Integrated Gasification Combined Cycle Power Research Articles

An economic comparison assessment of lignite and biomass IGCC power plants

Abstract An economic assessment between lignite and biomass integrated gasification combined cycle power plants (IGCC and BIGCC respectively) for power generation was carried out. The two alternative power plants are presented together with the selection of the appropriate equipment. An economic evaluation was carried out for the two power plants, taking into account a net power of 100 MW. The economic evaluation was carried out using the methods of the net present value and the internal rate of return. Finally, a sensitivity analysis was carried out. Calculations have been carried out with an Excel spreadsheet. It was shown that both investments are profitable throughout their economic life. However, because of the difference in the selling price of the MW h between the two power plants and to the cost of CO 2 emissions for the lignite power plant, the biomass plant is more profitable with a net present value up to 417 M€ and an internal rate of return of 23.33%. A threshold price of 27.28 €/t for CO 2 emissions was also determined.

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.

Biomass integrated gasification combined cycle power generation with supplementary biomass firing: Energy and exergy based performance analysis

A thermodynamic analysis of a Biomass Integrated Gasification Combined Cycle (BIGCC) plant has been performed based on energy and exergy balances in a proposed configuration. Combustion of supplementary biomass fuel is considered using the oxygen available in the gas turbine (GT) exhaust. The effects of pressure and temperature ratios of the GT system and the amount of fuel burned in the supplementary firing chamber on the thermal and exergetic efficiencies of the plant have been investigated. The plant efficiencies increase with the increase in both pressure and temperature ratios; however, the latter has a stronger influence than the former. Supplementary firing of biomass increases the plant efficiencies of a BIGCC plant till an optimum level of degree of firing. The other technical issues related to supplementary firing, like ash fusion in the furnace and exhaust heat loss maintaining a minimum pinch point temperature difference are accounted and finally a set of optimum plant operating parameters have been identified. The performance of a 50 MWe plant has been analyzed with the optimum operating parameters to find out equipment rating and biomass feed rates. Exergetic efficiencies of different plant equipments are evaluated to localize the major thermodynamic irreversibilities in the plant.

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...

The Steam Gasification of Coal under Milder Low Temperature Conditions—Nonisothermal Kinetics Studies for Reactor Design

Advanced systems of power generation, such as integrated gasification combined cycle power generation, are being demonstrated as the next generation of clean coal technology. It is important commercially to exploit the coal in such a way that premium and added value chemicals are recovered from coal before subjecting this to destructive gasification to yield the smallest molecules, such as H2 and CO, from coal macromolecules (C~20–C~240). In the present studies, original Talcher coal was subjected to organo-refining using coal-derived solvents, such as anthracene oil and liquid paraffin. The residual coal obtained from organo-refining was pyrolyzed in steam atmosphere. The kinetics of the low temperature steam gasification of the original coal, residual coal, and their chars was studied. These studies would help in designing the reactor for the steam gasification of coals, residual coals, and chars, thereof. These pretreatments beneficially disrupt the structure of coal by exposing more active sites on the surface, by exposing more mineral matter, and by affording sufficient residual volatile matter in treated coals/chars to render these reactive for the steam gasification.

Modeling the Steam Gasification Reactions for Reactor Design

Gasification of coal is important for hydrogen generation and also for the integrated gasification combined cycle power generation. Modeling of the gasification reaction is important for the reactor design and operation. Different models suggested for the gasification of coals and chars have been reviewed. The author and his research group have carried out studies on the steam gasification of coal after organo-refining and steam pyrolysis. Based on the studies of the author and his research group on the steam gasification of coal, preextracted coal residues and their chars, a modified model for the steam gasification of coal, has been suggested. This model is based on the shrinking core model and this incorporates the surface and chemical reactivities of coal along with adsorption equations and residual volatile matter.

Comparison of carbon capture IGCC with pre-combustion decarbonisation and with chemical-looping combustion

Carbon capture from conventional power cycles is accompanied by a significant loss of efficiency. One process concept with a potential for better performance is chemical-looping combustion (CLC). CLC uses a metal oxide to oxidize the fuel, and the reduced metal is then re-oxidized in a second reactor with air. The combustion products CO 2 and water remain unmixed with nitrogen, thereby avoiding the need for energy intensive air separation. In this paper, the performance of various configurations of CLC used in integrated gasification combined cycle power plants (CLC-IGCC) are analyzed and compared to a conventional IGCC design with pre-combustion carbon capture by physical absorption. The analysis is based on process simulation using Aspen Plus and GateCycle. Key design parameters are varied, and the results are interpreted using exergy analysis. The CLC-IGCC offers the advantages of higher plant efficiency and more complete carbon capture. The efficiency is very sensitive to changes in the gas turbine inlet temperature for both the CLC and the conventional IGCC designs. The development of oxygen carrier particles with a high thermal stability is therefore crucial for capitalizing on the potential efficiency advantage of CLC.

The sustainability of clean coal technology: IGCC with/without CCS

Integrated gasification combined cycle power generation (IGCC) is one of the emerging clean coal technologies for reducing greenhouse emissions in coal-fired electricity generation. IGCC technology, both with and without CO 2 capture and storage (CCS) is compared with conventional super-critical power generation based on pulverized coal. The comparison is based on an equal consumption rate of Queensland black coal. The sustainability parameters being investigated are: thermal efficiency, environmental performance, inherent safety and economics. The IGCC processes have been modeled using commercial steady-state mass and energy balance software. Both the gross and net thermal efficiencies of the IGCC power station are reduced when the plant is configured for CCS. The net efficiency is reduced from 32.1% to 26.1%, when 81% of the CO 2 is captured. This delivers an overall reduction in CO 2 emissions per unit of electrical energy output of 73.2% compared to the reference plant. However, environmental performance in other areas suffers as a result of switching to IGCC-CCS, particularly fresh water consumption is increased by 2.5 tonne/MWh for both coastal and inland locations. Inherent safety risks associated with IGCC are also greater with the gasifier being the highest risk unit in the facility with a Dow fire and explosion index of 168 compared with an index of 107 for a conventional boiler. Toxicity hazard also increases with carbon monoxide present at concentrations several thousand times higher than the TWA limit. The minimum viable selling price of electricity for a 7% IRR is calculated to increase from USD80 MWh −1 for a conventional power station to USD101 MWh −1 for IGCC and to USD145 MWh −1 for IGCC-CCS. It is concluded that the application of IGCC-CCS is highly effective in reducing carbon dioxide emissions, the highest-profile problem associated with coal-fired electricity. There is an economic penalty which has been previously documented. However, there are also drawbacks concerning inherent safety and other environmental factors apart from CO 2 emissions, which until now have been under emphasized.

Design and operation of pilot plant for CO 2 capture from IGCC flue gases by combined cryogenic and hydrate method

This project is a trial conducted under contract with CO 2CRC, Australia of a new CO 2 capture technology that can be applied to integrated gasification combined cycle power plants and other industrial gasification facilities. The technology is based on combination of two low temperature processes, namely cryogenic condensation and the formation of hydrates, to remove CO 2 from the gas stream. The first stage of this technology is condensation at −55 °C where CO 2 concentration is expected to be reduced by up to 75 mol%. Remaining CO 2 is captured in the form of solid hydrate at about 1 °C reducing CO 2 concentration down to 7 mol% using hydrate promoters. This integrated cryogenic condensation and CO 2 hydrate capture technology hold promise for greater reduction of CO 2 emissions at lower cost and energy demand. Overall, the process produced gas with a hydrogen content better than 90 mol%. The concentrated CO 2 stream was produced with 95–97 mol% purity in liquid form at high pressure and is available for re-use or sequestration. The enhancement of carbon dioxide hydrate formation and separation in the presence of new hydrate promoter is also discussed. A laboratory scale flow system for the continuous production of condensed CO 2 and carbon dioxide hydrates is also described and operational details are identified.

Surface tension measurements of coal ash slags under reducing conditions at elevated pressures

The aim of limiting the amount of CO 2 that is released together with other exhaust gases from power plants can be reached by technologies allowing for a systematic separation of this greenhouse gas. One such technology is the integrated gasification combined cycle power plant which makes use of a coal gasification step. For the gasification involving temperatures far higher than in typical pulverised combustion chambers, ash contained in the fuel is liquefied (slag) and must be removed from the cycle to guarantee safe operation of downstream equipment. To keep the efficiency of the power plant as high as possible, hot gas cleaning facilities are most desirable for this purpose. The design of these installations necessitates knowledge about thermophysical properties of coal ash slags, especially in reducing, pressurised atmospheres. In this work, the surface tension of 15 coal ash slags was measured in argon hydrogen gas of up to 10 bar absolute pressure according to the sessile drop method. Compared to experiments at 1 bar, surface tension values up to 42% lower were found on applying pressure. Additionally, shifts in the melting temperature interval of the ashes due to increased pressure were observed. The surface tension values obtained in pressurised atmospheres ranged from 270 to 490 mN/m with respect to temperature intervals where almost no data scattering occured.

Enhancing the Steam Gasification Reactivity of Coal by Boosting the Factors Affecting the Gasification Reactions in the Stepwise Coal Conversion

Factors affecting the steam gasification reactivity of coal have been reviewed. Studies have been performed on investigating the effects of organo-refining (solvent extraction) using coal-derived solvents, such as anthracene oil and liquid paraffin. The residual coals obtained from the organo-refining of coal were subjected to steam pyrolysis at 650°C to generate active chars. The steam gasification reactivity of original coal, anthracene oil extracted residual coals, anthracene oil–liquid paraffin (successively) extracted residual coals, and their chars were studied first in a laboratory gasifier and then by using thermogravimetric analysis apparatus in steam atmosphere. Nonisothermal kinetic studies revealed that organo-refining and steam pyrolysis are beneficial pretreatments for the steam gasification of coals/chars. These pretreatments leave sufficient residual volatile matter in coals/chars, increase the active surface area, and expose and make available the finely dispersed mineral matter of coal (which acts as catalysts). These observations were also supported by the DTG studies. Present studies led to the development of a stepwise coal conversion process, a clean coal technology to generate H2 or for use of the integrated gasification combined cycle power generation or of fuel cells.

Influence of the Temperature on the Release of Inorganic Species during High-Temperature Gasification of Hard Coal

Several volatile inorganic species are of concern in future integrated gasification combined cycle (IGCC) power systems because of their relation to erosion, corrosion, fouling, and slagging. The aim of this work was to obtain more information on the influence of the temperature on the release of Na, K, Cl, and S species during gasification. Therefore, six hard coals were gasified in lab-scale experiments in a helium/oxygen atmosphere at 1100, 1400, and 1700 °C. The results represent conditions in an entrained-flow gasifier. Hot-gas analysis was performed by molecular beam mass spectrometry. Species of interest were HCl, H2S, COS, SO2, NaCl, Na2SO4, KCl, and KOH. In principle, the results show a strong influence of the temperature and the coal composition on the release of the species under investigation; e.g., the release of KOH is strongly increased with an increasing temperature.

Studies of the thermal circuit of an advanced integrated gasification combined-cycle power plant

The results obtained from a study of the thermal circuit of a combined-cycle plant with coal gasification are presented, and a new-generation gas-turbine unit furnished with different fuel supply systems and using different methods for incorporating an air separation plant into the process circuit is described. Data on the composition of producer gas and calculated values of the combined-cycle power plant efficiency are given.

The Effects of Changing Fuels on Hot Gas Path Conditions in Syngas Turbines

Gas turbines in integrated gasification combined cycle power plants burn a fuel gas (syngas (SG)) in which the proportions of hydrocarbons, H2, CO, water vapor, and minor impurity levels may differ significantly from those in natural gas (NG). Such differences can yield changes in the temperature, pressure, and corrosive species that are experienced by critical components in the hot gas path, with important implications for the design, operation, and reliability of the turbine. A new data structure and computational methodology is presented for the numerical simulation of a turbine thermodynamic cycle, with emphasis on the hot gas path components. The approach used allows efficient handling of turbine components and variable constraints due to fuel changes. Examples are presented for a turbine with four stages, in which the vanes and blades are cooled in an open circuit using air from the appropriate compressor stages. For an imposed maximum metal temperature, values were calculated for the fuel, air, and coolant flow rates and through-wall temperature gradients for cases where the turbine was fired with NG or SG. A NG case conducted to assess the effect of coolant pressure matching between the compressor extraction points and corresponding turbine injection points indicated that this is a feature that must be considered for high combustion temperatures. The first series of SG simulations was conducted using the same inlet mass flow and pressure ratios as those for the NG case. The results showed that higher coolant flow rates and a larger number of cooled turbine rows were needed for the SG case to comply with the imposed temperature constraints. Thus, for that case, the turbine size would be different for SG than for NG. A second series of simulations examined scenarios for maintaining the original turbine configuration (i.e., geometry, diameters, blade heights, angles, and cooling circuit characteristics) used for the SG simulations. In these, the inlet mass flow was varied while keeping constant the pressure ratios and the amount of hot gas passing the first vane of the turbine. The effects of turbine matching between the NG and SG cases were increases—for the SG case of approximately 7% and 13% for total cooling flows and cooling flows for the first-stage vane, respectively. In particular, for the SG case, the vanes in the last stage of the turbine experienced inner wall temperatures that approached the maximum allowable limit.

Influence of system integration options on the performance of an integrated gasification combined cycle power plant

An IGCC (integrated gasification combined cycle) plant consists of a power block and a gasifier block, and a smooth integration of these two parts is important. This work has analyzed the influences of the major design options on the performance of an IGCC plant. These options include the method of integrating a gas turbine with an air separation unit and the degree of nitrogen supply from the ASU to the gas turbine combustor. Research focus was given to the effect of each option on the gas turbine operating condition along with plant performance. Initially, an analysis adopting an existing gas turbine without any modifications of its components was performed to examine the influence of two design options on the operability of the gas turbine and performance of the entire IGCC plant. It is shown that a high integration degree, where much of the air required at the air separation unit is supplied by the gas turbine compressor, can be a better option considering both the system performance and operation limitation of the gas turbine. The nitrogen supply enhances system performance, but a high supply ratio can only be acceptable in high integration degree designs. Secondly, the modifications of gas turbine components to resume the operating surge margin, such as increasing the maximum compressor pressure ratio by adding a couple of stages and increasing turbine swallowing capacity, were simulated and their effects on system performance were examined. Modification can be a good option when a low integration degree is to be adopted, as it provides a considerable power increase.

Valuing flexibility: The case of an Integrated Gasification Combined Cycle power plant

In this paper we analyze the choice between two technologies for producing electricity. In particular, the firm has to decide whether and when to invest either in a Natural Gas Combined Cycle (NGCC) power plant or in an Integrated Gasification Combined Cycle (IGCC) power plant, which may burn either coal or natural gas. Instead of assuming that fuel prices follow standard geometric Brownian motions, here they are assumed to show mean reversion, specifically to follow an inhomogeneous geometric Brownian motion. First we consider the opportunity to invest in a NGCC power plant. We derive the optimal investment rule as a function of natural gas price and the remaining life of the right to invest. In addition, the analytical solution for a perpetual option to invest is obtained. Then we turn to the IGCC power plant. We analyse the valuation of an operating plant when there are switching costs between modes of operation, and the choice of the best operation mode. This serves as an input to evaluate the option to invest in this plant. Finally we derive the value of an opportunity to invest either in a NGCC or IGCC power plant, i.e. to choose between an inflexible and a flexible technology, respectively. Depending on the opportunity's time to maturity, we derive the pairs of coal and gas prices for which it is optimal to invest in NGCC, in IGCC, or simply not to invest. Numerical computations involve the use of one- and two-dimensional binomial lattices that support a mean-reverting process for coal and gas prices. Basic parameter values are taken from an actual IGCC power plant currently in operation. Sensitivity of some results with respect to the underlying stochastic process for fuel price is also checked.

General fuel cell hybrid synergies and hybrid system testing status

FCT hybrid power systems offer the highest efficiency and the cleanest emissions of all fossil fuelled power. The engineering for the highest possible efficiency at lowest cost and weight depends on general system architecture issues and the performance of the components. Presented in this paper are system studies which provide direction for the most efficient path toward achieving the most beneficial result for this technology. Ultimately, fuel cell-turbine (FCT) hybrid systems applicable to integrated gasification combined cycle power systems will form the basis for reaching the goals for advanced coal-based power generation. The FCT hybrid power island will also be important for the FutureGen plant and will provide new options for carbon dioxide capture and sequestration as well as power and hydrogen generation. The system studies presented in this paper provide insight to current technology ‘benchmarks’ versus expected benefits from hybrid applications. Discussion is also presented on the effects of different balance of plant arrangements and approaches. Finally, we discuss the status of US DOE is sponsored projects that are looking to help understand the unique requirements for these systems. One of these projects, Hyper, will provide information on FCT dynamics and will help identify technical needs and opportunities for cycle advancement. The methods studied show promise for effective control of a hybrid system without the direct intervention of isolation valves or check valves in the main pressure loop of the system, which introduce substantial pressure losses, allowing for realization of the full potential efficiency of the hybrid system.

Novel concepts for near-zero emissions IGCC power plants

The paper aims in examining and evaluating the state-of-the-art in technological concepts towards zero-emission coal-fired power plants. The discussion is based on the evaluation of a novel concept dealing with the carbonation-calcination process of lime for CO2 capture from coal-fired power plants, compared to the integration of CO2 capture in an Integrated Gasification Combined Cycle power plant. Results from thermodynamic simulations dealing with the most important features for CO2 reduction are presented. Preliminary economic considerations are made, taking into account investment and operating costs, in order to assess the electricity cost related to the two different technological approaches. The cycle calculations were performed with the thermodynamic cycle calculation software ENBIPRO (ENergie-BIllanz-PROgram), a powerful tool for heat and mass balance solving of complex thermodynamic circuits, calculation of efficiency, exergetic and exergoeconomic analysis of power plants. The software code models all pieces of equipment that usually appear in power plant installations and can accurately calculate all thermodynamic properties at each node of the thermodynamic circuit, power consumption of each component, flue gas composition etc. [1]. The code has proven its validity by accurately simulating a large number of power plants and through comparison of the results with other commercial software. .

各種ガス化燃料用ガスタービン燃焼器の開発とその背景

Development of the integrated gasification combined cycle power generation of various gasifying meth-ods has been preceded in the world. The gasified fuels are chiefly characterized by the gasifying agent and the synthetic gas clean-up method, and divided roughly into four types. The calorific value of gasified fuel differs according to the type of gasification agent. On the other hand, to improve the thermal efficiency. it is necessary to use a hot/dry type synthetic gas clean-up, but ammonia originated from nitrogenous compounds in coal is not removed. And then it forms fuel-NOx. For these reasons, the combustion technology for each gasified fuel is important. In this paper, I review development of the gas turbine combustors for the gasified fuels of three types through numerical analyses, experiments using a small burner and the designed combustors.

H222 石炭ガス化複合発電用ガスタービン燃焼器の開発

Development of the integrated gasification combined cycle power generation of various gasifying methods has been preceded in the world. The gasified fuels are chiefly characterized by the gasifying agent and the synthetic gas clean-up method, and divided roughly into four types. The calorific value of gasified fuel differs according to the type of gasification agent. On the other hand, to improve the thermal efficiency, it is necessary to use a hot/dry type synthetic gas clean-up, but ammonia originated from nitrogenous compounds in coal is not removed. And then it forms fuel-NOx. For these reasons, the combustion technology for each gasified fuel is important. In this paper, we reviews our developments of the gas turbine combustors for the gasified fuels of three types through numerical analyses, experiments using a small burner and the designed combustors.