Economic Evaluation Of Dual-gas Polygeneration System

Polygeneration system can efficiently produce electricity, liquid fuels and chemical products through integration of the existing traditional process or technology. At present, the analysis and evaluation of polygeneration system focused on three aspects: energy efficiency, environmental impact and economic efficiency. After years of research and development, the research of polygeneration system's coupling integration theory, process configuration optimization and pollution control is more comprehensive, and is forming a complete system. As the process units involved in polygeneration system are more, and the system is complex, system maturity and economic limitation are the main reasons hindering the further commercial development. As the development of polygeneration, it is a meaningful work to properly evaluate the economic information to promote further development of polygeneration system.At present, the economic evaluation of polygeneration focused on the relevance of technical route choices and economy, thermodynamic properties associated with economy, or from emergy perspective to evaluate the economic feasibility of polygeneration system. As enterprises are the direct undertakers of investment consequences, and even the major forces to promote commercialization of technology. Therefore, it has more practical significance to evaluate economic feasibility from business perspective. We committed to the economic evaluation of polygeneration system, and from the perspective of economic evaluation, we gave economic reference data of the optimization polygeneration system. We used process simulation software Aspen Icarus Process Evaluator (Aspen IPE) to evaluate the economic feasibility of dual-gas polygeneration system producing alcohol ether fuels and electric power. We evaluated from the following aspects: synthesis unit, production scale, comparison of co-production and yield system, and obtained the following results and conclusions.1. We used Aspen IPE to evaluate the economic feasibility of chemical products synthesis unit in dual-gas polygeneration system: alcohol ether fuels synthesis unit which starts from clean gasified gas and coking-oven gas, the annual DME output is 476 tons, and got that when NPV is zero feed gas price and DME price are 0.288 RMB/Nm3 and 18029 RMB/t respectively, and meanwhile, IRR equals to the discount rate (8%). Further analysis shows that feed gas prices affect NPV most significantly, followed by the impact of discount rate, and the impact of DME prices is the minimum.2. Based on the alcohol ether fuels synthesis unit starting from clean gasified gas and coking-oven gas, to analyze which production scale has economic benefit and better comprehensive economy when DME sold as current market prices (3800 RMB/t～4600 RMB/t), we designed five different production scales without changing the process and operating conditions: DME annual output is 400,000 tons/year, 600,000 tons/year, 900,000 tons/year, 1,200,000 tons/year and 1,500,000 tons/year respectively, and analyzed the impact of production scales on system's economy. For these five production scales, the system's economic efficiency increases along with the expansion of production scales. When feed gas price is 0.6 RMB/Nm3, DME price is 4200 RMB/t and discount rate is 12% and considering system's investment, IRR, NPV and DME product cost, we got that the 900,000 tons/t production capacity is the optimal scale for this system.3. To analyze the economic benefit of dual-gas polygeneration under a high discount rate, we adjusted discount rate setting, be set to 12%. If the IRR is greater than 12%, the economic benefit is good. By evaluate the economic feasibility of dual-gas polygeneration system producing 1,057,140 tons/year DME and 4.786×109 kWh electric power, we got that when NPV is zero feed gas price, DME price and electricity price are 0.68 RMB/Nm3, 3597.20 RMB/t and 0.09 RMB/kWh respectively.4. By analyzing and comparing the economic feasibility of dual-gas polygeneration system producing 1,057,140 tons/year DME and 4.786×109 kWh electric power (A), dimethyl ether synthesis system producing 1,056,410 tons/year (B) and IGCC producing 4.799×109 kWh electric power (C), we analyzed the economic advantages of dual-gas polygeneration relative to yield system and IGCC. When feed gas price is 0.6 RMB/Nm3, DME price is 4200 RMB/t, electricity price is 0.2 RMB/kWh and discount rate is 12%, it can reflect that the economic benefit of polygeneration is the best, the economic benefit of ether synthesis system is the second, and the economic benefit of IGCC is the worst.5. Considering scale effect, based on dual-gas polygeneration system with alcohol ether fuels and electric power as goal products and without changing the process and operating conditions, we designed five different production scales: 705,770 tons/year DME and 2.870×109 kWh electric power, 1,057,140 tons/year DME and 4.786×109 kWh electric power, 1,408,490 tons/year DME and 7.466×109 kWh electric power, 1,810,040 tons/year DME and 7.703×109 kWh electric power, 2,111,200 tons/year DME and 9.077×109 kWh electric power respectively, and evaluated the economic feasibility of these systems. The syngas effective conversion (conversion to chemical products and electricity) ratios of these systems increased and then decreased along with the expansion of production scales, it is in accord with the economic benefit changes of these systems. The following conclusion can be drawn: the greater the syngas effective conversion ratio, the better the economic benefit will be, and the 1,408,490 tons/year DME and 7.466×109 kWh electric power production capacity has the best economic benefit.