JP4766562B2 - Wood pellet fired steam boiler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a woody pellet burning steam boiler allowing reduction in size, stable and efficient combustion of woody pellets, improvement in the efficiency due to good load followability, and prevention of reduction in the efficiency. <P>SOLUTION: The woody pellet burning steam boiler is constructed of an inner water cooling wall 2 forming a combustion chamber S2 inside, an outer water cooling wall 3, arranged on the outside of the inner water cooling wall 2, a combustion gas passage 4 formed between the both water cooling walls 2 and 3 and connected to the combustion chamber S2 and a flue 9, respectively; an upper header 5 and a lower header 6, respectively connected to the upper and lower end parts of the both water cooling walls 2 and 3 in a communicating manner; a combustion device 7 arranged below the combustion room S2 and using the woody pellets F as fuel; and a purge air supply mechanism 8 feeding purge air P to the bottom part of the combustion gas passage 4. From a woody pellet supply port 30a in the upper part of the combustion chamber S2, the woody pellets F are thrown into the combustion chamber S2, to be burnt by the combustion device 7, and generated combustion gas G and burnt ash are discharged from the combustion chamber S2 to the flue 9 via the combustion gas passage 4. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a steam boiler (through-flow boiler) in which a combustion chamber and a combustion gas passage for performing contact heat transfer are respectively formed by a water cooling wall composed of a plurality of water pipes and fins, and in particular, sawdust and wood waste such as sawdust and wood waste. The present invention relates to a wood pellet fired steam boiler (through-flow boiler) having an evaporation amount of 300 kg / h to 2000 kg / h in which wood pellets made from the remaining material are burned as fuel.

In recent years, global warming due to greenhouse gases such as carbon dioxide has become a problem, and reduction of carbon dioxide is required. With such environmental problems, biomass fuel, which is a cleaner fuel than fossil fuels such as oil and coal, has attracted attention.
Among biomass fuels, wood pellets are solid fuels that are compression-molded by crushing sawdust, wood waste, and other sawmill waste and woodland residue, and are characterized by carbon neutrality (carbon dioxide generated during combustion is photosynthesis during growth) This is a biomass fuel that has the property that it does not affect the increase or decrease of carbon dioxide in the atmosphere in the life cycle. In addition, wood pellets are high-quality fuels that are easier to handle than other biomass fuels and that have a stable quality such as shape and moisture content. Furthermore, wood pellets can be used as one of new energy in Japan, where most of the fuel such as oil is dependent on foreign countries, and is actually used as fuel for hot water supply / heating equipment.

That is, in the field of boilers that produce hot water and steam by burning fuel, a hot water boiler using wood pellets as a fuel has been developed and put into practical use (see, for example, Patent Document 1).
However, hot water boilers that use wood pellets as fuel are not widely used because hot water that can be used is 100 ° C. or lower and the energy level is low, and their use is limited to hot water supply and heating.
Steam boilers (through-flow boilers), on the other hand, have a high energy level that can be used and are widely used for absorption chiller / heater regenerators and dryer heat sources, but are small and efficient. Small steam boilers (small once-through boilers or once-through boilers with a heat transfer area of 30 m ² or less) that use wood pellets that do not require a license as fuel have not been developed yet, and their development is strongly desired.
JP-A-2005-300022

  The present invention has been made in view of such problems, and the object thereof is to reduce the size of the boiler and to stably and efficiently burn the wood pellets. It is an object of the present invention to provide a wood pellet fired steam boiler that is good, highly efficient, and has little reduction in efficiency.

  In order to achieve the above object, the invention according to claim 1 of the present invention comprises an annular inner water cooling wall that forms a circular combustion chamber inward, and a concentric or substantially concentric circle at an outer position of the inner water cooling wall. A ring-shaped outer water cooling wall, a ring-shaped combustion gas passage formed between the inner water cooling wall and the outer water cooling wall and communicating with the combustion chamber and the flue, respectively, Upper and lower headers connected to the upper and lower ends of the water pipe, respectively, a combustion device disposed at the lower part of the combustion chamber and combusting wood pellets as fuel, and purge air at the bottom of the combustion gas passage And a purge air supply mechanism that supplies wood pellets into the combustion chamber through a wood pellet supply port provided in the upper part of the combustion chamber and burns it with a combustion device, burning the generated combustion gas and incinerated ash The combustion gas passage from the chamber There is a feature to it has to be discharged to the flue.

  According to a second aspect of the present invention, one portion of the annular combustion gas passage is closed, and one end of the combustion gas passage is communicated with the combustion chamber via a combustion gas passage formed in an inner water cooling wall. Combustion gas and incineration ash which flowed into the combustion gas passage from the combustion chamber through the combustion gas passage through the other end of the combustion gas passage communicated with the flue through the combustion gas outlet formed in the outer water cooling wall This is characterized in that the gas is exhausted to the flue through the combustion gas outlet after having made one round in the combustion gas passage.

  According to a third aspect of the present invention, a combustion gas passage for communicating the combustion chamber and the combustion gas passage is formed in the inner water cooling wall, and the outer water cooling is performed at a position 180 degrees opposite to the combustion gas passage. A combustion gas outlet that connects the combustion gas passage to the flue is formed in the wall, and the combustion gas and incinerated ash that flowed into the combustion gas passage through the combustion gas passage through the combustion chamber flow in the left and right directions in the combustion gas passage. The combustion gas passage is substantially half-circulated and then discharged to the flue through the combustion gas outlet.

  According to a fourth aspect of the present invention, the interval between the annular combustion gas passages is gradually narrowed from the vicinity of the combustion gas passage opening to the vicinity of the combustion gas outlet, so that the flow velocity of the combustion gas flowing in the combustion gas passage is kept constant. There is a feature in that.

  According to a fifth aspect of the present invention, the combustion device has a cylindrical combustion cylinder that forms a primary combustion chamber that communicates with a combustion chamber formed inside the inner water cooling wall, and a lower position in the combustion cylinder. A perforated plate provided with a plurality of air ejection holes for uniformly distributing combustion air in the cross section of the primary combustion chamber, and a plurality of heat-resistant ceramic particles formed on the perforated plate in a point contact state. The laminated ceramic particle layer, the combustion cylinder is cooled from the outside, the combustion air supply section supplies the combustion air to the perforated plate in a swirling state, and the combustion air is supplied to the combustion air supply section Composed of a blower for combustion and an ignition burner that is inserted in the combustion cylinder and positioned above the ceramic particle layer, and supplies the wood pellet supplied to the ceramic particle layer from the wood pellet supply port for combustion air supply Combustion through the perforated plate With burning under fluidization by gas, it is characterized in that so as to scatter into the combustion chamber side incinerated ash remaining after combustion with the combustion gases.

  The invention according to claim 6 of the present invention is a pair of linear inner water cooling walls that are arranged opposite to each other to form a rectangular combustion chamber, and parallel to the water cooling walls at the outer positions of the inner water cooling walls or A straight combustion gas formed between a pair of straight outer water cooling walls and a pair of inner water cooling walls and an outer water cooling wall, which are arranged substantially in parallel, and communicates with the combustion chamber and the flue, respectively. A passage, an upper header and a lower header connected to the upper end and lower end of each water pipe of both water cooling walls, respectively, and a combustion device disposed on the upstream side of the combustion chamber and burning wood pellets as fuel And a purge air supply mechanism for supplying purge air to the bottom of the combustion gas passage and the bottom of the flue, and the wood pellets are introduced into the combustion chamber from the wood pellet supply port provided on the upstream side of the combustion chamber. Combustion gas generated by combustion using a combustion device It is characterized in that the fine ash and to discharge into the flue through the combustion gas passage from the combustion chamber.

  According to the seventh aspect of the present invention, the interval between the linear combustion gas passages is gradually narrowed from the upstream side to the downstream side so that the flow velocity of the combustion gas flowing in the combustion gas passage is kept constant. There are features.

  According to an eighth aspect of the present invention, there is provided a wind box in which the combustion apparatus includes an ignition burner, a pellet supply port, a combustion blower, and a secondary combustion blower, and an upstream side in the combustion chamber in a state adjacent to the wind box. The combustion section is provided in a state communicating with the wind box at the bottom on the upstream side of the combustion chamber, and the upper surface side ejects a large amount of primary combustion air upward. Combustion air supply unit formed on a perforated plate having ejection holes, and a number of heat-resistant ceramic particles formed on the perforated plate of the combustion air supply unit, one end side being located below the pellet supply port A ceramic particle layer that is laminated in a point contact state, and a height that is provided in a standing posture on both sides and downstream ends of the ceramic particle layer, prevents outflow of wood pellets and ceramic particles, and does not leave incineration ash in the ceramic layer The refractory wall and the flame A secondary combustion air supply unit that is provided in the air supply unit for supplying secondary combustion air to the downstream region of the combustion chamber. The wood pellets supplied to the ceramic particle layer from the pellet supply port are used for combustion air. Combustion is performed while flowing with primary combustion air from the supply unit, and the incinerated ash remaining after combustion is scattered together with the combustion gas to the outside of the ceramic particle layer. The fuel is characterized in that it is burned with the secondary combustion air supplied from the secondary combustion air supply unit, and the incinerated ash that has fallen to the bottom of the combustion chamber is transferred by the secondary combustion air.

  In the invention of claim 9 of the present invention, the air ejection holes of the perforated plate of the combustion air supply unit supply a large amount of primary combustion air to one end side upstream of the ceramic particle layer to which the wood pellets are supplied, An array is formed at the upper part of the combustion air supply unit so that the primary combustion air is gradually supplied to the other end side downstream of the ceramic particle layer, and the primary combustion air is uniformly supplied to the wood pellet layer. It is characterized by being.

The wood pellet fired steam boiler of the present invention can exhibit the following excellent effects.
(1) The wood pellet cooking steam boiler of the present invention connects the upper end and the lower end of each water pipe of the inner water cooling wall and the outer water cooling wall to the upper header and the lower header, respectively, Since the enclosed space is a combustion chamber and the structure is a once-through boiler with the space between the inner water cooling wall and the outer water cooling wall as a combustion gas passage for contact heat transfer, a boiler engineer license is required. In addition, a can body having a corresponding evaporation amount of 300 kg / h to 2000 kg / h can be a compact steam boiler. However, since the steam boiler has the structure of a once-through boiler, the load followability is good because the amount of retained water is small and the amount of refractory used is small.
(2) The wood pellet cooking steam boiler according to the present invention applies heat to the inner water cooling wall by radiant heat transfer by the combustion flame in the combustion chamber, and by the inner heat cooling wall by contact heat transfer by the combustion gas flowing in the combustion gas passage. Since heat is applied to both the outer water cooling wall and the outer water cooling wall, the heat absorption rate to the water cooling wall is greatly improved, and a steam boiler that is highly efficient and has little reduction in efficiency can be obtained.
(3) The wood pellet cooking steam boiler according to the present invention is configured such that wood pellets are put into a combustion chamber and burned by a combustion device, and the generated combustion gas and incinerated ash are discharged from the combustion chamber to the flue through the combustion gas passage. Therefore, there is no generation of clinker, no unburned matter, and ash can be separated and extracted.
(4) In the wood pellet cooking steam boiler according to the present invention, the interval between the annular combustion gas passages is gradually narrowed from the vicinity of the combustion gas passage port to the vicinity of the combustion gas outlet, or the interval of the linear combustion gas passage is upstream. The flow rate of the combustion gas is made narrower gradually from the side to the downstream side, and the flow rate of the combustion gas is made constant so that the flow rate of the combustion gas flowing in the combustion gas passage is the flow rate that prevents the incineration ash and unburned pellets from wearing the water-cooled walls. Since it keeps maintaining, the abrasion of the water pipe etc. of the both water-cooled walls by incineration ash and an unburned pellet can be prevented.
(5) The wood pellet cooking steam boiler of the present invention is provided with a ceramic particle layer formed by laminating a number of heat-resistant ceramic particles in a point contact state on a perforated plate, and supplying the wood pellets to the ceramic particle layer This is burned while flowing with the combustion air supplied from the perforated plate, and the incineration ash remaining after the combustion is scattered outside the ceramic layer, so the combustion air has excellent thermal conductivity when burning wood pellets The ceramic particles are cooled by flowing in a large number of micro spaces formed between the ceramic particles, and the ceramic particle layer is not excessively heated, and the generation of clinker can be further suppressed and The pellet can be continuously and stably burned.
(6) The wood pellet cooking steam boiler according to the present invention burns the incinerated ash and the unburned content in the combustion gas outside the ceramic particle layer with the secondary combustion air from the secondary combustion air supply unit and burns it. Since the incinerated ash that has fallen to the bottom of the chamber is transferred by the secondary combustion air, it is possible to perform combustion with extremely little unburned content and to further suppress the generation of clinker.
(7) The wood pellet cooking steam boiler of the present invention supplies a large amount of primary combustion air to the one end side upstream of the ceramic particle layer in which the air pellets of the perforated plate of the combustion air supply unit are dispersed. And the upper part of the combustion air supply unit so that the primary combustion air is gradually supplied to the other end side downstream of the ceramic particle layer and the primary combustion air is uniformly supplied to the wood pellet layer. Therefore, the local high-temperature combustion part does not occur, the generation of clinker can be further suppressed, and the wood pellets can be burned in a more stable state.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 to 7 show a wood pellet fired steam boiler 1 according to a first embodiment of the present invention. The wood pellet fired steam boiler 1 has an inwardly circular combustion chamber S2 (secondary combustion in this embodiment). An annular inner water cooling wall 2 forming the chamber S2) and an annular combustion gas passage 4 arranged concentrically or substantially concentrically at an outer position of the inner water cooling wall 2 and between the inner water cooling wall 2 An outer water cooling wall 3 that forms an annular shape, an upper header 5 and a lower header 6 that are connected to the upper and lower ends of the water pipes 2a and 3a of the two water cooling walls 2 and 3, respectively, and a combustion chamber S2. And a purge device for burning the wood pellet F as fuel and supplying purge air P to the bottom of the combustion gas passage 4 to prevent incineration ash and unburned matter from accumulating It consists of mechanism 8 etc. and is the upper part of combustion chamber S2 The wood pellet F is introduced into the combustion chamber S2 from the provided wood pellet supply port 30a and burned by the combustion device 7, and the generated combustion gas G and incineration ash are discharged from the combustion chamber S2 through the combustion gas passage 4 to the flue. It is what I did.

  In this steam boiler 1, the heat absorption to the boiler water flowing in the water pipe 2a of the inner water cooling wall 2 is mainly due to the radiant heat transfer by the generated combustion gas G and the combustion gas flowing in the secondary combustion chamber S2. Heat absorption by the boiler water flowing in the water pipe 3a of the outer water cooling wall 3 is performed by contact heat transfer (convection heat transfer) by G and contact heat transfer by the combustion gas G flowing in the combustion gas passage 4. Is performed only by contact heat transfer (convection heat transfer) by the combustion gas G flowing in the combustion gas passage 4.

  In FIG. 7, 10 is a service silo that receives a wood pellet F from a wood pellet storage silo (not shown) and stores it in a small volume, and 11 is connected to the service silo 10, and the wood pellet in the service silo 10. Inverter-controlled screw conveyor 12 for conveying F, 12 is connected to the screw conveyor 11, and a pellet supply pipe with a shut-off damper for supplying the wood pellet F to the wood pellet F combustion device 7, 13 is discharged from the screw conveyor 11 A push blower that pushes the wood pellet F into the pellet supply pipe 12 side and prevents the backflow of the combustion gas G, 14 is connected to the flue 9, and a cyclone dust collector that collects ash in the combustion gas G, 15 Is provided in the duct on the combustion gas outlet side of the cyclone dust collector 14, and controls the inside of the combustion chamber S2 to a negative pressure. Inverter-controlled induction fan, 16 is watering tank, 17 is a temperature detector, 18 is an ash storage box, 19 is an automatic softener, 20 is a water supply tank, 21 is a chemical tank, 22 is a water supply pump, and 23 is a steam outlet. A valve, 24 is a safety valve, 25 is a steam pressure switch, and 26 is a steam pressure gauge.

As shown in FIGS. 4 to 6, the inner water cooling wall 2 has a strip-like fin extending in the vertical direction with a plurality of water tubes 2a (thick bare tubes) arranged in parallel in an annular shape. It is formed by connecting at 2b, and is formed in an airtight structure with a circular cross-sectional shape. A space surrounded by the inner water cooling wall 2 is a combustion chamber S2 (secondary combustion chamber S2 in this embodiment).
Further, a plurality of combustion gas passages for allowing the combustion gas G in the secondary combustion chamber S2 to flow into the annular combustion gas passage 4 by notching the upper end portions of the plurality of fins 2b at the upper part of the inner water cooling wall 2. A mouth 2c is formed. The opening area of the combustion gas passage port 2c is set to a predetermined value in order to prevent wear of the water pipe 2a and the like due to scattered ash and partially unburned material. In this embodiment, the opening area of the combustion gas passage port 2c is such that the flow rate of the combustion gas G passing through the combustion gas passage port 2c is equal to or lower than a predetermined flow rate (such as the water pipe 2a made of scattered ash and partially unburned matter). The flow rate is set to be equal to or less than a flow rate at which wear can be prevented. Further, the area of the inner water cooling wall 2 is set so that the combustion gas G temperature at the combustion gas passage port 2c is 850 ° C. or lower.

As shown in FIGS. 4 to 6, the outer water cooling wall 3 has a plurality of water pipes 3a (thick bare pipes) arranged in parallel in the same manner as the inner water cooling wall 2, and the adjacent water pipes 3a are vertically moved. It is formed by connecting with a strip-like fin 3b extending in the direction, and has a hermetic structure with a circular cross-sectional shape. The outer water cooling wall 3 is disposed concentrically or substantially concentrically with the inner water cooling wall 2 at an outer position of the inner water cooling wall 2, and the combustion gas G passes between the outer water cooling wall 2 and the inner water cooling wall 2. An annular combustion gas passage 4 is formed.
Further, the water cooling wall 3 on the outer side is provided with a water pipe 3a and a fin 3b that are slightly deviated in the circumferential direction from the position of the combustion gas passage port 2c formed in the inner water cooling wall 2, thereby removing the water pipe 3a in the combustion gas passage 4 from the position. A combustion gas outlet 3c for allowing the combustion gas G to flow out is formed, and the combustion gas G flowing in the combustion gas passage 4 is discharged from the combustion gas outlet 3c to the flue 9.
Further, as shown in FIG. 5, the annular combustion gas passage 4 extends in the vertical direction between the water pipe 3 a near the combustion gas outlet 3 c of the outer water cooling wall 3 and the water pipe 2 a near the combustion gas passage 2 c of the inner water cooling wall 2. By connecting with a strip plate-shaped fin 3b 'extending to the center, one portion is closed, and the combustion gas G exiting the combustion gas passage port 2c flows in one direction in the annular combustion gas passage 4, and the combustion The gas passage 4 is exhausted from the combustion gas outlet 3c to the flue 9 after substantially making a full circle. The upper space and the lower space of the annular combustion gas passage 4 are filled with a refractory 27 for protecting the upper header 5 and the lower header 6 from the high-temperature combustion gas G.
In addition, an inspection port 3d is formed in the outer water cooling wall 3 by removing some of the water pipes 3a and fins 3b, and an inspection door 28 lined with a refractory 27 is opened and closed in the inspection port 3d. It is attached as possible.

  In this embodiment, the outer water-cooling wall 3 is eccentric with respect to the inner water-cooling wall 2 so that the interval between the portions where the combustion gas passage ports 2 c of the combustion gas passage 4 are formed becomes wide. It is arrange | positioned in the outer position of the water cooling wall 2 inside, and it makes so that the space | interval (passage area of the combustion gas G) of the cyclic | annular combustion gas passage 4 becomes so narrow that it goes to the combustion gas outlet 3c from the combustion gas passage 2c part. It has become. Thereby, the flow velocity of the combustion gas G flowing through the combustion gas passage 4 is kept constant. The higher the flow rate of the combustion gas G passing through the combustion gas passage 4, the better the heat transfer efficiency, but the wear of the water pipes 2a, 3a of the two water-cooled walls 2, 3 due to the ash in the combustion gas G and the like occurs. On the other hand, if the flow rate of the combustion gas G is too slow, the heat transfer efficiency is lowered, and incineration ash is attached and deposited on the two water cooling walls 2 and 3 (heat transfer surface). Therefore, the flow rate of the combustion gas G passing through the combustion gas passage 4 is set to a predetermined flow rate in order to prevent wear of the water pipes 2a, 3a, etc. of the water cooling walls 2, 3 due to ash or the like in the combustion gas G. Is set to

  In the above embodiment, the combustion gas G exiting the combustion gas passage 2c flows in one direction in the combustion gas passage 4 as shown in FIG. 5, but in other embodiments, In this case, a combustion gas outlet 3c is formed in the outer water cooling wall 3 at a position 180 degrees opposite to the combustion gas passage 2c, and the combustion gas G exiting the combustion gas passage 2c moves left and right in the combustion gas passage 4. It is possible to flow in the direction and exhaust the combustion gas passage 4 from the combustion gas outlet 3c to the flue 9 after being substantially half-circulated (not shown).

As shown in FIG. 4, the upper header 5 and the lower header 6 are formed in an annular shape having a rectangular cross section, and the headers 5 and 6 are provided with an inner water cooling wall 2 and an outer water cooling wall 3. The upper and lower ends of each of the water pipes 2a and 3a are connected in a continuous manner.
Further, the upper header 5 is provided with a refractory ceiling wall 29 that closes the upper surface side of the secondary combustion chamber S2, and at the center of the ceiling wall 29, there is a wood in the secondary combustion chamber S2. A pellet supply duct 30 that forms a wood pellet supply port 30a for charging the pellet F is provided in a penetrating manner.
Further, the upper header 5 is connected to a connecting pipe 32 that guides steam to the steam separator 31, and the lower header 6 is connected to the water feed pipe 33, the can water blow-out pipe 34, and the steam separator 31. Return pipes 35 and the like are connected to each other (see FIG. 1). A water level control cylinder 36 is attached between the upper header 5 and the lower header 6.

  As shown in FIG. 4, the wood pellet F combustion device 7 is provided with a cylindrical combustion cylinder 37 that forms a primary combustion chamber S1, and a lower position in the combustion cylinder 37, and has a transverse cross section of the primary combustion chamber S1. A perforated plate 38 for uniformly distributing and supplying the combustion air A; a ceramic particle layer 39 formed on the perforated plate 38 and formed by laminating many heat-resistant ceramic particles in a point contact state; The combustion air supply unit 40 that supplies the combustion air A to the lower space in a swirling state, the combustion blower 41 that supplies the combustion air A to the combustion air supply unit 40, and the combustion cylinder 37 are provided in a penetrating manner. And an ignition burner 42 located above the ceramic particle layer 39. The wood pellet F supplied to the ceramic particle layer 39 from the wood pellet supply port 30a is passed through the perforated plate 38 from the combustion air supply unit 40. Burning With burning in flowing by use air A, it is obtained so as to scatter into the combustion chamber side S2 the ash remaining after combustion with the combustion gas G.

The combustion cylinder 37 is formed by lining a refractory 27 in a cylindrical casing 37a, and the internal space is formed in a primary combustion chamber S1 communicating with the secondary combustion chamber S2. The combustion cylinder 37 is arranged in a vertical posture below the secondary combustion chamber S2.
The perforated plate 38 is mounted in a horizontal position at a lower position in the combustion cylinder 37, and a large number of air ejection holes for ejecting the combustion air A upward are evenly distributed with respect to the surface. The combustion air A is uniformly distributed and supplied to the transverse section of the combustion chamber S1.
Further, the ceramic particle layer 39 is formed by laminating a large number of ceramic particles having heat resistance and excellent thermal conductivity on the perforated plate 38 in a point contact state to an appropriate thickness. Between these ceramic particles, a fine passage through which the combustion air A passes is formed. The thickness of the ceramic particle layer 39 and the diameter of the ceramic particles are appropriately set according to the combustion conditions and the like, so that the fluidized combustion of the wood pellet F can be performed satisfactorily and reliably.
The combustion air supply unit 40 is provided at the outer peripheral position of the combustion cylinder 37 so as to surround the combustion cylinder 37, and is provided on the lower end surface of the combustion cylinder 37, and is used for combustion in the wind box 40a. Combustion air A from the combustion blower 41 connected to the wind box 40a is formed in the wind box 40a. The swirl vane 40b is configured to rotate the air A and supply it to the lower end space of the porous plate 38 in the combustion cylinder 37. While blowing in the tangential direction to cool the combustion cylinder 37, the combustion air A in the wind box 40a is swirled by swirl vanes 40b and supplied to the lower space of the perforated plate 38. This combustion air supply unit 40 is provided with ceramic particles from the perforated plate 38 so that the wood pellets F on the ceramic particle layer 39 or both the wood pellets F and the ceramic particles flow loosely to such an extent that they do not scatter to the secondary combustion chamber S2. Combustion air A is supplied to the layer 39.

  As shown in FIG. 6, the purge air supply mechanism 8 is connected to a purge air supply duct 43 having a U-shaped planar shape disposed at an outer position of the outer water cooling wall 3 and a purge air supply duct 43. The purge fan 44, the fin 3b at the lower end of the outer water cooling wall 3, the inspection door 28, and the flue duct 47 near the combustion gas outlet 3c are provided in a penetrating manner, and a hose 45 is connected to the purge air supply duct 43. The purge air supply pipe 46 is connected to the purge air supply pipe 46 through the purge air supply duct 43 and the purge air supply pipe 46 is connected to each purge air supply pipe 46. Purge air P is blown from the supply pipe 46 to the bottom of the combustion gas passage 4 to prevent incineration ash and unburned matter from accumulating on the bottom of the combustion gas passage 4.

The wood pellet fired steam boiler 1 is configured as a small once-through boiler having an equivalent evaporation amount of 500 kg / h, a maximum operating pressure of 0.98 MPa, a heat transfer area of 9.5 m ² and an efficiency of 85%. Moreover, the control of the wood pellet fired steam boiler 1 is three-position control (stop, low combustion, high combustion) by steam pressure.

Next, the operation of the wood pellet fired steam boiler 1 according to the above-described first embodiment will be described.
The blower of the ignition burner 42 is activated by the ignition signal, and at the same time, the induction blower 15, the combustion blower 41, the pusher blower 13, and the purge blower 44 are activated to purge the furnace and the combustion gas system. At this time, the induction fan 15 and the combustion blower 41 are controlled by an inverter, and the rotation is gradually increased as the operation starts.

  When the purging of the furnace and the combustion gas system is completed, the ignition burner 42 is ignited, and the screw conveyor 11 and the like are operated, so that the wood pellet F (moisture content is 8% to 13%, diameter is 5 mm to 8 mm, length) Supply 10 mm to 20 mm). That is, the wood pellet F in the service silo 10 is supplied to the pellet supply pipe 12 by the screw conveyor 11 and the pusher blower 13, and is supplied into the secondary combustion chamber S2 through the pellet supply duct 30 from the pellet supply port 30a. It is supplied onto the ceramic particle layer 39 of the combustion device 7. At this time, the screw conveyor 11 is controlled by an inverter so that an extremely small amount of wood pellets F is supplied at the time of start-up, and the supply amount is gradually increased. It has become.

  The wood pellet F charged into the secondary combustion chamber S2 is sprayed on the ceramic particle layer 39 and deposited there, ignited by the ignition burner 42, and after about 3 minutes (this time is the amount of combustion) The ignition burner 42 stops and enters a self-combustion state.

  Thereafter, the screw conveyor 11, the induction fan 15, and the combustion blower 41 gradually increase the rotational speed and enter a low-grade combustion state through a low output set value. At this time, the rotation speed of the induction fan 15 is set so that the pressure in the furnace is always a negative pressure of about −100 to −300 Pa.

  When the steam pressure rises and the low power combustion state is reached, the supply amount of the wood pellet F is changed to the low output combustion amount in a short time, but the supply of the combustion air A maintains the rated combustion state for a predetermined time. From low to high. This is because solid fuel such as wood pellet F requires a burning time. Note that combustion stops when the steam pressure rises even in a low output state.

When the combustion is stopped, the post-purge process is started, the combustion blower 41 and the induction fan 15 are rotated at high speed, the unburned wood pellets F on the ceramic particle layer 39 are burned out, and the incineration ash on the ceramic particle layer 39 is burned. Purge. Further, the pusher blower 13 and the purge blower 44 are also operated to purge the incineration ash at the bottom of the annular combustion gas passage 4.
If a combustion signal is input during the purge process, the purge is stopped and the combustion process is started.

  And the wood pellet F supplied on the ceramic particle layer 39 from the wood pellet supply port 30a flows in the wind box 40a, cools the combustion cylinder 37, is swirled by the swirl vanes 40b, and is blown out from the perforated plate 38. The combustion air A ejected from the holes above the ceramic particle layer 39 burns on the ceramic particle layer 39 in a gentle fluid state. At this time, in the primary combustion chamber S1, the wood pellet F burns while volatilizing moisture and volatile components, and burns while the fixed carbon components are scattered. Further, in the primary combustion chamber S1, a recirculation region of the combustion gas G is formed at the center by the swirling air supplied to the lower space of the perforated plate 38. Further, since the entire combustion chamber (primary combustion chamber S1 and secondary combustion chamber S2) is lengthened in the axial direction and the residence time of the combustion gas G is set longer, the unburned gas in the combustion gas G is completely burned. be able to.

  In the combustion device 7 for the wood pellet F, the ceramic particle layer 39 itself that performs combustion has a large number of minute spaces in which ceramic particles having excellent thermal conductivity are in point contact and the combustion air A flows between the ceramic particles. Therefore, the air is cooled by the combustion air A flowing in the minute space and is not heated excessively. Further, since the combustion cylinder 37 forming the primary combustion chamber S1 is cooled by the combustion air A flowing in the wind box 40a, the combustion temperature in the primary combustion chamber S1 is also lowered. Further, the wood pellet F combustor 7 burns the wood pellet F without causing a local high temperature part by supplying the combustion air A to the combustion part while flowing, and remains after the combustion. Combined with the incineration ash being scattered out of the ceramic particle layer 39, the wood pellet F can be continuously and stably burned without generating clinker in the combustion chamber.

  And the incinerated ash and the unburned matter in the combustion gas G scattered from the primary combustion chamber S1 are completely burned in the secondary combustion chamber S2, and then from the combustion gas passage port 2c formed in the upper part of the inner water cooling wall 2. It flows into the annular combustion gas passage 4 together with the combustion gas G. At this time, since the specific gravity (apparent specific gravity) of the incinerated ash is as light as 0.5, the incinerated ash is reliably and well discharged together with the combustion gas G from the combustion gas passage port 2c. In addition, the combustion gas G contains a small amount of unburned pellets. Furthermore, the flow rate of the combustion gas G passing through the combustion gas passage port 2c is set to be equal to or lower than a predetermined flow rate so as to prevent wear of the water-cooled walls 2 and 3 due to incinerated ash and unburned pellets. Wear of the water pipes 2a and 3a of the two water-cooled walls 2 and 3 due to the incinerated ash and unburned pellets is prevented.

  The combustion gas G that has flowed into the combustion gas passage 4 gives heat to the inner water cooling wall 2 and the outer water cooling wall 3 by contact heat transfer while making a round in the combustion gas passage 4, and then the outer water cooling wall. 3 is discharged from the combustion gas outlet 3 c formed in 3 through the flue 9 to the outside. Further, the incinerated ash and a part of the unburned matter flowing into the combustion gas passage 4 are burnt on the refractory 27 at the bottom of the combustion gas passage 4. At this time, in the contact heat transfer section where the combustion gas G and the water pipes 2a and 3a of the water cooling walls 2 and 3 are in contact, the flow of the combustion gas G becomes a cross flow intersecting the water pipes 2a and 3a. Compared with the pipe parallel flow in which the combustion gas G flows parallel to the water pipes 2a and 3a, the amount of heat absorption per unit area of the water pipes 2a and 3a can be increased, and the efficiency and size of the boiler can be increased. Can be planned. Further, the flow rate of the combustion gas G passing through the combustion gas passage 4 is such that the annular combustion gas passage 4 can prevent the water pipes 2a and 3a of the both water-cooling walls 2 and 3 from being incinerated with incinerated ash and unburned pellets. The interval (passage area of the combustion gas G) is gradually narrowed from the combustion gas passage 2c portion to the combustion gas outlet 3c so that the flow velocity of the combustion gas G flowing in the combustion gas passage 4 is kept constant. Therefore, wear of the water pipes 2a, 3a of the two water-cooled walls 2, 3 due to the incinerated ash and unburned pellets is prevented. Further, since purge air P is blown from the purge air supply mechanism 8 onto the refractory 27 at the bottom of the combustion gas passage 4, incineration ash and unburned matter accumulate at the bottom of the combustion gas passage 4. Can be prevented. The purge air supply mechanism 8 is operated intermittently during combustion, and continuously operated so that the purge air P can be continuously supplied at high speed during post purge.

  Combustion gas G, incineration ash, and some unburned matter in the combustion gas passage 4 are discharged to the flue 9 from the combustion gas outlet 3c formed in the outer water cooling wall 3, and pass through the flue 9 to form a cyclone dust collector. 14, where the combustion gas G and the incineration ash are separated. A part of the incineration ash and unburned matter discharged to the flue 9 is discharged (recovered) from the ash drop opening 48 to the ash storage box 18, where unburned matter is placed and burned. Further, the incinerated ash and unburned matter separated by the cyclone dust collector 14 are also discharged into an ash storage box 18 provided at the lower part of the cyclone dust collector 14, where unburned matter is placed and burned. As a result, the incinerated ash taken out from the ash storage box 18 does not contain unburned material.

  FIGS. 8 to 14 show a wood pellet fired steam boiler 1 according to a second embodiment of the present invention. The wood pellet fired steam boiler 1 is disposed in an opposing manner and has a rectangular combustion chamber S1, inwardly. A pair of linear inner water-cooling walls 2 forming S2 (in this embodiment consisting of a primary combustion chamber S1 and a secondary combustion chamber S2) and inner water-cooling walls 2 and 2 are disposed at outer positions; A pair of straight outer water cooling walls 3 forming a straight combustion gas passage 4 between the inner water cooling wall 2 and the upper and lower ends of the water pipes 2a, 3a of the two water cooling walls 2, 3 An upper header 5 and a lower header 6 connected in communication with each other, a combustion device 7 disposed on the upstream side of the primary combustion chamber S1 and combusting the wood pellet F as fuel, a bottom portion of the combustion gas passage 4, and a flue Purge air P is supplied to the bottom of the A purge air supply mechanism 8 or the like for preventing accumulation is provided. The wood pellet F is introduced into the primary combustion chamber S1 from the wood pellet supply port 30a provided on the upstream side of the primary combustion chamber S1, and the combustion device 7 The combustion gas G and the incinerated ash generated by the above are discharged from the secondary combustion chamber S2 to the flue 9 through the combustion gas passage 4.

  In this steam boiler 1, heat absorption to the boiler water flowing in the water pipe 2a of the inner water cooling wall 2 is performed by radiant heat transfer by the combustion flame, radiant heat transfer by the generated combustion gas G, and the combustion chamber S1. , S2 is performed by contact heat transfer (convection heat transfer) by the combustion gas G flowing in the combustion gas passage 4 and contact heat transfer by the combustion gas G flowing in the combustion gas passage 4, and in the water pipe 3a of the outer water cooling wall 3 Heat absorption into the flowing boiler water is performed only by contact heat transfer (convection heat transfer) by the combustion gas G flowing in the combustion gas passage 4.

As shown in FIGS. 10 to 13, the inner water cooling walls 2, 2 are strips in which a plurality of water pipes 2 a (thick bare pipes) are linearly arranged in parallel and the adjacent water pipes 2 a extend in the vertical direction. It is formed by connecting with plate-shaped fins 2b, and is arranged in an opposing manner to form a rectangular primary combustion chamber S1 and a secondary combustion chamber S2 between the two water cooling walls 2 and 2. . The upper and lower sides of the primary combustion chamber S1 and the secondary combustion chamber S2 and the upstream end of the primary combustion chamber S1 are respectively closed by a refractory 27 and the downstream end of the secondary combustion chamber S2. The part is closed by an openable / closable inspection door 28 formed by lining a refractory 27. Also, an ash dropping port 48 is provided at the bottom on the downstream side of the secondary combustion chamber S2.
Further, the combustion gas G in the secondary combustion chamber S2 is caused to flow into the linear combustion gas passage 4 by notching the upper ends of the plurality of fins 2b on the downstream side of the inner water cooling walls 2 and 2. A plurality of combustion gas passage ports 2c are formed. The opening area of the combustion gas passage port 2c is set to a predetermined value in order to prevent wear of the water pipe 2a and the like due to scattered ash and partially unburned material. In this embodiment, the opening area of the combustion gas passage port 2c is such that the flow rate of the combustion gas G passing through the combustion gas passage port 2c is equal to or lower than a predetermined flow rate (preventing wear of the water pipe 2a and the like due to scattered ash and some unburned matter) It is set to be less than the possible flow rate).

  As shown in FIGS. 11 to 13, the outer water cooling walls 3 and 3 are adjacent to each other by arranging a plurality of water tubes 3a (thick bare tubes) in a straight line in the same manner as the inner water cooling wall 2. It is formed by connecting the water pipes 3a with strip-like fins 3b extending in the vertical direction, and is parallel to or substantially parallel to the inner water cooling walls 2, 2 at the outer position of the inner water cooling walls 2, 2. Two linear combustion gas passages 4 through which the combustion gas G passes between the water cooling walls 2 and 2 disposed inside are formed. The upstream end portions of the two combustion gas passages 4 are closed by an openable / closable inspection door 28 that is lined with a refractory 27, and the downstream end portions of the two combustion gas passages 4 are open. And communicated with the rising portion 9 a of the flue 9. An ash dropping port 48 is provided at the bottom of the rising portion 9 a of the flue 9.

  In this embodiment, the outer water-cooling walls 3, 3 are in relation to the inner water-cooling walls 2, 2 so that the upstream space of the combustion gas passage 4 is slightly wider than the downstream space. It is arranged at the outer position of the inner water cooling walls 2 and 2 in an inclined state, and the interval between the straight combustion gas passages 4 (the passage area of the combustion gas G) is gradually narrowed from the upstream side to the downstream side. It is supposed to be. Thereby, the flow velocity of the combustion gas G flowing through the combustion gas passage 4 is kept constant. The higher the flow rate of the combustion gas G passing through the combustion gas passage 4, the better the heat transfer efficiency, but the wear of the water pipes 2a, 3a of the two water-cooled walls 2, 3 due to the ash in the combustion gas G and the like occurs. On the other hand, if the flow rate of the combustion gas G is too slow, the heat transfer efficiency is lowered, and the incinerated ash is deposited on both the water cooling walls 2 and 3 (heat transfer surface). Therefore, the flow rate of the combustion gas G passing through the combustion gas passage 4 is set to a predetermined flow rate in order to prevent wear of the water pipes 2a, 3a, etc. of the water cooling walls 2, 3 due to ash or the like in the combustion gas G. Is set to

As shown in FIG. 14, the upper header 5 and the lower header 6 have a hollow structure with a rectangular cross section and are formed in a rectangular ring shape. The upper and lower ends of the water pipes 2a and 3a of the outer water cooling walls 3 and 3 are connected in a continuous manner.
The upper header 5 is connected to a connecting pipe 32 for guiding steam to the steam separator 31, and the lower header 6 is connected to a water supply pipe (not shown), a can water blow-out pipe (not shown), and A return pipe 35 and the like from the steam separator 31 are connected to each other. A water level control cylinder 36 is attached between the upper header 5 and the lower header 6.

  As shown in FIG. 10, the wood pellet F combustor 7 includes a wind box 49 (wind box) including an ignition burner 42, a pellet supply port 30 a, a combustion blower 41, and a secondary combustion blower (not shown). A combustion air supply unit 50, a ceramic particle layer 39, a refractory wall 51, and a combustion unit 53 including a secondary combustion air supply unit 52. The dispersed wood pellet F is burned while flowing with the combustion air A from the combustion air supply unit 50, and the incineration ash remaining after the combustion is burned together with the combustion gas G outside the ceramic particle layer 39 (downstream of the ceramic particle layer 39). The unburned ash and the unburned portion in the combustion gas G outside the ceramic particle layer 39 are scattered by the secondary combustion air A2 from the secondary combustion air supply unit 52. Together to put the combustion, in which the ash that has fallen to the bottom of the secondary combustion housing S2 was set to be transferred by the secondary combustion air A2.

That is, the wind box 49 is attached in a state adjacent to the refractory 27 provided at the upstream end of the primary combustion chamber S1, and an ignition burner 42 (oil burner) and a pellet supply are provided therein. A pellet supply duct 30 that is connected to the pipe 12 and forms a pellet supply port 30a that communicates with the primary combustion chamber S1 is provided.
The wind box 49 includes a combustion blower 41 that supplies combustion air A into the wind box 49 and a secondary combustion blower that supplies secondary combustion air A2 to the secondary combustion air supply unit 52 ( (Not shown) are provided.

  On the other hand, the combustion part 53 is provided in the primary combustion chamber S1 in a state adjacent to the wind box 49, and a combustion air supply part 50 for ejecting combustion air A and a ceramic for fluidizing and burning the wood pellets F. A particle layer 39, a refractory wall 51 that prevents the wood pellet F and ceramic particles from flowing out, and a secondary combustion air supply unit 52 that ejects the secondary combustion air A2 are provided.

Specifically, the combustion air supply unit 50 is formed in a thin box shape with the central portion of the upper surface protruding upward, and is provided in a state communicating with the wind box 49 at the bottom of the primary combustion chamber S1. ing. The upper surface side of the combustion air supply section 50 (a central portion projecting upward from the thin box) is formed in a perforated plate 38 having a large number of air ejection holes for ejecting the combustion air A upward. ing.
By the way, the layer of the wood pellet F formed on the ceramic particle layer 39 becomes thick on the upstream side (the right side in FIG. 10) of the ceramic particle layer 39 on which the wood pellet F is dispersed, and the downstream side of the ceramic particle layer 39 ( As it goes to the left side of FIG. Therefore, each air ejection hole of the perforated plate 38 supplies a large amount of combustion air A to the upstream side of the ceramic particle layer 39 on which the wood pellets F are dispersed, and the combustion air as it goes downstream of the ceramic particle layer 39. An array is formed so that A is gradually supplied in a small amount and the combustion air A is uniformly supplied to the layer of the wood pellets F. In this example, the number of air ejection holes in the perforated plate 38 gradually decreases as the number of the air ejection holes increases from the upstream side to the downstream side.
Further, the combustion air supply unit 50 is provided from the perforated plate 38 so that the wood pellet F on the ceramic particle layer 39 or both the wood pellet F and the ceramic particles flow loosely to the extent that they do not scatter to the secondary combustion chamber S2. Combustion air A is supplied to the ceramic particle layer 39.

The ceramic particle layer 39 is formed by laminating a large number of ceramic particles having heat resistance and excellent thermal conductivity on the perforated plate 38 of the combustion air supply unit 50 in a point contact state to an appropriate thickness. The one end side is located below the pellet supply port 30a and is the upstream side where the wood pellet F is dispersed. A fine passage through which the combustion air A passes is formed between the ceramic particles of the ceramic particle layer 39.
Note that the thickness of the ceramic particle layer 39 and the diameter of the ceramic particles are appropriately set according to the combustion conditions and the like, so that the fluidized combustion of the wood pellet F can be performed satisfactorily and reliably.

  The refractory walls 51 are provided in a standing posture on both sides and downstream ends of the ceramic particle layer 39. The height of the refractory wall 51 is such that the wood pellet F and ceramic particles do not flow out to the downstream side (in the secondary combustion chamber S2) of the ceramic particle layer 39 and incineration ash does not remain in the ceramic particle layer 39. Is set.

  The secondary combustion air supply unit 52 is provided in the combustion air supply unit 50, and supplies the secondary combustion air A2 to the downstream region (secondary combustion chamber S2) from the semiconductive particle layer 39, The incineration ash that has exceeded the refractory wall 51 and the unburned matter in the combustion gas G are placed in the secondary combustion chamber S2 by the secondary combustion air A2 and burned, and the incineration ash that has dropped to the bottom of the secondary combustion chamber S2 Is transferred further downstream by the secondary combustion air A2 and discharged out of the secondary combustion chamber S2. In this example, the secondary combustion air supply unit 52 is formed from a secondary combustion air supply pipe disposed in the combustion air supply unit 50 along the longitudinal direction of the primary combustion chamber S1, and the base end side is The secondary combustion air A2 is supplied to the secondary combustion chamber S2 from a plurality of holes provided at the tip while being connected to the secondary combustion blower.

  As shown in FIG. 13, the purge air supply mechanism 8 is connected to a purge air supply duct 43 having a U-shaped planar shape disposed at an outer position of the outer water cooling wall 3 and a purge air supply duct 43. The purge blower 44, the fin 3a at the lower end of the outer water cooling wall 3, the inspection door 28, and the rising portion 9a of the flue 9 are provided in a penetrating manner, and the purge air supply duct 43 is connected via a hose 45, respectively. The purge air supply pipes 46 are connected to each other, and purge air P is supplied from the purge blower 44 to the purge air supply pipes 46 via the purge air supply ducts 43. Thus, purge air P is blown to the bottom of the combustion gas passage 4 to prevent incineration ash and unburned matter from accumulating on the bottom of the combustion gas passage 4.

Next, the operation of the wood pellet fired steam boiler 1 according to the above-described second embodiment will be described.
When the blower of the ignition burner 42 is actuated by the ignition signal, as with the steam boiler 1 according to the first embodiment, an induction blower (not shown), a combustion blower 41, a forced blower (not shown), and a purge blower 44. Operate simultaneously to purge the furnace and the combustion gas system. At this time, the induction fan and the combustion fan 41 are controlled by an inverter, and the rotation is gradually increased as the operation starts.

  When the purging of the furnace and the combustion gas system is completed, the ignition burner 42 is ignited in the same manner as the steam boiler 1 according to the first embodiment, and the screw conveyor (not shown) or the like is operated to activate the wood pellet F (water content). The rate is 8% to 13%, the diameter is 6 mm to 12 mm, and the length is 10 mm to 20 mm). That is, the wood pellet F in the service silo (not shown) is supplied to the pellet supply pipe 12 by the screw conveyor and the pusher blower, and is introduced into the primary combustion chamber S1 through the pellet supply duct 30 from the pellet supply port 30a. It is supplied onto the ceramic particle layer 39 of the combustion device 7. At this time, the screw conveyor is controlled by an inverter so that a very small amount of wood pellets F is supplied at the time of start-up, the supply amount is gradually increased, and the wood pellets F are supplied at a rated rate when a predetermined time has elapsed. It has become.

  The wood pellet F charged into the primary combustion chamber S1 is sprayed on the ceramic particle layer 39 and deposited there, and ignited by the ignition burner 42, and after about 3 minutes (this time varies depending on the amount of combustion) ), The ignition burner 42 stops and enters a self-combustion state.

  Thereafter, the screw conveyor, the induction fan, and the combustion blower 41 gradually increase the rotation speed and enter the low-grade combustion state through the low output set value. At this time, the rotation speed of the induction fan 15 is set so that the pressure in the furnace is always a negative pressure of about −100 to −300 Pa.

  When the steam pressure rises and the low power combustion state is reached, the supply amount of the wood pellet F is changed to the low output combustion amount in a short time, but the supply of the combustion air A maintains the rated combustion state for a predetermined time. From low to high. This is because solid fuel such as wood pellet F requires a burning time. Note that combustion stops when the steam pressure rises even in a low output state.

When the combustion is stopped, a post-purge process is started, the combustion blower 41 and the induction fan are rotated at a high speed, the unburned wood pellet F on the ceramic particle layer 39 is burned out, and the incineration ash on the ceramic particle layer 39 is removed. Purge. Further, the pusher blower and the purge blower 44 are also operated to purge the incineration ash at the bottom of the annular combustion gas passage 4.
If a combustion signal is input during the purge process, the purge is stopped and the combustion process is started.

The wood pellet F supplied from the pellet supply port 30a to the upstream side of the ceramic particle layer 39 flows in the wind box 49 and the combustion air supply unit 50 and passes through the air ejection holes of the porous plate 38 to the ceramic particle layer 39. The combustion air A spouted upwards causes fluid combustion while volatilizing moisture and volatile matter, and moves to the downstream side of the ceramic particle layer 39 to complete the combustion. Further, the incinerated ash and unburned matter remaining after the combustion of the wood pellet F, together with the combustion gas G, passes through the refractory wall 51 and scatters to the downstream side region (in the secondary combustion chamber S2) from the ceramic particle layer 39.
At this time, the combustion air A is supplied to the ceramic particle layer 39 so that both the wood pet or the wood pellet F and the ceramic particles flow loosely on the ceramic particle layer 39, and the wood pellet F is dispersed. A large amount is supplied to the upstream side of the ceramic particle layer 39, and gradually supplied to the downstream side of the ceramic particle layer 39 so as to be uniformly supplied to the layer of the woody pet.

  In the wood pellet combustion apparatus 7, the ceramic particle layer 39 itself that performs combustion has a large number of minute spaces in which ceramic particles excellent in thermal conductivity are in point contact and the combustion air A flows between the ceramic particles. Therefore, the air is cooled by the combustion air A flowing in the minute space and is not heated excessively. Further, the combustion device 7 for the wood pellet F causes the wood pellet F to flow and burn without causing a local high temperature portion by supplying the combustion air A uniformly to the combustion portion, and remains after the combustion. Combined with the scattering of the incinerated ash out of the ceramic particle layer 39, the wood pellets F can be continuously burned stably without generating clinker in the primary combustion chamber S1, and the combustion air Burnout of the supply unit 50 and the like can be prevented.

  Then, the incinerated ash and unburned matter scattered on the downstream side of the ceramic particle layer 39 (in the secondary combustion chamber S2) are supplied from the secondary combustion air supply unit 52 into the secondary combustion chamber S2. It burns with air A2. At this time, a part of the incineration ash and unburned matter is deposited on the surface of the refractory 27 at the bottom of the secondary combustion chamber S2, but is deposited by the secondary combustion air A2 supplied from the secondary combustion air supply unit 52. While combusting, it is transported downstream in the secondary combustion chamber S2 by the secondary combustion air A2 and discharged from the ash drop opening 48 to the ash storage box 18. Since the inside of the ash storage box 18 is kept at a high temperature, unburned components and the like are placed in the ash storage box 18 and burned to become complete ash.

  The combustion gas G in the secondary combustion chamber S2, the scattered incineration ash, and the unburned matter in the combustion gas G are straight from the combustion gas passage 2c formed at the downstream ends of the inner water cooling walls 2 and 2. Into the two combustion gas passages 4. At this time, since the specific gravity (apparent specific gravity) of the incinerated ash is as light as 0.5, the incinerated ash is reliably and well discharged together with the combustion gas G from the combustion gas passage port 2c. In addition, the combustion gas G contains a small amount of unburned pellets. Furthermore, the flow rate of the combustion gas G passing through the combustion gas passage port 2c is set to be equal to or lower than a predetermined flow rate so as to prevent wear of the water-cooled walls 2 and 3 due to incinerated ash and unburned pellets. Wear of the water pipes 2a and 3a of the two water-cooled walls 2 and 3 due to the incinerated ash and unburned pellets is prevented.

  The combustion gas G flowing into the combustion gas passage 4 gives heat to the inner water cooling wall 2 and the outer water cooling wall 3 by contact heat transfer while flowing in the combustion gas passage 4 from the upstream side to the downstream side. The gas is discharged from the downstream end of the combustion gas passage 4 to the rising portion 9 a of the flue 9. Incinerated ash and a part of unburned matter that have flowed into the combustion gas passage 4 are deposited on the refractory 27 at the bottom of the combustion gas passage 4, and are burned by the high temperature refractory 27 here. At this time, in the contact heat transfer section where the combustion gas G and the water pipes 2a and 3a of the water cooling walls 2 and 3 are in contact, the flow of the combustion gas G becomes a cross flow intersecting the water pipes 2a and 3a. Compared with the pipe parallel flow in which the combustion gas G flows parallel to the water pipes 2a and 3a, the amount of heat absorption per unit area of the water pipes 2a and 3a can be increased, and the efficiency and size of the boiler can be increased. Can be planned. The flow rate of the combustion gas G passing through the combustion gas passage 4 is such that the linear combustion gas passage 4 can prevent the water pipes 2a and 3a of the two water-cooled walls 2 and 3 from being incinerated with incinerated ash and unburned pellets. (The passage area of the combustion gas G) is gradually reduced from the upstream side to the downstream side, and the flow velocity of the combustion gas G flowing in the combustion gas passage 4 is kept constant. Wear of the water pipes 2a and 3a of the two water-cooled walls 2 and 3 due to unburned pellets is prevented. Further, the purge air supply mechanism 8 purges the refractory 27 at the bottom of the combustion gas passage 4, the refractory 27 in front of the inspection door 28, and the refractory 27 at the bottom of the rising portion 9 a of the flue 9. Since the air P is blown, it is possible to prevent incineration ash and unburned material from accumulating at the bottom of the combustion gas passage 4 and to burn unburned material and the like. A part can be discharged into the ash storage box 18 from the ash drop opening 48 formed at the bottom of the rising portion 9a. The purge air supply mechanism 8 is operated intermittently during combustion, and continuously operated so that the purge air P can be continuously supplied at high speed during post purge.

  The combustion gas G and the incineration ash discharged to the rising part 9a of the flue 9 reach the cyclone dust collector (not shown) through the flue 9, where the combustion gas G and the incineration ash are separated. Incinerated ash and unburned matter separated by the cyclone dust collector are also discharged into an ash storage box provided at the lower part of the cyclone dust collector.

In the above embodiment, the wood pellet fired steam boiler 1 is controlled at three positions. However, in other embodiments, the control of the wood pellet fired steam boiler 1 is ON- It may be OFF control or proportional control.
In the above embodiment, the wood pellet F is burned by the combustion device 7. However, in other embodiments, in addition to the wood pellet F, chicken droppings and chips with reduced components are also included. You may make it burn with the combustion apparatus 7 as a fuel.

1 is a front view of a wood pellet fired steam boiler according to a first embodiment of the present invention. It is a side view of a wood pellet fired steam boiler. It is a top view of a wood pellet fired steam boiler. It is a longitudinal cross-sectional view of a wood pellet fired steam boiler. It is the aa line expanded sectional view of FIG. FIG. 5 is an enlarged sectional view taken along line bb in FIG. 4. It is a systematic diagram of a wood pellet fired steam boiler. It is a front view of the wood pellet fired steam boiler which concerns on the 2nd Embodiment of this invention. It is a side view of a wood pellet burning boiler. It is an expanded vertical sectional view of a wood pellet fired steam boiler. FIG. 10 is an enlarged sectional view taken along the line cc of FIG. 8. FIG. 9 is an enlarged sectional view taken along the line dd in FIG. 8. FIG. 9 is an enlarged sectional view taken along line ee in FIG. 8. It is the ff sectional view taken on the line of FIG.

Explanation of symbols

  1 is a wood pellet fired steam boiler, 2 is an inner water cooling wall, 2a is an inner water cooling wall water pipe, 2c is a combustion gas passage, 3 is an outer water cooling wall, 3a is an outer water cooling wall water pipe, and 3c is combustion Gas outlet, 4 is a combustion gas passage, 5 is an upper header, 6 is a lower header, 7 is a combustion device, 8 is a purge air supply mechanism, 9 is a flue, 30a is a pellet supply port, 37 is a combustion cylinder, and 38 is porous Plate, 39 ceramic particle layer, 40 combustion air supply unit, 41 combustion fan, 42 ignition burner, 49 wind box, 50 combustion air supply unit, 51 refractory wall, 52 The secondary combustion air supply unit, 53 is the combustion unit, A is the combustion air, A2 is the secondary combustion air, F is the wood pellet, G is the combustion gas, and P is the purge air.

Claims (9)

  An annular inner water cooling wall forming a circular combustion chamber inward, an annular outer water cooling wall disposed concentrically or substantially concentrically at an outer position of the inner water cooling wall, and an inner water cooling wall; An annular combustion gas passage formed between the outer water cooling wall and communicating with the combustion chamber and the flue, respectively, and an upper header connected in communication with the upper and lower ends of the water pipes of both water cooling walls; Composed of a lower header, a combustion device disposed in the lower part of the combustion chamber and burning wood pellets as fuel, and a purge air supply mechanism for supplying purge air to the bottom of the combustion gas passage, the upper part of the combustion chamber It is characterized in that wood pellets are introduced into the combustion chamber from the wood pellet supply port provided in the combustion chamber and burned by the combustion device, and the generated combustion gas and incinerated ash are discharged from the combustion chamber to the flue through the combustion gas passage. Woody pe Tsu door-fired steam boiler.   One portion of the annular combustion gas passage is closed, and one end of the combustion gas passage is communicated with the combustion chamber via a combustion gas passage formed in an inner water cooling wall, and the other end of the combustion gas passage is disposed outside. The combustion gas is made to communicate with the flue through the combustion gas outlet formed in the water cooling wall of the gas, and the combustion gas and the incinerated ash that have flowed into the combustion gas passage from the combustion chamber through the combustion gas passage port are made to make one round in the combustion gas passage 2. A wood pellet burning combustion apparatus according to claim 1, wherein the combustion apparatus discharges the gas from a combustion gas outlet to a flue.   A combustion gas passage for communicating the combustion chamber and the combustion gas passage is formed in the inner water cooling wall, and the combustion gas passage and the flue are communicated with the outer water cooling wall at a position 180 degrees opposite to the combustion gas passage. The combustion gas outlet is formed, and the combustion gas and the incinerated ash that have flowed into the combustion gas passage from the combustion chamber through the combustion gas passage port are caused to flow in the left-right direction in the combustion gas passage, and then the combustion gas passage is substantially half-circulated. 2. The wood pellet fired combustion apparatus according to claim 1, wherein the wood pellet fired combustion apparatus is discharged to a flue through a combustion gas outlet.   3. The space between the annular combustion gas passages is gradually narrowed from the vicinity of the combustion gas passage opening to the vicinity of the combustion gas outlet, so that the flow velocity of the combustion gas flowing in the combustion gas passage is kept constant. Or the wood pellet burning combustion apparatus of Claim 3.   The combustion device is provided with a cylindrical combustion cylinder that forms a primary combustion chamber communicating with a combustion chamber formed inside an inner water cooling wall, and a lower position in the combustion cylinder. A perforated plate in which a large number of air ejection holes for uniformly distributing combustion air are formed, a ceramic particle layer formed on the perforated plate and laminated in a point contact state with a number of heat-resistant ceramic particles, and combustion A combustion air supply unit that cools the cylinder from the outside and supplies combustion air to the perforated plate in a swirling state, a combustion blower that supplies combustion air to the combustion air supply unit, and a combustion cylinder that is inserted into the combustion cylinder And an ignition burner positioned above the ceramic particle layer, and the wood pellets supplied to the ceramic particle layer from the wood pellet supply port by the combustion air passing through the porous plate from the combustion air supply unit Burn while flowing Together is, wood pellet burning combustion apparatus according to claim 1, characterized in that so as to scatter into the combustion chamber side incinerated ash remaining after combustion with the combustion gases.   A pair of straight inner water-cooling walls that are arranged opposite to each other to form a rectangular combustion chamber, and a pair of straight lines that are disposed parallel to or substantially parallel to the water-cooling walls at the outer positions of the inner water-cooling walls. The outer water cooling walls, the inner water cooling walls and the outer water cooling walls, respectively, and the straight combustion gas passages communicating with the combustion chamber and the flue respectively, and the water pipes of both water cooling walls. An upper header and a lower header connected to the upper end portion and the lower end portion, respectively, a combustion device disposed on the upstream side of the combustion chamber and burning wood pellets as fuel, a bottom portion of the combustion gas passage, and a flue Composed of a purge air supply mechanism for supplying purge air to the bottom, and the wood pellets are introduced into the combustion chamber from the wood pellet supply port provided on the upstream side of the combustion chamber and burned by the combustion device. And incineration ash from the combustion chamber Wood pellet-fired steam boiler, characterized in that so as to discharge into the flue through the scan path.   7. The wood according to claim 6, wherein the interval between the linear combustion gas passages is gradually narrowed from the upstream side to the downstream side so that the flow velocity of the combustion gas flowing in the combustion gas passage is kept constant. Pellet burning device.   The combustion device is composed of a wind box provided with an ignition burner, a pellet supply port, a combustion blower, and a secondary combustion blower, and a combustion section provided upstream of the combustion chamber in a state adjacent to the wind box. The combustion part is provided in a state communicating with the wind box at the bottom on the upstream side of the combustion chamber, and the upper surface side is formed as a perforated plate having a number of air ejection holes for ejecting the primary combustion air upward. Combustion air supply unit and ceramic particles formed on the perforated plate of the combustion air supply unit and laminated in a point contact state with a number of heat-resistant ceramic particles whose one end is located below the pellet supply port And a refractory wall with a height that prevents the outflow of wood pellets and ceramic particles and does not leave incineration ash in the ceramic layer, and a combustion air supply. Provided in the department The primary combustion air from the combustion air supply section is composed of a secondary combustion air supply section for supplying secondary combustion air to the downstream region of the combustion chamber, and the wood pellets supplied to the ceramic particle layer from the pellet supply port. The incinerated ash remaining after combustion is scattered outside the ceramic particle layer together with the combustion gas, and the unburned ash and the unburned content in the combustion gas are discharged from the ceramic particle layer outside the ceramic particle layer. The wood pellet burning according to claim 6, characterized in that the incinerated ash dropped on the bottom of the combustion chamber is transferred by the secondary combustion air while being burned by the secondary combustion air from the supply unit. Combustion device.   The air ejection hole of the perforated plate of the combustion air supply unit supplies a large amount of primary combustion air to the one end side upstream of the ceramic particle layer to which the wood pellets are supplied, and the other end portion downstream of the ceramic particle layer The primary combustion air is gradually reduced as it goes to the side, and the primary combustion air is uniformly supplied to the wood pellet layer. 8. A wood pellet fired steam boiler according to 8.

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