Combined cycle systems

One advantage of modem coal gasification combined cycle systems is excellent environmental performance. Not only are regulatory standards met, but emissions and effluents are well below accepted levels (13,16,28). 

Combined-cycle systems are used in both land and marine applications employing diesel engines or gas turbines (which usually provide the first power source) and by large process industries that produce significant heat-containing, by-product waste streams. 

Computer simulations have demonstrated that a combined cycle system with MCFC stacks networked in series is significantly more efficient than an identical system with MCFC stacks configured in parallel. 

IPCC International Panel on Climate Change ISCCS Integrated solar combined cycle system... 

Electric Power Research Institute Final Report AF-642 "Economic Studies of Coal Gasification Combined Cycle Systems for Electric Power Generation" EPRI, Palo Alto, California,... 

ENERGETIC EVALUATION OF A CASST/COMBINED CYCLE SYSTEM... 

At a carbon conversion of 80% in the gasification step, the performance of a CASST/CC system is lower than for air-blown gasification/combined cycle system (39.0 vs. 41.7%). The lower gross power output of the CASST/CC system is only partly compensated by a lower internal power use. Inaeasing the carbon conversion to 95% almost eliminates the difference in the performance of twth systems. 

The capital cost of STPs is one quarter to a half of that of PV power plant (Table 1). The LEC is defined by the total cost, [(capital cost)x(fixed charge rate) + O M + fuel cost], per annual net electricity production in kWh. It varies depending on the plant scale and solar share. The LEC ranges between 0.05kWh and 0.12/kWh for the STP, and attains 0.4/kWh- l/kWh for PV electricity. Thus, the solar H2 production cost by PV and STP electricity is not comparable in terms of capital cost and LEC. However, the cost of STP electricity is still not competitive with that of a conventional coal-fired power plant. To close the price gap, the solar thermal parabohc trough power plant industry has introduced integrated solar combined cycle systems (ISCCS) which are able to offer a competitive base-load electricity cost of 0.05-0.07/kWh at solar shares of 15-25% [7] (Fig.l). 

Figure 14.5. Biomass integrated gasification and combined cycle system.

Sulhvan TB, System and method for generation of high pressure air in an integrated gasiiication combined cycle system. U.S. Patent Appl., US 2008115478. Al 2008 05/22Publ2008. 

Combined cycle systems incorporate all components of the simple cycle configuration with the addition of... 

In a conventional combustion process, such as a power station boiler, the carbon dioxide is contained in the exit flue gas. The concentration is generally fairly low and ranges from about 4 vol.% for a combined-cycle system operating on natural gas to 12-14 vol.% for a traditional boiler fired by pulverized coal. The exhaust can be scrubbed with an amine solution, typically monoethanolamine, which is then heated to release the absorbed carbon dioxide. The low concentration of carbon dioxide in the exit gas means that a huge volume would have to be handled and this would entail the installation... 

This combination of gas and steam turbines accounts for the name combined cycle. Gasification combined-cycle systems are among the cleanest and most efficient of the emerging clean coal technologies. Sulfur species, nitrogen species, and particulate matter are removed before the fuel is burned in the gas turbine. Thus, there is a much lower volume of gas to be treated than in a postcombustion scrubber. 

While the overall combined cycle is more efficient than conventional pulverized coal plants, energy losses do occur in the transformation of coal into a gaseous fuel, mostly due to the heat input needed for gasification. As a result of the added gasification process needed for combined-cycle systems using coal, the IGCC process is less efficient than the same combined power generation cycle run on a fuel that does not require pretreatment such as natural gas or fuel oils. 

Combined cycle systems for near-zero emission power generation... 

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