A method for operating a continuous wet oxidation system for destroying cyanide in caustic cyanide and metal wastes which scale upon heating. Raw waste is introduced into the wet oxidation reactor without heating while a mixture of heated dilution water and oxygen containing gas is introduced into the reactor by a separate inlet. The reactor is fitted with a pair of valved effluent lines and corresponding valved lines for introducing dilute mineral acid into each effluent line at system pressure. Oxidized effluent and offgases exit through a first effluent line while dilute mineral acid flows through a second effluent line into the reactor to prevent scale buildup. Periodically the flows are alternated such that oxidized effluent and offgases exit through the second effluent line and dilute mineral acid flows through the first effluent line into the reactor to remove scale. The oxidized effluent and offgases are then cooled and separated.
The invention provides an apparatus for continuous thermal hydrolysis of cyanide ions and cyanide-containing ions contained in a liquid, comprising an elongated tubular reactor of a size selected to enable the liquid to be retained in the reactor for a predetermined reaction time, a conduit for supplying the liquid to the reactor, means for adding a base to the liquid prior to heating, and means, associated with the conduit, for instantaneously and uniformly heating the liquid to a preselected temperature. The apparatus preferably uses high pressure steam to heat the liquid and appears much less subject to fouling by scale. The invention also provides a continuous process for hydrolyzing a cyanide-containing liquid stream, comprising adjusting the pH of the liquid stream to render the liquid stream strongly basic; rapidly and uniformly heating the liquid stream to a predetermined elevated temperature; feeding the liquid to an elongated substantially vertical tubular reactor; maintaining the liquid in the reactor for a predetermined time to permit substantially complete degradation of cyanide ions and cyanide-containing ions in the liquid. The cyanide-containing liquid may preferably be uniformly and rapidly heated to the desired temperature by injecting steam under pressure into the liquid.
The present invention is a process for oxidation of a liquid which contains cyanide and soluble metal ions, using an oxygen-containing gas. Art example of such a liquid is the liquid waste produced during metal treatment processes. The disclosed process not only eliminates the cyanide completely, but also converts the metal dissolved in the liquid into granular metal oxides which can be readily recovered.
A pressurized feed material (30) in aqueous suspension is oxidized in a supercritical temperature reaction zone (20) in an upper region of a vertically elongated, cyclindrical walled, closed pressure vessel (10) to form an oxidized super fluid phase (46) which is removed from the upper region of the vessel and a brine (44) containing precipitates and other solids which are collected in and removed from a subcritical temperature zone (16) in the lower region of the vessel. The wall (12) of the cylindrical pressure vessel (10) is scraped by rotatable scraper means (60) which upon rotation will dislodge precipitated solids from the wall (12).
This is a process for wet oxidation of an ammonium salt containing waste liquor which prevents plugging of the vapor-carrying lines of the wet oxidation system. The vapor-carrying lines are maintained in an unobstructed condition by adding sufficient liquid water to dissolve condensed ammonium salt which can plug these lines. This provides for safe operation of the wet oxidation system.
A method for detoxifying cyanide waste using a reactive sugar having aldose functionality is provided. The reactive sugar is mixed with the cyanide waste to produce sugar acid, a non-toxic and environmentally safe compound.
