SULFUR DIOXIDE REMOVAL FROM WASTE GAS

Abstract

A process where a gas, containing SO.sub.2 and O.sub.2 is brought in contact with a mixture of from 95% vol. to 50% vol. of activated carbon catalyst and from 5% vol. to 50% vol. of an inert filler material, where the SO.sub.2 is converted to H.sub.2SO.sub.4 on the activated carbon catalyst and is then washed from the activated carbon catalyst to obtain a H.sub.2SO.sub.4 solution.

Claims

1. A process, comprising: bringing a gas, containing SO.sub.2 and O.sub.2 is brought, in contact with a mixture of from 95% vol. to 50% vol. of activated carbon catalyst and from 5% vol. to 50% vol. of an inert filler material; wherein the mixture is a mixture of separate, distinct particles of filler and separate, distinct particles of activated carbon catalyst; and wherein the SO.sub.2 is converted to H.sub.2SO.sub.4 on the activated carbon catalyst and is then washed from the activated carbon catalyst to obtain a H.sub.2SO.sub.4 solution.

2. The process as claimed in claim 1, wherein the filler material is between 10% vol. and 30% vol. of the mixture of activated carbon catalyst and a filler material.

3. The process as claimed in claim 1, wherein the mixture contains no other solid ingredients than the activated carbon catalyst and the filler material.

4. The process as claimed in claim 1, wherein the activated carbon catalyst is chosen from impregnated or activated carbon catalysts.

5. The process as claimed in claim 1, wherein the filler is chosen from fillers made of ceramic material, made of metal, fillers made of plastic mineral or mixtures thereof.

6. The process as claimed in claim 1, wherein the filler material is a shape comprising saddle shaped, ring shaped, ball shaped, torus shaped, prism shaped or irregular shaped.

7. The process as claimed in claim 1, wherein the mixture is in a fixed bed.

8. The process as claimed in claim 1, wherein the mixture is washed with water or an aqueous solution in an amount between 5 l/hour/m.sup.3 of catalyst and 100 l/hour/m.sup.3 of mixture.

9. The process as claimed in claim 1, wherein the mixture is washed by intermittent spraying with water or an aqueous solution in counterflow to the gas.

10. The process as claimed in claim 1, wherein the process is operated at a pressure from 0.9 to 1.1 atm, preferably at atmospheric pressure.

11. The process as claimed in claim 1, wherein the water saturated gas containing SO.sub.2 and O.sub.2 is a waste gas generated by chemical and metallurgical processes.

12. The process as claimed in claim 1 wherein the SO.sub.2 content of the gas is between 300 ppm and 200,000 ppm.

13. The process as claimed in claim 1, the gas being brought into contact with the mixture has a temperature of between 10 and 150 C.

14. The process as claimed in claim 1, wherein the O.sub.2 content of the gas is between 2 and 21% vol.

15. The process as claimed in claim 1, wherein the H.sub.2SO.sub.4 content of the H.sub.2SO.sub.4 solution is between 5 and 50% vol.

16. The process as claimed in claim 1, wherein heavy metals are removed from the gas.

17. The process as claimed in claim 1, wherein organic contaminants are removed from the gas.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Further details and advantages of the disclosure can be taken from the following detailed description of a possible embodiment of the disclosure on the basis of the accompanying FIG. 1. In the drawings:

[0068] FIG. 1 is a schematic view of the arrangement;

[0069] FIG. 2 is a graph showing the values measured during Test 1 of the SO.sub.2 content of the waste gases at the inlet and outlet of the reactor;

[0070] FIG. 3 is a graph showing the values measured during Test 2 of the SO.sub.2 content of the waste gases at the inlet and outlet of the reactor;

[0071] FIG. 4 is a graph showing the values measured during Test 3 of the SO.sub.2 content of the waste gases at the inlet and outlet of the reactor;

[0072] FIG. 5 is a graph showing the values measured during Test 4 of the SO.sub.2 content of the waste gases at the inlet and outlet of the reactor;

[0073] FIG. 6 is a graph showing the values measured during Test 5 of the SO.sub.2 content of the waste gases at the inlet and outlet of the reactor;

[0074] FIG. 7 is a graph showing the values measured during Test 6 of the SO.sub.2 content of the waste gases at the inlet and outlet of the reactor.

[0075] FIG. 8 is a graph showing the values measured during Test 7 and 8 of the SO.sub.2 loading capacity of an active carbon catalyst and of a mixture of an active carbon catalyst and a filler.

[0076] FIG. 9 is a graph showing the values measured during Test 7 and 8 of the drying time of an active carbon catalyst and of a mixture of an active carbon catalyst and a filler.

[0077] FIG. 10 is a graph showing the removal efficiency of an active carbon catalyst alone and different ways of mixing an active carbon catalyst with filler in relation to Test 9a, b, c and d.

[0078] FIG. 11 is a graph showing the removal efficiency of an active carbon catalyst mixed with different quantities of a first filler material in relation to Test 10,

[0079] FIG. 12 is a graph showing the removal efficiency of an active carbon catalyst mixed with different quantities of a second filler material in relation to Test 11,

[0080] FIG. 13 is a graph showing the removal efficiency of an active carbon catalyst mixed with 1/4 of different sized filler materials in relation to Test 12,

[0081] FIG. 14 is a graph showing the removal efficiency of different types of active carbon catalyst mixed with 1/3 of filler materials in relation to Test 13,

DETAILED DESCRIPTION

[0082] The test arrangement shown in FIG. 1 in order to illustrate the disclosure comprises a test reactor 10, to the lower part 12 of which a test gas is supplied and in the upper part 14 of which water is sprayed.

[0083] For the purpose of these tests, instead of waste gas a test gas is used to simulate the waste gases. The test gas comprises ambient air which is used as is, at a temperature between 10-12 C. and to which SO.sub.2 is subsequently added from a pressurized cylinder 18 via corresponding valve 22. A first measuring device 26 analyses the composition (SO.sub.2 content, O.sub.2 content), the temperature, the flow volume and the flow rate of the test gas.

[0084] The test gas is then cooled to saturation temperature in a quench 28 by evaporation of water. The test gas is drawn via the quench 28 into the reactor 10 by a fan 30. A coalescer, a droplet separator or a mist collector at the outlet of the quench 28 collects any droplets that might be contained in the test gas as it exits from the quench.

[0085] The test gas flows through the reactor 10 and through the activated carbon catalyst or the filling material or a combination of an activated carbon catalyst and filling material 32 arranged inside the test reactor 10. The test gas flows from the bottom to the top of the reactor 10 and is then examined once it is discharged from the test reactor 10 in a second measuring device 34 for the same parameters as in the first measuring device 26, i.e. composition (SO.sub.2 content, O.sub.2 content), the temperature, the flow volume and the flow rate, and is then released into the atmosphere.

[0086] The water required in the process is fed from a storage container 36 via a metering device 38, where the flow is measured, and a pump 40 into the upper part 14 of the test reactor 10, where the water flows through the activated carbon catalyst or the filling material or a combination of activated carbon and filling material 32 in counterflow to the test gas.

[0087] Alternatively however, the water required in the process can also be fed through the reactor in co-current flow with, i.e. in the same direction as, the test gas. The selection of a co-current or counterflow method depends for example on the local conditions.

[0088] The water required for the quench 28 comes directly from the water supply and is circulated within the quench.

[0089] The SO.sub.2 is catalytically converted into SO.sub.3 on the activated carbon catalyst, and is then converted into sulfuric acid if water is added.

[0090] The filling material is randomly mixed with the activated carbon catalyst and the mixture is located above the sieve i.e. a metallic mesh sieve with mesh inferior to the particle size of the mixture of catalyst and filler (e.g. >2 mm.

[0091] The sulfuric acid formed is rinsed off from the activated carbon catalyst by intermittent spraying with water, as a function of the volume of the catalyst and of the SO.sub.2/SO.sub.3 concentration, in counterflow to the gas.

[0092] The presence of filling material surprisingly improves the conversion efficiency during SO.sub.2 catalytic reaction and/or during spraying with water due to liquid/gas interaction. The presence of the filling material seems to enhance the liquid and gas flows as well as their repartition through the catalyst bed that allows a more uniform liquid and gas coverage of each catalyst grain and thus a higher SO.sub.3 to H.sub.2SO.sub.4 conversion. Indeed the regeneration of the activated carbon during dry process is quicker and more efficient leading to a shorter regeneration-cycle time.

[0093] It has been found that there is a

Good fluid distribution
Low pressure drop in the reactor
Less temperature gradient

[0094] These main parameters may explain the better performance of the system.

[0095] The filler material may optionally be impregnated as stated before.

[0096] In the test reactor described above, spraying with water was carried out 1-4 times/hour using an amount of water of 12.5-125 l/hour/m.sup.3 of mixture. The water is collected in a container 42 in the lower part 12 of the test reactor 10 together with the aqueous sulfuric acid solution produced during the process. The acid content is determined by means of a measuring device 44. The sulfuric acid solution is then pumped off by a pump 46 and the flow volume is ascertained using a further measuring device 48.

[0097] In the system described above, the sulfur dioxide of the waste gases is catalytically converted via SO.sub.3 on wet catalyst particles to form sulfuric acid. The method was tested successfully under the following conditions: [0098] Water saturation of the waste gases before entry into the reactor by quenching. [0099] SO.sub.2 content of the flue gases between 300 ppm and 6000 ppm. [0100] Gas temperature between 10 and 12 C. [0101] O.sub.2 content approximately 20% by volume. [0102] Water saturation and eventually cooling of the waste gases by quenching.

[0103] Tested catalysts were provided by CABOT NORIT Nederland B.V. of Postbus 105 NL-3800 AC Amersfoot and Jacobi Carbons GmbH Feldbergstrasse 21 D-60323 Frankfurt/Main under the names Norit_RST-3, respectively JACOBI_EcoSorb VRX-Super. These catalysts are an extruded wood/charcoal based activated carbon catalysts with a particle size of about 3 mm. The following general properties are guaranteed by the manufacturer: iodine number 900-1200 mg/g; inner surface (BET) 1000-1300 m2/g; bulk density 360-420 kg/m3; ash content 6-7% by weight; pH alkaline; moisture (packed) 5% by weight.

[0104] It must be noted that the active carbon catalysts do not contain: [0105] a. any iodine, bromine or a compound thereof, [0106] b. any water repellent [0107] c. any catalytically active metals such as Platinum, Palladium, Rhodium etc. or [0108] d. any organic/catalytically active metal complexes based on metals such as Platinum, Palladium, Rhodium etc.

[0109] The active carbon catalyst is not hydrophobized by means of hydrophobic polymer compounds such as polytetrafluoroethylene, polyisobutylene, polyethylene, polypropylene or polytrichlorfluorethylen. In the tests, flue gas analyzers of a German company named Testo were used. The devices were calibrated by the manufacturer. In addition, the analysis data of these flue gas analyzers was confirmed by wet-chemical measurements carried out in parallel. The results of all measurements fell within the admissible deviation tolerances.

[0110] The progression of the SO.sub.2 conversion by H.sub.2SO.sub.4 on the catalyst surface corresponds to the following total formula:

SO.sub.2+O.sub.2+nH.sub.2O(catalytically).fwdarw.H.sub.2SO.sub.4+(n1)H.sub.2O

[0111] Without wanting to be committed to a particular theory, it is assumed that: [0112] O.sub.2 and SO.sub.2 migrate toward the active centers of the catalyst where they are converted into SO.sub.3. [0113] SO.sub.3 migrates out from the active centers of the catalyst and forms H.sub.2SO.sub.4 with the aqueous covering around the catalyst core. [0114] SO.sub.2 reacts with oxygen and water to form sulfuric acid in accordance with the reaction equation above.

[0115] The filling material mixed with activated carbon catalyst enables an optimal liquid and gas interaction with catalyst active sites.

[0116] Softened or demineralized water is used to wash out the catalyst.

[0117] The specific level of SO.sub.2 saturation achieved in the pores of the catalyst in respect of the sulfuric acid formation occurs in the reactor once sufficient SO.sub.2 has been converted into SO.sub.3 and starts to form sulfuric acid.

[0118] Such a condition is reached after approximately 20 to 100 operating hours depending on the approach adopted (amount of SO.sub.2/SO.sub.3 fed and corresponding water spraying rate). The percentage by weight of acid produced is independent of the durationi.e. the time of contact between the gas and the catalyst. The SO.sub.2 to H.sub.2SO.sub.4 conversion is dependent on the SO.sub.2 to SO.sub.3 conversion efficiency and on the amount of water or aqueous solution used. For this reason, this process can produce solutions with different percentages by weight of sulfuric acids (H.sub.2SO.sub.4).

[0119] Test 1: (Comparative Test) The tests were carried out under the following conditions:

TABLE-US-00003 Raw gas volume flow min. 200 m.sup.3/h max. 300 m.sup.3/h SO.sub.2 content (inlet) min. 2000 ppm max. 3000 ppm Gas temperature min. 10 C. max. 12 C. Relative Humidity of the gas 100 % O.sub.2 content >20% by volume

[0120] The reactor is made of inert glass fiber reinforced plastics material, has a volume of approximately 2 m.sup.3 and is filled with 1.2 m.sup.3 of an activated carbon catalyst of the Norit_RST-3 type.

[0121] In a first phase the test system was run for approximately 50 hours with the addition of SO.sub.2 from gas cylinders, and in this instance between 2,000 and 3,000 ppm of SO.sub.2 were added. Overall, the reactor was charged with approximately 88 kg of SO.sub.2 (approximately 73 kg of SO.sub.2/m.sup.3 of catalyst bed). In accordance with this test, the addition of water at 15 l/hour was divided into 2 portions/hour (10.2 l/hour/m.sup.3 of catalyst bed). The SO.sub.2 content of the waste gases was measured at the inlet and at the outlet of the reactor, as illustrated in FIG. 1. The measurements were taken every 30 seconds and are shown in graphs in FIG. 2. The first measurements shown in this case were taken after saturation of the catalyst, i.e. 50 hours after start-up of the reactor. The SO.sub.2 outlet concentration fluctuated repeatedly between 600 ppm and 900 ppm, with a SO.sub.2 removal efficiency of 66%. The test was carried out continuously over approximately 9 hours.

[0122] Test 2: The tests were carried out under the following conditions:

TABLE-US-00004 Raw gas volume flow min. 200 m.sup.3/h max. 300 m.sup.3/h SO.sub.2 content (inlet) min. 2000 ppm max. 3000 ppm Waste gas temperature min. 10 C. max. 12 C. % of relative humidity 100 % O.sub.2 content >20% by volume

[0123] The reactor is made of inert glass fiber reinforced plastics material, has a volume of approximately 2 m3 and is filled with 1.2 m3 of an activated carbon catalyst of the JACOBI_EcoSorb VRX-Super type.

[0124] Contrary to the test 1, the reactor was charged immediately when running with the addition of SO.sub.2 from gas cylinders, and in this instance between 2,000 and 3,000 ppm of SO.sub.2 were added. In accordance with this test, the addition of water at 15 l/hour was divided into 2 portions/hour (10.2 l/hour/m.sup.3 of catalyst bed). The SO.sub.2 content of the waste gases was measured at the inlet and at the outlet of the reactor, as illustrated in FIG. 1. The measurements were taken every 30 seconds and are shown in graphs in FIG. 3. The first measurements shown in this case were taken directly after start-up of the reactor. The SO.sub.2 outlet concentration fluctuated repeatedly between 600 ppm and 900 ppm with a SO.sub.2 removal efficiency of 64%. The test was carried out continuously over approximately 6 hours.

[0125] Test 3: The tests were carried out under the following conditions:

TABLE-US-00005 Raw gas volume flow min. 200 m.sup.3/h max. 300 m.sup.3/h SO.sub.2 content (inlet) min. 2000 ppm max. 3000 ppm Waste gas temperature min. 10 C. max. 12 C. % of relative humidity 100 % O.sub.2 content >20% by volume

[0126] The reactor is made of inert glass fiber reinforced plastics material, has a volume of approximately 2 m.sup.3 and is filled with 1.2 m.sup.3 of an activated carbon catalyst of the Norit_RST-3 type modified by randomly mixing with 0.27 m.sup.3 of a ceramic filling material (Novalox saddle Acidur-Special-Stoneware supplied by Vereinigte Fllkrper-Fabriken).

[0127] Like the test 2, the reactor was charged immediately when running with the addition of SO.sub.2 from gas cylinders, and in this instance between 2,000 and 3,000 ppm of SO.sub.2 were added. In accordance with this test, the addition of water at 15 l/hour was divided into 2 portions/hour (10.2 l/hour/m.sup.3 of catalyst bed). The SO.sub.2 content of the waste gases was measured at the inlet and at the outlet of the reactor, as illustrated in FIG. 1. The measurements were taken every 30 seconds and are shown in graphs in FIG. 4. The first measurements shown in this case were taken directly after start-up of the reactor. The SO.sub.2 outlet concentration fluctuated repeatedly between 15 ppm and 95 ppm with a SO.sub.2 removal efficiency of 96%. The test was carried out continuously over approximately 7 hours.

[0128] Test 4: The tests were carried out under the following conditions:

TABLE-US-00006 Raw gas volume flow min. 200 m.sup.3/h max. 300 m.sup.3/h SO.sub.2 content (inlet) min. 2000 ppm max. 3000 ppm Waste gas temperature min. 10 C. max. 12 C. % of relative humidity 100 % O.sub.2 content >20% by volume

[0129] The reactor is made of inert glass fiber reinforced plastics material, has a volume of approximately 2 m.sup.3 and is filled with 1.2 m.sup.3 of an activated carbon catalyst of the JACOBI_EcoSorb VRX-Super type modified by randomly mixing with 0.27 m.sup.3 of a ceramic filling material (Novalox saddle Acidur-Special-Stoneware supplied by Vereinigte Fllkrper-Fabriken).

[0130] Like the test 2, the reactor was charged immediately when running with the addition of SO.sub.2 from gas cylinders, and in this instance between 2,000 and 3,000 ppm of SO.sub.2 were added. In accordance with this test, the addition of water at 15 l/hour was divided into 2 portions/hour (10.2 l/hour/m.sup.3 of catalyst bed). The SO.sub.2 content of the waste gases was measured at the inlet and at the outlet of the reactor, as illustrated in FIG. 1. The measurements were taken every 30 seconds and are shown in graphs in FIG. 5. The first measurements shown in this case were taken directly after start-up of the reactor. The SO.sub.2 outlet concentration fluctuated repeatedly between 15 ppm and 92 ppm with a SO.sub.2 removal efficiency of 97%. The test was carried out continuously over approximately 7 hours.

[0131] Test 5: The tests were carried out under the following conditions:

TABLE-US-00007 Raw gas volume flow min. 200 m.sup.3/h max. 300 m.sup.3/h SO.sub.2 content (inlet) min. 2000 ppm max. 3000 ppm Waste gas temperature min. 10 C. max. 12 C. % of relative humidity 100 % O.sub.2 content >20% by volume

[0132] The reactor is made of inert glass fiber reinforced plastics material, has a volume of approximately 2 m.sup.3 and is filled with 1.2 m.sup.3 of an activated carbon catalyst of the Norit_RST-3 type modified by randomly mixing with 0.27 m.sup.3 of a ceramic filling material (Novalox saddle Acidur-Special-Stoneware supplied by Vereinigte Fllkrper-Fabriken).

[0133] Like the test 2, the reactor was charged immediately when running with the addition of SO.sub.2 from gas cylinders, and in this instance between 2,000 and 3,000 ppm of SO.sub.2 were added. In accordance with this test, the addition of water at 71 l/hour was divided into 2 portions/hour (48.3 l/hour/m.sup.3 of catalyst bed). The SO.sub.2 content of the waste gases was measured at the inlet and at the outlet of the reactor, as illustrated in FIG. 1. The measurements were taken every 30 seconds and are shown in graphs in FIG. 6. The first measurements shown in this case were taken directly after start-up of the reactor. The SO.sub.2 outlet concentration fluctuated repeatedly between 9 ppm and 43 ppm, with a SO.sub.2 removal efficiency of 98%. The test was carried out continuously over approximately 4 hours.

[0134] Test 6: The tests were carried out under the following conditions:

TABLE-US-00008 Raw gas volume flow min. 200 m.sup.3/h max. 300 m.sup.3/h SO.sub.2 content (inlet) min. 2000 ppm max. 3000 ppm Waste gas temperature min. 10 C. max. 12 C. % of relative humidity 100 % O.sub.2 content >20% by volume

[0135] The reactor is made of inert glass fiber reinforced plastics material, has a volume of approximately 2 m.sup.3 and is filled with 1.2 m.sup.3 of an activated carbon catalyst of the Norit_RST-3 type modified by randomly mixing with 0.27 m.sup.3 of a plastic filling material (Pall-V-ring supplied by Vereinigte Fllkrper-Fabriken).

[0136] Like the test 2, the reactor was charged immediately when running with the addition of SO.sub.2 from gas cylinders, and in this instance between 2,000 and 3,000 ppm of SO.sub.2 were added. In accordance with this test, the addition of water at 15 l/hour was divided into 2 portions/hour (10.2 l/hour/m.sup.3 of catalyst bed). The SO.sub.2 content of the waste gases was measured at the inlet and at the outlet of the reactor, as illustrated in FIG. 1. The measurements were taken every hours and are shown in graphs in FIG. 7. The first measurements shown in this case were taken directly after start-up of the reactor. The SO.sub.2 concentration fluctuated repeatedly between 90 ppm and 160 ppm, with a SO.sub.2 removal efficiency of 95%. The test was carried out continuously over approximately 30 hours.

[0137] Test 7: The tests were carried out under the following conditions:

TABLE-US-00009 Raw gas volume flow min. 200 m.sup.3/h max. 300 m.sup.3/h SO.sub.2 content (inlet) min. 18000 ppm max. 22000 ppm Waste gas temperature min. 10 C. max. 12 C. % of relative humidity <10 % O.sub.2 content >18% by volume

[0138] The reactor is made of inert glass fiber reinforced plastics material, has a volume of approximately 2 m.sup.3 and is filled with 1.2 m.sup.3 of an activated carbon catalyst of the Norit_RST-3 type.

[0139] The quench was switched off during this test and dried activated carbon is used.

[0140] Like the test 2, the reactor was charged immediately when running with the addition of SO.sub.2 from gas cylinders, and in this instance between 18,000 and 22,000 ppm of SO.sub.2 were added without addition of water during the SO.sub.2-loading phase. The SO.sub.2 content of the waste gases was measured at the inlet and at the outlet of the reactor, as illustrated in FIG. 1. The measurements were taken each minute. The SO.sub.2 concentration fluctuated repeatedly between 18000 ppm and 22000 ppm, with a SO.sub.2 removal efficiency of more than 99%. The test was carried out over approximately 106 minutes until SO.sub.2 outlet was higher than 100 ppm. The SO.sub.2-loading efficiency was 23 kg of SO.sub.2 per cubic meter of activated carbon. After this SO.sub.2-loading step, the activated carbon was washed continuously for two hours through addition of water at 50 l/hour. In a next step, ambient air, heated at 80 C., is pulled through the catalytic bed and the activated carbon is dried after a time period of 74 hours.

[0141] Test 8: The tests were carried out under the following conditions:

TABLE-US-00010 Raw gas volume flow min. 200 m.sup.3/h max. 300 m.sup.3/h SO.sub.2 content (inlet) min. 18000 ppm max. 22000 ppm Waste gas temperature min. 10 C. max. 12 C. % of relative humidity <10 % O.sub.2 content >18% by volume

[0142] The reactor is made of inert glass fiber reinforced plastics material, has a volume of approximately 2 m.sup.3 and is filled with 1.2 m.sup.3 of an activated carbon catalyst of the Norit_RST-3 type modified by randomly mixing with 0.27 m.sup.3 of a ceramic filling material (Novalox saddle Acidur-Special-Stoneware supplied by Vereinigte Fllkrper-Fabriken).

[0143] The quench was switched off during this test and dried activated carbon is used.

[0144] Like the test 2, the reactor was charged immediately when running with the addition of SO.sub.2 from gas cylinders, and in this instance between 18,000 and 22,000 ppm of SO.sub.2 were added without addition of water during the SO.sub.2-loading phase. The SO.sub.2 content of the waste gases was measured at the inlet and at the outlet of the reactor, as illustrated in FIG. 1. The measurements were taken each minute. The SO.sub.2 concentration fluctuated repeatedly between 18000 ppm and 22000 ppm, with a SO.sub.2 removal efficiency of more than 99%. The test was carried out over approximately 117 minutes until SO.sub.2 outlet was higher than 100 ppm. The SO.sub.2-loading efficiency was 26 kg of SO.sub.2 per cubic meter of activated carbon. After this SO.sub.2-loading step, the activated carbon was washed continuously for two hours through addition of water at 50 l/hour. In a next step, ambient air, heated at 80 C., is pulled through the catalytic bed and the activated carbon is dried after a time period of 63 hours.

[0145] All the above tests have been carried out with 1.2 m.sup.3 of catalyst (activated carbon). In the tests carried out with addition of filler (whatever its shape): 0.27 m.sup.3 of filler were added to the initial 1.2 m.sup.3 of catalyst.

Vol % of the filler=0.27/(0.27+1.2)*100=18.36% vol.

[0146] A positive effect of the filler can be measured between 5% vol filler and 50% filler, the remaining being activated carbon catalyst.

[0147] The surprising effect is that the removal of SO.sub.2 is more efficient when the catalyst is mixed with fillers than the catalyst alone since more SO.sub.2 is converted with the same amount of catalyst as shown in FIG. 10.

[0148] In addition in case of dry process conditions, the SO.sub.2-loading capacity of activated carbon is higher and the regeneration cycle is shorter in case the activated carbon is mixed with fillers as shown in FIG. 8 and in FIG. 9.

[0149] In the tests conducted it was found that ceramic filler material having a saddle shape seem to be the most efficient. Saddle shape means in the context of the present disclosure: shaped in the form of a horse's saddle, a shape that is bent down at the sides so as to give the upper part a rounded form, respectively an object having the form of an anticlinal fold.

[0150] Test 9FIG. 10: Effect of Bed Design

[0151] In these tests different types of mixing and bed designs were tested and compared to each other in a reactor as depicted on FIG. 1.

[0152] The conditions were as follows: Test 9a [0153] Gas flow: 200-300 m3/h [0154] Gas temperature: starting from 10 C. [0155] Gas flow inlet: 2000-3000 ppm [0156] Activated carbon catalyst: 1.2 m.sup.3 of extruded activated carbon catalyst with particle size 2-4 mm [0157] Filler material: 0.27 m.sup.3 of 38.1 mm wide ceramic saddle filling material [0158] Mixing method: random mixture: most efficient with 90-100% SO.sub.2 cf. removal efficiency as shown on FIG. 10left hand side

Comparative Example Test 9bFIG. 10

[0159] The conditions were as follows: [0160] Gas flow: 200-300 m.sup.3/h [0161] Gas temperature: starting from 10 C. [0162] Gas flow inlet: 2000-3000 ppm [0163] Single activated carbon catalyst bed: 55-65% SO.sub.2 removal efficiency as shown on FIG. 10second from the left.

Comparative Example Test 9cFIG. 10

[0164] The conditions were as follows: [0165] Gas flow: 200-300 m.sup.3/h [0166] Gas temperature: starting from 10 C. [0167] Gas flow inlet: 2000-3000 ppm [0168] Activated carbon catalyst: 1.2 m.sup.3 of extruded activated carbon catalyst with particle size 2-4 mm [0169] Filler material: 0.27 m.sup.3 of 38.1 mm wide ceramic saddle filling material [0170] Two activated carbon catalyst beds (0.5 m.sup.3 and 0.7 m.sup.3 respectively) separated by a layer of 0.27 m.sup.3 of filling material: less efficient with 50-65% SO.sub.2 removal efficiency as shown on FIG. 10third from the left.

Comparative Example Test 9dFIG. 10

[0171] The conditions were as follows: [0172] Gas flow: 200-300 m.sup.3/h [0173] Gas temperature: starting from 10 C. [0174] Gas flow inlet: 2000-3000 ppm [0175] Activated carbon catalyst: 1.2 m.sup.3 of extruded activated carbon catalyst with particle size 2-4 mm [0176] Filler material: 0.27 m.sup.3 of 38 mm wide ceramic saddle filling material [0177] Multi layers design: activated carbon catalyst/filler material layers (0.3 m.sup.3 and 0.054 m.sup.3 respectively) was much less efficient with 70-80% SO.sub.2 removal efficiency as shown on FIG. 10right hand side

[0178] Test 10FIG. 11: Effect of filler material/activated carbon volume ratio

[0179] The conditions were as follows: [0180] Gas flow: 200-300 m3/h [0181] Gas temperature: starting from 10 C. [0182] Gas flow inlet: 2000-3000 ppm [0183] Activated carbon catalyst: extruded activated carbon with particle size 2-4 mm [0184] Filler material: 38 mm wide ceramic saddle filling material [0185] Mixing method: random mixture with different ratio in volume (Filler material/extruded activated carbon catalyst): [0186] 1/20: 5 vol % filler material and 95 vol % activated carbon catalyst [0187] 1/10: 9 vol % filler material and 91 vol % activated carbon catalyst [0188] 1/5: 17 vol % filler material and 83 vol % activated carbon catalyst [0189] 1/4: 20 vol % filler material and 80 vol % activated carbon catalyst [0190] 1/3: 25 vol % filler material and 75 vol % activated carbon catalyst [0191] This test shows the highest efficiency with 99% SO.sub.2 removal when operating with 20 vol % filler material and 80 vol % activated carbon catalyst (ratio 1/4) as shown on FIG. 11.

[0192] Test 11FIG. 12: Effect of filler material/activated carbon volume ratio

[0193] The conditions were as follows: [0194] Gas flow: 200-300 m3/h [0195] Gas temperature: starting from 10 C. [0196] Gas flow inlet: 2000-3000 ppm [0197] Activated carbon catalyst: extruded activated carbon with particle size 2-4 mm [0198] Filler material: 50 mm wide plastic pall ring filling material [0199] Mixing method: random mixture with different ratio in volume (Filler material/extruded activated carbon catalyst): [0200] 1/20: 5 vol % filler material and 95 vol % activated carbon catalyst [0201] 1/10: 9 vol % filler material and 91 vol % activated carbon catalyst [0202] 1/5: 17 vol % filler material and 83 vol % activated carbon catalyst [0203] 1/4: 20 vol % filler material and 80 vol % activated carbon catalyst [0204] 1/3: 25 vol % filler material and 75 vol % activated carbon catalyst [0205] Highest efficiency 82% SO.sub.2 removal when operating with 20 vol % filler material and 80 vol % activated carbon (ratio 1/4) as shown on FIG. 12.

[0206] Test 11FIG. 13: Effect of filler size

[0207] The conditions were as follows: [0208] Gas flow: 200-300 m3/h [0209] Gas temperature: starting from 10 C. [0210] Gas flow inlet: 2000-3000 ppm [0211] Activated carbon catalyst: extruded activated carbon catalyst with particle size 2-4 mm [0212] Filler material: saddle filling material with different size from 12.7 (normalized size 1) to 76.2 mm (normalized size 6) [0213] Mixing method: random mixture with 20 vol % filler material and 80 vol % activated carbon catalyst (ratio 1/4) [0214] Higher efficiency with 88-99% SO.sub.2 removal when operating with between 38.1 mm (normalized size 3) and 63.5 mm (normalized size 5) saddle filling material as shown on FIG. 13

[0215] Test 12FIG. 14: Effect of filler particle size

[0216] The conditions were as follows: [0217] Gas flow: 200-300 m3/h [0218] Gas temperature: starting from 10 C. [0219] Gas flow inlet: 2000-3000 ppm [0220] Activated carbon catalyst: bead, extruded or granulated activated carbon catalyst [0221] Filler material: 38.1 mm wide ceramic saddle filling material [0222] Mixing method: random mixture with 20 vol % filler material and 80 vol % activated carbon catalyst (ratio 1/4) [0223] Higher efficiency with 99% SO.sub.2 removal when operating with extruded activated carbon catalyst as shown on FIG. 14.

[0224] Although the present disclosure has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.

[0225] All the features disclosed in this specification (including any accompanying claims, abstract, and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar.