Multi-Pollutant Formation and Control in Pressurized Oxy-Combustion:SO_(x),NO_(x),Particulate Matter,and Mercury

Oxy-combustion is a promising carbon-capture technology,but atmospheric-pressure oxy-combustion has a relatively low net efficiency,limiting its application in power plants.In pressurized oxycombustion(POC),the boiler,air separation unit,flue gas recirculation unit,and CO_(2)purification and compression unit are all operated at elevated pressure;this makes the process more efficient,with many advantages over atmospheric pressure,such as low NO_(x)emissions,a smaller boiler size,and more.POC is also more promising for industrial application and has attracted widespread research interest in recent years.It can produce high-pressure CO_(2)with a purity of approximately 95%,which can be used directly for enhanced oil recovery or geo-sequestration.However,the pollutant emissions must meet the standards for carbon capture,storage,and utilization.Because of the high oxygen and moisture concentrations in POC,the formation of acids via the oxidation and solution of SO_(x)and NO_(x)can be increased,causing the corrosion of pipelines and equipment.Furthermore,particulate matter(PM)and mercury emissions can harm the environment and human health.The main distinction between pressurized and atmospheric-pressure oxy-combustion is the former’s elevated pressure;thus,the effect of this pressure on the pollutants emitted from POC—including SO_(x),NO_(x),PM,and mercury—must be understood,and effective control methodologies must be incorporated to control the formation of these pollutants.This paper reviews recent advances in research on SO_(x),NO_(x),PM,and mercury formation and control in POC systems that can aid in pollutant control in such systems.

Modeling ash deposition and shedding during oxy-combustion of coal/rice husk blends at 70%inlet O_(2)

Co-firing rice husk(RH)and coal with carbon capture using oxy-combustion presents a net carbon negative energy produc-tion opportunity.In addition,the high fusion temperature of the non-sticky,silica rich,RH can mitigate ash deposition as well as promote shedding of deposits.To identify the optimum operating conditions,fuel particle sizes,and blend ratios that minimize ash deposition,a Computational Fluid Dynamic methodology with add-on ash deposition and shedding models were employed to predict outer ash deposition and shedding rates during co-combustion of coal/RH in AIR and O2/CO_(2)(70/30 vol%,OXY70)oxidizer compositions.After ensuring that the fly-ash particle size distributions and particle Stokes numbers near the deposition surface were accurately represented(to model impaction),appropriate models for coal ash and RH ash viscosities that were accurate in the temperature region(1200-1300 K)of interest in this study were identified.A particle viscosity and kinetic energy(PKE)based capture criterion was enforced to model the ash capture.An erosion/shed-ding criterion that takes the deposit melt fraction and the energy consumed during particle impact into account was also implemented.Deposition rate predictions as well as the deposition rate enhancement(OXY70/AIR)were in good agreement with measured values.While the OXY70 scenario was associated with a significant reduction(60%-70%)in flue gas velocities,it also resulted in larger fly-ash particles.As a result,the PKE distributions of the erosive RH ash were similar in both scenarios and resulted in similar shedding rates.

Key CO_(2)capture technology of pure oxygen exhaust gas combustion for syngas-fueled high-temperature fuel cells

Integrated gasification fuel cells(IGFCs)integrating high-temperature solid oxide fuel cell technology with CO_(2)capture processes represents highly-efficient power systems with negligible CO_(2)emissions.Flame burning with pure oxygen is an ideal method for fuel cell exhaust gas treatment,and this report describes experimental and numerical studies regarding an oxy-combustor for treating the exhaust gas of a 10 kW IGFC system anode.The applied simulation method was verified based on experiments,and the key performance indices of the combustor were studied under various conditions.It was determined that 315 K was the ideal condensation temperature to obtain flame stability.Under these pure oxygen flame burning conditions,CO was almost completely converted,and the dry mole fraction of CO_(2)after burning was C 0.958 when there was up to 5%excess O_(2).Overall,5%excess O_(2)was recommended to maximize CO_(2)capture and promote other environmental considerations.Additionally,the optimal tangential fuel jet angle to control the liner temperature was approximately 25°.The total fuel utilization had to be high enough to maintain the oxygen flame temperature of the anode exhaust gas below 1800 K to ensure that the system was environmentally friendly.The results presented herein have great value for designing IGFCs coupled with CO_(2)capture systems.

Carbon Dioxide Emission Control Measures in Coal-Fired Power Plant

CO2 （carbon dioxide） emission reduction, especially removal from coal-fired power plants has become the highest priority in measures to combat global warming. In China, coal-fired power is the main generating electricity style; more than 2,000 millions tons coal has been consumed in coal-fired power plants in China. In order to control CO2 emission, three technologies has been introduced, CCS （carbon capture and storage）, oxy-combusion, and IGCC （integrated gasification combined cycle）. CCS and IGCC technologies are expensive and need too many facilities; besides, there are some concrete problems need to resolve on the oxy-combustion technology. The energy saving work is the other pattern of CO2 emission control.

Experimental Investigation on Heat Transfer and Combustion of a Stirling Engine Combustor Fueled by Reformed Gas and Diesel Fuel

Thermochemical recuperation heat recovery is an advanced waste heat utilization technology that can effectively recover exhaust waste heat from oxy-fuel Stirling engines.The novel combustor of a Stirling engine with thermochemical recuperation heat recovery system is expected to utilize both reformed gas and diesel fuels as sources of combustion.In this research,the effects of various factors,including the H_(2)O addition,fuel distribution ratio(FDR),excess oxygen coefficient,and cyclone structure on the temperature distribution in the combustor,combustion emissions,and external combustion system efficiency of the Stirling engine were experimentally investigated.With the increase of steam-to-carbon ratio(S/C),the temperature difference between the upper and lower heating tubes reduces and the circumferential temperature fluctuation decreases,and the combustion of diesel and reformed gas remains close to complete combustion.At S/C=2,the external combustion efficiency is 80.6%,indicating a 1.6%decrease compared to conventional combustion.With the increase of FDR,the temperature uniformity of the heater tube is improved,and the CO and HC emissions decrease.However,the impact of the FDR on the maximum temperature difference and temperature fluctuation across the heater is insignificant.When the FDR rises from 21%to 38%,the external combustion efficiency increases from 87.4%to92.3%.The excess oxygen coefficient plays a secondary role in influencing temperature uniformity and temperature difference,and the reformed gas and diesel fuel can be burned efficiently at a low excess oxygen coefficient of 1.04.With an increase in the cyclone angle,the heater tube temperature increases,while the maximum temperature difference at the lower part decreases,and the temperature fluctuation increases.Simultaneously,the CO and HC emissions increase,and the external combustion efficiency experiences a decrease.A cyclone angle of 30°is found to be an appropriate value for achieving optimal mixing between reformed gas and diesel fuel.The research findings present valuable new insights that can be utilized to enhance the performance optimization of Stirling engines.