Liquid purification or separation – Processes – Utilizing electrical or wave energy directly applied to...
Reexamination Certificate
1999-12-07
2001-10-09
Simmons, David A. (Department: 1724)
Liquid purification or separation
Processes
Utilizing electrical or wave energy directly applied to...
C210S750000, C210S758000, C210S767000, C210S188000, C210S198100, C210S908000, C205S338000, C205S633000, C095S172000, C096S193000
Reexamination Certificate
active
06299781
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention concerns removal of hydrocarbon components from a contaminated water stream. More specifically the invention relates to a system which uses oxidation/reduction, changes of vapor pressure and atomization of the liquid stream to separate and outgas difficult-to-remove components that typically are liquids at standard temperature and pressure.
Abatement of hydrocarbon contamination in soils and ground water is increasingly mandated in the United States, Canada and other countries. In California and several other states of the U.S., the addition to gasoline of MTBE has been required, supposedly to increase the efficiency of gasoline combustion in internal combustion engines, so as to release less pollutant to the air. However, this has turned out to be a serious mistake of monumental proportion, since the toxic MTBE has rapidly found its way into soils, ground water, lakes and streams. Moreover, once in soils, the MTBE produces a toxic organic byproduct, TBA (tributyl acryl). TBA in water such as ground water is extremely difficult to remove, and no efficient method or system has been found prior to the present invention.
U.S. Pat. No. 5,767,060, owned by the assignee of the present invention, discloses a multi-component medium through which contaminated water can be filtered to remove many noxious hydrocarbon components. The system is efficient at removing nearly all hydrocarbon components, including MTBE, but not TBA.
U.S. Pat. Nos. 4,979,886, 5,424,045 and 5,863,510 are concerned with remediation of contaminated water and soil which may contain combustible hydrocarbons. The first patent discloses separation of hydrocarbons from water by spray aeration of a heated water stream under vacuum. The first and second patents both describe combustion of the recovered hydrocarbon vapors in internal combustion engines.
It is an objective of this invention to remove TBA, MTBE and other hydrocarbon contaminants including BTEX from a contaminated water stream using an efficient process embodied in a compact and portable apparatus, to extract these contaminants down to a level below 0.2 parts per billion as is now required in some jurisdictions.
SUMMARY OF THE INVENTION
In the process and system of the invention, contaminated waste water is introduced into a preferably self-standing unit via a pressure pump mounted at an end of the unit housing and delivering preferably about 40 to 60 psi. The pressurized water passes through an electrolytic cell, which preferably operates on adjustable timed polarity reversal in order to avoid contaminant buildup and plating of electrodes.
Pressure is maintained as water and hydrolyzed gases pass into an oxygen contact tank, preferably sized for two minute retention time for the moving fluid stream. An eductor port may be provided in this tank for infusion of treatment chemicals such as peroxide or potassium permanganate for higher oxidative reduction.
The flow of fluid then continues under pressure to a plurality of pulsed spray heads. These nozzles break up the water column and inject the large droplets into a high shear turbine equipped with redirecting diverter baffles that return the liquid inwardly after each turbine stage, further atomizing the stream.
When the water is released through the spray nozzles into the turbine column, it not only experiences instant depressurization but also is then placed under vacuum. This vacuum, which may be about 30 inches of water, is induced by a vacuum pump on the casing or housing, pulling a vacuum through the interior of the entire casing, whose only inlet is at the top of the turbine column, adjacent to the spray nozzles. Thus, a rapid stream of air is drawn through the turbine column along with the atomized liquid. The system therefore combines instantaneous depressurization (which greatly increases vapor pressure for the contaminants) with very high surface area on the liquid, high shear caused by the turbines and baffles, and a rapid flow of air down through the column and commingling with the atomized liquids. The result is a high rate of outgassing of the volatile components which were contained in the water, releasing nearly all volatiles to the housing space above a liquid reservoir which remains at the bottom, fed by the turbine column discharge.
Water is discharged laterally at the bottom of the turbine sleeve into the liquid reservoir, which is then pumped via a regulated submersible pump out of the casing for discharge as decontaminated water or for further treatment. The liquid in the reservoir is constantly agitated by the lowermost turbine blade, which is under water.
An important feature of a preferred embodiment is the shape and location of the turbine column discharge. Discharge preferably straddles the liquid reservoir level, about half of the opening above the level and half the opening below. A stream of mixed liquid and gases (which may be about 80:1 gas to water) is ejected at high velocity toward a wall of the casing, or more preferably against a stainless steel splash plate. Evaporation of water occurs at the splash plate, lowering its temperature, under preferred parameters by about 10° F. This evaporation is from the primarily gaseous stream in the top half of the discharge, but containing enough water droplets to cause the evaporative cooling effect. The plate is cooled sufficiently that it re-condenses much of the water vapor contacting the plate, thus reducing the moisture content of the air and gases within the casing, to be discharged by the vacuum pump. This is important in the event the gaseous stream exiting the system needs further treatment. In addition, the half-submerged exit nozzle tends to retain most of the liquid from the flowing stream down in the liquid at the base of the turbine column, thus remaining within the liquid as it is discharged into the reservoir.
The liquid in the reservoir is retained within a prescribed range of water level by cycling of the submersible pump, which discharges water from the system. The anaeroid switch operating the pump is connected by a tube to atmospheric pressure outside the casing, so as to compare the liquid pressure head existing above a sensor on the pump with atmospheric pressure. The liquid level can be regulated from outside the casing, in one specific embodiment, by placing the end of the atmospheric communication tube adjacent to the vacuum pump on the top of the casing. The vacuum pump preferably is carbureted to adjust the strength of vacuum pulled, by mounting the pump such that it can be raised or lowered to let more or less air enter the vacuum pump directly, to mix with the air and gas pulled through the casing. Thus, atmospheric air is constantly being pulled from around the base of the vacuum pump, to be mixed with the discharged air/gases recovered in the system. The atmospheric communication line from the aneroid pump can be moved closer to the base of the vacuum pump to adjust the sensed “atmospheric” pressure lower, thereby increasing the differential from the sensed water head in the reservoir and causing the reservoir level to be lowered, or vice versa. This can be fine tuned to establish the reservoir at the desired level. A small hole can be provided in the exterior of the casing, to allow observation of the liquid level, after which the hole is sealed by a plug.
It is thus a primary object of this invention to recover difficult volatile hydrocarbons from a wastewater stream, in an efficient and cost-effective manner, and to do so with a transportable and compact unit which combines electrolysis, oxidation/reduction, high shear, sudden change in vapor pressure, very high liquid surface area and rapid air flow through the atomized droplets. These and other objects, advantages and features of the invention will be apparent from the following description of a preferred embodiment, considered along with the accompanying drawings.
REFERENCES:
patent: 4979886 (1990-12-01), Rippberger
patent: 5104525 (1992-04-01), Roderick
patent: 5424045 (1995-06-01), Orman et al.
patent
Advanced Water Systems
Freiburge Thomas M.
Hoey Betsey Morrison
Simmons David A.
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