Steam-turbine surface

Specimen Location Steam turbine surface condenser... 

I did not understand thermodynamics at university. It seemed to be an exotic subject with no relevance to my future as a refinery process engineer. It wasn t until I had spent many years working with steam turbines, surface condensers, steam distribution systems, and most especially vacuum ejectors that I realized that without a firm understanding of thermodynamics, I could not operate or troubleshoot such facilities with any degree of confidence. 

On the vapor outlet of steam turbine surface condensers, there is a two-stage ejector system and a two-stage condenser. Referring to Fig. 25.5, this two-stage condenser is actually a small condenser divided into two portions on the shell side by a partition baffle. 

Figure 25.5 Steam turbine surface condenser vacuum is bad due to a leak in the ejector condenser shell-side partition plate.

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. 

Steam-turbine lubricants Lubricants in steam turbines are not exposed to such arduous conditions as those in engines. The main requirement is for high oxidation stability. However, they may be exposed to aqueous condensate or, in the case of marine installations, to sea water contamination, so they have to be able to separate from water easily and to form a rustpreventing film on ferrous surfaces, and it is usual to employ rust inhibitors. The problem of tin oxide formation on white-metal bearings is associated with the presence of electrically conducting water in lubricants and can be over-come by keeping the lubricant dry . 

If silica (in the form of volatile silicic acid) is present in steam at concentrations greater than 0.02 ppm Si02, turbine deposit problems result. In some cases, volatile silica appears not to significantly affect superheaters but certainly will always form deposits in turbines. Silica appears in different forms, depending on the steam pressure, and affects all turbine surfaces, It is most noticeable on the blades, which eventually results in rotor unbalancing. 

Figure 8.10 shows the type of surface condenser widely used on older steam turbines. Note that it has both a vapor and a liquid outlet. The... 

Air-cooled surface condensers. Figure 8.11 shows a surface condenser elevated above the steam turbine. This creates an additional problem, in that moisture from the turbine exhaust steam will accumulate in the bottom of the turbine case. A special drain line from the turbine s case is needed to prevent condensate backup from damaging the spinning wheels. 

In Chap. 16 we reviewed several problems pertaining to steam jet precondenser and intercondenser problems. The surface condensers, which serve condensing steam turbines, are subject to all the same... 

In the 1950s Hickman developed a centrifugal vapor compression evaporator for seawater desalination (53). This device consisted of multiple spinning discs. Seawater sprayed on one side of the disc evaporated, while the centrifugal force removed the residue from the plate surface. The vapor was compressed and returned to the opposite side of the plate, where condensation provided the heat for evaporation and the desired freshwater for recovery. Overall heat transfer coefficients of 18 kW/m2-K are about three times higher than those achieved in steam turbine condensers. 

Geothermal Plant A plant in which the prime mover is a steam turbine. The turbine is driven either by steam produced from hot water or by natural steam that derives its energy from heat found in rocks or fluids at various depths beneath the surface of the earth. The energy is extracted by drilling and/or pumping. 

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.

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 ... 

Steam turbines competitive above 75 kW condensing 2 kg/h steam/kW with 1.8 m condenser surface area per kg/h steam. Multivalve, multistage efficiency 42 to 78%. 

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