Hydrogasification Process Research Articles

Investigation of the Kinetics of Pressure Coal Char Hydrogasification

The authors of the study focused on the problem of hydrogasifying coal extracted from a particular location. Since hydrogen is transparent to radiation, it can only be heated by convection. To achieve this, we developed a swirler and utilized Fluent software (version 19.0) to simulate the primary flow vectors and the temperature distribution of hydrogen in the hydrogasification reactor. The process was carried out under varying conditions, including temperatures ranging up to 1173 K, pressures of up to 8 MPa, and gas flow rates between 0.5 and 5 dmn3 min−1. The results showed that the carbon reactivity of the char was high up to a certain level of carbon conversion. In this study, the kinetic equations of the hydrogasification process were developed based on the theory of active centers. The researchers also evaluated the kinetic constants at the maximum reaction rate for the analyzed chars. The analysis was conducted for four extreme cases of process parameters, which included temperatures of 973 and 1173 K as well as pressures of 6 and 8 MPa. The results showed that the maximum hydrogasification reactivity of chars could be accurately described using equations for both the first- and second-order reactions toward hydrogen. This was likely due to the use of a narrow pressure range of 6–8 MPa during the experiments. The kinetic equations developed in the study could be used to model the process on a technical scale.

Refuse derived fuel hydrogasification coupled with methane steam reforming

The hydrogasification of Refuse Derived Fuel (RDF) consisting of non-recyclable plastic polymers was combined with methane steam reforming in a “hydrogen self-sustained” loop configuration. The hydrogasification unit fed by 1000 kg/h of RDF was initially modeled by Aspen plus to define best operating conditions, namely temperature, pressure and hydrogen feed flow rate. After the simulations, the temperature of the hydrogasification process has been fixed at 300 °C, the pressure at 10 bar and the hydrogen feed flow rate at 140 kg/h. The steam reforming unit operates at 850 °C while the water-gas shift is conducted at 350 °C. When all the methane produced by hydrogasification is used to feed the steam reformer, which yields H2 that is recycled back to the hydrogasifier, the net hydrogen production is 222 kg/h with an amount of CO2 released of 2265 kg/h. For the different process configurations adopted, the energy efficiency of the process ranges 84–89%.

Experimental simulations of methane-oriented underground coal gasification using hydrogen - The effect of coal rank and gasification pressure on the hydrogasification process

This paper presents a series of surface experimental simulations of methane-oriented underground coal gasification using hydrogen as gasification medium. The main aim of the experiments conducted was to evaluate the feasibility of methane-rich gas production through the in situ coal hydrogasification process. Two multi-day trials were carried out using large scale gasification facilities designed for ex situ experimental simulations of the underground coal gasification (UCG) process. Two different coals were investigated: the “Six Feet” semi-anthracite (Wales) and the “Wesoła" hard coal (Poland). The coal samples were extracted directly from the respective coal seams in the form of large blocks. The gasification tests were conducted in the artificial coal seams (0.41 × 0.41 × 3.05 m) under two distinct pressure regimes - 20 and 40 bar. The series of experiments conducted demonstrated that the physicochemical properties of coal (coal rank) considerably affect the hydrogasification process. For both gasification pressures applied, gas from “Six Feet” semi-anthracite was characterized by a higher content of methane. The average CH4 concentration for “Six Feet” experiment during the H2 stage was 24.12% at 20 bar and 27.03% at 40 bar. During the hydrogasification of “Wesoła" coal, CH4 concentration was 19.28% and 21.71% at 20 and 40 bar, respectively. The process was characterized by high stability and reproducibility of conditions favorable for methane formation in the whole sequence of gasification cycles. Although the feasibility of methane-rich gas production by underground hydrogasification was initially demonstrated, further techno-economic studies are necessary to assess the economic feasibility of methane production using this process.

Magnetic Carbon Composites Derived from Coal Hydrogasification Residue for Microwave Absorption

To cut the cost of microwave absorption materials (MAMs) and achieve the recycling of semicoke (SC), the by‐product in coal hydrogasification process, SC was applied to prepare composite MAMs. The facile synthesis process involves liquid‐phase impregnation, and then in situ carbothermal reduction treatment. Champion sample prepared under 800 °C (FeSC800) exhibits the minimum reflection loss (RLmin) of −39.3 dB under a coating thickness of 2.5 mm, and the effective absorption bandwidth (EAB) can reach 3.9 GHz (14.1–18 GHz) at a coating thickness of 1.5 mm. The enhancement of interfacial and dipole polarization, as well as the synergistic effect between the dielectric properties of SC matrix and the magnetic properties of Fe particles, can account for the excellent microwave absorption (MA) performance. In view of the source of SC matrix, the prepared FeSC800 was not only expected to become a candidate in the field of MAMs, but also presented a promising approach for the resource utilization of SC.

Gasification of wood biomass with renewable hydrogen for the production of synthetic natural gas

In this article we argue that the broad diffusion of renewables such as solar and wind power in the global energy system will probably require the development of efficient systems for the storage of excess electricity produced during off-peak hours. We also point out that in many places on Earth wood is a type of biomass that is available in large quantities as by-product of agricultural and industrial activities, which could be valorized through gasification processes that produce syngas. We combine these two observations by presenting an analysis of a power-to-gas system in which hydrogen obtained via electrolysis is used for the hydrogasification of wood. This process produces a synthetic natural gas (SNG) mixture that consists mostly of methane with only minor impurities of hydrogen. We show that the SNG generated in this sustainable way represents an efficient means for renewable energy storage. We also study wood hydrogasification processes with hydrogen production methods alternative to electrolysis, such as the partial oxidation of biomass, the water gas shift reaction, and the Sabatier reaction. We determine the process operating conditions that maximize the SNG yield and energy efficiency. Through an economic assessment we examine the applicability of the process to a plant located in Northern Italy. In all process types SNG exhibits characteristics that comply with methane grid quality requirements. We conclude that SNG production through wood hydrogasification can compete with methane market prices when using zero-cost renewable electricity produced during off-peak hours.

Cogeneration of power and substitute of natural gas using biomass and electrolytic hydrogen

Storing renewable energy sources is becoming a very important issue to allow a further reduction of greenhouse gas emissions. Most of such energy sources generate electric power which not always can be conveniently transferred to the grid and also its conversion to hydrogen presents some critical aspects connected mainly to hydrogen distribution and storage.Electrolysis generates not only hydrogen, but also oxygen which could be used to burn biomass or waste products (oxycombustion) in power plants with the result to obtain an exhaust gas containing mainly water and CO2. This last can be converted into a mixture of methane and hydrogen by reacting with electrolytic hydrogen, so that the power used for electrolysis is stored into a fuel which can be distributed and stored just like natural gas.In this paper, an innovative biomass fuelled plant has been designed and simulated for different layouts with an internal combustion engine as a main power system. Utilizing hydrogen and oxygen produced through electrolysis and applying a hydrogasification process, the plant produces electricity and a substitute of natural gas. The result of such simulations is that the electricity can be stored in a useful and versatile fuel with a marginal efficiency up to 60%.

Coal hydrogasification: Entrained flow bed design-operation and experimental study of hydrogasification characteristics

Coal hydrogasification processes including wire-mesh grid reactor, batch reactor, curie-point pyrolyzer, fixed bed reactor and so on were utilized or developed in laboratory researches. Although the experimental results could help to understand the basic behavior of coal hydrogasification, it was difficult to directly utilize such data for devising a new hydrogasifier. This paper designed a continuous entrained flow bed facility and described the hydrogasification characteristics. This device (15–30 kg/d) mainly consisted of a high-H2 pressure feed system, a high-temperature tube reactor. The capabilities were shown as follows: the temperature from 700 °C to 850 °C, H2 pressure from 0.1 MPa to 3.0 MPa, isothermal zone 300–600 mm, feeding rate from 15 to 30 kg/d and water yield was easy to obtained by tar-water separation. The good mass balance on the carbon and weight basis was established by analyzing the product distribution in detail. The results showed the yields of CH4 and light aromatic hydrocarbons increased through hydrogenation of tar and volatiles, hydrogasification of coal char. Although the small pilot plant had high heat loss through refractory with increasing H2 pressure, the typical results obtained from the continuous stable operation of the entrained flow bed reactor confirmed the design of new large-scale hydrogasification process was technical feasibility.

EU scenarios of renewable coal hydro-gasification for SNG production

The competitiveness of the substitute natural gas (SNG) production via hydrogasification of coal strongly depends on the availability of low-cost hydrogen. Today this could be obtained by renewable sources, particularly wind and solar, when energy production exceeds consumption (off-peak hours). In fact SNG not only can be considered as an attractive, versatile energy carrier for coal, but also can be used for storage of surplus power from renewables, promoting their penetration in the future energy systems.In this work, hydro-gasification processes are therefore evaluated as a novel option for the energy policy of the European Union (EU). The results of a process simulation on samples of European coals have been used to assess the energy and exergy efficiencies of the specific case studies.Particularly, this work shows that in EU the production of up to 100×109Nm3 of natural gas via coal hydro-gasification is achievable in a near future by requiring only a further acceleration of wind power investments. Such an energy policy could reduce significantly the EU imports of natural gas, develop the flexibility and competitiveness of the energy market and promote the deployment of clean and sustainable energy technologies.

Study on the evolution of the char structure during hydrogasification process using Raman spectroscopy

Abstract In the present study, the hydrogasification of chars produced from different rank coals was carried out in temperature up to 1123 K and in the pressure of 5 MPa using a high pressure fixed bed reactor. The experimental results show that the char hydrogasification process can be divided into two stages: an initial stage with sharp decline in hydrogasification rate and a stable stage with slower decline one. To further explore the hydrogasification mechanism, Raman spectroscopy was used to investigate the evolution of the char structure during hydrogasification. The initial stage can be attributed to the rapid reaction of hydrogen and the functional groups, amorphous carbon remaining in char. The stable stage owes to the gradual consumption of amorphous carbon and the ordering of the microstructure, which was indicated by the decrease in ID3/IG and the increase in IG/IALL with the increasing carbon conversion. Good linear correlations were found between the hydrogasification reactivity and the band area ratios of (ID3 + ID4)/IG and ID1/IG, which denote the active sites and the degree of graphitization of chars, respectively.

Sulcis coal char reactivity under high-pressure H2

The hydrogasification reactivity of charN2 and charH2, obtained from Sulcis coal pyrolysis at 900°C in inert and reductive atmospheres, respectively, was investigated in a commercial microreactor under temperature programmed reaction (TPR) at high-temperature (700–800°C) and high-pressure H2 (1.0–5.0MPa) conditions. The flue gases were analyzed online by FTIR spectrometry for the identification of volatile species produced. The emissions of carbon (CO2 and CO) coming from both chars reached the maximum releasing rate below 500°C, whereas nitrogen-based compounds (HCNO and NH3) were solely detected during the hydrogasification reaction of charN2. Meanwhile, the main product of char hydrogasification CH4 was detected at temperature as low as 450°C. Generally, the carbon conversion values of charN2 were higher than those of charH2. At low-temperature and pressure reaction conditions the carbon conversion of charH2 rapidly went down. A first-order reaction rate dependence on H2 pressure at 800°C was found for charN2, whereas the reaction order was almost double for charH2. The apparent activation energies of charN2–H2 reaction at 1.0 and 5.0MPa pressures were 96 and 78kJmol−1, respectively, whereas the apparent activation energy for charH2–H2 reaction under 5.0MPa pressure was 140kJmol−1. The Sulcis coal reactivity during the hydrogasification process was significantly impacted by the pyrolysis conditions used in getting chars.

Computational-Fluid-Dynamics-Based Evaluation and Optimization of an Entrained-Flow Gasifier Potential for Coal Hydrogasification

To evaluate and optimize a developed two-stage entrained flow bed gasifier when it is used for the coal hydrogasification (CHG) process, a series of comprehensive three-dimensional numerical simulations designed with the orthogonal method are carried out. The effects of different operating conditions, including the reaction pressure p, H2/coal mass ratio Rh/c, and O2/H2 mass ratio Ro/h on the fields and the evolution histories of the gasification parameters as well as the carbon conversion rate (CCR), the CH4 mole fraction (MMF), and the cold gas efficiency (CGE) are analyzed, and meaningful conclusions are obtained. The hydrogasifier proposed in this work performs well. Counter flow can be detected in the gasifier and is beneficial for char conversion. The gas temperature and MMF increase with the height of the gasifier, while the hydrogen mole fraction (HMF) decreases. The water mole fraction (WMF) increases with the height of the gasifier if the gasification temperature is high; otherwise, it will decreases slightly. The distribution of CH4 in the top zone of the reductor tends to be homogeneous with the increase of Ro/h. Ranked in descending order, the effect degrees of the operating conditions on CCR, MMF, and CGE are Ro/h > p > Rh/c, p > Rh/c > Ro/h, and Rh/c > Ro/h = p, respectively. The optimum combinations of the operating conditions for CCR, MMF, and CGE are p = 7 MPa, Rh/c = 0.7, and Ro/h = 1.5; p = 7 MPa, Rh/c = 0.3, and Ro/h = 1.5; and p = 3 MPa (p = 5 MPa), Rh/c = 0.7, and Ro/h = 1.25, respectively. After comprehensive analyses, a synthetically optimal combination of the operating condition is proposed. With this condition, CCR can reach 96.78%, MMF can reach 17.42%, and CGE can reach 76.4%.

Effect of polyethylene addition to coal on hydrogasification enhancement

Hydrogasification of a coal/polyethylene mixture was carried out using a low concentration of polyethylene in the samples with the aim of industrial application. Coal/polyethylene mixtures in the ratio of 90:10 and 75:25 were used in this study. A hydrogasification experiment was conducted using a unique batch reactor at 1073 K under a 7.1 MPa hydrogen atmosphere. The reaction time varied from 1 to 80 s. The results revealed a methane yield from the mixtures that was noticeably greater than the values calculated from experimental results obtained from coal and polyethylene respectively, assuming no mutual influences. A significant synergistic effect was observed even when the polyethylene content was as low as 10 %. It is suggested that there might be an advantage in hydrogasification processes if waste plastics are mixed with coal, such content being practically assumed.

Sorption enhanced steam hydrogasification of coal for synthesis gas production with in-situ CO2 removal and self-sustained hydrogen supply

The in-situ removal of CO2 and the increase of the energetic gas yield, including hydrogen and methane, by sorption enhanced steam hydrogasification (SE-SHR) process were investigated. Lignite was used in this study as the feedstock to the steam hydrogasification reaction (SHR) with the addition of calcined dolomite as a sorbent. CO2 was reduced dramatically with the introduction of the sorbent into the reactor. The production of hydrogen and methane was increased simultaneously. The hydrogen yield was increased by 60% when the calcium oxide to carbon molar ratio was increased to 0.86 as compared to the results without the sorbent. The hydrogen in the product gas was sufficient to maintain a self-sustained supply back to the SHR when the calcium oxide to carbon molar ratio was over 0.29. The performance of the SE-SHR was determined at different temperatures ranging from 650 °C to 800 °C and at different steam to carbon molar ratios. Additionally, the char conversion was also enhanced in all cases with the sorbent introduction. The synthesis gas production using SE-SHR coupled with steam methane reforming was also modeled by Aspen Plus. The simulation results showed that the H2/CO ratio of the synthesis gas generated based on SE-SHR process was 6 with higher overall energy efficiency of 74.5%. Summarily, the main findings of this study were that the overall performance of the SE-SHR was substantially improved compared to the conventional operation of the SHR and the quality of synthesis gas produced based on SE-SHR process was more flexible for the downstream processing.

Hydrogasification of Low-Oxygen Semi-Coke to Produce Methane by Consuming Less Hydrogen

The presented work aimed at investigating the hydrogasification of low-oxygen semi-coke. For comparison, the hydrogasification of lignite was conducted. Variation of gaseous products concentration and reaction rate of the semi-coke hydrogasification process were investigated. The results shown that the methane yield of low-oxygen semi-coke is 24.8% greater than the lignite, but also the hydrogen consumption reduced greatly; the hydrogasification process can be divided into three stages: hydro-pyrolysis stage, rapid hydrogasification stage and slow speed hydrogasification stage; the difference of the reactive is attributed to different carbon structure forms .

Kinetic model and prediction for coal hydrogasification

Coal hydrogasification is a key component of zero emission coal (ZEC) power generation system which discharges little CO2 and other pollutants at a thermal efficiency close to 70%. In addition, coal hydrogasification itself has many advantages. A hydrogasification kinetic model including ten homogeneous reactions and four heterogeneous reactions is established in this work and is validated against experiment data available in literatures. The validated model is then used to predict the effects of different reaction conditions including the reaction temperature T, the reaction pressure pt, the H2/coal mass ratio U and the reaction time t on coal hydrogasification properties. The results indicate that coal hydrogasification is facilitated by the increased pt and t. When T is not higher than 1273 K, the gasification process is promoted with T increment. Increasing U can promote the coal hydrogasification process on the whole. When U is larger than 0.5, however, the coal conversion ratio (xcoal) will slightly decrease with U increment.

An Experimental Investigation on Hydrogasification of Coal Chars in a Fixed Bed Reactor under High Pressure

The Characteristic of Coal Hydrogasification Was Carried Out in a Fixed Bed Reactor by Using Chars of Datong Bituminous, Spain Lignite and Pingdingshan Bituminous. it Was Investigated that the Effects of Reaction Temperature (973-1123K), Reaction Pressure (3-7Mpa), the Char Preparation Temperature (973-1073K) and Catalyst (CaO) on CH4 Yield. the Three Stages Model Was Provided to Explain the Coal Hydrogasification Process. the CH4 Yield Increases Rapidly in the First Stage which Is Dominated by the Reaction of Active Groups (-O-CH3,-COOH,-CH2OH,-CH3) and H2. the CH4 Yield Keeps Constant in the Second Stage. the Releasing Rate of C-O-(C) and C-O-(H) Active Groups Dominates the CH4 Yield Rate. the CH4 Yield Decreases in the Third Stage which Is Dominated by the Reaction Rate of Carbon and Hydrogen. there Is Higher CH4 Yield under Higher Pressure which Is Related to the Higher Reaction Rate of Graphite and H2 under Higher Pressure. the Structure of Raw Coals and Chars Was Identified by FTIR. in Additional, the Influences of Char Structure and Catalyst on the CH4 Yield Are Discussed in the Paper.

The kinetics of coal chars hydrogasification

Hydrogasification reaction of chars produced from two rank coals was investigated in temperature up to 1173 K and pressure up to 8 MPa. The reactivity of the lignite Szczerców char has been found to be slightly higher than of the subbituminous coal Janina char produced at the same conditions. A high value of the char reactivity was observed to certain carbon conversion, above which a sharp drop takes place. It has been shown that to achieve proper carbon conversion the hydrogasification reaction must proceed at temperature above 1200 K. Based on the active centres theory the kinetic equations of the hydrogasification process were developed and the kinetic constants at the maximum reaction rate evaluated for the analyzed chars.

Long-term coal gasification-based power plants with near-zero emissions. Part A: Zecomix cycle

These two part papers analyse three plant configurations for high efficiency, near-zero emissions power generation from coal, suitable for long-term installations. In the first part the Zecomix cycle, a novel power plant based on various innovative processes, is presented. Zecomix plant is based on a coal hydrogasification process, using recycled steam and hydrogen as gasifying agents, to produce a CH 4 rich syngas. Methane is then converted to an H 2/H 2O based syngas and CO 2 is captured, by reacting in two carbonator reactors with CaO-based solid sorbent. CaCO 3 produced in carbonators is thermally regenerated in a calciner. The synthetic fuel is burned with oxygen in a semi-closed high temperature steam cycle, with a supercritical heat recovery. The paper presents a detailed analysis of the thermodynamic aspects of the process, with the scope of assessing its potential performance in terms of efficiency and emissions. Main operating parameters of the chemical island (e.g. hydrogasifier and calciner pressure, steam flow rates to carbonators, syngas recycle fraction) and of the power island (e.g. pressure ratio, turbine inlet temperature and reheat pressure) were varied in order to evaluate their effect on plant performance and to optimize the process. Critical issues are specifically discussed: the calcination process, the calcium oxide utilization in carbonators, the cooling requirement of the high temperature turbine, the presence of incondensable species in the steam cycle. An accurate performance estimation is therefore developed by considering advanced components, as an evolution of today's technology, excluding unproven devices whose feasibility cannot be anticipated. Depending on sorbent utilization, a net plant efficiency of 44–47% with a virtually complete carbon capture was obtained, a very interesting result with respect to other proposed coal-fired power plants with carbon capture. The high complexity of the chemical island and the importance of a good sorbent performance should be however taken into account for a fair comparison with other plant concepts. Further experimental investigations are mandatory to demonstrate the technical and economical feasibility of the Zecomix plant.

Zecomix: A zero-emissions coal power plant, based on hydro-gasification, CO2 capture by calcium looping and semi-closed high temperature steam cycle

Abstract This paper analyzes various aspects of the Zecomix cycle, a novel coal fired power plant, based on various innovative processes to achieve elevated efficiency and zero-emissions. A coal hydro-gasification process, using recycled steam and hydrogen as gasifying agents, converts carbon to CH 4 , which is then processed by two carbonator reactors where CH 4 , mixed with steam and contacted with calcium oxide, is converted to an H 2 /H 2 O based syngas while CO 2 is absorbed by the solid sorbent generating CaCO3. The synthetic fuel produced in the chemical island is burned with oxygen in a semi-closed high temperature steam cycle, with a rather complex supercritical heat recovery steam cycle. The main relevant operating parameters for the chemical island are varied in order to evaluate their effect on plant performance and to optimize the process. In addition, the paper presents a rather detailed analysis of some critical issues, often neglected in previous works from the literature. Net plant efficiency of 44–47% with a virtually complete carbon capture was predicted, a very interesting results with respect to other proposed coal power plants with carbon capture. The high complexity of the chemical island and the importance of a good sorbent performance in the critical conditions typical of this plant should be however taken into account for a fair comparison with other plant concepts.

Chemical kinetics-based analysis for utilities of ZEC power generation system

Zero Emission Coal (ZEC) power generation, via Hydrogen Gasification and Solid Oxide Fuel Cell (SOFC), is a newly developed technology that could meet the future energy demand through the continuous utilization of abundant fossil fuel resources while overcoming potential environmental hurdles, especially greenhouse gas CO 2 emission. In this paper, chemical kinetics-based analysis for future ZEC system was conducted using the conceptual design operation conditions. The major finding from this research indicated that under a preferred condition, the major reactions occurred in ZEC system can perform with maintaining the high equilibrium rate of conversion. In the light of higher fractions converted by the hydro-gasification process, the reaction temperature in the gasification vessel should be controlled lower than 1100 K and the pressure a little higher than 60 atm in the practical operation. The temperatures for Reformers A and B should be kept under 1100 K and the pressure in Reformer B should be lower than that in Reformer A, which is almost the same as the SOFC in order to drive the CO 2 absorption reaction. The reaction temperature should be kept lower than 1500 K and the pressure higher than 3 atm, preferably higher than 10 atm for higher power generation by the electrochemical process in the fuel cell. These findings will provide necessary reference data for the future designs, guide practical operations, and build a solid foundation for further research on Zero Emission Coal power generation systems.