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1.
A novel methanol-based power system with Chemical-Looping Combustion (CLC) is proposed in this paper. CLC system is a promising approach to greatly decrease the energy penalty for CO2 removal, where iron oxides circulate between two reactors and an inherent CO2 separation occurs. The combustion process of CLC systems mainly include two steps: a reduction reaction of iron oxides, where the fuel is not mixed with air and the thermal energy for the endothermic reaction is supplied by the intercooling heat of the compressor of the gas turbine, and an oxidation reaction of iron oxides, where the compressed air is heated by the iron oxides. On the basis of the system's integration of cascade utilization of chemical energy of methanol and thermal energy, the thermal efficiency of this novel cycle is expected to be 56.8% with 90% of CO2 recovery, 10.2 percentage points higher than a combined cycle (CC) with the same CO2 capture. The promising results obtained here indicate that this novel thermal cycle is a promising approach to accomplish the efficient utilization of chemical energy of methanol without a decrease in thermal efficiency for CO2 removal.  相似文献   

2.
In this article, a novel cycle configuration has been studied, termed the extended chemical looping combustion integrated in a steam‐injected gas turbine cycle. The products of this system are hydrogen, heat, and electrical power. Furthermore, the system inherently separates the CO2 and hydrogen that is produced during the combustion. The core process is an extended chemical looping combustion (exCLC) process which is based on classical chemical looping combustion (CLC). In classical CLC, a solid oxygen carrier circulates between two fluidized bed reactors and transports oxygen from the combustion air to the fuel; thus, the fuel is not mixed with air and an inherent CO2 separation occurs. In exCLC the oxygen carrier circulates along with a carbon carrier between three fluidized bed reactors, one to oxidize the oxygen carrier, one to produces and separate the hydrogen, and one to regenerate the carbon carrier. The impacts of process parameters, such as flowrates and temperatures have been studied on the efficiencies of producing electrical power, hydrogen, and district heating and on the degree of capturing CO2. The result shows that this process has the potential to achieve a thermal efficiency of 54% while 96% of the CO2 is captured and compressed to 110 bar. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

3.
This paper analyzes a novel process for producing hydrogen and electricity from coal, based on chemical looping combustion (CLC) and gas turbine combined cycle, allowing for intrinsic capture of carbon dioxide. The core of the process consists of a three-reactors CLC system, where iron oxide particles are circulated to: (i) oxidize syngas in the fuel reactor (FR) providing a CO2 stream ready for sequestration after cooling and steam vapor condensation, (ii) reduce steam in the steam reactor (SR) to produce hydrogen, (iii) consume oxygen in the air reactor (AR) from air releasing heat to sustain the thermal balance of the CLC system and to generate electricity. A compacted fluidized bed, composed of two fuel reactors, is proposed here for full conversion of fuel gases in FR. The gasification CLC combined cycle plant for hydrogen and electricity cogeneration with Fe2O3/FeAl2O4 oxygen carriers was simulated using ASPEN® PLUS software. The plant consists of a supplementary firing reactor operating up to 1350 °C and three-reactors SR at 815 °C, FR at 900 °C and AR at 1000 °C. The results show that the electricity and hydrogen efficiencies are 14.46% and 36.93%, respectively, including hydrogen compression to 60 bar, CO2 compression to 121 bar, The CO2 capture efficiency is 89.62% with a CO2 emission of 238.9 g/kWh. The system has an electricity efficiency of 10.13% and a hydrogen efficiency of 41.51% without CO2 emission when supplementary firing is not used. The plant performance is attractive because of high energy conversion efficiency and low CO2 emission. Key parameters that affect the system performance are also discussed, including the conversion of steam to hydrogen in SR, supplementary firing temperature of the oxygen depleted air from AR, AR operation temperature, the flow of oxygen carriers, and the addition of inert support material to the oxygen carrier.  相似文献   

4.
Enhanced CO2 concentration in exhaust gas is regarded as a potentially effective method to reduce the high electrical efficiency penalty caused by CO2 chemical absorption in post-combustion capture systems. The present work evaluates the effect of increasing CO2 concentration in the exhaust gas of gas turbine based power plant by four different methods: exhaust gas recirculation (EGR), humidification (EvGT), supplementary firing (SFC) and external firing (EFC). Efforts have been focused on the impacts on cycle efficiency, combustion, gas turbine components, and cost. The results show that the combined cycle with EGR has the capability to change the molar fraction of CO2 with the largest range, from 3.8 mol% to at least 10 mol%, and with the highest electrical efficiency. The EvGT cycle has relatively low additional cost impact as it does not require any bottoming cycle. The externally fired method was found to have the minimum impacts on both combustion and turbomachinery.  相似文献   

5.
The techno-economic evaluation of the evaporative gas turbine (EvGT) cycle with two different CO2 capture options has been carried out. Three studied systems include a reference system: the EvGT system without CO2 capture (System I), the EvGT system with chemical absorption capture (System II), and the EvGT system with oxyfuel combustion capture (System III). The cycle simulation results show that the system with chemical absorption has a higher electrical efficiency (41.6% of NG LHV) and a lower efficiency penalty caused by CO2 capture (10.5% of NG LHV) compared with the system with oxyfuel combustion capture. Based on a gas turbine of 13.78 MW, the estimated costs of electricity are 46.1 $/MW h for System I, while 70.1 $/MW h and 74.1 $/MW h for Systems II and III, respectively. It shows that the cost of electricity increment of chemical absorption is 8.7% points lower than that of the option of oxyfuel combustion. In addition, the cost of CO2 avoidance of System II which is 71.8 $/tonne CO2 is also lower than that of System III, which is 73.2 $/tonne CO2. The impacts of plant size have been analyzed as well. Results show that cost of CO2 avoidance of System III may be less than that of System II when a plant size is larger than 60 MW.  相似文献   

6.
A major factor in global warming is CO2 emission from thermal power plants, which burn fossil fuels. One technology proposed to prevent global warming is CO2 recovery from combustion flue gas and the sequestration of CO2 underground or near the ocean bed. Solid oxide fuel cell (SOFC) can produce highly concentrated CO2, because the reformed fuel gas reacts with oxygen electrochemically without being mixed with air in the SOFC. We therefore propose to operate multi-staged SOFCs with high utilization of reformed fuel to obtain highly concentrated CO2. In this study, we estimated the performance of multi-staged SOFCs considering H2 diffusion and the combined cycle efficiency of a multi-staged SOFC/gas turbine/CO2 recovery power plant. The power generation efficiency of our CO2 recovery combined cycle is 68.5%, whereas the efficiency of a conventional SOFC/GT cycle with the CO2 recovery amine process is 57.8%.  相似文献   

7.
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 CO2 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.  相似文献   

8.
《Applied Thermal Engineering》2000,20(12):1075-1103
Much work is currently focussed on identifying economically and environmentally optimal strategies for increasing gas turbine based combined heat and power (CHP). In many such studies, only a few fixed parameters are used to describe the CHP plant. These are typically total and electrical efficiencies, investment and running costs, minimum and maximum acceptable size, and minimum acceptable part-load. However, for gas turbine based systems these characteristics are clearly functions of the operating conditions, especially for part-load operation. This study examines the effects of varying performance of the gas turbine on the overall heat production costs and CO2 emissions of a medium sized community district heating plant. Both single and double-shaft engines are considered in the study. The results show that the assumption of constant efficiencies for all operating conditions leads to an overestimation of the optimal CHP plant size, thereby underestimating the heat production costs and overestimating the CO2 emissions of the plant. The results also show marked differences according to the type of gas turbine used and part-load operating strategy adopted. In particular, the paper discusses the part-load operating difficulties for CHP plants running gas turbines equipped with low emissions burners.  相似文献   

9.
A power plant based on chemical-looping combustion offers both a possibility of high net power efficiency and separation of the greenhouse gas CO2. This is due to the way the oxidation of the fuel takes place. Instead of oxidizing the fuel with oxygen from the combustion air, the fuel is oxidized by an oxygen carrier, i.e., an oxygen-containing compound. The oxygen carriers that have been suggested in previous studies are metal oxides like NiO, Fe2O3 and Mn3O4. The reduced oxygen carrier is in the next step reoxidized by air in a second reactor and then recirculated to the first reactor. In this way, fuel and air are never mixed and the fuel oxidation products CO2 and water leave the system undiluted by air. All that is needed to get an almost pure CO2 product is to condense the water vapour and remove the liquid water.Chemical-looping combustion (CLC) is also claimed to reduce the fuel exergy destruction in the overall reaction of combustion of the fuel. This gives a possibility to increase the net power efficiency.This paper gives an introduction to chemical-looping combustion. Results from simulations and a detailed exergy analysis of two different CLC gas turbine (GT) systems are also presented. The first system utilizes methane as a fuel and NiO as oxygen carrier. The second system utilizes a fuel gas mixture consisting mainly of CO and H2, simulating a fuel gas from for instance coal gasification. Results for this system are given for simulations with both NiO and Fe2O3 as oxygen carrier. The two systems are compared to comparable simulated systems with conventional combustion of the same fuel. The exergy analysis shows that the irreversibilities generated upon combustion of the fuel are reduced. The net power efficiency of the CLC–GT systems is similar or higher than for the corresponding GT systems with conventional combustion. The net power efficiency of CLC systems could be even further increased if the exergy remaining in the exhaust could be utilized in an efficient way.  相似文献   

10.
The attractive features of a combined cycle (CC) power plant are fuel flexibility, operational flexibility, higher efficiency and low emissions. The performance of five gas turbine‐steam turbine (GT‐ST) combined cycle power plants (four natural gas based plants and one biomass based plant) have been studied and the degree of augmentation has been compared. They are (i) combined cycle with natural gas (CC‐NG), (ii) combined cycle with water injection (CC‐WI), (iii) combined cycle with steam injection (CC‐SI), (iv) combined cycle with supplementary firing (CC‐SF) and (v) combined cycle with biomass gasification (CC‐BM). The plant performance and CO2 emissions are compared with a change in compressor pressure ratio and gas turbine inlet temperature (GTIT). The optimum pressure ratio for compressor is selected from maximum efficiency condition. The specific power, thermal efficiency and CO2 emissions of augmented power plants are compared with the CC‐NG power plant at the individual optimized pressure ratios in place of a common pressure ratio. The results show that the optimum pressure ratio is increased with water injection, steam injection, supplementary firing and biomass gasification. The specific power is increased in all the plants with a loss in thermal efficiency and rise in CO2 emissions compared to CC‐NG plant. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

11.
An integrated power generation system combining solid oxide fuel cell (SOFC) and oxy-fuel combustion technology is proposed. The system is revised from a pressurized SOFC-gas turbine hybrid system to capture CO2 almost completely while maintaining high efficiency. The system consists of SOFC, gas turbine, oxy-combustion bottoming cycle, and CO2 capture and compression process. An ion transport membrane (ITM) is used to separate oxygen from the cathode exit air. The fuel cell operates at an elevated pressure to facilitate the use of the ITM, which requires high pressure and temperature. The remaining fuel at the SOFC anode exit is completely burned with oxygen at the oxy-combustor. Almost all of the CO2 generated during the reforming process of the SOFC and at the oxy-fuel combustor is extracted from the condenser of the oxy-combustion cycle. The oxygen-depleted high pressure air from the SOFC cathode expands at the gas turbine. Therefore, the expander of the oxy-combustion cycle and the gas turbine provides additional power output. The two major design variables (steam expander inlet temperature and condenser pressure) of the oxy-fuel combustion system are determined through parametric analysis. There exists an optimal condenser pressure (below atmospheric pressure) in terms of global energy efficiency considering both the system power output and CO2 compression power consumption. It was shown that the integrated system can be designed to have almost equivalent system efficiency as the simple SOFC-gas turbine hybrid system. With the voltage of 0.752 V at the SOFC operating at 900 °C and 8 bar, system efficiency over 69.2% is predicted. Efficiency penalty due to the CO2 capture and compression up to 150 bar is around 6.1%.  相似文献   

12.
This paper aims to evaluate part-load operation of a natural gas combined cycle (NGCC) power plant with exhaust gas recirculation (EGR) and a CO2 capture plant. Several studies have demonstrated the feasibility and the advantages of EGR at full load, but operation at part load is also important because it is a common condition when NGCC power plants are being used as backup for renewables. The results of this study show that the number of absorber trains is reduced from 4 to 3 with EGR. The efficiency of the NGCC plant with EGR was 0.5% points higher than a conventional NGCC at full load as a result of a higher CO2 concentration in the flue gas. However, this efficiency advantage decreased as the load was reduced from 100% to 50%, with both cases presenting the same efficiency at 50% load. This means that there was no benefit from the effect of EGR at lower loads. The efficiency of a NGCC plant with EGR and CO2 capture configuration decreased from 52.6% to 45.9% when the load was reduced from 100% to 50% compared with a conventional NGCC where the efficiency changed from 52.1% to 45.9%. It was concluded that a NGCC plant with EGR and CO2 capture is viable, results in lower capital costs due to the smaller number of absorber trains and yields slightly higher efficiencies, for operation at part-load down to 50%.  相似文献   

13.
The guiding idea behind oxy-fuel combustion power cycles is guaranteeing a high level of performance as can be obtained by today's advanced power plants, together with CO2 separation in conditions ready for transport and final disposal. In order to achieve all these goals, oxy-combustion – allowing CO2 separation by simple cooling of the combustion products – is combined with large heat recovery and staged expansions/compressions, making use of new components, technology and materials upgraded from modern gas turbine engines. In order to provide realistic results, the power plant performance should include the effects of blade cooling. In the present work an advanced cooled expansion model has been included in the model of the MATIANT cycle in order to assess the effects of blade cooling on the cycle efficiency. The results show that the penalty in efficiency due to blade cooling using steam from the heat recovery boiler is about 1.4 percentage points, mainly due to the reheat of the steam, which, on the other hand, leads to an improvement in specific work of about 6%.  相似文献   

14.
Due to the higher oxygen content and lower heating value, the amount of biomass required in a combined cycle, where it is used as supplementary fuel, to meet a given energy demand is such that the biomass consumes almost all of the oxygen remaining from gas turbine combustion process under certain conditions. This situation requires additional air for biomass combustion thus reducing the cycle efficiency and the net work output rate while increasing CO2 emissions. Three conditions at which the oxygen is completely consumed are identified based on alterations in net fuel utilization. The first condition is linked to fuel utilization, which is observed to be significantly affected by variations in temperatures at three locations in the combined cycle (air temperature entering the gas turbine combustion chamber, gas turbine inlet temperature and HRSG inlet temperatures). The second condition relates to the characteristics of the feedstock (oxygen content of the biomass and heating value of natural gas). The heat loss due to combustion of natural gas and biomass is the third condition that affects oxygen availability. The current work assesses these conditions in order to identify the proper condition at which no additional air is required for supplementary firing of biomass.  相似文献   

15.
Chemical-looping combustion (CLC) is a novel technology that can be used to meet growing demands on energy production without CO2 emissions. The CLC process includes two reactors, an air and a fuel reactor. Between these two reactors oxygen is transported by an oxygen carrier, which most often is a metal oxide. This arrangement prevents mixing of N2 from the air with CO2 from the combustion giving combustion gases that consist almost entirely of CO2 and H2O. The technique reduces the energy penalty that normally arises from the separation of CO2 from other flue gases, hence, CLC could make capture of CO2 cheaper. For the application of CLC to solid fuels, the char remaining after devolatilization will react indirectly with the oxygen carrier via steam gasification. It has been suggested that H2, and possibly CO, has an inhibiting effect on steam gasification in CLC. In this work experiments were conducted to investigate this effect. The experiments were conducted in a laboratory fluidized-bed reactor that was operating cyclically with alternating oxidation and reduction periods. Two different oxygen carriers were used as well as an inert sand bed. During the reducing period varying concentrations of CO or H2 were used together with steam while the oxidation was conducted with 10% O2 in N2. The temperature was constant at 970 °C for all experiments. The results show that CO does not directly inhibit the gasification whereas the partial pressure of H2 had a significant influence on fuel conversion. The results also suggest that dissociative hydrogen adsorption is the predominant hydrogen inhibition mechanism under the laboratory conditions, thus explaining why char conversion is much faster in a bed of oxygen carrying material, compared to an inert sand bed.  相似文献   

16.
In this work it is analyzed the performance of an iron waste material as oxygen carrier for a chemical-looping combustion (CLC) system. CLC is a novel combustion technology with the benefit of inherent CO2 separation that can be used as a source of energy for the methane steam reforming process (SR). The tail gas from the PSA unit is used as fuel in the CLC system.The oxygen carrier behaviour with respect to gas combustion was evaluated in a continuous 500 Wth CLC prototype using a simulated PSA off-gas stream as fuel. Methane or syngas as fuel were also studied for comparison purposes. The oxygen carrier showed enough high oxygen transport capacity and reactivity to fully convert syngas at 880 °C. However, lower conversion of the fuel was observed with methane containing fuels. An estimated solids inventory of 1600 kg MWth−1 would be necessary to fully convert the PSA off-gas to CO2 and H2O. An important positive effect of the oxygen carrier-to-fuel ratio up to 1.5 and the reactor temperature on the combustion efficiency was found.A characterization of the calcined and after-used particles was carried out showing that this iron-based material can be used as oxygen carrier in a CLC plant since particles maintain their properties (reactivity, no agglomeration, high durability, etc.) after more than 111 h of continuous operation.  相似文献   

17.
Post-combustion carbon capture is a valuable technology, capable of being deployed to meet global CO2 emissions targets. The technology is mature and can be retrofitted easily with existing carbon emitting energy generation sources, such as natural gas combined cycles. This study investigates the effect of operating a natural gas combined cycle plant coupled with carbon capture and storage while using varying fuel compositions, with a strong focus on the influence of the CO2 concentration in the fuel. The novelty of this study lies in exploring the technical and economic performance of the integrated system, whilst operating with different fuel compositions. The study reports the design of a natural gas combined cycle gas turbine and CO2 capture plant (with 30 wt% monoethanolamine), which were modelled using the gCCS process modelling application. The fuel compositions analysed were varied, with focus on the CO2 content increasing from 1% to 5%, 7.5% and 10%. The operation of the CO2 capture plant is also investigated with focus on the CO2 capture efficiency, specific reboiler duty and the flooding point. The economic analysis highlights the effect of the varying fuel compositions on the cost of electricity as well as the cost of CO2 avoided. The study revealed that increased CO2 concentrations in the fuel cause a decrease in the efficiency of the natural gas combined cycle gas turbine; however, rising the CO2 concentration and flowrate of the flue gas improves the operation of the capture plant at the risk of an increase in the flooding velocity in the column. The economic analysis shows a slight increase in cost of electricity for fuels with higher CO2 contents; however, the results also show a reduction in the cost of CO2 avoided by larger margins.  相似文献   

18.
Chemical-looping combustion (CLC) is a new combustion technology with inherent separation of CO2. Most of the previous investigations on CLC of solid fuels were conducted under atmospheric pressure. A pressurized CLC combined cycle (PCLC-CC) system is proposed as a promising coal combustion technology with potential higher system efficiency, higher fuel conversion, and lower cost for CO2 sequestration. In this study pressurized CLC of coal with Companhia Valedo Rio Doce (CVRD) iron ore was investigated in a laboratory fixed bed reactor. CVRD iron ore particles were exposed alternately to reduction by 0.4 g of Chinese Xuzhou bituminous coal gasified with 87.2% steam/N2 mixture and oxidation with 5% O2 in N2 at 970 °C. The operating pressure was varied between 0.1 MPa and 0.6 MPa. First, control experiments of steam coal gasification over quartz sand were performed. H2 and CO2 are the major components of the gasification products, and the operating pressure influences the gas composition. Higher concentrations of CO2 and lower fractions of CO, CH4, and H2 during the reduction process with CVRD iron ore was achieved under higher pressures. The effects of pressure on the coal gasification rate in the presence of the oxygen carrier were different for pyrolysis and char gasification. The pressurized condition suppresses the initial coal pyrolysis process while it also enhances coal char gasification and reduction with iron ore in steam, and thus improves the overall reaction rate of CLC. The oxidation rates and variation of oxygen carrier conversion are higher at elevated pressures reflecting higher reduction level in the previous reduction period. Scanning electron microscope and energy-dispersive X-ray spectroscopy (SEM-EDX) analyses show that particles become porous after experiments but maintain structure and size after several cycles. Agglomeration was not observed in this study. An EDX analysis demonstrates that there is very little coal ash deposited on the oxygen carrier particles but no appreciable crystalline phases change as verified by X-ray diffraction (XRD) analysis. Overall, the limited pressurized CLC experiments carried out in the present work suggest that PCLC of coal is promising and further investigations are necessary.  相似文献   

19.
A novel liquefied natural gas (LNG) fueled power plant is proposed, which has virtually zero CO2 and other emissions and a high efficiency. The plant operates as a subcritical CO2 Rankine-like cycle. Beside the power generation, the system provides refrigeration in the CO2 subcritical evaporation process, thus it is a cogeneration system with two valued products. By coupling with the LNG evaporation system as the cycle cold sink, the cycle condensation process can be achieved at a temperature much lower than ambient, and high-pressure liquid CO2 can be withdrawn from the cycle without consuming additional power. Two system variants are analyzed and compared, COOLCEP-S and COOLCEP-C. In the COOLCEP-S cycle configuration, the working fluid in the main turbine expands only to the CO2 condensation pressure; in the COOLCEP-C cycle configuration, the turbine working fluid expands to a much lower pressure (near-ambient) to produce more power. The effects of some key parameters, the turbine inlet temperature and the backpressure, on the systems' performance are investigated. It was found that at the turbine inlet temperature of 900 °C, the energy efficiency of the COOLCEP-S system reaches 59%, which is higher than the 52% of the COOLCEP-C one. The capital investment cost of the economically optimized plant is estimated to be about 750 EUR/kWe and the payback period is about 8–9 years including the construction period, and the cost of electricity is estimated to be 0.031–0.034 EUR/kWh.  相似文献   

20.
This paper evaluates nine types of electrical energy generation options with regard to seven criteria. The options use natural gas or hydrogen as a fuel. The Analytic Hierarchy Process was used to perform the evaluation, which allows decision-making when single or multiple criteria are considered.The options that were evaluated are the hydrogen combustion turbine, the hydrogen internal combustion engine, the hydrogen fuelled phosphoric acid fuel cell, the hydrogen fuelled solid oxide fuel cell, the natural gas fuelled phosphoric acid fuel cell, the natural gas fuelled solid oxide fuel cell, the natural gas turbine, the natural gas combined cycle and the natural gas internal combustion engine.The criteria used for the evaluation are CO2 emissions, NOX emissions, efficiency, capital cost, operation and maintenance costs, service life and produced electricity cost.A total of 19 scenarios were studied. In 15 of these scenarios, the hydrogen turbine ranked first and proved to be the most preferred electricity production technology. However since the hydrogen combustion turbine is still under research, the most preferred power generation technology which is available nowadays proved to be the natural gas combined cycle which ranked first in five scenarios and second in eight. The last in ranking electricity production technology proved to be the natural gas fuelled phosphoric acid fuel cell, which ranked in the last position in 13 scenarios.  相似文献   

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