Heat treatment device and method for powder and granular material

Abstract

To provide a heat processing apparatus and a heat processing method for granules capable of effectively using heat by recovering the heat when performing cooling processing to the high temperature granules discharged from a heating furnace.SOLUTION: A heat processing apparatus 1 of this invention comprises: a heating furnace 2 including a heated air supply burner 10 that heats granules at a predetermined temperature; a preheating furnace 3 that preheats unheated granules; and supply means 4 that supplies the preheated granules discharged from the preheating furnace 3 to the heating furnace 2. The preheating furnace 3 has an indirect heating-type double cylinder structure consisting of a rotatable inner cylinder 14 into which the unheated granules are supplied and an outer cylinder 15 which is provided to cover an outer periphery of the inner cylinder 14 and into which the high temperature granules discharged from the heating furnace 2 are supplied as a heat source.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a heat treatment device for powder or granular material used in cases where the powder or granular material to be treated needs to be heat-treated at a relatively high temperature, such as when thermally regenerating anhydrous gypsum from waste gypsum or when thermally purifying soil contaminated with oil or the like. [Background technology]

[0002] For example, when thermally regenerating type II anhydrous gypsum from waste gypsum, or when thermally purifying soil contaminated with oil, VOCs, or the like, it is necessary to heat treat the various powders and granules in a heating furnace at a relatively high temperature of several hundred degrees Celsius to several thousand and several hundred degrees Celsius. At this time, the powder and granules discharged from the heating furnace are at a high temperature and are difficult to handle as they are, so some furnaces are provided with an appropriate cooler or the like below the discharge section of the heating furnace to cool the high-temperature powder and granules immediately after discharge to an appropriate temperature that makes them easy to handle, and the present applicant has also filed an application for a powder and granule heat treatment device equipped with a cooler that cools the powder and granules that have been heat-treated at a relatively high temperature in a heating furnace to an appropriate temperature that makes them easy to handle.

[0003] For example, Patent Document 1 (JP 2013-150981 A) describes a contaminated soil heating purification device in which soil contaminated with oil, VOCs, etc. is fed successively into two kilns, a preheating kiln and a heat treatment kiln, where it is heated to approximately 600°C to volatilize and decompose the contaminants contained in the contaminated soil and purify the soil, while also including a soil cooling device in an approximately drum shape that directly sprays an appropriate amount of water onto the purified soil that is discharged at a high temperature to cool it down to a temperature that is easy to handle.

[0004] Furthermore, Patent Document 2 (JP 2016-75418 A) describes a powdered or granular heat treatment device in which powdered or granular waste gypsum is heated to approximately 800°C in a countercurrent kiln, and the waste gypsum in the state of gypsum dihydrate is recycled as type II anhydrous gypsum, while the type II anhydrous gypsum discharged at a high temperature is fed into a cooler having an approximately screw conveyor shape, and the type II anhydrous gypsum is indirectly cooled to a temperature that is easy to handle by cooling water supplied to a jacket portion that covers the outer periphery of the cooler. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-150981 A [Patent Document 2] JP 2016-75418 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, simply cooling the powder or granular material that has been heated to a high temperature in a heating furnace in a cooler as in the above-mentioned conventional device due to handling issues results in a large waste of thermal energy, and it is believed that there is room for improvement in terms of energy conservation.

[0007] In view of the above, an object of the present invention is to provide an apparatus and method for heat treating powder or granular material that enables effective use of heat recovery during cooling treatment of high-temperature powder or granular material discharged from a heating furnace. [Means for solving the problem]

[0008] In order to solve the above problems, the heat treatment device for powder or granular material according to the present invention has a hot air supply burner for heating the powder or granular material to a predetermined temperature. It is the first rotary kiln Preheat the furnace and the unheated powder Another rotary kilnA powder / granular material heat treatment device having a preheating furnace and a supply means for supplying the preheated powder / granular material discharged from the preheating furnace to the heating furnace, the preheating furnace having an indirect heating type double cylinder structure including an inner cylinder which is rotatable and into which unheated powder / granular material is introduced, and an outer cylinder which is provided to cover the outer periphery of the inner cylinder and into which the high-temperature powder / granular material discharged from the heating furnace is introduced as a heat source. A temporary storage bin is provided in the middle of the supply means to temporarily store the powdered material preheated in the preheating furnace before it is supplied to the heating furnace, and a rotary valve is provided at the lower end of the temporary storage bin, so that the preheated powdered material can be introduced into the heating furnace by the rotation of the rotary valve. It is characterized by the following.

[0009] In addition, in the powder / granular material heat treatment device described in claim 2, the preheating furnace is characterized by a counterflow type in which the flow direction of the heated powder / granular material fed into the outer tube is opposite to the flow direction of the unheated powder / granular material fed into the inner tube.

[0010] In addition, in the method for heat treating powder or granular material according to claim 3, ,before The preheated powder or granular material remaining in the inner cylinder when the operation of the heat treatment device is terminated is stored in the temporary storage bin, and when the operation is restarted, the preheated powder or granular material is fed from the temporary storage bin into the heating furnace. Effect of the Invention

[0011] According to the powder / granular material heat treatment device of claim 1 of the present invention, A powder / granular material heat treatment apparatus comprising: a heating furnace which is a rotary kiln having a burner for supplying hot air; a preheating furnace which is another rotary kiln for preheating unheated powder / granular material; and a supply means for supplying the preheated powder / granular material discharged from the preheating furnace to the heating furnace, The preheating furnace has an indirect heating type double cylinder structure consisting of an inner cylinder that can be rotated to feed unheated powder and an outer cylinder that covers the outer periphery of the inner cylinder and feeds the high-temperature powder discharged from the heating furnace as a heat source. A temporary storage bin is provided in the middle of the supplying means to temporarily store the powdered material preheated in the preheating furnace before it is supplied to the heating furnace. A rotary valve is provided at the lower end of the temporary storage bin, and the preheated powdered material can be introduced into the heating furnace by the rotation of the rotary valve. Therefore, when the high-temperature powder discharged from the heating furnace is cooled, unheated powder can be preheated, and heat can be recovered and effectively utilized.

[0012] Furthermore, according to the powder / granular material heating treatment device of claim 2 of the present invention, the preheating furnace is of a countercurrent type in which the flow direction of the heated powder / granular material fed into the outer tube is opposite to the flow direction of the unheated powder / granular material fed into the inner tube, so that heat can be efficiently exchanged between the high-temperature powder / granular material and the unheated powder / granular material, and heat can be recovered more effectively and utilized.

[0013] According to the method for heat treating powder or granular material according to claim 3 of the present invention, ,before When the operation of the heat treatment device is terminated, the preheated powder remaining in the inner cylinder is stored in the temporary storage bin, and when operation is restarted, the preheated powder remaining in the inner cylinder can be directly heat-treated in the heating furnace when operation is restarted, which is preferable in terms of little waste of thermal energy. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic explanatory diagram showing an embodiment of a powder / granular material heat treatment device and heat treatment method according to the present invention; [Diagram 2] FIG. 2 is an enlarged view of a main portion of a preheating furnace with a portion of an outer cylinder and an inner cylinder cut away. [Diagram 3] FIG. 2 is an enlarged view of a main portion of a preheating furnace with a part of the outer cylinder cut away. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The heating treatment apparatus and method for powdered or granular material according to the present invention include a heating furnace, such as a rotary kiln, having a burner for supplying hot air to heat various powdered or granular materials, such as waste gypsum and contaminated soil, to a predetermined temperature, a preheating furnace for preheating unheated powdered or granular material, and appropriate supply means for supplying the preheated powdered or granular material discharged from the preheating furnace to the heating furnace.

[0016] The preheating furnace has an indirect heating type double-cylinder structure consisting of a rotatable inner cylinder into which unheated powdered material is fed, and an outer cylinder which covers the outer periphery of the inner cylinder and into which the high-temperature powdered material discharged from the heating furnace is fed as a heat source for preheating.

[0017] In addition, suitable feed vanes are provided around the inner and outer wall surfaces of the inner cylinder, so that the unheated powder and granules put into the inner cylinder and the high-temperature powder and granules put into the outer cylinder can be sent out together to the discharge portions of the inner and outer cylinders as the inner cylinder rotates. If the feed vanes are made into a generally spiral shape, a larger contact area with the powder and granules being transported can be secured, and they can also serve as heat transfer fins, which is preferable because it increases the heat exchange efficiency (heat recovery rate) between the high-temperature powder and granules in the outer cylinder and the unheated powder and granules in the inner cylinder.

[0018] In addition, preferably, a counterflow system may be used in which the flow direction of the high-temperature powder and granular material fed into the outer tube of the preheating furnace is opposite to the flow direction of the unheated powder and granular material fed into the inner tube, which is similar to the above and is expected to further improve the efficiency of heat exchange between the high-temperature powder and granular material in the outer tube and the unheated powder and granular material in the inner tube.

[0019] When a suitable powder or granular material is heat-treated using the above-mentioned device, the powder or granular material is put into the heating furnace and exposed to hot air from the burner to be heat-treated to a predetermined temperature. The high-temperature powder or granular material discharged from the heating furnace after heat treatment is directly put into the outer cylinder of the preheating furnace, while unheated (room temperature) powder or granular material is put into the inner cylinder of the preheating furnace.

[0020] At this time, in the preheating furnace, heat is indirectly exchanged between the high-temperature powder flowing down inside the outer cylinder and the unheated powder flowing down inside the inner cylinder, and the high-temperature powder is cooled to a temperature that is easy to handle and collected, while the unheated powder is preheated. The preheated powder is then fed to the heating furnace by the feeding means and heat-treated to a predetermined temperature in the same manner as above. At this time, the powder fed into the heating furnace can be efficiently heat-treated to the predetermined temperature because it is preheated.

[0021] Preferably, a temporary storage bin is provided midway along the supply means, and the preheated powder remaining in the inner cylinder when the operation of the heat treatment device is terminated is temporarily stored in the temporary storage bin, and when the operation is restarted, the preheated powder can be fed from the temporary storage bin into the heating furnace. This allows the preheated powder remaining in the inner cylinder when the operation is terminated to be heat-treated in the heating furnace as is when the operation is restarted, which is preferable in terms of less waste of thermal energy.

[0022] In this way, according to the powder / granular material heating treatment device and heating treatment method of the present invention, the powder / granular material discharged from the heating furnace at a high temperature can be cooled to a temperature that makes it easy to handle, while at the same time preheating unheated powder / granular material. Despite the relatively simple configuration, heat can be efficiently recovered between the powder / granular material, allowing for efficient use without waste. EXAMPLES

[0023] An embodiment of the present invention will now be described with reference to the drawings.

[0024] Reference numeral 1 in the figure denotes a powder / granular heat treatment device for heat-treating powdered waste gypsum in a state of gypsum dihydrate obtained, for example, by crushing and separating waste gypsum boards, and rearranging it into type II anhydrous gypsum, etc., to regenerate it into a raw material for cement, etc., and the device is equipped with a heating furnace 2 having a rotary kiln structure, a preheating furnace 3 for preheating unheated waste gypsum while cooling the type II anhydrous gypsum that has been heat-regenerated, and a supplying means 4 such as a conveyor or an air pressure feeding device for supplying the preheated waste gypsum discharged from the preheating furnace 3 to the heating furnace 2.

[0025] The heating furnace 2 has a cylindrical kiln body 6 supported on a base 5 so as to be rotatable and tilted, and is rotated at a predetermined speed by a driving motor (not shown). Also, a counterflow system is adopted in which the flow direction of the waste gypsum to be heat-treated is opposite to the flow direction of hot air supplied from a burner, which will be described later.

[0026] The inner wall surface of the kiln body 6 is provided with heat-resistant casters (not shown) that do not have a scraping function, and a cold hopper 7 is provided at the upper end side (downstream side of hot air) and a hot hopper 8 is provided at the lower end side (upstream side of hot air). The cold hopper 7 is provided with a charging section 9 for charging powdered waste gypsum, while the hot hopper 8 is provided with a burner 10 for supplying hot air and a discharge section 11 for discharging type II anhydrite that has been rearranged by the thermal regeneration process.

[0027] Reference numeral 12 in the figure denotes a burner combustion controller that controls the combustion amount of the burner 10, and controls the combustion amount of the burner 10 based on the difference between the temperature detection value of the type II anhydrite discharged from the kiln body 6 detected by a temperature sensor 13 provided in the discharge section 11 and a preset arbitrary temperature set value. The temperature set value set in the burner combustion controller 12 may be any temperature value suitable for regenerating type II anhydrite having properties according to the application, but for example, when regenerating type II anhydrite having properties that can be effectively used as a raw material for cement, it is preferable to set a temperature value of about 800°C.

[0028] The preheating furnace 3 has an indirect heating type double-cylinder structure consisting of a rotatable cylindrical inner cylinder 14 into which unheated waste gypsum is introduced, and an outer cylinder 15 which is provided so as to cover the outer periphery of the middle part in the longitudinal direction of the inner cylinder 14 and into which high-temperature type II anhydrite discharged from the heating furnace 2 is introduced as a heat source for preheating. A counterflow system is adopted in which the unheated waste gypsum introduced into the inner cylinder 14 and the high-temperature type II anhydrite introduced into the outer cylinder 15 flow in opposite directions, thereby improving the heat exchange efficiency between the waste gypsum and type II anhydrite.

[0029] The inner cylinder 14 is supported on a base 16 so as to be rotatable and approximately horizontal in the longitudinal direction, and is rotated at a predetermined speed by a driving motor (not shown). A feed vane 17 having an approximately spiral shape is provided around the inner wall surface of the inner cylinder 14, and a supply hopper 19 and a screw conveyor 20 are provided at one end of the inner cylinder 14 for supplying unheated powdered waste gypsum through a partition wall 18, while a discharge hopper 21 is provided at the other end of the inner cylinder 14, and a discharge section 22 for discharging preheated waste gypsum is provided at the lower end of the discharge hopper 21. As shown in Fig. 2, the waste gypsum put into the inner cylinder 14 can be sent out in the direction of arrow A as the inner cylinder 14 rotates in the X direction (counterclockwise as viewed from the right side in Fig. 2).

[0030] On the other hand, the outer cylinder 15 passes high-temperature type II anhydrite as a heat source for indirectly heating the unheated waste gypsum supplied into the inner cylinder 14, and is fixedly supported on the base 16. At both longitudinal ends thereof, heat-resistant sealing members (not shown) are provided to close the gap between the outer cylinder 15 and the outer wall surface of the inner cylinder 14, which is supported rotatably, thereby preventing high-temperature type II anhydrite from escaping from inside the outer cylinder 15.

[0031] Further, heat-resistant casters 23 are provided around the inner wall surface of the outer cylinder 15, while a roughly spiral-shaped feed blade 24 that is formed by rotating in the opposite direction to the feed blade 17 is provided on the outer wall surface of the inner cylinder 14 covered by the outer cylinder 15. As shown in FIG. 3, as the inner cylinder 14 rotates in the X direction (counterclockwise as viewed from the right side in FIG. 3), high-temperature type II anhydrite inputted into the outer cylinder 15 (gap space F between the outer cylinder 15 and the inner cylinder 14) can be sent out in the direction of arrow B that is opposite to the flow direction A of the waste gypsum in the inner cylinder 14.

[0032] The feed vanes formed on the inner and outer wall surfaces of the inner cylinder 14 are not limited to the above structure and may be, for example, a plurality of discontinuous feed vanes. However, if a continuous spiral-shaped vane is used as in this embodiment, a larger contact area with the transported materials, that is, type II anhydrite and waste gypsum, can be secured and the vane itself can serve as a heat transfer fin, which is preferable because it increases the efficiency of heat exchange between type II anhydrite in the outer cylinder 15 and the waste gypsum in the inner cylinder 14.

[0033] Further, on the upstream side of the arrow B, there is provided an input section 25 for inputting high-temperature type II anhydrite into the outer cylinder 15, and on the downstream side of the arrow B, there is provided a discharge section 26 for discharging type II anhydrite which has been cooled through heat exchange with waste gypsum in the outer cylinder 15, and the input section 25 is directly connected to the discharge section 11 of the heating furnace 2. The type II anhydrite which has been cooled and discharged from the discharge section 26 is transported by an appropriate transport device (not shown) to a separately installed storage bin (not shown).

[0034] 1 denotes a temporary storage bin that can temporarily store the waste gypsum preheated in the preheating furnace 3 before it is supplied to the heating furnace 2, and is disposed in the middle of the supply means 4. The temporary storage bin 27 has casters (not shown) for heat retention around its inner wall surface, and is provided with a rotary valve 28 at its lower end, so that the preheated waste gypsum can be fed into the feed section 9 of the heating furnace 2 below by the rotation of the rotary valve 28.

[0035] In the figure, reference numeral 29 denotes an operation controller which controls the operation of the heat treatment device 1, and enables operation control of each device constituting the heat treatment device 1, such as the rotational drive of the kiln body 6 of the heating furnace 2 and the inner cylinder 14 of the preheating furnace 3, the ignition and extinguishing of the burner 10 of the heating furnace 2, the rotational drive of the screw conveyor 20 at one end of the preheating furnace 3 and the rotary valve 28 at the lower end of the temporary storage bin 27, etc.

[0036] When the powdered waste gypsum in a state of gypsum dihydrate is thermally regenerated into type II anhydrite using the powdered / granular heat treatment device 1 having the above-mentioned configuration, a temperature setting value suitable for regenerating type II anhydrite in a state usable as a raw material for cement, for example, about 800°C, is input in advance to the burner combustion controller 12. Then, the operation controller 29 ignites and burns the burner 10 of the heating furnace 2 to supply high-temperature hot air into the kiln main body 6, while feeding the waste gypsum in a state of gypsum dihydrate into the kiln main body 6.

[0037] The waste gypsum charged into the kiln body 6 of the heating furnace 2 is exposed to a high-temperature atmosphere by hot air from the burner 10 while flowing down on the casters in the kiln body 6, and is also exposed to radiant heat from the burner flame, and is heated to the set temperature and transformed from gypsum dihydrate to type II anhydrite. The type II anhydrite is then discharged from the discharge part 11 at the lower end of the hot hopper 8, and is successively charged into the outer cylinder 15 of the lower preheating furnace 3.

[0038] On the other hand, when the operation controller 29 detects a temperature value equal to or higher than a predetermined temperature (for example, about the set temperature) by the temperature sensor 13 provided at the discharge section 11 of the heating furnace 2, it determines that high-temperature type II anhydrite has been discharged from the kiln body 6, and uses this as a trigger to drive the screw conveyor 20 at one end of the preheating furnace 3, and supplies the unheated waste gypsum stored in the supply hopper 19 into the inner cylinder 14 of the preheating furnace 3.

[0039] In the preheating furnace 3, high-temperature type II anhydrite fed into the outer cylinder 15 is indirectly heat-exchanged with the waste gypsum flowing down inside the inner cylinder 14, and the waste gypsum at room temperature in the inner cylinder 14 is preheated to, for example, about 40 to 50°C, while the type II anhydrite in the outer cylinder 15 at about 800°C is cooled to about 300°C, which is relatively easy to handle.

[0040] The type II anhydrite cooled in the outer cylinder 15 is successively discharged from the discharge part 26 and transported to a separately provided storage bin by an appropriate transport device, while the waste gypsum preheated in the inner cylinder 14 is successively discharged from the discharge part 22 at the lower end of the discharge hopper 21 and transported to the temporary storage bin 27 by the transport means 4. The preheated waste gypsum is temporarily stored in the temporary storage bin 27 or immediately discharged, and then charged into the kiln body 6 through the charge part 9 of the lower heating furnace 2, where it is heated at a predetermined temperature in the same manner as above and regenerated into type II anhydrite. At this time, the waste gypsum charged into the kiln body 6 of the heating furnace 2 can be efficiently heated to the predetermined temperature because it has been preheated.

[0041] On the other hand, when the thermal regeneration process of the waste gypsum into type II anhydrite is terminated, the operation controller 29 first stops the rotary valve 28 at the lower end of the temporary storage bin 27 to stop the feeding of the waste gypsum into the kiln body 6 of the heating furnace 2. Then, when the temperature sensor 13 provided at the discharge part 11 of the heating furnace 2 does not detect a temperature value equal to or higher than a predetermined temperature (for example, about the set temperature) for a predetermined period of time or more, it determines that the discharge of type II anhydrite from the kiln body 6 has stopped, and takes this as an opportunity to stop the screw conveyor 20 at one end of the preheating furnace 3 to stop the feeding of the waste gypsum into the inner cylinder 14.

[0042] At this time, the waste gypsum (being preheated) remaining in the inner cylinder 14 is discharged for a while even after the screw conveyor 20 is stopped, but all of it is transported and fed into the temporary storage bin 27 via the supply means 4 and temporarily stored therein. As a result, when operation is restarted, preheated waste gypsum can be fed into the heating furnace 2 from the beginning, which is preferable in terms of little waste of thermal energy.

[0043] In this manner, when the waste gypsum is subjected to a thermal regeneration treatment to convert it into type II anhydrous gypsum in the powder / granular material thermal treatment device 1 having the above-mentioned configuration, the high-temperature type II anhydrous gypsum discharged from the heating furnace 2 is not simply cooled but is used as a heat source for preheating unheated waste gypsum, which enables heat recovery and effective utilization, which is preferable.

[0044] In addition, as in this embodiment, by preheating the unheated waste gypsum with the thermal energy of the type II anhydrite at about 800° C. immediately after the heat treatment, a part of the surface water contained in the waste gypsum can be volatilized and dried, and energy saving of about 15% can be expected compared with the case where the preheating furnace 3 is not provided. [Industrial Applicability]

[0045] The present invention can be widely used in heat treatment apparatuses that heat treat various powdered or granular materials such as gypsum and soil at relatively high temperatures. [Explanation of symbols]

[0046] 1... Powder and granular material heat treatment device 2... Heating furnace 3... Preheating furnace 4... Supply means 6...Kiln body 10...Burner 12...Burner combustion controller 13...Temperature sensor 14... Inner cylinder 15... Outer cylinder 17, 24...Feed blade 20...Screw conveyor 27...Temporary storage bin 29...Operation controller

Claims

1. 1. A powder / granular material heat treatment apparatus comprising: a heating furnace which is a rotary kiln having a hot air supply burner for heating the powder / granular material to a predetermined temperature; a preheating furnace which is another rotary kiln for preheating unheated powder / granular material; and a supply means for supplying the preheated powder / granular material discharged from the preheating furnace to the heating furnace, wherein the preheating furnace has an indirect heating type double-cylinder structure consisting of an inner cylinder which is rotatable and into which the unheated powder / granular material is fed; and an outer cylinder which covers the outer periphery of the inner cylinder and into which the high-temperature powder / granular material discharged from the heating furnace is fed as a heat source.

2. A powder / granular material heat treatment apparatus comprising: a heating furnace which is a rotary kiln having a hot air supply burner for heating the powder / granular material to a predetermined temperature; a preheating furnace which is a rotary kiln having a hot air supply burner for heating the powder / granular material to a predetermined temperature;

2. 2. The apparatus for heat treating powder or granular material according to claim 1, wherein the preheating furnace is of a countercurrent type in which the flow direction of the heated powder or granular material fed into the outer cylinder is opposite to the flow direction of the unheated powder or granular material fed into the inner cylinder.

3. 3. A method for operating a powdered or granular material heat treatment apparatus as claimed in claim 1 or 2, characterized in that the preheated powdered or granular material remaining in the inner cylinder when the operation of the heat treatment apparatus is terminated is stored in the temporary storage bin, and when the operation is restarted, the preheated powdered or granular material is introduced from the temporary storage bin into the heating furnace.

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