Steam-generating equipment, types

Boiler Deposits. Deposition is a principal problem in the operation of steam generating equipment. The accumulation of material on boiler surfaces can cause overheating and/or corrosion. Both of these conditions frequentiy result in unscheduled downtime. Common feed-water contaminants that can form boiler deposits include calcium, magnesium, iron, copper, aluminum, siUca, and (to a lesser extent) silt and oil. Most deposits can be classified as one of two types scale that crystallized directiy onto tube surfaces or sludge deposits that precipitated elsewhere and were transported to the metal surface by the flowing water. 

Steam-generating equipment is similar to a gas-fired furnace in that fuel gas is most always the heating source of the steam generator. The furnace is generally an A-type tube-shaped frame inside a rectangular box in which the steam is on the tube side. 

Steam-Generating Facilities These form the second largest investment item for chemical-plant auxiliaiy equipment. Variations in capacity, location indoors or outdoors, the type of fuel used, pressure and temperature levels, and the type of process served have an important effect on actual cost as well as on cost relative to other auxiliaiy items. Package boiler instaUations can be purchased as shop-built units which are assembled, piped, and wired ready to be erected on the owner s foundations. They are available in units up to about 136,000 kg/h (300,000 Ib/h), although units larger than about 45,360... 

Therefore, to minimize the certainty of waterside carbonate deposition, essentially all types of steam generating boilers should be provided with a water softener or some other equally effective form of pretreatment equipment. 

The synthesis loop boiler on the exit of the converter is also a very important piece of equipment. In some modern plants not equipped with an auxiliary boiler it supplies nearly half of the total steam generation. It may generate as much as 1.5 t of steam per tonne of ammonia, equivalent to about 90% of the reaction heat. Fire-tube versions have been also used, including Babcock-Borsig s thin-tubesheet design. But compared to the secondary reformer service, where the gas pressure is lower than the steam pressure, the conditions and stress patterns are different. In the synthesis loop boiler the opposite is the case, with the result that the tubes are subjected to longitudinal compression instead of being under tension. Several failures in this application have been reported [993], and there was some discussion of whether this type of boiler is the best solution for the synthesis loop waste-heat duty. 

Stage 1 Study was carried out to determine the effectiveness of reservoir steaming in general. Both stationary industrial boilers and transportable boilers (PPU-3M type) were used for steam generation. Requirements of ancilliary surface and downhole equipment for steam injection were also studied. 

For thermal EOR work one needs special monoblock steam-generating installations consisting of an entire complex of basic, auxiliary and electrotechnical elements integrated by means of piping, control and automation systems, and equipped with necessary armature. The entire system must be so designed that it can be readily assembled on the site, and then simply connected to an outside network. Installations of this type are now (1980) being tested in the oil fields. 

The steam-generating facilities consist of three package-type steam-generator units with fire-tube boilers and their associated equipment. Each unit has a maximum capacity of 16,500 Ib/hr at a design pressure of 150 psig. Two of the units are adequate to supply the maximum process and heating steam requirements, while the third unit serves as a stand-by. The units are oil-fired but can readily be converted to be oil-gas-fired at any time. The operation of the units is fully automatic. 

NGCC lay-out is based on two GTs, each equipped with a heat recovery steam generator (HRSG) and a single steam turbine. This type of arrangement (2 + 1) is quite popular among utilities, adding operational flexibility as required by a competitive electricity market. 

The fest flux test facility (FFTF) was a 400 MW(th) sodium cooled last reactor specifically designed for development and testing of fast breeder reactor fuels, materials, and components. The reactor was a loop-type plant with three parallel heat transport system loops. The plant has neither steam generators nor blanket assemblies for fissile breeding, consistent with its role as a test reactor. The FFTF was equipped with a great deal of instmmentation. Each core assembly was provided with instruments for measurement of sodium flow rates and sodium outlet temperature. Three instrument trees, one of which serves each of the three core sectors, provide outlet instrumentation for all fiiel assemblies, control and safety assemblies, and selected reflector assemblies. In addition, 8 of the 73 core positions were equipped for full in-core instrumentation. Two of these eight positions were available for closed-loop facilities. 

Apart from the prototype FBR MONJU, much research and development (R D) has already been performed to complete the design of the Demonstration FBR, sponsored by nine Japanese utilities, Electric Power Development Co., Ltd., and the Japan Atomic Power Company (JAPC). The R D included the development of new types of equipment for sodium cooled reactors such as highly reliable electromagnetic pumps and double-walled tube steam generators with leak detection systems for both sodium and water/steam. This new equipment is considered to become more important for the commercialization of sodium cooled reactors, and the 4S is adopting these technologies in its design. 

Some expensive primary circuit equipment items (main circulation pumps, steam generators, remote separators, etc.) are eliminated through use of the vessel-type boiling reactor with an integral arrangement of the primary circuit inside the vessel and natural circulation of the coolant ... 

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