Natural Gas Compression

Methane is a colorless, odorless, tasteless, flammable gas. It is the first member of the paraffin (aliphatic or saturated) series of hydrocarbons. It is the major constituent of natural gas. Methane is soluble in alcohol or ether, and slightly soluble in water. Methane is shipped as a nonliquefied compressed gas in cylinders at pressures up to 6000 psig at 70oF (41 370 kPa at 21.1oC). Liquefied methane (as natural gas-LNG) is shipped in bulk quantities as a cryogenic liquid on barges and tankers. Methane is a major constituent of coal gas and is present to an extent in air in coal mines.

Methane is typically available for commercial and industrial purposes in a C.P. Grade (minimum purity of 99 mole percent), a technical grade (minimum purity of 98.0 mole percent), and a commercial grade that is actually natural gas as it is received from the pipeline. (There is no guaranteed purity, but methane content usually runs about 93 percent or better.)  Tertiary-butyl mercaptan is added in trace amounts as an odorant. This grade of gas has a sulfur content of 0.002 grains/100 ft3 (0.0457mg/m3) and a typical gross heating value of 1044 Btu/ft3 (38 898 kJ/m3).

Methane is produced commercially from natural gas by absorption or adsorption methods of purification; supercooling and distillation are sometimes employed to secure methane of very high purity. Some California natural gas wells produce methane of high purity. It can also be obtained by cracking petroleum fractions. 

Safety, Storage and Handling:

Methane is generally considered nontoxic. Exposures to concentrations of up to 9 percent methane have been reported without apparent ill effects; inhalation of higher concentrations eventually causes a feeling of pressure on the forehead and eyes, but the sensation ends after returning to fresh air. Methane is a simple asphyxiant.

Methane is noncorrosive and may be contained by any common, commercially available metals, with the exception of cryogenic liquid applications. Handling equipment must, however, be designed to safely withstand the temperatures and pressures to be encountered. At the temperature of liquid methane, ordinary carbon steels and most alloy steels lose their ductility and are considered unsafe for liquid methane service. Satisfactory materials for use with liquid methane include Type 18-8 stainless steel and other austenitic nickel-chromium alloys, copper, Monel, brass and aluminum.

Methane poses hazards to personnel through its flammability. All the precautions necessary for the safe handling of any flammable compressed gas must be observed in working with methane. Any shipping mode or regulation applicable for methane may also apply for natural gas. It is important that ignition sources be kept away from containers, including situations when leakage could cause the gas to be ignited by such sources as a spark from a motor. All piping and equipment used with methane should be grounded. Methane should not be stored with cylinders containing oxygen, chlorine, or other oxidizing or combustible materials.

Storage and use areas should be monitored for leakage of methane, since methane (unless odorized) may not give adequate warning of its dangerous presence in the atmosphere. It is lighter than air and presents hazards similar to hydrogen with regard to its ignitability. In the absence of appropriate monitors, localized leaks may be difficult to detect unless the gas is odorized. Therefore, periodic checks should be made of connections and joints, flanges, and components subject to leakage. Sensitive instrumental detectors are available. Alternatively, leak detection solutions will indicate leakage through bubble formation. Caution: Eliminate all sources of ignition until leaks have been repaired. Once a leak is found, shut off the source of gas and lower the pressure in the system to minimize the leak. After the leak has been repaired, the system should be leak tested prior to use. If uncontrolled leakage is encountered that cannot be stopped by shutting off the closest appropriate valve or main supply valve (without risk), implement a plan for evacuation and quickly contact a local fire department. 

If a methane fire should occur, shut off the gas source if this can be done without risk. If the source cannot be shut off, let the fire burn itself out while making sure that gas storage receptacles and piping containing gas in close proximity, as well as combustible materials in the area, are kept cool by spraying with water. The local fire department should be called. Only personnel specifically trained and wearing appropriate PPE should be permitted to work at the fire scene.

• Inhalation: Inhalation of low concentrations can be remedied by promptly going to an uncontaminated area and inhaling fresh air or oxygen. In the event of a massive exposure wherein the victim has become unconscious or symptoms of asphyxiation are present, the person should be removed promptly to an uncontaminated atmosphere and given artificial respiration if breathing has stopped. This should be followed by administering oxygen after breathing has been restored.
• Skin Contact: Skin contact of liquid methane can result in frostbite. First aid treatment for frostbite consists of putting the frostbitten part in warm water, 100oF to 105oF (37.8oC to 40.6oC). If warm water is not available or is impractical to use, wrap the affected area gently in blankets. Encourage the victim to exercise the affected part while it is being warmed. This will aid circulation to re-establish itself naturally. Medical attention by a physician should be obtained.
• Eye Contact: In the event of eye contact with liquid methane, flush with tap water for 15 minutes. If irritation persists, the patient should be referred to a physician. 

Disposal of methane, as with other gases, should be undertaken only by personnel familiar with the gas and the procedures for disposal. Contact the supplier for instructions. In general, the best procedure for disposal of flammable gases, including methane, is to burn the gas if a burning unit is available in the plant. Disposal of methane by incineration or by other means may be subject to permitting by federal, state or provincial regulations. Persons involved with disposal of methane gas should check with the environment authorities having jurisdiction to determine the applicability of permitting regulations to disposal activities.

Uses:

Natural gas, which is mostly methane, is widely used as a fuel. In the chemical industry, methane is used heavily as a raw material for making important products that include acetylene, ammonia, ethanol, and methanol; its chlorination also yields carbon tetrachloride, chloroform, methyl chloride, and methylene chloride. It is used to produce carbon black for use in the manufacture of rubber products and printing inks. The burning of high-purity methane is used to make carbon black of special quality for electronic devices. In recent years compressed natural gas (CNG), at pressures between 3000 psig (20 680 kPa) and 3600 psig (24 820 kPa), has seen increased use in vehicles as an alternative fuel.

Reference the table below for common industries and applications using Natural Gas