INDUSTRIAL WAY TO USE NATURAL GAS

GAS TURBINE POWER PLANT

                A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in between.
                The basic operation of the gas turbine is similar to that of the steam power plant except that air is used instead of water. Fresh atmospheric air flows through a compressor that brings it to higher pressure. Energy is then added by spraying fuel into the air and igniting it so the combustion generates a high-temperature flow. This high-temperature high-pressure gas enters a turbine, where it expands down to the exhaust pressure, producing a shaft work output in the process. The turbine shaft work is used to drive the compressor and other devices such as an electric generator that may be coupled to the shaft. The energy that is not used for shaft work comes out in the exhaust gases, so these have either a high temperature or a high velocity. The purpose of the gas turbine determines the design so that the most desirable energy form is maximized. Gas turbines are used to power aircraft, trains, ships, electrical generators, or even tanks.

How does it works?

The combustion (gas) turbines being installed in many of today's natural-gas-fueled power plants are complex machines, but they basically involve three main sections:

i. The compressor, which draws air into the engine, pressurizes it, and feeds it to the combustion chamber at speeds of hundreds of miles per hour.

ii. The combustion system, typically made up of a ring of fuel injectors that inject a steady stream of fuel into combustion chambers where it mixes with the air. The mixture is burned at temperatures of more than 2000 degrees F. The combustion produces a high temperature, high pressure gas stream that enters and expands through the turbine section.

iii. The turbine is an intricate array of alternate stationary and rotating aerofoil-section blades. As hot combustion gas expands through the turbine, it spins the rotating blades. The rotating blades perform a dual function: they drive the compressor to draw more pressurized air into the combustion section, and they spin a generator to produce electricity.

Compressor:- The compressor sucks in air form the atmosphere and compresses it to pressures in the range of 15 to 20 bar. The compressor consists of a number of rows of blades mounted on a shaft. This is something like a series of fans placed one after the other. The pressurized air from the first row is further pressurised in the second row and so on. Stationary vanes between each of the blade rows guide the air flow from one section to the next section. The shaft is connected and rotates along with the main gas turbine.

Combustion chamber:- This is an annular chamber where the fuel burns and is similar to the furnace in a boiler. The air from the compressor is the Combustion air. Burners arranged circumferentially on the annular chamber control the fuel entry to the chamber. The hot gases in the range of 1400 to 1500 °C leave the chamber with high energy levels. The chamber and the subsequent sections are made of special alloys and designs that can withstand this high temperature.

Turbine:- The turbine does the main work of energy conversion. The turbine portion also consists of rows of blades fixed to the shaft. Stationary guide vanes direct the gases to the next set of blades. The kinetic energy of the hot gases impacting on the blades rotates the blades and the shaft. The blades and vanes are made of special alloys and designs that can withstand the very high temperature gas. The exhaust gases then exit to exhaust system through the diffuser. The gas temperature leaving the Turbine is in the range of 500 to 550 °C.

Advantages

There are several advantages to using a gas power plant to generate electrical power as compared to other systems.

i. Gas turbine power plants can be started up and run at full capacity in only 10 to 20 minutes, making them well suited as backup plants for utility companies that require additional electricity immediately.

ii. Because they are smaller than coal or nuclear plants, gas power plants can be built faster and at a lower cost.

iii. Gas turbine systems also require much less water than steam power plants, and they are easily converted into combined cycle power plants, which are much more efficient.

Disadvantages

Gas turbine power plants have disadvantages as well.

i. The power needed to drive the compressor reduces the net outputs, consuming more fuel to do the same amount of work.

ii. The operating temperature in gas turbines is higher than in other power plant systems and can shorten the lifespan of some of the system components.

iii. Furthermore, because the thermal energy is wasted when the exhaust is released, the efficiency levels of gas turbine plants are lower than those of other types of power plants.