Talal Ashraf 13CH10

QUIZ COMPITITION QUESTIONS AND ANSWERS

CHEMICAL ENGINEERING KINETICS

BYPROFESSOR DR. SHAHEEN AZIZ

Chemical Engineering Department

Mehran University of Engineering and Technology Jamshoro

1. What is a Chain Reaction?Achain reactionis a sequence of reactions where a reactive product or by-product causes additional reactions to take place.Chain reactions are one way in which systems which are inthermodynamicnon-equilibriumcan release energy or increase entropy in order to reach a state of higher entropy.2. What is the concept of free radical?Most chemical chain reactions have very reactive intermediates calledfree radicals. These atoms or fragments are usually derived from stable molecules due to photo- or heat-dissociation3. What is meant by Chain carrier?The intermediate that maintains the chain reaction is called achain carrier..What are the main steps of chain reaction?InitiationPropagation Termination4. What is initiation in chain reaction?Initiationis the formation of active particles, oftenfree radicals, in either a thermal or a photochemical step.5. What is propagation?Propagationmay comprise several elementary steps in a cycle, where the active particle through reaction forms another active particle which continues the reaction chain by entering the next elementary step.6. What is termination?Terminationis an elementary step in which the active particle loses its activity; e. g. byrecombinationof two free radicals.7. What is chain Length?Thechain lengthis defined as the average number of times the propagation cycle is repeated, and equals the overall reaction rate divided by the initiation rate.8. What is meant by Chain branching?Chain branching is the case of propagation step when more new active particles form in the step than enter it.9. What is the Chain transfer?Chain transferis the case in which one active particle enters an elementary reaction with the inactive particle which as a result becomes another active particle along with forming of another inactive particle from the initial active one.10. Examples of chain Reactions are?Nuclear chain reactionsPolymerization growth chain reactionsExplosion reactionsFood Spoilage reactions11. What is the Semi batch reactor?Asemi-batchreactor is avariationof abatchreactor in which one reactant may be added intermittently or continuously to another reactant contained in a vessel as reaction proceeds. The reaction may be single-phase or multi-phase. As in a batch reactor, the operation is inherently unsteady-state and usually characterized by a cycle of operation, although in a more complex manner.

12. What is a Semi Continuous reactor?Asemi-continuousreactor is a reactor for a multiphase reaction in which one phase flows continuously through a vessel containing a batch of another phase. The operation is thus unsteady-state with respect to the batch phase, and may be steady-state or unsteady-state with respect to the flowing phase, as in a fixed-bed catalytic reactor or a fixed bed gas-solid reactor respectively.13. What are the Advantages of Semi-Batch Operation?AdvantagesIn comparison with a batch reactor, the gradual or intermittent addition of a reactant in a semi-batch operation can result in improved control of the temperature; particularly for a highly exothermic reaction. This may be the case if the initial reaction rates are very high, which would result in uncontrollable temperature rises or gas evolution in the batch reactorThe concentration of a reactant can be kept relatively low (for the reactant introduced intermittently) or high (reactant charged initially) if either is advantageous for suppressing side reactions, thus improving product yield.The withdrawal of a product can result in higher conversion of a reactant, particularly if the reaction is equilibrium-limited.To react a gas with a liquid: this is inevitable when a batch reactor is desired but the gas is only sparingly soluble in the liquid14. What are the disadvantages of Semi-Batch Operation?DisadvantagesAs in the case of a batch reactor, the production rate may be limited because of the cyclic nature of the operation.Also, as in the case of a batch reactor, the operating cost may be relatively high.The design or performance analysis is complicated because of the unsteady-state operation.Semi-continuous operation may require intricate piping and valves.15. What are the advantages of semi batch reactor over the batch reactor?Improved selectivity of a reactionBetter control of exothermic reactionsProduct removal through a purge stream16. Semi Batch reactors are also known as?Fed batch reactor, because of continuous addition or removal of one or more components / streams17. What is the plug flow reactor?Theplug flow reactor model(PFR, sometimes calledcontinuous tubular reactor,CTR, orpiston flow reactors) is a model used to describechemical reactionsin continuous, flowing systems of cylindrical geometry. The PFR model is used to predict the behaviour of chemicalof such design, so that key reactor variables, such as the dimensions of the reactor, can be estimated.18. What is the key Assumption during the designing of ideal plug flow reactor?The key assumption is that as a plug flows through a PFR, the fluid isperfectly mixedin the radial direction but not in the axial direction (forwards or backwards). Each plug of differential volume is considered as a separate entity, effectively an infinitesimally small continuous,limitingto zero volume.19. Which type of equation models are used for the designing of plug flow reactor?The PFR is governed by ordinarydifferential equations, the solution for which can be calculated providing that appropriateboundary conditionsare known.20. Which state of matter work best with the PFR?The PFR model works well for many fluids: liquids, gases, and slurries.21. What are the applications of Plug flow reactor?Plug flow reactors are used for some of the following applications: Large-scale production slow reactions Homogeneous or heterogeneous reactions Continuous production High-temperature reactions22. What are the advantages of Plug flow reactor?Plug flow reactors have a high volumetric unit conversion, run for long periods of time without maintenance, and the heat transfer rate can be optimized by using more, thinner tubes or fewer, thicker tubes in parallel.23. What are the disadvantages of Plug Flow reactor?Disadvantages of plug flow reactors are that temperatures are hard to control and can result in undesirable temperature gradients. PFR maintenance is also more expensive than CSTR maintenance.24. What is the Material balance equation for the PFR ?[accumulation] = [in] - [out] + [generation] - [consumption]25. What are the assumptions to be carried out for industrial plug flow reactor designing?Assumptions:plug flowsteady stateconstantdensity(reasonable for some liquids but a 20% error for polymerizations; valid for gases only if there is no pressure drop, no net change in the number of moles, nor any large temperature change)singlereactionoccurring in the bulk of the fluid (homogeneously).26. What is the second name of Plug Flow reactor?The second name of plug flow reactor is tubular flow reactor.27. What type of flow is referred in tubular flow reactor?Turbulent flow generally is preferred to laminar flow, because mixing and heat transfer are improved. For slow reactions and especially in small laboratory and pilot-plant reactors, establishing turbulent flow can result in inconveniently long reactors or may require unacceptably high feed rates28. What are the Features of an ideal reactor? Uniform distribution Short residence time Advanced technique Smooth appearance Quality design Ensure safe heat transfer Static mixing of components 29. What is a trickle bed reactor?Atrickle-bed reactor (TBR)is achemical reactorthat uses the downward movement of a liquid and gas over a packed bed ofcatalyst particles. It is considered to be the simplest reactor type for performing catalytic reactions where a gas and liquid (normally both reagents) are present in the reactor and accordingly it is extensively used in processing plants.30. What are the applications of Trickle Bed Reactor?Typical applications are liquid-phasehydrogenation, hydrodesulfurization, andhydrodenitrogenationin refineries (three phasehydrotreater) andoxidationof harmful chemical compounds in wastewater streams or ofcumenein thecumene process. 31. Trickle bed reactor mostly known as?Three Phase reactor.32. Why trickle bed reactor also termed as three phase reactor:The gas and liquid co-currently flow downward over a fixed bed of catalyst particles. Concurrent down-flow of gas and liquid over a fixed-bed of catalyst. Liquid trickles down, while gas phase is continuous.33. What are the parameters are to be considered for trickle bed reactor designing: Gas flow rate Liquid Flow rate Fluid properties Packing Characteristics34. What are the approximate dimensions for trickle bed reactor?Approximate dimensions of commercial trickle-bed reactors are a height of 10 m and a diameter of 2 m.35. What is the ideal tubular reactor?An ideal tubular reactor is one in which there is no mixing in longitudinal direction and mixing takes place only in radial direction and there is a uniform velocity across the radius.36. Which type of reactor is most suitable for isothermal reactions?Back mix reactor is most suitable for isothermal reactions.37. When a semi batch reactor is preferred?A semi batch reactor is preferred when A highly exothermic reaction is to be controlled Undesirable reactions A gas reacted with liquid38. Homogeneous reactors include? PFR CSTR Batch Semi Batch39. Heterogeneous reactor include? Packed Bed Moving Bed Fluidized Bed40. What are the Reactor type Configuration? Gas-liquid reactor Liquid-liquid reactor Fluid-solid reactor41. Gas liquid reactor include? Absorption column Bubble column Tank reactor Distillation column Monolith reactor42. Liquid-Liquid reactor Include? Column reactor Mixer-settler reactor43. Fluid-Solid reactor includes? Packed Bed Fluidized Bed44. What are the advantages of Bed reactor? Flexible Same reactor for multiple fluids45. Tube reactor are mostly used for? Homogeneous reactions Liquid Phase reaction46. Which direction of flow is suitable for the reaction?Radial turbulent direction of flow is suitable for carry out effective reactions in reactors.

47. Define Reactor?It is reacting vessel designed for chemical reaction.48. . How reactor are classified according to method of operation Batch reactor Continuous reactor Semi batch reactor49. How reactors are classified according to shape? Tank reactor Tabular reactor50. How reactors are classified according to phase of reacting material? Homogeneous phase reactor Heterogeneous phase reactor51. Define Batch reactor?The reactor in which reaction material at feed at begging and bulk of product is obtained at last.52. Define continuous reactor?The reactor in which reacting is feed continuously and product is also obtained continuously.53. Which reactor is simplest b/w batch and continuous reactor with respect to maintenance?Batch reactor because it require minimum auxiliary equipments.54. Which is most important parameter in designing batch reactor?Volume of reactor because feed quantity entirely depend on it.55. Which type of reactor is most convenient in use when initial temperature require by reacting substance is too high?Continuous type reactor such as kiln.56. How reactors are classified according to geometry?Stirred tank, packed bed. Fluidized bed, gasifier reactor.57. Define semi batch reactor?A reactor that contain characteristics of both batch and continuous reactor.58. Function of semi batch reactor?First batch of material is feed then reaction start by feeding other reactant material.59. What is CSTR?It is continuous stirred tank reactor.60. What is BSTR?It is batch stirred tank reactor.61. What is SSTR?It is single stirred tank reactor.Is SSTR is batch or continuous type reactor?It is mostly batch reactor but can be continuous depends on operation type.62. Define Homogeneous phase reactor?A reactor in which reactant and catalyst used in one phase that may be liquid or gas.63. Define heterogeneous phase reactor?A reactor in which reactant and catalyst used in different phases.64. Which is more efficient b/w BSTR and CSTR?CSTR because large quantity of product is obtained in low period of time.65. Which are other well known names of tabular reactors?Plug flow reactor, piston flow reactor.66. Justify fluidized bed combustor is a reactor?FBC is a reactor because in which solid particles are combusted after fluidized by jet of air.67. Working mechanism of FBC reactor.In FBC reactor solid particles are feed inside reactor with proper ratio of air. Such as at Khanot power plant, 13mm coal and 6mm lime stone is feed within proper ratio with air.68. Why CaCO3 is used in FBC reactor at Khanot?Because of for capturing SO2 emission.69. What is reaction through which SO2 emission is captured in FBC reactor? CaCO3 CaO + CO2 CO2 + SO2 + 1/2 O2 CaSO4 70. How many power generation houses in Pakistan using FBC reactor?Only one power generation house at Khanot in Pakistan using FBC reactor.71. How many FBC reactors are being used at Khanot power generation house?Three FBC reactors.72. Enlist the main factors that must be considered during reactor designing?Chemical factor, mass transfer factor, heat transfer factor, safety and economical factor73. Define Exothermic reaction?Reactions which release energy for completion.74. Define endothermic reactions?Reactions which require energy for completion.75. Define Kc and K.Kc is equilibrium constant.K is rate constant.76. Define equilibrium?The condition at which neither reactant into product nor product into reactant changes.77. Importance of equilibrium in reactors?Whenever equilibrium in reactor exists there will be no yield of product.78. What are two main types of nuclear reactors?i) Boiling water reactor (BWR).ii) Pressurized water reactor (PWR).79. Define boiling water reactor?A reactor in which fuel is Uranium oxide and coolant and modector is water which is directly boiled to produce steam.80. Define Nuclear reactions?Reactions which changes the nucleus of an atom is called nuclear reactions.81. What are two types of nuclear reactions?i) Nuclear fission reaction.ii) Nuclear fusion reaction.82. Define nuclear fission reaction?Fission is the splitting of large nuclei into smaller nucleus.83. Define nuclear fusion reaction?Fusion is fusing of two or more lighter nuclei into larger nuclei.84. Which type of reaction occurs at sun?Nuclear fusion reaction occurs at sun.85. Justify gasifier is reactor?It is reactor because in which reaction take place as a result we get syn gas as product.86. Define coal gasification?It is a process of producing synthetic gas from coal by reacting coal with steam and O2 in gasifier reactor.87. What are three main sections of coal gasifier reactor?PyrolysisCombustionGasification.88. Define Pyrolysis?It is thermal decomposition of coal by application of heat to coal in absence of air.89. At what temperature coal begin to decompose in gasifier reactor?Coal begins to rapidly decompose when its temperature rises above around 2400c in gasifier reactor.90. What are combustion reactions in gasifier reactor.C + O2 COCO + O2 CO2H2 + O2 H2O

91: For which order of reaction tubular flow gives higher selectivity? For a first order reaction tubular flow reactor as compared to stirred tank reactor Provides higher overall selectivity. 92: At which condition the density of the process fluid in the tubular reactor holds Constant? When the space time and residence time for an isothermal tubular reactor is equal then the density of the process fluid is constant.93. For which order of reaction T.F.R heat generation is maximum? : When an exothermic second order reaction is carried out in an tubular plug Flow reactor the rate of heat generation is maximum94: The value of peclet no in tubular flow reactor is?Ans: The value of peclet no in T.F.R is zero because there isnt any thermal energy convected o the flQ no 95: Another name of T.F.R iAns: Ideal tubular plug flow reactor is also called continuous tubular reactor or piston flow reactor .Q no 96: Which function in ideal tubular flow reactor residence time distribution refers to In an ideal P.F.R the residence time distribution is the Dirac Delta function i.e a function on the real line which is zero every where except at the origin where it is infiniteQ no 97: Disadvantage of P.F.R is? The most common disadvantage is temp is hard to control in P.F.R and can result in undesirable temp gradient.

Q no 98: plug flow reactor used for? * Large scale production. For slow reactions. For continous production. For high temp reactions. Q no 99 : Which condition enhance the whole process of ideal flow reactor? Ans : It provides narrow residence time distribution which enhance the whole process of the ideal flow reactor. Q no 100 Who gave the idea of residence time distribution in the analysis of chemical reactor performance? Ans : The idea of residence time distribution in the analysis of chemical reactor Performance was first performed by McMullen and Weber. Q no 101: The purpose of long tube in the ideal flow reactor is ? Ans : In the ideal tubular reactor the long tube and the lack of provision for stirring prevents complete mixing of fluid. Q no 102: In T.B.R which assumption is to be made to proceed? Ans: In P.F.R it is to be assumed that there is no mixing in the axial direction i.e The direction of flow but complete mixing in the radial direction. Q no 103: Flow pattern in T.F.R for fluids and gases are?Ans : Flow in tubular reactor can be laminar as with viscous fluids with small diameter tubes and greatly deviate from ideal plug flow behavior or turbulent as with gases. Q no 104: Which type of flow pattern is mostly preferred in P.F.R? Ans : Turbulent flow preferred to laminar in P.F.R because mixing and heat transfer are improved. Q no 105: Which conditions are necessary to operate P.F.R? Ans: Ideal plug flow reactor is operated isothermally at constant pressure and steady state with unique residence time Q no 106: In P.F.R velocity as well as composition profile is? Ans: In plug flow reactor velocity profile is flat and both temp and composition are uniform at any cross section in the reactor. Q no 107: What does it means that flat velocity profile ? Ans: It means that the reactant concentration at a particular axial position in the tubular vessel does not vary in the radial direction. Q no 108: Which consideration is to be made for sizing of P.F.R? Ans : A plug flow reactor can be sized by considering an incremental slice of the reactor Q no 109: Where P.F.R is applicable in industry? Ans: P.F.R is applicable where high exothermic and explosive energy Involved in carrying the chemical reaction. Q no 110: Which type of mixing is carried out in it? Ans: It ensures the static mixing of the component i.e mixing without utilizing moving parts or Mixing achieved by redirecting the flow.

Q no 111: At which operating conditions P.F.R work effectively? Ans: P.F.R work effectively at constant density, balanced reactions, a single reaction and plug flow.

Q no 112: Features of ideal flow reactors are? Ans : Features of an ideal reactor Uniform distribution Short residence time Advanced technique Quality design Smooth appearance Q no 113: Which type of distribution of components is being carried out by P.F.R? Ans: P.F.R gives uniform distribution of the components that are to be fed in it. Q no 114: Which type of reactions is being carried out by P.F.R? Ans: Plug flow reactors are used to carry out the following reactions Hoffman Reaction Biocatalysis Grignard Reaction Hydrogenation Oxidation Reaction Bourne Reaction Q no 115: On which parameters size of plug flow reactor depend? Ans: The ratio of size of plug flow reactor will depend on the extent of reaction,stoichiometry and the form of rate equation. Q no 116: Which things are neglected in the elementry treatment of P.F.R? Ans: In the elementary treatment of P.F.R mixing by diffusion and other processes in the direction of flow is neglected. Q no 117: Variation in the temp in reactor will cause? Ans: If there are variations in the temperature across the reactor there will be local variation in the reaction rate Q no 118: Who describe the deviation from P.F.R? Ans: The deviation from ideal plug flow reactor is best explained by Robert Turner first. Q no 119: What is space velocity of a reactor? Ans: Space velocity refers to the quotient of the entering volumetric flow rate of the reactant divided by the reactor volume. Q no 120: What is the function of space velocity in a reactor? Ans: Space velocity for a conversion in a reactor is often used as a ready measure of the performance of the reactor. Q no 121: Pressure drop in the plug flow reactor is? Ans: In the plug flow reactor pressure drop corresponding to the desired flow rate is relatively small and does not impose any serious limitations on the condition of operation.

Q no 122: On lab scale T.B.R is used for? Ans: In lab tubular reactor is convenient for gas phase reactions and for the reactions which are so fast. Q no 123: For the most accurate data collection P.F.R is operated on which condition? In order to obtain most accurate data P.F.R is operated as closely as possible to the isothermal condition . Q no 124: The unit of space velocity is ? The space-velocity has the unit of time. Q no 125: Space velocity of 2 hr-1 means? That two reactor volumes of feed at specified conditions are being fed into the reactor per hour Q no 126: For identical feed compostion and flow rate, N plug flow reactors in series with a total volume V gives the same conversion as ? Ans: As a single plug flow reactor of volume NV. Q no 127: N plug flow reactors in series with a total volume V gives the same conversion as a single plug flow reactor of volume V The above statement is true for which order of reaction? Ans: The above statement is true for zero-order reactions only. Q no 128: The assumption of P.F.R is acceptable for which type of flow pattern? Ans: The assumption of plug flow is usually acceptable only for turbulent pipe flows. Q no 129: Which idea supports to calculate the residence time distribution in P.F.R Ans: It can be calculated on the basis of the idea that small groups of particles sticking together are like tiny closedbatch micro-reactors, wandering through the apparatus along different paths. Q no 130: Why in P.F.R reactions are so fast? Ans: Because it provides large surface area of heat exchange and offers high surface to volume ratio.

Q131 what is the another name of stirred tank reactor (CSTR)?Ans Continuous Stirred Tank Reactor (CSTR) also known as vat or backmix reactor, Is a common ideal reactor.Q132 what do you mean by batch stirred tank reactor?Ans A batch stirred tank reactor is the simplest type of reactor. It is composed of a reactor and a a mixture such as a stirrer, a turbine wing or a propeller.Q133 . what are the purposes of batch stirred tank reactor?Ans This reactor is useful for substrate solutions of high viscosity, and for immobilized enzymes with relatively low activity. However, a problem that arises is that an immobilized enzyme tends to decompose upon physical stirring. The batch system is generally suitable for the production of rather small amounts of chemicals.Q134 Which of the reactor type is more efficient batch or continuous stirred tank reactor?Ans The continuous stirred tank is more efficient than a batch stirred tank reactor but the equipment is slightly more complicated. Q135 What are the characteristics of continuous stirred tank reactor (CSTR)?Ans The characteristics of continuous stirred tank reactors are that they run at steady state with continuous flow of reactants and products; the feed assumes a uniform composition throughout the reactor, exit stream has the same composition as in the tank.Q136 What kinds of phases are present in (CSTR)?Ans The phases which are present in (CSTR) are liquid phase, gas liquid rxns , solid liquid rxns.Q137 What are the usage of single stirred tank reactors?Ans The usage of single stirred tank reactor are as under 1 When agitation is required.2 Series configurations for different concentration streamsQ138 What are the advantages of stirred tank reactors?Ans There are several advantages of stirred tank reactor as under1 Continuous operation2 Good temperature control3 Easily adapts two phase runs4 Good controls5 Simplicity of construction 6 Low operating (labor) cost7 Easy to cleanQ139 What are the disadvantages of continuous stirred tank reactor?Ans The disadvantages of continuous stirred tank reactors are 1 Convert conversion per unit volume2 By-passing and channeling possible with poor agitation.Q140 For what purpose CSTR is demonstrated in lab scale?Ans The continuous stirred tank reactor is designed to demonstrate the mechanism of chemical reaction in the stirred as well as the effects of varying process conditions such as reaction temperature, reactor volume, stirring rate, feed rate etc.Q141 For what purpose the continuous stirred tank reactor in series is demonstrated?Ans CSTR in series is designed to study the reaction mechanism as well as the dynamics of reactor with various types of input.Q142 For what purpose the CSTR are modeled?Ans The CSTR generally modeled as having no spatial variations in concentration, temperature or reaction rate throughout the vessel.Q143 In which of the industries the stirred tank reactor is used?Ans The continuous stirred tank reactor is used in the corrosion processing unit in chemical and polymer industries.Q144 For which feasibility continuous stirred tanks used?Ans A continuous stirred tank bioreactors are used to optimizefeasible and reliable bioprocess system in order to treat hydrocarbons such as industrial waste water.Q145 Which type of vessel is their in continuous stirred tank reactor?Ans A reaction vessel in which the feed is continuously added and the products continuously removed. The vessel (tank) is continuously stirred to maintain a uniform concentration within the vessel.Q146 In a continuous flow stirred tank reactor the composition of the exit stream lies between what?Ans In a continuous flow stirred tank reactor the composition of the exit stream is same as that in the reactor.Q147 How does a continuous stirred tank reactor behave like loop reactor?Ans A continuous stirred tank reactor can alsofunction as a loop reactor when a heated, pressurized fluid is injected into the system to facilitate the stirring. This allows for higher heat and mass transfer rates while simplifying maintenance because there is no agitator.Q148 What are the continuous usage examples of continuous stirred tank reactors?Ans Continuous stirred tank reactors are most commonly used in industrial processing, primarily in homogeneous liquid phase flow reactions, whose constant agitation is required. They mabe used by themselves, in series or in a battery. CSTR are also used in the pharmaceuticals industirs as a loop reactors.Q149 How far the fermenters are known as stirred tank reactors?Ans Fermentors are CSTR, used in biological processes in many industries, such as brewing antibiotics, and waste treatment. In fermentors, large molecules are broken down into smaller molecules, with alcohol produced as a byproduct.Q150 What are the cell culture reactor related with CSTR?Ans the cell culture reactors are CSTR because the initial amount of cells are placed in the fibrous bed basket. A nutrient rich medium is continuously fed into the reactor and products are harvested. As the cell grows they produce byproducts, which are continuously removed from the reactor.Q151 What is the residence time for CSTR reactor?Ans Residence time- average amount of time a discrete quantity of resents spend inside the tank. Residence time= volumetric flow rate / volume of the tankQ152 Which of the thing s should be considered when making a stirred tank reactor?Ans The things which may be considered are1 Rate of flow of energy in/out2 Heat of reaction3 Rate of change of energy (E)4 Arrhenius temperature dependenceQ153 With what things the stirred tank is fabricated?Ans The stirred tank reactors usually fabricated in steel, stainless steel, glass, lined steel,glass or exotic alloy.Q154 What should be the size of the stirred tank reactor?Ans The reactors may vary in size from less than 1 litre to more than 15,000 litres.Q155 With what things STR reactor may whrist of?Ans A typical STR reactor conisit of a tank with agitator and integral heating/cooling systems.Q156 In which of the scales the stirred reactors are used?Ans The stirred tank batch reactor is still the most widely used reactor type both in the laboratory and industry.Q157 STR reactor is particularly useful for what?The STR reactors are particularly useful when processing toxic or highly potent compounds.Q158 What are the heating and cooling parameters for stirred tank reactor?Ans These are the parametersProduct within batch reactor usually liberate or absorb heat during processing.Even the action of stirring stored liquids generates heat.In order to hold the reactor contents at the desired temperature, heat has to be added or removed by cooling jacket or cooling pipes.Within the chemical and pharmaceutical industries, external cooling jackets are generally preferred as they make the vessel easier to clean.The performance of these jackets can be defined by 3 parametersResponse time to modify the jacket temperature.Uniformity of jacket temperature.Stability of jacket temperature.Q159 What is the purpose of jacket in STR reactor?Ans Jacket consists of a agitation nozzles for providing higher turbulence and hence better heat transfer.Q160 For what loop reactors are used examples?Ans Loop reactors are used, for example, in the manufacture of poly (ethene) and the manufacture of poly (propene). Ethene (or propene) and the catalyst are mixed, under pressure, with the diluents, usually a hydrocarbon. A slurry is produced which is heated and circulated around the loops.Q161 What are the continuous stirred tank reactors in series?Ans Continuous flow stirred tank reactors in series are simpler and easier too design for isothermal operations than are tabular reactors.Q162 In what parameters the analysis of the STR reactor can be done?Ans The analysis of the reactor can be done by evaluating the quantitative behavior of more complex gas, liquid and solid flow behavior.Q163 What is the reaction composition in STR reactor?Ans Because the composition of mixtures leaving a CSTR are those within the reactor, the reaction driving forces, usually the reactant concentration, are necessarily low. Therefore, except for reaction orders. Zero and negative, a CSTR requires the layer volume of the reactor type to obtain desired conversion, however the low driving force makes possible better control of rapid exothermic and endothermic reactions.Q164 What are the applications of ideal stirred tank in chemical engineering?Ans In chemical engineering, reactors that features well-mixed conditions and liquid level control are quite common. Within such ideal stirred tank reactors, perfect mixing is assured and the output composition of material within the reactor. In such systems, reactants are constantly introduced into the reactor and products are continuously removed.Q165 Why it is economically beneficial to operate CSTR reactors in series?Ans Often it is economically beneficial to operate several CSTR in series. This allows, for example, the first CSTR to operate at a high reagent concentration and therefore a higher reaction rate. In these cases, the the size of the reactors maybe varied in order minimize the total capital investment required to implement process.Q166 What should be the behavior of stirred tank reactor?Ans A behavior of a CSTR is often approximated or modeled by that of a continuous ideally stirred tank reactors CSTRs assume perfect mixing time, this approximation considered valid for engineering purposes.Q167 Why CSTR reactors are easily constructed?Ans The continuous stirred tank reactor is an easily constructed, versatile and cheap reactor, which allows simple catalyst charging and replacement.Q168 What are the applications included in CSTR reactors?Ans The applications which are included ibn CSTR reactors are Homogeneous liquid phase reactions Heterogeneous gas liquid reactions Heterogeneous liquid-liquid reactions Heterogeneous solid-liquid reactions Heterogeneous gas-liquid-solid reactionsQ169 What is the principle of CSTR reactors?Ans The principle continuous stirred tank reactor is that one or more fluid reagents are introduced into a tank reactor equipped with aan impeller while the reactor efficiency is recovered. A stepped up concentration gradient exits.Q170 What are the limitations of continuous dtirred tank reactors?Ans The limitations are that more complex and expensive than tabular units. All calculations performed with CSTRs assume perfect mixing. At steady state, the flow rate in must equal the flow rate out, otherwise the tank will overflow or go empty.Q171 What are the areas involving CSTR?Ans The areas involving are chemical industry especially liquid/gas reactions.Q172 Why CSTR reactors are used as multiphase?Ans Multiphase CSTR can also be used when two immisible liquids or visous liquids are present and require a high agitation rate.Q173 How sizing of CSTR reactors are done in series?Ans One can also design any sequence of reactors in series provided there are no side streams by defining the overall conversion at any point.Q174 What should be done to know the dynamic behavior of CSTR reactor?Ans TO describe the dynamic behavior of a CSTR mass component and energy balance equations must be developed. This requires an understanding of the functional expressions that describe chemical reactions.Q175 What do you mean by stirring blades?Ans Stirring blades also called agitators are used to mix the reactants.

176. What is activated complex?Activated complex is that assembly of atoms which corresponds to an arbitrary infinitesimally small region at or near the col (saddle point) of apotential energy surface".[1]In other words, it refers to a collection of intermediate structures in achemical reactionthat persist whilebondsare breaking and new bonds are forming.177. What is meant by activated complex theory?which studies thekineticsof reactions that pass through a defined intermediate state withstandard Gibbs free energy of formationG.178. What are the differences between activated complex and transition state?The activated complex is often confused with the transition state and is used interchangeably in many textbooks. However, it differs from the transition state in that the transition state represents only the highest potential energy configuration of the atoms during the reaction while the activated complex refers to a range of configurations near the transition state that the atoms pass through in the transformation from products to reactants.179. What is the role of role of activated complex in reaction?An activated complex acts as an intermediary between the reactants and the products of the reaction.180. What are the effects of energy of activated complex?The energy of the activated complex is higher than that of reactants or the products, and the state is temporary. If there is not sufficient energy to sustain the chemical reaction, the activated complex can reform into the reactants in a backward reaction. With proper energy, though, the activated complex forms the products in a forward reaction.181. When was activated complex theory developed?The activated complex theory, which enables the rate constants in chemical reactions to be calculated usingstatistical thermodynamics, was developed by American chemistryHenry Eyringin 1930.182. Who proposed collision theory?Collision theoryis a theory proposed independently byMax Trautzin 1916[1]andWilliam Lewisin 1918.183. What collision theory explains qualitatively?Collision Theory qualitatively explains howchemical reactionsoccur and whyreaction ratesdiffer for different reactions.184. What does collision theory states?The collision theory states that when suitable particles of the reactant hit each other, only a certain percentage of the collisions cause any noticeable or significant chemical change; these successful changes are called successful collisions.185. What is the effect of catalyst in collision?When a catalyst is involved in the collision between the reactant molecules, less energy is required for the chemical change to take place, and hence more collisions have sufficient energy for reaction to occur. The reaction rate therefore increases.186. What is the second name of collision theory?Collision theory also known as kinetic molecular theory187. Which phase of reaction collision theory applies?The collision theory explains that gas-phase chemical reactions occur when molecules collide with sufficient kinetic energy.188. What are energetic collisons?Energetic collisions are collisions between molecules with enough kinetic energy to cause the reaction to occur.189. What is the relation of activation energy to the collision?Activation energy is the key to breaking the initial bonds. When collisions are too gentle, the adequate amount of energy is not brought to the bonds and a reaction fails to occur. The activation energy is crucial in the reaction rate because depending on how much kinetic energy is brought to the collision, the reaction will vary in speed and frequency.190. What is unimolecular reaction?Aunimolecular reactionoccurs when a single reactant molecule transforms into one or more products.Examples of a unimolecular reaction include racemization, thermal decomposition, and isomerization.191. What is bi molecular reaction?Abimolecular reactionoccurs when two reactant molecules collide in one elementary step. Bimolecular reactions are the most common reactions.An example of a bimolecular reaction is the collision of N2O and NO, forming the products N2and NO2. Another is the collision of glucose and O2, formingCO2and water.192. What is termolecular reaction?Atermolecular reactionoccurs when three reactant molecules collide simultaneously to cause a reaction and formation of products. Termolecular reactions are extremely rare.193. What is the effect of orientation of collision?In any collision involving unsymmetrical atoms, the orientations of the atoms during collision determine whether a reaction occurs; without the proper orientations during the collision, the reaction will not occur at all. Collisions need to be oriented in a specific way to generate a reaction.194. What is the collision frequency?Collisional Frequency is the average rate in which two reactants collide for a given system and is used to express the average number of collisions per unit of time in a defined system.195. What are the assumption for collision frequency? All molecules travel through space in straight lines. All molecules are hard, solid spheres. The reaction of interest is between only two molecules. Collisions are hit or miss only. They occur when distance between the center of the two reactants is less than or equal to the sum of their respective radii. Even if the two molecules barely miss each other, it is still considered a complete miss. The two molecules do not interact (in reality, their electron clouds would interact, but this has no bearing on the equation)

Q. No: 196List any three guidelines for mass and energy balance. Ans:Following are few basic guidelines for mass and energy balance:For a complex production stream, it is better to first draft the overall material and energy balance. While splitting up the total system, choose, simple discrete sub-systems. The process flow diagram could be useful here. Choose the material and energy balance envelope such that, the number of streams entering and leaving, is the smallest possible.Always choose recycle streams (material and energy) within the envelope.

Q. No: 197How material and energy balance helps in energy conservation? Ans:In material and energy balance study by assessing the input, conversion efficiency, output and losses helps in establishing the basis for improvements and potential savings. It helps in finding improvements in a prioritized manner. Q. No: 198How material and energy balance helps in energy conservation? Ans:In material and energy balance study by assessing the input, conversionefficiency, output and losses helps in establishing the basis for improvements and potential savings. It helps in finding improvements in a prioritized manner.

Q. No: 199In reheating furnace, which loss component will be recovered (or) recycled energy?Ans:In reheating furnace, a part of the waste heat in the flue gas losses is recoverable. Q. No: 200Why evaluation of energy and mass balance is important?. Ans:Material and energy balances are important, since they make it possible to identify and quantify previously unknown losses and emissions. These balances are also useful for monitoring the advances made in an ongoing project and while evaluating cost benefits.

Q. No: 201Why Sankey diagram is useful in energy balance calculations? Ans:The Sankey diagram is very useful tool to represent an entire input and output energy flow in any energy equipment or system such as boiler generation, fired heaters, furnaces after carrying out energy balance calculation. This diagram represents visually various outputs and losses so that energy managers can focus on finding improvements in a prioritized manner.

Q. No: 202Differentiate exothermic and endothermic reactions. Ans:Exothermic reaction: A chemical reaction in which Heat is released. Endothermic reaction: A chemical reaction in which heat is absorbed.

Q. No: 203List any three energy loss components in chemical plant. Ans:Energy loss components in chemical plants are: 1. Flue / exhaust gas losses (from boilers, reactors etc.) 2. Evaporation loss (from cooling tower, condenser) 3. Surface heat losses (boilers, process equipment etc.)

Q. No: 204Which one is second form of energy?Ans:Electricity is second from of energy.

Q. No: 205In an utility steam boiler, what is the range of heat loss due to radiation?Ans:1%

Q. No: 206What Sankey diagrams show in graphics?Ans:It shows energy input, energy output and energy balance.

Q. No: 207Losses in energy and material balance is considered as?Ans:It is considered as outputs.

Q. No. 208:What is heat of reaction?Ans:Heat of reaction is the amount of heat that must be added or removed during a chemical reaction in order to keep all of the substances present at the same temperature

Q. No. 209:What are the most important assumptions for mathematically modelling of continuous stirred tank reactor?Ans:Following are the basic assumptions.The mixture density (p) and heat capacity (Cp) are assumed constant.The reacting mixture is assumed to be well mixed.The heat losses from the process to the atmosphere are negligible.The overall heat transfer coefficient is assumed constant.

Q. No. 210:What is activation energy?Ans:Activation energy is defined as the minimum energy required starting a chemical reaction. The activation energy of a reaction is denoted by E, and unit is kilojoules per mole. Activation energy can be thought of as the height of the potential barrier (sometimes called the energy barrier) separating two minima of potential energy (of the reactants and products of a reaction). For a chemical reaction to proceed at a reasonable rate, there should exit an appreciable number of molecules with energy equal to or greater than the activation energy.

Q. No: 211What is continuous stirred tank reactor?Ans:Continuous stirred tank reactors (CSTR) are the most basic of the continuous reactors used in chemical processes.

Q. No: 212Highlight some advantages of CSTR?Ans:Following are the advantages of CSTR:

Good temperature control is easily maintained Cheap to construct Reactor has large heat capacity Interior of reactor is easily accessed

Q. No: 213What are disadvantages of CSTR?Ans:Conversion of reactant to product per volume of reactor is small compared to other flow reactors is the main disadvantage of CSTR.

Q. No: 214What is Fluidized bed reactors?Ans:Fluidized bed reactors are heterogeneous catalytic reactors in which the mass of catalyst is fluidized. This allows for extensive mixing in all directions. A result of the mixing is excellent temperature stability and increased mass-transfer and reaction rates.

Q. No: 215Where Fixed film reactors are used?Ans:Fixed film reactors see much use in water treatment.

Q. No: 216From Where nuclear reactors produce power?Ans:Fission is the source from where power is produced in nuclear reactors.

Q. No: 217What are the various levels of mass and energy balances? Ans:The material and energy (M&E) balances required to be developed at the various levels are: 1. Overall M&E balance: This involves the input and output streams for complete plant. 2. Section wise M&E balances: In the sequence of process flow, material and energy balances are required to be made for each section/department/cost centres. This would help to prioritize focus areas for efficiency improvement. 3. Equipment-wise M&E balances: M&E balances, for key equipment would help assess performance of equipment, which would in turn help identify and quantify energy and material avoidable losses.

Q. No: 218List the items to be represented for a preparation of a process flow chart.Ans: Items to be represented in flow charts are: 1. Input to the process 2. Process steps 3. Wastes / by products 4. Output from the process (or) final products

Q. No: 219List any three energy loss components of induction furnace Ans:Induction furnace energy loss components 1. Cooling coil loss 2. Auxiliary system losses 3. Radiation heat loss

Q. No: 220List any three guidelines for mass and energy balance. Ans: For a complex production stream, it is better to first draft the overall material and energy balance. While splitting up the total system, choose, simple discrete sub-systems. The process flow diagram could be useful here. Choose the material and energy balance envelope such that, the number of streams entering and leaving, is the smallest possible. Always choose recycle streams (material and energy) within the envelope. Q. No: 221Differentiate between CSTR and BSTR (Batch Stirred tank reactor)?Ans:A CSTR has input and outlet flows; the BSTR has none.

Q. No: 222What is batch reactor?Ans:The stirred tank batch reactor is still the most widely used reactor type both in the laboratory and industry. Abatch reactoris one in which a feed material is treated as a whole for a fixed period of time. Batch reactors may be preferred for small-scale production of high priced products, particularly if many sequential operations are employed to obtain high product yields. Batch reactors also may be justified when multiple, low volume products are produced in the same equipment or when continuous flow is difficult, as it is with highly viscous or sticky solids-laden liquids. Becauseresidence timecan be more uniform in batch reactors, better yields and higher selectivity may be obtained than with continuous reactors.

Q. No: 223Why Batch reactors are used in laboratory experiments?Ans:Batch reactors often are used because of their suitability and convenient use mainly in laboratory experimentation.

Q. No: 224Where CSTR configuration is widely used?Ans:The CSTR configuration is widely used in industrial applications and in wastewater treatment units (i.e. activated sludge reactors).

Q. No: 225What is anaerobic filter?Ans:The anaerobic filter is similar to a trickling filter in that a biofilm is generated on media. The bed is fully submerged and can be operated either upflow or downflow. For very high strength wastewaters, a recycle can be employed.

Q. No: 226What is anaerobic contact?Ans:This process can be considered as an anaerobic activated sludge because sludge is recycled from a clarifier or separator to the reactor. Since the material leaving the reactor is a gas-liquid-solid mixture, a vacuum degasifier is required to separate the gas and avoid floating sludge in the clarifier.

Q. No: 227What is packed bed reactor?Ans:Packed beds can either be run in the submerged mode (with or without aeration) or in the trickle flow.

Q. No: 228What are fixed stationary particles or surface reactors?Ans:The most common reactor configuration used for immobilized cells is that of packed bed of particles. The advantages of packed beds include simplicity of operation and reasonable high mass transfer rates. Problems in the operation of packed beds include obstruction by uncontrolled cell growth and compression of the particles leading to excessive pressure drops. For these reasons simple packed bed reactors are mostly used for the case of non viable cells.

Q. No: 229What is Air lift or Bubble column reactors?Ans:In these reactors mixing circulation and aeration is performed by gas injection and if needed by additional external liquid circulation to obtain the required mixing pattern.

Q. No: 230Define the phases of reactors?Ans:Most reactors contain three phases: Solid phase (biomass aggregates or biomass immobilized on carrier material) Liquid phase (water phase with pollutants / nutrient and products) Gas phase (air or gas feed, gaseous products CO2, N2, CH4).