Gas turbine heat recovery steam generator

ASME, Performance Test Code on Gas Turbine Heat Recovery Steam Generators, ASME PTC 4.4 1981, American Society of Mechanical Engineers Reaffirmed 1992. 

PTC 4.4-198KR1992) Gas Turbine Heat Recovery Steam Generators... 

Jack H. Karian(212) 591-8552 PTC 4.2 Coal Pulverizers Jack H. Karian(212) 591-8552 PTC 4.3 Air Heaters Jack H. Karian(212) 591-8552 PTC 4.4 Gas Turbine Heat Recovery Steam Generators... 

Fig. 6.1a shows diagrammatically the steam injection gas turbine (STIG) plant steam. raised in a heat recovery steam generator (HRSG) downstream of the turbine, is injected into the combustion chamber or into the turbine nozzle guide vanes. 

The basic idea of using TCR in a gas turbine is usually to extract more heat from the turbine exhaust gases rather than to reduce substantially the irreversibility of combustion through chemical recuperation of the fuel. One method of TCR involves an overall reaction between the fuel, say methane (CH4), and water vapour, usually produced in a heat recovery steam generator. The heat absorbed in the total process effectively increases... 

A gas turbine CHP scheme, with a heat recovery steam generator producing process steam, operates at the DOMO plant at Beilen in the Netherlands. The plant, which produces dairy products, originally took its electric power (up to 3.2 MW) from the grid and its heat load was met by two gas-fired boilers with a steam production of 25 t/h at 13 bar. 

Figure 23.14 Gas turbine with heat recovery steam generator (HRSG).

Example 25.5 A gas turbine exhaust is currently operating with a flowrate of 41.6 kg s-1 and a temperature of 180°C after a heat recovery steam generator. The exhaust contains 200 ppmv NOx to be reduced to 60 rng rn 3 (expressed as N02) at 0°C and 1 atm. The NOx is to be treated in the exhaust using low temperature selective catalytic reduction. Ammonia slippage must be restricted to be less than 10 mgm 3, but a design basis of 5 mg-rn 3 will be taken. Aqueous ammonia is to be used at a cost of 300 -1 1 (dry NH3 basis). Estimate the cost of ammonia if the plant operates... 

Combined Brayton-Rankine Cycle The combined Brayton-Rankine cycle. Figure 9-14, again shows the gas turbine compressor for the air flow to the cell. This flow passes through a heat exchanger in direct contact with the cell it removes the heat produced in cell operation and maintains cell operation at constant temperature. The air and fuel streams then pass into the cathode and anode compartments of the fuel cell. The separate streams leaving the cell enter the combustor and then the gas turbine. The turbine exhaust flows to the heat recovery steam generator and then to the stack. The steam produced drives the steam turbine. It is then condensed and pumped back to the steam generator. 

Figure 8.9 shows the turbine exhaust gas temperatures for the cathode recycle and recuperated cases. The cathode recycle has a comparatively higher quality of heat. Systems with temperatures above 800 K are a good candidate for heat recovery steam generation. Thus, up to a PR of about 20 there is some potential for the addition of a steam cycle to the cathode recycle analysis, which would increase both system power and efficiency. 

In order to decrease the nitrogen oxide (NO ) content in the flue gas, two methods can be applied. The first method is the injection of water into the gas turbine combustor. The second method is to selectively reduce the nitrogen oxide content by injecting ammonia gas in the presence of de-NOx catalyst that is packed in a proper position of the heat recovery steam generator. The latter is more effective than the former to lower nitrogen oxide emissions into the air. 

Combined Cycle An electric generating technology in which electricity is produced from otherwise lost waste heat exiting from one or more gas (combustion) turbines. The exiting heat is routed to a conventional boiler or to a heat recovery steam generator for utilization by a steam turbine in the production of electricity. Such designs increase the efficiency of the electric generating unit. 

The Combined (Brayton-Rankine) Cycle The 1990s has seen the rebirth of the combined cycle, the combination of gas turbine technologies with the steam turbine. This has been a major shift for the utility industry, which was heavily steam-turbine-oriented with the use of the gas turbine for peaking power. In this combined cycle, the hot gases from the turbine exhaust are used in a heat recovery steam generator or in some cases in a supplementary fired boiler to produce superheated steam. 

Heat to the steam system is provided by the flue gas from the gas turbine to the heat recovery steam generator (HRSG) and by the cooling of the fuel gas. The flue gas from the HRSG can be used to dry the fuel in an integrated dryer. 

The biomass fuelled IGCC demonstration plant at Vamamo consists of a 18 MW pressurised circulating fluidised bed gasifier, a 4,2 MW gas turbine and a 1,8 MW steam turbine. The low heat value gas produced in the gasifier is cooled in a gas cooler and cleaned in a candle filter at a temperature of 350-400°C before it is combusted in the gas turbine. The flue gas from the gas turbine is used for the production of steam in the heat recovery steam generator. The steam is superheated, together with steam from the gas cooler, and supplied to the steam turbine. Besides electricity, 9 MW heat for district heating purposes is produced. 

The hot flue gas from the gas turbine is ducted to the heat recovery steam generator (HRSG), where the steam generated, along with steam from the gas cooler, is super-heated and is then supplied to a steam turbine (40 bar, 455 C), generating 1.8 MWc. 

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