DEMINERALIZED WATER MAKEUP

The recycle of water from the distillation system also has the effect of reducing the demineralized water makeup requirement. 

Service Water Startup and Shutdown Non Class lE Uninterruptible Power Non Class lE DC Power Instrument and Service Air Demineralized Water Makeup Interfacing systems or subsystems which are currently described in detail for 10.14 10.15 8.6 8.7 9.2.8 . 10.9 PSID review. 1... 

A petrochemical facility with one cooling system containing two towers, each installed at the same time, but with some differences in construction materials. Makeup water was 45% demineralized water and 55% raw water. 

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 demineralized water and condensate as feed water are also susceptible to caustic and acid attack... 

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. 

Fill system with demineralized water at pH 4—7, and circulate at 90°C for at least 36 hr. Purge water from system and replace with makeup. Check washing sample for smell of styrene, drain batch if present, and repeat procedure. Drain system completely. 

Water chemistry control of the CCWS is accomplished by chemical additions to the chemical addition tank. A safety grade makeup source is provided by the demineralized water system or reactor makeup system (emergency makeup only) and delivered to the surge tank. 

The 163-N facility (Figure 3-17) produced high-quality, demineralized makeup water from filtered river water for the major coolant systems of the N Reactor. Demineralized water has virtually all dissolved and suspended matter removed by ion exchange. Demineralized water was used to prevent mineral deposits that would foul piping systems and to limit the generation of radioactive waste through neutron activation of dissolved and suspended matter (DOE-RL 1990). 

This subsection should provide relevant information on the water systems associated with the plant as described in paras 3.65-3.70. It should include, for example, the station service water system, the cooling system for reactor auxiliaries, the makeup system for demineralized water, the ultimate heat sink and the condensate storage facilities. 

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. 

The quahty of feed water required depends on boiler operating pressure, design, heat transfer rates, and steam use. Most boiler systems have sodium zeohte softened or demineralized makeup water. Feed-water hardness usually ranges from 0.01 to 2.0 ppm, but even water of this purity does not provide deposit-free operation. Therefore, good internal boiler water treatment programs are necessary. 

Demineralization and Evaporation. At drum pressures over 1000 psi (68 atm), demineralization or evaporation of the makeup water is generally desirable. A water that closely approaches theoretical chemical purity can be obtained by either of these processes. 

Boiler feed-water systems that use demineralized or evaporated makeup or pure condensate may be protected from caustic attack through coordinated phosphate and pH control. Phosphate buffers the boiler water, reducing the chance of large pH changes due to the development of high caustic or acid concentrations. Excess caustic combines with disodium phosphate and forms trisodium phosphate. Sufficient disodium phosphate must be available to combine with all of the free caustic in order to form trisodium phosphate. 

Use of RO for desalination of seawater for boiler makeup is a typical aj lkation. The availability of diis system has opened up die use of heretofore unavailable water siqiplies, and it has been used by the industry as a pretreatment to ion exchange demineralization. RO acts as an economical rou iing demineralizer, bringing down the overall cost and improving the life of resins and operation of the ion exchange equipment. 

Carbon dioxide is often ignored in steam systems. However, when absorbed in water, it forms carbonic acid, which can be corrosive to all parts of the steam and condensate system. Its potential presence is frequently overlooked in the design of heat exchangers, steam traps, condensate systems, deaerators, and water-treating systems. Most steam systems require continual addition of makeup water to replace losses. Makeup water must be adequately treated, by demineralization or distillation, to remove carbonates and bicarbonates. If these are not removed, they can be thermally decomposed to carbon dioxide gas and carbonate and hydroxide ions. The ions will normally remain in the boiler water, but the caron dioxide will pass off with the steam as a gas. When the steam is condensed, the carbon dioxide will accumulate since is is noncondensable) be passed as a gas by the steam trap or if the condensate and carbon dioxide are not freely passed by the steam trap, become dissolved in the condensate and form carbonic acid. If carbonic acid is formed it can have a pH approaching 4 and be very corrosive to copper and steel. Even if both the gas and condensate are passed freely by the steam trap, the gas will become soluble in the condensate when subcooling occurs. If oxygen is present, the corrosion rate Is accelerated. 

A blend of demineralized and deaerated water and concentrated boric acid to match the reactor coolant boron concentration for normal plant makeup... 

The TDS content of BFW should be minimized by upstream treating. In former days, hot lime water softening was employed. In most modern process units, ion exchange resin is used to demineralize BFW. "Blowdown" is the water that is drained out of the boiler to control the accumulations of TDS or silicates in the boiler. My old design value for this flow was 10 percent of the makeup BFW flow. Two types of blowdown from a boiler are used continuous blowdown from the steam drum, and intermittent blowdown from the mud drum both will reduce silica. Note that with the continuous blowdown, heat recovery equipment may be economically justified. 

Prevent leakage of regenerator chemicals from the makeup water demineralizer. 

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