Process Design and Control of 99.9% Isopropyl Alcohol

Isopropyl alcohol (IPA) is an important solvent in many industries, and its use is growing rapidly. Its unique properties make it a popular choice for solvent applications, including cleaning, degreasing, and solvent extraction. Besides, Isopropyl alcohol is an alternative to volatile organic compounds such as Freon.

High-purity IPA of at least 99.9%, with the moisture content below 200ppm is required to produce drugs that meet regulatory standards, and any deviations from these standards can result in delays in the approval process.

In the processing of integrated circuits (ICs), ultra-clean and high-purity chemicals are mainly used for cleaning and etching the surface of chips and silicon wafers, and their purity and cleanliness have a significant impact on the yield, electrical performance and reliability of ICs.

Ultra-clean, high-purity isopropanol has been widely used as an important microelectronic chemical for cleaning and drying in the processing of semiconductors and large-scale integrated circuits.

Similarly, in petrochemicals and organic synthesis, the removal of water in organic solvent is critical to produce high-quality products and to ensure the safety of the process. So Isopropyl alcohol dehydration is necessary for process operations.

As a process equipment supplier, it is crucial to understand the application of isopropyl alcohol in your industries that require dehydration so better facilitate to design effective processes and control for isopropyl alcohol dehydration.

Welcome to share us your specific process requirements for guaranteed dehydration performance!

The Process Design Of Isopropyl Alcohol Dehydration

It is critical to achieve these high-purity levels by removing water molecules from the solvent. Several procedures can help to achieve high-purity levels of IPA.

One method is azeotropic distillation with a drying agent, such as benzene or toluene, which can remove water molecules from the solvent, but the process operation is energy consuming and low efficiency. Another method is molecular sieves, which are porous substances that can absorb water molecules from liquids or gases, it is also a labor cost operation which is not efficient for industrial scale production plants.

In modern processing plants, there are more advanced, sustainable alternatives for IPA purification, the green process that our projects have been successfully applying is pervaporation membrane technology, which uses selective permeable zeolite membranes to separate water from IPA.

Let’s go deep to the process technology!

Azeotropic Distillation

Azeotropic distillation is a technique in which a solvent and a water-soluble component are combined to generate a constant-boiling mixture known as an azeotrope. Anhydrous IPA can be made by distilling the azeotrope. Benzene is a typical azeotropic substance used to dehydrate IPA.

The azeotrope has a 91% IPA by volume and 9% water content. As a result, ordinary distillation cannot achieve dryness levels lower than this.  However, dehydration of isopropyl alcohol using molecular sieves has proven to be an effective method of drying IPA beyond the azeotrope.

Molecular Sieves

Molecular sieves or zeolites are crystalline aluminosilicate materials with a three-dimensional network of uniform pores and channels. Molecular sieves are porous substances that can absorb water molecules from liquids or gases. A particular size of the pores allows for the selective adsorption of water molecules while rejecting bigger molecules like IPA.

Molecular sieves use the difference in molecular size between the solvent and water to separate them. Water has a molecular size of 2.6Å, while isopropyl alcohol (IPA) has a molecular size of ~16Å. The 3Å or 4Å molecular sieve adsorbs water while permitting IPA to pass through the bed due to their difference in size.

The molecular sieve beads are then regenerated to remove the adsorbed water. When wet IPA flows through the sieves during the following dehydration cycle, the sieves remove even more water.

Extractive Distillation

Extractive distillation is the process of distilling in the presence of a separating agent, also known as an entrainer. The entrainer interacts differently with the original mixture’s components and so changes their relative volatilities.

The key characteristics of the separating agent are a higher boiling point than the original combination’s constituents, miscibility with the mixture, recyclable nature, low toxicity, and biodegradability. In the extractive distillation of the (IPA + water) mixture, several salts and ionic liquids were observed to be viable separating agents.

However, industrial distillation methods do not allow stable control of product quality and cannot meet the industrial production requirements for the preparation of high-purity isopropanol.

The Mechanism of Pevaporation Process Technology

Pervaporation is a membrane separation technique that is used for the separation of liquid mixtures. It is an energy-efficient process that is ideal for the separation of near-boiling point and constant-boiling point mixtures, isomeric substrates, and chemicals with poor thermal stability that are difficult or impossible to separate using conventional distillation, extraction, or adsorption methods.

The process achieves continual separation of the permeable component in the membrane module based on different dissolution and diffusion rates. The membrane is the key component of the pervaporation equipment, and it is responsible for the separation of the feed mixture into the permeate and retentate streams.

Tubular NaA Type Zeolite Membranes contain pores sized to allow only water molecules to pass through, blocking isopropyl alcohol. When a vacuum is applied, water vaporizes and permeates the membrane, separating from the IPA.

The compatible design of a pervaporation membrane module with hydrophilic NaA zeolite membrane materials are preferred for IPA dehydration applications. They have a uniform pores and channels that are high flux ratio with above 10000g/㎡h. The pores in the zeolite membrane are 0.41 Nm in diameter, making them capable of separating water molecules of 0.29Nm from IPA.

We design and build Isopropyl Alcohol Dehydration System for both the liquid phase and gas phase based on the input water concentration and output dryness requirements.

The process technology is characterised by strong continuity, good separation, high purity and low impurity content and has been successfully used in industrial production.

Key Considerations To Optimize The Pervaporation Module Design

  • Optimizing the membrane morphology and orientation is critical to achieving high separation efficiencies in the pervaporation process.
  • Feed pretreatment is also necessary to remove suspended solids from the feed stream, such as 10μm filtration and activated carbon, are commonly used to remove impurities from the feed stream and maintain the service life of membrane material in the long run.
  • The feed material to be treated and separated shall be organic solvent like IPA, ethanol, tetrahydrofuran, etc. It is colorless, clear and transparent. there shall be no stratification, and the water content is below 30 wt.%.
  • The optimal temperature and pressure settings are determined based on the required final concentrations of the permeate stream.
  • Maximizing mass transfer through concentration gradients and balancing flux and energy costs through circulation flow rates are key considerations in the optimization of the pervaporation process.
  • Pilot trials determine differences in hydrodynamics and mass transfer relative to the lab scale. Adjustments to flow rates and other parameters are needed to account for larger membrane areas.
  • While maintaining consistent quality and optimized productivity, further with following defined procedures minimizes variability.
  • To achieve dynamic process optimization in IPA dehydration process equipment. Advanced process control systems and automation must be in place to ensure the reliability and consistency of the pervaporation process. Automated monitoring of the feed, retentate, and permeate streams, as well as the control of process parameters of vacuum degree, pressure rating and working temperatures, can optimize separation efficiency and prevent fouling through automated cleaning procedures.
  • Validating the dehydration process through product testing, certifying the equipment and process for current Good Manufacturing Practice (cGMP), and ensuring consistency and quality for end-user requirements are necessary steps to meet these specifications and regulations.

These key considerations, with optimizing these factors, process equipment can achieve dynamic process optimization in IPA dehydration, leading to a reliable and consistent pervaporation process that meets user requirements, is cost-effective, and environmentally friendly.

Process Configuration and Operation  – Engineering Case Study

  • 3,000T/A IPA Dehydration System
  • Target: 99.9wt% purity, Clear and transparent.
  • Keep the moisture content below 200ppm.
  • Flux 85kg/m2/hr;
  • 98 tubular modules
  • Feed pretreatment: 10μm filtration, activated carbon
  • Temperature: 65-85°C; Vacuum: 0.05bar; Circulation flow: 420 m3/hr
  • Energy consumption: 25kWh/m3 permeate
  • Feed Pump: Centrifugal; Circulation Pump
  • Vacuum system: Gear pump
  • PLC/DCS controlled; Automated TMP, flow rate, temperature control
  • Online analyzers for feed, retentate, permeate quality monitoring
  • Payback period: 2 years
  • Meeting Purity Specifications and Regulations

With the rapid development of semiconductor technology, the demand for ultra-clean and high-purity reagents is increasing.

When embarking on the process design and control of a 99.9% Isopropyl Alcohol (IPA) production system, there are several key aspects to consider.

Here are some important factors to explore:

  1. Raw Materials and Feedstock: Gather information on the quality and specifications of the raw materials used in IPA production. This includes the purity and concentration of the initial feedstock and any impurities or contaminants present. Understanding the composition of the feedstock is crucial for designing the appropriate purification processes.
  2. Purification Techniques: Investigate the purification methods employed to achieve the desired purity level of 99.9% IPA. This may involve distillation, fractional distillation, membrane separation or other separation techniques. Understanding the specific purification steps and the associated equipment is essential for process design and control.
  3. Reaction Chemistry: Familiarize yourself with the chemical reactions involved in the IPA production process. This includes understanding the reaction pathways, reaction kinetics, and any catalysts or conditions required for the reactions. This knowledge is vital for optimizing reaction conditions and ensuring efficient conversion.
  4. Process Flow Diagram: Develop a detailed process flow diagram (PFD) that outlines the sequence of operations, specific equipment used, and material flow throughout the IPA production system. This diagram provides an overview of the entire process, helping identify critical control points and potential bottlenecks.
  5. Equipment Specifications: Determine the specific equipment required for the IPA production process, such as reactors, distillation columns, heat exchangers, pumps, and control valves. Ensure that the equipment is capable of handling the desired production capacity and operating conditions while maintaining product quality.
  6. Process Control Strategy: Establish a process control strategy to ensure consistent production of high-quality 99.9% IPA. Identify key process parameters to monitor, such as temperature, pressure, flow rates, and concentrations. Define control limits and develop control loops to maintain the desired operating conditions.
  7. Safety Considerations: Prioritize safety in the design and control of the IPA production process. Identify potential hazards associated with the chemicals, equipment, and operating conditions. Implement appropriate safety measures, such as emergency shutdown systems, ventilation, and personal protective equipment.
  8. Environmental Impact: Assess the environmental impact of the IPA production process and explore ways to minimize it. Consider waste management, emissions control, and energy efficiency measures. Compliance with environmental regulations and sustainability goals should be a priority.
  9. Quality Assurance: Develop a robust quality assurance plan to ensure the consistent production of high-purity IPA. This may involve sampling and testing procedures, analytical methods, and quality control checks throughout the process.
  10. Process Optimization: Continuously evaluate and optimize the IPA production process to improve efficiency, reduce costs, and enhance product quality. Monitor process performance, analyze data, and implement changes as needed.

Integration of Distillation, Fractionation, and Membrane Separation:

The integration of these techniques can be achieved by incorporating multiple process units.

Here’s a possible sequence:

  1. The initial feedstock is first subjected to distillation to separate IPA from bulk impurities. The distillate, rich in IPA, is collected.
  2. The distillate is then directed to a fractionation column, where further separation occurs to remove impurities and obtain a higher-purity IPA fraction.
  3. The fractionated IPA stream can undergo a membrane separation process as a final purification step. The membrane system selectively removes remaining impurities, allowing the passage of purified IPA.
  4. The purified IPA is collected as the final product, meeting the 99.9% purity target.

During process integration, it is crucial to optimize operating conditions, including temperature, pressure, flow rates, and membrane properties, to achieve the desired purification level. Control systems should be implemented to monitor and adjust key parameters to maintain optimal performance.

Generally, the specific design and integration of these techniques will depend on the scale, capacity, and specific requirements of the IPA purification process. Detailed engineering calculations, simulations, and experimentation may be required to optimize the integration and achieve the desired purification target.

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