Parallel air coolers

Air-cooled reactor effluent coolers of hydrocracking and hydrotreating units are also prone to impingement-type corrosion. Poor flow distribution through large banks of parallel air coolers can result in excessive flow velocities in some coolers, usually those in the center. The resulting low flow velocities in the outer coolers can canse deposition of ammonium sulfide and/or chloride in these coolers this blocks the tubes and further increases velocities in the remaining air coolers. 

Anodic protection today allows safe and efficient protection of air coolers and banks of tubes in sulfuric acid plants. In 1966 the air cooler in a sulfuric acid plant in Germany was anodically protected. Since then more than 10,000 m of cooling surfaces in air- and water-cooled sulfuric acid plants worldwide have been protected. The dc output supply of the potentiostats amounts to >25 kW, corresponding to an energy requirement of 2.5 W per m of protected surface. As an example. Fig. 21-9 shows two parallel-connected sulfuric acid smooth tube exchangers in a production plant in Spain. 

A large process plant air cooler may have 10, 20, 30, or more banks of air coolers, arranged in parallel. Figure 14.6 shows such an arrange-... 

Individual flows to parallel banks of air coolers are rarely—if ever-measured. Regardless, we can gauge the approximate relative flow to each bundle. This can be done by checking the outlet temperature of the bundles or banks. 

The best way to handle the nonsymmetrical flow problem described above is to make the pressure drops in both the inlet and outlet tube bundle headers very small, as compared to the bundle pressure drop itself. Many of my clients add additional tube bundles in parallel with existing air coolers. This helps at first, but they find that the long-term benefits are quite disappointing, because of high pressure drop in the new header lines. 

Optimize compressor operation, reduce friction and air leakages in air distribution system, low pressure drop air coolers and instruments, reduction of air leaks, use of heat of compression dryers, cool compressor suction air, waste heat recovery at compressor inter-stage coolers, better control Install additional compressors in parallel. Use of heat of compression dryer Use cogeneration, ORC, KC or (hydraulic) power recovery turbines... 

When the reactor is operated in normal condition, the RHRS is working at the hot standby condtion. In this case the vaporizer of RHRS and primary heat e. changers work in parallel and a very small flow of the intermediate loop passes through the vaporizer to prev ent freezing in the air-cooler. In order to set up the second circulation-vaporization and condensation, the air in the shell side of vaporizer has to be discharged at its high temperaure. 

In addition to the main cooling system there is an auxiliary cooling system to remove decay heat from the core when the reactor is shut down for refueling, or in an emergracy. The auxiliary cooling system which is separated from the secondary sodium system, has an air cooler in parallel with the steam generator. When it is operating, the primary and secondary sodium are circulated by the primary and secondary main circulation pumps driven by pony motors. 

A large process plant air cooler may have 10, 20, 30, or more banks of air coolers, arranged in parallel. Figure 19.6 shows such an arrangement. Let s assume that the inlet header is oversized and has zero pressure drop. Let s also assume that the outlet header is oversized and also has no AP. The pressure drop across the tube side of all such air coolers arranged in parallel is then identical. 

For compressor cooling, the water from an outside source is taken out of a tank by three parallel working pumps, type 4KM-I2. It is then run through the coolers, working on air, and finally goes on to the compressors. 

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