1, single drum dryer
Single-drum dryer refers to a machine that completes the drying operation by one drum, and its composition is as described above. An important part of the dryer is the drum, which is a hollow metal cylinder. Drum body is welded by cast iron or steel plate, and drums used in food production are generally welded by stainless steel plate.
The drum diameter is in the range of 0.6 ~ 1.6m, and the length-diameter ratio (L/D) = 0.8 ~ 2.
According to the physical properties of materials, the distribution forms can be top feeding method, immersion feeding method, splash feeding method and so on. The thickness of the film attached to the drum is 0.5 ~ 65438 0.5mm. ..
The heating medium is mostly steam, the steam pressure is 200 ~ 600 kPa, and the outer wall temperature of the drum is 120 ~ 150℃.
The transmission mechanism for driving the drum is stepless speed regulation mechanism, and the drum speed is generally 4 ~ 10r/min.
After the material is dried, it is scraped off the roller by the scraper device. The position of the scraper depends on the inlet position of the material, generally in the III and IV quadrants of the barrel section, and the included angle with the horizontal axis is within the range of 30 ~ 45. The inlet and outlet of the heating medium in the drum are sealed with PTFE sealing rings, and the condensed water in the drum is siphoned and continuously discharged from the drum by using the pressure difference between the steam pressure of the drum and the steam trap.
2, double drum dryer
Double-drum dryer refers to a machine in which two drums complete drying operations at the same time. The two rollers of the dryer are operated by the same set of deceleration transmission device, and are meshed by a pair of gears with the same modulus and number of teeth, so that the two groups of rollers with the same diameter rotate relatively. According to the different distribution positions, the double-drum dryer can be divided into two types: the opposite-roller dryer and the same-trough dryer.
In the counter-rotating double-drum dryer, the feed liquid exists in the trough area between the two drums, and weir plates are arranged around it to stop the material. The gap between the two cylinders is controlled by a pair of meshing wheels, and the pitch diameter of the meshing wheels is the same as or close to the outer diameter of the cylinders, generally within the range of 0.5 ~ lmm, and no liquid leakage is allowed. The rotation direction of the pair of rollers can be determined according to the actual situation of the feed liquid and the requirements of equipment arrangement. When the bite angle of the rollers is at the feed end, the thickness of the feed film is controlled by the gap between the two rollers. If the biting angles are opposite, the film thickness between the two cylinders is controlled by the gap between the weir plate and the cylinder in the length direction of the cylinder. This dryer is suitable for drying slurry materials or high viscosity materials with precipitation.
Double drum dryer in the same tank. The gap between the two groups of rollers is large, and the pitch circle diameter of the relatively meshed gears is larger than the outer diameter of the cylinder. When feeding, the two rollers are immersed in the same tank to spread the film, and they rotate relatively without interfering with each other. Suitable for drying solutions, emulsions and other materials.
The drum diameter of double drum dryer is generally 0.5 ~ 2 m; Length-diameter ratio (l/d) = 1.5 ~ 2. The operating conditions such as rotating speed and steam pressure in the drum are the same as those of the single-drum dryer, but the transmission power is about twice that of the single-drum dryer. The feeding mode of double drum dryer is different from that of single drum dryer. If the double-drum dryer feeds from the upper part, the thickness of the material film is controlled by the weir, and a screw conveyor can be set in the middle of the bottom of the dryer to concentrate the discharge. For the counter-rotating double-drum dryer with lower feeding, the discharging devices are respectively arranged on the sides of the two groups of drums.
3. Vacuum drum dryer
The vacuum drum dryer completely seals the drum in the vacuum chamber, and the discharging mode takes the form of hopper sealing and intermittent discharging. Under vacuum condition, the heat transfer coefficient of drum dryer can be greatly improved. For example, when the temperature in the drum is 12 1℃ (i.e. 0.2MPa vapor pressure) and 870kPa, the heat transfer coefficient is 2 ~ 2.5 times higher than that under normal pressure. However, due to the complex structure and high drying cost, vacuum drum dryer is generally only used to dry fruit juice, yeast, baby food and other materials that are very sensitive to heat.
Application scope of drum dryer:
Chemical industry, miners, metallurgy and other industries, such as ore, slag, coal, metal powder, clay, diatomite, kaolin.
Agriculture, feed and fertilizer industries, such as straw, forage grass, leaves, fish meal, corn sauce, starch residue, distiller's grains, dregs, fruit residue, soy sauce residue, bagasse, peat, organic compound fertilizer, sludge, aquatic products waste, food factory waste, slaughterhouse waste, organic fertilizer, inorganic fertilizer and ammonium sulfate phosphate.
Dryers for powdery and granular materials with special requirements. Such as various crystals, light calcium carbonate, activated clay, magnetic powder, graphite, inorganic slurry, clay, lime slurry, pulp, phosphate rock residue, red mud from aluminum plant, etc.
Low temperature drying and a large number of continuously dried materials are needed. The choice of heat carrier and its maximum temperature depend on the properties of the solid material to be treated and whether it is allowed to be polluted.
If the treated solid material is not afraid of high temperature and is not the final product, it can be slightly polluted in the treatment process, and a hot stove or flue gas can be used as a heat carrier, so that a higher volume evaporation rate and thermal efficiency can be obtained. For example, when the gas inlet temperature is 300 degrees, the volume evaporation rate of the dryer is 5kg/m3/h and the thermal efficiency is 30%-50%. If the gas inlet temperature is 500 degrees, the volume evaporation rate is 35 kg/m3/h; The thermal efficiency is 50%-70%. Therefore, the rotary drying barrel for processing minerals, sand, coal, calcium superphosphate and other materials has a combustion furnace that directly produces flue gas, and the gas fuel can be coal, oil, natural gas and liquefied gas.
If the treated materials are not allowed to be polluted and the required temperature is high, we can use our new product gas producer as a heat carrier, which is energy-saving and environmentally friendly and has high thermal efficiency. If the local environmental protection requirements are very high, but also want to save energy and health, the use of gas producer will be the best choice. Compared with the combustion furnace, the gas producer can save energy by at least 20%, and also save a lot of manpower. Generally, the gas producer can be operated in one operation, and there is no need to keep adding coal. In addition, the gas producer can be used when it is stopped at any time, and it can be used for 10 days, and it can be used again next time.
There is also an indirect heating method, that is, heat is transferred from the metal wall to the dried material, such as an externally heated drum dryer.
1. Centrifuge and dehydrate the filter cake, and press-filter the filter cake in the form of raw materials; Dry free-flowing powders, granules, flakes, fibers and other materials.
2. From the application range of materials, it is widely used to dry mineral products, building materials, chemical products, compound fertilizers, organic powders, feeds, wine cans, starch residues, corn residues, bean residues, etc.
3. From the mechanism of drum dryer, it can be divided into direct heating, indirect heating, ventilation pipe heating, steam pipe indirect heating, compound heating and other structural forms.
4. From the point of drying temperature, it can be selected from 60℃-600℃. In principle, the higher the temperature, the higher the evaporation intensity. Therefore, the equipment is small in size, less in investment and low in unit energy consumption.