chemical reactors

Chemical reactors are undoubtedly the most important part of the chemical, biochemical, polymer and petroleum process manufacturing processes. A chemical reactor is a container that converts raw materials into chemicals that we will make as products. A wide variety of useful and important products are produced by reactions that convert reactants into products. Safety, economy, and consistent operation of chemical reactors are the main factors that make chemical reactors better.

Almost all chemical and materials industries use reactors to convert raw materials or raw materials into products. Many of the materials used for clothing, housing, cars, appliances, construction, electronics, and healthcare come from processes that utilize reactors. Reactors are important even in the food and beverage industry or agricultural product processing. The production of ammonia fertilizers for growing crops uses chemical reactors that consume hydrogen and nitrogen. Pesticides and herbicides used in crop fields are also supported by chemical reactors. Some of the drugs that form the basis of modern medicine are produced by reactor fermentation. It makes sense that modern society is now better off using chemical reactors extensively.

The reactor can operate at low temperatures (e.g. the C4 sulfuric acid alkylation reactor operates at 108 C) and at high temperatures (toluene hydrodealkylation reactor running at 6008 C). Some reactors operate in a wide variety.

Types of Chemical Reactors

Batch Reactors

Batch Reactors. Source: https://encyclopedia.che.engin.umich.edu/Pages/Reactors/Batch/Batch.html

A batch reactor is a vessel in which reactants are charged initially and the reaction proceeds over time. The reactants are placed into the reactor and then allowed to react, and the products are formed in the reactor. The unreacted products and reactants are then removed and the process is repeated.

Batch reactors contain ports for injecting reactants and removing products, and are equipped with a heat exchanger or stirring system. Although batch reactors generally have a constant volume, some reactors are designed to maintain a constant pressure by varying the reactor volume.

Batch reactors are used in a wide variety of applications. Usually, they are used for liquid phase reactions which require a fairly long reaction time. Batch reactors are often found in the beverage and pharmaceutical industries.

AdvantagesDisadvantages
High conversions can be obtained by leaving the reactants in the reactor for a long time.High labor costs per unit of production.
The batch reactor jacket allows the system to change the heating or cooling power at a constant jacket heat flux.It is difficult to maintain large-scale production.
Versatile, can be used to make many products in a row.Long downtime for cleaning leads to periods of no production.
Good for producing a product in small batches while it is still in the testing phase.
Easy to clean

Continuous Stirred Tank Reactors (CSTR)

CSTR. Source: https://encyclopedia.che.engin.umich.edu/Pages/Reactors/CSTR/CSTR.html

Continuous stirred tank reactors (CSTR) are the most basic continuous reactors used in chemical processes. (CSTR) is an open system, material is free to enter or leave the system, which operates at steady state, where conditions inside the reactor do not change over time. The reactants are continuously introduced into the reactor, while the products are continuously removed.

The CSTR consists of a tank, usually of constant volume, and a stirring system for mixing the reactants. Feed and outlet pipes are available to introduce reactants and remove products. Stirring blades, also called agitators, are used to mix the reactants.

CSTR is most commonly used in industrial processes, especially in homogeneous liquid phase flow reactions, where constant agitation is required. They can be used alone, in series, or in batteries. CSTR is also used in the pharmaceutical industry as a loop reactor.

CSTR is often used in biological processes The CSTR shown below can be used for high density animal cell culture in research or production. Vessels are used for single use only.

AdvantagesDisadvantages
Good temperature control that easy to maintainConversion of reactants to products per reactor volume is smaller than that of other flow reactors
Low building costsThere is a dead zone, where no mixing occurs, can develop
Has a large heat capacityThe reactants may escape over the limit if the outlet is placed incorrectly
Easily accessible reactor interior

Plug Flow Reactors

Plug Flow Reactor. Source: https://encyclopedia.che.engin.umich.edu/Pages/Reactors/PFR/PFR.html

Plug flow or tubular reactors consist of a perforated pipe or tube through which the reactants flow. The reactor consists of a cylindrical tube with an opening at each end for the reactants and products to flow. These reactors are usually operated at steady state. The reactants are continuously consumed as they flow along the reactor. The reactants will move like a flowing clump of bubbles.

Plug flow reactors may be configured as one long tube or a number of shorter tubes. Their diameters range from a few centimeters to several meters. Diameter selection is based on construction costs, pumping costs, desired residence time, and heat transfer requirements. Usually, long small diameter tubes are used with high reaction rates and large diameter tubes are used with slow reaction rates.

AdvantagesDisadvantages
Easy to maintain as there are no moving partsReactor temperature difficult to control.
High conversion rate per reactor volume.Hot spots may occur within reactor when used for exothermic reactions.
Mechanically simple.Difficult to control due to temperature and composition variations.
Unvarying product quality.
Good for studying rapid reactions.
Efficient use of reactor volume.
Good for large capacity processes.
Low pressure drops.
Tubes are easy to clean.

One of the most common methods for designing a chemical reactor process system is to use Computational Fluid Dynamics (CFD), which is a method of solving fluid mechanics equations and even chemical reactions using a computer, so that comprehensive and detailed results are obtained. >> Click here to learn more about CFD!

Contributor: Daris Arsyada

By Caesar Wiratama

aeroengineering services is a service under CV. Markom with solutions especially CFD/FEA.

References:

https://encyclopedia.che.engin.umich.edu/Pages/Reactors/Batch/Batch.html (accessed on 14 May 2021)

https://encyclopedia.che.engin.umich.edu/Pages/Reactors/CSTR/CSTR.html (accessed on 14 May 2021)

https://encyclopedia.che.engin.umich.edu/Pages/Reactors/PFR/PFR.html (accessed on 14 May 2021)

https://www.google.co.id/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjZwP_21sjwAhXO5nMBHTJDDBUQFjAQegQIRBAD&url=http%3A%2F%2Frepository.um-palembang.ac.id%2Fid%2Feprint%2F9085%2F1%2FCHEMICAL_REACTOR_DESIGN_AND_CONTROL.pdf&usg=AOvVaw37cHVZQT4B-3efU5tREVFC (accessed on 14 May 2021)

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