GB1601382A - Method for the thermal decomposition of waste water - Google Patents

Description

(54) METHOD FOR THE THERMAL DECOMPOSITION OF WASTE WATER (71) We, MoscovsKY ENERGETICHESKY INSTITUT OF ULITSA KRASNOKAZARMENNAYA 14, Moscow, Union of Soviet Socialist Republics (U.S.S.R.) a State Enterprise organised and existing under the laws of the USSR, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to methods for decontamination of liquid wastes (socalled waste waters) and, more specifically, to methods for the thermal decomposition of waste waters. The method of the present invention is useful in industries where the production process is accomplished by the formation of industrial waste waters.

According to the present invention a method of thermally decomposing waste waters comprises passing a gaseous fuel into a liquid including waste water and a surfactant to form a combustible foam including bubbles and gaseous fuel within the bubbles, and burning up the combustible foam.

An extensively developed surface of contact between (a) the high-temperature products of combustion of the gaseous fuel and (b) the foam means highly intensive heat- and mass-transfer processes. The bubbles are rapidly evaporated and the gaseous fuel is liberated therefrom and is burned up along with the residual particles from the bubbles.

It is desirable that the introduction of the gaseous fuel into the liquid be effected by bubbling under a gauge pressure to ensure a moving stream of the combustible foam.

The present invention is further explained by the following detailed description of embodiments thereof with reference to the accompanying drawing which shows an apparatus for use in decontaminating waste waters by methods embodying the present invention.

The method of said embodiments is based on the combustion of a foam pre-formed from the entire volume of the liquid and including bubbles and gaseous fuel englobed in the bubbles. For the formation of such foam it is necessary to pass the gaseous fuel into a liquid including the waste waters in the presence of surfactants. To provide a moving stream of statically stable cellular foam it is preferable to effect bubbling of the gaseous fuel under a gauge pressure through the liquid.

The addition of surfactants to the waste waters in an amount required to convert the entire volume of the waste waters to foam ensures the feasibility of the methods embodying the present invention. Said addition of surfactants should be made to such wastes waters which contain no surfactants or which have a very small surfactant content.

The method for the thermal decontamination of waste waters is performed by means of apparatus operating in the manner now described.

The waste waters to be decontaminated are delivered into a reservoir 1 (Fig. 1) for a preliminary treatment with surfactants in an amount required for the complete conversion of the entire volume of the waste waters to foam. From the reservoir 1 a liquid composed of waste waters and surfactant is fed onto a grate 2 in a foam-generating appratus. At the same time, a gaseous fuel is fed under the grate 2 to bubble through the liquid and form therewith statically stable cellular foam.

The resulting stream of foam moves along a column 3 towards a reactor consisting of a combustion chamber 4, an air-distributing grate 5 and an air chamber 6.

Simultaneously, due to the flotation properties of the foam, all solid and suspended impurities are entrained by the foam stream and burnt up along with the gaseous fuel. Air is fed into the combustion chamber 4 through the air-distributing grate 5 by means of a blower 7 to ensure stable burning of the gas and bubbles of the foam.

For inflammation of the foam, gaseous fuel is fed into the chamber 4 through a torch 8, or use is made of electrical ignition means.

To maintain stable combustion of the gas and bubbles of the foam, the chamber lining should be heated to a suitable temperature.

An extensively developed surface of contact between the flue gases and the foam obtained from the liquid including the waste water ensures a high intensity of heat- and mass-transfer. The foam is rapidly evaporated and the gas englobed in its bubbles is liberated thus forming a stable flame torch over the outlet of the column 3.

The combustion products may be delivered from the chamber to appropriate units for the removal of the resulting solid particles therefrom, and to apparatus for the utilization of heat and the condensation of water.

As the gaseous fuel there may be used natural gas, the off-gasses from petroleum refining, and coke gas obtained from the gasification of a solid fuel.

Example 1 Waste waters intended for thermal decontamination contain 184 g of dry solids per one litre of the waste water including 60 g/l of organic compounds, 74 g/l of mineral salts and 50 g/l of insoluble impurites. Upon the addition of 20 g/l of a surfactant, i.e. synthanol, to the waste waters, and the bubbling of natural gas through the resulting liquid, said liquid is completely converted to foam which is then fully burned-up in a combustion chamber.

Example 2 Waste waters intended for thermal decontamination and resulting from the machining of non-ferrous metals, contain 200 to 250 g of dry solids per one litre of the waste water, including 30-35 g/l of organic compounds, 100--150 g/l of mineral salts and 65 g/l of soluble impurities. Upon the addition of 5 10 g/l of a surfactant, i.e. sulphanol, to the -waste water, and the bubbling of natural gas -through the resulting liquid, the waste water is totally converted to foam which is well burnedup in a combustion chamber.

Example 3 Waste waters for thermal decontamination result from the manufacture of phenolic resins and contain 100 to 150g of dry solids per one litre of the waste water including 5070 g/l of organic compounds, 30-50 g/l of mineral salts and 20-30 g/l of soluble impurities. Upon the addition to the waste water of 2-6 g/l of a surfactant, i.e. synthanol, and the bubbling of natural gas through the resulting liquid, the latter is totally converted to a foam which is fully burned-up in a combustion chamber.

Decontamination of the above-mentioned waste waters is effected at the temperature of combustion of the gaseous fuel (i.e. within the range of from 1,400 to 2,0000C). The resulting combustion products consisting of inert gases (CO2, N2) and water vapours are, after utilization of heat and cleaning of the gases, vented to the atmosphere in compliance with the requirements of the health rules.

For the thermal decontamination of 1 kg of waste water, heat is consumed in an amount of 720-750 kCal (including the utilization of the heat of the combustion products) which ensures a coefficient of utilization of the calorific value of the gaseous fuel as high as 90 to 96%.

WHAT WE CLAIM IS: 1. A method of thermally decomposing waste waters comprising passing a gaseous fuel into a liquid including waste water and a surfactant to form a combustible foam including bubbles and gaseous fuel within the bubbles, and burning up the combustible foam.

2. A method according to claim 1, wherein the gaseous fuel is bubbled into the liquid under a gauge pressure to create a moving stream of the combustible foam.

3. A method according to claim 1 or 2, wherein the gaseous fuel is bubbled into a body of the liquid to convert substantially the entire volume thereof to combustible foam.

4. A method of thermally decomposing waste waters, substantially as hereinbefore described with reference to any one of the Examples.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   impurities are entrained by the foam stream and burnt up along with the gaseous fuel. Air is fed into the combustion chamber 4 through the air-distributing grate 5 by means of a blower 7 to ensure stable burning of the gas and bubbles of the foam.

   For inflammation of the foam, gaseous fuel is fed into the chamber 4 through a torch 8, or use is made of electrical ignition means.

   To maintain stable combustion of the gas and bubbles of the foam, the chamber lining should be heated to a suitable temperature.

   An extensively developed surface of contact between the flue gases and the foam obtained from the liquid including the waste water ensures a high intensity of heat- and mass-transfer. The foam is rapidly evaporated and the gas englobed in its bubbles is liberated thus forming a stable flame torch over the outlet of the column 3.

   The combustion products may be delivered from the chamber to appropriate units for the removal of the resulting solid particles therefrom, and to apparatus for the utilization of heat and the condensation of water.

   As the gaseous fuel there may be used natural gas, the off-gasses from petroleum refining, and coke gas obtained from the gasification of a solid fuel.

   Example 1 Waste waters intended for thermal decontamination contain 184 g of dry solids per one litre of the waste water including 60 g/l of organic compounds, 74 g/l of mineral salts and 50 g/l of insoluble impurites. Upon the addition of 20 g/l of a surfactant, i.e. synthanol, to the waste waters, and the bubbling of natural gas through the resulting liquid, said liquid is completely converted to foam which is then fully burned-up in a combustion chamber.

   Example 2 Waste waters intended for thermal decontamination and resulting from the machining of non-ferrous metals, contain 200 to 250 g of dry solids per one litre of the waste water, including 30-35 g/l of organic compounds, 100--150 g/l of mineral salts and 65 g/l of soluble impurities. Upon the addition of 5

   10 g/l of a surfactant, i.e. sulphanol, to the -waste water, and the bubbling of natural gas -through the resulting liquid, the waste water is totally converted to foam which is well burnedup in a combustion chamber.

   Example 3 Waste waters for thermal decontamination result from the manufacture of phenolic resins and contain 100 to 150g of dry solids per one litre of the waste water including 5070 g/l of organic compounds, 30-50 g/l of mineral salts and 20-30 g/l of soluble impurities. Upon the addition to the waste water of 2-6 g/l of a surfactant, i.e. synthanol, and the bubbling of natural gas through the resulting liquid, the latter is totally converted to a foam which is fully burned-up in a combustion chamber.

   Decontamination of the above-mentioned waste waters is effected at the temperature of combustion of the gaseous fuel (i.e. within the range of from 1,400 to 2,0000C). The resulting combustion products consisting of inert gases (CO2, N2) and water vapours are, after utilization of heat and cleaning of the gases, vented to the atmosphere in compliance with the requirements of the health rules.

   For the thermal decontamination of 1 kg of waste water, heat is consumed in an amount of 720-750 kCal (including the utilization of the heat of the combustion products) which ensures a coefficient of utilization of the calorific value of the gaseous fuel as high as 90 to 96%.

   WHAT WE CLAIM IS: 1. A method of thermally decomposing waste waters comprising passing a gaseous fuel into a liquid including waste water and a surfactant to form a combustible foam including bubbles and gaseous fuel within the bubbles, and burning up the combustible foam.
2. 2. A method according to claim 1, wherein the gaseous fuel is bubbled into the liquid under a gauge pressure to create a moving stream of the combustible foam.
3. 3. A method according to claim 1 or 2, wherein the gaseous fuel is bubbled into a body of the liquid to convert substantially the entire volume thereof to combustible foam.
4. 4. A method of thermally decomposing waste waters, substantially as hereinbefore described with reference to any one of the Examples.