Integrated Coal Gasification Combined Cycle Research Articles

2-02 石炭ガス化複合発電（IGCC）の微量元素挙動シミュレーション

2-02 石炭ガス化複合発電（IGCC）の微量元素挙動シミュレーション

Research and development of high efficiency low emission combined cycle power plant arrangements

Coal-fired steam turbine thermal power plants produce a large part of electricity. These power plants usually have low efficiency and high carbon dioxide emission. An application of combined cycle power plants with coal gasification equipped with carbon capture and storage systems may increase the efficiency and decrease the harmful emission. This paper describes investigation of the oxidizer type in the integrated gasification combined cycle combustion chamber and its influence upon the energy and environmental performance. The integrated gasification combined cycle and oxy-fuel combustion technology allow the carbon dioxide capture and storage losses 58% smaller than the traditional air combustion one. The IGCC with air combustion without and with carbon dioxide capture and storage has 53.54 and 46.61% and with oxy-fuel combustion has 34.94 and 32.67% net efficiency. Together with this the CO2 emission drops down from 89.9 to 10.6 gm/kWh. The integrated coal gasification combined cycle with air oxidizer has the best net efficiency.

Numerical Study of Ammonia/O2-Fired Semiclosed Cycle Gas Turbine for Oxy-Fuel IGCC Power Generation With CO2 Capture

Abstract With an increase in renewable energy generation, thermal power generation has been switched to standby power in various parts of the world. Ammonia, one of the storage and transport media for H2, is produced in a highly efficient oxyfuel integrated coal gasification combined cycle (IGCC) system with CO2 capture, for the future hydrogen-using society. Using ammonia as an industrial raw material, agricultural fertilizer, and transportation fuel, energy systems can be established by combining renewable energy and thermal power generation. Therefore, it is possible to simultaneously construct a thermal power supply system suitable for backup power source owing to the fluctuation of the renewable power generation and to improve the availability of the thermal power plant and the load-leveling. This will serve as an incentive to build a future zero-emission thermal power plant. In this study, an oxy-fuel IGCC power generation coproduced with ammonia and CO2 capture is conceptually proposed. Furthermore, the features and challenges of a gas turbine that fuels CO2-free NH3 are investigated. In particular, the combustion exhaust characteristics of ammonia/oxygen-fired semiclosed cycle gas turbine combustor in comparison with those of the conventional fuels are characterized through a kinetic analysis.

Characterization of clathrate hydrate formed in H2 + CO2 + tetrahydropyran + water system as carbon capture materials

This paper reports the thermodynamic and crystallographic characterization of the clathrate hydrate formed in H2 + CO2 + tetrahydropyran (THP) + water system by phase equilibrium measurements and powder X-ray diffraction measurements with a goal of developing a hydrate-based carbon capture technology in an integrated coal gasification combined cycle. The four-phase [(H2 + CO2) gas + water liquid + THP liquid + hydrate] equilibrium conditions were measured with two series of gas compositions (around H2:CO2 = 0.7:0.3 and 0.9:0.1 in mole fractions) in the range of 2.64 MPa to 7.51 MPa. At around H2:CO2 = 0.7:0.3 in gas phase, the equilibrium temperatures in (H2 + CO2) gas + THP + water system are always higher by approximately 9 to 10 K compared to the equilibrium temperatures of H2 + CO2 + water system. This means that THP acts as the hydrate thermodynamic promoter. The equilibrium conditions in (H2 + CO2) gas + THP + water system, which is only considered with CO2 partial pressure, greatly agree with those in CO2 + THP + water system. Therefore, the equilibrium conditions in (H2 + CO2) gas + THP + water system would only depend on the partial pressure of CO2. Moreover, the crystallographic structure of the hydrate formed in H2 + CO2 + THP + water system was identified to be structure II, which is the same structure as the hydrate formed in H2 + CO2 + water system. These results can contribute to the study of a hydrate-based gas separation and carbon capture.

Deep insight into phase transition and crystallization of high temperature molten slag during cooling: A review

High temperature molten slags, such as blast furnace slag, mold flux, coal slag, etc., exist widely in the metal manufacturing and energy power industries and play important roles in equipment operation, energy saving and emissions reduction as well as resource reuse. The treatment of high temperature molten slag usually involves a phase change cooling process coupled with crystallization behavior, which is a very challenging process and will significantly affect the high-temperature waste heat recovery, the vitreous content in slag, the quality of the as-cast slab, and the stable operation of the integrated coal gasification combined cycle system. This paper firstly reviews the main methods to explore the crystallization behaviors of molten slag. Then, the crystallization behaviors of molten slag are discussed under different cooling rates and main components. In what follows, the attempts on the prediction of molten slag crystallization behaviors are summarized. The major conclusions and future research priorities are as follows: The critical cooling rate of molten slag decreases gradually when it undergoes the isothermal temperature, continuous cooling and variable cooling condition. Moreover, the variation of the precipitated crystal phase is the essential reason that affects the crystallization behaviors of molten slag. To better guide the practical process, it has a long way to go in predicting the crystallization behavior of molten slag using the easy-to-obtain parameters.

Influence of removal efficiency on a moving granular bed filter

High power generation efficiency and environmental performance are obtained in the integrated coal gasification combined cycle (IGCC) power plants. Hot gas clean-up is a key technology in IGCC systems. In this paper, a moving granular bed filter was constructed to examine the effect on collection efficiency when variations in the working parameters, namely, the mass flow rate, the filtration superficial velocity, and the amount of dust particulates at the inlet were introduced. A method to enhance particulate removal was proposed and tested in a lab-scale experiment. In addition, the study analyses the motion of gas flow in the inlet gas device of filter system. The results indicated a low amount of dust in the outlet of filter system when a mass flow rate of 0.008 kg/s and a filtration superficial velocity of 0.42 m/s were used. Furthermore, this new method is suitable for IGCC and other industrial areas involving high-temperature environments.

Performance evaluation and carbon assessment of IGCC power plant with coal quality

Techno-economic and environmental impacts of coal type were evaluated using a 500 MW-class integrated coal gasification combined cycle(IGCC), including reheat combined cycle process with three-pressure level based on higher than 99.9% sulfur removal and 90% carbon capture. Efficiency and cost of electricity(COE) of four different coals in the IGCC power plant were compared: two bituminous and two sub-bituminous coals. As coal with higher heating value per unit weight was fed into a gasifier, higher cold gas efficiency of the gasifier and greater net overall plant efficiency was achieved. The highest overall plant efficiency of 31.62% could be achieved by using bituminous. Raw water consumption was also affected by the moisture content of the as-received coal. The as-received coal with the highest moisture content consumed the least amount of water. The exergy flow and destruction were presented in Grassmann diagrams to provide more detailed information on main units. However, according to the sensitivity test, the COE was mainly influenced by fuel prices and costs of CO2 transport and storage. If the price difference between bituminous coals and sub-bituminous coals is reduced, the utilization of bituminous coals becomes more competitive in terms of COE and capital cost.

Life cycle assessment of transformation from a sub-critical power plant into a polygeneration plant

Coal-fired power plants retirement is a worldwide problem due to the universal desire to control temperature increase less than 2 °C. Chinese government has also made clear plans to develop renewable electricity gradually in place of coal-fired electricity. The first to be affected are the small power units, which suffer from decreased operation hours and environmental protection problems simultaneously. The two possible fates of these small power plants are to be decommissioned or to be retrofitted into more advanced energy systems. Recently, we transformed a sub-critical power plant into a polygeneration plant using the dual fluidized bed pyrolysis technology and proposed two transformation methods, including the partial and complete transformation. A life cycle assessment (LCA) of the three scenarios, including two transformation scenarios and the original power plant scenario, is also performed to assess the transformation effect. The life cycle results are also compared with that of the ultra-supercritical (USC) unit and the integrated coal gasification combined cycle (IGCC) unit. As a result, 3600 MJ of energy output is adopted as the function unit. The LCA analysis indicates that the complete transformation for polygeneration is the best of all the five scenarios in view of almost all impact categories (CML 2001) and energy utilization performance. Compared with the original sub-critical power plant, the complete transformation can reduce greenhouse gas emissions by 36.5 percent. Besides, the complete transformation can also reduce acidification potential by up to 50.1 percent relative to IGCC. Moreover, the net energy efficiency of the complete transformation scenario is 3.65 percent higher than that of USC technology. Therefore, the current study may demonstrate the feasibility of transformation from the existing power plants to the polygeneration plants to achieve the goal of cleaner production, which may also provide a new idea for the upgrading of small power plants.

Estimation of cold gas efficiency and reactor size of low-temperature gasifier for advanced-integrated coal gasification combined cycle systems

In order to achieve power-generation efficiency higher than those of integrated coal gasification combined cycle plants, advanced integrated coal gasification combined cycle systems have been developed. Here, we developed a triple-bed combined circulating fluidized bed gasifier model using the commercial process simulator Aspen Plus® (version 8.6) and Excel®. The heat balance and reaction kinetics, including the inhibition of steam gasification by H2, were simulated for a combustor temperature of 950 °C using porous alumina particles as heat-carrying particles. The theoretical maximum cold gas efficiency of the triple-bed combined circulating fluidized bed gasifier model was 85.0% for a gasification temperature of 800 °C. However, when the temperature was increased to 900 °C, the efficiency decreased to 80.9%. This indicates that, for triple-bed combined circulating fluidized bed gasifiers, a relatively low gasification temperature is suitable for ensuring higher cold gas efficiency and reducing the amount of circulating heat-carrying particles needed. On the other hand, gasification temperatures lower than 850 °C resulted in significantly higher bubbling fluidized bed gasifier volumes even when an effective Ca-based catalyst was used. The cold gas efficiency can be increased further by 8.6% by converting and recovering the missing hydrogen as H2 gas. Hence, there is a trade-off between the cold gas efficiency, gasifier size, and heat-carrying particle/coal ratio. The optimal gasification temperature for triple-bed combined circulating fluidized bed gasifier is 850 °C.

An effective method for optimization of the flow chart of thermal power plant

In this work, a methodical approach to the optimization of schemes and parameters of power plants based on the development of the optimization method of the most complex scheme using discretely varying parameters is proposed. To solve the problem, the branch and bound method was used. A mathematical model of the integrated coal gasification combined cycle power plant is developed, which allows to jointly optimize the operating and design parameters and the flow chart. On the basis of a series of optimization calculations on the criterion of the minimum electricity price, a tree of potentially optimal variants was built. The optimal combination of the flow chart of the power plant, cycle parameters and the design parameters of the elements was found.

No.2-11 大崎クールジェンプロジェクトにおける酸素吹石炭ガス化複合発電(IGCC)実証試験状況報告

No.2-11 大崎クールジェンプロジェクトにおける酸素吹石炭ガス化複合発電(IGCC)実証試験状況報告

Critical assessment of oxy-fuel integrated coal gasification combined cycles

Critical assessment was performed for a type of oxy-fuel integrated coal gasification combined cycles (IGCC) that was comprised of proven components. A type of two-stage entrained-flow gasifier consisting of combustor and reductor sections was simulated by a one-dimensional model that has been proven through application to gasifiers of industrial scales. It was successfully reproduced on Aspen Plus® and integrated together with the other components into a commercial-scale IGCC system. The oxidizing agents were not only O2 and CO2 (carrier gas for conveying the coal) but also additional CO2 or CO2/H2O, that was required to suppress hydrocarbons formation and maintain the combustor temperature allowing molten ash to have sufficiently low viscosity. The net thermal efficiency was predicted as a function of steam/coal mass ratio (S/C) within a range of 0–0.4. Increasing S/C up to 0.2 increased the cold gas efficiency slightly but resulted in decrease in the net thermal efficiency of the system. This was mainly due to the extraction of steam from the high pressure steam turbine exhaust, causing loss of power output. Resulting in lower cold gas efficiency due to higher oxygen ratio, higher moisture content of the pulverized coal gave higher net thermal efficiency due to less steam consumption for coal drying. The net efficiency was optimized at approximately 39% on a higher-heating-value basis without steam feeding, which was higher by 6–7 points than that for conventional IGCC with oxygen-blown gasification combined with CO2 recovery.

Two-stage data envelopment analysis with undesirable intermediate measures: an application to air quality improvement in China

Air pollution continues to pose a major threat to human health in China and its neighbor countries including Japan. Although the general clean air trend in China is to replace older coal-fired generation with clean energy, $$60\%$$ coal consumption in the overall energy use still makes it the most coal-dependent country. Improvement of the coal-fired generation efficiency is fully expected to play a vital role for the foreseeable future. Focusing on the main air pollutants, this paper presents a comprehensive study from the target region selection in China to the benefit allocation analysis for a potential collaboration between China and Japan in Integrated coal Gasification Combined Cycle (IGCC). Both radial and non-radial two-stage data envelopment analysis models with undesirable intermediate measures are applied first to evaluate the regional air quality improvement efficiencies in China (2005–2014). Due to the extremely high initial and dynamic investment for IGCC, target regions with the highest priorities to be installed with this technology are selected by k-means clustering method based on the results of two-stage data transformation model under variable returns to scale. Finally, a benefit analysis by multi-criteria allocation game with the principal performance indices from two representative IGCC power plants in China and Japan provides further insights for the mutual motivations of this kind of collaboration and uncovers some international policy implications.

Multi-objective optimization of an integrated gasification combined cycle for hydrogen and electricity production

In this paper, an integrated coal gasification combined cycle system for the production of hydrogen and electricity is optimized in terms of energy and exergy efficiencies, and the amount and cost of the produced hydrogen and electricity. The integrated system is optimized by focusing on the conversion process of coal to syngas. A novel optimization process is developed which integrates an artificial neural network with a genetic algorithm. The gasification system is modeled and simulated with Aspen Plus for large ranges of operating conditions, where the artificial neural network method is used to represent the simulation results mathematically. The mathematical model is then optimized using a genetic algorithm method. The optimization demonstrates that the lower is the grade of coal of the three considered coals, the less expensive is the hydrogen and electricity that can be produced by the considered integrated gasification combined cycle (IGCC) system.

Progress of Osaki CoolGen Project of Oxygen-blown IGCC Demonstration

Coal-fired power plants, which provide stable power at low cost, will continue to serve as base load supporting the world's increasing power demands. However, the amount of CO2 emitted by coal utilization is larger than that of other fossil fuels. Therefore the Osaki CoolGen Project has been launched to realize innovative HELE (High Efficiency, Low Emissions) coal-fired power generation which combines an Integrated coal Gasification Combined Cycle (IGCC) / Integrated coal Gasification Fuel Cell combined cycle (IGFC) with CO2 capture. This project is subsidized by the Ministry of Economy, Trade and Industry (until 2015 FY) and New Energy and Industrial Technology Development Organization (from 2016 FY). The oxygen-blown IGCC demonstration test, which is the base technology for IGFC, commenced in March 2017. We've achieved world-class net efficiency, environmental performance, plant reliability and flexibility. Construction of CO2 capture unit started in April 2018 and is underway to start demonstration test.

Evaluation of Integrated Air Pollution and Climate Change Policies: Case Study in the Thermal Power Sector in Chongqing City, China

The cost of environmental degradation has already had a dramatic impact on the Chinese economy. In order to curb these trends, the government of China has introduced stricter regulations. With this in mind, it is important to quantify the potential co-benefits of introducing air pollution and climate change mitigation policies. This study proposes relevant scenarios ranging from the current trends (baseline) to the introduction of different policies in the thermal power sector, including different carbon tax rates, technology innovation promotion, and technology cost reduction methods. We aim to comparatively evaluate the impact of the proposed policies within the thermal sector and within the entire socio-economic system. To this end, we used a dynamic input–output (I-O) model, into which high-efficiency technologies were incorporated as new thermal power industries in order to estimate policy impact during the time period 2010–2025. The results of this study demonstrated that the introduction of one or more of the following policies: carbon taxes, subsidies, technology innovation, and technology cost reduction, has no notable impact on the environment or the economy without the implementation of environment regulations. In contrast, the strong support of a government subsidy coupled with strict environmental regulations will promote technological innovation, for example through the natural gas combined cycle (NGCC) and the integrated coal gasification combined cycle (IGCC). Our study also showed that the reduction of air pollution and greenhouse gas emissions as well as energy consumption would curb economic development to a certain extent. Taking this into consideration, innovation must also be promoted in other economic sectors. This research provides a strong reference for policy-makers to identify effective polices under different types of environmental regulations.

Performance, economic and exergy analyses of carbon capture processes for a 300 MW class integrated gasification combined cycle power plant

The techno-economic analysis of the CCPs was performed for a 300 MW class integrated coal gasification combined cycle (IGCC) power plant. In the study, the a-MDEA and Selexol processes were selected for the analysis as the representative of the chemical and physical solvent-based carbon capture process (CCPs). A rigorous evaluation of dual-stage CCPs, including power generation, economic evaluations, and exergy destruction, was performed. The net power of a-MDEA and Selexol processes was 267.3 MW and 291.4 MW, respectively, which corresponded to the thermal efficiencies of the dual-stage a-MDEA process of 32.3% and Selexol process of 35.2%. According to the economic analysis, the CAPEX of the Selexol process was approximately 1.39 times more expensive than that of the a-MDEA process. However, the OPEX of the Selexol process for removing a ton of CO2 was approximately one third of that of the a-MDEA process. The exergy flow and destruction were also discussed to evaluate the associated impact on the major components of CCPs. Based on the exergy analysis, the suggestion to improve thermal efficiency was made and result was also briefly discussed. These results can aid in decision-making and in process development for commercial-scale CCPs with respect to thermodynamic and economic analyses.

Thermal efficiency of advanced integrated coal gasification combined cycle power generation systems with low-temperature gasifier, gas cleaning and CO2 capturing units

Advanced integrated coal gasification combined cycle (A-IGCC) systems have been proposed to obtain higher thermal efficiency than that of IGCC systems by recuperating exhaust heat from a gas turbine to provide the heat source for a gasifier. The performances of the A-IGCC systems with a low-temperature dual-bed fluidized bed gasifier, gas cleaning, CO2 capturing, and the most advanced (1650°C-class) gas turbine units were evaluated using Aspen Plus®. Net thermal efficiency of the A-IGCC model with hot gas desulfurizing unit using ZnO and TiO2 was 53.6% and that with cold gas desulfurizing unit using Selexol® process was 52.0% without CO2 capturing when the cold gas efficiency (CGE) in the gasifier was 80.1%. The net thermal efficiency can be increased to 54.7–57.2% by improving CGE from 80.1 to 85.0%, suggesting the improvement of cold gas efficiency in the gasifier is critical. CO2 emission factors of the A-IGCC system are 505–520kg-CO2/MWh (CGE=80.1%) and 468–490kg-CO2/MWh (CGE=85.0%), and can be decreased to 39.7–112kg-CO2/MWh with 80–95% of CO2 capturing. Compliance to the CO2 emission factor target (<499kg-CO2/MWh) for coal-fired power generation systems can be achieved without CO2 capturing by developing gasifiers whose CGE is 85.0% and integration with 1650°C-glass gas turbine.

Insights to the microwave effect in the preparation of sorbent for H2S removal: Desulfurization kinetics and characterization

High temperature coal gas desulfurization is an efficient and environmental-friendly process for clean coal technologies such as the integrated coal gasification combined cycle. This study adopted microwaves as the energy source to prepare iron oxide desulfurization sorbents and investigated the effect of microwave heating on the properties of the sorbents. The desulfurization kinetics of H2S removal by the two kinds of sorbents heated using both microwave and conventional method were studied and the sorbents were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), N2-adsorption and energy dispersive spectrometry (EDS). The shrinking core model was used to describe the desulfurization reaction. The calculated activation energies of microwave-heated sorbent in the regions of chemical reaction and diffusion control were both smaller than those of the conventional-heated sorbent. The characterization data indicate that the sorbents prepared by microwave heating have higher contents of active metal elements on the surface, which improve the adsorption efficiency. Fractal dimensions were calculated based on Frenkel-Halsey-Hill theory and the results revealed that the fractal dimension of microwave-heated sorbent is 2.850 and that of conventional-heated sorbent is 2.832. The results indicate that microwave irradiation provides a more porous internal structure and irregular surface which facilitates gas transfer during the desulfurization process. Overall, the microwave heating method produced sorbents with better H2S removal performance, suggesting the potential of using this method to prepare improved industrial sorbents.

Development of advanced air-blown entrained-flow two-stage bituminous coal IGCC gasifier

Integrated gasification combined cycle (IGCC) technology has two main advantages: high efficiency, and low levels of harmful emissions. Key element of IGCC is gasifier, which converts solid fuel into a combustible synthesis gas. One of the most promising gasifiers is air-blown entrained-flow two-stage bituminous coal gasifier developed by Mitsubishi Heavy Industries (MHI). The most obvious way to develop advanced gasifier is improvement of commercial-scale 1700 t/d MHI gasifier using the computational fluid dynamics (CFD) method. Modernization of commercial-scale 1700 t/d MHI gasifier is made by changing the regime parameters in order to improve its cold gas efficiency (CGE) and environmental performance, namely H2 /CO ratio. The first change is supply of high temperature (900°C) steam in gasifier second stage. And the second change is additional heating of blast air to 900°C.