Air compressor

Air compressors supply compressed utility air and, if damaged, their function is quickly replaceable with rental compressor units. On the other hand, an air compressor may supply compressed air for a process stream, be very large in size, and not quickly replaceable. Air compressors that supply instrument air are critical to plant operations and must be installed, maintained, and protected to maximize reliability. 

There have been fires and explosions in compressed air systems. The fuel is a combustible lubricant that has entered the air system from the compressor. Al th 0 ugh m ai nte n an ce of th e ch eck val ves wi 11 m i n i m ize th e h aza rd, th e val ves can stick open from scale or other causes that can affect even recently serviced valves. The explosion potential can be minimized by replacing the combustible lubricants with noncombustible lubricants. 

Like flammable gas compressors, the external lubrication system for large air compressors can present a fire hazard. Oil flow rates above 25 gpm (95 Ipm) and or oil capacity greater than 100 gal (379 I) may require fire protection. 

If an air compressor is located such that a flammable release from nearby equipment could envelope the air compressor, then automatic deluge or sprinkler protection may be required to protect the air compressor from fire damage. 

It is ideal to have oil-fiw compressed air. Centrifugal machines generally are available up to 40,000 cfin. Oil free serew air compressors are available in smaller sizes. Regarding oil-free screw type compressors, it 

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For air compressors Operating safety Thermal stability, Volatility Resistance to oxidation Extreme pressure and anti-wear (compressors) properties Low coking tendency (hot reciprocating compressors)... 

This reduction in permeabiUty due to cake consoHdation or coUapse may be so large that it may nullify or even overtake the advantage of using high pressures in the first place and there is then no reason for using the generally more expensive pressure filtration hardware. While a simple Hquid pump may be cheaper than the vacuum pump needed with vacuum filters, if air displacement dewatering is to foUow filtration in pressure filters, an air compressor has to be used and is expensive. 

The hot gases from the combustor, temperature controlled to 980°C by excess air, are expanded through the gas turbine, driving the air compressor and generating electricity. Sensible heat in the gas turbine exhaust is recovered in a waste heat boiler by generating steam for additional electrical power production. 

Alkylated aromatics are used as the base fluid ia engine oils, gear oils, hydrauHc fluids, and greases ia sub2ero appHcations. They also are used as the base fluid ia power transmission fluids and gas turbine, air compressor, and refrigeration compressor lubricants. 

Phosphate ester fluids are the most fire resistant of moderately priced lubricants, are generally excellent lubricants, and are thermally and oxidatively stable up to 135°C (38). Fire-resistant iadustrial hydrauHc fluids represent the largest volume commercial use. AppHcations are made ia air compressors and continue to grow for aircraft use (tributyl and/or an alkyl diaryl ester) and ia hydrauHc control of steam turbiaes ia power generation (ISO 46 esters). 

Compressor systems for respirators should be completely separate from other uses. Air compressors that are designed to produce breathing-quahty air are required. In smaller systems, it may be preferable to use botded air rather than a compressor. The contents of bottles, however, should be analy2ed to ascertain that they do contain air and to assure that the concentrations of any contaminants are acceptably low. 

Fig. 5. Fermentative production of amino acids (140). A, pure culture B, inoculation C, boiler D, air compressor E, air filter F, seed tank G, ammonia water for pH control H, fermenter I, sterilizer , culture media K, preparation tank L, centrifugal separator M, ion-exchange column N, crystallizing...

Fig. 14. ICI—LCA process flow sheet PAC, purified air compressor HDS, hydrodesulfurization IP, iatermediate pressure LP, Hquefied petroleum BFW,...

Dense phase systems are at cost disadvantage when multiple feed points are required, or when incremental compressed air for conveying is not available from existing sources. In the latter instance, the entire investment cost of an air compressor and associated auxiUaries must be allocated to the cost of the conveying system. 

Both air and oxygen processes can be designed to be comparable in the following areas product quaUty, process flexibiUty for operation at reduced rates, and on-stream rehabiUty (97,182). For both processes, an on-stream value of 8000 h/yr is typical (196). The rehabiUty of the oxygen-based system is closely linked to the rehabiUty of the air-separation plant, and in the air process, operation of the multistage air compressor and power recovery from the vent gas is cmcial (97). 

Single-acting air-cooled and water-cooled air compressors are available in sizes up to about 75 kW (100 hp). Such units are available in one, two, three, or four stages for pressure as high as 24 MPa (3500 IbFin"). These machines are seldom used for gas compression because of the difficulty of preventing gas leakage and contamination of the lubricating oil. 

The surprise was finally clarified by remembering that this was an air operated plant built in a thermodynamic cycle, (the Brayton or gas turbine cycle) with a 18,000 HP air compressor. This generated 5 MW of salable... 

Figure 4-6. Ammonia combustion and absorption at air compressor discharge pressure of 3-12 bar (Process 2, elevated pressure), a = medium pressure, 3-6 bar b = high pressure, 6-12 bar, with interceding or booster compressor.

Figure 4-7. Combustion air compressor train. Mass flow = 98,000 Nm /h Pressures = 1.0/7.4 bar Power input = 10,000 kW Power recovered by expander = 8,900 kW.

Air compressor (axial or centrifugal type) without or with adjustable guide vanes (8) and guide vane setting 19... 

Figure 4-9. Ammonia combustion at air compressor discharge pressure of 2-5 bar, absorption at nitrous gas compressor discharge pressure of 7-15 bar (Process 3, dual-pressure cycle).

Figure 4-10. Compressor train for dual-pressure installation consisting of an axial flow air compressor with adjustable stator blades and a radial flow nitrous gas compressor and expander. Mass flow air = 139,000 Nm /h, nitrous gases = 122,500 Nm /h Pressure air = 0.82/4.75 bar, nitrous gases = 4.38/10.8 bar Power input total = 16,840 kW Power recovery by expander = 10,950 kW.

Digital control methodologies similar to the Elliott Digital System program evolved from successful and proven reliable high-speed air compressor management and control approaches. 

Several constraints were faced in the design phase of the project. For example, special attention was given to the fact that 400 Series stainless steel, carbon, and some grades of aluminum were not compatible with the process. Additionally, the expander discharge temperature was required to stay between 35-70°F. The operating rpm of the expander wheel was determined by the rpm required by the third stage of the air compressor. 

API Std 672, Packaged, Integrally Geared Centrifugal Air Compressors for Petroleum, Chemical, and Gas Industry Services, 3rd Edition, September... 

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