Compressor water injection

Water injection, or steam injection systems, are being used extensively to augment power. Corrosion problems in the compressor diffuser and combustor have not been found to be major problems. The increase in work and efficiency with a reduction in NO makes the process very attractive. Split-shaft cycles are attractive for use in variable-speed mechanical drives. The off-design characteristics of such an engine are high efficiency and high torque at low speeds. 

Water Injection—Mid-compressor flashing is used to cool the compressed air and add mass flow to the system. 

Injection of Water or Steam at the Gas Turbine Compressor Exit. Steam injection or water injection has been often used to augment the power generated from the turbine as seen in Figure 2-42. Steam can be generated from the exhaust gases of the gas turbine. The HRSG for such a unit is very elementary as the pressures are low. This technique augments power and also increases the turbine efficiency. The amount of steam is limited to about... 

Effect of water injection on generator output as a function of compressor inlet temperature... 

The discussion of the last section is then useful in considering the evaporative cycles. We shall see that the effect of water injection downstream of the compressor (and possibly in the cold side of the heat exchanger) may lead towards the [CBTJiXr type of plant, with increased cold side effective specific heat and hence increased heat exchanger effectiveness. Water injection in the compressor may lead to a plant with isothermal compression. 

Another water injection cycle proposed is the TOPHAT cycle [12] (see Fig. 6.16). As for the HAT cycle, the purpose is to introduce water into the cycle with low exergy loss and this is achieved by injecting water continuously in the compressor in an attempt to... 

In the search for higher plant thermal efficiency, the simplicity of the two basic STIG and EGT cycles, as described by Frutschi and Plancherel, has to some extent been lost in the substantial modifications described above. But there have been other less complex proposals for water injection into the simple unrecuperated open cycle gas turbine one simply involves water injection at entry to the compressor, and is usually known as inlet fog boosting (IFB) the other involves the front part of an RWI cycle, i.e. water injection in an evaporative intercooler, usually in a high pressure ratio aero-derivative gas turbine plant. 

Horlock, J.H. (2(K)1), Compressor performance with water injection, ASME Paper 2(K)l-GT-343. 

There are versions of the rotary screw compressor that utilize water injection (rather than oil). The water accomplishes the same purposes as the oil, but the air delivered in these machines is oil-free. 

Compressors (low pressure, water injected, screw type) 340/hp 30... 

The pipeline transport of H2 requires compression. The electrolysis plant uses low pressure, water injected, screw type compressors to compress H2 from 1.02 bar to 8.0 bar to transport the H2 a short distance ( 10 miles) to a pipeline compression station. The energy to compress H2 from 1.02 bar to 8.0 bar is 1.37 kWh/kg of H2. There is no need for H2 storage at the electrolysis plant. At the pipeline compression station, the H2 is compressed from 8.0 bar to a pipeline pressure of 69.0 bar by high-pressure reciprocating compressors. The energy to compress H2 from 8.0 bar to a pipeline pressure of 69.0 bar is 1.17 kWh/kg of H2. PV electricity is used to power the compressors and water pumps at the compression station. 

Reformed gas is compressed to 100 barg in a 27 MW split, three-stage compressor and injected into the converter loop at the suction of the 5 MW circulating compressor. Converter circulating gas plus make-up gas is heated and fed to a six-bed converter (ZnO/CuO/Al O catalyst). Part of the gas is fed to the inlet of the reactor at 210-240°C and the balance is fed, at a lower temperature, to the lower beds as quench gas. Reactor effluent is cooled both against reactor feed and saturator water feed before passing to the methanol condensers. The crude methanol is then rundown to off-site tankage and the MTG unit. 

The dryer-exhaust steam was split off and compressed the high-pressure steam gave up its latent heat to the incoming steam. He modeled two designs for comparison. One used a standard compressor that withstood the superheat. The other considered a compressor with water injection into the suction vapor to cool the steam during compression. The latter is about 10% more efficient due to reduction in steam volume at the reduced temperature. 

Offshore structures are relatively self-sufficient they provide electrical generators, water desalinators, sleeping facilities, communication stations, and modern amenities. Production platforms are connected by pipelines or floating storage units to onshore operations. Key process elements of oil and gas recovery include wellhead, production manifold, production separator, water injection pumps, gas compressors, glycol process to dry gas, oil and gas export metering, and main oil-line pumps. 

Water injection during the compression process may actually improve the efficiency of the compression process by simultaneously cooling the compressed gas,- however, this method is not applicable for all kinds of compressors. 

Fig. 22 (a) Water injection scroll compressor test system, (b) Schematic of water injection scroll compressor (from Zhao et al., 2005). 

The unit has virtually the same flow sheet (see Fig. 2) as that of methanol carbonylation to acetic acid (qv). Any water present in the methyl acetate feed is destroyed by recycle anhydride. Water impairs the catalyst. Carbonylation occurs in a sparged reactor, fitted with baffles to diminish entrainment of the catalyst-rich Hquid. Carbon monoxide is introduced at about 15—18 MPa from centrifugal, multistage compressors. Gaseous dimethyl ether from the reactor is recycled with the CO and occasional injections of methyl iodide and methyl acetate may be introduced. Near the end of the life of a catalyst charge, additional rhodium chloride, with or without a ligand, can be put into the system to increase anhydride production based on net noble metal introduced. The reaction is exothermic, thus no heat need be added and surplus heat can be recovered as low pressure steam. 

The steam used in this process is generated by the turbine exhaust gas. Typically, water at 14.7 psia (1 Bar) and 80 °F (26.7 °C) enters the pump and regenerator, where it is brought up to 60 psia (4 Bar) above the compressor discharge and the same temperature as the compressor discharged air. The steam is injected after the compressor but far upstream of the burner to create a proper mixture which helps to reduce the primary zone temperature in the combustor and the NO output. The enthalpy of State 3 hi,) is the mixture enthalpy of air and steam. The following relationship describes the flow at that point ... 

Mid-Compressor Flashing of Water. In this system, the water is injected into the mid-stages of the compressor to cool the air and approach an... 

The cooling of the inter-stage compressor air by injecting water is also another very effective way for getting more power from the gas turbine. The problem in most units is that there is no convenient place to inject the water. The gas turbines would require substantial modification to install such a system. Care would have to be taken that any modification would not affect the integrity of the system. This type of a system is very effective in units where there is a low and high-pressure compressor, providing a very convenient place to inject the water. This type of compressor are mostly available in aeroderivative units. 

The concept of injecting humidified and heated compressed air just after the gas turbine compressor is another very interesting way to increase power and efficiency. In this system, compressed air is added to the compressed discharge air. The compressed air is about 5% of the main gas turbine air and this air after it has been compressed using an external compressor is then injected into an air saturation device where steam obtained from the HRSG unit is then injected into the device to saturate the air with water and the saturated air then is further heated in the HRSG before it is injected into the compressor discharge of the gas turbine. 

The injection of steam in the compressor discharge has been utilized over the years and has been found to be very effective. The amount of steam to be injected can vary from 5-15%. The injection of steam created from properly treated water does not affect the life of the hot section of the turbines. This is based on a large number of units where steam injection has been used. Steam injection, with an evaporative cooling inlet system would be best suited for hot humid areas this application based on the efficiency and cost as shown in Figure 2-45. 

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