Reactor is a kind of equipment to realize reaction process, which is widely used in chemical industryoil refining、metallurgyAnd other fields.The reactor is used to realize liquid-phase single-phase reaction process and liquid-liquid, gas-liquid, liquid-solid, gas-liquid solid, etcHeterogeneous reaction process。
The application of reactors began in ancient timeskiln It is an original reactor.There are various types of reactors in modern industry, such as blast furnace and converter in metallurgical industry;In bioengineeringFermentation tankAnd variousburner, are all different types of reactors.
Reactor is a kind of equipment to realize reaction process, which is used to realize liquid-phase single-phase reaction process and liquid-liquid, gas-liquid, liquid-solid, gas-liquid solid, etcHeterogeneous reaction process。Stirring is often set in the device（Mechanical mixing、Air agitationEtc.).When the height diameter ratio is large, multi-layer mixing blades can be used.When the materials need to be heated or cooled during the reaction, the jacket can be set at the reactor wall, or the heat exchange surface can be set in the reactorExternal circulationConduct heat exchange.
Flexible operation, easy to adapt to different operating conditions and product varieties, suitable for small batch, multi variety, long reaction time product production.The disadvantage of batch kettle is that it needs auxiliary operations such as loading and unloading, and the product quality is not easy to be stable.But some reaction processes, such as some fermentation reactions andpolymerization, implementcontinuous production There are still difficulties, and the intermittent kettle is still used up to now.
Intermittent operationThe reactor system adds raw materials to the reactor at a certain ratio, and discharges the materials at a time after the reaction meets certain requirements.Continuous operationThe reactor system continuously adds raw materials and continuously discharges reaction products.When the operation reachesStationary stateThe composition, temperature and other state parameters of materials at any position in the reactor do not change with time.Semi continuous operationThe reactor is also called semi batch operation reactor, which is between the above two. Usually, one reactant is added at one time, and then another reactant is added continuously.After the reaction meets certain requirements, stop the operation and unload the materials.
The advantage of batch reactor is that the equipment is simple, and the same equipment can be used to produce a variety of products, especially suitable for small batch and multi variety production in pharmaceutical, dye and other industrial sectors.In addition,Batch reactorNo item exists inBackmixing, favorable for most reactions.The disadvantage is that auxiliary processes such as loading and unloading, cleaning, etc. are required, and the product quality is not easy to be stable.
)。The disadvantages of intermittent kettle can be avoided, but the stirring will cause the back mixing of fluid in the kettle.When stirring violently, liquid viscosity is low orAverage residence timeFor longer occasions, materials in the kettleflow patternCan be regarded asAll mixedStream,reaction kettleAccordingly, it is called full mixing kettle.On requestConversion rateIn case of high or series side reactionBackmixingPhenomenon is an adverse factor.This can be usedMulti reactor in seriesTo reduce the adverse effect of back mixing, and the reaction conditions can be controlled in separate kettles.
Mass production should adoptContinuous reactor。The advantages of continuous reactor are stable product quality and easy operation control.Its disadvantage is that there are different levels of back mixing in continuous reactors, which is an adverse factor for most reactions, and should be suppressed through rational reactor selection and structural design.
It refers to the reactor in which one kind of raw material is added at one time and another kind of raw material is added continuously. Its characteristics are between the intermittent kettle and the continuous kettle.
Feeding mode
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For those with more than two kinds of raw materialsContinuous reactorThe material flow direction can be concurrent or counter current.For equipment composed of several reactors in cascadeCrossflowFeeding, that is, one raw material passes through each reactor in turn, and the other raw material is added to each reactor separately.In addition to the flow outside, there are also raw materials added from one end (or both ends) of the reactor and added in sections.Staged feeding means that one raw material is added from one end, and the other raw material is added from different positions of the reactor in several sections. Cross flow can also be regarded as a staged feeding mode.The feeding method shall be determined according to the characteristics of the reaction process.
Heat exchange mode
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Most reactions have obvious thermal effects.In order to carry out the reaction under appropriate temperature conditions, it is often necessary to carry outheat transfer。There are indirect heat exchange and direct heat exchange.Indirect heat transfer refers to reaction material andHeat carrierDirect heat transfer refers to the direct contact between reaction material and heat carrier for heat transfer.yesExothermic reaction, which can be carried by reaction productsreaction heatTo heat the raw materials to reach the required reaction temperature, this reactor is called self heating reactor.
According to the heat exchange conditions in the reaction process, reactors can be divided into:
① Isothermal reactor: the reaction system temperature is equal everywhereIdeal reactor。The reaction heat effect is very small, or the heat exchange between the reaction material and the heat carrier is sufficient, or the heat feedback in the reactor is very large (such as violently stirredKettle reactor）This can be approximately regarded as an isothermal reactor.
② heat insulationAn ideal reactor with no heat exchange between the reaction zone of the reactor and the environment.The large industrial reactor without heat exchange device in the reaction zone can be approximately regarded as an adiabatic reactor when the heat exchange with the outside is negligible.
③ The non isothermal and non adiabatic reactor has heat exchange with the outside world, and there is also heat feedback in the reactor, but it can not reach the isothermal conditions, such as tubular reactorFixed bed reactor。
Heat exchange can be carried out in the reaction area, such as the stirred tank with jacket for heat exchange, or in the reaction area, such as the multi-stage reactor with interstage heat exchange.[1]
Operating conditions
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It mainly refers to the operating temperature and pressure of the reactor.Temperature is a sensitive factor affecting the reaction process, so it is necessary to select an appropriate operating temperature or temperature sequence so that the reaction process can be carried out under optimal conditions.For example, for reversibleExothermic reactionThe temperature sequence from high to low shall be adopted to give consideration toreaction rateandEquilibrium conversion rate(Seechemical equilibrium）。
The reactor can be operated under normal pressure, pressure or negative pressure (vacuum).The pressurized reactor is mainly used for the reaction process with gas participation. Increasing the operating pressure is conducive to accelerationGas phase reaction, for totalNumber of molesReduced gas phaseReversible reaction, it can improve the balance conversion rate, such assynthetic ammonia、Synthetic methanolEtc.Increasing the operating pressure can also increase the solubility of gas in liquid, so manygas-liquidreaction process 、Gas-liquid solid reaction processPressure operation is adopted to improve the reaction rate, such asParaxyleneOxidation, etc.
model selection
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For a specific reaction process, the selection of reactor should comprehensively consider technical, economic and safety factors.
In addition to the form of reactor,Reaction potThe operation mode and feeding mode of shall also be considered.For example, for processes with series or parallel side reactions, staged feeding may be better than single feeding.Temperature sequence is also an important factor for reactor selection.For example, for exothermicReversible reactionThe temperature sequence from high to low shall be adoptedHeat exchange reactorThe temperature sequence of the reactor can be rationalized.Reactor atProcess industryIt plays an important role in production.As far as the construction investment and operation cost of the whole process are concerned, the proportion of reactors may not be very large.However, its performance and operation have an important impact on the pre-treatment, output and quality of products, raw material consumption, energy consumption and product cost.Therefore, the research and development of reactors is of great significance for the development of various process industries.
