Flue Gas Flow Rate Research Articles

Hollow Fiber Membrane Contactors for Post-Combustion CO2Capture: A Scale-Up Study from Laboratory to Pilot Plant

Membrane contactors have been proposed for decades as a way to achieve intensified mass transfer processes. Post-combustion CO2 capture by absorption into a chemical solvent is one of the currently most intensively investigated topics in this area. Numerous studies have already been reported, unfortunately almost systematically on small, laboratory scale, modules. Given the level of flue gas flow rates which have to be treated for carbon capture applications, a consistent scale-up methodology is obviously needed for a rigorous engineering design. In this study, the possibilities and limitations of scale-up strategies for membrane contactors have been explored and will be discussed. Experiments (CO2 absorption from a gas mixture in a 30%wt MEA aqueous solution) have been performed both on mini-modules and at pilot-scale (10 m2 membrane contactor module) based on PTFE hollow fibers. The results have been modeled utilizing a resistance in series approach. The only adjustable parameter is in fitting the simulations to experimental data is the membrane mass transfer coefficient (km), which logically plays a key role. The difficulties and uncertainties associated with scaleup computations from lab scale to pilot-scale modules, with a particular emphasis on the km value, are presented and critically discussed.

Towards Ideal NOx and CO2 Emission Control Technology for Bio-Oils Combustion Energy System Using a Plasma-Chemical Hybrid Process

A pilot-scale low-emission boiler system consisting of a bio-fuel boiler and plasma-chemical hybrid NOx removal system is investigated. This system can achieve carbon neutrality because the bio-fuel boiler uses waste vegetable oil as one of the fuels. The plasma-chemical hybrid NOx removal system has two processes: NO oxidation by ozone produced from plasma ozonizers and NO2 removal using a Na2SO3 chemical scrubber. Test demonstrations of the system are carried out for mixed oils (mixture of A-heavy oil and waste vegetable oil). Stable combustion is achieved for the mixed oil (20 – 50% waste vegetable oil). Properties of flue gas—e.g., O2, CO2 and NOx—when firing mixed oils are nearly the same as those when firing heavy oil for an average flue gas flow rate of 1000 Nm3/h. NOx concentrations at the boiler outlet are 90 – 95 ppm. Furthermore, during a 300-min continuous operation when firing 20% mixed oil, NOx removal efficiency of more than 90% (less than 10 ppm NOx emission) is confirmed. In addition, the CO2 reduction when heavy oil is replaced with waste vegetable oil is estimated. The system comparison is described between the plasma-chemical hybrid NOx removal and the conventional technology.

Modeling of corona discharge combined with Mn2+ catalysis for the removal of SO2 from simulated flue gas

This study investigated a mass-transfer process of the removal of SO2 from simulated flue gas by corona discharge combined with Mn2+ catalysis in wet reactor, including gas migration, liquid phase diffusion, and chemical reaction. The novelty formula of desulphurization efficiency and the flow rate of flue gas, discharge voltage, reaction enhancement factor, and the flow rate of water were established. It is reported that desulphurization efficiency remarkably increased with the increasing of enhancement factor and discharge voltage at 4000mgm−3 of SO2 and 0.05m3s−1 of gas flow rate. However, the desulphurization efficiency had a slightly increase with the increasing of water flow rate. It is realizable that the energy consumption could be reduced to be lower than 0.3kJm−3, which was acceptable for industrial application. The experimental data were well in accord with the calculated results of theoretical model.

OAHT System Built and Off-Design Performance Analysis

Open cycle absorption heat transformer (OAHT) is built and the off-design performance is discussed with simulation method. Results show the COP changes little when parameters various. The COP increases and water recovery ratio decreases as the temperature and flow rate of flue gas or of cooling water increase. With the same heat flow ejecting, the system has more stable performance as the humidity of flue gas changes.

Numerical analysis of the combustion and fluid flow in a carbon monoxide boiler

Poor performance of a carbon monoxide (CO) boiler can have a detrimental influence on the operation and production of petrochemical industry, steel and iron industry and relevant industries. In this paper, the combustion and fluid flow in a carbon monoxide boiler is examined. Influences of some important parameters related to the geometry and operation of a CO boiler are discussed, including refractory thickness, insertion of an ellipsoidal cone, inlet air flowrate and inlet flue gas flowrate. It is found that when the refractory is thickened, the skin friction coefficient in the DeNOx section increases and arises later in the flow direction. Temperature and NO concentration increase in the DeNOx section and the larger the ellipsoidal cone angle is, the larger the skin friction coefficient will be. Compared with the original CO boiler, refractory thickening alleviates the temperature and NO rise in the DeNOx section. For moderate ellipsoidal cone angles, insertion of an ellipsoidal cone can alleviate the temperature rise in the DeNOx section and this leads to a lower NO emission. On the other hand, as the ellipsoidal cone angle becomes very large, the temperature rise in the DeNOx section is severer than for smaller ellipsoidal cone angles, leading to higher NO emission. A lower excess air flowrate can reduce the skin friction coefficient, NO formation and CO concentration, but the temperature increases. A higher flue gas flowrate can reduce the NO formation and the CO concentration, but the temperature and the skin friction coefficient increase. On the other hand, when the flue gas flowrate is reduced, the temperature and the skin friction coefficient decrease, but the NO formation and CO concentration in the product increase.

Dynamic Simulation of Post-Combustion Capture System

Post-combustion capture, as one of candidate technologies for carbon dioxide emission mitigation, has been employed in the chemical industry to separate CO2 from a gas mixture. However, the largest CO2 emission industry in China is the power industry, where CO2 is mainly released from coal-fired power plants. The study on the dynamic simulation of post-combustion capture system is indispensable for the future implementation of post-combustion capture system on coal-fired power plants, because the output of each coal-fired power plant is controlled by the grid and varies with time in China. Using DYNSIM software, we built a dynamic model for the typical post-combustion capture system, i.e. CO2 absorption/desorption process using aqueous MEA solution. A set of case studies were carried out to investigate the performance of post-combustion capture system. The simulation results show that the flow rate of flue gas and the flow rate of lean solution can greatly influent the stability and the capture ratio of a post- combustion capture system. Therefore, some special control strategies should be designed for them in order to keep the capture system running steadily.

Thermodynamic analysis of combined cycle gas turbine power plant with post-combustion CO2 capture and exhaust gas recirculation

Natural gas is expected to make up a significant proportion of the future global energy mix. Therefore, reducing greenhouse gas emissions from gas-fired processes is very essential for most countries, before emission reduction targets can be met. This article aims to carry out thermodynamic analysis of combined cycle gas turbine power plant with post-combustion CO2 capture through modelling and simulation. The combined cycle gas turbine power plant and the CO2 capture plant were simulated in Aspen Plus®. The combined cycle gas turbine power plant model was validated with simulation data from GateCycle® and the CO2 capture plant model was validated with experimental data from the pilot plant at the University of Texas at Austin. The CO2 capture plant was scaled up from pilot plant to commercial scale to process flue gas from a 250 MWe combined cycle gas turbine power plant. The integrated model for combined cycle gas turbine and CO2 capture plant was further used for performance study. Exhaust gas recirculation has been proposed to increase CO2 concentration in flue gas and reduce the flue gas flow rate. Its effect on combined cycle gas turbine power plant performance and capture plant sizing has been investigated. The analysis indicated that exhaust gas recirculation can reduce penalty on thermal efficiency without any major modification to the original power plant.

An experimental investigation on seawater SO2 scrubbing for marine application

A seawater spray scrubber was set up and tested with focus to desulfurization of marine engine exhaust gas. Experimental tests were carried out simulating typical exhaust conditions of a marine diesel engine burning heavy fuel oil and using real seawater. Different flue gas flow rates, seawater flow rates, and SO2 concentrations were tested. Liquid‐to‐gas ratios were in the range 1–10 × 10−3. A comparison between seawater and distilled water was also carried out to elucidate the effect of seawater alkalinity. In all conditions, the liquid phase was analyzed for alkalinity, pH, and sulfate content before and after the tests. Finally, the spray droplet size distribution was measured as a function of liquid flow rate.Experimental results indicated that seawater performed better than distilled water, by exploiting its inherent alkalinity. The desulfurization performance was improved by increasing the liquid flow rate and the gas residence time and by decreasing the SO2 concentration. SO2 capture efficiencies up to 93% were measured under the present operating conditions. The experimental data were further compared with calculations performed with an available model for SO2 absorption in fall‐down droplets within a simple plug‐flow reactor. Model calculations were carried out by using all parameters' values as measured in the present experimental campaign. Model results well fit the experimental data, even if a slight underestimation of the desulfurization efficiency is reported. The likely reasons are the assumed plug flow of gas as well as the neglected contribution to SO2 capture by water film falling at the wall. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 1179–1186, 2013

Experimental study on removal of NO using adsorption of activated carbon/reduction decomposition of microwave heating

Experimental studies were carried out on flue gas denitrification using activated carbon irradiated by microwave. The effects of microwave irradiation power (reaction temperature), the flow rate of flue gas, the concentration of NO and the flue gas coexisting compositions on the adsorption property of activated carbon and denitrification efficiency were investigated. The results show that: the higher of microwave power, the higher of denitrification efficiency; denitrification efficiency would be greater than 99% and adsorption capacity of NO is relatively stable after seven times regeneration if the microwave power is more than 420 W; adsorption capacity of NO in activated carbon bed is 33.24 mg/g when the space velocity reaches 980 per hour; adsorption capacity declines with increasing of the flow rate of flue gas; the change in denitrification efficiency is not obvious with increasing oxygen content in the flue gas; and the maximum adsorption capacity of NO was observed when moisture in flue gas was about 5.88%. However, the removal efficiency of NO reduces with increasing moisture, and adsorption capacity and removal efficiency of NO reduce with increasing of SO2 concentration in the flue gas.

Dynamic simulation of MEA absorption process for CO2 capture from power plants

Carbon dioxide (CO2) emissions reduction from combustion fossil fuel power plants is a key aspect in the stabilization of global climate change. Post-combustion CO2 capture from fossil fuel power plants using amine-based solvents, typically monoethanolamine (MEA), is one of the most promising technologies for the abatement of CO2 gas. In this work, a dynamic MEA absorption process model has been developed to predict the dynamic behaviour of the CO2 capture process. The resulting dynamic model was used to study the transient response of the MEA absorption process to changes in the flue gas flow rate and the reboiler heat duty. The changes in flue gas flow rate and reboiler heat duty are key process variables that affect the lean loading, liquid to gas ratio and percentage of CO2 removal. To represent the actual operation of a power plant, the dynamic response of the MEA absorption process to a sinusoidal change in the flue gas flow rate was also considered in the present analysis. The results show that the changes between the reboiler heat duty and CO2 removal follows a ratio of approximately 1:1.4. Also, the lean loading stream entering the absorber unit is key to maintain the feasible operation of the system. Moreover, the energy performance of the process (Joules per mole of CO2 captured) is directly affected by the operation of the reboiler. The outcomes from this study provide insights regarding the dynamic behaviour of this process and can be used as the basis to develop other aspects related to the dynamic operation of this plant, e.g., to develop control strategies for this system.

Study of an ammonia-based wet scrubbing process in a continuous flow system

A continuous gas and liquid flow, regenerative scrubbing process for CO2 capture was demonstrated at the bench-scale level. An aqueous ammonia-based solution captures CO2 from simulated flue gas in an absorber and releases a nearly pure stream of CO2 in the regenerator. After the regeneration, the solution of ammonium compounds is recycled to the absorber. The design of a continuous flow unit was based on earlier exploratory results from a semi-batch reactor, where a CO2 and N2 simulated flue gas mixture flowed through a well-mixed batch of ammonia-based solution. During the semi-batch tests, the solution was cycled between absorption and regeneration steps to measure the carrying capacity of the solution at various initial ammonia concentrations and temperatures. Consequentially, a series of tests were conducted on the continuous unit to observe the effect of various parameters on CO2 removal efficiency and regenerator effectiveness within the flow system. The parameters that were studied included absorber temperature, regenerator temperature, initial NH3 concentration, simulated flue gas flow rate, liquid solvent inventory in the flow system, and height of the packed-bed absorber. From this testing and subsequent testing, ammonia losses from both the absorption and regeneration steps were quantified, and attempts were made to maintain steady state during operations. Implications of experimental results with respect to process design are discussed.

Pilot plant study of four new solvents for post combustion carbon dioxide capture by reactive absorption and comparison to MEA

Reducing the solvent regeneration energy is one of the main challenges in CO2 capture from power plant flue gases. New tailored solvents are needed to achieve this goal. The present work describes tests of such new solvents in a gas-fired pilot plant which comprises the complete absorption/desorption process (column diameters 0.125m, absorber/desorber packing height 4.2/2.52m, flue gas flow 30–110kg/h, CO2 partial pressure 35–135mbar). Four new solvents are studied and compared to MEA. Two of the new solvents SOLVENT1 (0.25g/g N-methyldiethanolamine+0.15g/g N-methyl-1,3-propanediamine+0.6g/g H2O) and SOLVENT2 (0.25g/g 2-amino-2-methyl-1-propanol+0.15g/g N-methyl-1,3-propanediamine+0.6g/g H2O) are developed in an EU project; and two other solvents SOLVENT3 and SOLVENT4 are developed by BASF. The four new solvents and MEA are studied in the same way in the pilot plant and detailed results are reported for all solvents. The measurements are carried out at constant CO2 removal rate by an adjustment of regeneration energy in the desorber. The solvent flow rate is systematically varied. An optimal solvent flow rate leading to a minimum energy requirement is found from these studies. Direct comparisons of such results can suffer from differences in the kinetics of different solvent systems. These differences are experimentally studied by varying the flue gas flow rate at a constant ratio of solvent mass flow to flue gas mass flow and constant removal rate. Taking into account the results from these studies on kinetics allows a reasonable ranking of the solvents. The most promising of the studied solvents is SOLVENT4.

Hydrodynamics of a multistage wet scrubber incineration conditions

The objective of the study was to determine the hydrodynamics of the two stage counter-current cascade wet scrubbers used during incineration of medical waste. The dependence of the hydrodynamics on two main variables was studied: Inlet air flow rate and inlet liquid flow rate. This study introduces a new wet scrubber operating features, which are liquid accumulation, together with a detailed analysis of liquid-to-gas ratio and pressure drops. Liquid accumulation at the base of each scrubber helps to prevent the gas from short circuiting to the scrubber solution feed tanks. It was observed that liquid accumulation increases linearly with inlet scrubbing liquid flow rate beyond 0.2 L/s in the absence of flue gas flow. When flue gas is flowing into multistage wet scrubber the accumulation level increases abruptly starting from inlet scrubbing liquid of 0.45 L/s and stabilizes at accumulation level of 0.1 m beyond 0.75 L/s. Increasing the flue gas flow rate increases the minimum inlet scrubbing liquid flow rate at which initial accumulation was observed. The outlet scrubbing solution flow rate and liquid accumulation in the bottom of the scrubber increase as the inlet liquid flow rate increases. Beyond inlet liquid flow rate of 0.75 L/s, the outlet liquid flow rate does not increase any more, the wet scrubber enters flooding range, whereby, the volume of accumulated liquid increases faster with inlet scrubbing liquid flow rate. The maximum liquid-to-gas ratio was observed to be 1.9 L/m3 and the minimum liquid-to-gas ratio was 0.1 L/m3. Based on liquid accumulation and minimum flooding conditions, the operating liquid-to-gas ratio was recommended to be 0.6 to 1.9 L/m3, while the allowable inlet liquid flow rate ranged between 0.45 and 0.75 L/s, giving a constant accumulation of scrubbing liquid in the wet scrubber. The pressure drop across the wet scrubber remained constant at lower flow rate and increased linearly beyond Ug = 5 m/s. The maximum pressure drop of the multistage wet scrubber was 75 kPa. Key words: Wet scrubber, liquid accumulation, flooding, liquid-to-gas ratio, incineration, pressure drop

Group Separation of Water-soluble Organic Carbon Fractions in Ash Samples from a Coal Combustion Boiler

The chemical characterization of water-soluble organic carbon in ash emitted from a coal combustion boiler has not been reported yet. A total of 5 ash samples were collected from the outlet of an electrostatic precipitator in a commercial 500 ㎿ coal-fired power plant, with their chemical characteristics investigated. XAD7HP resin was used to quantify the hydrophilic and hydrophobic water-soluble organic carbons (WSOC), which are the fractions of WSOC that penetrate and remain on the resin column, respectively. Calibration results indicate that the hydrophilic fraction includes aliphatic dicarboxylic acids and carbonyls (＜4 carbons), amines and saccharides, while the hydrophobic fraction includes aliphatic dicarboxylic acids (＞4-5 carbons), phenols, aromatic acids, cyclic acid and humic acid. The average mass of the WSOC in the ash samples was found to depend on the bituminous coal type being burned, and ranged from 163 to 259 ㎍ C/g of ash, which corresponds to 59-96 ㎎ C of WSOC/㎏ of coal combusted. The WSOC mass accounted for 0.02-0.03 wt% of the used ash sample mass. Based on the flow rate of flue gas produced from the combustion of the blended coals in the 500 ㎿ coal combustion boiler, it was estimated that the WSOC particles were emitted to the atmosphere at flow rates of 4.6-7.2 g C/hr. The results also indicated that the hydrophilic WSOC fraction in the coal burned accounted for 64-82% of the total WSOC, which was 2-4 times greater than the mass of the hydrophobic WSOC fraction.

이산화탄소 5 ton/day 흡수분리 Pilot Plant 운전 특성

석탄화력 발전소의 연소 배가스를 시간당 1,000 <TEX>$Nm^3$</TEX>을 처리할 수 있는 이산화탄소 분리용 pilot plant를 설치하여 화학흡수제인 mono-ethanolamine(MEA)과 2-amino-2-methyl-1-propanol(AMP)를 이용해서 운전특성을 연소 배가스 유량과, 흡수용액 순환유량을 주 실험변수로 분석하였다. MEA 20 wt%를 기준으로 연소 배가스 유량이 100 <TEX>$m^3/hr$</TEX> 감소할수록 이산화탄소 제거율이 평균 6.7% 증가하였으며 흡수용액 순환유량이 1,000 kg/hr 증가에 따라 이산화탄소 제거율은 약 2.8% 상승하였고 <TEX>$110^{\circ}C$</TEX> 재가열기 온도에서 90% 이상의 이산화탄소 제거효율을 나타냈다. MEA가 AMP보다 높은 제거효율을 보였고 MEA(20 wt%) 실험에서 이산화탄소의 제거율이 75.5%인 ASPEN plus의 모사 결과보다 10% 높은 85.5%로 나타났다. The pilot scale experiments can handle the flue gas up to 1,000 <TEX>$Nm^3/hr$</TEX> for separation of carbon dioxide included in real flue gas at coal-fired power plant. The operational characteristics was analyzed with the main experimental variables such as flue gas flow rate, absorbent circulation rate using chemical absorbents mono-ethanolamine( MEA) and 2-amino-2-methyl-1-propanol(AMP). The more flue gas flow rate decreased in 100 <TEX>$m^3/hr$</TEX> in the MEA 20 wt% experiments, the more carbon dioxide removal efficiency was increased 6.7% on average. Carbon dioxide removal efficiency was increased approximately 2.8% according to raise of the 1,000 kg/hr absorbent circulation rate. It also was more than 90% at <TEX>$110^{\circ}C$</TEX> of re-boiler temperature. Carbon dioxide removal efficiency of the MEA was higher than that of the AMP. In the MEA(20 wt%) experiment, carbon dioxide removal efficiency(85.5%) was 10% higher than result(75.5%) of ASPEN plus simulation.

A Pulverized Coal-Fired Boiler Optimized for Oxyfuel Combustion Technology

This paper presents the results of a study on modifying a pulverized coal-fired steam boiler in a 250 MWe power plant for oxygen combustion conditions. The entry point of the study is a boiler that was designed for standard air combustion. It has been proven that simply substituting air by oxygen as an oxidizer is not sufficient for maintaining a satisfactory operating mode, not even with flue gas recycling. Boiler design optimization aggregating modifications to the boiler’s dimensions, heating surfaces and recycled flue gas flow rate, and specification of a flue gas recycling extraction point is therefore necessary in order to achieve suitable conditions for oxygen combustion. Attention is given to reducing boiler leakage, to which external pre-combustion coal drying makes a major contribution. The optimization is carried out with regard to an overall power plant conception for which a decrease in efficiency due to CO2 separation is formulated.

Post combustion CO2 capture by reactive absorption: Pilot plant description and results of systematic studies with MEA

Reactive absorption is one of the most promising technologies for post combustion CO2 capture (PCC). There is a need for methods and equipment that allow studying PCC efficiently on scales that are many orders of magnitude smaller than those of future installations in power plants. The present work describes in detail the set-up and operation of a pilot plant that is suited for that purpose. In that pilot plant the closed cycle of the absorption/desorption process is continuously operated (column diameters: 0.125m, absorber/desorber packing height: 4.2/2.5m, packing type: Sulzer Mellapak 250.Y™, flue gas flow rate: 30–110kg/h, CO2 partial pressure: 35–135mbar, solvent flow rate: 50–350kg/h). The plant is equipped with high-end measuring instrumentation and is operated using an automated process control system. Sampling points allow the determination of the liquid phase concentration profiles in both columns. Two reference experiments that were carried out with an aqueous solution of 0.3g/g monoethanolamine (MEA) are discussed in detail. The results give insight in the process behaviour in general and in the way such plants should be operated and how the evaluation of the results should be carried out. Based on comprehensive experimental studies with aqueous MEA solutions the influence of all important process parameters like CO2 partial pressure, CO2 removal rate, fluid dynamic load of the absorber, solvent flow rate, desorber pressure and solvent composition on the process behaviour is discussed in detail. These results allow a comprehensive understanding of the absorption/desorption process, which is important not only for the development of new tailor-made solvents but also for the design and operation of large scale plants. Furthermore the data establish a base line for comparisons with new solvents tested in the pilot plant and can be used for a validation of models of the PCC process with MEA.

순산소연소 조건에서 Drop tube furnace를 이용한 운전변수에 따른 석회석의 탈황특성 연구

순산소연소는 높은 연소 효율과 적은 배가스량, 낮은 질소산화물 농도를 장점으로 하고 있으며 연소온도 조절을 위한 배가스 재순환에 의해 배출되는 연소가스중의 <TEX>$CO_2$</TEX> 농도를 95%까지 농축이 가능하므로 석탄 연소설비에 대한 유망한 CCS 기술로 부각되고 있다. 본 연구는 순산소연소 조건에서 배가스의 재순환을 통한 <TEX>$CO_2$</TEX> 농도 증가에 기인하는 직접 황화반응이 탈황효율에 미치는 영향을 평가하고 반응온도, <TEX>$CO_2$</TEX> 농도, <TEX>$SO_2$</TEX> 농도상승이 <TEX>$SO_2$</TEX> 제거효율에 미치는 영향과 배가스 중 수분 등이 <TEX>$SO_2$</TEX> 제거효율에 미치는 영향을 실험적으로 고찰하였다. 반응온도 <TEX>$1,200^{\circ}C$</TEX>까지 온도 상승에 따라 <TEX>$SO_2$</TEX>의 제거효율은 증가하였고 Ca/S비, <TEX>$CO_2$</TEX> 농도와 수분이 증가할수록 <TEX>$SO_2$</TEX> 제거효율이 증가하였다. 이러한 운전변수는 영향인자 평가를 통하여 Ca/S 비>체류시간><TEX>$O_2$</TEX>농도>반응온도><TEX>$SO_2$</TEX>농도><TEX>$CO_2$</TEX>농도>수분농도의 순으로 탈황반응에 영향을 미치는 것으로 나타났다. 또한 운전변수별 실험결과를 이용하여 로내 건식탈황에 있어서 각 운전변수별 성능 영향인자를 평가할 수 있는 반경험적 모델식을 도출하였다. Oxy-fuel combustion with many advantages such as high combustion efficiency, low flue gas flow rate and low NOx emission has emerged as a promising CCS technology for coal combustion facilities. In this study, the effects of the direct sulfation reaction on <TEX>$SO_2$</TEX> removal efficiency were evaluated in a drop tube furnace under typical oxy-fuel combustion conditions represented by high concentrations of <TEX>$CO_2$</TEX> and <TEX>$SO_2$</TEX> formed by gas recirculation to control furnace combustion temperature. The effects of the operating parameters including the reaction temperature, <TEX>$CO_2$</TEX> concentration, <TEX>$SO_2$</TEX> concentration, Ca/S ratio and humidity on <TEX>$SO_2$</TEX> removal efficiency were investigated experimentally. <TEX>$SO_2$</TEX> removal efficiency increased with reaction temperature up to 1,200 due to promoted calcination of limestone reagent particles. And <TEX>$SO_2$</TEX> removal efficiency increased with <TEX>$SO_2$</TEX> concentrations and the humidity of the bulk gas. The increase of <TEX>$SO_2$</TEX> removal efficiency with <TEX>$CO_2$</TEX> concentrations showed that <TEX>$SO_2$</TEX> removal by limestone was mainly done by the direct sulfation reaction under oxy-fuel combustion conditions. From the impact assessment of operation parameters, it was shown that these parameters have an effects on the desulfurization reaction by the order of the Ca/S ratio > residence time > <TEX>$O_2$</TEX> concentration > reaction temperature > <TEX>$SO_2$</TEX> concentration > <TEX>$CO_2$</TEX> concentration > water vapor. The semi-empirical model equation for to evaluate the effect of the operating parameters on the performance of in-furnace desulfurization for oxy-fuel combustion was established.

Dynamic analysis of the absorption/desorption loop of a carbon capture plant using an object-oriented approach

Post-combustion capture of CO2 is regarded as a possible technology in order to reduce CO2 emission to the atmosphere. This paper provides a dynamic analysis of the absorption/desorption loop of a carbon capture plant with the help of a simulation model, built using the object-oriented Modelica Library Thermal Separation. The solvent used is an amino-acid salt.The dynamic behaviour is investigated for a reduction in regeneration heat flow rate but constant flue gas flow rate. Hereby four different control strategies are compared, one keeping the lean solvent loading constant, one keeping the solvent flow rate constant, one where flue gas bypasses the capture plant and a last one where an additional solvent tank is introduced. The simulation shows i.e. that for a constant lean solvent loading the response of the absorbed CO2 flow rate is much faster than for a constant solvent flow rate.Also the effect on the dynamic behaviour is investigated, comparing the whole cycle model to a stand-alone desorber model and to a stand-alone absorber model respectively. It was found that the dynamic responses on a short time scale are very similiar, but different on a long time scale.

Oxidation, reemission and mass distribution of mercury in bituminous coal-fired power plants with SCR, CS-ESP and wet FGD

Mercury (Hg) speciation variations in flue gas at the inlet and outlet of various air pollution control devices (APCDs) were studied, including a selective catalytic reactor (SCR), a cold side-electrostatic precipitator (CS-ESP), a wet flue gas desulfurization system (wet FGD) and the stack of bituminous coal-fired power plants. Effects of flue gas temperature, flow rate and selected flue gas components on Hg oxidation were also studied. The association of selected parameters on Hg0 oxidation and removal by the APCDs and the mass distribution of Hg within the system were estimated. Sampling and analysis were carried out using the Ontario Hydro Method. Solid and liquid samples were analyzed according to US EPA methods 7470A and 7471A, respectively. Hg concentration in the flue gas at the outlet boiler and stack ranged from 4.70 to 27.3μg/Sm3 and 3.1 to 0.48μg/Sm3, respectively. The overall Hg removal efficiency in the APCDs ranged from 43.8% to 94.9%, and oxidized Hg in flue gas decreased with increasing temperature. With an increase in HCl concentration, a decrease in flue gas flow rate and decreasing temperature, oxidation of elemental Hg in combustion flue gas increased. The effects of SOx and NOx concentrations on elemental Hg oxidation in flue gas were rather complex. Among the parameters studied, the most significant parameters affecting overall Hg removal in the APCDs, in order, were removal in the ESP, oxidation in the SCR system and removal in the wet FGD. Experimental data and statistical analysis confirmed the promotion of a co-beneficial control of Hg in the SCR, CS-ESP and wet FGD configurations. The mass distribution showed that 43.0% of Hg was collected in ESP fly ash, 49.4% in wet FGD by-products and effluents, 3.9% of Hg was removed in boiler bottom ash and 3.7% was released into the atmosphere. In the SCR+CS-ESP+wet FGD configuration, a major portion of Hg was distributed into the by-products and removed by the APCDs compared to the lower removal levels seen in the CS-ESP+wet FGD configuration.