Radiowave-based process recovers oil from sludge at Texas site

A new process that uses RF technology to break difficult emulsions in petroleum wastes and recover valuable oil is housed in a trailer. Aradio frequency (RF)-based sludge treatment process is proving successful in demonstration tests at a Texas site. The process separates petroleum-based sludges into salable oil, treatment-quality water, and disposable solids. The system, called MST-4000, is effective on most sludges, including: dissolved-air-flotation float, slop oil emulsion solids, heat

Dec. 2, 1996

4 min read

A new process that uses RF technology to break difficult emulsions in petroleum wastes and recover valuable oil is housed in a trailer.

Aradio frequency (RF)-based sludge treatment process is proving successful in demonstration tests at a Texas site.

The process separates petroleum-based sludges into salable oil, treatment-quality water, and disposable solids.

The system, called MST-4000, is effective on most sludges, including: dissolved-air-flotation float, slop oil emulsion solids, heat exchanger cleaning sludge, API separator sludge, and leaded tank bottoms.

The MST-4000 unit, designed and operated by Imperial Petroleum Recovery Corp., Alexandria, Va., is exceeding expectations, in terms of both performance and volume throughput, the developer says.

The unit

Imperial's MST-4000 unit is housed in a 48-ft air-ride trailer (photo). It is designed to process 4,000 b/d of sludge feed.

Major components of the system include:

Four high-power RF/ microwave transmitters
Four high-power RF/ microwave illuminators, which focus the energy on the sludge in a small, cylindrical "reactor"
Four computer-controlled, automatic RF tuners, which improve the quality of the RF/sludge interface by monitoring and adjusting vector impedance
A wave guide, which channels and controls the RF signals from the transmitters through the tuners and to the illuminators
A specially designed instrumentation and control system
Plumbing and piping systems.

The RF technology used in the unit was developed in cooperation with Phonon Technologies Inc., Houston. Imperial purchased the assets of Phonon earlier this year.

The process

The trailer houses the RF separation equipment and supplies compressed air for the pumps and chilled water for cooling the transmitter. Sludge feed comes from a 500-bbl stirred, heated tank. Typical feed temperature is 80-150° F.

The RF energy breaks the emulsion by differentially heating the water inside the oil matrix. This facilitates separation by creating differences in surface tension and density.

A flow diagram of the process is shown in Fig. 1 [21503 bytes].

The unit contains four treaters which normally are run as two parallel trains of two units each. For sludges that are difficult to separate, the four units can be operated in series. Each of the four units processes as much as 1,000 b/d of sludge.

The process effluent exits the unit at 135-155° F. A centrifuge, also outside the trailer, separates the broken emulsion into oil, water, and solids. The rag layer is recycled through the system.

The solids have a low enough oil content that they can be landfilled, says Brent Kartchner, executive vice-president of Imperial.

Test run

Imperial is testing the unit on a number of sludges at a Crosby, Tex., site near Houston. During the tests, the unit is processing several batches of varying quality.

Current tests involve oil field production sludge. The sludge producer processed this batch thermally, leaving what was thought to be an unprocessable emulsion.

The sludge contains about 70% water, 20% oil, and 10% solids, making it extremely difficult to process. (Sludges that have not been processed by some other means typically have an oil content of 80-90%.)

The unit is recovering 98-99% of the available hydrocarbons from the sludge, says Kartchner. The recovered oil is what Imperial calls "pipeline quality," with some oil as pure as 99.9% and can be refined without further treatment.

This feed is the third to be processed through the unit since it was installed at the site. Throughput, at times, has exceeded 4,000 b/d, according to Kartchner.

Imperial has found that the separation occurs so fast that the sediment falls out in the exit lines. For this reason, the company is planning to shorten the distance from the MST-4000 outlet to the centrifuge inlet. This, says Kartchner, should improve separation.

Imperial estimates that unit operating costs, compared to other separation processes, will be:

47% of the cost of the cost of systems that use a centrifuge as the primary means of separation
44% of the cost of systems that use heat and pressure to achieve separation
7% of the cost of incineration systems.

Imperial expects to begin operating MST-4000 units commercially next year.