First, the working principle of spray drying tower :
After filtering and heating, the air enters the air distributor on the top of the dryer, and the hot air enters the drying chamber uniformly in a spiral shape. The material liquid is sprayed into a very fine mist-like liquid bead through a high-speed centrifugal atomizer or a high-pressure atomizer on the top of the tower body, and can be dried into a finished product in a very short time in contact with the air in parallel. The finished product is continuously output from the bottom of the drying tower and the cyclone separator, the fine dust material is collected by the pulse bag collector, and the exhaust gas is evacuated by the fan.
Second, the characteristics of spray drying tower:
1.Fast drying speed, it only takes a few seconds to complete;
2.Suitable for drying heat-sensitive materials;
3.Wide range of application: According to the characteristics of the material, it can be used for hot air drying, centrifugal granulation and cold air granulation. Most products with very different characteristics can be produced with this machine;
4. Because the drying process is completed in an instant, the particles of the finished product can basically maintain the approximate spherical shape of the droplets, and the product has good dispersibility, fluidity and solubility;
5. Simplified production process and convenient operation control. Spray drying is usually used for solutions with a solid content of 60% or less. After drying, it does not need to be pulverized and screened, which reduces the production process and simplifies the production process. For the product's particle size, bulk density, and moisture, within a certain range, it can be adjusted by changing the operating conditions, and the control and management are very convenient;
6. In order to prevent the materials from being contaminated and extend the life of the equipment, all parts in contact with the materials can be made of stainless steel.
Three, the main types of spray drying tower:
1 ) Overview:
High speed centrifugal spray drying is the most widely used process in the liquid process forming and drying industry. Most suitable for producing powdery, granular solid products from solutions, emulsions, suspensions and pasty liquid raw materials. Therefore, when the particle size distribution, residual moisture content, bulk density and particle shape of the finished product must meet precise standards, spray drying is an ideal process.
2 ) Performance characteristics:
1) The drying speed is fast, and the surface area of the material liquid is greatly increased after being atomized. In the hot air current, 95% -98% of water can be evaporated instantly, and the drying time is only a few seconds. It is especially suitable for drying heat-sensitive materials.
2) The product has good uniformity, fluidity and solubility, high purity and good quality.
3) Simplified production process and convenient operation control. For liquids with a moisture content of 40-60% (special materials can reach 90%) can be dried into powder products at one time, the control and management are very convenient.
3 ) Adapted materials:
Chemical industry: sodium fluoride (potassium), basic dye pigments, dye intermediates, compound fertilizers, formaldehyde silicic acid, catalysts, sulfuric acid agents, amino acids, white carbon, etc.
Plastic resin: AB, ABS emulsion, urea-formaldehyde resin, phenolic resin, dense (urea) formaldehyde resin, polyethylene, polyvinyl chloride, etc.
Food industry: fat-rich milk powder, tickle, cocoa milk powder, milk substitute, blood hunting powder, egg white (yellow), etc.
Food and plants: oats, chicken juice, coffee, instant tea, flavoured meat, protein, soybean, peanut protein, hydrolysate, etc.
Sugars: corn pulp, corn starch, glucose, pectin, maltose, potassium sorbate, etc.
Ceramics: alumina, tile materials, magnesia, talc, etc.
1 ) Overview:
The working process of this unit is that the material liquid is input through the high pressure of the diaphragm pump, and the misty liquid droplets are ejected, and then it flows down with the hot air. Most of the powder particles are collected by the tower bottom discharge port. The exhaust gas is exhausted by the exhaust fan, and the powder is collected by the pollinator located at the lower end of the cyclone. The fan outlet can also be equipped with a secondary dust removal device, and the recovery rate is above 96-98%.
2 ) Performance characteristics:
1) The drying speed is fast, and the surface area of the material liquid is greatly increased after being atomized. In the hot air current, 95% -98% of water can be evaporated in an instant. The time required to complete the drying is only ten seconds to tens of seconds, especially Suitable for drying heat-sensitive materials.
2) All products are spherical particles with uniform particle size, good fluidity, good solubility, high product purity and good quality.
3) Wide range of application. Depending on the characteristics of the material, it can be dried with hot air or granulated with cold air.
4) The operation is simple and stable, the control is convenient, and it is easy to realize automatic operation.
3 ) Adapted materials:
Chemical industry: There are catalysts, resins, synthetic laundry powders, greases, ammonium sulfate, dyes, dye intermediates, white carbon black, graphite, ammonium phosphate and so on.
Food: amino acids and analogs, seasonings, proteins, starches, dairy products, coffee extracts, fish meal, meat extracts, etc.
Pharmaceutical: Chinese patent medicines, pesticides, antibiotics, pharmaceutical granules, etc.
Ceramics: magnesia, porcelain clay, various metal oxides, dolomite, etc.
Spray granulation : all kinds of fertilizer, alumina, ceramic powder, pharmaceutical, heavy metal super hard steel, fertilizer, granular laundry powder, proprietary Chinese medicine.
Spray cooling granulation : amine fatty acid, paraffin, glyceride, tallow, etc.
Spray crystallization, spray concentration, spray reaction and other aspects are often used.
3 , Chinese medicine spray
1 ) Overview:
The machine is fully enclosed, all parts are made of stainless steel, equipped with a three-stage purification device, and the filtered air reaches the 100,000 level requirement. The cylinder and the top are equipped with a cold wall device so that the wall temperature is <80 ° C. The drying tower is equipped with an air brush sweeping tower device.
The traditional Chinese medicine extract powder dried by the machine will not cause coking and deterioration, greatly increase the powder collection rate (more than 95%), and will not cause the phenomenon of mixed drugs and sticky walls.
2 ) Working principle:
The traditional Chinese medicine extract high-speed centrifugal spray device is the application of centrifugal spray drying technology in the drying of specific materials. It is also the use of high-speed centrifugal atomizers to disperse the materials into a mist, fully contact the hot air space, and complete instant drying to form a powder. Finished drying device.
3 ) Performance characteristics:
1) The tower has a cold wind jacket;
2) The tower is equipped with an automatic rapping device;
3) The tower body and pipeline are equipped with quick-open cleaning holes and sewage holes;
4) Can be equipped with automatic control thermostatic feeding tank;
5) Random accessories for manual high pressure washing tower can be equipped;
6) The parts in contact with the material are made of stainless steel; (or all stainless steel)
7) Material collection adopts a two-pole cyclone dust removal device, or a cyclone dust collector and a wet dust collector;
8) Automatic control and continuous device for inlet air temperature.
9) Can be equipped with air sweep device
4 , air spray
1 ) Working principle:
Mainly, air or water vapor is ejected from the nozzle at a high speed, and the material liquid is separated into fine mist droplets by friction, which makes it completely contact with hot air to form heat exchange. The whole process takes less than half a minute. It has a good effect on viscous materials, which is unmatched by other spray dryers . And easy to operate.
2 ) Product application:
The main applications are chemical industry: latex, dyes, resins, etc .; food industry has maltose, dextrin, starch, etc .; dairy industry, building materials industry is also often used.
Fourth, the operating rules of the spray drying tower:
The operation procedure of the spray drying system is: clear equipment technical characteristics → equipment inspection and confirmation → production operation → parking operation → cleaning system.
The specific procedures are as follows:
1 ) Clear equipment (spray drying tower)
Technical characteristics Liquid handling capacity: 270-400kg / h; Evaporated water capacity: 170-250kg / h; Finished product output: 100-150kg / h;
2 ）设备检查确认： Inlet air temperature ≥185-240 ℃; Outlet air temperature 2 ) Equipment inspection and confirmation:
1. Check whether the production water, electricity and steam are normal.
2. Check whether the voltage and current instrument signals are normal.
3. Check the oil level of the agitator in the middle tank and add lubricating oil in a timely manner; if the agitating paddle has fallen off, tighten it in time; start the agitator and observe whether the rotation is normal and whether there is noise.
4. Check whether the sealing material is installed at the joint of the pipeline, and then connect it to ensure that the unheated air does not enter the drying room.
5. Before starting and running, the parts and components that are in contact with the materials such as the drying room, material pipelines, intermediate tanks, and collecting cylinders should be cleaned and meet the sanitary requirements for product quality. (90 ° C hot water washing tank and high pressure pipe before driving)
6. Add lubricating oil to the lubrication points of the equipment as required.
7. Use the jog mode to check whether the transmission equipment is running flexibly and the steering is correct.
8. Close the observation window tightly, close the receiving cylinder, and check whether the sealing of the pipeline contacts and valves is good.
9. Whether the process parameters and operating procedures are clear.
10. Thoroughly drain the condensate from the sub-cylinders and pipes, and slowly open the steam valve. Degree≤95 ℃
3 ) Production operations:
1. First turn on the blower → turn on the exhaust fan and turn on the electric heating supplement → turn on the atomizer → keep the negative pressure 100-200 Pa, and drain the steam condensate in the drum and steam pipe, slowly open the steam valve, and preheat and dry The tower is about 0.5-1 hour (condensate in the air duct, the tower, etc. all become steam and the material pump can be turned on before feeding).
2. The normal negative pressure is maintained at 50-150Pa after feeding. Adjust the feed volume, control the tower temperature at 75-90 ° C, and the moisture content less than 5%. Pay attention to the material level in the material tank at any time during the drying process.
3. Finished product packaging: The seasoning (powder) products that are spray-dried and cooled to room temperature are qualified according to the standard inspection, and then bagged and weighed according to the quality requirements. Good ventilation and dryness).
4 ) Parking operation:
1. After each batch of material is dried, the hot water switch added to the intermediate tank is turned on to clean the atomizer, atomizer plate, material tube, pump, etc.
2. The stopping sequence is to stop the steam → feed pump → electric heater → atomizer (adjust the outlet air temperature so that the feed speed is between 15-20, the inlet air temperature drops to 150 ° C, turn off the atomizer) → Turn off the vibration → dry exhaust fan → air supply mechanism (the inlet air temperature drops to 110 ° C) → turn off the power.
5 ) Cleaning system:
1. In order to ensure the cleanliness of the drying tower body and its pipes and all parts in contact with the finished product, it is necessary to obtain first-class products and regular cleaning equipment.
2. When the product is replaced, or the equipment has been stopped for more than 24 hours without cleaning, a comprehensive and thorough cleaning should be performed.
Dry cleaning : Clean with a brush, broom, or vacuum cleaner. Wet washing: Wash with hot water at 60-80 ° C.
Pickling : Mix nitric acid (HNO3) into a 1-2% concentration solution, wash at a heating temperature not exceeding 95 ° C, and then wash with water.
Alkali washing : Sodium hydroxide (NaOH) is formulated into a 0.5-1% concentration solution, heated to 60-80 ° C for washing, and then washed with water.
3. After wet and chemical washing, the equipment and components should be installed and sterilized at high temperature for 15-30 minutes.
4. When cleaning this equipment, care should be taken not to use chlorine and its compounds.
5. The cleaning of the air filter should be based on the surrounding environmental conditions, that is, the level of dust in the air. Generally, it is cleaned once every 3-6 weeks and once every 6-8 weeks when the dust content is low.
V. Common fault repair methods:
1) Sticky wall phenomenon
(1) The feed amount is too large to be fully evaporated;
(2) Insufficient heating of the drying chamber before spraying begins;
(3) At the beginning of spraying, the feed flow rate is adjusted too much;
(4) The feed liquid is unstable.
Properly reduce the amount of feed;
Properly increase the inlet and outlet temperatures of hot air;
At the beginning of the spray, the flow rate should be small, gradually increased, and adjusted to the appropriate time;
Check whether the pipeline is blocked, adjust the solid content of the material, and ensure the fluidity of the material.
2) High moisture content
Generally the exhaust temperature is too low. Properly reduce the amount of feed to increase the exhaust temperature.
3) Low purity
(1) Poor air filtration effect;
(2) The accumulated powder is mixed into the finished product;
(3) the purity of the raw materials is not high;
(4) The equipment is not cleaned thoroughly.
Check whether the filter material is laid evenly in the air filter, and if the filter is used for too long, if it is, it should be replaced immediately;
Check the situation of coke powder at the hot air inlet to overcome the eddy current;
The material liquid should be filtered before spraying; clean the equipment again.
4) The powder is too fine
The solid content is too low or the feed is too small. Increase the solid content of the feed liquid, increase the feed volume, and increase the inlet air temperature.
5) Running powder phenomenon
The cyclone separator has a poor separation effect.
(1) Check whether the cyclone is deformed due to knocking or collision;
(2) Improve the airtightness of the inlet and outlet of the cyclone separator;
(3) Check whether there is a blockage of material accumulation on the inner wall and the discharge port.
6) Nozzle speed is low
Defective centrifugal nozzle unit. Check the inner parts of the print head.
7) Low evaporation
(1) The amount of air in the entire system is reduced;
(2) The inlet temperature of hot air is low;
(3) The equipment has air leakage, and cold air enters the drying room.
(1) Check if the speed of the centrifuge is normal;
(2) Check whether the position of the centrifuge regulating valve is correct;
(3) Check if the air filter and air heater pipes are blocked;
(4) Check whether the grid voltage is normal;
(5) Check whether the electric heater works normally;
(6) Check whether the components of the equipment are tightly connected.
8) Nozzle vibration
cause of issue
(1) Residual material in the disc or the main shaft is bent and deformed due to improper cleaning and maintenance of the nozzle;
(2) The dynamic balance of the centrifuge disk is not good.
(1) Check whether there is any residual substance in the spray tray, and if necessary, clean it in time;
(2) If the spindle is found abnormal, it needs to be replaced;
(3) Readjust or replace the dynamic balance of the centrifuge disk.
1. First turn on the centrifugal fan, then turn on the heater, and check whether there is air leakage. Preheating can be performed as normal. The hot air preheating determines the evaporation capacity of the drying equipment . Without affecting the quality of the material being dried, it should be Increase the inlet air temperature as much as possible.
2. When preheating, the atomizer is placed on the top of the drying chamber, and the drying chamber and the discharge opening of the cyclone separator must be sealed to prevent cold air from entering the drying chamber and reducing the preheating efficiency.
3. When the inlet temperature of the drying chamber reaches the set temperature, turn on the centrifugal spray head. When the spray head reaches the maximum speed, turn on the feed pump and replace it with the feed liquid after adding water spray for 10 minutes. The feed amount should be from small to large. Otherwise sticking will occur until it is adjusted to the appropriate requirements. The concentration of the material liquid should be formulated according to the drying nature of the material to ensure that the finished product has good fluidity after drying.
4. The temperature and humidity of the dried product depend on the exhaust air temperature. During the operation, it is extremely important to keep the exhaust air temperature at a constant value. This depends on the size of the feed, the stability of the feed, and the outlet temperature. stable. If the solid content and flow rate of the material liquid change, the outlet temperature will also change.
5, the product temperature is too high, you can reduce the amount of feed to increase the outlet temperature, the temperature of the product is too low, and vice versa. For products with low temperature, heat-sensitive materials can be added to reduce the exhaust temperature, but the temperature of the product will increase accordingly.
6. Collect finished products after drying. The pollinator in the lower part of the cyclone should be replaced before being filled. When changing the pollinator, the upper butterfly valve must be closed before proceeding.
7. If the dried product has hygroscopicity, the cyclone separator and its pipes, and the part of the pollinator should be wrapped with thermal insulation material, so as to avoid the moisture and moisture absorption of the dried product.