JP2017138032A - Furnace bottom structure of low carbon type shaft furnace - Google Patents

Abstract

A furnace bottom part structure having a through hole for discharging a melt from a furnace bottom part of a low carbon type shaft furnace, having excellent durability and a low carbon in a state where the through hole is constantly opened. A furnace bottom structure useful for operating a mold shaft furnace with sufficiently high thermal efficiency is provided. The present invention provides a furnace bottom portion having a through hole for allowing burner exhaust gas containing an oxidizing gas to flow into the furnace from the outside of the low carbon shaft furnace and discharging the melt from the inside of the furnace to the outside of the furnace. Concerning structure. This furnace bottom part structure includes an alumina-based refractory block constituting an upper inner peripheral surface in contact with the burner exhaust gas in an inner peripheral surface of the through hole, and a lower inner side including a bottom surface in contact with a melt in the inner peripheral surface of the through hole. A silicon carbide refractory block constituting the peripheral surface, and at least one pipe for flowing a cooling fluid embedded around the through hole. [Selection] Figure 5

Description

  The present invention relates to a furnace bottom structure having a through hole for discharging a melt from the furnace bottom of a low carbon shaft furnace to the outside of the furnace. The “low carbon type shaft furnace” referred to in the present invention includes a shaft portion for drying and thermally decomposing waste filled therein, a waste charging inlet and an in-furnace gas discharge port provided on the upper side of the shaft portion. The melting furnace part is provided below the shaft part and has a core at a position shifted laterally from the position of the core of the shaft part, and connects the bottom side of the shaft part and the upper side of the melting furnace part. It means a waste gasification and melting furnace provided with a communication part and a carbonization grate part that transfers waste from the shaft part toward the melting furnace part and carbonizes the waste.

  The waste gasification melting furnace has a through hole at the bottom of the furnace for discharging a melt (for example, molten slag) generated in the furnace. The through-hole for discharging the melt is also called a tap and a tap in the waste gasification melting furnace field. A high temperature melt flows through the through-hole and the vicinity thereof, and it may be exposed to a burner flame for preventing a temperature drop of the melt. The through hole exposed to such a harsh atmosphere and its periphery are made of a refractory. The spout 1 shown in FIG. 3 of Patent Document 1 is composed of an oxide-based refractory 3a having an excellent high-temperature gas resistance at the upper portion in contact with the high-temperature gas or flame passing through the discharge hole 2. The lower part in contact with the molten slag passing through is composed of a silicon carbide refractory 3b having excellent resistance to molten slag (see paragraphs [0022] to [0024] of Patent Document 1).

JP 2003-65683 A

  By the way, as an operation form of the waste gasification melting furnace, a form in which the melt is intermittently discharged from the bottom of the melting furnace (referred to as “intermittent hot water”) and a form in which the melt is continuously discharged (“continuous hot water”). ") Is known. In the case of intermittent hot water, the through-hole for discharging the melt is closed with a heat-resistant material, and the melt is discharged by opening the through-hole every predetermined time. Close with. Since this work has to be relied upon manually, the present inventors have repeatedly studied to realize a stable operation by continuous hot water. As a result, it was found that stable operation by continuous hot water has the following problems.

  First, not only the melt but also high-temperature furnace gas is discharged from the open through-hole to the outside of the furnace. For this reason, in order to maintain the furnace temperature at a predetermined temperature, it is necessary to increase the amount of fuel introduced into the furnace.

  Secondly, unless the temperature drop of the melt in the through hole and its periphery is not sufficiently suppressed, the through hole is blocked by the solidified product of the melt in a relatively short time. In the case of intermittent hot water, a relatively large amount of melt accumulated in the bottom of the furnace is discharged within a short period of time, so the problem associated with a decrease in the temperature of the melt has not become apparent. On the other hand, in the case of continuous hot water, a small amount of the melt is discharged continuously (intermittently in some cases) from the through hole, so that the temperature of the melt is likely to decrease in the through hole and its surroundings. When the melt is made highly viscous or solidified due to the temperature decrease, it is gradually closed from the lower part of the through hole, and if this state continues, the entire through hole may eventually be closed.

  In order to solve these problems, the present inventors provide a pressure holding chamber outside the through hole for discharging the melt, and arrange a burner for heating the through hole and its periphery in the pressure holding chamber. At the same time, by maintaining the pressure in the holding chamber higher than the pressure in the furnace, the low-carbon shaft furnace was operated in a state where the high-temperature burner exhaust gas was allowed to flow back into the holding chamber through the through hole. Although the above two problems could be solved by this operation method, it has been found that the refractory constituting the inner peripheral surface of the through hole may be worn out in a shorter period of time than the inventors have assumed.

  The present invention has been made to solve the above problems, and has a furnace bottom portion structure having a through hole for discharging a melt from a furnace bottom portion of a low carbon shaft furnace, and has excellent durability. It is another object of the present invention to provide a furnace bottom structure useful for operating a low carbon shaft furnace with sufficiently high thermal efficiency in a state where the through holes are constantly opened.

  The present invention allows the burner exhaust gas containing oxidizing gas to flow into the furnace from the outside of the furnace through the side wall of the bottom portion of the low carbon shaft furnace in the thickness direction and to discharge the melt from the inside of the furnace to the outside of the furnace. The present invention relates to a furnace bottom portion structure having a through hole. The furnace bottom structure according to the present invention includes an alumina-based refractory block configured such that an upper inner peripheral surface in contact with a burner exhaust gas from an inner peripheral surface of a through hole is formed from the outer side to the inner side of the furnace bottom side wall, and an inner peripheral surface of the through hole. Among them, a silicon carbide refractory block having a lower inner peripheral surface including a bottom surface in contact with the melt extending from the inside to the outside of the furnace bottom side wall, and at least one for flowing a cooling fluid embedded around the through hole With two conduits.

  The furnace bottom structure of the present invention operates the low carbon shaft furnace in a state where the pressure outside the melting furnace is higher than the pressure in the melting furnace and the high-temperature burner exhaust gas flows back into the furnace through the through hole. belongs to. Focusing on the flow of the melt and burner exhaust gas in the through hole, the melt and burner exhaust gas are counterflowing in the through hole. Under such conditions, the burner exhaust gas containing oxidizing gas (especially surplus oxygen) over the whole of the inner peripheral surface of the through hole from the upstream side to the downstream side (outside to the inner side of the side wall of the furnace bottom). In some cases, it is also exposed to a burner flame that has entered the through hole. Therefore, in the furnace bottom structure of the present invention, the entire upper inner peripheral surface of the through hole exposed to the burner exhaust gas and the flame is composed of an alumina refractory block having excellent high temperature oxidation resistance and thermal shock resistance. doing.

  The lower inner peripheral surface of the through hole has a bottom portion through which the melt flows, and is configured by a silicon carbide refractory block having excellent resistance to the melt. The lower inner peripheral surface is a part mainly in contact with the melt, but the upper region of the lower inner peripheral surface may be exposed to the burner exhaust gas. In the furnace bottom structure according to the present invention, a pipe line is embedded around the through hole, and a cooling fluid (for example, water or air) can be flowed through the pipe line. Thereby, it can fully suppress that the silicon carbide refractory block is worn out by being exposed to the burner exhaust gas under high temperature conditions.

  The silicon carbide refractory block constituting the lower inner peripheral surface of the through hole preferably has a thermal conductivity at 1000 ° C. of 10 to 15 W / m · K. By using a refractory block having a relatively high thermal conductivity, a sufficient distance from the buried pipe line to the lower inner peripheral surface (residual thickness of the silicon carbide refractory block) can be secured. Specifically, a film of the melt solidified by the cooling effect of the cooling fluid flowing through the pipe line is formed so as to cover the lower inner peripheral surface, and wear of the silicon carbide refractory block is suppressed by this film. Thereby, the remaining thickness of the refractory block from the pipe line to the lower inner peripheral surface can be sufficiently ensured. The remaining thickness is preferably stably maintained in a state where the thickness is 30 mm or more. The alumina-based refractory block constituting the upper inner peripheral surface of the through hole has a thermal conductivity at 1000 ° C. of 1.5 to 2.5 W / m · K from the viewpoint of suppressing the solidification of the melt due to supercooling. It may be in the range.

  The conduit for flowing the cooling fluid preferably has a metal tube and a built-up portion made of a nickel chromium alloy layer formed on the surface of the metal tube. By adopting such a pipe line, even if the pipe line is exposed due to wear of the silicon carbide refractory block or the alumina-based refractory block, durability can be maintained for a certain period.

  The bottom surface of the through hole is preferably inclined so that the melt from the bottom of the furnace flows down toward the outside of the furnace. In this case, at least one pipe line is embedded in the silicon carbide refractory block along the bottom surface at a position on the tip side of the bottom surface, and extends in a direction intersecting the flow direction of the melt on the bottom surface. It is preferable. By burying the pipe line at the position on the tip side of the bottom surface, it is possible to further reliably prevent the tip side of the bottom surface from being eroded by the flow of the melt.

  It is preferable that the lower inner peripheral surface of the through hole is constituted by a vertically long, substantially rectangular groove formed in the silicon carbide refractory block. In this case, the outer opening of the through-hole constituting the melt outlet has a slit portion constituted by a vertically long, substantially rectangular groove. In the present invention, a pair of overhanging portions extending in the vertical direction along the slit portion is provided on both sides of the slit portion, and the overhanging portion extends continuously from the lower inner peripheral surface of the through hole in the direction outside the furnace. It is preferable to have the 1st surface which has, and the 2nd surface which comprises an acute angle part with a 1st surface. By providing each of the overhanging portions having acute angle portions on both sides of the slit portion forming the outlet of the melt, it is possible to sufficiently suppress the spread of the melt in the left-right direction of the slit portion beyond the acute angle portion. It is possible to sufficiently prevent the melt from adhering to the vicinity of the product outlet and gradually depositing it, thereby closing the outlet of the through hole. From the viewpoint of more reliably suppressing adhesion of the melt in the vicinity of the melt outlet, it is preferable that the projecting portion further includes a plurality of protrusions provided on the second surface.

  According to the present invention, a furnace bottom part structure having a through hole for discharging a melt from a furnace bottom part of a low carbon type shaft furnace, having excellent durability and a state in which the through hole is constantly opened A furnace bottom structure useful for operating a low carbon shaft furnace with sufficiently high thermal efficiency is provided.

FIG. 1 is a longitudinal sectional view schematically showing an example of a low carbon shaft furnace having a furnace bottom structure according to the present invention. FIG. 2 is a cross-sectional view schematically showing the positional relationship between the four tuyere in the melting furnace section and the through holes for discharging the melt. FIG. 3 is a perspective view showing an embodiment of the furnace bottom structure according to the present invention. 4 is a cross-sectional view taken along line IV-IV shown in FIG. 5 is a cross-sectional view taken along line VV shown in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and a duplicate description is omitted.

<Waste gasification melting furnace>
A waste gasification melting furnace (low carbon type shaft furnace) 10 shown in FIG. 1 mainly includes a shaft part 1, a communication part 2, a carbonization grate part 3, a melting furnace part 4, and a holding pressure. A chamber 6, a burner 7, and a water tank 8 are provided. The shaft portion 1 dries waste in a reducing atmosphere and thermally decomposes it. The communication part 2 connects the shaft part 1 and the melting furnace part 4. The carbonization grate part 3 further thermally decomposes the waste from the shaft part 1 to carbonize the waste. The melting furnace section 4 burns and melts the carbonized waste. The melt M generated in the melting furnace section 4 is discharged to the pressure holding chamber 6 side through the through hole 5. The pressure holding chamber 6 is for maintaining the pressure in the space outside the through hole 5. The burner 7 is disposed in the pressure holding chamber 6 and is directed toward the through hole 5. The water tank 8 seals the lower part of the pressure holding chamber 6 and contains water for cooling the melt M discharged from the through hole 5. Each configuration will be described below.

  The shaft portion 1 is for drying and thermally decomposing waste in a reducing atmosphere. The cross-sectional shape of the shaft portion 1 is, for example, a cylindrical shape. A waste charging inlet 11 for charging waste into the furnace is formed at the upper portion of the shaft portion 1. On the upper side of the shaft portion 1, an in-furnace gas discharge port 12 that discharges gas generated when the waste is dried, burned, and thermally decomposed is formed. An opening 13 is formed at the lower end of the shaft portion 1, and the waste that descends in the shaft portion 1 by its own weight is discharged from the opening 13 to the communication portion 2. The inner diameter and height of the shaft portion 1 can be appropriately determined according to the processing capacity of the furnace. For example, it is preferable that the height of the shaft portion 1 is a height at which the waste filling height in the shaft portion 1 can be managed at least 1 m from the lower end surface. By securing the filling height to 1 m or more, the blow-in phenomenon of the gas in the furnace can be suppressed in the shaft portion 1.

  The communication part 2 connects the bottom side opening 13 of the shaft part 1 and the upper side opening 46 of the melting furnace part 4. The vertical cross-sectional shape of the communication portion 2 is, for example, a rectangle, and the carbonized fire lattice portion 3 is disposed along the bottom surface. The carbonized grate part 3 further thermally decomposes the waste dried and thermally decomposed by the shaft part 1.

  The bottom surface of the communication part 2 is constituted by a carbonized grate part 3. As described above, the carbonized grate part 3 has not only a function for thermally decomposing waste (dry distillation), but also a function as a supply device for supplying the carbonized waste to the melting furnace part 4. The carbonization grate part 3 is formed by combining a movable carbonization grate and a fixed carbonization grate alternately in a staircase shape or an inclined shape. Each movable carbonization grate is configured to reciprocate at a constant pitch in the lateral direction by drive devices 31a and 31b such as fluid pressure cylinders (see double arrows in FIG. 1). By combining the movable carbonization grate and the fixed carbonization grate, the waste on the carbonization grate unit 3 can be pushed out from the upstream side to the downstream side while stirring. In addition, the carbonization grate part 3 may be composed of only a fixed carbonization grate, and a supply device may be provided separately. An example of the supply device is a pusher. The bottom surface of the communication part 2 is composed of a plurality of carbonized grate, and the whole is not a flat surface, but as a whole, it is inclined so as to become lower from the shaft part 1 side toward the melting furnace part 4 side. doing.

  The carbonization grate portion 3 has a two-stage structure including a supply carbonization grate 3A on the upper stage side and a dry distillation carbonization grate 3B on the lower stage side. The supply carbonization grate 3 </ b> A is located directly below the shaft portion 1 and directly receives a load of waste filled in the shaft portion 1. The supply carbonization grate 3A further thermally decomposes the waste so that carbonization of the dry and pyrolyzed waste at the shaft portion 1 proceeds and supplies the waste by pushing it to the dry distillation carbonization grate 3B. It is preferable that the width of the carbonization grate part 3, particularly the width of the supply carbonization grate 3 </ b> A, is approximately the same as the inner diameter of the shaft part 1. By making the width of the carbonization grate part 3 and the inner diameter of the shaft part 1 approximately the same at the place where the shaft part 1 is switched to the carbonization grate part 3, the unloading of the waste can be stabilized.

  The dry distillation carbonization grate 3B is provided adjacent to the supply carbonization grate 3A. The dry distillation carbonization grate 3B further decomposes the waste from the supply carbonization grate 3A to generate carbide, and pushes the carbonized waste to the melting furnace unit 4 to supply it. The dry distillation carbonization grate 3B has the same configuration as the supply carbonization grate 3A. The dry distillation carbonization grate 3B may have the same width as the supply carbonization grate 3A or a different width. Since the volume of waste is reduced with the progress of drying and thermal decomposition, the furnace bottom inner diameter of the melting furnace part 4 may be smaller than the inner diameter of the shaft part 1 and the width of the communication part 2. The width of the dry distillation carbonization grate 3B may be set so as to gradually decrease from the upstream side toward the downstream side.

  The movable carbonization grate of the supply carbonization grate 3A is driven by the first drive unit 31a, and the movable carbonization grate of the dry distillation carbonization grate 3B is driven by the second drive unit 31b. If the first and second driving devices 31a and 31b are provided independently of each other in this way, the driving, stopping and driving speed of the carbonization grate 3A, 3B can be controlled independently. As a result, the carbonization grate 3A, The waste supply rate by 3B can also be controlled independently.

  The carbonization grate portion 3 is configured such that air can be blown into the furnace from the entire surface through gaps between the carbonization grate and / or blow holes (not shown) formed in the carbonization grate. That is, the carbonization grate part 3 also has a function of blowing waste drying and pyrolysis air into the furnace.

  On the back side of the supply carbonization grate 3A and the carbonization carbonization grate 3B, there is a recovery chamber 32 for recovering when fine ones of carbonized waste fall from the gaps between the carbonization grates. Has been placed. Each recovery chamber 32 is configured so that a predetermined amount of air can be supplied from the blower 33 through the air supply pipe L1. It is preferable that the clearance gap between carbonization grate and / or the ventilation hole formed in the carbonization grate is 400 mm pitch or less, for example. The air supplied from the supply carbonization grate 3A and the dry distillation carbonization grate 3B may be at normal temperature, and may be preheated to about 200 ° C., for example. The preheating of air can be performed, for example, by heat exchange with the high temperature gas discharged from the furnace gas discharge port 12.

  The melting furnace section 4 is for burning and melting carbonized waste. The melting furnace part 4 is arranged so as to shift the core in the lateral direction with respect to the shaft part 1 described above. The shaft portion 1 and the melting furnace portion 4 each extend in the vertical direction. By adopting such a configuration, coke (carbon-based solid fuel) can be directly introduced into the melting furnace section 4. The cross-sectional shape of the melting furnace part 4 is, for example, a cylindrical shape. An auxiliary material charging port 41 for charging coke or the like into the melting furnace unit 4 is provided above the melting furnace unit 4. In the present embodiment, the auxiliary material inlet 41 is formed on the upper surface of the communication portion 2 (see FIG. 1). A carbon-based combustible material other than coke may be charged from the auxiliary material inlet 41 together with coke, or limestone or slag as a basicity adjusting agent may be charged. The coke may be charged from the waste charging port 11 together with the waste.

  As shown in FIG. 2, four tuyere 42 a, 42 b, 42 c, 42 d are arranged in the circumferential direction on the furnace bottom side of the melting furnace section 4. Combustion oxygen is supplied into the melting furnace section 4 from the tuyere 42a, 42b, 42c, 42d. Note that oxygen may be supplied together with nitrogen or the like in the state of air or oxygen-enriched air, or high-purity oxygen may be supplied. Oxygen-enriched air means air having an oxygen concentration higher than that of normal air. By supplying oxygen into the melting furnace section 4, waste pyrolysis residue and coke C are combusted. The melting furnace section 4 may further include a plurality of tuyere (not shown) above the tuyere 42a, 42b, 42c, 42d.

  A through hole 5 for discharging the melt M (mixture containing molten slag and molten metal) is formed in the furnace bottom of the melting furnace section 4. The through hole 5 is formed from the inner surface to the outer surface of the melting furnace section 4 and is constantly opened. Thereby, the melt M can be continuously discharged from the through-hole 5. The melt M discharged from the through hole 5 falls into the water stored in the water tank 8. In addition, the furnace bottom part structure 50 which comprises the through-hole 5 in the furnace bottom part of the melting furnace part 4 is demonstrated in detail later.

  The pressure holding chamber 6 is for maintaining the pressure in the space outside the through hole 5. As shown in FIG. 1, the pressure holding chamber 6 is disposed outside the melting furnace section 4 and has an internal space 6 </ b> S communicating with the through hole 5. The internal space 6S is formed by a cylindrical member 6a extending in the vertical direction, an upper plate 6b that closes the upper opening of the cylindrical member 6a, and a water surface W that seals the lower opening of the cylindrical member 6a. The cylindrical member 6a and the upper plate 6b are made of, for example, a steel plate material. The longitudinal cross-sectional shape of the cylindrical member 6a is a shape defined by, for example, two semicircles that are spaced apart from each other and two straight lines that connect the ends of these semicircles. In the present embodiment, the case where the pressure in the pressure holding chamber 6 is maintained by water sealing is exemplified, but pressure holding means other than water sealing may be employed. Further, an opening (not shown) for supplying an oxygen-containing gas (for example, air) may be provided in the pressure holding chamber 6. By supplying an oxygen-containing gas into the pressure holding chamber 6 through this opening, the oxygen concentration of the gas flowing from the pressure holding chamber 6 into the melting furnace section 4 may be adjusted.

  A burner 7 is disposed in the internal space 6S. Specifically, the burner 7 is disposed toward the through hole 5, and the through hole 5 and its periphery are heated by the flame of the burner 7. The type of the burner 7 is not particularly limited, and a burner that uses propane, kerosene or the like as a fuel may be used. A heat insulating material 6c for keeping the internal space 6S warm is disposed in the pressure holding chamber 6 (except for the lower part immersed in water). It can suppress that the temperature of the combustion gas from the burner 7 falls by covering the inner surface of the steel plate (iron skin) which comprises the pressure-holding chamber 6 with the heat insulating material 6c. Thereby, when the pressure in the pressure holding chamber 6 is higher than the pressure in the melting furnace section 4, high-temperature combustion gas can be flowed into the melting furnace section 4 through the through holes 5.

  The pressure holding chamber 6 has an opening 6d for discharging the gas in the internal space 6S. A gas transfer pipe L2 is connected to the opening 6d. The gas discharged from the opening 6d is introduced into the gas combustion furnace 9 through the gas transfer pipe L2. A valve V is provided in the middle of the gas transfer pipe L2. By adjusting the opening degree of the valve V, the pressure in the pressure holding chamber 6 can be adjusted. For example, by maintaining the pressure in the pressure holding chamber 6 higher than the pressure in the melting furnace section 4 at a normal time, the gas (burner exhaust gas) in the pressure holding chamber 6 is passed through the through hole 5 in the melting furnace section 4. Can be allowed to flow into. Note that the valve V may be operated so that the pressure in the pressure holding chamber 6 becomes lower than the pressure in the melting furnace section 4 at the time of abnormality. As a specific example at the time of abnormality here, when the pressure in the pressure holding chamber 6 becomes excessively high for some reason and the water seal state of the pressure holding chamber 6 cannot be maintained, or such a situation is likely to occur. The viscosity of the melt M tends to increase due to the composition or temperature of the melt M, and the melt M is forced to be discharged together with the outflow of gas from the melting furnace section 4. Based on the pressure (differential pressure) and temperature data at a plurality of locations in the waste gasification melting furnace 10 and the temperature and viscosity data of the melt M, the operation of the waste gasification melting furnace 10 can be stopped urgently. It may be.

  The valve V may be configured to automatically open when the pressure in the pressure holding chamber 6 becomes equal to or higher than a threshold value. This threshold value may be set based on, for example, the height of the water seal by the water tank 8.

  The water tank 8 seals the lower part of the pressure holding chamber 6 and contains water for cooling the melt M discharged from the through hole 5. As shown in FIG. 1, the lower opening of the cylindrical member 6 a extends below the water surface. The melt M dropped from the through hole 5 is quenched with water in the water tank 8. As a result, slag (also referred to as “granulated slag”) and metal are obtained. A conveyor 8 a that conveys slag and metal out of the water tank 8 is installed at the bottom of the water tank 8. Slag (granulated slag) is a nonmagnetic component obtained by magnetic separation of a mixture obtained by cooling the melt.

  The furnace bottom structure 50 having the through hole 5 will be described with reference to FIGS. The furnace bottom part structure 50 is detachable from the main body of the melting furnace part 4, and is configured so that it can be replaced with a new one when the furnace bottom part structure 50 in use is worn out. 1 and 2, the furnace bottom structure 50 is not shown for simplification of the drawings.

  As shown in FIGS. 3 to 5, the through hole 5 is provided in the center of the furnace bottom structure 50. When the pressure in the holding pressure chamber 6 is set higher than the pressure in the melting furnace section 4, the burner exhaust gas containing the oxidizing gas in the melting furnace section 4 flows from the outside of the furnace into the furnace through the through-hole 5 and inside the furnace. The melt M is discharged out of the furnace. The furnace bottom structure 50 includes an alumina-based refractory block B1 that forms the upper inner peripheral surface 5a of the through hole 5, a silicon carbide refractory block B2 that forms the lower inner peripheral surface 5b, and around the through hole 5. A plurality of buried pipes P1 to P4 are provided.

  The alumina-based refractory block B1 constitutes the upper inner peripheral surface 5a of the through hole 5 from the outer surface F1 to the inner surface F2 of the side wall 4w of the bottom of the melting furnace unit 4. Alumina-based refractory block B1 is preferably resistant to high-temperature (for example, 1500 to 1800 ° C.) oxidizing gas, and there is a possibility that droplets of melt M may adhere. What has a certain amount of tolerance is preferable. Specific examples of the alumina-based refractory block B1 include a high-alumina refractory castable (alumina content: 90% by mass or more). The alumina-based refractory block B1 has a thermal conductivity at 1000 ° C. of preferably 1.5 to 2.5 W / m · K, more preferably 1 from the viewpoint of suppressing the solidification of the melt by supercooling. .5 to 2.0 W / m · K.

  The silicon carbide refractory block B2 constitutes the lower inner peripheral surface 5b of the through hole 5 from the inner surface F2 to the outer surface F1 of the side wall 4w of the bottom of the melting furnace portion 4. The lower inner peripheral surface 5b has a bottom surface 5d that is inclined so that the melt M flows down toward the outside of the furnace. The silicon carbide refractory block B2 is preferably resistant to a high-temperature (for example, about 1600 ° C.) melt M, and may be exposed to burner exhaust gas containing an oxidizing gas. Those having some degree of resistance are also preferable. Specific examples of the silicon carbide refractory block B2 include SiC refractory castable (SiC content: 67 to 95% by mass). Silicon carbide refractory block B2 has a thermal conductivity at 1000 ° C. of preferably 10 to 15 W / m · K, more preferably 12 to 15 W / m · K. When the thermal conductivity of the silicon carbide refractory block B2 is within the above range, the remaining thickness of the silicon carbide refractory block B2 is sufficiently secured by balancing the cooling effect by the pipe line P1 and the heat of the melt M. It's easy to do.

  As shown in FIG. 3, the upper inner peripheral surface 5a of the through hole 5 is a groove formed in the alumina-based refractory block B1 and having a substantially semicircular cross-sectional shape parallel to the outer surface F1. Has been. On the other hand, the lower inner peripheral surface 5b of the through-hole 5 is a groove formed in the silicon carbide refractory block B2 and having a cross-sectional shape parallel to the outer surface F1 that is a vertically long, substantially rectangular shape. . This vertically long and substantially rectangular groove constitutes a slit portion 5s formed of a vertically long and substantially rectangular groove in the outer opening of the through-hole 5 forming the melt outlet.

The opening width of the slit portion 5s is preferably set to a size that does not allow the unburned coke C (before charging into the furnace) to pass, and may be about 65 to 130 mm. By adopting such a configuration, it is possible to suppress the coke C charged in the furnace from being discharged from the through hole 5. What is necessary is just to set the opening area of the through-hole 5 according to the size of the coke C to be used, the scale of the waste gasification melting furnace 10, etc., for example, about 50-500 cm < ² >.

  In the present embodiment, a pair of projecting portions 5h, 5h extending in the vertical direction along the slit portion 5s are provided on both sides of the slit portion 5s constituting the melt outlet. The overhanging portions 5h and 5h are for preventing the melt M from adhering to the vicinity of the melt outlet and being gradually deposited, thereby blocking the melt outlet.

  As shown in FIG. 3, the overhanging portion 5h includes a first surface F5a extending continuously from the lower inner peripheral surface 5b of the through-hole 5 in the direction outside the furnace, and an acute angle portion 5j together with the first surface F5a. And a second surface F5b to be configured. By providing the protruding portions 5h having the acute angle portions 5j on both sides of the slit portion 5s, it is possible to sufficiently suppress the melt M from spreading in the left and right directions of the slit portions 5s beyond the acute angle portion 5j. The adhesion of the melt M in the vicinity of the outlet can be suppressed. The angle of the acute angle portion 5j may be about 20 to 60 ° (more preferably 20 to 45 °).

  In order to further enhance the adhesion suppressing effect of the melt M, a plurality of protrusions 5p may be provided on the second surface F5b and the outer surface F1 of the overhanging portion 5h. In the present embodiment, as shown in FIG. 3, the case where a plurality of (five steps) protruding portions 5p extending in the lateral direction is provided on the second surface F5b is illustrated. It is not limited. In order to prevent the melt from adhering to the second surface F5b, it is sufficient that the second surface F5b has irregularities instead of a flat surface. For example, a plurality of protrusions are provided on the second surface F5b. You may provide a some recessed part instead of providing.

  The pipes P1 to P4 are for flowing a cooling fluid (for example, water or air). As shown in FIGS. 4 and 5, the pipes P <b> 1 and P <b> 2 are embedded in the melt outlet side of the furnace bottom structure 50. The pipes P3 and P4 are embedded in the furnace bottom part structure 50 on the melting furnace part 4 side. The number of pipelines is not limited to five. The melt outlet side of the furnace bottom structure 50 may be configured to be separable from the melting furnace part 4 side of the furnace bottom structure 50. With this configuration, only the melt outlet side of the furnace bottom structure 50 can be replaced.

  Pipe line P1 is embedded in silicon carbide refractory block B2 along bottom surface 5d at a position on the tip side (outer furnace side) of bottom surface 5d and intersects the flow direction of melt M on bottom surface 5d. It extends to. By burying the pipe line P1 in the position on the tip side of the bottom surface 5d, it is possible to more reliably suppress the tip side of the silicon carbide refractory block B2 from being eroded by the flow of the melt M.

  As shown in FIG. 5, the pipe line P <b> 2 is embedded above the pipe line P <b> 1 and along the inner peripheral surface (excluding the bottom surface 5 d) of the through hole 5. That is, the pipe line P2 first extends in the lateral direction in the silicon carbide refractory block B2, and bends upward in the vicinity of the through hole 5 and extends upward along the side surface of the through hole 5 in the same manner as the pipe line P1. ing. And it extends so that a semicircle may be drawn along the upper inner peripheral surface 5a of the through-hole 5 in the alumina-based refractory block B1, and downward along the side surface of the through-hole 5 in the silicon carbide refractory block B2. It extends. And it bends in the horizontal direction before the pipe line P1.

  The pipes P3 and P4 are embedded in the melting furnace part 4 side in the furnace bottom part structure 50, and at the position on the melting furnace part 4 side, like the pipe P2 shown in FIG. (Excluding the bottom surface 5d).

  The distance from the pipe line P1 to the bottom surface 5d of the through-hole 5 (initial thickness at the time of construction of the silicon carbide refractory block B2) is preferably 1 to 100 mm, and more preferably 30 to 60 mm. The distance from the pipe P2, the pipe P3 and the pipe P4 to the upper inner peripheral surface 5a of the through hole 5 (initial thickness at the time of construction of the alumina refractory block B1) is preferably 1 to 100 mm, more preferably Is 30-60 mm.

  The pipes P1 to P4 preferably have a metal pipe (for example, a copper pipe) and a built-up portion made of a nickel-chrome alloy layer formed on the surface of the metal pipe. By adopting such a pipeline, durability can be maintained for a certain period even if the pipeline is exposed due to wear of the alumina-based refractory block B1 or the silicon carbide refractory block B2. The thickness of the nickel chromium alloy layer may be about 1 to 10 mm (more preferably 3 to 5 mm).

  The furnace bottom structure 50 according to the present embodiment has excellent durability and is useful for operating the waste gasification melting furnace 10 with sufficiently high thermal efficiency in a state where the through holes 5 are constantly opened. .

<Operation method of waste gasification melting furnace>
An operation method of the waste gasification melting furnace 10 will be described. Waste to be treated is charged into the shaft portion 1 from the waste inlet 11. The kind of waste is not particularly limited, and may be any of general waste and industrial waste. Shredding dust (ASR), excavated waste, incinerated ash, or the like, or a mixture of these and combustible waste can be treated. A waste filling layer 100 is formed in the shaft portion 1 by the waste. Waste or char that has been carbonized from the waste inlet 11 may be introduced together with the waste.

  In the shaft portion 1, the drying of the waste and the heat are performed by heat exchange when the air blown from the carbonization grate portion 3 and the melting furnace portion 4 and the gas generated in the furnace pass through the waste filling layer 100. Decomposition proceeds. The heat generated by the waste itself is also used for drying and pyrolysis of the waste. The waste gradually descends in the shaft portion 1, reaches the supply carbonization grate 3A, is further thermally decomposed by the supply carbonization grate 3A, and then is sent to the dry distillation carbonization grate 3B. The waste is further thermally decomposed by the carbonized carbonization grate 3B and carbonization proceeds. The waste falls from the upper side opening 46 and is supplied to the melting furnace section 4.

  Waste carbonized from the communication part 2 is supplied to the melting furnace part 4. A packed bed 101 is formed in the melting furnace section 4 by the carbonized waste. Coke C and a basicity adjusting agent (for example, limestone) are charged into the melting furnace section 4 from the auxiliary material charging port 41 as necessary. Also, coke C and waste fixed carbon are combusted by blowing oxygen-enriched air from the tuyere 42a, 42b, 42c, 42d. As a result, a high-temperature coke bed Bc is formed at the bottom of the furnace, and the ash and incombustible components contained in the waste are melted by the heat. On the other hand, the high-temperature gas discharged from the in-furnace gas discharge port 12 recovers waste heat with an apparatus such as a boiler, and then discharges it after detoxifying. In addition, by forming the coke bed Bc in the melting furnace part 4, the inside of the melting furnace part 4 can be stably maintained at a high temperature state (for example, higher than 1700 ° C.). Here, the case where the coke bed Bc is formed in the melting furnace unit 4 is illustrated, but the coke bed Bc may not be formed in the melting furnace unit 4.

  The filling height of the waste in the melting furnace section 4 during operation should be maintained within a range from +0.5 m above the tuyere 42 a, 42 b, 42 c, 42 d to the lowest end of the carbonized fire grate section 3. Is preferred. By maintaining within this range, oxygen leakage from the furnace bottom due to the thin layer thickness of the packed bed 101 can be suppressed. Furthermore, it is possible to suppress the degradation of the thermal decomposition efficiency of the carbonized grate portion 3 and the stagnation of the distribution in the melting furnace portion 4 due to overfilling.

  The filling height of the waste in the melting furnace part 4 can be controlled by adjusting the speed at which the carbonization grate part 3 supplies the waste to the melting furnace part 4. For example, a sensor (not shown) for detecting the height of the packed bed 101 is disposed in the melting furnace section 4 and the supply rate of the carbonization grate section 3 is controlled based on the height of the packed bed 101 detected by the sensor. May be. Alternatively, for example, the operator may monitor the filling height and control the supply speed based on the monitoring result.

  The supply rate (V1) of the supply carbonization grate 3A and the supply rate (V2) of the dry distillation carbonization grate 3B may be set to be relatively different or may be set to be the same. When the supply rate is set to be relatively different, it is preferable to set the supply rate (V2) of the dry distillation carbonization grate 3B to be higher than the supply rate (V1) of the supply carbonization grate 3A. Furthermore, it is more preferable to variably control the supply rate (V1) of the supply carbonization grate 3A while keeping the supply rate (V2) of the dry distillation carbonization grate 3B constant. By making the supply rate V2 higher than the supply rate V1, the waste sent from the supply carbonization grate 3A can be expanded so as to form a relatively thin layer on the dry distillation carbonization grate 3B. Thereby, the heat from the dry distillation carbonization grate 3B can be applied to the entire waste layer, and the carbonization state of the entire waste can be sufficiently improved.

  For example, the waste material may be charged not only from the waste material inlet 11 but also from the auxiliary material material inlet 41. For example, it is preferable that waste with a large amount of water is supplied from the waste inlet 11 and supplied to the melting furnace section 4 after being processed in the shaft section 1 and the carbonized fire grate section 3. On the other hand, waste with a large amount of ash and low moisture can be loaded from the auxiliary material inlet 41 to reduce drying and pyrolysis loads in the shaft portion 1 and the carbonized grate portion 3. An example of waste with a large amount of water is sludge, and an example of waste with a large amount of ash is incinerated ash. The waste loading port may be provided at a place other than the waste loading port 11 and the auxiliary material loading port 41. By appropriately changing the position where the waste is charged into the furnace based on the properties of the waste, the load on the entire furnace can be reduced as a result.

Next, regarding the operation of the waste gasification melting furnace 10 in a state where the through holes 5 are constantly opened, the operation method according to the present embodiment will be specifically described. According to this operation method, the waste gasification melting furnace 10 can be operated with sufficiently high thermal efficiency. The operation method according to the present embodiment includes the following steps.
The gas in the pressure holding chamber 6 is caused to flow into the melting furnace portion 4 through the through hole 5 by maintaining the pressure in the pressure holding chamber 6 higher than the pressure in the melting furnace portion 4.
The molten material M in the melting furnace section 4 is discharged from the through hole 5 to the pressure holding chamber 6 side.
Heat is applied to the melt M discharged from the through hole 5 by the burner 7.
Replacing the furnace bottom structure 50 with a new furnace bottom structure 50 when the furnace bottom structure 50 is worn out or the melt outlet is blocked.

  According to this operation method, the melt M discharged from the through hole 5 can be heated by the flame of the burner 7. Thereby, the viscosity rise of the melt M can be suppressed, and the blockage of the through-hole 5 can be suppressed. Further, the pressure in the holding chamber 6 (for example, 1.5 to 2.5 kPa (gauge pressure)) is changed to the pressure in the melting furnace section 4 (for example, 1.0 to 2.0 kPa (gauge) by the combustion gas generated from the burner 7. Pressure)). This differential pressure is preferably 0.5 to 2.0 kPa. Due to this differential pressure, the combustion gas flows into the melting furnace section 4 through the through hole 5. That is, by making the pressure in the pressure holding chamber 6 higher than the pressure in the melting furnace section 4, it is possible to prevent high-temperature furnace gas from being discharged outside the furnace through the through-holes 5, and a sufficiently high temperature. The combustion gas can flow from the pressure holding chamber 6 to the melting furnace section 4 through the through hole 5. As a result, a decrease in the temperature (in-furnace temperature) in the melting furnace section 4 can be suppressed, and an increase in fuel to be introduced into the furnace can be sufficiently suppressed. In addition, if the temperature of the combustion gas which passes the through-hole 5 is 1200 degreeC or more (preferably about 1300 degreeC), it can fully suppress that the melt M solidifies in the through-hole 5 periphery. The melting point of the slag contained in the melt M is about 1175 ° C. although it depends on its composition.

  When attention is paid to the flow of the melt M and the combustion gas in the through hole 5, the melt M and the gas are counterflowing in the through hole 5. In order to stably discharge the melt M from the through hole 5, it is preferable that the flow of the melt M is sufficiently separated from the flow of the combustion gas in the through hole 5. That is, when the fluid flow in the through-hole 5 is regarded as an opposed gas-liquid two-phase flow, it is preferable that the melt M forms a separated flow (a laminar flow or a wave flow). From such a viewpoint, the opening area of the through hole 5, the size of the coke C, the flow rate of the gas flowing into the melting furnace section 4 from the pressure holding chamber 6, and the like may be set. For example, the flow rate of the combustion gas passing through the through hole 5 is preferably 0 to 20 Bm / s, and more preferably 3 to 10 Bm / s. The unit of flow velocity “Bm / s” means the flow velocity under the in-situ temperature and pressure conditions.

  The replacement to the new furnace bottom structure 50 may be performed when the pipe line is exposed or the melt outlet is closed due to wear. Even if these phenomena are not recognized, they may be replaced periodically after a predetermined period.

  As mentioned above, although embodiment of this invention was described in detail, various substitution, a deformation | transformation, a change, etc. about a form and detail deviate from the mind and range of this invention as prescribed | regulated by description of a claim. It is clear to those having ordinary knowledge in the art that it can be done without any problems. Therefore, the scope of the present invention should not be limited to the above-described embodiment and the accompanying drawings, but should be determined based on the description of the claims and equivalents thereof.

  For example, in the above-described embodiment, the case where the pair of overhang portions 5h and 5h are provided on both sides of the melt outlet is illustrated, but the overhang portions 5h and 5h may not be provided depending on the properties of the melt M. Moreover, in the said embodiment, although the melt outlet comprised by the vertically long substantially rectangular groove | channel was illustrated, the shape of a melt outlet does not necessarily need to be a substantially rectangular shape, for example, a vertically long ellipse, polygonal shape, etc. There may be.

DESCRIPTION OF SYMBOLS 1 ... Shaft part, 2 ... Communication part, 3 ... Carbonization grate part, 4 ... Melting furnace part, 4w ... Side wall, 5 ... Through-hole, 5a ... Upper inner peripheral surface, 5b ... Lower inner peripheral surface, 5d ... Bottom 5h: Overhanging part, 5j ... Acute angle part, 5p ... Protrusion part, 5s ... Slit part, 6 ... Pressure holding chamber, 7 ... Burner, 10 ... Waste gasification melting furnace (low carbon shaft furnace), 11 ... Disposal Material inlet, 12 ... inlet gas outlet, 50 ... furnace bottom structure, M ... melt, B1 ... alumina refractory block, B2 ... silicon carbide refractory block, F5a ... first surface, F5b ... first 2 side, P1-P4 ... pipeline.

Claims (9)

Penetration through which the burner exhaust gas containing oxidizing gas flows from the outside of the furnace into the furnace and discharges the melt from the inside of the furnace to the outside of the furnace through the thickness of the bottom wall of the low carbon shaft furnace. A furnace bottom structure having holes,
Of the inner peripheral surface of the through hole, an alumina-based refractory block that configures an upper inner peripheral surface in contact with the burner exhaust gas from the outside to the inside of the side wall;
Of the inner peripheral surface of the through hole, a silicon carbide refractory block that configures a lower inner peripheral surface including a bottom surface in contact with the melt from the inner side to the outer side of the side wall,
At least one conduit for flowing a cooling fluid embedded around the through hole;
A furnace bottom structure comprising:   2. The furnace bottom structure according to claim 1, wherein the silicon carbide refractory block has a thermal conductivity at 1000 ° C. of 10 to 15 W / m · K.   The furnace bottom structure according to claim 1 or 2, wherein the alumina-based refractory block has a thermal conductivity at 1000 ° C in a range of 1.5 to 2.5 W / m · K.   The furnace bottom part structure according to any one of claims 1 to 3, wherein the pipe line has a metal pipe and a built-up part made of a nickel-chromium alloy layer formed on a surface of the metal pipe.   The furnace bottom part structure according to any one of claims 1 to 4, wherein the bottom surface of the through hole is inclined so that the melt from the furnace bottom part flows down toward the outside of the furnace.   At least one of the conduits is embedded in the silicon carbide refractory block along the bottom surface at a position on the tip side of the bottom surface, and in a direction intersecting the flow direction of the melt on the bottom surface. The furnace bottom structure according to claim 4, which extends.   The furnace bottom portion according to any one of claims 1 to 6, wherein the lower inner peripheral surface of the through hole is configured by a vertically long, substantially rectangular groove formed in the silicon carbide refractory block. Construction. The outer opening of the through-hole constituting the outlet of the melt has a slit portion constituted by the vertically long, substantially rectangular groove,
A pair of overhang portions extending in the vertical direction along the slit portion are provided on both sides of the slit portion,
The projecting portion includes a first surface continuously extending in a direction outside the furnace from the lower inner peripheral surface of the through hole, and a second surface constituting an acute angle portion together with the first surface. The furnace bottom structure according to claim 7, comprising:   The furnace bottom structure according to claim 8, wherein the projecting portion further includes a plurality of protrusions provided on the second surface.

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