Reduction of Greenhouse Gas Emissions from Gas,Oil, and Coal Power Plants in Pakistan by Carbon Capture and Storage (CCS): A Review

The production of energy in Pakistan as a developing country mainly depends on consumption of fossil fuels, which are the main sources of greenhouse gas (GHG) emissions. These emissions can be mitigated by implementing carbon capture and storage (CCS) in running plants. An overview of the current and future potentials of Pakistan for CCS is provided, indicating a great potential for this technology to capture CO₂ emissions. The amine CO₂ capture process as the most mature procedure is currently applied in many oil and gas companies in Pakistan, which can be employed to capture CO₂ from other industries as well. Pakistan has a great CO₂ storage potential in oil, gas, and coal fields and in saline aquifer as well as significant resources of Mg and Ca silicates suitable as feedstock in the carbon mineralization process. For further development and implementation of CCS technologies in Pakistan, economic and policy barriers as the main obstacles should be alleviated.     

Assessment of Industrial Greenhouse Gas Reduction Strategies Within Consistent System Boundaries

With respect to the climate goals of the greenhouse gas (GHG) neutrality in 2050, different GHG reduction strategies are discussed for industrial processes. For a comparison of the strategies carbon direct avoidance (CDA), carbon capture and storage, and carbon capture and utilization (CCU), the method system expansion is applied. Exemplarily, the CO₂ reduction potential and the energy demand are determined. The Carbon2Chem® project is described as an example of CCU for the steel and chemical production. The direct reduction with H₂ represents the CDA strategy for the steel industry.     

A Single Stage Membrane Process for CO2 Capture from Flue Gas by a Facilitated Transport Membrane

Carbon dioxide is the most important anthropogenic greenhouse gas and it accounts for about 80% of all greenhouse gases (GHG). The global atmospheric CO₂ concentrations have been increased significantly and have become the major source responsible for global warming; the greatest environmental challenge the world is facing now. The efforts to control the GHG emissions include the recovery of CO₂ from flue gas. In this work, feasibility analysis, based on a single stage membrane process, has been carried out with an in-house membrane program interfaced within process simulation program (AspenHysys) to investigate the influence of process parameters on the energy demand and flue gas processing cost. A novel CO₂-selective membrane with the facilitated transport mechanism has been employed to capture CO₂ from the flue gas mixtures. The results show that a membrane process using the facilitated transport membrane can also be considered as an alternative CO₂ capture process and it is possible to achieve more than 90% CO₂ recovery and 90% CO₂ purity in the permeate with reasonable energy consumption compared to amine absorption and other capture techniques.     

Using short‐term resource scheduling for assessing effectiveness of CCS within electricity generation subsector

A new methodology for assessing the effectiveness of carbon capture and storage (CCS) that does explicitly consider the detailed operation of the target electricity system is proposed. The electricity system simulation consists of three phases, each one using a modified version of an economic dispatch problem that seeks to maximize the producers’ and consumers’ surplus while satisfying the technical constraints of the system. The economic dispatch is formulated as a dynamic mixed‐integer nonlinear programming problem and implemented in general algebraic modelling system (GAMS). The generating unit with CCS is designed and simulated using Aspen Plus®. In the first case study, the operation of the IEEE RTS ’96 (Institute of Electrical and Electronics Engineers One‐Area Reliability Test System—1996) is simulated with greenhouse gas (GHG) regulation implemented in the form of CO₂ permits that generators need to acquire for every unit of CO₂ that it is emitted. In the second case study, CCS is added at one of the buses and the operation of the modified IEEE RTS ’96 is again simulated with and without GHG regulation. The results suggest that the detailed operation of the target electricity system should be considered in future assessments of CCS and a general procedure for undertaking this for any GHG mitigation option is proposed. Future work will use the novel methodology for assessing the effectiveness of generating units with flexible CO₂ capture. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4210–4234, 2015     

Optimization of energy usage for fleet‐wide power generating system under carbon mitigation options

This article presents a fleet‐wide model for energy planning that can be used to determine the optimal structure necessary to meet a given CO₂ reduction target while maintaining or enhancing power to the grid. The model incorporates power generation as well as CO₂ emissions from a fleet of generating stations (hydroelectric, fossil fuel, nuclear, and wind). The model is formulated as a mixed integer program and is used to optimize an existing fleet as well as recommend new additional generating stations, carbon capture and storage, and retrofit actions to meet a CO₂ reduction target and electricity demand at a minimum overall cost. The model was applied to the energy supply system operated by Ontario power generation (OPG) for the province of Ontario, Canada. In 2002, OPG operated 79 electricity generating stations; 5 are fueled with coal (with a total of 23 boilers), 1 by natural gas (4 boilers), 3 nuclear, 69 hydroelectric and 1 wind turbine generating a total of 115.8 TWh. No CO₂ capture process existed at any OPG power plant; about 36.7 million tonnes of CO₂ was emitted in 2002, mainly from fossil fuel power plants. Four electricity demand scenarios were considered over a span of 10 years and for each case the size of new power generation capacity with and without capture was obtained. Six supplemental electricity generating technologies have been allowed for: subcritical pulverized coal‐fired (PC), PC with carbon capture (PC+CCS), integrated gasification combined cycle (IGCC), IGCC with carbon capture (IGCC+CCS), natural gas combined cycle (NGCC), and NGCC with carbon capture (NGCC+CCS). The optimization results showed that fuel balancing alone can contribute to the reduction of CO₂ emissions by only 3% and a slight, 1.6%, reduction in the cost of electricity compared to a calculated base case. It was found that a 20% CO₂ reduction at current electricity demand could be achieved by implementing fuel balancing and switching 8 out of 23 coal‐fired boilers to natural gas. However, as demand increases, more coal‐fired boilers needed to be switched to natural gas as well as the building of new NGCC and NGCC+CCS for replacing the aging coal‐fired power plants. To achieve a 40% CO₂ reduction at 1.0% demand growth rate, four new plants (2 NGCC, 2 NGCC+CCS) as well as carbon capture processes needed to be built. If greater than 60% CO₂ reductions are required, NGCC, NGCC+CCS, and IGCC+CCS power plants needed to be put online in addition to carbon capture processes on coal‐fired power plants. The volatility of natural gas prices was found to have a significant impact on the optimal CO₂ mitigation strategy and on the cost of electricity generation. Increasing the natural gas prices resulted in early aggressive CO₂ mitigation strategies especially at higher growth rate demands. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Planning of carbon capture and storage with pinch analysis techniques

Carbon capture and storage (CCS) is a means for reducing carbon dioxide (CO₂) emissions from fossil fuel combustion in power generation and industrial processes. It involves the capture of CO₂ for subsequent storage in various geological formations. The selection and matching of the power plants and storage sites are often an issue of optimisation due to various constraints, i.e., time of availability, injection rate, and storage capacity limits. In this work, a novel graphical targeting tool based on pinch analysis is proposed to address the planning problem of the storage of captured CO₂ from power generating plants into corresponding reservoirs. The main consideration for the problem is the time of availability of the latter, since reservoirs need to be developed prior to CO₂ storage. The time limitation is addressed by the graphical technique where time is taken as the governing element in solving the problem. Hypothetical examples are used to elucidate the proposed approach.     

Optimal strategy for carbon capture and storage infrastructure: A review

To effectively reduce CO₂, CO₂ mitigation technologies should be employed tactically. This paper focuses on carbon capture and storage (CCS) as the most promising CO₂ reduction technology and investigates how to establish CCS strategy suitably. We confirm a major part of the optimal strategy for CCS infrastructure planning through a literature review according to mathematical optimization criteria associated with facility location models. In particular, the feasibility of large scale CCS infrastructure is evaluated through economic, environmental, and technical assessment. The current state-of-the-art optimization techniques for CCS infrastructure planning are also addressed while taking numerous factors into account. Finally, a list of issues for future research is highlighted.     

Simulation of a Lignite‐Based Polygeneration System Coproducing Electricity and Tar with Carbon Capture

Lignite‐based polygeneration systems for coproducing tar and electricity with and without carbon capture and storage (CCS) were proposed and simulated. Predried lignite was pyrolyzed into coal gas, tar, and char. Coal gas was fired in a gas turbine after the cleanup process, while char was combusted in circulating fluidized‐bed (CFB) boilers. The polygeneration plant without CCS turned out to be more efficient than the conventional CFB power plant, suggesting that the former is a promising and efficient option to utilize lignite resources. Moreover, the performance and emissions of polygeneration plants with and without CCS were compared. It was shown that the more CO₂ is captured, the larger energy penalty it will cost. Therefore, a trade‐off should be made between low emissions and high efficiency.     

我国碳减排模式探讨——CCS路线与生物甲烷路线的比较

碳捕获和封存路线(carbon capture and storage,简称CCS)和生物甲烷路线是实现二氧化碳减排的两种重要途径。但CCS路线存在捕集成本高的难题,而生物甲烷路线规模小、尚处于起步阶段。本文从经济和技术角度对比了两种路线减排二氧化碳的优缺点,发现生物甲烷路线理论捕集能耗仅为CCS路线的一半,且捕集条件温和,更有利于提高吸附剂材料的容量、降低捕集成本,因而生物甲烷路线更具有减排潜力。为了解决CCS和生物甲烷路线目前存在的困境,提出了CCS与生物甲烷耦合、借助CCS加速发展生物甲烷过程的新思路。     

Modeling and analysis of circulation variables of continuous sorbent loop cycling for CO<Subscript>2</Subscript> capture

Carbon capture and storage (CCS) technologies are a cornerstone for reducing CO₂ emissions from energy and energy-intensive industries. Among the various CCS technologies, solid sorbent looping systems are considered to be potentially promising solutions for reducing CO₂ capture energy penalty. We present an evaluation module for a carbonator with sorbent looping cycle to calculate the carbonation efficiency. The module incorporates a simple sorbent activity model, and the solid/gas balances are constructed by assuming simple reactor mixing quality. By conducting simulations, we examine the variation in the carbonation efficiencies as a function of the sorbent looping operation factors and discuss an optimum operating strategy.     

Thermodynamic and transport property models for carbon capture and sequestration (CCS) processes with emphasis on CO2 transport

Carbon capture and sequestration (CCS) is one of the most promising technologies for the reduction of carbon dioxide (CO₂) concentration in the atmosphere, so that global warming can be controlled and eventually eliminated. A crucial part in the CCS process design is the model that is used to calculate the physical properties (thermodynamic, transport etc.) of pure CO₂ and CO₂ mixtures with other components.     

Assessment of chemical looping-based conceptual designs for high efficient hydrogen and power co-generation applied to gasification processes

Carbon capture and storage (CCS) technologies are expected to play a significant role in the coming decades for curbing the greenhouse gas emissions and to ensure a sustainable development of power generation and other energy-intensive industrial sectors. Chemical looping systems are very promising options for intrinsically capture CO₂ with lower cost and energy penalties. Gasification offers significant advantages compared with other technologies in term of lower energy and cost penalties for carbon capture, utilization of wide range of fuels, poly-generation capability, plant flexibility, lower environmental impact, etc.     

Cover Chem. Eng. Technol. 2/2015

CO₂ Capture in a Bubble‐Column Scrubber Bubble columns are widely used in industry, such as on operations of reaction, fermentation, crystallization, desorption, and absorption. They can be operated in batch, continuously, or in semi‐batch, as well as in two or three phases. With the advantages of easy operation, simple structure, high mass transfer efficiency, high absorption factor, and low energy consumption, bubble columns have attracted wide attention in the industry. In recent years, as the carbon dioxide capture, storage, and regeneration are urgent issues, CCS and CCU have been used as the key point to solve greenhouse effect. This plays a great role in CO₂ capture and storage in thermal power plants, in which the CCS capture and regeneration account for 70 % of the power generation cost. How to achieve effective capture and regeneration has become a topical subject in the energy saving and carbon reduction. Among various technologies of CO₂ capture, absorption is the most mature, and MEA is used most widely. Although the capture of acid gases is still dominated by filling towers, many recent studies have confirmed the advantages of bubble towers that prevail over filling towers or other appliances. Thus, bubble columns have been adopted as the absorber and MEA as the absorbent for the new attempt of CO₂ capture. The operation variables include CO₂ concentration, pH, temperature, air flow rate, available gas‐liquid flow rate ratio, absorption efficiency, absorption velocity, overall mass transfer coefficient, and absorption factor, which are the important parameters for the design and operation of absorber. This study adopts the Taguchi experiment design to obtain the priority of parameter type and the optimal parameters of bubble towers for CO₂ capture, so as to achieve energy saving and carbon reduction. DOI: 10.1002/ceat.201400240 CO₂ Capture Using Monoethanolamine in a Bubble‐Column Scrubber Pao‐Chi Chen*, Yi Xin Luo, Pao Wein Cai Chem. Eng. Technol. 2015 , 38 (2), 274–282.     

Progress in carbon dioxide capture and separation research for gasification-based power generation point sources

The purpose of the present work is to investigate novel approaches, materials, and molecules for the abatement of carbon dioxide (CO₂) at the pre-combustion stage of gasification-based power generation point sources. The capture/separation step for CO₂ from large point sources is a critical one with respect to the technical feasibility and cost of the overall carbon sequestration scenario. For large point sources, such as those found in power generation, the carbon dioxide capture techniques being investigated by the Office of Research and Development of the National Energy Technology Laboratory possess the potential for improved efficiency and reduced costs as compared to more conventional technologies. The investigated techniques can have wide applications, but the present research is focused on the capture/separation of carbon dioxide from fuel gas (pre-combustion gas) from processes such as the Integrated Gasification Combined Cycle (IGCC) process. For such applications, novel concepts are being developed in wet scrubbing with physical sorption, chemical sorption with solid sorbents, and separation by membranes. In one concept, a wet scrubbing technique is being investigated that uses a physical solvent process to remove CO₂ from fuel gas of an IGCC system at elevated temperature and pressure. The need to define an “ideal” solvent has led to the study of the solubility and mass transfer properties of various solvents. Pertaining to another separation technology, fabrication techniques and mechanistic studies for membranes separating CO₂ from the fuel gas produced by coal gasification are also being performed. Membranes that consist of CO₂-philic ionic liquids encapsulated into a polymeric substrate have been investigated for permeability and selectivity. Finally, processes based on dry, regenerable sorbents are additional techniques for CO₂ capture from fuel gas. An overview of these novel techniques is presented along with a research progress status of technologies related to membranes and physical solvents.     

Mature <Emphasis Type="Italic">versus</Emphasis> emerging technologies for CO<Subscript>2</Subscript> capture in power plants: Key open issues in post-combustion amine scrubbing and in chemical looping combustion

Carbon capture and storage (CCS) have acquired an increasing importance in the debate on global warming as a mean to decrease the environmental impact of energy conversion technologies, by capturing the CO₂ produced from the use of fossil fuels in electricity generation and industrial processes. In this respect, post-combustion systems have received great attention as a possible near-term CO₂ capture technology that can be retrofitted to existing power plants. This capture technology is, however, energy-intensive and results in large equipment sizes because of the large volumes of the flue gas to be treated. To cope with the demerits of other CCS technologies, the chemical looping combustion (CLC) process has been recently considered as a solution for CO₂ separation. It is typically referred to as a technology without energy penalty. Indeed, in CLC the fuel and the combustion air are never mixed and the gases from the oxidation of the fuel (i.e., CO₂ and H₂O) leave the system as a separate stream and can be separated by condensation of H₂O without any loss of energy. The key issue for the CLC process is to find a suitable oxygen carrier, which provides the fuel with the activated oxygen needed for combustion. The aim of this work is to explore the feasibility of using perovskites as oxygen carriers in CLC and to consider the possible advantages with respect to the scrubbing process with amines, a mature post-combustion technology for CO₂ separation.

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Dynamic modeling of CO2 absorption from coal-fired power plants into an aqueous monoethanolamine solution

Among carbon capture and storage (CCS), the post-combustion capture of carbon dioxide (CO₂) by means of chemical absorption is actually the most developed process. Steady state process simulation turned out as a powerful tool for the design of such CO₂ scrubbers. Besides steady state modeling, transient process simulations deliver valuable information on the dynamic behavior of the system. Dynamic interactions of the power plant with the CO₂ separation plant can be described by such models. Within this work a dynamic process simulation model of the absorption unit of a CO₂ separation plant was developed. For describing the chemical absorption of CO₂ into an aqueous monoethanolamine solution a rate based approach was used. All models were developed within the Aspen Custom Modeler^® simulation environment. Thermo physical properties as well as transport properties were taken from the electrolyte non-random-two-liquid model provided by the Aspen Properties^® database. Within this work two simulation cases are presented. In a first simulation the inlet temperature of the flue gas and the lean solvent into the absorber column was changed. The results were validated by using experimental data from the CO₂SEPPL test rig located at the Dürnrohr power station. In a second simulation the flue gas flow to the separation plant was increased. Due to the unavailability of experimental data a validation of the results from the second simulation could not be achieved.     

Post-combustion CO2 capture with chemical absorption: A state-of-the-art review

Global concentration of CO₂ in the atmosphere is increasing rapidly. CO₂ emissions have an impact on global climate change. Effective CO₂ emission abatement strategies such as Carbon Capture and Storage (CCS) are required to combat this trend. There are three major approaches for CCS: post-combustion capture, pre-combustion capture and oxyfuel process. Post-combustion capture offers some advantages as existing combustion technologies can still be used without radical changes on them. This makes post-combustion capture easier to implement as a retrofit option (to existing power plants) compared to the other two approaches. Therefore, post-combustion capture is probably the first technology that will be deployed. This paper aims to provide a state-of-the-art assessment of the research work carried out so far in post-combustion capture with chemical absorption. The technology will be introduced first, followed by required preparation of flue gas from power plants to use this technology. The important research programmes worldwide and the experimental studies based on pilot plants will be reviewed. This is followed by an overview of various studies based on modelling and simulation. Then the focus is turned to review development of different solvents and process intensification. Based on these, we try to predict challenges and potential new developments from different aspects such as new solvents, pilot plants, process heat integration (to improve efficiency), modelling and simulation, process intensification and government policy impact.     

An overview of the Department of Energy's CarbonSAFE Initiative: Moving CCUS toward commercialization

The U.S. Department of Energy (DOE) Office of Fossil Energy (FE) National Energy Technology Laboratory (NETL) Carbon Storage Program helps develop technologies that safely and permanently store carbon dioxide (CO₂) without adversely impacting natural resources or hindering economic growth. Since 1997, the program has significantly advanced carbon capture, utilization, and storage (CCUS) science and technology, with more than 10.5 million metric tons (MMT) of CO₂ safely stored. However, key gaps in experience and knowledge remain (e.g., the technology, expertise, and processes needed to safely characterize and monitor 50+ MMT-scale geologic CO₂ storage sites). DOE's Carbon Storage Assurance Facility Enterprise (CarbonSAFE) Initiative (launched in FY16) is beginning to address this gap. The CarbonSAFE Initiative currently consists of 13 projects in Phase I: Integrated Carbon Capture and Storage (CCS) Pre-Feasibility and six projects in Phase II: Storage Complex Feasibility. This article includes the latest updates from the CarbonSAFE Initiative.     

ENERGY EFFICIENCY EVALUATION FOR A “GREEN” POWER GENERATION PROCESS WITH MINIMUM EFFORT ON CARBON DIOXIDE CAPTURE AND STORAGE

This study evaluates the use of cracking for the removal of carbon from fuels to be used in a power generation process. Unlike conventional power generation systems, the proposed system includes a cracking unit, the function of which is to convert primary fuels into H₂ rich syngas and solid carbon, thus avoiding the emission of CO₂ and the need for carbon capture and storage (CCS) in the power generation system. Based on the thermodynamic analysis of equilibrium reactions in the cracker, it is demonstrated that the operating temperature has a significant influence on the carbon capture rate achieved and the composition of the syngas. Carbon in the fuel can be captured in solid form from hydrocarbon fuels when operating the cracker at sufficiently high temperatures; however, only a portion of carbon can be captured in a solid form from oxygenated hydrocarbon fuels, with the maximum carbon capture rate being achieved at an optimum temperature. An energy analysis, which takes into account the energy penalty of CCS for the conventional power generation system, reveals that the net available energy from the proposed system is still not as high as that of the conventional system with CCS; however, the solid carbon can be of high commercial value when appropriate technology is employed to convert the carbon byproduct into a high-added-value carbon product such as carbon black or carbon nanotubes (CNTs).     

Safe storage of Co2 together with improved oil recovery by Co2-enriched water injection

The 2007 IEA's World Energy Outlook report predicts that the world's energy needs will grow by 55% between 2005 and 2030, with fossil fuels accounting for 84% of this massive projected increase in energy demand. An undesired side effect of burning fossil fuels is carbon dioxide (CO₂) emission which is now widely believed to be responsible for the problem of global warming. Various strategies are being considered for addressing the increase in demand for energy and at the same time developing technologies to make energy greener by reducing CO₂ emissions.One of these strategies is to ‘capture’ produced CO₂ instead of releasing it into the atmosphere. Capturing CO₂ and its injection in oil reservoirs can lead to improved oil recovery as well as CO₂ retention and storage in these reservoirs. The technology is referred to as CCS (carbon capture and storage). Large point sources of CO₂ (e.g., coal-fired power plants) are particularly good candidates for capturing large volumes of CO₂. However, CO₂ capture from power plants is currently very expensive. In addition to high costs of CO₂ capture, the very low pressure of the flue gas (1 atm) and its low CO₂ content (typically 10-15%) contribute to the high cost of CO₂ capture from power plants and the subsequent compression. This makes conventional CO₂ flooding (which requires very large volumes of CO₂) uneconomical in many oil reservoirs around the world which would otherwise be suitable candidates for CO₂ injection. Alternative strategies are therefore needed to utilize smaller sources of CO₂ that are usually available around oil and gas fields and can be captured at lower costs (due to their higher pressure and higher CO₂ concentration).We investigate the potential of carbonated (CO₂-enriched) water injection (CWI) as an injection strategy for improving recovery from oil reservoirs with the added benefit of safe storage of CO₂. The performance of CWI was investigated by conducting high-pressure flow visualization as well as coreflood experiments at reservoir conditions. The results show that CWI significantly improves oil recovery from water flooded porous media. A relatively large fraction of the injected CO₂ was retained (stored) in the porous medium in the form of dissolved CO₂ in water and oil. The results clearly demonstrate the huge potential of CWI as a productive way of utilizing CO₂ for improving oil recovery and safe storage of potentially large cumulative quantities of CO₂.