Determination of design scheme for spray dryer

The design of spray dryer should be completed by the designers and users of the dryer, which is the result of mutual cooperation between the two sides. This is because the various properties of the materials to be dried are often better understood by the equipment users than by the designers, and the requirements for product indicators are also put forward by the operators.

The development of spray drying technology has been completed in many fields. From the perspective of drying equipment, it can be said that it is both a universal device and a special equipment. It not only dried thousands of materials, but also achieved the expected purpose. The content of spray drying technology is not only the mass transfer, heat transfer and mechanical problems of chemical engineering, but also the complex nature and the different requirements of drying materials. Therefore, a successful design scheme should be completed jointly by the designer and user of the dryer, which is the result of mutual cooperation between the two sides. This is because the various properties of the materials to be dried are often better understood by the equipment users than by the designers, and the requirements for product indicators are also put forward by the operators. In other words, many of the original design data are first put forward by users, and designers just according to their own professional knowledge ^ to meet the needs of users. In this way, it is very important for the user to provide the designer with detailed information about materials and requirements for the product.

Determination of design scheme for spray dryer

1、 Properties of feed liquid

(1) High solid content of raw materials can be pumped.

(2) Surface tension.

(3) Liquid viscosity. The viscosity of materials is related to the conveying method and the form of atomizer. At present, the three kinds of atomizers are different to adapt to the viscosity of materials.

(4) Thermal fluidity. Some materials are paste or paste at room temperature, but when heated to a certain temperature, they have good fluidity. If there is such a property, heating equipment or insulation equipment should be added to the system. The heat tracing pipe may also be the material.

(5) Thixotropy. Some materials, in the static state, are paste like, but in the case of mixing, there will be fluidity, which can be transported smoothly. In the system, add beating equipment or mixing equipment.

(6) Type of solvent (wet fraction). For most materials, the moisture content is water, but there are also some chemical reagents in special cases, which plays an important role in the scheme of which gas is used to carry heat and moisture, or to treat the moisture content in the gas (emptying or recycling).

(7) Chemical characteristics. Special attention should be paid to the corrosivity, flammability, explosiveness, toxicity and taste of materials and moisture before the determination of drying scheme. The determination of system operation scheme largely depends on the chemical characteristics of materials.

(8) Material status. Whether the material to be dried is in the form of solution or suspension, it determines whether filtration is necessary to ensure normal atomization before entering the atomizer.

(9) The existence form of moisture content. The moisture in the material (take water as an example) includes bound water, crystal water or mechanical water. The energy consumed by evaporation of these water is different, and more attention should be paid when the moisture content of the product is strictly required.

(10) Liquid temperature.

(11) The heat sensitive temperature of the material. From the point of view of heat transfer, the higher the operating temperature of spray drying is, the higher the economic cost of equipment investment and operation is. However, most materials have high allowable temperature. The inlet temperature and outlet temperature of hot air have an impact on product quality. It is economical to work under allowable temperature, which is the main basis of process design.

2、 Natural conditions

The equipment has a fixed installation site, and the natural environment of the installation site is the basis of equipment process calculation.

(1) Annual average temperature of the installation site. The annual average temperature is the basic data for heat balance calculation of equipment and an important parameter for designing heat exchange equipment of drying system.

(2) Annual average relative humidity of the installation site. The annual average relative humidity of air is the parameter of material balance and heat balance. For example, in the case of the same evaporation water amount, the consumption of air with higher moisture content as the carrier will increase.

(3) Installation location. The installation site of the equipment is indoor or outdoor, which involves the insulation thickness of the equipment. If the tower type large spray drying tower is installed outside, we must pay attention to the local meteorological conditions, such as wind grade and seismic requirements.

3、 Product requirements

Product requirements are the concern of users. Before design, the specific requirements for products must be provided to designers in detail, mainly including the following aspects.

(1) Production capacity. All equipment in spray drying system is related to production capacity. It determines the scale investment and operation cost of the system, and is the basis of material balance and heat balance and equipment manufacturing.

(2) Residual moisture of the product. In general, it is very difficult to produce the product of ^, and the general product has a specified water content range. If allowed, a higher moisture content of the product can reduce the effective height of the equipment and the production cost.

(3) Particle size and distribution of products. As a powder product, there are specific requirements for the particle size and distribution of the product. The three atomizers produce different droplet sizes, so the atomization method should be determined according to the product size requirements.

(4) Product density. The density of the product refers to the bulk density. Similar to the above mentioned, the density of the product varies with the particle size.

(5) The yield of the product. Spray dried products are granular products obtained after gas-solid separation. There will always be a small amount of loss in this process. High yield is required for particularly expensive products. Special methods should be taken for collecting methods, and the shape of fans will also be involved.

(6) Hygroscopicity. Some powdery products, such as some inorganic salts, are easy to absorb moisture in the natural environment. When they come out of the drying chamber, the water content is qualified, but the moisture in the air may be absorbed at the moment of packaging. For such products, it is necessary to avoid contact with the air in the packaging process to prevent moisture absorption.

(7) Health requirements. For pharmaceutical and food products, the hygiene standards are strict. The air should be strictly filtered to dry such materials. No impurities can be brought into the atomization process. The operation method should be good. The micro positive pressure should be used. The design of discharge method should also meet the sanitary requirements.

4、 Environmental requirements

(1) Vibration of equipment. The spray drying system needs to be equipped with fan and other power equipment, and the large spray dryer fan is also very large. The vibration of fans and pumps will affect the environment and buildings of the factory. Vibration reduction measures should be taken in design and selection.

(2) Noise. The noise mentioned here mainly refers to the noise of fans, especially the high-pressure fans. Sometimes, the noise can reach more than $& - '(if you work in this environment for a long time, your body and mind will be damaged to a certain extent. In addition, it is not allowed to produce strong noise by environmental protection. Therefore, the high-pressure fan and other equipment that produce strong noise should be silenced.

(3) Emission requirements. The emission gas mainly includes two parts. One part is the emission of combustion gas when there is a combustion heat source. Some factories have special requirements for their emissions due to their different nature or geographical location. The other part is the emission of tail gas, which mostly depends on the properties of the powder. In general, the powder which can cause harm to human body and environment is strictly required in the exhaust emission, and the dust content requirements of different powder tail gas are also different. The above mentioned is from the perspective of yield, which is mainly from the perspective of environmental protection.

   what mentioned above is the specific requirements of the user to the designer, and also provide necessary supporting conditions, such as product standard samples and testing standards, allowable floor area, space height, possible installation position of equipment, types of heat source that can be provided, etc.

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The above content is something that must be known before spray dryer design. It must not be ignored. It is the key to the success of the design of spray dryer. The preparation work before the design requires meticulous, serious, practical and realistic. Only in this way can the foundation of successful design be laid.

Changzhou Haomai drying Engineering Co., Ltd. has a professional technical team to provide free scheme design for customers. In addition, our company has prototype and spot products all year round. Welcome new and old customers to visit and inspect!