Oil Water Separator Improves Hydraulic Oil Recovery Process at Carbon Dioxide Liquefaction Facility

Oil Skimmers, Inc. helps customer transform an expensive, time-consuming, and foul-smelling problem into a new income stream

Liquefying carbon dioxide

SAS Tank oil water separator for oily condensateA leading international company providing gases, technologies and services for industry serves more than 3 million customers and operates facilities in over 80 countries. One of their US plants is a state-of-the-art carbon dioxide liquefication plant.

This facility captures carbon dioxide emissions from a neighboring ethanol plant. They first purify the emissions, and then liquefy the carbon dioxide to meet the specifications required for the food and beverage manufacturing industry.

Liquid carbon dioxide is most commonly converted to dry ice but is also utilized in a wide variety of industries and applications.

  • Liquid carbon dioxide plays a vital role food preservation, as well as refrigeration and freezing in food processing and production. It is also key in the extraction of olive oil paste.

  • In welding processes, like in metal arc welding, it is used as a shield gas to protect the weld area from oxygen and water vapor.

  • At water treatment plants, liquid carbon dioxide is used to balance or reduce pH

  • Liquid CO2 is an important element in many fire suppression systems

  • At greenhouses, it is used to help stimulate plant growth

The role of compression in liquefying carbon dioxide

Large compressors utilize pressure and temperature to convert carbon dioxide from gas to liquid. These compressors draw in atmospheric air containing impurities and water moisture. Compression raises the pressure level and temperature of the air.

After the compression process, the hot, compressed air flows into an aftercooler to release heat created by compression. As the air cools, excess water vapor in the air condenses into liquid form. Additional condensation occurs as the air continues to cool in pipes and air-dyers.

The problem: hydraulic oil from compressors mixing with condensate

The hydraulic mechanisms which drive the compressors are lubricated, sealed, and cooled by oil. At the carbon dioxide liquefication plant, residual hydraulic oil mingles with condensate from the compressors and forms an oily water mixture. This oily water mixture is an unintended byproduct of the carbon dioxide liquefication process. But once oil mixes with water it must be dealt with in an environmentally appropriate manner. It cannot be dumped down the sewer drain because city treatment plants can be overwhelmed. As an initial, stop-gap solution, managers at the facility installed a tank to receive the oily water flow from the compressor, assuming that oil and water would separate easily; however, the reality turned out to be quite different. The process proved to be time consuming and required the oil to be removed manually. This process was inefficient and required too much labor. The end result was that the water not clean enough for reuse, while the oil contained too much water to have any value to recyclers. In all, the facility faced a situation that was time-consuming, expensive, and environmentally unacceptable. This drove the company to hire an outside firm to haul away the oil/water solution. While this was an effect solution, it turned out to be a very expensive way to get rid of mostly water.

Finding a solution: collaboration and customization

The plant’s District Manager sought more cost-effective solutions from existing equipment suppliers. One of the plant’s suppliers couldn’t offer a solution of their own, but was familiar with Oil Skimmers, Inc. oil skimmers and oil water separators, and recommended that they contact them. Subsequently, on a conference call, the plant’s facilities manager and the Oil Skimmers, Inc. engineering team discussed the challenge of dealing with the oil-water mixture from the plant’s compressors.

Implementing the solution

The plant manager informed the Oil Skimmers, Inc. engineering team that this challenge required prompt action since the plant was facing a scheduled maintenance shutdown. Oil Skimmers, Inc. engineers requested specific data parameters to help them develop a solution suited to the unique situation of the plant. After analyzing all the data and site specifications, the Oil Skimmers, Inc. team designed a SAS Tank oil water separator with an integrated Model 1H oil skimmer. A SAS Tank is an advanced design oil water separator that not only separates oil from water using coalescing media, causing oil to rise to the surface, but includes a Brill tube type oil skimmer sized for the SAS tank. The tube skimmer “actively” and continuously removes oil from the surface of the tank. Active Oil Removal™ is a feature unique to SAS Tanks making them significantly more efficient and effective than typical oil water separators.

The importance of Active Oil Removal

Oil water separators with Active Oil RemovalMost oil water separators feature passive oil removal methods like slotted pipes or overflow weirs that need to be manually adjusted to achieve proper removal of oil. When not closely monitored by maintenance personnel, an oil layer can form on the surface which can become a performance and efficiency issue in these types of separators. Oil build-up prevents oxygen from reaching the water which leads to growth of anaerobic bacteria that can emit foul odors and can lead to skin conditions for maintenance workers. Dirt and debris may also collect on the oil layer forming a sludge can potentially clog coalescing media and reduce the efficiency of the separator; as the oil layer continues to grow, it reduces the size of the separation chamber, directly effecting the separation process and overall performance of the separator.

Another issue that results from improperly set slotted pipes and weirs is that too much water can be removed with the oil. This defeats the purpose of the separator, decreases the value of recovered oil, and increases the cost of having the oil hauled away.

Active oil removal by a tube type oil skimmer with a free-floating collector tube is a 24/7 sentry guarding the performance of an oil water separator, eliminating these concerns, minimizing costs and maintenance requirements, and in general keeps the oil water separator performing at its peak efficiency.

The SAS Tank was the perfect solution for the oily water challenges at the liquefication plant, and the entire systems was designed, manufactured, delivered and installed before the scheduled shutdown.

The results: new income stream and 6-month ROI

The installation of the SAS Tank oil water separator has eliminated a problem that formerly drained employee time as well as money from the facility’s operation. The Oil Skimmers, Inc. equipment so successfully separates oil and water in the plant that they now sell back oil-free water to the neighboring ethanol plant. Plus, they can now re-use the oil in their facility. The District Manager for the plant enthusiastically told Oil Skimmers, Inc. that they achieved full ROI on their equipment within six months.

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