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Refinery Reactors
Published in James G. Speight, Refinery Feedstocks, 2020
Batch reactors are very versatile and are used for a variety of different unit operations (such as batch distillation, storage, crystallization, and liquid-liquid extraction) in addition to chemical reactions. Batch reactors represent an effective and economic solution for many types of slow reactions. In a batch reactor, good temperature control is achieved when the heat added or removed by the heat exchange surface is equal to the heat generated or absorbed by the process material. For flowing reactors made up of tubes or plates, satisfying the heat added to the heat generated relationship does not deliver good temperature control since the rate of process heat liberation/absorption varies at different points within the reactor. Controlling the outlet temperature does not prevent hot/cold spots within the reactor. Hot or cold spots caused by exothermic or endothermic activity can be eliminated by relocating the temperature sensor (T) to the point where the hot/cold spots exist. This however leads to overheating or overcooling downstream of the temperature sensor.
Fundamentals and Applications of Reaction Kinetics
Published in C. Anandharamakrishnan, S. Padma Ishwarya, Essentials and Applications of Food Engineering, 2019
C. Anandharamakrishnan, S. Padma Ishwarya
In a batch reactor, all the reactants are added to the reactor before commencing the reaction. The final product is removed after the completion of the reaction which is carried out under the desired conditions until the target conversion is attained. During the reaction, no material is added or withdrawn. Thus, the key variable in the operation of a batch reactor is the residence time for which the reactants are allowed to remain in the reactor to achieve the desired level of conversion. Typically, batch reactors are stirred tanks (Figure 8.2) attached to impellers, gas bubbles, or a pump. The stirrers facilitate the mixing of reactor contents. Owing to this simplicity of design, batch reactors are easy to be monitored and operated for almost all types of reaction. Temperature inside a batch reactor is regulated using internal cooling surfaces (coils or tubes), jackets, reflux condensers, or heat exchangers. A batch reactor is operated either isothermally or adiabatically.
Ideal Isothermal Batch Reactor
Published in Himadri Roy Ghatak, Reaction Engineering Principles, 2018
A batch reactor is essentially a vessel that holds the reacting system within its confines while the reactants chemically transform into products. Once filled, there is no entry of material into the vessel and no exit of material out of the vessel. Thus, the reacting system does not exchange material with its surroundings. Their importance and advantage lies in their flexibility and versatility. These are best suited for small production rates and/or multiple products from the same facility. Their major drawback is high operational cost compared to continuous reactors. Batch reactors are valuable in the experimental study of reacting systems before scale up. An ideal batch reactor is one that has no spatial variation of composition. In other words, at any given instant of time, the concentration of each of the chemical species is the same everywhere inside the reactor. Further, an isothermal batch reactor has constant temperature both with respect to time as well as with respect to position within the reactor. These ideal conditions may be approximated but not rigorously met in a real batch reactor. Nevertheless, the study of the hypothetical idealized system provides vital understanding that can be used for the real system as well. For gaseous-reacting systems, the reactor can be operated either at constant volume or at constant pressure. We start our analysis of the ideal isothermal batch reactor by writing a mole balance as follows:
Management, conversion, and utilization of waste plastic as a source of sustainable energy to run automotive: a review
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2018
Kiran Raj Bukkarapu, D. Siva Gangadhar, Y. Jyothi, Prasad Kanasani
The term 'pyrolysis' is derived from the Greek word ‘pyro’ (fire) and ‘lysis’ (break/decomposition). It is a process in which thermo-chemical decomposition of synthetic organic material occurs under the absence of oxygen at high temperatures (400°C–800°C). It is an endothermic reaction in which macro-molecules (polymers) are converted to simple ones (monomers) (Baskaran and Sathish Kumar 2015). The feedstock (waste plastic/waste tyre) is fed to the sizing machinery like crushers and cutters. The obtained material is graded into uniform size for easy handling. It is then fed to a reactor and heated in the absence of oxygen to a temperature of 400°C, for nearly four hours, at atmospheric pressure. The resulting products of pyrolysis are condensed to hydrocarbons which can be separated through fractional distillation. The pyrolytic gases yield different hydrocarbons of straight, branched, and cyclic aliphatic, cyclic aromatic compounds. The reactor shell should be strong enough in order to withstand the higher temperatures generated during pyrolysis. Several types of reactors have been developed so far which include fluidized bed reactor, batch/semi-batch reactor, fixed bed reactor, spouted bed reactor, microwave, and screw kiln type reactor (Jeng, Yin, and Li 2003; Syamsiro et al. 2014). Among all these, batch/semi-batch reactor is widely used owing to its simple design and ease of operation.
Model based evaluation of plant improvement at a large wastewater treatment plant (WWTP)
Published in Journal of Environmental Science and Health, Part A, 2018
Jakub Drewnowski, Anna Remiszewska-Skwarek, Francisco Jesus Fernandez-Morales
In order to accurately study the aeration requirements, the heterotrophic and the autotrophic bacterial respiratory activity were isolated and determined, by adding alil thiourea (ATU) as nitrification inhibitor. The nitrifying experiments were performed under anaerobic-aerobic conditions (two stage batch test) which better reflected the actual conditions occurring in the activated sludge bioreactors of the full-scale WWTP. Each experimental series, fall and spring seasons, comprised both types of batch tests including measurements (e.g. OUR, AUR and COD). Moreover, several parameters (pH, Temperature and ORP) were determined and recorded by using probes installed in the batch reactor and connected to the computer. Additionally, the total/soluble COD, NO3-N, NH4-N and PO4-P were analysed by Hach “test-in-tube” using Xion 500 spectrophotometer (Hach Lange GmbH, Germany). The Total Nitrogen (TN) concentrations were measured using TOC/TN analyser (SHIMADZU Corporation, Japan). All the chemical analyses, which were adapted by Hach Lange GmbH (Germany), and the gravimetrical procedures were performed in accordance with Standard Methods.[19]