The Key Role and Process of Mixer-Settlers in Phosphoric Acid Purification and Impurity Removal

As a core basic raw material in the fields of chemical industry, chemical fertilizers, new energy lithium batteries, and fine pharmaceuticals, industrial wet-process phosphoric acid production generally faces industry pain points such as high impurity content, insufficient separation precision, large material loss, and high subsequent refining costs. Traditional sedimentation separation and simple extraction equipment are difficult to achieve efficient graded removal of metal ions, organic acids, and suspended solid impurities. They also have problems such as limited processing capacity, poor working condition adaptability, and weak stability of continuous production, which seriously restrict the capacity and quality upgrading of high-purity phosphoric acid. Against the backdrop of the industry's growing demand for high-purity phosphoric acid and rising environmental production standards, the introduction of mature and stable liquid-liquid extraction separation equipment has become the core direction for the upgrading of phosphoric acid purification and impurity removal processes. With advantages such as strong structural adaptability, high separation efficiency, low operating energy consumption, and continuous large-scale operation, mixer-settlers have become the core key equipment in the wet-process phosphoric acid refining and impurity removal links, providing reliable process support and equipment guarantee for the industrial purification of phosphoric acid.

I. Core Advantages of Mixer-Settlers Adapted to Phosphoric Acid Purification Processes

Mixer-settlers are static separation equipment designed based on the principles of liquid-liquid contact mass transfer and gravity stratification. Different from traditional separation equipment, they have strong process adaptability in phosphoric acid purification and impurity removal scenarios.

Firstly, the mixing chamber inside the equipment can realize full turbulent contact between phosphoric acid feed liquid and extraction solvent, allowing target impurity components to quickly complete interphase transfer. The mass transfer reaction is sufficient and the reaction rate is controllable, effectively improving the overall impurity removal rate. Secondly, the clarification chamber adopts a large-volume stable sedimentation structure, which can realize natural stratification of light and heavy phase materials, with a clear and stable interface, avoiding material entrainment loss and greatly improving the yield of finished phosphoric acid.

At the same time, the overall structure of the mixer-settler is simple, without high-speed rotating wearing parts, resulting in low operating failure rate and small daily maintenance workload, which can be long-term adapted to the continuous production line of chemical wet-process phosphoric acid. In addition, the equipment can be modularly combined according to production capacity requirements, which can not only adapt to small and medium-sized phosphoric acid production devices, but also meet the working conditions of large-scale purification projects in large chemical parks, compatible with the treatment of crude phosphoric acid raw materials with different concentrations and different impurity contents.

II. Key Roles of Mixer-Settlers in Phosphoric Acid Purification and Impurity Removal

1. Directional Separation and Removal of Impurities

Crude phosphoric acid raw materials contain a large number of metal cations, inorganic acid radicals and soluble impurities, which are the main factors affecting the purity of phosphoric acid and the quality of downstream products. By accurately controlling the two-phase ratio, residence time and working condition temperature, the mixer-settler relies on the selectivity of the extraction system to directionally transfer harmful impurities in crude phosphoric acid to the organic phase, realizing effective separation from the phosphoric acid mother liquor, reducing impurity content from the source, and laying a foundation for the preparation of industrial-grade and battery-grade high-purity phosphoric acid.

2. Optimization of Material Mass Transfer Reaction Environment

Phosphoric acid purification and impurity removal have strict requirements on the contact uniformity and reaction time of the two-phase materials. The independent mixing and clarification zone structure of the mixer-settler can accurately control the two core links of material mixing mass transfer and static stratification, avoiding problems such as short circuit of two-phase materials and uneven residence time. A stable mass transfer environment can ensure the constancy of purification process parameters, keep the purity of phosphoric acid products consistent between batches, and improve the controllability of the production process and product stability.

3. Reduction of Comprehensive Production and Operation Costs

Traditional phosphoric acid impurity removal processes often require multiple processes in series and supporting a large number of auxiliary equipment, resulting in large floor space, high reagent consumption and energy consumption. After applying the mixer-settler, the purification process can be simplified, the investment in intermediate transfer equipment can be reduced, and the equipment covers a compact area. In addition, the equipment has low operating energy consumption, high reagent utilization rate and less material loss. Long-term large-scale production can effectively reduce reagent, energy consumption and manual operation and maintenance costs, and improve the overall production economic benefits of enterprises.

4. Adaptation to Environmental Compliance Production Requirements

Modern phosphoric acid production has strict requirements for waste liquid and waste treatment and clean production. The closed structure design of the mixer-settler can effectively inhibit the diffusion of volatile materials and improve the workshop production environment. At the same time, the centralized separation of impurities facilitates subsequent unified harmless treatment and resource recovery, which is in line with the energy conservation, consumption reduction and green environmental protection production standards of the chemical industry, helping enterprises meet the requirements of environmental compliance production.

III. Standard Process Flow of Mixer-Settlers Applied in Phosphoric Acid Purification and Impurity Removal

1. Raw Material Pretreatment and Material Preparation

The crude phosphoric acid raw material obtained by wet-process production is initially filtered to remove large-particle suspended solid impurities, and then the concentration and system acidity of the crude phosphoric acid are adjusted according to the process standards. At the same time, a special extraction solvent is matched for proportioning and blending to ensure that the physical and chemical properties of the two-phase materials meet the requirements of the extraction separation working conditions, making preparations for entering the mixer-settler.

2. Two-Phase Material Mixing and Mass Transfer

The prepared phosphoric acid feed liquid and extraction solvent are sent to the mixing chamber of the mixer-settler in a fixed ratio, and a uniform turbulent state is formed through the built-in baffle structure to make the two-phase materials fully contact and collide. Within the set residence time, various impurity components in the feed liquid are gradually transferred to the extraction solvent phase through mass transfer, completing the extraction and enrichment process of impurities.

3. Static Clarification and Two-Phase Stratification

The mixed liquid after full mixing and mass transfer naturally flows into the clarification chamber, and the light and heavy phases are stably settled and stratified by means of gravity density difference. The phosphoric acid mother liquor remains in the lower layer as the heavy phase, and the extraction solvent loaded with impurities floats in the upper layer as the light phase. The interface between the two phases is regular and clear, without obvious cross entrainment, realizing efficient separation of the phosphoric acid and impurity system.

4. Phase Diversion and Subsequent Refining

After stratification, the clarifier discharges the lower high-purity phosphoric acid mother liquor and the upper impurity-loaded organic phase respectively. The purified phosphoric acid mother liquor is sent to the subsequent concentration and refining processes to be further processed into finished phosphoric acid of different specifications; the impurity-loaded organic phase is sent to the stripping and recovery process to realize solvent regeneration and recycling, and impurities are collected and treated centrally to form a closed-loop production process.

5. Intelligent Regulation of Working Condition Parameters

During the operation of the entire process flow, the core parameters such as material feed flow rate, two-phase ratio, tank temperature and residence time can be adjusted in real time through the control system. The process conditions can be flexibly adjusted according to the fluctuation of impurity content in the crude phosphoric acid raw material, ensuring that the mixer-settler is always in the optimal separation working state and continuously and stably outputting high-purity phosphoric acid products.

IV. Process Application Summary and Industry Development Value

Under the industry trend of wet-process phosphoric acid transforming to high-purity and battery-grade high-end products, the equipment upgrading and process optimization of purification and impurity removal processes are an inevitable trend. With multiple advantages such as efficient mass transfer, stable stratification, strong adaptability and low operation and maintenance costs, mixer-settlers play a core role in impurity removal, process stability, cost control and environmental protection production in phosphoric acid purification and impurity removal.

The standardized process flow combined with modular mixer-settler equipment can not only effectively solve the industry problems such as insufficient purity, high loss and unstable process in traditional phosphoric acid production, but also help enterprises simplify production processes, expand production capacity, and improve product market competitiveness. With the continuous growth of demand for high-purity phosphoric acid in the new energy and high-end chemical industries, mixer-settlers will be more widely used in the field of phosphoric acid refining, becoming an important core equipment to promote the green, high-end and large-scale development of the phosphorus chemical industry.