Research On Carbon Capture And Desorption Technologies Based On Bipolar Membrane Electrodialysis

The greenhouse effect resulted by the slater of fossil fuels such as coal, oil and natural gas has become a global hot topic in recent years, so carbon emission reduction measures are imperative. Recent carbon capture technologies exit some problems, like large initial cost, equipment corrosion, difficult to recycle and so on, so it is an important task to study on carbon capture and desorption technology which are cheap, efficient and can be recycled.The self-designed bipolar membrane electodialysis system was used to study the solution desorption after ammonia carbon capture. In this system, firstly, decarburization solution was simulated with only ammonium bicarbonate, and influence of the feed concentration, velocity and working current on CO2 elctrical desorption rate, efficiency,current efficiency and power consumption were studied. Secondly, the reaction mechanism of SO2, NOx and CO2 in flue gas with NH3·H2O and mechanism of bipolar membrane electrodialysis were introduced, and with the adjustment of operation conditions, general rule of electrical desorption and influence of liquid coexistence impurities include(NH4)2SO3,(NH4)2SO4, NH4NO3, NaCl and NH4 Cl were studied. Then,general rule and mechanism of ion migration in bipolar membrane electrodialysis device were speculated based on the hydrolysis charater of bipolar membrane and fundamental principles of elecrodialysis, which were verified by experiments. Studying results show that desorption ratio can be as high as 71.66% and the power consumption can be as low as 2.21 kWh/kg-CO2. Considering a higher desorption ratio and lower power consumption, the appropriate operation conditions are as follows: concentration of NH4HCO3 is 0.5 M, the feed rate is 80 L/h, and the current density is 150 A/m2.Researches have shown that types of liquid coexisting components, mass fraction, pH values and surface tension all can have an impact on the bipolar membrane electrodialysis. Small amounts of NaCl, NH4 Cl and(NH4)2SO4 were good to electrodialysis of absorbing solution, and the effecting degree on electricity desorption was NaCl > NH4 Cl >(NH4)2SO4. Existence of(NH4)2SO3 should be avoided in absorption rich solution. Coexistence of NH4NO3 had no significant impact on the electrodialysis of rich solution after ammonia decarbonization. Thus, it is essential to control the amount of harmful gases befor carbon capture, in order to decrease their adverse effect on propertities of bipolar membrane electrical desorption and physicochemical property of stripping liquid. Ion exchange membrane has a big retardation for ions with opposite charges, and water can be dissociated into hydrogen ion and hydroxide ion by bipolar membrane. Ion migration in the desalting process takes the directional migration under the effect of direct-current electric field as the principlething, and takes the diffusion under the concentration difference as the complementary thing. In the end, the paper described the development prospect of this technology. The research aims to offer some basic experimental data for the bipolar membrane electrical desorption of ammonium decarburization solution.