Compression stages

Some horizontal belt vacuum filter designs incorporate a final compression stage for maximum mechanical dewatering. This is achieved by another compression belt which presses down on the cake formed in the preceding conventional filtration stage. 

Methods of Liquefaction and Solidification. Carbon dioxide may be Hquefted at any temperature between its triple poiat (216.6 K) and its critical poiat (304 K) by compressing it to the corresponding Hquefaction pressure, and removing the heat of condensation. There are two Hquefaction processes. In the first, the carbon dioxide is Hquefted near the critical temperature water is used for cooling. This process requires compression of the carbon dioxide gas to pressures of about 7600 kPa (75 atm). The gas from the final compression stage is cooled to about 305 K and then filtered to remove water and entrained lubricating oil. The filtered carbon dioxide gas is then Hquefted ia a water-cooled condenser. 

Before proceeding with the power calculation, the head for each cooled case will be calculated. In the idealized case, the most efficient division of work for minimum power is achieved by taking the nth root of the pressure l atio, where n is the number of uncooled sections or compression stages in the parlance of the process engineer. For one cooler, n = 2. 

The volumetric flowrate for a sliding vane compression stage (fU/min) is approximately... 

Centrifugal machines can be built for industrial use with ammonia and other refrigerants, and these mayhave up to seven compression stages. With the high tip speeds in use, it is not practical to build a small machine, and the smallest available centrifugal compressor for refrigeration dutyhas a capacityof some 260 kW. Semi-hermetic compressors are made up to 7000 kW and open drive machines up to 21 000 kW capacity. 

A two-stage compression is from ambient pressure (1.013 bar) to a final pressure of 10 bar. What should be the pressures across each compression stage for ... 

From the values of y and the pressure ratios, it is clear that the pressure ratio for ammonia is very high for a single-stage compression. The guidelines for gas compression given in Chapter 13 indicate that propylene and propane compressions should be able to be achieved in a single compression stage, but the ammonia would seem to require two compression... 

The pressure ratio is a little high for Cycle 2 to be carried out in a single compression stage. However, single-stage compression... 

Centrifugal compressors increase gas pressure by accelerating the gas as it flows radially out from a rotating impeller. The increase in velocity is then converted to increase in pressure as the gas leaves the compression stage. Unlike reciprocating compressors, centrifugal compressors involve a constant flow through the compressor. 

N Number of compression stages (-), or number of moles (kmol), or number of theoretical stages (-), or rate of transfer of a component (kmol-s-1 m-3)... 

Ambient air is compressed in a turbocharger, powered by the expansion of the hot pressurized exhaust gases. Following this first compression stage, the air is intercooled by a fm fan air cooler and fed into a second turbocharger. The high-pressure air is fed directly to the PEFC... 

One way to utilize a stabilizer Is illustrated In Figure 5, which is simply the Figure 4 process with the liquids from K and 4 diverted to a stabilizer. The stabilizer could be either refluxed or cold-feed, as a further variation. This process reduces the recycle load significantly in the two lower compression stages, as compared to the previous processes. This process also provides an additional control for the crude oil vapor pressure which can be independently varied, since the fractionator split can be controlled and the fractionator bottom product is blended with the crude stream. It may be desirable to blend this stream into separator 1... 

But what is the average compression ratio for each of the three jets Well, let s assume that the pressure drop for the first two condensers in Fig. 16.2 is zero. Then, let s remember that when compression stages work in series, their compression ratios are multiplied together, to calculate the overall compression ratio. Then the average compression ratio per jet is... 

We take the cube root of the average compression ratio, because the three jets represent three compression stages. 

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