SENSITIVITY ANALYSIS OF COAL GASIFICATION IN TWO-STAGE ENTRAINED-FLOW GASIFIER: SYNGAS AND CARBON CONVERSION PREDICTION

Abstract

The energy production from coal-fired power plant is increasing day by day, which result in increased CO₂ emission from the existing power plant. However, CO₂ emission from coal gasification can be reduced if an efficient CO₂/O₂/N₂ coal gasification is implemented in IGCC system. Numerical simulations of coal gasification under CO₂/O₂/N₂ gasification condition are carried out with the aim of describing the effects of model parameters, char reaction rates, operating conditions and heat losses to increase the syngas heating value and carbon conversion in a two stage entrained flow coal gasification process. The Eulerian–Lagrangian approach is applied to solve the Navier–Stokes equation and the particle dynamics. Finite rate/eddy dissipation model is used to calculate the rate of nine homogeneous gas-to-gas phase reactions. While only finite rate is used for the heterogeneous solid-to-gas phase reactions. It is found that the carbon conversions of combustor coal lie in the ranges from 97 wt% to 99 wt% for most of the calculated conditions. On the other hand, the carbon conversion of reductor coals varies from 45 wt% to 57 wt%. A noticeable change is obtained when the gasification occurs under a high-temperature condition. Remarkable outlet results of about 32 wt% CO, 0.58 wt% H₂ and 89 wt% overall carbon conversion are predicted if a high temperature of 1673K is maintained in the reductor. On the other hand, a reduced soot concentration is predicted if the O₂ concentration and/or the reductor gas temperature increase(s) in the gasifier.

Keywords

• Sensitivity Analysis,Two-stage Gasifier,Syngas Heating Value,CO2-blown

References

1. [1] Ministry of Economy, Trade and Industry, Energy in Japan 2010, Japan 13–14 (2010)
2. [2] Luan, Y.T., Chyou, Y.P., Wang, T.: Numerical analysis of gasification performance via finite-rate model in a cross-type twostage gasifier. Int. J. Heat Mass Transf. 57, 558–566 (2013)
3. [3] Chen, C., Masayuki, H., Toshinori, K.: Numerical simulation of entrained flow coal gasifiers Part I: modeling of coal gasification in an entrained flow gasifier. Chem. Eng. Sci. 55, 3861-3874 (2000)
4. [4] Chen, C., Masayuki, H., Toshinori, K.: Numerical simulation of entrained flow coal gasifiers Part II: effects of operating conditions on gasifier performance. Chem. Eng. Sci. 55, 3875-3883 (2000)
5. [5] Silaen, A., Wang, T.: Effect of turbulence models on gasification simulation. Proceedings of the 25th International Pittsburgh Coal-Gen Conference, Pittsburgh, Pennsylvania, September (2008)
6. [6] Silaen, A., Wang, T.: Effects of fuel injection angles on performance of a two stage coal gasifier. Proceedings of the 23rd Pittsburgh Coal Conference, Pittsburgh, Pennsylvania, September (2006)
7. [7] Silaen, A., Wang, T.: Effect of turbulence and devolatilization models on coal gasification simulation in an entrained-flow gasifier. Int. J. Heat Mass Transf. 53, 2074–2091 (2010)
8. [8] Alam, M.S., Agung, T.W., Nakaso, K., Fukai J.: Study on coal gasification with soot formation in two-stage entrained-flow gasifier. Int. J. Energy Environ. Eng. 6(3), 255-265 (2015)

9. [9] National Institute of Standards and Technology (NIST) chemistry web book.
10. [10] Hara, S., Oki, Y., Kajitani, S., Watanabe, H., Umemoto, S.: Examination of Gasification Characteristics of Pressurized Two-stage Entrained-flow Coal Gasifier - Influence of Oxygen Concentration in Gasifying Agent. CRIEPI Energy Engineering Research Laboratory Report No. M08019 (2009)
11. [11] Ansys Fluent 12.0 User’s Guide, Ansys Inc., 2009
12. [12] Kidoguchi, K., Kajitani, S., Oki, Y., Umemoto, S., Umetsu, H., Hamada, H., Hara S.: Evaluation of CO2 Enriched Gasification Characteristics Using 3t/d Bench Scale Coal Gasifier - Influence of CO2 Concentration in Gasifying Agent. CRIEPI Energy Engineering Research Laboratory Report No. M11019 (2012)
13. [13] Kobayashi, H., Howard, J.B., Sarofim, A.F.: Coal Devolatilization at High Temperatures. Symposium (International) on Combustion. 16, 411-425 (1977)
14. [14] Hashimoto, N., Kurose, R., Shirai, H.: Numerical simulation of pulverized coal jet flame employing the TDP model. Fuel 97, 277-287 (2012)
15. [15] Watanabe, H., Otaka, M.: Numerical simulation of coal gasification in entrained-flow coal gasifier. Fuel 85, 1935-1943 (2006)
16. [16] Wijayanta, A.T., Alam, M.S., Nakaso, K., Fukai, J.: Numerical investigation on combustion of coal volatiles under various O2/CO2 mixtures using a detailed mechanism with soot formation. Fuel 93, 670-676 (2012)
17. [17] Massachusetts Ins. of Tech., Combustion Research Website (http://web.mit.edu)
18. [18] Kazakov, A., Wang, H., Frenklach, M.: Detailed modeling of soot formation in laminar premixed ethylene flames at a pressure of 10 bar. Combust. Flame 100, 111-120 (1995)