INDIRECT ELECTRIC HEATER

An indirect electric heater has its heating elements encased in a secondary sheath. As mention in our electric immersion heater section, they are also found in Glycol Reboiler in Natural Gas dehydration plant. An indirect electric heater is commonly used as the heat source in a Glycol Reboiler.

Other application of indirect heating includes the heating of molten sulfur in reactors. These heaters are utilized in the melting and vaporizing sulfur for other chemical processes.

The advantage of an indirect heater is the ability to replace the element without draining the process since the heating element is not in direct contact with the process being heated.

Indirect heaters are often specified when

· Due to safety or corrosion issue, the process demands that the heaters element do not come in direct contact with the heating element. One application is the use of indirect heater in the heating of sulfur.

· Heater elements can be replaced without disturbing the process.

· Special metallurgy is required and the heater elements are not available in that material.

Glycol Reboiler - In gas processing plant, a Glycol Dehydration Unit (GDU) is commonly employed to dehydrate (dry) natural gas before it is compressed or distributed. A typically dehydrated pipeline gas would contain around 7 lbs of water per million standard cubic foot of gas.

In the GDU, wet natural gas is flowed through a glycol contactor tower. This glycol such as Triethylene Glycol (TEG) has an affinity for water. As the gas comes in contact with the glycol, the glycol will absorbed the water from the natural gas. Some means of scrubbing is provided at the discharge of the tower to minimize glycol carry over as the dehydrated gas leaves the tower.

The rich glycol (saturated with water) is then routed to the Glycol Reboiler. In the reboiler, electric heating or other means of indirect gas fired heater is utilized to heat up the rich glycol. The rich glycol temperature is raised above the boiling point of water but below the boiling point of glycol. Since glycol boils at a slightly higher temperature than water, the water will vaporize leaving behind the lean glycol. This lean glycol is then pumped back into the tower to complete another cycle.