Surface condensers compressors

Space needs to be provided for the auxiliaries, including the lube oil and seal systems, lube oil cooler, intercoolers, and pulsation dampeners. A control panel or console is usually provided as part of the local console. This panel contains instmments that provide the necessary information for start-up and shutdown, and should also include warning and trouble lights. Access must be provided for motor repair and ultimate replacement needs to be considered. If a steam turbine is used, a surface condenser is probably required with a vacuum system to increase the efficiency. AH these additional systems need to be considered in the layout and spacing. In addition, room for pulsation dampeners required between stages has to be included. Aftercoolers may also be required with knockout dmms. Reference 8 describes the requirements of compressor layouts and provides many useful piping hints. 

Figures 8.10 and 8.11 are based on the driver FOB fabrication shop cost only. For the completed driver package, additional items, such as a surface condenser for the condensing steam turbine or a starting motor or air piston starter for the gas engine, are required. Tables 8.29 to 8.32 are each dedicated to providing factoring for these specific costs. Such costs will again be based on the compressor horsepower, BHP.

Figure 106. Steam system o( a modern steam reforming a) Steam drum. 125 bar b) NH, loop c) Turbine for syngas compressor d) Turbine for process air compressor and alternator e) Surface condenser f) Condensate treatment g) BFW pump...

Often, there exists spare capacity in a surface condenser, one that condenses exhaust steam from a centrifugal compressor or from a steam turbine under vacuum. This spare capacity may often be over 10% of the normal operating capacity and can be attributed to one or more of the following ... 

The vacuum at the top of the flash column is often produced by a sequence of three elevated steam-jet eductors with intermediate and final surface condensers to remove the steam. A liquid-ring compressor can be substituted for one or more eductors to conserve steam. Mechanical vacuum pumps are seldom used because of the corrosive nature of the off-gas. The noncondensible sour compressed gas and condensate are led away through a water seal for safety in case of steam system failure. The seal pot is equipped to skim off condensed oil continuously. 

With turbine surface condensers, it often pays to choose a pump with a low NPSH, especially when die condenser is directly below the turbine. The compressor house floor can be lowered. With the lower elevated condenser, operation and maintenance access is improved. Vertical pumps are usually specified with a minimum height from grade to equipment because their suction inlet nozzle is below grade. 

Compressors and their related equipment are usually located in one area for conunon operation and servicing adjacent to the main pipe radk and the auxiliary road. The suaion drum for the machine should be positioned for flexibility in the piping and to accommodate orifice run requirements. If the compressor is driven by a condensing turbine, a surface condenser and condensate pumps are required. If servicing one machine, the condenser may be located beneath the turbine. If it services two or more, the condenser must be located ac acent to the machines it services. In both cases, space must be provided for condaaser tube bundle removal. 

Exhibit 4-1 shows a surface condenser mounted directly below the turbine. This arrangement is used when the condenser is designed to service only one steam turbine. The arrangement shown in Exhibit 4-2 is generally used when several turbines are exhausting into one condenser. Exhibit 4-3 shows the various compressor systems and their reciprocals. 

Surface condensers are used in conjunction with condensing steam turbines that drive large centrifugal compressors. As depicted in Exhibit 4-25 the exhaust steam enters the top of the condenser and passes through the shell, which is filled with tubes. Cold water is pumped through the tubes while hot exhaust steam passes around the outside. Hot water, called condensate, results and collects in the hot well at the bottom of die condenser. 

Improved and redesigned rotors of modem compressors save considerable power. The ethylene fractionator and the propylene refrigeration condensers can be replaced with extended surface tube bundles instead of conventional tube bundles. 

The conditions of water vapor transport between the chamber and condenser, the condenser surface, the capacity of the refrigerant compressors and the vacuum pumping capacity, must all be the same (pro rata) for the product dried in the laboratory as in the plant to which the process will be transferred. 

The tubes in the condenser required for subcooling steal heat-transfer surface area required for condensation. In effect, the condenser shrinks. This makes it more difficult to liquefy the refrigerant vapor. The vapor is then forced to condense at a higher temperature and pressure. Of course, this raises the compressor discharge pressure. And, as we have seen in the pressure section, this increase in compressor discharge pressure invariably reduces the compressor s capacity and may also increase the horsepower needed to drive the compressor. 

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