JP2008241133A - Fluid bed-type boiler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid bed-type boiler performing good combustion while securing fluidity in a fluid bed-type combustion furnace. <P>SOLUTION: This fluid bed-type boiler 1 comprises: the fluid bed-type combustion furnace 3 for burning a charged fuel; a circulation line 23 for circulating a bed material discharged from a bottom discharge opening 3d of the combustion furnace 3 to return the bed material to the combustion furnace again; and a selecting device 25 disposed on the circulation line 23 for selecting and removing undesirable substances improper to the combustion, from the circulated bed material. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fluidized bed boiler provided with a fluidized bed type combustion furnace.

Conventionally, as a technique in such a field, for example, a boiler described in Patent Document 1 below is known. This boiler is a power generation boiler that generates power by burning waste fuel. In particular, in recent years, the demand for this type of boiler is increasing in order to effectively use waste as fuel.
Japanese Patent Application Laid-Open No. 2006-064251

  However, the waste often contains unsuitable materials that are unsuitable for combustion in a boiler. When such waste is used as fuel for a fluidized bed boiler, unsuitable materials that could not be combusted accumulate in the combustion furnace, thereby deteriorating the fluidity in the combustion furnace and achieving good combustion. There is a risk of disappearing. In recent years, the need for solving the above-mentioned problems is particularly high, since it is increasingly required to deal with waste fuels that are often unsuitable.

  Therefore, an object of the present invention is to provide a fluidized bed boiler that ensures good fluidity in a fluidized bed combustion furnace and enables good combustion.

  A fluidized bed type boiler of the present invention includes a fluidized bed type combustion furnace that burns fuel that is input, a circulation line that circulates solids discharged from the bottom of the combustion furnace and returns them to the combustion furnace, and a circulation line And a sorting and removing unit that is provided on the line and sorts and removes unsuitable substances that are unsuitable for combustion from solids circulating in the circulation line.

  In this fluidized bed boiler, the solid matter discharged from the bottom of the combustion furnace is circulated so as to be returned to the combustion furnace again through the circulation line, and inappropriate substances contained in the solid matter are selected during the circulation. Removed. Therefore, unsuitable materials that could not be burned are removed from the combustion furnace, fluidity in the combustion furnace is ensured, and good combustion is possible.

  The fluidized-bed boiler according to the present invention further includes a fuel heat treatment unit that is provided in a preceding stage of the sorting and removing unit on the circulation line and performs a pretreatment of the fuel that is input to the combustion furnace, and the fuel heat treatment unit is disposed in the circulation line. The pretreatment may be performed by heat treatment using the heat of the solid material that is charged with fuel and passes through the circulation line. In this case, in front of the sorting and removing unit where the solid matter is in a high temperature state, fuel is introduced into the circulation line, and the fuel is heat-treated using the heat of the solid matter. Therefore, since the heat of the solid material that is originally discarded is effectively used as the heat used for the pretreatment of the fuel, the energy necessary for the operation of the boiler as a whole can be saved.

  In addition, the fluidized bed boiler of the present invention may further include a solid material cooling unit that is provided upstream of the sorting and removing unit on the circulation line and cools the solid material passing through the circulation line. In this case, since the solid matter from the combustion furnace can be cooled and introduced into the sorting / removing unit, the function of the sorting / removing unit can be prevented from being hindered by high temperatures, and efficient sorting can be performed.

  Further, the fuel heat treatment section may be provided at the subsequent stage of the solid material cooling section. In this case, since the heat of the solid matter after cooling is used for the heat treatment, it is possible to suppress the thermal decomposition of the fuel component in the raw fuel due to the temperature during the heat treatment being too high.

  Moreover, the solid material cooling part and the fuel heat treatment part may be provided integrally. With this configuration, the apparatus can be made compact.

  The fluidized bed boiler of the present invention further includes a gas processing unit that processes gas generated by heat treatment of the fuel in the fuel heat processing unit, and the gas processing unit sucks and discharges gas from the fuel heat processing unit. And a gas dissolving part that dissolves the gas discharged by the gas suction part into a liquid.

  According to this configuration, by removing the gas generated by the heat treatment of the fuel from the fuel heat treatment section and dissolving it in the liquid, it is possible to recover the gas in a form that facilitates subsequent processing. Further, since the generated gas is sucked and discharged in the fuel heat treatment section, the heat treatment accompanied with gas generation can be promoted in the fuel heat treatment section. Specifically, the gas suction unit may include a liquid ejector that ejects liquid.

  According to the fluidized bed boiler of the present invention, it is possible to ensure good fluidity in the fluidized bed combustion furnace and perform good combustion.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a fluidized bed boiler according to the present invention will be described in detail with reference to the drawings.

  An external circulation type (Circulating Fluidized Bed type) fluidized bed boiler 1 shown in FIG. 1 is a boiler using waste plastic and RPF as fuel, and includes a fluidized bed type combustion furnace 3 having a vertically long cylindrical shape. A fuel inlet 3a for introducing fuel is provided in the middle part of the combustion furnace 3, and a gas outlet 3b for discharging combustion gas is provided in the upper part. A cyclone 7 that functions as a solid-gas separator is connected to the gas outlet 3b. The discharge port 7a of the cyclone 7 is connected to a downstream gas processing system via a gas line. A return line 9 called a downcomer extends downward from the bottom outlet of the cyclone 7, and the lower end of the return line 9 is connected to the intermediate side surface of the combustion furnace 3.

  In the combustion furnace 3, the solid material containing the fuel introduced from the inlet 3a flows by the combustion / flowing air introduced from the lower air supply line 3c, and the fuel flows about 800 to 900 while flowing. Burn at ℃. The combustion gas generated in the combustion furnace 3 is introduced into the cyclone 7 with accompanying solid particles. The cyclone 7 separates solid particles and gas by a centrifugal separation action, returns the separated solid particles to the combustion furnace 3 through the return line 9, and sends the combustion gas from which the solid particles have been removed from the discharge port 7 a through the gas line. It is sent to the gas processing system at the subsequent stage.

  In this combustion furnace 3, a solid substance called “in-furnace bed material” is generated and collected at the bottom, and the bed material is sintered and melted and solidified by the concentration of impurities (low melting point materials, etc.) in the in-furnace bed material. Alternatively, it is necessary to suppress malfunctions caused by incombustibles. For this reason, in the combustion furnace 3, the in-furnace bed material is periodically discharged from the bottom discharge port 3 d to the outside. The discharged bed material is returned to the combustion furnace 3 through the circulation line 23 again. In addition, waste plastics used as fuel for the boiler 1 often contain unsuitable materials such as metals that are unsuitable for combustion, and it is necessary to remove these unsuitable materials from the combustion furnace 3.

  For this reason, a sorting device 25 having a sieve and a magnetic separation device is provided on the circulation line 23, and in this sorting device 25, a metal, potatoes, Unsuitable materials such as rubble and clinker are selected and removed. By such circulation and sorting of the bed material, unsuitable substances are removed from the combustion furnace 3 by the sorting device 25, so that the fluidity of the combustion substances in the combustion furnace 3 is ensured and good combustion is performed. At the same time, flow defects in the combustion furnace 3, the cyclone 7, and the return line 9 are suppressed.

  The gas treatment system includes a gas heat exchanger 13 connected to the gas outlet 7a of the cyclone 7 via a gas line, and a bug connected to the outlet 13a of the gas heat exchanger 13 via a gas line. And a filter (dust collector) 15. The gas heat exchanger 13 is provided with a boiler tube 13b that allows water to flow across the exhaust gas flow path. When the high-temperature exhaust gas sent from the cyclone 24 comes into contact with the boiler tube 13b, the heat of the exhaust gas is recovered in the water in the tube, and the generated high-temperature steam is sent to the power generation turbine through the boiler tube 13b. The bag filter 15 removes fine particles such as fly ash that are still accompanying the combustible gas. The clean gas discharged from the discharge port 15a of the bag filter 15 is discharged from the chimney 19 via the gas line and the pump 17 to the outside.

  As described above, in the boiler 1, waste plastic or RPF is used as fuel. Since such fuel contains chlorine and heavy metal, when the fuel is burned, exhaust gas containing chlorine and heavy metal is generated, and such exhaust gas advances corrosion of the boiler tube 13a and shortens its life. Therefore, it is preferable to reform such raw fuel before introducing it into the combustion furnace 3 and remove chlorine and heavy metals from the raw fuel as much as possible.

  In view of this, the boiler 1 has a fuel reforming function for reforming the raw fuel before being charged into the combustion furnace 3, and a function for selectively removing unsuitable substances by circulating the bed material through the above-described bed material circulation line 23. A reformed fuel generator 20 is provided that has the function of joining the reformed fuel to the circulating bed material and feeding it into the combustion furnace 3 together.

  The reformed fuel generator 20 includes a screw transfer device 31 connected to the bottom outlet 3 d of the combustion furnace 3. A pressure reducing device 37 is connected to the screw conveying device 31 to depressurize the bed material conveying path 31b. An outlet 31c at the downstream end of the screw conveying device 31 is connected to the fuel inlet 3a via a bed material conveying line 23a. On the bed material conveying line 23a, unsuitable combustion materials are conveyed from the conveyed bed material. In order to sort and remove, the sorting device 25 described above is provided. By such connection, the screw conveyance device 31 and the bed material conveyance line 23a constitute the above-described circulation line 23 for circulating the bed material. In FIG. 1, the “a” mark on the bed material transfer line 23 a immediately after the sorting device 25 means that it is connected to the “a” mark immediately before the fuel inlet 3 a of the fuel furnace 3. Yes.

  The upstream half of the screw conveying device 31 functions as a bed material cooling section 33 that cools the high-temperature bed material discharged from the bottom discharge port 3d. That is, in the half on the upstream side of the screw conveying device 31, a cylindrical jacket is provided on the outer side of the outer cylinder that defines the conveying path 31b, and the cooling water flows and circulates between the outer cylinder and the jacket. A cooling water flow path 33a is formed. The cooling water circulates between the cooling water flow path 33a and the water tank 43 having the cooler 43a through the cooling water circulation line 41. With this configuration, the bet material of about 800 ° C. discharged from the bottom discharge port 3d moves heat to the cooling water while being screw-conveyed in the conveyance path 31b. It is cooled efficiently.

  Further, the downstream half of the screw conveying device 31 functions as a fuel heat treatment section 35 that heat-treats and reforms the raw fuel. That is, the screw conveying device 31 is connected to a raw fuel input unit 39 for supplying raw fuel such as waste plastic or RPF downstream of the cooling water flow path 33a. The raw fuel input unit 39 moves the raw fuel introduced from the fuel introduction port 39a horizontally by the screw conveyor unit 39b, and then, from the input port 39c connected to the approximate center of the screw conveyance device 31, the conveyance path 31b. Raw fuel is put inside. The input raw fuel is transported horizontally toward the outlet 31c while being mixed with the bed material in the transport path 31b.

  This bet material is in a certain high temperature state after being cooled by the bet material cooling unit 33. Therefore, the raw fuel mixed with the bed material moves in the conveyance path 31b while being heated to about 400 to 600 ° C. by the heat of the bed material. And by heating and decompression, the chlorine contained in the raw fuel, the contained heavy metals (Pb, etc.), and some tar components are vaporized and removed from the raw fuel. Vaporized contained chlorine and the like are discharged through the suction line 37 a and drawn into the decompression device 37. In addition, when the heater which heats the inside of the conveyance path 31b is provided in the fuel heat treatment part 35, heat can be supplemented and the heat treatment of the fuel is possible even when the temperature of the bed material is not sufficiently high.

  The fuel thus reformed in the fuel heat treatment section 35 is discharged from the outlet 31c and then introduced into the magnetic separation device 25 together with the bed material. After the unsuitable material is removed, the fuel is passed through the bed material transport line 23a. It is charged into the combustion furnace 3 from the charging port 3a. Further, in this case, even if tar that could not be vaporized in the transport path 31b adheres to the fuel, the sticking property of the tar is reduced by the mixed bed material, and the occurrence of transport troubles in the circulation line 23 is suppressed. .

  As described above, the raw fuel introduced into the boiler 1 is reformed while passing through the fuel heat treatment section 35, and the contained chlorine and the contained heavy metals are reduced. And the chlorine and heavy metal in the exhaust gas which generate | occur | produce in the combustion furnace 3 are reduced because the fuel thrown into the combustion furnace 3 is reformed in advance. As a result, corrosion of the boiler tube 13b can be suppressed, and the life of the boiler 1 can be extended. In addition, since chlorine and heavy metals in the fuel are reduced, it is possible to reduce the amount of dioxins in the exhaust gas and ash residue, and to expand the application range of ash residue to civil engineering materials and cement raw materials. Can do. In addition, although it is a secondary effect, since the moisture in the fuel is also reduced in the fuel heat treatment section 35, the steam specification boiler 1 equivalent to the conventional boiler can be manufactured in a small size.

  In the boiler 1, the heat of the bed material mixed with the raw fuel is used in the heat treatment of the raw fuel in the fuel heat treatment unit 35. In other words, the heat that would otherwise be discarded outside the boiler 1 system after the cooling of the bed material is effectively utilized as the heat used for fuel reforming in the fuel heat treatment section 35, so that the operation of the boiler 1 as a whole is performed. The necessary energy can be saved.

  Further, in the screw conveying device 31, after the bed material is cooled to some extent by the upstream bed material cooling section 33, the downstream fuel heat treatment section 35 mixes and heat-treats the raw fuel with the bed material cooled to some extent. The Therefore, it can be suppressed that the temperature during the heat treatment is too high and the fuel component in the raw fuel is thermally decomposed. Further, after the raw fuel is mixed in the fuel heat treatment unit 35, the temperature is lowered, and the bed material and the raw fuel having an appropriate temperature that can be handled by the sorting device 25 are sent to the sorting device 25. Efficient magnetic sorting is performed without hindering the function of the sorting device 25 at a high temperature. Furthermore, in the boiler 1, since the bed material cooling unit 33 and the fuel heat treatment unit 35 are configured as an integrated screw conveying device 31, the device can be made compact.

  Moreover, since the conveyance path 31b of the screw conveyance device 31 is decompressed by the decompression device 37, vaporization of chlorine and heavy metals from the raw fuel is promoted. As a result, in this type of conventional heat treatment, dechlorination of the fuel is performed by heating at 400 ° C. or higher. In this fuel heat treatment section 35, not only dechlorination of the fuel but also deuterium metal treatment can be performed. Therefore, the corrosion of the boiler tube 13b is further suppressed by the heavy metal treatment of the fuel. Further, the pressure inside the fuel heat treatment section 35 is made negative by the decompression device 37, and there is an effect of suppressing leakage of chlorine / heavy metal gas to the outside. Hereinafter, a specific configuration of the decompression device 37 will be described.

  The decompression device 37 includes a water tank 51 in which water is stored, and a water ejector (gas suction unit) 53 is attached to the upper part of the water tank 51. The water ejector 53 jets water collected from the lower part of the water tank 51 downward toward the water surface. The water ejector 53 is connected to the above-described suction line 37a. The water ejector 53 generates suction force by the water injection, and sucks chlorine / heavy metal gas in the fuel heat treatment section 35. Pull through line 37a. The drawn-in gas collides with the water surface of the water tank (gas dissolving part) 51 together with the jetted water, thereby being dissolved in water. Thus, since the ejector 53 is used as the gas suction means, the operation of drawing the gas and the operation of feeding the drawn gas into the water in the water tank 51 are performed simultaneously. Further, at the lower part of the water tank 51, a discharge line 55a for discharging the water in which the gas is dissolved out of the system and a water supply line 55b for replenishing water are also provided.

  According to the configuration of the decompression device 37, the difficult-to-handle high-temperature chlorine / heavy metal gas generated by the fuel reforming process in the fuel heat treatment section 35 is dissolved in water and easily recovered from the drain line 55a. The subsequent processing can be performed. In this manner, the decompression device 37 also has a function as a gas processing unit that processes the gas generated in the fuel reforming process. In addition, when the gas is drawn in by a decompression device using a fan, the decompression device is likely to corrode and has a short life. However, if the decompression device 37 is used, corrosion due to the gas is small and the life is long.

  The present invention is not limited to the embodiment described above. For example, the boiler 1 of the embodiment is of an external circulation type fluidized bed type, but the present invention is an internal circulation type fluidized bed type boiler, a bubble type fluidized bed boiler (Bubbling Bed type boiler) or a turbulent flow. It can also be applied to type fluidized bed boilers (Turbulent Bed type boilers).

It is a figure showing one embodiment of a fluidized bed type boiler concerning the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fluidized bed type boiler, 3 ... Combustion furnace, 3d ... Bottom discharge port, 23 ... Bed material circulation line, 25 ... Magnetic sorting device (sorting processing unit), 31 ... Screw conveyance device, 33 ... Bed material cooling unit (solid) Object cooling unit), 35 ... fuel heat treatment unit, 37 ... depressurization device (gas treatment unit), 51 ... water tank (gas dissolving unit), 53 ... water ejector (gas suction unit).

Claims (7)

A fluidized bed type combustion furnace that combusts the input fuel;
A circulation line for circulating the solid matter discharged from the bottom of the combustion furnace to return it to the combustion furnace again;
A fluidized bed boiler, comprising: a sorting and removing unit that is provided on the circulation line and sorts and removes unsuitable substances unsuitable for combustion from the solids circulating in the circulation line. A fuel heat treatment unit that is provided in a stage before the sorting and removing unit on the circulation line and that performs a pretreatment of the fuel that is put into the combustion furnace;
2. The fluidized bed mold according to claim 1, wherein the fuel heat treatment unit performs the pretreatment by heat treatment using heat of the solid matter that is injected into the circulation line and passes through the circulation line. boiler.   3. The fluidized bed mold according to claim 1, further comprising: a solid material cooling unit that is provided in a preceding stage of the sorting and removing unit on the circulation line and cools the solid material passing through the circulation line. boiler.   The fluidized bed boiler according to claim 3, wherein the fuel heat treatment section is provided at a subsequent stage of the solid material cooling section.   The fluidized bed boiler according to claim 4, wherein the solid cooling unit and the fuel heat treatment unit are provided integrally. A gas processing unit for processing gas generated by the heat treatment of the fuel in the fuel heat treatment unit
The gas processing unit includes a gas suction unit that sucks and discharges gas from the fuel heat treatment unit, and a gas dissolution unit that dissolves the gas discharged by the gas suction unit into a liquid. Item 6. The fluidized bed boiler according to any one of Items 2 to 5.   The fluidized bed boiler according to claim 6, wherein the gas suction unit includes a liquid ejector that ejects the liquid.

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