SR Crystallization Machine

1. Background of SR High Efficiency Scraping Wall Hollow Plate Cooling Continuous Crystallization Machine

1.1 The Importance of Crystallization Process Crystallization is the process by which solid substances precipitate from steam, solution, or melt in a crystalline state. In the chemical industry, it is common to see solid substances crystallize from solutions and melts.

Crystallization is a very important chemical process in industries such as pharmaceuticals, chemicals, and food. Numerous chemical products and intermediate products appear in crystalline form because the crystallization process can form pure crystals from solutions with a considerable amount of impurities. As a separation process, crystallization has much lower energy consumption compared to distillation and other commonly used purification methods, and can be carried out at lower temperatures. For many substances, crystallization is often a good and economical method for large-scale production.

1.2 Backwardness and Delay of Crystallization Technology

Crystallization technology has a long history in China, but the theoretical progress of crystallization is relatively slow compared to other chemical processes, especially in the design and manufacturing of crystallizers, which are lagging behind compared to other pharmaceutical and chemical unit equipment, and there are few research and development personnel.

1.3 Disadvantages of commonly used cooling crystallizers currently:

At present, the most commonly used cooling crystallizers in China are kettle crystallizers and horizontal crystallizers, which have many disadvantages:

1.3.1 Due to jacket cooling, crystallization starts from the kettle wall first, causing the crystalline material to form on the kettle wall first. In severe cases, thick crystalline material can be formed on the kettle wall, greatly affecting heat transfer efficiency. Although the problem of crystalline material forming on the kettle wall can be reduced by increasing the stirring speed, crystallization is also limited by the stirring speed in many cases. If the stirring speed is too fast, the grain size will be greatly reduced, affecting the next step of filtration and washing operation. For situations where larger grains are desired,

It's even more inappropriate. In addition, for kettle type stirring crystallization, it is generally difficult for the stirring blade to achieve wall scraping stirring, which makes it difficult to scrape off the grains formed on the kettle wall and affects the heat transfer effect.

1.3.2 When stirring in a regular crystallization kettle, a central vortex is formed, and the crystallization effect is often better near the external cooling kettle wall. However, the material near the center of the kettle crystallizes slowly, causing uneven grain size and slow overall crystallization rate.

1.3.3 For crystallization kettles with added cooling coils, although the cooling area can be greatly increased, due to the stationary nature of the cooling coils, crystallization occurs first in the shape of the stationary coils, which seriously affects the heat transfer effect. In addition, the addition of coils will greatly affect the stirring effect of the crystallization kettle, and wall scraping stirring is even more impossible. After forming more crystalline substances on the kettle wall and coils, the heat transfer effect is worse, and the crystallization slurry is not easily discharged completely.

1.3.4 Due to the fact that the bottom of the crystallization kettle is often a standard elliptical head, for crystallization kettles with high material concentration and a large amount of crystalline solids, the discharge is often incomplete, and some crystalline solids may remain in the kettle and cannot be discharged, affecting production and energy consumption.

1.4 Wuxi Shuangrui Machinery has conducted extensive research and development work to address the shortcomings of the above-mentioned ordinary crystallization kettle. They have successfully developed SR horizontal high-efficiency internal rotating disc cooling crystallization machine and SR high-efficiency scraping wall hollow plate cooling crystallization machine. Compared with ordinary kettle type crystallization machines, these crystallization equipment have greatly improved crystallization efficiency and have been widely used in many fields such as medicine, food, metallurgy, mining, chemical industry, and fine chemical industry.  

2. Structure and working principle of SR high-efficiency scraping wall hollow plate cooling crystallization machine

2.1 SR efficient scraping wall hollow plate cooling crystallization machine, compared with the above-mentioned crystallization machine and kettle crystallization, although the efficiency has been greatly improved. During the crystallization process, crystals still precipitate on the surface of the internal cooling components of the rotating moving parts. Once crystals form on the cooling surface, even if they are very thin, it will affect the cooling effect. For the occasion of gap operation, this phenomenon is not very prominent yet, because the next batch of hot crystalline materials will dissolve this layer of crystal when added. However, for continuous crystallization, the above situation will be very prominent, because the crystals on the cooling surface will accumulate thicker and cannot be removed, seriously affecting the cooling effect.

In order to solve the above problems, after years of effort, we have designed and developed SR efficient scraping wall hollow plate cooling continuous crystallization machine and SR efficient scraping wall hollow plate cooling batch crystallization machine. The successful development of this crystallization machine can be said to be a major breakthrough in China's crystallization technology, because this crystallization machine can perform wall cleaning operations on the cooling surface during any crystallization process, making the cooling surface always clean, greatly improving the cooling heat transfer effect, and making one crystallization machine replace more than ten or even dozens of kettle type crystallization machines.

2.2 The main structural form of SR high-efficiency scraping wall hollow plate cooling crystallization machine adopts a new structure and working principle. Many hollow cooling plates are vertically arranged in a horizontal long groove container, and the central stirring shaft passes through all the cooling plates. A flow blocking partition plate and many rotary wheel pushing scraping wall stirring devices are installed between every two hollow cooling plates. Scraping wall stirring makes all cooling surfaces clean, greatly improving heat transfer and cooling effects.

The working principle of the SR high-efficiency scraping wall hollow plate cooling crystallization machine is that the saturated solution or hot crystallized material discharged from the reaction kettle, evaporator and other equipment is metered or controlled and added to the crystallization machine. It passes through many hollow cooling plates, flow blocking partitions, and many rotating wheel driven scraping wall stirring devices and other unique structures, allowing the crystallized material to fully contact a large number of cooling surfaces and rapidly cool. The material balance and heat balance, as well as the calculation of heat transfer coefficient and heat transfer area, are determined to meet the process requirements for material cooling crystallization. After the crystallization is completed, the crystal slurry is automatically discharged through the bottom non dead angle pneumatic discharge valve. The entire process is operated in a closed manner, with low labor costs and high efficiency.

3. The main advantages of SR high-efficiency scraping wall hollow plate cooling crystallization machine

3.1 Due to the combination and arrangement of a large number of hollow cooling plates in a horizontal long slot container, the cooling area is generally 15 to 20 times that of a kettle or horizontal crystallizer of the same volume, and the cooling area is very large;

3.2 All spaces within the crystallizer are equipped with cooling surfaces at close intervals, without any dead corners, ensuring even crystallization of the material;

3.3 All surfaces are equipped with wall cleaning stirring and pushing scraper blades, greatly improving the cooling efficiency of materials during the crystallization process, achieving true rapid cooling crystallization, and allowing one crystallization machine to replace more than ten or even dozens of kettle type crystallization machines;

3.4 Achieving true continuous crystallization, due to the constant scraping and cleaning effect during any crystallization process, the heat transfer coefficient and cooling efficiency of the crystallizer can be maintained unchanged, which cannot be achieved by other crystallizers;

3.5 can also be used for rapid batch crystallization;

3.6 Crystalline particle size can be controlled by adjusting different stirring and cooling speeds;

3.7 It can achieve closed operation, especially suitable for cooling and crystallization of flammable, explosive, toxic materials, fresh food, drugs, etc;

3.8 All cooling discs can be divided into multiple groups and supplied with cooling media of different temperatures, which conveniently saves energy and meets the needs of different crystallization temperatures;

3.9 The stirring device and stirring scraper are variable frequency speed regulation, and any stirring speed can be set to meet the requirements of the crystallization process;

4. Process conditions

4.1 Crystalline material name: Sodium sulfate

4.2 Processing capacity:

4.3 Crystallization slurry temperature: 40 degrees Celsius

4.4 Cooling crystallization endpoint temperature: -5 degrees Celsius

4.5 On site configuration of cooling medium: ethylene glycol chilled water at -15 degrees Celsius;

5. Equipment selection

5.1 Continuous Crystallization Machine

According to the process requirements of the demand side, it is proposed to use the SR-3.0 high-efficiency scraping wall hollow plate cooling crystallization machine for operation. First, use circulating cooling water for pre cooling, and wait until the crystallization temperature is reached. The crystallization slurry is fed into the equipment from the side inlet of the crystallization machine, and after a certain amount of slurry enters, the stirring is turned on (depending on the actual situation) to cool down and crystallize in the equipment. After reaching the crystallization process, the propeller blade is pushed from the bottom towards the discharge port. There is a discharge port on the right side of the equipment for discharge (which can be used as a mother liquor discharge port, or connected to the slurry feed port through a pipeline for continuous feeding, or transferred through a storage tank). The bottom is equipped with a special non-standard design structure and a no dead angle pneumatic discharge valve to prevent crystallization and stirring dead angles in the discharge area at the bottom of the shell, which is not easy to aggregate or bridge, and facilitates the smooth discharge of materials from the machine after crystallization. Opening the valve automatically discharges the materials. It can also be used as a cleaning and drainage outlet during maintenance.