Gasification Of Low-rank Coal Research Articles

Simulation Integrated Low Rank Coal Gasification SOFC Fuel Cell using Cycle Tempo: Energetic Analysis

Coal is currently the primary source of fuel for electricity generation. However, the use of low-rank coal as fuel in fuel cell power plants is still relatively uncommon. This study focuses on the simulation of integrating low-rank coal gasification with Solid Oxide Fuel Cells (SOFC) systems. This simulation was carried out in two modes. The first mode involves simulating the Solid Oxide Fuel Cell system with producer gas generated from the gasification of low-rank coal, which was directly inputted as SOFCs. Meanwhile, the second mode involves the simulation of a low-rank coal gasification system that was integrated with a Solid Oxide Fuel Cell system. These simulations were carried out with a constant parameter of the air-fuel ratio operation of gasification. Following this, the fuel cell operating parameters were varied in terms of the temperature, pressure, area, and current density of the cell. The obtained results indicated that modes 1 and 2 produced a similar amount of power. However, mode 1 was found to be twice as efficient as mode 2. The maximum power produced was around 34.5 MWe for both modes, with efficiency rates of 41.1% and 17% respectively.

Efficiency Enhancement of the Single Line Multi-Stage Gasification of Hungarian Low-Rank Coal: Effects of Gasification Temperature and Steam/Carbon (S/C) Ratio

Coal gasification is considered a promising solution for the production of synthetic fuels and eventually as a fuel for combined heat and power systems and heating buildings. There are several factors that affect the gasification efficiency and syngas quality, such as gasification parameters (temperature, pressure, etc.), reactants and their ratio, utilisation of catalysts, and gasifier design. The multi-stage gasifier is known as a promising approach in the enhancement of process efficiency, as well as the syngas quality. In this study, the Hungarian brown coal was gasified in a two-stage gasifier. The pyrolysis stage was kept at 600 °C. The gasification stage was conducted at 700, 800, and 900 °C. The steam per carbon (S/C) ratio was examined at 0.75, 1.00, and 1.25. The positive effects of increasing gasification temperature on char and dry gas yield were obviously shown at all S/C ratios. The increase in the S/C ratio did not show a positive effect at all temperature conditions, especially at 700 and 900 °C. The highest dry syngas yield was 1.14 Nm3/kgcoal obtained at 900 °C and the S/C ratio of 1.25. The increase in the gasification temperature also had a significant impact on the volume fraction of CO and CO2. Meanwhile, the syngas concentration varied slightly when the S/C ratio increased from 0.75 to 1.25. From a chemical utilization point of view, the gasification temperature at 900 °C and the S/C ratio of 1.25 resulted in the most promising H2/CO ratio of 1.99. In addition, the highest carbon conversion and cold gas efficiency were achieved at 900 °C and an S/C ratio of 1.00–1.25, respectively.

Characteristics of Char from Low-Rank Coal Gasification

Characteristics of Char from Low-Rank Coal Gasification

High-Ash Low-Rank Coal Gasification: Process Modeling and Multiobjective Optimization

The diversification of coal for its sustainable utilization in producing liquid transportation fuel is inevitable in countries with huge coal reserves. Gasification has been contemplated as one of the most promising thermochemical routes to convert coal into high-quality syngas, which can be utilized to produce liquid hydrocarbons through catalytic Fischer–Tropsch (F-T) synthesis. Liquid transportation fuel production through coal gasification could help deal with environmental challenges and renewable energy development. The present study aims to develop an equilibrium model of a downdraft fixed-bed gasifier using Aspen Plus simulator to predict the syngas compositions obtained from the gasification of high-ash low-rank coal at different operating conditions. Air is used as a gasifying agent in the present study. The model validation is done using published experimental and simulation results from previous investigations. The sensitivity analysis is done to observe the influence of the major operating parameters, such as equivalence ratio (ER), gasification temperature, and moisture content (MC), on the performance of the CL-RMC concerning syngas generation. The gasification performance of CL-RMC is analyzed by defining various performance parameters such as syngas composition, hydrogen-to-carbon monoxide (H2/CO), molar ratio, syngas yield (YSyngas), the lower heating value of syngas (LHVSyngas), cold gas efficiency (CGE), and carbon conversion efficiency (CCE). The combined effects of the major operating parameters are studied through the response surface methodology (RSM) using the design of experiments. The optimized condition of the major operational parameters is determined for a target value of a H2/CO molar ratio of 1 and the maximum CGE and CCE using the multiobjective optimization approach. The high-degree accurate regression model equations were generated for the H2/CO molar ratio, CGE, and CCE using the variance analysis (ANOVA) tool. The optimal conditions of the major operating parameters, i.e., ER, gasification temperature, MC for the H2/CO molar ratio of 1, and the maximum CGE and CCE, are found to be 0.5, 655 °C, and 16.36 wt %, respectively. The corresponding optimal values of CGE and CCE are obtained as 22 and 16.36%, respectively, with a cumulative composite desirability value of 0.7348. The findings of the present investigation can be decisive for future developmental projects in countries concerning the utilization of high-ash low-rank coal in liquid fuel production through the gasification route.

Syngas production from two-step CO2 gasification of low rank coal in an entrained flow reactor

Using CO2 as feedstock for syngas production is one hot topic in the field of clean energy due to the concern of global warming. Hence, two-step gasification (pyrolysis first and then subsequent char gasification) behaviour using CO2 as reactant was investigated under entrained flow conditions for one Inner Mongolia lignite and two Victorian brown coals (Maddingely and Morwell). The effects of CO2 concentration (5–30% CO2) and residence time(0–23 s) were assessed in the low temperature ranges of 700–1000 °C. High temperature improved H2 and CO yield in entrained flow pyrolysis. The higher CO2 concentration and longer residence time enhanced gasification syngas yield and carbon conversion. Three coal chars required around 23 s of residence time for 100% conversion under 20% CO2 and 1000 °C. It indicated that entrained flow gasification of the three chars was preferably performed above 1000 °C for industrial applications. Fe-rich Victorian brown coal achieved better pyrolysis performance than Inner Mongolia lignite because of the inherent catalytic effect of Fe oxides in coal. Morwell coal char achieved the best char-CO2 gasification performance due to higher gasification reactivity and better pore structure. This study provides essential information for the optimization of entrained flow gasifiers toward syngas production using CO2 as feedstock.

Experimental study of the catalytic effect of iron on low-rank coal gasification

Acid-washing low-rank coal samples were loaded with different content of iron catalyst and then pyrolyzed. FT-IR, Raman spectra, and temperature-programmed experiments were used to investigate the influence of iron on the coal char. The FT-IR results revealed that iron catalyst rises the number of –OH, –CH3, and –CH2 functional groups. The Raman spectra results showed that partial large polyaromatic ring structures transform into small polyaromatic ring structures after the addition of iron. The results of temperature-programmed desorption indicated that the number of surface active sites is increased due to the addition of iron. For low-rank coal char with 3% Fe, the number of active sites increased with the increase of adsorption temperature until 800 °C and then start to decrease. At 750 °C, the adsorption capacity of CO2 increased with the increase of time and reached saturation state after 45 min. The results of the char-steam isothermal gasification experiment suggested that the iron catalyst enhances the gasification reactivity of low-rank coal. It is verified that iron catalysts can improve the gasification reactivity of low-rank coal by increasing the number of surface active sites.

Techno-economic and environmental impact analysis of tuyere injection of hot reducing gas from low-rank coal gasification in blast furnace

Our goal is to find a strategy to reduce coke use during operation of a blast furnace (BF). This study focuses on the techno-economic and environmental impact analysis of tuyere injection of hot reducing gas (HRG) from low-rank coal (LRC) gasification in the BF. LRC gasification by entrained-flow gasifier is introduced to make gaseous fuel, and the cleaning process of the raw syngas is implemented using Aspen Plus V10. The effects of HRG injection are evaluated using a BF model derived from the Rist operating diagram. Integrated results from raw fuel to the BF were analyzed considering economic, energy, and environmental aspects. By injecting rich syngas (>95 vol %) into the BF at 1150 K, coke replacement ratio is estimated to be 0.354 kg/Nm 3 without adverse impact on the BF. The most sensitive economic factor is coke price. The energy efficiency of raw syngas cleaning process, relative energy intensity of LRC, gas utilization ratio are 57.5%, 90.6%, and 50.0% respectively. Utilization of HRG can reduce CO 2 emission by 21.88 kt CO2 /yr compared to the reference BF operation. • The hot reducing gas injection is proposed as a coke-saving strategy. • In technical aspect, the coke replacement ratio is estimated to be 0.354 kg/Nm 3 . • The suggested process is economically feasible. • The annual potential abatement of CO 2 is 21.88 ktCO 2 /yr.

Thermochemical utilization of low rank coal and flotation concentrate

Flotation concentrates are waste material from coal mine operation. The process of steam gasification seems to be an attractive option for their economic utilization and an alternative to their potential combustion in boilers. The gasification process is characterized by both higher efficiency and lower emission of pollution than conventional combustion systems. In this paper the results of the steam gasification of low rank coal and flotation concentrate into hydrogen-rich gas at the temperature of 800 °C are presented. The reactivity for 50% carbon conversion as well as the maximum reactivity in this process were calculated for the samples studied.

Catalysis and degradation of phenol in coking wastewater during low-rank coal coke gasification

The thermochemical-reaction characteristics of different concentrations of phenol water and gasification-coke at 1000 °C in a thermochemical reactor were experimentally studied.

Coal Type, Temperature and Gasifiying Agent Effects on Low-Rank Coal Gasification Using CFD Method

Low-Rank Coal (LRC) gasification utilising Fluidised Bed Gasifier (FBG) is more efficient for LRC that has higher reactivity, moisture, tar, volatile, and ash content but lower calorific value compared to other types of coals. This work investigated the application of Computational Fluid Dynamics (CFD) in simulating LRC gasification under different temperatures which is lower (873K), normal (973K) and higher (1073K) temperature atmosphere. Besides that, the effect of LRC type and gasifying agents on the producer gas CO+H2 composition, Lower Heating Value (LHV) and Cold Gas Efficiency (CGE) were also studied using High-rank Coal (HRC) as comparison. The results obtained showed that LRC gasification using oxygen increased LHV and CGE. Lower temperature gasification using oxygen at 873 increased CO+H2, LHV and CGE for LRC compared to higher temperatures at 973K and 1073K. This prediction suggests that LRC gasification using oxygen at lower temperature increases the LRC gasification efficiency.

Remediation with Semicoke-Preparation, Characterization, and Adsorption Application.

Development of low-cost contaminant sorbents from industrial waste is now an essential aspect of the circular economy since their disposal continues to threaten ecological integrity. Semicoke (SC), a by-product generated in large quantities and described as solid waste from gasification of low-rank coal (LRC), is gaining popularity in line with its reuse capacity in the energy industry but is less explored as a contaminant adsorbent despite its physical and elemental carbon properties. This paper summarizes recent information on SC, sources and production, adsorption mechanism of polluting contaminants, and summarizes regeneration methods capable of yielding sustainability for the material reuse.

The Impact of Coal’s Petrographic Composition on Its Suitability for the Gasification Process: The Example of Polish Deposits

In this paper, we discuss the impact of the rank of coal, petrographic composition, and physico-chemical coal properties on the release and composition of syngas during coal gasification in a CO2 atmosphere. This study used humic coals (parabituminous to anthracite) and lithotypes (bright coal and dull coal). Gasification was performed at temperatures between 600 and 1100 °C. It was found that the gas release depends on the temperature and rank of coal, and the reactivity increases with the increasing rank of coal. It was shown that the coal lithotype does not affect the gas composition or the process. Until 900 °C, the most intense processes were observed for higher rank coals. Above 1000 °C, the most reactive coals had a vitrinite reflectance of 0.5–0.6%. It was confirmed that the gasification of low-rank coal should be performed at temperatures above 1000 °C, and the reactivity of coal depends on the petrographic composition and physico-chemical features. It was shown that inertinite has a negative impact on the H2 content; at 950 °C, the increase in H2 depends on the rank of coal and vitrinite content. The physicochemical properties of coal rely on the content of maceral groups and the rank of coal. An improved understanding these relationships will allow the optimal selection of coal for gasification.

Biomass Waste and Low Rank Coal Gasification Technology with Carbon Capture System to Optimize A Clean Energy Production as An Alternative Solution to Achieve Energy Security in Indonesia

A shift into a more developed country means an increase in various aspects of economy, energy, social, and even environment. For Indonesia, a major change that the country needs to face is the increase of energy demand of 7% every year, reaching a final average expected energy consumption of 497.77 MTOE in 2050. In order to fulfil all upcoming energy demands and achieve energy security, it is crucial to utilize the available abundant resources that the country possesses. Two of these potential resources include coal (22.6 billion tons) and biomass (32.6 GW). Gasification is an alternative clean technology that can utilize low rank coal or biomass to convert it into syngas. The quality of syngas was characterized using the H2/CO ratio parameter. The greater the carbon density in a material, the greater H2/CO ratio will be. However, syngas produced from conventional gasification still emits CO2. Since CO2 is still emitted in coal gasification technology, a carbon capture system called HyPr-RING process is implemented as an alternative to reduce CO2 and increase the quality of syngas up to 91% volume of H2. The process uses CaO as a sorbent to capture CO2 and convert it into CaCO3 in a gasifier. Then, the CaCO3 is calcinated in a calciner to release back CaO that is recycled to capture more of the CO2. Aside from the high availability of coal and biomass, CaO as a major substance used in the CO2 capture process is also abundant in Indonesia (2,156 billion tons). This technology innovation is also economically feasible as it creates a net profit of USD 58,215 and ROI of 11%.

Exploration in ash-deposition (AD) behavior modification of low-rank coal by manure addition

High-alkali low-rank coal aggravates ash deposition (AD) during conversion. To mitigate AD formation during its gasification, the AD characteristics of Xiaolongtan lignite (XLT) and Yima coal (YM), their variations from chicken or pig manure addition under a reducing atmosphere, and their mechanisms were investigated by using ash fusion temperature tester, self-made AD analyzer, and X-ray diffractometer. The results indicated that the mass fraction of AD (MAD) of XLT was higher than that of YM because of the XLT with a high Ca, Fe, Na, and K content. At a low temperature (<950 °C), MAD increased with an increasing content of Na, K, and Fe due to their low melting-point eutectic formations; the MAD decreased with an increase in ash fusion temperature at a high temperature. The MAD of the XLT or YM decreased rapidly (1%–10%) and then decreased slowly (10%–15%) with manure ash addition. The XLT MAD decreased 50.32% for 4.93% chicken manure (CM) addition at 1000 °C. High-P and -Ca CM addition caused the formations of high melting-point Ca3P2O8 and KCaPO4, which inhibited alkali silicate generation and made the MAD decrease. Manure addition can mitigate AD formation effectively during low-rank coal gasification.

Prospect of near-zero-emission IGCC power plants to decarbonize coal-fired power generation in China: Implications from the GreenGen project

An integrated gasification combined cycle (IGCC) power plant with pre-combustion CO2 capture provides a solution to achieve energy security with CO2 emission reduction in China, which has a coal-dominant energy resource structure. This study utilizes the electricity generation and cost information of the GreenGen IGCC plant (265 MW), which is the first and, to date, the only IGCC facility in China, to evaluate the economic performance and competitiveness of this emerging clean coal technology. In the construction stage, the initial investment on the GreenGen plant was approximately $565 million (capital cost: 2133 $/kW; in constant 2017 US dollars). Compared with the US, China incurred significantly lower costs of initial investment for the construction of the IGCC plant, owing to the adoption of a self-developed gasifier. During the operation stage, the levelized cost of electricity (LCOE) without CO2 capture for the GreenGen plant was calculated as 103 $/MWh, whereas it increased to 131 $/MWh with pre-combustion CO2 capture (CO2 capture cost: 42 $/tonne). Currently, an IGCC plant with integrated CO2 capture remains too expensive to be widely used in China. However, simulation results indicate that the LCOE of China’s IGCC plants could be potentially reduced to 80 $/MWh in the future owing to technology innovation, large-scale application and cumulative production. Government policy and financial support to stimulate the research and development of gas turbine and low-rank coal gasification technologies and to subsidize the operation of IGCC plants owing to their environmental benefits would play critical roles in accelerating the development of near-zero-emission IGCC power plants in China.

Effect of the electronic state on low-rank coals with Ca2+ ion exchange

Ca2+-exchanged coal prepared from calcium hydroxide is a good catalyst for steam gasification of low-rank coal with a fixed-bed quartz reactor. However, it is difficult to clarify the effect of Ca2+ ion exchange on low-rank coal by experiment. To investigate the effect of Ca2+ ions on low-rank coals, this study determined the electronic states between Ca2+-exchanged and raw coal models and compared them by B3LYP/6-31G∗ and HF/6-311G∗ calculations. The experiments revealed that the Ca2+ ion exchange method significantly affects gasification of low-rank coal. It is considered that the molecular structure of low-rank coal presents significant changes in the electronic state before and after Ca exchange, even with a simple molecular structure. Therefore, a molecular model was created in which a COOH/OH H+ ion was exchanged with one Ca2+ ion, and quantum chemical calculations were subsequently performed. The results revealed that the –COOCa1/2 IR peak calculated from B3LYP/6-31G∗ appeared at approximately the same position as the experimental IR peak in low-rank coal after Ca exchange. The Ca structure was more stable following interaction with the O in the benzene OH group than with that in the OH group of the tetralin ring containing Ca. Furthermore, the increased negative charge of the benzene ring following Ca interaction was presumed to improve the reactivity between the low-rank coal and steam. In addition, weak bonds in the Ca2+-exchanged coal molecules were investigated by calculating the difference between the values of the Löwdin and Mulliken bond orders before and after Ca2+ exchange. The results indicated that the binding in the molecule was weakened by Ca coordination. From these facts, it is presumed that H+/Ca2+ ion exchange promotes the decomposition of low-rank coal.

Electronic State of Low-Rank Coals with Exchanged Sodium Cations.

Our previous experimental study showed that Na+-exchanged coal prepared from low-cost natural soda ash is an excellent catalyst for steam gasification of low-rank coals using fixed-bed quartz reactors. However, it is difficult to experimentally clarify the effect of Na ion exchange on low-rank coal. In order to investigate the influence of Na+ ions on low-rank coal, this study determined the electronic state between the Na+-exchanged coal model and raw coal model and compared them using RHF/6-311G* and B3LYP/6-31G*. The experiments revealed that Na ion exchange has a significant effect on low-rank coal gasification. The model structure of low-rank coal is considered to change significantly in terms of the electronic state before and after Na exchange even with a simple main molecular structure. Molecular models where H of COOH/OH was ion-exchanged with one, two, and three Na ions were developed, and quantum chemical calculations were performed. The results showed that when the number of Na+-exchanged sites is increased, the electron state on the coal molecule becomes more negatively charged in the case of the Na+-exchange coal model. It is presumed that this contributes to enhancing the reactivity of low-rank coal and water vapor. In addition, weak bonds in the Na+-exchanged coal molecule were examined by calculating the difference in the value of the Mulliken and Löwdin bond orders before and after Na+ exchange. The results showed that the increase in the number of exchanged Na+ in the low-rank coal molecule model increased the number of weak bonds in the molecule. It is presumed that this contributes to enhancing the decomposition of low-rank coal.

Thermochemical utilization of low rank coal and flotation concentrate

Abstract Flotation concentrates are waste material from coal mine operation. The process of steam gasification seems to be an attractive option for their economic utilization and an alternative to their potential combustion in boilers. The gasification process is characterized by both higher efficiency and lower emission of pollution than conventional combustion systems. In this paper the results of the steam gasification of low rank coal and flotation concentrate into hydrogen-rich gas at the temperature of 800 °C are presented. The reactivity for 50% carbon conversion as well as the maximum reactivity in this process were calculated for the samples studied.

Low-rank coal gasification using a bubbling fluidized bed reactor at low operating temperature

Coal gasification is one of coal utilizations that produces less CO2 emission than coal combustion. Coal gasification technology that has been used in Indonesia is generally a fixed bed gasification. Fixed bed is designed for high-rank coal and the majority of Indonesian coal is of a low-rank. Low ash and high moisture content of the Indonesian coal in a fixed bed can affect mechanical and thermal fragmentation, pressure drop, gas and particle flow distribution. The operation of gasifier may cause unstable condition. Another gasification technology is bubbling fluidized bed, which is operated above 1,200°C, so ash can melt. High operating temperature causes agglomeration and makes unstable gasification process. Therefore, in this study, low-rank coal is gasified in bubbling fluidized bed reactor at low operating temperature. The purpose of this study is to determine the optimal conditions of bubbling fluidized bed gasification. The research was conducted in bubbling fluidized bed coal gasification Process Development Unit (PDU) at Coal Utilization Technology Centre of R&amp;D Centre of tekMIRA, Palimanan. Coal was fed continuously as many as 20 kg/hour into a gasifier then was gasified to produce gas using air as a gasifying agent and silica sand as a bed material at 850- 950°C. The produced gas from the gasification was analyzed using the Orsat Analyzer. A simulation using a ChemCAD 7.1 CC steady state was applied to validate the experiment result. From the analyzed result of yield gas composition, the produced CO and CO2 were about 10-15 wt%. Gas compositions that are close to criteria of producer gas, no agglomeration, and stable process condition during study indicate that bubbling fluidized bed gasification at low operating temperature is suitable to be applied as gasification technology for Indonesian low-rank coal.

Gasifying agents type at lower temperature effect on bubbling fluidised bed gasification for low rank coal

Oxygen and steam as gasifying agents are preferred for gasification process compared to air due to the production of higher heating value of syngas and lower contents of diluents. Lower operating temperature is required for low rank coal (LRC) gasification process. This is because, carbon conversion will occur faster with high reactivity of LRC. Ash agglomeration formation is also prevented at lower operating temperature. Hydrodynamics of bubbling fluidisation and gasification process are expected to be affected with different gasifying agents and operating temperature. Computational fluid dynamics (CFD) method was used to select suitable superficial velocity for bubbling fluidised bed (BFB) simulation and explore the effects of different gasifying agents at a lower operating temperature. The model was validated with theoretical values and superficial velocities of three to four times the minimum velocity (3~4Umf) were selected due to its best uniform bubbling fluidisation. Different gasifying agents will produce different bubbling patterns which relates to the density and viscosity of the gasifying agents. Many and faster moving bubbles were produced when using oxygen and air at 1,073 K while no changes is detected when using steam. This concludes that air and oxygen as gasifying agents give higher effect to the bubbling hydrodynamics compared to selection of steam as gasifying agent.