Process and equipment for drying biogenic solid fuel

Abstract

A method for drying biogenic solid fuel, in particular wood, by means of a heated air-steam flow guided through the solid fuel (3) in a drying chamber (1), in which the heating device is fed from a biomass power plant which contains a boiler with a combustion chamber, a steam turbine (14) for generating electrical energy and a steam circuit with a condenser (29) for steam recooling, wherein the solid fuel (3) is heated by an air-steam flow which is heated by means of superheated steam diverted from an intermediate turbine stage, which is guided through the drying chamber (1) via pipes (30, 31) and which, after passing through the drying chamber (1), is returned as steam condensate to the main condensate section (33) of the turbine (14), wherein the vapors emerging from the solid fuel (3) during drying enter a superheated state,and wherein in the vapor condenser (7), the condensation of the vapor takes place in heat exchange with a condensate circuit (9) branched off from the main condensate section (33) of the turbine (14), wherein the air-vapor flow is heated by a heating device to a temperature which converts the moisture escaping from the solid fuel (3) as vapor into a superheated state, wherein the solid fuel is continuously passed through the drying chamber (1), and wherein excess vapor from the drying chamber (1) is condensed via a vapor condenser (7), and the superheated steam branched off from the turbine intermediate stage, at its steam temperature and at a pressure increased relative to the atmosphere, is passed through the drying chamber (1) in pipelines running in stages, which thereby heat the vapor flow conducted through the solid fuel. characterized in that - the solid fuel (3) is guided through the drying chamber (1) in a pushing process, wherein the solid fuel is moved in alternating directions through pushing sections arranged one above the other in tiers and designed to be gas-permeable, and wherein the solid fuel conveyed over the pushing sections is heated in each case by the air-steam flow which passes through the pipes running between the pushing sections arranged in tiers and is thereby superheated.

Description

[0001] The invention relates to a method according to the preamble of claim 1 and a device according to the preamble of claim 6 for drying biogenic solid fuel, in particular wood with a high moisture content for supplying fuel to a steam power plant.

[0002] Power plants fired by solid fuels such as wood, coal, and similar fuels can operate more efficiently when the fuel contains little moisture. Biogenic fuels generally have a high moisture content. Therefore, the combustion of biogenic fuels generally requires pre-drying to reduce high moisture levels, such as 50% for fresh wood, to around 10% before feeding it into the furnace. This can result in fuel cost savings of up to 20% compared to feeding undried wood.

[0003] While fuel drying can also be easily achieved through dry storage, this is uneconomical and logistically difficult to manage in a large power plant with electrical outputs exceeding 10 MW. Therefore, fuel drying is usually achieved through active air drying, in which the fuel is circulated in a drying bed with either heated or more or less dry air. The air can only absorb moisture up to a certain saturation level, which depends on the air temperature and the existing humidity. The required drying times can therefore be considerable.

[0004] In some cases, surplus heat is available from existing heating or power plant facilities that can be used for fuel drying. However, drying is generally associated with considerable costs, so it is desirable to recover some of the heat energy used for drying, e.g., by recovering latent heat of vaporization, and then transfer it to other consumers. However, this requires only a relatively low temperature.

[0005] EP744012B1 discloses a process for drying wood by circulating hot air around and through one or more stacks of wood that are treated in batches. The wood is first heated to a starting temperature for drying, then the actual drying process is carried out, and then re-humidified to prevent cracks and tensions caused by the drying process. Humidification is achieved by saturated water vapor supplied during the heating phase, which condenses on cooler wood surfaces.

[0006] However, when using wood as fuel, rehumidification is counterproductive.

[0007] In a wood drying system known from EP1118828A1, wood is also heated in batches in a treatment room. The resulting gases are combusted outside the treatment room and used to heat the treatment room itself, or alternatively, are passed through a condenser to recover valuable extracts from the resulting gases.

[0008] EP0457203A1 discloses the emission-free drying of substances in a drying drum. The described process is carried out in such a way that no unpleasant odors or dust are emitted to the outside by closing the drying circuit. Fossil fuels are used as the heat source for the burner to heat the air stream for drying.

[0009] Furthermore, DE202008005991 U1 discloses a system for converting thermal energy into electrical energy. The system comprises a heat exchanger whose cooling circuit is connected to a drying chamber. A vacuum drying process is carried out in the drying chamber.

[0010] DE 19518644 A1 a device for generating process steam, in which hot steam is taken from a tapping of the turbine to heat a continuously conveyed solid fuel.

[0011] WO2012075518A1 discloses another method for drying wood, in which moist wood is heated in a pre-drying chamber with heated supply air drawn in via a cross-flow heat exchanger. In a main drying chamber, the wood is then exposed to circulating air circulated via a heating register. A partial flow of this air is removed as exhaust air and replaced by supply air, which is heated in the cross-flow heat exchanger to achieve heat recovery.

[0012] It is also known to dry wood in batches using steam. However, leaks or a lack of insulation can easily result in cold spots during the drying process, where the steam condenses, thus increasing the residual moisture content in the wood. While a relatively large proportion of the heat used can be recovered by using a condenser, suitable heat consumers are rarely available.

[0013] A further problem arises when wood is dried down to low moisture levels: due to exothermic processes, precautions must be taken in the relevant storage containers or silos to prevent spontaneous combustion, such as inerting with neutral gases.

[0014] In a steam power plant using fossil or biogenic fuels, the thermal energy generated by combustion is converted into electrical energy in a steam turbine. To achieve high energy conversion efficiency, certain volumes of the water-steam cycle of such a power plant are passed through various heat exchangers, for example, to preheat the feedwater. For this purpose, steam is extracted at a suitable point in the turbine and condensed in a heat exchanger. Part of the condenser waste heat from the main condensate line can also be used to supply additional heat consumers.

[0015] Another known method for pre-drying fuels is to use waste heat from a power plant, which is passed through the fuel via a heated air stream. A significant problem here is that the dried fuel must be inerted with nitrogen or other inert gases to prevent the risk of fire from spontaneous ignition in the fuel bunker or during transport.

[0016] It is also known that the vapors, an air-steam mixture produced during the drying of biogenic fuels with high moisture content, can either be released into the atmosphere or used economically for energy recovery, e.g., to generate hot / heating water, whereby the heat exchangers used must be adapted to the specific properties of the vapors.

[0017] The invention is based on the object of specifying a method and a device for drying biogenic solid fuel, in particular wood chips, in which both a high drying performance can be achieved and an economical heat recovery is possible.

[0018] In particular, the invention is based on the object of using such a method or such a device in a biomass power plant in such a way that the overall efficiency of the power plant is improved and the operating costs of the power plant can be significantly reduced.

[0019] This object is achieved by a method according to claim 1 and a device according to claim 6 and claim 9, respectively. Advantageous developments of the invention are specified in subclaims.

[0020] According to the process according to the invention, the fuel is continuously passed through a drying chamber in which a heated air stream circulates, heating the solid fuel to such an extent that moisture escaping from the solid fuel is superheated, thus drying the wood. The air stream mixes with the steam escaping from the solid fuel to form vapor, the air-steam mixture. Excess vapor is condensed in a condenser.

[0021] A device according to the invention contains a solid fuel bunker from which the moist solid fuel is continuously discharged and guided via a conveyor line through a drying chamber, which then leaves the chamber for discharge into an intermediate storage facility. The conveyor line is designed in tiers, each with drop stages at its end, with the individual tiers containing pipes through which superheated steam is passed. This steam heats the air or vapor flowing between the pipes, which in turn heats the solid fuel as it flows further through it. The vapor is heated to such an extent by the steam in the pipes that the moisture escaping from the solid fuel at each tier is superheated, resulting in effective drying of the solid fuel. The excess portion of the circulating vapor is extracted from the air-steam mixture and transferred to a vapor condenser, where it is condensed.The heat energy obtained is transferred to various heat consumers.

[0022] The invention can therefore be used with great advantage in a biomass power plant with a steam turbine for generating electrical energy and a water-steam cycle with a condenser for steam recooling. The superheated steam flowing in the pipes of the drying chamber to heat the air-steam mixture (vapor) is extracted from a first bleed of the turbine, preferably a bleed for a low-pressure condensate preheater, and, after passing through the drying chamber, is fed back into the main condensate line as condensate upstream of the low-pressure condensate preheater.

[0023] The cooling circuit of the vapor condenser is preferably fed from the main condensate line behind the main condensate pump of the exhaust steam condenser of the turbine.

[0024] The vapor condensation heat can advantageously be used to feed the main condensate back into the steam, for example, upstream of the first low-pressure preheater, in order to raise the main condensate temperature upstream of the first low-pressure preheater. The higher main condensate inlet temperature upstream of the first low-pressure preheater enables a reduction in the amount of steam from the first turbine tap. This increases the steam mass flow in the turbine downstream of the first tap up to the exhaust steam section of the turbine, thus increasing the turbine output. Considering the overall situation, the drying heat for wood drying in this preferred case is extracted from the turbine section between the first tap and the second tap. Alternatively, the drying heat can also be extracted from another turbine section between two taps.

[0025] Any excess vapor heat can also be used to preheat the combustion air for the combustion chamber. This air heat component replaces the fuel requirement to an equal extent. The fuel is heated during drying. If the dried fuel is fed into combustion immediately after drying with the added vapor heat, this heat component also replaces a portion of the fuel requirement to an equal extent.

[0026] If there is a further excess of vapor heat, this excess can preferably be used for pre-drying and heating the fuel in the fuel bunker.

[0027] The conveying section preferably contains a belt-shaped pusher device with pusher beams, which conveys the solid fuel with alternating horizontal conveying directions over the individual superimposed levels, which in particular consist of heated pipes arranged parallel to one another, through which the steam flow used to heat and dry the solid fuel flows from the first tap of the turbine.

[0028] The hot steam extracted from the turbine has a temperature of preferably 130 - 150°C, so that the circulating air vapor to be heated in the drying chamber also receives a nearly corresponding temperature.

[0029] The invention is explained in more detail below using an exemplary embodiment. Shown are: Fig. 1 is a schematic view of a drying device used in a biomass power plant, Fig. 2 a view of one level of the drying facility, Fig. 3 a cross-section through one level of the drying facility, Fig. 4 a side view of a floor, and Fig. 5 a Ht diagram.

[0030] Fig. Figure 1 schematically shows a turbine 14 of a biomass power plant in which solid fuel, such as wood chips or other biogenic fuels, is used as heating fuel. The term "solid fuel" generally refers to materials that contain combustible substances despite their high moisture content. The steam generated in the boiler of the biomass power plant is fed to the turbine 14 at high pressure and high temperature, and drives a generator (not shown) to generate electrical energy. At the output stage of the turbine 14, the steam is cooled and condensed via a condenser 29. In the main condensate line 33 of the turbine 14, which is connected to the condenser 29, there is a main condensate pump 40 and two low-pressure preheaters 12 and 16, to which steam is fed from the taps 26 and 32 of the turbine 14, respectively.Hot steam with a temperature of approximately 140°C and 4 bar is extracted via the first tapping line 13 and the first tap 27 of the line connection between the first tapping point 26 and the second low-pressure preheater 16 and transferred to the drying chamber 1.

[0031] In the drying chamber 1, the hot steam, which is fed from the tap 27 via the line connection 30, flows through a pipe coil system that forms heated floors 2 over which the solid fuel is fed. The heated floors 2 are arranged one above the other in tiers and each contain a feed device 17 for moving the fuel 3 forward over the individual tiers 5. The heating coils of the heated floors 2 are spaced apart by a distance through which the air or vapor circulated through the drying chamber 1 can pass. As the solid fuel passes through the drying chamber 1, it is conveyed over the tiers 5 and simultaneously heated by the air or vapor flow to such an extent that the water in the fuel evaporates.The steam generated on each level penetrates through the openings 4 of the floor above, is superheated, and thus heats the next layer of fuel on the floor above. This process, in turn, evaporates the water in the fuel. This process is repeated on all levels 5.

[0032] After the superheated steam supplied from the tap 27 of the drying chamber 1 has passed through the heating coils of the drying chamber 1, it is fed into the main condensate line 33 of the turbine 14 between the first low-pressure preheater 12 and the second low-pressure preheater 16 at the condensate inlet 28. A condensate drain 25 is arranged in the return line 31 of the heating circuit to drain any condensate formed.

[0033] The solid fuel to be dried is advanced tier by tier by a feed device 17 across the heated floors 2 from the fuel bunker 18 to the exit 19 of the drying chamber. At the end of each tier, the solid fuel falls onto the feed device of the tier below and finally falls into the intermediate storage 20. The dry solid fuel that has entered the intermediate storage 20 can then be directly fed to the boiler's combustion system to generate steam for the turbine 14.

[0034] The air or vapor flow through the drying chamber is circulated by means of a vapor blower 6.

[0035] The vapor generated during drying is directed via a vapor blower 8 to the vapor condenser 7, where it is condensed. The vapor condenser 7 is cooled via the condensate circuit 9, which is fed by a second tap 34 of the main condensate line 33 downstream of the main condensate pump 40. A condensate circulation pump 10 is provided for this purpose.

[0036] Part of the vapor condensation heat generated in the condensate circuit 9 is 1) is preferably fed into the main condensate line 33 directly upstream of the first low-pressure preheater 12, thus increasing the temperature of the main condenser upstream of the first low-pressure preheater 12. The steam demand of the first low-pressure preheater 12 from the second tap 32 is thereby reduced. The steam no longer required from the tap 32 generates electricity in the turbine 14. 2) The excess vapor heat can also be recovered via heat exchangers 11, which can preferably be used to heat the combustion air and, for example, to heat additional water for the biomass power plant, to heat building equipment or other devices that require heat. 3) If there is still a further surplus of vapor heat, this heat can be used to pre-dry the fuel in the fuel bunker 18 by means of an air pre-heat exchanger 22, to which an air blower 21, pipes 23 and several hot air distributors 24 in the fuel bunker 18 are assigned, so that the steam requirement for drying the solid fuel is reduced.

[0037] It is advantageous if there is a slight negative pressure in the drying chamber, which is generated by the vapor blower 8, which supports a steam flow to the vapor condenser.

[0038] Since the turbine condensate is taken from the main condensate line 33 for cooling the vapor condenser 7 upstream of the first low-pressure preheater 12 and is heated to 90°C - 95°C and fed back upstream of the first low-pressure preheater 12, the higher condensate inlet temperature reduces the steam requirement of the first low-pressure preheater 12 from the second tap 32 of the steam turbine 14.

[0039] The amount of steam required to heat the trays 2 is already taken from the first tap 26, so that the thermal steam required for drying is only taken from the corresponding turbine section.

[0040] Since the steam from the first tap 26 is discharged at approximately 140°C, the heating temperature of all stacked trays is approximately 140°C, which is approximately 40°C higher than the exhaust steam temperature of 100°C at 1 bar emerging from the fuel. This means that the exhaust steam temperature during drying is above 100°C and is and remains dry upon entering the next drying stage.

[0041] The heat released by the vapor condenser 7 is preferably released in the sequence of the above-mentioned steps 1, 2, and 3. In stage 3, the heat requirement of the fuel is reduced accordingly by the heat introduced externally into the bunker of the drying chamber.

[0042] By means of the device according to the invention, the heating of the entire combustion air, the additional water, the heat requirement for the operation of the power plant heating system for the power plant and the office building can be covered by the heat emitted by the vapor condenser and can replace the quantities of steam that would otherwise have to be taken from the steam turbine.

[0043] Fig. Figure 2 shows a plan view of a heated floor 2 of the drying chamber 1. The floor is formed from several tubes 37 spaced apart by a gap 38. The solid fuel can be moved forward along the floors by means of the pusher beams 36. The pusher beams can either be moved repeatedly, whereby during the forward movement, the solid fuel is pushed forward along the vertical flanks of the wedge-shaped shape of the pusher beams, while during the backward movement, the wedge-shaped shape of the pusher beams allows the solid fuel to pass under the solid fuel. Alternatively, the pusher beams can be designed as revolving chain conveyors on each level.

[0044] Fig. Figure 3 shows a cross-section through a heated floor 2 formed from parallel tubes 37, on which the pusher beam 36 runs. To prevent the gap 38 between the tubes 37 from becoming clogged, the pusher beam includes fingers 35 on the underside running between the tubes 37 to clear the gap 38, through which the air flow for drying the conveyed solid fuel is to flow freely.

[0045] Fig. Figure 4 shows a side view of the feed mechanism running on the tubes 37. Here, the push bars are attached to a conveyor chain 39 and are thus moved together.

[0046] Fig. Figure 5 shows a Ht diagram plotting the achievable enthalpy in kJ / kg of solid fuel versus temperature. It shows a significant enthalpy gain by heating the fuel at 4 bar and 140°C compared to the steam temperature of 100°C at 1 bar when the exhaust steam enters the superheated state.

[0047] Compared to the fuel requirement when moist fuel is supplied to the combustion chamber of the boiler, the fuel drying according to the invention can therefore save a significant amount of fuel and thus a large part of the fuel costs.

[0048] In a simulated example calculation, it was demonstrated that the fuel cost savings reached around 20%.

[0049] Although the steam extraction for heat demand from the first tap 26 reduces the electrical power of the turbine 14, this reduction is limited by the heat input into the condensate of the main condensate line 33 upstream of the second low-pressure preheater 16. The stated gross advantage of 20% is therefore reduced to only about 17% when comparing fuel costs without the method according to the invention with the costs when using the fuel drying specified by the invention.

[0050] In a calculated example, the firing capacity of a power plant with 83 MW was assumed, with fresh wood with a water content of 50% being used as the fuel. With an annual wood requirement of approximately 320,000 t, fuel costs of approximately EUR 16 million per year were to be expected. With the help of the drying device according to the invention, the fuel requirement and its costs could be reduced by approximately 20%. By extracting steam at the first tap 26 of the steam turbine and utilizing the heat from the vapor, the overall benefit is reduced by approximately EUR 400,000 per year, so that an adjusted overall benefit of 17%, or approximately EUR 2.7 million per year, can be achieved for a biomass power plant according to the invention.

[0051] The reduced biomass requirement for the same electrical power generation achieved with the process according to the invention also has the advantage of producing significantly less ash, thus reducing the burden on the environment. These disposal costs are not yet taken into account in the above calculation. Furthermore, the amount of exhaust gas that must be discharged via the chimney is reduced. It was determined that the amount of exhaust gas could be reduced by approximately 30%.

[0052] Since the drying air in the drying system is highly superheated by the heated floors 2, this prevents the exhaust vapor from cooling down and condensing in the fuel. This eliminates the risk of fire due to spontaneous ignition. Reference symbol 1 drying chamber 2 heated floors 3 Fuel / fuel layer 4 openings in the heated floor 5 floors 6 recirculation fans 7 Vapor condenser 8 steam blowers 9 Condensate circuit 10 Condensate circulation pump 11 heat exchangers 12 first low-pressure preheater 13 first tapping line 14 steam turbine 15 second tapping line 16 second low-pressure preheater 17 Feed device 18 fuel bunkers 19 Exit of the drying chamber 20 slots or buffers 21 air blower 22 air preheat exchangers 23 air ducts 24 hot air distributors 25 condensate drains 26 first tap 27 first tap 28 Condensate inlet 29 Capacitor 30 Line connection 31 Return 32 second tap 33 Main condensate line 34 second tap 35 fingers 36 push beams 37 Pipeline 38 gap 39 Conveyor chain 40 Main condensate pump

Claims

[1] A method for drying biogenic solid fuel, in particular wood, by means of a heated air-steam flow guided through the solid fuel (3) in a drying chamber (1), in which the heating device is fed from a biomass power plant which contains a boiler with a combustion chamber, a steam turbine (14) for generating electrical energy and a steam circuit with a condenser (29) for steam recooling, wherein the solid fuel (3) is heated by an air-steam flow which is heated by means of superheated steam diverted from an intermediate turbine stage, which is guided through the drying chamber (1) via pipes (30, 31) and which, after passing through the drying chamber (1), is returned as steam condensate to the main condensate section (33) of the turbine (14), wherein the vapors emerging from the solid fuel (3) during drying enter a superheated state,and wherein in the vapor condenser (7), the condensation of the vapor takes place in heat exchange with a condensate circuit (9) branched off from the main condensate section (33) of the turbine (14), wherein the air-vapour flow is heated by a heating device to a temperature which converts the moisture escaping from the solid fuel (3) as vapor into a superheated state, wherein the solid fuel is guided in continuous flow through the drying chamber (1), and wherein excess vapor from the drying chamber (1) is condensed via a vapor condenser (7), and the superheated steam branched off from the turbine intermediate stage is guided at its vapor temperature and at a pressure increased compared to the atmosphere through the drying chamber (1) in pipelines running through stages, which in the process heat the vapor flow guided through the solid fuel. characterized by , that - the solid fuel (3) is guided through the drying chamber (1) in a pushing process, wherein the solid fuel is moved in alternating directions through pushing sections arranged one above the other in tiers and designed to be gas-permeable, and wherein the solid fuel conveyed over the pushing sections is heated in each case by the air-steam flow which passes through the pipes running between the pushing sections arranged in tiers and is thereby superheated. [2] Method according to claim 1, characterized by that the solid fuel is dried in the drying chamber (1) via a circulating air-steam flow, from which excess vapors are extracted and fed to the vapor condenser (7). [3] Method according to claim 1, characterized by that at least part of the return flow (31) of the cooling circuit of the vapor condenser (7) is passed via heat exchangers (11) to release heat to external heat users. [4] Method according to claim 3, characterized by that a heat exchanger (11) is used to preheat the combustion air of the combustion chamber and air preheat the air flow guided in the drying chamber (1). [5] Method according to claim 1, characterized by that the steam branched off from the intermediate stage of the turbine (14) has a superheated steam temperature of 130-150°C, preferably 140°C. [6] Drying device for drying biogenic solid fuel, in particular wood, by means of an air-steam flow circulated through the solid fuel in a drying chamber (1), in which the heating device is fed from a biomass power plant which contains a boiler with a combustion chamber, a steam turbine (14) for generating electrical energy and a steam circuit with a condenser (29) for steam recooling, wherein the solid fuel (3) is heated by an air-steam flow which is heated by means of superheated steam diverted from a turbine intermediate stage, which is guided through the drying chamber (1) via pipes (30, 31) and which, after passing through the drying chamber (1), is returned as steam condensate to the main condensate section (33) of the turbine (14), wherein the vapors emerging from the solid fuel (3) during drying enter a superheated state,and wherein in the vapor condenser (7), the condensation of the vapor takes place in heat exchange with a condensate circuit (9) branched off from the main condensate section (33) of the turbine (14), with a solid fuel bunker (18), from which the solid fuel (3) is continuously conveyed via a heated conveying section of the drying chamber (1) and transferred in the dried state to an intermediate storage unit (20), wherein the conveying section is designed in tiers, via which the solid fuel can be conveyed from one tier (5) to the next, wherein the individual tiers of the conveying section each contain spaced-apart pipes through which superheated steam extracted from a steam power plant can be conducted, which can heat the air-steam flow guided through the tiers (5) of the conveying section to such a temperature that moisture escaping from the solid fuel is superheated, and wherein a vapor condenser (7) is provided,in which excess vapors are separated from the air-steam flow passing through the drying chamber (1) and heat is recovered by vapor condensation, and the superheated steam branched off from the turbine intermediate stage, with its steam temperature and pressure increased relative to the atmosphere, is passed through the drying chamber (1) in tiers through pipes which heat the vapor flow passing through the solid fuel. characterized by , that - the solid fuel (3) is guided through the drying chamber (1) in a pushing process, wherein the solid fuel is moved in alternating directions through pushing sections arranged one above the other in tiers and designed to be gas-permeable, and wherein the solid fuel conveyed over the pushing sections is heated in each case by the air-steam flow which passes through the pipes running between the pushing sections arranged in tiers and is thereby superheated. [7] Drying device according to claim 6, characterized by in that the conveyor line comprises a belt-shaped pushing device (17) with pushing beams (36) which conveys the solid fuel over the individual superimposed levels (5) with alternating conveying directions, wherein the pushing device (17) pushes the solid fuel forward over the heated pipes and the vapor flow is guided between the pipes and through the solid fuel on the levels of the conveyor line. [8] Drying device according to claim 7, characterized by that the push bars (36) contain downwardly directed fingers (35) which are displaceable between the parallel pipes. [9] Drying device for use in a biomass power plant, which contains a boiler with a combustion chamber, a steam turbine (14) for generating electrical energy and a steam circuit with a condenser (29) for steam recooling, in which the heating device is fed from a biomass power plant, which contains a boiler with a combustion chamber, a steam turbine (14) for generating electrical energy and a steam circuit with a condenser (29) for steam recooling, wherein the solid fuel (3) is heated by an air-steam stream, which is heated by means of superheated steam diverted from an intermediate turbine stage, which is guided through the drying chamber (1) via pipes (30, 31) and which, after passing through the drying chamber (1), is returned as steam condensate to the main condensate section (33) of the turbine (14), wherein the vapors emerging from the solid fuel (3) during drying enter a superheated state,and wherein in the vapor condenser (7) the condensation of the vapor takes place in heat exchange with a condensate circuit (9) branched off from the main condensate section (33) of the turbine (14), wherein the hot steam for heating a continuously conveyed solid fuel is taken from a tap (26) of the turbine (14) so ​​that moisture escaping from the solid fuel is superheated and the hot steam is returned to the main condensate section (33) of the turbine (14) after passing through the drying chamber (1), and wherein the recooling of the vapor condenser (7) takes place via a cooling circuit (9) led out from the main condensate section (33) of the turbine (14), and the hot steam branched off from the turbine intermediate stage is guided at its steam temperature and at a pressure higher than the atmosphere through the drying chamber (1) in pipes running through the drying chamber (1) in stages, which pipes heat the vapor flow guided through the solid fuel. , characterized by , that - the solid fuel (3) is guided through the drying chamber (1) in a pushing process, wherein the solid fuel is moved in alternating directions through pushing sections arranged one above the other in tiers and designed to be gas-permeable, and wherein the solid fuel conveyed over the pushing sections is heated in each case by the air-steam flow which passes through the pipes running between the pushing sections arranged in tiers and is thereby superheated. [10] Drying device according to claim 9, characterized by that the cooling circuit of the vapor condenser (7) is passed through a heat exchanger (22) for preheating the air flow passing through the solid fuel. [11] Drying device according to claim 9, characterized by that the heat extracted from the vapor condenser is reintroduced into the main condenser circuit in such a way that the steam extraction from the turbine is reduced.

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