The center of any chemical process is the reactor, where chemical reactions are carried out to transform feeds into products. Reactor design is a vital step in the overall design of a process. It is important to ensure that the equipment specified will be capable of achieving the desired yields and selectivity. In a batch reactor, the reagents are added together and allowed to react for a given amount of time. The compositions change with time, but there is no flow through the process.
Additional reagents may be added as the reaction proceeds, and changes in temperature may also be made.
Reactors and inductors
Products are removed from the reactor after the reaction has proceeded to completion. A PFR with tubular geometry has perfect radial mixing but no axial mixing. Equation for PFR is given by:.
This equation can be integrated along the length of the reactor to yield relationships between reactor resident time and concentration or conversion. The stirred tank reactor models a large scale conventional laboratory flask and can be considered to be the basic chemical reactor. In a CSTR, shown in Figure 1, there is no spatial variation- the entire vessel contents are at the same temperature, pressure, and concentration. Therefore the fluid leaving the reactor is at the same temperature and concentration as the fluid inside the reactor.
Some of the material the enters the reactor can leave immediately, while some leaves much later, so there is a broad distribution in residence time as shown in Figure 1.
More information on stirred tanks can be found in the Mixing section. The design of the reactor should not be carried out separately from the overall process design due to the significant impact on capital and operating costs on other parts of the process Towler and Sinnott, Out of all process equipment, reactor design requires the most process input data: reaction enthalpies, phase-equilibrium constants, heat and mass transfer coefficients, as well as reaction rate constants.
All of the aforementioned parameters can be estimated using simulation models or literature correlations except for reaction rate constant constants, which need to be determined experimentally Towler and Sinnott, A major determining factor in reactor type selection is the choice of operating conditions.
Optimal process operation usually involves optimizing process yield and not necessarily reactor yield. Based on the preliminary economical analysis a target range of yields and selectivities can be chosen. The final reaction conditions must be verified experimentally to ensure target yields and selectitivities are realized Towler and Sinnott, If the desired product is to be produced by a biochemical reaction the chosen conditions must maintain the viability of the biological agent e.To browse Academia.
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Some content that appears in print may not be available in electronic formats. For more information about Wiley products, visit our web site at www. Wiley Bicentennial Logo: Richard J. Includes index. ISBN cloth 1. Chemical reactors—Design and construction. A vast variety of useful and essential products are generated via reactions that convert reactants into products. Much of modern society is based on the safe, economic, and consistent operation of chemical reactors.
In the petroleum industry, for example, a significant fraction of our transportation fuel gasoline, diesel, and jet fuel is produced within process units of a petroleum refinery that involve reactions. Reforming reactions are used to convert cyclical saturated naphthenes into aromatics, which have higher octane numbers. Light C4 hydrocarbons are alkylated to form high-octane C8 material for blending into gasoline.
Heavy longer-chain hydrocarbons are converted by catalytic or thermal cracking into lighter shorter-chain components that can be used to produce all kinds of products. The unsatu- rated olefins that are used in many polymerization processes ethylene and propylene are generated in these reactors. The polluting sulfur components in many petroleum products are removed by reacting them with hydrogen.
The chemical and materials industries use reactors in almost all plants to convert basic raw materials into products. Many of the materials that are used for clothing, housing, automobiles, appliances, construction, electronics, and healthcare come from processes that utilize reactors.
Reactors are important even in the food and beverage industries, where farm products are processed. The production of ammonia fertilizer to grow our food uses chemical reactors that consume hydrogen and nitrogen. The pesticides and herbicides we use on crop fields and orchards aid in the advances of modern agriculture.
Reactors and inductors
Some of the drugs that form the basis of modern medicine are produced by fermentation reactors.From the physics point of view, the main differences among reactor types arise from differences in their neutron energy spectra.
The main idea of the spectral shift is based on neutron spectrum shifting from the resonance energy region with lowest p — resonance escape probability at the beginning of the cycle to the thermal region with highest p — resonance escape probability at the end of the cycle.
From the neutronic utilization aspect, compensation by absorbing neutrons in a poison is not ideal, because these neutrons are lost. These fissile nuclei would contribute to obtain more energy from the fuel. There are many different ways of such regulation in the core. Some of current advanced reactor designs use for spectrum shift movable water displacers to change the moderator-to-fuel ratio.
A decrease in reactivity caused by fuel burnup is simply compensated by withdrawal of these movable water displacers while changing the moderator-to-fuel ratio. This makes it possible to completely exclude chemical shim from the operational modes. See also: Teplov, P. They are cooled and moderated by high-pressure liquid water e. The hot water that leaves the pressure vessel through hot leg nozzle and is looped through a steam generatorwhich in turn heats a secondary loop of water to steam that can run turbines and generator.
See also: Pressurized Water Reactor. Unlike a PWR, there is no primary and secondary loop. The thermal efficiency of these reactors can be higher, and they can be simpler, and even potentially more stable and safe. See also: Boiling Water Reactor. These reactors are heavy water cooled and moderated pressurized water reactors. PHWRs generally use natural uranium 0.
There is a heavy water as the moderator in this tank. The calandria is penetrated by several hundred horizontal pressure tubes. The moderator in the tank and the coolant in the channels are separated.
An advanced gas-cooled reactor AGR is a British design of nuclear reactor. AGRs were developed from the Magnox type reactor. These are the second generation of British gas-cooled reactors.
AGRs are operating at a higher gas temperature for improved thermal efficiency, thus requires stainless steel fuel cladding to withstand the higher temperature. The fuel is uranium oxide pelletsenriched to 2. Control rods penetrate the moderator and a secondary shutdown system involves injecting nitrogen to the coolant. See also: Advanced Gas-cooled Reactor. A fast neutron reactor is a nuclear reactor in which the fission chain reaction is sustained by fast neutrons.
The concept was introduced in the mid nineteen sixties. By continuing refinements, ABB has learned to master critical operating parameters like vibrations and noise. ABB variable shunt reactors help increase controllability and flexibility to the Norwegian national grid. Submit your inquiry and we will contact you.
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Reactors and inductors. Are you looking for support or purchase information? Contact us. Our offering. Shunt reactors. Variable shunt reactors VSR. Series reactors. Dry-type reactors.To browse Academia. Skip to main content. Log In Sign Up. Structured Catalysts and Reactors: Revised and Expanded corsi.
Isabella Nova. Structured Catalysts and Reactors: Revised and Expanded. SCR catalysts II. SCR reactor configurations for power plants II. Honeycomb catalysts II. Plate-type catalysts II. Other catalysts II. Effect of operating variables II. Effect of catalyst morphology II. Modeling of SCR monolith catalysts under unsteady conditions. Nitrogen oxides are mainly formed during the combustion of fossil fuels and biomasses; they are blamed for the production of acid rains, the formation of ozone in the troposphere and for causing respiratory problems to mankind.
The mechanisms of formation of NOx are well-known: 1 the reaction between N2 and O2 in air at high flame temperature according to the Zeldovich mechanism  thermal NOx2 the oxidation of N-containing compounds in the fuel or biomass fuel NOx3 the formation of intermediate HCN via the reaction of nitrogen radicals and hydrocarbons, followed by the oxidation of HNC to NO prompt NOx.
Other sources of NOX exist in nature nitrogen fixation by lightning, volcanic activity, oxidation of ammonia in the troposphere, inflow of NO from the stratosphere, ammonia oxidation from the decompositions of proteinsbut it is the combustion of fossil fuels and especially vehicles the main cause of emissions.
Limits on the NOX emissions from stationary or mobile sources have been established in most countries by setting standards of concentration in ppm related to reference oxygen concentration on dry basis in the flue gases.
The control of NO x emissions from stationary sources includes techniques of modification of the combustion stage primary measures and techniques of treatment of the effluent gases secondary measures. Among the secondary measures, a well established technology is represented by the Selective Catalytic Reduction SCR process which is world-wide applied due to its efficiency and selectivity . In this chapter, an overview of the key factors that affect the operation of the monolithic de-NOxing catalysts is presented.
After a brief illustration of the SCR technology, the chemical and mass transfer phenomena which control the SCR reaction are addressed together with the steady-state modeling of the monolithic reactor. It is also shown that the study of the effect of the morphological and geometrical properties of the catalyst, the effect of feed composition and the effect of the interaction between DeNOX reaction and SO2 oxidation offer space for improving both the catalyst and the reactor design.
The main aspects connected to dynamic operation of the SCR catalysts are also addressed. Since then, the diffusion of SCR systems in the Japanese utility power sector has reached the estimated order ofMWe. SCR process has undergone a wide diffusion in Europe, sincewhen it has been first introduced in Austria and West Germany.
China and Republic of South Korea. In addition to the most common applications in coal-fired, oil-fired and gas-fired power stations, industrial heaters and cogeneration plants, the NOx SCR control system has been proved and applied to industrial and municipal waste incinerators, chemical plants HNO3 tail gases, FCC regenerators, explosives manufacture plantsand in the glass, steel and cement industries.
Besides it has been proved that SCR catalysts, used in combination with a specifically designed Dioxin catalyst, are effective for the combined reduction of NOx and oxidation of dioxins and furans polychlorinated dibenzodioxins and polychlorinated dibenzofurans from waste incineration plants.
These reactions are observed over the SCR catalysts in the absence of NO in the feed, but they become negligible in the presence of NOx. The ability to react selectively with NOx in excess oxygen has not been observed in the case of other simple reagents such as carbon monoxide and hydrocarbons. This motivates the choice of ammonia as the unique reducing agent in the SCR process.Nuclear plants split atoms to heat water into steam. The steam turns a turbine to generate electricity.
In most power plants, you need to spin a turbine to generate electricity. Coal, natural gas, oil and nuclear energy use their fuel to turn water into steam and use that steam to turn the turbine. The nuclear reactors currently operating in the United States are either boiling water reactors or pressurized water reactors. The names can be a bit misleading: Both use steam to power a generator, but the difference is how they create it.
Innovative entrepreneurs and startups are developing new types of reactors to be more efficient and flexible in operations, reach remote and developing areas, reduce—and possibly even recycle—waste, and even turn seawater into drinking water. A nuclear reactor is like an enormous, high-tech tea kettle. Nuclear plants are different because they do not burn anything to create steam. Instead, they split uranium atoms in a process called fission.
As a result, unlike other energy sources, nuclear power plants do not release carbon or pollutants like nitrogen and sulfur oxides into the air. Nuclear reactors are designed to sustain an ongoing chain reaction of fission; they are filled with a specially designed, solid uranium fuel and surrounded by water, which facilitates the process. When the reactor starts, uranium atoms will split, releasing neutrons and heat.
Those neutrons will hit other uranium atoms causing them to split and continue the process, generating more neutrons and more heat. This heat is used to create the steam that will spin a turbine, which powers a generator to make electricity. Two Types of Reactors in the United States The nuclear reactors currently operating in the United States are either boiling water reactors or pressurized water reactors.
A boiling water reactor heats up the water in the reactor until it boils into steam and spins the turbine. A pressurized water reactor heats up the water in the reactor too. New Nuclear Reactor Technology Innovative entrepreneurs and startups are developing new types of reactors to be more efficient and flexible in operations, reach remote and developing areas, reduce—and possibly even recycle—waste, and even turn seawater into drinking water. Several of these new designs do not use water for cooling; instead they use other materials like liquid metal, molten salt or helium to transfer heat to a separate supply of water and make steam.
SMRs are advanced reactors that produce megawatts or less of electricity. Some advanced reactors will operate at higher temperatures or lower pressures than traditional nuclear reactors. They also will offer other applications like water desalination and hydrogen production.
Other reactors will be very fuel efficient by producing less waste or by having extended fuel cycles and not having to stop and refuel for a decade or more. Watch the Video. Mobile Site Navigation. Fundamentals Expand Navigation. What Is Nuclear Energy? How a Nuclear Reactor Works. Nuclear Fuel.
Nuclear Waste. Nuclear Powers the U.
Types of Reactors
With Clean Energy. Beyond Electricity.A chemical reactor is an enclosed volume in which a chemical reaction takes place. The design of a chemical reactor deals with multiple aspects of chemical engineering.
Chemical engineers design reactors to maximize net present value for the given reaction.
Designers ensure that the reaction proceeds with the highest efficiency towards the desired output product, producing the highest yield of product while requiring the least amount of money to purchase and operate. Normal operating expenses include energy input, energy removal, raw material costs, labor, etc.
Energy changes can come in the form of heating or cooling, pumping to increase pressure, frictional pressure loss or agitation. Chemical reaction engineering is the branch of chemical engineering which deals with chemical reactors and their design, especially by application of chemical kinetics to industrial systems.
The most common basic types of chemical reactors are tanks where the reactants mix in the whole volume and pipes or tubes for laminar flow reactors and plug flow reactors. Both types can be used as continuous reactors or batch reactors, and either may accommodate one or more solids reagentscatalystsor inert materialsbut the reagents and products are typically fluids liquids or gases.
Reactors in continuous processes are typically run at steady-statewhereas reactors in batch processes are necessarily operated in a transient state. When a reactor is brought into operation, either for the first time or after a shutdown, it is in a transient state, and key process variables change with time. There are three idealised models used to estimate the most important process variables of different chemical reactors:. A tubular reactor can often be a packed bed.
In this case, the tube or channel contains particles or pellets, usually a solid catalyst. Chemical reactions occurring in a reactor may be exothermicmeaning giving off heat, or endothermicmeaning absorbing heat. A tank reactor may have a cooling or heating jacket or cooling or heating coils tubes wrapped around the outside of its vessel wall to cool down or heat up the contents, while tubular reactors can be designed like heat exchangers if the reaction is strongly exothermicor like furnaces if the reaction is strongly endothermic.
The simplest type of reactor is a batch reactor. Materials are loaded into a batch reactor, and the reaction proceeds with time. A batch reactor does not reach a steady state, and control of temperature, pressure and volume is often necessary. Many batch reactors therefore have ports for sensors and material input and output. Batch reactors are typically used in small-scale production and reactions with biological materials, such as in brewing, pulping, and production of enzymes.
One example of a batch reactor is a pressure reactor.