RU2496579C1 - Method of preparing catalyst and method for catalytic fuel combustion in fluidised bed - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to catalysts. Described is a method of preparing a catalyst for fuel combustion in a fluidised bed based on open-hearth slag, wherein granules of the open-hearth slag are treated with water vapour at maximum hydrogen release temperature, followed by deposition of complete oxidation catalyst components on the surface of the slag, said components containing transition metal oxides or mixtures thereof. Described is a method for catalytic fuel combustion in a fluidised bed of dispersed particles of an inert material and a catalyst while maintaining temperature of 300-800°C in the presence of a catalyst preparing using said method.

EFFECT: high catalyst activity and strength.

2 cl, 7 ex

Description

The invention relates to a power system and can be used in the combustion of fuel for heating working fluids, where the combustion of various fuels takes place in a fluidized bed.

A known method of burning fuels for heating the working medium by supplying air with a = 1.0-1.1 through the gas distribution grid to the fluidized bed of a dispersed catalyst for the complete oxidation of organic substances with the simultaneous introduction of fuel into the latter (SU 826798, F23C 10/00, 05/30/1983). The temperature in the layer is maintained constant in the range of 300-800 ° C due to changes in the flow rate of the working medium.

The disadvantage of this method is the significant attrition of the catalyst when it is used in the fluidized bed. To reduce the catalyst consumption during its preparation, hardened alumina-based carriers with a complex multi-stage preparation technology are used, for example (RU 2080293, C01F 7/02, 05.27.1997), while the degree of abrasion and consumption of expensive and scarce catalysts remain high.

There is also known a method of burning fuels (RU 2057988, F23C 11/02, 04/10/96) by supplying air with a = 1.0-1.1 through a gas distribution grid to a fluidized bed of a dispersed catalyst for the complete oxidation of organic substances with the simultaneous introduction of fuel into the latter and maintaining a constant temperature in the range of 300-800 ° C due to changes in the flow rate of the working medium, characterized in that the fluidized bed additionally includes particles of an inert coolant in an amount of 75-80%. The disadvantages of this method are the relatively high consumption of inert coolant and catalyst due to their abrasion, as well as the need to use an expensive catalyst for the complete oxidation of substances.

The closest in technical essence to the method of catalytic combustion of fuel (SU 1666862, F23C 10/00, 07/30/1991) by feeding the latter and air into the fluidized bed of a solid intermediate coolant, consisting of a mixture of granules of equal catalyst size and open-hearth slag, while maintaining a temperature of 300 -800 ° C. The disadvantage of this method is the low catalytic activity of open-hearth slag and high wear of the catalyst, which in terms of abrasion resistance is inferior to open-hearth slag. Therefore, during operation, the catalyst is primarily abraded and the catalytic activity of the layer decreases rapidly.

There is also a method of preparing a catalyst based on open-hearth slag (SU 1756331, C10J 3/46, 08/23/1992) for oxidizing gasification of solid fuel by applying iron acetate in the amount of 0.5-8.0% based on metallic iron on the surface of the slag . According to the method, the open-hearth granules are mixed with a 2% solution of iron acetate, followed by evaporation from a mixture of water. The disadvantage of this method is the almost complete absence of the inner surface of the open-hearth slag, the specific surface of which does not exceed 0.1 m ² / g, all of the iron acetate is on the outer surface of the granules, and the resulting active component of the catalyst, when used in a fluidized bed, quickly peels off and is removed from the composition catalyst, which leads to a decrease in its activity.

The problem solved by the present invention is to develop a method for preparing a catalyst based on open-hearth slag, which is not inferior in its activity to known catalysts for the complete oxidation of substances while maintaining high abrasion resistance of open-hearth slag, and also to develop a method of burning fuels using a prepared catalyst.

The problem is solved by using a catalyst for the complete oxidation of substances based on open-hearth slag pre-treated with water vapor at a maximum hydrogen evolution, followed by applying to the slag surface components of the catalyst for the complete oxidation of substances containing transition metal oxides or mixtures thereof.

The problem is also solved by the method of catalytic combustion of fuel in a fluidized bed of dispersed particles of an inert material and a catalyst while maintaining a temperature of 300-800 ° C using an oxidation catalyst based on open-hearth slag treated with water vapor.

The invention is illustrated by the following examples:

Example 1

Granules of crushed open-hearth slag are treated at a temperature of 700 ° C with water vapor until the intense evolution of hydrogen ceases. Then the granules are cooled, impregnated with an aqueous solution of copper dichromate, dried and calcined at a temperature of 700 ° C.

Example 2 (prototype)

Granules of crushed open-hearth slag with a diameter of 1-2 mm are mixed with a 10% solution of copper dichromate. Then, with stirring, the solution is evaporated to completely remove water, and the granules are calcined at 700 ° C. The content of the active component on the surface of the granules in terms of copper chromite CuCr ₂ O ₄ 3%.

Example 3 (analog)

2.5 l of aluminum-magnesium-copper chromium catalyst IK-12-73 (TU 6-68-102-89) with a diameter of granules of 1-2 mm is loaded into a reactor with a diameter of 80 mm. Under the gas distribution grid serves air for fluidization and oxidation in an amount of 20 m ³ / h An external electric heater is used to heat the catalyst layer to 300-400 ° C. Then, with a screw batcher, brown coal of the Irsha-Borodinsky deposit is fed into the layer in an amount of 10 kg / h, and the electric heater is turned off. In the upper part of the layer is a coil-type heat exchanger cooled by cold water. The temperature in the layer is controlled by the amount of water supplied for cooling to the heat exchanger and maintained at 750 ° C. The fluidized bed is organized by wire gratings with a cell side of 10 mm and a distance between gratings of 10 mm (4 gratings) and gratings with a cell side of 25 mm and a distance between gratings of 25 mm (10 gratings). The temperature of the vapor-gas mixture and solid products at the outlet of the layer is maintained at 200 ° C by cooling on the surface of the heat exchanger in the upper part of the layer. At the outlet of the reactor, the resulting ash residues are separated from the flue gases in the cyclone. Flue gases are analyzed for toxic impurities. The activity of the catalyst was determined by the amount of methane CH ₄ and CO in the exhaust flue gases. The content of CH ₄ in the exhaust gas is less than 0.01%. The CO content in the exhaust gas is less than 0.03%. The degree of abrasion of the catalyst is 0.4% per day.

Example 4 (analog)

Similar to example 3. In the reactor load a mixture of aluminum-magnesium-copper chromium catalyst IR-12-73 (TU 6-68-102-89) with a diameter of granules of 1-2 mm and quartz sand with a diameter of granules of 1-2 mm in the ratio of 1 / 6 (catalyst content in the mixture 16.7%). The content of CO and CH ₄ in the exhaust gas is less than 0.01%. The degree of abrasion of the catalyst is 0.3% per day.

Example 5 (prototype)

Similar to examples 3-4. A mixture of aluminum-magnesium-copper chromium catalyst IK-12-73 (TU 6-68-102-89) with a diameter of granules of 1-2 mm and open-hearth slag with a diameter of granules of 1-2 mm in a ratio of 1/6 are loaded into the reactor. The content of CO and CH ₄ in the exhaust gas is less than 0.01%. The degree of abrasion of the catalyst is 0.5% per day.

Example 6

Similar to examples 3-5. A mixture of a catalyst with a diameter of 1-2 mm prepared according to claim 1 and quartz sand with a diameter of granules of 1-2 mm in a ratio of 1/6 are loaded into the reactor. The content of CO and CH ₄ in the exhaust gas is less than 0.01%. The degree of abrasion of the catalyst is 0.1% per day. After operation of the catalyst for 120 hours, the content of CO and CH ₄ in the exhaust gas is less than 0.01%

Example 7

Similar to examples 3-6. A mixture of a catalyst with a diameter of 1-2 mm prepared according to claim 2 and quartz sand with a diameter of granules of 1-2 mm in a ratio of 1/6 are loaded into the reactor. The content of CO and CH ₄ in the exhaust gas is less than 0.01%. After working for 20 hours, the CO content in the exhaust gas increases to 0.2%, and the CH ₄ content to 0.1%.

The above examples show that the oxidation catalyst prepared on the basis of open-hearth slag treated with water vapor is not inferior in activity to the known oxidation catalyst IK-12-73. Moreover, more than 3 times higher than the known catalyst in its abrasion resistance.

Claims (2)

1. A method of preparing a catalyst for burning fuel in a fluidized bed based on open-hearth slag, characterized in that the open-hearth granules are treated with water vapor at a maximum hydrogen evolution, followed by the application of complete oxidation catalyst components containing transition metal oxides or a mixture thereof to the slag surface. 2. The method of catalytic combustion of fuel in a fluidized bed of dispersed particles of an inert material and a catalyst while maintaining a temperature of 300-800 ° C, characterized in that when the catalytic combustion of fuels in a fluidized bed using a catalyst prepared according to claim 1.