RU2631812C2 - Method of gasifying fuel biomass and device for its implementation - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method involves gasification of fuel biomass in a dense layer moving along the axis of an inclined cylindrical reactor rotating around its axis, including charging solid ground biofuel to the reactor, feeding air to the reactor of the gasifying agent from the reactor side, where solid residues of gasification-ash are accumulated, transfer of the loaded fuel biomass along the reactor axis, removal of the solid gasification residues and combustible fuel gas from the reactor with gas flow filtration through the layer of loaded fuel by successive passage of the reactor zones in countercurrent to the fuel movement. Water is supplied to the reactor by vapourization in the evapourator cavities 13 directly adjacent to the reactor working chamber 2 due to the heat flow from the active oxidation/reduction zone 7 with the injection of steam through the perforated/porous wall of the working chamber. The removal of ash is carried out through a buffer layer 17 of solid particles, forcibly stirred while the reactor rotates. The reactor is equipped with a steam-water curtain belt comprising an annular water reservoir 12 and associated evapourating cavities 13 directly adjacent to the perforated or porous wall of the working chamber and forming a cellular (honeycomb) structure and introducing a regulating unit 4 to the discharge device with an air channel blast 22 and an internal water tank with a temperature sensor.

EFFECT: improving the quality of the produced fuel gas, reducing heat losses, increasing the compactness, economy, reliability, and durability of the reactor, simplifying its design.

7 cl, 12 dwg, 1 tbl

Description

The invention relates to the field of chemical technology and power engineering based on the use of renewable energy sources and local fuels, in particular biomass, including the utilization of solid organic (carbon-containing) waste, by gasification to produce combustible gas containing carbon monoxide and hydrogen, for the subsequent production of heat and electricity in power plants.

The priority area of scientific and technological progress in the energy sector is the creation and development of effective technologies for the use of local energy resources, including new fuels derived from various types of biomass, to build a sustainable decentralized energy supply system with the accompanying solution to an increasingly urgent problem of solid urban (household) utilization waste.

The “Energy Strategy of Russia for the Period until 2030” provides for “... the development of small energy in the decentralized energy supply zone by increasing the efficiency of the use of local energy resources, including new fuels derived from various types of biomass”, which refers to low-grade fuels with high humidity (up to 85% or more), low energy density, low heat of combustion, heterogeneity of fractional composition, but at the same time it has significant advantages compared to fossil E carbonaceous feedstocks (oil, natural gas, coal, peat, oil shale): renewability, the almost complete absence of sulfur and other harmful to equipment and the environment of the chemical elements and compounds, the prevalence and availability.

The most universal way to use various types of fuel biomass, which we mean solid biofuel / GOST 33104-2014. Solid biofuels. Terms and definitions /, obtained directly or through intermediate stages from biomass (primary biomass and solid waste from its processing, the organic part of municipal solid (household) waste), is its high-temperature thermochemical conversion, or gasification (biomass gasification) - burning of biomass at temperatures of 800 -1300 ° C in the presence of air or oxygen and water vapor to produce fuel gas - a mixture of H ₂ , CO, CO ₂ , NO _x , CH ₄ / GOST R 54531-2011. Unconventional technologies. Renewable and alternative energy sources. Terms and definitions / carried out in gasification reactors (otherwise: gas generators, converters).

In this regard, the urgent problem is the creation of high-tech compact gasification equipment for modular autonomous small power plants for use in local small-scale energy, as sources of deep reserve electricity in territories with possible long-term emergency situations, for equipping electric vehicle charging stations in environmental and other territories, environmentally friendly waste management (as an alternative to incineration technologies).

Existing technologies and designs for gasification of solid (condensed) carbon-containing fuels, including biomass fuel, are very diverse / A. Samylin, M. Yashin. Modern designs of gas generating units. - LesPromInform, No. 1, 2009, p. 78-85; Zheleznaya T.A., Geletukha G.G. Overview of modern biomass gasification technologies. - Prom. heat engineering, 2006, v. 28, No. 2, p. 61-75; Kopytov V.V. Gasification of condensed fuels: a retrospective review, current state of affairs and development prospects - M .: Infra-Engineering, 2012 - 504 p., P. 263-271 /. From an environmental point of view, their main advantage is the relatively low level of negative impact on the environment. This is primarily due to the rather long (especially for gasification in a dense layer) presence of gaseous products of gasification of condensed fuels, first in the oxidation (combustion) zone at temperatures from 1000 ... 1200 ° C and higher, and then in the reduction (oxygen-free) formation zone combustible fuel gas. Under such conditions, thermal decomposition and reductive dechlorination of the most dangerous substances - dioxins, furans, polychlorobiphenyls, benzo (a) pyrenes and other polycyclic aromatic hydrocarbons occur.

At the same time, existing gasification equipment (plants, reactors ...) has low energy efficiency, does not meet modern requirements for a number of operational and technical characteristics, and first of all, for compactness, simplicity and ease of maintenance, reliability, work resource, versatility in raw materials, as well as environmental safety, which limits its competitiveness in the global energy market.

Significant advantages in the development of effective technical solutions are gasification technology according to the direct process scheme in a dense layer with a counter supply of a gasifying agent (in particular, air) and fuel, since it makes it possible to use low-calorific fuels with a humidity of up to 40 ... 50% with a high thermal process efficiency (up to 95%), ensuring the environmental cleanliness of gas emissions / Handbook. “Boiler houses and biofuel power plants. Modern technologies for producing heat and electric energy using various types of biomass. ” Ovsyanko A.D., Pechnikov S.A., St. Petersburg, Biofuel portal WOOD-PELLETS.COM. 2008, 360 p. with ill., p. 111-151; Biomass as a source of energy. Ed. S. Soufer, O. Zaborski. - M., Mir, 1985; Kopytov V.V. Gasification of condensed fuels: a retrospective review, current state of affairs and development prospects - M .: Infra-Engineering, 2012. - 504 pp. /.

The general scheme of this gasification technology can be presented as follows.

A gasifying agent containing an oxidizing agent - oxygen and possibly water and / or carbon dioxide - enters the combustion zone (otherwise, into the active zone of oxidation / reduction), in which oxygen interacts with the carbon of solid fuel in the form of coke or semi-coke at temperatures of about 900 -1300 ° C. The gasification agent is fed into the reactor countercurrent to the fuel in such a way that the oxidizing gas is at least partially preliminarily passed through a layer of hot solid combustion products in which carbon is already absent. In this zone, solid combustion products are cooled and the gasification agent is heated before it enters the combustion zone. In the combustion zone, the free oxygen of the gasifying agent is completely consumed and hot gaseous products of combustion, including carbon dioxide and water vapor, enter the next layer of solid fuel, called the reduction zone, in which carbon dioxide and water vapor react chemically with the carbon of the fuel, forming combustible fuel gas. The thermal energy of the gases heated in the combustion zone is partially consumed in these reduction reactions. The temperature of the gas stream decreases as the gas flows through the solid fuel and transfers its heat to the latter. The fuel heated in the absence of oxygen undergoes pyrolysis. Pyrolysis produces coke, pyrolysis resins and combustible gases. Fuel gas (containing hydrocarbon vapors, water vapor, and pyrolysis resins) is discharged for later use.

During gasification, reactions occur both with the release of heat and with its absorption, therefore, to maintain the process, the condition of autothermality must be ensured, in which the total thermal effect of all reactions will be zero. High temperatures necessary for the process to occur are achieved due to super-adiabatic heating caused by heat recovery in the combustion zone with countercurrent supply of a gaseous oxidizer. Therefore, it is advisable to introduce water vapor (the so-called steam-air blasting) into the composition of the gaseous oxidizer, which at temperatures above 800 ° C enters endothermic reactions with carbon, which allows you to control the temperature regime and increase the content of combustible components (hydrogen and carbon monoxide) in the fuel gas, which characterizes the quality of the gas.

Within the framework of this technology, the design of shaft-type reactors has spread, which, however, has significant drawbacks that limit their practical application. So, to solve the problem of thermal insulation, structures with refractory (lined) walls are used / Biomass as an energy source. Ed. S. Soufer, O. Zaborski.- M., Mir, 1985, p. 214-216, 226; G.G. Tokarev. Gas generating cars. Gos. scientific publishing house lit., M., 1955, p. 42-44 /, which determines low operational and technical characteristics (cumbersome design, the complexity of maintenance and repair, low availability, low working life, high operating costs, low level of automation).

The localization of the combustion zone in the center of the chamber by means of a central blast allows the use of metal walls with steam-water cooling (steam-water jacket) / Reference book in known designs. “Boiler houses and biofuel power plants. Modern technologies for producing heat and electric energy using various types of biomass. ” Ovsyanko A.D., Pechnikov S.A., St. Petersburg, Biofuel portal WOOD-PELLETS.COM. 2008, 360 p. with ill., p. 120; A. Samylin, M. Yashin. Modern designs of gas generating units. - LesPromInform, No. 1, 2009, p. 78-85; Zheleznaya T.A., Geletukha G.G. Overview of modern biomass gasification technologies. - Prom. heat engineering, 2006, v. 28, No. 2, p. 61-75 /. However, the use of external cooling is associated with significant heat loss, as well as a decrease in the quality (combustible component) of the gas near the walls (the so-called "edge" gas) and a corresponding decrease in the efficiency of gasification.

Ensuring the stability of the flow of combustion also remains a significant problem that has not been solved for such reactors. Since the processed materials often have uneven gas permeability and are prone to sticking together during pyrolysis, the front of the pyrolysis and gasification can also propagate unevenly over the reactor cross section. In the layer of processed raw materials, “burnouts” can form, through which the gas stream mainly flows, material collapses in the cavities formed during combustion, and almost gas-tight regions can form at the same time. As a result, the temperature distribution in the combustion zone is heterogeneous and poorly controlled, which leads to a decrease in gas quality.

The problem noted above is largely solved by the use of rotating cylindrical inclined gasification reactors (see, for example, “A method for processing condensed fuel by gasification and a device for its implementation”, patent RU 2322641, Dorofeenko, Manelis et al., Publication date 27.11. 2007), where the process of gasification of solid lump (crushed to ensure mixing and gas permeability) fuel is carried out in the filtration combustion mode with super-adiabatic heating in a "dense" layer.

However, the efficiency of the gasification process for this method is limited by the lack of solutions to ensure the supply of water (water vapor) to the reactor, as well as thermal protection (cooling) of the walls of the reactor.

Such solutions are proposed in the "Method for processing condensed fuel and a device for its implementation (Patent RU 2376527, Zhirnov, Zaichenko, Manelis, Polyanchik, published date 20.12.2009), which are closest to the claimed invention in terms of essential features.

The specified method implements the general scheme of gasification of solid organic fuels described above in countercurrent gasification agent (direct gasification process) and includes loading lump (ground) fuel into a cylindrical reactor, feeding the gasification agent containing oxygen to the reactor from the side of the reactor where the accumulation of solid products processing (gasification residues), moving loaded fuel along the axis of the reactor, removing solid gasification residues from the reactor, removing drying products from the reactor and, pyrolysis and combustion in the form of a combustible fuel gas (product gas) in such a way that gasification is carried out by sequentially staying fuel in the heating and drying zone, the pyrolysis zone, the combustion zone (active oxidation / reduction zone) and the cooling zone, and the gas stream formed by the supply of a gasifying agent passes successively a cooling zone, a combustion zone, a pyrolysis zone, a heating and drying zone, and the final product, fuel gas, is filtered through a layer of loaded fuel.

In the reactor, in the zone where the temperature is maximum / exceeds 400 ° C, water is supplied in liquid form. To ensure uniform distribution over the reactor cross section of water vapor evaporated on heated solid materials of the mixture, the process is carried out in an inclined rotating reactor installed at an angle to the horizon in the range from 22 to 65 °. The temperature in the core is limited by evaporative internal cooling in conjunction with passive cooling due to endothermic reactions. The advantages of this method are the high efficiency of the process of gasification of fuels, including finely dispersed and prone to sintering, namely, high efficiency of gasification, the absence of unreacted fuel in the waste, low level of harmful emissions into the atmosphere. However, the significant disadvantages of the method are the complexity and unreliability due to the presence of additional devices in the high-temperature zone (water supply pipe; temperature sensors; seals ensuring the tightness of the reactor during rotation). With changes in the parameters of the raw materials (bulk density, fractional composition, etc.), the gas permeability of the layer of processed products (ash) may be deteriorated due to sintering of fuel, which does not allow maintaining the optimal parameters of steam-air blasting and complicates the operation of the unloading device. Also, the problem of thermal protection of the reactor structure (side wall, unloading device) has not been solved to reduce heat loss and ensure its reliability and durability. The shell lining is usually used with insulating masonry, however, such protection is insufficient, reliability, maintainability and the service life of such structures are low, insufficient compactness, high mass and dimensional characteristics limit the use of reactors in small-sized, mobile and semi-stationary power plants intended for decentralized power supply. In this case, an additional energy consumption is required for the rotation of the reactor due to its large mass.

In addition, the presence of only one water supply point prevents the uniform distribution of steam, especially with a large reactor, which reduces the ability to control the operating parameters of gasification in order to optimize them for various types of fuels.

The present invention is directed to solving the problems of technical implementation of water supply to a countercurrent dense bed gasification reactor, thermal protection of the reactor wall, as well as unloading of solid gasification residues - ash with stabilization of gasification process parameters.

To solve this problem, we propose a method of gasification of fuel biomass in a dense layer in an inclined cylindrical reactor rotating around its axis, including loading fuel biomass in the form of solid lumped (crushed) biofuel into the reactor, supplying gasification agent to the reactor — air from the side of the reactor, where the accumulation of solid gasification residues, the movement of the loaded fuel biomass along the axis of the reactor, the withdrawal of solid gasification residues and fuel gas from the reactor, while gas The ication is carried out by sequentially storing the fuel biomass in the heating and drying zone, the pyrolysis zone, the active oxidation / reduction zone and the cooling zone, and the gas flow passes through the cooling zone, the active zone, the pyrolysis zone and the heating and drying zone, the final gasification product being combustible fuel gas is filtered through a layer of loaded biomass fuel, supplying water to the reactor.

In contrast to the known prototype, the water is supplied to the reactor in the form of water vapor, while vaporization occurs due to the heat flux from the active oxidation / reduction zone in the cavities adjacent to the wall of the working chamber (working volume) of the reactor. As a result of heating, superheated steam is injected into the active zone of oxidation / reduction through the perforated / porous wall of the working chamber of the reactor, moreover, it is distributed along the perimeter and along the length of the active zone of oxidation / reduction, which contributes to uniform distribution of steam and allows thermal protection of the wall of the reactor by means of temperature control with localization of the high-temperature zone in the center of the reactor chamber, which, in turn, ensures the achievement of technical results in the form of an increase in the quality of the resulting fuel gas and reducing heat loss, as well as increasing the compactness, efficiency, reliability and durability of the reactor, simplifying its design by eliminating structural elements (assemblies) in the high-temperature zone (water supply pipes).

In this case, a combination of various mechanisms of internal cooling of the walls of the reactor is used, namely, active regenerative-evaporative, transpiration (perforation) and curtain cooling in the near-wall region of the reactor core / analogue see, for example, “Rocket propulsion systems. Terms and definitions ": textbook. allowance / D.A. Yagodnikov, N.Ya. Iryanov. - M.: Publishing House of MSTU. N.E. Bauman, 2012; GOST 17655-89. Liquid rocket engines. Terms and definitions of /, as well as passive thermochemical control of endothermic gasification reactions:

С + Н ₂ О = СО + H ₂ - 28380 kcal,

С + 2Н ₂ О = СО ₂ + 2Н ₂ - 17970 kcal.

The flow of water vapor into the chamber is automatically controlled thermally / analog see, for example, G.G. Tokarev. Gas generating cars. Gos. scientific publishing house lit., M., 1955, p. 37 /, when the speed and amount of steam change depending on the temperature in the core and the degree of heating of the evaporation cavities, while the amount of water supplied to the evaporators from the outside can be limited by a predetermined weight ratio of water and fuel biomass corresponding to the required gasification mode and / or fuel gas composition .

Distinctive features of the gasifier, ensuring the achievement of the above technical results, are that the reactor is equipped with a steam-water curtain belt integrated into the space inside the double side wall of the reactor, consisting of an external wall - a casing and an internal wall - the wall of the working chamber (working volume) of the reactor. The belt of the steam-water curtain includes an annular reservoir for water, which is supplied externally under pressure through a non-return valve, and evaporation cavities connected to it through pressure-relief valves, which form a cellular (honeycomb) structure on the wall of the working chamber. The wall of the working chamber is perforated or has a porous structure along the length of the active zone of oxidation / reduction of the reactor to ensure the passage of superheated steam from the evaporation cavities (cells) into the wall region of the active zone of the working chamber of the reactor.

To further enhance thermal protection, the inner surface of the wall of the working chamber of the reactor preferably has a high heat reflectivity (low degree of blackness) due to the choice of material and polishing of the surface, and the free space inside the double wall of the reactor, not occupied by the belt of the steam-water curtain, can be evacuated or filled with heat-insulating material and / or include heat-reflecting screens made, for example, of materials such as aluminum foil (alpha).

To simplify the design by reducing the sealing seals, a pendulum rotation mode of the reactor is provided, i.e. with a periodic change in the direction of its rotation after rotation by a certain angle (for example, 180 °).

In addition, an adjustment block, fixed relative to the rotation of the reactor, was introduced into the unloading device, as well as a bulk buffer layer of solid particles of a spherical or other shape made of solid wear-resistant inert heat-resistant material adjacent to it from above. The removal of gasification waste (ash) is carried out by grinding and sifting through a bulk buffer layer, loosened and mixed during the rotation of the reactor. In this case, to stabilize the position of the active zone and the temperature regime, stepwise (discrete) or smooth (continuous) regulation (switching) of the gasifier control parameters — the reactor rotation speed and air blast speed — is carried out in the thermal way: inversely with the temperature in the control unit, where water is supplied from outside, which during heating, when the temperature threshold is exceeded, in particular 100 ° C, turns into steam with its automatic injection into the core of the reactor Naturally with air blast.

For this purpose, an adjustment block design is proposed with a housing in the form of a truncated cone or a truncated pyramid (or other similar shape) with an internal reservoir - a water cavity and a through central axial channel for air blasting, moreover, the reservoir and the duct are connected by openings for passage of steam from the reservoir during boiling water, also on the case on its outer conical surface / side faces can be attached elements (ribs, vanes, staples, pins and / or other parts) for loosening and mixing the adjacent layer of s (including the buffer layer).

The invention is illustrated in FIG. 1-12.

In FIG. 1 shows a general diagram of a gasifier device for implementing a method of gasification of fuel biomass in a dense layer in an inclined rotating reactor with internal combined cooling (the position of the reactor is vertical).

In FIG. 2 and FIG. 3, respectively, section A-A and section B-B according to FIG. one.

In FIG. 4 shows the extension member B of FIG. one.

In FIG. 5 shows the extension element G according to FIG. one.

In FIG. 6 is a diagram of an adjustment unit.

In FIG. 7 shows a view D according to FIG. 6 with the housing of the adjustment unit in the form of a truncated cone (option 1) and a truncated pyramid (option 2).

In FIG. Figure 8 shows a general view of the gasifier with the reactor in the working (inclined) position.

In FIG. Figures 9-11 show exemplary cyclograms of controlling control parameters (speed of rotation, air blasting) of a gasifier reactor - stepped or discrete (Fig. 9 - a simple single cycle, Fig. 10 - a complex multi-step cycle) and smooth, or continuous (Fig. 11 )

In FIG. 12 shows graphs of the dependence of the minimum internal diameter of the reactor chamber D on the required / permissible operating temperature T of the chamber walls for various process parameters: temperature T _{ps of the} peripheral (wall) part of the core, bulk density (BD) ^{Y of the} feedstock.

The method of gasification of fuel biomass is carried out by means of a device (Fig. 1-8), which operates as follows.

Raw materials - fuel biomass "F", if necessary pre-crushed, is loaded into the working chamber 2 of the reactor through a loading device 3, including a lock chamber, and then enters the reactor through a vertical cylinder. At the same time, the level of processed raw materials in the working chamber 2 of the reactor is kept constant, since during the rotation of the reactor, the raw material precipitates from the cylinder. The feed in the reactor passes sequentially through a drying zone 5, a pyrolysis zone 6, an active oxidation / reduction zone 7 and a cooling zone 8.

The solid gasification residue - ash "R" - comes from the oxidation / reduction zone 7 to the cooling zone 8 with a discharge device, forming a layer 20 above the bulk buffer layer 17 of solid particles 19 (for example, spherical, the same or different size, from inert wear-resistant heat-resistant material). During the rotation of the reactor, there is a mutual movement of particles by 19 elements for loosening (mixing) - ribs 24, pins 25 and / or the like, mounted on the conical surface (side faces of the pyramid) of the fixed (non-rotating) adjustment block 4, as a result of which the ash is sieved through a buffer layer and pours out through openings in the lower (end and / or side) part of the reactor into the ash bin 9.

Air "A" is supplied to the reactor's oxidation / reduction zone 7 along its axis (central blast), for example, by means of a fan (blower) through the central axial channel 22 of the control unit 4. Water "W" is supplied (under the required pressure) through the inlet pipe 15 with a check valve into the tank 12 of the belt of the steam-water curtain, built into the space 11 inside the double side wall of the reactor, consisting of the outer wall - the casing 1 and the inner wall 10 of the working chamber 2, and then through the pressure relief valves 18 from the tank 12 into evaporation cells 13 of the belt of the steam-water curtain, formed by radial walls 14 in the annular space between the cylindrical wall 26 and the inner wall of the chamber 10, where it is heated and converted into steam under the influence of heat flux (radiation) from the active oxidation / reduction zone 7 of the working chamber 2. Increasing pressure in each individual evaporation cell 13, it forces steam to enter through the perforated / porous inner wall of the chamber 10 into the active zone of oxidation / reduction 7, forming a wall heat insulation there the heating layer of superheated steam and entering into endothermic reactions with carbon of hot coke: С + Н ₂ О = СО + Н ₂ - 28380 kcal, С + 2Н ₂ О = СО ₂ + 2Н ₂ - 17970 kcal, resulting in the formation of "water" gas and the temperature decreases (limited) in the near-wall layer and then in the active zone of oxidation / reduction 7 as a whole during mixing of the raw materials and steam distribution during rotation of the reactor. High temperature in the core is a prerequisite for ensuring high gas quality; almost complete recovery of CO ₂ in CO is ensured at a temperature of at least 950 ... 1000 ° С / Г.Г. Tokarev. Gas generating cars. Gos. scientific publishing house lit., M., 1955, p. 23, 31 /. At the same time, to eliminate slagging, it is necessary to limit the maximum temperature in the active zone (the temperature of the onset of ash melting for biomass is about 1150 ° C). The supply (injection) of water vapor into the chamber 2 of the reactor is automatically controlled thermally / G.G. Tokarev. Gas generating cars. Gos. scientific publishing house lit., M., 1955, p. 37 /, when the amount of steam generated in each individual evaporation cell 13 and entering from it into the reactor chamber 2 is directly dependent on the intensity and degree of heating (temperature) of the cell. Thus, in order to locally lower / limit the temperature of the walls and the wall region inside the chamber, the reactor uses cooling (heat protection) mechanisms similar to those of liquid-propellant rocket cooling technologies, where heat removal is carried out using fuel / oxidizer components / GOST 17655-89. Liquid-propellant rocket engines . Terms and Definitions"/:

- active internal transpiration cooling by injection of steam into the active zone 7 of gasification through the perforated (porous) wall 10 of the working chamber 2;

- active regenerative-evaporative cooling by evaporation of water in the evaporation cells 13 and injection (injection) of steam into the working chamber 2;

- active internal curtain (steam) cooling / thermal protection of the wall 10;

- passive cooling through thermochemical control of the endothermic gasification reactions in the active zone 7 of the chamber 2 of the reactor.

With the release of steam, a pressure drop occurs in the evaporation cells 13 of the curtain belt and they again receive water from the reservoir 12. The flow of water from the outside through the pipe 15 can be controlled (in particular, limited) by a predetermined weight ratio of water and the fuel biomass loaded into the reactor, corresponding to the desired mode gasification and / or composition of the resulting fuel gas.

Possible deposits (deposits) on the inner surface of the wall 10 in the reactor core can drown out the perforations in individual cells 13, however, the local temperature increase accelerates the gasification process, eliminating deposits, and a temporary increase in steam pressure in these cells contributes to its passage into the chamber.

Fuel gas "G" is taken at the top of the reactor and sent for further use, which may include burning it in an energy device.

The stabilization of the position (constant position) of the active zone 7 with maintaining in it (in the center, in the near-wall region) the temperature required for gasification of the raw material is achieved by regulating (adjusting) the control parameters (rotation speed Vвп, air blast speed V _A ) of the gasification reactor by thermostatic control mechanism of the control unit 4 with negative feedback. Depending on the heating temperature in the cooling zone 8 of the reactor chamber (in the control unit 4), namely, upon reaching (exceeding / decreasing) the established water temperature threshold T _w in the tank 21, the rotation speed stepwise (or smoothly) changes (decreases / increases), the speed of air blasting can also stepwise (or smoothly) change (decrease / increase) in the specified range.

So, when the temperature of the water T _w in the tank 21 drops to T ₁ , the controller of the operating parameters of the reactor (the control system is not shown in the diagram), having received a signal from the temperature sensor, increases the speed of the reactor to V _max (a variant of stepwise adjustment is shown in Fig. 9 , transition 1-1 'of the cyclogram), which leads to an increase in the speed of unloading of ash and a corresponding decrease in the thickness of the layer of ash 20, a shift of the active zone 7 down and increased heating of water in the tank 21.

Moreover, if after that the water temperature T _w decreases to a critical value T _min (point 3), the controller switches (increases) the air blast speed by a set value (transition 5-5 '), which leads to an increase in temperature in the active oxidation zone / recovery 7 due to the acceleration of oxidation processes. As a result, the water temperature T _w rises and upon reaching the value of T ₂ , the reactor rotates (decreases to V _min ) (rotation 2-2 '). This leads to a decrease in the rate of unloading of the ash and a corresponding increase in the thickness of the layer of ash 20, the shift of the active zone of oxidation / reduction 7 upward and a decrease in the heating of water in the tank 21.

Moreover, if after that the water temperature T _w continues to increase and reaches a critical value of T _max (point 4), the controller switches (decreases) the air blast speed by a set value (transition 6-6 '), which leads to an increase in temperature in the active zone of oxidation / recovery 7 due to the acceleration of oxidation processes. To accelerate transient processes and eliminate possible overheating of the elements of the unloading device, as well as reduce heat loss, T _max should be close, but not exceed 100 ° C. In this case, the inertia of the heating will lead to vaporization in the tank 21 and the inclusion of the evaporative cooling mechanism of the housing of the control unit 4.

When water boils, steam enters through openings 23 into the central channel 22 for air blasting and, together with air, passes into the active oxidation / reduction zone 7, where it enters into endothermic reactions with carbon, which leads to a rapid local decrease in temperature, while the water flow is replenished through inlet pipe 15.

As a result, the temperature of the water in the tank 21 drops and, upon reaching the Ti value, the reactor rotation speed (increase to V _max ) is switched (transition 1-1 '), and thus the adjustment cycle closes, ensuring stabilization of the core position and the required temperature in the core . Adjustment of the control parameters of gasification (V _BP , V _A ) can be carried out by other control options, for example, on the basis of a complex multi-step cycle (polycycle) of step (discrete) control (Fig. 10) with intermediate switching points - increase (point 1) and lowering (point 2) or smooth (continuous) regulation (Fig. 11).

To justify the effectiveness of the proposed technical solutions, we take the following initial data:

1) Bulk density (BD) ^{Y of} raw materials - fuel biomass - in terms of dry matter, kg / m ³ :

- low density biomass one hundred - unrefined (typical) biomass 300 - refined raw materials - biofuel (pellets, briquettes) 650

2) Ash melting temperature, ° С, not less than 1150

3) Type of gasification process: direct with steam-air blasting, without slag formation

4) The shape of the reactor is cylindrical, the inner diameter of the working chamber D, length L

5) Physical parameters of the heat carrier (water):

specific heat of water C _w , J / kgK 4187.2 (std), 4 227.3 (95 ° C) latent heat of vaporization _of C, kJ / kg 2250 specific heat capacity of water vapor C _vp , J / kgK 2510

6) Temperature parameters (in steady state), ° С:

- maximum temperature in the central part of the active zone T _int 1150 - the average temperature in the peripheral parts (in the parietal layer) of the active zone (taking into account endothermic reactions) T _ps 900 ... 1100 - water temperature at the inlet to the tank (standard condition.) T _W twenty - the temperature of the steam when it enters the chamber T _p 150 - temperature of superheating of steam in the working chamber (until completion of the reactions) T _pp 500

Key Assumptions:

1) The heat flux to the inner wall of the chamber is determined by radiant heat exchange for the following reasons.

Firstly, the heat transfer mechanism by the method of heat conduction (when the hot fuel is in direct contact with the walls in the core) is basically blocked by the steam curtain at the walls, as well as by the permanent process of soot formation on the inner cooled surface of the reactor chamber (the Bell-Boudoir reaction 2CO → СО ₂ + C + 38790 kcal).

Secondly, the convective heat transfer mechanism during the upward movement of the generated hot fuel gas also does not contribute to wall heating due to the predominance of the solid phase in the reactor chamber and the presence of a vapor curtain at the walls of the active zone in conjunction with central air blasting (localization of the high temperature zone along the axis of the cylindrical chamber).

2) The required time for the main recovery reactions of gasification (empirical estimates, see G. G. Tokarev. Gas-generating cars. State Scientific and Technical Publishing House of Machine-Building Literature, Moscow, 1955, pp. 22-24) presented in table 1.

Heat balance calculation

Radiant heat transfer coefficient in the reactor chamber (according to the Stefan-Boltzmann law):

where ε is the degree of blackness of the inner surface of the chamber wall,

- коэффициент излучения.

- emissivity.

Specific heat flux to the wall of the reactor:

,

,

Note - Temperature parameters - in degrees K.

The specified heat flux must be compensated (regenerated) by means of the evaporative-regenerative transpiration (perforation) cooling mechanism.

The heat flux of radiant heat transfer can be defined as

,

,

where qn is determined in accordance with clause 7.1, and the area S of the heated inner wall surface is calculated as S = π⋅D⋅La, where D is the inner diameter of the cylindrical chamber of the reactor, La = ka⋅D is the height of the active (cooled) zone.

The heat flux that can be compensated is defined as

,

,

- скорость поступления (кг/ч) пара в камеру, определяемая из соотношения воды и биотоплива

- производительность реактора по сухому сырью, кг/ч; Kw - доля воды,

).Where

- the rate of entry (kg / h) of steam into the chamber, determined from the ratio of water and biofuel

- reactor productivity in dry raw materials, kg / h; Kw is the proportion of water

)

The performance of the reactor G is defined as

,

,

, a

- время пребывания сырья в активной зоне (в минутах) определяется временем, необходимым для завершения реакций газификации (см. табл. 1).where is the volume of the reactor core

, a

- the residence time of the raw materials in the core (in minutes) is determined by the time required to complete the gasification reactions (see table. 1).

A prerequisite for the effective operation of the proposed gasification reactor is the fulfillment of the ratio Qw≥Qn.

Substituting the expressions obtained above for Ql and Qw and the numerical values of the physical parameters, we finally obtain:

The optimal weight ratio of water and biofuel (fuel biomass) in the real gasification process corresponds to the value Kw = 0.4 ... 0.5 / G.G. Tokarev. Gas generating cars. Gos. scientific publishing house lit., M., 1955, p. 35-38 /, therefore, assuming Kw = 0.4 without taking into account the reflectivity of the inner surface of the chamber wall during radiant heat transfer (ε = 1), we obtain the dependences of the minimum internal diameter of the reactor chamber D on the parameters of the gasification process shown in FIG. 12.

The analysis of dependencies allows us to draw the following conclusions regarding the effectiveness of the proposed technical solutions:

на стенки камеры реактора

.1. There is a range of operating parameters of the proposed reactor, in which its effective operation with compensation of heat flux is possible.

on the walls of the reactor chamber

.

, в том числе рафинированного сырья (гранулы и т.п.), реакторы, реализующие предлагаемый способ газификации, могут быть наиболее компактными (D≤40 см).2. When using raw materials with a sufficiently high (above average) bulk density with

, including refined raw materials (granules, etc.), reactors that implement the proposed method of gasification can be the most compact (D≤40 cm).

, требуемая компактность установок может быть достигнута посредством применения материалов для внутренней поверхности стенки камеры с повышенной отражательной способностью при лучистом теплообмене (ε<1). Так, для жаростойких сталей и сплавов (10Х23Н18, ХН32Т, ХН60Ю, ХН78Г и др.) степень черноты ε=0,5…0,6, полированные поверхности стали и сплавов (титана, алюминия) позволяют получить значительно лучшие характеристики, для полированного титана ε=0,2, для полированного алюминия ε=0,04…0,06 /М.А. Михеев, И.М. Михеева. Основы теплопередачи. М.: Энергия, 1977/.3. In other conditions / modes (in particular, for processing poorly compacted raw materials

, the required compactness of the installations can be achieved by using materials for the inner surface of the chamber wall with high reflectivity during radiant heat transfer (ε <1). So, for heat-resistant steels and alloys (10X23H18, KhN32T, KhN60Yu, KhN78G, etc.) the degree of blackness ε = 0.5 ... 0.6, the polished surfaces of steel and alloys (titanium, aluminum) allow to obtain significantly better characteristics for polished titanium ε = 0.2, for polished aluminum ε = 0.04 ... 0.06 / M.A. Mikheev, I.M. Mikheeva. The basics of heat transfer. M .: Energy, 1977 /.

4. Maintaining a high temperature in the core (at least 1000 ° C), including in the peripheral (near-wall) layer, by limiting the water supply at a predetermined ratio also helps to improve the compactness of the reactor and increase the productivity of the reactor and gas quality.

Claims (7)

1. The method of gasification of fuel biomass in a dense layer, moving along the axis of a cylindrical reactor, installed at an angle to the horizon in the range from 22 to 65 ° and rotating around its axis, comprising loading into the reactor fuel biomass, which is used as a solid crushed biofuel, feed to the air reactor as a gasification agent from the side of the reactor, where the accumulation of solid gasification residues, the movement of the loaded biomass fuel along the axis of the reactor, the removal of solid gas residues ikation from the reactor, removal of drying, pyrolysis and oxidation / reduction products from the reactor in the form of combustible fuel gas, water supply to the reactor, gasification being carried out by sequentially storing fuel biomass in the heating and drying zone, the pyrolysis zone, the oxidation / reduction active zone and cooling zone, and the gas stream formed by the supply of a gasifying agent passes through the cooling zone, the active oxidation / reduction zone, the pyrolysis zone and the heating and drying zone, and the final pr the gasification duct — combustible fuel gas — is filtered through a layer of loaded fuel biomass, characterized in that the water is supplied to the reactor in the active oxidation / reduction zone in the form of steam, the formation of which occurs in the evaporation cavities of the belt of the steam-curtain, directly adjacent to the inner wall of the working chamber reactor, due to the heat flux from the active oxidation / reduction zone, while superheated steam is injected into the active oxidation / reduction zone through the perforations this or porous inner wall of the working chamber of the reactor is distributed around the perimeter and along the length of the active zone of oxidation / reduction, providing thermal protection of the inner wall of the working chamber of the reactor with localization of the high-temperature zone in the center of the active zone of oxidation / reduction, while the position of the active zone of oxidation / reduction and temperature in stabilize it by adjusting the control parameters of gasification - the speed of the reactor and the speed of air blast inversely with perature water accumulated in the reservoir, located in the discharge device in the cooling zone, the injection of steam produced when reaching the boiling point, together with the central air blast into an active oxidation / reduction zone. 2. The method of gasification of fuel biomass according to claim 1, characterized in that the removal of solid gasification residues - ash - is carried out by grinding and sifting through a bulk buffer layer of spherical solid particles, forcibly loosened and stirred during rotation of the reactor. 3. A device for the gasification of fuel biomass in the form of solid crushed biofuel in a dense layer, including a loading device, a cylindrical reactor mounted at an angle to the horizon from 22 to 65 °, rotatable around its axis, a discharge device, a gasifier supply device - air to the lower part of the reactor, the drive rotation of the reactor, seals, ensuring the tightness of the reactor during rotation, temperature sensors in the reactor, characterized in that the reactor is equipped with catfish of a steam-water curtain integrated into the space inside the double side wall of the reactor, consisting of an outer wall — a casing and an inner wall of the working chamber, the belt of the steam-water curtain comprising an annular tank for water, which is supplied externally under pressure through a non-return valve, and connected to it through pressure and overflow valves evaporation cavities forming a cellular honeycomb structure on the inner wall of the working chamber, which is perforated or has a porous structure along the length of the oxidation active zone / rebuilt reactor to ensure the passage of steam from the evaporation cavities into the wall region of the working chamber of the reactor, and an adjustment unit is introduced into the discharge device, the casing of which is made in the form of a truncated cone or a truncated pyramid and equipped with a water tank and a through central axial channel for air blasting, connected for steam injection from the tank, while the tank of the control unit has an inlet pipe to replenish the flow of water from the outside. 4. The device for gasification of fuel biomass according to claim 3, characterized in that on the outer side surface / side faces of the control unit body and / or on the inner side wall of the reactor in the cooling zone there are installed elements - ribs, staples, pins for loosening and mixing adjacent a layer of solid gasification residues - ash during rotation of the reactor relative to the stationary control unit. 5. The device for gasification of fuel biomass according to claim 3, characterized in that the part of the reactor cooling zone is filled with spherical particles from a solid wear-resistant inert heat-resistant material, forming a buffer layer adjacent to the control unit, forcibly loosened and stirred during rotation of the reactor for grinding and sieving solid gasification residues - ash before disposal through an unloading device. 6. The device for gasification of fuel biomass according to claim 3, characterized in that the reservoir of the control unit is equipped with a temperature sensor, the output of which is connected to a control system for regulating the parameters of the reactor - the speed of the reactor and air blast speed to stabilize the position of the oxidation / reduction active zone and temperature in it. 7. Device for gasification of fuel biomass according to paragraphs. 3-6, characterized in that they use the pendulum mode of rotation of the reactor with a change in the direction of rotation of the reactor to the opposite after rotation by a certain angle, for example 180 °.

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