Research On Carbon Capture Performance Of Flue Gas By Mixed Monoethanolamine Solvent System

CO2,a kind of greenhouse gas which has caused the greenhouse effect.So from last century,the emissions of it has aroused widespread concern around the world.International Energy Agency proposed to reduce the emissions of CO2 to 50%of CO2 emissions of 2002 in 2050.Although there are many reasons for the occurrence of CO2,in China,fossil fuel as the main source in the production of electricity emitted more than 80%of total CO2 emissions,so electricity is a centralized CO2 emission source.And power plant is the best field of large-scale emission reduction of CO2,for its stable concentrated and large features of CO2 emissions.It is of great significance to study CO2 emissions from thermal power plants to solve the problem of controlling the greenhouse gas emissions in China.Post combustion CO2 capture technology using chemical solvents is one of the most mature commercial and industrial CO2 capture technologies of coal-fired power plants.But the problem which obstructed the development of this technology is high technical cost and regeneration energy consumption.In this paper,the feasibility of improving the CO2 capture efficiency and reducing the cost was provided by the screening of new high efficiency solvent and the optimization of the process.The main contents are as follows:Using the lab-scale experimental apparatus,the absorption and regeneration properties of MEA-H2O,DEA-H2O,TEA-H2O,MEA/PZ-H2O,MEA/K2CO3-H2O,MEA/NH3-H2O,the absorption and regeneration properties and densities and viscosities of MEA-Methanol,MEA/TEA-Methanol and MEA/Glycerol-Methanol were studied.The results showed that:The absorption rate of CO2 was significantly higher than that of DEA-H2O and TEA-H2O(The maximum absorption rate of MEA was 7.2×10-5 mol/s,while the maximum absorption rate of DEA and TEA was 4.1 mol/s and 1.4 mol/s).PZ,K2CO3 and NH3 are not suitable for using as an additive of MEA.The maximum absorption rate of MEA-Methanol was 8.1 mol/s,which was significantly higher than that of MEA-H2O,DEA-H2O and TEA-H2O.The addition of TEA and glycerol did not improve the absorption and regeneration properties of MEA-Methanol.So MEA-Methanol is used as an alternative solvent for the next steps.Using the pilot-plant CO2 capture device which was packing with Sulzer packing BX500,Mellapale 500Y and Pall Rings 16×16,absorption and regeneration performance were studied under different absorption and regeneration operating conditions.In order to obtain the optimum absorption and regeneration operating conditions,orthogonal experiments were carried out under three kinds of packing,and the absorption-regeneration experiment was carried under the optimum conditions.The results showed that CO2 capture efficiency was all over 94%,CO2 volume fraction after stripping methanol can reach more than 99%,and the regeneration heat duty was 3.0 MJ/kg CO2(Sulzer packing),3.2 MJ/kg CO2(Mellapale packing)and 3.3 MJ/kg CO2(Pall Rings).The reaction of CO2 in MEA-H2O and MEA-Methanol was investigated.The effects of solubility,physicochemical properties,reaction order of CO2 and MEA,and effect of methanol on reaction rate were investigated.Also,reaction rate of CO2 absorpion into MEA-H2O and MEA-Methanol was investigated.The results showed that:The rate of CO2 absorption into MEA-Methanol was higher than that of MEA-H2O.But the reason was not due to the increase of enhancement factor,it was caused by the enhancement of the diffusivity and solubility characteristics by adding methanol.Under the same operating conditions,absorption heat of CO2 in MEA-Methanol was lower than that in MEA-H2O by 30%,which means regeneration energy consumption of MEA-Methanol is lower than MEA-H2O by about 30%.In the cycle CO2 capture device,effects of several operating parameters on regeneration energy consumption were studied.The results showed that:Regeneration energy consumption of MEA-Methanol was significantly lower than that of MEA-H2O when CO2 capture efficiency was kept about 90%(2.97 MJ/kg CO2 and 3.89 MJ/kg CO2,respectively).In the cycle CO2 capture device,absorption and regeneration properties of two kinds of new solvents(BZA-H2O and DETA-H2O)-were tested and compared with the traditional solvent MEA-H2O to evaluate the application potential of them in industry.The results showed that:There is a large amount of milky white precipitate in rich CO2 BZA-H2O solvent,which caused the packing clogged.So BZA-H2O is not suitable for capturing large amount of CO2 in industry.Under the optimum operating conditions and different gas flow rate,the order of CO2 capture efficiency was MEA-Methanol>DETA-H2O>MEA-H2O,and the order of regeneration energy consumption was MEA-Methanol<DETA-H2O<MEA-H2O.In summary,MEA-Methanol has a great potential to replace MEA-H2O as an industrial CO2 chemical solvent.