RU2781054C1 - Method for continuous pyrolysis of small-sized organic materials and apparatus for implementation thereof - Google Patents

Abstract

FIELD: heating.

SUBSTANCE: invention relates primarily to forestry and can be used in the process of recycling small-sized lumber and woodworking waste for producing charcoal. Invention relates to a method for continuous pyrolysis of small-sized organic materials, including forming a layer of material of a constant density, forming self-destructing plugs of the material at the input and output of the pyrolysis zone, drying, subjecting the material to pyrolysis, removing the resulting pyrolysis gas from the pyrolysis zone, and unloading the carbon product. The organic material from the supply hopper is supplied to the drying zone, wherein said material moves along a screw spiral conveyor; the organic material is dried by means of the uniform distribution of heat flows emitted from the fire box and the pyrolysis reactor; the evaporated free moisture is discharged into the atmosphere, and if the material enters the zone of oppositely directed coils of the screw spiral conveyor, a high density zone is formed continuously — a self-destructing preventing the entry of air into the reactor and the uncontrolled entry of pyrolysis gases into the drying zone, destroyed by the passage of the diffuser. The bound moisture in the reactor in the process of pyrolysis is transformed into water vapour, displaces the pyrolysis gases from the reaction zone, and participates in the reduction reaction with carbon, resulting in combustible gases. The process of pyrolysis of the material passes without access of oxygen, the thermal energy required for the process is formed while burning the resulting pyrolysis and combustible gases in the combustion zone, and the incandescent carbon product is moved by a screw spiral conveyor to the output of the reactor. If the material enters the zone of oppositely directed coils of the screw spiral conveyor, a high density zone is formed continuously — a self-destructing preventing the entry of air into the reactor and the uncontrolled entry of pyrolysis gases into the cooling zone. The plug is destroyed by passing the diffuser, and the carbon-containing material enters the cooling module, wherein the drying, pyrolysis, combustion, and cooling zones are located in a closed heat-insulated volume, and the material is constantly intensively mixed at all stages. The invention also relates to an apparatus for the implementation of the method.

EFFECT: reduced costs of producing a carbon-containing product by fully utilising the thermal energy continuously generated in the process of pyrolysis, without using additional heat sources, and organising the production process so as to prevent the coking of pyrolysis gases and the formation of production waste.

2 cl, 2 dwg

Description

The invention relates primarily to the timber industry and can be used in the process of recycling small-sized sawmill and woodworking waste for the production of charcoal.

In recent years, there has been a steady trend towards greening the requirements of buyers for the quality of products, services, and the environment. The concept of "environmental competitiveness" is becoming increasingly relevant, more and more attention is being paid to the development, implementation and dissemination of green technologies that positively affect the environment [Smirnova G.A. Green technologies - the direction of innovation in the light industry / G.A. Smirnova, M.N. Titova // Innovations. - 2010. - No. 1 (135). - S. 58-63.]. The above forces manufacturers in many industries to design new types of materials, products, technologies for their production, mainly from natural types of raw materials or with their predominance in the total composition, excluding, if possible, a large number of chemical, strong thermal effects and not causing damage in the process of their consumption and recycling. Of particular relevance is the introduction of environmentally friendly, low-cost technologies and mobile equipment for the disposal of industrial waste in order to obtain additional types of commercial products in places of their mass accumulation using a minimum amount of additional resources. Such technologies include technologies for processing waste from logging and woodworking, vegetable waste from agriculture, etc. with the production of charcoal and other carbon materials, as well as thermal energy. Such technologies currently used for the most part are characterized by high resource intensity, high production costs, and low mobility. Their high resource intensity is largely due to the need to dry the processed raw materials to a moisture content of 5-15%, to attract additional energy sources: electricity, combustible gases, liquid fuels, etc. As a result of the implementation of technological processes, by-products are formed, for example, pyrolysis gases, liquid, which require the involvement of additional funds to bring them into a marketable form or disposal. In addition, structurally, such technologies are implemented, as a rule, in stationary conditions with the need to erect buildings, structures and organize a communications system.

A known method for the production of charcoal [US Pat. No. 2463331. Russian Federation. Method for the production of charcoal / Timerbaev N.F. and etc.; patent holder LLC "NTC AE". Published 10.10.2012. - Access mode: http://www1.fips.ru]. Before drying, the wood is conductively heated at a wall temperature of 95-105°C due to the condensation of water vapor coming from the cooling zone, and dried by convection with flue gases at a temperature of 240-250°C with wood heating up to 180°C. A part of wet flue gases with a temperature of 150°C from the drying zone is emitted through the absorber into the atmosphere, the other part is mixed with flue gases with a temperature of 600°C from the pyrolysis zone and sent to the drying zone. The dried wood is pyrolyzed due to the conductive heat supply from the flue gases coming from the furnace with a temperature of 600-700°C in the countercurrent mode. The pyrogases formed in the pyrolysis zone are ejected by the pyrogases condensed in the condenser, the uncondensed pyrogases are removed to the furnace, where air is supplied, and the pyrogas coolant in the furnace is converted into steam. The coal residue with a temperature of 500°C is conductively cooled to 120°C with water condensate coming from the heating zone, then it is additionally conductively cooled in countercurrent mode to 50°C with a recirculating absorbent. The method allows to increase the efficiency of the pyrolysis process. The disadvantages of the method include a complex circuit of the circulation of pyrogases, their condensation, filtration, as well as the inability to constructively implement this method in a mobile version.

A known method of dry distillation of wood, implemented in a continuous installation for the pyrolysis of carbonaceous materials [US Pat. No. 2408654. Russian Federation. Installation of continuous action for the pyrolysis of carbon-containing materials / Skurydin Yu.G.; Patent holder Yuriy Gennadievich Skurydin. Published 01/10/2011. - Access mode: http://www1.fips.ru]. In the installation, by means of a screw feeder-compacter, a continuous supply of crushed carbon-containing wastes is realized inside the retort while achieving its tightness, where, continuously, with the gradual movement of the material by the screw to the unloading unit, drying and pyrolysis of the overcooked material are carried out and the resulting gaseous products are removed through the gas exhaust system. Between the retort and the discharge zone, a plug is formed from the resulting carbon material to ensure the tightness of the retort and the thermal stability of the process. EFFECT: invention makes it possible to continuously, without stopping the operation of the plant and the charcoalization process, to load raw materials into the pyrolysis zone, as well as to unload finished coal. The retort is heated externally by an electric heater located along the entire length of the retort tube. The constant use of an electric heater for the implementation of the pyrolysis process is a significant disadvantage, since it increases the cost of the coal produced and reduces the mobility of the installation, which requires a stable source of electric current. Also, the disadvantages include a complex system for removing pyrolysis gases outside the premises, which increases the material consumption and cost of the installation, as well as the formation of an additional product (liquid) that requires further processing. This method is inherently closest to the claimed, therefore, taken as a prototype.

The technical objective of the invention is the development of a method for continuous pyrolysis of small-sized organic materials, ensuring the efficient use of processed raw materials, reducing the energy intensity and cost of the finished product, improving its quality.

The technical result of the invention is to reduce the cost of obtaining a carbon-containing product through the full use of thermal energy, continuously generated in the pyrolysis process, without the use of additional heat sources, as well as the organization of the technological process, which excludes the coking of pyrolysis gases and the formation of production waste.

In FIG. 1 shows a diagram of the technological process that implements the method of continuous pyrolysis of small-sized organic materials.

The method is implemented as follows.

At the inlet to the installation, a zone of constant density of the loaded raw material is formed, which ensures its uniform flow into the drying zone. The drying zone is a closed cylindrical volume with a screw spiral conveyor located inside it, which provides constant intensive mixing of the raw material, its drying and advancement to the entrance to the pyrolysis zone. In this case, a uniform heating of the raw material layer occurs, and in the upper part of the drying zone, a free space is formed for collecting and moving evaporated moisture. The movement of material in this zone is organized in such a way that a self-destructing plug is constantly formed at the entrance to the pyrolysis zone, which ensures tightness and the absence of air from the drying zone into the pyrolysis zone and pyrolysis gases from the pyrolysis zone into the drying zone. The free (unbound) moisture evaporated from the raw materials is completely removed from the drying zone by means of a fan installed in its upper part. In the pyrolysis zone, constant mixing and movement of the processed material is carried out by a screw spiral conveyor. Helical belt or helical paddle conveyor can be used. This ensures uniform entry of material particles into the area of the thermochemical process and its stable flow, including due to the gas-permeable form of the conveyor. Dry distillation of wood (in the absence of air in the process zone) ensures efficient decomposition of organic substances and the production of highly purified carbon material and pyrolysis gases. The processed material in the pyrolysis zone is intensively mixed, ensuring the free exit of pyrolysis gases and their entry into the upper part of the zone, from where they are discharged into the combustion zone through a gas duct heated to 800°C. By means of a screw spiral conveyor, the material moves from the entrance to the pyrolysis zone to the exit from it, gradually and completely decomposing and transforming into a carbon product (charcoal). In the course of movement, the density of the material and the volume occupied by it gradually decrease, freeing up space for the circulation of pyrolysis gases and water vapor (evaporated bound moisture, internal moisture of the material). Since the density of pyrolysis gases and water vapor is significantly different in magnitude, their separation occurs in the free space of the pyrolysis zone. Water vapor moves towards the hot carbon material, where, with constant stirring by a screw spiral conveyor, they enter into a reduction reaction with the formation of combustible gases, which, like pyrolysis gases, are discharged into the combustion zone through a gas duct heated to 800 ° C. The rate of exit of carbon material from the pyrolysis zone and the rate of its entry into the cooling zone are correlated in such a way that a self-destructive carbon plug is also constantly formed at their boundary, preventing air from entering the pyrolysis zone and uncontrolled release of pyrolysis gases from it. Next, the carbon product enters the cooling zone, where its temperature is gradually reduced, for example, by means of an air, water or air-to-water cooling system.

To start a stable pyrolysis process, a single heating of the material by an external heat source, such as a burner, is required. Further, the process is supported by the heat generated during the combustion of pyrolysis gases. The concentration of the gas-air mixture is selected in such a way that its complete combustion occurs and the content of harmful substances in the flue gases emitted into the atmosphere does not exceed the permissible values regulated by the current regulatory documents. If necessary, it is possible to supply part of the flue gases to the drying zone to intensify the drying process of the incoming raw materials. All zones of the technological process implementation are located in a closed heat-insulated volume in such a way that convective heat exchange occurs within this volume - the main amount of heat is uniformly transferred from the combustion zone to the pyrolysis zone, providing the temperature of the environment in the pyrolysis zone of 500-750 ° C, structurally the raw material drying zone is located above the pyrolysis zone, the thermal energy from which provides the temperature of the environment in the drying zone of 200-300°C and uniform heating of the material layer. The concentration of the gas-air mixture is chosen so that the temperature in its combustion zone is 900-1000°C. At the exit from the pyrolysis zone, the carbon material has a temperature of 200-210°C, which decreases in the cooling zone to 40°C. The resulting carbon product is then sent for stabilization and is ready for further use as intended.

The principal feature of the claimed method is the possibility of processing raw materials with a moisture content of up to 85%. Small-sized organic materials are mainly sawmill and woodworking wastes up to 70 mm in size, including sawdust and dust.

Removal of part of the moisture from the material before it enters the pyrolysis zone, constant intensive mixing of the material in the direction of travel, the implementation of the thermochemical process without air access ensure the thermal stability of the latter, the full use of raw materials without the formation of waste, obtaining a homogeneous high-quality carbon product. The use of an external heat source only to start the process reduces the resource intensity of the proposed method and reduces the cost of the resulting finished product.

A significant advantage of the claimed method is obtaining additional thermal energy for the pyrolysis process due to reduction reactions during the passage of water vapor over a hot carbon product, as a result of which part of the water vapor is converted into combustible gases. The output of pyrolysis gases through a gas duct heated to 800°C eliminates the possibility of their aggregate state, coking and ensures their complete combustion in the combustion zone of the gas-air mixture without the formation of any by-products (waste).

This method can be used in the processing of sawmill and woodworking wastes (wood chips, sawdust, pieces of wood, etc.), agricultural production wastes (bast fires, reeds, straw, flooring, waste obtained from seed cleaning, shells and other parts of plants, waste animal husbandry and other solid-phase organic materials).

Known installation of continuous action for the pyrolysis of carbonaceous materials [US Pat. No. 2408654. Russian Federation. Installation of continuous action for the pyrolysis of carbon-containing materials / Skurydin Yu.G.; Patent holder Yuriy Gennadievich Skurydin. Published 01/10/2011. - Access mode: http://www1.fips.ru]. It consists of a storage hopper connected to a screw feeder, which forms a sealed plug at the border of the feeder - retort and continuously feeds the processed material into the retort, while the retort is made in the form of a steel pipe with a longitudinal screw for smooth movement of particles of the processed material through the zones pre-drying and pyrolysis, located in the retort from the place of loading the material into the retort to the unloading zone, and between the retort and the unloading zone, a variable-section coupling is installed for the subsequent formation of a plug from the resulting carbon material to ensure the tightness of the retort and thermal stability of the process, the unloading zone includes a drain-accumulator and a receiving hopper of coal, hermetically connected to the outlet by means of a connector, the retort is heated by an electric heater located outside the retort tube along its entire length, and a gas exhaust and gas condensation system is also connected to the retort. The main disadvantages of this technical solution are significant power consumption, low mobility of the installation, and a complex system for the disposal of pyrogases. The specified device is essentially the closest to the claimed, therefore, taken as a prototype.

The technical objective of the invention is the development of a device for the continuous pyrolysis of small-sized organic materials, mainly of plant origin.

The technical result of the invention is to reduce the energy intensity of the device through the use of heat generated by thermochemical processes implemented in the device, the rational placement of individual nodes inside the structure, and the simplification of the device design as a whole.

In FIG. 2 shows a schematic diagram of the claimed device.

A metal plate is installed in the lower part of the hopper, coinciding with its longitudinal axis of symmetry, to divide the flow of raw materials in half. The drying module consists of two horizontally located steel pipes, inside of which it is installed along a helical spiral conveyor equipped with a geared motor. The transition zone from the drying module to the reactor is designed in the form of a diffuser. In this case, the pair of the last turns of the spiral screw conveyor is directed opposite to the main turns, the connection line of the opposite turns coincides with the vertical axis of the diffuser. In the upper part of each pipe, a fan is installed, connected to it by a branch.

The reactor is made in the form of two pipes made of stainless heat-resistant steel, inside each of which there is a helical spiral conveyor equipped with a gear motor. The reactors are located at an angle to the horizon in the direction of material movement. In the upper part of each reactor, a system for removing pyrolysis gases from the core is organized through a system of gas ducts. A diffuser is also located at the outlet of the reactor - the transition zone of the reactor-cooling module. In this case, the pair of the last turns of the helical spiral conveyor of the reactor is directed opposite to the main turns, the connection line of the opposite turns coincides with the vertical axis of the diffuser.

A combustion chamber is located around the reactors, its longitudinal axis is located exactly in the middle between the reactor tubes. A burner is built into the lower part of the combustion chamber. A vertical flue emerges from the end of the combustion chamber, which, at the level of the drying module, passes into a horizontal position, strictly in the middle between the module pipes. The combustion chamber is equipped with a system of air ducts and fans, which provides the supply of pyrolysis gases from the reactor and fresh air for their mixing to obtain a gas-air mixture of a rationally selected concentration.

The cooling module is located in the lowest part of the installation (below the combustion chamber) and consists of at least two steel pipes, inside of which there is a helical spiral conveyor equipped with a geared motor. The module has at least two fans that create air flows to each of the pipes to ensure efficient cooling of the carbon product leaving the reactor. At the outlet of each pipe, holes are arranged for the withdrawal of the cooled carbon product from the installation, for example, into a storage bin.

All of the above elements of the installation, from the drying module to the cooling module, are located in a closed heat-insulated housing, so that the heat flows generated in the furnace, rising up, wash the reactor and the drying module in turn, ensuring that the temperature of the environment required for each zone is maintained.

The division of the material flow is at least halved by design. This makes it possible to rationally select the standard sizes of structural elements, use their internal volume and all the generated thermal energy most fully and efficiently, and ensure the high-quality flow of all stages of the process of continuous pyrolysis of high-humidity organic materials.

All screw spiral conveyors are made with a rigid spiral, which significantly increases their service life to failure and ensures the efficient movement of all fractions of the processed raw materials and the gas permeability of the material flow. Screw conveyors, screw blade conveyors and other conveying mechanisms with a gas permeable design can be used to move material flows in the plant.

The device functions as follows.

With the help of an external burner, part of the processed material in the combustion chamber is heated and the combustion process is started, providing heating of the furnace, individual components and the installation as a whole.

The processed raw material is loaded into the feed hopper, leaving which it is divided into two identical streams and enters the drying module. The pipes are washed by heat flows emanating from the combustion chamber and the reactor. If necessary, a horizontal air duct can be used, located between the pipes of the drying module, into which flue gases from the combustion chamber are supplied. Rotating screw spiral conveyors provide constant mixing and uniform heating of the raw material inside the pipes, as well as its advancement to the reactor inlet. Under the action of temperature, water vapor (free moisture) exits the raw material flow, rising into the upper zone of the pipes, and is removed from it through the fan outlet to the atmosphere. When the material enters the zone of oppositely directed turns of the screw spiral conveyor, a zone of increased density is continuously formed - a self-destructing plug, which prevents air from entering the reactor and uncontrolled entry of pyrolysis gases into the drying zone. When passing through the diffuser, the plug is destroyed, and the material enters the beginning of the reactor. The material is constantly mixed by a screw spiral conveyor and gradually enters the zone of the thermochemical process. As a result of exposure to high temperatures and the occurrence of chemical reactions, a partial decomposition of the material occurs, a decrease in the thickness of the material layer, pyrolysis gases and water vapor exit from it into the upper part of the reactor, which continue to participate in chemical reactions. The free space inside the reactor increases due to the reduction of the material layer, here the substances in the gaseous state are separated by density, their circulation rate changes. The lightest pyrolysis gases move to the upper zone of the pipe and are removed from the reactor through the gas duct system in order to then enter the furnace. The location of the reactor at an angle to the horizon guarantees the direction of water vapor to the core of the reactor (to the zone of hot carbon product) and its participation in the reduction reaction with the formation of combustible gases, which also, rising upwards, are removed from the reactor through the gas duct system. The heated carbon product is moved by a screw spiral conveyor to the exit from the reactor. When material enters the zone of oppositely directed turns of the conveyor, a zone of increased density is continuously formed - a self-destructing plug, which prevents air from entering the reactor and uncontrolled entry of pyrolysis gases into the cooling module. As it passes through the diffuser, the plug is destroyed and the carbonaceous material enters the beginning of the cooling module. Moving by helical spiral conveyors in the pipes of the cooling module, the carbon product gradually and evenly cools down and is discharged into the accumulator located under the outlet. The resulting carbon product is then sent for stabilization and is ready for further use as intended.

After the pyrolysis process has been established, and the flow of pyrolysis gases into the furnace has become constant, the process is continuously maintained by the combustion of the gas-air mixture - a mixture of fresh air and combustible gases coming from the reactor. The concentration of the gas-air mixture is such that its complete combustion occurs and the concentration of harmful substances in the flue gases emitted into the atmosphere does not exceed the permissible values regulated by the current regulatory documents. If necessary, it is possible to supply part of the flue gases to the drying zone to intensify the drying process of the incoming raw materials.

All elements of the device are placed inside a single metal case, which can be fixed on a transport platform, chassis and other structures with propellers, and can be moved to the places of storage of raw materials. The external burner is used only to start the combustion process in the combustion chamber, and then the unit operates offline due to the pyrolysis gases generated in the reactor. The constructive solution of the installation allows its operation in open space (no buildings, structures, communications are required) in almost any climatic conditions. Also, a significant advantage of the claimed invention is the possibility of complete processing of organic raw materials of almost any humidity without the formation of any production waste, for example, liquid. The combustible gases formed in the process of pyrolysis are fully used to organize the continuous operation of the installation.

In order to increase the economic efficiency of the claimed technical solution, it is possible to utilize excess heat by installing an additional element on the chimney.

Claims (2)

1. The method of continuous pyrolysis of small-sized organic materials, containing the formation of a layer of material of constant density, the formation of self-destructive material plugs at the inlet and outlet of the pyrolysis zone, drying, pyrolysis of the material, removal of the resulting pyrogases from the pyrolysis zone, unloading the carbon product, characterized in that the organic material from of the feed hopper enters the drying zone, where it moves along a helical spiral conveyor, the drying of organic material occurs due to the uniform distribution of heat flows emanating from the combustion chamber and the pyrolysis reactor, the evaporated free moisture is removed into the atmosphere, when the material enters the zone of oppositely directed turns of the helical helical of the conveyor, a zone of increased density is continuously formed - a self-destructing plug, which excludes the ingress of air into the reactor and the uncontrolled ingress of pyrolysis gases into the drying zone, which is destroyed when passing through the diffuser, in the reactor during during pyrolysis, the bound moisture passes into water vapor, displaces pyrolysis gases from the reaction zone and participates in a reduction reaction with carbon and the production of combustible gases, the pyrolysis process of the material proceeds without access to oxygen, the formation of the thermal energy necessary for the process occurs when the resulting pyrolysis and combustible gases are burned in the zone combustion, the hot carbon product is moved by a screw spiral conveyor to the exit from the reactor, when the material enters the zone of oppositely directed turns of the conveyor, a zone of increased density is continuously formed - a self-destructive plug that prevents air from entering the reactor and uncontrolled ingress of pyrolysis gases into the cooling zone, when passing through the diffuser plug is destroyed, and the carbon-containing material enters the cooling module, while the zones of drying, pyrolysis, combustion and cooling are located in a closed heat-insulated volume, at all stages the material is constantly intensively mixed tsya. 2. A device for implementing the method according to claim 1, containing a supply hopper connected to a drying module, which is two horizontally located steel pipes, inside of which it is installed along a screw spiral conveyor, while the last pair of turns of the helical screw conveyor is directed opposite to the main turns to form zones of increased density, the pyrolysis reactor is made in the form of two pipes of stainless heat-resistant steel, inside each of which is located along a helical spiral conveyor, while the pair of the last turns of the helical spiral conveyor of the pyrolysis reactor is directed opposite to the main turns to form a zone of increased density, the reactor is located at an angle to the horizon in the direction of material movement, a combustion chamber is located around the reactor tubes, in the lower part of which a burner is built in, a gas duct exits from the end of the combustion chamber, the cooling module consists of at least two steel pipes, inside which x is located along the helical spiral conveyor, the transition zones from the drying module to the pyrolysis reactor and from the pyrolysis reactor to the cooling module are structurally designed in the form of diffusers, all helical spiral conveyors are made with a rigid spiral; drying module, pyrolysis reactor, combustion chamber and cooling module are located in a single heat-insulated mobile housing.

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