查看更多>>摘要：Abstract A numerical model of a 75 t/h gas‐fired boiler burning blast furnace gas (BFG) and coke oven gas (COG) was developed to study the effect of O2/CO2 conditions on the combustion characteristics, verified by comparing with the results measured in field experiments. The results showed that the ignition distance of COG was shorter than that of BFG, and COG reached the stable combustion temperature of 1000 K earlier in the condition of O2/CO2 combustion with 31% O2 than in the condition of air combustion. Under different O2/CO2 conditions, the overall temperature of gas‐fired boiler decreased. The maximum temperature of air combustion, O2/CO2 combustion with 26% O2, and O2/CO2 combustion with 31% O2 were 1867, 1678, and 1834 K, respectively. Under the condition of O2/CO2 combustion, the radiation heat transfer of mixed gas was enhanced, and the overall heat flux was obviously improved. Under the O2/CO2 condition, the overall temperature was lower than that of air combustion, but the wall heat flux increased. The NOx production decreased after the change to O2/CO2 combustion, and the NOx generation at the furnace arch decreased from 70.28?mg/m3 to 6.94?mg/m3 under the condition of O2/CO2 combustion with 26% O2. ? 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.
查看更多>>摘要：Abstract This paper presents an investigation on simultaneous freshwater production and CO2 capture using the flue gases of a 500 MWe coal‐fired power plant. Generally, a fan/cooler is used to reduce the temperature of flue gas before flowing into the absorber column of a CO2 capture unit. It has been replaced with a heat exchanger in this study. Seawater and flue gas were passed through the heat exchanger to raise the temperature of seawater and reduce the temperature of flue gas. The high‐temperature seawater was subsequently fed into a membrane distillation (MD) unit for freshwater production. The cold flue gas was directed to the CO2 capture unit. The heat exchanger and CO2 capture unit were modeled with Aspen Plus software. Whereas MATLAB software was used to develop and solve the MD mathematical model software for freshwater production. The seawater flow rate was varied from 4000 L/min to 7000 L/min in the heat exchanger. As a result, the flue gas (flow rate 781.6 t/h) and the outlet seawater temperatures were reduced from 27.498 to 22.360°C and 73.384 to 52.670°C, respectively. However, higher inlet seawater temperature in the MD unit produced more freshwater. An increase in inlet seawater feed temperature in the MD unit from 52.670 to 73.384°C increased the freshwater production from 211,956.5 to 299,244 L/day. Furthermore, the CO2 capture process has been analyzed by varying the methyldiethanolamine (MDEA) and piperazine (PZ) concentrations in weight% (45 and 5, 40 and 10, 35 and 15, and 30 and 20, respectively). It was observed that the energy requirement reduced from 3.55 to 3.26?MJ/kg CO2 by increasing the PZ content from 5 to 20?wt.%. At 15 and 20?wt.% of PZ content in the blended solution of MDEA/PZ, the energy required to regenerate the solvent was 3.31 and 3.26?MJ/kg CO2, respectively. PZ emissions from the absorber were also increased with the raising of PZ content in the blended solution. The energy requirement was not much higher at 15?wt.% than 20?wt.%. Therefore, MDEA/PZ solution (15/35?wt.%) was considered an optimal concentration. The reboiler duty was reduced up to 3.25?MJ/kg CO2 at 15/35?wt.% concentration with stripper pressure of 2.3?bar. ? 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.
查看更多>>摘要：Abstract While nonaqueous organic‐amine absorbents have great potential in reducing energy consumption of CO2 capture, their absorption/desorption behaviors are still poorly understood when high‐concentration polyamines are used. On the other hand, large scale CO2 capture demands the use of high‐concentration polyamines absorbents. Therefore, we investigated the absorption and microwave regeneration behavior of high‐concentration triethylenetetramine (TETA) in three typical organic solvents, including polyethylene glycol 200 (PEG200), diethylene glycol (DEG), and ethylene glycol (EG). The results showed that high‐concentration TETA nonaqueous absorbents demonstrate advantages in absorption rate and regeneration energy consumption. The average absorption rate of 2.0 and 5.0?mol/L TETA/EG was 2.84 and 4.70 times that of 0.6?mol/L, respectively. The energy consumption of TETA/EG and TETA/DEG decreased by 29.4 and 25.6% as the concentration increased from 0.6 to 5.0?mol/L. In addition, the high‐concentration TETA/PEG200 absorbent demonstrated observable tolerance for water vapor, which usually exists in flue gas. Results also showed that microwave regeneration was superior to conventional conduction heating especially when high‐concentration TETA/PEG200 absorbent were used. The energy consumption of microwave regeneration of the absorbent with a concentration of 0.6, 2.0, and 5.0?mol/L was reduced by 65.9, 81.2, and 86.0%, respectively when compared with conduction heating. ? 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.
查看更多>>摘要：Abstract In this work, the high‐pressure methane adsorption/desorption tests were conducted in four coal samples (from low‐rank bituminous coal to anthracite) under different temperature and pressure conditions to reveal the mechanism of desorption hysteresis effect in the deep‐buried coal seams. The experimental and fitting results show that the presence of free methane molecules in the adsorption phase results in an obvious difference between the measured methane adsorption amount with the actual adsorption capacity. The Langmuir, Langmuir–Freundlich (L–F) and Dubinin–Astakhov (D–A) models have their own advantages and disadvantages in fitting the experimental adsorption/desorption data. As residual adsorption capacity C fitted by the D–A model would be negative at high temperatures and lose the meaning of the constant, the Langmuir model is more suitable to describe methane desorption process. The residual adsorption capacity fitted by Langmuir model tended to decrease as the temperature increased until it is almost completely desorbed at 373 K. Meanwhile, because the adsorption sites with lower energy are gradually occupied by methane molecules in the high‐pressure stage, intermolecular forces increased and methane molecules are more easily desorbed. Therefore, the desorption hysteresis coefficient trends to increase exponentially with the decrease of pressure and temperature, which indicated that the original gas content of the coal seams may decrease with the increase of the burial depth, but the risk of coal and gas outburst accidents may increase. ? 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.
查看更多>>摘要：Abstract Carbon capture technologies have been recognized as a potential alternative to alleviate global warming. Carbon capture and storage (CCS) is preferred over carbon conversion and utilization (CCU) due to its lower operating costs and higher CO2 reduction capability. Nevertheless, CO2 utilization has the potential to be more economical if value‐added products are produced. This highlights the importance of assessing CO2 utilization routes and alternatives in carbon management. This review paper aims to evaluate the carbon utilization potential of major CO2‐capturing absorbents including amine, hydroxide, ionic liquid, amino acids and carbonate absorbents. All absorbents show potential application for CO2 utilization except for ionic liquids (ILs) due to their unclear CO2 capture mechanisms. Absorbents that require a desorption process for CO2 utilization include MEA, MDEA, K2CO3 and Na2CO3 due to their high absorption capacity. Industries have utilized the desorbed CO2 as chemical feedstocks, enhanced oil recovery (EOR) and mineral carbonation. For hydroxide absorbents and CaCO3, desorption of CO2 is unnecessary as the absorbed CO2 can be directly utilized to produce construction materials. Apart from that, the incorporation of advanced technologies and business models introduced by the fourth industrial revolution are plausible considerations to accelerate the development of carbon capture technologies. ? 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.
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