The relationship between briquette and binder


    The use of pulverized coal cold, medium and low pressure molding technology, the adhesive technology is essential. The quality of the adhesive is an important guarantee of the quality of the briquette, which is directly related to the combustion, furnace condition and gas production of the industrial gas furnace and industrial furnace. Therefore, the choice of adhesive and research is particularly important. Briquette binder is through a kind of powder can be different particle size of the powder so that each other adhesion of a medium. This medium requires not only the adhesion of coal molecules to each other, but also through the bonding of mechanical pressure forming briquette is a certain cold strength and heat intensity. 

    Adhesives for industrial briquette should have the following performance requirements:

     1.Cold strength. Bonding, molding, drying briquette (ball, stick) in the furnace before to have a certain cold strength. The cold strength of briquette in addition to meet the general transport not to damage, the furnace into the furnace after the weight of the load of briquettes are also directly related. General industrial gas furnace In the process of combustion gas, coal as raw material in the furnace as a whole three-tier movement: the bottom is the combustion layer, the middle of the gas layer, the top of the fabric layer. In the process of gas, briquette (ball, rod) but also by the impact of compressed air and steam, plus the total weight of the furnace coal. Therefore, the adhesive bonding of the coal must have a certain resistance to load (compressive strength), this resistance to load will be through a certain cold strength to ensure. The compressive strength (compressive strength) of the cold strength comes from the adhesive index of the binder and the density of the interior of the briquette. The bonding index of the coal from the binder material, the content of the ratio and the adhesive processing technology; briquette density depends largely on the mechanical equipment configuration and molding pressure. Briquette cold strength is not enough, in industrial production applications, the furnace coal without normal gasification, due to tolerance to load force (compressive strength) is not enough and broken, resulting in furnace. Or due to fragmentation by the compressed air, steam erosion caused by increased extraction, that is, a waste of production of raw materials, and easy to bring out too much blocked gas nozzle, thus affecting the normal operation of gas and gas. At present, from the domestic use of adhesive made of coal cold strength in different specifications of the gas furnace application results, the adhesive index of the adhesive required to produce the briquette (ball, rod), the cold strength by Drying or drying the dry ball strength in the static pressure state, a / ball compressive strength to reach 65-95kg can meet the use of industrial gas furnace.

     2.Heat intensity. The thermal strength of briquette (briquettes, coal bars) is also a key indicator in the combustion of industrial boilers, industrial furnaces and gas furnaces. At the temperature of 950 ~ 1250 ℃, the melting point of coal lime on the normal operation of the stove is very obvious, boilers, industrial furnaces in the combustion process, requiring the coal group to open and not loose, so as to promote the complete combustion or increase coal Group of gasification rate or combustion. Gas furnace in the combustion process requires a coal can form a skeleton role. Submerged coal ash is too low melting point, then a certain temperature caused by melt flow, resulting in furnace, slagging and other phenomena, the normal operation of the stove has a great impact. Therefore, the use of coal made of briquette (briquettes, coal rods) thermal strength to have enough attention. In general, to improve the thermal strength of coal means in addition to the physical and chemical indicators of coal itself, those who have low coal ash melting point, should be appropriate to add some high alumina content, good plastic at room temperature clay, bentonite or Kaolin and other substances to improve the ash into the group after the ash melting point, so as to achieve a variety of stove combustion performance indicators. (It should be noted that these materials are almost non-combustible substances, excessive addition, it will affect the fixed carbon content of briquette.) From the current practice has proved that in order to improve the briquette (coal ball, coal rod) ash melting point , The amount of material added from the holding effect should be 3-5%, some of the coal itself and the ash structure of the mineral structure to meet the role of the support, then no longer need to add other substances to ensure that the fixed carbon content. In order to ensure that these additives can be evenly combined with coal molecules to play a solid role. The number of these added substances should be between 80-120 mesh. 

    3. drop strength. In the industrial kiln and gas furnace coal raw material to add the process, there is often a certain gap, which requires the production of briquette (briquettes, coal rods) to have a certain drop strength. The index requires the coal group at a height of 1.5 meters, free fall on the hardened ground, the degree of breaking> 13mm, the drop strength is infiltrated by the adhesive into the coal particles within the pores, through the mechanical pressure molding and curing by the drying equipment It is the result of the adhesive force of the adhesive and the mechanical pressure.

     4.water immersion strength. Where the water intensity is that people often say that the waterproof performance. In the past, many enterprises made pulverized coal as briquette, as lump coal as a commodity to flow, to produce the briquette due to transport takes a few days, or even a month can be used to burn units in the transport process and dumping process , Often because of weather or regional problems, the air moisture is dry coal group by the absorption, resulting in decreased strength, so waterproof performance was also used as a binder index to assess. However, with the people after the formation of coal powder can replace the price of all the way to climb the burning of the understanding of coal, as well as the field of adhesives in the field of new research and application of certain, a large number of enterprises need to use lump coal to expand the use of energy Channel, and second to see the formation of coal after the replacement of lump coal for the enterprise to save a lot of kinetic energy costs and raw material costs, the application of large coal enterprises have their own pulverized coal production line, to produce direct or storage of briquette A short time to be applied in each furnace, a reduction in the transport process, the two was soaked in moisture shortened time, briquette waterproofing is not so important. But the coastal areas and the rainy season, wet air on the production of briquette is still the existence of erosion, resulting in decreased strength of briquette. Because of the temperature sensitivity and price factors, the author here recommended the use of appropriate amount of clean glass water to join the adhesive, still play a certain role in water.

     5. thermal stability. The thermal stability of coal in the combustion process depends mainly on the volatiles in the nature of the coal. For the anthracite, the thermal stability is mainly due to the effect of the crystal water in the coal, and the heat stabilization Agent, then change the quality of coal has a certain impact on the poor thermal stability of coal, heat stabilizer added, so that the briquette can reach the ash before the melting point does not burst, do not collapse. From the above points to see: 1, the adhesive on the quality of industrial briquette play a key role. 2, coal selective for the adhesive, different coal, coal need to choose a different adhesive. 3, adding heat stabilizer adhesive on the change of coal has a certain influence. 4, different adhesives may require different molding pressures. There are a wide variety of adhesives for industrial briquette, but in general terms can be divided into three categories: one, organic class. Such as: coal tar pitch, coal tar, starch, animal and vegetable tar residue, waste liquid, lignocellulose and polymer PAA, PAA and so on. Second, inorganic class. Such as: clay, bentonite, kaolin, cement, water glass, raw lime, calcium carbide, sulfate and so on. Three, complex class. Organic and inorganic load, such as: coal tar and low pulp. Organic compounds and inorganic compounds, such as: bentonite and sodium polyacrylate and sodium dihydrogen pyrophosphate complex. At present, the widely used humic acid binder, mainly humic acid content of 50-70% of the brown coal fine grinding into 80-120 head, together with industrial caustic soda and according to different coal and add a certain percentage of other materials, Pyrolysis of humic acid sodium binder. It is characterized by a small effect on the fixed carbon of coal, made of baking coal with good activation, low cost of binder raw material, small amount of used, cold strength, thermal strength, thermal stability, ash melting point Drying down the intensity, can achieve industrial briquette application indicators, which is generally accepted and applied. But the preparation process is different from the formula with different, add the other materials are different, to produce the indicators of the briquette is also different. Briquette binder itself is an experimental science, it must be carried out on the basis of the experiment, according to the results of the test to be improved, otherwise it is impossible to produce qualified, in line with industrial production, gas requirements of briquette products. Briquette adhesives have been continuously developing, especially in the development of composite adhesives, the prospects are more bright, composite adhesives mainly through different adhesive properties of materials, after pyrolysis, played a complementary role, play The combined effect, improve the plethropoda of the adhesive, thus ensuring the briquette industry combustion of the indicators.