CCS Feasibility Improvement in Industrial and Municipal Applications by Heat Utilisation

Abstract

This paper describes implications of applying carbon capture and storage in combined heat and power (CHP) production and in steel industry through three case study approaches conducted in Finland. Utilisation of low temperature process heat from capture plant, air separation unit or CO2 compression in district heating system and/or industrial solutions offers significant potential to increase overall efficiency and feasibility of CCS processes. The effects of CCS on the local CHP systems were included within the studied system boundaries in order to evaluate the economics and emissions from investor's (local energy company) point of view. Effect of CCS on greenhouse gas (GHG) emissions and operation economics of the CCS cases are compared to the reference system with varying parameters of operation. Regarding the GHG emissions, besides the site emissions, the main effects on global GHG emissions are also taken into account by using system modeling and streamlined LCA.In the case studies the whole CCS chain, including CO2 capture, processing, transport and storage, was included. Carbon capture processes were modeled using Aspen Plus and Prosim process modeling software and the results were used in CCS plant economics toolkit (CC-Skynet™) to estimate CO2 emission reduction possibilities and carbon abatement costs. Studied case studies included three main applications which were studied in different operational situations. The properties of reference plants and CHP systems are based on the real operational CHP units and steel mill in Finland.The first presented application is retrofit of about 1000 MWfuel CHP plant with post combustion capture technology. Natural gas fired GTCC plant is part of relatively large district heating network including also other CHP units in the same network. The plant is situated on the coastal area of Southern Finland and it emits approximately 1.3 Mtn CO2/year.The second application is a greenfield about 500 MWfuel CHP plant situated on the coast of the Gulf of Bothnia and emitting approximately 1.5 Mtn CO2/year. The plant is based on a modern CFB-boiler which is equipped with oxy- fuel technology in the CCS case. The studied fuel-shares with and without CCS consisted of pure biomass, pure peat and biomass-peat co-firing. In the study it is assumed that the economic incentive for negative CO2 emission is included in EU ETS for Bio-CCS. The plant is connected to the existing district heating network where older CHP plant already exists. Another plant and limited district heat consumption in the area limits the benefits obtained from CCS heat recovery.The third application is an integrated steel mill situated on the coast of the Gulf of Bothnia and emitting approximately 4.0 Mtn CO2/year altogether. The mill is retrofitted for post combustion capture and implications of different capture amounts, different solvents and process integration levels are compared to the base case steel production with varying operational parameters. Process heat is utilized also as district heat but heat consumption in the district heat network is smaller than the amount of recoverable process heat in the mill.The results showed that significant improvements can be achieved by CHP in plants utilizing CCS, especially in the case of oxy-fuel. The feasibility of CCS is heavily dependent not only on the characteristics of the facility and the operational environment but also on the chosen system boundaries and assumptions. In combined heat and power plants, major improvements can be obtained with heat integration, especially, in the production of district heat. In the near future particularly large, new and flexible CHP plants, which can burn coal, biomass or peat, are seen as promising candidates for CCS in Finland.