Oxidation method, nozzle and system for treating waste water

Abstract

The present invention relates to a device, particularly a nozzle, for treating waste water, said nozzle having an outer tube and an inner tube. An intermediate space is formed between the outer tube and the inner tube and said intermediate space between the outer tube and the inner tube is divided into at least two chambers in the longitudinal direction of the tubes. The inner tube tapers in the longitudinal direction and then widens again and has at least one opening into each chamber at the constricted area. On the inner side of the inner tube and/or in the interior thereof, the device preferably has a catalyst. The present invention further relates to a method for oxidizing polluted waste water and a system for performing the method.

Claims

1. A device for feeding waste water, an oxygen containing gas and a radical starter into a reactor, which is characterized by an outer tube (3) and an inner tube (2) which inner tube forms an intermediate space with the outer tube, wherein the intermediate space between the outer tube and the inner tube comprises at least two separating walls, extending radially and in a longitudinal direction between the inner tube and the outer tube, separating the intermediate space into at least two chambers (3a, 3b), wherein the inner tube comprises a tapered portion and a widening portion in the longitudinal direction, wherein the inner tube has at least one opening (4a, 4b) at a constricted area, between the tapered portion and the widening portion in the longitudinal direction, that opens into each of the at least two chambers (3a, 3b), and wherein at least one catalyst is provided at an inner side of the device or at the inner tube.

2. A device for treatment of waste water, comprising an outer tube (3) and an inner tube (2) wherein an intermediate space is formed between the outer tube and the inner tube wherein the intermediate space between the outer tube and the inner tube comprises at least two separating walls, extending radially and in a longitudinal direction between the inner tube and the outer tube, separating the intermediate space into at least two chambers (3a, 3b) wherein the inner tube comprises a tapered portion and a widening portion in the longitudinal direction, wherein the inner tube has at least one opening (4a, 4b) at a constricted area, between the tapered area and the widening area in the longitudinal direction, that opens into each of the at least two chambers (3a, 3b), and wherein at least one catalyst is provided at an inner side of the device or at the inner tube.

3. A device according to claim 1 or 2, characterized in that the inner tube comprises a sintered metal at the constricted area thereof which has openings (4a, 4b) in the form of pores, through which substances from both chambers (3a, 3b) may enter the inner tube.

4. A device according to claim 1 or 2, characterized in that it has a coating containing at least one catalyst on at least one part of the inner side of the inner tube.

5. A device according to claim 4, characterized in that the coating comprises a priming coat of aluminum oxide.

6. A device according to claim 4, characterized in that the catalyst is selected from the following compounds/metals: CuO, CoO, Ag.sub.2O, Fe, FeSO.sub.4, MnO.sub.2, ZnO, V.sub.2O.sub.5, Pd, Pt.

7. A device according to claim 6, characterized in that the compounds/metals are present in the form of nano particles.

8. A device according to claim 1 or 2, characterized in that each of the at least two chambers are of approximately equal size.

9. A device according to claim 1 or 2, wherein said device is a nozzle.

10. A process for the treatment of organically polluted waste water by the addition of a radical starter and an oxygen containing gas in a reactor containing at least one device according to claim 1 or 2, characterized in that the waste water is introduced into the reactor via the at least one device, whereby the radical starter and the oxygen containing gas are added to the waste water in the device.

11. A nozzle system for a system for the treatment of organically polluted waste water comprising at least one device according to claim 1 or 2.

12. A process for the treatment of organically polluted wastewater by the addition of a radical starter and an oxygen containing gas in a reactor containing at least one nozzle system according to claim 11, characterized in that the waste water is introduced into the reactor via at least one nozzle system according to claim 11, whereby the radical starter and the oxygen containing gas are added to the waste water in the nozzle system.

Description

(1) The process, the corresponding system and the nozzle are described below. the figures show:

(2) FIG. 1 Schematic representation of radical chain reactions

(3) FIG. 2 Side view of the nozzle

(4) FIG. 2a Cross sectional view of the nozzle

(5) FIG. 2b Plan view of the nozzle

(6) FIG. 3 Schematic representation of the oxidation system (from WO 98/57895)

(7) FIG. 1 shows a schematic representation of possible radical chain reactions on which the process is based.

(8) The autoxidation of the organic waste water contaminants is initiated by a radical starter, or by a radical-forming oxidant. As such, compounds from the group of azo compounds such as azobisisobutyronitrile (AlBN) and azobis(cyclohexanecarbonitrile) or compounds from the group of peroxide compounds such as benzoylperoxide, di-tert-butylperoxide and hydrogen peroxide, preferably hydrogen peroxide, can be used. In FIG. 1 hydrogen peroxide is used as a representative of a radical starter or a radical-forming oxidant.

(9) The radical chain reaction I starts by the reaction of the peroxide with the higher-valence catalyst ion in that it is transposed into a lower oxidation level with the formation of a hydroperoxide radical HOO*. The hydroperoxide radical subsequently reacts with the substrate RH(1) or with the substances contained in the waste water, thereby releasing peroxide and a carbon radical R*(1). Both species are recycled back into the circuit (I or III).

(10) As a catalyst, salts of transition metals such as those of iron, manganese, copper, chrome and others can be used. Ferrous sulfates are preferred.

(11) Catalyst reaction II corresponds to a reaction cycle, in the course of which the higher-valence catalyst ion is transformed by the peroxide into the lower-valance ion, and the lower-valence ion by the infused oxygen back into the higher-valence ion.

(12) Oxygen chain reaction III starts with the infeed of a O.sub.2 containing gas into the reaction mixture. The oxygen reacts on the one hand with the lower valence catalyst ion, thereby producing a hydroxy radical HO* which with the substrate RH(2) forms a carbon radical R*(2), and on the other hand with the carbon radicals R* present in the reaction mixture to form peroxide radicals ROO*. In a subsequent reaction with the substrate RH(3) the product ROOH is formed, and further carbon radicals R*(3) are released. As the O.sub.2 containing gas air, oxygen/air mixtures and pure oxygen can be used. The use of air is thereby preferred.

(13) Considered in isolation the radical chain reaction I and the catalyst reaction II form the known Fenton circuit in the event that hydrogen peroxide is used as a radical starter and a ferrous salt as the catalyst.

(14) According to the present invention an oxygen chain reaction III is superimposed on radical chain reaction I and on catalyst reaction II, thereby producing a combination of just-in-time chain reactions in which the O.sub.2 containing gas takes over the function of the principal oxidant. The reaction chain is maintained by the interaction of circuits I, II and III in the manner described.

(15) The use of predominantly air as a source of oxygen has proven to be of advantage, yielding substantial cost reductions in conjunction with the consumption of overall much smaller amounts of chemicals.

(16) In this context particular care must be taken that the ratio of radical starter to oxygen of the O.sub.2 containing gas or the hydrogen peroxide/oxygen ratio, and that a specific catalyst activity are correct. Typical ratios of the substrate fractions or waste water impurities oxidized by hydrogen peroxide and oxygen are 1:5 or above, especially 1:6 or above, up to 1:10 or even 1:20. This means that up to five times the amount of the hydrogen peroxide fraction can be oxidized by the infused oxygen.

(17) According to the procedure described in WO 98/57895 the oxygen which is delivered by the peroxide could be limited to 20% of the total oxygen required during the course of the oxidation. The process of the present invention makes it possible to limit the amount of peroxide to 5% or less. The rest is oxidized by gaseous oxygen.

(18) Such high turnover rates are made possible by using the nozzle of the present invention.

(19) Alternatively, the nozzle of the present invention makes it also possible to work without metal salts in solution if the nozzle has a coating containing at least one catalyst on the inner side of the inner tube.

(20) FIGS. 2, 2a and 2b show an embodiment of the nozzle of the present invention in side view (longitudinal section), in cross section view and in plan view. The nozzle is preferably constructed rotationally symmetric. A representation of the connection elements and the fastening elements has been dispensed. The stream of waste enters the inner tube 2 of the nozzle through opening 1. The inner tube tapers and widens again providing a tapered portion and a widening portion, with a constricted area between the tapered portion and the widening portion. The space between the outer tube and the inner tube is divided in two parts by at least two separating walls, extending radially and in a longitudinal direction between the inner tube 2 and the outer tube 3. The O.sub.2 containing gas is introduced into chamber 3a. The radical starter (e.g. H.sub.2O.sub.2) is introduced into chamber 3b. At the constriction area of the tube there is an opening 4a to chamber 3a and an opening 4b to chamber 3b. According to the principle of the venturi tube the O.sub.2 containing gas and the radical starter (e.g. H.sub.2O.sub.2) enter the inner tube at least partially.

(21) The head of the nozzle has e.g. 6 bores (6a, 6b) which are arranged around the outlet opening 5 of the inner tube. By means of this, for example, that part of the gases which has not entered the waste water through opening 4a is infused in a finely disperse form into the stream when entering the reactor in order to ensure a maximum exchange of substances between the gas bubbles and the surrounding fluid. Furthermore e.g. that part of the H.sub.2O.sub.2 solution which has not entered the waste water through opening 4b is infused into the stream when entering the reactor.

(22) As already described above, the device (nozzle) of the present invention may be part of a nozzle system as e.g. described in WO 98/57895. Preferably the device (nozzle) of the present invention is used as motive jet nozzle in the procedure described in WO 98/895. Further the device (nozzle) of the present invention is preferably used in an oxidation system as described in WO 98/57895.

(23) FIG. 3 shows an exemplified schematic representation of an oxidation system as described in WO 98/57895.

(24) The water flow contaminated with organic impurities V.sub.0 or the waste water flow, respectively, which has been preheated in a heat exchanger 2 to a temperature difference of 5-20 C. relative to the reaction temperature, is fed via pipe 10, a control valve RV.sub.1, a pipe 10 to the reactor circulation flow V.sub.2 consisting of the pipes 11, 11 and 11 in the intake section of pump P.sub.1. Pipe 11 connects a discharge branch of a reactor 1 with the intake of pump P.sub.1, and pipe 11 the discharge branch of pump P.sub.1 with a nozzle system 100 which is arranged in the lower part of the reactor and which comprises at least one nozzle 110 according to the present invention. The circulation flow recirculation ratio is e.g. 1:0 to 1:20.

(25) Acid or alkaline 20 is fed into the system via an apportioning circuit with apportioning pump DP.sub.2, apportioning valve RV.sub.2 and pipes 21, 21 and 21 and discharges into pipe 10.

(26) A radical starter 30 is fed into the system via an apportioning circuit with apportioning pump DP.sub.3, apportioning valve RV.sub.3 and pipes 31, 31 and 31 and discharges into pipe 11.

(27) A catalyst 40 is fed into the system via an apportioning circuit with apportioning pump DP.sub.4, apportioning valve RV.sub.4 and pipes 41, 41 and 41 and discharges into pipe 11.

(28) The circulation pump P.sub.1 serves both as a mixing device for the chemicals apportioned into the system, and also for the generation of a stream TS in connection with nozzle system 100 comprising at least one nozzle according to the present invention.

(29) An O.sub.2 containing gas 50 is fed to the nozzle of the present invention 110 via a flowmeter 52, an apportioning valve RV.sub.5 and pipes 51, 51 and 51.

(30) The outlet flow V.sub.0 out of the reactor passes via a control valve RV.sub.6, the heat exchanger 2 and pipes 61 and 61. The reactor is vented 80 via a control valve RV.sub.7 and pipes 71 and 71. A heater 90 supplies the reactor with the energy necessary for the starting conditions via pipe 91.

(31) From pipe 11 part of the circulation flow is fed via control valve RV.sub.8 and pipes 81, 81 and 81, which are also referred to as shower pipes, to a spraying device 82 located in the upper part of the reactor and which is used, amongst other purposes, to combat foam. Additives 95 for microdispersion initialization and stabilization are also provided which are fed into the pipe 81 or the spraying device 82, respectively, via an apportioning pump DP.sub.5 and pipes 96 and 96.

(32) The shower pipes 81, 81 and 81 are also supplied by the circulation pump P.sub.1, and the flow is regulated by valve RV.sub.8. The gas mixture, which is low in oxygen, leaves the reactor via pipes 71 and 71 and control valve RV.sub.7. If necessary, the heat-up energy required in the startup phase can be provided by an electrical heater installed in the reactor.

(33) The present invention moreover relates to a process for the continuous operation of a system for the treatment of organically polluted waste water in a reactor, optionally with an upstream heat exchanger and with at least one device (nozzle) of the present invention, by the addition of a radical starter, an O.sub.2 containing gas and optionally a catalyst wherein the waste water is optionally preheated in a heat exchanger and subsequently introduced as a stream into the reactor through at least one device (nozzle) of the present invention, wherein a radical starter and optionally a catalyst are added to the stream and wherein an O.sub.2 containing gas is added to the stream in the device (nozzle). Thereby an unstationary flow can optionally be produced and a radical chain reaction can be started and maintained. In this chain reaction a superimposition of the radical chain reaction initiated by the radical starter and of the O.sub.2 chain reaction initiated by the O.sub.2 containing gas occurs, as a result of which the catalyst cyclically changes its valence and wherein the degradation of the ingredients of the waste water to be oxidized is thereby effected.

(34) The reactor pressure range is preferably 0 to 4 bars, especially preferably 1 to 3 bars. The temperature range is preferably 80 to 140 C., especially preferably approx. 110 C. Possible materials for the reactor are e.g. V4A steels. Microdispersion stabilization may e.g. be achieved by the addition of a low-foam surfactant or by a polyether mixture, e.g. a polyethylene/polypropylene oxide copolymerisate. At the same time the height of the bubble column is kept as low as possible to facilitate degassing of the water. The infusion of the polyether can also be done into the reactor circulation flow. If necessary, the heat-up energy required in the startup phase can be provided by an electrical heater installed in the reactor.

EXAMPLE

(35) The process was carried out in an oxidation system as shown in FIG. 3: A 4 l reactor which was equipped with a nozzle according to the present invention, a mammoth tube as well as measurement and control technology is charged with 3 l of a 30% aqueous potassium hydrogenphthalate solution (waste water) and 0.2 g of iron sulfate (FeSO.sub.4*7H.sub.2O). This corresponds to a chemical need of oxygen (CSB) of approx. 12,000 mg O.sub.2 per liter. The pH is adjusted to 3 and the mixture is heated to 120 C. As soon as 120 C. are reached, 2.5 g of a 35% hydrogen peroxide solution are added over 20 minutes via the nozzle. Simultaneously, an air stream of a total of 22 l air are added over 20 minutes via the nozzle. The pH is maintained at 3. This leads to a reduction of the CSB of 85%.