Design And Optimization Of IGCC Gasification Multi-Generation System Based On Waste Plastics And Economic Analysis

Plastic products are widely used due to their superior performance.The current recycling methods and technologies for waste plastics still have major limitations,resulting in waste of resources,causing serious environmental pollution and large amounts of carbon emissions.Research shows that the hydrocarbon content of plastic products is extremely high and the calorific value is comparable to that of coal,so gasification of waste plastics is a highly promising treatment method.Integrated Gasification Combined Cycle Power Generation System-IGCC is an advanced power system combining coal gasification technology and high-efficiency combined cycle.It has high power generation efficiency and very low pollutant emission.At the same time,it can capture carbon dioxide released during coal combustion at a lower cost,which is a promising clean coal power generation technology.The 14th Five-Year Plan points out the implementation of green and low-carbon in segments,and China has announced to achieve‘carbon peak’by 2030 and‘carbon neutral’by 2060.In this paper,we design three different gasification multi-generation systems based on the traditional integrated coal gasification combined cycle power generation system with waste plastics as the gasification raw material to address the problems of waste plastics treatment and CO₂emission.The main research contents are as follows:（1）Each subsystem involved in the three waste plastic gasification systems was designed based on the characteristics of the waste plastic raw materials and gasification characteristics.Simulation models were developed for each subsystem using a process simulator.At the same time,the key operating variables were optimized by sensitivity analysis,and the optimal process operating parameters were derived.（2）Three process systems have been designed with different objectives.Design 1is based on a conventional IGCC system as the design framework,using a low-temperature air separation process to produce oxygen,mixed with water vapor and scrap plastic to be sent to the gasifier together.The recovered plastic scrap has to go through sorting and pretreatment steps to become qualified gasification feedstock.The syngas generated from the gasifier is first sent to the methanol synthesis unit through desulfurization,denitrification and dust removal.The residual gas is passed to the gas turbine and waste heat boiler to realize the multi-production of heat,electricity and methanol.Design 2 adopts the vacuum variable pressure adsorption process to produce oxygen,which greatly reduces the energy consumption of the oxygen production unit and improves the economy of the whole system.Design 3 introduces calcium cycle reaction coupled with water gas conversion to improve hydrogen efficiency while capturing the generated carbon dioxide,and calcium carbonate calcination to obtain high purity carbon dioxide and calcium oxide re-circulation.（3）The efficiency,power generation,and product yield of the three designs are compared by the common efficiency evaluation indexes of power plants.Meanwhile,this paper establishes an Emissions Trading Scheme model based on historical intensity as well as industrial benchmarks,which gives incentives and penalties according to the actual emissions of enterprises and calculates the benefits/costs of system carbon.The cost/benefit of carbon is also incorporated into the techno-economic analysis to calculate the economic indicators such as net present value of the three systems.The research results show that the waste plastic gasification multi-generation system can realize the multi-generation of heat,electricity and chemicals.With the improvement of emission trading market,design 3 has the most potential in energy saving and emission reduction and economic benefits.