Electric Heaters in Fuel Gas conditioning focusing on Al-Shaheen Field

EXHEAT using its knowledge and expertise in the design and manufacture of electric process heating equipment, has been successful in winning a number of orders for the Maersk Al-Shaheen offshore installation. Custom designed products were incorporated including but not limited to Fuel Gas Conditioning Systems, Dehydration Systems and Tail Gas Treating Units.

EXHEAT specializes in manufacturing Electric Heaters for use in Zone 1 and Zone 2 Hazardous Areas with accompanying certification such as ATEX, IECx, CSA, and NEC amongst others.

EXHEAT Heating Design Solutions at Al-Shaheen are:

• 2,620kW Fuel Gas Super Heater and Control Panels
• 1,070kW Condensate Heater and Control Panels
• 2,400kW Glycol Heater and Control Panels
• 1,232kW of Tail Gas Heater and Control Panels

Overview and EXHEAT Contribution
Fuel Gas Conditioning System:
High Pressure Gas is normally available from an HP Gas Compression System. The HP gas is cooled in the fuel gas cooler and then throttles to a fuel pressure that covers requirements of the gas compressor turbine. The cooled and throttled gas is then routed to the fuel gas KO drum where gas and liquid are separated; the KO drum also provides buffer volume during compressor start up. Gas from the KO drum is filtered in the fuel gas filters and finally super heated before leaving the package. The filtered and super heated gas is then routed to various consumers via a distribution system. EXHEAT supplied custom designed 1,050kW fuel gas super heaters and has recently won business for the supply of 1,570kW fuel gas super heaters which are yet to be installed in the service.

Condensate from the KO drum is super heated, and throttled under level control before leaving the skid. The condensate is in liquid form and the flux density requirement to heat the condensate is very critical. EXHEAT specializes in designing such heaters, and EXHEAT supplied 280kW condensate heaters and has recently won business for 790kW condensate heaters which are yet to be installed in the service.

Fuel Gas Dehydration: Glycol Regeneration
Glycol Dehydration is a liquid dessicant system for the removal of water from natural gas and natural gas liquids (NGL). Lean, water-free glycol (purity >99%) is fed to the top of an absorber where it is combined with the wet natural gas stream. The glycol removes water from the natural gas by physical absorption and is carried out at the bottom of the column. Upon exiting the absorber the glycol stream is often referred to as "rich glycol". The dry natural gas leaves the top of the absorption column and is fed either to a pipeline system or to a gas plant.

After leaving the absorber, the rich glycol is fed to a flash vessel where hydrocarbon vapors are removed and any liquid hydrocarbons are skimmed from the glycol. Due to the composition of the rich glycol, a vapor phase will form when the pressure is lowered leaving a high hydrocarbon content. After leaving the flash vessel, the rich glycol is heated using an electric heater and fed to the stripper (also known as a regenerator). EXHEAT is recognized as one of the world leaders in the design and manufacture of electric process heaters for glycol regeneration and associated thyristor control systems, and has won orders to supply 2,400kW glycol heating solutions for this project.

Tail Gas Treatment:
The raw natural gas is pipelined to a gas processing plant where the initial purification is usually the removal of acid gases (hydrogen sulfide and carbon dioxide). There are many processes but amine treating is the most widely used process. In the last ten years, a new process based on the use of polymeric membranes to dehydrate and separate the carbon dioxide and hydrogen sulfide from the natural gas stream is gaining acceptance.

The acid gases removed by amine treating are then routed into a sulfur recovery unit which converts the hydrogen sulfide in the acid gas into elemental sulfur. The residual gas from is commonly called tail gas and that gas is then processed in a tail gas treating unit (TGTU), when it is super heated to recover and recycle residual sulfur-containing compounds. EXHEAT has developed electric process heaters specially suitable for this service and have won orders to supply 1232kW tail gas heating on this project.