Semicoke powder is blue carbon in the production, transportation, storage and other processes of the particle size is less than 6mm powder, dalan carbon output about 10%, a huge amount of resources. This part of the material particle size is small, can not be directly used in calcium carbide, metallurgy and other industries, is basically treated as low-cost fuel, a large amount of accumulation or direct combustion will cause dust, haze and other serious environmental pollution and resource waste, visible effective development and utilization of blue charcoal is also an urgent problem to be solved.
Barbecue charcoal is used for catering industry or life heating and other activities of a kind of civil clean fuel, smokeless and tasteless, easy to deash, easy to ignite, high calorific value, low environmental pollution characteristics. At present, the barbecue charcoal on the market is mainly based on charcoal, and with the serious felling of trees, the supply of charcoal resources is increasingly tight, the environmental protection situation is more and more serious, so that the mechanism of charcoal "less raw materials, difficult to get, high price" problem. The rich orchid charcoal and charcoal in the specific gravity, activity and other aspects are very similar, with many of the same characteristics. Therefore, there are some on the market using cheap orchid charcoal powder, adding a certain amount of traditional adhesive and water, after cold pressing forming drying or natural drying system, the cost of barbecue charcoal is reduced, so that orchid charcoal powder resources are recycled, not only save energy, but also increase production.
The technological process of preparing barbecue carbon by cold pressing of blue carbon powder is as follows:
Raw materials, crushing, mixing with water, forming, drying or drying, finished products
When manufacturers choose blue charcoal powder to prepare barbecue charcoal by cold pressing, there are still problems such as strong smoke smell, easy crack, low strength, charcoal ash does not fall off naturally, which is closely related to the production process. The actual production of a large number of customers proves that we should control the raw materials, additives, processing equipment and so on.
① Raw material selection of orchid charcoal powder
Blue charcoal is produced by the non-cohesive or weakly cohesive high volatile bituminous coal pyrolysis at 600℃. The size range of blue charcoal powder is 0~3mm and 0~6mm. Different particle size and content will affect the strength and stability of carbon rod. Generally, when making bars, the granularity of raw materials should be uniform, especially the mixture of fabric and granular materials. Before forming, materials must be mixed evenly before use.
The better the formability, the higher the strength and price. The formability of LAN carbon is closely related to the source and carbonization process of bituminous coal. The better the mechanical properties of bituminous coal, the easier it is to be formed. After a large number of experiments, the general forming of orchid carbon: Inner Mongolia orchid carbon > God Mulan carbon > Xinjiang orchid carbon, different regions, bituminous coal, firing orchid carbon forming relatively large difference, strength and shatterability is also relatively large.
In the production process of blue charcoal in China, water quenching method is widely used to cool blue charcoal, including water quenching coke and ammonia quenching coke two forms. Ammonia quenching coke can make the volatile content of blue charcoal is high, ammonia and other harmful gases are high; Low ash content, smokeless and tasteless, less harmful substances, low volatile content, ammonia water coke than the high quality of the blue carbon, but the production cost is relatively high, and the coke after the blue carbon is easy to loose, the strength is reduced.
(2) selection of additives
Blue carbon powder strength and shatterability is poor, with its cold pressing to prepare barbecue carbon, usually need to add combustion agent, smoke elimination and flavor agent, adhesive and other additives to achieve high molding rate, high strength, smokeless and tasteless, easy to deash, easy to ignite, high calorific value, low environmental pollution characteristics, in line with the requirements of civil fuel.
Combustifier generally has potassium nitrate, sodium nitrate, potassium permanganate, etc., in the carbon rod potassium nitrate add 6~7%, generally 6400 yuan/ton; Sodium nitrate needs to double the amount to replace potassium nitrate, and the effect is not good potassium nitrate, the price is generally 4000 yuan/ton.
Nitrate class under the condition of heat decomposition of oxygen, the gap in carbon prompted intense combustion of volatile matter, volatile put out the heat and can make the temperature rise of carbon, which shortens the lighting time of carbon, but itself has a certain toxicity, under the condition of heating not only can release oxygen, can also emit NO2 or NO poisonous gas, So in the premise of ignition can be achieved as far as possible to reduce the amount of nitrate.
Potassium permanganate's combustion-supporting principle is the same as potassium nitrate, but the temperature rise also promotes the decomposition of potassium permanganate, and then forms a cycle to accelerate the combustion of carbon rods. There will be no spark and no toxic gas is released, but the combustion-supporting effect per unit mass is not as good as potassium nitrate. Generally, potassium permanganate and potassium nitrate will be mixed in a certain proportion to play their respective advantages as an oxidizing agent, so that the carbon rod has good combustion performance, as far as possible to reduce the spark and shorten the ignition time.
Smoke elimination and flavor removal agents generally include quicklime, calcium sulfate, barium carbonate, etc., which can play the role of sulfur fixation, and can oxidize more than 70% of sulfur in the combustion process.
Commonly used traditional adhesive with bentonite, syrup, humic acid sodium, sodium carboxymethyl cellulose, sodium carboxymethyl starch, such as cement, can be used as an effective binder, helped shape the pellets, but also add large amount, low ball rate, poor wet strength and low cooling intensity, ash content, such as the introduction of harmful impurities more shortcomings, will increase the harmful elements in carbon, taste. Adhesive selection must choose strong bonding ability, good liquidity, easy diffusion and uniform distribution on the surface of blue charcoal powder particles, and do not increase ash and do not reduce the heat, the price is cheap, do not cause secondary pollution. But the amount of adhesive should be appropriate, the greater the viscosity will cause the time and space of the rod can not be spun out. Such as henan built jie industrial research and development of a composite adhesive SK02, plus the amount of 5% can increase that carbon powder of the plasticity, obtained carbon intensity is high, the smokeless tasteless, ash from sex strong, high calorific value, wet bar 2 meters sets complete for many times, cold pressing strength can reach more than 800 n, 2 h at 1100 ℃ calcination, smokeless tasteless, does not affect the charcoal grey colour and lustre, Charcoal ash can fall off naturally, the thermal intensity of 0.5 meters can be repeatedly not broken.
(3) the choice of adding water
The amount of water will affect the wet strength, cold strength and hot strength of the carbon rod. The amount of water added during mixing is related to the carbon powder raw material and equipment model. Such as charcoal needs more water, orchid charcoal is less; Carbon rod forming equipment has spiral extruder, punching machine, general oil pressure (pressure) add less water, stamping multi-point, spiral extrusion more, add more water between 20~40%, and spiral extrusion is more commonly used.
When the screw extruder is formed, the amount of water added to the material should be appropriate. When the spiral propulsion surface is relatively large and the material is added with too little water, it is easy to jam the machine. If forced extrusion, it will also lead to local heating of the forming mold, and eventually lead to the cracking of the carbon rod prepared. But the moisture is added, the carbon rod is too soft, one is not good to pick up, two is the density of carbon rod is too low, the carbon rod is not burning.
Punching machine molding, the material added water is small, not easy to shape, even if the shape, carbon rod is easy to loose. More water, there will be a kind of flexibility between materials, resulting in compaction, will also affect the cold and hot strength.
It is also useful for the production of barbecue charcoal by roller press ball machine, and the water is generally added about 20%.
④ Use of processing equipment
Mixers generally have horizontal mixers, wheel grinding mixers. Horizontal mixer general mixing time is 25 min, mixing time to control appropriate, too short time, adhesive and water can not fully permeate, low adhesion, wet strength is reduced, leading to carbon rod is not easy to shape, and too long time, will also reduce the adhesion. Commonly used is the wheel mill mixer, can not only crush the large particles of blue carbon, but also make the material mix evenly, so that the quality of the carbon rod is stable, good strength.
Forming equipment has spiral extruder, punching machine and so on. Screw extrusion machine number, 140, 160, 180, 220 and so on, by the sleeve to distinguish inner diameter, the smaller models, but the smaller inner diameter of the feed, encounter big viscosity material, the less easy to feed and discharge, so when choosing screw extrusion mechanism for carbon, should choose appropriate adhesive viscosity, instead, the greater the viscosity is not easy to out of the bar. The pitch of the screw is 15, 14.5, 14, 13, 12.5, 6cm gradually decreasing. The carbon powder is squeezed from the large inner diameter to the small inner diameter by the twist dragon, and the density gradually increases and becomes more and more compact. The carbon rod is more resistant to burning and the thermal strength is higher. The inner wall of the sleeve has a longitudinal groove and spiral with heating effect, heating extrusion carbon rod density is high, the temperature of the rod in 50~70℃, but the quality of equipment, model does not meet the requirements, will make the groove smooth, easy to cause temperature, density drop, and lead to carbon rod heat resistance, cold and hot strength is low.
Punching machine has 12, 13, 15, 20, 30, 50, 80, 120 and other tonnage models, commonly used is 30 tonnage, 20 tonnage price in more than 40,000, 12~13 tonnage price in more than 10,000. The punch also has power size, 18.5KW, 22KW, 50KW, etc., the higher the tonnage and power, the greater the pressure provided, the more compact the carbon rod prepared, the higher the cold and hot strength.
Therefore, manufacturers should not only choose suitable texture of charcoal powder according to their own conditions, but also pay attention to the control of adding water, additives, processing equipment and other aspects to prepare products that meet the requirements of civil fuel.
Carbon powder of the development use, in the comprehensive utilization of barbecue charcoal, charcoal industry has important significance, not only can solve the barbecue charcoal industry "less raw material, hard to get, high price" of the problem, also can alleviate carbon powder caused by environmental pollution and resource waste, and provides manufacturers with a feasible way.