Catalyst for oxidation of sulfur dioxide, method thereof and method of oxidation of sulfur dioxide

 

(57) Abstract:

Solid catalyst for oxidation of SO2in the oxygen-containing gas flows, contains vanadium oxide and an oxide or sulfate of an alkali metal as the active substances, silicon and/or aluminum oxide in the form to increase the surface and titanium dioxide in the anatase and/or rutile form as the material of the carrier and the ceramic binder. The metals of these perform discrete functions vysokodispersnoi sintered components are in certain atomic ratios. Superfine sintering takes place according to the method of obtaining primarily through differentiated conditions of drying, calcination and sintering. The basic scope of the invention is the desulfurization of flue gases from combustion processes and industrial installations. 3 C. p. F.-ly, 5 Il. 5 table.

The invention relates to a catalyst for oxidation of contained in the oxygen-containing gas stream of sulfur dioxide, including:

AND1) vanadium oxide and

AND2) oxide and/or sulfate of an alkali metal as catalytically active substances and

B) silicon and/or aluminum in the form of oxides as increasing the surface kom is also of flue gases of combustion processes and industrial installations. Contained mainly in flue gases harmful to air substances nitrogen oxides, carbon monoxide, hydrocarbons and sulphur dioxide quite well-known because of their polluting actions.

If the primary measures to reduce emissions of harmful substances have only a minor impact on overall emissions of harmful substances, it is necessary to use secondary measures, such as catalytic methods for cleaning flue gases.

Most combustion processes of fossil combustible proceeds at sverdsrikhimmash the composition of the fuel-air. Suitable for this purpose catalytic methods for cleaning flue gases are sufficiently known SLE method of removing nitrogen using ammonia (selective catalytic reduction) and containing a noble metal oxidation catalysts for oxidation of carbon monoxide, hydrocarbons and sulfur dioxide, which can be processed further in sulfuric acid. The combination of both methods is a method described in patent Germany 36 01 378, through which the flue gases generated upon receipt of sulfuric acid, it is important to release from the NOxand SO2.

Still who can gain is not in the form of products with the required large geometric dimensions. Still need to place a separate monoliths small amount over each other to get the required amount of catalyst. As in the joints between adjoining to each other monoliths of containing dust flue gases are covered with dust, must be installed in the apparatus for Stripping from dust. Along with this, in particular components of precious metals these catalysts represent a significant cost factor, which can allow for smaller treatment plants for flue gases, in the case of large installations, as combined heat and power plants or large power stations, it leads to unacceptable investment costs. Finally, the catalytically active components of the noble metals are particularly sensitive to information contained in the flue gas poisonous components that cause deactivation of the catalyst.

Maintaining cleanliness of catalysts for containing dust flue gases is carried out through the so-called apparatus for Stripping soot or dust, which vzvikhrivayut otlogetswe side skidding of catalysts and at the joints of the masonry catalysts dust with hot steam or hot air, again served eora. In order to have a small number of expensive units as blowers to remove soot in the catalytic reactor, it is necessary to have a possible minor swept surface and the joints filled in this monolithic or honeycomb catalyst reactor. The prerequisite for this is that the used monolithic or honeycomb body can be prepared in the form of pieces of great length. It is however not yet implemented in the case of containing a noble metal catalysts on the media.

Also use blower to remove soot or dust, only in the case of catalysts in solid or cellular form. Catalysts in the form of a granular material thus cannot be cleaned as dust only penetrates into the deeper places of the loose mass of the catalyst and the blockage remains. At the same time there exists the danger of uncontrolled vzvihrennaja catalyst in the form of bulk material.

Used so far to move in the so-called contact method of sulfur dioxide to sulfur trioxide is the anhydride of sulfuric acid, catalysts based on noble metals (e.g. platinum) or especially catalysts based on oxides of sublateral media) will be used only in the form of a granular material (in the form of extruded products by extrusion or in the form of rings). For the above reasons, this technology treatment containing sulfur oxide flue gases, in particular when they contain dust, problematic.

Dust deposits must be removed by sieving catalyst. The service life of such catalysts, therefore, is mainly determined by the mechanical strength.

The basis of the invention is the development of a catalyst which is suitable for transferring to sulfur trioxide in sulfur dioxide contained in any oxygen-containing, respectively, mixed with oxygen or oxygen-containing gas flows of gases. He should easily be prepared in a form suitable for bulk layer molded particles for processing dust free gas streams and in the form of a monolithic or honeycombed products for use in sensitive to the pressure loss treatment plants for waste and flue gases and/or air containing dust flows, flows of exhaust or flue gases: can be easily constructed in any usual for catalysts in the form of bulk material shaped and constructed in the form of a monolith or products in the form of honeycombs. For this purpose, the composition of the catalyst, which is different from the compounds used so far on this AP is the abrasion resistance or can be recycled in the cell body only with unsatisfactory strength.

The applicant serves as a prototype catalysts of unaccepted bids Germany (DE) 39 10 249.

The mentioned application Germany 39 10 249 describes a catalyst for the oxidation of sulphur dioxide (SO3in a honeycomb structure and a method of producing catalyst. This catalyst comprises a catalytically active component vanadium oxide and salt and potassium as base material kieselguhr (diatomaceous earth).

The aim of the invention is a catalyst for oxidation of contained in the oxygen-containing current gas sulfur dioxide, comprising the following components:

AND1) vanadium oxide and

AND2) oxide and/or sulfate of an alkali metal

as catalytically active substances and

B) oxides of silicon and/or aluminum as increasing the surface components.

The catalyst is characterized in that it contains another

C) titanium oxide in anatase and/or rutile form as the material of the carrier and the ceramic binder and made in the form of a "whole" (solid) catalyst, if necessary, in a solid or cellular form, in which components (a) are contained in amounts corresponding atomic ratio between materialjnoj form.

Proposed according to the invention, the oxidation catalyst in the specified field of application meets the following requirements.

He is able to translate more than 90% of sulfur dioxide one-stage method to sulfur trioxide. He turns in a solid or cellular form up to a length of 1000 mm and fully satisfies the requirements in terms of purity while supplying dust-intensive gas. The temperature region in which the necessary conversion, very wide, especially at low temperatures. Kinetic characterization of the catalyst is greatly improved, as in the case known, is still the most often used, containing a noble metal catalysts, the oxidation reaction proceeds not according to the law of the first order, which can cause problems when measuring the required amount of catalyst primarily at the high requirements for the degree of conversion. The catalyst is a so-called "full" (full) catalyst, i.e., it contains only fully catalytically active material, which continuously detects the active surface during abrasion using, for example, contained in the flue gas dust.

The following subject disperses form, with the addition of the usual molding or extrusion of ceramic masses additives humidifier, the reinforcing component, the binder raw products, auxiliary for forming tools and, if necessary, pore-forming intensively processed into a homogeneous mass, the mass is pressed or ekstragiruyut in desirable inconclusive (raw) products, preferably in a monolithic or honeycomb body, inconclusive (raw) products at a slow temperature rise to (at most) 60aboutWith at controlled humidity environmental air dried and then when stupenchataya the temperature in the ambient air calcined at least at 500aboutAnd most if 800aboutWith and at a temperature in this area is sintered for at least 12 hours, preferably 14-48 h, in particular 18-36 hours

As a moisturizer, you can apply demineralized water, aqueous ammonia, monoethanolamine and alcohols.

As reinforcing components can be used, for example, fiberglass different sizes. As a binder, which izgotovliaemye compound after molding in a state of so-called inconclusive (raw) tel impart sufficient stability, suitable derivatives of cellulose, as carboximetilzellulozu injuly alcohol, the polyethylene oxide, polyacrylamide or polystyrene as a binder.

In order to facilitate the pressing or to improve the ability to extrusion, add auxiliary for forming and/or imparting slipperiness means as bentonite, alumina, organic acids, paraffin, waxes, silicone oils.

Finally, the porosity (pore volume, pore radii) proposed according to the invention the solid catalysts can be adjusted by additives suitable pore. Such substances are, for example, finely ground coal (active charcoal) or wood pulp, which fade when used annealing temperatures.

For intensive mixing of the starting compounds to the homogeneous moldable mass can be applied mainly kneading machine. While I prefer faucets with sigmaprime or scissor blades. The method is very simple. He does not technically expensive, polluting the environment and therefore also expensive stages. The processes of deposition and grinding to obtain a homogeneous mixture of oxides falling away.

This leads to a noticeable decrease in the cost of production and at the same time the mouth of the receipt is as starting substances used commercially available oxides, respectively, are chemically stable at high temperatures, the sulfates and thus can no longer use the preliminary stages of getting hydroxides or oxides, which cause additional measures.

In contrast to the often used, containing titanium oxide catalysts for removal of nitrogen, in which this component is attributed to the catalytic action of this compound is proposed according to the invention the catalyst for the oxidation of sulfur dioxide as a component) performs only the function of the ceramic carrier and binder for the catalytically active substances (A) and increasing its surface additives B).

Used as the binding of catalytically active substances are the alkali metal oxide or sulfate of an alkali metal AND2in the proposed according to the invention the composition of the catalyst performs the function of the flux for the active substance AND1) at the operating temperature 380-500aboutC. (a1and a2) also contribute to the process of sintering binder) and increasing the surface additives B) during sintering source Vasistha according to the invention a catalyst for the oxidation of sulfur dioxide in air or in oxygen-containing exhaust gas or flue gas stream.

P R I m e R 1. In a kneading machine with Sigma blades are mixed and subjected to the process of mixing within 7 h following substances, g titanium Oxide (anatase) 4950 silicon Dioxide 146 vanadium Pentoxide 297 potassium Sulfate 297 Water 4542 Clay 213 Fiberglass 550 Organic additives 164 Ammonia 1150

The mixed mass is then ekstragiruyut on screw extruder in a molded particles are heated at a temperature increasing at a rate of 1aboutC/h and at a relative humidity of about 100-80% to 50aboutWith, then dried and then continue to heat with a heating rate maximum 50aboutFrom 2 h up to 600aboutC. and Then sintering calcined for 24 h at this temperature in air. Cell bodies are of 3 x 3 cells of square cross-section, the cell width of 5.5 mm and a wall thickness of 1.3 mm

Test activity test is carried out on a laboratory setup under the following conditions:

V 1,13 m3/h; N wet

AV*)16-52 m/h

LV**)0.6 m/s; N

T 350-450oC

NO 100 pp, dried

SO2600 pp, dried

ABOUT25% dried

H2O about 7. wet

N2else

*)the load on the surface [flow volume/surface catalyst] the spine of this catalyst with surface load AV=52 m/h, which corresponds to a flow rate of about 20000 h-1. Up to 375aboutWith the transformation remains low, but increases sharply when the temperature rises to 50aboutWith and stabilizes ranging from about 425aboutWith at 36-37%

In Fig. 2 shows the dependence of the conversion of SO2the load on the catalyst surface. The AV Value is first of 16.4 m/h when the honeycomb catalyst length 350 mm Due to abrasion every 30 mm AV is gradually increased up to 52 m/am Interesting for the real functioning of the AV region between 4 and 10 m/h, however, cannot be installed in this laboratory test device, however, since AV=15 m/h, found the degree of conversion of 80% so you have to expect that the achieved values of the degree of conversion in the field of over 90% and even clearly exceeded.

P R I m e R s 2-6. In a kneading machine with criseyde - scissor blades are mixed for 12 h stir until paste the following substances. The data are given in table. 1.

Paste after mixing (kneading) is placed in an extruder and pressed into cellular products. In the case of examples 2, 5 and 6 ekstragiruyut so-called quarter monoliths width 75 x 75 mm and a length of 500 mm; in Priestley tests, on the one hand, on the pilot plant after drying the burning of coal and, on the other hand, in the industrial setting after drying the burning of coal. The composition of the flue gases in both units is within the specified in example 1 with the usual amount of variance with the difference that there is still about 12 rpm. CO2and the dust content is a value less than 50 mg/m3.

For pilot plant flue gases after dedusting appear isokinetic and using the electric heater is heated to the desired temperature. The catalysts are thermally insulated reactor, which generally has more than 12 sampling gas sampling and temperature measurement. According DESONOX-the way of the applicant, the flue gases are first freed from nitrogen SCR method (selective catalytic reduction). Right after catalyst for reduction of nitrogen oxides with NH3enter proposed in the invention, the oxidation catalysts. Received on the proposed in the invention method, the catalysts with the length of 1000 mm, respectively, 500 mm, with lengths of the lateral edges 150 x 150 mm, respectively, 75 x 75 mm for detailed measurements of the degree PR is awayda each other 8 such elements. Division cell is 4.2 mm

In Fig. 3 and 4 show the evaluation results of measurements on samples from selected examples at 450aboutWith, respectively 425aboutWith, and in the sense of first order reactions selected application-1n (1-) 1/AV. The value of the ordinate of 2.3 corresponds to a conversion of 90%

Found the results show that the degree of conversion of SO2in SO3above 90% are achieved without any problems, no longer necessary in necessary in the case of a catalyst based on a noble metal fixation at a minimum temperature of 450aboutWith the kinetics of the oxidation of SO2obeys approximately the law of the first order.

Used in industrial setting pieces samples during the duration of functioning for more than 1000 h then extracted and placed in a pilot plant to determine activity. Not recorded any reduction activity.

P R I m e R s 7-10. In a kneading machine with a spatial blades are mixed and subjected to the procedure stirring for 5 h the following substances. The data are given in table. 2.

After mixing (kneading) the resulting paste is processed into mouldings in the form of bundles. H the/SUP>And the final relative humidity of 70%, the Temperature during annealing there is increased only up to 500aboutWith, and then is sintered in air for 48 h at this temperature.

In Fig. 5 shows the temperature-dependent characteristic of the activity of the thus obtained catalysts in the above mentioned example 1 test conditions.

P R I m e R 11-15. In a kneading machine with the cutting scissor blades are mixed and subjected to the process of mixing (kneading) for 5 h following substances. The data are given in table. 3.

Obtaining according to examples 11-14 is carried out as in example 1. The obtained catalysts confirm the boundary values of the declared concentration of the component areas AND1AND2A , b and C. it Turned out that all stages of the preparation of the claim, the invention related to method, as the process of mixing, extrusion, drying, calcining, and sintering can be carried out without any problems in this framework. In any case are mechanically stable molded product with the measured catalytic activity.

Example 11 shows that the catalyst with the same composition has particularly high activity is at a low temperates.

The applicant shall submit as an application table with the atomic ratios for examples 1-15. Atomic ratios were calculated from the examples of quantitative data and listed below are the molar weights of the used compounds.

Al2O3120 g/mol

Cs2SO4362 g/mol

K2SO4174 g/mol

NH4VO3117 g/mol

SiO260 g/mol

TiO280 g/mol

V2O5182 g/mol

When calculating atomic ratios in accordance with the requirements of paragraph 1 of the claims must be considered that the molecules of Al2O3Cs2SO4and K2SO4contain respectively 2 metal atom, and molecule NH4VO3, SiO2and TiO2have respectively only 1 atom of metal.

Table. 4 and 5 make it easy to control the calculated atomic ratio. As can be seen from the tables, the sample 14 with the atomic ratio of Si:Ti= 0,85: 1,0 is beyond the scope of the claims sought in paragraph 1 of the claims.

Addition to the examples.

The magnitude of the atomic ratios for examples.

For each item:

1st line number in grams

2-I strenia sulfur dioxide, contained in the oxygen-containing gas flow is performed in a solid or cellular form and comprising components (a1) a vanadium oxide and a2) sulfate of an alkali metal as catalytically active substances and (B) the oxides of silicon and/or aluminum as increasing the surface of the component, characterized in that the catalyst contains advanced) titanium oxide in anatase and/or rutile form as the material of the carrier and a ceramic binder, and components And are contained in amounts corresponding atomic ratios of the metal components AND1AND2B 0,01 0,2 0,2 0,001 0,01 0,5 1 preferably 0,02 0,08 0,02 0,08 0,005 0,05 1, and they are in homogeneous distributed sintered form.

2. A method of producing a catalyst for the oxidation of sulfur dioxide contained in the oxygen-containing gas stream, made in monolithic or honeycomb form, by mixing a mixture that contains A1) vanadium oxide, AND2) sulfate of an alkali metal and (B) the oxides of silicon and/or aluminum in homogeneous distributed form, as well as humidifier and binder for semi-finished raw product, then pressed or ekstragiruyut mixed mass to the semi-finished product, cotot In) titanium oxide in the form of anatase and/or rutile as a carrier and a ceramic binder, and also, in addition to the usual molding or extrusion of ceramic masses humidifier and a binder for inconclusive raw products, yet reinforcing material, auxiliary for forming tools and, if necessary, poroshkoobraznoe, and the components of the mixture taken in such quantities that in the finished catalyst the atomic ratio of the metal component AND1AND2B 0,01 0,2 0,2 0,001 0,01 - 0,5 1, preferably 0,02 0,08 0,02 0,08 0,05 0,05 1, obtained by intensive mixing homogeneous mass to the desired crude product is dried at a slow temperature increase up to a maximum of 60oWith a controlled humidity of the surrounding air and then calcined at stepwise increasing temperature in ambient air at least at 500oWith maximum at 800oC, and the temperature in this area is sintered for at least 12 hours, preferably 14 to 48 h, in particular 18 to 36 hours

3. The method of oxidation of sulfur dioxide contained in the oxygen-containing gas flow on a monolithic or a finished catalyst containing components (a1) vanadium oxide, AND2) sulfate of an alkali metal as a catalytically active substance and (B) a silicon oxide and/or aluminum in chelno containing) the titanium oxide in the form of anatase and/or rutile as a carrier and a ceramic binder, moreover, the components in the catalyst contained in amounts corresponding atomic ratios AND1AND2B 0,01 0,2 0,2 0,001 0,01 0,5 1, preferably 0,02 0,08 0,02 0,08 0,005 0,05 1, and are in homogeneous distributed match the form, and the oxidation of sulfur dioxide is carried out at a load on the catalyst surface 16 of 52 m/h and 350 450oC.

 

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