Production equipment is located in remote gas or oil fields on a single well or a multiple well location. Production and dehydration equipment removes free liquids (hydrocarbon, water, paraffin, etc.) from the gas stream utilizing mainly TEG glycol, due to its affinity with water vapor. The gas flows at low pressure (less than 150 psi) into a centralized site where it is compressed to a higher pressure and free liquids are separated. Compression creates a higher pressure, making dehydration economical and functionally achievable. The process is like squeezing a water-soaked sponge: the higher pressure you put on a gas stream through a compression process, the more water/condensate fallout occurs. Without this process at the well, these liquids fall out in the gathering system.
When the gas is dehydrated, it flows without obstruction and does not damage the gathering system. Liquids take up space in a pipeline, water will freeze, hydrocarbon and water mixed will create hydrates that freeze, water mixed with CO2 in a pipeline creates carbonic acid which corrodes the pipeline—and the list goes on. The production and dehydrator units are the first line of defense for protecting the pipeline in a gas gathering system and allowing the gas to flow freely.
During the dehydration process, harmful VOC and BTEX emissions are created. Historically, vapors from the glycol regeneration systems, a major component of the dehydration unit, have been vented to the atmosphere. These vapors contain hydrocarbon compounds that are becoming increasingly regulated by Federal, State, and local agencies.
The quick solution to the emissions control challenge would be to discontinue use of all dehydrators in the field and flow the gas at the lower pressures through a wet gas gathering system to a large process or CO2 removal plant where it can be compressed, dehydrated, and emissions can be destroyed. This has been tried in certain areas with very little success due to the remoteness of the well sites and the many miles of gathering system along difficult terrain. In addition, once the gas reaches the plant, most plants are not equipped to handle this volume of water and hydrocarbon.
There have been many attempts at solving the BTEX emissions problem. One method involves the use of condensers alone, without a dehydrator. The problems created with this technique is that the condensers alone require a constant condenser outlet temperature of 160° F or less to maintain the liquid fall-out required for the hydrocarbons. These did not reach the required efficiency of a constant 98% destruction.
Because these methods were ineffective at achieving the required goal, it was necessary that dehydration unit emissions destruction flares be designed. The design required giving consideration to the gas compositions cycling through the dehydration unit, the emissions composition, the flow rate of the emissions, and any other variables that affect the total system.