Crystallization tanks are commonly used in the pharmaceutical industry for mixing materials, cooling and freezing, and crystallization of finished products. They are also widely used in industries such as food, chemical, and beverage. The crystallization tank is generally composed of a stirrer, a motor and reducer, a crystallization tank body, a heating chamber, and related instruments and meters. The crystallization tank can achieve processes such as heating rise, material mixing, vapor-liquid separation, and material descent through natural convection. However, due to the nature and actual situation of the materials, it is necessary to use explosion-proof motors and reducers installed at the top of the tank to drive the agitator inside the crystallization tank and change the flow field state inside the tank. By adjusting the speed of the agitator, the size of the fluid circulation generated by the agitator and the strength of the convective shear effect can be controlled, allowing the concentrated liquid to circulate strongly in the tank, maintaining a suspended state of solid particles, facilitating crystal adsorption and growth, thereby improving the heat transfer coefficient and evaporation intensity, accelerating the crystallization rate, and enhancing the crystallization efficiency of the crystallization tank.

However, in use, it has been found that existing crystallization tanks have problems such as poor heat transfer, uneven mixing, local undercooling, and uneven evaporation, which can easily lead to uneven solute concentration. In research, it has been found that the main factors causing these problems are solution supersaturation, uniformity, and stirring intensity, which are the main factors affecting crystal nucleation and growth. Among them, promoting the circulation of materials in the crystallization tank and ensuring uniform heat transfer effect are the key to designing and improving the crystallization tank.

Therefore, all structural designs inside the tank must revolve around good material circulation and effective temperature control. Ensuring sufficient mixing and uniform heat transfer of the fluid inside the crystallization tank, controlling the formation of ideal supersaturated solution concentration, and avoiding uneven solute concentration caused by local supercooling and evaporation are key to ensuring product quality.

Our company's crystallization tank includes a tank body, a power device, and a stirring device. The lower part of the stirring device is installed inside the tank body, and the top is connected to the power device. Its characteristics are: the bottom of the tank body is a W-shaped head protruding upwards at the center, and a heating and flow device for circulating steam is installed inside the tank body. The heating and flow device is set on the outer ring of the lower part of the stirring device, and the inlet end of the heating and flow device passes through the bottom of the tank body and is connected to an external steam source, while the outlet end passes through one side of the middle of the tank body; There is a jacket on the outer side of the lower part of the tank, and the fluid circulating inside the jacket is used to heat the materials inside the tank. The tank contains materials that need to be stirred and crystallized inside, and the fluid inside the jacket can be heated by circulating it. The flow inside the heating and guiding device can cooperate with the high-temperature fluid inside the jacket to simultaneously heat the steam inside the tank; By using both internal and external heating methods, the material is heated. In conjunction with the specially designed W-shaped head at the bottom of the tank, the bottom of the W-shaped head, which protrudes upwards at the center, is less likely to experience trailing and dead corners where material accumulates, resulting in more thorough mixing of the fluid.

Both the inner and outer layers are heated simultaneously and can be controlled together, effectively ensuring the uniformity of material temperature, improving the crystallization effect, changing the internal flow field shape, and having a good diversion effect, ensuring the full mixing of materials and avoiding the influence of excessive solute saturation on the crystallization effect locally.

The heating and guiding device includes a suction tube and a support plate. The suction tube is installed on both sides of the tank body through the support plate at the lower part. The suction tube includes an outer tube, an inner tube, an upper half tube, and a lower half tube. The outer tube is fitted with an inner tube of equal height, and a steam flow channel is left between the outer and inner tubes. The upper and lower sides of the outer and inner tubes are connected and sealed by circular upper and lower half tubes. The left end of the lower half tube is connected to the steam inlet pipe, and the upper right part of the steam flow channel is connected to the steam outlet pipe. The combination of the air cylinder structure and the agitator changes the internal flow field shape, while also playing a good guiding effect, strengthening the overall axial flow of the upper and lower liquids in the crystallization tank. The setting of the air cylinder structure makes the distribution of the agitator flow field more ideal.

The jacket includes a cylinder section, an elliptical head, and a jacket outlet connection. The lower part of the cylinder section is fixedly connected to the elliptical head, and a jacket outlet connection is provided at the outer center of the bottom of the elliptical head. A ring-shaped protective plate is provided between the two sides of the bottom of the elliptical head and the W-shaped head, and a flow hole is formed between the bottom of the W-shaped head and the bottom of the tank body through the ring-shaped protective plate. By controlling the flow rate of the fluid inside the jacket, the temperature of the material inside the tank can be controlled to a certain extent; By forming a circulation hole between the bottom of the W-shaped head and the bottom of the tank through a circular protective plate, the corrosion of the weld structure by the fluid inside the jacket can be reduced.

The mixing device includes a mixing shaft and a mixing blade. The mixing shaft is vertically installed inside the tank, and the mixing blade is fixedly installed at the lower part of the mixing shaft. The top of the mixing shaft extends out of the tank and connects to the power device. The power device is installed on the top of the tank through the mixing flange.

The mixing shaft and mixing blade are hollow structures, and a connected flow channel for heating fluid is set inside the mixing shaft and mixing blade. A flow inlet and a flow outlet are set on the mixing shaft, and the flow inlet and outlet are set on the top side of the mixing shaft extending out of the tank. Heating channels are also set inside the mixing shaft and mixing blade, and steam and other fluids are introduced. The heating fluid inside the tank is heated together with the heating fluid in the jacket or air cylinder, and the material is heated while mixing, further ensuring the uniformity of material heating.

The tank body is divided into two parts: the upper tank body and the lower tank body. The upper tank body and the lower tank body are fixedly connected by container flanges. The upper side of the upper tank body is equipped with a feeding pipe, and the bottom side of the lower tank body is equipped with a discharging pipe.

1. Change the internal structure of the tank and optimize the heating mode: a jacket structure is used for external heating, and a gas cylinder container is set up for internal heating. The temperature control of the material inside the tank is achieved through the combination of the gas cylinder and the hot fluid flowing through the jacket, instead of relying solely on the jacket to control the temperature of the traditional crystallization tank. The combination of the gas cylinder structure and the stirrer strengthens the overall axial flow of the upper and lower liquids in the crystallization tank, and the stirring flow field distribution is ideal, effectively ensuring the uniformity of the material temperature and improving the crystallization effect

Adopting a completely new structure of the head: In order to improve the internal structure of the traditional crystallization tank, a W-shaped head is used instead of the standard elliptical head. The bottom of the W-shaped head is less prone to following rotation, thus avoiding blind spots for material accumulation and ensuring more thorough fluid mixing; Improved the uniformity of solution mixing, avoided excessive solute saturation locally, and achieved better crystallization effect.

The joint control of internal and external factors effectively ensures the uniformity of material temperature and improves the crystallization effect. The combined action of the W-shaped head and the air cylinder changes the internal flow field shape, with good diversion effect, ensuring sufficient mixing of materials. At the same time, the uniformity of the flow field significantly improves the variation of the load on the blade, thus effectively reducing the risk of damage to the mixing shaft.

Simultaneously set up heating channels in the mixing shaft and mixing blade, and introduce steam and other fluids. Use the heating fluid in the jacket or air cylinder to heat the materials inside the tank, while stirring the materials, to further ensure the uniformity of material heating.