Pressure steam raising

Fig. 7.7. (a) Overall efficiency of CCGT plant with feed water heating by bled steam and single pressure steam raising (after Rufli (9)). (b) Overall efficiency of CCGT plant with feed water heating with bled steam and dual... 

However, the source of MU water for higher pressure steam-raising plants is important because it is generally the case that no matter the origin of the water, it will not be entirely suitable for the purpose and some form of water conditioning will be required. This conditioning requirement necessitates the provision of a (pre-boiler section) water pretreatment plant system (external treatment/external conditioning) to render the water fit for purpose. 

Steam jet thermocompressors or steam boosters are used to boost or raise the pressure of low pressure steam to a pressure intermediate bettveen this and the pressure of the motive high pressure steam. These are useful and economical when the steam balance allows the use of the necessary pressure levels. The reuse of exhaust steam from turbines is frequently encountered. The principle of operation is the same as for other ejectors. The position of the nozzle with respect to the diffuser is critical, and care must be used to properly posidon all gaskets, etc. The thermal efficiency is high as the only heat loss is due to radiation [5]. 

However, if the turbine back pressure is raised to above atmospheric pressure so that the turbine exhaust steam can be transported to the process heat load then the steam will give up its latent heat usefully rather than reject this to the condenser cooling water. Although the steam turbine output is reduced, the overall efficiency is increased significantly as the generated steam is used to provide both heat and electrical power. 

In almost all countries today, safety codes and regulations exist for the construction, operation, and inspection of all boilers and associated pressure vessels and boiler systems. Both HW and steam-raising plants are provided with several vital boiler appurtenances (appliances or fittings) and various subsystems containing auxiliaries (accessories) that must be maintained, monitored, and controlled. However, for small HW and LP steam boiler plants the inspection process may be rather cursory with regard to the pressure vessel internals and tends to concentrate primarily on ensuring the proper operation of the various appurtenances that provide for boiler safety. 

Most HW and LP steam boilers (i.e., those that operate below 15 psig) and many smaller high-pressure (HP) steam-raising boilers employ, at best, relatively simple methods of FW pretreatment and a basic internal chemical treatment program. Many times no pretreatment is provided. 

It is better not to use a steam inlet control valve when using low-pressure steam. The channel head pressure will then always equal the steam header supply pressure. The flow of steam to the reboiler can then be controlled only by raising or lowering the water level in the channel head, as shown in Fig. 8.5. This sort of control scheme will work perfectly well until the water level drops to the bottom of the channel head. If the condensate drain control valve then opens further, in an attempt to increase steam flow into the reboiler, the condensate seal is blown, and the reboiler heat duty drops. 

To remove excess chlorine, hydrogen chloride and isopropyl chloride, the well-stirred mixture was subjected to a pressure of 12 to 100 mm of mercury for 2 hours. The temperature was gradually raised to 20°C during this time by passing steam into the jacket of the reactor. 10 gallons of benzene was then added and distilled off under reduced pressure, gradually raising the... 

Of course, no cost effective opportunities to reduce any consumption or loss should be overlooked. Often, the best opportunities are where the larger consumptions (and losses) occur. For example, if the steam pressure were raised, the average temperature and, therefore, the average value of (1 - Tq/T) for heat addition to steam would be raised and a significant decrease in Ac,ht could be effected. (Design modifications may have to be made in the equipment utilizing the steam as "fuel," in order to... 

Description Gas feedstock is compressed (if required), desulfurized (1) and sent to the optional saturator (2) where some process steam is generated. The saturator is used where maximum water recovery is important. Further process steam is added, and the mixture is preheated and sent to the pre-reformer (3), using the Catalytic-Rich-Gas process. Steam raised in the methanol converter is added, along with available C02, and the partially reformed mixture is preheated and sent to the reformer (4). High-grade heat in the reformed gas is recovered as high-pressure steam (5), boiler feedwater preheat, and for reboil heat in the distillation system (6). The high-pressure steam is used to drive the main compressors in the plant. 

ILPM [Improved Low-Pressure Methanol] A process for making methanol from natural gas, which has two stages. The first stage converts the gas to CRG. The second stage converts this gas to methanol in a Kvaemer Steam Raising Reactor. Developed by Kvaerner Process Technology in 2000, and proposed for use in Germany from 2003. 

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