4. Conclusion

3.2.4. Performance of integrated system

272 Gasification for Low-grade Feedstock

Combustor and gas turbine

Air to fuel ratio ()

HRSG and steam turbine HRSG outlet pressure (MPa)

HRSG pressure drop (%)

Compressor outlet pressure (MPa) Compressor polytrophic efficiency (%) Combustor pressure drop (%) Gas turbine inlet temperature (C) Gas turbine adiabatic efficiency (%)

Heat exchanger temperature difference (C)

Steam turbine inlet temperature (C) Steam turbine polytrophic efficiency (%) Minimum outlet vapor quality (%)

Figure 10 shows the relationship between total energy efficiency, ηtot, and fluidization velocity for different gasification pressures of 25 and 30 MPa. Subsequently, about 3.5 t-H2 h<sup>1</sup> can be converted to MCH by hydrogenation process with toluene. The increase of fluidization velocity leads to lower total energy efficiency. Therefore, gasification carried out under a lower

The increasing in fluidization velocity leads to more water for the fluidizing steam which thus increases the flow rate of steam exhausted from the SCWG reactor. As a result, the heat available as hot stream in the HRSG decreases, leading to a decrease in actual work obtained from the steam turbine. On the other hand, the increasing of gasification pressure leads to more flow rate of the fluidizing steam under same fluidization velocity. Thus, the increase in

gasification pressure at 25 MPa has better total energy efficiency than that at 30 MPa.

gasification pressure finally leads to lower actual work by the steam turbine.

Table 8. Assumed conditions for the combined cycle, including combustion and gas and steam turbines.

Figure 10. Relationship between total energy efficiency and fluidization velocity under different gasification pressures.

Property Value

Novel integrated gasification systems for coproduction of electricity and MCH from low-rank coal and microalgae have been proposed. Enhanced process integration technology is applied for both systems to minimize exergy losses throughout the integrated system, thus improving the total energy efficiency. However, the models are carried out in the condition of ideal zero heat loss. Therefore, approximately 5–10% of heat losses are necessary to consider for the investigation in the actual case of the systems. For the case of microalgae, the effects of the fluidization velocity and gasification pressure on the total energy and electricity generation efficiencies were evaluated for optimum integrated system, while for the case of low-rank coal, the optimization is subjected to the investigation of fluidization velocity, steam-to-fuel ratio, and the chemical looping pressure. Finally, the integrated system for microalgae is capable to provide more than 60% of total energy efficiency, while the integrated system for low-rank coal delivers the total energy efficiency of 84%.
