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2015-06-17 - Colloque/Présentation - poster - Anglais - 1 page(s)

Laribi Sinda , Meunier Nicolas , Dubois Lionel , De Weireld Guy , Thomas Diane , "Simulation of a CO2 purification unit applied to flue gases coming from oxy-combustion cement industries" in 8th Trondheim Conference on CO2 Capture, Transport and Storage (TCCS-8), Trondheim, Norway, 2015

  • Codes CREF : Traitement des effluents gazeux (DI3843), Génie chimique (DI2721), Chimie (DI1300)
  • Unités de recherche UMONS : Génie des Procédés chimiques et biochimiques (F505), Thermodynamique, Physique mathématique (F506)
  • Instituts UMONS : Institut de Recherche en Energétique (Energie)

Abstract(s) :

(Anglais) Carbon dioxide emitted from cement industries represent 30% of the total annual CO2 emitted from industrial sectors. Approximately 2/3 of the CO2 emission is a result of the limestone calcination and 1/3 from the combustion of fuels. In addition to CO2, formation and emissions of SO2, NOx, HCl, heavy metals, TOC and dust are inevitable. For industrial applications, Carbon Capture and Storage (CCS) is one option for reducing these harmful CO2 emissions. Another option on which we are focusing in this work is the reutilization of CO2 for its conversion into valuable products, namely Carbon Capture and Re-Use (CCRU). For this purpose, the ECRA Chair, scientific convention between the UMONS Research Institute for Energy and ECRA (European Cement Research Academy), aims the valorization of carbon dioxide and focuses on methanol catalytic production which uses conventionally CuO/ZnO/Al2O3 as catalyst. The CO2 conversion needs hydrogen produced by a water electrolysis using renewable energy. A gas treatment chain is therefore necessary for capturing and purifying the gas at the outlet of a cement manufacturing process in order to obtain a purity level of CO2 suitable for its valorization. Electrostatic precipitators and fabric filters for dedusting, Selective Catalytic and Non Catalytic Reduction (SCR and SNCR) for denitrification and the addition of adsorbents for desulphurization are the best available gas purification techniques applied to the cement industry operating with a conventional combustion. Among the CO2 capture technologies we focused on the purification of a gas issued from an innovative combustion process in the cement industry, the oxy-fuel combustion, consisting on realizing the combustion with only oxygen and requiring a previous air separation step. This technique leads to a high concentration level of CO2, namely between 70 and 90% both for oxy-fuel power plants and cement plants. In this case, the usual procedures to remove classical impurities (H2O, O2, Ar, N2, SOx, and NOx) to increase the CO2 concentration are mostly based on three main steps: a desulphurization/denitrification step (with compression of the flue gas), a water adsorption step, and a separation step using either a distillation column or a double flash unit, to remove the residual inert gases. In the present work, a CO2 Purification Unit (CPU) has been simulated with Aspen Plus. The CPU block is divided into three CO2 purification steps. The gas is firstly desulfurized and denitrified in a double-column unit called “Sour Compression Unit” (see flow sheet on Fig. 1) where it is compressed to a high pressure (namely 15 bar in the first column and 30 bar in the second one) and purified counter-currently with water to remove SOx and NOx components by absorption. The pressure levels promote the oxidation of NO into NO2. The identification of the most suitable thermodynamic model (ELEC-NRTL due to the presence of ionic species) and chemical mechanism to model SOx and NOx reactions (equilibrium and kinetics) in the gas/liquid absorbers, as the definition of the dimensional parameters related to treated flow rate constitute preliminary steps of the study. Regarding the composition of the gas to treat, as no oxy-fuel CO2 capture pilot units are already installed in a cement plant, the gas compositions at the inlet of the CO2 Processing Unit were provided by ECRA thanks to specific simulations for oxy-fuel cement kilns. Based on the Schwarze Pump oxy-fuel power plant and especially on the Air Product Process, the simulation model was successfully validated and globally the simulation results showed that both for a power plant and a cement plant, the studied process can be used to remove efficiently SOx (up to 100%) and NOx (up to 90-99%) from the feed CO2 stream. Nevertheless, the conditions of high pressure levels require an important demand of energy (0.135 kWh/kgCO2 represent electrical needs of the Sour-Compression Unit). Thus, an optimization of the SCU for the cement plant case is necessary considering the financial, energetical and environmental aspects through the variation of operating parameters (such as the recirculation rate and the operational pressures) and design parameters (such as the height of the columns). Moreover, the de-SOx and de-NOx performances of such a system will be studied for different NOx and SOx inlet concentrations, and for different values of the NO/NO2 ratio.