CATALYZED CERAMIC CANDLE FILTER AND METHOD OF CLEANING PROCESS OFF- OR EXHAUST GASES

Abstract

Ceramic candle filter and use of the filter in the removal of particulate matter in form of soot, ash, metals and met-al compounds, together with hydrocarbons and nitrogen oxides being present in process off-gas or engine exhaust gas, the filter includes a combined SCR and oxidation catalyst being arranged on the dispersion side and within wall of the filter; and a palladium including catalyst arranged on the permeation side and within wall of the filter facing the permeation side.

Claims

1. A ceramic candle filter suitable for the removal of particulate matter in form of soot, ash, metals and metal compounds, together with hydrocarbons and nitrogen oxides being present in process off-gas or engine exhaust gas, the filter comprises a combined SCR and oxidation catalyst arranged at least on the dispersion side and/or within wall of the filter; and a palladium comprising catalyst arranged on the permeation side of the filter and within wall of the filter facing the permeation side.

2. The ceramic candle filter of claim 1, wherein the combined SCR and oxidation catalyst comprises a vanadium oxide and titania.

3. The ceramic candle filter of claim 1, wherein the palladium comprising catalyst further comprises a vanadium oxide and titania.

4. The ceramic candle filter of claim 1, wherein the palladium comprising catalyst contains palladium in an amount of between 20 and 1000 ppm/weight of the filter.

5. The ceramic candle filter according to claim 1, wherein the ceramic material of the filter is selected from the group of silica-aluminate, calcium-magnesium-silicates, calcium-silicates fibers, or a mixture thereof.

6. The ceramic candle filter according to claim 5, wherein the ceramic material of the filter consists of bio-soluble fibres selected from the group of calcium-magnesium-silicates.

7. A method for the removal of particulate matter in form of soot, ash, metals and metal compounds, together with hydrocarbons and nitrogen oxides being present in process off-gas or engine exhaust gas, comprising the steps of providing a process off-gas or engine exhaust gas containing a nitrogenous reductant or adding the nitrogenous reductant to process off- or exhaust gas; passing the off- or the exhaust gas to a ceramic candle filter and capturing the particulate matter on dispersion side of the filter; reducing amounts of soot in the particulate matter captured on the dispersion side of the filter and reducing amounts of hydrocarbons in the off- or exhaust gas by oxidation and reducing amounts of nitrogen oxides by selective catalytic reduction (SCR) of the nitrogen oxides with the nitrogenous reductant in contact with a combined SCR and oxidation catalyst being arranged on the dispersion side and/or within wall of the filter; and passing the gas through the wall of the filter and reducing amounts of carbon monoxide and ammonia in the gas passing through the filter wall by contact with a palladium comprising catalyst arranged on the permeation side of the filter and/or within the wall of the filter facing the permeation side.

8. The method of claim 7, wherein the combined SCR and oxidation catalyst comprises a vanadium oxide and titania.

9. The method according to claim 6, wherein the palladium comprising catalyst further comprises a vanadium oxide and titania.

10. The method according to claim 6, wherein wherein the palladium comprising catalyst contains palladium in an amount of between 20 and 1000 ppm/weight of the filter.

11. The method according to claim 6, wherein the ceramic material of the filter is selected from silica-aluminate, calcium-magnesium-silicates, calcium-silicates fibers, or mixtures thereof.

12. The method according to claim 6, wherein the ceramic material of the filter comprises bio-soluble fibres selected from the group of calcium-magnesium-silicates.

Description

EXAMPLE 1

[0035] The following example illustrates the performance obtainable with a ceramic candle filter prepared from calcium-magnesium-silicate fibres with a length of 3 m and wall thickness of 20 mm. The filter was coated within the wall with the V/Ti catalyst containing 1.26 wt % V and 2.36 wt % Ti calculated on the total weight of the filter. The porosity of the coated filter was 83%. The filter was tested in the oxidation of toluene in an inlet gas containing 40 ppm, dry toluene, 19% vol O.sub.2, 8% vol H.sub.2O.

[0036] Toluene oxidation on a V/Ti coated filter

TABLE-US-00001 Conversion Temp. Face vel. of Toluene CO, out ° C. m/min % ppm, wet 220 1.28 96 16 240 1.34 98 35

[0037] As apparent from the table above, 85% of toluene was converted at 240° C. The CO emission at the same temperature was equal to 35 ppm, wet.

EXAMPLE 2

[0038] The following example illustrates the CO oxidation performance of the ceramic candle filter of Example 1, but additionally coated with 36 ppm Pd. The tests were conducted with a gas containing around 150 ppm, wet CO, 19% O.sub.2 and 8% H.sub.2O.

TABLE-US-00002 Conversion Temp. Face vel. CO, in CO, out of CO ° C. m/min ppm, wet ppm, wet % 220 1.28 148 36.5 75 240 1.35 157 4 97

[0039] At 240° C., 97% of the CO was oxidized to CO.sub.2.

[0040] By combining the performance of the ceramic candle filter reported in EXAMPLE 1 and EXAMPLE 2, it is possible to conclude that only 1 ppm CO is emitted by a candle filter catalyzed with a V/Ti catalyst on the dispersion side and a Pd/V/Ti catalyst on the permeation side.