RU2631456C1 - Method for producing electricity from sub-standart (wet) fuel biomass and device for its implementation - Google Patents

Abstract

FIELD: power industry.

SUBSTANCE: method provides, in the first stage, the supply of feedstock - ground fuel biomass of various origins - and its steam-air gasification in a dense bed in a direct-process gasification reactor, werein, during the gasification process, gasifying agents - air and water vapor and/or water - are supplied countercurrent the raw material flow through the lower part of gasification reactor, where accumulation and withdrawal of solid products - gasification wastes is carried out to the active gasification zone by means of, for example, blowing, in ratios with gasified raw material needed for behaviour of oxidation-reduction gasification reactions, and combustible fuel gas, obtained as a result of gasification, is filtered through a bed of feedstock, loaded in gasification reactor, and is withdrawn from the upper part to be used in the second stage, comprising burning the resulting fuel gas with conversion of thermal energy into mechanical energy through a heat engine and into electrical energy through a generator. Wherein, feedstock for the production of electricity is subjected to complete deep drying before the gasification, including convective air-calorifer drying to remove external moisture using the heat of the working medium that has been spent in heat engine by means of its air cooling and, possibly, condensation in the closed circuit of circulation of the working medium, as well as conductive-convective drying by exhaust flue gases to remove residual, including reaction, moisture.

EFFECT: increasing the efficiency of electricity production.

10 cl, 14 dwg, 1 tbl

Description

IPC F01K 17/06 - recovery of steam energy in steam power plants, for example, the use of spent steam to dry solid fuel burned in the same installation

IPC F23G 5/00 - incineration of waste or low-grade fuels,

5/027 - with the stage of pyrolysis or gasification

5/04 - drying

5/08 - with additional heating

5/20 - with burning in rotating or oscillating drums

5/46 - heat recovery

IPC F28C 3/00 - Other direct contact heat exchangers

3/18 - ... finely divided solid material moves in rotating drums

The invention relates to bioenergy, and in particular to electric energy based on renewable energy sources and local fuels, in particular biomass, decentralized electricity supply, and also to the processing and disposal of solid organic, including household waste.

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 an accompanying solution to the problem of utilization of municipal solid (household) waste.

Biomass refers to all types of substances of plant and animal origin, the waste products of organisms and organic waste generated in the processes of production, consumption of products and at the stages of the waste technological cycle (GOST R 52808-2007. Non-traditional technologies. Energy biowaste. Terms and definitions), and under fuel biomass - solid primary biomass, solid waste from processing primary biomass, solid urban (household) waste (MSW) that can be used as energy of raw materials.

Biomass as an energy resource refers to low-grade fuels with high relative humidity (up to 85% or more), low energy density, low heat of combustion, heterogeneity of fractional composition, while it has the following advantages compared to fossilized carbon-containing raw materials (oil, natural gas, coal, peat, oil shale):

- renewability, i.e. neutrality of CO ₂ emission (relative to the carbon dioxide balance in the atmosphere), thereby reducing anthropogenic environmental load;

- an almost complete absence of sulfur, which removes the problem of acid precipitation, as well as other chemical elements and compounds that are harmful to equipment and the environment;

- prevalence and availability.

The energy use of biomass involves either direct combustion or the production of intermediate energy carriers: solid, gaseous or liquid biofuels.

Biomass can be used to produce energy without additional processing, which refers to refined or prepared according to the parameters (particle size or fractional composition, humidity, ash, bulk density, etc.) in accordance with the technical specifications of the fuel biomass, or with minimal preparation for unrefined substandard biomass, which is a cheap (with low, zero or negative cost) and practically not currently used source of local energy resources.

The production of electricity from solid biomass, which is a universal type of energy of high quality, is based both on traditional methods of direct combustion and on modern thermochemical technologies / GOST R 54531-2011 Non-traditional technologies Renewable and alternative energy sources. Terms and definitions / and is carried out through the use of thermal power plants (TPPs), in particular, condensing power plants, however, their electrical efficiency, especially in terms of low-power power plants, is extremely low and its growth potential in the framework of existing technologies is limited due to the fact that most of the energy comes from to the so-called "waste" heat, which is often impossible or difficult to use effectively in practice.

Known methods and devices for generating electricity (electric power) in a power plant - a thermal power plant (TPP), which converts the combustion energy of solid fuel, in particular biomass, into steam energy using direct combustion technologies - in a fixed bed, in a fluidized (boiling and circulating) bed, dust burning (in a flare, in a whirlwind) - in relation to the type of fuel used and the thermal power of the boiler unit with further conversion of steam energy into mechanical energy of a heat engine (in particular, steam engine (including turbines) and associated electric generator / 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 s. with ill .; “The use of biomass energy for heating and hot water in the Republic of Belarus. Guidelines for the application of best practices. Part A: Biomass burning. ”- ESCO. Electronic journal of the energy service company Ecological Systems, No. 2, February 2006 /. Since the fuel biomass and the combustion (flue) gas generated during its combustion contain elements that can cause engine damage, such as fly ash particles, metals and chlorine impurities, modern technologies for energy production through biomass combustion are based on closed-cycle processes, where Combustion and energy production processes are separated by transferring the heat of the hot flue gas to the coolant used in the secondary cycle, which reduces the amount of harmful emissions .

For direct combustion, fairly simple equipment has been developed and is widely used, such as boilers, which are a combination of furnaces of various designs with heat exchangers between hot flue gases and a working fluid. The furnaces of combustion plants are usually equipped with a mechanical or pneumatic fuel supply device and equipped with process control systems that automate the operation.

So, a well-known common example of the technical implementation of the method of power generation based on direct combustion of biomass is a technological process implemented in the work of a traditional steam-turbine condensing power plant / cm. The above reference. “Boiler houses and biofuel power plants. …", from. 152-230; Trukhny A.D., Losev S.M. “Stationary steam turbines”, M., 1981 / as part of a steam power (steam turbine) installation with an electric generator, as well as a fuel preparation and storage section.

At the fuel preparation and storage area, the initial biomass, which usually does not fully comply with the technical conditions of the combustion technology, i.e. substandard, is prepared as part of the technological mechanical operations of grinding, cleaning and sorting, as well as drying (drying). To ensure smooth operation, the section contains a mechanized fuel sectional warehouse for storing the operational stock of prepared raw materials, as well as technological transport (feed conveyor) of the required type and capacity (belt and scraper conveyors and elevators, flexible and inflexible screws, stocker floors, pneumatic conveying systems).

The prepared biomass from the fuel depot is fed by the conveyor to the hopper and then burned in the furnace - the combustion chamber of the boiler (steam generator), turning the feed water into dry saturated steam, which in turn enters (usually in an overheated state) through the steam line to the steam turbine. Expanding in it, the steam rotates its rotor, connected to the rotor of the electric generator, which generates an electric current. The waste steam enters a condenser - a heat exchanger, through the tubes of which cold water flows continuously, supplied by a circulation pump from a reservoir or a special cooling device (cooling tower). The steam condenses in the annulus and flows down, the condensate is supplied to the deaerator and returned to the boiler with a feed pump, which closes the technological steam-water cycle of converting the chemical energy of the fuel into mechanical rotational energy of the rotor of the turbine unit. Flue gases, having given the bulk of the heat to the feed water, go to the pipes of the water economizer and the air heater, giving off heat to the feed water and air for burning fuel, and then using a smoke exhauster through electrostatic precipitators that capture fly ash and the chimney into the atmosphere.

Variants of the above-described method of electric generation are also known, where instead of a steam turbine installation (PTU), a different type of closed-cycle heat (steam) machine can be used, namely, a steam piston engine (PPD), a steam screw machine (FDA), and a Rankine organic cycle heat turbine (ORC) et al. / See above source: Use of biomass energy ..., sec. four/.

The most significant disadvantages of methods for generating electricity based on direct biomass burning technologies:

- low overall and electrical efficiency (significant heat loss), which does not allow them to build a stable energy system;

- the problem of harmful emissions into the atmosphere (fly ash containing heavy metals; soot; carbon monoxide; oxides of sulfur and nitrogen; chlorine compounds; dioxins and polyaromatic hydrocarbons) has not been solved; complex, expensive flue gas treatment is required (the cost of a modern incinerator is more than 60 % consists of the cost of treatment facilities);

- slags, as a rule, contain unburned carbon and polyaromatics;

- the possibilities of using wet and high-ash biomass are limited, the lower limit of the calorific value of wet and high-ash organic matter, in which it is possible to autogenously (self-sustaining) burning it without using additional fuel, meets the Tanner condition: relative humidity W <50%, ash content A <60%, carbon content C> 25%;

- the complexity of the automation of technological processes, because due to the low heat of combustion, high humidity and heterogeneity of the biomass, its preliminary processing (grinding, compaction, drying, homogenization, etc.) or refining (production of fuel pellets - pellets, fuel briquettes) is required.

- requires the removal of a large amount of "waste" heat and, accordingly, a large flow rate of cooling water;

- bulkiness of equipment.

Of the known technologies for converting biomass into electrical energy, the most preferable are technologies, methods, and devices based on a two-stage or two-stage process for the thermochemical conversion of raw materials, namely, with preliminary (in-cycle) gasification of raw materials, since they make it possible to obtain a cheap, convenient and environmentally friendly energy carrier - fuel (generator) ) gas, during the combustion of which the concentration of harmful substances in flue emissions is significantly reduced.

This allows you to significantly save on expensive equipment for gas flue gas treatment and equipment for disinfection of recyclable waste. In addition, during gasification, the underburning of fuel is significantly lower in comparison with direct combustion, and there is practically no soot in the produced gas and ash residue (unreacted carbon).

A large number of diverse methods for the gasification of solid fuels and designs of gasification reactors (gas generators) / cm have been developed. The above reference. Boiler houses and biofuel power plants. ... "; Biomass as a source of energy. Ed. S. Soufer, O. Zaborski. - M., Mir, 1985; A. Samylin, M. Yashin. Modern designs of gas generating units. - LesPromInform, No. 1, 2009, p. 78-85; Kopytov V.V. Gasification of condensed fuels: a retrospective review, current state of affairs and development prospects - M .: Infra-Engineering, 2012. - 504 p .; G.G. Tokarev. Gas generating cars. Gos. scientific - those. publishing house lit., M., 1955 /, while the fuel (generator) gas obtained as a result of gasification can be used as fuel for internal engines (subject to the use of cleaning and cooling equipment) and external (subject to the use of burners similar to boiler rooms) combustion followed by the conversion of mechanical energy into electricity.

So, there is a known method of producing electricity from biomass (wood chips) according to a two-stage technological scheme by means of a mini-CHP based on gas piston internal combustion engines (ICE), implemented in a gas-generating electric power plant / cm. the above reference "Boiler houses and power plants on biofuel ...", p. 248-253 /, consisting of four sections: fuel preparation, gasification, power generation, circulating water system for cooling fuel gas. The fuel preparation section consists of a conveyor with a metal detector for separating metal inclusions, a crusher for grinding wood pieces into chips, a vibrating screen for screening substandard chips, a conveyor for feeding the conditioned chips to the loading station, a transport system for supplying fuel from the loading station to the lock of the gas generator, a control system and automatics. At the gasification section, a WBG400 gas generator was installed with purification plants for cooling and purifying fuel gas before being fed to the gas piston engine. The power generation section consists of an electric generator with a gas engine and control cabinets. A block-modular treatment plant consisting of pipelines, pumps, tanks, purification units, a control panel, a cooling tower or a heat exchanger is installed on a section of the recycled water system. The gas-generating power plant operates in the CHP mode, providing an output electric power of 250 kW and a thermal power of 469 kW, with a total efficiency of about 50% in the nominal mode, taking into account useful heat recovery.

This method of power generation based on gas piston units has received practical distribution / G.G. Tokarev. Gas generating cars. Gos. scientific - those. publishing house lit., M., 1955 /, however, it has significant shortcomings:

- low electrical efficiency (~ 18%) due to the need to cool the fuel gas (energy losses up to 20%), as well as the prevailing share (2/3 or more) of the thermal component in the output power;

- high content of harmful emissions (СО, NOx) into the atmosphere due to the use of gas-piston units in the power generation technological chain;

- restrictions on raw materials (moisture content not higher than 20%);

- low operational and technical characteristics of the plants (significant specific gravity per unit of power and dimensions, the presence of a complex multi-stage system for cleaning, cooling and drying gas, low degree of automation).

The properties of the produced gas (high temperature, the presence of moisture, dust and resins, low calorie content, low pressure) when it is used to produce electricity using technologies effective for natural gas (in open and semi-closed cycle plants - in gas piston units, gas turbine units), to a significant complication and appreciation of equipment (requires multi-stage cleaning, cooling and drying systems, booster compressors), a significant decrease in operating efficiency is applied Mykh power units, cumbersome installations.

To a considerable extent, the known methods and installations for generating electricity based on a two-stage technological scheme providing for gasification of fuel biomass in the first stage and burning of the obtained fuel gas and conversion of thermal energy into mechanical energy in a heat engine (external engine combustion) of a closed cycle, where the working fluid circulates in a closed circuit without any connection with the atmosphere.

Such a scheme should be recognized as preferable from the point of view of minimizing the harmful effects on the environment by reducing harmful emissions into the atmosphere. As a result of reduction or removal of requirements for fuel gas purification, gas cleaning equipment is not only simplified and cheapened, but also the calorific value of the gas is increased due to the combustible low and high molecular weight organic compounds contained in it (for example, alcohols and, especially, resins). In addition, with the exception of the operation to cool the produced gas at the same time as saving on the corresponding equipment, the physical heat of the hot gas contributes to the heating of the working fluid of the power plants, and the issue of recycling liquid secondary waste (gas condensate) is also addressed.

In power plants of low power (up to 100 ... 500 kW), proven technologies can be used on the basis of well-known closed-loop external combustion engines (PTU, PPD, FDA, ORC turbine, Stirling engine).

Closest to the invention in terms of essential features is a known method and device for the production of heat and electricity through the thermal processing of carbon-containing materials (combustible waste) / see, for example, the above source: Kopytov V.V. Gasification of condensed fuels ..., p. 298-300 / based on a two-stage technological scheme, which provides for the first stage of gasification of biomass, including the supply of raw material - crushed solid (fuel) biomass of various origins, including organic waste, for vapor-air gasification in a dense layer in a direct process gasifier. In the process of gasification, in counter-flow to the movement of raw materials through the lower part of the gasification reactor, where solid products - gasification waste (ash) are accumulated and removed, gasification agents - air and water vapor and / or water - are supplied to the active gasification zone by, for example, blowing depending on the design of the gasifier reactor) - in the ratios necessary for the occurrence of redox reactions of gasification with gasified raw material. The resulting combustible fuel gas (generator or product gas) containing hydrogen H ₂ , carbon monoxide CO and, in some cases, methane and other hydrocarbons and / or other organic compounds (volatile fractions, fumes of resins) is filtered through a layer of raw material loaded into the reactor and discharged from the top of the reactor. At the second stage, the resulting hot fuel gas is burned in the gas furnace of the steam boiler (steam generator), the thermal energy of the steam is converted into mechanical energy in a heat (steam) machine, and then into electrical energy by means of an electric generator, while a part of the spent steam can be selected for supply to the reactor -gasifier as a gasifying agent in the volume necessary for gasification reactions, flue gases are filtered with a purifier with lime (a special filter-neutralizer sulfur) and are released into the atmosphere through a chimney.

The process of gasification of fuel is carried out in a shaft type gasifier reactor of a direct gasification process, in particular, in an inclined rotating cylindrical gasifier reactor in the filtration combustion mode with super-adiabatic heating in a “dense” layer / see, for example, patent RU 2376527, Manelis, etc. , date publ. 12/20/2009; patent RU 2322641, Dorofeenko et al., date publ. 11/27/2007; Kislov V.M. Gasification of wood and its components in a filtration mode. Abstract of diss. Ph.D. IPCP RAS, Chernogolovka, 2008 /.

The advantages of these methods and devices are high gasification efficiency, lack of a cooling and gas purification system, low level of harmful emissions into the atmosphere. There are a number of significant drawbacks:

- limited opportunities for the use of substandard raw materials for gasification (humidity - up to 25 ... 50%, ash - up to 10 ... 25%, etc. / see the above sources: Reference. "Boilers and power plants using biofuels ...", p. 220; Kopytov VV Gasification of condensed fuels ..., p.280-290 /);

- significant heat loss and, consequently, low electrical efficiency (up to 0.15 ... 0.25), a harmful effect on the environment due to the large consumption of cooling water and the possible presence in the flue gases of products of incomplete combustion and entrainment (dust);

- low operational and technical indicators (bulkiness of equipment - gasification reactor, working fluid condensers, low adaptation to load fluctuations, limited automation capabilities).

The present invention is aimed at solving the problem of increasing the efficiency of electricity production (electrical efficiency) in low-power autonomous power plants operating on local renewable energy - biomass, with the expansion of the range of raw materials used, including cheap substandard fuel biomass, in particular, with a high moisture content, while minimizing harmful effects on the environment of the electricity production process.

The invention provides technical results, which are expressed, firstly, in increasing the electrical efficiency of the method and device for generating electricity according to a two-stage scheme with gasification of raw materials with the subsequent conversion of the thermal energy of the burned fuel gas into electricity through a heat (in particular, steam) machine ( external combustion engine) with an electric generator, and, secondly, in expanding the range of used cheap low-grade raw materials, including substandard (in terms of moisture content) about 70 ... 85%), fuel biomass, and are achieved by means of recovery mechanisms for unused ("waste") heat from the engine’s working fluid and the heat of flue (flue) gases, when the feedstock for generating electricity before being fed to gasification is first subjected to convective air -caloriferous drying using thermal energy from cooling and, possibly, condensation of the working fluid spent in the heat engine to remove external (hygroscopic) moisture, and then drying by exhaust flue (furnace u) to remove residual gases, including reaction (chemical) water.

To implement the method, a fuel preparation section is additionally introduced into the device, including a drying apparatus, for example, a drum type, for primary convective air-caloriferous drying of raw materials and a drying and filtering apparatus for subsequent convective-conductive drying of raw materials with flue gases.

Thirdly, the technical result of the invention is expressed in minimizing the environmental impact of the proposed method and device for generating electricity and is achieved through the following set of actions and conditions:

- in terms of reducing harmful emissions into the atmosphere - by building a technological chain based on the use of a renewable resource as biomass, implementing a two-stage scheme with gasification of biomass, using closed-circuit heat machines (engines);

- in terms of reducing (eliminating) the harmful effect (pollution, violation of the natural temperature regime) on water resources - by eliminating water cooling to remove “waste” heat during condensation of the heat carrier (steam) and using air cooling;

- in terms of waste reduction - due to the completeness of processing and exclusion of non-recyclable waste (in particular, special filters for gas purification).

Fourth, the technical result is expressed in ensuring the autonomy of the electricity production process and is achieved through a combination of actions and conditions through the components of this characteristic, including:

practical independence from external sources of water resources through the use of air-cooled heat exchangers;

independence from external energy sources;

lack of communication requirements for transporting the resulting fuel gas, for the transmission of electricity (local users are supplied), as well as in special stationary (capital) facilities.

Also, to achieve a technical result in the form of expanding the range of output electric power, as well as improving operational and technical characteristics when implementing the present invention, such as working in a wide range of electricity consumption and with different steam quality, full automation of processes, compactness (low overall mass characteristics) ), for gasification of biomass a cylindrical inclined rotating reactor-gasifier is used in the mode of filtration combustion from super diabetic heating, and as a heat (steam) machine, various types of closed-loop external combustion engines can be used (PTU, PDP, FDA, ORC turbines, Stirling engine).

The invention is illustrated in FIG. 1-14.

In FIG. 1 shows a general diagram of a device for implementing a method of generating electricity from substandard (in terms of moisture content) fuel biomass according to a two-stage technological scheme with two recovery circuits — the heat of the spent working fluid and flue gases — for drying moist raw materials using condensation-type heat engines (ПТУ, ППД , FDA, ORC turbines).

In FIG. 2-5 shows a diagram of the construction of a drying and filtering apparatus, including a general view (FIG. 2), section AA along the loading and unloading locks according to FIG. 2 (FIG. 3), a section BB along the cone drum according to FIG. 2 (FIG. 4), view B on an annular screen filter - biomass cutter according to FIG. 2 (Fig. 5).

In FIG. 6-7 are general schemes of a device for a particular case of a method for producing electricity from substandard (in terms of moisture content) fuel biomass according to a two-stage technological scheme with complete deep drying of wet raw materials in a drying unit (Fig. 6 - when using heat condensation type machines - ПТУ, PPD, FDA, ORC turbines, Fig. 7 - using a Stirling engine).

In FIG. Figures 8-11 show a diagram of the construction of the drying unit, including a general view (Fig. 8), section AA (Fig. 9) along the loading and unloading locks according to Figs. 8, section BB (FIG. 10) along the cone drum of FIG. 8, view B (FIG. 11) on the annular screen filter - biomass cutter according to FIG. 8.

In FIG. 12 shows graphs of the dependence of the lower calorific value (STV) of the initial biomass on its relative humidity (total moisture).

In FIG. 13 shows graphs of the dependence of the electrical efficiency of the proposed device on the relative humidity (total moisture) of the initial biomass at various values of the dry biomass NTS for a practicable range of values of the operating parameters of the device (heat exchange efficiency, electrical and thermal efficiency).

In FIG. 14 is a graph of the dependence of the electric efficiency of the proposed device on the efficiency of heat transfer during heat recovery of the spent working fluid.

A method of producing electricity from substandard (wet) fuel biomass is carried out by means of a device (Fig. 1), which operates as follows.

At the first stage 1, gasification of the prepared (conditioned) biomass F in the gasification reactor 3 of the direct process of vapor-air gasification in a dense layer is provided. The raw material comes from the fuel preparation section 12 to the gasifier reactor 3 through the loading device 4, in countercurrent to the movement of the raw material F through the unloading device 5, where the accumulation and removal of solid gasification waste R to the ash collector 11 takes place, into the active gasification zone by, for example, blowing gasification agents - air A and water vapor and / or water (depending on the type of gasifier) W - in the ratios necessary for the occurrence of redox gasification (stoichiometric) ratios with gasified gas evym pictures, and resulting from the gasification of the fuel gas G, containing hydrogen H _2, carbon monoxide CO and, in some cases, methane and other hydrocarbons and / or other organic compounds (volatile fractions pair resins), filtered through a bed of charged raw material F and is discharged from the top of the gasification reactor 3. Examples of the technical implementation of direct process gasification reactors are widely known / cm. the above sources: "Biomass as a source of energy ..."; Kopytov V.V. "Gasification of condensed fuels ..."; A. Samylin, M. Yashin. "Modern design of gas generating units." - LesPromInform, No. 1, 2009, p. 78-85).

In the second stage 6, which is an energy (in particular, steam-powered) installation, the resulting fuel gas G is directly (without purification and cooling) burned in the gas furnace 33 of the steam boiler (steam generator) 7, transferring thermal energy to the working fluid (depending on the type of used engine it can be water / steam, organic coolant, gas) through a heat exchanger 34 (which constructively, as a rule, is part of the steam boiler 7), which is then converted into mechanical energy into heat (steam) m tire 8 - an external combustion engine and into electricity by means of an electric generator 9.

In addition to the known two-stage scheme, in the implementation of the proposed method, a fuel preparation section 12 was introduced, where the initial raw material, the biomass F, which is substandard in terms of moisture content, is fed to the gasification using, for example, conveyor 2, continuously or dosed continuously in a drying apparatus 13, for example drum type / GOST 28115-89. Devices and installations drying. Classification. Atmospheric with rotating drums, nozzles /, where it is subjected to convective air-caloriferous drying with heating of the dried material by means of air A as a drying agent, which is forcedly pumped out of the atmosphere through an air condenser (steam-air heat exchanger) 10 of the steam that has been exhausted in the steam engine 8.

Air A in the drying apparatus 13 absorbs moisture during the drying process and is directed to the gasification reactor 3 as the gasification agent in the required (regulated) volume, the excess exhaust air is returned to the atmosphere, and the coolant condensate collected in the condenser 10 is returned to the heat exchanger 34 .

The dried raw material F from the drying apparatus 13 is continuously or metered into the gasification reactor 3 through its loading device 4, the solid mineral residue from the biomass gasification - ash R - is continuously or metered (in batches) discharged through the discharge device 5 (the design of such a device may be different for various types of reactor) in ash collector 11.

The main structural element of the drum-type drying apparatus 13 is, as a rule, a rotating drying drum, in which the solid particles of wet biomass F are mixed and blown by a stream of forcibly circulating drying agent - atmospheric air A, which is both a heat carrier and a desiccant. Biomass F enters the drum through the loading gateway and is removed from it through the discharge gateway.

Direct-flow or counter-flow modes of biomass F and drying agent A can be used (alternatively or alternately). In this case, the drying drum can be installed at an angle to the horizontal to provide the necessary biomass speed (for known technical examples, this is 3-4 °). The rotational speed of the drum can be variable and determined by the parameters of the dried biomass (for well-known technical examples it is 1.5-9 rpm). The inclination of the drum and its rotation provide biomass movement under the action of gravity (and, possibly, air pressure for direct flow mode) from the loading lock to the discharge lock. In the middle part of the drying drum, on its inner side wall, as a rule, blade, sector, screw or other nozzles are installed that provide mixing of the raw material, which intensifies the drying process, providing a large contact surface area between the biomass particles and the drying agent.

At the gasification stage 1, in order to ensure the stability of the process, in particular, an inclined rotating cylindrical gasification reactor 3 can be used, in which gasification is carried out in the filtration combustion mode with super-adiabatic heating, and air and water supplied in a liquid state are used as gasification agents reactor core gasifier (For examples of the technical implementation of reactors see patent RU 2322641 C2, priority dated 05/02/2006, Dorofeenko et al .; patent RU 2376527 C2 priority dated 12/19/2007, Zhirnov, Za Ychenko, Manelis, Polyanchik).

Substandard, i.e. not meeting the standards or technical specifications and requiring preliminary preparation, fuel biomass is a cheap and practically not currently used source of local energy resources. The parameters that determine the conditions of biomass as energy raw materials and on which its cost and, accordingly, the efficiency of its use depend on such performance characteristics as calorific value, total moisture, ash content, carbon content, bulk density, particle shape, fractional composition ( homogeneity), etc. / GOST R 54220-2010 Solid biofuel Technical characteristics and fuel classes. Part 1. General requirements; GOST R 54236-2010 Solid fuel from household waste. Specifications and classes.

The energy, and, accordingly, consumer value of fuel is determined mainly by its calorific value - the amount of energy per unit mass of fuel that can be used to produce heat / electricity. In particular, the quality of biomass as fuel is estimated by the lower calorific value (LF) Q, which is largely dependent on the moisture content of the fuel. Its quantitative indicator - relative humidity (total moisture) W - is one of the most important variable characteristics of the fuel, which largely determines its cost and, ultimately, the efficiency of its energy use in practice.

For reference data / cm. the above sources: Reference book “Boiler houses and biofuel power plants ...; “Biomass as a source of energy ...” / the average relative humidity of low-grade cheap raw materials can be 33 ... 50% for freshly cut timber and 50 ... 80% for wet (transported by water) wood, up to 70% for sludge from urban wastewater, 60 ... 85% - for manure, up to 55% and more - for agricultural waste, 15 ... 35% - for solid waste.

The relationship between the above characteristics can be expressed by the following ratio:

where Δt _w is the temperature of heating the moisture of the raw material from the current value to 100 ° C;

Q _c - NTS of dry matter of fuel;

C _w = is the specific heat of water;

L _γ = is the specific heat of vaporization.

Taking Δt _w = 80 ° (from 20 ° C to 100 ° C); C _w = 4.1872 kJ / kgK; L _γ = 2 250 kJ / kg, we get

The dependence of the STC of the feedstock on its moisture content W for a given range of source data is shown in FIG. 12.

For complete drying of the feedstock, namely the production of 1 kg of dry feedstock, heat energy is required in an amount (kcal):

The experimental data on the energy efficiency of existing small power plants with closed-circuit heat engines (machines) are given in table 1 / cm. sources indicated above: “Use of biomass energy ...”; A. Samylin, M. Yashin. "Modern design of gas generating units." - LesPromInform, No. 1, 2009, p. 78-85 /

We take the following range of parameters of energy efficiency of power plants, including for well-known close analogues:

electrical efficiency η _e = 0.10 ... 0.20; thermal efficiency η _t = 0.45 ... 0.65.

The achievable (potential) level of electrical efficiency η _e ^(y) for the proposed method and device during complete drying of the feedstock due to the heat of the spent steam can be determined as follows:

or

The maximum humidity W _max of the feedstock, at which its intrasystem autothermal complete (to air-dry state) drying is possible (without external energy, namely, due to the utilization (recovery) of "waste" thermal energy at the outlet of the heat engine), can be determined from ratios:

,

,

where γ is the heat transfer coefficient during heat recovery of the exhaust steam,

from here

Substituting (7) into (5), we obtain the expression for the attainable level of electrical efficiency of the device (at W = W _max ):

предлагаемого способа и устройства, которое не зависит от НТС Q_c сухого вещества сырья и превышает электрический КПД η_е известных аналогов в 1,5 раза.The dependences of the electric efficiency η _e ^{(y) of the} device on the relative humidity W of the initial biomass at different values of the TCF Qc of dry biomass are shown in FIG. 13. The dashed line shows the dependence in the range of values W> W _max , where the efficiency η _e ^(y) decreases due to a decrease in the calorific value of the produced gas due to its saturation with water vapor in the gasification reactor / V. Kislov. Gasification of wood and its components in a filtration mode. Abstract of diss. Ph.D. IPCP RAS, Chernogolovka, 2008. - p. 10-13 /. From the graphs it follows that for the practical range of possible values of the parameters of the raw materials (dry-fueled dry matter Q _c = 2000 ... 5000 kcal / kg) and technological processes (thermal efficiency of the power (steam-powered) installation η _t = 0.45 ... 0.65; heat transfer coefficient for drying raw materials γ = 0.5) the technical result, expressed in an increase in electrical efficiency, is confirmed, however, it is uneven, while there is an optimal value of the relative humidity of the feedstock W _opt = W _max and the maximum value of electric Efficiency

the proposed method and device, which does not depend on the NTS Q _c dry matter of raw materials and exceeds the electrical efficiency η _e known analogues in 1.5 times.

Note - The effectiveness of the proposed solutions may be slightly reduced, taking into account the possible operational costs of the electricity consumed by the rotary drying drum, pumps, fans (blowers).

So, according to calculations, the proposed device with a rated electric power of 100 ... 500 kW should have a consumption of raw materials (Q _c = 2000 ... 5000 kcal / kg, W = W _opt = 0.5 ... 0, .7 - see Fig. 5) in the range of 215 ... 1535 kg / h. Existing models of BSL drum-type dryers of a given capacity have a power consumption per drum rotation of 1 ... 4 kW, which does not exceed ~ 1% of the output power.

Taking into account the energy consumption by the fan systems of power plants (~ 0.5 ... 0.7% of the output power), the increase in the share of the minimum required operational energy consumption is within 2% of the output power, which allows us to consider the decrease in the electrical efficiency of the proposed device to be insignificant.

The non-linear character of the dependence of electrical efficiency η _e ^(y) devices from the heat transfer coefficient at at steam and drying the raw material of condensation (FIG. 14) determines the possibility of its significant increase in finding effective technical solutions for heat recovery of exhaust steam (especially in γ> 0 values, 5).

Taking into account the temperature of the spent (“crumpled”) steam for the proposed types of heat (steam) machines, drying can only be realized only to the air-dry state of the raw material, i.e. with the removal of external (hygroscopic) moisture. At the same time, fuel biomass, depending on its origin, in particular wood, may also contain reaction (chemical) moisture (up to 20 ... 25%), which is separated at a temperature of 150 ... 220 ° C.

To remove it at the fuel preparation section 12 between the drying apparatus 13 and the gasification reactor 3, a drying and filter apparatus 14 is additionally introduced through which the flue gas Fg leaving the gas furnace 33 of the steam boiler (steam generator) 7 passes through, drying and heating the feed F loaded from drying apparatus 13 and discharged into the gasifier reactor 3 through its loading device 4.

Drying and filtering apparatus 14 (Fig. 2-5) works as follows.

The biomass F, dried in the drying apparatus 13, is continuously or dosed through the loading gateway 15 into the internal cavity of the conical drum 16 to the level 17, covering the perforated chimney 18, into which the smoke (flue) gases Fg from fuel gas combustion G. When the cone drum 16 is rotated by means of nozzles 19 (blades, blades, ribs, etc.) mounted on its inner surface, raw materials are mixed, flue gases as a heat carrier and moisture the absorbers penetrate the voids formed during this, heating and drying the moving particles of raw materials, and pass through a ring strainer - biomass cutter 20 with a shutter 29 into the smoke collection cone 21, from where through an organic adsorber 22 with working filtering elements and a chimney 23 using an exhaust fan 24 are released into the atmosphere. Purification of exhaust flue gases from ash particles that may be present due to the burning of crude fuel gas is carried out by filtering the flue gases through the biomass in the cone drum 16, as well as (fine finishing) with the multi-layer filter elements of the adsorber 22 (analogue is the scheme of the soot trap with multi-layer nozzle, Vetoshkin AG Processes and apparatuses for gas purification. Textbook. - Penza: Publishing house of PSU, 2006, p. 179), consisting of an organic filter material / carbon adsorbent (for example, based on activated carbon, peat, sorption-active carbon fibrous materials, etc., it is also possible to produce from the same wet biomass), which also purifies the exhaust flue gases from dust contaminants that may appear after drying and heating of the biomass in the conical drum 16. The cartridges with the spent organic filter material are alternately replaced with new replaceable cartridges 25 as they are worked out, the stock of which is stored in the pipe closed by the shutter 28 using a pusher 26, p Bulking into particles and doing the processing with biomass through the discharge sluice 27.

According to experimental data, the energy balance of thermal power plants includes heat loss with flue gases, which can be ~ 8 ... 10% of the energy of the original fuel / see the above source: Reference. “Boiler houses and biofuel power plants ..., p. 226 /. Taking the heat transfer coefficient as a result of the process of drying and heating the biomass with flue gases (temperature 180 ... 350 ° C and more) in the bunker-heater 14 in the range of 0.3 ... 0.5 and using expression (7) taking into account the corresponding increment of the electric values (η _e + Δη _e ) and thermal (η _t + Δη _t ) efficiency (for the accepted initial values η _e = 0.2 and η _t = 0.65) we obtain that the increment Δη _e ^{(y) of the} total electrical efficiency of the device can be ~ 0.02, which gives a total

increase in achievable electrical efficiency η _e ^{(y) of the} device to 0.32.

In addition, the complete drying and heating of the biomass in the drying and filtering apparatus 14 can reduce the requirements for the design of the gasifier reactor 3 in terms of its size, since the drying zone, as well as the heating and pre-pyrolysis of gasified raw materials, can be eliminated.

For greater compactness of the equipment, as well as reducing heat loss (increasing the efficiency of heat transfer, i.e., heat transfer coefficient γ), it is advisable to structurally dry the drying apparatus 13 and the drying and filtering apparatus 14 into a single drying unit 30 (Fig. 6). The air after the air condenser 10 is pumped directly into the internal cavity of the rotary drying unit 30, where the raw material F is additionally conductively (contact) heated by flue gases while passing through the muffled chimney 18 with a perforated end section. The mixture of flue gases and air from the inner cavity of the drying unit is filtered through an organic adsorber 22 before being discharged into the atmosphere.

A feature of the invention in the case of the use of the Stirling engine (Fig. 7) is the construction of the circulation circuits of the working fluid, which is used as a gas. Fuel gas G is burned in a mixture with atmospheric air A in an external gas furnace (combustion chamber) 33, hot combustion products enter a hot heat exchanger 34, which is part of the Stirling engine 31, where they transfer their heat to the working fluid of the kinematic part (cylinder block) 32 of the engine and as the exhaust flue gases F _g fed to the drying section 30. The working fluid is cooled by the heat exchanger 10 is a heat exchanger-cooler part of the Stirling engine 31) through the discharge weatherp Foot air A, which is then fed to a drying unit 30. A number of modifications of the Stirling engine to increase efficiency is provided the use of a special heat exchanger - heat regenerator 35.

Claims (11)

1. A method of producing electricity from substandard (wet) fuel biomass according to a two-stage technological scheme, providing for the first stage to supply the feedstock - shredded (if necessary) fuel biomass of various origins and its vapor-air gasification in a dense layer in a direct process gasifier, in the process of gasification in countercurrent to the movement of raw materials through the lower part of the gasifier reactor, where the accumulation and withdrawal of solid products - gasification waste (ash), gasification agents — air and water vapor and / or water — are supplied to the active gasification zone by, for example, blasting, in the ratios necessary for the occurrence of oxidation-reduction gasification reactions with gasified raw materials, and the combustible fuel gas resulting from gasification is filtered through the layer loaded into the reactor gasifier of raw materials and is removed from its upper part for use in the second stage, including the combustion of the resulting fuel gas with the conversion of thermal energy into mechanical energy by means of a heat (steam) machine and into electric energy by means of an electric generator, characterized in that the feedstock for electric power production is subjected to complete deep drying, including convective air-caloriferous drying to remove external (hygroscopic) moisture using the heat spent in thermal machine of the working fluid (in particular, steam) through its air cooling and, possibly, condensation in a closed circuit of the working fluid, as well as duct-convection drying by exhaust flue (furnace) gases to remove residual, including reaction (chemical) moisture. 2. The method according to p. 1, characterized in that after the air-caloriferous drying of raw materials, the exhaust air in the required (controlled) volume is supplied to the gasification reactor as a gasifying agent. 3. A device for producing electricity from substandard (wet) fuel biomass according to a two-stage technological scheme, including a conveyor for supplying raw materials - crushed fuel biomass of various origin - to the gasification reactor of the direct process of vapor-air gasification in a dense layer, having a loading device with a lock chamber in the upper parts and unloading device with a collection of gasification waste (ash) in the lower part, as well as an outlet in the upper part for supplying fuel gas resulting from gasification, for burning in a gas furnace (combustion chamber), external or as part of a steam boiler (steam generator), connected or combined with a heat exchanger-heater of the working fluid of a heat engine, in particular in a steam boiler (steam generator) , to the lower part of the gasification reactor, there are inputs for supplying, for example, blowing gasification agents - air and water vapor / water in countercurrent to the movement of raw materials into the active gasification zone, while the output of the heat exchanger is a working fluid heater, in particular a steam boiler (steam generator), is connected to the input of a heat (steam) machine, which is structurally connected to an electric generator, characterized in that it includes a fuel preparation section as part of a drying apparatus for convective air-caloriferous drying of the feedstock and a drying and filtering apparatus for conductively convective drying of raw materials with exhaust flue gases, as well as a closed loop for circulating the working fluid (in particular, water / steam or organic heat a cooler) of a heat (steam) machine, formed by introducing into the device a heat exchanger-cooler of the working fluid (in particular, an air condenser of spent steam), while the input of the heat exchanger-cooler is connected to the outlet for the spent working fluid of a heat (steam) machine, the output of the heat exchanger -cooler is connected to the inlet of the heat exchanger-heater of the working fluid, moreover, the heat exchanger-cooler also has an inlet for a cooling agent - injected atmospheric air, and an outlet for exhaust air spirit through the dryer to the gasifier reactor for controlled supply as a gasifying agent, as well as to the atmosphere, while the dryer is equipped with a gateway for loading the feedstock and a gateway for unloading the dried feed into a rotating cone-cylindrical drying and filtering apparatus installed in a horizontal position and equipped with an axial perforated chimney pipe plugged at one end connected to a heat exchanger-heater of the working fluid, in particular a steam boiler (steam generator), for supplying exhaust flue (furnace) gases into it with their passage into the internal cavity of the rotary drying filter apparatus equipped with a discharge gateway for loading the dried raw materials into the gasifier reactor, the internal cavity of the drying filter apparatus having an outlet to the atmosphere for exhaust flue gases through The organic adsorber installed in it with replaceable filter elements, which, after their change, enter the gasifier reactor together with the dried feed. 4. The device according to p. 3, characterized in that the drying apparatus and the drying and filtering apparatus are structurally combined into a single rotating conical-cylindrical drying unit, placed in a horizontal or inclined position, with an entrance to the internal air cavity from the air condenser and axial a chimney pipe, partially perforated in the final section in front of the blanked end. 5. The device according to p. 3 or 4, characterized in that for the gasification of fuel biomass a cylindrical inclined rotating reactor-gasifier is used in the filtration combustion mode with super-adiabatic heating. 6. The device according to claim 3 or 4, characterized in that a condensing type steam turbine is used as a heat engine. 7. The device according to p. 3 or 4, characterized in that a steam screw machine is used as a heat engine. 8. The device according to p. 3 or 4, characterized in that a steam piston engine is used as the heat engine. 9. The device according to p. 3 or 4, characterized in that the heat engine uses a Rankine Organic Cycle Turbine (ORC) with an organic coolant as a working fluid. 10. The device according to p. 3 or 4, characterized in that the Stirling engine with a gas coolant as a working fluid and an external gas furnace is used as a heat engine, while the heat exchanger-heater and the heat exchanger-cooler of the working fluid are part of the Stirling engine and in special cases, engine modifications are interconnected by means of a heat regenerator.

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