RU2360196C2 - Device for pulsed heat treatment of bulk materials - Google Patents

Abstract

FIELD: motors and pumps.

SUBSTANCE: device for pulsed heat treatment of bulk materials consists of a cylindrical operating chamber of thermal activation with cover and beveled bottom. The operating wall of the housing is heated to 700-800°C to contact and activate thermally the particles of bulk material under action of centrifugal forces. The device also includes bulk material supply unit, steam and gas mixture discharge unit, hardening refrigerator adjoining the beveled bottom of operating chamber from outside, finished product unit to collect it under the refrigerator. The device also includes fluid-bed furnace where thermal activation chamber, hardening refrigerator with product accumulation chamber and gate valve are installed. The bulk material is supplied as gas suspension. The bulk material supply unit is represented as a nozzle with adjustable cap, which is cut into the internal wall of fluid-bed furnace.

EFFECT: device allows for producing thermally activated products with preset structure and properties.

5 cl, 2 dwg

Description

The invention relates to devices for pulsed heat treatment of bulk materials (thermal activation of particles) and can be used at the stage of their thermochemical activation in the production of catalysts, carriers, adsorbents, desiccants, fillers, ceramics, magnetic materials, inorganic pigments, solid electrolytes, pharmaceutical and cosmetic preparations etc., as well as for carrying out drying / cooling processes of bulk materials in the chemical, food, woodworking industries, etc.

Pulse heat treatment of bulk material in the device is carried out at a speed of more than 100 ° C per second when moving along a heated surface, while surface moisture evaporates from the particles and structural moisture is removed. As a result of such rapid heating, decomposition products with valuable chemical properties are formed. In order to fix the amorphous state, quenching-cooling of the products of thermal activation at the exit of particles from the hot zone is carried out. Heating due to heat transfer upon contact of the particles of the bulk material with a hot metal surface is more efficient than heating them upon contact with each other or during convective heat transfer when moving in a stream of hot gas. For example, in the production of oxide supports and catalysts, crystalline oxygen-containing compounds must be heated to a temperature of 300 ° C or more. In this case, the thermolysis of the starting compounds is carried out under conditions far from thermodynamic equilibrium, which allows us to form qualitatively new metastable structures of an amorphous solid phase from crystalline substances, characterized by stored energy and increased reactivity, which are widely used in the production of chemical products.

There are a number of analogues of the described method with devices for its implementation, the most effective of which is, for example, a device for the thermal activation of particles of the starting material, in which particles are heated by heat transfer during contact with a hot surface to temperatures of 400-600 ° C for 5-30 s ( SU 528733, C01F 7/44, 1973).

A similar technical solution is a device (US Pat. RF 2186616, B01J 8/10, 08/10/2002) for the treatment of particles of bulk materials by thermal activation, comprising: a container for the source material, heaters and a contact surface rotation drive, a dosed feed of particles of bulk material, its movement along heated surface and descent of the finished product into the drive.

As a prototype adopted the device for processing bulk materials in the mode of thermal activation of particles described in US Pat. RF 2264589, F26B 7/00, 11/12, 04/01/2004.

The invention of the prototype solves the following tasks:

supply and regulation of the flow of bulk material into the zone of thermal activation; ordered distribution of material, with its tight contact, over a heated surface; an increase in the rate of heating of bulk material and evaporation from surface particles and the removal of structural moisture from them by thermal activation; quick hardening - cooling the heat treatment product to fix its metastable structure; the ability to change and improve the performance of the device with a decrease in specific energy consumption.

These tasks of the prototype are solved on a device that includes:

- a cylindrical body with a conical bottom and a flat cover on which are installed: a vertical electric drive with a rotating shaft and a cylindrical drum fixed to it; storage hopper for bulk material, equipped with a worm dispenser and agitator of the loaded material, driven into rotation by electric drives; a branch pipe for exhaust (suction) of steam released during thermal activation of particles;

- electric heating elements - (heating elements) located in the housing and placed outside and inside the rotating drum;

- a distribution plate in the form of a conical ring, rigidly attached in the area of the hole with ribs to the drive shaft sleeve;

- a cylindrical drum placed with a gap of 2-5 mm on the outside of the plate and rigidly fastened with it with pins;

- a protective screen installed with a gap on the internal cavity of the refrigerator;

- removable storage tank for the finished product.

In the prototype of the device, the nodes for loading, controlling the flow of bulk material, its quick quenching, cooling and collecting the finished product in the drive are solved by any known methods. The device operates in continuous or variable mode as follows. From the hopper, the loaded dry or wet (in the form of granules) granular material with a slowly rotating agitator is fed by a dispenser through the estrus to the surface of a rotating conical plate, through which the material, under the action of centrifugal force, slides to the periphery of the plate and is discarded through the gap of 2-5 mm onto the inner surface heated by the heating elements of the rotating drum. In this case, the granules are destroyed and the particles of the material, under the action of centrifugal force and gravity, slide along the inner surface of the drum down a helical line, while the force of pressing the particles to the drum (their contact time) is controlled by changing the number of revolutions of the drum. Upon contact with a heated drum, evaporation of particles of surface moisture occurs and removal of structural moisture from them under the action of short-term thermal activation of the particles. For example, short-term heating of 100 microns of particles to 350 ° C, sliding on a drum heated to 700 ° C, is enough within 1 s. And the smaller the particle size of the bulk material (<100 μm), the faster the process of their heating. From the drum, the heat-treated product falls on the refrigerator for quenching-cooling, which then goes into the storage tank.

It is known that upon contact of wet particle granules with a surface heated to temperatures of the order of 600-700 ° C, they instantly heat up and the granules break in pairs of surface moisture evaporating from the particles, because the bond strength (autogesia) between the particles in the granules by means of surface moisture and some of their compaction when supplied to the device by extrusion is fragile. It is known that in industrial apparatuses, when bulk material moves along a heated surface (in contact heat exchangers with moving layers of a coolant, etc.), the minimum time of heat exchange processes is much shorter than the contact times in these apparatuses. So, for example, for river sand with a particle diameter of 100 μm moving along a heated surface, the minimum time for their heating is about 0.07 s, with a diameter of 2 mm - about 2.8 s. Values of the same order are obtained for other bulk materials. And since most of the powder materials processed according to the prototype and in the device of the invention are the same and have particles of 5-150 microns in size, the time of evaporation of surface moisture from them will be almost instantaneous. If it is commensurate with the thermal activation time, then they can be folded and the process adjusted by the number of surface revolutions. As shown by experiments at the Institute of Catalysis, for the destruction of granules with a diameter of 2-3 mm into individual particles, the duration of the process of evaporation of moisture from them during thermal activation was about 1 s.

The main disadvantages of the prototype device identified during the operation of the experimental-industrial apparatus at the Institute of Catalysis of the SB RAS include the following:

1. It was found that when particles slip along the heated inner wall of the drum, the process of their heating and the intensity of evaporation of surface and structural moisture occurs unevenly, since it is not possible to distribute particles in one layer on the surface of revolution, since they are distributed over the wall in several layers. In the most favorable conditions for the contact of particles with the wall, their first layer is located, and in the rest, unequal conditions are created for heat transfer and evaporation of moisture. As a result, this leads to difficulties in the thermal regulation of the process of thermal activation of all particles, the temperature of the mixture of which when they leave the drum varies in the range of 350-420 ° C. This drawback significantly complicates the thermal activation of heterogeneous batches of bulk materials having different initial surface and structural moisture content.

2. When the diameter of the drum according to the prototype is 0.7 m, its working length is 0.43 m and the TENs are densely arranged outside and inside the drum, their total power is 50 kW, and the drum is heated to 600-700 ° C mainly by convection, thermal density flow (the ratio of the amount of heat to the duration of its transfer through a surface unit, W / m ² ) which is not enough for wall heating to thermally activate a multilayer particle stream in a short contact time.

3. Due to such difficulties identified in the prototype, it is often not possible to obtain the structure of the finished product with the desired properties, which does not make the installation universal for heat treatment of a wide class of bulk materials.

The invention solves the problem of developing such a design, which is almost universal and allows to obtain a product of a given quality.

Technical result - the proposed device allows to obtain thermal activation products with a given structure and properties.

The proposed device is a cyclone thermal activator eliminates the main disadvantage of the prototype due to the smooth regulation of the process of heat treatment of particles, which will make the installation more universal for heat treatment of a wide class of bulk materials.

The essence of the design of the proposed device is a more efficient supply of heat (heat flux density) to the heating surface, which in the process of thermal activation of the particles will provide a sufficient and almost constant in time temperature of the heated surface, which will allow to obtain thermal activation products with a given structure and properties.

The implementation of the thermal shock treatment method in a cyclone thermal activator is carried out with a gas suspension of bulk material that is prepared, for example, in front of the thermal activator by metering the material into a gas supply pipeline (air, water vapor, etc.). When particles are thermally activated in the device, external and structural moisture is removed, which in the form of water vapor, mixed with a gas stream heated in front of the device, forms an overheated vapor-gas mixture, which is removed from the working chamber (if necessary) for dust removal with further heat recovery, which it is advisable to use for heating (through a heat exchanger) the gas entering the device. To process a number of bulk materials, it is possible to create a circulation or flow-circulation circuit to return to the device a heated vapor-gas mixture.

The problem is solved by the design of the device for pulsed heat treatment of bulk materials, including a cylindrical working chamber of thermal activation with a lid and a conical bottom, heated to 700-800 ° C of the working wall of the chamber for contact and thermal activation of particles of bulk material under the action of centrifugal forces; node input source material, node removal of superheated water vapor; adjacent to the outside of the conical bottom of the working chamber of the quenching refrigerator; assembly of the finished product under the refrigerator, it also includes a fluidized bed furnace, inside which there is a thermal activation chamber; quenching cooler with product storage chamber and shut-off valve. Moreover, the device does not contain moving units and parts.

The unit for introducing bulk material in the form of a gas suspension is a pipe with an adjustable damper that is tangentially cut into the inside wall of the fluidized bed furnace.

The cover has a conical shape and is equipped with a discharge pipe and a lens compensator.

The nozzle of the gas suspension input unit is square or preferably rectangular.

The thermal activation working chamber contains a cylindrical shell with a truncated cone, forming an annular channel with the chamber wall, while the shell diameter is equal to the diameter of the working chamber wall minus two widths of the gas suspension inlet pipe, while the length of the cylindrical shell is 0.4-0.5 the length of the working chamber wall , the height of the cone welded from below is 0.3-0.35 of the length of the wall, and the area of its neck is 1.1-1.3 of the inlet area of the gas suspension.

Device - cyclone thermal activator consists of:

- a cylindrical working chamber for the thermal activation of gas suspension particles, which is fed with a predetermined speed through the tube tangentially onto the inner surface of the working chamber wall, as a result of which the particles are pressed centrifugally against the heated wall and, under the action of the swirling flow, move down the helix along the wall. In this case, the contact time of particles with the heating surface depends on the properties of each class of bulk materials — their particle size and concentration in the gas stream, its temperature, viscosity, etc. Therefore, the contact time of the particles is controlled by the rate of flow twist by setting the velocity of the gas suspension at the inlet, for which the gas suspension inlet is equipped with a flow rate control unit. A cylindrical shell with a truncated cone from below is built inside the working chamber, which forms an annular channel with the wall of the working chamber to maintain stability of the gas suspension twist speed, while the channel width is equal to the width of the inlet pipe. The length of the cylindrical shell is 0.4-0.5 of the length of the wall of the working chamber, and the height of the cone is 0.3-0.4 of its length and the neck area is 1.1-1.3 of the inlet area of the gas suspension. Since the principle of operation of the thermal activator does not differ from the work of cyclones in collecting particulate matter from gas, depending on the maximum productivity, the diameter of the cylindrical working chamber of the device is chosen according to the calculation method of cyclones developed by NIIOGAZ, which is available in many textbooks and reference books in the form of calculation formulas and efficiency nomograms (A.G. Kasatkin. The main processes and apparatuses of chemical technology, M., AllianS, 2004; Yu.V. Krasovitsky and others. Dust removal of industrial gases in faience production, M., Chemistry, 1994).

- located on the bottom of the working chamber of the conical refrigerator of the prototype design, on the surface of which the particles of the product of thermal activation descend (by inertia) from the working cylindrical chamber for quick quenching-cooling to a given temperature. The dimensions of the refrigerator are calculated according to the method of calculating heat exchangers according to the given performance of the thermal activator;

- a storage chamber at the bottom of the refrigerator with a shut-off valve (of any known design), the volume of which is selected according to the performance of the thermal activator, where the finished product is accumulated and cooled until the time specified by the project, from where it is periodically unloaded into the container for collecting the finished product;

- a collection unit for the finished product, the volume of which exceeds the volume accumulated in the storage chamber of the product and can be of any design;

- a fluidized bed furnace located outside the working chamber in the heating zone, the wall of which is heated by contacting the fluidized particles of an inert material (or catalyst) from the outside. Due to the high heat transfer coefficient, the high-temperature fluidized bed transfers a constant (set by the oven temperature) amount of heat to the particles of the processed material through the chamber wall, which makes the process of their thermal activation easily controlled. The temperature of the fluidized bed in the chamber is maintained by known methods — by blowing the flue gases obtained by burning outside a layer of gas or liquid fuel, or by burning fuel in a layer. According to the furnace parameters set by the project — device productivity, furnace heat intensity per unit volume, fuel burning location, choice of working material (inert or catalyst) for a fluidized bed furnace, etc., the furnace, its components and parts are calculated according to well-known formulas and nomograms published in many sources - see, for example, A.G. Kasatkin. The main processes and apparatuses of chemical technology, M., AllianS, 2004; S.S. Zabrodsky. High-temperature installations with a fluidized bed, M., Energy, 1971.

The invention is illustrated in figure 1 and figure 2.

The proposed method of processing bulk materials by thermal activation of particles is implemented in a device - a cyclone thermal activator, shown in Figure 1 in two versions: to the right of the vertical axis - not working, and to the left - the thermal activator in operation (the movement of bulk material is shown by dots). The arrows indicate the direction of flow, where: SM - bulk material; GV - gas suspension of bulk material; PT - product of thermal activation; GP - finished product; ASG - gas-vapor mixture; KS - fluidized bed; TG - flue gases; Exhaust gas - exhaust gases; ХВ - cold water. Figure 2 shows in section a node for controlling the tangential velocity of entry of a gas suspension into the device.

Figure 1 also shows the components of the device: a working chamber for thermal activation of a cyclone type I, a quenching water cooler II, a storage chamber for the finished product of thermal activation III, a removable collection tank for product IV and a fluidized bed furnace V.

The working chamber I includes:

- a cylindrical shell 1, which is also the inner wall of the KS furnace, the sizes of which are selected, depending on the performance of the thermal activator, according to the tangential velocity of the inlet of hot water according to the method developed by NIIOGAZ for the selection of industrial cyclones for cleaning gases from solid particles. A conical cover 2 is welded from above to the cylindrical shell 1;

- a nozzle 3 for inputting the starting material — GW, which is inserted tangentially into the inner wall of the KS furnace pos. 1 under the lid 2, and in which a rotary damper 26 with a fixed manual or drive shaft 27 (of any known design) is installed (adjustable GW flow rate). The dimensions of the tangential branch pipe 3 are also selected by the method of NIIOGAZ, in the form of a round, square or preferably rectangular section, the larger side of which is located vertically;

- the outlet pipe ASG pos.4 with a lens compensator 5;

- built-in cylindrical shell 9, the diameter of which is selected based on the equality of the width of the annular channel between the parts 1 and 9 (see Figure 2), equal to the width of the pipe 3. The length of the cylindrical shell 9 is 0.4-0.5 length wall 1, and the height of the cone 10 welded from below is 0.3-0.35 of the length of wall 1, with the neck area of the cone equal to 1.1-1.3 of the inlet pipe 3;

- a conical bottom 6, which is the inner wall of the refrigerator II, with a pipe 7, in which a shut-off rotary valve 8 (manual or actuating - of any known design) is built-in.

The quenching water cooler II is adjacent to the bottom of the chamber I and includes a cylindrical body 11, equal to the diameter of the shell 1, with a conical bottom 6. A flat bottom 12 is welded at the bottom of the refrigerator, and refrigerant inlet and outlet pipes 13 are welded into the shell 11. In FIG. 1, the refrigerator It is shown as single-section, and for smooth regulation of the hardening process of a number of thermal activation products, it can be two or more sectional, with blind partitions between sections. The dimensions of the conical bottom 6 are selected on the surface of the cone, which is calculated according to the method of calculating heat exchangers for a given performance of the thermal activator;

- the storage chamber of the finished product of thermal activation, located at the bottom of the refrigerator, where the finished product is accumulated and cooled, from where it is periodically unloaded. The camera includes a storage pipe 7, of any known design, a shut-off valve 8 and a fastening assembly 28 of the container for collecting the finished product. The sizes of all parts are selected according to the performance of the thermal activator.

The fluidized bed furnace V with an expansion chamber on top includes:

- a cylindrical body 14 with a bottom 15, a truncated cone 16, a cylindrical shell 17, a flat welded (or removable, on the flanges) cover 18 with a pipe 19 of exhaust gases from the furnace. To load the material into the furnace, a muffled hatch 22 is welded on the lid 18, and a muffled pipe 23 is welded to unload the material;

- adjacent to the refrigerator II sublattice chamber with a nozzle 21, for the distribution of TG, with a lattice 20 of any design (wireless, cap, etc.).

The dimensions of the listed furnace parts are selected according to well-known calculations of fluidized bed furnaces, depending on its thermal load. Outside, the hot sections and parts of the furnace are covered with thermal insulation 24. The device is mounted on a support 25 (of any design).

The site for controlling the velocity of the entrance of the gas suspension into the working chamber is shown in Figure 2, which consists of: a nozzle 3 integrated in its horizontal sides of the movable flap 26, fixed to a manual rotating axis 27, having a lock fastener (of any design) with a latch for a predetermined position of the flap 26.

The device operates as follows.

Initially, furnace V is filled with an inert material (or catalyst) through the loading hatch 22. Then, the quench cooler II is filled with refrigerant (water), the removable product collection tank IV is installed and secured from below, and the rotary valve 8 is closed 8. According to the selected HS flow rate (see above) , by turning the axis 27 establish the estimated clearance between the valve 26 and the wall of the pipe 3.

Start start with heating the oven. The high (predetermined) temperature of the TG for the CS is realized by any known method. For example, by blowing from the bottom of the layer through the nozzle 21 TG obtained in a chamber located outside the device by burning gas or liquid fuel. In the case of using a catalyst in KS, it is also heated at start-up by known methods to the temperature at which the reaction began and then a cold combustible mixture is supplied. The calculated amount of bulk material is blown into the stream of hot gas supply to the thermal activator (by any known method) and the resulting HS through the tangential pipe 3 is fed into the thermal activator. Particles of material, under the action of centrifugal force, are pressed against the wall 1 heated from the CS and slide down a helical line. When particles of bulk material come in contact with a heated surface, rapid heat transfer to them is transmitted in the form of heat stroke with instant evaporation from particles of surface and internal moisture. The residence time of particles in contact with the surface 1 in the working chamber is set by the feed rate of the hot water. After the particles pass through the zone of the KS furnace (on wall 1), the product obtained after thermal activation enters the quenching cooler II for quenching-cooling, the temperature of which is controlled by the supply of HV by intensive heat removal from the material to obtain a given degree of cooling. Then the product enters the product accumulation zone III, from where it is periodically poured into the removable container of the finished product IV by turning the valve 8. Water vapors released during thermal activation from particles, together with heated gas and dust particles, are removed from the thermal activator in the form of an ASG through a nozzle 4, filtered off from dust outside it, and ASG heat is used, for example, to heat the gas components of the HV or TG flows. The high-temperature exhaust gas from the fluidized-bed furnace IV through the nozzle 19 is removed and also disposed of and cleaned by analogy with the ASG stream.

Claims (5)

1. A device for pulsed heat treatment of bulk materials, including a cylindrical working chamber of thermal activation with a lid and a conical bottom, heated to 700-800 ° C of the working wall of the chamber for contact and thermal activation of particles of bulk material under the action of centrifugal forces; a unit for introducing bulk material, a unit for removing the vapor-gas mixture; quenching refrigerator adjacent to the outside of the conical bottom of the working chamber; assembly of the finished product under the refrigerator, characterized in that it includes a fluidized bed furnace, inside which there is a thermal activation chamber; quenching cooler with product storage chamber with shut-off valve. 2. The device according to claim 1, characterized in that the node for introducing bulk material in the form of a gas suspension is a pipe with an adjustable damper that is tangentially cut into the inner wall of the fluidized bed furnace. 3. The device according to claim 1, characterized in that the cover has a conical shape and is equipped with an outlet pipe for the vapor-gas mixture and a lens compensator. 4. The device according to claim 2, characterized in that the pipe of the gas suspension input unit is square or, preferably, rectangular. 5. The device according to claim 1, characterized in that the working chamber of thermal activation contains a cylindrical shell with a truncated cone, forming an annular channel with the chamber wall, while the diameter of the shell is equal to the diameter of the wall of the working chamber minus two widths of the nozzle of the gas suspension input unit, while the length of the cylindrical the shell is 0.4-0.5 of the length of the wall of the working chamber, the height of the cone welded from below is 0.3-0.35 of the length of the wall, and the area of its neck is 1.1-1.3 of the area of the nozzle of the gas suspension input unit.

Images