Experimental Study On Separation Of CO₂ From Flue Gas By Polypropylene Hollow Fiber Membrance

CO₂ is one of the most important anthropogenic emissions of greenhouse gases which cause global warming, and the flue gas of power plant emission plays a decisive role in the problem of the significant increase in CO₂ emissions. In today’s society, alleviate greenhouse effect problem in the global scope are imperative, therefore the flue gas decarbonization research is urgently needed. The methods of removing CO₂ from flue gas include physical adsorption, chemical absorption, oxygen enriched combustion, chemical chain combustion, ionic liquid and electrochemical method. Among the numerous methods, this experiment selected a kind of absorption method, which is very promising and overcomes many disadvantages.The reaction mechanism of the absorption liquid and CO₂ is different, the common absorption liquid has the alcohol amine solution, the glycine salt and so on. In the test of alcohol amine solution to absorb CO₂, primary amine and secondary amine absorption rate is faster than that of the tertiary amine, which by their respective molecular structure determined, tertiary amine nitrogen atoms no proton and need to rely on CO₂ hydrolysis can react with the indirect. According to the technological process, the membrane absorption and desorption test platform was assembled, and a series of comparative experiments were carried out on the test platform. For the same absorption solution under different conditions, the same kind of test conditions different absorption solution for CO₂ removal effect of CO₂ mass transfer efficiency were studied, and select the MEA aqueous solution as absorption liquid and Study on the optimum absorption effect of testing conditions. At the same time, it also makes a series of experiments on membrane desorption.In membrane absorption test, the selection of PG aqueous solution, mea aqueous solution and MDEA aqueous solution as absorption liquid absorption liquid in a continuous cycle test performance, including PG, mea aqueous solution under the same conditions of CO₂ removal rate and mass transfer efficiency of was higher than that of MDEA and MDEA absorbing load is greater than the other two. And for the same absorption solution, concentration of the absorption liquid in 2mol/L below. To increase the absorption of liquid concentration, the removal rate increases and that removal rate from high to low in order for: 2mol/L>1.5mol/L>1mol/L>0.5mol/L, when higher than 2mol/L, and the removal rate 2mol/L>3mol/L. This shows that when the concentration is higher than the critical value, the increase of concentration will lead to the decrease of the removal rate. For industrial use of the wide range of MEA aqueous solution as CO₂ removal of absorption solution using a single variable principle test, the results show that when absorbing solution concentration is maintained at around 1mol/L, the liquid temperature control is 35℃, liquid flow rate 0.057m/s. Simulation of flue gas temperature of 25℃, velocity 0.160m/s. Through the polypropylene hollow fiber membrane contactor, the removal rate of the most ideal, can reach more than 90%. Continuous cycle test also showed that no matter what kind of absorption liquid in the long run will make the membrane contactor wetting, removal effect is significantly reduced. Therefore, in the industrial application, it is needed to consider the wettability of the membrane and the cost economy, and choose the best plan.In membrane desorption experiment, by changing the absorption liquid type, temperature, concentration and flow rate, under the same conditions the desorption rate of MDEA is higher than that of MEA and PG. The absorption liquid temperature increased from 60℃ to 80℃, MEA, CO₂, MDEA and PG corresponding to the desorption rate were increased by 17%, 44% and 25%. The absorption liquid concentration increased from 0.5mol/L to 3mol/L, MEA, MDEA and PG absorption rate growth rate were 111.76%, 95.12% and 96.15%. Accelerate the absorption liquid flow rate, it will make the desorption rate decreased. The flow rate of 0.001m/s, MEA, MDEA and PG water solution desorption rates were 23%, 46% and 32%. When the flow rate increased to 0.020m/s, the desorption rate of the three kinds of absorption liquid decreased to 11%, 27% and 16%.At the same time, a preliminary study of the membrane absorption and membrane desorption cycle test, draw the conclusion: when the membrane with the membrane absorption desorption test cycle, to improve the absorption effect of membrane absorption test. And by the comparison test results show that not only the thermal desorption membrane desorption energy consumption is relatively low, but the desorption effect is better.At the end of the article, also pointed out that this experiment possible defects and deficiencies, and to the future put forward corresponding prospect, of which the most important is expectations about how the industry membrane absorption and membrane solution attraction as a whole.