Carbon dioxide recovery from flue gases of a conventional coal-fired power plant by low-temperature distillation

To reduce the emission of carbon dioxide from a conventional coal-fired power plant, carbon dioxide can be separated from the flue gases by using polymer membranes. In this chapter a theoretical investigation into the technological and economic outlook of this option is described.At present the best types of membranes available for separating carbon dioxide from nitrogen are non-porous polymer membranes based on polyimide, polydimethylphenyleneoxide, polydimethylsiloxane and cellulose acetate. The carbon dioxide can be recovered by applying a single membrane stage configuration. The disadvantage of such a configuration is that it leads to a carbon dioxide gas that is highly diluted with nitrogen. This is an unwanted situation because the carbon dioxide is a liquid in the conditions (8000 kPa and 10°C) under which it will be transported, whereas nitrogen remains gaseous under these conditions. Moreover, the transport facilities and storage capacity for carbon dioxide will not be utilized optimally.Three methods for purifying the carbon dioxide are considered. In the first method the carbon dioxide product gas is purified by feeding it to a second membrane unit. This configuration is called the two-stage cascade. The second method makes use of the different phases of nitrogen and carbon dioxide at high pressures. In this method the carbon dioxide product gas is compressed to 8000 kPa and cooled down to 25°C. Subsequently the nitrogen, contaminated with some carbon dioxide vapour, is separated from the condensed carbon dioxide. This nitrogen off-gas is released to the atmosphere. The third method is similar to the second one, except that the nitrogen off-gas is recycled back to the membrane unit.With a computer program based on a cross-flow permeation model for polymer membranes, the recovery design is optimized to obtain the lowest recovery costs per tonne carbon dioxide avoided.For the membranes examined, a lowest cost figure of 51 US$ per tonne carbon dioxide avoided is calculated. This figure is found for a polyimide-based membrane in a single membrane stage configuration combined with separation of the carbon dioxide by compression and venting the nitrogen off-gas. In this set-up 75% of the carbon dioxide is recovered and the carbon dioxide is nearly pure. For a 90% recovery either the two-stage cascade or the single membrane stage with recycling of the nitrogen off-gas are attractive routes, leading to recovery costs of about 65 US$ per tonne carbon dioxide avoided. Recovery with polymer membranes is calculated to be 50 to 100% more expensive than recovery using cold distillation or a chemical absorption technique. Although some cost reductions are feasible, membrane separation is not expected to become a competing option for carbon dioxide recovery from flue gases of conventional coal-fired power plants in the near future.KeywordsInvestment CostPolymer MembraneRecovery CostMembrane UnitIsentropic EfficiencyThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Carbon dioxide has been identified as a major greenhouse gas responsible for a large part of the enhancement of global warming. CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> capture and storage (CCS) from power plants is drawing increasing interest as a potential method for the control of greenhouse gas emissions. Technically, the capture of CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> from the flue gas of power plants, using a monoethanolamine (MEA) absorption process is a viable shortcut to medium term strategy for the mitigation of the atmospheric CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> emissions from large point sources. An economical performance study for a CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> removal plant from flue gas of a NGCC syngas-fired power plant was performed, based on absorption/regeneration process with MEA solutions, using ASPEN Plus. The conclusion is that the efficiency drop due to CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> removal plant is approximately 12.9%; and the cost of CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> captured and the cost of CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> avoided are respectively 13 euros/tCO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and 18 euros/tCO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> . In order to popularize large-scale CCS to power plants, technology improvement is greatly needed.

The existing forms and their inter-transformations are important to study the behavior of arsenic and its capture technology in the flue gas of power plants. In this study, a density functional theory was applied to study the thermodynamic and kinetic aspects of arsenic substances in flue gas. Gibbs free energy comparison was used to evaluate the thermodynamic stability of various arsenic species at four temperatures (1200, 800, 370, and 25 °C), which represent the temperatures of flue gas in the area of the combustion center, horizontal flue, NOx removal reactor, and atmosphere, respectively. The results show that trivalent arsenic molecules are thermodynamically stable at high temperatures and pentavalent species are stable at low temperatures. The arsenic species vary with the temperature. At high temperatures, dehydrated compounds are the major species. These compounds will be hydrated and oxidized by O2 when the temperature declines, as implied by the reaction path study. Arsenic acid becomes the mos...

In order to realize the storage of the residual coal in the goaf on the flue gas of the power plant, the adsorption characteristics of nitrogen dioxide in the flue gas of the power plant were studied. The Gaussian09 was used to study the adsorption process of NO2 molecules on coal at the density functional (DFT) B3LYP/6-311G level, and the model of NO2 adsorption by coal was established. Different quantities were obtained using orbital energy changes and molecular bond length changes. According to the principle of molecular adsorption, the adsorption of NO2 by coal is considered to be physical adsorption with endothermic heat. On the basis of simulation, using self-organized experimental devices, the single-component NO2 gas and the simulated coal-fired power plant flue gas were introduced into anthracite, bituminous coal and lignite. In single-component adsorption, the adsorption of NO2 by lignite increases with time. The time to reach equilibrium is related to the properties of the coal itself. In the process of simulated flue gas adsorption, the order of the adsorption amount of coal to flue gas is CO2 > NO2 > N2 > O2. In the simulated flue gas, coal is easy to absorb NO2 and CO2, and the competition between gases reduces the frequency of contact between NO2 and the coal surface. Simulation and experimental results show that coal has obvious adsorption characteristics for NO2, and it is feasible for the residual coal in the goaf to adsorb NO2 in the flue gas of power plants.

Abbreviations. I. Introduction. II. Simulation and Optimization of Carbon Dioxide Recovery from the Flue Gases of a Coal-Fired Power Plant Using Amines. III. Carbon Dioxide Recovery from Flue Gases of a Conventional Coal-Fired Power Plant Using Polymer Membranes. IV. Carbon Dioxide Recovery from Flue Gases of a Conventional Coal-Fired Power Plant by Low-Temperature Distillation. V. Carbon Dioxide Recovery from an Integrated Coal Gasifier Combined Cycle Plant Using a Shift Reactor and a Scrubber. VI. Carbon Dioxide Recovery from an Integrated Coal Gasifier, Combined Cycle Plant Using Membrane Separation and a CO2 Gas Turbine. VII. Underground Storage of Carbon Dioxide. VIII. Summary and Conclusions. Index.

Characteristics of the large-scale circulation during episodes with high and low concentrations of carbon dioxide and air pollutants at an arctic monitoring site in winter

Pilot scale separation of CO2 from power plant flue gases by membrane technology

The new waste heat and water recovery technology based on a nanoporous ceramic membrane vapor separation mechanism has been developed for power plant flue gas application. The recovered water vapor and its latent heat from the flue gas can increase the power plant boiler efficiency and reduce water consumption. This report describes the development of the Transport Membrane Condenser (TMC) technology in details for power plant flue gas application. The two-stage TMC design can achieve maximum heat and water recovery based on practical power plant flue gas and cooling water stream conditions. And the report includes: Two-stage TMC water and heat recovery system design based on potential host power plant coal fired flue gas conditions; Membrane performance optimization process based on the flue gas conditions, heat sink conditions, and water and heat transport rate requirement; Pilot-Scale Unit design, fabrication and performance validation test results. Laboratory test results showed the TMC system can exact significant amount of vapor and heat from the flue gases. The recovered water has been tested and proved of good quality, and the impact of SO{sub 2} in the flue gas on the membrane has been evaluated. The TMC pilot-scale system has been field tested with amore » slip stream of flue gas in a power plant to prove its long term real world operation performance. A TMC scale-up design approach has been investigated and an economic analysis of applying the technology has been performed.« less

Environmental control technology for atmospheric carbon dioxide

Development of energy saving technology for flue gas carbon dioxide recovery in power plant by chemical absorption method and steam system

The oxygen content in flue gas of power plant is one of the important variables for keeping the boiler combustion process stable and secure. Real-time monitoring and control for the oxygen content in flue gas of power plant is difficult at present. To address this problem, we propose a soft measurement method based on back-propagation neural network (BPNN) and genetic algorithm (GA) to predict the oxygen content in flue gas of power plant. In the algorithm, partial least squares (PLS) method is used to reduce dimensions of input variables. The model based on the data collected from the historical data of power plant is constructed by BP. The GA algorithm is utilized to optimize the parameters of BP for improving the accuracy of the model. The proposed method has been proved effective through iterative experiments.

This paper presents a thermodynamic and economic comparative analysis of a conventional gas-steam power plant with a modified gas-steam power plant. The modification involves replacing the gas turbine present in the conventional power plant with a High Temperature Gas-cooled Reactor (HTGR) and a turboexpander. In the Joule cycle modified power plant, the circulating medium is helium, while in the conventional power plant it is the exhaust gas produced from the combustion of natural gas. The results obtained show that the innovative dual-circuit gas-steam power plant with a high-temperature HTGR nuclear reactor and TE turboexpander has significantly higher economic efficiency than a conventional gas-steam power plant. This is despite the fact that the unit capital expenditures for a power plant with HTGR and TE are many times higher (about 8 times) compared to those for a conventional gas-steam power plant. Increasing the temperature T3 of the outlet helium from the TE above the value of T3opt= 709.1K with temperature T2 = 1300 K, is possible by reducing the compression ratio p1/p0. This will result in a significant increase in the energy efficiency of the gas-steam power plant ηG-S and of its output NG-S=NTE+NST. Increasing the temperature T3 is advantageous also for economic reasons.

Methane hydrate exists in huge amounts in certain locations, in sea sediments and the geological structures below them, at low temperature and high pressure. Production methods are in development to produce the methane to a floating platform. There it can be reformed to produce hydrogen and carbon dioxide, in an endothermic process. Some of the methane can be burned to provide heat energy to develop all needed power on the platform and to support the reforming process. After separation, the hydrogen is the valuable and transportable product. All carbon dioxide produced on the platform can be separated from other gases and then sequestered in the sea as carbon dioxide hydrate. In this way, hydrogen is made available without the release of carbon dioxide to the atmosphere, and the hydrogen could be an enabling step toward a world hydrogen economy.

The dry carbonate process: Carbon dioxide recovery from power plant flue gas

We propose an experimental adsorption device, imitating the environment of a coal-mine goaf and the composition of the flue gas in Tashan Mine Power Plant. The characteristics of the coal adsorbing flue gas were studied with the atmospheric volumetric method. The factors affecting the seal of CO2 were analyzed and the effect of power plant flue gas on fire prevention in the goaf was investigated at normal temperature and pressure. It can be inferred from the experiment that N2, SO2, and H2O can also reduce CO2 adsorption capacity. The increase or decrease in pH can increase the adsorption capacity of CO2, which is apparently larger when the pH is decreasing than when the pH is increasing. The O2 adsorption capacity can evidently be reduced when the power plant flue gas is injected into the goaf. The activation energy of coal burned in air is greater than that of coal burned in flue gas, indicating that the use of power plant flue gas, with N2 and CO2 as the main components, to replace the traditional inert gas can not only save N2 generation cost, but also reduce the emission of greenhouse gases, while the power plant flue gas can be adsorbed by coal.