Integrated Coal Gasification Combined Cycle Research Articles

Study of Selected Factors Affecting Hydrate-Based Carbon Dioxide Separation from Simulated Fuel Gas in Porous Media

Hydrate-based gas separation is one of the potential methods of carbon dioxide capture from fuel gases (CO2/H2) for an integrated coal gasification combined cycle (IGCC) power plant. In this study, the influences of selected factors, including porous properties, tetrahydrofuran (THF) concentration, sodium dodecyl sulfate (SDS) concentration, and initial pressure, of the operation system on hydrate phase equilibria, gas consumption, and gas separation are experimentally investigated by a designed orthogonal test method. It is found that the porous property is the most important factor on hydrate phase equilibria and CO2 gas separation, where the gas separation becomes better in silica gel. The presence of THF moderates the hydrate phase equilibrium and improves the gas consumption and CO2 gas recovery, and 3 mol % THF should be a suitable value for gas separation. The initial pressure has an important effect on the hydrate equilibrium pressure. With the increase of the driving force, the gas consumption in...

Effects of supplementary biomass firing on the performance of combined cycle power generation: A comparison between NGCC and IGCC plants

In the present work, effects of biomass supplementary firing on the performance of fossil fuel fired combined cycles have been analyzed. Both natural gas fired combined cycle (NGCC) and integrated coal gasification combined cycle (IGCC) have been considered in the study. The efficiency of the NGCC plant monotonically reduces with the increase in supplementary firing, while for the IGCC plant the maximum plant efficiency occurs at an optimum degree of supplementary firing. This difference in the nature of variation of the efficiency of two plants under the influence of supplementary firing has been critically analyzed in the paper. The ratings of different plant equipments, fuel flow rates and the emission indices of CO2 from the plants at varying degree of supplementary firing have been evaluated for a net power output of 200 MW. The fraction of total power generated by the bottoming cycle increases with the increase in supplementary firing. However, the decrease in the ratings of gas turbines is much more than the increase in that of the steam turbines due to the low work ratio of the topping cycle. The NGCC plants require less biomass compared to the IGCC under identical condition. A critical degree of supplementary firing has been identified for the slag free operation of the biomass combustor. The performance parameters, equipment ratings and fuel flow rates for no supplementary firing and for the critical degree of supplementary biomass firing have been compared for the NGCC and IGCC plants.

Comparative lifecycle inventory (LCI) of greenhouse gas (GHG) emissions of enhanced oil recovery (EOR) methods using different CO2 sources

This study uses a process lifecycle inventory (LCI) to compare the lifecycle greenhouse gas (GHG) emissions of enhanced oil recovery (EOR) operations using different sources for CO2 and to non-CO2 EOR methods. All EOR techniques were compared to the base case of natural-source CO2-EOR, which had net emissions of 0.52±0.03 metric tons of CO2-e per barrel of oil recovered (t/bbl) (85.1±4.9gCO2-e/MJ oil (g/MJ)), the same as the net emissions of 0.52±0.02t/bbl (84.3±3.0g/MJ) when using CO2 derived from a coal-fueled synthetic natural gas (SNG) plant. Net emissions were lowered to 0.36±0.03t/bbl (58.5±5.2g/MJ) for EOR using CO2 derived from a coal-fed Integrated Gasification Combined Cycle (IGCC) plant. Net emissions were further reduced to 0.18±0.11t/bbl (28.6±18.7g/MJ) using switchgrass grown on marginal land in an IGCC plant. Similar to coal, net emissions were 0.34±0.03t/bbl (55.3±5.5g/MJ) for EOR using CO2 derived from a Natural Gas Combined Cycle (NGCC) plant, and 0.39±0.03t/bbl (63.3±4.4g/MJ) when using livestock manure biogas for NGCC. Net emissions of methane- and nitrogen-EOR were 10–15% greater than for natural-source CO2-EOR. For the allocations used in this study, all sources of CO2 derived from IGCC or NGCC plants resulted in between about 25% and 60% lower net CO2-e emissions per barrel of oil recovered compared to natural-source CO2-EOR, and were also approximately 25–60% lower than average domestic U.S. oil lifecycle emissions of 0.50±0.02t/bbl (82.4±2.5g/MJ). These results suggest that coal and biomass IGCC CO2-EOR, as well as natural gas and biogas NGCC CO2-EOR, may be alternatives for reducing GHG emissions associated with fossil fuel use during the slow transition from fossil fuels to other energy sources.

Corrosion of Type 316L Stainless Steel Piping in Synthetic Gas Plants

Corrosion behavior of Type 316L (UNS S31603) stainless steel piping used in integrated coal gasification combined cycle (IGCC) plant facilities processing coal (0.9 MPa to 1.1 MPa and 150°C to 300°C) and industrial waste (0.11 MPa and 40°C to 60°C) was explained using scanning electron microscopy-energy dispersive x-ray spectrometry (SEM/EDS), x-ray diffraction (XRD), and a thermodynamic Ellingham-Pourbaix stability diagram. Material wastage and pitting were observed on the inner wall of Type 316L stainless steel piping used in Institute for Advanced Engineering (IAE) coal and industrial waste syngas plant facilities after 720 h and 170 h (total hours) of operation, respectively. Relevant corrosion mechanism was suggested based on SEM/EDS examination and thermodynamic inferences: the observed material wastage and corrosion behavior of the Type 316L piping material cut off from the coal syngas IGCC plant were explained by combined effects of evaporation of iron chlorides and subsequent transformation into thin oxides. On the other hand, the pitting corrosion phenomenon observed on the inner wall of Type 316L piping cut off from industrial waste processing IGCC plant was attributed to modified pitting mechanism caused by the preferential growth of corrosion pits in horizontal direction under aqueous condensate environment containing hydrochloric acid (HCl).

Flow and heat transfer characteristics in the syngas quench system of a 300 MWe IGCC process

In the Shell coal gasification process, the hot syngas at about 1550 °C leaving the gasifier exit is immediately quenched by recycled cold syngas for protection of the system from corrosion and fly slag deposition. As the gas quench system is composed of membrane walls with evaporating water inside, understanding the heat transfer is important in the design and operation of gasification process. This study investigated the detailed flow and heat transfer characteristics of the gas quench system by computational fluid dynamics (CFD) for operational loads of 50–100% in a 300 MWe integrated coal gasification combined cycle (IGCC) process. Based on the CFD results, one-dimensional process model for heat transfer was proposed. The approach for considering three gas streams (hot, cold and mixed syngas) was effective in predicting the trends of heat transfer and gas temperature in the quench system.

Alkali removal at 1400 °C under gasification conditions

Power stations with Integrated Coal Gasification Combined Cycle (IGCC) are highly efficient and flexible regarding fuel and products, e.g. power and synthesis gas. To avoid the efficiency loss in state of the art “cold” gas cleaning processes, it is necessary to develop high temperature gas cleaning processes. One of the main problems is the release of alkali species during coal gasification. This investigation was conducted to assess the potential for the reduction of alkali species by different aluminosilicate sorbents under simulated gasification conditions at a temperature of 1400°C. Qualitative and quantitative analysis of the hot gas downstream the sorbent bed was carried out using molecular beam mass spectrometry (MBMS). The obtained results were used to estimate the remaining risk of fouling by means of thermodynamic calculations.

S082012 O_2/CO_2吹き2室2段噴流層石炭ガス化炉の数値解析([S082]高効率火力発電およびCCS技術)

A technology of carbon dioxide capture and storage (CCS) is the one of global warming countermeasure. As an oxidizer in advanced integrated coal gasification combined cycle (A-IGCC), the utilization of mixture gas including carbon dioxide (CO_2) and oxygen (O_2) is discussed. In the present study, a coal gasifier with two-stage entrained bed was numerically simulated to investigate the adaption of O_2/CO_2-blown system in gasifier. Thermal loss on the gasifier furnace wall was considered in this simulation. Because the reaction of coal gasification was promoted by CO_2, we can operate the gasifier system for low oxygen ratio compared with the conventional system. By the control of the reactor/total coal ratio, we can easily operate the gasifier system. At the O_2/CO_2-blown system, high level gas heating value was obtained and the operation range with safety combustion became wide. We can expect the enhancement of thermal efficiency of power generation and the reduction of reductor length for the operation of low oxygen ratio.

Economic Evaluation of the UCSRP-HP Process in IGCC Applications

With financial assistance from the US Department of Energy and the Illinois Clean Coal Institute, Gas Technology Institute (GTI) has been working with the University of California, Berkeley, for further development of their UCSRP-HP (University of California Sulfur Recovery Process-High Pressure) technology. The key focus of the UCSRP-HP technology is integrated multi-contaminant removal of hydrogen sulfide (H2S), carbonyl sulfide (COS), ammonia (NH3), chlorides and heavy metals present in coal-derived syngas. The process has two major components: 1) removal of various trace components with a solvent (e.g., diethylene glycol or water) using a high-pressure scrubbing unit and 2) removal of H2S as sulfur via reaction with SO2 (in the presence of a solvent mixed a small quantity of a homogeneous catalyst) at 120?C to 150?C and at any syngas pressure. During this research, data critical to developing and evaluating UCSRP-HP technology for multi-contaminant removal from syngas derived from Illinois #6 coal were obtained. In this paper, we have presented key economic evaluations of the UCSRP-HP process, including potential integrations with other technology options for CO2 and hydrogen separations, for a nominal Illinois #6-coal-based 550-MWe Integrated Coal Gasification Combined Cycle (IGCC) facility with CO2 capture and sequestration. GTI is exploring various options to demonstrate this technology in a pilot plant using actual syngas from a coal gasifier.

Performance of a Multiple-Injection Dry Low NOx Combustor With Hydrogen-Rich Syngas Fuels

An oxygen-blown integrated coal gasification combined cycle (IGCC) plant with precombustion carbon dioxide capture and storage (CCS) is one of the most promising means of zero-emission generation of power from coal. In an IGCC plant with CCS, hydrogen-rich syngas with a wide variation of hydrogen contents is supplied to a gas turbine. Such hydrogen-rich syngas poses a great challenge to a low NOx combustor based on premixed combustion technology, because its high flame speed, low ignition energy, and broad flammability limits can cause flashback and/or autoignition. On the contrary, a diffusion combustor suffers from the high flame temperature of syngas and the resulting high NOx emission. The authors applied a “multi-injection burner” concept to a preliminary burner for hydrogen-rich syngas simulating that from IGCC with CCS. In a preliminary experiment under atmospheric pressure, the multi-injection burner worked without any flashback or any blowout. A prototype multicluster combustor based on the results of that preliminary study was made to be a dry low NOx combustor for hydrogen-rich syngas of IGCC with CCS. It was tested in experiments, which were carried out under medium pressure (0.6 MPa) using test fuels simulating syngas from IGCC with a 0% carbon capture rate, a 30% carbon capture rate, and a 50% carbon capture rate. The test fuels contained hydrogen, methane, and nitrogen, and had a hydrogen content ranging from 40% to 65%.The following conclusions were drawn from the test results: (1) the tested combustor allows the stable combustion of fuels simulating 0%, 30%, and 50% CCS, (2) a convex perforated plate swirler is effective to suppress combustion oscillation, which allows NOx emissions to be less than 10 ppm through the variation of fuel simulating 0%, 30%, and 50% CCS, (3) the extended stable combustion region and enhanced entrainment and mixing due to the convex perforated plate improves the cooling of the combustor liner metal to be less than the liner metal temperature criterion.

Poly(amidoamine) dendrimer/poly(vinyl alcohol) hybrid membranes for CO2 capture

Poly(amidoamine) (PAMAM) dendrimers were incorporated into a cross-linked poly(vinyl alcohol) (PVA) matrix to improve CO2 separation performance at elevated pressures. An organic metal compound was selected as a cross-linker of PVA. The resulting self-standing PAMAM/ cross-linked PVA membrane containing 41.6wt% of PAMAM dendrimer had both good pressure tolerance and CO2 permeance. The CO2/H2 selectivity was almost constant when the CO2 partial pressure in feed gas was from 80 to 560kPa at 40°C. CO2/H2 selectivity and CO2 permeance of the membrane were 32 and 1.6×10−12m3(STP)/(m2sPa), respectively, at 560kPa CO2 partial pressure in the feed gas. Both CO2 permeance and CO2/H2 selectivity increased as the operation temperature of the membrane was increased from 25 to 60°C. A membrane containing 63.3wt% of the dendrimer showed CO2/H2 selectivity and CO2 permeance of 42 and 1.2×10−11m3(STP)/(m2sPa), respectively, at 560kPa of CO2 partial pressure and 60°C. The PAMAM/ cross-linked PVA hybrid membranes are durable under high pressure operation and thus show promise for applications requiring the separation of CO2 from H2 under pressurized conditions, such as in the integrated coal gasification combined cycle (IGCC) processes.

Combustion Performance in a Semiclosed Cycle Gas Turbine for IGCC Fired With CO-Rich Syngas and Oxy-Recirculated Exhaust Streams

Our study found that burning a CO-rich gasified coal fuel, derived from an oxygen–CO2 blown gasifier, with oxygen under stoichiometric conditions in a closed cycle gas turbine produced a highly-efficient, oxy-fuel integrated coal gasification combined cycle (IGCC) power generation system with CO2 capture. We diluted stoichiometric combustion with recycled gas turbine exhaust and adjusted for given temperatures. Some of the exhaust was used to feed coal into the gasifier. In doing so, we found it necessary to minimize not only CO and H2 of unburned fuel constituents but also residual O2, not consumed in the gas turbine combustion process. In this study, we examined the emission characteristics of gasified-fueled stoichiometric combustion with oxygen through numerical analysis based on reaction kinetics. Furthermore, we investigated the reaction characteristics of reactant gases of CO, H2, and O2 remaining in the recirculating gas turbine exhaust using present numerical procedures. As a result, we were able to clarify that since fuel oxidation reaction is inhibited due to reasons of exhaust recirculation and lower oxygen partial pressure, CO oxidization is very sluggish and combustion reaction does not reach equilibrium at the combustor exit. In the case of a combustor exhaust temperature of 1573 K (1300 °C), we estimated that high CO exhaust emissions of about a few percent, in tens of milliseconds, corresponded to the combustion gas residence time in the gas turbine combustor. Combustion efficiency was estimated to reach only about 76%, which was a lower value compared to H2/O2-fired combustion while residual O2 in exhaust was 2.5 vol%, or five times as much as the equilibrium concentration. On the other hand, unburned constituents in an expansion turbine exhaust were slowed to oxidize in a heat recovery steam generator (HRSG) flue processing, and exhaust gases reached equilibrium conditions. In this regard, however, reaction heat in HRSG could not devote enough energy for combined cycle thermal efficiency, making advanced combustion technology necessary for achieving highly efficient, oxy-fuel IGCC.

Carbon chain analysis on a coal IGCC — CCS system with flexible multi-products

A carbon chain analysis is applied to assess a complex energy conversion system with CO2 capture and storage (CCS). A coal integrated gasification combined cycle, with CCS, which co-produces electricity and liquid fuels (IGCC–LF–CCS) is taken as a case study. A process simulation method is used to estimate the technological data, and balance the heat and electricity for the whole system. Carbon and energy flows are calculated to evaluate the mass conversion efficiency and the energy efficiency. The results show that in the case in which one third of the coal is allotted to synthesize liquid fuels, globally 60% carbon is captured for storage, 19% transferred to liquid fuels, 19% emitted to the atmosphere, while the remaining carbon is discharged as waste. For the energy flow, 28.1% of total higher heating value of coal is converted into the liquid fuels. The net electricity efficiency is 20.7% accounting for the power demands by air separation, CO2 capture and compression. Three scenarios with different ratio of resource to produce electricity and liquid fuels with or without CCS have been studied. This work will provide useful information for the coal utilization with CCS in a carbon-constrained world.

CO<SUB>2</SUB>回収型高効率IGCC用クローズドサイクルガスタービンの開発 ―排気循環ガスの分割供給による燃焼促進―

Oxy-fuel IGCC (integrated coal gasification combined cycle) power generation employing the oxygenfired, semiclosed cycle gas turbine with exhaust recirculation enables the realization of highly efficient, zeroemission power generation. In order to realize the oxy-fuel IGCC, we have to develop the combustion promotion technologies of the CO-rich gasified fuel/oxygen-fired stoichiometric combustion with recirculated exhaust. In this study, the effects of the recirculated exhaust split supply in gas turbine combustors on the emission characteristics have been examined through numerical analyses based on reaction kinetics with multistage reactor models of combustors. It was clarified that the fuel oxidation reaction rates increased and the chain initiation reaction in the primary combustion zone was hastened by the recirculated exhaust split supply, and then combustion efficiency improved.

Development of Closed-Cycle Gas Turbine for Oxy-Fuel IGCC Power Generation with CO2 Capture - Emission Analysis of Gasified-Fueled Gas Turbines with Circulating Exhaust & Stoichiometric Combustion -

A CO-rich gasified coal fuel, derived from an oxygen-CO2 blown gasifier, is burnt with oxygen under stoichiometric conditions in a closed cycle gas turbine for the highly-efficient, oxy-fuel IGCC (integrated coal gasification combined cycle) power generation system with CO2 capture. Stoichiometric combustion is diluted with the recycled gas turbine exhaust and adjusted for given temperatures. Since some of the exhaust is used to feed coal into the gasifier, it is necessary to minimize not only CO and H2 of unburned fuel constituents but also residual O2, not consumed in the gas turbine combustion process. In this study, reaction characteristics of reactant gases in the combustor and exhaust have been clarified through numerical analysis based on reaction kinetics. As a result, it was clarified that since fuel oxidation is inhibited due to reasons of exhaust-recirculation and stoichiometric combustion, combustion efficiency was estimated to be lower than those in the cases of the developed H2/O2, LNG/O2 fired closed-cycle gas turbines and a conventional LNG fired-gas turbine. Meanwhile, unburned constituents in exhausts were slowed to oxidize in an HRSG, and exhaust gases reached equilibrium. However, reaction heat in HRSG couldn't devote enough energy for combined cycle thermal efficiency, making advanced combustion technology necessary for achieving highly-efficient oxy-fuel IGCC.

Exergy recuperative CO2 gas separation in pre-combustion capture

The integrated coal gasification combined cycle (IGCC) can achieve higher power generation efficiency than conventional pulverized coal combustion power plants. However, a CO2 capture process prevents improving power generation efficiency of IGCC, because CO2 separation from gas mixtures requires huge amounts of energy. Therefore, in this study, we analyzed the CO2 separation process in the pre-combustion capture process using a process simulator (PRO/II) in the steady state, and proposed a new process using a modularity based on self-heat recuperation (SHR) technology to decrease energy consumption. Pre-combustion capture was applied in the IGCC plant, which involved coal gasification and CO-shift conversion with CO2 capture. The results show that the energy consumption for the CO2 separation process using SHR was decreased by two-thirds. This means that the power generation efficiency can be improved by SHR compared with conventional IGCC with a CO2 capture process.

Gravity separation and its effect on CO2 gasification

The CO2-blown integrated coal gasification combined cycle (IGCC) is a promising electric power generation technology that will reduce CO2 emission, due to its high efficiency. Recent studies have found that base metals improve the coal char gasification in cases when they can interact with the char matrix at an atomic level. In this paper, we clarified the effect of heavy medium separation, which is one of the most popular coal cleaning technologies, on the CO2 char gasification. Before sink and float test and thermogravimetric analysis, Datong Coal from China was ground to below 20 mesh, which is a size usually used for a coal cleaning process. The float and sink test revealed that the highest separation efficiency would be obtained at a specific gravity of 1.45. The ash content would be reduced dramatically from 10.2% to ca. 4% and about 85% of combustibles would be recovered. The chars derived from different specific gravity fractions showed different gasification reactivity; the char from heavier fraction has gasification reactivity higher than the lighter fraction-derived char. This tendency agrees with the ash content; the heavier fraction has a higher ash content. Removal of ash from well-ordered holes in Fusinite and Semi-fusinite in Inertinite might increase the gasification reactivity.

Convective heat transfer characteristics of high-pressure gas in heat exchanger with membrane helical coils and membrane serpentine tubes

Since the heat transfer performance of syngas cooler affects the efficiency of the power generating system with integrated coal gasification combined cycle (IGCC) directly, it is important to obtain the heat transfer characteristics of high-pressure syngas in the cooler. Heat transfer in convection cooling section of pressurized coal gasifier with the membrane helical coils and membrane serpentine tubes under high pressure is experimentally investigated. High pressure single gas (He or N 2) and their mixture (He + N 2) gas serve as the test media in the test pressure range from 0.5 MPa to 3.0 MPa. The results show that the convection heat transfer coefficient of high pressure gas is influenced by the working pressure, gas composition and symmetry of flow around the coil, of which the working pressure is the most significant factor. The average convection heat transfer coefficients for various gases in heat exchangers are systematically analyzed, and the correlations between Nu and Re for two kinds of membrane heat exchangers are obtained. The heat transfer coefficient of heat exchanger with membrane helical coils is greater than that of the membrane serpentine-tube heat exchanger under the same conditions. The heat transfer coefficient increment of the membrane helical-coil heat exchanger is greater than that of the membrane serpentine-tube heat exchanger with the increase of gas pressure and velocity.

Shell coal IGCCS with carbon capture: Conventional gas quench vs. innovative configurations

The Shell coal integrated gasification combined cycle (IGCC) based on the gas quench system is one of the most fuel flexible and energy efficient gasification processes because is dry feed and employs high temperature syngas coolers capable of rising high pressure steam. Indeed the efficiency of a Shell IGCC with the best available technologies is calculated to be 47–48%. However the system looses many percentage points of efficiency (up to 10) when introducing carbon capture. To overcome this penalty, two approaches have been proposed. In the first, the expensive syngas coolers are replaced by a “partial water quench” where the raw syngas stream is cooled and humidified via direct injection of hot water. This design is less costly, but also less efficient. The second approach retains syngas coolers but instead employs novel water–gas shift (WGS) configurations that requires substantially less steam to obtain the same degree of CO conversion to CO 2, and thus increases the overall plant efficiency. We simulate and optimize these novel configurations, provide a detailed thermodynamic and economic analysis and investigate how these innovations alter the plant’s efficiency, cost and complexity.

Dynamic modeling and simulation of shell gasifier in IGCC

A dynamic model of the Shell gasifier in an integrated coal gasification combined cycle (IGCC) is established based on physical principles, focusing on the time-dependent accumulation and flow on the walls. Numerical simulations are carried out to explore the system dynamic performance with respect to step changes in the inlet oxygen-to-coal ratio and steam-to-coal. The dynamic responses of key outlet variables, including the gas temperature, exiting slag mass flow rate, thicknesses of the solid and fluid slag layer, volume percentages of H 2, CO 2 and CO in syngas etc., are obtained. Three different coals are analyzed in this paper, and similar trends in their dynamic behaviors are found by using the gasifier model. The model and simulation method may be useful for providing insights to the operation and control of the IGCC process with respect to complex varying working conditions.

Operation window and part-load performance study of a syngas fired gas turbine

Integrated coal gasification combined cycle (IGCC) provides a great opportunity for clean utilization of coal while maintaining the advantage of high energy efficiency brought by gas turbines. A challenging problem arising from the integration of an existing gas turbine to an IGCC system is the performance change of the gas turbine due to the shift of fuel from natural gas to synthesis gas, or syngas, mainly consisting of carbon monoxide and hydrogen. Besides the change of base-load performance, which has been extensively studied, the change of part-load performance is also of great significance for the operation of a gas turbine and an IGCC plant.In this paper, a detailed mathematical model of a syngas fired gas turbine is developed to study its part-load performance. A baseline is firstly established using the part-load performance of a natural gas fired gas turbine, then the part-load performance of the gas turbine running with different compositions of syngas is investigated and compared with the baseline. Particularly, the impacts of the variable inlet guide vane, the degree of fuel dilution, and the degree of air bleed are investigated. Results indicate that insufficient cooling of turbine blades and a reduced compressor surge margin are the major factors that constrain the part-load performance of a syngas fired gas turbine. Results also show that air bleed from the compressor can greatly improve the working condition of a syngas fired gas turbine, especially for those fired with low lower heating value syngas. The regulating strategy of a syngas fired gas turbine should also be adjusted in accordance to the changes of part-load performance, and a reduced scope of constant TAT (turbine exhaust temperature) control mode is required.