| Nowadays, the rapidly growing of economies and population around the world causes an increasing demand of energy and electricity. In order to maintain power supplies, industries worldwide need to replace large quantities of power generation plants. Coal represents an attractive option for new-built power plants due to the high price of oil and gas. However, as CO2is the main greenhouse gas which causes the global warming, the large amount of CO2from coal-fired power plants should be gathered and used.Carbon capture and storage technology is to separate CO2from the emission source, transport to geological formations, which makes CO2isolated from the atmosphere for a long time. For coal-fired power plants, CCS mainly means capture the CO2from the flue gas. Chemical absorption is a worthwhile alternative especially for power plants. And among those chemical absorbent, MEA is one of the most frequently used to absorb CO2, which is often used as the reference. Besides, aqueous ammonia is also proved to be a potential absorbent. This paper chose both MEA and ammonia as absorbent to analyze the best operation conditions of the two absorbent by simulate CO2capture process using Aspen Plus, and chose the better absorbent for the design of Capture-Ready power plants by comparing the advantages and disadvantages of MEA and ammonia.CO2can be captured from fossil fuel fired power plants but it is not currently economically feasible to build power plants fitted with CO2capture. However, when the emission reduction policies must be implemented, those power plants which are not qualified for CO2capture equipments can not achieve the emission reduction targets, then a large amount of CO2emission to the atmosphere will be ’locked-in’. A capture ready power plant is a plant which can be retrofitted with CO2capture when the necessary regulatory or economic drivers are in place.This paper discusses3options for the steam turbines of the capture ready power plants in order to find out how to design a capture ready power plant and the efficiency changes before and after the CO2capture retrofit of the power plants. By simulating the CO2capture process using two kinds of absorbent, MEA and ammonia, we found out the best operating conditions of them. The best operating conditions of MEA system:CO2recovery rate as90%, the concentration of absorbent is20%, the temperature of lean solution is40℃, the pressure of absorption tower is under1.2bar, the lever of absorption and regeneration tower is above6and0is0.30.The best operating conditions of ammonia system:CO2recovery rate as90%, the concentration of absorbent is10%, the temperature of lean solution is0～10℃, the pressure of absorption tower is under1.5bar, the level of absorption and regeneration tower is above6and0is0.35.The result shows the regeneration energy of the CO2capture system using ammonia as absorbent is lower than that of MEA. However, the reaction between ammonia and CO2have strict requirement for temperature, the energy consumption of condensing compressor to cool the absorbent and the flue gas will be much higher under the best operating condition. In contrast, the efficiency of the absorption reaction between MEA and CO2is better and the process using MEA is more economically feasible and easier to operate, which is more convenient for the design of the capture ready power plants.CO2capture significantly reduces the thermal efficiency of power generation. The gross efficiency of the capture-unready power plant discussed in this paper decreased by7.5%after capture retrofit. The design of capture ready power plants is to consider the space and equipment reserved for CO2capture equipment in the future retrofit of the power plants, so that once the power plant need to be retrofit with capture equipment, the efficiency of the plant will not drop that much. The research of the3options for turbine retrofit shows that compared with normal capture unready power plants, the efficiency of the3capture-ready power plant decreased by6.2%,5.7%and5.2%respectively. The efficiency of the capture ready plants depend on the pre-investment of those plants before retrofit, the better designed, the more pre-investment, then the better efficiency after capture retrofit. Besides, the pre-investment should be decided according to the actual situation. |
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