Coal Gasification Unit Research Articles

Analysis and Optimization of Black Water Angle Valve in Coal Gasification Unit

Analysis and Optimization of Black Water Angle Valve in Coal Gasification Unit

An efficient and durable solid oxide fuel cell integrated with coal gasification system

In this work, we prepare an efficient and durable electrolyte-support solid oxide fuel cell (SOFC) with perovskite type Sr2Fe1.5Mo0.5O6-δ (SFM) anode to verify the integrated system consisting of a SOFC and coal gasification unit. The cell exhibits a considerable high output power density of 0.188 Wcm−2 and good short-term stability at 800 °C when exposing the anode and cathode to CO–CO2(2:1) and ambient air, respectively, which is attributed to its good electrocatalytic activity and intrinsic property against carbon coking. In addition, the rate-limiting step is determined by recording the electrochemical impedance spectra and their corresponding distribution of relaxation times analysis results. It is found that the electrode reaction process is limited by the low-frequency gas adsorption, dissociation, and conversion.

Applied mineralogical investigation on coal gasification ash

This work aims to perform the applied mineralogical characterization of coal gasification ash (CGA) generated from a commercial fixed bed downdraft gasification plant in eastern India. Analytical and characterization techniques such as stereomicroscopy, optical microscopy, field emission scanning electron microscopy (FESEM) with energy dispersive spectroscopy (EDS) attached, X-ray fluorescence (XRF), energy dispersive x-ray spectrometer associated scanning electron microscope (SEM-EDX), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) were applied for analyzing the coal and the corresponding gasification ash sample. These analytical techniques illustrate that SiO2 and Al2O3 are the major gasification ash phases, accounting for almost 85% of the entire CGA composition. The dominant mineral phases, such as quartz, mullite, and other aluminosilicates, provide an opportunity for utilization in construction and refractory material manufacturing. Moreover, confirming the presence of rare and valuable earth elements (RVEEs) in the CGA sample with SEM-EDX analysis unearths a new application window in meeting the requirement of the RVEEs starved nation like India, where very few commercial-scale coal gasification units are operational.

Corrosion inhibition effect of four inhibitors on SA106 Gr.B steel in coal-based syngas produced water

Stripper tower of coal gasification unit easily occurs severe corrosion, which may induce the damage of relative equipment and the leakage of toxic gas. Introducing the organic corrosion inhibitors is an effective and promising way for this system. In this article, the effects of medium concentration on corrosion behavior in coal-based syngas produced water are firstly investigated with X-ray diffraction (XRD) and scanning electron microscopy (SEM). In addition, the protection performance of inhibitors including imidazoline (ID), imidazoline amide (IDA), mannich base quaternary ammonium salt (MBQA), and pyridine (PD) are further explored with electrochemical measurement and the experiment of weight loss. The results indicate that the H2S volume fraction and the volume ratio of C(CO2)/C(H2S) exert significant effects on corrosion behavior. Thus, it is critical to control their concentration within a reasonable range for practical situation. Four inhibitors, especially the MBQA and PD, display prospective inhibition performance under appropriate concentration. Furthermore, compounding inhibitors of MBQA and PD exhibit an optimal inhibition performance with 95.5 % inhibition efficiency. This study provides a new route to protect the stripper tower top of coal gasification unit effectively.

Birleştirilmiş kömür gazlaştırma ve metanlaştırma sisteminin parçacık sürü optimizasyon yöntemiyle performans değerlendirmesi

Carbon dioxide hydrogenation is a promising method of producing alternative fuels in an environmentally friendly way. Researchers in the current literature have mainly investigated the performance of carbon dioxide hydrogenation systems that use carbon dioxide from various sources and hydrogen from water electrolysis units. In the present study, the performance of a combined coal gasification and methanation unit is investigated to produce methane and power. The carbon dioxide and hydrogen for the methanation unit are provided from the coal gasification system. A Particle swarm optimization (PSO) method is applied to optimize the carbon dioxide and hydrogen values here. Therefore, the water electrolysis unit, which needs high amounts of energy is removed from the system, effectively. The results from the studied system showed that it is possible to produce ~225 kilotons of methane annually by using ~946 kilotons of coal per year. In addition, the results revealed that annual carbon dioxide utilization of ~624.3 kilotons is possible. The system efficiency is estimated at around 49%.

Multifaceted evaluation of distribution, occurrence, and leaching features of typical heavy metals in different-sized coal gasification fine slag from Ningdong region, China: A case study

The coal gasification fine slag (CGFS) from the entrained-flow coal gasification unit faces the challenge of safe disposal and clean utilization in the Ningdong region, China. This study aims to provide complete and thorough understanding of the distribution features, chemical speciation, environmental impact, and leaching behavior of typical heavy metals (i.e., V, Cr, Mn, Ni, Cu, Zn, Ba, and Pb) in the CGFS with different size fractions. The results show that the distribution of selected heavy metals in the CGFS has evident particle size dependence. Except for Zn, the other heavy metals in different size fractions mainly exist in chemical speciation of residual form with the ratio of 50.11–86.69 wt%. Moreover, it is found that the heavy metals in the different-sized CGFS show different RAC (risk assessment code) environmental risk levels and TCLP (Toxicity Characteristic Leaching Procedure) leaching concentrations. Especially, Zn in SGFS-C and SGFS-D posed a high-risk level to the environment, while the heavy metal elements of Cr, Mn, Ni, Zn, and Ba in other size fractions are classified as a medium environmental risk. In addition, the TCLP test results indicate that the leaching concentration of Cr, Mn, Ni, Zn, Ba, and Pb exceeds the groundwater-related regulatory limit in China. The pH-dependent leaching experiments suggest that Pb shows the amphoteric behavior, while the leaching mode of other heavy metals seems to be the cationic pattern. Furthermore, the leachability of the selected heavy metals in small-size fractions of the CGFS should be given more consideration at both acid and alkaline pH ranges. The leaching kinetic results demonstrate that the most effective mechanism to describe the leaching process of Cr, Ni, Zn, and Pb in different CGFS size fractions is the diffusion-controlled theory, which is supported by the different morphological traits of spherical mineral particles and carbon particles in the CGFS.

Techno-economic analysis of a solar thermochemical cycle-based direct coal liquefaction system for low-carbon oil production

Direct coal liquefaction turns solid coal into transportable liquid fuel with a high energy conversion efficiency of nearly 60%. However, the hydrogen used in the direct coal liquefaction process mainly comes from coal gasification units, and gasification coal consumption accounts for about 30% of the total coal consumption. The authors of this article have proposed a solar thermochemical cycle-based direct coal liquefaction system and conducted a corresponding thermodynamic analysis. In this work, the economic feasibility, environmental impact, and the influence of key factors (coal price, oil price, carbon tax) for the industrial-scale low-carbon oil production system are analyzed. Compared with the traditional direct coal liquefaction system, the total coal consumption of the new system is reduced by ∼40%. Under low carbon constraints, the economics of the new system is comparable to that of the traditional one with a lower solar thermochemical hydrogen production cost (<13–16 yuan/kg H2). With the help of the solar thermochemical hydrogen production process, CO2 emissions of the new system can be reduced by 63%. Moreover, the solar thermochemical cycle could generate additional pure oxygen and profits. The methodology and results can provide important references for coal-to-liquid technology with high efficiency and low carbon emissions.

Methanol to olefins conversion: state of the art and prospects of development

The production of olefins by catalytic transformation of methanol on zeolites and zeotypes is of great interest to scientists and specialists in various fringe areas of national economy. Due to implementation of this process on industrial level, the attention gradually shifts from scientific studies devoted to the synthesis and modification of zeolites and zeotypes with different structure to investigation of pilot and industrial plants and determination of the main economic and environmental characteristics of both the existing and the future plants. In 2019, the development of 26 production sites in China with the annual output of 14 million tons of ethylene and propylene was licensed and 14 plants with the total capacity of 7.67 million tons of ethylene and propylene were launched. The created plants provide a complete cycle of coal processing, which consists of coal gasification units yielding syngas, units for the synthesis of methanol and olefins, their refinement and production of polyethylene and polypropylene. The total output of ethylene and propylene at the launched plants was more than 21 million tons. The paper presents a review of publications on the development and modification of catalysts as well as the technological, economic and environmental aspects of olefins production from methanol, which appeared in foreign journals in the recent five years.

Energy consumption and greenhouse gas emissions of shale gas chemical looping reforming process integrated with coal gasification for methanol production

Abstract More than 65% methanol in China is produced by a coal-to-methanol route, which suffers from low carbon utilization, high energy consumption, and serious CO2 emission. On the other side, shale gas chemical looping reforming is an efficient syngas production technology, but its hydrogen content is much higher than the requirement of methanol production. Therefore, this study proposes a novel high-efficient methanol production process integrating coal gasification and shale gas chemical looping reforming & combustion via systems engineering method. At the cost of additional shale gas consumption of 0.485 t/t, the coal consumption of the novel process is reduced from 1.45 t/t to 0.20 t/t, which leads to the high exergy efficiency of 71.04% achieved in the novel process. From the aspect of life cycle, the abiotic depletion fossil consumption of the novel process is reduced to 37.2 GJ/t (41.8% lower than that of the coal-to-methanol process) due to the mass and energy integration between coal gasification and chemical looping units. The impact ratios of the novel process/coal-to-methanol are 0.35, 0.39, 0.53, and 0.59 for the global warming potential, acidification potential, eutrophication potential, and photochem ozone creation potential, respectively. It is concluded that the above coupling process has significant application prospects in improving mass-energy utilization efficiency and reducing air pollutant emissions of the coal-based methanol production process.

Thermodynamic and Economic Analysis of Oxy-Fuel-Integrated Coal Partial Gasification Combined Cycle.

A novel partial gasification combined cycle (PGCC) system integrating coal partial gasification, oxy-fuel combustion, combined cycle, and CO2 separation is proposed. The coal–CO2 partial gasification technology is introduced in the coal gasification unit, and the oxy-fuel combustion technology is employed in the char combustion unit and gas turbine (GT) unit. The thermodynamic and economic analysis of the proposed system is carried out, showing that both energy and exergy efficiency have an increasing/decreasing tendency when the recycled flue gas (RFG) ratio of char combustion and GT increase. When the RFG ratios of char combustion and GT are 0.43 and 0.34, energy and exergy efficiencies reach maximum values of 48.18 and 45.11%, respectively. The energy efficiency of the PGCC-Oxy system is higher than that of the integrated gasification combined cycle (IGCC)-Oxy system by approximately 3%. It can be concluded from the economic analysis that the total investment on the PGCC-Oxy system is 3272.71 million RMB, and the internal rate of return (IRR) and payback time is 8.07% and 12.38 years, respectively.

The synergetic effects of carbon and hydrogen metabolism on the exergy destruction and loss in a coal-to-SNG process

The carbon utilization and exergy efficiency in coal to synthetic natural gas (coal-to-SNG) industry have always been the focuses of researchers and engineers. But few studies concern the linkage between carbon metabolism, hydrogen metabolism, and exergy destruction and loss, which significantly dominates the productivity and environmental performances of coal-to-SNG. Taking a typical coal-to-SNG project with 4 billion Nm3SNG/y as a case study, the effects of carbon and hydrogen metabolism on exergy destruction and loss are explored in detail. Coal gasification unit as the core of the entire coal-to-SNG process, results in 4.52% of total carbon emissions, 45.93% of total water consumption, and 46.83% of total exergy destruction and loss. The pursuit of high material utilization does not necessarily bring about less exergy destruction and loss, taking coal gasification and methanation units as typical representatives. While low carbon and hydrogen utilization efficiencies often mean certain exergy loss, taking rectisol and phenol ammonia recovery units as examples. The exergy loss per unit of carbon emission and wastewater discharge are 1.58 MJ/kg and 0.05 MJ/kg, respectively. According to regression analysis, the unilateral impact of carbon or hydrogen utilization on exergy destruction and loss is not so obvious, but synergetic effects between them play important roles in causing exergy destruction and loss. Raising exergy efficiency of each unit to the optimization point will lead to reduction of coal consumption by 158.61 t/h (0.32 kg/Nm3SNG), water consumption by 255.12 t/h (0.51 kg/Nm3SNG) and carbon emission by 54.76 t/h (0.11 kg/Nm3SNG). The way of exergy analysis coupled with material metabolism is benefit for comprehensively analyzing resource and energy utilization of industrial processes.

Designing of Underground Coal Gasification Unit

Pakistan is one of the biggest country for coal reserves in the world. Those coal reserves if exploited, will help in fulfilling the growing need of Pakistan’s energy sector. The ultimate goal for “Underground Coal Gasification” is to design a new system that can produce sufficient electricity and is relatively cleaner and environment-friendly. The coal reserves that are unfeasible to mine may be utilized by UCG technology. The process can be categorized according to the material injected air-steam injection, oxygen-steam injection. Both categories have their advantages and drawbacks and the process oxygen-steam injection was selected as being more economical. The project being relatively new is still in an experimental and research stage. Thus, the approach of the research throughout is experimental. In this research, formed several models using software like MathCAD and MS Excel that might be useful for further researchers and designers to improve the process.

Study on distribution, chemical states and binding energy shifts of elements on the surface of gasification fine ash

Using feed coal as a reference, a series of modern advanced analysis and measurement technologies such as X-ray photoelectron spectroscopy, scanning electron microscopy–energy dispersive X-ray spectroscopy and X-ray diffraction have been used to analyze the gasification fine ash obtained from a pulverized coal gasification unit. The results show that the fine ash mainly consists of elemental carbon, oxygen, silicon, and aluminum. The elemental carbon distributes primarily on the foams structure, while the spherical particles mainly consisted of silicon and aluminum are embedded in the foams structure. The C1s spectrum is composed of five components in which the content of graphitized carbon is up to 38.36%, and the content of aromatic C–C or C–H, the main existing form on coal surface, is only 25.75%. The 67.31% of elemental silicon is combined with bridging oxygen (Si–O) and 32.69% of that connected to non-bridging oxygen (Si–O2). The existence of aluminum is in the form of aluminum oxides with two coordinated modes ([AlO6] and [AlO4]), and the content of [AlO6] group is nearly double that of [AlO4]. Simultaneously, the binding energies of silicon and aluminum increase by approximately 3 eV, while that of carbon almost no change because of the number of carbon atoms is significantly higher than that of other elements. The silicon atoms and aluminum atoms are surrounded by masses of carbon atoms for the special microstructure of FA. The different chemical states of carbon with higher electronegativity along with the role of high temperature and pressure make the binding energies of silicon and aluminum changed dramatically.

Thermodynamic and techno-economic analysis of coal to ethylene glycol process (CtEG) with different coal gasifiers

Coal gasification unit, one of the most important units of the coal to ethylene glycol (CtEG) process, determines the amount and composition of syngas and is crucial to the overall performance of the CtEG process. Thus, the effect of coal gasifiers on the thermodynamic and techno-economic performance of coal to ethylene glycol (CtEG) process is analyzed and compared in this study. A rigorous steady-state modeling and simulation of the CtEG process with three different gasifiers (GSP, Shell and Texaco) is firstly performed and validated with literature data. Then the CO2 emissions, thermodynamic and economic performance of three cases of CtEG process with GSP, Shell and Texaco are detailed analyzed and compared. Moreover, the sensitivity analysis of the effect of economic parameters on the production cost of the CtEG process with different gasifiers is investigated. Results show that the exergy efficiency of the Case GSP is the highest, 43.98%, followed by Case Shell, 41.61% and Case Texaco, 39.22%. The capital cost of Case Shell is the highest, 2904.38 $/t-EG, followed by Case GSP, 2642.08 $/t-EG, and Case Texaco 2418.75 $/t-EG. The total production cost of Case Texaco is highest, 717.25 $/t-EG, followed by Case Shell, 705.05 $/t-EG, and Case GSP, 666.09 $/t-EG. The internal rate of return of Case GSP, Shell and Texaco are 18.01%, 14.24% and 17.72%, respectively. The CO2 emissions of Case GSP is the largest, 3.27 t/t-EG, followed by Case Shell, 3.12 t/t-EG and Case Texaco 2.89 t/t-EG.

Process simulation, analysis and optimization of a coal to ethylene glycol process

With the rapid development of polyester industry, the increasing demand of ethylene glycol (EG) is in conflict with the shortage of supply in China. Large project of EG production from coal has been receiving more and more attention. However, little work has been done to model and simulate the complete coal to ethylene glycol (CtEG) process, and there is a lack of research analyzing or optimizing its system performance. In this paper, the CtEG process was modeled and simulated to calculate and analyze its mass and energy balance. The models were validated by comparison with industrial data. The element balance and thermodynamic performance of the CtEG process were analyzed to identify the technical bottleneck and provide theoretical support for the actual production. Key parameters were investigated and optimized for increasing the yield of product as well as improving the system performance of the CtEG process. Results indicate that, the process produce 37.50 t/h EG from 118.98 t/h coal. The exergy efficiency of the CtEG process is 30.68%. The coal gasification and EG synthesis units have the greatest potential for decrease in exergy destruction. After optimization, the production and the exergy efficiency of the process is increased by 3.04% and 2.64%.

Carbon flow and energy flow analyses of a Lurgi coal-to-SNG process

Developing coal-to-SNG can alleviate the shortage of natural gas supply in China. In this paper, a commercial process of coal-to-SNG is modeled and simulated. Based on the simulation, the carbon flow and exergy flow of the coal-to-SNG process are analysed. The results show that the carbon element utilization efficiency is 35.7%. The unused carbon is almost discharged in the form of CO2. The acid gas removal unit and the power generation unit are the major emission units, which occupy 67.2% and 32.8% of the total carbon emission. By the exergy analysis, the results show that the major exergy destruction occurs in the power generation unit, followed by the coal gasification unit and the acid gas removal unit. Finally, several improvement methods are proposed to estimate energy saving and carbon emission reduction. The results show that the utilities consumption of the air separation unit, the coal gasification unit, the acid gas removal unit and the phenol recovery unit can be reduced by 29.8%, 85.7%, 17.9%, and 18.6%, respectively. The reduced utilities consumption would lead to decrease of the entire carbon emission by 19%.

Introducing a novel air separation process based on cold energy recovery of LNG integrated with coal gasification, transcritical carbon dioxide power cycle and cryogenic CO2 capture

An integrated coal gasification process with a novel double-column cryogenic air separation unit (ASU) based on the LNG (liquefied natural gas) cold energy recovery is proposed and analyzed. The process consists of a trans-critical carbon dioxide power generation cycle, a shift converter unit and cryogenic CO2 capturing system. ASU is used to produce high purity oxygen (99.99%) and nitrogen (99.99%). The specific power demand per flow rate of pure oxygen is 0.11 kWh/kg. Due to effective integration between two distillation columns in the ASU, the latent heat of the condenser in high pressure column is exchanged with reboiler of the low pressure column. The outlet LNG stream from ASU is utilized as cold source of the condenser in the trans-critical CO2 power cycle. The results show energy saving in the ASU and trans-critical power generation are 2301.6 kW and 14,217.6 kW respectively. The produced high purity gaseous oxygen is sent to the coal gasification unit to participate in the gasifier reactions. In this process, 99.83% of carbon dioxide with 99.80% purity, is captured and the required power is about 0.10 kWh/kg CO2.

Modeling, simulation, and techno-economic analysis of Lurgi gasification and BGL gasification for coal-to-SNG

Developing coal-to-SNG is an important way to deal with the shortage of natural gas supply. Lurgi gasification and BGL gasification are both adaptive for coal-to-SNG because of the rich content of CH4 in raw gas after gasification. In this paper, the coal gasification unit and WGS units in the two coal-to-SNG processes are modeled and simulated. The numerical model of the two units are based on industrial data.Technical analysis shows that the Lurgi gasifier and BGL gasifier are consistent on the effect of steam to coal ratio and oxygen to coal ratio. As the increase of oxygen to coal ratio, the productivity firstly increases and then decreases. As the increase of steam to coal ratio, the “quality” of productivity decreases and the flowrate increases. The exergy loss of the Lurgi process is higher than that of the BGL process. So is that of the Lurgi gasification unit.Economic analysis shows that the investment for the Lurgi gasification unit is 5.9×107USD more than that of the BGL gasification unit. Investment of the WGS unit in the Lurgi process is 1.8×106USD less than that in BGL process. The income from steam generated in the WGS unit in the Lurgi process is higher than that in the BGL process. However, production cost for the Lurgi process is 88USD while producing 1000Nm3 effective gases, much higher than the cost for the BGL process, 50USD.

Development and analysis of an integrated system with direct splitting of hydrogen sulfide for hydrogen production

This paper analyzes the thermodynamic performance of the combination of a water gas shift membrane reactor and an integrated coal gasification unit with a combined cycle, a carbon capture unit, and a unit for direct splitting of hydrogen sulfide into hydrogen and sulfur. The latter operates as an alternative process for disposing of hydrogen sulfide, while producing hydrogen. The purpose of the thermodynamic analysis is to determine whether the integration proposed is beneficial to the system in terms of thermodynamic performance, compared to the proposed systems in the open literature. The proposed system is simulated using Aspen Plus software, with two models for gasification. Some parametric studies are performed on the system to determine the effect of type of coal, steam flow rate in the single reheat supercritical Rankine cycle, and the main parameters of the membrane reactor on the overall energy and exergy efficiencies of the proposed system. The overall energy and exergy efficiencies of the proposed system are found to be 66.9% and 62.0% for Illinois #6 coal, and 60.7% and 57.0% for the Turkish coal Tuncbilek.

Low Carbon Cycle Mining Technology of Fossil Energy and Demonstration Project in Xinjiang

Combined with the unique resources of coal seams and oil reservoirs in Xinjiang area, the application and demonstration projects of deep fossil energy low carbon cycle mining technology are developed. In the reservoir formation containing both coal seam and oil, the underground gasifier is constructed by drilling or waste oil-well in the upper coal seam and the coal resources is gasified by using underground coal gasification (UCG)technology. Gas is separated into CO₂, CH₄, CO and H₂. CH₄ is liquefied to natural gas (LNG). CO and H₂ are used to generate electricity. And CO₂ is injected into oil displacement at the bottom of the coal seam to enhance oil recovery, which can be stored up at the same time. The technical system comprises an underground coal gasification unit, a gas separation and compression unit, a generating unit and a drive oil storage unit. The demonstration project would reduce carbon dioxide of 208900 tons per year.