Practical - Lab report for reaction engineering PDF

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Faculty of Science and Engineering Department of Chemical Engineering

CHEN3 0 1 0Re a c t i onEngi ne e r i ng La bor a t or yRe por t Se me s t e r12 0 1 6

Ex pe r i me nt1 : TUBULARFL OWREACT OR( TF R)

Gr o u pA1 “ Wed e c l a r et h a t t h i sr e p o r t i ss o l e l yo u ro wnwo r k .Al l c o n t r i b u t i o n sma d eb yo t h e r sh a v eb e e nd u l y a c k n o wl e d g e d . ” No . 1 . 2 . 3 . 4 .

Pe r t hI D 1 7 9 2 6 0 7 0 1 8 0 9 8 4 5 9 1 7 9 0 1 0 2 2 1 8 0 2 3 2 9 9

St u d e n t ’ sNa me Da r r e nGa nKi nWa i J a s o nTi o n gSi eY e e n Mu h a mma dSy a fi qBi nAb uBa k a r Ch e a n gL a i T e n g

Da t eo f Ex p e r i me n t :

s t 2 1 Ma r c h2 0 1 6

Da t eo f Re p o r t Su b mi s s i o n :

t h 4 Ap r i l 2 0 1 6

Na meo f L e c t u r e r :

Dr . J i b r a i l Ka n s e d o

Si g n a t u r e Darren Tiong Syafiq Teng

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Faculty of Science and Engineering Department of Chemical Engineering

Executive Summary The saponification reaction of ethyl acetate with sodium hydroxide was carried out in this experiment. From the reaction, the operations of Tubular Flow Reactor (TFR) or Plug Flow Reactor (PFR) was controlled and studied. Three sets of experiment with different parameters were carried out to determine the effect of pulse input, step change input as well as residence time on the reaction in a TFR by comparing the conductivity, rate constant and rate of reaction. The rate of reaction and conversion can be analysed based on the conductivity. All the data calculations are based on the basis of calibration data and rate law equation. Data produced is used to plot graphs of outlet conductivity against time in order to obtain the effluent concentration vs. time curve which is referred to as the C(t) curve in Residence Time Distribution (RTD) analysis. The experimental results obtained deviates from the theoretical value due to the errors occurred while conducting the experiment. The accuracy of the results could be improved by several approaches which will be further explained in Discussion.

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Faculty of Science and Engineering Department of Chemical Engineering

Contents Executive Summary....................................................................................................................................2 List of Figures..............................................................................................................................................4 List of Graph...............................................................................................................................................4 List of Tables...............................................................................................................................................4 1.0 Introduction..........................................................................................................................................5 2.0 Underlying Theory................................................................................................................................5 3.0 Description of Apparatus......................................................................................................................9 4.0 Experimental Procedures....................................................................................................................10 5.0 Assumption and Justification..............................................................................................................11 6.0 Results and Analysis............................................................................................................................12 6.1 Experiment 1.1................................................................................................................................12 6.2 Experiment 1.2................................................................................................................................15 6.3 Experiment 1.3................................................................................................................................17 7.0 Discussion...........................................................................................................................................19 8.0 Conclusion and Recommendation......................................................................................................20 9.0 References..........................................................................................................................................21 10.0 Appendix A.......................................................................................................................................21

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Faculty of Science and Engineering Department of Chemical Engineering

List of Figures Figure 1:Balance on the system volume..........................................................................................6 Figure 2: Tubular Flow Reactor ......................................................................................................7 Figure 3:Residence Time Distribution Measurement…………………………………………8 Figure 4:Process flow diagram for Tubular Flow Reactor Unit....................................................11

List of Graph Graph 6.1.1 Graph of Outlet Conductivity against Time for Experiment 1.1..........................15 Graph 6.1.2 Graph of Residence Time Distribution Function for Experiment 1.1..................15 Graph 6.2.1 Graph of Outlet Conductivity against Time for Experiment 1.2..........................18 Graph 6.2.2 Graph of Residence Time Distribution Function for Experiment 1.1..................18 Graph 6.3.1 Graphs of Conversion Rate against Residence Time for Experiment 1.3............20

List of Tables Table 5.0 Assumptions and Justification.................................................................................13 Table 6.1 Table of Results for Experiment 1.1........................................................................14 Table 6.2 Table of Results for Experiment 1.2........................................................................17 Table 6.3 Table of Results for Experiment 1.3........................................................................20

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Faculty of Science and Engineering Department of Chemical Engineering

1.0 Introduction In chemical engineering, chemical reactors play an important role as designed equipment for chemical reactions to take place. There are several chemical reactors available in conducting various chemical processes such as Plug Flow Reactor (PFR), ConstantlyStirred Tank Reactor (CSTR), Batch Reactor and Semi-Batch Reactor. The main focus of this experiment is Tubular Flow Reactor.(TFR) or known as Plug Flow Reactor (PFR) usually used to contain chemical reactions that occur in liquid phase under isothermal and adiabatic conditions. In this reactor, fluids flow with high velocities so that there will be no condition where the products re-diffuse or back-mixing. This will result in reduction of side reactions and thus increase the yield of the desired reactions. The rate of reaction is higher at the pipe inlet and lower at the pipe outlet. This is due to the highest concentration of reactants at the pipe inlet and the concentration decrease as the reaction occurs along the pipe (CIEC Promoting Science, 2016). The objectives of this experiment are: 1. 2. 3. 4. 5. 6.

To study the effect of a pulse input in Tubular Flow Reactor (TFR) To construct a residence time distribution (RTD) function for TFR To study the effect of a step change input in TFR To perform a saponification reaction between NaOH and Et(Ac) in TFR To calculate the reaction rate constant of the saponification reaction. To determine the effect of residence time on the conversion in TFR

2.0 Underlying Theory General Mole Balance Equation

Figure 1: Balance on the system volume In the system volume shown above, a mole balance is performed on species j where it represents the particular chemical species of interest. The mole balance on species j at any instant in time, t is given by:

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Faculty of Science and Engineering Department of Chemical Engineering ¿ ¿ ¿ ¿ Rateof accumulation of j within the system ¿ Rateof generation of j bychemical reaction within =¿ the system ¿ Rate of flow of j out of + ¿ the system ¿ Rate of flow of jinto – ¿ the system ¿ ¿ where

¿− Out+ Generation= Accumulation

Nj = number of moles of Gj = rate of generation of species j

species

j

in

F j 0−F j +G j =

the

system

dN j (1) dt

at

time

t

If all the system variables such as temperature and concentration are uniform throughout the system volume, the rate of generation of species j, Gj is given by : Gj = rjV (2) If rate of formation of species j, rj is not constant throughout the system volume, the total rate of generation is given by : V

G j =∫ r j dV (3) ❑

Thus, the general mole balance equation for species j is given by : V dN F j 0−F j +∫ r j dV = j (4) dt ❑ For a plug reactor at steady state, the general mole balance is given by :

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Faculty of Science and Engineering Department of Chemical Engineering

Figure 2: Plug Flow Reactor (PFR) dN A (5) =0 dt FA (y) – FA(y + Δy) + rAΔV = 0 (6) where FA(y) = molar flow rate of A into volume ΔV FA(y+Δy) = molar flow rate of A out of the volume In a spatially uniform subvolume ΔV, V

r j dV =¿ ∫ ❑

rAΔV (7)

The volume, ΔV is obtained by multiplying cross-sectional area, A and the reactor length Δy. ΔV=AΔy (8) Substituting Equation (8) into Equation (6) : F A ( y +Δy) −F A ( y ) [ ] = -ArA (9) Δy As Δy approaches zero : ❑ dF A F A ( y + Δy ) −F A ( y) = = ArA (10) lim dy Δy Δy →0 dy can be changed to dV to obtain a design equation for TFR dF A =r A (11) dV The plug-flow reactor volume necessary to get a specified conversion X is given by :

(

)

X

V=

F A 0∫ 0

dX rA

(12)

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Faculty of Science and Engineering Department of Chemical Engineering Where

FA0 =

molar

flow rate

of

species A fed

to

a steady-state

system

Residence Time Distribution Function Figure 3: RTD measurements RTD can be determined experimentally by injecting a tracer which is inert, into the reactor at t = 0 before the tracer concentration, C in the effluent stream is measured as a function of time. Pulse Input For a small time increment Δt, the amount of tracer C(t) exiting between time t and (t+Δt) is : ΔN=C(t)vΔT (13) Where ΔN = amount of material that has spent amount of time between t and (t+Δt) Divided by total amount of material that was fed into the reactor, N 0 : 8

Faculty of Science and Engineering Department of Chemical Engineering

ΔN vC (t ) Δt (14) = N0 N0 For pulse injection : E ( t) =

vC (t) N0

ΔN =E (t) Δt N0

(15) (16)

Where E(t) = residence time distribution function. To equation to determine N0 is given by : ∞

N 0=∫ vC ( t ) dt (17) 0

With constant volumetric flow rate, v, residence time distribution function E(t) can be defined as : C (t) E ( t) = ∞ (18) ∫ vC ( t ) dt 0

Step Input The output concentration from a vessel is related to the input concentration by the convolution integral. t

' ' C out (t )=∫ C ¿ (t −t ) E ( t ) dt

(19)

0

Consider a constant rate of tracer addition to a feed that is started at t = 0 0 t< 0 C 0( t )={ } (20) 0 ( ) constant t ≥0 As the inlet concentration is constant wit time, C0, it is taken out from the integral sign. t

C out=C 0∫ E ( t ' ) dt ' (21) 0

Divided by C0 gives :

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Faculty of Science and Engineering Department of Chemical Engineering

[ ] C out C0

t

=∫ E ( t ') d t' =F (t ) (22) step

0

RTD function E(t) is then defined as : E(t )=

[ ]

d C (t) dt C 0

(23)

step

3.0 Description of Apparatus The apparatus used in this experiment is SOLTEQ® Tubular Flow Reactor (Model: BP 101). As mentioned before, it has specifications to contain chemical reactions in liquid phase under isothermal and adiabatic conditions. This unit has been completed with a jacketed plug flow reactor, individual reactant feed tanks and pumps, temperature sensors and conductivity measuring sensor.

Figure 4: Process flow diagram for the tubular flow reactor unit This reactor consists of two 20-L cylindrical vessels of feed tanks labelled as B1 and B2. In this experiment, water deionizer is filled into tank B2. Besides that, two peristaltic feed pumps labelled as P1 and P2 also attached to this reactor. These pumps have speed rate ranged from 1 to 300 rpm. In addition, there are valves labelled from V1 to V19 to control the flow of the fluids throughout the reactor.

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Faculty of Science and Engineering Department of Chemical Engineering

4.0 Experimental Procedures Experiment 1.1 : Pulse Input in a Tubular Flow Reactor P2 was switched on and the de-ionized water was allowed to continue flowing through the reactor. This step was done until the inlet (QT 01) and outlet (QT 02) conductivity values are low and stable. These values were then recorded. Then, pump P2 was switched off and pump P1 was switched on while the timer was started simultaneously. The salt solution was allowed to flow for 1 minute. After that, P1 pump was switched off and P2 pump was switched on. Both inlet (QT 01) and outlet (QT 02) was recorded at regular intervals of 30 seconds. This was done until all readings were almost constant and stable at low level values. Then pump P2 was switched off. Experiment 1.2 : Step Change Input in a Tubular Flow Reactor Pump P2 was switched on and the de-ionized water was allowed to continue flowing through reactor until the inlet (QT 01) and (QT 02) conductivity values are low and stable. These values were then recorded. Then pump P2 was switched off and pump P1 was switched on. The timer was started and the salt solution was allowed to flow. Both the inlet (QT 01) and outlet (QT 02) conductivity values were recorded at regular intervals of 30 seconds. This was done until all readings were almost constant and stable. Experiment 1.3 : Effect of Residence Time on the Reaction in a TFR The speed of pump is set to be 97 RPM to get a desired flow rate of solutions entering the reactor which was 0.3 L/min. P1 and P2 were switched on to let both NaOH and Et(Ac) solutions to enter plug reactor R1 and emptied into waste tank B3. Both inlet and outlet steady-state conductivity were recorded. 50 ml sample was collected by opening valve V12. Back titration was performed to manually determine the concentration of NaOH in the reactor and extent of conversion. The experiment was repeated for different residence times by reducing the feed flow rates of NaOH and Et(Ac) to about 82 RPM, 64 RPM, 48 RPM, 32 RPM and 16 RPM.

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Faculty of Science and Engineering Department of Chemical Engineering

5.0 Assumption and Justification

No.

Table 5.0: Table of Assumption and Justification Assumption Justification

1

Operate under steady state conditions

The flow is flowed under constant flow rate at 0.15L/min.

2

No heat loss to the surroundings

3

Negligible change in kinetic and potential energy.

No chemical reaction occur, so no heat is generated or absorbed. Heat outside the tube is adiabatic.

4

Constant fluid properties

The fluid in the stream is under the same phase.

5

Conductivity measured is the concentration of chemicals.

Chemical used is ionic compound so it can conduct electricity.

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Faculty of Science and Engineering Department of Chemical Engineering

6.0 Results and Analysis 6.1 Experiment 1.1 Table 6.1: Table of results for Experiment 1.1 Time (min )

Conductivity (mS/cm) Outle Inlet t

Intergrate C(t)

E(t)

tm

Variance

Skewness

0.0

7.53

0.19

0

0

0

0

0

0.5

7.20

0.19

0.095000

2.000000

0.250000

0.010417

1.837117

1.0

2.82

0.18

0.092500

1.945946

0.729730

0.002671

5.038880

1.5

1.01

0.16

0.085000

1.882353

1.176471

0.008861

3.170937

2.0

0.58

0.17

0.082500

2.060606

1.803030

-0.018011

#NUM!

2.5

0.44

0.74

0.227500

3.252747

3.659341

-1.697801

#NUM!

3.0

0.34

2.93

1.074173

2.727679

3.750558

1.032352

-0.968139

3.5

0.28

3.97

1.827010

2.172949

3.531042

0.306232

-1.017302

4.0

0.25

3.53

1.877536

1.880123

3.525231

0.067086

1.374351

4.5

0.23

2.51

1.615552

1.553649

3.301504

0.836120

1.022370

5.0

0.22

1.59

1.304612

1.218753

2.894539

3.092354

0.985457

5.5

0.20

1.00

1.113343

0.898196

2.357765

6.494518

1.056040

6.0

0.19

0.65

1.143938

0.568213

1.633612

9.890953

1.214711

6.5

0.19

0.47

1.457846

0.322393

1.007479

8.860497

1.670378

7.0

0.19

0.36

2.098651

0.171539

0.578943

5.663226

2.513228

7.5

0.19

0.30

3.112125

0.096397

0.349440

3.241254

3.776418

8.0

0.18

0.25

4.563489

0.054783

0.212283

1.948470

5.357346

8.5

0.18

0.24

6.551841

0.036631

0.151103

1.338721

6.978904

9.0

0.19

0.21

0.022772

0.099628

0.934456

8.928059

9.5

0.18

0.20

0.015659

0.072423

0.693473

11.010534

10.0

0.18

0.19

9.221789 12.77225 7 17.46249 0

0.010880

0.053042

0.530444