Integrated Gasification Combined Cycle Plant Research Articles

Role of steam, hydrogen and pretreatment in chrysotile gas–solid carbonation: Opportunities for pre-combustion CO2 capture

Enhancing gas–solid carbonation of serpentines could prefigure the emergence of new dry processes that may compete with aqueous carbonation. The hypothesis of pre-combustion CO2 capture to decarbonize shifted syngas in integrated gasification combined cycle plants was examined in this work from a chemistry standpoint. A systematic gas–solid carbonation study of chrysotile was carried out in a basket reactor using model (H2O/H2/CO2) shifted syngas where CO2 uptakes were measured after 1h carbonations between 100°C and 220°C at 3.2MPa total pressures. Partial dehydroxylation and steam mediation substantially enhanced meta-chrysotile carbonation achieving uptakes as high as 0.7 CO2 moles per Mg mole at 130°C. Also, combined X-ray powder diffraction, X-ray photoelectron spectra and CO2 uptake studies indicated that the presence of H2 did not prevent carbonation of meta-chrysotile nor derailed Mg availability towards hydrides or metallic Mg. Chrysotile pre-dehydroxylation in the conditions of gasification was also emulated using catalytic steam reforming of a model-tar compound. However, post-carbonation of spent chrysotile, before and after coke burn-off, achieved at best ca. 0.02 CO2 uptakes suggesting that using the same magnesium silicate batch in gasification then in carbonation may be impractical.

Simulation of Water-Gas Shift Membrane Reactor for Integrated Gasification Combined Cycle Plant with CO2 Capture

The effectiveness of energy conversion and carbon dioxide sequestration in Integrated Gasification Combined Cycle (IGCC) is highly dependent on the syngas composition and its further processing. Water gas shift membrane reactor (WGSMR) enables a promising way of syngas-to-hydrogen conversion with favourable carbon dioxide sequestration capabilities. This paper deals with a numerical approach to the modelling of a water gas shift reaction (WGSR) in a membrane reactor which promotes a reaction process by selectively removing hydrogen from the reaction zone through the membrane, making the reaction equilibrium shifting to the product side. Modelling of the WGSR kinetics was based on Bradford mechanism which was used to develop a code within Mathematica programming language to simulate the chemical reactions. The results were implemented as initial and boundary conditions for the tubular WGSMR model designed with Aspen Plus software to analyze the broader system behaviour. On the basis of selected boundary conditions the designed base case model predicts that 89.1% CO conversion can be achieved. Calculations show that more than 70% of carbon monoxide conversion into hydrogen appears along the first 40% of reactor length scale. For isothermal conditions more than two thirds of the heat released by WGSR should be extracted from the first 20% of the reactor length. Sensitivity analysis of the WGSMR was also performed by changing the membrane’s permeance and surface area.

Materials challenges and gasifier choices in IGCC processes for clean and efficient energy conversion

In the 1970 and 1980s, gasifiers were envisaged for synthesising substitute natural gas (SNG) as well for IGCC (integrated gasification combined cycle) systems. Component temperatures were above 700°C, but stainless alloys did not have the required corrosion resistance. Experimental alloys developed in the UK were alumina formers, incorporating Ta, W, and Mo as gettering elements for sulphidation resistance. Sulphidation corrosion is solvable, but attack by HCl in gasification environments seems intractable. The supposed materials problems of gasification, plus the complexity of IGCC, have led to them being sidelined for power generation. However, commercial IGCC plants are not dependent on high temperature materials and offer higher efficiency than Rankine cycle steam. Best near term prospects for IGCC are for CO2 capture, but this constrains the type of gasifier. Gasifiers incorporating carbon capture and storage produce hydrogen, or with less capture, SNG. Such systems will supply SNG for space heating as well as electricity, and can cope with the intermittency of wind energy. High efficiency IGCCs will need very advanced gas turbines with 100 bar, 1500-1600°C turbine inlet conditions. Key requirements will be thermal barrier coatings and catalytic combustor materials. Such gas turbines would offer efficiencies of 70% in straight CCGTs, or 50% when used in carbon capture IGCCs.

Analysis of Membrane and Adsorbent Processes for Warm Syngas Cleanup in Integrated Gasification Combined-Cycle Power with CO2 Capture and Sequestration

Integrated gasification combined cycle (IGCC) with CO2 capture and sequestration (CCS) offers a promising approach for cleanly using abundant coal reserves of the world to generate electricity. The present state-of-the-art synthesis gas (syngas) cleanup technologies in IGCC involve cooling the syngas from the gasifier to room temperature or lower for removing sulfur, carbon dioxide, and other pollutants, leading to a large efficiency loss. Here we assess the suitability of various alternative syngas cleanup technologies for IGCC with CCS through computational simulations. We model multicomponent gas separation for CO2 capture in IGCC using polymeric membranes and H2 separation from the syngas using both Pd-alloy based composite metallic membranes and polymeric membranes. In addition, we develop a pressure swing adsorption model to estimate the energy efficiency of regenerable sorbent beds for CO2 capture. We use our models with Aspen Plus simulations to identify promising design and operating conditions for membrane and adsorption processes in an IGCC plant. On the basis of our analysis, the benefits of warm gas cleanup are not as great as previously reported in the literature, and only CO2 separations performed using H2-permeable Pd-alloy membranes and CO2 adsorbents produce overall higher heating value (HHV) efficiencies higher than that of Selexol. In addition, many of the technologies surveyed require a narrow operating range of process parameters in order to be viable alternatives. We identify desired material properties of membranes and thermodynamic properties of sorbents that are needed to make these technologies successful, providing direction for ongoing experimental efforts to develop these materials.

Optimal design and integration of an air separation unit (ASU) for an integrated gasification combined cycle (IGCC) power plant with CO 2 capture

The air separation unit (ASU) plays a key role in improving the efficiency, availability, and operability of an oxygen-fed integrated gasification combined cycle (IGCC) power plant. An optimal integration between the ASU and the balance of the plant, especially the gasifier and the gas turbine (GT), has significant potential for enhancing the overall plant efficiency. Considering the higher operating pressure of the GT, an elevated-pressure air separation unit (EP-ASU) is usually favored instead of the conventional low-pressure air separation units (LP-ASU). In addition, a pumped liquid oxygen (PLOX) cycle is usually chosen if the operating pressure of the gasifier is high. A PLOX cycle helps to improve plant safety and availability and to decrease the capital cost by reducing the size of the oxygen compressor or by eliminating it completely. However, the refrigeration lost in withdrawn liquid oxygen must be efficiently recovered. This paper considers five different configurations of an ASU with PLOX cycle and compares their power consumptions with an EP-ASU with a traditional gaseous oxygen (GOX) cycle. The study shows that an optimally designed EP-ASU with a PLOX cycle can have similar power consumption to that of an EP-ASU with GOX cycle in the case of 100% nitrogen integration. In the case of an IGCC with pre-combustion CO 2 capture, the lower heating value (LHV) of the shifted syngas, both on a mass and volumetric basis, is in between the LHV of the unshifted syngas from an IGCC plant and the LHV of natural gas, for which the GTs are generally designed. The optimal air integration in the case of a shifted syngas is found to be much lower than that of an unshifted syngas. This paper concurs with the existing literature that the optimal integration occurs when air extracted from the GT can be replaced with the nitrogen from the ASU without exceeding mass/volumetric flow limitations of the GT. Considering nitrogen and air integration between the ASU and the GT, this paper compares the power savings in an LP-ASU with a PLOX cycle to the power savings in an EP-ASU with GOX cycle and EP-ASU with PLOX cycle. The results show that an LP-ASU with a PLOX cycle has less power consumption if the nitrogen integration levels are less than 50–60%. In addition, a study is carried out by varying the concentration of nitrogen and steam in the fuel diluents to the GT while the NOx level was maintained constant. The study shows that when the nitrogen injection rate exceeds 50%, an EP-ASU with a PLOX cycle is a better option than an LP-ASU with a PLOX cycle. This paper shows that an optimal design and integration of an ASU with the balance of the plant can help to increase the net power generation from an IGCC plant with CO 2 capture.

Integrated gasification combined cycle and carbon capture: A risky option to mitigate CO 2 emissions of coal-fired power plants

The power sectors of many big economies still rely on coal-fired plants and emit huge amounts of carbon dioxide. Emerging countries like Brazil, China and South Africa plan to expand the use of coal-fired thermal plants in the next decade. Integrated gasification combined cycle (IGCC) is an innovative technology that facilitates the implementation of carbon capture (CC). The present work analyzes the maturity and costs of the IGCC technology, with and without CC, and assesses the effect of the technology risk on its economic viability. Findings show that the inclusion of the risk in the economic analysis of IGCC plants raises the cost of CO 2 avoided from 36 US$/t CO2 to 106 US$/t CO2 in the case of Shell Gasifiers and from 39 US$/t CO2 to 112 US$/t CO2 in the case of GE Gasifiers. Thus, the introduction of IGCC with CC on a wider scale faces huge uncertainties. The feasibility of these plants will rely heavily on the overcoming of the technology risk. Besides, its implementation in the short run will depend on government incentives to bear with the additional cost incurred in the first-generation plants.

Numerical optimization of heat recovery steam cycles: Mathematical model, two-stage algorithm and applications

Most of the advanced integrated energy systems need a heat recovery steam cycle (HRSC), either fired or unfired, that recovers the waste heat from gas turbines and process units in order to generate electric power and supply mechanical power to compressors, heat to endothermic processes, and steam to external users. The key feature of such HRSCs is the integration between the heat recovery steam generator (HRSG) and the external heat exchangers. This paper presents a rigorous mathematical programming model, a linear approximation, and a two-stage algorithm for optimizing the design of integrated HRSGs and HRSCs, simultaneously considering the HRSG together with the heat recovery steam network and the intensive steam cycle variables. A detailed application of the methodology is described for an integrated gasification combined cycle plant with CO 2 capture and results for other interesting plants are reported. A significant efficiency gain is obtained with respect to usual practice designs.

Combined Electric Power and Carbon-Dioxide Separation (CEPACS) Technology

FuelCell Energy, Inc. has developed novel system concepts for separation of carbon dioxide from greenhouse gas emission sources, using its patented Direct FuelCell® (DFC®) technology. DFC is based on carbonate fuel cells featuring internal reforming. The unique chemistry of carbonate fuel cells offers an innovative approach for separation of CO2 from fossil-fuel power plant exhaust streams (flue gases). DFC-based CO2 separation systems are suitable for many types of coal-based power plants, from existing pulverized coal-fired boiler steam cycle plants to future integrated gasification combined cycle plants. The carbonate fuel cell system also produces electric power at high efficiency. Cost of electricity analysis of the DFC system indicates that the simultaneous generation of power and CO2 capture is an attractive scenario for re-powering the existing coal-fueled power plants.

Structured exergy analysis of an integrated gasification combined cycle (IGCC) plant with carbon capture

In order to identify approaches for integrated gasification combined cycle (IGCC) plant optimization it is necessary to analyse where and why the losses in the process occur. Therefore a structured exergy analysis of an IGCC with carbon capture was performed to identify losses on a plant, subsystem and individual component level. The investigation of the IGCC base case revealed an exergetic efficiency of 40%. Thus, 60% of the whole fuel exergy is lost in the process. On the subsystem level it was found that the major loss contributor is the combined cycle followed by the gas treatment section and the gasification island. Furthermore, it was demonstrated that the significance of the losses is higher in upstream processes than in downstream processes. On the individual component level it is shown that 80% of all exergy losses in the plant are caused by just 4 components. Since two of them are related to the gas conditioning an advanced hot gas clean-up (HGCU) system was proposed which improves exergy efficiency of the IGCC plant by 5.2%-points. However, assuming an ideal IGCC process an exergy efficiency of 54.1% was calculated demonstrating significant potential for further optimization of the technology.

Advanced simulation environment for clean power production in IGCC plants

Abstract Oxygen-blown biomass integrated gasification combined cycle (IGCC) plants are one of the most promising options for clean energy generation with CO 2 abatement potential. However, the integrated nature of IGCC leads to difficult design problems. In this study, we present an advanced simulation environment for the preliminary design and retrofit of IGCC plants. We describe the modelling approach, the model validation strategy and the plant behaviour, as determined by sensitivity analyses. The simulation environment uses Pareto curves to examine various co-gasification and co-production case studies in terms of technical, economic and environmental performance. It serves as a decision support tool in the design stage, which can be used to explore ways to improve plant performance and to analyse the influence of raw materials and the unit’s operational parameters. The test and validation results are discussed.

Integrated gasification and Cu–Cl cycle for trigeneration of hydrogen, steam and electricity

This paper develops and analyzes an integrated process model of an Integrated Gasification Combined Cycle (IGCC) and a thermochemical copper–chlorine (Cu–Cl) cycle for trigeneration of hydrogen, steam and electricity. The process model is developed with Aspen HYSYS software. By using oxygen instead of air for the gasification process, where oxygen is provided by the integrated Cu–Cl cycle, it is found that the hydrogen content of produced syngas increases by about 20%, due to improvement of the gasification combustion efficiency and reduction of syngas NO x emissions. Moreover, about 60% of external heat required for the integrated Cu–Cl cycle can be provided by the IGCC plant, with minor modifications of the steam cycle, and a slight decrease of IGCC overall efficiency. Integration of gasification and thermochemical hydrogen production can provide significant improvements in the overall hydrogen, steam and electricity output, when compared against the processes each operating separately and independently of each other.

CAESAR: SEWGS integration into an IGCC plant

Abstract This paper investigates the performance of SEWGS (Sorption Enhanced Water Gas Shift), an innovative reactor for CO 2 capture, applied to Integrated Gasification Combined Cycle (IGCC). Firstly, two IGCC reference cases based on dry feed slagging Shell gasifier, with and without CO 2 capture, are defined. Then, two different integrations of SEWGS are investigated. The first assumes a conventional low-temperature acid gas removal process adopted upstream the SEWGS; this solution shows slight thermodynamic advantages towards the reference case with CO 2 capture (higher efficiency of 1% point), but not from lay-out simplification and equipment savings. The second solution assumes a simultaneous CO 2 and sulphur separation from the syngas; this results in a net electric efficiency gain over the reference case of about 2 percentage points. Moreover, this solution allows a significant plant simplification and equipment reduction with further advantages from economic point of view, which is not evaluated in this work. This activity is carried out under the FP7 project CAESAR financed by the EU community.

Technical evaluations of carbon capture options for power generation from coal and biomass based on integrated gasification combined cycle scheme

Abstract Integrated Gasification Combined Cycle (IGCC) is a technology for power generation in which the feedstock is partially oxidized with oxygen and steam to produce syngas. In a conventional IGCC design without carbon capture, the syngas is purified for dust and hydrogen sulphide removal and then sent to a Combined Cycle Gas Turbine (CCGT) for power production. The hot GT flue gases are sent to Heat Recovery Steam Generator (HRSG) for steam generation. Additional power is produces by expanding the steam generated in a steam turbine. Carbon capture and storage (CCS) technologies are expected to play a significant role in the coming decades for reducing the greenhouse gas emissions. Integrated Gasification Combined Cycle is one of the power generation technologies having the highest potential to capture carbon dioxide with the low penalties in term of plant energy efficiency and cost. The modification of the IGCC design for carbon capture can be done in various plant concepts considering the carbon capture method to be used (e.g. pre- and post-combustion capture, syngas chemical looping etc.). This paper investigates various carbon capture methods suitable to be applied for an IGCC plant for power generation. The coal blended with biomass (sawdust) based IGCC case study investigated in the paper produces around 400–500 MW net electricity with more than 90% carbon capture rate. An important focus of the paper is concentrated on overall energy efficiency optimization of the IGCC plant concepts with various carbon capture options by better heat and power integration of the main plant sub-systems (e.g. steam integration between gasification island, syngas conditioning line and the steam cycle, influence of heat and power demand for Acid Gas Removal unit etc.). A particular attention of the paper is focused on the quality specification for the captured carbon dioxide stream considering various capture options but also the storage options (enhanced oil recovery, storage in depleted oil and gas fields, saline aquifers etc.).

Steady-State Simulation and Optimization of an Integrated Gasification Combined Cycle Power Plant with CO2 Capture

Integrated gasification combined cycle (IGCC) plants are a promising technology option for power generation with carbon dioxide (CO2) capture in view of their efficiency and environmental advantages over conventional coal utilization technologies. This paper presents a three-phase, top-down, optimization-based approach for designing an IGCC plant with precombustion CO2 capture in a process simulator environment. In the first design phase, important global design decisions are made on the basis of plant-wide optimization studies with the aim of increasing IGCC thermal efficiency and thereby making better use of coal resources and reducing CO2 emissions. For the design of an IGCC plant with 90% CO2 capture, the optimal combination of the extent of carbon monoxide (CO) conversion in the water−gas shift (WGS) reactors and the extent of CO2 capture in the SELEXOL process, using dimethylether of polyethylene glycol as the solvent, is determined in the first phase. In the second design phase, the impact of local...

Gas hydrate formation method to capture the carbon dioxide for pre-combustion process in IGCC plant

In this study, we investigated the effect of tetra-n-butyl ammonium bromide (TBAB) on separation and/or collection of CO 2 from CO 2/H 2 (40:60) gas mixture via hydrate crystallization. The phase equilibrium conditions shifted to milder conditions as increasing the amount of TBAB additive up to 3.0 mol%. The existence of the critical concentration of the additive effects on the phase equilibrium conditions was also observed. The hydrate formation rate in 1.0 mol% TBAB solution showed the highest value while the hydrate formation rate in 3.0 mol% TBAB solution showed the lowest value. Raman analyses revealed that only CO 2 gas molecules enclathrated under experimental conditions carried out in this study. The phase equilibrium temperature of CO 2–H 2 (40:60) mixture gas hydrate systems with TBAB additive located in the range of between 283 and 290 K at the integrated gasification combined cycle (IGCC) process pressure range of 2.5–5.0 MPa. This study provides the potential of hydrate process to separate the CO 2 gas from CO 2–H 2 (40:60) mixture gas in IGCC process without significantly lowering the processing temperature.

Carbonate Fuel Cell Application for Synergistic Power Generation and Carbon Dioxide Capture

FuelCell Energy, Inc. (FCE) has developed novel system concepts for separation of carbon dioxide from greenhouse gas emission sources, using Direct FuelCell® (DFC®) technology. DFC is based on carbonate fuel cells featuring internal reforming. The unique chemistry of carbonate fuel cells offers an innovative approach for separation of CO2 from fossil-fuel power plant exhaust streams (flue gases). DFC-based CO2 separation systems are suitable for many types of coal-based power plants, from existing pulverized coal (PC) plants to future integrated gasification combined cycle (IGCC) plants. The carbonate fuel cell system also produces electric power at high efficiency. Cost of electricity (COE) analysis of the DFC system suggests that the simultaneous generation of power and CO2 capture is an attractive scenario for re-powering the existing coal-fueled power plants.

Combined production of hydrogen and power from heavy oil gasification: Pinch analysis, thermodynamic and economic evaluations

Integrated Gasification Combined Cycle (IGCC) represents a commercially proven technology available for the combined production of hydrogen and electricity power from coal and heavy residue oils. When associated with CO 2 capture and sequestration facilities, the IGCC plant gives an answer to the search for a clean and environmentally compatible use of high sulphur and heavy metal contents fuels, the possibility of installing large size plants for competitive electric power and hydrogen production, and a low cost of CO 2 avoidance. The paper describes two new and realistic configurations of IGCC plant fed by refinery heavy residues and including a CO 2 capture section, which are proposed on the basis of the experience gained in the construction of similar plants. They are based on oxygen blown entrained bed gasification and sized to produce a large amount of hydrogen and to feed one or two gas turbines of the combined cycle unit. The main thermodynamic and technological characteristics of the total plants are evaluated focusing on the heat integration between syngas cooling and combined cycle sections. Moreover, the overall performance characteristics and investment cost are estimated to supply a reliable estimate for the cost of electricity, given a value for the hydrogen selling price.

가스화 복합화력발전 플랜트에서 CO2제거가 성능에 미치는 영향 해석

In the power generation industry, various efforts are needed to cope with tightening regulation on carbon dioxide emission. Integrated gasification combined cycle (IGCC) is a relatively environmentally friendly power generation method using coal. Moreover, pre-combustion capture is possible in the IGCC system. Therefore, much effort is being made to develop advanced IGCC systems. However, removal of prior to the gas turbine may affect the system performance and operation because the fuel flow, which is supplied to the gas turbine, is reduced in comparison with normal IGCC plants. This study predicts, through a parametric analysis, system performances of both an IGCC plant using normal syngas and a plant with capture. Performance characteristics are compared and influence of capture is discussed. By removing from the syngas, the heating value of the fuel increases, and thus the required fuel flow to the gas turbine is reduced. The resulting reduction in turbine flow lowers the compressor pressure ratio, which alleviates the compressor surge problem. The performance of the bottoming cycle is not influenced much.

Co-gasification Reactivity of Coal and Woody Biomass in High-Temperature Gasification†

While biomass has been co-fired at pulverized coal boilers in power stations for a high-efficiency use of biomass, there have been few reports on the co-gasification using entrained flow gasifiers, which are adopted for the major integrated gasification combined cycle plants. In this work, two bituminous coals, cedar bark, and the mixtures of coal and cedar bark were gasified with carbon dioxide at high temperature using a drop tube furnace. As a result, distinguished synergy between coal and cedar bark to improve their gasification reactivity was not observed through the high-temperature co-gasification. The product yields during the co-pyrolysis in nitrogen gas at high temperature agreed with the equilibrium yields, and the char reactivity of the mixtures of coal and biomass was almost the same as that of single coals at the high-temperature gasification. In the case of low-temperature gasification, however, a little improvement of the char gasification reactivity of the mixtures was found because of the catalysis of alkaline and alkaline-earth metal species in biomass.

Performance analysis of a syngas-fed gas turbine considering the operating limitations of its components

As the need for clean coal technology grows, research and development efforts for integrated gasification combined cycle (IGCC) plants have increased worldwide. An IGCC plant couples a gas turbine with a gasification block. Various technical issues exist in designing the entire system. Among these issues, the matching between the gas turbine and the air separation unit is especially important. In particular, the operating condition of a gas turbine in an IGCC plant may be very different from that of its original design. In this study, we analyzed the impact of the use of syngas on operating conditions of the gas turbine in an IGCC plant. We evaluated the performance of a gas turbine under operating limitations in terms of compressor surge and turbine metal temperature. Although a lower degree of integration may theoretically allow higher gas turbine power output and efficiency, it causes a reduction in compressor surge margin and overheating of the turbine metal. The turbine overheating problem may be solved using several methods, such as a reduction in the firing temperature or an increase in the turbine cooling air. The latter yields a much smaller performance penalty. To achieve an acceptable margin for the compressor surge, either further reduction in the firing temperature or further increase in the coolant is required. Ventilation of some of the nitrogen generated by the air separation unit, i.e., a reduction of the nitrogen supply to the combustor, is another option. Coolant modulation yields the lowest performance penalty. Reduction of the nitrogen supply provides much greater system power output than control of the firing temperature. For nitrogen flow and firing temperature controls, there are optimal levels of integration degrees in terms of net system power output and efficiency.