| In the process of coal conversion（coking,gasification,etc.）,the sulfur emissions will be inevitable and the effective removal of sulfide from coal gas is the key to its further utilization.The hydrogen sulfide has been the focus of attention in various forms of gas purification,but only the sulfur is recovered,and the higher value of hydrogen generates water without special purpose.H2 S chemical splitting for the production of hydrogen and sulphuric acid system not only provides the feasibility for the conversion of sulfur containing pollutants,including hydrogen sulfide,into high quality and high values of hydrogen and sulfuric acid,but also greatly reduces the energy consumption of the system.The technical route has sustainable development in energy-saving and emission-reduction,social and economic benefits and other aspects.The content of H2 S in the feedstock gas is a key factor in the H2 S chemical splitting for the production of hydrogen and sulphuric acid system.In this paper,Rectisol was used to recover the H2 S gas produced in the process of coal conversion,simulation and optimization of process parameters of Rectisol device and H2 S in a factor.At the same time,the design of mass balance and heat exchange simulation was carried out for the process of sulfur-iodine cycle of H2 S splitting for the production of hydrogen and sulphuric acid,providing a basis for future industrial application.1)Applying the general chemical process simulation software Aspen Plus,this paper selects the physical property method of PSRK to simulate and design the whole process of the Rectisol.The temperature and flow rate of methanol in absorption column,the temperature and pressure of the CO2 desorption column,the regeneration N2 flow of H2 S concentrate column,the temperature and pressure of the thermal regeneration column condenser,the reflux ratio of regeneration column were researched and the sensitivity in those conditions were analyzed.The hydraulic modeling analysis of each column and the plate design and accounting were also carried out.The results after retrofit show that H2 S content in gas can be effectively improved through properly reducing the temperature and increasing the pressure of the condenser in the thermal regeneration tower,selecting the appropriate reflux ratio of the thermal regenerator.The best operating parameters optimized for Rectisol are described as follows: the temperature and flow rate of methanol in absorption column were –50 °C and 21000 kmol/h,the temperature and pressure of the CO2 desorption column were –35 °C and 6 bar,the temperature and pressure of the thermal regeneration column condenser were 20 °C and 3 bar,the reflux ratio of regeneration column was 0.45.After optimization,the mole fraction of H2 S was increased from 0.38% to 68.90%,from raw gas to product gas.In addition,the yield of H2 S was up to 99.32%,most of the H2 S was recovered,the volume fraction of H2 S can meet the requirements of iodine sulfur cycle H2 S decomposition combined with hydrogen and sulfuric acid.2)Whole process simulation and analysis for H2 S chemical decomposition combined with hydrogen and sulfuric acid system is carried out by using Aspen Plus.The ELECNRTL method was used in Bunsen reaction and H2 S oxidation reaction,the NRTL method was used for the separation of HI.The mass balance of the system and the optimization of heat transfer are calculated,and the results show that:（a）Water vapor with 250 °C temperature and 4 MPa pressure of 118 kmol/h,that is,1.86×104 ton/y can be obtained through 104 °C,4 MPa soft water for sulfur burning heat recovery.（b）The higher the pressure is,the less heat is needed for the concentrated sulfuric acid distillation,but the difference is smaller.Taking into account the actual industrial applications,atmospheric distillation operation is easier to achieve,so the atmospheric distillation method is considered to enhance the concentration of sulfuric acid.（c）Temperature and pressure had little effect on the rate of HI decomposition,so it is not too realistic through adjusting the temperature and pressure to improve the decomposition rate of HI in the actual application.It can be considered to improve the decomposition rate of HI using membrane separation technology,electrolysis and other ways.3)On the basis of the accurate simulation,the paper makes the whole material balance of the process of the hydrogen sulfide decomposition combined with hydrogen and sulfuric acid.（a）Rectisol system: The processing capacity of raw gas can be reached 3.32×106 ton/y,and the H2 S gas of 1.99×104 ton/y,methanol synthesis gas（CO+H2）of 9.55×105 ton/y and CO2 product gas of 2.11×106 ton/y can be obtained through purification.（b）S-I cycle system: The input quantity of air gas is 1.06×105 ton/y,and the outputs of N2,H2 and the concentrated sulfuric acid with mass fraction of 96 wt% are respectively 7.94×104 ton/y,4.30×102 ton/y and 5.73×104 ton/y through iodine sulfur cycle with H2 S decomposition.（c）Circulation loss: Rectisol absorption column methanol circulation was 5.88×106 ton/y,the circulating amount of iodine was 7.53 × 103 ton/y and the amount of toluene was 1.88 × 104 ton/y.The consumption quantity of methanol,iodine and toluene are calculated by 0.1%,that is,the cycle loss amounts of methanol,iodine and toluene is respectively 5.88×103 ton/y,7.53 ton/y and 18.84 ton/y.A study on process simulation of cogeneration hydrogen and sulfuric acid through H2 S chemical splitting cycle for clean coal technology,the obtained simulation results have practical guiding significance for pilot scale enlargement and industrial application of the following projects. |
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