Heat generating plants

The afore mentioned production lines comprise heat-generating plants and cabinets accommodating various test instruments and controls, which provide for control of the mechanisms and devices in local and automatic blocked control modes indication and digital recording of preset and current values of monitored parameters in thenatural system of units, periodically and in response to a call automatic warning and protective interlocking. 

Within its various specialties, the TRACTEBEL Group is active in about one hundred countries. The presence of TRACTEBEL in the CIS is well known, more specifically in the Russian Federation in the engineering studies and backfitting for safety and reliability (EU-TACIS-BERD) for VVER-1000 and RMBK and a reactor simulator for the Beloyark reactor. In Ukraine, TRACTEBEL made feasibility studies for a nuclear power plant. The company developed a simulator for an RBMK reactor in Lithuania and is very active in the construction and operation of electrical power and heat generation plants in Kazakhstan. 

Fig. 6. In a binary electricity generation plant, the hydrothermal water from the weU, A, is passed through a heat exchanger, B, where its thermal energy is transferred to a second, more volatile working fluid. The second fluid is vaporized and deflvered to a turbine, D. After exiting the turbine the spent working fluid is cooled and recondensed in another heat exchanger, E, using water or air as the coolant, F. It is then fed back to the primary heat exchanger to repeat the cycle. Waste hydrothermal fluid, C, can be reinjected into the producing field.

Industrial use of cogeneration leads to small, dispersed electric-power-generation installations—an alternative to complete reliance on large central power plants. Because of the relatively snort distances over which thermal energy can be transported, process-heat generation is characteristically an on-site process, with or without cogeneration. 

PAFC systems are commercially available from the ONSI Corporation as 200-kW stationary power sources operating on natural gas. The stack cross sec tion is 1 m- (10.8 ft"). It is about 2.5 m (8.2 ft) tall and rated for a 40,000-h life. It is cooled with water/steam in a closed loop with secondary heat exchangers. The photograph of a unit is shown in Fig. 27-66. These systems are intended for on-site power and heat generation for hospitals, hotels, and small businesses. Another apphcation, however, is as dispersed 5- to 10-MW power plants in metropolitan areas. Such units would be located at elec tric utihty distribution centers, bypassing the high-voltage transmission system. The market entiy price of the system is 3000/kW. As production volumes increase, the price is projec ted to dechne to 1000 to 1500/kW. 

The considerable amount of heat generated in nitric acid plants suggests that steam be produced and used to drive the compressors. 

Modern nitric acid plants are designed for energy self-sufficiency during normal operation. Except for the startup phase, process heat generated will equal energy consumed by the compressors. Moreover, in many cases surplus energy can be exported in the form of steam, for example. 

A back-pressure (noncondensing) turbine may also be used if there is a profitable use for intermediate-pressure steam. In the unlikely event that large quantities of steam are required, additional high-pressure steam from an external source might be necessary. However, while it is theoretically possible that the amount of heat generated in the nitric acid plant will be insufficient to cover the entire demand, this is not usually a valid concern. 

The basic requirements of a reactor are 1) fissionable material in a geometry that inhibits the escape of neutrons, 2) a high likelihood that neutron capture causes fission, 3) control of the neutron production to prevent a runaway reaction, and 4) removal of the heat generated in operation and after shutdown. The inability to completely turnoff the heat evolution when the chain reaction stops is a safety problem that distinguishes a nuclear reactor from a fossil-fuel burning power plant. 

Reliability Data Book for Components in Swedish Nuclear Power Plants Power, Nuclear 30,000-t recorded events Safety and commercial grade components, i.e. pumps, valves, diesels, filters, tanks, and heat exchangers from 4 nuclear and non nuclear power generating plants 70. 

Alternatively, the option that a steam plant offers of the provision of process steam coupled with power generation may be the key element in the selection of generating plant. The turbo-generators and their auxiliaries for use in such applications tend therefore to be relatively unsophisticated, with no feed heating, except for probably the provision of a deaerator. Again, in the turbine itself, machine efficiency tends to be sacrificed for robustness and the ability to accommodate varying load conditions. 

The most recent major expln in a US TNT plant occurred in May 1974 at the Radford Army Ammunition Plant. The accident completely destroyed one of the three continuous nitration lines at the plant. According to the AMC News, Sept 1974, the investigation board reported that an operator inadvertently introduced a 5 to 6-foot rubber hose to clean out unwanted material that had collected in a transfer line leading to the nitrator, when the hose was pulled from his hands into the nitrator. This resulted in a rapid temp rise and subsequent explosion. The hose was commonly used in this manner . The material causing the blockage in the transfer line was believed to be an oxidation product of TNT, 2,2 -dicarboxy-3,3, 5,5,-tetra-nitroazoxybenzene, also referred to as White Compound. The introduction of the rubber hose caused a rapid, exothermic oxidation reaction between the hose material and the mixed acid present. The heat generated by this reaction caused a local acceleration of the normal nitration/oxidation reactions which occur in the nitrator until a critical temp was reached, at which point rapid oxidation of DNT/TNT proceeded as a runaway reaction, igniting the material present in the vessel. 

Most steam generating plants operate below the critical pressure of water, and the boiling process therefore involves two-phase, nucleate boiling within the boiler water. At its critical pressure of 3,208.2 pounds per square inch absolute (psia), however, the boiling point of water is 374.15 C (705.47 °F), the latent heat of vaporization declines to zero, and steam bubble formation stops (despite the continued application of heat), to be replaced by a smooth transition of water directly to single-phase gaseous steam. 

Very large, modem WT boilers with sophisticated heat-recovery auxiliaries may attain efficiencies approaching 88 to 90%. However, the overall efficiency of a fossil fuel utility power generation plant system falls to only 32 to 38% when the efficiency of electricity generation and condenser cooling is included. Nevertheless, it only requires 10% more in fuel costs to operate a boiler at 1,250 psig than... 

Typically, there are several different types of water or steam commonly employed in most HW heating and steam-generating plants. In a large, complex steam system there may be a dozen or more different... 

Reference 2 is a well written report that discusses power plant coal utilization in great detail. It gives a thermal efficiency of 80-83% for modem steam generation plants and 37-38% thermal efficiency for modem power generating plants at base load (about 70%). A modem base load plant designed for about 400 MW and up will run at steam pressures of 2,400 or 3,600 psi and 1,000°F with reheat to 1000°F and regenerative heating of feedwater by steam... 

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