JPS5915117B2 - Manufacturing method of chimney material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the manufacturing method of a calcium silicate chimney material.

Combustion gas from ion-containing twisted materials, such as heavy oil and coal, contains sulfur oxides and oxyacids in addition to large amounts of water vapor and carbon dioxide.

Therefore, the lining material (chimney material) of the duct through which this combustion gas flows needs to have acid resistance as well as heat resistance and heat insulation properties that can withstand high temperatures. Calcium silicate molded bodies have excellent heat resistance and heat insulation properties, but they do not have enough acid resistance to withstand the acidic components in the combustion gas of the sulfur-containing twisted material as mentioned above. Due to the collapse of the crystalline form of calcium silicate, the molded product shrinks, cracks, and even becomes powder, and finally collapses. For this reason, calcium silicate molded bodies cannot be used as chimney materials as they are, and must be made acid-resistant by some means.
must be given. Conventionally, the method of increasing the acid resistance of calcium silicate molded bodies is to convert two or all of calcium silicate into ■-type anhydrite and amorphous silica through the action of sulfur oxide and/or oxyacid. 15
(Japanese Patent Laid-Open No. 48-85618) A method is known in which water and a silicic acid substance such as silica sol or sodium silicate are impregnated by coating or dipping.

However, the method of JP-A No. 48-85618 has the drawback that care must be taken in handling strong acidic processing agents such as sulfur dioxide gas, and that the manufacturing steps and equipment become complicated. Furthermore, if a molded product is simply impregnated with a silicic acid binder and used for a long period of time, the molded product will gradually shrink, crack, and become powder due to calcination and carbonation of the calcium silicate. Therefore, the present inventors25 conducted various studies with the aim of providing a calcium silicate chimney material that has a high degree of acid resistance in addition to the excellent heat resistance and heat insulation properties inherent to calcium silicate molded products. , they have completed the following invention. 30 That is, the present invention provides CaQ/SiO2 from silicic acid raw material, lime raw material, reinforcing fiber, and water.
Slurry of forming raw material A having (molar ratio) of 0.05 to 0.30 and CaO/SiO2 (molar ratio) of 0.60 to 1
．． A slurry of 35 molding raw materials B was prepared, and a slurry of these 35 molding raw materials was molded into a plate with a two-layer structure, one having a layer consisting of molding raw material A and a layer consisting of molding raw material B, and the plate was This invention is an invention of a method for producing a chimney material, characterized in that a layer formed from forming raw material A of a steam-treated, cured, handled, dried, and cured board is impregnated with a siliceous binder and dried.

According to the manufacturing method of the present invention, 6. Good heat resistance and heat insulation properties are achieved.
If a chimney material with a two-layer structure consisting of a layer made of calcium silicate and a layer mainly made of silicic acid with good acid resistance is obtained, and a flue is constructed in such a way that the surface of the acid-resistant layer comes into contact with combustion gas, 6. A chimney that is excellent in all properties such as heat resistance, heat insulation, and acid resistance is formed.

The method for manufacturing a chimney material according to the present invention will be described in detail below.

As the silicic acid raw material, lime raw material, and reinforcing fiber, any of those used as raw materials for manufacturing ordinary calcium silicate molded bodies can be used. For example, as the silicic acid raw material, silica powder, silica sand, diatomaceous earth, etc. can be used, as the lime raw material, slaked lime, quicklime, cement, etc. can be used, and as the reinforcing fiber, asbestos rock fiber, etc. can be used. . In addition to these, xonotlite,
Pearlite, permiculite, etc. may be used in combination as appropriate. From these raw materials and water. Slurries of the following two types of molding raw materials are prepared.

Molding raw material A: CaO/SlO2 is 0.05 to 0.30
．． It contains silicic acid raw material and lime raw material in a ratio that is preferably 0.10 to 0.25.

If CaO/SiO2 is less than 0.05, the cured product will have insufficient mechanical strength, and if it exceeds 0.30, acid resistance will be poor. Note that it is better not to include auxiliary materials with poor acid resistance such as xonotlite. Molding material B: A material containing silicic acid raw material and lime raw material in a ratio such that CaO/SlO2 is 0.60-1.20, preferably 0.80-1.0.

The composition of the molding material B is not particularly different from that of the raw material for ordinary calcium silicate molded bodies.The amount of water used for slurrying is approximately 5 to 15 times the total solid raw material.

Examples of methods for forming the slurry of the above two types of forming raw materials into a plate having a two-layer structure having layers made of each forming raw material include the following method.

1 One slurry is dehydrated press molded to within twice the target thickness (layer thickness), then the other slurry is poured on top of that and dehydrated press molded to create a board with the two layers crimped together. Obtain a molded product.

2. After dewatering and press-molding one slurry to within twice the target thickness, 6. remove it from the formwork, then pour the other slurry into the formwork, and place the preformed plate on top of it as described above. Then, dehydrate and form the breath again.

3 Each slurry is dehydrated and press-molded to a thickness 1.5 to 2 times the target thickness, and 6 the resulting two plates are stacked and compressed.

In either method, the molding pressure is desirably adjusted so that the bulk density of each layer is within the following range after the molded product is steam-treated, further dried and cured.

Layer from forming raw material A: 0.5 to 1.2 g/ml (if the bulk density is too high, the required amount of subsequent siliceous binder will not be impregnated.

Also, if the bulk density is too low, there are many coarse voids, and if a large amount of siliceous binder is impregnated to fill these voids, cracks are likely to occur after curing. ) Layer from molding raw material B: 0.2 to 0.69/d (considering the balance between heat insulation and strength. Set within this range.

) Also, the thickness of each layer is not particularly limited, but the layer from 6 molding raw material A should not be made unnecessarily thick. It is desirable to set it to about 5-20 mm.

The plate-shaped molded product obtained as described above is then placed in an autoclave and subjected to steaming treatment.

The conditions for the steaming treatment may be the same as those in the manufacturing process of a normal tricalcium silicate molded body. In other words.
The silicic acid raw material and the lime raw material are reacted by heating for 6 to 12 hours under a steam pressure of 6 to 15 kg/CTlt. Through this treatment, tobermorite-based or xonotrite-based calcium silicate crystals are produced from the forming raw material B (6) depending on the processing conditions. On the other hand, a small amount of topamolite-based calcium silicate crystals are produced from forming raw material A, which binds a large amount of unreacted silica, so that the plate is cured with the two layers completely integrated. Preferred specific examples of silicic binders to be impregnated into the layer formed from molding material A of the cured plate include sodium silicate, potassium silicate, lithium silicate, silica sol 6-ethyl silicate, and the like. The amount of impregnation is 1 CT of impregnated layer.
SiO2 per It is about 0.01 to 0.209. When the siliceous binder is impregnated and dried, the binder hardens within the binder-impregnated layer as water evaporates, filling and bonding the structure made of calcium silicate and unreacted silica.

The chimney material made by the manufacturing method of the present invention exhibits far superior durability compared to the conventional calcium silicate chimney material, and the following two reasons can be considered for this.

First, this chimney material has a two-layer structure, and the layer placed on the combustion gas side is mainly composed of connective tissue of silica, which has good acid resistance, and a siliceous binder filled with acidic gas. This means that surface erosion by water and mist is less likely to occur.

Even if a small amount of calcium silicate turns into gypsum due to long-term operation, the bonding effect of the silica and silicic acid binder will prevent the chimney material from shrinking, cracking, or turning into powder. Second, since the dense surface structure mainly composed of silica acts as a gas barrier layer, corrosion due to condensation with acidic components inside the chimney material is prevented.

The present invention will be explained below with reference to Examples.

In addition, "parts" in the examples mean parts by weight. Example
1 Silica stone powder and Portland cement, CaQ/SiO2
Molding raw material A is made by adding 20 parts of amosite asbestos to 100 parts of each mixture in various ratios so that the values are as shown in Table 1. Molding raw material B consisting of 70 parts of silica powder, 90 parts of slaked lime, 80 parts of xonotlite, and 40 parts of amosite asbestos was slurried with 10 times the amount of water.

Next, first, slurry of molding raw material A was placed in a mold of 15m77!
A layer formed from the forming raw material A has a thickness of 107 nm0) and a layer formed from the forming raw material B has a thickness of 40 m7! Eight types of plates having a two-layer structure consisting of L(7) and B layers were molded. These were steamed in an autoclave under a steam pressure of 9k9/d for 7 hours and then dried for 6 hours. The A layer of the obtained plate was impregnated with 0.039 μl of sodium silicate as SlO2, and then dried. The bulk density of the obtained product was 0.709/D for layer A and 0.419/d for layer B. These products and boards obtained in exactly the same manner except without the sodium silicate treatment were
The flue of a B heavy oil boiler was lined so that the A layer was in contact with the combustion gas, and it was used continuously for 6 months. Table 1 shows the compressive strength of the test piece before and after this test and the condition of the surface of layer A after the test. After the test, Ca of the untreated product
For those with O/SiO2 = 0.4 to 1.0, there were many yellowed areas on the surface, and cracks were formed in those areas due to shrinkage.

X-ray diffraction confirmed that anhydrite was formed in the yellow part and calcium carbonate was formed throughout. Furthermore, when the surface was rubbed with a finger, it became rough and powdery, and the compressive strength was significantly reduced. CaO/SiO2=
In the case of 0.03 to 0.3, there were few cracks due to shrinkage, but the 6-pulverization was significant and the 6-strength decreased significantly. On the other hand, products treated with sodium silicate. CaO/SiO2=0.4~1
．． In the case of No. 0, cracking and powdering were considerably improved, but not only was it still insufficient, but the strength after the test was significantly reduced.

However, in the case of CaO/SiO2=0.05 to 0.3, the yellowing was very slight and remained on the surface, and showed good results in all test items. Note that CaO/SiO2O. When O3 was impregnated with sodium silicate and dried, cracks occurred in layer A. Furthermore, after 6 months of use, the joint between the two layers peeled off. Example 2 The same procedure as Example 1 was carried out except that the CaO/SiO2 of layer A was 0.15 and the amount of sodium silicate impregnated was O~0.069/d (as SiO2), and the results shown in Table 2 were obtained. .

Example 3 Silica sand and slaked lime with CaO/SiO2 of 0.2
Molding raw material A6, which is obtained by adding 20 parts of tremolite asbestos to 100 parts of a mixture as follows, and 130 parts of silica powder,
Slaked lime 160 parts, Zonotrylo 00 parts, Perlite 60 parts
Molding raw material B consisting of 60 parts of amosite asbestos and 60 parts of amosite asbestos was mixed with 12 times the amount of water to form a slurry.

Claims (1)

[Claims] 1 Ca from silicic acid raw material, lime raw material, reinforcing fiber and water
A slurry of molding raw material A having an O/SiO_2 (molar ratio) of 0.05 to 0.30 and a slurry of molding raw material B having a CaO/SiO_2 (molar ratio) of 0.60 to 12.0 were prepared. The slurry of the forming raw material is formed into a two-layer plate having a layer consisting of forming raw material A and a layer consisting of forming raw material B, and the plate is cured by steam treatment, and then dried and cured. A method for producing a chimney material, which comprises impregnating the layer formed from A with a siliceous binder and drying it.