JP4777058B2 - Anhydrous gypsum manufacturing method and anhydrous gypsum firing system - Google Patents

Description

  The present invention relates to a method for producing anhydrous gypsum and a system for calcining anhydrous gypsum by calcining gypsum waste and the like, and calcining anhydrous gypsum, particularly type II anhydrous gypsum.

  Along with the increase in demand for gypsum products in recent years, the amount of gypsum waste generated due to the dismantling of buildings has increased. In particular, waste gypsum boards generated at construction sites and the like are mostly landfilled because they are difficult to separate at the time of dismantling or the recycling market is insufficient.

  When landfilling waste gypsum board, it is supposed to be disposed of at a managed industrial waste final disposal site. For this reason, the processing cost is increased, and there is a problem of depletion of the final disposal site, and effective use of gypsum waste is expected.

  Therefore, the present applicant uses a rotary kiln, and controls the burning point temperature to 500 to 1200 ° C. and the kiln bottom temperature to 300 to 950 ° C. to fire the gypsum waste material, so that the content of type II anhydrous gypsum is 80 wt. % To produce anhydrous gypsum with a total content of hemihydrate gypsum and type III anhydrous gypsum of 10% by weight or less, CaO content of 10% by weight or less, and total organic carbon content of 0.3% by weight or less. Proposed (see Patent Document 1).

  Patent Document 2 also extended toward at least one bottom for hot gas opened adjacent to the non-porous bottom, the inlet and outlet for the material, and the bottom of the inverted conical container. In a granular material heat treatment apparatus comprising a vessel with a tube, the bottom is formed to limit the material at the bottom near the tube, where the hot gas exiting the tube heats and circulates the material, so-called It refers to producing anhydrous gypsum using a conical kettle furnace and carrying out the reaction in two stages using two furnaces.

  Further, in Patent Document 3, when gypsum is baked to recover gypsum powder substantially made of calcium sulfate anhydrite, the gypsum powder is supplied into the first kettle by a conveyor, and the gypsum powder is preferably about 204. The gypsum powder is then heated to a temperature of about 260 ° C. to about 426 ° C. by flowing the gypsum powder through the overflow tube into the second kettle, and the gypsum powder is separated into another overflow tube. Via a third kettle and heated to a final temperature of at least about 482 ° C.

JP 2001-146420 A JP 55-94634 A Japanese Patent Publication No. 2001-507661

  However, when gypsum waste is used as a raw material to produce anhydrous gypsum, if it is baked using a conventional rotary kiln or the like, a part that is excessively heated is generated and mixed with gypsum waste as a high-performance water reducing agent. There is a problem that the naphthalene sulfonic acid group is decomposed to generate sulfur oxides. Further, the gypsum itself has a problem that when it is heated to 1000 ° C. or more, it may be thermally decomposed to generate a large amount of sulfur oxide.

  In addition, regardless of the type of furnace used, such as a rotary kiln, conical kettle furnace, etc., it has been required to maintain high purity of the type II anhydrous gypsum obtained as a product and to reduce fuel consumption.

  On the other hand, in the calcining method described in Patent Document 2, it is mentioned that two conical kettle furnaces can be connected in two stages to produce anhydrous gypsum. Because only dispersible powder is supplied, simply connecting two furnaces brings together a large amount of dust into the former furnace and circulates together with the exhaust from the latter furnace. Problems such as a significant loss of electricity costs are foreseen.

  Furthermore, in the anhydrous product manufacturing method described in Patent Document 3, gypsum is fired in multiple stages to produce an anhydrous product, but the combustion gas flows only in the furnace tube and is only used for heating. Therefore, it is necessary to separately introduce compressed air as a fluid medium and to install a stirring blade, and there is a problem that the structure of the system is complicated and the energy efficiency is low.

  Therefore, the present invention has been made in view of the above-described problems in the prior art, and can significantly suppress the generation of sulfur oxides and obtain a high-purity type II anhydrous gypsum. An object of the present invention is to provide an anhydrous gypsum manufacturing method and an anhydrous gypsum firing system that have a simple structure and can reduce fuel consumption and power consumption.

In order to achieve the above-mentioned object, the present invention is provided with two stages of furnaces each including an inner cylinder having an opening in the lower part and a main body surrounding the inner cylinder and having a lower part formed in an inverted conical shape. Combusting the fuel inside the inner cylinder of the latter furnace and injecting combustion gas from the lower opening of the inner cylinder, supplying the gypsum particles calcined in the former furnace to the main body of the latter furnace, with obtaining the type II anhydrous gypsum by calcining the gypsum particles, evacuation of the latter stage furnace through a dust remover is supplied to the inner cylinder of the front of the furnace, from the bottom of the opening of the inner tube of the furnace of the front stage The exhaust gas is ejected, gypsum particles are supplied to the main body of the previous stage furnace, and the gypsum particles are calcined inside the main body.

  And, according to the present invention, the exhaust of the latter furnace for firing the gypsum particles is used for pre-calcining the gypsum particles in the former furnace, so that high-temperature combustion waste gas is not discharged out of the system, When collecting dust contained in the combustion waste gas with a bag filter or the like, it is not necessary to install a spray tower or the like for lowering the temperature of the combustion waste gas, and a simple system and a compact system can be configured.

  In addition, according to the present invention, when calcining or calcining gypsum particles in a furnace, the gypsum particles are fluidized while being heated by combustion gas or the like. There is no need to install it, and a method for producing anhydrous gypsum with a simple furnace structure and low fuel consumption can be provided.

  Furthermore, according to the present invention, an indirect heating method is employed in which the powder is fluidized and brought into contact with high-temperature combustion gas and heated, so that the powder layer is in a completely mixed state and is substantially uniform as a whole. Since the temperature of the gypsum particles is not excessively heated locally, the gypsum particles as a raw material have a decomposition temperature of the gypsum itself (1000 ° C. or higher) or a decomposition temperature of a naphthalenesulfonic acid group contained as an admixture ( 850 ° C. or higher) can be avoided. Thereby, generation | occurrence | production of sulfur oxide can be suppressed significantly.

  Furthermore, according to the present invention, since the exhaust from the latter furnace is supplied to the inner cylinder of the former furnace through the dust remover, the calcined powder having good dispersibility supplied to the latter furnace is obtained. The dust remover, especially the dust remover that can handle high dust concentration, can be prevented from scattering into the previous furnace, so that a large amount of powder circulates between the two furnaces. It can prevent and significant loss of fuel consumption and power cost can be avoided.

  In the anhydrous gypsum manufacturing method, the temperature of the gas discharged from the preceding furnace can be controlled to 100 ° C. or more and 250 ° C. or less. Thereby, the dust contained in the combustion waste gas can be collected by the bag filter.

  In the anhydrous gypsum manufacturing method, the temperature of the combustion gas discharged from the subsequent furnace can be controlled to 330 ° C. or higher and 840 ° C. or lower. As a result, the dihydrate gypsum can be completely converted to type II anhydrous gypsum with little generation of sulfur oxides.

  In the anhydrous gypsum manufacturing method, dust contained in the gas discharged from the preceding furnace can be collected and returned to the preceding furnace. As a result, scattered dust having low purity of type II anhydrous gypsum is not mixed into the product, and gypsum particles that are insufficiently calcined can be efficiently calcined in the preceding furnace.

  In the anhydrous gypsum manufacturing method, the dust collected by the dust remover can be returned to the subsequent furnace. As a result, scattered dust having low purity of type II anhydrous gypsum is not mixed into the product, and high purity type II anhydrous gypsum can be produced.

  The temperature of the gas discharged from the preceding furnace can be controlled by the amount of water sprayed into the preceding furnace. When the temperature of the exhaust gas from the preceding furnace rises abnormally, for example, it is necessary to lower the exhaust gas temperature in order to protect the subsequent bag filter. Therefore, water is sprayed to the previous furnace to lower the exhaust gas temperature. At this time, since the gypsum particles are fluidized and constantly moving in the furnace, the gas temperature can be controlled efficiently without the water nozzle being blocked.

Further, the present invention includes an opening in the lower part, an inner cylinder from which the high temperature gas is ejected, and surrounding the inner cylinder, the lower part is formed in an inverted cone shape, and the supplied gypsum particles are 2 the furnace comprising a main body to fluidize with heating by gas Dansonae, gypsum particles is calcined at the preceding stage of the furnace, the type II anhydrous gypsum by burning the temporary baked gypsum particles in a subsequent furnace In the obtained anhydrous gypsum firing system, a dust remover is provided for removing dust from the latter furnace exhaust when supplying the exhaust from the latter furnace to the inner cylinder of the preceding furnace. According to the present system, as described above, the equipment is simple and compact, the furnace structure is simple, and fuel consumption and power cost can be reduced.

  As described above, according to the present invention, the generation of sulfur oxides can be significantly suppressed, and high-purity type II anhydrous gypsum can be obtained, the structure is simple, and the fuel consumption and power cost are low. An anhydrous gypsum production method and an anhydrous gypsum firing system can be provided.

Next, embodiments of the present invention will be described with reference to the drawings. In the following description, a case where the type II anhydrous gypsum is fired by firing the gypsum waste material generated when the building is demolished will be described as an example.

  FIG. 1 is a flowchart showing an embodiment of an anhydrous gypsum firing system according to the present invention. This anhydrous gypsum firing system includes a calcining furnace (front furnace) 1, a calcining furnace (second stage furnace) 2, a hopper 4 for supplying gypsum waste M to the calcining furnace 1, a screw feeder 5, and a screw conveyor. 6, a roots blower 3 for transporting the gypsum waste CG calcined in the calcining furnace 1 to the calcining furnace 2, and a gas discharged from the calcining furnace 1 are introduced, and dust contained in this gas is removed. The cyclone 7 as a dust remover, the compressor 14 that supplies the compressed air CA to the main body 23 of the baking furnace 2, the roots blower 13 for supplying the combustion air A to the main body 23 of the baking furnace 2, and the discharge from the baking furnace 2 To the gas discharged from the cyclone 12 and the cyclone 12 as a dust remover that removes dust contained in the combustion gas, particularly a dust remover that can cope with a high dust concentration. A bag filter 9 for collecting the dust to be collected, a fan 8 for releasing the collected gas to the atmosphere, and a screw conveyor 10 for returning the dust collected by the bag filter 9 to the calcining furnace 1 or the baking furnace 2. , 11 etc.

  As shown in FIGS. 2 to 4, the firing furnace 2 has an inner cylinder 22 having a slit (opening) 25 in the lower part and a lower part 23 a formed in an inverted conical shape so as to surround the inner cylinder 22. And a main body 23.

  The inner cylinder 22 is arranged at the center of the main body 23, and includes a combustion air pipe 29 at the upper part, and a fuel supply pipe 21 for supplying city gas as fuel is arranged along the central axis of the inner cylinder 22. Is done. A plurality of slits 25 are formed at the lower end of the inner cylinder 22, and combustion gas is ejected into the main body 23 from the slits 25. In addition, since the inside of the inner cylinder 22 is exposed to a high temperature of about 1200 ° C. by combustion heat, it is preferable to cool the inner wall of the inner cylinder 22.

  The combustion air pipe 29 is provided for introducing air for fuel combustion in the inner cylinder 22, and air is supplied from the roots blower 13 shown in FIG.

  The fuel supply pipe 21 is disposed so as to penetrate the top plate 22a of the inner cylinder 22 from above, and a perforated plate 32 for obtaining a divided flame is provided at the lower end portion of the fuel supply pipe 21. The fuel supply pipe 21 is surrounded by a pipe 30 for guiding air from the inside to the fuel supply pipe 21 except for a part of the upper end portion.

Body 23, as described above, the bottom 23a is reverse conical, upper 23b is formed in a cylindrical shape, II type anhydrous gypsum inside fed gypsum waste CG of the body 23 by heat exchange with the combustion gas It becomes. A raw material supply pipe 26 and a scattered dust return pipe 27 are disposed so as to penetrate the top plate 23c of the main body 23, and an exhaust pipe 28 is further connected to the top plate 23c. An air lance 24 for introducing compressed air is disposed along the inner wall of the lower portion 23a. The vicinity of the boundary between the lower part 23a and the upper part 23b is opened, and a product discharge pipe 33 communicating with the opening part 23d is provided. In addition, when maintaining the temperature inside the main body 23 high, a refractory is provided on the inner wall of the main body 23.

  The raw material supply pipe 26 is provided for supplying the gypsum waste material CG to the inside of the main body 23, and further a scattering dust return pipe 27 is further provided for supplying the raw material.

  The exhaust pipe 28 communicates with the inside of the main body 23, and discharges the combustion gas generated in the inner cylinder 22 out of the system through the inside of the main body 23.

Air lance 24 is provided for introducing compressed air into the bottom of the bottom 23a of the body 23, II-type anhydrous gypsum P as a product is discharged by the compressed air.

Product discharge pipe 33 is provided for discharging the type II anhydrous gypsum P as a product discharged from the opening 23d to the outside of the system.

  The calcining furnace 1 shown in FIG. 1 has a main body 43 and an inner cylinder 42 which are substantially the same as the main body 23 and the inner cylinder 22 of the baking furnace 2. However, since the fuel is not supplied to the inner cylinder 42 of the calcining furnace 1 and the combustion gas of the firing furnace 2 is introduced through the cyclone 12, the fuel provided in the inner cylinder 22 of the firing furnace 2. The supply pipe 21, the combustion air pipe 29, the pipe 30 for guiding air and the perforated plate 32 are not provided in the inner cylinder 42 of the calcining furnace 1.

  Next, an operation procedure of the anhydrous gypsum firing system having the above-described configuration will be described with reference to FIGS. 1 to 4.

  First, calcination of gypsum waste material in the calcination furnace 1 will be described.

  Exhaust gas from the firing furnace 2 is introduced into the inner cylinder 42 of the calcining furnace 1 through the cyclone 12, and gypsum waste material is introduced into the main body 43 of the calcining furnace 1 through the hopper 4, screw feeder 5, and screw conveyor 6. M is supplied and the gypsum waste material M is calcined. The gypsum waste material M and the high-temperature gas are completely mixed in the main body 43, and the exhaust gas temperature in the main body 43 and the calcining furnace 1 is usually controlled to about 130 ° C., depending on the type of gypsum waste material or product. The temperature is controlled in the range of 100 ° C to 250 ° C.

  The differential pressure at two predetermined locations of the powder layer inside the main body 43 is measured, and the supply amount of the gypsum waste material M to the calciner 1 is controlled so that the powder particle level in the main body 43 is constant. In addition, in order to control the exhaust gas temperature of the calciner 1, the water spray W can be applied to the main body 43 of the calciner 1. Sprinkling W is performed through a nozzle, but since the gypsum waste material M inside the main body 43 is fluidized and constantly moving, the watering nozzle can be stably and uniformly sprinkled without being blocked. .

  The gypsum waste material CG calcined in the calcining furnace 1 is conveyed to the calcining furnace 2 by the roots blower 3. On the other hand, the exhaust from the calciner 1 is introduced into the cyclone 7, and the dust D <b> 1 collected by the cyclone 7 is returned to the calciner 1. Further, the gas discharged from the cyclone 7 is collected by the bag filter 9, and the collected gas is discharged to the atmosphere by the fan 8. The dust D3 collected by the bag filter 9 can be returned to the calcining furnace 1 or the calcining furnace 2 via the screw conveyors 10 and 11, but the dust D3 contains gypsum particles that are insufficiently calcined. Since it is contained in a large amount, it is preferable to return the total amount of dust D3 to the calcining furnace 1.

  Next, firing of the gypsum waste material CG calcined by the calcining furnace 1 by the calcining furnace 2 will be described.

  The combustion air A is supplied from the Roots blower 13 through the combustion air pipe 29 and the city gas G as fuel is supplied through the fuel supply pipe 21 into the inner cylinder 22 of the firing furnace 2. The city gas G burns inside the inner cylinder 22, and the inside of the inner cylinder 22 is maintained at about 1200 ° C. On the other hand, the gypsum waste material CG calcined in the calcining furnace 1 is supplied into the main body 23 of the calcining furnace 2 by the roots blower 3. The gypsum waste material CG and the high-temperature gas are completely mixed in the main body 23, and the exhaust gas temperature in the main body 23 and the firing furnace 2 is normally controlled to about 460 ° C., depending on the type of gypsum waste material CG or product. In the range of 330 ° C. or higher and 840 ° C. or lower. Moreover, the differential pressure | voltage of two predetermined places of the granular material layer inside the main body 23 is measured, and the supply amount of the gypsum waste material CG to the firing furnace 2 is controlled so that the granular particle level in the main body 23 becomes constant. To do.

The combustion gas generated by burning the city gas G inside the inner cylinder 22 is ejected from the slit 25 to the lowermost part of the main body 23. The jetted combustion gas causes the gypsum waste material CG to fluidize in the lower portion 23a of the main body 23 and exchange heat with the combustion gas. When the heat exchange is complete, gypsum waste CG is changed to type II anhydrous gypsum P as a product, is fluidized by the compressed air CA from the compressor 14 introduced through the air lance 24, product discharged from the opening 23d It is discharged out of the system through the pipe 33.

  On the other hand, the combustion gas discharged from the main body 23 is introduced into the cyclone 12, and the dust D <b> 2 removed by the cyclone 12 is returned to the firing furnace 2. Here, since the gypsum waste material CG supplied from the calcining furnace 1 to the calcining furnace 2 has been calcined, it has good dispersibility, and is easily scattered with the combustion gas in the calcining furnace 1, so dust is removed by the cyclone 12, A large amount of powdery gypsum waste CG is prevented from circulating between the calcining furnace 1 and the firing furnace 2. The gas discharged from the cyclone 12 is introduced into the main body 43 of the calcining furnace 1 and used for calcining the gypsum waste material M in the calcining furnace 1.

In addition, there is a case where a metal object is mixed in the gypsum waste material generated when the building is dismantled or the like, but the mixed metal object is deposited on the bottoms of the main bodies 43 and 23 in the calcining furnace 1 and the baking furnace 2. , without mixed in a type II anhydrous gypsum P, it can be taken out at the time of rest calciner 1 and calciner 2.

It is a flowchart which shows one Embodiment of the anhydrous gypsum baking system concerning this invention. It is a partially broken front view which shows the baking furnace of the anhydrous gypsum baking system of FIG. 3 is a cross-sectional view taken along the line AA in FIG. 2 (however, the vicinity of the firing air pipe 29 and the air lance 24 is not a cross-sectional view taken along the line AA). FIG. 3 is a top view of the firing furnace of FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Calcining furnace 2 Firing furnace 3 Roots blower 4 Hopper 5 Screw feeder 6 Screw conveyor 7 Cyclone 8 Fan 9 Bag filter 10 Screw conveyor 11 Screw conveyor 12 Cyclone 13 Roots blower 14 Compressor 21 Fuel supply pipe 22 (Causing furnace) inner cylinder 22a Plate 23 (of the baking furnace) Main body 23a Lower part 23b Upper part 23c Top plate 23d Opening 24 Air lance 25 Slit 26 Raw material supply pipe 27 Scattering dust return pipe 28 Exhaust pipe 29 Combustion air pipe 30 Air is introduced from the inside to the fuel supply pipe Pipe 32 for porous plate 33 Product discharge pipe 42 Inner cylinder 43 (for calcining furnace) Body A (for calcining furnace) Main body A Combustion air CA Compressed air CG Calcined gypsum waste materials D1 to D3 Dust G City gas M Gypsum waste P II type anhydrous gypsum W water (watering)

Claims (7)

Two stages of furnaces including an inner cylinder having an opening in the lower part, a main body surrounding the inner cylinder and having a lower part formed in an inverted cone shape,
Combusting the fuel inside the inner cylinder of the latter furnace and injecting combustion gas from the lower opening of the inner cylinder, supplying the gypsum particles calcined in the former furnace to the main body of the latter furnace, with obtaining the type II anhydrous gypsum by calcining the gypsum particles,
The exhaust from the latter furnace is supplied to the inner cylinder of the former furnace through a dust remover, and the exhaust is ejected from an opening in the lower part of the inner cylinder of the former furnace, so that gypsum particles are placed on the main body of the former furnace. , And calcining the gypsum particles inside the main body.   The method for producing anhydrous gypsum according to claim 1, wherein the temperature of the gas discharged from the preceding furnace is controlled to 100 ° C. or more and 250 ° C. or less.   The method for producing anhydrous gypsum according to claim 1, wherein the temperature of the combustion gas discharged from the subsequent furnace is controlled to 330 ° C. or higher and 840 ° C. or lower.   The method for producing anhydrous gypsum according to claim 1, wherein dust contained in the gas discharged from the preceding furnace is collected and returned to the preceding furnace.   The method for producing anhydrous gypsum according to any one of claims 1 to 4, wherein the dust collected by the dust remover is returned to the subsequent furnace.   The method for producing anhydrous gypsum according to any one of claims 1 to 5, wherein the temperature of the gas discharged from the preceding furnace is controlled by the amount of water sprayed into the preceding furnace. An opening is provided in the lower part, an inner cylinder from which the hot gas is ejected, and an inner cylinder surrounding the inner cylinder, the lower part is formed in an inverted cone shape, and the supplied gypsum particles are heated while being heated by the hot gas. body and the furnace 2 Dansonae having a to of the gypsum particles is calcined at the preceding stage of the furnace, the anhydrite firing system for obtaining type II anhydrous gypsum by burning the temporary baked gypsum particles in a subsequent furnace ,
An anhydrous gypsum firing system, comprising: a dust remover that removes dust from the exhaust of the latter furnace when supplying the exhaust of the latter furnace to the inner cylinder of the preceding furnace.

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