Closed loop cooling water systems

Polyethylene plants are small process water consumers. Process water consumption is restricted to water for steam production (high pressure polyethylene plants), cooling water towers and pellet cooling water systems. To reduce the consumption of water, plants are equipped with closed loop cooling tower systems. 

However, some plants located at the coast or a river delta, also use seawater or river water in a one-pass operation. 

Driving force for implementation Economic and environmental reasons. 

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NOTE Many closed-loop cooling water systems are not, in fact, closed, as they contain open-top, return-water tanks. This provides a continuous source of oxygen from the air into the system, with the result that the risk of corrosion greatly increases. Adequate attention should be paid to countering this risk, perhaps by an improved corrosion-inhibitor treatment or a floating blanket or plastic balls in the water tank (which help to minimize the ingress of air). 

Any possible radioactive leakage from the foregoing reactor equipment would be to, and would be confined in, the closed loop cooling water system, which is monitored continuously for radioactivity. A surge tank is used to accommodate system volume swell and shrinkage and to provide a means for adding makeup water and inhibitors. 

Reactor coolant primary circulation system Depending on design, this closed-loop cooling system may recirculate high-purity treated water or other fluid at 300,000 to 450,000 US gpm (1,136-1,704 m3/m), and at velocities of 15 to 16 ft/s 4.5 to 4.9 m/s. 

Water is one of the most widely used raw materials in the manufacture of aqueous paint formulations. But as well as being used in production it can have a number of other uses, e.g. cooling and cleaning. Because of the cost of "new" water and disposal of contaminated water most manufactures have introduced closed loop or recycling systems. 

Chemical that, in water, resists changes in pH, such as sodium borate in Nitrite/Borate Programs for closed-loop cooling systems. 

Three steps eliminate these odor problems. The first is a distillate recovery system that recovers most of the fatty acid as a byproduct and many of the associated odors in the deodorizer vapor discharge. The second is a closed-loop cooling system that keeps the fat-laden hot well water out of the cooling tower. The third is a vapor scrubbing or oxidation system to eliminate volatile organic compounds that are not removed in the previous two steps. 

The closed cooling water system consists of a separate, forced circulation loop. This system uses water piped from the site service water source to provide a heat sink for selected nuclear system equipment. Its purpose is to provide a second barrier between the primary systems containing radioactive products and the service water system that is the final heat... 

The component cooling water system is a closed loop cooling system that transfers heat from various plant components to the service water system during normal phases of operation. It removes heat from various components needed for plant operation and removes core decay heat and sensible heat for normal reactor shutdown and cooldown. 

CAS 111-30-8 8001-54-5 EINECS/ELINCS 203-856-5 204479-9 Uses Microbicide, slimicide, bactericide, algicide, surfactant for water treatment, recirculating cooling towers, air washer systems, recirculating process water, closed loop cooling systems, reverse osmosis, to clean and penetrate microbiologically fouled suifs. 

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. 

Nitrite formulations are employed for both hot and cold water closed loops (and also occasionally for open cooling systems). Unfortunately, nitrite is easily oxidized to nitrate and is very susceptible to microbiological attack (by Nitrobacter agilis and other microorganisms). Nevertheless, it is a good low-cost passivating inhibitor. 

NOTE Strongly alkaline, closed loop LPHW system formulations, such as nitrite/borates, typically include an azole product at about 4 to 5% (50% solution). Lower alkalinity products (often the molybdates) have significantly less, perhaps only 0.5%. For comparison, open cooling water and chilled water system formulations typically contain about 2 to 3 % (50% solution) azole. 

Most disturbances in chemical engineering systems are load disturbances, such as changes in throughput, feed composition, supply steam pressure, cooling water temperature, etc. The feedback controller s Auction when a load disturbance occurs is to return the controlled variable to its set-point by suitable changes in the manipulated variable. The dosedloop response to a load disturbance is called the regulator response or the closed-loop load response. 

The most appropriate system for the plotform wos considered to be on indirect seawater cooling system which uses seawater to cool recirculating inhibited fresh woter in o closed loop system. The fresh water is circulated on the shell side of the process exchangers to minimise corrosion problems ond eliminate the need to use exotic materials which would be... 

Widespread practice has always existed, unfortunately, by owners and operators of cooling systems, or their general contractors and consultants, to specify chemical treatment operating standards in isolation, with little or no actual contact with prospective vendors of water treatment service companies before the issuance of such standards. There is now a growing tendency for particularly low corrosion rates to be specified as a part measure of the quality of water treatment and technical services to be provided in water management contracts (say below 1 mpy for steel in closed-loop systems and below 2 mpy for steel in open-recirculating systems). These low rates are often unattainable in practice. 

Polysilicates, incorporated in various formulations that may include P-P04 or molybdate and phosphonates/TTA/polymer, have found application for smaller, light duty, open cooling systems and closed-loop circuits, especially where naturally soft or ion-exchange-softened makeup waters have been used. The reported effectiveness of such programs has been mixed. 

Nevertheless, there are still some cooling systems (especially closed-loop systems) that do not receive any form of chemical inhibitor dosing or other treatment. This situation typically persists because the operator either remains uneducated or skeptical concerning the benefits and cost-effectiveness of water treatment or relies on low-cost labor to provide regular manual cleaning. 

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