CA1119782A

CA1119782A - Wet oxidation of waste liquor

Info

Publication number: CA1119782A
Application number: CA000309900A
Authority: CA
Inventors: Gerald L. Bauer
Original assignee: Sterling Drug Inc
Current assignee: STWB Inc
Priority date: 1977-09-19
Filing date: 1978-08-23
Publication date: 1982-03-16
Also published as: GB2004532A; DE2840041A1; GB2004532B; FR2403304B1; NL7809242A; BE870285A; CH628254A5; FR2403304A1; JPS5451247A

Abstract

ABSTRACT OF THE DISCLOSURE
A safe method for mixing pure oxygen, or an oxygen enriched gas, at high pressure, with waste liquor in a wet oxidation system, such that inter-mittent drying conditions are avoided, thereby pre-venting possible spontaneous combustion, fire or explosion; comprising adding the oxygen to pure water before it is mixed with the waste liquor.

Description

The present invention relates to a process for the wet oxidation of waste liquor.
Pollution control by oxidation of aqueous ~ solutions or suspensions of organic waste products : 5 with an oxygen-containing gas at high temperature and pressure is a well-known procedure known as wet oxidation; see for example U.S. Patent 2,665,249.
In all priox art wet oxidation processes, the oxygen-;` containing gas i5 ad~ed directly to the aqueous waste solution or susp.ension either before or after ;; the waste is introduced into the wet oxidation re~ :
' actor.
: In prior art w~t oxidation prooess~s, waste liquor and compres3ed air can be directly - 15 mixed wlth no hazard, hut if pure oxygen or an oxy-gen enriched gas is used to supply oxygen for the oxidation pro~ess, special precautions have to be taken to prevent a spontan~ous combustion occurring at the point oxygen and waste liquor are being mixed.
~. 20 The primary hazard is caused by a condition o~ inter-- mittent wetting and drying in a section of pipe, : leadins to the formation oE a dry film of combustible material in direct contact with the oxygen or cxygen bearing gas. This dry combustible film ignites-spontaneously, leading to fire, explosion and ailure of pressurized equipment. The wetting-drying con-: dition may be cau~ed by an interruption in the flow of gas or liyuid or even by normal variation in the flow of the gas and the liquor.
Xn accordance with the present invention there is provided a process for carrying out a wet oxl~ation o~ a waste liquor with oxygen or oxygen ,: ~ , . . ~ , . . . .

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enriched gas in a reactor, the imp~ovement which comprises mixing said oxygen or oxygen enriched ga~ with pure water prior to adding said oxygen or oxygen enriched gas to said waste liquor, In order to obviate the possibility of spontaneous combustion, the oxygen or oxygen-con-taining yas flows at high pressure to a point where it is mixed with a stream of pure water which shGuld be distilled, deionized, or potable water from which lQ the hardness and substantially all oils, grease or other oxidizable substances have been removed. This ~; water flows through an intake to e.g., a conven-tional tee where it is mixed with the oxygen or oxygen enriched gas.
The water-oxygen material now mixed then flows through a pipe to another tee or the like where it ls mixed with the waste liquor flowing to th~ reactor. This may be a location in a pipe line carrying the waste liquor to wet oxidation re-actor, but it may also be at a point inside the reactor itself where the oxygen is to be injected.
:~ This eliminates the possibility of the formation of any dry deposits of combustible mate-'! rials which may come in direct contact with high pressure oxygen or oxygen~enriched gas.
The invention will now be described with reference to the figure of the accompanying draw-ing which is a diagrammatic representation of a preferred embodiment.
A pipe 10 leads oxygen or oxygen enriched gas through a check valve 12 and thence to e.g., a tee 14, the other leg of which is a pipe 16 accommo-dating the flow of pure water in the direction of the arrow through another check valve 18 into the tee to mix with the oxygen.
This mixture then flows through a third check valve 20, a pipe 22 and another tee 24, one leg of the tee accommodating the waste liquor as at 26. The water and oxygen bearing gas are mixed in the tee 24 and thence proceed through another pipe , . ` , ~ ~

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or equivalent 28 to the reactor.
It is to be understood that the mlxture of the water and oxygen or oxygen-enriched gas and the waste liquor may actually take place inside the reactor should this be found advantageous or desirable.
In this invention it is emphasized that the oxygen or oxygen-enriched gas must be mixed wlth water before it is used in wet oxidation.
The purpose of the water injection is to eliminate any possibility of the formation of any dry deposits of combustible material in direct contact with the high pressure oxygen. This is accomplished by pre-venting any liquid containing combustible materials from flowing into or contaminating the oxygen supply line and by preventîng the formation of dry spots in the areas which have been in contact with waste liquor, and forming more positive and cleaner seals in the check valves 12 and 20 in case of any inte~ruption to the flow of oxygen~
The amount of water mixed with the oxygen or oxygen-enriched ~as is also irnportant. If too little water is used, the surface of pipes 14 and 22 may not be sufficiently wetted to prevent com-bustion. There may also not be ~snough water to pre-vent backflow of waste liquor into lines 22, 14 and 10. This would lead to the type of hazardous situa-tion which this invention is intended to prevent.
On the Gther hand, if too much watar is mixed with the oxygen or oxygen-enriched gas, the waste liquor will be excesslvely diluted and the wet oxidation process will be uneconomical.
The amount of water that should be mixed with the oxygen or oxygen-enriched gas is between one-hundredth of a pound and tan pounds of water per pound of oxygen, preferably between one-tenth of a pound and one pound of water per pound of oxygen.
For the purpose of the present invention, an oxygen enriched gas is a gaseous mixture pro-duced by adding substantial amounts of oxygen to air ~, -4-or an inert gas such that the resultant mixture : contains at least about 25 per cent by volume o~
. oxygen.

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Claims

C L A I M S

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a process for carrying out a wet oxidation of a waste liquor with oxygen or oxygen enriched gas in a reactor, the improvement which comprises mixing said oxygen or oxygen enriched gas with pure water prior to adding said oxygen or oxygen enriched gas to said waste liquor and adding said mixture of oxygen or oxygen enriched gas and pure water to the waste liquor before the latter is introduced into the reactor.

2. A process according to claim 1, in which the amount of pure water mixed with the oxygen or oxygen enriched gas is in the proportion of between one-hundredth of a pound and ten pounds of water per pound of oxygen.