Product Introduction

　　 Forced-Circulation Crystallizer (also known as FC Crystallizer) It is a highly efficient industrial crystallization equipment based on the principle of “forced turbulent circulation plus controllable supersaturation crystallization.” At its core, it adopts a combined structure of an “external circulation pump plus heat exchanger,” which uses high flow rates to force the feed liquid to circulate continuously within the crystallization system. This precise control over the distribution of supersaturation prevents crystal adhesion and scaling, enabling rapid crystallization and crystal growth. The equipment’s key advantages—“strong anti-scaling capability, high crystallization efficiency, stable operation, and adaptability to complex feedstocks”—make it widely applicable in medium- and large-scale crystallization processes across industries such as chemical engineering, salt chemical industry, environmental protection, and metallurgy. It is particularly well-suited for handling feedstocks with high salt content, high viscosity, tendency to scale, and containing suspended solids. Based on the specific characteristics of the feedstock (such as solubility, viscosity, and corrosivity) and production capacity requirements (ranging from 0.5 t/h to 200 t/h), the equipment can be customized with tailored circulation systems, heat exchanger materials, and crystallization parameters to produce crystal products with uniform particle size.

Product Category

　　According to the crystallization process, equipment structure, and application scenarios, forced-circulation crystallizers are mainly classified into the following categories:

　　 1. Classified by crystallization process

　　 ▪ Cooling-type forced-circulation crystallizer: By cooling the feed liquid through a heat exchanger, the solubility is reduced, creating supersaturation that triggers crystallization. This process is particularly suitable for materials whose solubility varies significantly with temperature, such as potassium nitrate, potassium sulfate, and citric acid.

　　 ▪ Evaporative forced-circulation crystallizer: Combining heating and evaporation with forced circulation, the concentrated feed liquid achieves supersaturation, making it suitable for materials whose solubility changes gradually with temperature (such as sodium chloride, sodium sulfate, and ammonium chloride).

　　 ▪ Vacuum-cooled forced-circulation crystallizer: In a vacuum environment, the feed liquid is cooled and evaporated simultaneously, generating supersaturation in the process. This method boasts high crystallization efficiency and operates at low temperatures, making it particularly suitable for heat-sensitive materials (such as pharmaceutical intermediates and fine chemical products).

　　 ▪ Reactive Forced-Circulation Crystallizer: Integrating chemical reactions with crystallization processes, this approach enables the immediate crystallization of reaction products by precisely controlling reaction rates and cycling conditions. It is particularly suitable for crystallization in chemical synthesis (e.g., the preparation of calcium carbonate and barium carbonate).

　 　2. Classified by Equipment Structure

　　 ▪ Internal-loop forced-circulation crystallizer: The heat exchanger is built inside the crystallization chamber, featuring a compact structure and a small footprint, making it suitable for medium- and small-scale production capacities (0.5 t/h to 20 t/h).

　　 ▪ External circulation forced-circulation crystallizer: The heat exchanger is arranged separately from the crystallization chamber and connected via an external circulation pump. It features high heat exchange efficiency, convenient maintenance, and is suitable for medium- to large-scale production capacities (20 t/h to 200 t/h). It is the mainstream type used in industrial applications.

　　 ▪ Forced-circulation crystallizer with grading device: Add a grading screen or flow-guiding structure to the top of the crystallization chamber to achieve crystal size grading, producing crystals with a narrow particle size distribution (0.3–3 mm in diameter), suitable for applications requiring high-quality crystal products.

　 　3. Classified by operating method

　　 ▪ Continuous forced-circulation crystallizer: The entire process—from feed addition, crystallization, to product discharge—is continuous, ensuring a stable crystal growth environment with production capacity fluctuations of no more than 5%. This makes it suitable for large-scale industrial production (e.g., in the salt chemical and fertilizer industries).

　　 ▪ Batch forced-circulation crystallizer: Complete the process of feeding—temperature rise—circulating crystallization—discharging in a single batch. With precise temperature control, this method is ideal for crystallizing small-batch, multi-variety materials (such as fine chemicals and pharmaceutical excipients).

　　 ▪ Semi-continuous forced-circulation crystallizer: The crystallization process is carried out continuously in a cyclic manner, with intermittent feeding and discharging operations, balancing both stability and flexibility. It is well-suited for medium-scale production of products with multiple specifications.

Performance Features

　 　1. Extremely strong anti-scaling capability: The feed liquid circulates in turbulent flow at a high velocity of 2–5 m/s, significantly reducing crystal deposition on the heat-exchanger tube walls and the inner walls of the crystallization chamber, thereby effectively inhibiting scaling and clogging. The equipment can operate continuously for 3–8 months, an improvement of more than 50% compared to conventional crystallizers.

　 　2. High crystallization efficiency: In turbulent flow conditions, the heat transfer coefficient of the feed liquid is high (1500–4000 W/(m²·℃)), the supersaturation distribution is uniform, and the crystal growth rate is fast (0.2–0.8 mm/h). For evaporative models, the evaporation intensity can reach 30–80 kg/(m²·h), and the production capacity is 2–3 times higher than that of natural circulation crystallizers.

　　 3. Operation is stable and controllable: By precisely controlling parameters such as circulating pump flow rate, heat exchanger temperature, and vacuum level, the degree of supersaturation can be accurately adjusted, resulting in uniform crystal particle size (CV value ≤ 25%), regular crystal morphology, and minimal product quality fluctuations. The process can be automated via a PLC system, reducing the need for manual intervention.

　　4. Wide compatibility: It can handle solutions with salt concentrations ranging from 5% to 30% and viscosities up to 1000 mPa·s. It is compatible with materials containing suspended solids (up to 5%), as well as those prone to scaling, high in hardness, and corrosive (by selecting corrosion-resistant materials such as 316L stainless steel, titanium, and Hastelloy alloys). At the same time, it is suitable for a variety of crystallization processes—including cooling, evaporation, and vacuum operations—offering flexible application scenarios.

　 　5. Energy Consumption Optimization: The selection of forced-circulation pumps is precise, and energy consumption is reasonably controlled. Evaporative models combined with multi-effect or MVR systems can reduce energy consumption by 60% to 80%. Vacuum-cooling models operate at lower temperatures, further reducing energy consumption.

　 　6. Easy maintenance: The external circulation design makes key components such as the heat exchanger and circulation pump easy to disassemble and maintain, allowing cleaning and maintenance to be carried out without shutting down the entire system. The heating/cooling tubes feature a straight-tube design that is resistant to clogging and offers high cleaning efficiency.

　 　7. Easy to scale: Modular design supports capacity expansion. Capacity can be increased by boosting the power of circulation pumps, replacing heat exchangers with larger surface areas, or connecting crystallization chambers in parallel. The investment cost remains controllable and is well-suited to meet companies’ growing capacity needs.

Application scenarios

　　Thanks to their core advantages of strong anti-scaling capability and high efficiency, forced-circulation crystallizers are widely used in the following industries:

　 　1. Salt chemical industry: Large-scale production of salt crystals such as sodium chloride, sodium sulfate, potassium chloride, ammonium chloride, and sodium nitrate—particularly well-suited for continuous crystallization of high-salt solutions (purity ≥ 99.5%);

　　 2. Chemical industry: Crystallization of fine chemical products (such as citric acid, lactic acid, and sodium benzoate); crystallization and purification of organic intermediates (such as terephthalic acid and adipic acid); preparation of inorganic compounds (such as calcium carbonate and magnesium hydroxide).

　　 3. Environmental Protection Industry: Recovery of salt crystals from zero-discharge high-salinity wastewater (such as wastewater from chemical industrial parks, electroplating wastewater, and coal chemical wastewater); crystallization of solid byproducts after advanced treatment of landfill leachate; concentration and crystallization of organic wastewater to reduce its volume.

　　 4. Metallurgical Industry: Recovery of byproducts from non-ferrous metal smelting (such as copper sulfate, nickel sulfate, and zinc sulfate); crystallization and separation of rare earth elements (such as rare earth chlorides and rare earth nitrates); refining and crystallization of precious metals.

　　 5. Fertilizer Industry: Crystallization of fertilizer products such as potassium dihydrogen phosphate, ammonium sulfate, and ammonium chloride yields granular crystals with excellent flowability and uniform particle size, thereby enhancing the effectiveness of product application.

　 　6. Other fields: Crystallization of food additives (such as monosodium glutamate, xylitol, and maltitol), crystallization and purification of pharmaceutical excipients (such as mannitol and lactose), and crystallization for the preparation of battery materials (such as lithium sulfate, lithium carbonate, and lithium hexafluorophosphate).