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Flow properties of solids in an inclined standpipe were investigated while the solid particle was fed to the bottom of a bubbling fluidized bed (diameter 0.1m, 1.34m tall) via the standpipe and discharged out of the bed through the overflow exit. A group of K-based CO adsorbent particles was used as solids. The pressure drop of the fluidized bed, the height of solids bed in the standpipe, and flow rate of gas bypassing the fluidized bed through the standpipe were measured at room temperature and pressure as varying the fluidizing gas velocity, solids flow rate, and height of the overflow exit of fluidized solids. The pressure drop of the fluidized bed, the height of the solids bed in the standpipe, and the ratio of gas bypassing through the standpipe to the total gas in flow rate decreased with increasing the fluidizing gas velocity. Both the pressure drop of the fluidized bed and the height of the solids bed in the standpipe increased a little with the solids feed rate. The effect of the solids feed rate on the flow rate of gas bypassing through the standpipe could be ignored. The pressure drop of the fluidized bed and the height of the solids bed in the standpipe increased as the height of the overflow exit for solids increased in the fluidized bed. However, the effect of the height of the overflow exit on the flow rate of gas bypassing through the standpipe was negligible. Correlations on the pressure drop of the fluidized bed, the height of the solids bed in the standpipe, and the flow rate of gas bypassing through the standpipe were proposed successfully. [ABSTRACT FROM AUTHOR]

Effects of temperature on pressure drop across a riser due to solids holdup in the riser of a circulating fluidized bed (CFB) were investigated at the atmospheric pressure condition. The bed material was a group of sorbent particles and the experimental variables included temperature, gas velocity, and solids flux in the riser. With gas velocity and solids flux held constant, the riser pressure drop decreased as temperature increased. However, temperature effects decreased with increase in gas velocity. The effects of temperature on riser pressure drop were confirmed qualitatively by the same effects on the average ratio of gravity to drag force on a single spherical particle while the particle was accelerated. The pressure drop across the riser increased almost linearly with the ratio of solids flux to gas flux at the given gas velocity. Because gas momentum per unit mass of gas transferred to solids increased, the slope of the linear relationship decreased as temperature increased. This result confirmed the validity of the concept of momentum transfer from gas to particles at high temperature, proposed at ambient temperature in the prior study. The amount of gas momentum per unit mass of gas available to carry over the solid particles was finite; thus as the solids flux increased at the given gas velocity, the gas momentum shared to the unit mass of solids decreased and the mean residence time of solids in the riser, i.e., the pressure drop across the riser increased linearly. The slope of the linear relationship was proportional to the ratio of momentum flux by gravity and buoyancy forces on solids to gas momentum per unit mass of gas by drag force transferred to solids. Correlations were proposed to predict effects of temperature on the pressure drop across the riser and the solids flux in the riser within the range of experimental conditions. [ABSTRACT FROM AUTHOR]

Korea Institute of Energy Research (KIER) and Korea Electric Power Corporation Research Institute (KEPCORI) have been developing a CO capture technology using dry sorbents. In this study, KEP-CO2P1, a potassium-based dry sorbent manufactured by a spray-drying method, was used. We employed a bench-scale dry-sorbent CO capture fluidized-bed process capable of capturing 0.5 ton CO/day at most. We investigated the sorbent performance in continuous operation mode with solid circulation between a fast fluidized-bed-type carbonator and a bubbling fluidized-bed-type regenerator. We used a slip stream of a real flue gas from 2MWe coal-fired circulating fluidized-bed (CFB) power facilities installed at KIER. Throughout more than 50 hours of continuous operation, the temperature of the carbonator was maintained around 70-80 °C using a jacket-type heat exchanger, while that of the regenerator was kept above 180 °C using an electric furnace. The differential pressure of both the carbonator and regenerator was maintained at a stable level. The maximum CO removal was greater than 90%, and the average CO removal was about 83% during 50 hours of continuous operation. [ABSTRACT FROM AUTHOR]

There are corrosive gases such as HS and HCl in a coal- or biomass-derived syngas. HCl can be removed by NaCO or KCO at hot temperatures. Hot syngas cleaning has the advantage of improving thermal efficiency. We investigated HCl removal by spray-dried potassium-based solid sorbents which were originally developed for post-combustion CO capture. Both fresh and spent CO sorbents were tested to confirm the applicability as a sorbent for HCl cleaning. Saturation chlorine sorption capacity was measured using a fixed-bed reactor at a temperatures of 300-500 °C under an ambient pressure. Both fresh and spent CO sorbents showed saturation chlorine sorption capacity above 15 wt%. HCl removal performance of the sorbents was investigated in a micro fluidized-bed reactor and a bench-scale bubbling fluidized-bed reactor. HCl concentration was lowered from 150-900 ppmv to less than 5 ppmv and from 130-390 ppmv to less than 1 ppmv in a micro fluidized-bed reactor and in a bench-scale bubbling fluidized-bed reactor, respectively, at 300-540 °C and 20 bar. It could be concluded that both fresh and spent spray-dried potassium-based CO sorbents could be utilized as a disposable HCl sorbent for hot syngas cleaning. [ABSTRACT FROM AUTHOR]

Solids circulation rate and static bed height in the riser of a circulating fluidized bed (CFB) process, which consisted of a riser and two bubbling-beds, were investigated and discussed at ambient temperature and pressure. Three kinds of powder (FCC catalyst, glass bead, plastic powder) were used as bed materials. The static bed height in the riser increased with the solids circulation rate. However, it decreased with an increase of gas velocity. The effect of gas velocity diminished as the gas velocity increased. The riser static bed height could be used to estimate the solids circulation rate in reasonable accuracy. A correlation on static bed height in the riser, relating to the solids circulation rate, was proposed for the present experimental ranges. [ABSTRACT FROM AUTHOR]

We simulated a bubbling bed process capturing CO from flue gas. It applied for a laboratory scale process to investigate effects of operating parameters on capture efficiency. The adsorber temperature had a stronger effect than the regenerator temperature. The effect of regenerator temperature was minor for high adsorber temperature. The effect of regenerator temperature decreased to level off for the temperature >250 °C. The capture efficiency was rather dominated by the adsorption reaction than the regeneration reaction. The effect of gas velocity was as appreciable as that of adsorber temperature. The capture efficiency increased with the solids circulation rate since it was ruled by the molar ratio of K to CO for solids circulation smaller than the minimum required one (G). However, it leveled off for solids circulation rate >G. As the ratio of adsorber solids inventory to the total solids inventory (x) increased, the capture efficiency increased until x=0.705, but decreased for x>0.705 because the regeneration time decreased too small. It revealed that the regeneration reaction was faster than the adsorption reaction. Increase of total solids inventory is a good way to get further increase in capture efficiency. [ABSTRACT FROM AUTHOR]

A coal gasification pilot plant operation with hot fuel gas desulfurization (HGD) was performed taking two coals (Indonesian ABK and MSJ) that differ in their carbon and sulfur contents. A dry-feeding entrained-bed type gasifier was used for gasification with oxygen and capable of operating at 30 bar pressure and 1,550 °C. The HGD unit consisted of a transport desulfurizer, a bubbling regenerator and a multi-cyclone. Attention was focused on attaining high carbon conversion and cold gas efficiency in the entrained bed reactor and the sulfur removal efficiency of the hot fuel gas desulfurization unit. The optimum conditions for achieving high performance of the operation are reported. [ABSTRACT FROM AUTHOR]

A bench-scale continuous hot gas desulfurization system using Zn-based solid sorbents was developed to remove HS and COS simultaneously in a 110 Nm/h of real coal-gasified syngas. The bench-scale unit, which consisted of a fast fluidized-bed type desulfurizer and a bubbling fluidized-bed type regenerator, was integrated with a 3 ton/day-scale coal gasifier installed at the Institute for Advanced Engineering. The solid sorbents, which consisted of 50 wt% of ZnO for sulfides sorption and 50 wt% of supporters for mechanical strength, were manufactured by a spray drying method and supplied by Korea Electric Power Corporation Research Institute. The bench-scale unit was designed to operate at the high temperature of above 500 °C and the high pressure of 19 kg/cm gauge. Integration of the bench-scale unit with a coal gasifier was first performed to investigate the operation stability of the integrated system. And the long-term continuous operation above 30 h was performed to analyze the desulfurization performance of the bench-scale unit. The concentration of both HS and COS in the syngas was measured by a continuous UV gas analyzer and an online gas chromatograph and that of both HS and COS after desulfurization was measured by an online gas chromatograph. Through the above 30-h continuous operation, the sulfur removal reached up to 99.9%. [ABSTRACT FROM AUTHOR]

The effect of CO or steam partial pressure in the regeneration of CO solid sorbents was studied in the two-interconnected bubbling fluidized-beds system. Potassium-based dry solid sorbents, which consisted of 35 wt% KCO for CO sorption and 65 wt% supporters for mechanical strength, were used. To investigate the CO capture efficiency of the regenerated sorbent after the saturated sorbent was regenerated according to the CO or steam partial pressure in the regeneration, the mole percentage of CO in the regeneration gas was varied from 0 to 50 vol% with N balance and that of steam was varied from 0 to 100 vol% with N balance, respectively. The CO capture efficiency for each experimental condition was investigated for one hour steady-state operation with continuous solid circulation between a carbonator and a regenerator. The CO capture efficiency decreased as the partial pressure of CO in the fluidization gas of the regenerator increased, while it increased as that of steam increased. When 100 vol% of steam was used as the fluidization gas of the regenerator, the CO capture efficiency reached up to 97% and the recovered CO concentration in the regenerator was around 95 vol%. Those results were verified during 10-hour continuous experiment. [ABSTRACT FROM AUTHOR]

simplified model has been developed to investigate effects of important operating parameters on performance of an entrained-bed absorber and bubbling-bed regenerator system collecting CO from flue gas. The particle population balance was considered together with chemical reaction to determine the extent of conversion in both absorber and regenerator. The calculated CO capture efficiency agreed with the measured value reasonably well. Effects of absorber parameters - temperature, gas velocity, static bed height, moisture content of feed gas on CO capture efficiency - have been investigated in a laboratory scale process. The CO capture efficiency decreased as temperature or gas velocity increased. However, it increased with static bed height or moisture concentration. The CO capture efficiency was exponentially proportional to each parameter. Based on the absolute value of exponent of the parameter, the effect of gas velocity, static bed height, and moisture content was one-half, one-third, and one-fourth as strong as that of temperature, respectively. [ABSTRACT FROM AUTHOR]

The effect of bed height on CO2 capture was investigated by carbonation/regeneration cyclic operations using a bubbling fluidized bed reactor. We used a potassium-based solid sorbent, SorbKX35T5 which was manufactured by the Korea Electric Power Research Institute. The sorbent consists of 35% K2CO3 for absorption and 65% supporters for mechanical strength. We used a fluidized bed reactor with an inner diameter of 0.05 m and a height of 0.8 m which was made of quartz and placed inside of a furnace. The operating temperatures were fixed at 70 °C and 150 °C for carbonation and regeneration, respectively. The carbonation/regeneration cyclic operations were performed three times at four different L/D (length vs diameter) ratios such as one, two, three, and four. The amount of CO2 captured was the most when L/D ratio was one, while the period of maintaining 100% CO2 removal was the longest as 6 minutes when L/D ratio was three. At each cycle, CO2 sorption capacity (g CO2/g sorbent) was decreased as L/D ratio was increased. The results obtained in this study can be applied to design and operate a large scale CO2 capture process composed of two fluidized bed reactors. [ABSTRACT FROM AUTHOR]

Two-interconnected fluidized bed systems are widely used in various processes such as Fisher-Tropsch, hot gas desulfurization, CO2 capture-regeneration with dry sorbent, chemical-looping combustion, sorption-enhanced steam methane reforming, chemical-looping hydrogen generation system, and so on. However, conventional two-interconnected fluidized bed systems are very complex, large, and difficult to operate because most of these systems require a riser and/or pneumatic transport line for solid conveying and loopseals or seal-pots for gas sealing, recirculation of solids to the riser, and maintaining of pressure balance. To solve these problems, a novel two-interconnected fluidized bed system has been developed. This system has two bubbling beds, solid injection nozzles, solid conveying lines, and downcomers. In this study, the effects of operating variables on solid circulation rate and gas leakage between two beds have been investigated in a cold mode two-interconnected fluidized bed system. The solid circulation rate increased as the hole diameter on the injection nozzle, the diameter of the injection nozzle, the solid height above the holes, and the number of holes on the injection nozzle increased. The gas leakage between the beds was negligible. Moreover, long-term operation of continuous solid circulation up to 60 hours was performed to check the feasibility of stable operation. The pressure drop profiles in the system loop were maintained steadily and solid circulation was smooth and stable. [ABSTRACT FROM AUTHOR]

A bubbling fluidized bed reactor was used to study CO2 capture from flue gas by using a potassium-based solid sorbent, sorbKX35 which was manufactured by the Korea Electric Power Research Institute. A dry sorbent, sorbKX35, consists of K2CO3 for absorption and supporters for mechanical strength. To increase initial CO2 removal, some amount of H2O was absorbed in the sorbent before injecting simulated flue gas. It was possible to achieve 100% CO2 removal for more than 10 minutes at 60°C and a residence time of 2 s with H2O pretreatment. When H2O pretreatment time was long enough to convert K2CO3 of sorbKX35 into K2CO3 · 1.5H2O, CO2 removal was excellent. The results obtained in this study can be used as basic data for designing and operating a large scale CO2 capture process with two fluidized bed reactors. [ABSTRACT FROM AUTHOR]

To investigate the feasibility of a chemical-looping hydrogen generation system, we investigated the reduction and water splitting reaction characteristics for three mediators and two reducing gas in a bubbling fluidized bed reactor (0.02 m I.D.). For three oxygen carrier particles (NiO/bentonite, Fe2O3/bentonite, (NiO:Fe2O3)/bentonite), hydrogen was used as a reduction gas and water was used as an oxidation gas. For (NiO: Fe2O3)/bentonite particle, carbon monoxide, which is the main component in the syngas from coal or heavy residue, was used as a reducing gas to check reactivity for the carbon containing fuels and carbon deposition characteristics. Based on the reactivity tests, (NiO: Fe2O3)/bentonite particle was selected as the best mediator for the chemical-looping hydrogen generation system to achieve stable continuous operation. [ABSTRACT FROM AUTHOR]

Hot Gas Desulfurizarion for IGCC is a new method to efficiently remove H2S in fuel gas with regenerable sorbents at high temperature and high-pressure conditions. The Korea Institute of Energy Research did operation of sulfidation in a desulfurizer and regeneration in a regenerator simultaneously at high pressure and high temperature conditions. The H2S concentration at exit was maintained continuously below 50ppmv at 11,000 ppmv of inlet H2S concentration. The sorbent had little effect on the reducing power in the inlet gas in the range from 11% to 33% of H2. As inlet H2S concentration was increased, H2S concentration in the product gas was also increased linearly. The sorbent was maintained at low sulfur level by the continuous regeneration and the continuous solid circulation at the rate of 1.58× 10−3 kg/s with little mean particle size change. [ABSTRACT FROM AUTHOR]