Optimal Design of Solvent Based Post Combustion CO2 Capture Processes in Quicklime Plants

Abstract

cCaO-Hellas S.A., 6 th km Langada-Thessalonikis Rd., 57013,Thessaloniki, Greece seferlis@cperi.certh.gr The optimal design of a solvent based post combustion CO2 capture unit in a quicklime production plant is investigated. A 30 % weight aqueous monoethanolamine (MEA) solution is used as the absorption agent for the treatment of a 14 % mol CO2 flue gas stream. The objective function in the design optimization incorporates several equipment capacity and operating factors that have a direct impact on capital expenditure and energetic cost of the unit. A reliable and accurate equilibrium model is developed for the prediction of the process behavior. The model employs an orthogonal collocation on finite element formulation enabling structural flexibility for design purposes and efficient model reduction for computational facilitation. Nonlinear programming techniques are used for the identification of the optimal column configuration and the operating conditions. The ability of the optimally designed absorption/desorption column to achieve acceptable performance under varying separation operating conditions such as flue gas CO2 concentration, flowrate, and temperature is investigated. European policies on greenhouse gas (GHG) emissions reduction have already been adopted in order to meet the ambitious but necessary targets set for climate change prevention. Satisfaction of such targets will not only affect the global economy and specifically the energy intensive industrial sector, but also secure the competitiveness of industry in a constantly demanding market. Amongst the industrial contributors in GHG emissions, the cement and quicklime industry are significant contributors to the overall amount of released CO2. In 2008 alone, 38.5 % of the total European industrial CO2 emissions came from the cement industry, a percentage corresponding to 3.2 % of the total CO2 emitted (European Commission DG JRC, 2010). Especially in the case of the cement plants, up to 60 % of the emitted CO2 is derived from the calcination of limestone (Bosoaga et al., 2009). It is therefore evident that emissions control during the production of quicklime through the calcination step is a major contribution towards the overall reduction of CO2.