Cycle Compressors

The reciprocating compressor is generally in the lower flow end of the compressor spectrum. Inlet flows range from less than 100 to approximately 10,000 cfm per cylinder. It is particularly well-suited for high-pressure service. One of the highest pressure applications is at a discharge pressure of 40,000 psi. Above approximately a 1.5-to- i pressure ratio, the reciprocating compressor is one of the most efficient of all the compressors. 

The rotary compressor portion of the positive displacement family is made up of several compressor configurations. The features these compressors have in common are  

They impart energy to the gas being compressed by way of an input shaft moving a single or multiple rotating element. 

The helical and spiral-lobe compressors are generally similar and use two imermeshing helical or spiral lobes to compress gas between the lobes and the rotor chamber of the casing. The compression cycle begins 

The helical-lobe compressor is further divided into a dry and a flooded form. The dry fonn uses timing gears to hold a prescribed timing to tlie relative motion of the rotors the flooded form uses a liquid media to keep the rotors from touching. The helical-lobe compressor is the most sophisticated and versatile of the rotary compressor group and operates at the highest rotor tip Mach number of any of the compressors in the rotary family. This compressor is usually referred to as the screw compressor or the SRM compressor.  

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Fig. 12. Open-cycle compressors (a) simple and (b) multiple product schematic.

Ward reported power consumption for a plant using the mixed-refrigerant cycle. Compressor power was 9,460 kw for an LNG production rate of 28,550 m /hr. This converts to 3.37 kw-hr/lb-mole of liquid. The minimum work for a feed-gas pressure of 37 atm, an assumed feed-gas temperature of 80°F, and an assumed heat-sink temperature of 80°F = 1.09 kw-hr/lb-mole of liquid. This gives an efficiency of 32.4%. 

Determine temperature of all states of the cycle, compressor power required, power produced by turbine 1, power produced by turbine 2, and cycle efficiency. 

Determine the pressure and temperature of each state, power required by the top-cycle compressor, power produced by the top-cycle turbines, thermal efficiency of the combined cycle, thermal efficiency of the top cycle, thermal efficiency of the bottom cycle, power input to the combined cycle, power output by the combined cycle, power net output of the combined cycle, rate of heat added to the combined cycle, rate of heat removed from the combined cycle, power input to the top cycle, power output by the top cycle, power net output of the top cycle, rate of heat added to the top cycle, rate of heat removed from the top cycle, power input to the bottom cycle, power output by the bottom cycle, power net output of the bottom cycle, rate of heat added to the bottom cycle, and rate of heat removed from the bottom cycle. 

Determine the pressure and temperature of each state, power required by the top-cycle compressor, power produced by the top-cycle turbines, thermal efficiency of the combined cycle, thermal efficiency of the top cycle, thermal efficiency of the bottom cycle, power input to... 

Fig. I. LP Oxo gas recycle flow scheme A, feedstock pretreatment B, reactor C. catalyst preparation and treatment systems D, condenser E. separator F, snipper G, stabilizer H, cycle compressor and T, stabilizer overhead gas compressor.

Nowadays, the standard cryostats are closed-cycle helium refrigerators. They are commercially available. We use either the Displex Closed-Cycle System CSA from Air Products or the Closed-Cycle Compressor Unit RW 2 with Coldhead Base Unit 210 and Extension Module ROK from Leybold. These systems can run for thousands of hours with minimal maintenance. The sample holder can be cooled to temperatures from room temperature to about 10 K. A typical example of a closed-cycle helium matrix apparatus is shown in Figure 1.1. 

In the case of higher plant capacities per train, limiting factors are above all the main dimensions of the mixed refrigerant cycle compressor (6) and the heat... 

Fixing these parameters implies that for recuperator thermal ratings lower than the 539 kW load the gas cooler and reactor loads would need to increase to supply the same cycle compressor and turbine inlet temperatures relative to the 539 kW case. 

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