DE2354842A1 - METHOD FOR REMOVING ORGANIC POLLUTION FROM LIQUID AND GAS FLOWS - Google Patents

Description

Patent Attorneys DIpl.-Ing. Π. r2 Il ETZ
n ". te. i.Af:?. ii
r.-ir.cj. R. D -2 Ii TZ Jr, Munich 22, Steinedorfetr

08-21.63OP

November 2 , 1973

A W T Systems, Inc., Wilmington (Delaware), V.St.A.

Process for removing organic contaminants from liquid and gas streams

The present invention relates to a method for removing impurities from liquid and gas streams using an iron-carbon complex with magnetic susceptibility for adsorption of the impurities with subsequent separation of the iron complex containing the impurity from the liquid. On the other hand, this invention relates to a method for the regeneration of an iron-carbon complex with magnetic susceptibility ₃ which contains impurities adsorbed from a liquid or gas stream. It has been known for many years that powdered activated carbon can be used to treat water and other liquids containing impurities in order to reduce the concentration of impurities therein. Powdered activated charcoal is particularly desirable for use in aqueous systems because the carbon particles contain about 90 % of their total adsorptive capacity

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adsorb in less than 5 minutes. The main drawbacks when using powdered carbon to remove impurities from liquids in losses of powdered carbon either during the working process or during the re- ' generation of carbon to remove impurities from it. An additional problem that one encountered when using powdered carbon as an adsorbent in liquid systems in the long settling times required to recover the carbon. These for recovery of the carbon require long settling times in turn, large retention tanks in order to completely remove the carbon from the water and recover it of powdered carbon.

Various procedures have been used ₉ to reduce "the time required for the settling of powdered carbon after treatment of a liquid system to remove impurities. One such procedure uses a flocculant with the carbon. Another procedure uses weighting agents of magnetite or clay with the carbon added to contaminated water to increase the settling rate It has been found that it is necessary to add flocculants even when weighting agents have been used to cause the powdered carbon to settle in a reasonable time.

In copending U.S. patent application serial no. 207.5 ^ 7 become an iron-carbon complex with magnetic susceptibility and a method for making this iron

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"» 3

Carbon complex fully disclosed. This pending patent application is hereby expressly referred to. The iron-carbon complex described in the patent application mentioned contains a heterogeneous aggregate of tuft-shaped or grape-shaped form of powdered activated carbon with the underneath and on the powdered activated Carbon adhering particles of iron oxide ₉ with the iron oxide mainly _{containing Fe 5} O ₁ ^, This iron-carbon complex with magnetic susceptibility _s . is the hereinafter sometimes simply referred to as complex _s can readily be removed by magnetic auxiliaries from the Flüssigkeitss ^ Roemen.

According, the present invention is a method for removing organic contaminants from a liquid or Gas.ström created wherein _s is used the above-described iron-carbon complex magnetic susceptibility, and comprises said learn the ¥:

(a) dispersing the iron-carbon complex with magnetic susceptibility in the flowing feed stream

(b) maintaining the iron-carbon complex with magnetic susceptibility in dispersed state in the flowing feed stream until the adsorption capacity of the complex as a result of the adsorption of the Impurities from the flowing stream is significantly reduced,

(c) passing the dispersion from step (b) through a magnetic one Filter in which the dispersion is subjected to a magnetic field, whereby the dispersion in

(1) a flowing stream with a reduced con-

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concentration of impurities and

(2) a complex containing the adsorbed impurities is separated,

(d) regenerating the complex separated from step (c) by heating the complex in an inert atmosphere, and at one, to desorb the impurities from the complex and to evaporate the impurities sufficient temperature, and maintaining heating and atmospheric conditions until desorption is substantial is complete, and

(e) recovering the regenerated complex.

The flowing streams containing organic impurities, which can be treated according to the present invention include both gas streams and Liquid streams of any composition, which contain organic impurities, which by means of activated carbon can be adsorbed. That Process is especially for the removal of soluble or dispersed organic materials from water are suitable. The method of the present invention is. to treat suitable for aqueous streams containing impurities such as insecticides, detergents, phenols, Dyes, enzymes, virus types, fats, proteins, polysaccharides, oils, colloids, odorous or color-producing organic compounds, and the like. The method is special useful for the tertiary treatment of industrial or sanitary wastewater to eliminate such liquid streams suitable for a discharge into the rivers. Non-aqueous streams can also according to the present Invention to be treated. Illustrative non-aqueous streams that can be treated include liquid ones synthetic organic resins, the color bodies as impurities

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Cleaning agents contain dry cleaning agents, glycerin, the organic, which produces both color and odor Contains impurities, and the like.

Examples of gas flows made in accordance with the present invention can be treated include airborne contaminants such as organic gases or finely divided organic particles. The method of the present invention can also be used for removal of numerous organic contaminants from hydrocarbon gas streams are used »

The iron-carbon complex used in the process of the present invention is mechanically stable. The complex can be suspended in water and, if the complex is subjected to a magnetic field, all of the complex, "carbon as well as the iron oxide, is essentially completely removed from the suspension. The complex can be subjected to mechanical mixing in the dry state, The iron-carbon complex was examined by electron microscopy for the purpose of comparing the complex with physical mixtures of iron oxide (Fe ^ (K) ₃ made from EJeSOi ,, and carbon powder. In the physical mixtures of carbon powder and iron oxide particles, the individual particles of both materials were easily recognized by means of electron microscopy. In contrast, the iron-carbon complexes according to the invention appeared as heterogeneous aggregates of tufted or grape-shaped form. Very thin sections of such a tufted aggregate were examined .These thin bü cup-shaped or grape-shaped aggregates enable the use of the electron microscope

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Preparation of a picture ₃ showing that the iron oxide particles were in the form of polygonal coins randomly distributed in the powdery carbon particles.

The iron-carbon complex having magnetic susceptibility used in the process of the present invention can be prepared by a process ₃ which comprises the following steps:

(a) Forming a slurry by mixing powdery activated carbon, an iron (II) salt solution and a sufficient amount of a basic reagent to adjust the resulting slurry a pH in the range of about 6 to about 11, where the slurry has a continuous phase containing ferrous salt solution and the basic reagent and a having dispersed phase containing powdery activated carbon, and

(b) mixing the slurry from step (a) in the presence of air for a time and at a temperature which is sufficient to form a slurry which has a continuous phase containing a ferrous salt solution with reduced concentration and a basic reagent, and containing a dispersed phase Particles of the iron-carbon complex, and port setting heating until essentially all of the particles of the iron-carbon complex respond to the application a magnetic field on which the particles can be moved. The iron-carbon complex can be made from the Slurry is rapidly separated by applying a magnetic field to the slurry to detect the particles and decanting the liquid phase from the iron complex particles. The complex can also use

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Filtration processes are separated. The obtained iron-carbon complex particles are dried and stored for a required application.

The carbon that can be used in the iron-carbon complex includes all types of activated carbon in particulate form which have particle sizes in the range of about 200 microns up to about 200 microns in their largest dimension. The term "activated" carbon means a porous carbon _s which has an adsorption capacity _s and which is derived from organic substances of vegetable origin, such as lignite, and wood pulp by-products and animal substances, or which is derived from carbon-like minerals:

Any iron (II) salts can be used to produce the complex are used, which are precipitated by adding a basic reagent to an aqueous solution of the iron (II) salt can be.

Illustrative iron salts used, the _s can be, iron (II) include -sulfatj iron (II) chloride, iron (II) -aeetat "iron (II) bromide _s iron (II) nitrate, and. The like. Illustrative Basic reagents which can be used to adjust the pH of the slurry include sodium hydroxide, potassium hydroxide, ammonium hydroxide, ammonium carbonate, calcium oxide, and the like. The adjustment of the pH of the slurry for the preparation of the iron-carbon complex is important in order to ensure the precipitation of the ferrous hydroxide and to obtain an iron-carbon complex which exhibits sufficient magnetic susceptibility to to be attracted by magnetic forces. Accordingly, it was generally found that those produced in slurry insulation

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Iron-carbon complexes in which the pH is less than about 6 or greater than about 11 have very poor magnetic properties. It is generally desirable to maintain the slurry at a pH of between about 6 and 11, and to provide preferably between about 7 to about S ₃ around an iron-carbon complex, which has an optimum magnetic susceptibility.

In the manufacture of the iron-carbon complex is it is desirable to heat the ingredient slurry above room temperature (21 C) to prevent oxidation accelerate from iron (II) hydroxide to iron oxide. It is preferred to bring the slurry to about 100C heat. Heating the slurry to about 100 ° C under atmospheric pressure is desirable because it does the oxidation process further accelerated. The formation of an iron-carbon complex with magnetic susceptibility Time required according to the invention will vary from about 120 minutes at room temperature to about 10 minutes at 100 ° C.

The iron-carbon used in the present process complex with magnetic susceptibility contains from about 5 to about 35 wt .- ^ iron oxide as Fe ^ O _2, and from about 65 to about 95 wt -.% Carbon. It is generally preferred to prepare an iron-carbon Komp'lex, at least about 10 wt -.% Iron oxide contains, in order to allow easy removal of the complex when the complex is subjected to an applied magnetic force.

The term "magnetic susceptibility" as used here is used in relation to the iron-carbon complex,

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is defined as an increase in the magnetic moment of the iron-carbon complex due to the application of a magnetic field. If no increase in the magnetic moment by the application of a magnetic field enters _y or if the increase is so small that it the iron-carbon complex, does not permit recovery by the application of a magnetic field, the iron-carbon complex is not as a complex with magnetic susceptibility. The greater the magnetic susceptibility of the iron-carbon complex according to the invention, the greater the attraction of the iron-carbon complex to a magnetic field of a given size for the separation of the complex. The lower the magnetic susceptibility of the iron-carbon complex is _s -is greater the strength of the separation of the complex from the liquid, or continuous phase of the slurry in which it was made, or for the separation of the complex from the system, in which it was applied required magnetic field.

The method according to the invention is further referred to described on the drawing, in which an explanatory flow diagram for the treatment of a liquid stream, which contains organic impurities (liquid stream) is shown. The liquid stream and the complex are in Contact devices, such as a batch mixer, a continuous, located within the pipeline Mixer, or the like., Mixed. The amount of complex applied is related to the nature of the pollution, the pollution level, and the desired reduction in the. Contamination levels vary. The mixer used must be able to move the complex over the entire liquid

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Dispersion of the complex throughout the liquid is important in order that the impurities and the complex are essentially fully contacted, whereby the impurity is adsorbed by the activated carbon portion of the complex. The time required for a dispersed complex to adsorb its capacity to impurities will depend on the impurities present in the liquid stream and the temperature at which adsorption occurs. The capacity of the complex will vary between different types of impurities, the complex reaching a state of equilibrium upon extended contact with the impurities, in which state no further adsorptive capacity of the complex is realized. It is therefore possible in the practice of the process of the invention simple experimental operations are carried out in practice to determine the complex quantity corresponding to a necessary liquid stream to be treated for addition to X ₅ to determine the concentration the past. reduce impurities to an acceptable level. Similarly, the contact time required for the complex to reach its adsorptive capacity can be determined by contacting several samples of the liquid to be treated with fresh complex and measuring the reduction in the concentration of impurities in the liquid. The rate of adsorption for the contaminants will decrease over time. In this way, an approximate state of equilibrium can be estimated which exists between the impurities in the liquid and the adsorbed impurities on the complex. Under general conditions of use, this equilibrium will be reached in about 5 minutes of contact time.

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Subsequent to the adsorption of the liquid impurities "from the liquid stream in the contact device, the mixture obtained, which contains the complex and liquid, is passed into a magnetic filter device in which the mixture is subjected to a magnetic field applied thereto. If necessary, the mixture can be settled to enable a major amount of the purified liquid to be decanted from magnetic fi lterations The complex containing the contaminant is drawn into the magnetic filter by the magnetic field and continuously separated from the major part of the liquid stream ^;

Suitable magnetic filters are known to those skilled in the art. A typical filter, which is suitable for use in the method of the present invention ₃ is a Ferro Frantz Filter, Model 42, cylindrical with a 3 7/8 "χ 6" (98 mm _a 425-χ 152.4 mm) mesh core (mesh core) This electromagnetic filter has a field strength of around 1,000 Gauss. At a flow rate of about 10

gal./min/sq.ft. (approx. 40.7 ml / min. / cm) of the cross-sectional area, such a filter is able to cover almost the entire area powdery iron-carbon complex from an aqueous suspension with a content of 1 000 ppm des Remove complexes to about 50 ppm. ·

It becomes a purified liquid stream and a slurry, which contains the complex and remaining liquid from the liquid stream, recovered. The cleaned one Liquid flow can, if necessary, by repeating the adsorption, ..Fi-It rat ions and separation steps can be further purified using the complex described above.

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Subsequent to the cleaning, the complex ₃ containing the impurity, which is generally in the form of a slurry with residual liquid, is transferred to a regeneration furnace in which the complex containing the impurity is heated to a temperature at which the impurities and the remaining liquid are removed evaporated from the complex. Optionally, the slurry can be filtered in a conventional manner to remove a substantial amount of residual liquid prior to transferring the complex to the regeneration oven.

The regenerator may be a fluidized bed furnace which is operated at a temperature in the range of about 600 ° C to about 900 ⁰ C and at atmospheric pressure. The regeneration furnace is preferably operated under conditions such that oxygen is essentially absent. It is preferred to carry out the regeneration in an inert atmosphere containing some steam. A particularly suitable inert gas is nitrogen. The required heat can be supplied by hot inert particles, such as sand, which are introduced into the regeneration furnace. To the activation of the complex, required residence time of the complex that is for stripping adsorbed impurity in the regenerator is in the range of several seconds at temperatures of about 900 ⁰ F (482 ⁰ C) to about 1 min., At temperatures of about 600 ° F (316 ° C). The residence time for the activation of the complex will depend mainly on the impurity to be removed and the regeneration temperature. The vaporized impurities and the activated complex are withdrawn overhead from the regeneration furnace and placed in a separation device such as

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separated in a cyclone separator. If desired, can the vapor is easily separated from the decomposition products will. . .

The regenerated complex can be in the separator in the form recovered from dry particles. Optionally, the regenerated complex in the separator, for example with water, quenched and recovered in the form of a slurry. The Reclaimed Complex is put back in the contact device for reuse promoted.

Although the described. Process a fluidized bed furnace used for the regeneration of the complex, it will be understood that other types of ovens, such as the The tube furnace described in Example 1 can also easily be used. .

In summary, the present invention relates to a Process for the removal of organic impurities from a liquid stream, the organic impurities contains. The method comprises dispersing a Iron-carbon complex with magnetic susceptibility did in the liquid stream that, maintaining the iron complex with magnetic susceptibility in dispersed State until a substantial amount of the impurities have been adsorbed from the liquid stream, and the transfer of the iron-carbon complex with magnetic susceptibility-containing dispersion through a magnetic filter for separation the dispersion into one. Liquid flow with a reduced concentration of impurities and a adsorbed complex containing the impurities.

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The regeneration of the adsorbed complex can be accomplished by heating the complex in an inert atmosphere a temperature sufficient to desorb and evaporate the impurities.

The following examples illustrate various features of the present invention. Example 1 illustrates the adsorption and Regeneration Stages of the Present Invention. Example 2 shows that the iron-carbon complex works as well or nearly as well as fresh activated carbon for adsorbing Impurities from sewage. Example 3 illustrates the process of the present invention. In the examples the parts and percentages are parts by weight and. Weight percentages unless specifically stated other is noted.

example 1

2 parts of the disclosure in the pending patent application Serial No. 207.5 ^ 7 prepared complex are mixed with 1,000 parts of an aqueous filtered raw wastewater (liquid stream with a content of impurities), which has a total oxygen demand (GSB) of 185 ppm, in a batch contact vessel. The complex contains a heterogeneous collection of gepulvertei ⁴ including activated carbon with mixed · particles of iron oxide adhering to the powdered activated carbon, and it contains about 85% carbon and about 15% iron oxide as Pe O _{3. 11}

The mixture is agitated sufficiently to make the complex within the entire liquid waste water

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disperse. After 1 hour of mixing, the Mixture allowed to settle for 1 hour and the bulk of it the purified liquid is decanted off. The complex containing the contaminant and remaining liquid are filtered through a 0.45 micron glass filter paper Vacuum filtered and the complex in an oven at 110 for 1 hour -long to remove essentially all, dried water adhering to the complex.

The complex is then turned into one for regeneration Tubular furnace placed. First, air-purged nitrogen saturated with water is used to flush the furnace passed through the furnace. The furnace will then heated to 700 ° C and held at 700 ° C for about 10 minutes. During the heating, gases released by'der Evaporation of the contaminants originate and residual liquid present on the complex is created and removed removed from the oven. When the proportion of gas generation is constant is switched off the heat supply to the furnace and. lets the oven cool down. A regenerated complex is recovered. .

B e i s ρ i e 1 2

Example 1 is repeated with the exception that fresh activated charcoal is used in place of the complex will. It became the carbon adsorption isothms on the regenerated complex and on fresh activated coal determined, each for about 1 hour. Long in the same Quantities of an aqueous, filtered wastewater with a total oxygen requirement (GSB) of about 145 mg / 1 dispersed had been. These isotherms show that the adsorption capacity of the regenerated complex is essentially the same

■■ · "., ■■, - 16 -

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is the same as that of fresh activated charcoal. ■ "' Example 3

Two parts of an iron-carbon complex with magnetic susceptibility, which contained a plurality of heterogeneous aggregates of powdered activated charcoal with iron oxide mixed therewith attached to the powdered activated charcoal, were in a contact device with 1,000 parts of an aqueous, filtered raw sewage mixed, which had a total oxygen demand (GSB) of 185 ppm. The complex contains about 85 % carbon and about 15 % iron oxide as FeJDu. The mixture is mixed sufficiently to disperse the complex throughout all of the liquid wastewater. The dispersion is maintained for a period of about 5 minutes. The mixture obtained is then passed through a cylindrical electromagnetic filter which has a magnetic field of about 1,000 Gauss. Essentially all of the complex was retained on the screens of the magnetic filter. When the sieves of the filter were filled with the complex, power to the filter was cut and the magnet removed. The complex was then washed off the filter with a small amount of water. This aqueous slurry of the complex obtained is fed into a fluidized bed furnace which ^{operates at a temperature of 900 °} C. and at atmospheric pressure. Sand was used as a heat transfer medium, and the sand was vortexed using nitrogen gas. The heat is supplied to the sand particles through separate heat exchange devices. The residence time of the complex in the fluidized bed furnace is about 20 seconds, during which time the impurities are removed

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removed from the complex and. the complex and impurities are stripped overhead. The complex will of the evaporated impurities in a Cyclön separator severed. The regenerated complex is recovered with essentially no degradation or comminution and if necessary in the contact device for a Recycled recycling.

The above-described method of the present invention is particularly compared to the prior art for the removal of organic contaminants from liquids using activated carbon Advantage because no flocculants and no large settling tanks are required. This procedure is also also to a large extent for cleaning a gas stream useful containing organic impurities.

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Claims (4)

Claims 1. Process for the removal of organic impurities from a liquid stream, the organic Contains impurities, characterized in that that he (a) dispersing in the liquid feed stream an iron-carbon complex with magnetic susceptibility which contains a plurality of heterogeneous aggregates of powdered activated carbon with intermingled particles of iron oxide including Pe, CK ₃ adhering to the powdered activated carbon; (b) maintaining the iron-carbon complex with magnetic 'susceptibility in a dispersed Condition above the liquid feed stream until the Adsorption capacity of the complex as a result of adsorption of impurities from the liquid is essential is reduced; (c) passing over the dispersion from step (b) a magnetic filter in which the dispersion is subjected to a magnetic field, thereby reducing the dispersion in (1) a liquid stream with a reduced concentration of organic impurities and (2) an adsorbed complex containing the impurities is separated; (d) regenerating the separated complex from step (c) by heating the complex in an inert atmosphere and at a temperature sufficient to desorb the impurities from the complex and the impurities to vaporize and maintain until the desorption is essentially complete, and - 19 - 409820/0816 -.19 -. (e) recovery of the regenerated complex. 2. Process for removing organic contaminants from a liquid stream, containing organic impurities, thereby g e k e η η ζ e i c hn e t that it includes:> (a) dispersing an iron-carbon complex with magnetic susceptibilityy containing a multitude activated by heterogeneous aggregates Coal with particles of iron oxide mixed in with it, containing Fe, Oj,, and adhering to the powdered activated carbon, in the liquid stream, (b) maintaining the complex in a dispersed state Condition over the entire liquid flow. until the adsorption capacity of the complex is essentially as Result of the adsorption of impurities from the liquid is reduced, (c) passing the dispersion from step (b) through magnetic filter in which the dispersion is a magnetic Field is subjected, thereby reducing the dispersion in . (1) a liquid flow with a decreased Concentration of impurities and. . .- (2) a slurry containing a complex with a content of adsorbed impurities and • remaining liquid is separated, (d) regenerating the separated complex from step (c) by heating the complex in an inert atmosphere at a temperature sufficient to desorb and remove the impurities from the complex. evaporate and maintaining the conditions »until desorption is essentially-complete, and (e) recovering the regenerated complex. - 20 - 40982Ö / 0816 3. The method according to claim 1, characterized in that that the liquid stream is a gas feed stream. 4. The method according to claim 2, characterized in that the contaminated complex from step (c) ^{is regenerated by heating the complex at a temperature in the range from about 600 °} C. to about 900 ^° C. in an atmosphere of nitrogen and steam. A0y820 / 08 1 6