Heat-insulating refractory brick and preparation method thereof

Abstract

The invention belongs to the technical field of heat-insulating bricks, and particularly relates to a heat-insulating refractory brick and a preparation method thereof. The heat-insulating refractory brick is prepared from the following raw materials in percentage by mass: 20-60% of secondary quartzite aggregate of 0.5-0.1 mm, 30-70% of secondary quartzite fine powder of less than 0.1 mm, 5-10% of clay and 3-10% of a mineralizer, 30-40% of modified straw powder and 3-5% of a binding agent are additionally added. The heat-insulating refractory brick disclosed by the invention is excellent in high-temperature volume stability, low in preparation cost, small in volume density and light in weight, the apparent porosity is up to 60%, and the requirements of the heat-insulating refractory brick for a high-temperature kiln are met.

Description

Technical Field

[0001] The invention belongs to the technical field of refractory bricks, and in particular relates to a heat-insulating refractory brick and a preparation method thereof. Background Art

[0002] Energy saving and consumption reduction of kilns is one of the important development directions of high temperature industry. Insulating refractory materials are of great significance to energy saving and emission reduction of kilns. Siliceous refractory bricks are a type of insulating refractory materials. The preparation method of siliceous insulating refractory bricks includes adding burnt materials, such as adding anthracite powder, coke powder, etc., and preparing siliceous insulating bricks by burning combustibles. For example: Chinese invention patent application with publication number CN103880439A discloses a preparation method of lightweight silica bricks, firstly 30-60wt% of silica particles, 10-30wt% of silica fine powder, 2-6wt% of limestone, 5-15wt% of silica sol and 10-30wt% of coke are mixed, stirred evenly, and vibrated or rammed into shape; then the formed green body is dried at 110°C for 4-24 hours, and then kept warm at 1200-1400°C for 3-15 hours. The Chinese invention patent application with publication number CN104944976A discloses a method for preparing a siliceous thermal insulation brick, which is prepared by using 75-85% quartz sand, 15-25% expanded perlite, 0.3-0.4% iron oxide powder, 8-10% lime milk, 4-6% pulp waste liquid, etc. as raw materials, through batching, mixing, molding, drying, and high-temperature sintering (1380-1420°C). However, both of the above patents use a variety of non-metallic mineral resources, and the production cost is relatively high. Summary of the invention

[0003] In order to overcome the above-mentioned defects, the object of the present invention is to provide an insulating refractory brick and a preparation method thereof, which has a wide source of raw materials, low preparation cost and excellent performance.

[0004] To achieve the above object, the present invention adopts the following technical solution:

[0005] An insulating refractory brick is made of the following raw materials in percentage by mass:

[0006] 0.5-0.1mm secondary quartzite aggregate 20-60%, <0.1mm secondary quartzite fine powder 30-70%, clay 5-10%, mineralizer 3-10%; plus modified straw powder 30-40% and binder 3-5%.

[0007] Preferably, the secondary quartzite aggregate or secondary quartzite fine powder comprises the following phases in percentage by mass: 60-80% quartz, 15-40% kaolinite, and the remainder being impurities.

[0008] Preferably, the mineralizer is limestone powder.

[0009] Preferably, the method for preparing the modified straw powder comprises the following steps: pouring silica sol and straw particles into a mixer and stirring, and then drying, crushing and sieving to obtain the modified straw powder.

[0010] Preferably, the mass ratio of the silica sol to the straw particles is 3-4:6-7.

[0011] Preferably, the binder is dextrin or calcium lignosulfonate.

[0012] The method for preparing the above-mentioned insulating refractory brick comprises the following steps:

[0013] (1) Pour the secondary quartzite aggregate and the binder into a wet mill and mix them, then add clay, secondary quartzite fine powder, mineralizer and modified straw powder to mix;

[0014] (2) Put the evenly mixed materials into a sealed bag to trap the materials;

[0015] (3) Pressing the trapped material into shape;

[0016] (4) drying the formed bricks;

[0017] (5) The dried bricks are fired in a high-temperature kiln.

[0018] Preferably, the sintering temperature in step (5) is 1300-1400°C and the holding time is 8-10 hours.

[0019] 1. Secondary quartzite is a kind of associated mineral, which is a metamorphic rock mainly composed of secondary quartz formed by long-term leaching and weathering of intermediate-acidic volcanic rocks. The associated mineral reserves are huge and the sources are wide. Secondary quartzite is directly used as a refractory raw material without calcination, which is simple to process and has low mining cost. The present invention uses secondary quartzite as the main raw material to prepare insulating refractory bricks, which reduces the cost of brick making and is conducive to the industrial application of secondary quartzite.

[0020] 2. The main components of agricultural straw are cellulose, hemicellulose and lignin. The straw itself is porous, loose in structure and elastic. The interfacial bonding force between the straw and the inorganic non-metallic raw material matrix is ​​low, the elastic aftereffect of the blank is large, and it is difficult to be machine-pressed. The present invention uses silica sol to modify the straw particles. The silica sol is converted into silica gel after heating. The inside of the straw is filled with silica gel, and the surface is also coated with silica gel to harden the straw structure. As a pore-forming agent for brick making, the forming performance of refractory bricks is improved.

[0021] 3. The thermal conductivity of the insulating refractory brick obtained by the present invention is 0.18-0.28 W / m·K at 400°C, the thermal conductivity is low, and the heating line change rate (1300°C×3h) is +0.05-+0.14%, indicating that the insulating brick has excellent high-temperature volume stability; and the pore diameter of the insulating brick is between several microns and tens of microns, the pores are through holes, the apparent porosity is as high as 60%, and the volume density is 0.99-1.23 g / cm 3 , small volume density, light weight, compressive strength of 1.1-2.6MPa, meeting the requirements of insulating refractory bricks for high temperature kilns. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with some specific implementation methods.

[0023] Example 1

[0024] An insulating refractory brick is made of the following raw materials in percentage by mass:

[0025] 58% of secondary quartzite aggregate with a particle size of 0.5-0.1mm, 30% of secondary quartzite fine powder <0.1mm, 9% of clay, 3% of limestone powder; and 30% of modified straw powder and 5% of dextrin.

[0026] Furthermore, the secondary quartzite aggregate or secondary quartzite fine powder consists of the following phases in percentage by mass: 66% of quartz, 32% of kaolinite, and the remainder being impurities.

[0027] Furthermore, the preparation method of the modified straw powder comprises the following steps:

[0028] The silica sol and straw particles ≤ 20 mm were poured into a blender and stirred evenly, and then dried at 140° C. for 24 hours. The dried straw was crushed and passed through a 50-mesh sieve to obtain modified straw powder.

[0029] Furthermore, the mass ratio of silica sol to straw particles is 4:6.

[0030] The method for preparing the above-mentioned lightweight insulating refractory brick comprises the following steps:

[0031] (1) Batching: Pour the secondary quartzite aggregate and binder into a wheel mill and mix for 5 min, then add clay, secondary quartzite fine powder, limestone powder and modified straw powder and mix for 10 min;

[0032] (2) Material trapping: Put the evenly mixed material into a sealed bag and trap it for 24 hours;

[0033] (3) Molding: The trapped material is machine-pressed into shape;

[0034] (4) Drying: The formed bricks are dried at 120°C for 48 hours;

[0035] (5) Firing: The dried bricks are fired in a high temperature kiln at 1350°C and kept warm for 8 hours.

[0036] Example 2

[0037] The preparation method of the heat-insulating refractory bricks in this embodiment is basically the same as that in embodiment 1, and the similarities are not repeated here. The difference is that 35% of modified straw powder is added.

[0038] Example 3

[0039] The preparation method of the heat-insulating refractory bricks in this embodiment is basically the same as that in embodiment 1, and the similarities are not repeated here, except that 40% of modified straw powder is added.

[0040] Example 4

[0041] The preparation method of the lightweight insulating refractory bricks in this embodiment is basically the same as that in Example 1, and the similarities are not repeated. Some differences are: the secondary quartzite aggregate or secondary quartzite fine powder is composed of the following phases in percentage by mass: quartz 59%, kaolinite 38%, and the remainder is impurities.

[0042] Example 5

[0043] The method for preparing the insulating refractory bricks in this embodiment is basically the same as that in Embodiment 1, and the similarities are not repeated here. Some differences are as follows: the mass ratio of silica sol to straw particles is 3.5:6.5.

[0044] Example 6

[0045] The method for preparing the insulating refractory bricks in this embodiment is basically the same as that in Embodiment 1, and the similarities are not repeated here. Some differences are as follows: the mass ratio of silica sol to straw particles is 3:7.

[0046] Example 7

[0047] The preparation method of the insulating refractory bricks in this embodiment is basically the same as that in embodiment 2, and the similarities are not repeated. Some differences are: an insulating refractory brick for a high-temperature kiln is made of the following raw materials in percentage by mass:

[0048] 40% secondary quartzite aggregate with a particle size of 0.5-0.1mm, 50% secondary quartzite fine powder <0.1mm, 7% clay, 3% limestone powder; and 35% modified straw powder and 5% dextrin.

[0049] Example 8

[0050] The preparation method of the insulating refractory bricks in this embodiment is basically the same as that in embodiment 2, and the similarities are not repeated. Some differences are: an insulating refractory brick for a high-temperature kiln is made of the following raw materials in percentage by mass:

[0051] 22% of secondary quartzite with a particle size of 0.5-0.1mm, 70% of secondary quartzite fine powder ≤0.1mm, 5% of clay, 3% of limestone powder; and 35% of modified straw powder and 5% of dextrin.

[0052] Example 9

[0053] The preparation method of the insulating refractory bricks in this embodiment is basically the same as that in embodiment 2, and the similarities are not repeated here. The difference is that: an insulating refractory brick is made of the following raw materials in the following mass percentages:

[0054] 49% of secondary quartzite with a particle size of 0.5-0.1mm, 31% of secondary quartzite fine powder ≤0.1mm, 10% of clay, 10% of limestone powder; and 35% of modified straw powder and 5% of dextrin.

[0055] The performance indicators of the insulating refractory bricks prepared in Examples 1 to 9 of the present invention are shown in Tables 1 to 2 below.

[0056] Table 1 Performance indicators of thermal insulation refractory bricks in Examples 1 to 6 of the present invention

[0057]

[0058] As shown in Table 1, comparing Examples 1, 2, and 3, the amount of the added straw modified by the ignition loss agent is 30%, 35%, and 40%, respectively, which increases successively, resulting in the porosity of the insulating bricks increasing successively, and the bulk density, heating line change rate, thermal conductivity, and compressive strength indicators all decreasing successively. Comparing Example 1 and Example 4, the kaolinite content in the secondary quartzite of the two is different, increasing from 32% to 38%. The apparent porosity of the insulating refractory bricks prepared in Example 4 increases slightly, the bulk density decreases, and the heating line change rate, thermal conductivity, and compressive strength all decrease slightly.

[0059] Comparing Examples 1, 5, and 6, the weight ratio of the silica sol to the straw used to process the straw is different. The proportion of the silica sol decreases successively, and the proportion of the straw increases relatively. Therefore, the porosity of the corresponding three insulating refractory bricks increases successively, and the bulk density, heating line change rate, thermal conductivity, and compressive strength indicators all decrease successively.

[0060] Table 2 Performance indicators of insulating refractory bricks in Examples 7 to 9 of the present invention

[0061]

[0062] As shown in Table 2, the thermal conductivity of the insulating refractory bricks in the present invention increases slightly with the increase of the test temperature, which is in line with the characteristics of the insulating bricks. Compared with Example 2, the amount of straw powder added in Examples 7 and 8 is the same, but the ratio of secondary quartzite aggregate to secondary quartzite fine powder is different, which is 58 / 30, 40 / 50, and 22 / 70 respectively, thereby affecting the bulk density of the insulating refractory bricks, which are 1.15 g / cm 3 , 1.03g / cm 3 , 0.99g / cm 3 ,With the decrease of the proportion of secondary quartzite aggregate, the proportion of secondary quartzite fine powder increases relatively, and the bulk density shows a decreasing trend.

[0063] Compared with Examples 1 to 8, the amount of limestone powder added as the mineralizer in Example 9 is higher, the conversion rate of quartz to tridymite in the insulating refractory bricks is high, the heating line change rate of the insulating refractory bricks is low, and the thermal stability of the insulating refractory bricks is stronger.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in the field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. An insulating refractory brick, characterized in that: Made of the following raw materials in percentage by weight: 0.5-0.1mm secondary quartzite aggregate 20-60%, <0.1mm secondary quartzite fine powder 30-70%, clay 5-10%, mineralizer 3-10%; plus modified straw powder 30-40% and binder 3-5%.

2. The insulating refractory brick according to claim 1, characterized in that: The secondary quartzite aggregate or secondary quartzite fine powder comprises the following phases in percentage by mass: 60-80% of quartz, 15-40% of kaolinite, and the remainder being impurities.

3. The insulating refractory brick according to claim 1, characterized in that: The mineralizer is limestone powder.

4. The insulating refractory brick according to claim 1, characterized in that: The preparation method of the modified straw powder comprises the following steps: pouring silica sol and straw particles into a mixer and stirring them, and then drying, crushing and sieving to obtain the modified straw powder.

5. The insulating refractory brick according to claim 4, characterized in that: The mass ratio of the silica sol to the straw particles is 3-4:6-7.

6. The insulating refractory brick according to any one of claims 1 to 5, characterized in that: The binder is dextrin or calcium lignosulfonate.

7. A method for preparing the insulating refractory brick according to any one of claims 1 to 6, characterized in that: The steps include: (1) Pour the secondary quartzite aggregate and the binder into a wet mill and mix them, then add clay, secondary quartzite fine powder, mineralizer and modified straw powder to mix; (2) Put the evenly mixed materials into a sealed bag to trap the materials; (3) Pressing the trapped material into shape; (4) drying the formed bricks; (5) The dried bricks are fired in a high-temperature kiln.

8. The method for preparing insulating refractory bricks according to claim 7, characterized in that: The sintering temperature in step (5) is 1300-1400° C. and the holding time is 8-10 hours.

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