Simulation And Assessment Of Clean Fuel Processes Manufactured By Calcium Carbide Furnace Off-Gas

As an important branch of coal chemical industry, coal-based calcium carbide process has significant economic advantages. Oxygen-thermal calcium carbide production process is a new coal-to-calcium carbide process, in which the calcium carbide furnace off-gas (CCFG) is one of the products. Compared with the traditional oxygen-thermal calcium carbide production process, oxygen-thermal process performs better in the energy conservation and emissions reduction, and a high concentration of CO in the CCFG can be used as a main raw material to produce Cl chemicals and clean fuels. This paper focused on exploring the effective chemical utilization of CCFG. Three different kinds of calcium carbide furnace off-gas-based clean fuel synthesis processes were simulated and evaluated using Aspen Plus simulation software. The main research is as follows:A new multi-product system evaluation method was established and product character weight coefficient was defined to represent multi-product distribution characteristic. Multi-product comprehensive energy consumption, multi-product comprehensive exergy loss, multi-product comprehensive carbon emission and effective atom yield were proposed as a series of new system evaluation indices to assess the system on aspect of material conversion, energy utilization and carbon emission. And the effective atom yield and the multi-product comprehensive exergy loss were as core indices to evaluate systems.The simulation of CCFG-based dimethyl ether (DME) single-step and two-step process, lower carbon alcohols (LCA) and fuel oil synthesis processes were established in this paper. On the basis of the reliable model validation, the mass balance, energy balance, exergy balance as well as carbon emission data were obtained. Based on the energy balance and exergy balance, energy flow diagrams and exergy flow diagrams of each process were drawn and the distribution of energy and exergy were obtained. Based on the mass balance and carbon emissions, the carbon footprint diagrams as well as the carbon emission distribution were also obtained.According to the simulation data and the new assessment method, each system was compared and analyzed on material conversion, energy consumption and carbon emission. Firstly, the two CCFG-based DME synthesis processes, single-step and two-step processes, were compared and the result showed that the single-step process was a better CCFG-to-DME process. Secondly, the CCFG-based single-step DME process, LCA process and fuel oil synthesis process were compared and assessed. In terms of the effective atom yield, the value of three processes are 34.13%?30.81% and 26.30%, respectively. Namely, the DME process is the highest effective atom yield of three processes. On the aspect of the multi-product comprehensive exergy loss, the value of each process is 5.24 MW-t-prod-1?5.46 MW-t-prod-1 and 12.37 MW·t-prod-1. It showed that the DME process has the minimum exergy losses, which mean the highest thermodynamic perfect degree among three systems. In conclusion, the CCFG-based single-step DME process is the most reasonable, clean and efficient CCFG to clean fuel solution.