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INVENTION
Patent of the Russian Federation RU2206835

AIR HEATER AND METHOD OF ITS WORK

The name of the inventor: Kirillov VA; Kuzin NA; Kulikov A.V .; Lukyanov BN; Zakharchenko VB; Yermakov Y.P .; Nikiforov VN; Kozodoev L.V.
The name of the patent holder: G.K. Boreskov SB RAS; Open Joint Stock Company "Zapsibgazprom"
Address for correspondence: 630090, Novosibirsk, Acad. Lavrentyeva, 5, Institute of Catalysis named after. G.K. Boreskov, Patent Department, Т.D. Yudina
Date of commencement of the patent: 2001.09.27

The invention relates to thermal power engineering - to the technique of generating thermal energy on the principle of flameless catalytic oxidation of natural gas and can be used for autonomous heating of residential and industrial premises, but also for drying various materials, fertilizing carbon dioxide of plants and creating a protective atmosphere for vegetable stores. The invention solves the problem of creating an efficient air heater with a power of up to 25 kW, in the waste gases of which the carbon monoxide content is not more than 1 ppm, methane is not more than 30 ppm, there are no nitrogen oxides. The problem is solved by the design of an air heater in which a catalytic generator of synthesis gas serves as a burner, which is a radial type reactor containing a gas distribution tube with a catalytic layer made in the form of gas permeable flat and corrugated reinforced belts wound and sintered with a gas distribution tube, with gaps between Turns with the formation of gas-air channels between the belts. The catalyst is a reinforced porous material containing the active components: rhodium, nickel, platinum, palladium, iron, cobalt, rhenium, ruthenium or a mixture thereof. The way the air heater works is to burn natural gas in two stages.

DESCRIPTION OF THE INVENTION

The invention relates to heat power engineering - to the technique of generation of thermal energy on the principle of flameless catalytic oxidation of natural gas. The invention can be used for autonomous heating of residential and industrial premises: garages, greenhouses, storages, farms, country houses, and for drying various materials, fertilizing carbon dioxide with plants and creating a protective atmosphere for vegetable stores.

It is known that for local heating of premises gas air heaters of radiation or convective action are used [MBRavich. "Gas and the effectiveness of its use in the national economy." Publishing house "Nedra", 1987, p.238]. Amra gas-fired heater with flue gas discharge to the chimney is equipped with an infrared burner with a ceramic nozzle and operates on liquefied gas [NL Staskevich, GN Severinets, D.Ya.Vigdorchik. Handbook on gas supply and use of gas. L .: Nedra, 1990, p.762]. The AOG-5 gas heater, like the Amra unit, is a fireplace equipped with an injection torch with a flame nozzle and a flue gas outlet from the heated space. Heating rooms with air heated by mixing with combustion products from flame burners is undesirable due to high concentrations of carbon monoxide and nitrogen oxides. Air heaters direct mixing air with combustion products are used for heating greenhouses or as a drying apparatus. Unlike flaring in chimneys where a significant part of the useful heat leaves with the exhaust gases, which leads to thermal losses and a decrease in efficiency, catalytic combustion systems have an efficiency of about 100%.

Known are devices using catalytic tent heaters [United States Patent 4,588,373, F 23 D 014/12, 1986], car parlors and aircraft cabins [British Patent 2,173,123, F 23 D 14/18, 1986]. The main advantage of such heaters is a low concentration of nitrogen oxides and carbon monoxide in the combustion products. Gas catalytic heaters of the diffusion type "Termokat-1", "Termokat-2", "Termokat-3", working on premixed gas-air mixtures [ZR Ismagilov, MA Kerzhentsev. Catalysts and processes of catalytic combustion. Khim.prom., 1996, 3, p. 197]. The Termokat-1 and Termocat-2 devices operate on liquefied gas, a propane-butane mixture, and the Termokat-3 apparatus uses natural gas. In these stoves, full-oxidation catalysts of the IR-12-30 type are used.

Known air heater gas mixing catalytic (VGSK) [ZR Ismagilov, MA Kerzhentsev. Catalysts and processes of catalytic combustion. Khim.prom., 1996, 3, p. 197]. The well-known HSCS is a two-stage combustion plant for natural gas. At the first stage, flaring of natural gas is carried out. The flue gases, diluted with additional air supply, are then fed into the second chamber, where a catalytic cassette is assembled from the catalytic units. The cassette is a circle with a diameter of 500 mm and a height of 50-150 mm, assembled from a catalyst in the form of hexagonal blocks of honeycomb structure. The temperature of the flue gases in front of the catalytic cassette 427-827 ^° C is sufficient for complete oxidation of the products of incomplete combustion of fuel and carbon monoxide, as well as the reduction of nitrogen oxides in excess of carbon monoxide. The flue gases, which are additionally diluted with air, are supplied from the HVLC to heat the room.

In this air heater, the combustion of natural gas in the first stage in the flare burner results in the formation of thermal nitrogen oxides that can not be completely suppressed in the second catalytic stage. The presence of unreacted methane in the combustion products after the first stage leads to the formation of a "hot spot" in the frontal part of the catalytic cassette, which is the reason for its thermal destruction. Therefore, the catalytic unit must have a number of unique properties: minimum wall thickness and minimum hydraulic resistance, and on the other hand, to be as stable as possible to large temperature differences during long-term operation. The material for making blocks with such properties is expensive zirconium ceramics, silicon carbide, cordierite, mullite, special alloys and ferritic steels. The use of platinum group metals as an active component deposited on honeycomb structures or spiral blocks leads to a further increase in the cost of catalytic devices.

The closest to the claimed device and method is a gas heater [Patent RF 215050, F 24 H 3/00, 27.01.2000]. The known air heater comprises a gas burner in the form of a burner unit with a three-stage combustion of gas; a heat exchanger is attached to the combustion chamber of the burner unit in the form of a curved tube, on the outer side of which mesh intensifiers are mounted, a catalytic nozzle is mounted on the end of the heat exchanger, and a mixing chamber is mounted on the end of the stove Purified combustion products and heated air from the fan-supercharger.

A disadvantage of the known solution is the use of a traditional atmospheric burner with a ventilating charge as a combustion device, having CO ~ 10-35 ppm emissions, NO _x ~ 60-320 ppm [TBJannemann. The Development of Atmospheric Burners with Respect to the Increasing Emissions Restictions. In: Proceedings of the First European Conference on Small Burner Technology and Heating Equipment. Zurich, September 25-26, 1996, v.1, p. 23-34]. The catalytic nozzle used in the known air heater does not solve the problem of elimination of nitrogen oxides in combustion gases and, therefore, their considerable dilution with additional air is required before entering the room.

The invention solves the problem of creating an efficient air heater with a power of up to 25 kW, in the waste gases of which the carbon monoxide content is not more than 1 ppm, methane is not more than 30 ppm, there are no nitrogen oxides.

The problem is solved by the design of an air heater containing a frame to which an air and fuel mixer is mounted, a combustion device, a mixer of flue gases and additional air, a heat exchanger, a gas-air mixture outlet unit, as a combustion device, it contains a catalytic synthesis gas generator located behind an air mixer and Fuel, and said heat exchanger, made catalytic. The synthesis gas generator is a radial type reactor comprising a gas distribution tube with a catalytic bed made in the form of gas permeable flat and corrugated reinforced belts wound and sintered with a gas distribution tube with gaps between the turns to form gas-air channels between the tapes having a heating device for starting Reactor in a work comprising a gas distribution tube with a diameter of perforation holes smaller than the critical diameter to prevent the flame from penetrating into the gas distribution tube placed in the water-cooled enclosure.

The catalyst is a reinforced porous material containing the active components: rhodium, nickel, platinum, palladium, iron, cobalt, rhenium, ruthenium or a mixture thereof. The catalytic heat exchanger is a set of catalytic fuel rods having an outer catalytic layer in the form of tube-sintered flat and corrugated ribbons or a finned monolithic layer or a set of flat catalyst panels having a catalytic layer on the outside in the form of sintered flat and corrugated ribbons forming channels along the axis of the panel Or at an angle to its axis.

The method of operating the air heater is to oxidize natural gas in two stages, wherein in the first stage, the catalytic oxidation of natural gas occurs in the synthesis gas generator with a lack of oxygen in the synthesis gas, and in the second stage in the catalytic heat exchanger, Oxidation of synthesis gas to produce carbon dioxide and water.

In Fig. 1 shows the process flow diagram of an air heater. In it, after mixing of natural gas and air in the mixer 1 and supply of the mixture to the synthesis gas generator 2 after the catalytic layer has been preheated by the device 3, a catalytic partial oxidation of the natural gas is carried out to form a synthesis gas and products of complete oxidation of methane according to the reaction equation

CH ₄ + 0.66 (O ₂ + 3.76 N ₂ ) -> 0.89 CO + 1.79H ₂ + 0.11 CO ₂ + 0.21 H ₂ O + 2.48 N ₂

Then, after the addition of secondary air, from the calculation of the ratio CH ₄ / O ₂ = 1: 2.1 to the mixer 4, the synthesis gas is oxidized on the catalytic tubes (cassette) 5 to the final products of combustion according to the reaction equation

0.89 CO + 1.79H ₂ + 0.11C0 ₂ + 0.21H ₂ O + 2.48 N ₂ +1.54 (O ₂ + 3.76 N ₂ ) = CO ₂ + 2H ₂ O + 0.20 O ₂ + 8.27 N ₂

The air heater consists of a mixer 1, a synthesis gas generator 2, placed in the housing 6. The housing is provided with a gas outlet slot 7 above which is located the air distribution pipe 4. A catalytic heat exchanger 5 is attached to the synthesis gas generator by means of a flange 8 In the casing 9, consisting of a set of plates 10 with the catalytic layer 11; In the upper part of the casing there is a tube 12 for air supply.

The operating principle of the heater is as follows. When the heater is started, the heating system 3 (FIG. 1) of the synthesis gas generator 2 is turned on. After the thermocouple has been established that the temperature of the catalytic bed of the synthesis gas generator has reached 600 ^° C, the heating is switched off and the gas is supplied, and air ( Air I) through the mixer 1; Then this mixture is fed through the gas distribution tube into the synthesis gas generator 2 and oxidized in the catalytic bed that is located outside the tube. The surface temperature of the catalyst is heated to an operating temperature of 750-850 ^° C, which corresponds to the nominal operating mode of the synthesis gas generator.

The mixture of gases from the synthesis gas generator is mixed with additional air (air II) in the mixer 4 and sent to the catalytic heat exchanger 5. The gas mixture is oxidized on the catalytic tubes, while the temperature of the mixture at the outlet rises to 500-550 ^° C. Adding in the case The need for air (air III) in the mixture of gases at the outlet of the catalytic heat exchanger, obtain the desired temperature of the gas-air mixture.

The heater is switched off by shutting off the gas valve, which blocks the gas supply to the mixer 1. The air supply for cooling the device continues to work for several minutes, which protects the catalyst from destruction. Then the air is turned off.

Thus, heat generation is carried out in an air heater with the help of two main apparatuses: a synthesis gas generator 2 and a catalytic heat exchanger 5, allowing the oxidation of natural gas in two stages. With this method of burning natural gas, almost no nitrogen oxides are formed, and carbon monoxide is completely converted to carbon dioxide.

The catalytic partial oxidation of natural gas in the synthesis gas generator is carried out with a lack of oxygen and is carried out mainly at atmospheric pressure and at a temperature of no higher than 1000 ^° C., the catalysts are Group VIII metals such as Ni, Rh, Ru, Pt, Ir and Pd Or a mixture thereof [M.A. Turnip, JP Gomes, JLG Fierro. New catalytic routes for syngas and hydrogen production (review), Appl. Catal. A 144 (1996), p. 7-57].

The proposed synthesis gas generator is a cylindrical structure with flanges 18, inside which there is a gas distribution device, which is a perforated pipe 13 with apertures 17 and heating 6, damped on one side, into which the gas-air mixture is supplied (FIG. The catalyst layer 14 is formed from flat 15 and corrugated 16 mesh-reinforced gas-permeable belts wound on the gas distribution tube and sintered therefrom. The ribbons are arranged in such a way that their odd rows are corrugated, and the even ones consist of flat non-corrugated ribbons, but the turns of the subsequent cover the turns of the previous one. The tapes form catalytically active channels, on the walls of which the gas-air mixture is oxidized with the formation of carbon monoxide and water, which through the channels between the tapes are removed into the body of the gas generator. Nitrogen oxides are not formed due to low (~ 900 ^o C) temperature and lack of oxygen. Selecting the thickness of the catalytic bed achieves complete conversion of methane.

The working principle of the synthesis gas generator is as follows. For start-up, the reactor is heated up and, when the temperature inside the apparatus rises to 600 ^° C, the heating is switched off. A pre-prepared gas-air mixture with an airflow coefficient of 0.47 relative to the stoichiometric required for complete combustion of gas is fed into the gas distribution tube 13 and then into the catalyst bed. Due to the partial oxidation reaction, the temperature rises to ~ 900 ^° C, and closer to the outer surface of the layer is reduced to 750-850 ^° C. By selecting the number of perforation holes and their diameter, the condition is achieved when the air-gas mixture is distributed uniformly along the length of the tube, Catalyst bed. For safety reasons, the diameter of the holes is chosen to be less critical to prevent the penetration of a possible flame inside the gas distribution tube.

The catalytic heat exchanger 5 can be implemented in the form of a set of catalytic fuel rods (KTT) 19 (FIG. 4) or flat catalyst panels (FIG. 2) located in a metal casing above the synthesis gas generator.

The principle of operation of the tubular catalytic heat exchanger is as follows. Synthesis gas from the synthesis gas generator is sent from below into the catalytic cassette and mixed with additional air (air II) fed through the air distribution pipe 4 (FIG. 4). The air distribution pipe has a perforation along the entire length. For better mixing, the flow of air from it occurs towards the flow of synthesis gas. The gas-air mixture is directed by baffles 20 to catalytic fuel rods 19 made of metal tubes 21 with catalyst layer 11 sintered on their outer side 11. To increase the outer surface of the catalyst layer, the fuel pipes have fins. The exhaust gases are discharged from the top of the apparatus. The fuel rods 19, the partition walls 20 and the air distribution pipe are housed in a casing 9 which is connected to the synthesis gas generator via a flange 8.

The catalytic layer on the outside of the fuel-generating tube can be made using flat and corrugated ribbons that are laminated and sintered together with the metal tube to form a bidisperse porous structure that provides a high degree of utilization of the catalytic bed. The thickness of the winding is determined by the required degree of conversion of the hydrocarbon-containing gas. The catalytic layer can be made in the form of a monolith, but to increase the external surface, fins are necessary.

Similarly, a catalytic bed 11 is formed on flat catalyst panels that fills the entire space between the plates 10 and the casing 9 (FIG. 2).

Catalysts for the oxidation of synthesis gas in a catalytic cassette are reinforced porous material containing rhodium, nickel, platinum, palladium, iron, cobalt, rhenium, ruthenium or mixtures thereof as active components.

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

Example 1. A natural gas of the composition (vol%) is supplied to the air heater: methane - 97.46, ethane - 1.11, propane - 0.37, isobutane - 0.06, butane - 0.06, pentane - 0.02 . Nominal flow rate (nm ³ / h): gas - 0.54; Air - 14.76; Gas-air mixture - 15.3. The pressure of the gas-air mixture at the inlet to the air heater is 350 Pa.

As a result of the operation of the air heater,

- rated heat output, kW - 5.6

- nominal air capacity, nm / h - 14.0

- temperature, ^o С:

- synthesis gas at the generator output - 750-850

- gas-air mixture at the entrance to the

Catalytic cassette - 290

- gas-air mixture at the outlet from

Catalytic cassette - 500-550

- coefficient of efficiency - 99,0

- content in waste gases, ppm:

- carbon monoxide - traces

- methane - 13

- nitrogen oxides - traces

Example 2. A natural gas of the same composition as in Example 1 is supplied to the air heater. Nominal flow rate (nm ³ / h): gas - 1.08; Air - 29.7; Gas-air mixture - 30.78. The pressure of the gas-air mixture at the inlet to the boiler is 700 Pa.

As a result of the operation of the air heater,

- rated heating capacity, kW - 11,3

- nominal air capacity, nm ³ / h - 28,3

- temperature, ^o С:

- synthesis gas at the generator output - 750-850

- gas-air mixture at the entrance to the

Catalytic cassette - 290

- gas-air mixture at the outlet from

Catalytic cassette - 500-550

- coefficient of efficiency - 99,0

- content in waste gases, ppm:

- carbon monoxide - traces

- methane - 13

- nitrogen oxides - traces

EXAMPLE 3 A natural gas of the same composition as in Example 1 is fed to the air heater. Nominal flow rate (nm ³ / h): gas - 1.26; Air - 34.78; Gas-air mixture is 36.04. The pressure of the gas-air mixture at the entrance to the boiler is 1000 Pa.

As a result of the operation of the air heater,

- rated heat output, kW - 13,2

- nominal air capacity, nm ³ / h - 33.2

- temperature, ^o С:

- synthesis gas at the generator output - 750-850

- gas-air mixture at the entrance to the

Catalytic cassette - 290

- gas-air mixture at the outlet from

- catalytic cassette - 500-550

- coefficient of efficiency - 99,0

- content in waste gases, ppm:

- carbon monoxide - traces

- methane - 13

- nitrogen oxides - traces

As can be seen from the examples, the proposed invention makes it possible to create an air heater with a power of 3-25 kW, which uses for the production of heat the principle of two-stage catalytic oxidation of natural gas, as well as other hydrocarbon gases. An air heater operating on the above principle ensures an environmentally friendly oxidation of hydrocarbon gases so that the CO content in the waste gases corresponds to a concentration of no more than 1 ppm, methane - no more than 20 ppm in the absence of nitrogen oxides.

CLAIM

1. An air heater comprising a frame to which an air and fuel mixer is mounted, a combustion device, a gas and auxiliary air mixer, a catalytic cassette, an air-gas mixture discharge unit, characterized in that, as a combustion apparatus, it comprises a catalytic synthesis gas generator Mixer of air and fuel and is a radial type reactor containing a gas distribution pipe with a catalytic layer made in the form of gas permeable flat and corrugated reinforced strips wound and sintered with a gas distribution tube with gaps between the turns to form gas-air channels between the tapes having a heating device for Starting the reactor in operation, containing a gas distribution tube with a diameter of perforation holes smaller than the critical diameter, in order to prevent the flame from penetrating into the gas distribution tube, placed in a metal casing.

2. An air heater according to claim 1, characterized in that the catalyst is a reinforced porous material containing rhodium, nickel, platinum, palladium, iron, cobalt, rhenium, ruthenium or a mixture thereof as active components.

3. The heater according to claim 1, characterized in that the catalytic cassette is a set of catalytic fuel rods having outside the catalytic layer in the form of flat-sintered and corrugated ribbons sintered with a tube or a finned monolithic layer.

4. An air heater according to claim 1 or 3, characterized in that the catalyst is a reinforced porous material containing rhodium, nickel, platinum, palladium, iron, cobalt, rhenium, ruthenium or a mixture thereof as active components.

5. The heater according to claim 1, characterized in that the catalytic cassette is a set of flat catalyst panels having, from the outside, a catalyst layer in the form of sintered flat and corrugated ribbons forming channels along the axis of the panel or at an angle to its axis.

6. An air heater according to claim 1 or 5, characterized in that the catalyst is a reinforced porous material containing rhodium, nickel, platinum, palladium, iron, cobalt, rhenium, ruthenium or a mixture thereof as active components.

7. A method of operating an air heater, comprising the oxidation of natural gas in two stages, one of which is catalytic, characterized in that the oxidation of natural gas is carried out in the first stage in a synthesis gas generator, where a catalytic oxidation of natural gas occurs with a lack of oxygen in the synthesis- Gas, and in the second stage in the catalytic cassette, after addition of an additional amount of air oxygen, complete oxidation of the synthesis gas to produce carbon dioxide and water is carried out.

print version
Date of publication 25.01.2007gg

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