How do dissolving and stirring tanks optimize the synchronization of stratified dissolution of solid materials in solvents?
Publish Time: 2025-10-02
In numerous industrial fields, including chemical, pharmaceutical, food, and new materials, dissolving and stirring tanks are critical equipment for uniformly dispersing and fully dissolving solid materials in solvents. However, in practice, after solid materials are added to the solvent, stratification often occurs due to density differences, insufficient wettability, or uneven mixing. Light materials float on the liquid surface, while heavy particles quickly settle and accumulate at the bottom of the tank. This leads to uneven dissolution, inefficiency, and even the formation of difficult-to-disperse clumps or "fish eyes." This not only prolongs process time but also affects the uniformity of the final solution and product quality. Therefore, optimizing the dissolution process and achieving synchronized stratified dissolution of solid materials has become a core technical issue in the design and operation of stirring tanks.
1. Scientific Dosing Methods: Reducing Stratification at the Source
The first step to achieving synchronized dissolution is optimizing the dosing strategy. Traditional methods of manual pouring or high-level dosing easily cause concentrated material accumulation, exacerbating stratification. Modern mixing tanks are often equipped with a tangential feeding system or vacuum suction device to slowly and evenly introduce solid materials into the solvent along the direction of the mixing liquid flow. Some high-end equipment also utilizes a powder injection system, which utilizes the shear force of the high-speed liquid to break up the powder upon entry into the tank, directing it into the turbulent flow zone, preventing it from floating or settling and thus reducing stratification at the source.
2. High-Efficiency Mixing System: Breaking Down Stratification and Promoting Uniform Mixing
The selection and layout of the agitator are key to resolving stratification issues. A single agitator cannot achieve both surface dispersion and bottom suspension, so a multi-layer mixing configuration is required. Typically, a radial or axial flow impeller is installed in the upper layer to break surface tension and accelerate wetting of floating powders. A high-shear turbine or anchor agitator is installed in the lower layer, generating a strong downward flow to prevent solid settling and continuously draw the bottom material into the main flow zone. Using variable frequency speed control, the agitator speeds of the upper and lower layers can be controlled separately, achieving three-dimensional mixing (top, middle, and bottom), ensuring simultaneous dissolution of materials from the liquid surface to the tank bottom.
3. Synergistic Effect of a Draft Cylinder
Installing a draft cylinder inside the mixing tank can significantly improve mixing efficiency. The draft cylinder guides the liquid into a stable upward and downward circulation flow, enhancing axial flow, effectively shortening the residence time of solid particles in the liquid phase and preventing localized accumulation. Especially for high-viscosity systems, the draft cylinder reduces dead zones, promotes uniform distribution of materials with varying densities, and improves dissolution synchronization.
4. Optimizing Solvent Wetting and Dispersion Processes
The dissolution of solid materials begins with wetting. If wetting is inadequate, air entraps the surface of the particles, forming agglomerates and making further dispersion difficult. To address this, pre-adding an appropriate amount of wetting agent or surfactant to the solvent can reduce surface tension and accelerate particle wetting. Furthermore, controlling the initial solvent volume to create a high-shear slurry and then adding additional solvent to dilute the slurry after the solids are fully dispersed can effectively prevent uneven dissolution, which occurs when the solids dissolve first and then settle.
5. Auxiliary Control of Temperature and Pressure
Temperature significantly affects the dissolution rate. Heating reduces solvent viscosity, increases molecular motion, and accelerates solid dissolution. Some dissolving and stirring tanks are equipped with jacketed or coil heating systems for precise temperature control. For poorly soluble materials, pressurized dissolution can also be used to improve solvent penetration. The synergistic effect of temperature and stirring can significantly shorten dissolution time and reduce unevenness caused by stratification.
6. Process Monitoring and Intelligent Control
Modern dissolving and stirring tanks integrate sensors such as pH meters, density meters, and online particle size analyzers for real-time monitoring of dissolution status. Through a PLC or DCS system, parameters such as stirring speed, temperature, and feed rate can be automatically adjusted based on feedback data, enabling dynamic optimization of the dissolution process and ensuring synchronized dissolution of materials at each stage, avoiding over- or under-mixing.
By optimizing the feed pattern, configuring a multi-layer stirring system, using draft tubes, and adjusting process parameters, dissolving and stirring tanks effectively address the issue of stratification of solid materials in the solvent, achieving synchronized optimization of the dissolution process. This not only improves production efficiency but also ensures solution uniformity and batch stability.
