RU2631455C1 - Method of producing electricity from substandard (wet) fuel biomass and device for its implementation - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: method involves the production of electricity in a two-stage process scheme with the gasification of raw materials in a gasification reactor of the direct steam-air gasification process in a dense layer, in particular a cylindrical inclined rotary gasification reactor in the filtration combustion mode with superadiabatic heating, followed by direct combustion of the resulting hot fuel gas and conversion of the thermal energy of the resulting steam into electricity through a thermal (steam) machine and an electric generator. The invention provides for the recovery of the "waste" heat of the exhaust steam by condensing it in a closed loop of the working fluid (water/organic coolant) of the thermal (steam) machine through the two-stage air cooling scheme, including a continuous interstage combined convective air-heater and conductive (contact) drying of the initial raw materials in the condensation-drying unit, the air used in the required volume is supplied to the gasification reactor as a gasifying agent. The embodiment of the invention is assumed by introducing a condensation drying unit in the device connected to the output of a thermal (steam) machine for exhaust steam and constructively representing the two-stage air condenser of steam comprising a steam pipeline in the form of series-connected units - a module of the 1st stage of condensation, a steam and condensate drain with the integrated (built-in) rotating drying drum, a module of the 2nd stage of condensation. It is proposed to use different types of thermal (steam) machines - a steam turbine, a steam screw machine, a steam piston engine, an organic cycle turbine.

EFFECT: invention allows to increase the electrical efficiency and expand the range of cheap low-grade raw materials used in terms of substandard, including moisture content, fuel biomass, including utilized substandard solid municipal waste, while minimizing the harmful impact on the environment and ensuring the autonomy of the power generation process.

10 cl, 9 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

A method of producing electricity from substandard (wet) fuel biomass and a device for its implementation

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 the possibilities for its growth in the framework of existing technologies are limited because most of the energy to the so-called "waste" heat that is often 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 the associated electric generator generating electric energy / Reference. “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 ...”, p. 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 that 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 boiler chamber (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 source indicated above: “Use of biomass energy ...”, sect. 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;

- cumbersome equipment (primarily steam condensers).

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 status and development prospects - M .: Infra-Engineering, 2012. - 504 s; 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 generating 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, implemented in a gas-generating electric power plant / cm. The above reference. “Boiler houses and biofuel power plants ...”, 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 / cm. source indicated above: G.G. Tokarev. "Gas-generating cars ..." /, however, it has significant disadvantages:

- 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, NO _x ) 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: a significant specific gravity per unit of power and dimensions, the presence of a complex multistage system for cleaning, cooling and drying gas, a 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 the gasification of fuel biomass in the first stage and burning of the resulting fuel gas and the conversion of thermal energy into mechanical energy in a heat engine (engine) are largely free from these drawbacks. closed loop, where the working fluid circulates in a closed loop without communication 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 based on well-known closed-cycle engines (PTU, PDP, FDA, ORC turbine) can be used.

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, Kopytov V.V. Gasification of condensed fuels: a retrospective review, current state of affairs and development prospects - M .: Infra-Engineering, 2012. - 504 p., 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, blasting (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 a 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 gasifier reactor as a gasification agent in the volume necessary for gasification reactions, flue gases are filtered by a purifier with lime (a special sulfur neutralizing filter) and emissions They are emitted 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.

Technical results 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, followed by the conversion of the thermal energy of the fuel gas burned in a steam boiler (steam generator) into electricity through a heat (steam) machine with an electric generator secondly, in expanding the spectrum of used cheap low-grade raw materials, including substandard (in terms of moisture content up to 70 ... 85%) fuel biomass, and are achieved due to the fact that for A closed working circuit of a steam-powered installation for circulating a working fluid (water / steam or an organic coolant) is formed by a two-stage air cooling system for exhaust steam combined in a condensation-drying unit with processes of continuous continuous (permanent) convective air-caloriferous drying and conductive heating of raw materials due to heat of condensed steam, and the air used for cooling and drying in the required volume is used in the gasification reactor as gasification agent.

In this case, the condensation-drying unit is structurally performed as a two-stage air condenser of the steam spent in the heat (steam) machine, into which the drum-type dryer is integrated (built-in).

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:

- use as a raw material of a renewable resource - biomass,

- implementation of a two-stage scheme with biomass gasification,

- the use of energy (steam-powered) closed-cycle installations;

in terms of reducing (eliminating) the harmful effect (pollution, violation of the natural temperature regime) on water resources - by completely replacing water cooling to remove the "waste" heat during condensation of the coolant (steam) by air cooling.

Fourth, the technical result is expressed in ensuring in the proposed invention 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 an air-cooled exhaust steam condenser;

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 operating range of the rated output electric power, as well as improving the operational and technical characteristics during the implementation of the invention, such as working in a wide range of energy consumption and various steam quality, full automation of processes, compact equipment for gasification biomass a cylindrical inclined rotary gasifier reactor is used in the filtration combustion mode with super adiabat eskim heating, and as heat (steam) engines can be applied to different types of external combustion engines of the closed cycle (PTU, PDI, PVM, ORC turbine).

The invention is illustrated in FIG. 1-9.

In FIG. 1 shows a general diagram of a device for implementing a method for producing electricity from substandard (wet) fuel biomass according to a two-stage scheme with air-caloriferous drying and conductive (contact) heating of raw materials by means of a condensation-drying unit in a closed working circuit of an energy (steam-power) installation

In FIG. 2 shows a general diagram of a device for implementing a method for producing electricity from substandard (wet) fuel biomass according to a two-stage technological scheme with air-caloriferous drying and conductive heating of raw materials in a closed working circuit of an energy (steam-powered) installation when using a cylindrical inclined rotary reactor-gasifier for gasification in the filtration combustion mode with super-adiabatic heating.

In FIG. 3-6 shows a construction diagram of a condensation-drying unit according to FIG. 1, including a general view (FIG. 3), section AA through the dryer drum according to FIG. 3, section BB along the loading gateway according to FIG. 3, section BB of the discharge gate according to FIG. 3.

In FIG. Figure 7 shows graphs of the dependence of the lower calorific value (STV) of the initial biomass on its relative humidity (total moisture).

In FIG. Figure 8 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 practically feasible range of device operating parameters (heat transfer efficiency during steam condensation and drying of raw materials, electrical and thermal efficiency).

In FIG. Figure 9 shows a graph of the electrical efficiency of the proposed device versus the heat transfer efficiency during steam condensation and drying of raw materials (heat recovery from a steam-powered plant).

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, gasification of the crushed (if necessary) biomass F in the gasification reactor 3 of the direct process of vapor-air gasification in a dense layer is provided. The raw material enters the gasifier reactor 3 through the loading device 4, while in countercurrent to the movement of the raw material F through the unloading device 5, where the solid products - gasification waste (ash) R are accumulated and removed, gasification flows are fed into the active gasification zone, for example, by blowing agents - air A and water vapor and / or water W - in the ratios required for the occurrence of redox gasification (stoichiometric) ratios with gasified raw materials, and g hot 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, resin vapors), is filtered through a bed of loaded raw material F and is discharged from the top of the reactor -gasifier 3. Examples of technical implementation of direct process gasification reactors are widely known / see 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 ...").

In the second stage, the resulting fuel gas G is directly (without purification and cooling) burned in a steam boiler (steam generator) 7 equipped with a gas burner, the thermal energy of the steam is converted into mechanical energy in a thermal (steam) machine 8 - an external combustion engine, and into electrical energy by means of an electric generator 9, while part of the spent steam can be selected for supply to the gasification reactor 3 as a gasification agent in the volume necessary for gasification reactions (for gasification reactors in a steam-blowing). As an alternative to steam, for some designs of gasification reactors, it is possible to supply liquid in the active zone.

In addition to the known two-stage scheme, in the implementation of the proposed method, the initial raw material — fuel biomass F substandard in moisture content — is fed continuously or dosed continuously through a loading gateway 23 into the drying drum 15 of the drying and condensing unit 2 before being fed to gasification using a conveyor 1 steam from the output of the heat (steam) machine 8 is passed through the inlet pipe of the steam line 21 into the cone-shaped module of the 1st stage of condensation 16, which is a steam air heat exchanger - radiator / examples of technical implementation, see Klevtsov A.V., Pronin V.A. “Air-cooled TPP condensers. Ecology of Energy ”: a textbook for students enrolled in the field of“ Power Engineering ”, Sec. 7.1.5. M .: Publishing House MPEI, 2003; Yushkov B.V. "Development of a new generation air condenser and study of its characteristics." Diss. Candidate of Technical Sciences, M., 2001 - 234 pp. /, where it passes through a bundle of finned tubes blown by atmospheric air A, which is sucked in from the outside by means of a blower 18 into the internal working cavity 28 of the drying drum 15, where solid particles wet biomass F, mixing, blown by a stream of drying agent - heated by the heat of the exhaust steam of atmospheric air A, which is both a heat carrier and a desiccant.

The steam is cooled and partially condensed, and the remaining non-condensed part of the steam is passed through the steam bypass and condensate drain manifold 27 to the module of the 2nd condensation stage 17, similar in design to the module of the 1st condensation stage 16, through the heat-conducting wall of the drying drum 15 gives heat to wet biomass particles that are intensively in contact with the heat transfer surface of the inner working cavity of the drum 28 during the drying process, and the draining condensate is collected in the collector 27 and is discharged through the pipe the pipeline 20 to the feed water tank 14, returning to the working circuit of the power (steam-powered) installation 6, while the non-condensed gases are finally sucked off by the ejector 22.

The collector 27 is the space between two coaxial cylinders, the inner one is a rotating drying drum 15, the outer one is a fixed shell (casing).

During drying, alternate-flow or counter-flow modes of biomass F and a drying agent, air A, can be used (alternatively or alternately), for which one of two symmetric loading and unloading schemes is used. (A variant of the placement of loading 23 and unloading 24 locks when implementing oncoming movement of biomass and drying agent (air) is shown by the dotted line in Fig. 3). In this case, the drying drum 15 can be installed at an angle to the horizontal to provide the necessary biomass speed F (for known technical examples, this is 3-4 °). 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 gateway 23 to the discharge gateway 24. The frequency of rotation of the drum can be variable and determined by the parameters of the dried biomass (for known technical examples, this 1.5-9 rpm), side and angle of the drum can also vary.

On the inner surface of the drying drum 15, blade, sector, screw or other nozzles 30 are installed, providing mixing of the raw material and its uniform distribution over the cross section of the drum, which intensifies the drying process, providing a large contact surface area between the biomass particles and the drying agent.

The drying drum 15 is closed from the ends by mesh filters - biomass cut-offs 26, which limit the biomass movement and direct it to the discharge gateway 24 using nozzles 30 on remote console holders 31.

The flow of the drying agent — air humidified and cooled as a result of drying the biomass — is directed by an exhaust fan 19 to blow around the finned tubes of the cone-shaped module of the 2nd condensation stage 17, in which the steam condensation is completed, and the exhausted (heated and humidified) air in the required (regulated) ) the volume is sent to the gasification reactor 3 as a gasifying agent, and its excess is returned to the atmosphere.

As a thermal (steam) machine 8, an external combustion engine with a closed thermal cycle (in particular, a steam turbine, a steam piston engine, a steam screw machine, a Rankine organic cycle heat turbine) is considered. For a special case of using an ORC turbine as a heat engine, the working fluid of the heat engine is an organic heat carrier.

In the particular case of using at the gasification stage an inclined rotating cylindrical gasifier reactor 3 (Fig. 2) with a charging device 4 with a lock chamber and a vertical cylinder, gasification is carried out in the filtration combustion mode with super-adiabatic heating, and air and water are used as gasification agents, fed in a liquid state to the active zone of a gasification reactor 3 (Examples of technical implementation of reactors see patent RU 2322641 C2, priority dated 05/02/2006, Dorofeenko et al .; patent RU 2376527 C2 priority of 12/19/2007, Zhirnov, Zaichenko, 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. sources indicated above: Handbook. “Boiler houses and biofuel power plants ...”; “Biomass as an energy source ...”, / 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 _y = is the specific heat of vaporization.

Taking Δt _w = 80 ° (from 20 ° C to 100 ° C); C _w = 4.1872 kJ / kgK; L _γ = 2250 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. 7.

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 Wmax of the feedstock, at which its intrasystem autothermal (without energy from the outside, namely due to the utilization (recovery) of "waste" heat energy at the outlet of the heat engine) drying is possible, can be determined from the ratio:

,

,

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

from here

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

Investigate how the amount of electric efficiency η _e for deviation parameter [W, Q _c] raw material depending on the current relative humidity W of the feedstock in the range of possible values W = (0; W _before), where the limiting value of the relative humidity of the feedstock

a) For the case 0 <W <W _{max, the} current 'electrical efficiency is determined by the relation (5),

b) For the case W _max <W <W _before, it is necessary to take into account the system heat losses due to the humidity of the resulting fuel gas / Kislov V.M. Gasification of wood and its components in a filtration mode. Abstract of diss. Ph.D. IPCP RAS, Chernogolovka, 2008. - p. 10-13 /.

The STC of the feedstock is determined by (1), the STV of the dried raw material is defined as:

where C _VP - specific heat of water vapor,

Δt _VP = heating temperature of water vapor in flue gases,

ΔW - humidity reduction as a result of drying.

Taking With _VP = 2510 J / kg, Δt _VP = 125 ° and supplying numerical values to (10), we obtain:

Given the drying of raw materials, the following ratio is true:

Substituting (12) in (11) we obtain

Defining the electrical efficiency of the device as

and, substituting (13) in (14), we obtain the resulting expression for the electrical efficiency of the device:

at the specified limit value of relative humidity:

The plots of the electric efficiency η _e ^{(y) of the} device as a function of the relative humidity W of the initial biomass for different values of the TCF Q _{c of} dry biomass are shown in FIG. 8.

Note: Some approximation of the calculations is due to the fact that taking into account the temperature of the exhausted (“crushed”) steam for the proposed types of heat (steam) machines, drying can only be realized only to the air-dry state of the raw material. At the same time, fuel biomass, depending on its origin, in particular wood, may also contain reaction (chemical) moisture, the separation of which begins at temperatures above 150 ° C.

Regarding the effectiveness of the proposed technical solutions, the following conclusions can be made.

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.1. For a range of possible values of raw parameters (STRP solids Q _c = 2000 ... 5000 kcal / kg) and process (heat energy efficiency (steam power) Fitting η _m = 0.45 ... 0.65, the heat transfer coefficient on the raw material drying γ = 0.5) the technical result, expressed in an increase in electrical efficiency, is confirmed, however, it is uneven, and there is an optimum value of the relative humidity of the feedstock W _opt = W _max ∈ (0.42 ... 0.72), and the maximum electrical efficiency value

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 somewhat reduced, taking into account the possible operational costs of the energy consumed by the rotating dryer 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.

указанная граница соответствует значениям W_доп=0,7…0,85, что существенно выше возможностей рассмотренных выше аналогов (W_доп=0,2…0,5) и подтверждает достижение технического результата, заключающегося в расширении спектра материалов, а именно по параметру влажности, используемых в качестве сырья для производства электроэнергии.2. The upper limit of the range of acceptable values of humidity W _additional feedstock can be determined based on requirements for energy efficiency. In particular, subject to

the specified boundary corresponds to the values of W _add = 0.7 ... 0.85, which is significantly higher than the capabilities of the above analogues (W _add = 0.2 ... 0.5) and confirms the achievement of the technical result, which consists in expanding the spectrum of materials, namely, the parameter humidity used as raw material for electricity production.

устройства от коэффициента теплообмена γ при конденсации пара и сушке сырья (фиг. 9) определяет возможности его существенного повышения при эффективной рекуперации тепла отработавшего пара (при γ>0,5). В предлагаемом изобретении это достигается за счет:3. The non-linear nature of the dependence of electrical efficiency

the device from the heat transfer coefficient γ during steam condensation and drying of the raw material (Fig. 9) determines the possibility of its significant increase with effective heat recovery of the exhaust steam (for γ> 0.5). In the present invention, this is achieved due to:

- exclusion of air ducts and, accordingly, heat losses between the condensation modules and the drying apparatus (drum);

- use in addition to the convective also conductive heat transfer mechanism when drying raw materials.

The intensification of heat transfer processes and a corresponding increase in the heat transfer coefficient γ is achieved by the fact that the wet biomass particles are in intensive contact with the internal heat transfer surface of the drying drum 15 during the drying process (the intensification mechanism is analogous to mixed dry cooling towers using evaporative cooling with irrigation of the radiator with water).

The proposed technical solution also makes it possible to smooth out the dependence of efficiency (electrical efficiency) on the ambient temperature (cold air is more efficient in heat exchange with steam, hot air in drying biomass).

Claims (10)

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 burning the resulting fuel gas in a steam boiler (steam generator), converting those steam energy into mechanical energy in a heat (steam) machine and into electric energy by means of an electric generator, characterized in that in the second stage they form a closed loop of the working fluid (water / steam or organic coolant) circulation of the heat (steam) machine, in which the condensation of the spent the steam is produced according to a two-stage air cooling scheme, including a continuous interstage combined - convective air-calorifer and conductive (contact) - drying of the feedstock into dryer-drying unit, while the dried raw material is fed into the gasifier reactor. 2. The method of generating electricity according to claim 1, characterized in that the air used in the condensation-drying unit in the required controlled volume is supplied to the gasification reactor as a gasifying agent. 3. A device for generating electricity from substandard (wet) fuel biomass, including a conveyor for feeding raw materials - crushed solid 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 part and an unloading device with a hopper for collecting gasification waste (ash) in the lower part, as well as an outlet in the upper part for supplying fuel gas resulting from gasification for combustion in steam in the boiler (steam generator), the inputs for supplying, for example, blowing gasification agents - air and water vapor / water into the active gasification zone in countercurrent to the movement of raw materials, are connected to the lower part of the gasification reactor, while the steam boiler (steam generator) is connected to the feed tank water, and its output for the produced steam is connected to the input of a heat (steam) machine, which is structurally connected to an electric generator, characterized in that it has a closed circulation circuit of the working fluid (water / steam) thermal (pa a new) machine formed by introducing into the device a condensation-drying unit connected to the output of a heat (steam) machine for exhaust steam and structurally representing a two-stage air steam condenser containing a steam pipe in the form of series-connected units - the module of the 1st stage of condensation, steam bypass collector and condensate drain with integrated (built-in) rotating dryer drum, module of the 2nd stage of condensation, while the module of the 1st stage of condensation is an image is a cone-shaped bundle of finned heat exchanger tubes, inlet openings connected to the steam inlet pipe, and outlet openings connected to the steam bypass and condensate drain manifold and arranged so that there are distances between them for the passage of atmospheric air, for which forced axial circulation is established directly behind the tubes a fan for pumping air into the dryer drum, which is a rotating cylinder, inside of which there is a pneumomechanical e the movement of raw materials due to rotation and forced circulation of air, and the collector for steam bypass and condensate drainage is formed by the outer surface of the drying drum and the shell (casing) that is stationary with respect to the drum, and the walls of the drum are a heat exchange surface, the inner space of the collector closes to the inlets of the conical beam finned heat exchanger tubes of the module of the 2nd stage of condensation, arranged so that between them there are distances for the passage of air from the inside the lower cavity of the dryer drum into the atmosphere, for which an axial exhaust fan is installed directly in front of the tubes, the exits of the heat exchange tubes are closed to the ejector, the dryer drum is equipped with at least one loading gateway for feedstock supplied by a feed conveyor, and at least one discharge gateway for reloading dried raw materials in a gasifier reactor. 4. A device for generating electricity according to claim 3, 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. 5. A device for generating electricity according to claim 3 or 4, characterized in that a condensing type steam turbine is used as a heat (steam) machine. 6. A device for generating electricity according to claim 3 or 4, characterized in that a steam screw machine is used as a heat (steam) machine. 7. A device for generating electricity according to claim 3 or 4, characterized in that a steam piston engine is used as a heat (steam) machine. 8. A device for generating electricity according to claim 3 or 4, characterized in that the Rankine Organic Cycle Turbine (ORC) with organic heat carrier as a working fluid is used as a heat (steam) machine. 9. A device for generating electricity according to claim 3, characterized in that the drying drum has one or more loading locks and one or more discharge locks for the dried raw materials with the possibility of operating in continuous and / or metered loading / unloading, direct-flow (raw and air moves in one direction) and / or countercurrent (raw materials and air move in opposite directions) drying with the possibility of varying the angle of inclination (together with the condensation-drying unit and / or independently) during operation For the movement of air inside the drum, the rotation speed of the drum, on the inner surface of the drum, blades, blades, spiral ribs or other nozzles are attached to mix and move the raw materials. 10. A device for generating electricity according to claim 3, characterized in that the exhaust air outlet of the condensation-drying unit is also connected to a gasification reactor for controlled blasting.

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