DE19729814C1 - Process and assembly to remove impurities from esp. effluent process air - Google Patents

Abstract

In a process to remove impurities from a flow of gas, the gases flow pasta surface bearing a colony of micro-organisms growing as a film (11) on a membrane substrate surface (10) which is maintained in a moist condition by a spray or flow of water or fluid containing an aqueous solution of salts. The novelty is that: (a) the flow of gas passes simultaneously over both sides (front and rear) of the same substrate membrane (10); (b) the substrate is a semi-permeable membrane in whole or in part; (c) depending upon the gas impurities, the gas passes first over that part of the surface with no colony of micro-organisms, or with a colony of micro-organisms;(d) the gas pressure is regulated according to the nature of the impurities and their concentration; (e) the substrate material, the gas, and/or the fluid which moistens the substrate surface are heated; (f) the substrate material (11) is exposed to a continuous or semi-continuous supply of a wetting agent; (g) the membrane (10) is selective with respect to given substances; (h) also claimed is a suitable assembly.

Description

The invention relates to a method according to the Oberbe handle of claim 1 and a device to carry out the method, in particular the purification of exhaust air is intended.

It is for example for the purification of exhaust air known to use biological processes to contained pollutants with the help of microorganisms to convert enzymatically to low molecular weight compounds put.

The biological processes taking place here can but usually only in an aqueous environment be carried out so that it is necessary to contained in the air or in other gases too dissolving separating substances in water beforehand. The Separation of organic substances in the gas or in  the exhaust air is contained in three parts steps. In doing so, the damage (s) becomes substance (s) by an absorption step from the con removed contaminated gas and subsequently convex tive or diffusive mechanisms to the respective Microorganisms run as suspended Cells or as a biofilm on a surface of a Growth carriers are available.

The conversion of pollutants to carbon dioxide and Water takes place through oxidation with simultaneous Consumption of oxygen. It also includes a part the substrate for the construction of biomass uses, so that normally nutrient salts and trace elements elements must be added.

In many cases, however, the pollutants cannot to be completely converted so that it becomes the un desired formation of by-products (acids, inorganic salts u. a.), the higher concentration the intended biological reaction even prevent.

It is known for these applications or biofilters Use bio-washer, but the above Disadvantage, so that alternatively Biorie Selbed or biomembrane reactors developed and before have been beaten.

In a bioriesel bed reactor, the specifi microorganisms that contain the respective pollutants break down or convert, on inert packing immobilized. The gas to be cleaned or the Exhaust air flows through a fixed bed designed in this way  with a nutrient salt solution in cocurrent or countercurrent is sprinkled. This will supply the Mi microorganisms and at the same time moistening the Systems achieved, and it is possible to at the biodegradation products close, so that another undesirable leg the subsequent biological reactions can be avoided. Such well-known bio-drizzle Bed reactors are for example in DE 39 16 737 A1, DE 32 27 678 A1, DE 34 28 798 A1 and US 4,421,534 be wrote.

In the known bioriesel bed reactors there is but the problem is that the free flow cross section for the gas to be cleaned or the exhaust air through over moderate biomass production increases:

VDI reports 1104: "Biological emission control", Conference report March 9th to 11th, 1994, Heidelberg, VDI publishing house Düsseldorf (1994);

Diks R., Ottengraf S., Vrijland, S .: "The existence of a biological equilibrium in a trickling filter for waste gas purification ", Biotech. Bioeng. 44 (1994) Pages 1279 ff .;

Kirchner K., Gossen C.A., Rehm H.-J., "Purification of exhaust air containing organic pollutants in a trickle-bed bioreactor ", Appl. Microbiol. Biotechnol. 35 (1991), pages 396-400.

So far, this disadvantage has been countered by that structured beams with large gap diameters be used, the loading with microorganism men is reduced and the biomass morphology be is influenced, so that the risk of clogging the  Bio trickle bed reactor reduced but not full can always be excluded.

The microbio's disability has a particular effect logical growth - for example through limitation the addition of nutrient salts and growth inhibitors - insofar as negative that the capacity of the biological reactions, i.e. the amount of degraded Pollutants is restricted, as described by K. Kirchner and others in "Purification of exhaust air containing organic pollutants in a trickle-bed biore actor ", Appl. Microbiol. Biotechnol. 35 (1991), pages 396-400 has already been named.

Another known possibility is the use the so-called bio-membrane reactors for hydrophobic Exhaust air ingredients by Bäuerle U., Fischer K., Bardtke D., in "Biological Exhaust air purification with the help of a new type of permea tion reactor / keeping the air clean ", 46 (1986) 5, pages 233-235, and in DE 35 42 599 (1987) have been described. The principle of Steam permeation applied. It is gas permeable sige membrane between the gas phase and the liquid Phase arranged so that on the surface of the mem bran the hydrophobic pollutants as gases adsorbie Ren. After the permeation of the gaseous pollutants through the membrane these are attached to the liquid side surface with the grown there biodegradable microorganisms.

However, this method can be used for water-soluble substances fe can only be used to a very limited extent, since the hydro  phile substances only very limited in the hydrophobic Membrane are detachable.

Furthermore, DE 196 08 834 C1 describes a method described for biological exhaust air purification, in which Exhaust air containing pollutants in a stream of a tech biological unit consisting of an activated carbon adsor a washer, a heat exchanger and the actual bioreactor with a fixed bed with a Biocatalyst is supplied. The one described there Process can be batch or continuous with fluctuating pollutant concentrations for biolo contaminated exhaust air flows can be used.

It is therefore an object of the invention, a method and specify a device with which both hydro phobic as well as hydrophilic substances from gas streams biodegradation can be separated.

According to the invention, this object is achieved by the features of claim 1 solved. Advantageous Ausge Forms and developments of the invention arise when using the in the below ordered claims features.

In the method according to the invention, the in Gases containing pollutants or where appropriate other materials to be separated in the desired manner components by enzymatic conversion using Mi microorganisms after separation on biological Paths converted into harmless components. Therefor a carrier is used, which at least one Side on its surface with a corresponding Overgrown biofilm containing microorganisms,  sprinkled with water or an aqueous solution becomes.

According to the invention, the gas stream to be cleaned is both on both sides preferably opposite guided surfaces of the carrier, being on the uncovered side of the permeable and / or semi-permeable wearer especially little what ser soluble (hydrophobic) substances from this and by diffusion through the membrane Carriers are directed to the microorganisms.  

In contrast, the readily water-soluble (hy drophilic) substances through the liquid film (water, aqueous mineral salt solution) on the overgrown side washed out of the carrier and thereby the biological System made available.

There is in the method according to the invention according to the pollutants contained in the gas stream, that are to be biologically converted, the poss the gas or air flow first on the side past the surface of the membrane-shaped support lead on which there is no biofilm, so that the not or only slightly soluble in water components separated from the gas or air flow can be and the separation of the hydrophilic Pollutants only after the continuation of the gas or air flow along the other surface side of the membrane-shaped carrier that in the biofilm contained microorganisms are supplied.

However, it can be the opposite of the gas Electricity should be routed so that the water is good first soluble (hydrophilic) substances are separated. A appropriate gas flow guidance should be dependent the respective proportions of corresponding hydrophobic or hydrophilic substances in the gas or air flow be performed.

Another way to influence the Ver driving is that the volume flow and / or the pressure of the gas when performing the Procedure depending on the different poss contained types of pollutants or the various where concentrations are regulated. Takes place at  for example the diffusion of certain material components through the membrane-shaped support with a relative low speed, so a lowering of the Volume flow or a slight increase in Pressure affect the conversion rate. If necessary, for example, by extension the dwell time are ensured that the almost ge entire undesirable proportion of a particular substance can be separated from the gas or air flow.

The support designed as a membrane can be of various types Show shapes, but should be at least two dimes sional be trained so that the gas or air current on both surfaces of the membrane-shaped Trä gers can be led past. That for the wearer preferably porous material used should pass sig for at least one of the gas or air electricity to be separated substances, whereby the Separa tion can be selective or non-selective, so that all substances contained in the gas or air flow can be separated or the separation on be agreed selected substances is limited.

Suitable carrier materials are, for example, sili rubber, porous inorganic materials (metal oxides, ceramics, metals and intermetallic Pha sen), but also porous carbonaceous materials lien, however, prefers a certain level of sorp capacity for the substance or substances sen. The sorption capacity then ensures that conc fluctuations due to an appropriate buffer who compensates for the effect of the membrane-shaped support that can, so that the course of the biological reac tion becomes evenly feasible.  

In the method according to the invention and the equivalent However, it is not a properly designed device absolutely necessary, the entire carrier from one Form material that is permeable and / or semiper is meabel. This can be the case in particular be when the proportion of hydrophilic to be separated Substances larger than the proportion of hydrophobic substances is.

The diffusion and / or sorption capacity of the membrane-shaped carrier can be influenced by Temperature increased or decreased as needed the. For example, the gas flow, the actual carrier, the water and / or the aqueous Mineral salt solution can be tempered by heating. Heating usually leads to the dif fusion and sorption can be increased nen.

Suitable carrier materials with a sorption ver like are z. B. activated carbons, oxidic sorbents.

The membrane-shaped supports can already be in addition to the mentioned two-dimensional form also in various geometrical contours as hollow bodies be det, preferably the surface area ei of such a body, which points inside, with Biofilm is overgrown. The body can be tubular mig trained or from several flat plates be assembled accordingly. Such structures can then be carried out in multiple or plate reactors are used so that for the cleaning of the gas or air flow is relatively large Contact areas due to large surface-volume ver  ratios are available. Such a structure avoids that with great reliability State of the art known strong growth of bio mass through the given geometries and offers easy cleaning options.

The device according to the invention is almost constant conditions that are characterized by low and almost constant pressure losses during operation of a suitably trained reactor.

Due to the separate separation of the hydrophobic and hydrophilic contained in the gas or air flow Pollutants on the two different surfaces of the membrane-shaped carrier arise very efficiently Simultaneous deposition conditions, which in particular re when cleaning gas or exhaust air flows that contain several different pollutants, advantage has an impact.

The simple and manageable structure of the invention modern device and the simple procedure allow according to the required procedure conditions, d. H. considering ver different gases to be treated with possibly ver different concentrations of pollutants that a ange appropriate growth of the biofilm can be achieved if this is necessary.

There are also very good control options through the influences of Volu already mentioned flow, pressure and temperature. It can be body cohesively trained membrane-shaped supports alone their contours and dimensions already influence  Take pressure and volume flow. For example, it can the entry for the gas inside such Body are designed as a throttle point, so that the outer area, i.e. the surface of the membrane-shaped carrier, which is uncoated, with a higher pressure than the inside lying surface.

The membrane-shaped carrier is made of one material formed, which has a certain level of sorption capacity for at least some of the substances to be separated shows, fluctuations in stress and stressful situations ions in the reactor due to the buffer effect of the carrier materials balanced and thus the process verver be mastered casually.

The invention is based on exemplary embodiments len are described in more detail. Show it:

Fig. 1 is a schematic representation of a tube bundle reactor, and

Fig. 2 shows the schematic structure of a single tube res.

Fig. 1 shows the basic structure of a Rohrbün delreaktors, which makes use of the structure according to the invention.

Inside the tube bundle reactor 1 , a number of individual tubes 7 are added, to the basic construction of which will still be described in the description of FIG. 2.

In the tube bundle reactor 1 , air is introduced via the inlet 2 , and along the outer surface of the individual tubes 7 , the permeable carrier 10 allows diffusion of, in particular, hydrophobic substances contained in the air to the biofilm 11 , so that the The majority of the hydrophobic substances to be separated can be fed to the biological conversion in the biofilm 11 . The air then passes through the air outlet 4 through a second air inlet 9 back into the Rohrbün delreaktor 1 and is led from there into the interior of the various individual tubes 7 , the hydrophilic substances still contained in the air via the Rie selfilm 12 in dissolved form can be treated biologically with the microorganisms in the biofilm 11 .

The individual tubes 7 are held in the tube bundle reactor 1 at both outer ends with a sealing socket 5 , which prevents an undesired gas exchange between the air, which is guided past the outer surface of the individual tubes 7 Man, and the air content that follows through which a single pipe 7 is to be guided.

After the biological treatment, the air is drawn off via outlet 3 .

In this example, a mineral salt solution is passed through the individual tubes 7 in the circuit 6 in the form that the air and the mineral salt solution run in countercurrent.

The mineral salt solution passes through the individual tubes 7 from the upper area of the tube bundle reactor 1 into a sump 8 of the single reactor 1 , in which the mine ralsalzlösung is collected and pumped with a pump in the mine ralsalzlösung circuit 6 back into the upper range of the tube bundle reactor 1 and from there through the individual pipes 7 back to the swamp 8 can run.

In Fig. 2 the basic structure of a single tube 7 is shown.

The single tube consists of a membrane-shaped carrier 10 , which is permeable or semi-permeable for the various substances contained in the gas or in the air. On the inner circumferential surface of the single tube 7 , a biofilm 11 is formed in which microorganisms are included to carry out the desired biological reactions. Through the single tube 7 , liquid is conducted in the form of water and preferably in the form of a mineral salt solution, so that a liquid trickling film 12 forms on the biofilm 11 .

The air to be cleaned is, as shown by the arrows, first out along the outer surface of the individual tube 7 , so that there the poorly water-soluble substances contained in the air can diffuse through the membrane-shaped carrier material 10 to the biofilm 11 , what is represented by arrow 13 .

Subsequently, the air flow can enter the interior of the single tube 7 , the air can be counter-current in Ge. Inside the single tube 7 , the readily water-soluble components can then be fed into the biofilm 11 in dissolved form by the trickle film 12 and biologically converted. Certain components formed in the biological reaction can be removed with the water stream or the mineral salt solution stream.

The separation of the readily water-soluble components in the air is shown schematically in FIG. 2 with the arrow 14 .

Of course, other shapes that are of the tube shape deviate, for example square or other polygon shapes, find use.

Claims (11)

1. Process for the separation of pollutants contained in gases by enzymatic reaction using microorganisms which are grown on one side as a bio film on a surface of a support and are sprinkled with water and / or an aqueous mineral salt solution, characterized in that the gas stream subsequently on both sides of the carrier ( 10 ), which consists at least partially of permeable and / or semi-permeable material. 2. The method according to claim 1, characterized in that one passes the gas stream depending on the pollutant first of the biofilm ( 11 ) overgrown or overgrown surface of the carrier ( 10 ). 3. The method according to claim 1 or 2, characterized in that the volume flow and / or the pressure of the gas flow in dependence of the type (s) of pollutant and / or regulates their concentration. 4. The method according to any one of claims 1 to 3, characterized in that the gas stream, the carrier ( 10 ), the water and / or the aqueous mineral salt solution is heated. 5. Device for carrying out the method according to one of claims 1 to 4, characterized in that a carrier ( 10 ) which is covered on at least one of its surfaces with a microorganism-containing biofilm ( 11 ) and at least partially from one for pollutants by meablen or semi-permeable material, can be sprinkled on the vegetated surface. 6. The device according to claim 5, characterized in that the carrier ( 10 ) is a membrane. 7. The device according to claim 5 or 6, characterized in that the carrier ( 10 ) consists of inorganic, organic and / or biological material which is permeable in its consistency and structure for at least some gaseous substances contained in the gas stream. 8. The device according to claim 7, characterized in that the carrier ( 10 ) se is selectively permeable to certain substances. 9. Device according to one of claims 5 to 8, characterized in that the carrier ( 10 ) for at least one of the pollutants that are contained in the gas stream has a sorption capacity. 10. Device according to one of claims 5 to 9, characterized in that the carrier ( 10 ) is tubular or plate-shaped. 11. Device according to one of claims 5 to 10, characterized in that a plurality of supports ( 7 , 10 ) are arranged in a tube bundle or plate reactor ( 1 ).