Raw natural gas usually contains various contaminants which mainly consist of acid gases (CO2, H2S, etc.), water, other gases (nitrogen, helium) and mercury. In this particular process, raw gas was first fed into a three-phase separator, where gas was separated into sour gas, condensate, and water condensate respectively. After proper filtration treatment, the condensate was then sent to a condensate stabilization plant and then was fractionated into sales LPG/gasoline. The water was purified with proper treatments in a water treatment plant, meanwhile, sent to a stripper to recover hydrocarbon carried over.
Sour gas first flows through an amine absorber where CO2, H2S are removed by lean amine. Rich amine then flows into a regeneration column, where acid gases are released into a claus unit and the lean amine is regenerated and recycled. Following the amine absorber, there is a dehydration unit where sweet gas is dehydrated by using MEG. Dry gas is then sent through a chiller to a fractionation column where condensates are sent to fractionation plant, and sales gas will be transferred through transmission plant. Meanwhile, rich MEG needs to be regenerated by a stripping column. However, rich MEG contains traces amount of rust, dust and solid particles and must be removed prior to the Stripper column, otherwise, it will cause corrosion of re-boiler.
After evaluating this process and reviewing the spec sheet provided by the client, Pentair recommended and provided a particle separator; ProcessOR and an AdsorbOR which were sized to fit the application. As indicated in the process flow diagram on the PDF version, a pre-filter with 25um rating is applied to remove large particles to protect Activated Carbon bed (AC bed), which is for removing color and odors in lean amine. A 10 um rating PrecessOR is positioned after the AC bed to remove active carbon powder carried over if any.
Pentair assisted a 155,000 bpd Midwest refiner, who was experiencing fouling challenges associated with two vertical style heat exchangers on their Platformer (i.e. Platinum Reformer) Unit.
A gas producer in Southeastern Wyoming has recently completed their evaluation of our ProcessOR® particle rental skids for removing particulate contaminants on both produced water and condensate.
A gas processing facility in Western Colorado was having challenges with building differential pressure across a cold box heat exchanger on the inlet to their cryogenic plant. The plant processes 450 MMSCFD of gas through a dehydration unit prior to feeding their cryo plant. The plant utilizes Pentair separation equipment to remove desiccant fines downstream of a molecular sieve. The plant contacted Pentair field services when they started to see appreciable differential pressure building on their cold box. Pentair field services were on-site to complete a plant survey and troubleshoot the process in order to determine the cause of the fouling.
Pentair Field Services along with plant personnel conducted a thorough inspection of the dust filter. The inspection included review of vessel preparation and commissioning procedures. The inspection revealed that the presence of liquid and solid contaminant on the downstream side of the vessel. Samples on the downstream side were captured using a boroscope submitted to Star Laboratories. Since this material was downstream of the filter it was not clear whether the contaminant was passing through the filter or if it had been introduced from another source. Pentair’s Star Laboratories used our SEM or scanning electron microscope to identify the elemental composition of the contaminants downstream of the dust filter as depicted.
The analysis revealed that the contaminant in question was made up of desiccant fines less than 0.4 micron in diameter that had been agglomerated into a paste with hydrocarbon present on the downstream side of the vessel. As a result of the field visit Pentair and the plant have done the following:
• Pentair worked with the plant to revise their vessel preparation procedure to prevent liquid from getting into the vessel as it would appear the presence of hydrocarbon and submicron particulates is causing the differential pressure on the cold box heat exchanger.
• Pentair also conducted training for the plant’s operations and maintenance crews for changing out elements to assure a positive seal is maintained.
• Prior to leaving the site we conducted online gravimetric testing downstream of the dust filter to assure that there were no solids carrying over downstream of the dust filter.
Upon completion of our inspection and recommendations, the plant has not experienced heat exchanger fouling. We continue to keep in close contact with the plant regarding element change out and differential pressure monitoring.
A refiner in the Midwest was faced with expensive catalyst bed “clean-out” shutdowns and fouling heat exchangers on a light oil process treating an aromatic feed stream. This 2,500 BPD stream, consisting of Benzene, Xylene and Toluene, was elevated in temperature to 200 degrees F (80 psig) before being fed to their tower.