Central station

For central station power generation the open cycle system using electrically conducting coal combustion products as the working fluid is employed. The fuel typically is pulverized coal burned directly in the MHD combustor, although in some plant designs cleaner fuels made from coal by gasification or by beneficiation have been considered (8—10) (see Fuels, synthetic). 

Demineralizers are often used to treat raw makeup water or condensate where high purity is required, such as in large central station boHers that operate at high steam pressures. Demineralizers employ a combination of cation and anion exchange to remove additional material, including sodium and ammonium cations. VirtuaHy aH salt anions, such as bicarbonate, sulfate, and chloride, are removed and replaced by hydroxide ions in the demineralizer. 

Figure 11-69 describes a typical central system. Either water or direct-expansion refrigerant coils or air washers may be used for cooling. Steam or hot-water coils are available for heating. Humidification may be provided by target-type water nozzles, pan humidifiers, air washers, or sprayed coils. Air cleaning is usually provided by cleanable or throwaway filters. Central-station air-conditioning units in capacities up to about 50,000 cu ft/min are available in prefabricated units. 

FIG. 17-69 Design curves for electrostatic precipitators for fly ash. Collection efficiency for various levels of percent sulfur in coal versus a) specific collecting surface, and (h) bus sections per 100,000 ftVmin (4.7 mVs). °C = (°F — 32) X (Ramsdell, Design Criteria for Precipitators for Modern Central Station Power Plants, Amen c m Power Conference, Chicago, III., 1968. )... 

Modern central stations use the other burner-furnace configurations shown in Fig. 27-16, in which the coal and air are mixed rapidly in and close to the burner. The primary air, used to transport the pulverized coal to the burner, comprises 10 to 20 percent of the total combustion air. The secondary air comprises the remainder of the total air and mixes in or near the burner with the primary air and coal. The velocity of the mixture leaving the burner must be high enough to prevent flashback in the primaiy air-coal piping. In practice, this velocity is maintained at about 31 m/s (100 ft/s). 

Figure 27-43 shows the amount of energy available for power by using a fire-tube boiler, an industrial bofler, and subcridcal- and supercritical-pressure boilers. Condensing losses decrease substantially, and regeneration of air and feedwater becomes increasingly important in the most advanced central-station boilers. 

Water need not be stored within the unit this is often the case where the equipment used for humidification forms part of a central station plant or where a suitable source of steam is available. 

Central station A central ventilation or air-conditioning unit that provides treated air to various zones within a building. 

Zentrale,/. central ofifice, center central station median (line) line joining centers. Zentral-gruppe, /. central group, -heizung, /. 

The first central station steam turbine in the United States was built for the I lartford Electric Light Co. in... 

October. The pioneering firm of United States Electric Illuminating Company starts up South Carolina s first central station for incandescent electric lighting one month after Thomas Edison opened his central station on New York City s Pearl Street. In the following years, U.S. Electric becomes one of Edison s main competitors. 

Fans are classified according to the discharge pressure. Reprinted per written permission from the Air Movement and Control Association International, Inc., the AMCA Standard 99-1401-66 from Standards Handbook 99-56 1986, the total static pressure classification for operating limits for central station units is as follows ... 

Intruder alarms are designed to give a warning of the presence of an intruder within or attempting to enter the protected area. Alarm systems may act as a deterrent to the casual or opportunist thief but they will do little or nothing to prevent a determined intrusion, and to be effective they must provoke an early response from the appropriate authority (in most cases the police). The warning may be a local audible device, but normally the alarm signal is transmitted by the telephone network to a central station operated by a security company on a 24-hour basis. 

Since about 0.1 m /s of air flow is required for each kilowatt of cooling, the mass air flow for a large central station system will be... 

The chilled air of the central station system serves the purpose of providing the proportion of fresh air needed, and carrying heat energy away from the space. These functions can be separated, using a more convenient fluid for the latter. Since the heat is at a temperature well above 0°C the obvious choice of fluid is water, although brines are used for some applications. 

Noise of central station machinery transmitted hy air, huilding conduction, and duct-horne... 

A 376 Seamless Austenitic Steel Pipe for High-Temperature Central-Station Service... 

From the perspective of greenhouse gases, electrolysis is unsettled for the foreseeable future since both electrolysis and central-station power generation are relatively inefficient processes and most U.S. electricity is generated by the burning of fossil fuels. Nuclear and renewables make up only about 1 / 3 of total generation. 

In contrast to systems that are set up to transmit local only alarms when the sensors are triggered, systems can also be set up to transmit signals to a central location, such as to a control room or guard post at the utility, or to a police or fire station. Most fire/smoke alarms are set up to signal both at the location of the event and at a fire station or central monitoring station. Many insurance companies require that facilities install certified systems that include alarm communication to a central station. For example, systems certified by the Underwriters Laboratory (UL) require that the alarm be reported to a central monitoring station. 

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