Compressed air, injection

Injection of Humidified and Heated Compressed Air. Compressed air from a separate compressor is heated and humidified to about 60% relative humidity by the use of an HRSG and then injected into the compressor discharge. Figure 2-41 is a simplified schematic of a compressed air injection plant, which consists of the following major components ... 

A commercial combustion turbine with the provision to inject, at any point upstream of the combustor, the externally supplied humidified and preheated supplementary compressed air. Engineering and mechanical aspects of the air injection for the compressed air injection plant concepts are similar to the steam injection for the power augmentation, which has accumulated significant operating experience. 

Humidified Compressed Air Injeetion System are about the same. This is due to the faet that though the initial eost to install the Compressed Air System, for a turbine of about 100 MW, is about 3.7 million as compared to about 1.7 million for a steam injection system, the power generated by the Heated and Humidified Compressed Air Injection System is much higher. 

The rate of return on the steam injection system is higher than the Compressed Air Injection System. This is due to the fact that though the efficiency of the steam injection system and the compressed air injection system is about the same, however, the initial cost of the steam injected system being over 50% lower than the compressed air injection system accounts for the difference. 

Generator Power Output Capacity. The generator, as a general rule of thumb is oversized by about 20% above the turbine rated load. The changes have to be limited to that region by limiting the steam or Compressed Air Injection. 

Open containers, e.g. securitainers or bottles, should always be inverted, blown with clean dry, oil-free compressed air injected by a dip tube from the base and vacuum sucked to remove as many particles as possible. 

A more convenient means of media comparison, whilst still retaining some of the above practical elements, is described by Anand et al. In this procedure, a single sleeve of smaller size is mounted on a plastic cage and located in a clear Perspex cylindrical enclosure. A quantity of dust is added and this is then transformed into a cloud by means of compressed air injected at the base of the unit. The dust-laden air is drawn onto the surface of the sleeve and the subsequent pressure differential monitored by computer. Any particle emissions through the fabric are captured by an ultrafilter and measured gravimetricaUy. Once again, the gas velocity, cleaning frequency, pulse pressure, and pulse duration can be adjusted and, by virtue of the clear Perspex cylinder, the effects of these can be visually observed. 

Add Bleaching - Acid produced in most absorber units is invariably yellow or brown in color because of dissolved nitrogen dioxide. This is not acceptable for the handling of nitric acid and for most applications. The nitrogen dioxide is removed either in a separate smaD bleaching tower or in an additional, lower section of the main absorber column by means of compressed air injection. The gases are recycled to the oxidation tower. 

In another time and place, a lube oil tank experienced a dramatic failure of the wall-to-floor seam of an oil tank. A vertical lubricating oil storage tank, 19 ft. (6.1 m) in diameter and 24 ft. (7.4 m) high, failed catastrophically when it was accidentally overpressured with compressed air injected into the tank. A stream of compressed air injected below the liquid level provided internal mixing within the tank. There were no injuries and no lire [4]. 

All vessels, valve, pipes operating under pressure should meet stamtory requirements. They should be provided with standard safety relief valves Position of compressed air injection point in to the recycled water (in the piping itself or in the air saturation tank through control valve operation)... 

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

Injection of Compressed Air, Steam, or Water for Increasing Power... 

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. 

Injection Pre.s.sure. The injeetion pressure must be between 75-100 psia (5-7 Bar) above the Compressor Diseharge Pressure. In the ease of the Heated and Humidified Compressed Air injeeted system, the air must be saturated. 

Consider next a recuperative STIG plant (Fig. 6.5, again after Lloyd [2]). Heat is again recovered from the gas turbine exhaust but firstly in a recuperator to heat the compressed air, to state 2A before combustion and secondly in an HRSG, to raise steam S for injection into the combustion chamber. 

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. 

Aerated Mud. In aerated mud drilling operations, the drilling mud is injected with compressed air to lighten the mud. Therefore, at the bottom of the well in the annulus, the bottomhole pressure for an aerated mud will be less than that of the mud without aeration. However, an aerated mud drilling operation will have very significant bottomhole pressure capabilities and can easily be used to control potential production fluid flow into the well annulus. 

The volumetric flowrate of water to be injected into the compressed air depends upon the saturation pressure of the water vapor at the bottomhole temperature. The saturation pressure p (psia) at the bottom of the hole depends only on the bottomhole temperature and is given by [76,77]. 

In the compression ignition cycle, the air is compressed and the fuel is injected into the compressed air at a temperature sufficiently high to spontaneously ignite the fuel. The heat released is converted to mechanical work by expansion within each cylinder and, by means of the reciprocating motion of the piston, is converted to rotary motion at the crankshaft. 

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