Condensers makeup water

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. 

Makeup. Makeup water is the water suppHed to replenish the steam system for any losses. In most systems it is introduced into the condenser or the feed pump suction. In steam systems where the makeup is a small fraction of the total feedwater, its purity may be somewhat lower than the feedwater requirement because it is diluted by condensate. In systems where there is Httie condensate return, such as heating steam suppHes, the makeup purity must be essentially the same as the feedwater. 

High Pressure Boiler Water Treatment. High pressure boilers usually have feed water composed of demineralized makeup water and a high percentage of condensate returns. Because of these conditions, high pressure boilers are prone to caustic and acid attack. Low pressure boilers that use dernineralized water and condensate as feed water are also susceptible to caustic and acid attack. 

Knox has provided the following graphs for estimating the required vent steam from boiler feedwater deaerators. Vent steam rate depends upon the type of deaerator (spray or tray type) and the percentage of makeup water (in contrast to returning condensate). Low makeup water rates require relatively lower steam vent rates, but there is a minimum rate required to remove CO2 from the returning condensate. 

Answer Figure 15.5.2-2 shows an automatic depressurization valve that opens on excessive conditions to release the steam which passes through a turbine to drive an electric generator to provide makeup water and operate other cooling equipment. After the steam has cooled in the low pressure turbine it discharges under water in the cooling reservoir and condensed. The reservoir cools by evaporation. 

AVMT = Average mix temperature CR = Condensate return MU = Makeup water... 

Example 23.1 A small package fire-tube boiler has makeup water that contains 500 ppm dissolved solids. The steam system operates with 50% condensate return. Estimate the blowdown rate. Assume that the maximum limit for the TDS is 4500 ppm. Assume that there are no solids in the evaporation or the condensate return. 

Increasing condensate return for steam systems to reduce makeup water requirements, reduce aqueous waste from boiler feedwater treatment and boiler blowdown (see Chapter 23). 

Copper alloys are used extensively in power plant condensers, and as a result, copper can usually go into a corrosion product film or directly into solution as an ion or as a precipitate in the initial stages of condensation by tube corrosion. As corrosion products form and increase in thickness, the corrosion rate decreases until a steady state is achieved. Studies indicate that copper release is a function of flow rate more so than of the salt content of the makeup water. 

According to the vendor, the major benefits of TPVE are (1) that the rate of liquid extraction can be greatly increased over that of conventional pumping, (2) the technology lowers the water table, exposing contaminants that were previously trapped below the water table, (3) the reduced need (and expense) of additional makeup water, and (4) achieving vapor condensation... 

The simplest way to lower the compressor discharge pressure is to reduce the cooling-water temperature to the condenser. One neat trick I have used is to use the cooling-tower makeup water on a once-through basis, to the refrigerant condensers. This supply of water is almost always 10 to 20°F cooler than the cooling-water supply. 

In most cases, condensate does not require treatment prior to reuse. Makeup water is added directly to the condensate to form boiler feedwater. In some cases, however, especially where steam is used in industrial processes, the steam condensate is contaminated by corrosion products or by the inleakage of cooling water or substances used in the process. Hence steps must be taken to reduce corrosion or to remove the undesirable substances before the condensate is recycled to the boiler as feedwater. 

Capital Cost Costs of basic system, condenser, circulating water piping, makeup pumps and blowdown facilities, and intake and discharge systems. Cooling Capacity System sizing, air-to-water surface contact, dry- and wet-bulb temperatures for relative humidity, wind speed and direction, range and approach. 

The paper notes that the most economical solution for any design is a combination of conventional wet cooling towers with direct air cooled condensers. Various limitations at particular sites, such as ambient air conditions which require that wet cooling tower plumes be avoided, makeup water quantity available, and maximum turbine backpressure acceptable only dictate the individual design data for the wet and dry sections. The author describes simple methods to determine the design of both individual sections. To meet makeup water and/or backpressure requirements the wet and the dry section must not necessarily be combined into one unit. However, one combined cooling system is required to avoid wet cooling tower plumes. 

The extremely small volume of water in an evaporative condenser, and the relatively high ratio of evaporation and makeup water, means that the potential rate of change of water chemistry and cycles of concentration can be exceedingly high. 

A nuclear power plant produces 1000 MW of electricity with a power cycle thermodynamic efficiency of 30%. The heat rejected is removed by cooling water that enters the condenser at 293 K and is heated to 313 K. The hot water flows to two identical natural-draft cooling towers, where it is recooled to 293 K, and makeup water is added as necessary. The available air is at 298 K with a wet-bulb temperature of 285 K, and it will flow at a rate 1.2 times the minimum. Specialized packing will be used for which Kya is expected to be 1.0 kg/m3-s if the liquid mass velocity is at least 3.4 kg/m2-s and the gas mass velocity is at least 2.75 kg/m2-s. Compute the dimensions of the packed sections of the cooling towers and the makeup water requirement due to evaporation. 

BOILER FEED WATER - The total water fed to a boiler producing steam. This water is the mixture of return steam condensate and makeup water. 

MAKEUP WATER - Water fed to a system to replace that which is lost -for example, water fed to a boiler to replace that lost as steam or condensate water fed to a cooling tower to repiace that lost by evaporation, drift, or other causes. 

The deacidifier bottom product, which still contains a small quantity of sour gases, is fed to the top of the total stripper to expel all the gaseous components which are still in the condensate. The condensate leaving the total stripp bottom is cooled and can then be discharged to a biological treatment unit. It contains less than SO ppm of NH3 and less than 1 ppm of H2S. Its BOD is less than 20 ppm. Low-salt condensates as they are normally obtained from coal gasification may be used as makeup water for cooling water systems. 

Sulfuric acid plants need water that has three qualities demineralized water for boiler feed, process makeup water to absorb SO3, and cooling water. The water treatment installations do not produce harmful wastes. Recycled process condensate or demineralized water is-used-for the absorption tower. The cooling water amount and quality depend on the type of heat exchangers used and water available. 

The air from the prilling tower or granulator is scrubbed on a packed bed with aqueous urea solution (approximately 20% urea concentration). Any mist in the exit air is caught by a demister. Process condensate is used as makeup water for the scrubber. 

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