At present, our country's glass production are ranks first in the world. The main task for the future development of refractory materials for glass kilns is to improve the design, masonry and maintenance of the kiln, reduce the adverse effects on the quality of the glass, and extend the service life of the glass kiln. Silica brick is the main refractory material in the masonry of the glass furnace, which is mainly used for the top of the arch, the upper part of the hanging wall and the front and back walls of the glass furnace. To increase the service life of glass furnaces, higher requirements must be put forward on the quality of silica bricks. Therefore, the study of high-quality silica bricks for glass kilns with high purity and corrosion resistance can extend the service life of glass kilns .
The main way to develop high-quality silica bricks for glass kilns is to select high-quality raw materials and reduce the content of alkaline oxides in the raw materials to increase the purity of the silica bricks; by adjusting the ratio of raw material particles, the apparent porosity is reduced during molding to increase density, to achieve anti-corrosion effect.
The performance requirements for the development of silica bricks: SiO2>96%, (A12O3 +2R2O) <0.45%, (Fe2O3) <0.5%; volume density>1.9 g • cm-3, apparent porosity <20%, load softening start temperature> 1690℃, linear change rate of reburning <0.2% (1500℃2h), creep rate <0.8% (1 550℃50 h), normal temperature compressive strength>65 MPa; phase composition is reasonable, residual quartz <0.8% , True density＜2.33 g • cm-3
1.1 Selection of raw materials
There are many natural silica ore, most of which can be used to produce silica bricks. The high content of impurities in cemented silica is not conducive to the production of high-purity silica bricks for glass kilns, while crystalline silica is pure and dense, with greater hardness and strength, and a slower conversion rate. It is an ideal raw material for the production of high-quality silica bricks for glass kilns. Next, Zhengzhou Shennan Refractories Co., Ltd. will introduce a test of high-quality silica brick. The raw material used in this experiment is super dense crystalline silica, and its chemical composition (mass fraction, the same below) is: SiO2≥99%, Al2O3 ≤0.22%, Fe2O3 ≤0.20%, CaO≤0.15%, R2O≤ O.O8%, refractoriness≥1750℃.
According to experience, fluorite and lime are used as mineralizers, and lime needs to be placed in a storage barrel for more than 16 hours before being digested into liquid of lime. The sulfite pulp is used as the binder, and the pulp concentration is 1.15% to 1.17%.
1.2 Test process
Use the fully automatic batching vehicle to batch, the amount of Gucheng silica cone material (≤1.65 mm), fine powder (≤O.1mm), clinker material (≤2.18 mm), compound additives, iron-free lime liquid, and sulfite pulp They are 80%-85%, 10%-20%, 5%, 1%, 8%, 0.75%.
After weighing, use a wet mill for mixing. The order of addition is: cone material-clinker-fine powder, additives-dry mixing 3 min-lime liquid-pulp. The total mixing time is not less than 20 min. After mixing, the particle size of the mud ≥2 mm accounts for 3%～5%, ≤0.1 mm accounts for 32%～40%, the moisture content is 4.8%～5.2%, and the alkalinity is 1.2%～1.6%.
Press molding with more than 300 t presser, and strictly control the unit weight and punching, so that the semi-finished product has a porosity of less than 18.5%, and the size deviation is controlled within ±0.5 mm. It is fired in a 202.5 m tunnel kiln. During operation, the trucks and carts are entered strictly according to the firing system, and the firing curve, pressure system and other thermal parameters are strictly implemented to ensure the stability of the kiln temperature.
Results and conclusions
After 170 hours of firing, the dimensional tolerances of the samples are all within ±1 mm, and the physical and chemical indicators are shown in Table 1.
It can be seen from Table 1: (1) The use of special-grade crystalline silica raw materials and suitable mineralizers reduces the content of Al2O3 and Na2O through reasonable proportioning and strict process control, and can produce high-purity and high-quality silicon brick for glass kilns.
(2) A small amount of clinker is added in the production, which not only increases the SiO2 content of the product, but also slows down the impact of the rapid expansion of SiO2 crystal form conversion during the firing process, which improves the product qualification rate. In addition, the small size tolerance makes the masonry more convenient.
(3) The developed product has the characteristics of high purity and low impurity content, especially A12O3 +2R2O and Fe2O3 are less than 5%, and the residual quartz content is less than 0.8%, which ensures the high temperature performance of the product, and its bulk density reaches 1.92 g .cm-3, which makes the product resistant to erosion.
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