JP6099083B2 - Method for producing quicklime-based expansion material and rotary kiln - Google Patents

Description

  The present invention relates to a method for producing a quicklime-based expansion material containing free quicklime as an active ingredient and a rotary kiln used for the production of a quicklime-based expansion material.

  In order to improve the durability of concrete structures, it is effective to suppress cracks, which are the main cause of durability deterioration. As one of the measures for this, the shrinkage that leads to the occurrence of cracks using concrete expansion material is effective. Suppressing attention. It is also attracting attention as a static crushing agent for concrete structures and bedrock in places where blasting and dismantling is not possible.

  As expansion materials for concrete, those with various expansion components have been proposed. Recently, ettringite-based expansion materials containing ettringite-producing substances such as calcium sulfoaluminate as active ingredients and quick lime containing free quick lime as active ingredients. Two types of system expansion materials are used as representatives of high practicality. In particular, a lime-based expansion material containing free quick lime as an active ingredient has a high hydration reaction activity, and is therefore considered to have a great effect of suppressing self-shrinkage, drying shrinkage, and temperature stress generated in concrete.

  The production of the lime-based expansion material includes a firing step. The firing process is generally performed in a furnace or rotary kiln (Patent Document 1).

  There are Merz furnaces, Beckenbach furnaces, etc., which are supplied with raw materials and fuel from above, fired for a long time inside the furnace, and discharged products from below. Since the time required for thermal contact can be sufficiently secured in the furnace, a high-quality product can be obtained. On the other hand, there is a limit to industrial productivity. Specifically, the productivity of the furnace is about 10% of the productivity of the internal heat type rotary kiln.

JP 2010-228971 A

  Therefore, the production with an internal heat type rotary kiln is common. However, the quick lime-based expansion material currently provided on the market has a limit in expansion performance, and its application or use conditions are limited.

  As the use of the expandable material expands, further improvement in the expansion performance of the quicklime-based expandable material is required.

  This invention solves the said subject, and it aims at providing the technique which further improves the expansion | swelling performance of a quicklime type | system | group expansion material, maintaining the productivity of a rotary kiln.

  The inventor of the present application has made various studies on the limitation of the expansion performance improvement of the quicklime-based expansion material manufactured by the conventional internal heat rotary kiln.

  First, the comparative quick observation of the free lime crystal diameter of the quicklime expanded material produced by the kiln and the free lime expanded material produced by the internal heating rotary kiln revealed that the latter was smaller. It was. From this, the improvement of the expansion performance of quicklime expansion material considered that it was necessary to enlarge a crystal diameter by the growth of the free quicklime existing in the material.

  Next, we focused on the growth mechanism of free quicklime. As a growth mechanism of free quick lime, first, the viscosity of the matrix is reduced by heating the raw material, and further, the continuous free quick lime is considered to grow by continuing heating. On the other hand, in the internal heating type rotary kiln, it was considered that the growth of free quick lime was not sufficient because the firing zone (described later) and the firing zone passage time (described later) were short. Therefore, I came up with the idea of improving the internal heat rotary kiln and increasing the frequency of thermal contact.

  Based on the above study, the present invention has been made.

  The present invention for solving the above problems is a method for producing a quicklime-based expansion material including a baking step, wherein the baking step uses a rotary kiln, and the baking step reduces the viscosity inside the raw material, and A growth promoting step of promoting the growth of free quick lime while maintaining the viscosity-decreasing state.

  Due to the viscosity reduction step, the free quick lime is easily fluidized. In the growth promotion step, the free quick lime is kept fluidized, so that the free quick lime joins and grows. By growing free quick lime, the expansion performance of the quick lime-based expansion material can be further improved. Productivity can be maintained because a rotary kiln is used.

  In the method for producing quicklime-based expanded material of the present invention, preferably, in the viscosity reduction step, the temperature of the object to be fired is increased by direct heating of the internal heat burner from the rotary kiln inlet side, and in the growth promotion step, the rotary kiln outlet side Holding the temperature of the object to be fired by indirect heating of an external heat burner provided in the above.

  Further preferably, in the viscosity reduction step, the firing object is heated to a maximum temperature of 1350 to 1550 ° C., and in the growth promoting step, the firing object is set to a holding temperature of 1250 ° C. or higher.

  Further preferably, in the viscosity reducing step, the object to be fired is rapidly heated at a temperature gradient of 100 to 200 ° C./min.

  With such a temperature distribution, the baking process can realize a viscosity reduction step and a growth promotion step.

  More preferably, in the firing step, the firing zone passing time is 1 hour or longer.

  Thereby, a thermal contact frequency increases, As a result, free quick lime grows and the expansion | swelling performance of quick lime type | system | group expansion material improves.

  In the method for producing a quicklime-based expanded material of the present invention, preferably, in the firing step, the material to be fired is stirred so as to inhibit the progress of the raw material in addition to stirring by rotation of the rotary kiln.

  More preferably, the radiant heat is increased by increasing the surface area of the inner wall of the rotary kiln.

  Thereby, a thermal contact frequency increases, free quick lime grows further, and the expansion | swelling performance of quick lime type | system | group expansion material further improves.

  The present invention that solves the above-mentioned problems is provided in the rotary kiln for producing quicklime-based expansion material by firing, an internal heat burner that raises the temperature of the object to be fired by direct heating from the inlet side, and by the indirect heating. And an external heat burner for maintaining the temperature of the object to be fired.

  Thereby, the temperature distribution can be obtained.

  The rotary kiln of the present invention is preferably a refractory member that is uniformly provided in an inner wall of the rotary kiln and is in a temperature-affected range of the internal heat burner, and a plurality of stirring enhancement members that are provided in a protruding shape on the refractory brick. Is further provided.

  The frequency of thermal contact is further increased by the stirring and advancing member.

  According to the present invention, the expansion performance of the quicklime-based expansion material is further improved by growing free quicklime while maintaining the productivity of the rotary kiln.

Configuration diagram of rotary kiln according to this embodiment Detailed illustration of stirring brick Conceptual diagram of temperature distribution and firing zone according to this embodiment Conceptual diagram of temperature distribution and firing zone according to comparative example 1 (steaming furnace) Conceptual diagram of temperature distribution and firing zone according to comparative example 2 (internal heat rotary kiln) Free quicklime crystals by Comparative Example 2 (internal heat rotary kiln) Free quicklime crystals according to this embodiment

~Constitution~
FIG. 1 is a diagram illustrating a configuration of a rotary kiln according to the present embodiment.

  The rotary kiln 1 includes a supply port 2 for supplying raw materials, a discharge port 3 for discharging the material to be fired after the firing process, a shell 4 made of stainless steel, etc., an internal heat burner 5 inserted from the shell inlet side, An external heating furnace 7 is provided on the shell outlet side and houses an external heat burner 6 that heats the outer surface of the shell.

  The shell 4 has, for example, a cylindrical shape with an inner diameter of 3 m and a length of 35 m, and is installed in a lateral direction with an inclination (slope of several percent) so that the axis is slightly lowered toward the outlet side. An annular drive mechanism (not shown) is integrally attached to the outer peripheral surface of the shell 4 in the vicinity of both ends of the shell 4, and the shell 4 is rotatably supported. Can be rotated.

  The internal heat burner 5 outputs a frame from the inlet side toward the inside of the shell 4 to generate combustion gas and to heat the inside of the shell 4. Thereby, a to-be-baked thing can be heated up rapidly.

The shell 4 is installed so as to penetrate the external heating furnace 7. That is, the external heating furnace 7 accommodates the shell 4 outlet side. Inside the external heating furnace 7, outside the shell 4 and at the bottom,
A plurality of external heat burners 6 are arranged along the traveling direction of the object to be fired. By adjusting the output of the external heat burner 6, the shell 4 can be indirectly heated to adjust the temperature of the shell 4. Thereby, a to-be-baked object can be hold | maintained at predetermined temperature. Combustion gas generated inside the external heating furnace 7 is discharged from the exhaust port to the outside of the furnace.

  That is, the rotary kiln 1 of the present embodiment is characterized by being composed of an internal heat kiln and an external heat kiln continuously provided in the subsequent stage.

  On the inner wall of the shell 4, refractory bricks 8 for protecting the shell are uniformly provided in the temperature affected range of the internal heat burner 5. On the refractory brick 8, a plurality of stirring enhancement bricks 9 are provided in a protruding shape.

  As will be described later, the temperature distribution of the object to be fired in the shell 4 is rapidly increased by the internal heat burner 5 to form a peak at 1500 ° C., and then gradually decreased while leaving the influence of the residual heat. The temperature is maintained at 1250 ° C. or higher by the heating furnace 7. At this time, the range in which the influence of the residual heat of the internal heat burner 5 remains was defined as the temperature influence range of the internal heat burner 5. That is, the refractory brick 8 is not provided on the inner wall of the shell 4 at the position corresponding to the external heating furnace 7.

  FIG. 2 is a detailed configuration of the stirring enhancement brick 9. The stirring enhancement brick 9 is the same member as the refractory brick 8 and has a block shape of, for example, 200 mm × 300 mm × 500 mm. Staggeredly arranged at four locations in the circumferential direction and at intervals of 1500 mm in the longitudinal direction. The stirring-enhanced brick 9 stirs the material to be fired so as to inhibit the progress of the raw material.

  In place of the refractory brick 8 and the stirring-enhanced brick 9, a metal or ceramic having the same thermal expansion coefficient as that of the brick may be used.

~ Device operation ~
The operation of the rotary giraffe 1 will be described.

  The raw material is supplied to the supply port 2. Due to the inclination and rotation of the shell 4, the object to be fired passes through the shell 4 for about 1 hour and 15 minutes.

  Due to the direct heating of the internal heat burner 5, the object to be fired is rapidly heated. For example, the temperature rises to 1500 ° C. in a passage time of 10 minutes. The temperature gradient at this time is 150 ° C./min. Since the internal heat burner 5 is directly heated, the temperature of the object to be fired can be rapidly increased. After reaching the maximum temperature at 1500 ° C., while being affected by the residual heat of the internal heat burner 5, the material to be fired gradually falls as it moves away from the internal heat burner 5.

  By the indirect heating of the external heating furnace 7, the object to be fired is held at 1250 ° C. or higher. When shifting from a temperature drop to a constant temperature, the temperature distribution is made to continue gently. The external heating furnace 7 is easier to control the temperature than the internal heating burner 5.

  The product is discharged from the discharge port 3 through the baking process. Heating by the external heating furnace 7 is lost, and the object to be fired cools down rapidly.

  FIG. 3 is a conceptual diagram of a temperature distribution and a firing zone according to the present embodiment.

  Due to the operation of the rotary giraffe 1, the object to be fired in the shell 4 has a temperature distribution as shown in FIG. That is, the temperature is rapidly increased and a peak at 1500 ° C. is formed, then the temperature is gradually decreased, the temperature is maintained at 1250 ° C. or higher, and the temperature is rapidly decreased. As a result, a time of passing through a region of 1250 ° C. or higher, that is, a firing zone (described later) is secured for 1 hour or more, and the thermal contact frequency is increased.

  In addition, the said temperature distribution is an example and it is preferable that peak temperature is 1350-1550 degreeC. On the other hand, the holding temperature is preferably 1250 to 1350 ° C. In addition, 1350 degreeC is a peak temperature lower limit.

  The temperature gradient of the rapid temperature increase is preferably 100 to 200 ° C./min. If it is less than 100 ° C./minute, the temperature cannot be rapidly increased to 1500 ° C. in a short time. On the other hand, the rapid temperature increase exceeding 200 ° C./min exceeds the capacity of the existing general internal heat burner 5.

  Moreover, the rotary giraffe of this embodiment assumes the same magnitude | size as the existing rotary kiln, Based on the premise, the baking zone passage time is made into 1 hour or more. If the size of the rotary kiln is increased (the shell length is increased), the firing zone passing time is also increased, but in practice, 3 hours is the limit.

  Next, the operation of the stirring enhancement brick 9 will be described.

  As described above, the material to be fired proceeds from the shell inlet side to the outlet side while being stirred by the inclination and rotation of the shell 4. At that time, the stirring-enhanced brick 9 inhibits the progress of the object to be fired. In other words, the object to be fired is blocked by the stirring enhancement brick 9. Heating by the internal heat burner 5 is also transmitted to the stirring enhancement brick 9, and the object to be fired is heated through the stirring enhancement brick 9. As a result, the amount of radiant heat increases and the frequency of thermal contact increases as the surface area of the inner wall of the rotary kiln is increased by the stirring-enhanced brick 9.

  If the material to be fired further accumulates in front of the stirring-enhancing brick 9, the mountain collapses and is stirred so as to be reversed with respect to the traveling direction. As a result, the uniformity is improved, and the material to be fired during stirring is exposed to the combustion gas from the internal heat burner 5 and heated. As a result of increased agitation, the frequency of thermal contact increases.

~ Free quicklime growth ~
The growth of free quick lime when the temperature distribution shown in FIG. 3 is formed in the rotary giraffe 1 will be described.

By starting material rapidly heated to 1500 ° C., alite and (3CaO · SiO ₂₎ interstitial phase (calcium aluminate: 3CaO · _Al 2 _{O 3} calcium alumino _{ferrite: 4CaO · Al 2 O 3 ·} Fe 2 O) and Free quicklime (f.CaO) is produced. By the way, when the interstitial phase exceeds 1250 ° C., it becomes a liquid phase, and the viscosity of the matrix decreases. Thereby, free quick lime becomes easy to fluidize.

When the temperature is not rapidly raised, the interstitial phase does not become a liquid phase, and free quick lime is difficult to fluidize, and subsequent growth is limited. Further, when the temperature is not rapidly increased, belite (2CaO · SiO ₂ ) is generated. When belite is heated further, it reacts with free quick lime to become alite. Thereby, since free quick lime is consumed, the growth of free quick lime is restricted. Therefore, the step of reducing the viscosity of the matrix by rapid temperature increase as in this embodiment is important.

  In the present embodiment, the object to be fired forms a peak at 1500 ° C., and then slowly cools down and is held at 1250 ° C. or higher. That is, the interstitial phase is a liquid phase, the viscosity of the matrix is lowered, and free quick lime is easily fluidized to maintain the state. While maintaining this state, the free quick limes grow together so that the crystal diameter increases.

  At this time, since alite has already been generated, free quick lime is consumed when changing from belite to alite, and the growth of free quick lime is not limited.

  When the temperature is lower than 1250 ° C., the interstitial phase is not a liquid phase, and free quick lime becomes difficult to fluidize, and subsequent growth is restricted. On the other hand, if the temperature is maintained at 1500 ° C., the object to be fired may be burnt on the wall surface. Therefore, the step of maintaining the temperature at 1250 ° C. or higher and promoting the growth of free quick lime as in this embodiment is important.

  As described above, the region of 1250 ° C. or higher in the temperature distribution is an important region for the firing process. In this embodiment, this region is called a firing zone.

-Comparison with conventional technology-
Consider the firing zone of the prior art. FIG. 4 is a conceptual diagram of a temperature distribution and a firing zone according to Comparative Example 1 (steaming furnace). FIG. 5 is a conceptual diagram of a temperature distribution and a firing zone according to Comparative Example 2 (internal heating rotary kiln). In a general internal heat type rotary kiln, an internal heat burner is inserted from the shell outlet side.

  In Comparative Example 1, the firing zone seems to be short, but since the progress is slow, the firing zone passing time can be sufficiently secured as 5 hours. As a result, sufficient free quicklime growth can be expected.

  In Comparative Example 2, as in the present embodiment, the object to be fired passes through the shell over about 1 hour and 15 minutes. However, the firing zone is short and the firing zone passage time cannot be sufficiently secured at 15 minutes. As a result, sufficient free quicklime growth cannot be expected.

  The crystal diameter of the product was actually confirmed.

Table 1 compares the free quicklime crystal diameters of the present embodiment with the free quicklime crystal diameters of Comparative Examples 1 and 2. In addition, productivity and expansion amount are described. For comparison, it is assumed that the firing volumes of the present embodiment, comparative example 1, and comparative example 2 are comparable. The peak temperature was changed to 1350 ° C., 1450 ° C., and 1550 ° C., and it was confirmed that the effect was obtained at the peak temperature of 1350 to 1550 ° C.

  Comparing Comparative Example 1 (steaming furnace) and Comparative Example 2 (internal heating rotary kiln), it can be seen that the free quick lime crystal diameter of Comparative Example 1 is larger. The free quick lime crystal diameter of Comparative Example 2 is small, and there is a limit to the expansion performance improvement. On the other hand, the productivity of Comparative Example 1 is about 10% of the productivity of Comparative Example 2, and Comparative Example 1 is not suitable for industrial production.

  FIG. 6 shows free quick lime crystals according to Comparative Example 2 (internal heating rotary kiln), and FIG. 7 shows free quick lime crystals according to this embodiment.

  Comparing Comparative Example 2 with the present embodiment, the free quick lime crystal diameter of the present embodiment is about twice the free quick lime crystal diameter of Comparative Example 2. Along with this, the expansion performance is improved by about 1.4 times. On the other hand, the productivity of this embodiment is equal to or higher than the productivity of Comparative Example 2.

  Therefore, in this embodiment, it was confirmed that the quick quick lime was grown while maintaining the productivity, and the expansion performance of the quick lime-based expansion material was further improved.

  Furthermore, in this embodiment, it compared about the presence or absence of the stirring increase brick 9.

  Comparing the presence of the stirring-enhanced brick 9 and the absence of the stirring-enhanced brick 9, the free quick lime crystal diameter of the stirring-enhanced brick 9 is slightly larger than the free quick lime crystal diameter of the stirring-enhanced brick 9. Along with this, the expansion performance is also slightly improved. Productivity has also improved slightly.

  Therefore, the effect by the stirring increase brick 9 was confirmed.

~effect~
The rotary kiln 1 of the present embodiment is characterized in that it is composed of an internal heat kiln having an internal heat burner 5 and an external heat kiln having an external heat burner 6 provided continuously in the subsequent stage. With such a configuration, the temperature distribution in the shell 4 rapidly rises, forms a peak at 1500 ° C., then slowly falls, is maintained at 1250 ° C. or higher, and rapidly drops.

  With such a temperature distribution, the baking process can realize a viscosity reduction step and a growth promotion step. As a result, the firing zone passage time is secured for 1 hour or more, and the thermal contact frequency increases.

  By increasing the thermal contact frequency, free quick lime grows and the expansion performance of the quick lime-based expansion material is improved.

  In addition, this embodiment maintains the productivity of the conventional internal heating type rotary kiln.

  Moreover, with the stirring-enhanced brick 9, the thermal contact frequency is increased, free quick lime is further grown, and the expansion performance of the quick lime-based expansion material is further improved.

DESCRIPTION OF SYMBOLS 1 Rotary kiln 2 Supply port 3 Discharge port 4 Shell 5 Internal heat burner 6 External heat burner 7 External heat furnace 8 Refractory brick 9 Stir increase brick

Claims (6)

By using a raw material that produces alite, interstitial phase and free quick lime by rapidly raising the temperature to 1350 to 1550 ° C.,
A method for producing a quicklime-based expansion material including a firing step,
In the firing step, a rotary kiln is used,
The firing step includes
A viscosity reducing step for reducing the viscosity inside the raw material;
Possess a growth promoting step of promoting the growth of free lime while holding the decrease in viscosity state,
In the viscosity reduction step, the object to be fired is rapidly heated at a temperature gradient of 100 to 200 ° C./min, and the temperature is increased to a maximum temperature of 1350 to 1550 ° C.,
In the growth promotion step, the firing object is set to a holding temperature of 1250 ° C. or higher,
In the firing step, the calcined zone passage time is 1 hour or longer, and the method for producing a quicklime-based expanded material. In the viscosity reduction step, by directly heating the internal heat burner from the rotary kiln entrance side, the temperature of the object to be fired is increased,
The method for producing a quicklime-based expansion material according to claim 1, wherein the growth promoting step includes maintaining the temperature of the object to be fired by indirect heating of an external heat burner provided on the rotary kiln outlet side. In the firing step,
The method for producing a quicklime-based inflatable material according to claim 1 or 2 , wherein, in addition to stirring by rotation of a rotary kiln, the material to be fired is stirred so as to inhibit the progress of the raw material. In the firing step,
Radiant heat is increased by increasing the surface area of the inner wall of the rotary kiln. The method for producing a quicklime-based expansion material according to any one of claims 1 to 3 . By causing 1350 to 1,550 ° C. until KyuNoboru temperature of, in a rotary kiln to produce quicklime-based intumescent material by calcining raw materials such as to produce the free lime and alite and interstitial phases,
A viscosity reducing means for rapidly raising the temperature of the object to be fired at a temperature gradient of 100 to 200 ° C./min, raising the temperature to a maximum temperature of 1350 to 1550 ° C., and reducing the viscosity inside the raw material;
Growth promoting means for promoting the growth of free quick lime while maintaining the temperature of the fired product at a holding temperature of 1250 ° C. or higher, and maintaining a reduced viscosity state ,
The firing zone transit time is 1 hour or more,
The viscosity reducing means has an internal heat burner for heating the object to be fired by direct heating from the inlet side ,
The said growth promotion means is provided in the exit side, and has an external heat burner which hold | maintains the temperature of to-be-baked material by indirect heating. A refractory member uniformly provided in the temperature-affected range of the inner heat burner on the inner wall of the rotary kiln;
The rotary kiln according to claim 5 , further comprising: a plurality of stirring enhancement members provided in a protruding shape on the refractory brick.