Techno-economic assessment of a chemical looping splitting system for H2 and CO Co-generation

The natural gas(NG)reforming is currently one of the low-cost methods for hydrogen production.However,the mixture of H2 and CO_(2) in the produced gas inevitably includes CO_(2) and necessitates the costly CO_(2) separation.In this work,a novel double chemical looping involving both combustion(CLC)and sorption-enhanced reforming(SE-CLR)was proposed towards the co-production of H2 and CO(CLC-SECLRHC)in two separated streams.CLC provides reactant CO_(2) and energy to feed SECLRHC,which generates hydrogen in a higher purity,as well as the calcium cycle to generate CO in a higher purity.Techno-economic assessment of the proposed system was conducted to evaluate its efficiency and economic competitiveness.Studies revealed that the optimal molar ratios of oxygen carrier(OC)/NG and steam/NG for reforming were recommended to be 1.7 and 1.0,respectively.The heat integration within CLC and SECLRHC units can be achieved by circulating hot OCs.The desired temperatures of fuel reactor(FR)and reforming reactor(RR)should be 850
C and 600
C,respectively.The heat coupling between CLC and SECLRHC units can be realized via a jacket-type reactor,and the NG split ratio for reforming and combustion was 0.53:0.47.Under the optimal conditions,the H2 purity,the H2 yield and the CH4 conversion efficiency were 98.76%,2.31 mol mol-1 and 97.96%,respectively.The carbon and hydrogen utilization efficiency respectively were 58.60% and 72.45%in terms of the total hydrogen in both steam and NG.The exergy efficiency of the overall process reached 70.28%.In terms of the conventional plant capacity(75 × 103 t y^(-1))and current raw materials price(2500$t^(-1)),the payback period can be 6.2 years and the IRR would be 11.5,demonstrating an economically feasible and risk resistant capability.

Characterization on the hydrodynamics of a covering-plate Rushton impeller

A modified Rushton impeller with two circular covering-plates mounted on the upper and lower sides of the blades was designed.There are gaps between the plates and the blades.The turbulent hydrodynamics was analyzed by the computational fluid dynamics(CFD) method.Firstly,the reliability of the numerical model and simulation method was verified by comparing with the experimental results from literature.Subsequently,the power consumption,flow pattern,mean velocity and mixing time of the covering-plate Rushton impeller(RT-C) were studied and compared with the standard Rushton impeller(RT) operated under the same conditions.Results show that the power consumption can be decreased about 18%.Compared with the almost unchanged flow field in the lower stirred tank,the mean velocity was increased at the upper half of the stirred tank.And in the impeller region,the mean axial and radial velocities were increased,the mean tangential velocity was decreased.In addition,the average mixing time of RT-C was shortened about 4.14% than the counterpart of RT.The conclusions obtained here indicated that RT-C has a more effective mixing performance and it can be used as an alternative of RT in the process industries.

Numerical simulation on optimization of structure and operating parameters of a novel lean coal decoupling burner

Due to its low volatile characteristics of lean coal,it is difficult to catch fire and burn out.Therefore,high temperature is needed to maintain combustion efficiency,while,this leads to high nitrogen oxide emission.For power plant boilers burning lean coal,stable combustion with lower nitrogen oxide emission is a challenging task.This study applied the 3D numerical simulation on the analysis of a novel de-coupling burner for low-volatile coal and its structure and operation parameters optimization.Results indicate that although it was more difficult for lean coal decoupling burner to ignite lean coal than high volatile coal,the burner formed a stepwise ignition trend,which promoted the rapid ignition of lean coal.Comparison of three central partition plate structure shows that in terms of characteristics of the flow field distribution,rich and lean separation and combustion,the structure with an inclination of 0°showed good performance,with its rich-lean air ratio being 0.85 and concentration ratio being 22.94,and there was an apparent decoupling combustion characteristic.Finally,the structure of the selected burner was optimized for its operational conditions.The optimal operating parameters was determined as the primary air velocity of 24.9 m·s^-1 and the mass flow rate of pulverized coal of 2.5 kg·s^-1,in which the pyrolysis products were utilized as reductive agent more fully.Eventually,the nitrogen oxide was efficiently reduced to nitrogen,which emission concentration was 61.88%lower than that in the design condition.

基于Aspen Plus的燃煤电厂烟气污染控制单元模拟

采用Aspen Plus软件对烟气污染控制单元进行模拟,以电厂实际运行数据验证模型的正确性,建模过程中考虑SO_3转化和烟气中烟尘浓度的变化,并通过影响因素分析考察操作参数对污染物脱除效果的影响。结果表明,在选择性催化还原(SCR)脱硝过程中,部分SO2转化为SO_3,除尘过程中飞灰对SO_3有吸附作用,脱硫塔与除尘器对SO_3和灰分脱除具有协同作用;SCR脱硝过程的最佳氨氮摩尔比范围为0.8～1.0,氨氮比低于0.6、反应温度低于400℃时,SO_3浓度呈上升趋势;湿法脱硫过程中,入口烟气温度上升会阻碍SO2吸收和SO_3去除;湿式除尘过程中,除尘效率随温度升高而降低,随气体流速增加先升高后降低,最佳流速为0.8～1.2 m/s。