Liquid purification or separation – Processes – Making an insoluble substance or accreting suspended...
Reexamination Certificate
1999-03-24
2001-02-13
Hruskoci, Peter A. (Department: 1724)
Liquid purification or separation
Processes
Making an insoluble substance or accreting suspended...
C159S047300, C210S737000, C210S748080, C210S758000, C210S761000, C210S769000, C210S180000, C210S192000, C210S205000, C422S184100, C422S227000, C422S906000, C423S130000, C588S253000, C588S253000, C588S253000, C588S253000
Reexamination Certificate
active
06187206
ABSTRACT:
TECHNICAL FIELD
This invention relates to thermal reactor systems. More particularly, the invention relates to thermal reactor systems employing one or more preferably submerged energy sources, and to processes for treating wastewater using such thermal reactor systems.
BACKGROUND ART
Treatment of industrial wastewater streams presents numerous difficult challenges, including efficient and effective degradation of dissolved compounds or ions and/or organic materials, with minimum investment, and with minimum interference with industrial efficiency and output. In other words, the treatments which are often mandated by government statute or regulation need to make effective use of energy, manpower, capital and other resources, while returning wastewater to be disposed of or recycled containing acceptable amounts of contaminants.
U.S. Pat. No. 5,470,559, issued Nov. 28, 1995 (Grolman et al.), assigned to the same assignee as the present application, discloses a method and apparatus for recycling used linings of aluminum reduction cells, more commonly called spent potlinings (SPL). The potlinings, composed primarily of carbon, refractory brick, and cryolite, include fluorine, alumina and sodium, along with free and complexed cyanides. The process involves grinding the spent potlining material to a powder, and treating the powder with aqueous sodium hydroxide to produce a slurry. The slurry is separated into solids and liquid; the liquid is then diluted (if necessary) to produce a solution containing the cyanide or complexed cyanide ions suitable for cyanide destruction and sodium fluoride crystallization.
U.S. Pat. No. 5,160,637, issued Nov. 3, 1992 (Bell et al.), also assigned to the same assignee as the present application, discloses a method and apparatus for treatment and degradation of cyanides and ferrocyanides contained in wastewater resulting from the conversion of alumina into aluminum metal. The patent discloses a vertical tubular reactor in which the wastewater is treated under heat and pressure. In some applications, cyanide and ferrocyanide ions can be effectively degraded using high pressures and temperatures as disclosed in that patent. The equipment necessary to carry out the process, however, is quite expensive to purchase and install, and uses considerable amounts of energy to produce the temperatures and pressures useful therein. Accordingly, a less expensive system for accomplishing that goal would be desirable.
European patent application 469 737 A2 published on Feb. 5, 1992 in the name of Tioxide Group Services Limited discloses a destruction process in which chemical waste is burned in oxygen using an electric plasma flame to heat a stream of gas which contains at least 70% by weight oxygen. Liquid waste in fine droplet form is introduced into the gas stream via a two-fluid atomiser.
U.S. Pat. No. 3,051,639, which issued on Aug. 28, 1962 and was assigned to Union Carbide Corporation, discloses a process and apparatus for carrying out chemical reactions, particularly the conversion of liquid or gaseous hydrocarbons into acetylene. The process involves creating a stream of hot arc gas from a wall-stabilized electric arc and injecting a gaseous or liquid hydrocarbon is injected into the stream, or the stream is directed into a relatively large volume of liquid hydrocarbon.
U.S. Pat. No. 4,438,706, which issued on Mar. 27, 1984 and was assigned to Villamosipari Kutato Intezet, discloses a procedure and equipment for destroying fluid waste containing vaporizable organic materia by a plasma technique. The procedure involves producing a plasma, creating a plasma torch at one end of a reactor, introducing the waste in vapour form and oxygen into the torch for interaction with the reactor and discharging end products from the reactor. The reactor is a double-walled tube, the inner wall being perforated to allow the passage of air into the reaction zone.
German patent DE 44 40 813 A1, which was published on May 18, 1995 and was assigned to Fraunhofer-Gesellschaft zur Förderung der angewandten Forschng e.V., discloses a method for the treatment of liquids, including liquids containing cyanide. The liquid is held in a discharge zone between two opposed electrodes supplied with alternating current. Micro discharge filaments are formed in the discharge zone extending from the liquid surface to the opposing electrode. The method destroys hazardous matter in the waste water and converts it into harmless compounds.
DISCLOSURE OF THE INVENTION
It is therefore an object of the present invention to provide an improved thermal reactor capable of treating wastewater and other fluids.
More particularly, it is an object of the invention to provide an improved reactor system suitable for treating wastewater containing spent potlining leachate including cyanide and cyanide complexes such as ferrocyanides, and other undesired impurities.
It is a further object to provide a thermal reactor system suitable for treating wastewater such as spent Bayer process liquor, which heats the wastewater to evaporate and concentrate the liquid, causing precipitation of compositions dissolved therein, and degradation of organic materials contained therein.
The foregoing disadvantages of the prior art are overcome and the objects are achieved by providing an improved thermal reactor comprising an elongated tube having a liquid inlet and outlet. Intense energy is generated in the tube from a suitable source, preferably adjacent to the inlet of the elongated tube, so that the liquid flows past the source and absorbs energy therefrom. The intense energy is preferably a plasma (a mixture of electrons, ions and neutral particles), e.g. a thermal plasma having temperatures in excess of 4000° C. generated by an arc struck between electrodes or by induction. A direct current (DC) plasma torch has proven to be preferable operating at a power range of up to 2 MW and at an efficiency of up to 90% at atmospheric pressure.
While the energy should be generated within the reactor tube for direct contact with the wastewater, the energy source or generator (e.g. a plasma torch) may itself be positioned partially or fully outside the reactor tube, provided it directs the energy into the tube. The energy source is preferably submerged in the wastewater solution.
The elongated reactor tube may be, for example, a draft tube, an eductor tube or a venturi tube. The following are the definitions of the terms “draft”, “eductor” and “venturi” tubes as used herein:
Draft Tube:
In a draft tube, the energy of the jet is transferred to the liquid and forces the liquid away from the jet. Here the primary high velocity gas of the jet enters at a position at the axis of the tube, and in mixing with the secondary low velocity fluid imparts an initial momentum. However, in an embodiment of this invention, the hot plasma gas increases in volume and transfers most of its thermal energy to the entrained secondary phase. The primary upward force in the draft tube is provided by the difference in density between the hot mixture of liquid and gas in the draft tube and the cooler liquid outside the tube. This difference depends on the volume fraction occupied by the gas in the liquid/gas mixture that is primarily determined by the local temperature and secondly by the plasma gas mass flow. The secondary fluid thus receives the momentum to carry it to the opposite end of the tube and causes fresh liquid to be drawn into the opposite end of the draft tube.
Eductor Tube:
An eductor tube is similar to a draft tube, except that there are additional openings located in the walls of the tube. The jet causes the liquid inside the tube to be carried to the far end, and the volume so generated is filled by liquid drawn in through the openings in the wall as well as by the liquid drawn in through the open end of the tube.
Venturi Tube:
A venturi tube is a tube with a restriction located between the two openings. The restriction can be created by narrowing the diameter in the middle portion, which results in the two ends being flared away from the middl
Bernier Jean Luc
Boulos Maher I.
Fortin Luc
Kasireddy Vijay
Kimmerle Frank M.
Alcan International
Cooper & Dunham LLP
Hruskoci Peter A.
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