SE418283B - Process for burning chlorinated organic substances - Google Patents

Abstract

The amount of molecular chlorine present in the flue gases formed in the combustion of chlorinated organic substances can be reduced by injecting a certain amount of hydrogen into the rapid cooling zone of the combustion furnace or incinerator. The amount of hydrogen used depends on the amount of air introduced into the combustion zone, which is fixed to ensure an oxygen excess of 1-40%. When the wall temperature in the combustion zone is about 800-1500 degrees C, the temperature at which hydrogen is introduced into the rapid-cooling zone is about 450-1000 degrees C. Hydrogen chloride, which is formed from the molecular chlorine and the hydrocarbons, is washed out by water more easily than chlorine, so that flue gases with a lower impurity level are obtained. <IMAGE>

Description

10 15 20 25 30 35 H0 7900755-5 The efficiency of chlorine transfer to hydrogen chloride can improved, for example, by injecting superheated steam into the combustion zone of the kiln. This prior art method is shows the inconvenience of vapor injection in the combustion zone tends to result in lower incinerator temperature so that additional energy is required to maintain the required temperature level. Furthermore, the presence of steam in the combustion zone the effective volume of the incinerator and consequently its transit time.

Finally, it accelerates corrosion and destruction of incinerator materials including the refractory feed in the incinerator zones.

Consequently, it is obvious that more effective methods for combustion of chlorinated organic materials are desirable.

The present invention relates to a method in which air and chlorinated organic materials containing about 20-70 chlorine, (preferably about 20-55%) is continuously introduced into the combustion chamber. zone of an incinerator whose walls are kept at a temperature rature of about 800-150006; whereby the gaseous combustion products the products are introduced into a rapid cooling zone which is cooled by spraying of aqueous hydrochloric acid; and wherein hydrogen gas is injected into the rapid cooling zone at one or more points where the temperature is about Å50-1000 ° C; wherein the amount of air introduced into the combustion zone is such that there is an excess of oxygen 'of approx 1-H0% in addition to the theoretical amount required for complete combustion of the organic materials by transfer of all carbon atoms to carbon dioxide, all chlorine atoms and sufficient many hydrogen atoms are allowed to be combined into hydrogen chloride and wherein all hydrogen atoms remaining after the formation of hydrogen chloride brought to water; and wherein the amount of hydrogen introduced into the rapid cooling zone is determined by the equation Z = (0.1 to 1) -m, - wherein Z represents the volume percentage of hydrogen based on the volume air fed into the combustion zone and m denote the volume the amount of oxygen in the rapid cooling zone based on all gases present in the quench zone in addition to water vapor and hydrogen chloride gas.

The drawing schematically illustrates a waste incinerator and indicates the movement of the materials thereby.

It is well known that molecular chlorine can be transferred to hydrogen chloride by hydrogen in a reducing atmosphere. Emeller- 10 15 20 25 50 35 40 7900755-5 3 time, it is not generally known that this can be accomplished in the presence of air or oxygen However, with the present process, carried out in the presence of a small excess of air, molecular learned chlorine effectively to hydrogen chloride, which can be washed out with water ten. Preferred conditions are determined by the equation Z = (0.3 to 0.5) m, where Z and m have the meaning given above.

Although the most effective chlorine removal occurs un- these preferred conditions and adequate chlorine removal hits within the wide range of Z = (0.1 to 1) -m can one Part chlorine removal also occurs when the flow of hydrogen is reduced to less than the lower limit. However, this modification may is not expected to meet most environmental requirements. the flow beyond the maximum limit means waste of hydrogen.

However, chlorine is removed very efficiently at these high amounts. there.

An increase in hydrogen The drawing shows a suitable incinerator that exists of the combustion zone A, the rapid cooling zone B and the outlet line or the flue gas duct C. The combustion zone is lined with a refractory material, for example refractory bricks. clean in the center of zone A is estimated at about 2000-250000, but The necessary Flame temperature the measured wall temperature is about 800-1500 ° C. the temperature is obtained by combustion of the actual material but this can be supplemented by incineration of a hydrocarbon therein, for example natural gas or liquid propane.

Zone B, which communicates with zone A, may be, for example built of a refractory brick, ceramic-lined steel or of any got other suitable acid-resistant material. The typical the kiln has, as shown in the drawing, a vertical configuration, zone A being located above zone B. Several generally parallel rows of openings are arranged along periphery of zone B. These were mainly used for injection of the fast-cooling hydrochloric acid solution but part of the openings were used for the introduction of hydrogen according to the procedure: according to the invention. There is a decreasing temperature gradient in the downward direction in zone B and the hydrogen is introduced through located in the highest row, namely D, where the temperature is about 1 ° C. The distance between rows is such that efficient cooling is achieved, for example row D can be arranged 50 cm below the upper part of zone B, row E be arranged 90 cm below row D and row F be Other lines are indicated by E and F. 10 15 20 25 30 35 U0 7900755-5 arranged 90 cm below row E and 366 from the bottom of zone B.

The rapid cooling zone shown in this schematic drawing is cylindrical and has an inner diameter of l33 about.

Liquid coolant is injected into zone B through nozzles in- inserted in the openings E and F as well as in a part of the openings D.

The gaseous mixture taken through line C (denoted) hereinafter flue gas) has a temperature of about 100-200 ° C.

The line C is arranged above the bottom of zone B5, for example the distance from the center of line C to the bottom of zone B as shown in drawing 155 if.

Under normal operating conditions, the flow rate is too the flue gas in an incinerator having a rapid cooling zone of above stated dimensions about 0.79 ~ 1.98 m3 / s and the residence time for the gas in the quench zone is about 0.3Ä-1.05 seconds.

The refrigerant, which originally consisted of diluted water hydrochloric acid, continues to dissolve some additional hydrogen chloride rid that is present in the rapid cooling zone B and accumulates on bottom of zone B. It is then returned by a system of a pump and a pipeline (not shown) for various spray nozzles in the openings D, E and F. Preferably this is accumulated coolant first to a holding tank (not shown) and then to the nozzles. When the refrigerant is repeatedly returned, the the concentration of HCl in this solution gradually to a point where additional HCl absorption is not sufficiently effective. At the point, this solution is either rejected or recycled other purposes.

The invention is further illustrated by the following examples in which a preferred representative embodiment is described.

'Example Chlorinated organic wastes containing about 35% by weight cent chlorine was burned in the presence of 2.6% excess air in a apparatus substantially equivalent to that shown schematically the drawing. Control search without hydrogen injection gave the basic values for the chylated chlorine (determined by first removing HCl from the gas stream, that molecular chlorine was then converted to chloride ions in one caustic soda / arsenic scrubber and that the chloride ions are Injection into rapid The wall temperature of the boiler was 1370 ° C. by standard titration according to Volhard). the cooling zone of 0.85% by volume of hydrogen (based on the combustion air) at a point 60 cm from the top of the 7900755-5 3 UI the cooling zone reduced the molecular chlorine content from 690 mg / m to H8 mg / m3.

Claims (5)

7900755-5 6 Patent claims A process for the combustion of chlorinated organic materials containing about 20-70 & chlorine comprising rapidly cooling gaseous combustion products with aqueous hydrochloric acid and characterized in that air and the materials are continuously introduced into an incineration zone of an incinerator whose walls are maintained at a temperature of about 800-1500 ° C, after which the gaseous combustion products are introduced into a rapid cooling zone, which is cooled by spraying with the aqueous hydrochloric acid; hydrogen being injected into the quench zone at one or more points where the temperature is about 450-1000 ° C; that the amount of air introduced into the combustion zone is such that there is an excess of oxygen of about 1-40% in addition to the theoretical amount required for complete combustion of the organic materials by conversion of all carbon atoms to carbon dioxide, all chlorine atoms and sufficient a large number of hydrogen atoms may be combined into hydrogen chloride and all hydrogen atoms remaining after the formation of hydrogen chloride are transferred to water; and that the amount of hydrogen introduced into the quench zone is determined by the equation Z = (0.1 to 1) -m, wherein Z denotes the volume percent of hydrogen, based on the volume of air fed into the combustion zone, and m denotes volume percent amounts of oxygen in the quench zone, based on all gases present in the rapid cooling zone except steam and hydrogen chloride gas. Process according to Claim 1, characterized in that Z = (0.3 to 0.5) -m. _ 3. A method according to claim 1, characterized in that the combustion zone and the rapid cooling zone are arranged substantially vertically, the combustion zone being arranged above the rapid cooling zone. 4. A process according to claim 1, characterized in that the aqueous hydrochloric acid injected into the quench zone is recovered at the bottom of the quench zone and returned to injection points as long as it can absorb hydrogen chloride efficiently. A method according to claim 1, characterized in that; that the chlorine content of the organic materials is about 20-55%.