FUEL GAS CONDITIONING SOLUTIONS
Engineering Technology, Inc. (ETI) provides a complete line of engine and turbine fuel gas conditioning equipment. These items are available as individual components or assembled complete. Skids for simple cycle or combined cycle applications can be packaged complete with all interconnecting piping, valves and instrumentation.
REASONS FOR FUEL GAS CONDITIONING
Engine and/or turbine manufacturers may impose certain criteria on the gas to be utilized as fuel. These criteria serve as the basis for minimum quality standards, insuring that output, efficiency, emissions guarantees and service life are met.
Often fuel gas requirements can be can categorized in the following areas as listed:
1. Heating Value - The acceptable range of calorific values (BTU content) for the turbine gas. A sample of the gas analyzed by a chromatograph will tell the heating value of the gas at the time of the sample. This sample is analyzed for components in accordance with recognized standards such as ASTM D1945.
2. Contaminants - The type and acceptable level of contaminants is established for the turbine fuel gas. Several types of contaminants include:
- Water - The amount of water allowable in the gas stream. This is usually measured as pounds of water per MMscf. Water is often measured with a dew point analyzer. The amount of water present in the gas determines the water dew point of the gas stream. The water dew point for a given quantity of water in the gas stream varies with the operating pressure and consequently is expressed at a given pressure.
- Hydrocarbons - The amount, if any, of liquid hydrocarbons allowable in the gas stream. This is usually expressed as a hydrocarbon dew point. Hydrocarbon dew point can be measured via a sample of gas taken into a dew point analyzer or can be calculated from a sample of gas taken and analyzed for components through C14. An industry standard for this analysis is GPA 2286. This extended analysis differs from the standard analysis for caloric value, in that heavier components through C14 are identified individually and not lumped together as C6+. The hydrocarbon dew point for a gas stream varies with the operating pressure and consequently, hydrocarbon dew point is expressed at a given pressure.
- Rust/Oxides - These items are products of equipment and piping fabrication, installation and testing.
- Iron Sulfide - Iron sulfide is present as a result of sulfur present in the fuel gas.
- Lubricating Oil - Lubricating oil can be introduced into the fuel gas by valves and compressors located upstream of the turbine, including those associated with natural gas pipeline booster stations and natural gas storage facilities.
- Glycol - Glycol is widely utilized throughout the natural gas production, transportation and storage industry because of its hydrophilic properties. Triethylene glycol (TEG), ethylene glycol (EG) and less frequently propylene glycol (PG) are used to remove water from gas streams. Common equipment/processing specifications allow 1/10 of a gallon carryover of glycol per MMscf of gas processed.
3. Fuel Gas Pressure - Controlled fuel gas pressure is critical to proper turbine operation. Two area of concern include:
- Pressure Regulation - Fuel gas is often transported or stored at pressures other than that which is required by the turbine. Often compressors are required to boost the pressure or pressure regulation valves (PRV) are required to reduce the pressure.
- Rate of Change - The rate at which pressure varies is called pressure excursion. Turbine manufacturers often limit this rate of change, or excursion, to promote smooth operation and eliminate spikes or voids in the operating profile.
4. Fuel Gas Temperature - Temperature is a critical component of turbine fuel gas conditioning equipment. Temperature affects several aspects of fuel gas.
- Limits - There are normally minimum and maximum temperature restrictions imposed on the fuel gas depending on the type of turbine and its application.
- Superheat - To superheat fuel gas is to heat a fuel gas (not in contact with its own liquid) so as to cause it to remain free from suspended liquid droplets. Superheat is applied to prevent the formation of liquid droplets in subsequent equipment, such as piping and or pressure reduction valves and regulators.
- Performance Heat - Performance heating of the turbine fuel gas often requires adding additional heat to the gas above that which is required to meet the superheat requirements. Performance heat added to the fuel gas improves the efficiency of the overall power plant operation. Performance heating is often associated with combined cycle operation.
- Rate of Change - The rate of change of the heating of the fuel gas is critical to proper operation. Failure of the heating system to react to changes in fuel demand results in temperature spikes and plant upsets and inefficiencies.
EQUIPMENT PROVIDED BY ETI FOR FUEL GAS CONDITIONING
- LIQUID KNOCKOUTS/VANE SEPARATORS
- FILTER SEPARATORS
- FUEL GAS METERING SKIDS
- PRESSURE REGULATION SKIDS
- PIPELINE WATER BATH HEATERS
- DEW POINT HEATERS
- START-UP HEATERS
- PERFORMANCE HEATING SKIDS
- CYCLONE SEPARATORS
- DRAINS TANKS
- SIMPLE CYCLE FUEL GAS MODULES
- COMBINED CYCLE FUEL GAS MODULES
- JOULE-THOMPSON TREATMENT SKIDS