Sodium Sulfate
Sodium sulfate (Na₂SO₄), commonly known as anhydrous sodium sulfate, is widely used inorganic chemical raw material. It is extensively used in papermaking, glassmaking, detergents, printing and dyeing, and pharmaceuticals, among other industries. Its purity and morphological stability directly determine its application value. Tianli specializes in the refined production of sodium sulfate, focusing on optimizing two core processes of MVR evaporation and fluid bed drying. Leveraging advanced technologies, we create high-purity, low-energy-consumption, and environmentally friendly sodium sulfate products to comprehensively meet the stringent production needs of various industries.
I. Core Properties of Sodium Sulfate
Sodium sulfate is white crystalline solid or powder with the molecular formula Na₂SO₄, relative molecular mass of 142.04, density of 2.671 g/cm³, melting point of 884℃, and boiling point of 1430℃. It is odorless, salty and bitter in taste, with strong hygroscopicity. When exposed to air, it easily absorbs water to form sodium sulfate decahydrate (mirabilite). Its aqueous solution is neutral, and its solubility exhibits significant temperature-dependent characteristics. From 0-32℃, solubility increases with increasing temperature, while above 32℃, it decreases with increasing temperature. This characteristic is a core basis for the process design of the MVR evaporation section. Sodium sulfate is highly stable, does not react with most substances, is readily soluble in water and glycerol, but insoluble in ethanol. It is widely found in salt lakes, rock salt mines, and industrial wastewater, making it a high-quality raw material source for resource recovery. Furthermore, the product can be processed into different specifications to suit diverse application scenarios.
II. Core Process Flow Introduction
(I) MVR Evaporation Section: Energy-Saving Concentration and Precise Crystallization
The MVR (Mechanical Vapor Recompression) evaporation section is the core concentration and crystallization stage in sodium sulfate production. Its core purpose is to recycle the pretreated sodium sulfate solution through vapor recompression, achieving efficient water evaporation and precise crystal precipitation while minimizing energy consumption, aligning with green production principles. Our company employs a forced circulation MVR evaporation system paired with an OSLO crystallizer, adapted to the solubility characteristics of sodium sulfate, significantly improving production efficiency and product purity.
The process flow follows the core logic of pretreatment - evaporation concentration - crystallization separation - mother liquor circulation. First, the pH of the raw material solution is adjusted, and scale inhibitors are added to prevent scaling. Purification treatment removes impurities, ensuring that the turbidity and COD of the influent meet standards. The pretreated solution enters the forced circulation evaporator, where a centrifugal steam compressor pressurizes and heats the secondary steam generated during evaporation, converting it into a high-quality heat source for recycling, eliminating the need for large amounts of additional live steam. A stable negative pressure is maintained within the evaporator, controlling the evaporation temperature. The solution flows in the forced circulation system at a velocity ≥1.5 m/s to prevent localized overheating and crystallization agglomeration. Simultaneously, seed crystals are added to induce uniform crystal growth. Once the feed solution reaches saturation concentration, it enters the crystallizer to complete crystal precipitation. After centrifugation, wet sodium sulfate crystals are obtained. The separated mother liquor is returned to the evaporation system for recycling, which greatly improves the utilization rate of raw materials.
(II) Fluid Bed Drying Section: High-Efficiency Dehydration and Stable Formation
The fluid bed drying section follows the MVR evaporation section for wet sodium sulfate crystals. Its core task is to remove moisture adhering to the crystal surface while ensuring the crystals remain intact and free of agglomeration. This also lowers the product temperature, facilitating subsequent packaging and storage, and enhancing the product's market competitiveness.
Tianli utilizes fluid bed drying system, optimizing process parameters based on the characteristics of sodium sulfate crystals: Wet sodium sulfate crystals enter the dryer via a sealed feeder. Hot air is evenly distributed in the air distribution chamber, suspending the material particles in the airflow and creating a fluidized state. The material continuously tumbles, preventing static accumulation. The drying hot air temperature is precisely controlled between 135-185℃, rapidly removing moisture through conduction and convection. After drying, the sodium sulfate crystals are cooled and screened for impurity removal, ultimately yielding a finished product with a purity ≥99.6%. Dust-laden gas carrying a small amount of fine powder is treated by a cyclone separator before being discharged in compliance with standards, achieving clean production.
III. Core Technological Advantages
1. Low Overall Energy Consumption
MVR technology recycles and utilizes the latent heat of secondary steam, resulting in an energy consumption of only 25-35 kWh per ton of water, saving over 60% energy compared to traditional multi-effect evaporation. The system requires only a small amount of live steam during startup and no external steam supplementation is needed during normal operation.
2. High Product Quality
Using DTB or OSLO crystallizers, the crystals have large particle size (up to 0.6-1.0 mm), uniform distribution, and a smooth appearance. The final anhydrous sodium sulfate product has a purity ≥98% (up to 99% or more), a moisture content ≤0.2%, meeting or exceeding the Class II Grade 1 standard of GB/T6009 "Industrial Anhydrous Sodium Sulfate".
3. Stable and Reliable System
The forced circulation evaporator is designed with a high flow rate, effectively preventing scaling and clogging on the inner wall of the heating tubes; the fluid bed dryer is highly adaptable to crystalline materials, is not easily broken, and produces products with good flowability and no agglomeration. PLC/DCS fully automatic control enables precise regulation of key parameters such as temperature, liquid level, density, and discharge.
4. High Resource Recovery Rate
The mother liquor reflux and recycling design enables a total sodium sulfate recovery rate of over 95%. For mixed systems containing sodium chloride and other miscellaneous salts, salt-nitrate separation can be achieved by utilizing solubility differences, allowing for the separate recovery of high-purity sodium sulfate and sodium chloride products.
5. Strong Adaptability
This process is suitable for treating sodium sulfate solutions from various sources, including mirabilite ore production, industrial wastewater containing sodium sulfate (pharmaceutical intermediates, coal chemical industry, printing and dyeing, etc.), and zero-discharge projects for high-salinity wastewater. A single unit can handle 10-200 tons/day.
Technology empowers quality, professionalism creates value. Our company focuses on the characteristics of sodium sulfate materials, deeply cultivating core technologies in MVR evaporation and fluid bed drying. Leveraging our core advantages of energy saving, high efficiency, environmental protection, and high quality, we provide high-quality sodium sulfate products and one-stop production solutions to various industries, working hand-in-hand with customers to promote industrial upgrading and achieve mutual benefit.