JP7017958B2 - Method of preparing aggregate raw material and method of manufacturing aggregate - Google Patents

Description

The present invention relates to a method for preparing an aggregate raw material and a method for producing an aggregate, and more particularly to a method for producing an aggregate from waste such as coal ash.

In recent years, in view of the tightness of landfill sites, technologies for effectively utilizing waste such as coal ash, municipal waste incineration ash, and blast furnace slag as aggregates have been developed. For example, in Patent Documents 1 and 2, a calcined product containing anorsite (CaAl ₂ Si ₂ O ₈ ) containing coal ash as a main component is obtained while suppressing the formation ratio of an amorphous phase to a low level, and a cement mixed material is obtained. And the technology used for fine aggregates, etc. will be disclosed.

On the other hand, in order to treat waste such as soil containing radioactive cesium generated by a major accident at a nuclear power plant, for example, Patent Document 3 describes waste contaminated with radioactive cesium and a calcium oxide source or / and. By mixing and heating a magnesium oxide source and a chlorine source, fired aggregates, etc. are manufactured, and radioactive cesium is removed from waste containing radioactive cesium to reduce its volume while reducing the concentration of radioactive cesium. A method of manufacturing low building materials is provided.

Japanese Unexamined Patent Publication No. 2015-145319 Japanese Unexamined Patent Publication No. 2017-147708 JP-A-2017-150955

However, in order to stably operate the firing device using waste as a raw material and obtain high-quality aggregate, it is necessary to appropriately adjust the chemical composition and powderiness of the raw material, and analysis, measurement and of these are performed. There was a problem that the preparation of raw materials was complicated.

Furthermore, it is also required to stably operate the firing apparatus using waste contaminated with radioactive cesium as a raw material and to obtain high-quality aggregate while maintaining a high volatilization removal rate of radioactive cesium.

Therefore, the present invention has been made in view of the above-mentioned problems in the prior art, and thus, the preparation of the aggregate raw material is made efficient, and the high-quality aggregate is stably maintained while maintaining the high volatilization removal rate of radioactive cesium. The purpose is to get.

In order to achieve the above object, the present invention is a method for preparing an aggregate raw material as an aggregate material, in which the peak of heat generation measured by a differential thermal analysis method or a differential scanning calorimetry method is 1150 ° C. or higher and 1300 ° C. or lower. It is characterized by preparing an aggregate raw material as described above.

According to the present invention, in preparing the aggregate raw material, only the measurement result of the differential thermal analysis method or the differential scanning calorimetry method is used, so that the measurement of the chemical composition, the degree of powder, etc. of the aggregate raw material is complicated. No raw material preparation is required, and aggregate raw materials can be efficiently prepared.

In the method for preparing an aggregate raw material, the aggregate raw material may contain waste contaminated with radioactive cesium. As a result, while removing radioactive cesium from soil or the like, waste such as soil containing radioactive cesium can be effectively used as an aggregate raw material.

Further, the present invention is a method for producing an aggregate, wherein the prepared aggregate raw material is used at a temperature of 1250 ° C. or higher and 1350 ° C. or lower according to the peak of heat generation of the aggregate raw material prepared by the above preparation method. It is characterized by firing.

According to the present invention, good quality aggregate can be stably obtained by firing at a firing temperature corresponding to the peak of heat generation measured by a differential thermal analysis method or a differential scanning calorimetry method for an aggregate material. In the case of an aggregate raw material containing radioactive cesium, good quality aggregate can be stably obtained while maintaining a high volatilization removal rate of radioactive cesium.

In the method for producing an aggregate, the aggregate raw material can be fired with a rotary kiln to obtain an aggregate having a free lime content of 2% by mass or less and an aggregate having a removal rate of radioactive cesium of 80% or more. ..

As described above, according to the present invention, it is possible to streamline the preparation of aggregate raw materials and stably obtain high-quality aggregate while maintaining a high volatilization removal rate of radioactive cesium.

It is a process drawing for demonstrating one Embodiment of the manufacturing method of the aggregate which concerns on this invention. It is a graph which shows the example which performed the differential scanning calorimetry (DSC) of a certain aggregate raw material. It is a graph for demonstrating the test example of the manufacturing method of the aggregate which concerns on this invention.

Next, a mode for carrying out the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of an aggregate manufacturing method according to the present invention, in which the two types of aggregate raw materials A and B are heated at the temperature of the aggregate raw material and at the temperature. A step of measuring the relationship between the temperature difference or the calorific value difference from the reference material of the above, a step of adjusting the mixing ratios of the aggregate raw materials A and B based on the measurement result, and a step of preparing the aggregate raw material, and the prepared bone. Includes a step of firing the raw material.

The measurement step is performed by using a differential thermal analysis method or a differential scanning calorimetry method. In Differential Thermal Analysis (DTA), a sample and a reference material are placed in symmetrical positions in a heating furnace, and the temperature of the heating furnace is changed according to a program by a heater, and the temperature difference between the sample and the reference material is measured. It is a method of measuring as a function of temperature (JIS K 0129 "general rule of thermal analysis"), and is measured by using a differential thermal analyzer or a thermal weight differential thermal analyzer (TG-DTA). On the other hand, differential scanning calorimetry (DSC) uses a differential scanning calorimetry to measure the difference in calories between the sample and the reference material when they are heated at a constant rate, thereby causing a phase transition of the sample. It estimates the chemical reaction.

FIG. 2 shows an example of differential scanning calorimetry (DSC) of a certain aggregate raw material. FIG. 2A is a DSC diagram, and FIG. 2B is a DDSC (corresponding to the derivative of DSC) diagram. The vertical axis of the graph shows the heat flow (Heat Flow / mW), and the horizontal axis shows the temperature (° C) of the aggregate material. Further, in the DSC diagram, the upward transition indicates an exothermic reaction, and the downward transition indicates an endothermic reaction.

In the DSC diagram of FIG. 2 (a), a peak of heat generation (maximum value, 0 on the vertical axis in the DDSC diagram of FIG. 2 (b)) exists at 1280 ° C.

In the preparation step, the peak of heat generation of each of the aggregate raw materials A and B is measured as described above, the mixing ratio of the aggregate raw materials A and B is adjusted based on each measured value, and the peak of heat generation is 1150 ° C. This is a step of preparing an aggregate raw material so that the temperature becomes 1300 ° C. or lower. When the peak of heat generation of the aggregate raw material A or B is already in the range of 1150 ° C. or higher and 1300 ° C. or lower, it is also possible to use only the aggregate raw material A or B. Further, even when the peak of heat generation of either or both of the aggregate raw materials A and B is already in the range of 1150 ° C. or higher and 1300 ° C. or lower, the mixing ratio of the aggregate raw materials A and B is adjusted so that the heat generation peak becomes. Aggregate raw materials having a temperature of 1150 ° C. or higher and 1300 ° C. or lower may be prepared. Although the case where two kinds of aggregate raw materials are used is exemplified, three or more kinds of aggregate raw materials can also be used.

To adjust the peak of heat generation, components such as CaO, SiO ₂ , Al ₂ O ₃ may be added, or wastes having various compositions may be mixed to adjust the basicity and the Ca / Si ratio. Basically, the higher the basicity and the Ca / Si ratio, the higher the peak of heat generation can be. In addition, additives such as Cl and P may be used as necessary to remove radioactive cesium by volatilization at high temperature and to improve the stability of the aggregate.

The firing step is a step of firing the aggregate raw material prepared in the above procedure at a temperature in the range of 1250 ° C. or higher and 1350 ° C. or lower. This temperature range corresponds to the peak of heat generation of 1150 ° C. or higher and 1300 ° C. or lower, and is adjusted to the range of 50 ° C. or higher and 100 ° C. or lower of the actual heat generation peak. A rotary kiln or the like is used as the firing device. By setting the firing temperature to 50 ° C or higher and 100 ° C or lower, which is the peak of actual heat generation, stable operation due to fusion of raw materials in the kiln is not hindered, a solid aggregate can be obtained, and radioactive cesium is removed. The rate can also be maintained high. In addition, the peak of heat generation of the raw material can be monitored while firing, and the firing temperature can be changed according to the fluctuation to maintain the stable operation of the kiln.

Next, examples of the present invention will be described.

As shown in FIG. 3, differential thermal analysis (DTA) was performed on 11 kinds of aggregate raw materials, and the peak of heat generation was measured. The maximum points marked in the figure indicate the peak of heat generation. The peaks of these heat generations are shown in Table 1. Examples 1 to 9 had a peak of heat generation of 1150 ° C. or higher and 1300 ° C. or lower, Comparative Example 1 had a peak of heat generation of less than 1150 ° C., and Comparative Example 2 had a peak of heat generation of more than 1300 ° C.

The above 11 kinds of aggregate raw materials were fired at the operating temperatures shown in the table using a rotary kiln. In Examples 1 to 9, the rotary kiln can be operated in a stable state, the radioactive cesium removal rate (Cs removal rate) is 90% or more, the free lime (f-CaO) is 2% by mass or less, and the non-defective product rate. More than 80% of aggregate could be produced. On the other hand, in Comparative Example 1, a part of the aggregate raw material was melted in the rotary kiln, and the rotary kiln could not be operated stably. Further, in Comparative Example 2, it could not be sufficiently fired due to insufficient heat, the radioactive cesium removal rate was low, the free lime exceeded 2% by mass, and the non-defective rate remained at 34%. From Examples 1 to 9, the operating temperature at which an aggregate having a non-defective rate of 80% or more can be produced is 1250 ° C. or higher and 1350 ° C. or lower, and the high temperature side of the heat generation peak of 50 ° C. or higher and 100 ° C. or lower can be used as a guide. Recognize.

Claims (5)

A method for preparing an aggregate raw material, which comprises preparing an aggregate raw material so that the peak of heat generation measured by a differential thermal analysis method or a differential scanning calorimetry method is 1150 ° C. or higher and 1300 ° C. or lower. The method for preparing an aggregate raw material according to claim 1 , wherein the aggregate raw material contains waste contaminated with radioactive cesium. The prepared aggregate raw material is fired at a temperature of 1250 ° C. or higher and 1350 ° C. or lower according to the peak of heat generation of the aggregate raw material prepared by the method for preparing the aggregate raw material according to claim 1 or 2 . A characteristic method of manufacturing aggregate. The method for producing an aggregate according to claim 3 , wherein the aggregate raw material is fired in a rotary kiln to obtain an aggregate having a free lime content of 2% by mass or less. The method for producing an aggregate according to claim 3 or 4 , wherein the aggregate raw material is fired in a rotary kiln to obtain an aggregate having a removal rate of radioactive cesium of 80% or more.

Images