Efficiency steam injection turbine

The Steam Injection Cycle Steam injection has been used in reciprocating engines and gas turbines for a number of years. This cycle may be an answer to the present concern with pollution and higher efficiency. Corrosion problems are the major hurdle in such a system. The concept is simple and straightforward Steam is injected into the compressor discharge air and increases the mass flow rate... 

Figure 2-21 show the effect of 5% by weight of steam injection at a turbine inlet temperature of 2400 °F (1316 °C) on the system. With about 5% injection at 2400°F (1316 °C) and a pressure ratio of 17 1, an 8.3% increase in work output is noted with an increase of about 19% in cycle efficiency over that experienced in the simple cycle. The assumption here is that steam is injected at a pressure of about 60 psi (4 Bar) above the air from the compressor discharge and that all the steam is created by heat from the turbine exhaust. Calculations indicate that there is more than enough waste heat to achieve these goals. 

This system, as can be seen from Figure 2-27, indicates that the net work is about the same as one would expect in a steam injection cycle, but the efficiencies are much higher. The disadvantages of this system are its high initial cost. However, just as in the steam injection cycle, the NO content of its exhaust remains the same and is dependent on the gas turbine used. This system is being used widely because of its high efficiency. 

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... 

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. 

This design has a number of tubes embedded inside the turbine biade to provide ehanneis for steam. In most cases these tubes are constructed from copper for good heat-transfer conditions. Steam injection is becoming the prime source of cooiing for gas turbines in a combined cycie appiication. The steam, which is extracted from the exit of the HP Turbine, is sent through the nozzie biades, where the steam is heated, and the biade metai temperature decreased. The steam is then injected into the flow stream entering the IP steam turbine. This increases the overaii efficiency of the combined cycie. 

Stodola in his great book of 1925 [4] describes several gas turbines for power generation, and Whittle spent much time studying this work carefully. Stodola tells how in 1904, two French engineers, Armengaud and Lemale, built one of the first gas turbines, but it did little more than turn itself over. It appears they used some steam injection and the small work output produced extra compressed air-but not much. The overall efficiency has been estimated at 2-3% and the effective work output at 6-10kW. 

Steam injection. Steam injection reduces combustion temperature by adding an inert to the combustion process. In principle, water or steam could be injected, but dry superheated steam is usually used. This reduces the furnace efficiency as energy is used to produce the steam, and the latent heat in the steam cannot be recovered. It is only used for moderate NO reduction. Steam injection can also be used in gas turbines. 

The maximum speed of the LH2 carrier is about 17.5 kn (32.4 km/h). The propulsion power is 41 MW. The propulsion of the SWATH carrier is based on a steam-injection gas turbine with an efficiency of 50% (Wursig, 1996). The investment for the SWATH carrier is indicated at about 440 million, including five LH2 tanks. The investment for one LH2 tank is 40 million. The investment for the LH2 terminals (both export and import terminal) is indicated at about 820 million (G. M. Wursig, Germanischer Lloyd, Hamburg, personal communication, January 1999). 

The injection of water or steam in gas turbines has been known (Nicolin, C., A gas turbine with steam injection. Swedish Patent application No.8112/51, Stockholm, Sweden, 1951) as an efficient method for NO abatement and power boosting. Several cycle configurations are possible with respect to water/steam injection. Figure 4.36 is the schematic diagram of the Steam-injection gas turbine cycle. Air is compressed from state 1 to state 2. Water is pumped from state 7 to state 8. Steam at state 9 is generated in a recovery boiler (heat exchanger) from state 8 by the hot exhaust gas. Steam at state 8... 

Steam Injection (SI) and Water Injection (WI). SI and WI are commonly applied to gas turbines to limit NO emissions. SI reduces the PFT by diluting oxygen near the burner front and directly removing heat from the burner flame. WI functions in a similar way, but removes even more heat from the burner flame due to its heat of vaporization. Both SI and WI lower boiler thermal efficiency—typically by no more than 1 or 2 percent. Most industrial boilers can handle these losses, although utility units cannot. SI or WI may be the lowest-cost option for reducing NO to less than 40 ppmvd, if simple combustion modifications are not successful. 

New units can be ordered having dry, low NO burners that can reduce NO emissions below 25 ppm on gaseous fuels in many cases, without back-end flue-gas cleanup or front-end controls, such as steam or water injection which can reduce efficiency. Similar in concept to low NO burners used in boilers, dry low NO gas turbine burners aim to reduce peak combustion temperatures through staged combustion and/or improved fuel—air mixing. 

As of the mid-1990s, many older conventional steam plants have been converted to combined cycle. The old boiler is removed and replaced by a combustion turbine and heat recovery steam generator. Although the cycle efficiency is not as high as completely new plants, substantial capital cost is avoided by the modification and reuse of existing steam turbine and auxiHary equipment. In many combined cycle power plants, steam is injected into the combustors of the combustion turbine to lower peak flame temperatures and consequendy lower NO. ... 

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. 

Lloyd argues that for a plant with fixed pressure ratio and top temperature, the turbine work output (and hence the net work output) is increased linearly with the. steam quantity 5 that is injected, but the (2n and Qa terms increase more slowly. Thus, the efficiency similarly increases with S. but also more slowly. 

Heat recovery tor steam generation, pre-heating combustion air, and high efficiency burners Adjustable speed drives, heat recovery coke oven gases, and dry coke quenching Efficient hot blast stove operation, waste heat recovery for hot blast stove, top gas power recovery turbines, direct coal injection... 

A gas turbine with power output of 10.7 MW and an efficiency of 32.5% burns natural gas. In order to reduce the NOx emissions to the environmental limits, 0.6 kg steam is injected into the combustion per kg of fuel. The airflow through the gas turbine is 41.6 kg-s 1. The composition of the natural gas can be assumed to be effectively 100% methane with a molar mass of 16 kg-kmoU1. The kilogram molecular volume can be assumed to occupy 22.4 m3 at standard conditions. 

It provides an increase in both power output and overall efficiency. For a given temperature at inlet to the gas turbine, extra fuel has to be supplied in order to heat the injected steam to that temperature, but the additional power arising from the expansion of the injected steam as it passes through the gas turbine more than offsets the otherwise adverse effect on the overall efficiency of the cycle of the increase in fuel supply. 

Finally, the steam turbine s buckets can foul with hardness deposits from the steam. This reduces the turbine efficiency, and may prevent a pump from running at its rated speed. Injecting steam condensate into the steam supply can remove such deposits. 

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