**2. Modeling of municipal solid waste and coal co-combustion to generate syngas**

This section develops a theoretical model applied to the specific case of municipal waste. The basic information for this is the composition of the MSW and of the coal to be used, plus their heat powers. **Tables 1** and **2** show the data used. These tables have been prepared by authors based on several studies made during their work with coal boilers and power plants at Colombia. Two cases are considered for the waste. In the first one, waste as currently generated, the average quality of the MSW is considered in the city of Medellin, which is quite rich in organic materials and, so, very high in water content. In the second case, previously separated waste is


#### **Table 1.**

*Coal properties considered [35].*


#### **Table 2.**

*MSW properties considered [35].*

*Sustainable Alternative Syngas Fuel*

considered, removing 75% of organic material, 50% of paper, 20% of plastics, 55% of glass, 60% of cardboard, and 50% of metals of the generated waste. This would amount to 45% of the initial as generated MSW.

Gasification is modeled considering three combinations for co-gasification, identified by the mass ratio of coal to MSW: 0, 0.25, and 0.50. Saturated steam was supplied at 4 bar relative pressure (ambient pressure 1 bar) with steam-to-MSW mass ratios between 0.0 and 1.0 and heated air (120°C) was supplied with air-to-MSW rates between 1.70 and 5.0. **Figure 1** schematizes the basic model used.

The following chemical reactions were considered for the equilibrium calculations in the simulations. No methane generation was considered. Sulfur was controlled by the addition of calcium carbonate at a mass ratio of 0.0163 to coal.

$$\text{C} \star \text{CO}\_2 \leftrightarrow \text{2CO} \tag{1}$$

$$\text{CO} + \text{H}\_2\text{O} \leftrightarrow \text{CO}\_2 + \text{H}\_2\tag{2}$$

$$\text{H}\_2 \star \text{1/2O}\_2 \leftrightarrow \text{H}\_2\text{O} \tag{3}$$

$$\text{C} \star \text{H}\_2\text{O} \leftrightarrow \text{CO} \star \text{H}\_2\tag{4}$$

$$\text{C} \star \text{1/2O}\_2 \leftrightarrow \text{CO} \tag{5}$$

$$\text{CO} \star \text{1/2O}\_2 \leftrightarrow \text{CO}\_2 \tag{6}$$

$$\mathbf{C} \star \mathbf{O}\_2 \leftrightarrow \mathbf{CO}\_2 \tag{7}$$

**9**

*Waste to Energy and Syngas*

chemical equilibrium.

are found.

found.

than 5%.

established.

*DOI: http://dx.doi.org/10.5772/intechopen.85848*

Iterations were performed as follows:

• Final syngas temperature is assumed.

An iterative model calculation was developed using the solver routine of MS excel in which the concentrations of syngas were iterated with temperature until the expected convergence was found with species mass balance, energy balance, and

• Volumetric fractions of CO2, CO, H2, and H2O in syngas are assumed.

• Fraction of C converted as per reactions (1), (4), and (5) are assumed.

• Fraction of CO converted as per reaction (2) is assumed.

• Fraction of O2 converted as per reaction (3) and forming CO are assumed.

• With the partial fractions of syngas, equilibria constants for reactions (1) to (7)

• With syngas temperatures, equilibria constants for reactions (1) to (7) are also

• A convergence limit was established for the comparison of these two equilibria constants. This was set as less than 15% maximum error for each reaction.

• Mass balance was checked for each species with a convergence limit of less

• Energy balance was performed comparing energy formation based on reactions (1) to(7), outgoing syngas enthalpy, incoming vapor and air enthalpy and heat losses (sensible heat, wall and ashes loses). A convergence limit of 5% was

Energy formations (kJ/kmol) used were as follows for syngas forming reactions.

C + 2H2 ↔ CH4(g),−74.520

H2 + 1/ 2O2 ↔ H2O(g),−241.818

C + 1/ 2O2 ↔ CO(g),−110.525

C + O2 ↔ CO2(g),−393.509

Enthalpy of syngas was calculated based on syngas composition and specific heat values for each component, depending on temperature, using the expressions of the form: Cp/R = A + B·T + C·T2 + D·T − 2; T (K) where A–D are constants for

**Figures 2**–**12** show the results of the iterations for all major resulting variables.

Syngas temperatures tend to increase with higher coal-to-MSW ratios. For each ratio, there is a characteristic curve which indicates higher temperatures for

each gas component and R is the universal gas constant.

Comments are included for them.

**Figure 1.** *Scheme of the basic model used.*

*Waste to Energy and Syngas DOI: http://dx.doi.org/10.5772/intechopen.85848*

*Sustainable Alternative Syngas Fuel*

amount to 45% of the initial as generated MSW.

considered, removing 75% of organic material, 50% of paper, 20% of plastics, 55% of glass, 60% of cardboard, and 50% of metals of the generated waste. This would

Gasification is modeled considering three combinations for co-gasification, identified by the mass ratio of coal to MSW: 0, 0.25, and 0.50. Saturated steam was supplied at 4 bar relative pressure (ambient pressure 1 bar) with steam-to-MSW mass ratios between 0.0 and 1.0 and heated air (120°C) was supplied with air-to-MSW rates between 1.70 and 5.0. **Figure 1** schematizes the basic model used.

The following chemical reactions were considered for the equilibrium calculations in the simulations. No methane generation was considered. Sulfur was controlled by the addition of calcium carbonate at a mass ratio of 0.0163 to coal.

C + CO2 ↔ 2CO (1)

CO + H2O ↔ CO2 + H2 (2)

H2 + 1/ 2O2 ↔ H2O (3)

C + H2O ↔ CO + H2 (4)

C + 1/ 2O2 ↔ CO (5)

CO + 1/ 2O2 ↔ CO2 (6)

C + O2 ↔ CO2 (7)

**8**

**Figure 1.**

*Scheme of the basic model used.*

An iterative model calculation was developed using the solver routine of MS excel in which the concentrations of syngas were iterated with temperature until the expected convergence was found with species mass balance, energy balance, and chemical equilibrium.

Iterations were performed as follows:


Energy formations (kJ/kmol) used were as follows for syngas forming reactions.

C + 2H2 ↔ CH4(g),−74.520 H2 + 1/ 2O2 ↔ H2O(g),−241.818 C + 1/ 2O2 ↔ CO(g),−110.525 C + O2 ↔ CO2(g),−393.509

Enthalpy of syngas was calculated based on syngas composition and specific heat values for each component, depending on temperature, using the expressions of the form: Cp/R = A + B·T + C·T2 + D·T − 2; T (K) where A–D are constants for each gas component and R is the universal gas constant.

**Figures 2**–**12** show the results of the iterations for all major resulting variables. Comments are included for them.

Syngas temperatures tend to increase with higher coal-to-MSW ratios. For each ratio, there is a characteristic curve which indicates higher temperatures for lower air-to-MSW ratios and lower temperatures for higher steam-to-MSW ratios. Temperatures tend to be higher for the case of the separated MSW. **Figure 1** indicates the real working ranges for the simulations. With no coal use, the only range of airto-MSW ratios that gave convergence in the simulations was in the neighborhood of

**Figure 2.** *Resulting syngas temperature.*

#### **Figure 3.**

*Resulting heat value in syngas as % of feed heat value.*

**11**

**Figure 6.**

*Syngas heat value and sensible heat, kg/kg MSW.*

**Figure 5.**

*Syngas heat value, kg/kg MSW.*

*Waste to Energy and Syngas*

*DOI: http://dx.doi.org/10.5772/intechopen.85848*

and tends to decrease with air to MSW ratios.

5.0. Syngas temperatures will be between 600 and 940°C.

1.70. At higher coal-to-MSW ratios, the air-to-MSW ratio can be higher, all the way to

Syngas heat values tend to increase for higher coal-to-MSW ratios, but this was not entirely consistent. Syngas heat value simulations showed percentages between 60 and 80% of feed heat value and this does not change with steam-to-MSW ratios

Syngas flow is linearly related to the studied variables. It increases with airto-MSW ratio and with steam-to-MSW ratios. The values for the simulated range oscillate between 2.5 and 5.0 kg of syngas per kg of feed. The syngas flow is, basically, the result of adding the incoming flows, discounting the ash emissions. The behavior and the ranges are quite similar for both situations of MSW studied.

As shown in **Figure 5**, syngas heat value is quite independent of steam-to-MSW ratio. It increases with air-to-MSW ratios and, of course, with coal-to-MSW ratios. As compared to the MSW's lower heat value, it tends to be lower, as expected, for the case of no coal co-gasification. Maximum values tend to be double as compared to MSW heat value, obviously because of the impact of coal co-gasification. The values in **Figure 5** are consistent with the ones shown in **Figure 3**. **Figure 6** shows the total energy content of the syngas, adding its heat value to the sensible heat associated to syngas temperature. Those two amount to a value close to the energy value coming from the total feed. It must be said that the incoming hot air and the

**Figure 4.** *Syngas flow, kg/kg feed.*

*Sustainable Alternative Syngas Fuel*

lower air-to-MSW ratios and lower temperatures for higher steam-to-MSW ratios. Temperatures tend to be higher for the case of the separated MSW. **Figure 1** indicates the real working ranges for the simulations. With no coal use, the only range of airto-MSW ratios that gave convergence in the simulations was in the neighborhood of

**10**

**Figure 4.**

*Syngas flow, kg/kg feed.*

**Figure 2.**

**Figure 3.**

*Resulting heat value in syngas as % of feed heat value.*

*Resulting syngas temperature.*

1.70. At higher coal-to-MSW ratios, the air-to-MSW ratio can be higher, all the way to 5.0. Syngas temperatures will be between 600 and 940°C.

Syngas heat values tend to increase for higher coal-to-MSW ratios, but this was not entirely consistent. Syngas heat value simulations showed percentages between 60 and 80% of feed heat value and this does not change with steam-to-MSW ratios and tends to decrease with air to MSW ratios.

Syngas flow is linearly related to the studied variables. It increases with airto-MSW ratio and with steam-to-MSW ratios. The values for the simulated range oscillate between 2.5 and 5.0 kg of syngas per kg of feed. The syngas flow is, basically, the result of adding the incoming flows, discounting the ash emissions. The behavior and the ranges are quite similar for both situations of MSW studied.

As shown in **Figure 5**, syngas heat value is quite independent of steam-to-MSW ratio. It increases with air-to-MSW ratios and, of course, with coal-to-MSW ratios. As compared to the MSW's lower heat value, it tends to be lower, as expected, for the case of no coal co-gasification. Maximum values tend to be double as compared to MSW heat value, obviously because of the impact of coal co-gasification. The values in **Figure 5** are consistent with the ones shown in **Figure 3**. **Figure 6** shows the total energy content of the syngas, adding its heat value to the sensible heat associated to syngas temperature. Those two amount to a value close to the energy value coming from the total feed. It must be said that the incoming hot air and the

#### **Figure 5.**

*Syngas heat value, kg/kg MSW.*

#### **Figure 6.**

*Syngas heat value and sensible heat, kg/kg MSW.*

steam contribute with some energy also, which adds to the outgoing syngas heat value and sensible heat.

The behavior of the total energy in the syngas (**Figure 6**) is quite similar to the behavior of the heat value of **Figure 5**. The heat value corresponds to the chemical (combustion potential) energy associated to H2 and CO in the syngas.

Some calculations were carried out in the model to determine the potential of syngas to generate electricity. First, the sensible heat potential was determined based on the hot temperature of the syngas. This can be used to generate mechanical work and electricity removing the sensible heat (lowering the temperature, as indicated in **Figure 1**) in a cycle similar to a Rankine cycle. To determine the potential for this, a Carnot cycle's efficiency was calculated using as hot temperature the syngas temperature and as cold temperature the ambient value (25°C). With this Carnot efficiency, an estimation was obtained of a real efficiency based on existing Rankine cycles in which it is possible to get about 35% of the Carnot efficiency. The second estimation was based on expecting an efficiency of 30% for the cycle that employs the combustion heat value of the syngas. This, considering that it could be taken to an internal combustion engine. Combining these two efficiencies, in proportion to the existing contributions (that of heat value and that of sensible heat in the energy content of the syngas), it was possible to estimate the total efficiency

#### **Figure 7.**

*Potential for electricity generation, kW/kg MSW.*

**13**

**Figure 9.**

*Syngas CO2 concentrations and specific emissions.*

*Waste to Energy and Syngas*

which appears in **Figure 7**.

as generated MSW case).

of MSW per day.

day per capita.

*DOI: http://dx.doi.org/10.5772/intechopen.85848*

syngas which will be shown in the next figures.

of transformation to electricity and the total potential for electricity generation,

This potential is not affected by steam-to-MSW ratios. It is highly dependent, of course, on coal-to-MSW ratio and it is higher for lower air-to-MSW ratios. The potentials are higher for the case of separated MSW (between 0.75 and 2.2 kW per kg of MSW as compared to a range between 0.5 and 2.0 kW per kg of MSW for the

With these potentials, it is possible to estimate the expected electrical generation for a given flow of MSW. **Figure 8** shows the results for a plant processing 200 tons

These capacities will be between 4800 and 16,000 kW for the as generated MSW and between 6500 and 17,000 kW for the separated MSW. They are not affected by steam-to-MSW ratio, increase clearly with coal-to-MSW ratio, and decrease with air-to-MSW ratio. The ranges indicated in the graphs correspond to the ones for which convergence was found in the iterations, as already mentioned. These plants could generate amounts of electricity quite useful for a given small city in a country like Colombia. Considering a generation of solid waste (as generated) of 0.50 kg/day per habitant, the plant would produce the amounts indicated in **Table 3** for the cases considered. The table compares these figures to the electric consumption of a country like Colombia, estimated at 3.90 kWh per

Finally, the simulations permitted to obtain the expected composition of the

#### **Figure 8.**

*Electricity generation, in kW, for the processing of 200 tons per day of MSW.*

#### *Waste to Energy and Syngas DOI: http://dx.doi.org/10.5772/intechopen.85848*

*Sustainable Alternative Syngas Fuel*

value and sensible heat.

steam contribute with some energy also, which adds to the outgoing syngas heat

(combustion potential) energy associated to H2 and CO in the syngas.

The behavior of the total energy in the syngas (**Figure 6**) is quite similar to the behavior of the heat value of **Figure 5**. The heat value corresponds to the chemical

Some calculations were carried out in the model to determine the potential of syngas to generate electricity. First, the sensible heat potential was determined based on the hot temperature of the syngas. This can be used to generate mechanical work and electricity removing the sensible heat (lowering the temperature, as indicated in **Figure 1**) in a cycle similar to a Rankine cycle. To determine the potential for this, a Carnot cycle's efficiency was calculated using as hot temperature the syngas temperature and as cold temperature the ambient value (25°C). With this Carnot efficiency, an estimation was obtained of a real efficiency based on existing Rankine cycles in which it is possible to get about 35% of the Carnot efficiency. The second estimation was based on expecting an efficiency of 30% for the cycle that employs the combustion heat value of the syngas. This, considering that it could be taken to an internal combustion engine. Combining these two efficiencies, in proportion to the existing contributions (that of heat value and that of sensible heat in the energy content of the syngas), it was possible to estimate the total efficiency

**12**

**Figure 8.**

**Figure 7.**

*Potential for electricity generation, kW/kg MSW.*

*Electricity generation, in kW, for the processing of 200 tons per day of MSW.*

of transformation to electricity and the total potential for electricity generation, which appears in **Figure 7**.

This potential is not affected by steam-to-MSW ratios. It is highly dependent, of course, on coal-to-MSW ratio and it is higher for lower air-to-MSW ratios. The potentials are higher for the case of separated MSW (between 0.75 and 2.2 kW per kg of MSW as compared to a range between 0.5 and 2.0 kW per kg of MSW for the as generated MSW case).

With these potentials, it is possible to estimate the expected electrical generation for a given flow of MSW. **Figure 8** shows the results for a plant processing 200 tons of MSW per day.

These capacities will be between 4800 and 16,000 kW for the as generated MSW and between 6500 and 17,000 kW for the separated MSW. They are not affected by steam-to-MSW ratio, increase clearly with coal-to-MSW ratio, and decrease with air-to-MSW ratio. The ranges indicated in the graphs correspond to the ones for which convergence was found in the iterations, as already mentioned. These plants could generate amounts of electricity quite useful for a given small city in a country like Colombia. Considering a generation of solid waste (as generated) of 0.50 kg/day per habitant, the plant would produce the amounts indicated in **Table 3** for the cases considered. The table compares these figures to the electric consumption of a country like Colombia, estimated at 3.90 kWh per day per capita.

Finally, the simulations permitted to obtain the expected composition of the syngas which will be shown in the next figures.

**Figure 9.**

*Syngas CO2 concentrations and specific emissions.*

#### *Sustainable Alternative Syngas Fuel*

CO2 specific emissions increase with steam-to-MSW ratios, with air-to-MSW ratios, and with coal-to-MSW ratios, although in this case depending on the air-to-MSW ratios. Specific emissions are quite similar for both MSW cases.

CO2 concentrations show a similar behavior but their concentrations in the syngas tend to be somewhat lower for the case of the separated MSW.

CO specific generations decrease with steam-to-MSW ratios and also with air-to-MSW ratios and increase with coal-to-MSW ratios. Specific generations are

#### **Figure 10.**

*Syngas CO concentrations and specific generations.*


**15**

**Figure 11.**

*Syngas H2 concentrations and specific generations.*

*Waste to Energy and Syngas*

*DOI: http://dx.doi.org/10.5772/intechopen.85848*

nents of syngas and contributes to its heat value.

MSW, especially for the case in which no coal is used.

the high humidity of the MSW, as shown in **Figure 12**.

to be higher for the low coal-to-MSW ratios.

higher for the case of the separated MSW. CO is one of the two important compo-

CO concentrations show a similar behavior and their concentrations in the

**Figure 11** shows the behavior for the H2 gas as a component of syngas, also one

H2 specific generations increase with steam-to-MSW ratios. This indicates the impact of the conversion of steam to H2. They decrease also with air-to-MSW ratios. The impact of coal-to-MSW ratios is not entirely clear and is different for the two MSW cases considered. Specific generations are higher for the case of the separated

H2 concentrations show similar behavior and their concentrations in the syngas tend to be somewhat higher for the case of the separated MSW. Concentrations tend

The water content in the syngas generated with MSW tends to be high, due to

H2O specific generations increase with steam-to-MSW ratios. This indicates a direct relationship coming from the steam added, which is to be expected. They decrease also with air-to-MSW ratios. The impact of coal-to-MSW ratios is evident. When adding coal, the water generation diminishes, as the coal water content is much lower than the one in MSW. Specific generations are clearly lower for the case of the separated MSW, again something to be expected given the lower water content for separated MSW.

H2O concentrations show a similar behavior in relationship of the direct impact of the steam-to-MSW ratios. The influence of the air-to-MSW ratio is very small.

syngas tend to be somewhat higher for the case of the separated MSW.

of its two important components and a major contributor to its heat value.

#### **Table 3.**

*Per capita electricity generation potential with syngas plants for the considered cases in Colombia.*

#### *Waste to Energy and Syngas DOI: http://dx.doi.org/10.5772/intechopen.85848*

*Sustainable Alternative Syngas Fuel*

CO2 specific emissions increase with steam-to-MSW ratios, with air-to-MSW ratios, and with coal-to-MSW ratios, although in this case depending on the air-to-

CO2 concentrations show a similar behavior but their concentrations in the

CO specific generations decrease with steam-to-MSW ratios and also with air-to-MSW ratios and increase with coal-to-MSW ratios. Specific generations are

**Parameter Units As generated Separated** MSW in Colombia kg/person day 0.50 0.24 Electricity generated—low kWh/kg MSW 0.55 0.70 Electricity generated—high kWh/kg MSW 1.80 2.00 Electricity generated—low kWh/kg person-day 0.28 0.17 Electricity generated—high kWh/kg person-day 0.90 0.49

Electricity generated—low % of national use 7.05 4.38 Electricity generated—high % of national use 23.08 12.51

Average electricity consumption in Colombia kWh/kg person-day 3.90

*Per capita electricity generation potential with syngas plants for the considered cases in Colombia.*

MSW ratios. Specific emissions are quite similar for both MSW cases.

syngas tend to be somewhat lower for the case of the separated MSW.

**14**

**Table 3.**

**Figure 10.**

*Syngas CO concentrations and specific generations.*

higher for the case of the separated MSW. CO is one of the two important components of syngas and contributes to its heat value.

CO concentrations show a similar behavior and their concentrations in the syngas tend to be somewhat higher for the case of the separated MSW.

**Figure 11** shows the behavior for the H2 gas as a component of syngas, also one of its two important components and a major contributor to its heat value.

H2 specific generations increase with steam-to-MSW ratios. This indicates the impact of the conversion of steam to H2. They decrease also with air-to-MSW ratios. The impact of coal-to-MSW ratios is not entirely clear and is different for the two MSW cases considered. Specific generations are higher for the case of the separated MSW, especially for the case in which no coal is used.

H2 concentrations show similar behavior and their concentrations in the syngas tend to be somewhat higher for the case of the separated MSW. Concentrations tend to be higher for the low coal-to-MSW ratios.

The water content in the syngas generated with MSW tends to be high, due to the high humidity of the MSW, as shown in **Figure 12**.

H2O specific generations increase with steam-to-MSW ratios. This indicates a direct relationship coming from the steam added, which is to be expected. They decrease also with air-to-MSW ratios. The impact of coal-to-MSW ratios is evident. When adding coal, the water generation diminishes, as the coal water content is much lower than the one in MSW. Specific generations are clearly lower for the case of the separated MSW, again something to be expected given the lower water content for separated MSW.

H2O concentrations show a similar behavior in relationship of the direct impact of the steam-to-MSW ratios. The influence of the air-to-MSW ratio is very small.

**Figure 11.**

*Syngas H2 concentrations and specific generations.*

The impact of coal-to-MSW ratios is evident as already said. When adding coal, the water generation diminishes as the coal water content is much lower than the one in MSW and their concentrations in the syngas tend to be clearly lower for the case of the separated MSW for the same reasons.

The water content of the syngas has an impact that should be considered in the options for its use. The water concentrations are so high that there could be possibilities of having water condensations on the gases if they reach the dew point

#### **Figure 12.**

*Syngas H2O concentrations and specific generations.*

**17**

**Acknowledgements**

and Technology Council (WTERT).

*Waste to Energy and Syngas*

tion is presented in **Figure 13**.

MSW ratios in the range of 0.0–0.5.

**3. Conclusions**

*DOI: http://dx.doi.org/10.5772/intechopen.85848*

lower for the case of the separated MSW as expected.

temperatures, which could occur at low process temperatures near cold areas, for example in the walls of cooling or transportation equipment. To study this, simulations were made of the wet bulb temperatures assuming cooling under constant total pressure and getting the corresponding saturation temperatures. This simula-

The minimum cool wall temperatures estimated in **Figure 13** include a protection of 20°C, over the calculated dew point temperatures. The dew point temperatures were estimated using psychrometry. The minimum temperatures increase with steam-to-MSW ratio, and decrease with coal-to-MSW ratios, as should be expected. The air-to-MSW ratio did not influence significantly. Temperatures are

These minimum temperatures can be guaranteed with adequate insulation of the

processing equipment and pipe walls for the systems handling the syngas.

The theoretical model showed quite consistent results. It was possible to develop a way of estimating syngas characteristics for the gasification of MSW in co-gasification, within practical working ranges for the studied variables. This was done under two extreme conditions for the MSW: as generated in a town with high organic material content and after separation of 55% of the initial waste for recycling and organics treatment (e.g., by biological composting and digestion). The model allowed to find the working ranges for steam-to-MSW ratios (between 0 and 1.0); air-to-MSW (between 1.7 and 5), for co-gasification with coal; and cola-to-

The gasification can generate electricity in all these ranges, with potentials that go from 0.5 to 2.2 kWh per kg of MSW. For the case of a plant processing 200 tons of MSW per day, the generation capacities would be between 4800 and 17,000 kW. These capacities are entirely within the electricity needs of a country like Colombia. They are between 0.28 and 0.90 kWh per person per day, for the current per capita MSW generated in the country. These figures are to be compared

From the practical point of view, it is important to use this as a conceptual basis for future work seeking indications on systems that could be feasible. This will help doing the correct steps. Engineering and design are very important components of the technology necessary to impulse WtE in a country. These systems require detailed studies and planning activities and it is advisable to do the projects considering all the engineering stages. There is always the temptation and the idea that the projects can be accelerated and put into place based on the experience and support of suppliers and makers. This by means of EPC developments, in such a way that engineering stages can be simplified or even avoided. This normally is a much costlier and rigid solution and does not contribute to developing local technology and prosperity. With regard to the solution of the problems, there is ample space to develop a region, as compared to relying only on externally provided solutions.

The authors express their gratitude to HATCH, WTERT—Colombia, ACIEM, and to the Earth Institute at Columbia University and its Waste to Energy Research

to the current daily electricity per capita use, which is 3.90.

MSW co-gasification with coal seems to be a possible alternative.

#### **Figure 13.**

*Minimum cool wall temperatures to avoid water condensation.*

temperatures, which could occur at low process temperatures near cold areas, for example in the walls of cooling or transportation equipment. To study this, simulations were made of the wet bulb temperatures assuming cooling under constant total pressure and getting the corresponding saturation temperatures. This simulation is presented in **Figure 13**.

The minimum cool wall temperatures estimated in **Figure 13** include a protection of 20°C, over the calculated dew point temperatures. The dew point temperatures were estimated using psychrometry. The minimum temperatures increase with steam-to-MSW ratio, and decrease with coal-to-MSW ratios, as should be expected. The air-to-MSW ratio did not influence significantly. Temperatures are lower for the case of the separated MSW as expected.

These minimum temperatures can be guaranteed with adequate insulation of the processing equipment and pipe walls for the systems handling the syngas.
