DE102007052920A1 - Method for biological treatment of pollutant-loaded gases, involves guiding pollutant-loaded gas through reaction chamber with filling material ballast with small granular swirlable filling material - Google Patents

Abstract

The method involves guiding the pollutant-loaded gas through a reaction chamber with a filling material ballast (2) with a small granular swirlable filling material. The filling material is flown through an artificially generated strong air flow in opposite direction towards trickling water by attaining a technologically specified loss of pressure. The biomass is discharged from the filling material ballast (2) with the liquid flow. The abraded biomass is extracted from the reaction chamber in an adjacent manner. The filling material is made of foamed polystyrene.

Description

The The invention relates to a method for the biological treatment of gases contaminated with organic pollutants and for treatment of gases loaded with hydrogen sulphide and ammonia. With the Process, the pollutants are absorbed in water or on a Biofilm adsorbs and at the same time biologically under aerobic conditions reduced. The method can be used anywhere Exhaust gases from industry, commerce and the waste management treated should be.

The environmental pollution caused by human activities by volatile organic compounds (VOC - Volatile Organic Compounds) has risen sharply in recent decades. This group of substances includes a variety of different Compounds which in many cases are harmful to the environment and to health are.

For the long-term preservation of a healthy and natural Environment became the European and national laws as well Tightening of regulations and administrative provisions on air pollution control. The aim of the laws is through stricter air quality standards the air pollution caused by reduction of man-made Reduce emissions.

When secondary measures to reduce VOC emissions by a pollutant destruction become chemical-physical or biological methods used.

biological Processes are chemically-physical with microbially convertible substances Preferable because they are ecologically and economically optimal run, d. H. Convert a lot of pollutant with little energy. The Transformation is made by naturally occurring microorganisms completed. That's why they've been reinforced in recent years Technologies for biological waste air purification developed.

at biological processes, the pollutants serve the microorganisms for energy production. The one for the metabolic process of Microorganisms necessary oxygen is in the polluted Air carried. Through the growth of microorganisms continuously creates new cell substance.

Accordingly is formed in proportion to the biological activity and excess between the filler material Biomass, which causes an increase in pressure loss over leads to the packed bed, thus the gas flow rate difficult and lead to complete blockage of the packed bed can.

main problem the bioreson bed reactors used in the prior art For exhaust air purification is the tendency to blockage or a very high Effort to remove the renewable biomass. With the goal to work with as high a biomass concentration as possible, there is a risk of instability of the process Clogging of the pore spaces opposite.

The previously used methods for preventing blockages characterized by a high mechanical and technological Effort to remove the excess biomass.

In the DE 196 08 805 C1 describes a method for mechanical Biomasseabrieb by the use of stirrers when exceeding a certain pressure loss. The main disadvantages of this technology are the high mechanical load, which significantly reduces the service life of the fillers used, and the formation of stationary zones in the packed bed.

The DE 196 09 053 C1 describes a process for the separation of excess biomass, in which the reactor is completely flooded and traversed by air. The separation of the biomass is carried out by shear forces. For the subsequent purification, the reactor is re-flooded with water and air is passed through the bed. The deduction of the excess biosludge is done according to patent specification on the reactor head by the floating effect of the rising air flow. In addition to this air entrainment, high speed reactor flooding is required.

One considerable disadvantage of this method is the high water consumption and the high energy demand for generating a strong air flow through the packed with water packing.

Next Process with a high mechanical and technological effort For biomass removal, there exist methods that are optimal conditions counteract for microorganisms and thus consciously a diminished performance of the process.

Some Procedures follow the approach to limiting the settlement area for microorganisms.

The DE 42 13 814 A1 describes a grid-shaped, vertically arranged filler material with a mesh size of about 8 mm, which is to avoid clogging according to the principle of increasing inter mediate spaces in the packing material. Disadvantages here are the low filler surface and the associated low active microorganism surface.

The VDI guideline 3478 part 2 (draft 2005) describes as a summarizing document the state of the art for bioreson bed processes for the exhaust air treatment. As methods for avoiding blockages by excess biomass, the guideline (pages 10, 13, 18, 19) proposes a specific nutrient or substrate limitation, a high liquid loading, for generating a high flow rate or drying of the packed bed. In addition, high pollutant concentrations from 1.5 g / m ³ in the raw gas should not be exceeded. For increased dust or aerosol concentrations in the exhaust gas, an additional deduster or aerosol separator stage is recommended.

The Executions of the VDI guideline show that an effective Method for separating the excess biomass, which nevertheless ensures optimal living conditions for microorganisms, not yet used.

Of the Invention is based on the object, a stable working method to develop with which pollutants from exhaust gases by absorption in Water or adsorption on biomass and simultaneous biological Degradation can be eliminated. This is supposed to cause instability the process by clogging the pore spaces in one Packed bed, even with one out high pollutant load resulting in strong biomass growth and high dust or aerosol clothing, safely excluded.

The The object is achieved by the features solved the method claim 1. Outstanding features are described in the subclaims 2 to 10.

The polluted gas is in a wet or trickled by water and not underwater bed of a fluidizable Introduced filler material. The filler material on the one hand serves to transfer the pollutants from the gas into the water or into the biofilm and on the other hand as a vegetation area for pollutant-degrading aerobic microorganisms. Upon reaching a certain degree of compaction of the packed bed is the filler material in the opposite direction to the continuously, or only during this cleaning, from flowing downwards through a stream of liquid flowing downwards artificially generated strong air flow as long flows through it and moved against each other until a part of the on the surface and between the individual Füllkörpermaterialteilchen adhering biomass and filtered off dust particles rubbed off becomes. The abraded biomass gets mixed with the liquid stream discharged from the Füllkörpermaterialschüttung and then removed from the reaction space.

The filler material has a particle size of <15 mm. Due to this small particle size, a very large specific surface exists in a range between 200 and 2000 m ² / m ³ , which forms very favorable conditions both for the mass transfer and for the growth of the microorganisms. Thus, the conditions for a very large population density and a high mass transfer of the pollutants and necessary for the aerobic biodegradation oxygen from the gas phase into the biofilm are available.

Due to the low density of <0.1 g / cm ³ , the filler material can already be fluidized by strong air with a relatively low volume flow and a relatively low pressure. The spherical shape allows a displacement of the individual carriers against each other, without the reactor having to be filled with water and without the carrier material must be discharged from the reaction space.

Particularly advantageous is the use of foam polystyrene (styrofoam) as a packing material with a density of <0.05 g / cm ³ .

Even with a very strong biomass growth, it is sufficient if, for cleaning the packing with a fan, a volume flow of> 50 m ³ / (m ² × h), preferably in the range between 50 and 1000 m ³ / (m ² × h), and a pressure of> 20 mbar, preferably in the range between 20 and 200 mbar, per meter of material height is passed through the filler material. Depending on the degradability of the dissolved pollutants and the resulting rate of biomass growth, the regeneration of the packing material at intervals of several days to weeks may be necessary. For this purpose, the gas flow is interrupted and pressed in countercurrent to the downwardly flowing water several short bursts of strong air through the packed bed until the packed bed is so vortexed and durchmengt that the excess biomass is abraded.

In addition to the low density and the spherical shape of the carrier material also carried out during the time of Starkluftzugabe sprinkling at a rate between 3 and 20 m ³ / m ² × h a prerequisite for sufficient mixing of the carrier material ge against each other and thus the sufficient abrasion Excess biomass is. With the trickling water at the same time the abraded biomass in the water reservoir below the packed bed transported.

The Regeneration is when exceeding a certain Pressure loss across the packed bed or triggered after a certain time. The pressure loss limit is dependent on the exhaust gas volume flow to be treated selected. The regeneration process can be triggered automatically. Thus, blockages are reliably prevented and for an undisturbed process necessary free passage of Air and water are kept stable at all times.

The Introduction of the strong air flow takes place in the form of several successive following pressure surges. The short-term interruption and re-raising the bed causes abrasion of a part the adhering to the filler material biomass and adhering dust or aerosol particles. Preferably, the strong air flow periodically switched on for approx. 10-40 s and for about 20-60 s interrupted. As a rule, a 5-10 times is enough Repeat this process to effectively erode the excess To achieve biomass.

The Water to trickle over the packed bed is completely circulated and only upon reaching a critical for the microorganisms Value, by the concentration of nutrient salts or Degradation products, replaced. Thus, the water consumption is low held. For certain applications there is the possibility of continuous supply and discharge of a portion of the circulating water volume. This can be the case, for example, for specialized and fluctuating environmental conditions sensitive microorganisms may be necessary.

The sprinkling density in normal operation is preferably in a range of 3-20 m ³ / (m ² × h). Thus, the filler material is evenly wetted and supplies the biofilm with nutrients dissolved in the circulating water.

Of the Exhaust air flow can be in counter or direct current to the sprinkling water be guided.

in the Trap of heavy or non-soluble air pollutants the Überrieslung over a longer Period interrupted, maximum until the moisture of the biofilm falls below a critical value for the microorganisms. Thus, sparingly soluble or water-insoluble Compounds brought into direct contact with the biofilm and by adsorption be bound. The duration of the irrigation interruption depending on the humidity of the polluted gas and after the nutritional needs of pollutant-degrading microorganisms.

Because of its low weight is the filler material also with increasing operating time as a loose bed and forms thus the prerequisite for the optimal mass transfer between gas, water and biofilm.

The biologically highly active bed is flowed through by exhaust and in the treatment of water-soluble air pollutants simultaneously trickled by circulating water. The sprinkling of the packed bed serves the equal and sufficient supply of Bed with fluid and nutrients to optimal Aufwuchsbedingun conditions for the microorganisms and a large Phase interface for the gas-liquid transition to create.

In most applications of bioreson bed reactors is not the transition of pollutants from the exhaust into Water or to the biofilm, but the biodegradation of these Pollutants the rate-limiting step.

in the Contrary to many techniques, which constipation of the bioreactor be avoided by limiting biological growth created by the present procedure the conditions to in the reactor a high population density with high biological activity to achieve.

The Use of a small-grained packing material with a large surface deliberately offers the possibility for a very high population density. This is only in connection with the possibility described above of impeccable Regeneration possible.

With According to the present invention, it is possible to load high loads To treat exhaust air streams, which by a high pollutant concentration and a high dust load for the state of the art Technique represent a high constipation potential.

The Basis for a stable and cost-effective Operation of the present invention eliminates the periodic rinse Biomass and separated dust or aerosol particles from the System, which runs automatically and no extra effort caused.

following The invention will be closer to an embodiment explained.

In 1 is a plant described by the method according to the invention, with which a solvent-containing exhaust air from the woodworking industry is to be treated.

The exhaust air to be treated passes through the exhaust air line 6 in the cylindrical reactor 1 made of polyethylene. The exhaust air flows through the on a sieve bottom 14 lying packed bed 2 , The filler material consists of spherical foam polystyrene with a density of 0.03 g / cm ³ and a grain size in the range of 8 mm on average. The structured surface of the packing is populated with microorganisms that metabolize the pollutants. The microorganisms form on the packing and in the interstices a biofilm, which consists of a variety of different bacteria and other microorganisms. The nutrients necessary for microbial growth are supplied via the nutrient supply as needed 13 in the circulation water pipe 4 brought in. The cleaned exhaust air leaves the reactor 1 over the line 7 , The continuous sprinkling of the packed bed 2 takes place from the water distribution 5 via the circulation pump 3 and the water distribution 5 at the reactor head.

Due to the biological pollutant degradation the biofilm thickness increases and the free passage of water and exhaust air is restricted. Upon reaching a predetermined pressure loss on the packed bed of the regeneration process begins. For this purpose, the exhaust duct 6 and the line 7 closed and the vent line 8th open. The strong air is over the blower 9 through the strong air line 10 in the reactor 1 brought in. The introduction of the strong air flow takes place in the form of several successive pressure surges. After regeneration of the packing, the strong air flow and the water cycle are interrupted until the regeneration consisting of water and abraded biomass 12 from the packed bed 2 has drained off as well as in the water supply 15 collected and by means of Regeneratpumpe 11 was removed from the system. After the deduction of Regenerstes the process by filling the water mask 15 and connecting the exhaust air stream 6 and the circulation 4 the water started up again.

The reactor 1 itself has a height of 4000 mm, a diameter of 3000 mm and a packing height of 3400 mm. The volume flow of the exhaust air is 3000 Nm ³ / h. The sprinkling density of the circulated water is adjusted to 9 m ³ / (m ² × h). The pollutant concentration resulted mainly from ethanol and other alcohols as well as from formaldehyde. After a six-week adaptation period of the biomass, the pollutant concentration is reduced by absorption in the circulating water and simultaneous biodegradation of 300 mg C / Nm ³ in the raw gas to <20 mg C / Nm ³ in the clean gas. In operation after this adaptation time, a regeneration of the packed bed was automatically triggered when the pressure loss increased to 0.33 bar above the bed. For this purpose, a blower with a maximum flow rate of 2200 m ³ / h and a maximum pressure increase of 400 mbar was used. During the regeneration process, about 5 to 20% of the biomass slurry and filtered fine solids were abraded from the surface and from the spaces between the packings with five high-velocity bursts of air. The abraded biomass was transferred to the water reservoir by the irrigation water 15 rinsed and with the Regeneratpumpe 11 from the reactor 1 deducted. After that, the water mask became 15 again filled with washing water. The automatic regeneration process took a total of 18 minutes to resume normal operation.

1

reactor

2

packed bed

3

Circulation pump

4

Circulation water line

5

water distribution

6

exhaust duct

7

management

8th

vent line

9

fan

10

Strong air line

11

Regeneratpumpe

12

regenerated

13

nutrient management

14

sieve tray

15

water seal

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 19608805 C1 [0010]
• - DE 19609053 C1 [0011]
• - DE 4213814 A1 [0015]

Claims (10)

Process for the biological treatment of polluted substances Gases with the following characteristics: - polluted Gas is trickled through a reaction space with a stream of water and non-submerged fill from a small-grained, passed swirlable filler material, - the Packing material is technologically when it reaches a predetermined pressure loss by an artificially generated Strong air flow in the opposite direction to the trickling water as long flows through it and thereby moved against each other until a part of the on the surface and between the individual Füllkörpermaterialteilchen adhering biomass is abraded, - the biomass becomes with the liquid flow from the Füllkörpermaterialschüttung discharged, - then the abraded Biomass taken from the reaction space. Method according to claim 1, characterized in that that the filler material has a particle size <15 mm. A method according to claim 1 or 2, characterized in that the filler material has a density <0.1 g / cm ³ . Method according to one of claims 1 to 3, characterized in that the filler material is formed spherical. Method according to one of claims 1 to 4, characterized in that the filler material made of foam polystyrene (styrofoam). Method according to one of claims 1 to 5, characterized in that the strong air flow with a volume flow> 50 m ³ / (m ² × h) and a pressure> 20 mbar per meter of material height is introduced. Method according to one of claims 1 to 6, characterized in that the artificially generated air flow triggered automatically depending on the pressure loss becomes. Method according to one of claims 1 to 7, characterized in that the introduction of the strong air flow with several consecutive pressure surges he follows. Method according to one of claims 1 to 8, characterized in that the water to trickle over the packed bed completely is circulated and only on reaching a for the microorganisms critical value, by the concentration of nutrient salts or degradation products. Method according to one of claims 1 to 9 for the treatment of difficult or insoluble air pollutants characterized in that the Überrieslung so long is interrupted until the moisture of the biofilm for a the microorganisms falls below critical value.