GAS TURBINE AND ENVIRONMENT

GAS TURBINE AND ENVIRONMENT

                          Natural gas is a clean fuel as compared to coal and can be efficiently used in power generation. As the domestic coal supply is generally of low quality with low calorific values, high degree of ash content and its adverse impacts to the environment, Government of India encourage gas based power generation in India. The use of gas in power-generation was initially promoted by the Government primarily with a view towards environmental considerations.

                        Production of natural gas is at present at the level of around 132.83 million metric standard cubic meters per day (MMSCMD). The main producers of natural gas are Oil & Natural Gas Corporation Ltd. (ONGC), Oil India Limited (OIL), JVs of Tapti, Panna-Mukta and Ravva and Reliance Industries Limited (RIL) which has discovered gas in the Krishna Godavari basin at its KG D6 block in the east cost of Andhra Pradesh. Out of the total domestic production of 132.83 MMSCMD of gas about 43% is produced by Reliance Industries Ltd. (as of December 2009) and approximately 57% of the gas is produced by others.

Many of the simple-cycle gas turbine projects are being permitted as non-Prevention of Significant Deterioration (PSD) projects by limiting operating hours, or fuel Consumption, to ensure that annual emissions do not exceed PSD trigger levels. The calculation of annual emissions based on normal operating loads, without taking into consideration the increased NOx/CO/VOC emission levels during startups/shutdowns, is technically wrong and will be challenged by regulators –ENFORCING AUTHORITIES

In addition to emission increases, lower plume buoyancy (due to lower air flow and stack exit temperature) during the startup sequence must be considered in the air dispersion modeling study to ensure that exceedances of the National Ambient Air Quality Standards (NAAQS) 2009, or PSD significance levels, do not occur.

GAS TURBINES

•         Invented in 1930 by Frank Whittle

•         Patented in 1934

PRINCIPLE OF OPERATION

•         Intake

–        Slow down incoming air

–        Remove distortions

•         Compressor

–        Dynamically Compress air

•         Combustor

–        Heat addition through chemical reaction

•         Turbine

–        Run the compressor

•         Nozzle/ Free Turbine

–        Generation of thrust power/shaft power

Advantages  Great power-to-weight ratio compared to reciprocating engines.

Smaller than their reciprocating counterparts of the same power. Lower emission levels

Disadvantages

Expensive: high speeds and high operating temperatures  designing and manufacturing gas turbines is a tough problem from both the engineering and materials standpoint Tend to use more fuel when they are idling

They prefer a constant rather than a fluctuating

Emissions from gas turbines vary significantly as a function of ambient temperature, load, and pollutant concentration. Combustion turbine NOx emissions as a function of load and ambient temperature for a typical gas turbine operating at a constant NOx concentration (ppmvd at 15% O2) in the exhaust.

Kane May - 9106 Quintox Upgradeable Combustion Analyser

 The Kane May Quintox has established itself as one of the most versatile instruments for flue gas measurement and emissions monitoring in the world, and now the newest model, KM9106, has many enhanced features:

- Long life oxygen sensor with 2 year warranty
- Accurate carbon monoxide sensor with hydrogen compensation
- Sensors can be retrofitted for future requirements and changes in legislation.
- Quintox measures flue and inlet temperature simultaneously
- On the spot recording with integral printer
- Operate and view combustion information with a remote handset with four line display, each of which can be configured for oxygen, carbon monoxide, efficiency, flue and net temperature, and excess air.
- Protective rugged case
- Powerful pump to draw gas sample from flue
- Store up to 1926 boiler tests with the data logging handset
- "Fireworks" Windows Software to graph the running profile of a boiler (included!)
- Outside mount water trap for easy viewing (automatic drain for continuous monitoring available as an option)
- Rugged combustion probe with detachable stainless steel shaft and 5m long neoprene hose, incorporating integral thermocouple. Optional probes available for high temperatures, smoke measurement available.
- Display reference to either ppm or mg/m3
- Over 70 different fuels are programmed into the Quintox. 

In order to account for engine-to-engine variations in performance, fuel composition, uncertainty in measurements during stack testing (and continuous monitoring), and future upgrades (e.g., increase power output at a later date), another useful strategy is to provide a safety margin to all emission rates in the initial permit application.

CleanBlade Application Data

•         Turbine model

•         Amount of actual employed detergent used

•         Temperature and amount of wash water used

•         How much is the actual product diluted

•         Ambient temperature

•         Site location: Industrial? Rural? Suburban? Seashore?

•         When was the turbine cleaned last?

•         Was the spent cleaning solution…trucked away? Discharged to a sanitary sewer system? Directly discharged?---------------------ETP PLANT

•         Performance/efficiency data, before and after cleaning

•         Performance/efficiency data of a competitive product, before and ater cleaning

•         Was the foaming that was observed during cleaning excessive?

GT Performance Influencers

•         Air humidity

•         Inlet and exhaust losses

•         Fuels

•         Fuel heating

•         Diluent injection

•         Air extraction

NEW SOURCE PERFORMANCE STANDARDS (NSPS)

In the New Source Performance Standards, it states “Operations during periods of startup, shutdown, and malfunction shall not constitute representative conditions for the purpose of a performance test, nor shall emissions in excess of the level of the applicable emission limit during periods of startup, shutdown, and malfunction be considered a violation of the applicable emission limit unless otherwise specified in the applicable standard.”

1. Use of the control strategy for this source category must be technically infeasible during startup or shutdown periods;

2. The frequency and duration of operation in startup or shutdown mode must be minimized to the maximum extent practicable;

3. As part of its justification of the SIP revision, the state should analyze the potential worst-case emissions that could occur during startup and shutdown;

4. All possible steps must be taken to minimize the impact of emissions during startup and shutdown on ambient air quality;

•         THANKS