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The overall corrosion behavior of S304 stainless steel and A3 carbon steel in 30 wt.% MEA (monoethanolamine) and AMP/MEA (2‐amino‐2‐methyl‐1‐propanol / monoethanolamine) blended amine solutions at 40–100°C was investigated. The characterization analysis of the corroded material surfaces was performed, and the changes in the properties of both solvents after long‐term immersion corrosion were measured, including the accumulation of heat stable salts (HSS) and viscosity changes. The results of the long‐term immersion corrosion experiments showed that the corrosion rate of S304 stainless steel was significantly lower than that of A3 carbon steel in both amine solutions. However, the corrosion rate of both materials exhibited a similar trend, initially decreasing and then stabilizing over time. Due to the higher concentration of carbonate ions in the AMP/MEA system, it exhibited better overall corrosion resistance and degradation resistance compared to the MEA system. The main component of the corrosion product on carbon steel was identified as Fe2(OH)2CO3. The electrochemical test results showed that the corrosion current of S304 stainless steel was much smaller than that of A3 carbon steel, and its charge transfer resistance was much higher, indicating that it was less prone to electron loss in the organic amine solutions. Additionally, the AMP/MEA system exhibited superior corrosion resistance. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The industrial application of emerging water‐lean solvents to CO2 capture from flue gas is challenged by their high viscosity. In this work, we report a novel water‐lean CO2 solvent which possesses lower viscosity and higher CO2 cyclic capacity than other water‐lean solvents reported in the literature. The new solvent consists of N, N‐dimethyl‐1, 2‐ethanediamine (DMEDA), physical cosolvent N‐methyl‐2‐pyrrolidone (NMP) and up to 15% water (named ENH). We evaluated the effect of the solvent composition on the viscosity, CO2 cyclic capacity and regeneration energy of ENH and compared it with the reference monoethanolamine (MEA) based solvents. It was found that ENH containing 5% H2O (ENH‐5%H2O) with a CO2 loading of 0.767 mol CO2·mol amine–1 had a viscosity of 7.603 mPa·S at 40 ˚C, which was comparable with that of traditional blended amines. Excellent cyclic capacity performance was also observed, with ENH‐5% H2O showing a 140% improvement compared to aqueous MEA. Regeneration energy of ENH‐5% H2O was estimated to be 2.418 GJ·tCO2–1 which is 36% lower than the 30 wt. % aqueous MEA solvent. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

To reveal the effect mechanism of CO atmosphere on coal pyrolysis, a study on raw and demineralized lignite was carried out in a horizontal tube furnace under N2 and CO/N2 atmosphere. CO had a negligible effect on the char yield at low temperatures, whereas it enhances the char yield at temperatures higher than 550 °C. The release of tar was higher in the presence of CO above 450 °C because of more free radicals, which reduced low‐temperature crosslinking, and higher selectivity of hydroxyl groups to phenols in the CO‐containing atmosphere. The yields of CO2 and H2 increased, water and CO yields decreased under CO/N2 atmosphere. Light hydrocarbon gases were not affected by changing the reaction atmosphere. The difference between product yields from raw and demineralized coal confirmed that the catalysis of inherent minerals had a great catalytic effect on the water‐gas shift reaction and Boudouard reaction. [ABSTRACT FROM AUTHOR]

Steady‐state process simulation and techno‐economic analysis of a pyrolysis‐based coal staged conversion polygeneration (CSCP) plant, integrated with wastewater biochemical treatment after phenol‐ammonia recovery, are studied using Aspen Plus software. Appropriate models for the proposed system are set up in detail. Furthermore, by optimization of a methanation unit, a conventional supercritical circulating fluidized bed (SCCFB) power plant with the same capacity is chosen for comparison. Simulation results reveal that system energy and exergy efficiency of the CSCP system can reach much higher values than those of a conventional SCCFB power plant. In conclusion, a CSCP plant will have practical and economic advantages in the near future. A coal staged conversion polygeneration plant for the coproduction of coal gas, tar, and electricity power, integrated with wastewater biochemical treatment after phenol‐ammonia recovery, is proposed and simulated. Appropriate models for the proposed system are assessed. Such kind of plant exhibits practical and economic advantages, with excellent values of system energy and exergy efficiency. [ABSTRACT FROM AUTHOR]

The kinetic and thermodynamic studies of CO2 adsorption on activated carbon were carried out in a fixed bed. Six different CO2 concentrations (from 5% up to 18 vol.%) and four temperatures (303 K, 313 K, 323 K, and 333 K) were applied to investigate dynamic adsorption behaviors. It showed that the increase in temperature led to faster adsorption kinetics, but also reduced the adsorption capacity. An isotherms modeling was made by the Langmuir isotherm model. The experimental isotherms data were well fitted. Then, based on the adsorption isotherms, the isosteric heats of CO2 adsorption were determined by Clausius-Clapeyron equation. The calculated isosteric heat declined slightly with the adsorbed amount on activated carbon, and had an average value of 16.09 kJ/mol, which is much lower than the actual heat of adsorption measured by calorimeter. Moreover, regeneration experiments by vacuum evacuation (<10 kPa) were conducted to assess the regeneration efficiency (RE) of activated carbon. Regeneration efficiency increased with the reduction of vacuum pressure and reached over 90% at the vacuum of 4 kPa. A temperature swing integrated into the vacuum evacuation process resulted in a remarkable increase of RE with an increase in regeneration temperature, which confirmed the favorable effect of temperature on regeneration of activated carbon and providing almost full regeneration. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

The structural characteristics and reactivity of char derived from lignite were studied to explore the mechanism of char gasification and existence of a maximum reaction rate under an atmosphere of CO2 and H2O in a pressured thermogravimetric analyzer system. Gasification was carried out at temperatures of 1123, 1173, and 1223 K. When the temperature was below 1173 K, the mechanism of char gasification in the mixture of H2O and CO2 proceeded through the separate active sites assumption, whereas if the temperature was higher than 1173 K, it favored common active sites. The reaction rate increased and then decreased during the remaining time, which was in agreement with the total surface area. The existence of a maximum reaction rate depended highly on the surface area: a larger surface area resulted in a higher reaction rate. The total surface in H2O was the largest and the addition of CO2 inhibited the formation of pores. The reaction of char with CO2 mainly took place on the microporous surface first, and then took place on a mesoporous surface, and the reaction of char with H2O took place on both the micro- and mesoporous surfaces simultaneously. [ABSTRACT FROM AUTHOR]

Coal chars are usually produced under complex atmospheres in industrial production. However, most of the research about char characteristics and gasification reactivity uses the coal char samples prepared under an inert atmosphere. In this study, the influences of the pyrolysis atmosphere and temperature on coal char characteristics and gasification reactivity were investigated. A Shanxi bituminous coal was pyrolyzed in a bubbling fluidized bed to produce char samples. A mixture of hydrogen (H2), carbon dioxide (CO2), carbon monoxide (CO), and methane (CH4) was used as simulated pyrolysis gas (SPG). The coal was pyrolyzed in the SPG and N2 atmospheres, respectively. SEM, Raman spectroscopy, and FTIR spectroscopy were used to study the influences of the pyrolysis atmosphere and temperature on the coal char characteristics. The char-H2O and char-CO2 gasification reactivities were measured by using a modified thermogravimetric analysis (TGA) system. The experimental results indicate that the SPG atmosphere has no obvious influence on the coal char morphology, but it has significant influences on the carbon structures and surface chemical groups. The SPG char samples have lower gasification reactivity. The disproportionation reaction of CO, the decomposition reaction of CH4, and the loss of oxygen-containing structures induced by H2 lead to a higher-ordered degree of char, and the graphite generated from the disproportionation reaction and the decomposition reaction can decrease the specific surface area of the coal char. These two reasons result in the lower gasification reactivity of SPG char. [ABSTRACT FROM AUTHOR]

Scrubbing CO2 directly from the ambient air (air capture) by sorbent is an emerging technology to address climate change due to anthropic emission of greenhouse gases. A good understanding of thermodynamics and reaction kinetics under ultra-low CO2 concentration and variable humidity is fundamental to the design of economic air capture. In this study, the adsorption kinetics of a novel moisture swing process for air capture is characterized. The variation of humidity alters not only the adsorption equilibrium but also the adsorption kinetics, due to a water involved chemical reaction. A heterogeneously structured sorbent sheet with strong based ion exchange resin inside as active constituent is employed to capture the atmospheric CO2 under different humidity. Traditional shrinking core model (SCM) is modified to reveal the mass transfer resistance inside of the sorbent for CO2 adsorption under ultra-low CO2 concentration. The modified SCM reveals that, at most cases, the adsorption kinetics is controlled by diffusion inside of the sorbent particle. A transition from physical diffusion controlled kinetics to chemical reaction controlled kinetics is observed as humidity increases. Further kinetic analysis suggests that, among the optimization technologies such as seeking functional group with faster chemical reaction or fabricating thinner support layer, preparing sorbent particle with smaller size or higher porosity should have much more potential on the enhancement of air capture kinetics. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

Nanoparticles suspended in solutions are considered to have the potential to enhance gas-liquid mass transfer and have been studied for gas separation. In order to reveal the mechanisms of kinetics enhancement, the diffusion and reaction process should be carefully examined. In this paper, CO2 absorption kinetics of amine-based solutions with additive of SiO2 and Al2O3 nanoparticles were investigated by wetted-wall column experiments. Measurements at different conditions, including solid loading, pressure, and solvent flow rate, show a significant enhancement on CO2 absorption kinetics. The experiment and model analysis indicate that the micro convective motion induced by particle Brownian movement plays a primary role in mass transfer enhancement. Three solutions, MEA, MDEA, and PZ which have different kinetics were selected to study the impact of nanoparticles on absorption kinetics of solutions with different reaction rate. It is interesting to find that the increased ratio of absorption kinetics by nanoparticle follows the same order with increased solvent reaction rate with CO2, which is PZ > MEA > MDEA. The wetted-wall kinetic model indicates that a diffusion controlled kinetics for PZ solution could result in much more significant kinetic enhancement with additives of nanoparticles. By operation conditions optimization, the liquid side mass transfer rate of MEA solution can be increased over 15%.© 2015 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

Char is the solid product of coal pyrolysis and its utilization is closely related to the scale of coal pyrolysis and tar processing. Char gasification is a promising choice for char utilization as it can provide hydrogen, which is needed for tar hydrogenation and chemical synthesis. However, reliable and mature coal char gasification technology has not yet been developed. The fluidized bed has been adopted as a gasifier in many studies, and its gasification temperature is relatively low. In this work, the feasibility of char gasification using a fluidized bed has been studied. A pyrolyzed bituminous coal char was gasified in a mixture of O2 and steam using a circulating fluidized bed. The height of the fluidized bed is 2360 mm and the inner diameter is 66 mm. The reactor is made of Ni-Cd alloy steel, and a loopseal was used for solid circulation. In the experiments, the gasification temperature was varied between 870 and 900 °C, and the effects of O2/char and steam/char mass ratios on the gasification results were analyzed. The volume fraction of combustible gas, dry gas yield, carbon conversion, and lower heating value of the best case were 43.92 %, 1.64 Nm3 kg−1, 0.85, and 5.17 MJ N m−3, respectively. In addition, a simple model and a complex model were established by using Aspen Plus software. The two models were used to simulate char gasification, and the simulation results were validated with the experimental results. The results indicated that the complex model is more accurate than the simple model and is more suitable to simulate char gasification in a circulating fluidized bed. [ABSTRACT FROM AUTHOR]

Aiming to solve the problem of high ammonia loss during ammonia-based CO2 chemical absorption process, an ammonia wash system was recommended to be added after the absorber column. Hence, we need to deal with a lot of wash water. Recently, we proposed a vacuum membrane distillation (VMD) system to regenerate ammonia from ammonia wash water. The stripping gaseous ammonia can be used for producing a high-concentration ammonia solution for solvent make-up in the CO2 capture system, and the wash water after distillation can be reused. In this work, we investigated 0.3 M ammonia solutions on different operation factors such as feed flow rate, feed temperature, pressure in the permeate side, and CO2 loading. The experimental results show that both temperature and pressure in the permeate side have significant influences on the ammonia stripping process. Increasing feed temperature and reducing pressure in the permeate side will not only improve ammonia removal efficiency, but also enhance total transmembrane flux and overall mass transfer coefficient. The increase of feed flow rate can improve the total transmembrane flux, but will lower the ammonia removal efficiency. The increase of CO2 loading in the feed ammonia solution will decrease the ammonia removal rate. Furthermore, we investigated a continuous circulation experiment and found that the ammonia removal efficiency largely depended on the removal time. The removal efficiency can be up to 95.6% with a 120 min continuous circulation time. We think this VMD system has the potential to recover ammonia and solve the solvent loss problem. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

The low CO2 absorption rate and high ammonia volatile loss rate are two major issues for the ammonia-based CO2 capture technology. In this work, we investigated the effect of total pressure on CO2 absorption and ammonia vaporization in ammonia solutions on a wetted-wall column. We found that the elevated pressure absorption process was an effective way to increase CO2 absorption rate and suppress ammonia vaporization at the same time. We also studied the mass transfer mechanism at elevated pressure and found the overall mass transfer coefficients of CO2 absorption in both ammonia and MEA solutions at elevated pressures were lower than that under atmospheric pressure. The overall mass transfer coefficients of CO2 absorption in 3 M NH3 (298 K) at 1, 1.5, 2, 2.5 bar were 0.723 × 10−6, 0.652 × 10−6, 0.591 × 10−6, 0.555 × 10−6 mol/(s m2 Pa) and the corresponding gas side mass transfer coefficients were 13.8 × 10−6, 4.52 × 10−6, 2.61 × 10−6, 2.03 × 10−6 mol/(s m2 Pa), respectively. We also found the gas side mass transfer coefficient in the wetted-wall column was not only dependent on the hydrodynamic conditions of the column but also influenced by the total pressure. © 2014 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

Lignite-based polygeneration systems for coproducing tar and electricity with and without carbon capture and storage (CCS) were proposed and simulated. Predried lignite was pyrolyzed into coal gas, tar, and char. Coal gas was fired in a gas turbine after the cleanup process, while char was combusted in circulating fluidized-bed (CFB) boilers. The polygeneration plant without CCS turned out to be more efficient than the conventional CFB power plant, suggesting that the former is a promising and efficient option to utilize lignite resources. Moreover, the performance and emissions of polygeneration plants with and without CCS were compared. It was shown that the more CO2 is captured, the larger energy penalty it will cost. Therefore, a trade-off should be made between low emissions and high efficiency. [ABSTRACT FROM AUTHOR]

A novel power generation system based on coal partial gasification has been proposed of which the coal feed rate is 50kg/s. It is mainly composed of oxygen‐blown CFB gasifier, CFB char combustor, heat recovery boiler and power generation unit. Coal is partly gasified with oxygen and steam to produce syngas and the syngas is sent to GT for power generation. The residue char is combusted in char combustor for power generation. Supercritical power generation technology is adopted in ST power generation unit and the parameter of the main steam is 560°C, 22.4MPa. Techno‐economic analysis of Partial Gasification Combined Cycle (PGCC) system is conducted and compared with IGCC. Law of conservation of energy and production capacity index method are adopted for thermodynamic and economic analysis, respectively. Efficiency of power generation, internal rate of return, and payback period are obtained by detailed calculation. The simulation results show that the efficiency of power generation of APGCC and PPGCC system are 49.44% and 51.37%, respectively, which are higher than that of IGCC. The fixed capital investment of PGCC is much lower than that of IGCC. The internal rate of return and payback period of APGCC 13.38% and 7.24 years, respectively which are ~9% higher and 8 years shorter than that of IGCC, respectively. This article provides a detailed analysis of PGCC which indicates that the PGCC technology has a promising prospect. [ABSTRACT FROM AUTHOR]