Principle and application of lab spray dryer

1 Working principle of lab spray dryer

The centrifugal lab spray dryer is currently the most widely used lab spray dryer in industrial production. The material liquid is pumped from the material through the filter to the high-speed rotating centrifugal atomizing plate on the top of the dryer, and it is sprayed into very small mist droplets instantly , The misty droplets evaporate quickly after contacting with hot air. The finished powder is collected by the barrel at the bottom of the cyclone separator, and the remaining waste gas is discharged after passing through the bag dust chamber or water film dust collector. On the surface of the dispersion plate, the liquid spreads in a thin film and is thrown out at a high speed on the circumference. The atomization effect depends on the circumferential linear speed and the feeding rate, and is also related to some physical and chemical properties of the liquid.

Figure 1 Centrifugal atomization disc

Figure 2 Centrifugal atomization state of materials

The powder product dried by the lab spray dryer is mainly collected by the principle of cyclone separation. The total dust-containing gas of the equipment generates a high-speed whirling motion through the inlet swirler to form a rotating airflow. The dust is separated from the airflow under the action of centrifugal force and its own gravity, moves downwards and gathers and is collected. The dust-removed gas is sent from the upper outlet to the bag dust collection room or the water film dust collector to continue adsorption and collection.

Figure 3 Cyclone structure

2.Application field of lab spray dryer

In the more than 100 years of development of spray drying technology, it was initially limited to the production of egg powder, milk powder, detergents, cosmetics and other products. With the continuous deepening of research and application, it has been widely used in chemical, biological, food, and pharmaceutical industries. , Ceramics and other industries in the production of ultrafine powder and nano powder.

Chemical industry: battery raw materials, dye intermediates, compound fertilizers, sulfuric acid, amino acids, white carbon black, etc.;

Biology: bacterial cells, enzyme preparations, proteins, peptides or other heat-sensitive biologically active materials;

Resins: AB, urea-formaldehyde resin, phenolic resin, polyethylene, polyvinyl chloride, etc.;

Food: fat-rich milk powder, muscle protein, animal blood meal, egg white and whole egg powder, oats, chicken juice, coffee, instant tea, flavored meat, protein, soybeans, etc.;

Sugars: corn syrup, corn starch, glucose, pectin, maltose, potassium sorbate, etc.; ceramics: alumina, ceramic tile materials, magnesium oxide, talc, etc.;

Chinese medicine: Chinese medicine extract, Chinese medicine formula granule, Chinese medicine extract, oral solid preparation, etc.

Figure 4 Large lab spray dryer

3.Types and applications of laboratory lab spray dryers

1) Pressure lab spray dryer:

Pressure lab spray dryer is a device that can complete drying and granulation at the same time. According to the process requirements, the pressure, flow rate and size of the nozzle hole can be adjusted to obtain the required spherical particles in a certain size ratio. Suitable for industries such as chemical, food, pharmaceutical, ceramics, spray granulation, fertilizer, spray cooling granulation, etc. The working process is that the material liquid is input through the diaphragm pump at high pressure, spraying out misty droplets, and then descending in parallel with the hot air. Most of the powder particles are collected by the discharge port at the bottom of the tower, and the waste gas and its tiny powder are separated by the cyclone separator. The exhaust gas is discharged by the exhaust fan, and the powder is collected by the pollinator at the lower end of the cyclone separator. The outlet of the fan can also be equipped with a secondary dust removal device, and the recovery rate is above 96-98%. The materials of the tower body, pipes and separators in contact with materials are all made of SUS304. There is a sufficient insulation layer between the inside of the tower body and the outer shell, and the filling material is ultra-fine glass wool. The tower body is equipped with an observation door, a sight glass, a light source and a control instrument, which are controlled and displayed by an electric control console. The heat source device adopts steam heating or electric heater, which has the advantages of convenient operation, fast start-up, compact structure, clean hot air and so on. In addition, an electric heater control and adjustment device is installed in the electric control cabinet to enable stepless adjustment of the inlet temperature. For power-deficient areas, steam heating or coal-fired or oil-fired hot-blast stoves can be used to partially or completely replace electric heating devices.

Features of pressure lab spray dryer:

(1) The drying speed is fast, and the surface area of ​​the material liquid is greatly increased after atomization. In the hot air flow, 95-98% of the water can be evaporated in an instant, and the drying time is only ten seconds to tens of seconds, especially Suitable for drying heat sensitive materials.

(2) The resulting product is spherical particles with uniform particle size, good fluidity, good solubility, high product purity and good quality.

(3). It has a wide range of applications. According to the characteristics of the material, it can be dried with hot air or granulated with cold air, which has strong adaptability to the material.

(4), the operation is simple and stable, the control is convenient, and it is easy to realize automatic operation.

2) Centrifugal lab spray dryer:

The so-called centrifugal lab spray dryer is the use of a centrifugal atomizer to dry certain liquid materials. It is currently one of the most widely used dryers in industrial production. Spray drying is the most widely used process in the liquid process shaping and drying industry. It is most suitable for generating powdery and granular products from solutions, emulsions, suspensions and pumpable lake-like liquid materials. Therefore, when the particle size distribution, residual moisture content, bulk density and particle shape meet the precise standards, spray drying is a very ideal process.

Features of centrifugal lab spray dryer:

(1), the drying speed is fast, the surface area of ​​the material liquid is greatly increased after atomization, in the hot air flow, 95%-98% of the water can be evaporated instantly. It only takes 5-15 seconds to complete the drying, with instant drying characteristics.

(2). The special air distribution device reduces the resistance of the equipment and effectively provides the air handling device of the dryer.

(3) The production process is simplified, suitable for continuous production control, the liquid with a moisture content of 40-90% can be dried into powder at one time, reducing crushing, screening and other processes to improve product purity.

(4) The material can complete the drying process in a short time, which is suitable for the drying of heat-sensitive materials and can maintain the color, fragrance and taste of the material.

(5), the product has good dispersibility, fluidity, and solubility, and the product particle size, looseness, and moisture are adjustable within a certain range

3) Airflow lab spray dryer:

Airflow lab spray dryer has a high degree of automation and flexible operation (the particle size of the finished product can be controlled). It is especially suitable for drying solutions, emulsions, pastes, suspensions and even viscous materials. Especially suitable for medium-scale or experimental-scale material drying.

Features of airflow lab spray dryer:

(1) The drying time is only 10-30 seconds. Due to the short drying time, lab spray dryer can maintain uniform fine particles (the product has good dispersibility, fluidity and solubility).

(2), flexible control. Regarding the product’s grain diameter, bulk density, moisture, product properties (no dust, fluidity, wettability, instant dissolution), the operating conditions can be adjusted within a certain range, and the control and management are convenient.

(3). It has a very good effect on paste materials with high viscosity.

(4) The finished product is of good quality. Can retain the color, fragrance, taste, and other biological activities of the material; the moisture content of the final product;

(5), the nozzle structure is simple (the cost of the atomization system is only 1/3 of the pressure type, 1/5 of the centrifugal type), the possibility of clogging is small, the one-time input cost is low, and the later use cost is also very low.

3. Application fields of laboratory lab spray dryer

In the history of spray drying for more than 100 years, it was initially limited to the production of egg powder, milk powder, detergent, cosmetics and other small products. With the continuous deepening of research, it is now in the production of various industrial ultrafine powders and nano powders. Widely used, such as battery raw materials in the chemical industry, white carbon black; alumina in the ceramic industry; dry granulation of drugs in the pharmaceutical field, etc. Compared with the non-spray drying method, spray drying can effectively reduce the agglomeration of ultrafine powder. Through the spray drying process, particles with high sphericity, good fluidity and high fineness can be produced to meet the requirements of specific fields. The following will briefly introduce some related fields.

1. Lab spray dryer is used for spray dryer & granulation of special ceramics. Before the ceramic material is shaped and sintered, the forming of the green has a direct impact on the performance of the product. The characteristics of the powder have a great influence o

   

   n the uniformity of the green and the density after dry pressing. Spray granulation technology is widely used to prepare special ceramic powder. Usually pressure spray is used to spray and granulate the special ceramic powder. Under suitable process conditions, the prepared powder has good chemical uniformity, high fineness, good fluidity, and high compaction density, which can be applied to special ceramics. Powder forming process such as dry pressing or isostatic pressing. Example: Alumina spray granulation process: Alumina ceramic spray granulation process flow chart

1. Application of lab spray dryer in lithium iron phosphate cathode material for lithium batteries Lithium batteries are mainly composed of cathode materials, anode materials, electrolytes and separators. Cathode materials restrict the development of lithium-ion batteries in terms of cost and performance. Therefore, the research and development of cathode materials is the key to promoting lithium-ion battery technology updates. At present, the domestic cathode materials mainly include lithium cobalt oxide, lithium nickel oxide, lithium iron phosphate and ternary materials. Among them, lithium iron phosphate has the advantages of good safety, long cycle life, good thermal stability, wide sources of raw materials, and low price, but it has low tap density and poor low-temperature conductivity. The simple preparation process of lithium iron phosphate/C cathode material: take LiOH and FePO4 into a ball mill tank and add purified water, add a certain amount of carbon source after ball milling, take out the slurry after 3 hours of spherical ink and blow it into a lab spray dryer for spray drying. Spray drying is performed at a certain inlet and outlet temperature (200-250°C inlet, outlet temperature <100°C). After the material is dried, it is placed in an atmosphere furnace for low-temperature calcination for 2 hours, and after high-temperature calcination for 6 hours, LiFePO4/C cathode material is obtained. Experiments show that the spray drying step gives the precursor material before sintering a good sphericity, with a particle size of 20-20 microns. Under spray drying conditions, the chemical composition of the material is relatively uniform. During calcination, there is no solid phase change between the spherical particles. The production of LiFePO4/C crystal grains is limited to one spherical particle. Therefore, small LiFePO4/C crystal grains can be obtained, and the fine crystal grains are very important for LiFePO4/C. The electrical properties are favorable.
2. The dry precipitated silica used in lab spray dryer for white carbon black is also called white carbon black. The expression is mostly mSiO2·nH2O. It is an important reinforcing material in the rubber industry because its microstructure and aggregation form are similar to carbon black. , And has similar reinforcing properties in rubber, so it is called white carbon black. The production methods of white carbon black include gas phase method and precipitation method. The product of gas phase method has high purity and good performance, but the production process consumes large energy, has high technical difficulty and high cost. In contrast, the precipitation method to prepare white carbon black has mature technology, simple operation and great cost advantages. However, in the drying and dehydration process, ultrafine particles are prone to agglomeration, which affects performance. Research shows that spray drying can obtain white carbon black with uniform particle dispersion, high specific surface area and high oil absorption value, which meets the recommended oil absorption value and specific surface area matching curve, and is suitable for high-performance tire reinforcement and color tire reinforcement Agent. Color tires & black tires
3. Application of lab spray dryer in pharmaceutical preparations Drying plays an important role in pharmaceutical production, especially in the production of traditional Chinese medicine. The medicament prepared by spray drying has the following characteristics: a. Good uniformity of the finished product: During lab spray dryer, the chemical liquid is sprayed into an atomized dispersion under constant stirring, and the drying is completed instantly, so the uniformity is better. b. The finished product has good fluidity, looseness and solubility: when spray drying, the water vaporizes quickly, the particle size of the finished product is small, the fluidity is good, and the tablet is flat; when the divided dose is packaged, the dosage is more accurate. When in contact with water, it is easier to enter the inside of the particles, which is more conducive to the dissolution of the drug. c. Simplify the production process: spray drying can complete the concentration and drying in one step, and the drying time is also relatively short, which is conducive to maintaining the efficacy of the heat-sensitive drug product. d. Clean production: a closed spray environment is used to prevent the drug from being contaminated by bacteria and reduce dust pollution in the workshop. Therefore, spray drying is very suitable for drying in the pharmaceutical process of Chinese medicine. Traditional Chinese medicine products require high cleanliness, so multiple air purifiers are installed. The simple process of spray drying of medicinal materials: medicinal materials → extraction → concentration → lab spray dryer → collecting medicinal powder.