RU2750802C1 - Method for preparing deep oxidation catalyst and method for catalytic combustion of sludge from municipal wastewater treatment plants - Google Patents

Abstract

FIELD: waste treatment.

SUBSTANCE: method is proposed for preparing a catalyst for burning sludge from municipal wastewater treatment plants, containing as an active component transition metal oxides or mixtures thereof and an oxide carrier, characterized in that the catalyst granules are obtained by rolling powders of the active component based on transition metal oxides or mixtures thereof with a content of, weight percentage, at least 50 % wt., aluminum hydroxide, peptizer acid and water, where HNO₃ and/or CH₃COOH are used as a peptizer acid, followed by drying and calcination, while a spherical catalyst is obtained, containing as an oxide carrier aluminum oxide in an amount, weight percentage, not exceeding 50 % wt., and as an active component Fe₂O₃ in an amount of 48-75 % wt., as well as CuO, and/or Mn₂O₃, and/or Co₂O₃, and/or Cr₂O₃ in an amount of 2-10 % wt. A method for burning sludge from municipal wastewater treatment plants in a fluidized bed of a catalyst obtained by the method described above is also proposed.

EFFECT: high activity of the claimed deep oxidation catalyst prepared by the pelletizing method, which affects the degree of burnout of sludge from municipal wastewater treatment plants during their combustion, and the high mechanical strength of the catalyst in the fluidized bed mode.

4 cl, 1 dwg, 14 ex, 1 tbl

Description

The invention relates to the development of methods for the preparation of catalysts for the deep oxidation of CO and organic substances and methods of burning sludge from municipal treatment facilities.

Known catalyst for fuel combustion (SU 1216862, B01J 23/26, 23.12.1991), which is an aluminum oxide containing magnesium chromite and aluminum oxide of the following composition: magnesium chromite 10-26 wt. %, aluminum oxide 74-90%. This catalyst has increased thermal stability and durability, however, in some technological processes with increased environmental requirements, the activity of this catalyst is not enough to completely eliminate the emission of carbon monoxide (Regularities of deep catalytic oxidation of some classes of organic compounds and the development of scientific foundations of catalytic fuel combustion in catalytic heat generators: Dis. Doctor of Chemical Sciences: 02.00.15 / Ismagilov ZR.In-t of Catalysis named after G.K.Boreskov SB RAS. - Novosibirsk, 1988. - 502 p.).

Known catalyst for fuel combustion (SU 1295566, B01J 23/86, 06/18/1985), which is an aluminum oxide containing at the same time copper-magnesium chromite of the general formula: Mg _1-x Cu _x Cr ₂ O ₄ , where x = 0.08-0.40. This catalyst has increased thermal stability, wear resistance and activity in the oxidation of organic substances and CO. As a carrier for this catalyst, spherical alumina granules obtained by a complex multistage technology by liquid molding are used. This raises the problem of the high cost of the carrier and, accordingly, the catalyst based on it.

The closest to the claimed technical essence and the achieved effect is a method for preparing a deep oxidation catalyst (RU 2591955, B01J 37/02, 20.07.2016). The oxide support is impregnated with transition metal salts, then dried and calcined. The catalyst obtained by this method contains as an active component oxides of transition metals or mixtures thereof, supported on an oxide support. In this case, as an oxide carrier, it contains granules of proppant, consisting of quartz and magnesium silicates, or its modifications. The proposed catalyst has high activity and high mechanical strength. However, due to the low specific surface area of the oxide support, the modified proppant, its activity turned out to be insufficient to efficiently and ecologically safely implement the process of combustion of sludge in a fluidized bed of catalyst.

The problem solved by the present invention is to develop a method for preparing a catalyst that is not inferior in its activity in the process of burning sludge from municipal treatment facilities to known catalysts for deep oxidation of CO and organic substances based on transition metal oxides.

The problem is solved by the method of preparing a catalyst for the oxidation of CO and organic substances, containing as an active component oxides of transition metals or mixtures thereof and an oxide support. Catalyst granules are obtained by rolling powders of an active component based on transition metal oxides or mixtures thereof, with a content of at least 50 wt. % (in terms of dry matter), aluminum hydroxide, peptizer acid and water, followed by drying and calcining. In this case, a spherical catalyst is obtained containing alumina as an oxide carrier in an amount of not more than 50 wt. %, and as an active component Fe ₂ O ₃ in an amount of 48-75 wt.%, as well as CuO and / or Mn ₂ O ₃ and / or Co ₂ O ₃ and / or Cr ₂ O ₃ in an amount of 2-10 wt. .%.

_{HNO 3} and / or CH ₃ COOH are used as peptizing acid. The acid modulus in the mixture is no more than 0.01. The water content in the mixture is not more than 20% by weight.

The problem is also solved by the method of burning the sludge of municipal sewage treatment plants in a fluidized bed of catalyst obtained by the proposed method.

The technical result is the high activity of the inventive deep oxidation catalyst prepared by the pelletizing method, which affects the degree of burnout of sludge sediments of municipal treatment facilities during their combustion and high mechanical strength of the catalyst in the fluidized bed mode.

The essence of the invention is illustrated by the following examples.

Example 1 (Prototype)

Proppant granules with a diameter of 2-3 mm are treated with a KOH solution (the molar fraction of KOH in the solution is 40%) for 3 hours (at a temperature close to the boiling point of the solution), after cooling, they are washed with distilled water to neutral pH and treated with an excess of 20% nitrogen solution acid. It is washed with distilled water to neutral pH, dried at 110 ° C for 2 h. The resulting support granules with a specific surface area of 15 m ² / g, which, according to XRD data, consists of quartz SiO ₂ and magnesium silicates (enstatite MgSiO ₃ and forsterite Mg ₂ SiO ₄ ) containing SiO ₂ 50 wt. %, MgO 31 wt. %, impregnated with a solution of copper dichromate, dried at 100 ° C for 3 hours and calcined at 600 ° C for 4 hours. The content of the active component CuCr ₂ O ₄ is 6 wt. %.

As a measure of the catalytic activity of catalysts in the process of burning sludge from municipal wastewater treatment plants, the degree of sludge burnout during combustion was chosen. The tests were carried out in a fluidized bed reactor according to the method described in the work (Simonov A.D., Chub OV, Yazykov N.A. Catalytic combustion of sewage sludge from municipal services. Chemistry for sustainable development. 2010. Vol. 18. No. 6. P.749-753.).

The figure shows a schematic diagram of a catalytic fluidized bed combustion plant. The installation includes a reactor 1, a heat exchanger 2, an external electric heater 3, rotameters 4, a silt sludge bunker 5, a conveyor 6, an ejector 7, a cyclone 8, a container for collecting ash residues 9, control valves 10.

The method of incineration of sludge from municipal sewage treatment plants was carried out as follows.

Reactor 1 is charged with 400 ml of catalyst with a particle size of 1.5-2.0 mm. Reactor diameter 40 mm, height 1000 mm. Using an external electric heater, the catalyst layer 3 in the reactor is heated to the required operating temperature of 500-700 ° C. Then, air is supplied through rotameters 4 under the gas distribution grid to fluidize the catalyst bed and to the ejector 7. The total air flow rate is 3 m ³ / h. The precipitate in the amount of 360 g / h from the bunker 5 is fed through the conveyor 6 to the ejector 7, then the waste is supplied with air to the lower part of the fluidized bed of the catalyst. Excess heat released during the combustion of waste is removed using a water-cooled heat exchanger 2. Solid products of waste combustion are separated from flue gases in cyclone 8 and collected in containers 9. The content of moisture, volatile substances and ash in the original sludge and solid combustion products is determined by technical analysis according to GOST 11014-2001, GOST 6382-2001, GOST 11022-95, respectively. The degree of burnout of the combustible mass of the sediment is determined by the formula:

where A is the ash content of solid combustion products, B is the initial ash content of the dry sludge.

The activity of the catalyst in the CO oxidation reaction is determined on a Chemosorb device by the pulse method at the temperature of 50% CO conversion. The strength of the catalyst granules is determined using the MP-9S device as the average value of 30 measurements.

The 50% CO conversion temperature is 225 ° C. The degree of sludge burnout is 94.3%. The mechanical strength is 49 MPa. Granule size 1.5 ± 0.5 mm. The resulting catalyst granules have an ideal spherical shape.

Example 2

Such as aluminum hydroxide, pseudoboehmite, pulverized powder of the active ingredient (nanocomposite obtained by calcination of salts of nitrates, with a surface area of at least 10 m ² / g, obtained by the method described in (Fedorov AV, Tsapina AM, Bulavchenko OA, Saraev AA, Odegova GV, Ermakov DY, Zubavichus YV, Yakovlev VA, Kaichev VV, Structure and Chemistry of Cu-Fe-Al Nanocomposite Catalysts for CO Oxidation, Catalysis Letters. 2018. - V.148., N12. - P.3715-3722. DOI: 10.1007 / s10562-018-2539-5), water and acid peptizer are mixed in a disc granulator, poured to obtain spherical catalyst granules.The value of the acid modulus (molar ratio of acid to aluminum oxide) is 0.005. The water content in the plasticized mass is 10 wt. The granules are dried in air for 24 h, at 110 ° C for 2 h and calcined at 700 ° C for 1 h. The resulting catalyst contains 3.0 wt% CuO, 50.0 wt% Fe ₂ O _3, and 47.0% Al ₂ O ₃ .

The 50% CO conversion temperature is 210 ° C. The degree of sludge burnout is 98.2%. The mechanical strength is 18 MPa. Granule size 3.0 ± 2.1 mm. The resulting catalyst granules have an ideal spherical shape.

Example 3

Similar to example 2.

The resulting catalyst contains 75.0 wt. % Fe ₂ O ₃ and 25.0% Al ₂ O ₃ .

The 50% CO conversion temperature is 225 ° C. The degree of sludge burnout is 97.8%. The mechanical strength is 11 MPa. Granule size 2.8 ± 1.8 mm. The resulting catalyst granules have an ideal spherical shape.

Example 4

Similar to example 2.

The resulting catalyst contains 5.0 wt. % Mn ₂ O ₃ , 60.0 wt. % Fe ₂ O ₃ and 35.0% Al ₂ O ₃ .

The 50% CO conversion temperature is 230 ° C. The degree of sludge burnout is 98.1%. The mechanical strength is 13 MPa. Granule size 2.5 ± 1.7 mm. The resulting catalyst granules have an ideal spherical shape.

Example 5

Similar to example 2.

The resulting catalyst contains 4.5 wt. % Cr ₂ O ₃ , 60.0 wt. % Fe ₂ O ₃ and 35.5% Al ₂ O ₃ .

The 50% CO conversion temperature is 230 ° C. The degree of sludge burnout is 98.0%. The mechanical strength is 14 MPa. The size of the granules is 3.2 ± 2.0 mm. The resulting catalyst granules have an ideal spherical shape.

Example 6

Similar to example 2.

The resulting catalyst contains 4.0 wt. % Co ₂ O ₃ , 61.0 wt. % Fe ₂ O ₃ and 35.0% Al ₂ O ₃ .

The 50% CO conversion temperature is 205 ° C. The degree of sludge burnout is 98.9%. The mechanical strength is 12 MPa. Granule size 3.4 ± 2.0 mm. The resulting catalyst granules have an ideal spherical shape.

Example 7

Similar to example 2.

The resulting catalyst contains 4.0 wt. % Co ₂ O ₃ , 6.0 wt. % CuO, 55.0 wt. % Fe ₂ O ₃ and 35.0% Al ₂ O ₃ .

The 50% CO conversion temperature is 185 ° C. The degree of sludge burnout is 99.6%. The mechanical strength is 14 MPa. Granule size 3.2 ± 2.1 mm. The resulting catalyst granules have an ideal spherical shape.

Example 8

Similar to example 2.

The resulting catalyst contains 7.0 wt. % Mn ₂ O ₃ , 3.0 wt. % CuO, 52.0 wt. % Fe ₂ O ₃ and 38.0% Al ₂ O ₃ .

The 50% CO conversion temperature is 185 ° C. The degree of sludge burnout is 99.0%. The mechanical strength is 15 MPa. Granule size 3.5 ± 2.2 mm. The resulting catalyst granules have an ideal spherical shape.

Example 9

Similar to example 2.

The acid modulus was 0.01.

The 50% CO conversion temperature is 210 ° C. The degree of sludge burnout is 98.5%. The mechanical strength is 13 MPa. Granule size 3.5 ± 2.3 mm. The resulting catalyst granules have an ideal spherical shape.

Example 10

Similar to example 2.

The acid modulus was 0.0001.

The 50% CO conversion temperature is 215 ° C. The degree of sludge burnout is 99.0%. The mechanical strength is 15 MPa. Granule size 3.2 ± 2.1 mm. The resulting catalyst granules have an ideal spherical shape.

Example 11

Similar to example 9.

Acetic acid CH ₃ COOH is used instead of nitric acid HNO _3.

The 50% CO conversion temperature is 220 ° C. The degree of sludge burnout is 98.6%. The mechanical strength is 16 MPa. Granule size 3.5 ± 2.2 mm. The resulting catalyst granules have an ideal spherical shape.

Example 12

Similar to example 9.

Instead of nitric acid HNO ₃ , a mixture of nitric and acetic acid CH ₃ COOH is used.

The 50% CO conversion temperature is 215 ° C. The degree of sludge burnout is 98.5%. The mechanical strength is 14 MPa. Granule size 3.4 ± 2.0 mm. The resulting catalyst granules have an ideal spherical shape.

Example 13

Similar to example 2.

The water content in the plasticized mass is 10 wt. %.

The 50% CO conversion temperature is 220 ° C. The degree of sludge burnout is 98.4%. The mechanical strength is 12 MPa. Granule size 3.0 ± 2.1 mm. The resulting catalyst granules have an ideal spherical shape.

Example 14

Similar to example 2.

The water content in the plasticized mass is 5 wt. %.

The 50% CO conversion temperature is 215 ° C. The degree of sludge burnout is 98.3%. The mechanical strength is 17 MPa. Granule size 3.5 ± 2.5 mm. The resulting catalyst granules have an ideal spherical shape.

Comparative characteristics of deep oxidation catalysts are shown in the Table.

Table

Comparative characteristics of catalysts

Temperature to reach 50% CO conversion, ° C Sediment burnout,% Strength, MPa Granule size, mm Example 1 225 94.3 49 1.5 ± 0.5 Example 2 210 98.2 eighteen 3.0 ± 2.1 Example 3 225 97.8 eleven 2.8 ± 1.8 Example 4 230 98.1 13 2.5 ± 1.7 Example 5 230 98.0 fourteen 3.2 ± 2.0 Example 6 205 98.9 12 3.4 ± 2.0 Example 7 185 99.6 fourteen 3.2 ± 2.1 Example 8 185 99.0 fifteen 3.5 ± 2.2 Example 9 210 98.5 13 3.5 ± 2.3 Example 10 215 99.0 fifteen 3.2 ± 2.1 Example 11 220 98.6 sixteen 3.5 ± 2.2 Example 12 215 98.5 fourteen 3.4 ± 2.0 Example 13 220 98.4 12 3.0 ± 2.1 Example 14 215 98.3 17 3.5 ± 2.5

The above examples show that the catalysts for deep oxidation prepared by the method of pelletizing are not inferior in activity to the known catalysts for deep oxidation. At the same time, the degree of sludge burnout when using the claimed catalysts exceeds 97.8%, which is higher than that of the known catalysts (94.3%). The catalysts have high mechanical strength (≥11 MPa), which meets the requirements (10 MPa) for deep oxidation catalysts for a fluidized bed (Parmon V.N., Simonov A.D., Sadykov V.A., Tikhov S.F. Catalytic Combustion: Achievements and Problems // Physics of Combustion and Explosion. 2015. V. 51. No. 2. P. 5-13.).

Claims (4)

1. A method of preparing a catalyst for the combustion of sludge from municipal sewage treatment plants containing as an active component oxides of transition metals or mixtures thereof and an oxide support, characterized in that the catalyst granules are obtained by rolling powders of the active component based on transition metal oxides or their mixtures containing their not less than 50 wt%, aluminum hydroxide, peptizer acid and water, where HNO ₃ and / or CH ₃ COOH is used as a peptizer acid, followed by drying and calcination, thus obtaining a spherical catalyst containing alumina as an oxide carrier in an amount of not more than 50 wt.%, and as an active component Fe ₂ O ₃ in an amount of 48-75 wt.%, as well as CuO, and / or Mn ₂ O ₃ , and / or Co ₂ O ₃ , and / or Cr ₂ O ₃ in an amount of 2-10 wt.%. 2. The method according to claim 1, characterized in that the value of the acid modulus in the mixture is not more than 0.01. 3. A method according to claim 1, characterized in that the water content in the mixture is not more than 20 wt.%. 4. A method of incineration of sludge from municipal treatment facilities in a fluidized bed of catalyst obtained by the method according to claims 1 to 3.

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