Steam generating systems waste heat boilers

While this basic definition of cogeneration efficiency seems straightforward, complications are created by the process steam generated from waste heat recovery that can be used for power generation or process heating and that does not require any fuel to be fired in the utility system. The heat supply can be defined as the sum of the heat from fuel (both in the utility boilers and fired heaters) and steam generation from the waste heat recovery (see Figure 23.44)17 ... 

The yield loss in this process, depending on the alkylation system design and control, is between 0.6 and 0.9 lb flux oil per 100 lb ethylbenzene. Steam is generated by waste-heat boilers. These together with the alkylation reactor waste-heat boiler account for 90 percent of the energy required for the entire ethylbenzene unit. 

Option 1 is a conventional stoker incineration system with heat recovery. Electric power will be generated with the steam from the waste heat boiler. To meet the air pollution standards, exhaust gas has to be cleaned by an electrostatic precipitator and... 

Process Steam Generation. Steam generated in the process sections of the plant may be at the highest plant pressure level or an intermediate level. Also, the process area may have fired boilers, waste heat boilers, or both. There may be crossties between utility and process generated steam levels. Enough controls must be provided to balance far-ranging steam systems and protect the most critical units in the event of boiler feedwater shortage situations. 

Vessels, e g., waste heat boilers, in which steam is generated incidental to the operation of a processing system containing a number of pressure vessels, such as are used in chemical and petroleum products manufacture. (Equipment which may fire a supplemental fuel should be considered as a fired pressure vessel.)... 

The utility system has as typical units steam and gas turbines, electric motors, electric generators, fired or waste heat boilers, steam headers at different pressures and auxiliary units (e.g., vacuum condenser, water treater, deaerator), and provides the required electricity, power, and utilities. 

Significant energy conservation is achieved by the well-established method of combined heat and power generation (cogeneration). The heat is usually in the form of intermediate or low-pressure steam, and the power as direct mechanical drives or as electricity generated with turbo-altemators. The choice of systems is usually between back-pressure steam turbines, or gas turbines with waste-heat boilers for the process steam. The amount of power generated is usually determined by the demand for heat. 

Shell-side effluent from the reforming exchanger is cooled in a waste-heat boiler, where HP steam is generated, and then flows to the CO shift converters containing two catalyst types one (4) is a high-temperature catalyst and the other (5) is a low-temperature catalyst. Shift reactor effluent is cooled, condensed water separated (6) and then routed to the gas purification section. C02 is removed from synthesis gas using a wet-C02 scrubbing system such as hot potassium carbonate or MDEA (methyl diethanolamine) (7). 

The exhaust heat from the combustion turbine is recovered in the heat recovery steam generator to produce steam. The waste heat is passed to a steam turbine system, while heat is recovered from both the gasification process and the gas turbine exhaust in advanced boilers producing steam. The steam is then used in steam turbines to produce additional electrical power, while the syngas mixture could also feed a fuel cell plant (IGFC). 

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