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Refinery Reactors
Published in James G. Speight, Refinery Feedstocks, 2020
The most familiar form of the continuous reactor of this type is the continuous stirred-tank reactor (CSTR) (Figure 8.1), which is essentially a batch reactor used in a continuous flow. In fact, the reactor is better described as a batch reactor equipped with an impeller or other mixing device to provide efficient mixing. In chemical engineering the name continuous stirred-tank reactor is often used to refer to an idealized agitated-tank reactor used to model operation variables required to attain a specified output. In flow chemistry, a continuous stirred-tank reactor equipped with features to continuously feed and exhaust reactants is an example of a mechanically mixed flow reactor. A continuous stirred-tank reactor often refers to a model used to estimate the key unit operation variables when using a continuous agitated-tank reactor to reach a specified output. The behavior of a continuous agitated-tank reactor is often approximated or modeled by that of a continuous stirred-tank reactor. All calculations performed with continuous ideally stirred-tank reactors assume perfect mixing. The disadvantage with a single-stage continuous stirred-tank reactor is that it can be relatively wasteful on products during start-up and shut-down. The reactants are also added to a mixture that is rich in product. For some types of processes, this can have an impact on quality and yield. These problems are managed by using multistage continuous stirred-tank reactors. At the large scale, conventional batch reactors can be used for the continuous stirred-tank reactor stages.
Chemically Reacting Flows
Published in Greg F. Naterer, Advanced Heat Transfer, 2018
In chemical reaction engineering, two common types of reactors are batch and continuous reactors. A batch reactor is a tank with a mixer and heating or cooling system. Continuous reactors have inflow and outflow streams that typically bring in reactants and move the resulting products through an exit stream. An exothermic reactor releases heat and therefore requires a cooling system to maintain a uniform temperature, whereas an endothermic reactor requires heat input to drive the chemical reaction. The residence time is an important parameter for incoming reactants in continuous reactors. It characterizes the amount of time a reactant spends inside a reactor before it reacts to the product(s).
CSTR and BSTR Chemical Reactors
Published in Béla G. Lipták, Optimization of Industrial Unit Processes, 2020
Two types of reactors are used in chemical plants: continuous reactors and batch reactors. Continuous reactors are designed to operate with constant feed rate, withdrawal of product, and removal or supply of heat. If properly controlled, the composition and temperature can be constant with respect to time and space. In batch reactors, measured quantities of reactants are charged in discrete quantities and allowed to react for a given time, under predetermined controlled conditions. In this case composition is the function of time.
Continuous methyl ester production with low frequency ultrasound clamps on a tubular reactor
Published in Biofuels, 2021
Krit Somnuk, Tanongsak Prasit, Dunyawat Phanyusoh, Gumpon Prateepchaikul
At a methanol content of 20 vol.% (Figure 3d), the methyl ester purity profiles with 4, 6, 8, 10 and 12 g L−1 KOH were as described in a previous paper [20]. Four types of continuous reactor: plug flow reactor (PF), static mixer reactor (SM), ultrasound clamp on tubular reactor (US), and static mixer combined with ultrasound (SM/US) were tested. The results showed that the US reactor was superior to the other reactor types tested, based on methyl ester purity in biodiesel produced from RPO. In the present study, the purity of the methyl ester increased along the whole length of the reactor tube as the KOH loading increased from 4 to 12 g L−1. Moreover, the methyl ester purity increased to 37.5 wt.%, 45.4 wt.%, 81.4 wt.%, 80.8 wt.% and 87.3 wt.% with 5, 10, 15 and 20 vol.% methanol, respectively, by only 100 mm reactor length. With KOH loadings of 4 and 6 g.L−1, the methyl ester reached its equilibrium level by 600 mm reactor location, and the methyl ester purity reached its equilibrium level by 500 mm of the reactor tube for KOH loadings of 8, and 10 g.L−1. With the highest catalyst level of 12 g.L−1, the methyl ester purity rapidly increased and reached its equilibrium with only 200 mm reactor length, showing higher purity methyl ester than with all the other KOH loadings. With 20 vol.% methanol, the maximum purities of methyl ester were 93.3 wt.%, 96.0 wt.%, 95.6 wt.%, 96.6 wt.% and 99.0 wt.% for KOH loadings of 4 g.L−1 (at 800 mm), 6 g.L−1 (at 800 mm), 8 g.L−1 (at 700 mm), 10 g L−1 (at 900 mm), and 12 g L−1 (at 700 mm), respectively. However, the purity of methyl ester decreased by 5%, 4%, 4%, 3% and 0%, respectively, when compared to the highest purities achieved with 10 vol.% methanol (or 2.2:1 M ratio of methanol to RPO), because the KOH concentration was diluted by excessive methanol contents of 15 vol.% (3.3:1 M ratio) or 20 vol.% (4.4:1 M ratio) when transesterification was accelerated by the low frequency ultrasound.