Batch reactors are tanks used for chemical or biological reactions, where all ingredients are added at once. They are used for wastewater treatment, pharmaceutical production, and fermentation. Aeration and temperature control may be necessary. Sequential batch reactors are used in wastewater treatment plants, while fed-batch reactors combine batch and continuous reactors.
Batch reactors are tanks used to contain chemical or biological reactions. The term “batch” distinguishes this type of reactor from continuous reactors: in a batch reactor, all the necessary ingredients are put into the tank and the chemical reaction or fermentation is allowed to take place, while in a continuous reactor, the ingredients are continuously fed into the tank. Batch reactors are used for processes such as wastewater treatment, pharmaceutical production and the fermentation of various products.
The simplest type of batch reactor consists of only a tank with holes in the top for reactant entry and product removal, although some type of stirring mechanism should also typically be included. A jacket that fits over the tank can also be used for temperature control. Batch reactors may also require some type of aeration system.
Adding ingredients to a batch reactor is known as “charging” and is the first step in running a batch reaction. The reactor user calculates the amount of each ingredient needed to produce the desired product, based on chemical reaction formulas or microbial growth formulas. Similar calculations allow the user to determine how long the reaction will take. Once the reactor is charged, it can be left mostly alone while the reaction takes place. The user may need to monitor the temperature and aeration within the reactor, depending on the type of reaction.
A common type of batch reactor is a sequential batch reactor or sequential batch reactor, both abbreviated SBR. SBR reactors are typically used in wastewater treatment plants for activated sludge processing, a procedure that uses a wide range of bacteria to remove contaminants from water. The bacterial cultures grow in a thick sludge, which is where the procedure gets its name.
For batch reactor sequencing, a reactor containing activated sludge is first filled with wastewater. The sludge and water are aerated to add oxygen and to allow the components to mix, both of which help the bacteria feed on contaminants in the wastewater. Once the bacteria have consumed most of the nutrients in the water, they begin to die and aeration is shut off so the sludge can settle to the bottom of the reactor. After the sludge has settled, the treated wastewater is removed from the reactor and sent to the next stage of the treatment process.
Fed-batch reactors are a combination of batch and continuous reactors. In a fed-batch reactor, the limiting substrate, the ingredient that is depleted first during the reaction, is continuously fed into the reactor. The other ingredient is added at the start of the reaction and none is added as the reaction progresses.
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