A major energy company with off-shore operations in the Gulf of Mexico was drawing gas from a pipeline to fuel turbines at a topside facility. The gas at 800 PSI and 70°F was saturated with water. To prevent condensation in the pipeline, the gas had been treated with methanol, but as the pressure of the fuel gas was regulated downward for use in the turbines, it could no longer inhibit condensation, and freeze-ups were occurring.

The energy company approached Van Air Systems for a solution. Van Air engineers quickly determined that the saturated fuel gas, which contained nearly 30 pounds of water per MMCF, could be dried to 3.7 pounds per MMSCF using a combination of the deliquescent desiccants Dry-O-Lite and 10BF. This moisture content would allow the pressure regulation of the fuel gas to proceed without freeze-ups while supplying the turbines with low-humidity fuel.

Van Air technical staff worked closely with the energy company to design and manufacture a dehydration system that could withstand harsh off-shore operating conditions. This included coating the system with epoxy paint to resist corrosion. Among other special features, the Van Air dehydration system, which requires no outside electricity or power, allows for remote monitoring of desiccant levels. The system is also specially sized so that desiccant replenishment cycles match the interval between regular visits of maintenance personnel. This feature eliminates costly, unscheduled trips to the platform.

Case Study – Single Tower Dryers for Well-head Dehydration

An independent energy exploration and production company drilled multiple natural gas wells in southwestern Pennsylvania, installing conventional horizontal and vertical separator units on the new wells to protect against fluid problems. Many of the wells were also equipped with line heaters or catalytic heaters which required steady upkeep and constant attention.

Still, when production began, water and water vapor in the gas prompted costly freeze-ups, well shut-downs, and metering malfunctions. The company contacted Van Air, explaining that on a typical well, gas flowed at 2 million cubic feet per day at a pressure of 350 PSIG and a temperature of 60°F with a water vapor content of more than 40 pounds per million cubic feet. To avoid hefty fines from its customer, the company needed to deliver gas at 7 pounds per million cubic feet. Van Air recommended the installation of a PLD dryer using the high-performance deliquescent desiccant 10BF.

The PLD is a single vessel that does not require any external source of heat or power. Gas from the wellhead enters a large chamber in the lower portion of the vessel where free liquids are separated by gravity and drop into a claim area. The gas flows upward through a bed of desiccant tablets, which are an inert and non-toxic compound. The tablets absorb moisture from the gas, gradually dissolve, and drop into the claim area. Finally dry gas exits the vessel.

The energy company ordered a demonstration PLD to be placed on one well. Van Air promptly delivered the dryer from stock, and the unit was quickly placed into service. Soon the energy company sampled gas at the dryer outlet and discovered a water vapor content slightly above 5 pounds per million cubic feet, comfortably satisfying the customer's requirement.

The energy company subsequently installed PLDs on 68 additional wells, eliminating the need for separators, alcohol bottles, line heaters, catalytic heaters, and pot drips. Operating costs have been cut in half, and a well tender can now handle twice as many wells. Most importantly, expensive line freeze-ups and fines for putting wet gas into the pipeline have been eliminated.

Case Study - Coalescing Pre-filters Eliminate Oil Contamination of TEG Dehydrators

A midstream gas company in Wyoming's Powder River basin operated five compressor stations, each handling 25 million cubic feet per day of coalbed methane. Aging reciprocating gas compressors were depositing approximately 10 gallons per day of lubricating oil into the gas stream at each compressor station. Downstream of the compressors, triethylene glycol (TEG) dehydrators were being contaminated with oil. The diminished TEG purity meant that the dehydrators could not meet contract dew points, especially on hot summer days.

To solve the problem, the midstream company ordered Van Air GF102 coalescing filters. GF102 filters feature a large sump area for liquid separation. Van Air filter elements are constructed of wrapped borosilicate glass and supported with stainless steel cores for superior crush resistance. Element efficiencies down to .01 micron are available.

The company ordered five GF102 filters in the early spring. With hot weather quickly approaching, it was vital that the filters be delivered by the start of the summer. Van Air delivered the filters in 8 weeks, complete with factory installed dump valves and controls allowing for quick installation in the field.

With the GF102 filters in place, the company reported at the end of the summer that contract dew points were reliably met and that oil contamination of its dehydrators had been virtually eliminated.