Development of a Coupling Oil Shale Retorting Process of Gas and Solid Heat Carrier Technologies

Oil shale is one of the most potential alternative resources for crude oil. Its exploration and exploitation are of increasing interest. In China, oil shale is mainly used by retorting technology. Fushun-type retorting technology, a typical gas heat carrier retorting technology, accounts for the largest proportion in China. However, this retorting technology is only applicable of coarse oil shale particles bigger than 10 mm in diameter. A lot of fine oil shale particles are discarded, resulting in waste of resources. Besides, this technology is criticized by low economic benefit. The main objective of this paper is to develop a coupling oil shale retorting process. The novel process can use fine oil shale particles as the raw materials of solid heat carrier retort to produce more shale oil. The novel process is modeled, and next, the simulation is carried out to build its mass and energy balance. From the techno-economic point of view, the advantages of the novel process are demonstrated by comparison to the traditional Fushun-type oil shale retorting process. Results indicate that the novel process is promising because coupling the two retorting process can increase the shale oil production from 13.86 to 17.34 t/h, the exergy efficiency from 32.46 to 38.01%, and the return on investment from 11.04 to 18.23%

Development of a Coke Oven Gas Assisted Coal to Ethylene Glycol Process for High Techno-Economic Performance and Low Emission

Developing a coal to ethylene glycol (CtEG) process is of great interest to many countries, especially China. However, because the hydrogen to carbon ratio of the coal-gasified gas is far less than the desired value, the CtEG process suffers from high CO₂ emission and wastes precious carbon resources. At the same, most coke oven gas (COG) is discharged directly or used as fuel, resulting in a waste of resources, serious environmental pollution, and economic loss. To develop efficient and clean utilization of coal and COG resources, we propose a novel coke oven gas assisted coal to ethylene glycol (CaCtEG) process. The proposed process introduces the hydrogen-rich COG to adjust the hydrogen to carbon ratio and reduce CO₂ emission by integrating a dry methane reforming unit. Key operational parameters are investigated and optimized based on the established mathematical model. The advantages of the process are studied by a detailed techno-economic analysis. Results show that, compared with the conventional CtEG process, the CaCtEG process is promising since it increases the carbon element and exergy efficiency by 18.35% and 10.59%. The CO₂ emission ratio of the proposed process is reduced from 2.58 t/t-EG to 0.44 t/t-EG. From an economic point of view, the CaCtEG process can save production costs by 5.11% and increase the internal rate of return by 3.41%. The capital investment, however, is slightly increased because of the two additional units

Integrated Process of Coke-Oven Gas Tri-Reforming and Coal Gasification to Methanol with High Carbon Utilization and Energy Efficiency

The hydrogen to carbon (H/C) ratio of coal gasified gas in the range 0.2–1.0, far less than the desired value for the coal to methanol process. Therefore, a water gas shift unit is needed to raise the H/C ratio, which results in a great deal of CO₂ emission and carbon resource waste. At the same time, there is 7 × 10¹⁰ m³ coke-oven gas (COG) produced in coke plants annually in China. The hydrogen-rich COG consists of 60% hydrogen and 26% methane. However, a massive amount of COG is utilized as fuel or discharged directly into the air, which makes a waste of precious hydrogen resources and causes serious environmental pollution. This paper proposes an integrated process of coke-oven gas and coal gasification to methanol, in which a tri-reforming reaction is used to convert methane and CO₂ to syngas. The carbon utilization and energy efficiency of the new process increase about 25% and 10%, whereas CO₂ emission declines by 44% in comparison to the conventional coal to methanol process

Development of an Oil Shale Retorting Process Integrated with Chemical Looping for Hydrogen Production

The increasing demand of crude oil is in conflict with the shortage of supply, forcing many countries to seek for alternative energy resources. Oil shale is welcomed by many countries that are short of conventional fossil fuels. China mainly uses retorting technology for shale oil production. Fushun-type oil shale retorting technology takes the largest share in the oil shale industry. However, this technology is always criticized by its unsatisfactory economic performance. It is caused by many reasons. One of the most important problems is the inefficient utilization of retorting gas. The idea of our research is to utilize the retorting gas to produce higher valued chemicals. For this, chemical looping technology is integrated into the retorting process for hydrogen production. This proposed process is modeled and simulated to build its mass and energy balance. Techno-economic analysis is conducted and compared to the analysis of the Fushun-type oil shale retorting process. The results show that the exergy destruction of the proposed process is 235.62 MW, much lower than that of the conventional process, 274.76 MW. In addition, the proposed process is less dependent on shale oil price. Two shale oil price scenarios have been investigated, showing that the proposed process can still be of benefit, 10.62% ROI, at low shale oil price, while the ROI of the conventional process is −2.07%

Process Development and Technoeconomic Analysis of Different Integration Methods of Coal-to-Ethylene Glycol Process and Solid Oxide Electrolysis Cells

The conventional coal-to-ethylene glycol (CtEG) process is criticized for its high CO2 emissions. Because most CtEG projects are located in areas rich in renewable energy such as wind energy and solar energy, two novel green hydrogen-assisted CtEG processes are proposed and analyzed by the integration of solid oxide electrolysis cell (SOEC) technology: the CtEG process integrated with the SOEC technology of only steam electrolysis (SOEC-CtEG) and that of steam and carbon dioxide electrolysis (CoSOEC-CtEG). The effects of the operating temperature, current density, and inlet gas composition on the electrochemical performance of the solid oxide steam electrolytic and coelectrolytic processes are investigated and compared based on their electrochemical and flowsheet-based models. The thermodynamic and technoeconomic advantages of the two proposed processes are manifested by comparison with a conventional process. The results show that the two proposed processes are promising because they increase the carbon utilization efficiency by 26.13 and 22.48%, increase the exergy efficiency by 14.82 and 17.34%, decrease the total capital investment by 23.60 and 19.38%, decrease the levelized production cost by 20.55 and 27.47%, and increase the internal rate of return by 8.85 and 9.18%. In addition, the sensitivity analysis results show that the two proposed processes have stronger antirisk ability than the conventional process

An Overview of Flue Gas SO₂ Capture Technology Based on Absorbent Evaluation and Process Intensification

Highly efficient and low-energy SO2 capture technology is a key measure to control SO2 pollution and sulfur supply side and demand-side balancing. This paper reviews the current development of SO2 capture technology by chemical absorption from two aspects of absorbent and process enhancement. The SO2 absorption mechanism of various absorbents are first described, and it was divided into aqueous solvents and nonaqueous solvents. Four prediction models for the SO2 absorption capacity of different absorbents are proposed, providing an effective tool for the selection of efficient and low-energy absorbents. The advantages, bottlenecks, and development directions of each absorbent are analyzed. The diversity of organic amines provides a possibility for enhancing the market competitiveness of organic amine aqueous solutions in aqueous solvents, while the high energy consumption in the absorbent regeneration process is a disadvantage. The ionic amino acid aqueous solution reduces the volatilization of the effective components of the absorbent and has better SO2 absorption potential than the organic amine aqueous solution. The greatest advantage of the nonaqueous solvents is the avoidance of ineffective latent heat consumption. High-throughput screening has become a bridge for the application of aqueous and nonaqueous solvents to industrial SO2 capture processes. Finally, the application potential of a process intensification strategy in SO2 capture technology is discussed, in which solvent intensification can avoid latent heat consumption, equipment intensification can improve the efficiency of gas–liquid mass transfer and process matching can recover the available energy of SO2 capture system. The comprehensive evaluation of SO2 capture process based on various absorbents is the primary task to promote the development of promising absorbents. It is hoped that this paper can provide reference for the development of SO2 capture processes

Thermodynamic and Mechanistic Analyses of Direct CO₂ Methylation with Toluene to <i>para</i>-Xylene

Direct CO2 methylation with toluene, as one of the CO2 hydrogenation technologies, exhibits great potential for the CO2 utilization to produce the valuable para-xylene (PX), but the tandem catalysis remains a challenge for low conversion and selectivity due to the competitive side reactions. The thermodynamic analyses and the comparation with two series of catalytic results of direct CO2 methylation are conducted to investigate the product distribution and possible mechanism in adjusting the feasibility of higher conversion and selectivity. Based on the Gibbs energy minimization method, the optimal thermodynamic conditions for direct CO2 methylation are 360–420 °C, 3 MPa with middle CO2/C7H8 ratio (1:1 to 1:4) and high H2 feed (CO2/H2 = 1:3 to 1:6). As a tandem process, the toluene feed would break the thermodynamic limit and has the higher potential of >60% CO2 conversion than that of CO2 hydrogenation without toluene. The direct CO2 methylation route also has advantages over the methanol route with a good prospect for >90% PX selectivity in its isomers due to the dynamic effect of selective catalysis. These thermodynamic and mechanistic analyses would promote the optimal design of bifunctional catalysts for CO2 conversion and product selectivity from the view of reaction pathways of the complex system

Viable Alternative Prospective Option for Liquid Methanol Industry’s Long-Term and Cost-Effective Development: CO₂ to Methanol Conversion and Ethylene Glycol Coproduction

The CO2-to-methanol (CTM) process can realize the recycling of carbon resources and mitigate the global greenhouse effect. However, the low CO2 conversion rate is a consequence of the thermodynamic equilibrium, which restricts the direct hydrogenation of CO2 to methanol (CTMI). Furthermore, there exists a state of kinetic competition between the reaction that produces methanol and the reaction that reverses the water–gas shift, which leads to the low selectivity of methanol. To solve these problems, a new process of indirect hydrogenation of CO2 to methanol and the coproduction of ethylene glycol (CTMII) was proposed in this paper. The steady state modeling, energy integration, and technoeconomic evaluation of the new process were carried out. It was found that the carbon and hydrogen utilization rates of the CTMII process were 98.95% and 98.63%, respectively, corresponding to increases of 2.99% and 34.21%, respectively, compared to those of the CTMI process. The selectivities of methanol and ethylene glycol in the CTMII process are 47.44% and 52.56%, respectively. Under the current economic conditions (0.35 CNY/kWh electricity, 1.8 CNY/m3 natural gas, 5000 CNY/t ethylene glycol, and 17.5 CNY/kg H2), the production cost of the CTMII process was 2572 CNY/t-CH3OH, 38.82% lower than that of the CTMI process. The net present value was calculated, and a sensitivity analysis of the relationship between hydrogen and production costs was performed. When the H2 price dropped to 13.6 CNY/kg, the product cost of CTMII could compete with that of the coal-to-methanol process, showing great economic potential for the future. This study presented a novel approach for the utilization of CO2 resources and broadened the path for green and low-carbon production of methanol

Multiobjective Evaluation of Amine-Based Absorbents for SO₂ Capture Process Using the p<i>K</i>_a Mathematical Model

The screening of high-efficiency and low-energy consumption absorbents is critical for capturing SO2. In this study, absorbents with better performance are screened based on mechanism, model, calculation, verification, and analysis methods. The acidity coefficient (pKa) values of ethylenediamine (EDA), piperazine (PZ), 1-(2-hydroxyethyl)­piperazine (HEP), 1,4-bis­(2-hydroxyethyl)­piperazine (DIHEP), and 1-(2-hydroxyethyl)-4-(2-hydroxypropyl)­piperazine (HEHPP) are calculated by quantum chemical methods. A mathematical model of the SO2 cyclic absorption capacity per amine (αc) in the amine-based SO2 capture process is built based on the electroneutrality of the solution. Another model of desorption reaction heat (Qdes) is also built based on the van’t Hoff equation. Correspondingly, αc and Qdes of the above five diamines are calculated and verified with the experimental data. The results show that αc of the diamine changes with the increase in the pKa value, and the increase in the pKa value directly leads to changes in Qdes. The order of αc of the above five diamines is EDA > PZ > HEHPP > HEP > DIHEP, and the order of Qdes is EDA > PZ > HEHPP > DIHEP > HEP. The multiobjective analysis between αc and Qdes suggests that it is not advisable to simply pursue a higher αc while ignoring Qdes. The compound quaternary system absorbent has a wider range of αc than the single ternary absorbent, which is the direction of absorbent development. This study is expected to strengthen absorbent screening for the amine-based SO2 capture process from flue gas

Comparative Life Cycle Assessment of Energy Consumption, Pollutant Emission, and Cost Analysis of Coal/Oil/Biomass to Ethylene Glycol

The industrialized coal-to-ethylene glycol (CtEG) route has become a potential competitor for the conventional oil-to-ethylene glycol (OtEG) route, and the emerging biomass-to-ethylene glycol (BtEG) route is also recognized because of its good environmental performance. In this study, life cycle assessment (LCA) is used to compare and analyze the life cycle energy consumption, pollutant emissions, and life cycle costs (LCC) of CtEG, OtEG, and BtEG routes. According to the results, the ethylene glycol production process is the main contributor to energy consumption and pollutant emissions. Compared with the OtEG route, the BtEG route has lower environmental costs but high direct production costs. The CtEG route provides a viable alternative for coal-rich and oil-deficient countries. However, as a promising production route for ethylene glycol, the CtEG route has the disadvantages of high energy consumption and high pollutant emissions, resulting in large environmental costs and not in line with the concept of sustainable development. Therefore, how to reduce energy consumption and pollutant emissions in the production process, especially carbon emissions, is an urgent problem to be solved. This research provides an important basis for improving the production of ethylene glycol and helps decision makers choose the most suitable production route for ethylene glycol based on actual conditions