RU2232347C2 - Solid fuel gasifier - Google Patents

Abstract

FIELD: processing of peat, poor-quality coal, wood-working waste, solid domestic garbage, etc. by interaction of fuel with gasifying agent and pyrolysis with production of fuel product-gas, this fuel gas-product may be used for heating of steam and hot-water boilers, in driers as fuel for gas turbines, it may be widely used in power generation/

SUBSTANCE: the solid fuel gasifier has a vertical shaft furnace with zones of drying, pyrolisis and combustion of solid fuel placed in succession, from top to bottom, in it. A charging device and a branch pipe for extraction of product-gas are located in the upper section of the furnace, a branch pipe for supply of the gasifying agent and a device for accumulation and removal of solid processing products - ash are located in the lower section. One or several sections are positioned between the upper and lower parts of the gasifier, they serve as components of the gasifier and have inner through cavities in the center located in the direction of the vertical axis of the gasifier and communicate with the inner cavities of the upper and lower parts, as well as with the inner cavities of the other components of the gasifier. The sections have a housing with a lining, fastened in it are the ends of the thermoaccumulating elements located in the inner cavity of the section. One or several furnace sections are made for rotation relative to the upper and lower parts of the gasifier about its vertical axis.

EFFECT: simplified structure, enhanced reliability and capacity.

7 cl, 4 dwg

Description

The solid fuel gasifier is designed for the processing of peat, low-grade coal, wood processing waste, municipal solid waste, etc. by reacting fuel with a gasifying agent and pyrolysis to produce a combustible product gas.

The gasifier is a vertical shaft furnace, inside of which are sequentially, from top to bottom, drying, pyrolysis and solid fuel combustion zones. In the upper part of the gasifier there is a loading device in the form of a lock chamber and a pipe for the selection of product gas. In the lower part there is a device for the accumulation and withdrawal of solid processed products (ash) and a pipe for supplying a gasifying agent. Currently, such a design is well known, for example, the Bioner gas generator of the Finnish company Perusyukhtyum (1). The product gas is formed in the gasifier as a result of the interaction of the fuel with a gasifying agent, as well as a result of thermal decomposition of the fuel (pyrolysis) and secondary chemical reactions. This combustible gas product can be used to heat steam and hot water boilers, in drying units as fuel for gas turbines, and can also be widely used in the energy sector. It should be noted that gasification of municipal solid waste (MSW) simultaneously solves another equally important problem for the environmentally friendly destruction of them, since two-stage burning (first gasification, and then burning the product gas in the boiler) is much cleaner than ordinary, and practically does not require additional purification of combustion products.

The gasification process itself is well known and has been used for decades. It is as follows. From below, a gasifying agent (moist air) is supplied to the gasifier. After passing through the ash, it heats up and enters the combustion zone. In the combustion zone, all the free oxygen of the gasification agent is consumed. Next, hot gaseous products of combustion enter the pyrolysis zone. In it, basically, the processes associated with the formation of combustible gas occur. In this zone, secondary chemical reactions and thermal decomposition (pyrolysis) of solid fuel occur with the formation of volatile combustible components (product gas) and a solid residue (coke). Next, the hot products of combustion and pyrolysis pass through fresh fuel, heat and dry it, while they cool down themselves. At the exit, the combustible product gas has a temperature of about 150 °. The resulting gas product has a low calorie content, but sufficient for use in heating boilers.

In a gasifier, solid waste with a moisture content of up to 60% can be burned. The process is super-adiabatic. Coke burns in the combustion zone of the gasifier with the release of heat, which is sufficient to maintain a continuous process. Otherwise, some high-calorie fuel (for example, coal, wood waste, etc.) is added to the MSW to support the process.

This process is described in more detail in the work of the Institute of Chemical Physics in Chernogolovka (see RF patent No. 2079051) and was implemented by him together with a Finnish company. A variant of the gasifier of the Institute of Chemical Physics in Chernogolovka should be considered as an analogue of the proposed gasifier. The analogue provides for mixing solid waste with pieces of refractory material before burning to improve heat transfer and gas permeability. However, this greatly complicates the equipment for loading the gasifier and unloading the ash, and does not exclude it, and therefore, complicates the process of mixing the solid waste inside the gasifier, which becomes an insurmountable obstacle at high temperatures.

The proposed version of the gasifier is structurally easier to manufacture and operate. Therefore, it is much cheaper, more reliable and more competitive than its counterpart. It uses thermal storage elements that provide a uniform distribution of temperature and gas permeability of the fuel over the horizontal sections of the furnace, which is the main condition for the quality of the gasification process. Uniform heating and uniform gas permeability of the fuel contribute to more intensive chemical reactions and the pyrolysis process, as well as the release of a higher percentage of combustible gases in the product gas.

Very often, solid fuel has a bulk density unevenly distributed over the volume, or it can sinter under the influence of temperature. For example, municipal solid waste (MSW). In places of fuel sintering or in places of increased density, gas permeability and heat transfer deteriorate, local temperature decreases and, as a result, the combustion process and pyrolysis slow down. A gasifying agent containing oxygen rushes in the area where there is good gas permeability, forming deep burns in fresh fuel while contributing to an increase in the size of existing ones and the formation of new cakes. The gasification process is finally violated when burnout exits to the upper fuel boundary.

To ensure uniform distribution of temperature and gas permeability of the fuel across the horizontal sections of the furnace, various devices and methods are used. For example, the method described in patent RU 2079051, in which the non-combustible part is increased in MSW by adding pieces of refractory material to them to improve heat transfer and gas permeability. However, this method does not exclude burnouts and cakes in fresh fuel.

As a prototype, consider the method described in US patent 4732091, when solid fuel passes through a sequence of chambers of a shaft furnace, separated by horizontal movable gratings, in which the fuel is pyrolyzed and burned in countercurrent gasification agent. The disadvantages of such a gasifier include the presence of movable gratings in it. In high temperature conditions with various types of fuel it is very difficult to ensure the long-term and reliable operation of these grids. Lattices should have a sufficiently high strength and resistance at high temperature in an aggressive environment.

For the normal course of the process, no cakes should form on the gratings. Otherwise, the gasification process will slow down, which leads to a decrease in productivity.

The proposed gasifier has a simpler and more reliable device to ensure uniform distribution of temperature and gas permeability across the horizontal sections of the furnace in comparison with the prototype and analogues and allows to obtain a higher productivity of the process.

It, like the prototype, is made in the form of a vertical shaft furnace, inside of which are sequentially, from top to bottom, drying, pyrolysis and combustion zones of solid fuel. In the upper part there is a loading device and a nozzle for product gas extraction, in the lower part there is a nozzle for supplying a gasifying agent and a device for accumulating and removing solid processing products - ash. Between the upper and lower parts of the gasifier there are one or several sections, which are components of the gasifier, having central through cavities in the center located in the direction of the vertical axis of the gasifier and communicating with the internal cavities of the upper and lower parts, as well as with the internal cavities of the other components of the gasifier.

In the proposed gasifier, the inner sections have a casing with a lining located in it, in which the ends of the thermal storage elements are fixed. The elements themselves are located in the internal cavities of the sections. They are evenly distributed over the volume of internal cavities and have a sufficiently large heat capacity. One or more sections of the furnace are made to rotate relative to the upper and lower parts of the gasifier around its vertical axis.

Thermal storage elements are rods made of ceramic, round or any other section, with a diameter of 100-200 mm. Ceramics has a sufficiently large heat capacity and strength at high temperature, as well as high resistance in aggressive and oxidizing environments.

The location of the thermal storage elements in the internal cavity of the section may be different. It is most expedient to arrange them diametrically in the inner cavity, one above the other, at an angle to each other or in the form of a volumetric lattice, where the elements of one row are at an angle to the elements of the other row. The ends of the ceramic rods must be fixed in the lining, taking into account thermal expansion, for example, using heat-resistant mineral wool.

The sections are made in the form of a metal casing with a lining located in it, in which the ends of the thermal storage elements are fixed. Sections are supported through thrust bearings on the same sections or on the lower part of the gasifier. On the outer surface of the casing of the section there is a device through which the force is transmitted to rotate the section from the drive, for example, in the form of a gear for a mechanical or hydraulic drive.

The direction of rotation of the sections can be arbitrary, in any direction. Advantageously, adjacent sections rotate in different directions. This will significantly improve the mixing of the fuel and create a more uniform distribution of temperature and gas permeability over the horizontal sections of the furnace. The rotation speed is selected based on the type of fuel burned.

The gaps between the components of the gasifier - between the sections and / or between the sections and the upper and / or lower parts of the gasifier - are sealed with labyrinth seals filled with liquid. They are made in the form of a cylindrical ring fixed on the upper, relative to the gap, part and located inside the annular cavity formed on the lower, relative to the same gap, component of the gasifier. A liquid is poured into the annular cavity, the level of which is higher than the lower end surface of the cylindrical ring. The liquid level should be sufficient to compensate for the slight excess pressure inside the gasifier and to prevent the outflow of hot gases. Used liquid can be used engine oil, and to compensate for more significant excess pressure inside the gasifier, a high-density filler, for example, metal powder, can be added to the oil.

In the gaps formed between the parts and sections of the gasifier, there is air. Air has a very low thermal conductivity. Therefore, it will serve as a good thermal insulation, provided that no hot gases flow through the gaps.

For ease of installation, maintenance and operation of the gasifier, a special design can be provided consisting of supports and service platforms, a fuel loading conveyor and an ash unloading conveyor. You can also fully automate this process, as the Finnish company did on the Bioner gasifier.

The essence of the invention is illustrated by the accompanying illustrative material. Figure 1 presents a General view of the gasifier; figure 2 is a section along BB; figure 3 is a section along aa; figure 4 - the gaps between the sections.

The gasifier is made in the form of a vertical shaft furnace, inside of which are sequentially, from top to bottom, drying, pyrolysis and combustion zones of solid fuel (see figure 1). In the upper part 1 there is a loading device 2 and a pipe 3 for sampling the product gas, in the lower part 4 - a pipe 5 for supplying a gasifying agent and a device 6 for the accumulation and withdrawal of solid processed products (ash). Between the upper and lower parts of the gasifier there are one or several sections 7, which are components of the furnace, having in the center internal through cavities 8 located in the direction of the vertical axis of the gasifier and communicating with the internal cavities of the upper and lower parts, as well as with the internal cavities of other components . The internal cavities of the sections have a lining 9, in which the ends of the thermally accumulating elements 10 are fixed. The elements 10 themselves are located in the internal cavities of the sections. They are evenly distributed over the volume of internal cavities and have a sufficiently large heat capacity.

Thermally storage elements 10 are expediently made of ceramic in the form of round rods with a diameter of 100-200 mm, since the ceramic has a sufficiently large heat capacity and strength at high temperature, as well as high resistance in aggressive and oxidizing environments.

The shape and location of the thermal storage elements in the internal cavity of the section may be different. It is most expedient to arrange them diametrically in the inner cavity, one above the other, at an angle to each other (see figure 2), or in the form of a volumetric lattice, where the elements of one row are at an angle to the elements of the other row (see figure 3) , depending on the type of fuel and the process. The ends of the ceramic elements must be fixed in the lining taking into account thermal expansion, for example, using heat-resistant mineral wool 11.

Section 7 is recommended to be performed in the form of a metal casing 12 with a lining 9 located in it, in which the ends of the thermal storage elements 10 are fixed. Sections 7 are supported through thrust bearings 13 on the same sections or on the lower part of the gasifier. A device 14 is located on the outer side surface of the section, which is part of a rotation drive, for example, in the form of a gear for a mechanical or hydraulic drive 15.

The rotation of the sections can be arbitrary, in any direction, but it is desirable that the neighboring sections rotate in different directions. This will significantly improve the mixing of the fuel and create a more uniform distribution of temperature and gas permeability over the horizontal sections of the furnace.

The gaps between the sections and parts of the gasifier are sealed with labyrinth seals filled with liquid. They are made in the form of a cylindrical ring 16 mounted on the upper part relative to the gap of the gasifier and located inside the annular cavity 17 (see Fig. 4) formed on the lower part of the gasifier relative to the same gap 18. A liquid is poured into the annular cavity, the level of which is higher than the lower end surface of the cylindrical ring 16. The liquid level must be sufficient to compensate for the slight excess pressure inside the gasifier and to prevent the outflow of hot gases. Used liquid can be used engine oil, and to compensate for more significant excess pressure inside the gasifier, a high-density filler, for example, metal powder, can be added to the oil.

In the gaps 18 formed between the parts and sections of the gasifier, there is air. Air has a very low thermal conductivity, so it will serve as a good thermal insulation, provided that no hot gases flow through the gaps.

For ease of installation, maintenance and operation of the gasifier, a special design can be provided, consisting of supports 19, service platforms 20, fuel loading conveyor 21 and ash unloading conveyor 22. You can also completely automate this process, as the Finnish company did on the Bioner gasifier .

The gasifier works as follows. Initially, the gasifier is loaded using a conveyor 21 and a loading device 2 with relatively light fuel, so as not to damage the thermal storage elements, for example, wood chips or peat. A gasifier with fuel is heated through special openings from below using hot air or gas burners until the fuel ignites and a gasifying agent containing oxygen is supplied through pipe 5. Subsequently, all the main parameters of the continuous gasification process are held at the required level by adjusting the flow rate of the gasification agent.

For quick heating of the lining and thermal storage elements to the required temperature, high-calorie fuel can be additionally loaded. After their heating, they switch to the existing type of fuel. In accordance with the prescribed technology, sections 7 are started to rotate using drive 15.

When using unsintered fuels such as woodworking wastes and the like, rotation of the sections is not necessary provided that uniform gas permeability is ensured when loading. But if the fuel is sintered or uniform gas permeability is not ensured during loading, it is necessary to impart rotation to sections with thermal storage elements. Specks and fuel seals formed above or at the section level, in contact with hot thermo-accumulating elements, are heated intensively and are destroyed during rotation. At the same time, gas permeability and heat transfer in the cakes and seals are improved and, as a result, the pyrolysis process is accelerated, burnouts are eliminated, and the performance of the gasifier increases.

The rotation of the sections with thermal storage elements improves heat transfer between the particles of fuel. This happens as follows. At the first moment, the thermal storage element is located in a hot region where there is good gas permeability and the heating process is intensively underway, including thermal storage elements. At the next moment, for example, when turning, the element enters a cold region with a low temperature and gas permeability, which gives off heat and destroys it, increasing temperature and gas permeability. Thus, in the zone of thermally accumulating elements, a region is created that is uniformly distributed over horizontal sections of temperature and gas permeability, which significantly accelerates the gasification process. If solid fuel has a high tendency to form cakes (for example, solid waste), then it is necessary to install several rotating sections with thermo-accumulating elements in different zones of the gasifier.

Sources of information

1. “Science and Life”, 1987, N 2, p.31, “Bioner”.

2. RF patent No. 2079051, 06/23/94.

3. US Patent No. 798032, 1928.

4. US Patent No. 796390, 1928.

5. US patent No. 732091, 1927.

Claims (7)

1. A solid fuel gasifier containing a vertical shaft furnace, inside which drying, pyrolysis and burning zones of solid fuel are sequentially arranged, from top to bottom, a charging device and a pipe for sampling product gas are located in the upper part of the furnace, and a supply pipe is located in the lower part a gasifying agent and a device for accumulating and removing solid products of processing - ash, between the upper and lower parts of the gasifier there are one or more sections that are components of the gasifier, having internal through cavities in the center located in the direction of the vertical axis of the gasifier and communicating with the internal cavities of the upper and lower parts, as well as with the internal cavities of the other components of the gasifier, characterized in that the sections have a casing with a lining located in it, in which the ends are fixed thermal storage elements located in the inner cavity of the section, and one or more sections of the furnace are made to rotate relative to the upper and lower parts of the gasifier District its vertical axis. 2. The gasifier according to claim 1, characterized in that the furnace sections are rotatable relative to each other around the vertical axis of the gasifier. 3. The gasifier according to claim 1 or 2, characterized in that the casing of the section is made of metal, a thrust bearing is mounted on its lower end surface, resting on the lower part of the gasifier or on the same casing of the section, and on the outer surface of the casing there is a device through which force is transmitted to rotate the section from the drive. 4. The gasifier according to any one of claims 1 to 3, characterized in that the thermal storage elements are made of ceramic in the form of rods. 5. The gasifier according to any one of claims 1 to 3, characterized in that the thermal storage elements are located in the internal cavity of the section in the form of a volumetric lattice, where the elements of one row are at an angle to the elements of the other row. 6. The gasifier according to any one of claims 1 to 3, characterized in that the thermal storage elements are diametrically located in the inner cavity of the section, one above the other at an angle to each other. 7. The gasifier according to any one of claims 1 to 3, characterized in that the gaps between the components of the gasifier - between the sections and / or between the sections and the upper and / or lower parts of the gasifier - are sealed with labyrinth seals filled with liquid, made in the form a cylindrical ring fixed on the upper part of the gasifier relative to the gap and located inside the annular cavity formed on the lower part of the gasifier relative to the same gap, liquid is filled into the annular cavity, the level of which is tsya above the lower end surface of the cylindrical ring.

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