KR910005004B1 - Heat exchange brick - Google Patents

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Description

Heat exchange brick

1 is a flow chart illustrating that waste heat is stored in the heat storage material and the heat stored in the heat storage chamber of the glass melting furnace is sent to the burner.

Figure 2 is a graph illustrating the use of the stored heat storage material in the heat storage material to store the power of the surplus power time in the sensible heat storage device.

3 is a graph showing the relationship of thermal conductivity to apparent porosity in the conventional heat exchange brick based on magnesia prepared in Example 1.

4 is a graph showing a change in specific heat with respect to the MgO change amount of the heat exchange brick prepared in Example 2.

5 is a graph showing a change in thermal conductivity according to the composition of (Al ₂ O ₃ + Fe ₂ O ₃ ) and SiO ₂ composition of the heat exchange brick prepared in Example 3.

6 is a graph showing the change in specific heat and thermal conductivity according to the change of Fe ₂ O ₃ component in the heat exchange brick prepared in Example 4.

The present invention is to use to use the waste heat generated in industrial furnaces and yaw and relates to a heat exchange brick having a high specific heat and thermal conductivity and magnesia as a main component. As a method for utilizing waste heat generated in industrial furnaces and urine, it is supplied to secondary heat sources heated by using a heat exchanger (Recuperator), or the heat of waste heat is stored in the material and used when necessary using a material having excellent heat exchangeability. There is a way. Recently, sensible heat storage has been developed by using surplus power. Here, water, medium, or solid materials are used as heat storage materials. Among them, water or medium has a relatively high specific heat but a relatively high specific gravity. Because of the low temperature range is small, there is a disadvantage that the heat storage tank is large.

On the other hand, in the solid material, the oxide, which is an inorganic solid material, has a relatively low specific heat but has a high specific gravity and a high temperature range, and thus has been applied to various heat storage chambers or heat storage tanks of sensible heat storage equipment. Among the inorganic solid materials, materials having high specific heat and thermal conductivity are shown to have excellent effects as a basic condition for obtaining the heat storage effect.

In general, materials with high specific heat include magnesia, forsterite, corundum, mullite, dolomite and magnesia chrome. It contains high graphite, which is known to be effective by the characteristics of graphite.

Based on these characteristics, the prior art for heat exchange bricks is similar to that for heat storage chamber refractory materials shown in pages 23-27 of Japanese Refractory No. 38-387 (1986.No. 6). Medium purity magnesia brick, magnesia chromium brick, magnesia-alumina (Spinel) brick and the like are used. In addition, water, an oil medium, and a solid material are variously used in the heat storage device of the sensible heat storage method, and magnesia, poster light, and magnet are the main solid materials.

As described above, the conventional heat exchange technology is mainly used for each type, characteristic or part in a state having advantages and disadvantages according to general material characteristics. In particular, magnesia is a very excellent material, and has high spot resistance (MP: 2830 ℃), thermal structural stability, constant linear expandability, hot chemical resistance, and high specific heat. . However, recent heat exchange technologies require a combination of high specific heat characteristics of magnesia and high thermal conductivity to increase heat storage efficiency due to the development of a new furnace, improvement of heat storage structure, and utilization of surplus power.

In detail, in the heat storage chamber of the glass melting furnace, waste heat is stored in the heat storage material, and the heat stored in the heat storage material is sent to the burner as secondary air to save raw materials. In this case, when the heat storage effect is high (if heat is stored for a short time), the secondary air of high heat can be supplied to the burner to increase the operating temperature inside the furnace and save fuel. At this time, magnesia, which is currently used, has high specific heat characteristics, but a material having high thermal conductivity is needed to save the current process time (reduce heat storage time).

In the case of the sensible heat storage device, the power of the surplus power time is stored in the heat storage material and the heat of the heat storage material is utilized if necessary. The process and method thereof are shown in FIG. If the surplus power use time is short here, a material of high thermal conductivity is required.

Currently used heat exchange bricks are MgO 95.0-98.0%, CaO 0.5-0.8%, Al ₂ O ₃ 0.4-0.6%, Fe ₂ O ₃ 0.3-0.7% and SiO ₂ 1.6-2.0% Consists of. In summary, it consists of 95.5-98.8% by weight of MO (MgO + CaO), 0.7-1.3% by weight of M ₂ O ₃ (Al ₂ O ₃ + Fe ₂ O ₃ ), and 1.6-2.0% by weight of MO ₂ (SiO ₂ ) have. However, conventional heat exchange bricks based on magnesia having such a composition have a high specific heat but have a poor thermal conductivity, which is not satisfactory. Accordingly, an object of the present invention is to provide a heat exchange brick that maintains high specific heat and improves thermal conductivity, using magnesia as a main component of heat exchange materials.

The present invention has reached the present invention as a result of research and development of the material with a focus on this purpose.

Magnesia heat exchange material according to the present invention is MgO 80-95% by weight, CaO 5.0% by weight or less, Al ₂ O ₃ 1% by weight, Fe ₂ O ₃ 1.0-10% by weight, SiO ₂ per 100 parts by weight of the total oxide composition It consists of up to 10% by weight. To sum it up, 80-95% by weight of MO (MgO + CaO), 2-11% by weight of M ₂ O ₂ (Al ₂ O ₃ + Fe ₂ O ₃ ) and 10% by weight of MO ₂ (SiO ₂ ) Consists of

The heat exchange brick of the present invention having the above composition is manufactured by molding by dry molding, unlike the general brick manufacturing method, and then firing it at a high temperature of 1200 ° C. or higher.

In MgO-based heat exchange bricks, the specific heat generally varies depending on the amount of MgO added. If the MgO is 80% or less of the total weight of the oxide, the specific heat is drastically reduced. This means that the heat accumulation effect of the heat exchange brick is not good.

Fe ₂ O ₃ also plays a decisive role in the high specific heat and high thermal conductivity properties of the magnesia heat exchange brick, the thermal conductivity is high, but the specific heat is relatively reduced when more than 10% of the total weight of the oxide. Therefore, the Fe ₂ O ₃ component is preferably 1.0-10% of the total weight of the oxide.

In addition, when the M ₂ O ₃ (Al ₂ O ₃ + Fe ₂ O ₃ ) content is 11% or more of the total weight of the oxide and MO ₂ (SiO ₂ ) is 10% or more, the specific heat is remarkably dropped and loses its value as a heat exchange material. do. Therefore, the specific heat characteristics are best when MgO is 80% or more based on the total weight of oxide and M ₂ O ₃ (Al ₂ O ₃ + Fe ₂ O ₃ ) is 11% or less and MO ₂ (SiO ₂ ) is 10% or less. Excellent.

Hereinafter, the present invention will be described in more detail with reference to the following Examples.

Example 1

In this embodiment, using a raw material belonging to the conventional category to produce a heat exchange brick and to measure its physical properties.

First, an impeller grinder and a ball mill were prepared using a raw material of magnesia clinker containing 95.9 wt% MgO, 1.2 wt% CaO, 0.3 wt% Al ₂ O ₃ , 0.4 wt% Fe ₂ O _3, and 2.2 wt% SiO _2. Pulverized using a grinder, and then kneaded according to the following Table 1 and molded into a standard brick (230 x 114 x 65 mm) under a pressure of 1000 kg / cm ² , and then 1500 ℃ in the tunnel kiln (tunnel kiln) It manufactures by x3Bx16 units / day.

TABLE 1

In Example 1, when the brick was manufactured at the mixing ratio according to Table 1, the thermal conductivity change is shown in FIG. 3. As shown in FIG. 3, the thermal conductivity (kcal / m.hr. ° C.) according to the pore change shows a sharp drop in samples 4 and 5 of Table 1, while samples 1,2 and 3 are 4.2-4.5 kcal /. It can be seen that it is about the same as m.hr. ° C. This is because samples 4 and 5 have a specific surface area with increasing amount of fine powder by Andreasen's closest packing theory. That is, in Example 1, when manufactured by the conventional manufacturing method as shown in Samples 1, 2 and 3, the change in thermal conductivity is limited by physical properties, which means that the thermal conductivity improvement of the magnesia brick for heat exchange should be developed as a composition change. Experimentally.

Example 2

Example 2 relates to an example of measuring the change in specific heat according to the mixing ratio of the MgO component in the heat exchange brick according to the present invention.

According to the table of FIG. 4, Al ₂ O ₃ , Fe ₂ O ₃ , SiO ₂ and CaO components are blended and theoretically added high purity MgO components to the mixture to prepare a kneaded material, according to the method of Example 1 To prepare.

TABLE 2

The change of specific heat according to the addition of MgO component is shown in FIG. From Figure 4 it can be seen that the change in specific heat is small when the MgO composition is more than 80 by weight ratio (sample 4-7 in Table 2), which proves good in terms of thermal accumulation effect. However, if the MgO composition is less than 80 by weight ratio (sample 1-3 in Table 2), it can be seen that the specific heat rapidly decreases, indicating that the ratio of the high specific heat, which is the MgO component, should be at least 80% by weight.

Example 3

Example 3 relates to an example of measuring the change in specific heat according to the change of M ₂ O ₃ (Al ₂ O ₃ + Fe ₂ O ₃ ) composition and MO ₂ (SiO ₂ ) composition in the heat exchange brick according to the present invention will be.

Each component is blended according to the following Table 3 to prepare a kneaded product, and a brick for heat exchange is prepared according to the method of Example 1. Here, Sample 1-7 showing the change of M ₂ O ₃ (Al ₂ O ₃ + Fe ₂ O ₃ ) composition shows the ratio of MO (MgO + CaO) composition and MO ₂ (SiO ₂ ) composition according to the table of FIG. Al ₂ O ₃ and Fe ₂ O ₃ components were combined in a ratio of 1: 1 by weight, and Samples 8-13 consisted of MO (MgO + CaO) composition and M ₂ O ₃ (Al ₂ O ₃ + Fe ₂ O ₃ ). The composition is formulated in the ratio of Table 3, and the SiO ₂ component is theoretically added and combined in the composition according to the table of FIG.

TABLE 3

The results of the specific heat change are shown in Figure 5, from which the M ₂ O ₃ (Al ₂ O ₃ + Fe ₂ O ₃ ) composition of magnesia is 11 or more (samples 6,7) and MO ₂ (SiO ₂ ) by weight ratio. When the composition is 10 or more (samples 12 and 13) by weight, the specific heat is remarkably low, and thus it is not suitable as a heat exchange material. That is, the specific heat characteristics of the magnesia material is 80% by weight or more of the MgO component, 5% by weight or less of the CaO component, 11% by weight or less of the M ₂ O ₃ (Al ₂ O ₃ + Fe ₂ O ₃ ) component, and 10 weight of the SiO ₂ component. It can be seen that when the% or less, it is suitable as a material for heat exchange.

According to the conventional technique that the known magnesia material having a high MgO component is excellent in heat exchange bricks from Example 3, the magnesia material having an MgO component of at least 80% by weight and other components at 20% by weight or less has excellent results for heat exchange. Achievable means significant advances in the field.

Example 4

Example 4 relates to an example of measuring the change in thermal conductivity and specific heat according to the increase of the Fe ₂ O ₃ component in the heat exchange brick according to the present invention.

Samples of the test were prepared using the magnesia raw materials used in Table 1.

The test sample was prepared using a magnesia raw material used in Table 1, whereby a high purity Fe ₂ O ₃ component was combined as shown in Table 4 below to prepare a kneaded material, under a pressure of 1000 kg / cm ² (230 × 114 × 65MM). ) And then produced in a tunnel kiln at 1500 ° C. × 3B × 16 units / day.

TABLE 4

In this embodiment, the change in the conductivity and specific heat according to the increase of the Fe ₂ O ₃ component is shown in FIG. From FIG. 6, it can be seen that in the case of the known sample 1, the specific heat is very good, but the thermal conductivity is somewhat lowered, and in the case of the sample 2-8 in which the Fe ₂ O ₃ component is combined, the thermal conductivity is significantly increased. have. On the other hand, in the case of Sample 7,9 having a Fe ₂ O ₃ component of 10% by weight or more, the thermal conductivity is high, but the specific heat is relatively lowered. As a result, the samples 1, 7, and 8 are not suitable for the high specific heat and high thermal conductivity of the present invention. It can be seen. Therefore, the components of Fe ₂ O ₃ was also demonstrated clearly is a key role in high-boiling heat, high thermal conductivity characteristics at the magnesia brick for heat exchangers, yiettara content of Fe ₂ O ₃ component is suitably in the range of 1-10% by weight.

[Examples 5, 6 and 7]

In this example, the raw materials were combined and kneaded as shown in Table 5 below, and then molded under a pressure of 1000 kg / cm ² , dried at 110 ° C. for 24 hours, and fired at 1460 ° C. × 3B × 16 units / day. Likewise, on-site manufacturability and general properties of the heat exchange brick were measured. At this time, the same result as in the embodiment according to the present invention was obtained and in particular, there was no problem in the field application.

Examples 5 and 6 relates to a heat exchange brick according to the present invention, and Example 7 relates to a conventional heat exchange brick. As shown in Table 5, it is confirmed that the general properties are improved in Examples 5 and 6 as shown in Table 5. Can be. This is the result of fluctuation of low melting point material (Flux) during the firing process of the brick to improve the product quality. In other words, the glassy bonding by the low melting point material in the raw material improves the plasticity effect to increase the bonding force and form a continuous structure of the internal structure. This is a clear proof of providing high specific heat and high thermal conductivity to the heat exchange brick according to the invention.

Meanwhile, as shown in Table 5, the conventional heat exchange brick of Example 7 can be confirmed that the general properties remain different from those of Examples 5 and 6 according to the present invention.

TABLE 5

As described above, the present invention relates to a composition having high specific heat and high thermal conductivity in the case of magnesia brick in heat exchange materials, and it has been proved that the improvement of thermal conductivity by the combination ratio, that is, by the manufacturing technology, is limited. See also 3). In addition, in the existing technique that a known high material of MgO component shows excellent performance in heat exchange bricks, technical proof has been made that MgO component is more than 80% by weight and that other components are appropriately adjusted (Fig. 4, 5). See also). In particular, products having high specific heat and high thermal conductivity have been produced by the addition and adjustment of the Fe ₂ O ₃ component.

Claims (2)

A heat exchange brick having an oxide composition of 80-95% by weight of (MgO + CaO), 2-11% by weight of (Al ₂ O ₃ + Fe ₂ O ₃ ) and 10% by weight of SiO ₂ . The brick of claim 1, wherein the Fe ₂ O ₃ component is in the range of 1-10% by weight.

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