Experiments And Simulations Of Cryogenic Sulfur Dioxide Flue Gas Desulfurization Process

Nowadays,our country's social economy developing rapidly and industrial capacity increasing significantly,but pyramidally serious atmospheric environment pollution has become the shackles of the people's life quality improvement and the economic sustainable development.Therefore,the Chinese government enacted a series of laws and regulations to control the exhaust emissions of different industries,and stringent emission requirements for sulfur dioxide?SO₂?in flue gas are put forward.Boiler flue gas treatment can effectively reduce the emission of SO₂ and other toxic gases.At present,there are many kinds of desulfurization processes in various industries at home and abroad,such as dry,semi-dry and wet flue gas desulfurization,each have advantages and disadvantages.It has become the current focus to research efficient flue gas desulfurization technology.Based on the research of others,the cryogenic liquefaction desulfurization process is put forward in this paper,in which the cryogenic technology is applied to the treatment of sulfur-containing flue gas.The SO₂ in the flue gas can be liquefied into small droplets by cryogenic cooling through the heat exchange system,it is removed by a gas-liquid separation device finally.The cryogenic liquefaction desulfurization process was designed,and the cryogenic liquefaction desulfurization experimental bench was established.Combined with Aspen Plus 8.4,the steady state and dynamic simulation of cryogenic liquefaction desulfurization process were carried out,preliminary energy was analyzed in the end.First of all,the effects of cryogenic temperature,cryogenic pressure and SO₂concentration on the desulfurization efficiency of cryogenic liquefaction desulfurization process were studied experimentally.The results show that cryogenic temperature has a decisive effect on the removal efficiency,the removal efficiency increases with the decrease of cryogenic temperature,for 1000 mg/m³ SO₂ flue gas,removal efficiency increased from40.2%to 87.1%when the cryogenic temperature reduced from-15?to-75?.The removal efficiency increases with the increase of cryogenic pressure,the effect on removal efficiency is obvious in the range of 0.5² MPa,the effect of pressure above 2 MPa on removal efficiency is less than 2 MPa.The SO₂ concentration will affect the removal efficiency from the pressure level.The partial pressure of SO₂ increases with increasing concentration,which increase the removal efficiency.Secondly,a large number of simulation studies were carried out by using Aspen plus process simulation software on the basis of experiment,the effects of cryogenic temperature,cryogenic pressure,sulfur dioxide concentration and flue gas velocity on removal efficiency were studied in detail within a larger working condition range.Based on a large number of simulation results,the MAP of cryogenic process removal efficiency is drawn,the suitable range of process parameters were summarized with removal efficiency not less than 80%,90%and 95%.The influence of flue gas flow rate was studied,it is found that the increase of flow rate will shorten the residence time of flue gas in separator,thus its removal efficiency was reduced.The influence of water vapor concentration to removal efficiency was investigated by using ELECNRTL method in Aspen plus,it is found that increasing the content of water vapor can increase the separation specific gravity of the first stage gas-liquid separator.The water solubility of SO₂ can improve the removal efficiency of the process,and the removal efficiency increases with the increase of water vapor volume fraction.The effect of water vapor content on the removal efficiency of flue gas with high SO₂ concentration is greater than that of low.Then,the dynamic simulations were carried out in Aspen plus dynamics,the operation stability of single-stage cryogenic desulfurization process?SCDP?,two-stage cryogenic desulfurization process?TCDP?and regenerative type two-stage cryogenic desulfurization process?RTCDP?were investigated.was found more stable than the other two processes,which kept higher stable removal efficiency,the minimum change in temperature and the lowest SO₂ molar flow at separator outlet.The RTCDP can be quickly stabilized within 2hours after startup.Finally,process energy was analyzed in the Aspen energy analyzer software,heat exchange networks?HENs?of the regenerative type two-stage cryogenic desulfurization process was extracted,shifted composite curves?SCC?and grand composite curves?GCC?are obtained,and the pinch point analysis is carried out.The cooling load required by the RTCDP is 599.4 W,the energy recovered is about 177.8 W according the SCC,TCDP's cooling load is 777.2W.The energy analysis results of the two processes were matched that the RTCDP can reduce energy consumption by 22.9%.