Gasification Combined Cycle Power Generation Research Articles

Comprehensive Assessment and Empirical Research on Green and Low-Carbon Technologies in the Steel Industry

The iron and steel industry is the leading industry supporting China’s industrial sector. Currently, there is less assessment work on green and low-carbon technologies for the iron and steel industry. This study clarifies the overall strategy of technology assessment by researching the relevant theories and methods of technology assessment. The study further establishes a scientific and reasonable comprehensive assessment index system of green and low-carbon technologies for the iron and steel industry from the aspects of technology index, economy and promotion, and application, including factors such as 11 indexes, the amount of energy saving, carbon dioxide emission reduction, and the resource recovery rate by utilising analytical and comprehensive methods and combining with the characteristics of the technologies. By analysing and comparing the advantages and disadvantages of the commonly used assessment methods, the entropy weighting method, grey correlation analysis method, and TOPSIS (technique for order preference by similarity to an ideal solution) method are combined and optimised to construct a comprehensive assessment model. The Latin hypercube sampling method is also introduced to analyse the technical parameters in combination with the evaluation model. Finally, fourteen iron and steel green and low-carbon technologies were selected for case assessment and uncertainty analysis of technical parameters, and it was found that the comprehensive assessment result of gas combined cycle power generation technology was optimal. After determining the weights of each assessment indicator through the entropy weighting method, it is concluded that the technical performance indicator > economic indicator > promotional indicator. A comparative analysis of the results under the three preference decisions concludes that technical performance is the main obstacle to improving the comprehensive assessment score of the technology, followed by the economics of the technology. Finally, the uncertainty analysis of the technical parameters shows that the fluctuation of the technical parameters not only affects the performance of the technology, but also affects the weights of the indicators and the comprehensive evaluation results of the technology.

High efficient pre-combustion CO2 capture by using porous slurry formed with ZIF-8 and isoparaffin C16

Integrated gasification combined cycle (IGCC) power generation has drawn more and more attention because of the increasing demand for zero CO2 emission. H2/CO2 mixture with middle/higher pressure like IGCC gas is usually separated by using low energy consumption physical absorption approach. Here, for upgrading traditional physical absorbents, we report a new porous slurry formed with ZIF-8 and isoparaffin C16 to raise CO2 capture capacity and selectivity. The properties and sorption behaviors of this slurry have been experimentally investigated, and the content of ZIF-8 is optimized as 20 wt%. The optimized slurry exhibits low viscosity (11.02–2.75 mPa·s when temperature ranges from 273.15 to 303.15 K), sufficiently high sorption speed, low CO2 sorption heat (9.39–18.47 kJ/mol, decreasing with increasing CO2 loading). More importantly, the slurry exhibits much higher CO2 sorption capacity (e.g., 3.39 mol/L/MPa at 0.1 MPa and 273.15 K, vs. 2.48 mol/L/MPa for dimethyl ethers of polyethylene glycol (DEPG) and 2.22 mol/L/MPa for propylene carbonate (PC)) and selectivity over H2 (17.4–205, which could be one time higher than DEPG and three times higher than PC). The recyclability of this slurry system is also excellent. The 98% sorption capacity is recovered by vacuuming for 5 min without heating, showing that the easy sorption-desorption cycle can be completed only via pressure swing. We believe ZIF-8/isoparaffin C16 slurry would be a promising alternative to existing commercial CO2 absorbent for separating IGCC gas with higher efficiency and lower energy cost.

Basic intensity regulation of layered double oxide for CO2 adsorption process at medium temperature in coal gasification

High purity hydrogen for integrated gasification combined cycle power generation (IGCC) can be produced by efficient adsorption of CO2 after water gas shift reaction in coal gasification. Based on adjustability of composition in layered double hydroxides (LDH) precursor, basicity intensity was modified and exhibited different adsorption capacity. Relationship among basic sites, CO2-bound modes, and adsorption capacity were established. Furthermore, by utilizing LDH anionic exchangeability, we introduced laurate ion into LDH interlamellar, and further mediated surface structure using methyl cellulose with long carbon chain. As-obtained Mg3Al-LDO-C12-MC effectively increased the number of medium/strong basic sites. Consequently, CO2-adsorption capacity at medium temperature of 300 °C was further increased to 0.85 mmol/g with the maximum rate of 0.37 mmol/g·min. This work develops a strategy to regulate basic site of adsorbents according to structural mechanism for CO2 elimination under medium temperature, and thus improve adsorption performance in industrial coal gasification process.

A low energy consumption de-carbonization natural gas combined cycle power generation system based on LiBr/H2O absorption heat transformer

An integrated system of natural gas combined cycle (NGCC) with monoethanolamine-based (MEA-based) CO2 capture was proposed in this study aiming to reduce the efficiency penalty of CO2 mitigation. In the proposed system, three measures were adopted: (1) utilizing absorption heat transformer (AHT) and ejector to recover the waste heat as well as providing suitable steam for solvent regeneration; (2) recirculating part of reboiler condensate to fully utilize the superheat degree of the extracted steam, and (3) injecting reboiler condensate into the regenerative system of power cycle to reuse the surplus heat of reboiler condensate. Thermodynamic benefits and economic viability of the proposed system were compared with the de-carbonization NGCC power plant without integration. Results indicated the efficiency penalty of CO2 capture in the proposed system decreased by 2.67 percentage points. Meanwhile, the cost of electricity and the cost of CO2 avoided were reduced by 4.73% and 15.08%, respectively, while the adopted additional devices caused an increase of the investment by 19.12 M$.

Emergy evaluation of the integrated gasification combined cycle power generation systems with a carbon capture system

An Integrated Gasification Combined Cycle (IGCC) power generation system has a significant effect on improving resource utilization efficiency. Carbon capture and storage (CCS) has been widely adopted to control greenhouse gas emissions. The integration of the two systems can further reduce CO2 emissions but cause elevated investment costs. As an effective tool to evaluate resource utilization efficiency and environmental impact, emergy analysis on coal and biomass based IGCC power generation systems with/without CCS is conducted in this paper. The coal based IGCC systems are simulated in Aspen plus to obtain the electricity generated under different CCS scales. For other systems, the data for emergy evaluation are from references. The sustainabilities under different CO2 tax values are compared. The factors impacting the sustainabilities are discussed. The results show that when CCS is not considered, all IGCC systems are superior to coal and biomass direct-fired systems in terms of sustainability. After CCS is integrated, the sustainability of biomass based IGCC system is still higher than that of biomass direct-fired systems, while coal based IGCC systems are less sustainable than coal direct-fired systems under low CO2 tax. The sustainabilities of Texaco-IGCC systems increase with CCS scales when CO2 tax is higher than 0.0220 $/kg, emphasizing CCS at a larger scale. For the Shell-IGCC systems, a higher CO2 tax (0.3880 $/kg) is preferred for the promotion of large scale CCS. In the scenario that the cost emergy transformity improves, the CO2 tax value at the point of sustainabilities reversal will decrease.

Simulation of a new biomass integrated gasification combined cycle (BIGCC) power generation system using Aspen Plus: Performance analysis and energetic assessment

A new biomass integrated gasification combined cycle (BIGCC), which featured an innovative two-stage enriched air gasification system coupling a fluidized bed with a swirl-melting furnace, was proposed and built for clean and efficient biomass utilization. The performance of biomass gasification and power generation under various operating conditions was assessed using a comprehensive Aspen Plus model for system optimization. The model was validated by pilot-scale experimental data and gas turbine regulations, showing good agreement. Parameters including oxygen percentage of enriched air (OP), gasification temperature, excess air ratio and compressor pressure ratio were studied for BIGCC optimization. Results showed that increase OP could effectively improve syngas quality and two-stage gasification efficiency, enhancing the gas turbine inlet and outlet temperature. The maximum BIGCC fuel utilization efficiency could be obtained at OP of 40%. Increasing gasification temperature showed a negative effect on the two-stage gasification performance. For efficient BIGCC operation, the excess air ratio should be below 3.5 to maintain a designed gas turbine inlet temperature. Modest increase of compressor pressure ratio favored the power generation. Finally, the BIGCC energy analysis further proved the rationality of system design and sufficient utilization of biomass energy.

Emergy evaluation of power generation systems

With the increasing demand of power sources, it is of great significance to evaluate different power generation systems and optimize the energy structure. The emergy is proved to be a comprehensive and powerful way to evaluate the sustainability of a system. In this paper, emergy is used to compare ten power generation systems by two calculation methods of emergy indices. The emergy data of integrated gasification combined cycle and wind power generation systems are gathered from the studies of life cycle assessment, while those of the other eight systems are taken from existing emergy evaluations and converted to the same baseline. The study of hydropower generation systems shows the influence of technical progress and geographical location to the sustainability. The comparison of ten power generation systems shows that the hydropower generation system has the best sustainability while the wind and solar systems demonstrate relatively low sustainability. Besides, the sustainability is relative to the carbon dioxide tax. The sustainability of wind and concentrated solar power generation systems is tend to be better than that of integrated gasification combined cycle power generation system with an increase in the carbon dioxide tax. The results indicate that the technology, investment cost and carbon dioxide emission are essential factors to sustainability of power generation systems.

Scenario-based DEA assessment of energy-saving technological combinations in aluminum industry

This study deals with technology evaluation by employing the data envelopment analysis (DEA) methodologies from a life-cycle analysis (LCA) perspective. Aluminum production is associated with high electricity consumption. Thus, the environmental pressures of the whole production chain largely rely on the electricity generation process. This is particularly true for China, because coal-fired power generation dominates China’s electricity supply. Many of aluminum plants in China consume electricity which is directly supplied by coal-fired plants. Given these facts, LCA perspective in this study is believed to be of distinctive significance. Therefore, this paper discusses the process requiring high-energy consumption and causing high pollution from the LCA perspective and combines data envelopment analysis with LCA to evaluate and select energy-saving technological routes throughout for the complete supply chain. In total, 16 technological combinations are considered, and three models are established for different sets of efficiency indicators: energy performance indicator, energy performance indicator with undesirable output, and total performance indicator. Moreover, four scenarios with different policy considerations are designed: baseline scenario, subsidy scenario, low-carbon-price scenario, and high-carbon-price scenario. The results show that upon only considering energy input and output at the same price, a power generation mode has the greatest impact on energy consumption. After considering undesirable output, such as pollutant emissions, the technological routes including coal-fired power generation have the worst performance. Considering all inputs and outputs with the same price, the most crucial factor affecting efficiency is cost, followed by anode; subsidies have a low effect. For the four scenarios, two technological routes including a biomass-integrated gasification combined cycle power generation and inert anode rank in the top 50% decision-making units with three efficiency indices. This paper proposes an effective decision-making method for evaluating and selecting energy-saving technology routes for the aluminum industry, which can be easily applied to other sectors with similar characteristics. This provides a generic framework for a profound analysis to promote clean production and environmental sustainability.

Life cycle environmental impact assessment of coupled underground coal gasification and CO2 capture and storage: Alternative end uses for the UCG product gases

Underground coal gasification (UCG) has the potential to provide a source of energy or chemical feedstock derived from coal seams, where traditional mining methods are not suitable or are uneconomical. This paper presents the life cycle inventory models developed for the UCG processes and three alternative syngas utilisation options with and without CO2 capture and storage. The paper compares the life cycle carbon footprint of two different conventional above ground coal fired power generation options with UCG Integrated Gasification Combined Cycle power generation with/without CCS for two different lignites and one bituminous coal. One of the lignites is then used to compare the life cycle performance of different syngas utilisation options: power generation, ammonia production with power generation, and methanol production with power generation. It was found that the life cycle carbon footprint of conventional above ground coal fired power generation is very much dependent on the in-situ methane content of the coal used, and methane emissions experienced during mining and accompanying upstream processes, whereas the same for UCG-IGCC power depends more on the process dependent syngas composition. UCG methanol production with associated power and CCS is shown to release more life cycle CO2-eq emissions per tonne of lignite consumed than that of UCG ammonia production with associated power and CCS and UCG CCGT power generation with CCS. Furthermore, when chemicals production from UCG is considered as the main objective, the most substantial improvements in comparison to conventional methods are associated with UCG ammonia process per tonne of chemical produced.

Development of reusable mercury sorbents for an oxy-fuel IGCC power generation system

Gaseous elemental mercury (Hg0) removal tests, using copper-based sorbents (CBS) developed in-house, were performed in a laboratory scale fixed-bed reactor. The aim was to find potential candidate sorbents to use in a dry syngas purification process plant. The dry purification process is under development for oxy-fuel integrated gasification combined cycle (IGCC) power generation with an efficient carbon dioxide separation function. The performance of CBS was evaluated as a function of two major characteristics. First, Hg0 removal performance of the CBS is improved by pre-sulfidation. Second, Hg0 removal performance of the spent CBS is recovered through moderate heating under diluted O2 conditions. A honeycomb type sorbent was prepared by impregnating raw material of the CBS onto the honeycomb-shaped support. Since copper sulfide will effectively capture Hg0 in a reducing gas atmosphere, the CBS honeycomb was initially pre-sulfurized by H2S diluted with N2 at 120 °C in a fixed-bed reactor until complete breakthrough of H2S. The simulated syngas from the oxy-fuel IGCC was fed into the reactor with conditions set at 140 °C and 0.98 MPa, where the Hg0 in the syngas was reduced to below 1.0 µg/m3N by the CBS honeycomb. The spent CBS honeycomb was regenerated by introducing 1 vol-% of O2 diluted with N2 at 280 °C. The sequential operation of pre-sulfidation, mercury removal, and regeneration steps was performed cyclically three times, during which the CBS honeycomb maintained a satisfying Hg0 removal performance. These results revealed that the A-CBS honeycomb is a potential candidate for the dry mercury removal process in the Oxy-fuel IGCC power generation plant.

Co2 Capture from Natural Gas Combined Cycle Power Generation Using Carbonate Fuel Cells

Co2 Capture from Natural Gas Combined Cycle Power Generation Using Carbonate Fuel Cells

Life Cycle Analysis of Integrated Gasification Combined Cycle Power Generation in the Context of Southeast Asia

Coal remains a major source of electricity production even under the current state of developments in climate policies due to national energy priorities. Coal remains the most attractive option, especially to the developing economies in Southeast Asia, due to its abundance and affordability in the region, despite the heavily polluting nature of this energy source. Gasification of coal running on an integration gasification combined cycle (IGCC) power generation with carbon capture and storage (CCS) represents an option to reduce the environmental impacts of power generation from coal, but the decarbonization potential and suitability of IGCC in the context of Southeast Asia remain unclear. Using Singapore as an example, this paper presents a study on the life cycle analysis (LCA) of IGCC power generation with and without CCS based on a generic process-driven analysis method. We further evaluate the suitability of IGCC with and without CCS as an option to address the energy and climate objectives for the developing economies in Southeast Asia. Findings suggest that the current IGCC technology is a much less attractive option in the context of Southeast Asia when compared to other available power generation technologies, such as solar photovoltaic systems, coal with CCS, and potentially nuclear power technologies.

Dry syngas purification process for coal gas produced in oxy-fuel type integrated gasification combined cycle power generation with carbon dioxide capturing feature

Electricity production from coal fuel with minimizing efficiency penalty for the carbon dioxide abatement will bring us sustainable and compatible energy utilization. One of the promising options is oxy-fuel type Integrated Gasification Combined Cycle (oxy-fuel IGCC) power generation that is estimated to achieve thermal efficiency of 44% at lower heating value (LHV) base and provide compressed carbon dioxide (CO2) with concentration of 93 vol%. The proper operation of the plant is established by introducing dry syngas cleaning processes to control halide and sulfur compounds satisfying tolerate contaminants level of gas turbine. To realize the dry process, the bench scale test facility was planned to demonstrate the first-ever halide and sulfur removal with fixed bed reactor using actual syngas from O2–CO2 blown gasifier for the oxy-fuel IGCC power generation. Design parameter for the test facility was required for the candidate sorbents for halide removal and sulfur removal. Breakthrough test was performed on two kinds of halide sorbents at accelerated condition and on honeycomb desulfurization sorbent at varied space velocity condition. The results for the both sorbents for halide and sulfur exhibited sufficient removal within the satisfactory short depth of sorbent bed, as well as superior bed conversion of the impurity removal reaction. These performance evaluation of the candidate sorbents of halide and sulfur removal provided rational and affordable design parameters for the bench scale test facility to demonstrate the dry syngas cleaning process for oxy-fuel IGCC system as the scaled up step of process development.

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.

5-12.石炭ガス化複合発電実現のための新しい技術開発(Session(5)実用化を迎える石炭利用技術)

5-12.石炭ガス化複合発電実現のための新しい技術開発(Session(5)実用化を迎える石炭利用技術)

Carbon behavior in the cyclic operation of dry desulfurization process for oxy-fuel integrated gasification combined cycle power generation

The dry sulfur-removal process is essential to provide suitable syngas treatment for the oxy-fuel integrated gasification combined cycle power generation plant. It is required that the dry sulfur-removal process to be durable to the carbon deposition due to syngas containing high concentration of carbon monoxide in addition to achieve sufficient performance for sulfur removal. Zinc ferrite sorbent is the most promising candidate for the dry sulfur-removal process. The sorbent was improved to enhance durability to the carbon deposition by modifying preparation. The improved sorbent was prepared from sulfates as the raw materials of zinc ferrite, while the former sorbent was using nitrates as the raw materials. The improved sorbent as well as the former sorbent were evaluated on the performance and carbon deposition tendency in oxy-fuel syngas condition in a fixed bed reactor at elevated pressure and temperature. The results expressed that the improved sorbent has higher desulfurization performance and durability to carbon deposition in the condition expected for cyclic operation of the sulfur-removal process in comparison with the former sorbent. The improved sorbent possessed the superior desulfurization performance as well as the capability for inhibit carbon deposition in the oxy-fuel syngas conditions. The results confirmed the enhanced feasibility of the dry sulfur-removal process by utilizing the improved sorbent.

Correlation between the critical viscosity and ash fusion temperatures of coal gasifier ashes

Coal gasification yields synthesis gas, an important intermediate in chemical manufacturing. It is also vital to the production of liquid fuels through the Fischer-Tropsch process and electricity in Integrated Gasification Combined Cycle power generation. Minerals naturally present in coal become molten in entrained-flow slagging gasifiers. Molten coal ash slag penetrates and dissolves refractory bricks, leading to costly plant shutdowns. The extent of coal ash slag penetration and refractory brick dissolution depends on the slag viscosity, the gasification temperature, and the composition of slag and bricks. We measured the viscosity of several synthetic coal ash slags with a high-temperature rotary viscometer and their ash fusion temperatures through optical image analysis. All measurements were made in a carbon monoxide-carbon dioxide reducing atmosphere that approximates coal gasification conditions. Empirical correlation models based on ash fusion temperatures were used to calculate critical viscosity temperatures based on the coal ash compositions. These values were then compared with those obtained from thermodynamic phase-transition models. An understanding of slag viscosity as a function of ash composition is important to reducing refractory wear in slagging coal gasifiers, which would help to reduce the cost and environmental impact of coal for chemical and electricity production.

Performance evaluation of porous sodium aluminate sorbent for halide removal process in oxy-fuel IGCC power generation plant

Integrated coal gasification combined cycle power generation that adopts oxy-fuel concept has potential to achieve thermal efficiency of 44% at lower heating value besides its CO2 separation ability. Halide control as well as dry gas sulfur removal is inescapable process to the proper operation of the plant. This study investigates performance of dry halide sorbents to establish suitable halide control procedure for the power plant. The most appropriate position of the process is considered to be in the upper stream of the dry sulfur removal process, where the process is able to prevent both corrosion of gas turbine and halogenation of zinc in the desulfurization sorbent. Preproduction sorbents for the dry-gas halide removal process were prepared as pellets containing sodium aluminate as a main ingredient. The sorbents could absorb stoichiometric amount of hydrogen chloride at 450 °C and 0.98 MPa absolute in a simulated coal derived gas environment. The fresh and spent sorbents were examined for dependence of kinetics of halide removal reaction on their pore structures. The results showed that the pore structure comprising of macropore peak at around 5.0 μm and smaller peaks at 1.0 μm or below was suitable to attain affordable kinetics on halide removal and sodium conversion of the sorbent.

Characterization of a Nitrogen Diluted Hydrogen Diffusion Flame for Model Validation

Dilute hydrogen diffusion flames have been considered as a gas turbine combustion strategy that provides relatively low levels of NOx emissions for application in integrated gasification combined cycle power generation. These flames also represent a challenging environment for computational modeling efforts due to the complexity of molecular transport effects, turbulence-chemistry interaction, and near extinction flame conditions. In order to provide data for validation of computational modeling efforts, measurements of major species concentration and flame temperature were made in such a flame using spontaneous Raman scattering. Experimental results demonstrate the importance of differential species diffusion, which occurs due to the disparity between diffusion characteristics of hydrogen and nitrogen. Additionally, the flame temperatures observed were quite low relative to the equilibrium flame temperature, due to flame strain. This confirms the fact that suppression of the thermal mechanism of NOx formation plays a significant role in reducing NOx emissions from this type of flame.

Comparative life cycle analyses of bulk-scale coal-fueled solid oxide fuel cell power plants

Detailed cradle-to-grave life cycle analyses are performed for bulk-scale solid oxide fuel cell power plants fueled by gasified coal. These results are compared to cradle-to-grave life cycle analyses of the supercritical pulverized coal and integrated gasification combined cycle power generation plants, which are also performed as a part of this study. Life cycle inventories for each plant including the inputs (resources and fuels) and outputs (emissions and waste) of the gate-to-gate plants and their associated up- and down-stream sub-processes are computed. The impact of carbon capture and sequestration on each plant is quantified and assessed using the ReCiPe 2008 life cycle inventory method for three socioeconomic perspectives. The results of each coal plant are compared to one another and to plants generating power from natural gas at the end-point level. Results indicate that not only do coal-fed SOFCs generate power with a significantly lower life cycle impact than the current state-of-the-art coal plants, but when carbon capture is enabled they can do so with a lower impact than the most modern plants utilizing natural gas, as well.