Continuous stirred tank reactor

Types of Continuous Stirred Tank Reactors

A typical continuous stirred tank reactor consists of a cylindrical tank with an in-built impeller that stirs the contents of the tank. A continuous stirred tank reactor (CSTR) comes in different variations to suit specific industrial needs.

• Horizontal CSTRs: Horizontal continuous stirred tank reactors are the most common CSTR types available. They have a horizontal cylindrical tank, an impeller, a feed inlet, a product outlet, and an auxiliary system. The reactor feeds and discharges products from the top and bottom parts of the tank, respectively. The horizontal position of the tank makes it easy to scale up production by increasing the width of the tank. This also allows the uniform mixing of materials to take place. In various industries such as the chemical, food and beverage, and wastewater treatment, manufacturers use horizontal CSTRs for different chemical processes and reactions.
• Multi-stage Horizontal CSTRs: Essentially, multi-stage horizontal CSTRs have two or more horizontal continuous stirred tank reactors that are connected in a sequence. This allows the product to go through different horizontal CSTRs and attain better chemical reaction and processing. Also, the auxiliary systems of the reactors can be interconnected, and this creates a more continuous production process. The part where the substances mix can also be increased through interconnecting the auxiliary systems. The combination of two or more continuous stirred tank reactors into one system is an efficient way of scaling up industrial production. It eventually results in economic productivity. Furthermore, the multi-stage horizontal CSTRs are suitable for big-scale industries and for use in the chemical industry, food and beverage industry, and environmental industry, among others.
• Vertical CSTRs: Manufacturers use vertical CSTRs when space-saving is a high priority. Additionally, the vertical impeller axes create shorter mixing times, which improve reaction speed. Like the horizontal variants, vertical CSTRs have similar components. However, product and feed entry points are in the upper and lower sections of the tank, respectively. Operators can easily maintain and clean vertical CSTRs. Furthermore, accessibility is easy. For specific tasks that need quick turnaround times, horizontal CSTRs are preferable over their horizontal counterparts.
• Multi-stage Vertical CSTRs: Just like the multi-stage horizontal CSTR, the multi-stage vertical CSTR also has two or more vertical continuous stirred tank reactors that are connected in a sequence. The combination of two or more vertical reactors into one system creates a more continuous production process and enhances the reaction efficiency. The vertical space-saving design of the multi-stage vertical CSTRs makes them suitable for use in industrial areas that have limited space, and they need efficient production facilities. In addition, the system is an ideal option for scaling up industrial production and meeting big-scale demands.

Specification & Maintenance

The working volume of a continuous stirred tank reactor is equal to or less than the total volume of the reactor. The following specifications should be considered when purchasing a CSTR:

• Height-Diameter Ratio (H: D)

  The ratio of height to diameter in a CSTR can affect mixing efficiency, heat transfer, and reaction kinetics. Hemispherical head CSTRs offer uniform flow patterns and good mixing but may have a high H:D ratio. The high H:D ratio can enhance heat transfer and simplify the separation process.

• Location of Agitator and Outlet

  The location of the agitator and outlet in the CSTR can affect the mixing efficiency and the residence time distribution of the reaction mixture. Off-centered agitators can enhance mixing and reduce dead zones, while multiple outlets can improve throughput and flexibility for downstream processing.

• Insulation and Cladding

  Insulation and cladding in a CSTR can improve energy efficiency and reduce heat loss. Insulation keeps the reaction mixture at the desired temperature and cladding protects the reactor from environmental factors like moisture and UV radiation.

Maintenance

The CSTR needs to be cleaned and inspected periodically to ensure it works well and prolong its service life. The maintenance steps are as follows:

• Preparation

  First, prepare the tools, such as brushes, clean water, and protective gear. Then, shut down the reactor, cut the power and ventilate the site to ensure safety.

• Cleaning

  Start from the outside of the reactor, use clean water and brushes to wash the dirt and deposits on the surface, and make sure to clean the inlet and outlet. Then, clean the stirrer and reactor wall using clean water and detergent to remove the remaining materials and stains thoroughly. Pay more attention to the areas that are not easily reached. Finally, rinse the detergent thoroughly with clean water, and make sure no residue is left.

• Drying

  Use clean water to wipe the interior of the thoroughly cleaned reactor, and use a dry cloth to wipe the water. Then, keep the vent open for a while to dry it completely. Or use a hairdryer or heat gun to blow it dry. Ensure everything is completely dry before closing the lid.

• Inspection

  After cleaning the CSTR, it's time to check various parts to see if there's any wear and tear or loose areas. The power cables need to be checked for security and wear; the stirrer bearings and seals should be smooth and well functioned. The cleaning process will be easier if the user is familiar with the structure of the CSTR.

• Other Parts

  In addition to the CSTR, the ancillary components also need maintenance. There should be no air leakage or water leakage in the pipes, and the valves need to be flexible and lubricated. The electric components like contactors and relays should be dry and clean.

Applications of CSTRs in various industries

Continuous stirred tank reactors are being used in various industrial applications, including the following:

• Chemical industry

  CSTRs are primarily used to manufacture a wide array of chemicals ranging from organic chemicals, inorganic chemicals, fine chemicals, household chemical products, specialty chemicals, and many more. It's estimated that over 60-70% of the chemical reactions taking place in chemical industries use CSTRs. This illustrates just how important and useful these types of reactors are.

• Pharmaceutical industry

  The drug that people take daily are produced through chemical reactions that occur inside of a continuous stirred tank reactor. Drug manufacturers and biotech companies produce antibiotics, vitamins, anti-depressants, anti-inflammatories, and more using CSTRs. The good thing about using these reactors is that they provide a stable environment where precise parameters can be maintained. This allows for consistent product quality - which in this case is important for human health.

• Food and beverage industry

  This is yet another area where continuous stirred tank reactors shine. They are employed in the large-scale production of dairy products such as ice cream and cheese, fruit juices, sauces, jams, liquors, and many other edible items. CSTRs help keep preservatives, flavoring substances, and fermentation microorganisms active to extend the shelf life of these products. Additionally, fermentation processes for products like ethanol and citric acid take place in CSTRs.

• Energy industry

  CSTRs play a vital role in the production of biofuels such as biodiesel and bioethanol from renewable biomass sources like vegetable oils, sugarcane, and corn. They are also used in wastewater treatment plants to stabilize organic matter through anaerobic digestion, thereby reducing pollutants before discharge into water bodies.

• Plastic and Polymer industry

  Continuous stirred tank reactors are used to produce free radical graft copolymer latex emulsions and other polymer dispersions for plastic manufacturing. Those polymer products include PVC plastics. The latex emulsion is polymerized in the CSTR before being transferred to another piece of equipment for further processing. Aside from the plastic mentioned above, numerous other plastic products are made through continuous stirred tank reactors.

• Textile industry

  CSTRs are employed for the polymerization of synthetic fibers like polyester and nylon. Such continuous stirred tank reactors not only guarantee that the reaction is uniform throughout, but they also offer flexibility in processing different kinds of feedstocks. This even includes the ones that are acidic or alkaline.

How to Choose Continuous Stirred Tank Reactors

When buying an industrial stirred tank reactor, buyers need to consider several factors such as the size, shape, material, mixing mechanism, temperature control system, safety features, and budget.

Firstly, they need to determine the volume of the reactor they require for their processes. The size of the reactor will affect the volume of the products that can be produced. They also need to decide on a suitable geometry for the reactor, as this will affect the flow and mixing efficiency.

Generally, the material of the reactor is important when it comes to resistance to corrosion and high temperatures. Buyers should get reactors that can withstand their production processes' temperature and pressure requirements. Those with sensitive chemical processes can look for reactors with temperature control features like cooling jackets or insulation.

Moreover, the mixing mechanism is also essential to the efficiency of the production process. Consider the type of stirrer and motor required for the specific application. Consider the energy consumption of the reactor and look for models that have efficient motors.

Continuous stirred tank reactors may come with various safety features, such as pressure relief valves, emergency stop buttons, or fire-resistant materials. These safety features help to reduce the risks associated with handling chemicals and operating industrial equipment.

Finally, the buyer should consider the maintenance and cleaning requirements of the reactor. They should choose a model that is easy to clean and comes with replaceable parts.

Finally, get continuous stirred tank reactors from reputable vendors to ensure their quality and safety compliance certifications. Check the return policy to be on the safe side in case of a product defect.

Continuous stirred tank reactor Q & A

Q1: Can someone control temperature and pH in a continuous stirred tank reactor?

A1: Yes. An advantage of using the CSTR is the ability to control different environmental conditions inside the reactor. There are CSTRs with external jackets where users can control temperature by passing hot water or steam. Also, there are external devices for controlling pH in a CSTR and other parameters like pressure and oxygen content.

Q2: What are the applications of a continuous stirred tankreactor?

A2: The CSTR is popular in industries like chemical, food, and pharmaceutical. Citric acid, ethanol, and acetic acid are some chemicals produced in CSTR. The CSTR is also a good model to study the behavior of microorganisms and enzymes. Therefore, it can be used for the continuous production of organic compounds by microorganisms or enzymes. When used with a controller, the CSTR can also be a digesting reactor for waste treatment.

Q3: Is there a规模大 that a CSTR can have in the continuous production of a chemical?

A3: The scale of a CSTR can be very large depending on the required flow rate of substrate input and product output. There are industrial CSTRs with a few meter diameters that are used to produce chemicals. The search for more efficient and more economical CSTRs is on.

Q4: What's the ideal mixing speed for a continuous stirred tank reactor?

A4: There is no ideal mixing speed suitable for every continuous stirred tank reactor. The mixing speed will depend on the size of the stirrer, the size of the reactor, the nature of the material to be mixed, and the objective of mixing. Usually, the mixing speed is between 1 and 5 m/s. Engineers test the mixing speed before starting the continuous production process.

Q5: Can someone custom the continuous stirred tankreactor?

A5: Yes. There are different types and models of CSTR available. Users can ask the manufacturer to customize the size or replace a device like a stirrer or heater for their particular requirements.