The use of waste glass to develop foam glass Li Yueming Li Hua Zou Zhuochen (Jingdezhen Ceramic Institute, 333001) foam glass formulation and foaming process system; trial production of foam glass with low bulk density, high compressive strength, firing cycle moment, easy to control Features.
1 Introduction Foam glass refers to a kind of glass material filled with innumerable openings or closed cells in the glass body. The glass pores have a diameter of approximately 0.5 to 5 mm, which is characterized by good thermal insulation, sound absorption, and flame retardancy. It is an excellent low temperature. Ultra-low temperature insulation, heat insulation and sound insulation materials.
As a new kind of lightweight inorganic thermal insulation material, foam glass is widely used in thermal insulation pipelines, reaction tanks, oil storage tanks, and underground refrigeration pipelines in refrigeration and refrigeration industries such as petroleum, chemical, electronics, and metallurgical industries. It can also be used as a heat-insulating wall material in cold areas. It is a kind of energy-saving material with wide application value. In recent years, due to the increase in social spending power, waste glass is inevitably produced. Such waste glass is difficult to rot naturally, and its accumulation not only pollutes the environment, but also consumes a large amount of farmland, causing waste of resources. These glass wastes are used to make foam glass. , It can reduce the production cost of foam glass, protect the environment, turn waste into treasure, and has extensive economic and social benefits.
With the increase of dosage, the performance of foam glass shows an upward trend. When the amount is less, the quality of gaseous substances generated is less, and its role in reducing viscosity and surface tension is very significant, and therefore it has a foaming effect, but the performance is slightly poor. With the increase of the amount of added gas, the amount of generated gas increases, and the continued decrease in viscosity and surface tension is conducive to the polymerization and growth of gases, and the quality of foam glass rapidly rises; when the amount is large, the amount of gas is large, and the viscosity and surface tension rapidly decrease, making The bubble diameter is too large, the foaming is uneven, and the quality is degraded.
3.3 The influence of various factors on the blister during the firing process This study was conducted from room temperature to 300°C and the temperature was raised at 5°C/min to preheat the batch materials. Because the raw materials used are powdery and naturally accumulate in the mold, their thermal conductivity is poor. If the temperature is increased rapidly, the surface carbon will oxidize and the surface glass powder melts prematurely, causing excessive temperature difference between the inner and outer layers of the batch material. Non-uniformity must be preheated below the ignition point of the blowing agent.
In the temperature range of 680°C, the heating rate is 680°C. Since the softening temperature of the glass is higher than 680°C, and the carbon in this temperature range is oxidized, NaN3 will decompose, and the gas they produce can easily be discharged from the powdery glass powder gap. Since the foaming gas is reduced and the foaming effect is not good, the temperature increase control at this stage is extremely important. From the results of orthogonal analysis (), it can be seen that when the heating rate Vi increases from 10C/minute to 20C/minute, the performance shows a declining trend. The reason is that the heating rate is too high. Due to the poor heat transfer capability of the powder, the temperature difference between the inside and outside surfaces is different. Large, may cause the surface has been vitrified inside the unsintered, even surface foaming, intermediate sintering phenomenon, so the performance will decline.
Within this temperature range, the melting of the glass frit produces a liquid phase and swells, which is an important stage for obtaining the desired performance. It can be seen that the higher the heating rate, the better. If the heating rate is small at this stage, the gas generated by the decomposition or reaction may be volatilized, and the rapid temperature increase may enclose the gas in the interior of the molten glass to generate a foam.
The foaming temperature and foaming time, with proper foaming temperature and foaming time, are the key to the production of foam glass with excellent performance, indicating that the higher the temperature, the better the performance. This is because in the temperature range of 770-810°C, the viscosity decreases but the surface tension remains basically unchanged, so the performance will become better. However, as the temperature continues to increase, the viscosity will drop and the gas will not wrap around and the performance will decline. The foaming time refers to the holding time under the foaming temperature. A certain holding time can ensure that the inside and outside temperature of the product is uniform, the foaming is sufficient, and the foaming time is too short or too long, all of which make the foam structure non-uniform. Therefore, this experiment adopts Incubate at 810C for 30 minutes.
When the foaming is complete, it is rapidly cooled to stabilize the temperature of the foam after it has dropped to 580C, enter the annealed state, hold for 30 minutes, and then slowly cool, so that the residual stress in the foam glass can be eliminated to ensure that the product has a certain mechanical strength .
4 Conclusions Foamed glass can be produced by using recycled scrap glass and bottle glass, selecting the right foaming agent and other additives.
The developed foam glass has a low bulk density (0.3g/cm3), high compressive strength (1MPa), low thermal conductivity (0. reasonable foaming process system is the key to the production of foam glass, this experiment uses the following firing system : Room temperature -300 °C, heating rate 5C/min; 300 - 680C heating rate 10C/min; 680 - 810C heating rate 15C/min, keep warm at 810C for 30 minutes, then quickly cool to 560C, heat annealing for 30 minutes, slowly Cooled to room temperature, this low temperature foaming process saves energy and reduces costs.
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