In the production of fine chemicals involving alkali washing and water washing, the purification and recovery of organic solvents are critical factors determining both product quality and production costs. Especially for key solvents such as benzene and xylene, the traditional manual operation of reactor can no longer meet the increasingly stringent demands for capacity and environmental compliance. Many companies encounter issues such as incomplete acid removal during alkali washing and residual salts after water washing.

Zhengzhou Tiei Extraction Technology Co., Ltd. has innovatively developed the CWL-M series centrifugal extractor. Designed for the dual-stage process of “alkali washing for acid removal + water washing for salt removal,” these machines offer a systematic solution that integrates high-efficiency mass transfer, rapid phase separation, and continuous operation.They are rapidly becoming the preferred equipment for process upgrades in fine chemical production.

Alkali Washing for Acid Removal: Centrifugal Extraction Redefines Reaction Efficiency

The purpose of alkali washing for acid removal is to efficiently remove both organic and inorganic acids from benzene-containing solutions, achieving purified benzene ready for recycling. Traditional reactor operations rely on mechanical stirring, which suffers from uneven reactions, long processing times, and high alkali consumption.

In the selection of alkali washing equipment, the CWL-M centrifugal extractor demonstrates revolutionary performance in the alkali washing stage:

Acid-containing benzene solution is continuously pumped into the light-phase inlet, while sodium hydroxide solution and water are precisely metered into the heavy-phase inlet. Under the intense centrifugal field generated by high-speed rotation, the two phases are instantly and thoroughly mixed at a micrometer scale, allowing organic acids to neutralize with the alkali within seconds. The mixture then enters the separation zone, where the organic and aqueous phases form a clear interface under centrifugal force. The de-acidified benzene is continuously discharged while the reaction wastewater is simultaneously removed.

This process not only increases acid removal efficiency to over 99.5%, but also reduces alkali consumption by 30–50%, while simultaneously decreasing wastewater discharge, achieving both high efficiency and environmental sustainability.

Water Washing for Salt Removal: Multi-Stage Countercurrent Ensures Minimal Residue

Trace salts may remain in the de-acidified benzene solution and require further purification through the water washing stage. The CWL-M centrifugal extractor supports multi-stage countercurrent operation to achieve deep salt removal with minimal water consumption.

For example, in a two-stage countercurrent water washing process, the benzene solution from the first stage enters the second-stage equipment, contacting fresh wash water in a countercurrent manner. Salt concentration decreases progressively at each stage, and the final benzene product can achieve residual salt levels below 10 ppm. Within each equipment, instantaneous mixing and rapid phase separation are realized, preventing the accumulation of emulsified layers and interphase entrainment commonly encountered in traditional washing operations.

Notably, the CWL-M series centrifugal extractor comes standard with an electrostatic discharge system. When handling flammable solvents such as benzene and xylene, it continuously eliminates static charge buildup, fundamentally ensuring the safety of continuous production.

CWL-M Centrifugal Extractor: Systematic Integration of Technical Highlights

As a new-generation liquid-liquid extraction equipment, the CWL-M series centrifugal extractor demonstrates multi-dimensional technical advantages in the combined process of “alkali washing for acid removal + water washing for salt removal”:

1.Quantum Leap in Separation Efficiency: With centrifugal force thousands of times stronger than gravity, phase separation is completed within seconds, eliminating the long wait associated with gravity settling.
2.Significant Footprint Reduction: A single equipment integrates mixing, mass transfer, and separation. A system handling 5 m³/h occupies less than 20 m²—only one-fifth the space required by traditional processes.
3.Corrosion Resistance and Long Service Life: Flow-through components are made of fluoropolymers and high-performance composite materials, capable of withstanding prolonged exposure to alkali, brine, and organic solvents.
4.Substantial Reduction in Resource Consumption: Minimal internal hold-up volume means residual liquid during shutdown is only one-tenth of that in traditional equipment, reducing consumption of alkali, wash water, and extraction agents simultaneously.
5.Seamless Automation Integration: Supports DCS system integration with real-time adjustment of parameters such as flow rate and rotational speed, enabling fully unmanned, continuous operation of the extraction stage.

Industrial Validation: From Single-Point Breakthrough to System Upgrade

In a large petrochemical benzene purification project, the original process used three stage reactor in series for alkali and water washing. The single-batch processing cycle was approximately 4 hours, with alkali consumption at 8 kg/ton of benzene and wash water usage of 12 tons/day. Additionally, the system required monthly shutdowns 2–3 times to remove emulsified layers.

After upgrading to a four-stage CWL-M centrifugal extraction system (two stages of alkali washing + two stages of countercurrent water washing), the processing cycle was shortened to 45 minutes. Alkali consumption dropped to 4.2 kg/ton of benzene, wash water usage decreased to 5 tons/day, and continuous operation reached 12,000 hours without emulsified layer accumulation. Annual comprehensive operating costs were reduced by over 3 million CNY.

Zhengzhou Tiei Extraction not only provides high-performance liquid-liquid extraction equipment but also aims to be a technical partner for fine chemical enterprises in their continuous, green process upgrades.
Email: sales@tieiextraction.com
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