Carbon capture from natural gas combined cycle power plants: Solvent performance comparison at an industrial scale

Natural gas is an important source of energy. This article addresses the problem of integrating an existing natural gas combined cycle (NGCC) power plant with a carbon capture process using various solvents. The power plant and capture process have mutual interactions in terms of the flue gas flow rate and composition vs. the extracted steam required for solvent regeneration. Therefore, evaluating solvent performance at a single (nominal) operating point is not indicative and solvent performance should be considered subject to the overall process operability and over a wide range of operating conditions. In the present research, a novel optimization framework was developed in which design and operation of the capture process are optimized simultaneously and their interactions with the upstream power plant are fully captured. The developed framework was applied for solvent comparison which demonstrated that GCCmax, a newly developed solvent, features superior performances compared to the monoethanolamine baseline solvent

Carbon capture from pulverized coal power plant (PCPP): Solvent performance comparison at an industrial scale

Coal is the most abundant fossil fuel on the planet. However, power generation from coal results in large amounts of greenhouse gas emissions. Solvent-based carbon capture is a relatively mature technology which can potentially mitigate these emissions. Although, much research has been done on this topic, single-point performance analysis of capture plant and ignoring operational characteristics of the upstream power plant may result in unrealistic performance assessments. This paper introduces a new methodology to assess the performance of CO2 capture solvents. The problem is posed as retrofitting an existing pulverized coal power plant with post-combustion carbon capture using two solvents: CDRMax, a recently developed amine-promoted buffer salt (APBS) solvent by Carbon Clean Solutions Limited (CCSL) and the monoethanolamine (MEA) baseline solvent. The features of interest include model development and validation using pilot plant data, as well as integrated design and control of the capture process. The emphasis is on design and operation of the capture plant, when integrated with the upstream coal-fired power plant, subject to variations in the electricity load. The results suggest that optimal design and operation of capture plant can significantly mitigate the energetic penalties associated with carbon capture form the flue gas, while providing effective measures for comparing solvent performances under various scenarios

Modern Thermal Power Plants - Aspects on Modelling and Evaluation

The European Union (EU) has laid down very clear objectives for the reduction of greenhouse gases in the hope that it will prevent or mitigate climate change. Political incentives are used to make the power industry adopt changes in order to reach these EU targets. In this thesis, some solutions that could help power companies meet the EU objectives are evaluated. Thermodynamic models have been developed to evaluate the proposed methods. A description of the models and the way in which they are used to model power plant cycles in off-design mode is included in this thesis. The focus was on combined-cycle power plants, which have the highest efficiency among commercial power plants today. Three ways of adapting power plants so as to meet the EU targets were formulated: • reduced CO2 emissions • increased use of biofuels • improved part-load abilities A new method based on using low-grade heat when implementing carbon capture in a combined cycle power plant is presented. The results show that the method can increase the total efficiency and reduce the initial cost of the power plant. The method is applicable for both retrofitting to existing plants and for new plants. The effect of using low-calorific bio-fuels in a combined-cycle power plant was investigated. The results show that below a heating value of about 20-25 MJ/kg the plant quickly departs from its design point. The supply of power to the national grid is expected to be fluctuate more in the future due to the uneven availability of wind and solar power. Therefore, two part-load operation strategies were evaluated. The first involves a strategy that entails less wear on the gas turbine, which could extend the maintenance interval of the unit. The second method combines two well-established part-load strategies for part-load operation of steam-cycle power plants. The combination of the two methods will increase the part-load efficiency of the power plant

Zinc-bromine battery for energy storage

The performance of a 2 kW, 10 kW h zinc-bromine battery is reported. The battery uses new carbon/PVDF bipolar electrodes and a circulating polybromide/aqueous zinc-bromine electrolyte. A turn-around efficiency of 65–70% is achieved. Disclosure is also given of an innovative non-flowing-electrolyte cell. This system is less complex and, hence, gives increased reliability and a higher return efficiency. A 25 A h single cell has completed over 400 cycles (100% depth-of-discharge) with a total return energy efficiency of over 75%. Such technology is extremely attractive for remote-area power-supply applications

Improved load control for a steam cycle combined heat and power plant

The problem of optimum load control of steam power plants has been dealt within many technical papers during the last decades. Deregulation of the power markets and close to the (bio-) fuel source thinking has lead to a trend of small scale combined heat and power plants. These plants are usually operated according to the heat demand and therefore they spend a significant time on partial load. The load control of such plants is in general done by partial arc control. This work applies a hybrid control strategy, which is a combination of partial arc control and sliding pressure control. The method achieves further improvement in performance at partial load. Hybrid control itself is not novel and has earlier been used on traditional coal-fired condensing plants. This has, to the author's knowledge, not earlier been applied on combined heat and power plants. The results show that there is a potential for improved electricity production at a significant part of the load range. (C) 2009 Elsevier Ltd. All rights reserved

A Novel Approach of Retrofitting a Combined Cycle With Post Combustion CO2 Capture

Most state-of-the-art natural gas-fired combined cycle (NGCC) plants are triple-pressure reheat cycles with efficiencies close to 60%. However, with carbon capture and storage, the efficiency will be penalized by almost 10% units. To limit the energy consumption for a carbon capture NGCC plant, exhaust gas recirculation (EGR) is necessary. Utilizing EGR increases the CO2 content in the gas turbine exhaust while it reduces the flue gas flow to be treated in the capture plant. Nevertheless, due to EGR, the gas turbine will experience a different media with different properties compared with the design case. This study looks into how the turbomachinery reacts to EGR. The work also discusses the potential of further improvements by utilizing pressurized water rather than extraction steam as the heat source for the CO2 stripper. The results show that the required low-pressure level should be elevated to a point close to the intermediate-pressure to achieve optimum efficiency, hence, one pressure level can be omitted. The main tool used for this study is an in-house off-design model based on fully dimensionless groups programmed in the commercially available heat and mass balance program IPSEPRO. The model is based on a GE 109FB machine with a triple-pressure reheat steam cycle. [DOI: 10.1115/1.4001988

Low-Calorific Fuel Mix In A Large Size Combined Cycle Plant

This paper will address the effects of mixing low-calorific fuel in to a natural gas fuelled large size combined cycle plant. Three different biofuels are tested namely; air blown gasification gas, indirect gasification gas and digestion gas. Simulations have been performed from 0-100% biofuel natural gas mixtures. The biofuel impacts on the full cycle performance are discussed. Some more in-depth discussion about turbo-machinery components will be introduced when needed for the discussion. The compressors pressure ratio will increase in order to push the inert ballast of the low calorific fuels trough the turbine. Despite the increased expansion ratio in the gas turbine, the exhaust temperature raises slightly which derives from changed gas properties. The work is based on an in-house advanced off-design model within the software package IPSEPro. Sweden's newest plant "Oresundsverket", which is a combined heat and power (CHP) plant, is used as a basis for the Investigation. The plant is based on a GE Frame-9 gas turbine and has a triple-pressure reheat steam cycle

Postcombustion CO2 Capture for Combined Cycles Utilizing Hot-Water Absorbent Regeneration

The partly hot-water driven CO2 capture plant offers a significant potential for improvement in performance when implemented in a combined-cycle power plant (CCPP). It is possible to achieve the same performance with a dual-pressure steam cycle as in a triple-pressure unit. Even a single-pressure plant can attain an efficiency competitive with that achievable with a triple-pressure plant without the hot-water reboiler. The underlying reasons are better heat utilization in the heat recovery unit and less steam extraction to the absorbent regenerating unit(s). In this paper, the design criteria for a combined cycle power plant utilizing hot-water absorbent regeneration will be examined and presented. The results show that the most suitable plant is one with two steam pressure levels. The low-pressure level should be much higher than in a conventional combined cycle in order to increase the amount of heat available in the economizer. The external heat required in the CO2 capture plant is partly supplied by the economizer, allowing temperature optimization in the unit. The maximum value of the low-pressure level is determined by the reboiler, as too great a temperature difference is unfavorable. This work evaluates the benefits of coupling the economizer and the reboiler in a specially designed CCPP. In the CO2 separation plant both monoethanolamine (MEA) and ammonia are evaluated as absorbents. Higher regeneration temperatures can be tolerated in ammonia-based plants than in MEA-based plants. When using a liquid heat carrier the reboiler temperature is not constant on the hot side, which results in greater temperature differences. The temperature difference can be greatly reduced by dividing the regeneration process into two units operating at different pressures. The possibility of extracting more energy from the economizer to replace part of the extracted steam increases the plant efficiency. The results show that very high efficiencies can be achieved without using multiple pressure-levels. [DOI: 10.1115/1.4004146