Spherical asphalt

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Research on Preparing Spherical Asphalt from Coal Tar Pitch Xie Jianming (Wuxi Coking Plant Research Institute) Spherical asphalt is an asphalt product made from coal tar pitch through a special molding process. It has been widely used in the castables of blast furnace tap trenches, and has good market demand and export prospects. To this end, we used the asphalt resources of our factory to develop spherical asphalt. The results were very satisfactory after being tested by Taihu Refractory Materials Factory. We have used the test equipment to produce more than ten tons of spherical asphalt products. 1 Test: Because the tar distillation of our factory produces medium-temperature asphalt, in order to meet the requirements of the softening point of the test raw materials, the asphalt was specially treated in advance to ensure that the softening point of the raw asphalt (ball and ball method) is ≥115°C. The test device is shown in Figure 1. http://www.meijiaohua.com/WebUpLoadFile/ArticlePhoto/200861938319313.gif Figure 1 The test device for producing spherical asphalt from coal tar pitch is shown in Figure 1. The raw asphalt for the test is added to the asphalt dissolving kettle and heated and dissolved. After the temperature in the kettle reaches 200~230°C, it is maintained with low heat. At the same time, turn on the power supply of the electric heating coil, open the compressed air inlet valve after about 5 minutes, and then open the asphalt outlet valve at the bottom of the kettle. The liquid asphalt is sprayed from the nozzle and atomized into fine particles by the air. The asphalt particles are naturally cooled by air in the cooling tower into semi-finished products, which are sent to the three-dimensional vibrating screening filter from the bottom of the cooling tower for classification, and spherical asphalt products that meet the requirements are obtained. 2 Problems and Discussions During the development and trial production of spherical asphalt, there are many factors that affect asphalt molding and product quality, mainly the following points. (1) Nozzle. Since the nozzle is the key equipment for producing spherical asphalt, we cooperated with relevant manufacturers to carry out specialized design and manufacturing based on the properties of the raw asphalt and the requirements of the spherical asphalt. The test results show that the nozzle basically meets the test requirements. The production capacity of a single nozzle is about 60kg/h. The particle size composition of the product can also be adjusted within a certain range (2) The dissolution temperature of asphalt. Tests have found that when the dissolution temperature of asphalt is too low, the asphalt sprayed from the nozzle will be in the shape of filaments. When it is too high, not only will the asphalt in the kettle undergo thermal polymerization, but also adhesion and agglomeration will occur at the bottom of the tower because the atomized asphalt is not completely cooled in the cooling tower. Tests show that the optimal asphalt dissolution temperature should be controlled between 200 and 230°C. (3) Heating power of electric heating coil. Tests have shown that when the heating power of the electric heating coil is too low, it is difficult to ensure the fluidity of the asphalt in the nozzle, and it is easy to become clogged. When it is too high, local overheating may occur at the nozzle outlet, causing coking and clogging. The optimal heating power is 600W. (4) Air flow. Since air flow is one of the main means of controlling product particle size, the air flow entering the nozzle must be adjusted at any time according to the particle size composition of the semi-finished product. Since the pressure of compressed air used for testing in our factory fluctuates from time to time, only by strictly controlling the flow of compressed air can the quality of spherical asphalt be ensured. Tests have shown that when the pressure of compressed air is between 0.5 and 0.6MPa, the air flow should be controlled at 2 to 6m3/h. (5) Cooling tower diameter and height. The mist asphalt sprayed from the nozzle is scattered in a fan shape in the cooling tower, so the cooling tower is required to have sufficient diameter and height. If the diameter is too small, the atomized asphalt will easily stick to the inner wall of the tower and agglomerate. If the height is insufficient, it will be difficult for the atomized asphalt to be completely cooled. Tests have shown that the optimal cooling tower diameter is 2m and the height is 8m. (6) Screening. Because the particle size of the spherical asphalt semi-finished products collected at the bottom of the cooling tower cannot meet the requirements, it must be screened and classified. A three-dimensional vibrating screening filter was selected for the test. The obtained spherical asphalt products can meet the particle size requirements, and the equipment has good sealing performance. During the screening process, the spherical asphalt will not agglomerate or block the network, and its processing capacity is about 100kg/h. 3 The product quality test results show that it is feasible to produce spherical asphalt using coal pitch spray granulation, molding and screening processes. The product quality has fully met the requirements of refractory materials plants. The indicators are as follows. Softening point (ring and ball method), ℃ 121 Fixed carbon content, % 61 Ash content, % 0. 15 Volatile content, % 38. 85 Particle size composition, % > 0.45mm 13.8 0.3～0.45mm 45.8 0.2～0.3mm 13.4 0.15～0.2mm 12.8 0.125～0.15mm 9.6 <0.125mm 4. 6 According to preliminary calculations, if the pretreated raw asphalt is 1,500 yuan/t and the market price of spherical asphalt products is 4,000 yuan/t (market price in 1997), its economic benefits are very considerable. It can be predicted that with the expansion of production scale and further development of the market, its economic benefits will be more optimistic.