Compressors roots

Bulletin S-5627, LAL Spiraxial Compressors, Roots-Dresser Industries, Roots Blower Operation, Conner ille, Ind. 

Many users consider rotaiy compressors, such as the Rootes -type blower, as turbomachines because their behavior in terms of the rotor dynamics is very close to centrifugal and axial flow machineiy. Unhke the reciprocating machines, the rotary machines do not have a veiy high vibration problem but, like the reciprocating machines, they are positive displacement machines. 

An alternate method not used too much at this time is the drum design. The drum construction is somewhat different from the disc, in that the rotor body is of cylindrical construction. By using the hollow drum, conical roots, of bolted construction, can be used for the rotor, again, allowing for stagger adjustments to fine tune the axial compressor to the application if the need arises. The setting is done to a gauge at the factory, as with the stators. 

Thanks go to Brown and Root for scanning the first edition, and for giving me an electronic form on which to build the revised edition. Thanks also to Buddy Wachel of EDI for giving me an assist at the reciprocating compressor acoustics, and to Susan Dally, Terryl Matthews, Rick Powell, Kelly Fort, Rich Lewis, Carl Fredericks, and Mary Rivers of Dow Chemical for their reviews of the revised chapters. 

Figure 12-111. Typical constant-speed performance of spiral screw rotor compressor. (Used by permission 1961. Roots Division, Dresser-Rand Industries, Inc.)...

Rotary piston or rotary lobe or roots compressors use two counterrotating matching lobe-shaped rotors (Figure 13.11b). Each revolution of the lobes delivers four pulses of gas. Maximum discharge pressures in a single stage are up to 2.5 bar. Suction flowrates of up to 3 m3s 1 are possible. 

In selecting a compressor for this type of operation, the main difficulty is the very large volume of vapour to be handled. Rotary compressors of the Rootes type, described in Volume 1, Chapter 8, are suitable for small and medium size units, though these have not often been applied to large installations. Mechanical compressors have been used extensively in evaporation systems for the purification of sea water. 

After C02 removal, final purification includes methanation (8) gas diying (9) and ciyogenic purification (10). The resulting pure synthesis gas is compressed in a single-case compressor and mixed with a recycle stream (11). The gas mixture is passed to the ammonia converter (12), which is based on the Kellogg Brown Root Advanced Ammonia Process (KAAP). It uses a precious metal-based, high-activity ammonia synthesis catalyst to allow for high conversion at the relatively low pressure of 90 bar. 

Figure 7.19. Some rotary positive displacement compressors (a) A two-lobe blower, (b) Performance of a two-lobe blower Roots-Connersville Co.), (c) A screw pump with one power and two idle rotors (Kristal and Annett, 1940). (d) Performance ot 3 5 screw pump handling oils at 1150 rpm against 325 psig Kristal mi Annett, 1940). (e) Rinciple of Ihe liquid ring seM compressor (Nash Et meemg Co.), (f) A shding vane Mower (Beach-Russ Co.).

The flrst U.K. uranium isotope separation plant, built in the early 1950 s, was based on gaseous difiusion. This phenomenon depends on the observation that the rate of passage of molecules through a membrane is inversely proportional to the square root of the molecular weight. The application of this principle in a cascade stage requires a compressor, membrane, control valve, and cooler. 

Instances of damage caused by sliding occur quite frequently in piston machines. In a roots type rotary compressor, for ammonia compression, the damage occurred after approximately 60,000 h of operation. 

Dry Vacuum Pumps (DVPs) These use the operating principles of rotary-lobe roots blowers, claw compressors or screw compressors, and hence require electrical power. They run dry and hence at very high temperature due to the heat of compression. Usually,... 

---