Method for producing cement clinker

Abstract

To provide a method for producing cement clinker capable of producing cement clinker and recovering high concentration potassium chloride.SOLUTION: A method for producing cement clinker is characterized by adjusting a chlorine concentration of chlorine bypass dust collected from a chlorine bypass device 11 installed in cement clinker production equipment 1 to 12 mass% or higher.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing cement clinker from which potassium chloride (KCl) can be recovered. [Background technology]

[0002] Potassium chloride is widely used for agricultural and industrial purposes, but domestic procurement is difficult, and most of it is imported. However, due to recent changes in the international situation, it is becoming more difficult to import as it is now difficult to obtain a stable supply of potassium chloride.

[0003] On the other hand, the cement industry is a mass production and mass consumption industry, and resource and energy conservation are continuing to be top priorities. The production of cement clinker involves a burning process using a burning kiln, and the effective use of this kiln for waste disposal contributes to resource circulation.

[0004] In such cement clinker production facilities, potassium chloride is generated in the production facilities due to the influence of chlorine contained in the cement clinker raw materials, incineration waste, burner fuel, etc., and this causes the potassium chloride to adhere to the inner walls of the facilities and block ducts, impairing stable operation. For this reason, a chlorine bypass device is installed to extract and treat chlorine-containing gas from the production facilities (see, for example, Patent Documents 1 and 2).

[0005] In a cement clinker manufacturing facility equipped with such a chlorine bypass device, gas is usually extracted from near the entrance (end of the kiln) of the calcination kiln, where the chlorine component is most concentrated, to the chlorine bypass device, and the chlorine concentration in the manufacturing facility is controlled so that the chlorine concentration of the cement clinker raw material before being supplied to the calcination kiln is 1.0 mass% or less. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2022-154608 A [Patent Document 2] JP 2022-128169 A Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a method for producing cement clinker, which can recover potassium chloride while producing cement clinker. [Means for solving the problem]

[0008] As described above, in conventional cement clinker production, in order to prevent the adverse effects of potassium chloride generation and to perform stable operation, chlorine is extracted from the production facility to the chlorine bypass device. In this chlorine bypass device, dust (chlorine bypass dust) is recovered, but the chlorine bypass dust has little value as a resource and is actually disposed of as waste.

[0009] The present inventors focused on the fact that this chlorine bypass dust contains potassium chloride, and discovered that by increasing the chlorine concentration in the production facility as much as possible and supplying high-concentration chlorine to the chlorine bypass device, the potassium chloride concentration in the chlorine bypass dust can be sufficiently increased and dust with a high potassium chloride content, which is valuable as a resource, can be recovered, thereby completing the present invention.

[0010] As described above, in the past, attention was focused on keeping the chlorine concentration low in the production facility in order to prevent the adverse effects of potassium chloride generation and ensure stable operation. However, in the present invention, under the new concept of obtaining potassium chloride in the cement clinker production facility, cement clinker is produced based on an idea that is the opposite of the conventional common sense of making the chlorine concentration in the production facility as high as possible.

[0011] That is, the present invention is as follows. [1] A method for producing cement clinker, comprising adjusting the chlorine concentration of chlorine bypass dust recovered from a chlorine bypass device installed in a cement clinker production facility to 12 mass% or more. [2] The method for producing cement clinker according to the above [1], wherein in the cement clinker production facility, a chlorine concentration of the cement clinker raw material before being supplied to a calcination kiln is adjusted to 1.2 mass% or more.

[0012] [3] The method for producing cement clinker according to the above [1] or [2], characterized in that a chlorine-containing fuel is supplied as fuel for a burner of a calcination system of the cement clinker production facility, and the chlorine concentration of the chlorine bypass dust is adjusted. [4] The method for producing cement clinker according to [3] above, wherein the chlorine-containing fuel is waste plastic. [5] The method for producing cement clinker according to any one of the above [1] to [4], characterized in that the amount of air extracted from the cement clinker production facility to a chlorine bypass device is adjusted to adjust the chlorine concentration of the chlorine bypass dust.

[0013] [6] A method for producing cement clinker, comprising adjusting a chlorine concentration of a cement clinker raw material before supplying it to a calcination kiln to 1.2 mass% or more in a cement clinker production facility. [7] The method for producing cement clinker according to the above [6], characterized in that the chlorine concentration of chlorine bypass dust recovered from a chlorine bypass device installed in the cement clinker production facility is adjusted to 12 mass% or more. [8] The method for producing cement clinker according to the above [6] or [7], characterized in that a chlorine-containing fuel is supplied as fuel for a burner in a calcination system of the cement clinker production facility, and the chlorine concentration of the cement clinker raw material before being supplied to the calcination kiln is adjusted. [9] The method for producing cement clinker according to [8] above, wherein the chlorine-containing fuel is waste plastic.

[10] The method for producing cement clinker according to any one of the above [6] to [9], characterized in that the amount of air extracted from the cement clinker production facility to a chlorine bypass device is adjusted to adjust the chlorine concentration of the cement clinker raw material before it is supplied to the calcination kiln. Effect of the Invention

[0014] According to the method for producing cement clinker of the present invention, it is possible to produce cement clinker while recovering dust containing potassium chloride. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic explanatory diagram of a cement clinker production facility used in the production method of the present invention. [Diagram 2] FIG. 2 is a schematic diagram for explaining the behavior of chlorine components in a cement clinker production facility used in the production method of the present invention. [Diagram 3] FIG. 1 is a schematic diagram of a chlorine bypass device installed in a cement clinker production facility used in the production method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The method for producing cement clinker of the present invention is characterized in that the chlorine concentration of chlorine bypass dust recovered from a chlorine bypass device installed in a cement clinker production facility is adjusted to 12 mass % or more.

[0017] The chlorine concentration of the chlorine bypass dust is preferably adjusted to 20% by mass or more, and more preferably 25% by mass or more. Since potassium, which acts as a counter to chlorine, is brought in in excess from cement clinker raw materials, etc., a large amount of potassium chloride is recovered according to the chlorine concentration.

[0018] Here, chlorine bypass dust refers to a deposit (dust) that precipitates when gas extracted from a cement clinker manufacturing facility is cooled. Usually, air is extracted from the cement clinker manufacturing facility through an extraction duct from the vicinity of the inlet (end of the kiln) of the burning kiln where the chlorine component is most concentrated in the cement clinker manufacturing facility. The chlorine concentration of chlorine bypass dust is measured using X-ray fluorescence analysis.

[0019] In the manufacturing method of the present invention, the chlorine concentration of the cement clinker raw material in the cement clinker manufacturing facility is increased as much as possible, and high-concentration chlorine is supplied to the chlorine bypass device, thereby increasing the potassium chloride concentration of the chlorine bypass dust. Therefore, potassium chloride, which is valuable as a resource, can be obtained from this chlorine bypass dust. The method for obtaining potassium chloride from the chlorine bypass dust is not particularly limited as long as it is a method capable of separating or purifying potassium chloride, and a method utilizing a difference in solubility in water or a difference in the temperature dependency of solubility can be used.

[0020] [Cement clinker manufacturing facility] The cement clinker production equipment used in the production method of the present invention is not particularly limited as long as it is equipment that can produce cement clinker by burning cement clinker raw materials. For example, general equipment that has been conventionally used for producing cement clinker, as shown in FIG. 1, can be used.

[0021] As shown in FIG. 1, a cement clinker production facility 1 has a rotary kiln (calcination kiln) 3, a preheater 5, a calciner 4, and a cooler 7, which are generally referred to as a calcination system.

[0022] The preheater 5 is equipped with multiple cyclones. The raw materials are supplied to the cyclones at the top of the preheater 5 and are preheated by the high-temperature exhaust gas from the rotary kiln 3. In the rotary kiln 3, the raw materials are fired at high temperatures by a burner 9 arranged on the outlet side (in front of the kiln) while rotating. In the rotary kiln 3, the side connected to the preheater 5 is called the kiln end, and the side connected to the cooler 7 is called the kiln front. The cooler 7 is used to cool the high-temperature fired material (clinker) discharged from the kiln front.

[0023] Here, in the rotary kiln 3 of the cement clinker production facility 1, the raw material flow and the gas flow intersect, and chlorine brought into the rotary kiln 3 together with the cement clinker raw materials is vaporized in the rotary kiln 3, and the vaporized chlorine gas is returned to the calciner 4 and the preheater 5, adheres to the cement clinker raw materials again, and circulates through the firing system (see symbol A in Figure 2).

[0024] Meanwhile, in the cement clinker production facility 1, gas is extracted to a chlorine bypass device 11 through an extraction duct 10 extending from the vicinity of the end of the rotary kiln 3. Reference numeral 12 denotes a raw material chute leading from the lowest cyclone to the calcination kiln, which is a location where clogging due to potassium chloride is likely to occur (see reference numeral B in FIG. 2).

[0025] As shown in Fig. 3, the chlorine bypass device 11 is connected to an extraction duct 10 extending from near the end of the rotary kiln 3 of the cement clinker production facility 1, and relatively heavy dust is recovered in a cyclone 13 and returned to the cement clinker production facility 1. Meanwhile, gas containing fine dust particles is sent to a cooler 14 and cooled, and the precipitate is recovered in a dust tank 15 as dust called chlorine bypass dust. In the production method of the present invention, the chlorine concentration of the chlorine bypass dust recovered in the dust tank 15 is adjusted to 12 mass% or more.

[0026] Components that do not precipitate in the cooler 14 are returned to the cement clinker production facility after fine particles are collected by a bag filter 16.

[0027] In the manufacturing method of the present invention, as described above, the chlorine concentration of the chlorine bypass dust is adjusted to 12 mass% or more. This can be achieved, for example, by adjusting (increasing) the chlorine concentration of the cement clinker raw material before it is supplied to the calcination kiln to 1.2 mass% or more.

[0028] Methods for adjusting (increasing) the chlorine concentration of the cement clinker raw material before it is fed to the calcination kiln include adjusting the composition and / or amount of the fuel fed to the burner of the calcination system, adjusting the composition and / or amount of the waste incinerated in the calcination kiln, and adjusting the composition of the cement clinker raw material. Among these methods, the method for adjusting the composition and / or amount of the fuel fed to the burner of the calcination system and the method for adjusting the composition and / or amount of the waste incinerated in the calcination kiln are preferred because they allow for rapid adjustment of the chlorine concentration in the cement clinker facility, and the method for adjusting the composition and / or amount of the fuel fed to the burner of the calcination system is particularly preferred. Note that the adjustment of the composition refers to changing the input material to one containing more chlorine, and the adjustment of the amount refers to increasing the input amount (input ratio) of the material containing chlorine.

[0029] A specific example of a method for adjusting the composition and / or amount of fuel supplied to the burner of the firing system is to supply a fuel with a higher chlorine content as the fuel for the burner of the firing system, and to increase the amount (proportion) of the chlorine-containing fuel. Normally, a carbon-containing fuel such as heavy oil or coal is used as the fuel (thermal energy source) for the burner, but in the present invention, a chlorine-containing fuel is used as part or all of the fuel.

[0030] An example of a chlorine-containing fuel is waste plastics. Examples of waste plastics include used plastic packaging materials, PET bottles, and ASR (Automobile Shredder Residue). Specific examples include chlorine-containing waste plastics including polyvinyl chloride, polyvinylidene chloride, chlorinated polyethylene, chlorinated rubber, and chloroprene. The waste plastics may be a mixture of multiple types of plastics or may be separated by type. However, since the chlorine concentration in the cement clinker facility can be quickly adjusted, separated waste plastics are preferred because the approximate chlorine concentration can be grasped. By changing the type and input amount of these waste plastics, the chlorine concentration in the manufacturing facility can be increased, and the chlorine concentration of the cement clinker raw material before being supplied to the firing kiln can be increased.

[0031] Examples of the burner in the calcination system that supplies the chlorine-containing fuel include a burner installed in the calcination kiln and a burner installed in the calciner.

[0032] Another method for adjusting (increasing) the chlorine concentration of the cement clinker raw materials before they are supplied to the calcination kiln is to adjust the amount of air bleed from the cement clinker production facility to the chlorine bypass device. Specifically, by reducing the amount of air bleed compared to the conventional method, the chlorine concentration in the production facility can be increased, and the chlorine concentration of the cement clinker raw materials before they are supplied to the calcination kiln can be increased.

[0033] As described above, the chlorine concentration of the cement clinker raw material before being supplied to the calcination kiln is preferably 1.2% by mass or more, more preferably 1.7% by mass or more, even more preferably 2.0% by mass or more, and particularly preferably 2.3% by mass or more. The upper limit is not particularly limited as long as it does not interfere with stable operation of the production equipment, but is preferably 2.8% or less, and more preferably 2.6% or less. The chlorine concentration of the cement clinker raw material before being supplied to the calcination kiln is usually measured by taking out the cement clinker raw material flowing through a raw material chute leading from the lowest cyclone to the calcination kiln. The specific method for measuring the chlorine concentration of the cement clinker raw material is the same as the method for measuring the chlorine concentration of chlorine bypass dust.

[0034] Another aspect of the present invention is a method for producing cement clinker, characterized in that the chlorine concentration of the cement clinker raw material before being supplied to a calcination kiln is adjusted to 1.2 mass% or more in a cement clinker production facility to produce cement clinker. Preferably, the chlorine concentration of the chlorine bypass dust recovered from a chlorine bypass device installed in the cement clinker production facility is adjusted to 12 mass% or more. Other details are the same as those described above, and therefore will not be described. EXAMPLES

[0035] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.

[0036] The chlorine concentration of the cement clinker raw material flowing through the raw material chute leading from the lowest cyclone to the calcination kiln (hereinafter referred to as the chlorine concentration in the manufacturing facility) was increased to 1.29 mass%, 1.77 mass%, and 2.49 mass%, respectively, using pulverized coal and chlorine-containing waste plastics as fuel for the main burner of the calcination kiln, and the chlorine concentration of the chlorine bypass dust recovered from the chlorine bypass device was adjusted. The manufacturing facility was operated for a specified period with this chlorine concentration in the manufacturing facility, but no particular problems occurred in operation. The chlorine concentration in the manufacturing facility during operation is usually controlled to 1.0 mass% or less, and specifically, the chlorine concentration in the manufacturing facility on one day was 0.93 mass%.

[0037] The chlorine concentration in the chlorine bypass dust in each of the above manufacturing facilities was as follows. Note that the KCl concentration in the chlorine bypass dust indicates the theoretical value when all the chlorine reacts with potassium.

[0038] [Table 1]

[0039] As shown in Table 1, by increasing the chlorine concentration in the manufacturing facility, it was possible to increase the chlorine concentration in the chlorine bypass dust from the chlorine bypass unit. Since the chlorine bypass dust also contains sufficient potassium, which is a counter to the chlorine, it is possible to recover a large amount of potassium chloride by using a method that utilizes the difference in solubility in water or a method that utilizes the difference in the temperature dependency of solubility.

[0040] In addition, when waste plastics were used as fuel for the burner of the calciner instead of the main burner of the calcination kiln, the chlorine concentration in the manufacturing facility was similarly increased, and it was also possible to increase the chlorine concentration of the chlorine bypass dust. [Industrial Applicability]

[0041] INDUSTRIAL APPLICABILITY The method for producing cement clinker of the present invention is industrially useful since it can produce cement clinker while recovering potassium chloride. [Explanation of symbols]

[0042] 1. Cement clinker manufacturing facility 3. Rotary Kiln 4. Calcination furnace 5 Preheater 7. Cooler 9. Burner 10 Extraction Duct 11 Chlorine Bypass Unit 12 Raw material chute 13. Cyclone 14 Cooler 15 Dust Tank 16 Bag Filter

Claims

1. A method for producing cement clinker, comprising adjusting a chlorine concentration of chlorine bypass dust recovered from a chlorine bypass device installed in a cement clinker production facility to 12 mass % or more.

2. 2. The method for producing cement clinker according to claim 1, wherein in the cement clinker production facility, the chlorine concentration of the cement clinker raw material before being supplied to the calcination kiln is adjusted to 1.2 mass % or more.

3. 2. The method for producing cement clinker according to claim 1, wherein a chlorine-containing fuel is supplied as fuel for a burner in a calcination system of the cement clinker production facility, thereby adjusting the chlorine concentration of the chlorine bypass dust.

4. 4. The method for producing cement clinker according to claim 3, wherein the chlorine-containing fuel is waste plastic.

5. 2. The method for producing cement clinker according to claim 1, wherein the amount of air extracted from the cement clinker production facility to a chlorine bypass device is adjusted to adjust the chlorine concentration of the chlorine bypass dust.

6. A method for producing cement clinker, comprising adjusting a chlorine concentration of a cement clinker raw material to 1.2 mass% or more before being supplied to a calcination kiln in a cement clinker production facility.

7. 7. The method for producing cement clinker according to claim 6, wherein the chlorine concentration of the chlorine bypass dust recovered from a chlorine bypass device installed in the cement clinker production facility is adjusted to 12 mass % or more.

8. 7. The method for producing cement clinker according to claim 6, further comprising the step of supplying a chlorine-containing fuel as fuel for a burner in a calcination system of the cement clinker production facility, thereby adjusting the chlorine concentration of the cement clinker raw material before it is supplied to the calcination kiln.

9. 9. The method for producing cement clinker according to claim 8, wherein the chlorine-containing fuel is waste plastic.

10. 7. The method for producing cement clinker according to claim 6, wherein the amount of extracted air from the cement clinker production facility to a chlorine bypass device is adjusted to adjust the chlorine concentration of the cement clinker raw material before it is supplied to the calcination kiln.

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