Plug flow reactor advantages and disadvantages


  • Journal Archive
  • Types of Reactors
  • Advantages of continuous flow production
  • Advantages of continuous flow production
  • Industry goes with the Flow
  • Applications
  • Journal Archive

    This ensures that highly exothermic reactions can be safely controlled. Continuous Flow Production allows small amounts of hazardous intermediate to be formed at any instant and then reacted to achieve the desired and less hazardous product. The inventory of hazardous material being processed at any one time can be minimised in flow when compared with batch. Safer reactions involving gas evolution Reactions that evolve gas are much safer if flow as the maximum rate of gas evolution is limited by the rate at which the reagents are pumped.

    Safer reactions at high pressures Flow reactors do not require a head space. The pressure within the reactor is controlled by a device called a back pressure regulator BPR and not by pressurising the gas within the head space as with traditional batch reactors. Reaction conditions simply not possible in batch reactors Reaction times in Continuous Flow Production can be precisely controlled down to a few seconds or less, allowing the rapid generation of reactive intermediates to be reacted immediately in another reaction step.

    Multistep, telescoped reactions provide a route to complex organic transformations avoiding the steps of isolating intermediates. This allows reaction temperatures well above the normal boiling point of the solvents e. Rapid route to scale-up The difficulties of scaling up batch reactions are well documented. Continuous Flow Production can be scaled up much more easily, simply by running for longer or by using higher flow rates and correspondingly larger reactors.

    However, the requirements for mass transfer and heat transfer in the larger reactors must be considered. Photochemical reactions in continuous flow production Traditional batch photochemical reactors have limitations particularly when scaling up photochemical reactions.

    Combining continuous flow with photochemistry provides a powerful synthetic tool for accessing reaction pathways utilizing singlet and triplet states. The key benefits of continuous flow are; product of the reactions are removed from the irradiated area, problems of photon penetration depth and mixing can be largely avoided, reactions are safer as the volume of solvent in proximity to a hot lamp is significantly reduced.

    Integration of downstream processes Downstream processes, work-up and analysis can be integrated into the flow process. Operations such as aqueous work up, metal scavenging columns or ion exchange resins can be added into the flowing process. Parameters can be rapidly varied, stoichiometry reaction time, temperature.

    A solvent is used to clean the reactor between separate reactions. In this way kinetic data can be rapidly derived. To read the article please visit the website via the link:.

    Types of Reactors

    Types of Reactors July 8, Types of Reactors:- A chemical reactor is a process equipment where in chemicals are fed in order to make them chemically react with each other for the purpose of making a desired product. Chemical reactors are designed in such a way to increase the net present value for a given reaction and it is done by ensuring highest efficiency to output the desired product.

    R Plug Flow Reactor P. R Semi-Batch Reactor 1. Batch Reactor A batch reactor is a closed vessel in which reactions happen and it is a non-continuous type of reactor. The reactants are fed in to the reactor all at once initially. The vessel contains an agitator. The purpose of the agitator is to mix the reactants thoroughly so that the contact makes them react together efficiently and produce products.

    Types of Reactors:- Batch Reactor Types of Reactors:- Batch Reactor In order to handle exothermic reactions the batch reactor is often equipped with cooling coils. In order to work with endothermic reactions the batch reactor has provisions for heating the reaction mixture. The batch reactor is a non-steady, transient reactor. It means the extent of conversion within the reactor depends on time. Due to agitator the batch reactor is highly uniform in nature.

    It means the extent of conversion does not depend on location within the reactor. At a given time the extent of reaction at any location of the volume of the reactor will be equal to each other.

    Advantage The greatest advantage of operating a batch reactor is its versatility. Same batch reactor can be used to chemically react quite different variety of reactants. Batch reactors are especially used in cases where the reaction produces lots of products.

    Batch reactors are often used in labs to study kinetics of the liquid phase reaction systems. Disadvantage The disadvantage of batch reactor is that it requires lots of labour force to constantly charge reactants, discharge products and then to clean the reactor for the next batch. Continuous Stirred Tank Reactor C. R A continuous stirred tank reactor C. R is also often called a mixed flow reactor M.

    In this reactor also the reaction occurs in a closed tank. The tank also has agitator in order to mix the reactants thoroughly. It is different from batch reactor in the sense that the name itself indicates it is continuous type of equipment. Types of Reactors:- Continuous Stirred Tank Reactor The reactants enter the reactor at a certain mass flow rate, the react inside the vessel for sometime dictated by the space time of the reactor and then they form products.

    The products flow out of the reactor at the same mass flow rate. One space time is the time required to process one reactor volume.

    The C. R is steady sate equipment. It means the extent of conversion does not depend on the time. The agitator makes the concentration uniform throughout the reactor. It means the extent of conversion does not depend on the location also. The extent of conversion depends on the volume of the reactor. Advantage The biggest advantage of using a C.

    R in industries is that it can produce a large amount of products and being a continuous steady state reactor the reactor can keep on operating hours on end. Disadvantage The disadvantage is that a C. R cannot be used for reactions which have very slow kinetics because it will require a reactor of very large volume. The fabrication and operational cost of the reactor may make it infeasible.

    Batch reactor is used in this case. Plug Flow Reactor P. R A plug flow reactor P. R is also sometime called a continuous tubular reactor C. In an idealised model, the profile of the reaction mixture can be considered to be made up of a number of plugs and each plug having a uniform concentration. R The idealized P. R model has an assumption that there is no axial mixing.

    It means that there is no back mixing inside the reactor. Advantage The advantage of P. R over C. R is that for same space time and same level of conversion, the volume of the P. R is relatively smaller than a C. R, It means a smaller space is needed for the reactor also for same volume of reactor the level of conversion is higher in P. R than in C. Often the P. R are used to study kinetics of gas phase catalytic reactions. Disadvantage The disadvantage is that if we carry out an exothermic reaction in a P.

    R then the temperature gradients are difficult to control. The operational and maintenance cost of a P. R are also greater than a C. Semi-Batch Reactor A semi-batch reactor is a semi-flow reactor. It is a modification of batch reactor. It is also a closed vessel which contains agitator for the purpose of mixing the reactants thoroughly. The difference is that one of the reactants is charged completely initially in the reactor and the other reactant is charged continuously in the reactor as the time progresses.

    Types of Reactors:- Semi-Batch Reactor Advantage The advantage of using a semi-batch reactor is that if we are carrying out multiple reactions then we have a greater control over yield or selectivity of the products. This reactor is extremely useful when we are carrying out an exothermic reaction as the continuous flow of the other reactant can be varied to better control the exothermic reaction Disadvantage If we want to scale up the semi-batch process then disadvantage over the continuous process reactors C.

    R and P. R is that capital costs per unit scales up relatively a lot. Greater man power is required to charge and discharge the contents of the reactor, to clean blades, to clean reactors etc.

    Chemical reactors are designed in such a way to increase the net present value for a given reaction and it is done by ensuring highest efficiency to output the desired product. R Plug Flow Reactor P. R Semi-Batch Reactor 1. Batch Reactor A batch reactor is a closed vessel in which reactions happen and it is a non-continuous type of reactor. The reactants are fed in to the reactor all at once initially. The vessel contains an agitator. The purpose of the agitator is to mix the reactants thoroughly so that the contact makes them react together efficiently and produce products.

    Advantages of continuous flow production

    Types of Reactors:- Batch Reactor Types of Reactors:- Batch Reactor In order to handle exothermic reactions the batch reactor is often equipped with cooling coils. In order to work with endothermic reactions the batch reactor has provisions for heating the reaction mixture. The batch reactor is a non-steady, transient reactor.

    It means the extent of conversion within the reactor depends on time. Due to agitator the batch reactor is highly uniform in nature. It means the extent of conversion does not depend on location within the reactor. At a given time the extent of reaction at any location of the volume of the reactor will be equal to each other. Advantage The greatest advantage of operating a batch reactor is its versatility. Same batch reactor can be used to chemically react quite different variety of reactants.

    Batch reactors are especially used in cases where the reaction produces lots of products.

    Advantages of continuous flow production

    Batch reactors are often used in labs to study kinetics of the liquid phase reaction systems. Disadvantage The disadvantage of batch reactor is that it requires lots of labour force to constantly charge reactants, discharge products and then to clean the reactor for the next batch. Continuous Stirred Tank Reactor C. R A continuous stirred tank reactor C. R is also often called a mixed flow reactor M.

    In this reactor also the reaction occurs in a closed tank. The tank also has agitator in order to mix the reactants thoroughly. It is different from batch reactor in the sense that the name itself indicates it is continuous type of equipment. Types of Reactors:- Continuous Stirred Tank Reactor The reactants enter the reactor at a certain mass flow rate, the react inside the vessel for sometime dictated by the space time of the reactor and then they form products.

    The products flow out of the reactor at the same mass flow rate. One space time is the time required to process one reactor volume. The C. R is steady sate equipment. It means the extent of conversion does not depend on the time. The agitator makes the concentration uniform throughout the reactor.

    It means the extent of conversion does not depend on the location also. The extent of conversion depends on the volume of the reactor. It also has excellent fluid properties which minimises diffusion limitations, to give an effective heterogeneous biocatalyst which is suitable for use in batch reactions and flow chemistry applications. The enzyme can be stripped off and the support reused. Examples were given where EziGTM-lipase in flow outperforms the commercially available catalyst 7 — The phase separator from Zaiput Flow Technologies was installed at the outlet of the G1 reactor to separate the organic phase from the aqueous phase.

    Within ten seconds, the 1H-NMR spectrum was obtained which allowed for an accurate monitoring of the reaction processing. In recent years photochemistry has seen a revival thanks to the advent of photoredox catalysis, development of irradiation sources and continuous flow reactors.

    The HANU-reactor is a unidirectional continuous flow plate reactor equipped with static mixing elements and is scalable by widening the process channel. The unit will enable scale-up of photochemical processes that were developed and optimised in the laboratory HANU-reactor. Full implementation of the pilot reactor in a GMP environment will follow in InnoSyn has a range of innovative technologies falling film photoreactor, cryogenics, continuous flow reactors and mixers, three-dimensional 3D metal printed assets for challenging chemistries catalytic hydrogenations, catalysed deuterations, enzymatic resolutions, asymmetric transformations, preferential crystallisations, photochemistry racemisation of quaternary carbon centre and organometallics.

    He showed 3D printed flow reactors and static mixers with intricate details possible in mm sized channels giving full flexibility. He gave several examples for instance, Matteson reaction where flow reactors were used from laboratory to full scale demonstration. Computational fluid dynamics CFD modelling for the intense mixing in the agitation zone was shown.

    He gave other examples of flow operation and companies for example Lilly, GSK and Vertex Pharmaceuticals, USA who are incorporating continuous into manufacturing operations. He gave examples of rare metal recovery liquid-liquid extraction with reduced processing compared to mixer settlerhomogeneous liquid-liquid reaction and mentioned gas to liquids for gas-liquid-solid reactions.

    The capabilities include liquid-liquid, gas-liquid processes, catalysis homogeneous and heterogeneous processessolid-liquid slurry and downstream processing. The FloWorks facility will be a m2 industry-facing facility for flow chemistry due for completion by the end of November The facility will house up to eight researchers and is intended to be a collaborative space for chemists and engineers from academia and industry to facilitate technology transfer solutions for continuous chemical manufacturing.

    The catalytic static mixer CSM technology was shown as a tubular reactor system with static mixer inserts. The static mixers were produced using additive manufacturing techniques and were design optimised CFD and engineering fluid dynamics EFD for surface area, fluid flow pressure drop and heat and mass transfer.

    Industry goes with the Flow

    The surface morphology of the static mixers was developed by cold-spray, electrochemical and chemical coating techniques wash-coating, carbonisation. A prototype reactor was used for continuous hydrogenation showing selective hydrogenation of vinyl acetate to ethyl acetate. Nitro reductions were also highlighted, for example linezolid first oxazolidinone drug leading into the second generation synthesis of linezolid by Pfizer, USA He showed that no or negligible leaching of the metal from the static mixer occurred.

    He showed the combination of CSM with photocatalysts. The SpinPro Reactor is a continuous reactor that allows chemical reactions to take place in seconds in a highly controlled and safe manner.

    The claim is that it performs reactions under process intensified conditions resulting in high energy and resource efficiency, improved product quality and flexibility in production and development. The SpinPro Reactor is another type of spinning disc reactor rotor-stator type. Significantly large shear rates in the gasses and liquid can be induced, which in turn leads to a much larger interfacial area available for mass transfer and a higher degree of turbulence and micro mixing.

    In addition, the volume of the reactor is completely filled with liquid. The SpinPro technology is well suited for multiphase chemistry, liquid-gas, liquid-liquid or combinations. Furthermore, it can handle precipitation reactions and controlled emulsifications. Its services include assessment of flow reaction feasibility, design of prototypes, process definition and optimisation, equipment design and validation and technology transfer to production.

    Applications

    It has developed different types of equipment to support a wide range of reaction types and implemented processes on a wide range of scales. To the dismay of the audience he announced that there was a range of pump types for liquid and gas and there was no universal pump system that covered all applications. He showed the consequences of a pulsating feed producing erratic stoichiometric conditions in static mixers and capillaries, unwanted reactions and therefore lower yield of desired product Selecting a pump with the manitowoc police blotter pulsatile effects was advocated and the use of two or more pumps giving hydraulic interaction was shown.

    He did give solutions such as flow meters in a closed loop control. He advocated the use of micro annular gear pumps of the hermetic inert series giving high chemical resistance against oxidising and reducing media, acids and bases.

    They are hermetically sealed, long service life, wear-resistant, ultra-hard materials giving precise dosage low pulsation via rotary micro annular gear technology with no valves. He illustrated the use of pumps for feed modules and modular plants showing the example of a system used by GSK for an API production system made by Zeton, Canada. For continuous manufacture the requirements of at-line analysis require fast decision making.

    The panel included the speakers with questions and comments from the audience. There was agreement about the statement in the article that continuous processing at scale has primarily been about enabling reaction chemistry, while postprocessing and analytical remain in the very early stages of development and implementation. Digital and process analytical technology PAT were mentioned in this context as well as auxiliary equipment and supply chain issues.

    Data and control systems will be key as well as standardised systems, i. There were many stories regarding flow chemistry from the last ten years with more examples. Pharmaceutical companies appear to be using CMOs more big pharma is risk averse and CMOs have teams working on continuous.

    A big talking point was that many of the realised industrial processes employing continuous are based in China, while few were in Europe. This could be due to factors such as existing assets and the risk averse nature of the industry. A discussion point was also training, for example education for chemists undergraduate courses still rely on batch systems for practical training, can we have continuous examples in synthesis for undergraduate or graduate chemists?

    A theme that most of the panel agreed with was culture and integration of skills education requirement; use of teams: analytical chemists, organic chemists, process safety, mechanical and chemical engineers to work together. The mood of the panel was optimistic in that the last ten years had seen a shift towards continuous flow and although there was still learning required, more implementation of flow continuous chemistry by industry would be realised in the near future.

    Conclusions The key messages from the event: The main key advantage that the speaker s advocated for the use of flow chemistry or continuous processing was environment, health and safety EHS. This was emphasised in the majority of the talks The next ten years for flow chemistry is going to be crucial. There was optimism that flow is going to happen. This is more evident in China than Europe and there was a feeling that the pace would accelerate if examples from Europe are publicised.

    CMOs also commented that they were sometimes not allowed to publicise the route i. References 1. Pichon, Chem. Yasukouchi, A. Nishiyama and M. Mitsuda, Org. Process Res. Zotova, K. Hellgardt, G.

    Kelsall, A. Jessiman and K. Hii, Green Chem. Engelmark Cassimjee, and H. Knaus and F. Lechner, P. Soriano, R. Poschner, H. Hailes, J. Ward and W. Kroutil, Biotechnol. Engelmark Cassimjee, M. Kadow, Y. Wikmark, M. Svedendahl Humble, M. Rothstein, D. Rothstein and J. Gardiner, X. Nguyen, C. Genet, M. Horne, C. Hornung and J.

    Tsanaktsidis, Org.


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