Process Dynamics and Control

UNIVERSITY OF LAGOS Chemical Engineering Department 20!"20# SESSION$ %t SE&ESTER

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Question 1 A process furnace heats a process stream from near ambient temperature to a desired temperature of  300oC. The process stream outlet temperature is regulated, by manipulating the flow of fuel gas to the furnace, as shown below.

a. b. c. d. e. f.

What What are are the the obje object ctiv ives es of this this cont contro roll stra strate tegy gy  What is the measured output What is the manipulated input what ar are th the po possible di disturbances !s this this a fee feed" d"fo forw rwa ard or feed feedba bac# c# contr ontrol ol syst system em  $isc $iscus uss s saf safet ety y, envi enviro ronm nmen enta tall and and econ econom omic ic issu issues es..

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Question 2 The process in the figure below vapourises li%uid butane and mi&es the vapour with compressed air. air. The mi&ture flows to a pac#ed bed reactor after it has been cooled in a heat e&changer. !n order to meet our control objectives of safety and %uality control, the following needs to be implemented' The pressure in the vapouriser (P1), which is important for safety, should be controlled by adjusting the vapour vapour release release from the vapou vapouris riser er (v3); i!uid i!uid level level in the vapour vapourise iserr (1), (1), should should not  overflow the vessel or drain empty, and this can be controlled by adjusting the flow of li!uid butane from storage to the vapori"er (v1); the percentage of butane in the mi#ed stream ($1), which is important in order to avoid an e#plosive concentration, can be controlled by adjusting the flow of  air through the valve in the compressor suction, suction, v%& a.

 b.

(ist the output )controlled* and input )manipulated* variables. +how the implementation of the above control schemes on a simple -!$.

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Question 3 $raw $raw the process process instru instrumen mentt diagra diagram m for for the Control of the Sugar-Re Sugar-Refinin fining g Process Process discussed below. 'se either $uto$, *icrosoft +ffice isio, the draw toolbar of *icrosoft -ord or PowerPoint or any  other flow.sheeting /oftware. /oftware . The process units, shown below, form part of the process to refine sugar. aw sugar is fed to the process through a screw conveyor. Water is sprayed over it to form sugar syrup. The syrup is heated in the dilution tan#. /rom the dilution tan# the syrup flows to the preparation tan# where more more heati heating ng and mi&ing mi&ing is acc accomp omplis lished hed.. /rom /rom the prepar preparat ation ion tan# tan# the syrup syrup flows flows to the blending tan#. hosphoric acid is added to the syrup as it flows to the blending tan#. !n the blending tan# lime is added. This treatment with acid, lime, and heat serves two purposes. The first is that of clarification, that is, the treatment causes the coagulation and precipitation of the no" sugar sugar organics organics.. The second purpose purpose is to eliminate eliminate the coloratio coloration n of the raw sugar. sugar. /rom the blending tan# the syrup continues to other processes in the refinery plant.

Sugar refining process The following variables are thought to be important to control. i. ii. ii. iii. iii. iv. v.

Temperature in in th the di dilution ta tan#. Temper mpera ature ture in the prepa eparation ion tan tan#. $ens $ensit ity y of of the the syr syrup up leav leavin ing g the the pre prepa para rati tion on tan tan#. #. (evel in in pr preparation ta tan#. (evel (evel in in 01 01 aci acid d tan# tan#.. The The leve levell in the the 21 21 aci acid d tan# tan# can can be be assu assume med d cons consta tant nt..

vi.

The streng strength th of of the the 01 acid acid.. The The streng strength th of of the the 21 acid acid tan# tan# can can be be assum assumed ed constan constant. t.

vii. vii. viii viii.. i&. i&. &.

The The flo flow w of of syr syrup up and and 01 01 acid acid to the the ble blend ndin ing g tan tan# # The The p p of of the the solu soluti tion on in the the ble blend ndin ing g tan tan#. #. Temper mpera ature ture in the blend lendin ing g ta tan#. The The ble blend ndin ing g tan tan# # re% re%ui uire res s onl only y a high high"l "lev evel el alar alarm. m.

Question 4

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Consider the conical water tan# shown below. 4btain the model of the process if the flowrate out of the tan# is a function of the s%uare root of height of water in the tan# )  F0 = β  h *. (ist state variables, variables, input variables and parameters. parameters. )int' 5se height as a state variable.*

Question 5 6odel a mi&ing tan# with two feed streams, as shown below. Assume Assume that there are two components, A and 7. C represents the concentration of A. )C 8 is the mass concentration of A in stream 8 and C 9 is the mass concentration of A in stream 9*' 6odel the following cases' a. Consta Constant nt volum volume, e, const constan antt densit density y b. Constant Constant volume, volume, density density varie varies s linearly linearly with with concentra concentration tion c. :ariabl :ariable e volume, volume, density density vari varies es linearly linearly with with concent concentrati ration on

Question 6 Consider two tan#s in series where the ;ow out of the This tutorial is to help your learning process and un#erstan#ing of un#erstan#ing of what was taught in class, and note that this understanding will be tested as soon as possible. Therefore, be wise )"is#o$ ) "is#o$ is  is the application of understood #nowledge*

All the very best in your learning/understanding process. 7