Molecular Sieve Units

The basic function of a Molecular Sieve Unit is to remove water vapor from natural gas. A mole sieve unit is a solid desiccant dehydration system, which possesses the physical characteristics to adsorb water from natural gas and produces the lowest water dewpoint temperatures.

QBJ Molecular Sieve Dehydration units provide an effective means to remove water vapor from a natural gas and other water rich streams. These units are capable of achieving cryogenic temperatures (-150°F and less) in natural gas processing requires the inlet gas to be free of water vapor. High water vapor can freeze at low temperature forming hydrates, and these hydrates can be problematic in a cryogenic process. Use of a molecular sieve is an effective method to solve this issue.

The mol sieve design usually consists of a silicate compound containing very small pores of precise uniform size. The spaces between the silicate molecules act as a “trap” for the water vapor as it passes through the silicate bed.

The QBJ basic design consists of two or more mol sieve adsorbers. In a simple two-unit design, one adsorber operates in the adsorption (dehydration) mode while the other adsorber is in the regeneration mode. Switching from dehydration to regeneration is done by use of automatic switching valves. As the dehydrated adsorber becomes saturated with water vapor, it is automatically switched to regeneration mode while the regeneration adsorber becomes active in dehydration mode.

For the regeneration cycle, the regeneration gas (a 10% to 20% side stream) is heated up to 550 ˚F and is sent to the adsorber to be regenerated to absorb the water from the saturated molecular sieves bed. As the saturated regeneration gas leaves the top of the adsorber, it is cooled in a condenser and then separated in the regeneration gas separator.

The regeneration gas is normally then boosted to inlet pressure via centrifugal compressor and mixed with the inlet gas stream.

Standard molecular sieve applications:

  • Upstream of NGL extraction plants
  • Upstream of cryogenic gas plants
  • Upstream of an LNG plant


QBJ has designed, engineered, and manufactured molecular sieve units for 30 years and has installed units to dehydrate up to 200 MMSCFD. We have produced units designed for both domestic and international standards.

QBJ Molecular Sieve Units job site installations