DK156814B - PLANT FOR THE REMOVAL OF OXIDIZABLE INGREDIENTS FROM POLLUTANEOUS GASES, AS FROM POLLUTANEOUS AIR - Google Patents

Description

DK 156814 B

The present invention relates to an installation of the kind specified in the preamble of claim 1 for the removal of oxidizable, particularly gaseous constituents from polluted gases, especially polluted air. The plant consists of at least one reactor with an active sort adsorbent and at elevated temperature as well as an oxidation catalyst as well as a conduit for feeding the contaminated gas to the reactor and a conduit for purifying gas away from the reactor.

In a number of industries such as printing plants, color and varnish-10 factories, polymer processing companies, food and feed processing companies, chemical companies and a large number of smaller workshops, oxidable sulfur and gases that can be odorous, flammable and / or toxic can be produced during production. . These substances are removed with air-15 currents and, for economic reasons, are often sent directly into the atmosphere without prior purification. However, increasingly stringent regulations from authorities and increasing demands from the public are increasingly necessitating the purification of such airflows, even in cases where this has not been necessary. Purification of such air streams is expensive and technically difficult because there is often a lot of volume, up to 100,000 3

Nm pr. hour, which usually contains small quantities, less than approx.

1.5 g per Nm of the substances to be removed.

The known methods for purifying air stream 25 can be roughly divided into four categories: leaching, adsorption, thermal oxidation and catalytic oxidation.

Washing out is typically done with water, often with chemicals that react with the undesirable substances in the air stream. The disadvantage of this method is, besides being expensive, that the real problem is that damage to the undesirable substances is only partially solved, simply transferring it to the water.

Adsorption is most often carried out on activated charcoal. The main problem with this process is that the regeneration of the active coal necessary to make the process sufficiently economical cannot be fully satisfactory. The reason for this is that the regeneration must be carried out in an oxygen-free atmosphere, which will typically be an atmosphere of

DK 156814 B

2 superheated steam. Many of the substances to be removed from the coal tend to form polymerization products, which clog the pores of the coal particles. Partial removal of these polymerization products can be accomplished by keeping 5 temperatures in the oxygen-free atmosphere in the range 700-800 ° C, but at such high temperatures, decomposition of the activated carbon occurs. Other adsorbents such as molecular sieves and refractory ceramic oxides, e.g. alumina, A ^ O ^, can also be used. Molecules, however, are significantly more expensive than activated charcoal, and refractory 10 ceramic oxides have less adsorption capacity than activated charcoal. An advantage of these non-combustible adsorbents is that they can be regenerated with air.

Thermal oxidation is characterized by being a simple and relatively reliable process. The disadvantage of the method is that heating the large volumes of air to 700-800 ° C in a combustion chamber requires large amounts of energy. Generally the air is heated by direct firing. with oil or any gas. However, while it is possible to utilize a portion of the heat contained in the large volumes of air, the process is expensive to operate.

Catalytic oxidation differs from thermal oxidation in that the oxidation itself takes place not in a combustion chamber but in a catalyst bed. The advantage of this process is that the catalytic oxidation can take place at a temperature of 250-35 ° C, thereby substantially reducing energy consumption. It is a disadvantage of the catalytic oxidation that certain catalyst types are poisoned by contact with substances such as hydrogen sulfide and sulfur dioxide SC 2. Of particular importance is that although the energy consumption of catalytic oxidation is substantially less than that of thermal oxidation, it is however, considerable when large air masses are to be heated. At the said small amounts of pollution, the oxidation of the pollutants is not sufficient to supply the sufficient amount of energy for heating the air masses.

35 From Danish Patent Application No. 3698/68, corresponding to US Patent No. 3,548,728, there is known a method for removing unwanted gaseous components from

DK 156814 B

3 effluent gases; it consists in adsorbing these components on a solid surface area adsorbent, applying heat to the adsorbent to striate the undesired components and contacting them with an oxidation catalyst incorporated in and placed on the adsorbent to convert them into carbon dioxide and water. The adsorbent is solid and porous and is made up of activated charcoal, pumice, bauxite molecular sieve material and / or one or more oxides of Si,

Al, alkaline earth and rare earth metals and Ce, 2 10 and its surface area are> 100 m / g. No system for the practice of the above categories is described.

U.S. Patent No. 3,150,922 discloses a process for purifying exhaust gases from internal combustion engines in which the gases are passed through bearings containing similar alumina-grain impregnated manganese oxide and copper oxide catalysts. This method is not intended for and cannot be used in a stationary system as set forth in the preamble of this specification.

Danish Patent No. 145,817 discloses an apparatus for combined heat exchange and catalytic combustion in which resinous exhaust gases are preheated by means of a rotary heat exchanger containing a porous material impregnated with oxidation catalytically active substances.

Thus, there is no mention of a catalytic post-purification of the exhaust gases to obtain additional heat of reaction as described herein.

From U.S. Patent No. 1,527,897, which corresponds to U.S. Patent No. 4,025,505 and GB No. 1,527,827, a method for removing (low concentrations of) oxidizable organic constituents, especially vinyl chloride monomers, is known from a oxygen-containing inert gas by i) adsorbing the components on a sorption material in a reactor containing an oxidation catalyst of platinum, palladium or salts thereof; ii) removing the purified gas from the reactor exit and simultaneously in another reactor;

DK 156814 B

Iii) interrupts the flow of the oxygen-containing inert gas into the sorption material, closing the reactor's inlet and outlet portions when the concentration of organic constituents reaches a desired level; and iv) oxidizing the desorbed organic constituents in the vicinity of the oxidation catalyst and oxygen in the oxygen-containing inert gas by raising the temperature to preferably about 120 ° -180 ° C by an externally heated heating medium, e.g., steam, heat gases or hot water, whereby an overpressure is built up in the reactor / which is offset by venting the reaction products from the reactor directly to the environment and cooling the reaction zone to ambient temperature.

Furthermore, it is apparent from these patent specifications 15 that the process is carried out in a plant comprising at least two reactors equipped with cooling and heating means, the reactors operating alternately in the sorption and desorption phase.

This known plant requires external energy supply 20 to effect the desorption and catalytic reaction, which otherwise acidifies the gas purification.

It is the object of the invention to provide a system which, in particular, alleviates this disadvantage and which, according to the invention, is characterized by the characterizing part of claim 1. In addition to the preamble stated, it thus contains means, preferably formed by a combustion chamber with a burner, for intermittent regeneration of the catalyst in the reactor as well as means for purifying the gas emitted from the reactor.

30 The present plant is thus constructed in a manner which differs in material respects from the known. The desorbed and catalytically partially purified air leaving the adsorbent catalyst bed during regeneration is subjected to a catalytic post-purification in a post-purification section. In addition to 35 environmental benefits such as cleaner exhaust air, hereby quite significant energy benefits are obtained.

DK 156814 B

5

The hot air obtained in the adsorption beds is represented together with the unreacted oxidizable air components which are released at the beginning of the heating of the bed before the catalytic reaction is set, a calorific value which, apart from the start-up phase, covers the entire system's energy requirements, and which can further be utilized after further catalytic turnover in the post-cleaning section to units outside the system, eg stoves or boilers.

Part of the post-purified heated air from the post-purification reactor is fed back to the adsorption reactors where it is utilized to heat the catalyst bed during the regeneration phase. Thus, at the present plant, there is surprisingly little concern for an autothermal or substantially exothermic plant, which differs substantially from that known from PR patent no. 2,310,150 where desorption and catalytic reaction are required. energy that must be fed to the system from the outside.

During the operation of the plant, regeneration is effected by raising the temperature intermittently to a temperature at which catalytic oxidation occurs: conveniently the contaminated gas is passed through the adsorption bed at a temperature of 0-250 ° C.

By using the system, the advantage is obtained of taking the contaminated air at the temperature it actually has and, without preheating, direct it to the treatment.

Most of the air volumes to be purified pass through the bed of the adsorbent, which at elevated temperature as the oxidation catalyst - it is referred for the briefness of the following adsorbent catalyst - at its formation temperature or possibly slightly lower temperature due to heat loss and is used. not any energy to heat them. If desired, the heat of the gases can be utilized prior to adsorption by passing them through a heat exchanger. During passage, the pollutants 35 or most of them are adsorbed on the adsorbent catalyst and the air can be diverted to the surroundings in substantially purified condition. As the adsorbent catalyst becomes more and more 6

DK 156 814 B

more saturated with the pollutants, breakthroughs of such to the environment will occur and when the concentration of undesirable substances has reached the permissible or acceptable maximum value, the adsorbent catalyst is regenerated by raising the temperature 5 to the catalytic oxidation required. , most frequently in the range of 250-350 ° C.

Heat supply is thus only needed during the periods of regeneration, which is of course a very significant saving. In addition, under certain circumstances, except for start-up, heat supply or even a heat gain can be avoided, which must be explained later. in the description.

As the adsorbent catalyst, preferably a porous ceramic carrier having a large internal surface and impregnated with an elevated temperature as the oxidation catalyst is impregnated. The porous support will itself act as an adsorbent, but not or only to a small extent as an oxidation catalyst. Particularly suitable are a number of ceramic materials in the form of oxides, in particular of the elements of groups II, III and 20 IV of the Periodic Table. Examples of suitable materials are alumina, A₂O ^, hereinafter referred to as alumina, magnesium-aluminum spinel, MgA ^O ^, and silicic anhydride, SiC₂, hereinafter referred to as silica. It has been found that γ-alumina is a particularly suitable material, but also oxides of Ti and Zr and 25 increasing ceramic oxides can be found. The carrier may consist of a mixture of two or more of said materials.

The carrier is impregnated with an oxidized catalytic material at elevated temperature.

As such, Group VIII metals in the Periodic Table 30 and their compounds, especially oxides, can come in handy, especially the platinum metals. Other suitable metals are copper as well as those of Group Va, Via and Vlla and their oxides, and especially oxides of copper, chromium, manganese, iron, vanadium and cérium should be emphasized.

The catalysts mentioned have excellent catalytic activity and can withstand good regeneration. However, it has surprisingly been found that copper chromite, CuO.Cr203, unites h

DK 156814B

7, the ability to oxidize air pollutants that will come to fruition with high oxidation catalytic activity. According to the invention, therefore, a particular embodiment of the plant may advantageously contain an oxidation catalyst consisting of γ-alumina impregnated with copper chromite.

A particular advantage of this adsorbent catalyst is that it has the ability to adsorb large amounts of polymerizable substances such as styrene. Many pollutants such as styrene, for example, will undergo partial polymerization following the adsorption of the adsorbent catalyst, and copper chromite has the ability to accelerate this polymerization. Such polymerization will help increase the adsorption capacity and thereby extend the periods of adsorption without re-generation.

When the adsorbent catalyst, in its capacity as the adsorbent, is saturated with the contaminants, which is readily found to be less effective in purification, the temperature is raised so as to catalytically oxidize the adsorbed contaminants. The fact that some of the 20 adsorbed substances may be polymerized will not complicate regeneration.

In regeneration, the temperature may be raised to preferably 250-350 ° C in any convenient manner. Thus, hot gas can be recirculated from the regeneration, or directly, for example, by means of electric heaters, can be fed to the adsorbent catalyst bed, but in general it will be most convenient to do so, calculated in the direction of flow of the polluted air. fire a combustion chamber with a burner that is fired with, for example, oil or gas.

Generally, the air leaving the adsorbent catalyst bed during regeneration, as opposed to leaving it during adsorption, will contain undesirable components. It can therefore. According to the invention, it is appropriate to subject this air to a post-purification. The post-purification can be by any of the above-mentioned main methods of leaching, adsorption, thermal or catalytic

DK 156814 B

8 oxidation, i.a. depending on the unwanted substances leaving the bed during regeneration. If these are oxidizable substances, it is advantageous to carry out the post-purification by catalytic oxidation. One can use a catalyst other than the one used as an adsorbent catalyst, but for the sake of making the plant and operation simplest possible it is most practical as a catalyst to use the same material as the adsorbent catalyst used in the adsorption. cf. requirement 4.

According to the invention, the means for purifying gas emanating from the reactor during regeneration of the adsorbent catalyst are preferably as defined in claim 2, i.e. an additional combustion chamber with a burner is interconnected in a branch of the discharge line and connected to an additional re-15. reactor with an oxidation catalyst such that the gas emanating therefrom goes either to the chimney or to the discharge line from the first reactor.

Under certain circumstances, the plant may be arranged so that a portion of the purified air is fed to the reactor 20 with the adsorbent catalyst. This applies if the plant as claimed in claim 3 has a number of reactors with adsorbent catalyst and is operated so that the adsorbent catalyst in one of these sites is under regeneration, while the other adsorb the pollutants. Such a system is particularly advantageous for contents of more than approx. 0.5 g of organic matter per m ^ hot gas, enabling the burning value of the oxidizable substances, for example for heating purposes, whereby the whole system becomes autothermal or even exothermic. The details of this are explained in the detailed parts of the present description.

The plant according to the invention will now be described in more detail with the aid of the drawing and some examples. In the drawing, FIG. 1 and 2 are schematic diagrams of two different embodiments of a plant according to the invention; 3 shows a test plant in which certain attempts to illuminate the effect of the plant have been made; and

DK 156814 B

9 FIG. 4-5 curves illustrating the results of such experiments.

In the embodiment of FIG. 1 (where auxiliary means such as pumps, valves and control means have been omitted for the sake of clarity), 5 illustrated plants enter the polluted air via a conduit 10 and pass through a chamber 12 where a burner 14. A burner 14 is connected. most of the time, when the unwanted substances are adsorbed on the adsorbent, do not function and only turn on when the adsorbent is to be regenerated. Thereafter, the air enters a reaction chamber 16 where there is an adsorbent catalyst 18. The manner in which the adsorbent catalyst 18 is disposed does not form part of the invention. However, it is always desirable to arrange it so that the pressure drop in the reactor 16 is minimized.

The air stream is discharged from the reaction chamber 16 via a rudder 20 divided into two; partly a pipe 22 which leads to a chimney and partly a pipe 30 which leads to a post-cleaning section. In normal operation, ie. during adsorption, the purified gas is sent directly from the reactor 16 via the pipes 20, 22 to the chimney. During regeneration, burner 14 is started and heats the incoming air in chamber 12, preferably to a temperature of 250 DEG-450 DEG C., as well as jet 18 of adsorbent catalyst, preferably copper chromite impregnated on porous bodies of γ. alumina, will become oxidation catalytically active and burn away the adsorbed oxidizable contaminants. Below, the exhaust air from the reactor 16 can also be discharged to the chimney via the pipes 20,22, but preferably the air streams are passed through the pipe 30 to the post-cleaning section, from which the purified air stream is passed through a pipe 30 4Q to a pipe 42 leading to the pipe 22 or chimney. The post-cleaning of FIG. 1 is a catalytic oxidation. The air stream is heated directly in a combustion chamber 32 by means of a burner 34 to the desired temperature and then conducted to a reaction chamber 36, where a catalyst 38 is located.

35 By means of the oxidation catalyst 38, unwanted components in the air stream are removed to the desired level. The oxidation catalyst 38 in the reaction chamber 36 can be independently selected

DK 156814 B

10 of the adsorbent catalyst 18 in the reactor 16, but for practical reasons it is particularly advantageous to use the previously mentioned copper chromite / alumina adsorbent catalyst both in reactor 16 and the reaction chamber 36.

5 A calculation example, cited as Example 1, serves to more thoroughly elaborate the gas purification in a system similar to that shown in FIG. First

Another embodiment of the system according to the invention is shown in FIG. 2, which is also very simplified in that 10 a number of objects such as various blowers, pumps, valves and the whole control technique which does not directly relate to the invention and whose use and function will be obvious to one skilled in the art are omitted.

The polluted air enters the system via a conduit 10 which is divided into two conduits 42 and 44. A smaller portion of the air flow is conducted via conduit 42 to the post-purge section. The bulk is passed from line 44 through branches 461, 4611 ... to a number of reactors containing the adsorbent catalyst 18. The plant in the figure has six reactors designated 481, 4811, 48111, 48IV, 48V and 48VI. The number of reactors determines the length of the regeneration period relative to the length of the adsorption period in the reactors.

The number of reactors 461 ---- will include e.g. depend on the amount of air for treatment and its degree of pollution.

25 The purified air is conducted from the reactors via wires

I II

50, 50 ..., all of which are assembled in a common pipe 22 which directs the purified air to a chimney. In practice, in practice, five reactors are in the adsorption phase and one is under regeneration.

The air for regeneration is fed to reactors 481 ...

from a line 52 with branches 54, 54 ... to the individual reactors. A second row of tubes 561, 56 ^ 1 ... directs the air away from the reactors to a common conduit 58 which conducts the air to the post-purge section.

35 From the conduit 58, the air emanating from a reactor where the adsorbent catalyst 18 is under regeneration goes to a combustion chamber 60 inserted in the conduit 58

DK 156814 B

11 connected to a burner 62; these two organs are normally in operation only at the start of the system and the air passes straight through them without heating when the system is in full operation. From the combustion chamber 60, which in normal operation is thus functionally just a part of the conduit 58, the air passes through the remainder of the conduit 58 to a junction 64 where a desired amount of hot recirculating air is supplied from a conduit 66. In this way, with a desired temperature in a conduit 68 an input stream to a reaction chamber 76 with an oxidation catalyst. The purified air stream is conducted from the chamber 76 via a conduit 70 to a junction 72. Prior, the said recirculation stream is discharged through the conduit 66 as well as a subcurrent through a conduit 74. The purified air stream from the chamber 76 will have a considerable temperature (400-500 ° C), for which the subset diverted via line 74 will generally be utilized for heating purposes. At the junction 72, the hot purified air is mixed with polluted air from line 42 to form the air stream which is passed through line 52 to one of reactors 481 ... to be used during regeneration.

A significant advantage of the system of FIG. 2 is that burner 62 is used only when the system is started. Thus, during normal industrial operation, there is no energy consumption in the burner, or at all in the plant. On the contrary, it is impracticable in the plant to utilize the calorific value of the substances in the polluted air, with the amount of heat in the air stream 72 typically being utilized, either as hot air for drying ovens or for heating water.

Otherwise, the recirculation line 66 is of particular importance. If not found, the temperature of the reaction chamber (where the catalyst may be an oxidation catalyst and suitably the same as used soin adsorbent catalyst 18) would fluctuate strongly and in a complicated manner, as will be elucidated later in the description. By appropriate regulation 35 of the amount of recirculating air in conduit 66 and of the amount of air to the reactor under regeneration, e.g., 4811, the temperature of the reaction chamber 76 can be kept fairly constant, 12

DK 156 814 B

which is of interest in connection with the utilization of the air in conduit 74 for heating purposes, and may have an impact on the catalyst; certain catalyst and especially carrier materials may sinter or otherwise reduce activity if the temperature rises too high, but this can be effectively prevented by regulating the amount of recirculation. Conversely, the purge in the chamber 76 may become unsatisfactory if the temperature becomes too low, in which case the amount of recirculation can also be adjusted.

10 A calculation example for illustrating the operation of the device shown in FIG. 2 illustrated systems are given in Example 2 below.

A small pilot plant in which some contaminated air tests are carried out is outlined in FIG. 3. Atmospheric air is fed into the system via a conduit 90. In a flowmeter 78 15, the amount of air that is regulated by a valve 80 is measured.

From the flow meter, the air is fed via a conduit 82 into a cylindrical preheater 84 in which is located an electric heater. By regulating the power deposited in the heater, the temperature of a conduit 10 which feeds 20-20 of the heated air away from the preheater can be set to a desired value. A conduit 88 conducts pollutant liquid to a pump 92 which, via conduit 94, feeds the liquid to conduit 10 where an evaporation takes place. The conduit 10 conducts the now contaminated air to a reactor 16. In the upper part of the reactor is arranged a heating element 96, by means of which it is possible to adjust the temperature of the contaminated gas. In the lower part of the reactor, an adsorbent catalyst 18 is placed in a cylindrical clay 18 up to 450 mm high, with a diameter of 73 mm, corresponding to the inner diameter of the reactor. In the bearing axis there is a thermal pocket 30 98 extending from the bottom of the bearing to the top of the bearing. In the thermocouple there is a displaceable thermocouple, which allows the temperature to be determined at different depths of the catalyst bed. The output stream from the catalyst bed is fed from the reactor via line 20. By means of a line 22 and a control valve 100, it is possible to conduct a partial stream for analysis on a continuously working hydrocarbon analyzer 102. The hydrocarbon analyzer used was a flame ionization analyzer of type Beckmann Model 400 Hydrocarbon Analyzes.

DK 156814 B

13

Example 1

This is a calculation example in which a treatment plant shown in FIG. 1 is used to purify an exhaust gas from the production of styrene-containing polymers. In the reaction chamber 16 3 5 are installed 22 m of adsorbent in the form of 3-6 mm particles, the adsorbent consisting of γ-alumina impregnated with 20% CuQ.C ^ O ^. The amount of catalyst in reactor 36 depends on the amount of air flow during regeneration. In this example, it is stipulated that the air volume can be reduced to 10-20% 10 of the volume during normal operation. In this way, the amount of catalyst in the reactor is reduced to 3 to 3 m. The catalyst is identical to the adsorbent catalyst 18 in the reactor 16.

3 45.0Q0 Nm per per hour of the exhaust gas with a content of the controller of 0.25 g per hour. Nm is passed to the purification plant, the Styrene content of the purified gas passed through the chimney will slowly increase with time from about an initial value of about 0, and after approx. After 40 hours of operation, the styrene content of the purified gas will have increased to approx. 10 mg per Nm. At this point, approx. 20 g of styrene per kg of adsorbent. The re-generation will typically take 2-3 hours. The adsorbed styrene has a certain calorific value, which causes the temperature of the adsorbent to rise during regeneration. In extreme cases, the temperature may become so high that the adsorbent loses its adsorptive properties, for example due to surface loss; and / or 25 1 lose their catalytic properties, for example due to sintering. An efficient regeneration which ensures that the temperature of the adsorbent does not exceed 850 ° C can be done by reducing the air volume to 6.00Q Nm per minute. hour. The air stream is conducted to the post-cleaning section through line 30. The temperature 30 in the combustion chamber 12 is maintained at 250 ° C by the burner 14.

3

After 45 minutes, the air volume is increased to 10,000 Nm per hour. and the temperature is raised to 270 ° C. After a further 45 minutes the burner 14 is switched off and the airflow is increased to 20,000 Nm / hour. 45 minutes thereafter, the regeneration must be considered 35 completed. The air flow is increased to 45,000 Nm / h and is routed through the wires 40.42 to the chimney. Throughout the regeneration

DK 156814 B

14, the inlet temperature of the reactor 36 is maintained at 300 ° C, possibly by means of the burner 34. An adsorption and regeneration cycle lasts for approx. 42 1/4 hour, and the total energy consumption corresponds to 35 kg of oil distributed with 110 kg of oil on the burner 14 and 240 kg of oil on the burner 34, which means that the exhaust air from the reactor 16 during the regeneration represents some calorific value.

Example 2

1Q

This is a calculation example using the one shown in FIG.

2. 25,000 Niri / h of an air stream from the dry furnaces of an offset printing press is fed to the plant. The contaminated 3 air contains 1.5 g of hydrocarbons per liter. Nm and has a temperature of 130 ° C. The hydrocarbons, which have been used as a solvent for printing inks, consist of approx. 20% aromatic hydrocarbons and 80% aliphatic hydrocarbons and has a boiling range of approx. 240 to approx. 27Q ° C. The total contaminated dry air 3 is fed to the system via line 10. A partial flow of Nq per meter. hour for use in the regeneration is discharged via line 20 3 42. The remaining 25, OÜO-vq Nm / h is passed through line 44 to the reactors 48, which are in the adsorption phase, 3 and distributed at £ 5,000-vq) / 5 Nm / h to each of the five reactors. Each of the reactors 48 contains 1500 kg of the same ad-2 sorbent catalyst as in Example 1. The post-purification reactor 76 also contains 1500 kg of the same adsorbent catalyst.

The length of the adsorption period is limited for two reasons. First, it must not be so long that the hydrocarbon concentration in the air stream from the adsorption becomes greater than the allowable value. Second, no more than approx. 15 g of hydrocarbons per kg of adsorbent catalyst. This value will cause the maximum temperature of the adsorbent catalyst during regeneration not to exceed 800-850 ° C.

^ As the length of the adsorption period is set at 175 minutes, 12.8 g of hydrocarbon per day will be adsorbed. kg of adsorbent catalyst corresponding to the maximum temperature of the adsorbent catalyst not exceeding the desired value below the re-

DK 156814 B

15, especially a value which does not destroy the catalyst. During the adsorption, the hydrocarbon concentration 3 in the purified gas fed to the chimney will be approx. 2 mg / Nm 3 for the first 100 minutes and rise to 5 mg / Nm at the end 5 of the adsorption. Since the number of reactors is six, the re-generation time becomes 35 (175: 5), minutes.

V v denotes the amount of air in conduit 52 directed to regeneration, v reactors 48, T3 denote the temperature in line 68 of reactor 76, Table 1 below shows how the regeneration of the adsorbent in a reactor 48 proceeds.

In the first 12 minutes of regeneration, a temperature in the conduit 54 is reached at approx. 318 ° C by mixing 1000 Nm / h (v) of polluted air from conduit 42 with 3 ° 2000 Nm / h (v ^ -v) purified hot air from conduit 70 at the junction 72. At the temperature reached, the adsorbed hydrocarbons in the input layer of the reactor 48 thanks to the catalytic properties of the catalyst adsorbent are ignited and burned. The hydrocarbons from the contaminated gas used in the regeneration will be oxidized along with some of the hydrocarbons adsorbed. The remainder of the adsorbed 25 hydrocarbons will, due to the rise in temperature, be desorbed and fed with the air stream to the reactor 76, where oxidation takes place. 5-10 minutes after the start of regeneration, the hydrocarbon concentration in the air stream has grown to a maximum of 2-3 g / Nm. In the first 15-20 minutes, when the hydrocarbon content of air in conduit 58 is large, the temperature will be relatively low. To ensure sufficient oxidation in the reactor 76, the air stream must be heated to at least 260 ° C, which is obtained by recirculating hot air over the reactor via line 66. The temperature of the air stream from the reactor 76 will maintain a constant value of approx. 418 ° C despite the temperature variations in line 58. This is partly because the catalyst in reactor 76 has a certain capacity as 16

DK 156814 B

heat buffer and partly that hot air is recirculated via conduit 66. The temperature of conduit 74 will therefore also be almost constant 418 ° C. The amount of purified air in conduit 74 will be identical to v.

12 minutes after the start of regeneration, the supply of hot air from the conduit 70 to the junction 72 is stopped, and at the same time the amount of polluted air in the conduit 42 is increased.

The rest of the regeneration is carried out with 130 ° C hot, polluted 3 air in an amount of 4000 Nm / h. Recirculation over reactor 3 10 76 can be reduced to 3500 Nm / h as the temperature of the air at the outlet of the reactor 48 has begun to rise. This temperature will reach a maximum of approx. 600 ° C approx. 25 minutes after the start of regeneration. At the same time, the temperature of the purified air stream from the reactor 76 will also reach a maximum of approx. 600 ° C. The hydrocarbon content of line 58 will have dropped to below 20 mg / Nm after 3 15-20 minutes of regeneration.

The burner 62 does not come into operation during regeneration, but is only used at the start of the plant and thus there is no consumption of energy for heating air currents during the normal operation of the plant, which is a great advantage in the design. In the hot purified air stream discharged via conduit 74 there are, as mentioned, large quantities of heat.

When cooling the air stream to 130 ° C, a heat quantity corresponding to the calorific value of 27 kg oil is used. hour.

25 30 35

DK 156814 B

17

Table 1

Number of minutes from the start of the regeneration period 0-12 12-20 20-25 25 25-30 30-35 5 Vq (Nm3 / h) 1000 4000 4000 4000 4000 4000 νχ (Nm3 / h) 3000 4000 4000 4000 4000 4000 v2 ( Nm3 / h) 4000 3500 3500 3500 3500 3500 Τχ (° C) 318 130 130 130 130 130 T2 (° C) 130 200 450 600 450 350 10 T3 (° C) 290 300 450 600 450 350

Hydrocarbon concentration in line 58 (g / Νπι) max 2-3 1-0.02 <0.01 <0.01 <0.01 <0.01

Example 3

In a first attempt with the one shown in FIG. 3 experiments, air contaminated with styrene was used. The adsorbent catalyst was the aforementioned copper chromite Y-alumina adsorbent catalyst, in the form of spheres having a diameter of 3-6 mm.

4.4 Nm per hour of air containing 0.22 g styrene per hour.

Nm3 was fed into the adsorbent catalyst bed at a temperature of 50 ° C. The amount of adsorbent catalyst was 1.67 kg, corresponding to 1.8 liters. The styrene content of the starting stream from the reactor was painted on the hydrocarbon analyzer as volume ppm methane equivalents, i. It may be mentioned, 3 l at 100 mg styrene per day. Nm corresponds to 179 vol.-ppm C During the first 30 hours of the adsorption period, the styrene content of the purified air was measured below 20 vol. Ppm C After 40 hours of 30 liters of operation, the contents increased to 3Q vol.-ppm C 2, and after 45 hours the styrene content had increased to 50 vol.-ppm C 2. The adsorption period was thus over, and the regeneration was imminent. The air stream 3 was reduced to 1.1 Nm per hour while raising the temperature of the air stream to the catalyst bed to 35 n 300 C. The adsorbed substance at the bed entrance was ignited at approx. 280 ° C and a hot zone then moved down again.

DK 156814 B

18 easy to rent. The hot zone reached its highest temperature of 700 ° C approx. 150 mm down in the bearing. The hot zone reached the reactor exit after approx. 1 hour. At the beginning of regeneration, the styrene content of the starting air from the reactor was 30 vol.-ppm C In the 10th of the first approx. 17 minutes of the regeneration period, the styrene content increased to over 1000 vol.-ppm C1, which is the upper limit of what the hydrocarbon analyzer could measure. After approx. After 40 minutes, the styrene content again dropped to below 1000 vol. Ppm. Cog. In the 10th of the following 10 minutes, the styrene content dropped to 20 vol. Ppm. The regeneration thus lasted a total of 50 minutes. The experiment was repeated 3 times and the result was essentially as described above. Calculations of the experimental data show that the adsorption capacity under the used air conditions is approx.

25 g of styrene per kg of the adsorbent catalyst ..

After 45 hours of adsorption operation, a sample of a few grams of adsorbent catalyst was taken and analyzed. The sample contained 33 g of organic carbon per day. kg. The sample was then heat treated at 20 ° C in nitrogen. After staying at this temperature for 2 hours, the sample was re-analyzed. The organic carbon content was determined to be 15 g per liter. kg of adsorbent catalyst. It is believed that this amount of organic carbon corresponds to styrene adsorbed in more or less polymerized form.

25

Example 4 In this test series, which consisted of four single experiments, the reactor contained 1.6 liters (1.5 kg) of the adsorbent catalyst placed in a bed 40 cm high. The air flow to the 30 adsorbent catalyst bed was 4.0 Nm / h in all experiments. The air stream was contaminated with a hydrocarbon mixture having a boiling range of 240-270 ° C, typically used as a solvent in heatset offset printing.

The temperature and hydrocarbon content of the air stream at the inlet (Z = 0) of the adsorbent catalyst bed is shown in Table 2 below.

DK 156814 B

19

Table 2

Test No. Temperature, ° C Hydrocarbon content, g per Nm ^, 1 -. M ........... .I - '»' '- * -'" ----— "" '* ......' 1 155 1.40 2 125 1.40 5 3 122 0.78 4_100_0.91_

The hydrocarbon concentration in the starting reactor from the reactor was ground on the hydrocarbon analyzer as volume ppm C

10

FIG. 4 shows graphically the hydrocarbon concentration in vol. Ppm C time in hours for the four trials. In the figure is a line indicating the concentration of 20 mg C per day.

3

Nm, which is often the maximum allowable emission limit for the atmosphere.

1 R

In FIG. 4 it appears that the adsorption capacity in the temperature range investigated is very temperature dependent, since a slight increase in temperature or a decrease in temperature will result in a sharp decrease or increase in the adsorption capacity respectively.

The adsorbent catalyst had, before the test series, been used in 1Q adsorption and regeneration cycles, the maximum temperature during the regenerations being in the range 9QQ-920 ° C; the front-mounted limit of 800-850 ° C thus provides a good safety margin. During a further 10 adsorption and o c regeneration circuits, the adsorption capacity was ground. There was no evidence of any significant decrease in adsorption capacity.

In Experiment 2, the adsorption period was completed after 6 1/2 hours and regeneration commenced. By this time, according to calculations, the adsorbent catalyst had adsorbed a total of 39 g of hydrocarbon acid to 26 g per liter. kg. The process of regeneration performed with clean air is shown in FIG. 5. The time from the beginning of regeneration is indicated in minutes along the abscissa. The left ordinate indicates the content of 35 methane equivalents in the air stream from the reactor, the higher ordinate temperature measured at various depths (Z) in the adsorbent catalyst bed. Since the length of the bed is 40 cm, Z = 0 to 20

DK 156814 B

the input layer in the bearing, and Z = 40 corresponds to the output layer in the bearing. The temperature in Z = Q is identical to the temperature of the air stream used in the regeneration; the temperature of Z = 4Q is identical to the temperature of the air stream conducted from the reactor.

In FIG. 5 it appears that the temperature of the regeneration air in the first approx. 10 minutes was approx. 290 ° C and the temperature of the remaining part of the regeneration was approx. 100 ° C.

It can be seen from the figure that the highest temperature in the bearing, namely approx. 930 ° C, was found at a depth of 10 cm.

Corresponding regenerations with smaller amounts of adsorbate show that ca. 15 g of hydrocarbon per liter kg of adsorbent will give a maximum temperature in the bed of approx. 825 ° C.

The hydrocarbon concentration in the exhaust air, as also shown in the figure, decreased to below 10 vol. Ppm after approx. 2Q minutes. The regeneration was completed after 30 minutes. For the last 10 minutes of regeneration, the adsorbate was completely oxidized on the adsorbent catalyst. Generally, in the 10th of the entire regeneration period, approx. half of the adsorbate will be oxidized on the adsorbent catalyst while the remainder will be fed with the air stream to the post-purification section.

25 30 35

Claims (6)

An installation for the removal of oxidizable constituents from polluted gases, especially polluted air, and consisting of at least one reactor (16) with a soin adsorbent and at elevated temperature, also as an oxidation catalyst material (18), a conduit ( 10) for conveying the gas under treatment to the reactor and a conduit (20,22) for conveying purified gas away from the reactor, characterized in that it also contains means (12,14), preferably in the form of of a combustion chamber (12) with a burner (14), for intermittent regeneration of the catalyst in the reactor (16) and means (32-42) for purifying gas from the reactor. Installation according to claim 1, characterized in that 1. the means for the post-purification of gas from the reactor (16) during regeneration are constituted by a burner (34) connected to a branch (30) from the discharge line (20). combustion chamber (32), a subsequent reactor (36) with an oxidation catalyst (38) and a conduit (42) thereof to the chimney or outlet conduit (22) of the first reactor (16). Installation according to claim 1, characterized in that it has (i) at least two parallel connected reactors (48 *, II 48 ..) with adsorbent / catalyst material Π8), (ii) a branching supply line (10) and (42) ) to an I II post-purification section, partly (44; 46, 46 ...) to the reactors (48 *, 48 ** ...), and (iii) discharge lines from these (50 *, 50 **). ..; 22) to the chimney, partly (56 *, 56 ...; 58) to the post-cleaning section consisting of 2. a combustion chamber (60) with a burner (62), a conduit from this combustion chamber (60) to a reactor (76) with an oxidation catalyst and a discharge line (70) from the reactor (76) with branches (74) via wiring out of the system and (52; 54 *, 54 ** ...) to the reactors (48 35, and partly a return line (66) to the line (56.68) between the after-cleaning section's combustion chamber (60) and the reactor (76) together. DK 156 814 B Plant according to claim 3, characterized in that the oxidation catalyst in the reactor (76) in the post-purification section comprises the same material as the adsorbent / catalyst present in the parallel connected reactors (48 ^, 481 ^). .) · Installation according to claim 3, characterized in that the branch line (42) for the post-cleaning section is met with the outlet line (70) from the reactor (76) in the post-cleaning section at a junction (72) from which also the branch (52) for the parallel connected reactors. (48 ^, 4811 ...) is deleted. Installation according to claim 3, characterized in that the oxidation catalyst consists of gamma-alumina impregnated with copper chromite. 15 20 25 30 35