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MSR OIL WATER SEPARATORS FOR CHEMICAL PLANTS
MSR Coalescing plate separators are one of the best ways to separate two non-mixing liquids. Almost any hydrocarbon oil and most non-hydrocarbon oils such as corn, orange, or other vegetable oils may be separated from water very satisfactorily. The MSR separator is an enhanced gravity separation system for removing oil droplets from water. The design utilizes the difference in specific gravities between the oil and the water to perform the separation. MSR has many years experience in designing systems for varying applications. Please contact MSR to discuss all of your separation needs for process improvement or effluent control.
 Coalescing plate separators can be used to:
- Separate oil from wastewater as an industrial pretreatment system prior to directing the water to sewer or other disposal.
- Separate oil from circulating water or other aqueous phase systems to remove the oils so that the stream can more economically be reused or so that the oil in the water stream does not cause problems elsewhere in the system by fouling heat exchangers or catalysts.
- Separate oil from water or water from oil so that either the oil or water or both may be purified and reused or recycled. It is also possible to separate a mixed oil and water stream to both remove the oil from water to low concentrations and remove the water from the oil to low concentrations in a single system.
Industrial pretreatment of waste streams prior to disposal to sanitary sewer systems:
When the choice exists of either discharging wastewater effluent into a lake or stream, or to the sanitary sewer, the best choice is often the sanitary sewer. This is because the outlet oil concentration requirements are usually less stringent. Sanitary sewer plant operators usually require that any plant wastewater streams meet certain required characteristics - or be pretreated to meet those requirements.
The requirements for pretreatment may in certain instances be very stringent, but usually range from 50 mg/l of oil to about 150 mg/l. These treatment levels are readily achieved by the use of MSR's technology.
Pretreatment systems can be any size or configuration, but are generally relatively small in chemical plants because plants try to minimize their waste streams. MSR Pretreatment Systems are designed to handle either gravity or pumped flow on a single-pass or re-circulating basis. The separator vessel is usually constructed of carbon steel, provided with a special corrosion resistant coating both internally and externally. Systems are also available in stainless steel, aluminum or corrosion resistant plastic and may also be used in existing tanks or concrete pits.
CASE HISTORY:
The following is a case history of one pretreatment system MSR recently designed for a chemical company in Texas:
The facility is a large surfactant (surface active agent) plant belonging to a major international chemical company. The plant had a relatively simple oil interception system consisting of a couple of small concrete lined pits with a skimming device and underflow/overflow system.
The effluent hydrocarbon content was often over the requirements of the local sanitary sewer authority and the sewer authorities were becoming impatient.
MSR reviewed the existing system and discussed the various aspects of the design with local plant engineers and chemists. We determined that the presence of the surfactants (everywhere in the plant and process) would cause the hydrocarbons to be present as very small and therefore difficult to remove droplet sizes. After further consultation with the plant personnel concerning other operating parameters, MSR designed a special separator to meet the plant's needs using our coalescing plates molded in polyoxymethylene plastic to meet the compatibility requirements of the service. We also provided an integral oil holding tank with high and low level switches and an oil discharge pump (vertical centrifugal type). The drawing below shows the final design flow scheme.
Aqueous phase with hydrocarbons enters the system from the main process through the inlet nozzle into the preseparation chamber. This chamber is separated from the main separator by an inlet baffle. Most of the entering aqueous phase flows under the baffle and into the inlet chamber. The inlet baffle is provided with holes to allow any free oil that enters with the inlet flow to pass across to the inlet chamber where a high-capacity oil skimmer is located. This skimmer is adjustable so that it will skim the captured oil off of the top of the aqueous phase to the oil holding tank.
After the inlet chamber, the water passes through the coalescing plates where most of the small oil droplets are removed. The droplets are captured on the plates, coalesce to form large drops, and the drops migrate upward to the surface of the separator. Downstream of the coalescing plates a second skimmer helps remove the oil layer.
The cleaned water then passes under the oil dam and exits the separator through an adjustable water weir and clearwell. After the separator, the water is directed to the sanitary sewer through the previously installed effluent system.
Hydrocarbons captured in the system are skimmed to the oil tank and automatically pumped to a separate oil holding tank.
The photo below shows this unit during field assembly.
OPERATING RESULTS:
After the system was installed and operations started, it was discovered that, in addition to the light hydrocarbon the system was designed to capture, there was also some hydrocarbon heavier than water present. It appears that the heavy hydrocarbon may appear in the separator when a process upset happens upstream. The separator successfully captured large quantities of this heavy hydrocarbon in addition to the light hydrocarbon. A separate detection system was subsequently installed to detect the presence of the heavy hydrocarbon so that it can be removed.
 While it is extremely difficult to separate oil in the presence of surfactants, this special design has operated very satisfactorily consistently producing water effluent quality that meets the local sanitary sewer authority requirements. And - the heavy hydrocarbon recovered is a salable product. The plant has recovered over 3000 gallons of product using this separator - a very profitable though unexpected effect of installing the system. The chart below shows some of the analyses done to prove the effectiveness of the system.
Plant Process Improvement
There are dozens of places in any chemical plant where it is necessary to separate aqueous and hydrocarbon streams. These have often been mixed intentionally to facilitate a chemical reaction or may result from water phases condensing within the process. Rain water may also enter the tops of storage tanks and migrate to the bottom of the hydrocarbon phases.
MSR Coalescing systems can be used almost anywhere there are two non-mixing phases to be separated and can improve process operations and increase recovery of valuable products. MSR designs have many advantages:
- May be installed in existing vessels, tanks, concrete pits or other housings.
- Can be used in either atmospheric tanks or pressure vessels.
- Possible flow rates are almost unlimited. MSR engineers have designed systems up to 20,000 US gpm flow rates.
- They have relatively wide spaced plates which do not plug easily like coalescing cartridges.
- No absorbents to be used up and require disposal.
- They are suitable for installation in systems where some surface active agents such as soaps or detergents are present. Note: coalescing plate separators are not suitable for all such systems and special designs are necessary. Please consult MSR if you have a system of this type and would like suggestions on design.
- Unlike cartridge type coalescers, coalescing plate separators can recover from large amounts of surfactants which would require replacement of cartridge type coalescers.
The photo below shows the internals of a plant test unit - designed to test the operations of the coalescing plates under extreme operating conditions.
Please contact MSR to discuss all of your separation needs for process improvement or effluent control.
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