attention to the potential hazards, which are associated with flammable biofuels, such as the bioethanol. One of the main hazards, referred to such biofuel, is the formation of potentially explosive atmospheres due to its evaporation from pools in case of accidental releases. In fact, in a bioethanol production plant (biorefinery), there are several components (flanges, valves, pumps, etc.), which can become potential emission sources in case of failure. Bioethanol is a high-boiling liquid, because its boiling temperature (Tboiling = 78°C) is higher than ambient temperature. Therefore, in case of release and spreading on a certain medium, evaporation occurs because of vapor diffusion. The chapter is focused on a case study. In particular, the chapter illustrates a comparison between two predictive models aimed at estimating the bioethanol evaporation rate, which is a fundamental parameter for determining the dilution degree and classifying the workplaces, where potentially explosive atmospheres could occur. The study investigates the influence of bioethanol release temperature

**Keywords:** bioethanol, evaporation rate, safety, potentially explosive atmospheres,

One of the most demanded challenges for human being in the near future is the development of new energy strategies, which are alternative to fossil energy and characterized by low environmental impacts. In the European Union (EU), the original renewable energy directive 2009/28/EC (RED I) establishes an overall policy for the production and promotion of energy from renewable sources. It requires to fulfill at least 20% of total energy needs with renewables by 2020 [1]. All EU countries must also ensure that at least 10% of their transport fuels come from renewable sources by 2020. In December 2018, the revised renewable energy directive 2018/2001/EU (RED II) came into force as part of the clean energy for all European package. Such directive is aimed at keeping the EU as a global leader in renewables and, more broadly, helping the EU to meet its emission reduction commitments [2] under the Paris Agreement. A common biofuel is the bioethanol, which is a leading candidate to substitute the gasoline as a transport fuel. In the chapter, "bioethanol" is used to indicate ethanol produced by fermentative processes, which convert the sugars into energy. The fermentation mainly uses

#### **Chapter 1**

## Biorefinery Safety: A Case Study Focused on Bioethanol Production

*Roberto Lauri and Biancamaria Pietrangeli*

#### **Abstract**

With reference to the framework for energy and climate, the European Union (EU) has stated that at least a 32% share of renewable energy consumption has to be achieved within 2030. This context generates attention to the potential hazards, which are associated with flammable biofuels, such as the bioethanol. One of the main hazards, referred to such biofuel, is the formation of potentially explosive atmospheres due to its evaporation from pools in case of accidental releases. In fact, in a bioethanol production plant (biorefinery), there are several components (flanges, valves, pumps, etc.), which can become potential emission sources in case of failure. Bioethanol is a high-boiling liquid, because its boiling temperature (Tboiling = 78°C) is higher than ambient temperature. Therefore, in case of release and spreading on a certain medium, evaporation occurs because of vapor diffusion. The chapter is focused on a case study. In particular, the chapter illustrates a comparison between two predictive models aimed at estimating the bioethanol evaporation rate, which is a fundamental parameter for determining the dilution degree and classifying the workplaces, where potentially explosive atmospheres could occur. The study investigates the influence of bioethanol release temperature and therefore of its vapor pressure on evaporation rate.

**Keywords:** bioethanol, evaporation rate, safety, potentially explosive atmospheres, high-boiling liquids

#### **1. Introduction**

One of the most demanded challenges for human being in the near future is the development of new energy strategies, which are alternative to fossil energy and characterized by low environmental impacts. In the European Union (EU), the original renewable energy directive 2009/28/EC (RED I) establishes an overall policy for the production and promotion of energy from renewable sources. It requires to fulfill at least 20% of total energy needs with renewables by 2020 [1]. All EU countries must also ensure that at least 10% of their transport fuels come from renewable sources by 2020. In December 2018, the revised renewable energy directive 2018/2001/EU (RED II) came into force as part of the clean energy for all European package. Such directive is aimed at keeping the EU as a global leader in renewables and, more broadly, helping the EU to meet its emission reduction commitments [2] under the Paris Agreement. A common biofuel is the bioethanol, which is a leading candidate to substitute the gasoline as a transport fuel. In the chapter, "bioethanol" is used to indicate ethanol produced by fermentative processes, which convert the sugars into energy. The fermentation mainly uses

biomass. Bioethanol is a renewable fuel, which can be made from grains, such as corn or wheat, or from cellulose sources, such as prairie grass or agricultural, forestry, or municipal wastes. It can be used in vehicles or small engines, which are fed by conventional fuels, and it is utilized as a fuel extender and octane improver with blends that usually are 10% ethanol and 90% unleaded gasoline. Indeed, several researches showed that ethanol/gasoline blends had the potentiality to reduce petroleum fuel use and greenhouse gas emissions. In the last years, the bioethanol use has undergone a fast growth, because it can make easier the replacement of fossil fuels with renewable fuels. In particular, in Europe, the framework for climate and energy, established by the European Council in 2014, caused this growth. Indeed, a specific target for 2030, included in this framework, has stated that at least a 32% share of renewable energy consumption has to be achieved. This context generates attention to the potential hazards, which are associated with flammable biofuels, such as the bioethanol, and has given birth to this chapter, which is focused on the study of bioethanol evaporation rate from liquid pools. In fact, one of the main hazards, referred to such biofuel, is the formation of potentially explosive atmospheres due to its evaporation from pools in case of accidental releases. Indeed, in a bioethanol production plant (biorefinery), there are several components (flanges, valves, pumps, etc.), which can become potential emission sources in case of failure. Bioethanol can be considered as a high-boiling liquid, because its boiling temperature (Tboiling = 78°C) is higher than ambient temperature. Therefore, in case of release and spreading on a certain medium, evaporation occurs because of vapor diffusion. This is the result of the difference in terms of vapor pressure between the liquid surface and surrounding area. The chapter carries out a comparison between two predictive models (the model referred to low mass transport and the generally applicable formula) aimed at estimating the bioethanol evaporation rate, which is a fundamental parameter for determining the dilution degree and classifying the workplaces, where potentially explosive atmospheres could occur. It is important to highlight that Atex Directive 99/92/EC obliges the employers to carry out such classification [3]. The dilution degree is a parameter, which measures the ventilation (natural or artificial) ability to dilute a release to a safe level (flammable substance concentration is lower than its lower flammability limit) and is reported in International Standard IEC EN 60079-10-1. In particular, the study investigates the influence of bioethanol release temperature and therefore of its vapor pressure on evaporation rate. Finally, the difference between the bioethanol evaporation rates is calculated to determine the reliability range of the model, referred to low mass transport. Therefore, the work is aimed at giving some guidelines about the vapor pressure (such parameter is strictly dependent on temperature) range, where the simplified model is able to provide reliable predictions.

#### **2. Occupational health and safety (OHS) in the biofuel industry**

In accordance with the Renewable Fuels Association [4], at 2018 year end, the ethanol industry approximately comprised 210 plants in 27 states with nameplate capacity equal to 16.5 billion gallons. According to the Biotechnology Innovation Organization (BIO), the direct job creation from advanced biofuel production could reach 190,000 units by 2022 [5]*.* This context generates attention to occupational safety, which has to take into account all actions aimed at protecting the safety, health, and welfare of people engaged in such industrial sector. This can include safety assessments, accident investigations, training programs, and other

**5**

**Table 1.**

*Chemical bioethanol properties.*

*Biorefinery Safety: A Case Study Focused on Bioethanol Production*

activities, which can reduce or eliminate workplace injuries and illnesses. In the face of growing development of the biofuel industry and the consequent increase in employed workforce, there are still limited data, which are referred to the occupational health and safety of these production processes. Petrochemical processing industry is very advanced in terms of risk assessment and management, while the biofuel production industry has not yet gained enough experience in these topics [6]. Indeed, occupational health and risks during all phases of the processes are not always considered. The former available data suggest that renewable energy will also offer benefits to workers in terms of reduced occupational injury, illness, and death [7], but considering that the biofuels industry is a developing and growing sector and many of the involved companies are small entrepreneurial activities, studies of worker safety and health should be implemented. In Europe, there are a high number of small-scale industrial units, such as the biogas production plants, which are generally characterized by lower quantities than the thresholds for the application of legislation (the Seveso Directive) aimed at the control of major accidents [8]*.* Such industrial activities have neither the ability for thinking about the risks and the hazards nor the resources or the expertise for managing those. This aspect is generally underestimated for occupational health and safety management. In Italy, INAIL experience showed that providing the biogas industry with a practical tool, such as the checklist approach, could be useful to carry out the analysis of the main hazards (biohazard, fires, and potentially explosive atmospheres) and a valuable support for the plant operators in order to evaluate periodically the actual effectiveness of the overall safety measures [9]. Furthermore, a tailored database, which collects information about accidents of the biofuel industry, should be implemented. The Institut National de l'Environnement Industriel et des Risques (INERIS) database was aimed at collecting all accidents (explosions, fires, spills, derailments, road accidents, etc.), which occurred during the life cycle of biofuel production plants [10]*.* The accidents study is a very useful tool, which can surely

**3. Bioethanol: classification according to CLP Regulation (CLP)** 

nol, which is produced by the processes of the traditional chemistry [11].

**Parameter Value** Lower flammability limit (% v/v) 3.5 Upper flammability limit (% v/v) 15 Boiling temperature (°C) 78 Vapor pressure at 20°C (Pa) 6000 Flash point (°C) 13

Bioethanol is characterized by the same chemical properties (**Table 1**) of etha-

With reference to its boiling temperature, bioethanol is classified as a highboiling liquid. In accordance with Regulation No. 1272/2008 EC, such biofuel belongs to Category 2 (**Table 2**), and therefore it is classified as highly flammable

*DOI: http://dx.doi.org/10.5772/intechopen.87990*

improve the plant safety level.

**No. 1272/2008 EC**

liquid and vapor [12] (**Figure 1**).

#### *Biorefinery Safety: A Case Study Focused on Bioethanol Production DOI: http://dx.doi.org/10.5772/intechopen.87990*

*Biorefinery Concepts, Energy and Products*

biomass. Bioethanol is a renewable fuel, which can be made from grains, such as corn or wheat, or from cellulose sources, such as prairie grass or agricultural, forestry, or municipal wastes. It can be used in vehicles or small engines, which are fed by conventional fuels, and it is utilized as a fuel extender and octane improver with blends that usually are 10% ethanol and 90% unleaded gasoline. Indeed, several researches showed that ethanol/gasoline blends had the potentiality to reduce petroleum fuel use and greenhouse gas emissions. In the last years, the bioethanol use has undergone a fast growth, because it can make easier the replacement of fossil fuels with renewable fuels. In particular, in Europe, the framework for climate and energy, established by the European Council in 2014, caused this growth. Indeed, a specific target for 2030, included in this framework, has stated that at least a 32% share of renewable energy consumption has to be achieved. This context generates attention to the potential hazards, which are associated with flammable biofuels, such as the bioethanol, and has given birth to this chapter, which is focused on the study of bioethanol evaporation rate from liquid pools. In fact, one of the main hazards, referred to such biofuel, is the formation of potentially explosive atmospheres due to its evaporation from pools in case of accidental releases. Indeed, in a bioethanol production plant (biorefinery), there are several components (flanges, valves, pumps, etc.), which can become potential emission sources in case of failure. Bioethanol can be considered as a high-boiling liquid, because its boiling temperature (Tboiling = 78°C) is higher than ambient temperature. Therefore, in case of release and spreading on a certain medium, evaporation occurs because of vapor diffusion. This is the result of the difference in terms of vapor pressure between the liquid surface and surrounding area. The chapter carries out a comparison between two predictive models (the model referred to low mass transport and the generally applicable formula) aimed at estimating the bioethanol evaporation rate, which is a fundamental parameter for determining the dilution degree and classifying the workplaces, where potentially explosive atmospheres could occur. It is important to highlight that Atex Directive 99/92/EC obliges the employers to carry out such classification [3]. The dilution degree is a parameter, which measures the ventilation (natural or artificial) ability to dilute a release to a safe level (flammable substance concentration is lower than its lower flammability limit) and is reported in International Standard IEC EN 60079-10-1. In particular, the study investigates the influence of bioethanol release temperature and therefore of its vapor pressure on evaporation rate. Finally, the difference between the bioethanol evaporation rates is calculated to determine the reliability range of the model, referred to low mass transport. Therefore, the work is aimed at giving some guidelines about the vapor pressure (such parameter is strictly dependent on temperature) range, where the simplified model is able to provide

**2. Occupational health and safety (OHS) in the biofuel industry**

In accordance with the Renewable Fuels Association [4], at 2018 year end, the ethanol industry approximately comprised 210 plants in 27 states with nameplate capacity equal to 16.5 billion gallons. According to the Biotechnology Innovation Organization (BIO), the direct job creation from advanced biofuel production could reach 190,000 units by 2022 [5]*.* This context generates attention to occupational safety, which has to take into account all actions aimed at protecting the safety, health, and welfare of people engaged in such industrial sector. This can include safety assessments, accident investigations, training programs, and other

**4**

reliable predictions.

activities, which can reduce or eliminate workplace injuries and illnesses. In the face of growing development of the biofuel industry and the consequent increase in employed workforce, there are still limited data, which are referred to the occupational health and safety of these production processes. Petrochemical processing industry is very advanced in terms of risk assessment and management, while the biofuel production industry has not yet gained enough experience in these topics [6]. Indeed, occupational health and risks during all phases of the processes are not always considered. The former available data suggest that renewable energy will also offer benefits to workers in terms of reduced occupational injury, illness, and death [7], but considering that the biofuels industry is a developing and growing sector and many of the involved companies are small entrepreneurial activities, studies of worker safety and health should be implemented. In Europe, there are a high number of small-scale industrial units, such as the biogas production plants, which are generally characterized by lower quantities than the thresholds for the application of legislation (the Seveso Directive) aimed at the control of major accidents [8]*.* Such industrial activities have neither the ability for thinking about the risks and the hazards nor the resources or the expertise for managing those. This aspect is generally underestimated for occupational health and safety management. In Italy, INAIL experience showed that providing the biogas industry with a practical tool, such as the checklist approach, could be useful to carry out the analysis of the main hazards (biohazard, fires, and potentially explosive atmospheres) and a valuable support for the plant operators in order to evaluate periodically the actual effectiveness of the overall safety measures [9]. Furthermore, a tailored database, which collects information about accidents of the biofuel industry, should be implemented. The Institut National de l'Environnement Industriel et des Risques (INERIS) database was aimed at collecting all accidents (explosions, fires, spills, derailments, road accidents, etc.), which occurred during the life cycle of biofuel production plants [10]*.* The accidents study is a very useful tool, which can surely improve the plant safety level.

#### **3. Bioethanol: classification according to CLP Regulation (CLP) No. 1272/2008 EC**

Bioethanol is characterized by the same chemical properties (**Table 1**) of ethanol, which is produced by the processes of the traditional chemistry [11].

With reference to its boiling temperature, bioethanol is classified as a highboiling liquid. In accordance with Regulation No. 1272/2008 EC, such biofuel belongs to Category 2 (**Table 2**), and therefore it is classified as highly flammable liquid and vapor [12] (**Figure 1**).


**Table 1.** *Chemical bioethanol properties.*


#### **Table 2.**

*Criteria for flammable liquids.*


#### **Figure 1.**

*Bioethanol classification (Regulation No. 1272/2008 EC).*

#### **4. Investigation of evaporation of high-boiling liquids**

In order to calculate the evaporation rate of high-boiling liquids, no exact calculation procedure can be found in literature. In most cases, equations, based on experimental results coming from tests, are used. The main relations are referred to:

1.Low mass transport (simplified equation)

2.High and low mass transport (general equation)

In the chapter, the bioethanol evaporation rate is calculated by the two mentioned models in order to quantify the result difference and determine the validity range of simplified model as function of variation of biofuel vapor pressure (pv). The following diagram [13] has been used to determine the vapor pressure variation as function of bioethanol release temperature (**Figure 2**). An accurate calculation of evaporation rate is extremely important, because such parameter has strong outcomes on classification of zones, where explosive mixtures could occur, and on

**7**

*Biorefinery Safety: A Case Study Focused on Bioethanol Production*

eters, which have to be determined to classify the areas [14]:

International Standard IEC EN 60079-10-1 (**Figure 3**), where:

• Wg is the mass flow of flammable compound (kg/s).

• K represents a safety factor (dimensionless parameter).

• LFL is the lower flammability limit of flammable substance.

• ρg indicates the gas or vapor density (kg/m3

plant safety. Indeed, one of the main hazards, referred to bioethanol, is the formation of potentially explosive atmospheres due to its evaporation from pools in case of accidental releases. In fact, in a bioethanol production plant, there are several components (flanges, valves, pumps, etc.), which can become potential emission

**5. Hazards associated with bioethanol production: possible formation of** 

One of the main hazards, associated with bioethanol production, is the formation of potentially explosive atmospheres due to its evaporation from pools in case of accidental releases. Such biofuel can be considered a high-boiling liquid, because its boiling temperature (Tboiling = 78°C) is higher than ambient temperature. Therefore, in case of release and spreading on a certain medium, evaporation mainly occurs by vapor diffusion. This is the result of the difference in terms of vapor pressure between the liquid surface and surrounding area. In order to classify the hazardous zones due to the possible formation of explosive mixtures, International Standard IEC EN 60079-10-1 can be used. It indicates three param-

In particular, in case of flammable liquid releases, the last parameter depends

In case of flammable liquid releases, the calculation of Wg becomes particularly complex, because several phenomena (solar heat flux, heat transfer from subsoil, convective heat flux from air, and mass transfer due to diffusion) have to be examined. For liquids (such as the bioethanol), which have boiling temperature above ambient temperature, mass transfer by diffusion is the predominant factor. Indeed, the wind removes vapor from the pool surface and because of resultant concentration gradient, mass transfer is induced. Liquid evaporates for restoring the partial pressure, which is in thermodynamic equilibrium with the liquid in the pool at its temperature. Therefore, the high-boiling liquid evaporation strongly depends on the rate, at which vapor can be removed by the airflow above the pool. With reference to this topic, the chapter carries out a comparison between two predictive models aimed at estimating the bioethanol evaporation rate from pool. The evaporation rate

).

on evaporation rate and can be determined by the diagram [14] reported in

*DOI: http://dx.doi.org/10.5772/intechopen.87990*

**potentially explosive atmospheres**

sources in case of failure.

1.Release grade

3.Dilution degree

2.Ventilation availability

• uw is the ventilation velocity (m/s).

**Figure 2.** *Bioethanol vapor pressure.*

*Biorefinery Safety: A Case Study Focused on Bioethanol Production DOI: http://dx.doi.org/10.5772/intechopen.87990*

plant safety. Indeed, one of the main hazards, referred to bioethanol, is the formation of potentially explosive atmospheres due to its evaporation from pools in case of accidental releases. In fact, in a bioethanol production plant, there are several components (flanges, valves, pumps, etc.), which can become potential emission sources in case of failure.

#### **5. Hazards associated with bioethanol production: possible formation of potentially explosive atmospheres**

One of the main hazards, associated with bioethanol production, is the formation of potentially explosive atmospheres due to its evaporation from pools in case of accidental releases. Such biofuel can be considered a high-boiling liquid, because its boiling temperature (Tboiling = 78°C) is higher than ambient temperature. Therefore, in case of release and spreading on a certain medium, evaporation mainly occurs by vapor diffusion. This is the result of the difference in terms of vapor pressure between the liquid surface and surrounding area. In order to classify the hazardous zones due to the possible formation of explosive mixtures, International Standard IEC EN 60079-10-1 can be used. It indicates three parameters, which have to be determined to classify the areas [14]:

1.Release grade

*Biorefinery Concepts, Energy and Products*

**4. Investigation of evaporation of high-boiling liquids**

**Category Criteria**

3 23°C ≤ flash point ≤60°C

1 Flash point <23°C and initial boiling point ≤35°C 2 Flash point <23°C and initial boiling point >35°C

1.Low mass transport (simplified equation)

*Bioethanol classification (Regulation No. 1272/2008 EC).*

2.High and low mass transport (general equation)

In order to calculate the evaporation rate of high-boiling liquids, no exact calculation procedure can be found in literature. In most cases, equations, based on experimental results coming from tests, are used. The main relations are referred to:

In the chapter, the bioethanol evaporation rate is calculated by the two mentioned models in order to quantify the result difference and determine the validity range of simplified model as function of variation of biofuel vapor pressure (pv). The following diagram [13] has been used to determine the vapor pressure variation as function of bioethanol release temperature (**Figure 2**). An accurate calculation of evaporation rate is extremely important, because such parameter has strong outcomes on classification of zones, where explosive mixtures could occur, and on

**6**

**Figure 2.**

*Bioethanol vapor pressure.*

**Figure 1.**

**Table 2.**

*Criteria for flammable liquids.*


In particular, in case of flammable liquid releases, the last parameter depends on evaporation rate and can be determined by the diagram [14] reported in International Standard IEC EN 60079-10-1 (**Figure 3**), where:


In case of flammable liquid releases, the calculation of Wg becomes particularly complex, because several phenomena (solar heat flux, heat transfer from subsoil, convective heat flux from air, and mass transfer due to diffusion) have to be examined. For liquids (such as the bioethanol), which have boiling temperature above ambient temperature, mass transfer by diffusion is the predominant factor. Indeed, the wind removes vapor from the pool surface and because of resultant concentration gradient, mass transfer is induced. Liquid evaporates for restoring the partial pressure, which is in thermodynamic equilibrium with the liquid in the pool at its temperature. Therefore, the high-boiling liquid evaporation strongly depends on the rate, at which vapor can be removed by the airflow above the pool. With reference to this topic, the chapter carries out a comparison between two predictive models aimed at estimating the bioethanol evaporation rate from pool. The evaporation rate

**Figure 3.** *Dilution degree assessment.*

calculation is an extremely important phase for determining successively the dilution degree. Indeed, an accurate estimate of such parameter is fundamental for classifying the zone (hazardous or non-hazardous) generated by the potential release source.

#### **5.1 Bioethanol evaporation: predictive models**

Bioethanol is a high-boiling liquid, and the evaporation of high-boiling liquid pools mainly depends on the rate, at which the vapor can be removed by the wind, which blows above the pool. Thus, for high-boiling liquids, the mass transfer by diffusion is the predominant factor, especially after the initial stages of the spill [15]. The mass transfer is induced by the resultant concentration gradient [16]. The driving force is the difference between the liquid vapor pressure and the partial pressure of liquid in the atmosphere. In literature, a simplified model, referred to low mass transport, uses the following expression for calculating the evaporation rate [17]:

nsport, uses the following expression for calculating the evaporation rate [17]:

$$m = \frac{k \cdot MW\_b \cdot (p\_v - p\_{amb})}{RT} \tag{1}$$

**9**

*Biorefinery Safety: A Case Study Focused on Bioethanol Production*

• T represents the biofuel release temperature (K).

ing expression, which can be applied to all cases:

*k*1(*m*/*s*) = \_\_\_\_\_\_\_\_\_\_

• patm is the atmospheric pressure (101,325 Pa).

which is applicable to high and low mass transport [17]:

*k* ⋅ *MWb* ⋅ *patm*

*m* = \_\_\_\_\_\_\_\_\_\_\_

*k*(*m*/*s*) = 0.005 ⋅ *v*<sup>10</sup>

• rp is the radius of the bioethanol pool (m).

• v10 represents the wind speed at 10 meters of height (m/s).

• Sc is the Schmidt number (dimensionless parameter).

reported in the Yellow Book in case of gases and vapors [18].

(radius) and wind velocity [18]:

**6. Results and discussion**

where:

where:

The properties of air, flowing over the liquid pool, are included in the material

transfer coefficient (k). Equation (1) is often used for the calculation of highboiling liquid evaporation rate. However, it has been found that this model is not applicable in case of high mass transport. This is due to the fact that the material transfer coefficient is not independent of the mass flow. Therefore, the chapter goal is aimed at investigating the applicability range of simplified model. Based on the film theory, a correction (k1) of mass transfer coefficient is given [17] in the follow-

*k* ⋅ (*patm* − *pv*)

The abovementioned film theory is based on the following principles: it is considered that wind velocity, temperature, and partial vapor pressure of the evaporating liquid are only dependent on the direction, which is perpendicular to the liquid surface, while in the other directions, the values of all the abovementioned parameters are assumed constant. The introduction of the corrected material transfer coefficient (k1) gives the following expression (generally applicable equation),

*RT* <sup>⋅</sup> ln(<sup>1</sup> <sup>+</sup> \_\_\_\_\_\_\_

0.78 ⋅ (2 *rp*)

In literature, different relations for the coefficient k have been derived. In this study, the model given by MacKay and Matsugu has been used. Such model has been validated by experimental tests and takes into account both the pool geometry

In the analysis, it has been assumed that the Schmidt number is equal to 0.8 as

In order to estimate the wind velocity, a bioethanol production plant, sited in the Northern Italy (Piedmont), has been considered. In particular, the Italy wind Atlas reports an annual average wind velocity, which is lower than 3 m/s for the place

*pv* − *pamb*

*pv* <sup>−</sup> *pamb* <sup>⋅</sup> ln(<sup>1</sup> <sup>+</sup> \_\_\_\_\_\_\_

*pv* − *pamb*

*patm* <sup>−</sup> *pv*) (2)

*patm* <sup>−</sup> *pv*) (3)

−0.11 ⋅ *Sc*−0.67 (4)

*DOI: http://dx.doi.org/10.5772/intechopen.87990*

where:


*Biorefinery Safety: A Case Study Focused on Bioethanol Production DOI: http://dx.doi.org/10.5772/intechopen.87990*

• T represents the biofuel release temperature (K).

The properties of air, flowing over the liquid pool, are included in the material transfer coefficient (k). Equation (1) is often used for the calculation of highboiling liquid evaporation rate. However, it has been found that this model is not applicable in case of high mass transport. This is due to the fact that the material transfer coefficient is not independent of the mass flow. Therefore, the chapter goal is aimed at investigating the applicability range of simplified model. Based on the film theory, a correction (k1) of mass transfer coefficient is given [17] in the following expression, which can be applied to all cases:

$$k\_1 \text{(} m/s\text{)}\quad = \frac{k \cdot (p\_{atm} - p\_v)}{p\_v - p\_{amb}} \cdot \ln\left(1 + \frac{p\_v - p\_{amb}}{p\_{atm} - p\_v}\right) \tag{2}$$

where:

*Biorefinery Concepts, Energy and Products*

calculation is an extremely important phase for determining successively the dilution degree. Indeed, an accurate estimate of such parameter is fundamental for classifying the zone (hazardous or non-hazardous) generated by the potential release source.

Bioethanol is a high-boiling liquid, and the evaporation of high-boiling liquid pools mainly depends on the rate, at which the vapor can be removed by the wind, which blows above the pool. Thus, for high-boiling liquids, the mass transfer by diffusion is the predominant factor, especially after the initial stages of the spill [15]. The mass transfer is induced by the resultant concentration gradient [16]. The driving force is the difference between the liquid vapor pressure and the partial pressure of liquid in the atmosphere. In literature, a simplified model, referred to low mass transport, uses the following expression for calculating the evaporation rate [17]:

*<sup>m</sup>* <sup>=</sup> *<sup>k</sup>* <sup>⋅</sup> *MWb* <sup>⋅</sup> (*pv* <sup>−</sup> *pamb*) \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ *RT* (1)

).

**5.1 Bioethanol evaporation: predictive models**

• m is the bioethanol evaporation rate (kg/s m2

• k indicates the mass transfer coefficient (m/s).

• R indicates the gas constant (8314 J/kmol K).

• MWb is the molecular weight of bioethanol (46.07 kg/kmol).

• pamb is the partial pressure of biofuel in the atmosphere (Pa).

• pv represents the bioethanol vapor pressure at its temperature (Pa).

**8**

where:

**Figure 3.**

*Dilution degree assessment.*

• patm is the atmospheric pressure (101,325 Pa).

The abovementioned film theory is based on the following principles: it is considered that wind velocity, temperature, and partial vapor pressure of the evaporating liquid are only dependent on the direction, which is perpendicular to the liquid surface, while in the other directions, the values of all the abovementioned parameters are assumed constant. The introduction of the corrected material transfer coefficient (k1) gives the following expression (generally applicable equation), which is applicable to high and low mass transport [17]:

$$m = \frac{k \cdot MW\_b \cdot p\_{atm}}{RT} \cdot \ln\left(1 + \frac{p\_v - p\_{amb}}{p\_{atm} - p\_v}\right) \tag{3}$$

In literature, different relations for the coefficient k have been derived. In this study, the model given by MacKay and Matsugu has been used. Such model has been validated by experimental tests and takes into account both the pool geometry (radius) and wind velocity [18]:

$$k \text{(m/s)} = \text{0.005} \cdot \nu\_{10} \,^{0.78} \cdot \left( \mathcal{D}r\_p \right)^{-0.11} \cdot \text{Sc}^{-0.67} \tag{4}$$

where:


In the analysis, it has been assumed that the Schmidt number is equal to 0.8 as reported in the Yellow Book in case of gases and vapors [18].

#### **6. Results and discussion**

In order to estimate the wind velocity, a bioethanol production plant, sited in the Northern Italy (Piedmont), has been considered. In particular, the Italy wind Atlas reports an annual average wind velocity, which is lower than 3 m/s for the place

[19], where the plant has been built. Therefore, the wind velocity has been assumed equal to 3 m/s. In order to calculate m, the pool radius has been assumed equal to 1 m. The following temperatures of bioethanol release have been examined to calculate the evaporation rate: 20, 30, 40, 50, and 60°C. Such temperatures are usually found in bioethanol production plants. In **Table 3** the vapor pressures, referred to such temperatures, are reported. As the examined temperatures are lower than biofuel boiling temperature, the liquid pool is high-boiling, and therefore the partial pressure of the biofuel in the atmosphere (pamb) is negligible. The study results are shown in **Table 4**, where m1 indicates the evaporation rate calculated by the equation, referred to low mass transport, whereas m3 indicates the evaporation rate, determined by the generally applicable model.

The variation (Δ) between the generally applicable equation and the simplified expression is calculated by the following formula:

$$
\Delta(\text{\%}) = \text{100} \cdot \left(\frac{m\_3 - m\_1}{m\_1}\right) \tag{5}
$$

The values of such difference are reported in **Table 5**, whereas its trend as function of vapor pressure is shown in **Figure 4**.

The increase of bioethanol release temperature and therefore of vapor pressure causes a difference growth, which is moderate and acceptable (the difference does not exceed 10%) till the pressure is lower than 18,000 Pa, whereas Δ is equal to 32.2% at 45,000 Pa. Therefore, Eq. (1) (simplified model) can be used in the case of bioethanol vapor pressure, which is lower than 18,000 Pa, because it shows an adequate reliability. Such pressure represents a threshold, which determines the range of reliability of the model, referred to low mass transport. Over 18,000 Pa the expression (3) (generally applicable model) has to be used to achieve a more accurate estimate of the evaporation rate, which is a fundamental parameter in order to determine the dilution degree and classify the workplaces, where there is the possibility of formation of potentially explosive atmospheres due to bioethanol releases. It follows that the evaporation rate estimate has a strong influence on the safety of an industrial plant, which uses or produces bioethanol, because it allows to assess if the biofuel release source is able to generate an hazardous or a non-hazardous zone. Indeed, a less accurate calculation of bioethanol evaporation rate could generate a mistake during the area classification procedure, and therefore the hazard of explosive atmosphere formation could be underestimated. Such scenario could decrease the plant safety level, because the choice of equipment and protective systems, which must be used in hazardous zones, depends on area classification as reported in Atex Directive 99/92/EC. This choice is aimed at avoiding that equipment and protective systems become active ignition sources. Therefore, there is a strong connection between the evaporation rate calculation


**11**

tion beginning.

*Biorefinery Safety: A Case Study Focused on Bioethanol Production*

 0.00144 0.00148 0.0023 0.0024 0.004 0.0044 0.0063 0.0074 0.0095 0.0125

**Temperature (°C) Δ (%)** 20 3.1 30 5.3 40 10.1 50 17.8 60 32.2

 **s) m3 (kg/m2**

 **s)**

**Temperature (°C) m1 (kg/m2**

and safety of plants, which use or produce bioethanol. Finally, it has to be mentioned that the two models are based on the assumption that the partial vapor pressure can be considered constant [20]. This is correct as long as the tempera-

*Difference between the generally applicable equation and the expression for low mass transport.*

Such condition occurs, as long as there is equilibrium among the convective heat flow produced by the air flowing over the pool, the solar heat flow, the heat flow from the subsoil, and the heat flow required for the evaporation. In reality, the evaporating pool temperature gradually decreases. It follows that the evaporation rate, calculated by Eqs. (1) and (3), represents a maximum quantity, referred to isothermal conditions, and therefore it can be considered valid only at the evapora-

ture of the evaporating pool does not change.

*DOI: http://dx.doi.org/10.5772/intechopen.87990*

*Predictive models: Bioethanol evaporation rates.*

**Table 4.**

**Table 5.**

**Figure 4.**

*Calculated variation (Δ).*

**Table 3.** *Bioethanol vapor pressures.*

#### *Biorefinery Safety: A Case Study Focused on Bioethanol Production DOI: http://dx.doi.org/10.5772/intechopen.87990*


**Table 4.**

*Biorefinery Concepts, Energy and Products*

rate, determined by the generally applicable model.

expression is calculated by the following formula:

Δ(%) = 100 ⋅ (

tion of vapor pressure is shown in **Figure 4**.

[19], where the plant has been built. Therefore, the wind velocity has been assumed equal to 3 m/s. In order to calculate m, the pool radius has been assumed equal to 1 m. The following temperatures of bioethanol release have been examined to calculate the evaporation rate: 20, 30, 40, 50, and 60°C. Such temperatures are usually found in bioethanol production plants. In **Table 3** the vapor pressures, referred to such temperatures, are reported. As the examined temperatures are lower than biofuel boiling temperature, the liquid pool is high-boiling, and therefore the partial pressure of the biofuel in the atmosphere (pamb) is negligible. The study results are shown in **Table 4**, where m1 indicates the evaporation rate calculated by the equation, referred to low mass transport, whereas m3 indicates the evaporation

The variation (Δ) between the generally applicable equation and the simplified

The values of such difference are reported in **Table 5**, whereas its trend as func-

The increase of bioethanol release temperature and therefore of vapor pressure causes a difference growth, which is moderate and acceptable (the difference does not exceed 10%) till the pressure is lower than 18,000 Pa, whereas Δ is equal to 32.2% at 45,000 Pa. Therefore, Eq. (1) (simplified model) can be used in the case of bioethanol vapor pressure, which is lower than 18,000 Pa, because it shows an adequate reliability. Such pressure represents a threshold, which determines the range of reliability of the model, referred to low mass transport. Over 18,000 Pa the expression (3) (generally applicable model) has to be used to achieve a more accurate estimate of the evaporation rate, which is a fundamental parameter in order to determine the dilution degree and classify the workplaces, where there is the possibility of formation of potentially explosive atmospheres due to bioethanol releases. It follows that the evaporation rate estimate has a strong influence on the safety of an industrial plant, which uses or produces bioethanol, because it allows to assess if the biofuel release source is able to generate an hazardous or a non-hazardous zone. Indeed, a less accurate calculation of bioethanol evaporation rate could generate a mistake during the area classification procedure, and therefore the hazard of explosive atmosphere formation could be underestimated. Such scenario could decrease the plant safety level, because the choice of equipment and protective systems, which must be used in hazardous zones, depends on area classification as reported in Atex Directive 99/92/EC. This choice is aimed at avoiding that equipment and protective systems become active ignition sources. Therefore, there is a strong connection between the evaporation rate calculation

**Temperature (°C) Vapor pressure (Pa)** 20 6000 30 10,000 40 18,000 50 29,000 60 45,000

\_\_\_\_\_\_ *m*<sup>3</sup> − *m*<sup>1</sup>

*<sup>m</sup>*<sup>1</sup> ) (5)

**10**

**Table 3.**

*Bioethanol vapor pressures.*

*Predictive models: Bioethanol evaporation rates.*


and safety of plants, which use or produce bioethanol. Finally, it has to be mentioned that the two models are based on the assumption that the partial vapor pressure can be considered constant [20]. This is correct as long as the temperature of the evaporating pool does not change.

Such condition occurs, as long as there is equilibrium among the convective heat flow produced by the air flowing over the pool, the solar heat flow, the heat flow from the subsoil, and the heat flow required for the evaporation. In reality, the evaporating pool temperature gradually decreases. It follows that the evaporation rate, calculated by Eqs. (1) and (3), represents a maximum quantity, referred to isothermal conditions, and therefore it can be considered valid only at the evaporation beginning.

### **7. Conclusions**

One of the main hazards, referred to bioethanol, is the formation of potentially explosive atmospheres due to its evaporation from pools in case of accidental releases. In order to classify the workplaces, characterized by possible formation of potentially explosive mixtures, as the bioethanol is a high-boiling flammable liquid, a particular attention has to be addressed to the thermodynamic release parameters, such as the temperature, because it influences the vapor pressure. In particular, the study has shown that:


The calculated evaporation rates are referred to isothermal conditions and represent maximum values, because the majority of the evaporating liquids cool down after the evaporation beginning; therefore, the evaporation rate decreases. In order to improve the calculation accuracy, computational fluid dynamics that is able to solve simultaneously the equations, which govern the liquids spreading and evaporation, has to be used. However, the illustrated predictive models are abundantly used in technical international standards, concerned with the classification of areas where flammable gases or vapors can generate potentially explosive atmospheres.

#### **Author details**

Roberto Lauri\* and Biancamaria Pietrangeli Department of Technological Innovations and Safety of Plants, Products and Human Settlements, INAIL Research, Rome, Italy

\*Address all correspondence to: r.lauri@inail.it

© 2019 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.

**13**

*Biorefinery Safety: A Case Study Focused on Bioethanol Production*

Human Health. Workshop Summary. Washington DC: The National Academies Press; 2014. pp. 37-46

[7] Sumner SA, Layde PM. Expansion of renewable energy industries and implications for occupational health. Journal of the American Medical Association. 2009;**302**(7):787-789. DOI:

[8] European Union. Directive 2012/18/ EU of the European Parliament and of the Council of 4 July 2012 on the control of major-accident hazards involving dangerous substances, amending and subsequently repealing Council Directive 96/82/EC. Official Journal of the European Union. L197/1, 24.07.2012. pp. 77-113

[9] Pietrangeli B, Lauri R. Biogas production plants: A methodological approach for occupational health and safety improvement. In: Nageswara-Rao M, Soneji JR, editors. Advances in Biofuels and Bioenergy. London: IntechOpen; 2018. pp. 183-200. DOI:

10.5772/intechopen.72819

Instituut; 2010. pp. 35-42

2015;**2**:161-168

[10] Riviere C, Marlair G, Vignes A. Learning of the root factors of incidents potentially impacting the biofuel supply chains from some 100 significant cases. In: Proceedings of the International Symposium on Loss Prevention and Safety Promotion in the Process Industry Proceedings; 6-9 June 2010; Bruges. Antwerpen: Technologisch

[11] Accardi DS, Lauri R, Pietrangeli B. Comparative study in the safety aspects of the production of ethanol from renewable and non-renewable sources. Procedia Environmental Science, Engineering and Management.

[12] European Union. Regulation (EC) n° 1272/2008 of the European Parliament and of the Council of 16

10.1001/jama.2009.1214

*DOI: http://dx.doi.org/10.5772/intechopen.87990*

[1] European Union. Directive 2009/28/ EC of the European Parliament and the Council of 23 April 2009 on the promotion of the use of energy from renewable sources and amending and subsequently repealing Directives 2001/77/EC and 2003/30/EC. Official Journal of the European Union. L 140/16, 5.6.2009. pp. 16-62

[2] European Union. Directive 2018/2001/EC of the European Parliament and the Council of 11 December 2018 on the promotion of the use of energy from renewable sources. Official Journal of the European Union.

L 328/82, 21.12.2018. pp. 82-209

[4] Renewable Fuels Association (RFA). 2018 U.S. ethanol exports and imports. Statistical Summary. 2019. Available from: https://ethanolrfa.org/ wp-content/uploads/2019/03/2018-US-Ethanol-Trade-Statistics-Summary.pdf

[5] Bio Economic Research Associates. U.S. Economic Impact of Advanced Biofuels Production: Perspectives to 2030. 2009. Available from: https:// www.bio.org/sites/default/files/files/ EconomicImpactAdvancedBiofuels.pdf

[6] Reynolds SJ. Occupational health and biofuel production. In: National Academy of Sciences, The Nexus of Biofuels, Climate Change and

[Accessed: 10 May 2019]

[Accessed: 10 May 2019]

28.1.2000. p. 59

[3] European Union. Directive 1999/92/ EC of the European Parliament and of the Council of 16 December 1999 on minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres (15th individual Directive within the meaning of Article 16(1) of Directive 89/391/EEC). Official Journal of the European of the European Communities. L 23/59,

**References**

*Biorefinery Safety: A Case Study Focused on Bioethanol Production DOI: http://dx.doi.org/10.5772/intechopen.87990*

#### **References**

*Biorefinery Concepts, Energy and Products*

One of the main hazards, referred to bioethanol, is the formation of potentially

• Analysis of thermodynamic parameters is very important, because it allows to choose the best predictive model for calculating the evaporation rate, which is

• In case of bioethanol releases, the simplified model, referred to low mass transport, cannot be always used, because its reliability is strongly dependent

• The simplified model is only applicable when the partial vapor pressure is

• For all other cases, Eq. (3), based on the film theory, has to be used to achieve a

The calculated evaporation rates are referred to isothermal conditions and represent maximum values, because the majority of the evaporating liquids cool down after the evaporation beginning; therefore, the evaporation rate decreases. In order to improve the calculation accuracy, computational fluid dynamics that is able to solve simultaneously the equations, which govern the liquids spreading and evaporation, has to be used. However, the illustrated predictive models are abundantly used in technical international standards, concerned with the classification of areas where flammable gases or vapors can generate potentially explosive atmospheres.

Department of Technological Innovations and Safety of Plants, Products and

© 2019 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,

explosive atmospheres due to its evaporation from pools in case of accidental releases. In order to classify the workplaces, characterized by possible formation of potentially explosive mixtures, as the bioethanol is a high-boiling flammable liquid, a particular attention has to be addressed to the thermodynamic release parameters, such as the temperature, because it influences the vapor pressure. In particular, the

successively used to determine the dilution degree.

more accurate estimate of the evaporation rate.

**7. Conclusions**

study has shown that:

on the vapor pressure.

lower than 18,000 Pa.

**12**

**Author details**

Roberto Lauri\* and Biancamaria Pietrangeli

Human Settlements, INAIL Research, Rome, Italy

\*Address all correspondence to: r.lauri@inail.it

provided the original work is properly cited.

[1] European Union. Directive 2009/28/ EC of the European Parliament and the Council of 23 April 2009 on the promotion of the use of energy from renewable sources and amending and subsequently repealing Directives 2001/77/EC and 2003/30/EC. Official Journal of the European Union. L 140/16, 5.6.2009. pp. 16-62

[2] European Union. Directive 2018/2001/EC of the European Parliament and the Council of 11 December 2018 on the promotion of the use of energy from renewable sources. Official Journal of the European Union. L 328/82, 21.12.2018. pp. 82-209

[3] European Union. Directive 1999/92/ EC of the European Parliament and of the Council of 16 December 1999 on minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres (15th individual Directive within the meaning of Article 16(1) of Directive 89/391/EEC). Official Journal of the European of the European Communities. L 23/59, 28.1.2000. p. 59

[4] Renewable Fuels Association (RFA). 2018 U.S. ethanol exports and imports. Statistical Summary. 2019. Available from: https://ethanolrfa.org/ wp-content/uploads/2019/03/2018-US-Ethanol-Trade-Statistics-Summary.pdf [Accessed: 10 May 2019]

[5] Bio Economic Research Associates. U.S. Economic Impact of Advanced Biofuels Production: Perspectives to 2030. 2009. Available from: https:// www.bio.org/sites/default/files/files/ EconomicImpactAdvancedBiofuels.pdf [Accessed: 10 May 2019]

[6] Reynolds SJ. Occupational health and biofuel production. In: National Academy of Sciences, The Nexus of Biofuels, Climate Change and

Human Health. Workshop Summary. Washington DC: The National Academies Press; 2014. pp. 37-46

[7] Sumner SA, Layde PM. Expansion of renewable energy industries and implications for occupational health. Journal of the American Medical Association. 2009;**302**(7):787-789. DOI: 10.1001/jama.2009.1214

[8] European Union. Directive 2012/18/ EU of the European Parliament and of the Council of 4 July 2012 on the control of major-accident hazards involving dangerous substances, amending and subsequently repealing Council Directive 96/82/EC. Official Journal of the European Union. L197/1, 24.07.2012. pp. 77-113

[9] Pietrangeli B, Lauri R. Biogas production plants: A methodological approach for occupational health and safety improvement. In: Nageswara-Rao M, Soneji JR, editors. Advances in Biofuels and Bioenergy. London: IntechOpen; 2018. pp. 183-200. DOI: 10.5772/intechopen.72819

[10] Riviere C, Marlair G, Vignes A. Learning of the root factors of incidents potentially impacting the biofuel supply chains from some 100 significant cases. In: Proceedings of the International Symposium on Loss Prevention and Safety Promotion in the Process Industry Proceedings; 6-9 June 2010; Bruges. Antwerpen: Technologisch Instituut; 2010. pp. 35-42

[11] Accardi DS, Lauri R, Pietrangeli B. Comparative study in the safety aspects of the production of ethanol from renewable and non-renewable sources. Procedia Environmental Science, Engineering and Management. 2015;**2**:161-168

[12] European Union. Regulation (EC) n° 1272/2008 of the European Parliament and of the Council of 16 December 2008 on classification, labelling and packaging of substances and mixtures, amending and repealing Directives 67/548/EEC and 1999/45/ EC, and amending Regulation (EC) n° 1907/2006. Official Journal of the European Union. L353/1, 31.12.2008. p. 60

[13] University of Turin. 2004. Available from: https://digit.biblio.polito. it/1292/2/tema02.pdf [Accessed: 30 April 2019]

[14] IEC. International Standard IEC EN 60079-10-1: Classification of areas – explosive gas atmosphere. 2016; 163 p

[15] Brighton PWM. Further verification of a theory for mass and heat transfer from evaporating pools. Journal of Hazardous Materials. 1990;**23**:215-234

[16] Cavanaugh TA, Siegell JH, Steinberg KW. Simulation of vapor emissions from liquid spills. Journal of Hazardous Materials. 1994;**38**:41-63

[17] TNO. Methods for the Calculation of Physical Effects. 2nd ed. The Hague: Directorate General of Labour of the Ministry of Social Affairs and Employment; 1988. pp. 36-37. ISSN: 0921-9633/2.10.014/9203

[18] Van den Bosch CJH, Weterings RAPM, editors. Methods for the Calculation of Physical Effects (Yellow Book). 3rd ed. Vol. 3. The Hague: Directorate General for Social Affairs and Employment; 2005.40 p

[19] Interactive wind Atlas. 2019. Available from: http://atlanteeolico. rse-web.it/index.phtml [Accessed: 16 April 2019]

[20] Briscoe F, Shaw P. Spread and evaporation of liquid. Progress in Energy and Combustion Science. 1980;**6**:127-140

**15**

Section 2

Energy and Chemicals

Section 2
