UNIVERSITI TEKNOLOGI MARAFAKULTI KEJURUTERAAN KIMIACHEMICAL ENGINEERING LABORATORY 3CHE (574)

NAME : NIK NUR SHAHIRA BINTI IBRAHIM (2012209148)GROUP : EH220(4A)EXPERIMENT : EXPERIMENT OF TUBULAR FLOW REACTOR BP 101BDATE PERFORMED : 9 APRIL 2014SEMESTER : 4PROGRAMME / CODE : CHE 574SUBMIT TO : DR JEFRI JAAPAR

No.TitleAllocated Marks (%)Marks

1Abstract/ Summary5

2Introduction5

3Aims5

4Theory5

5Apparatus5

6Methodology/ Procedure10

7Result10

8Calculations20

9Discussion20

10Conclusion10

11Recommendations5

12Reference5

13Appendix5

TOTAL MARKS100

Remarks:Checked by:_________________Date:

Contents

Abstract3Introduction3Aims3Theory4Apparatus5Procedure8Result10Discussion10Conclusion17Recommendations18Reference18Appendix19

AbstractReactors are widely used in the chemical industrys processes. One of type of reactors is tubular reactor. The flow in tubular flow reactor is continuous and in a steady state condition and configured so that conversion of the chemicals and other dependent variables are functions ofposition within the reactor. A unit called SOLTEQ Tubular Flow Reactor (Model:BP 101-b) is used in this experiment. This experiment is divided into two which are to examine the effect of pulse input in a tubular flow reactor and the other is to examine the effect of step change input in a tubular flow reactor. Besides that, to compare the residence time distribution (RTD) graph between these two experiments. The mean residence time, variance, and skewness are also calculated for both experiments.

Introduction

Chemical reactor is a place where chemicalreactions take place and it is one of the important part of any chemical process design. In the ideal tubular reactor, the fluids flow as if they were solid plugs or pistons, and reaction time is the same for all flowing material at any given tube cross section. Tubular reactors are likely as the batch reactors in providing initially high driving forces. Flow in tubular reactors can be laminar with viscous fluids in small diameter tubes and greatly deviate from ideal plug flow behavior; or turbulent as with gases. Establishing turbulent flow can result in inconveniently long reactors or may require unacceptably high feed rates for slow reactions and especially in small laboratory and pilot plant reactors. The design of systems with tubular reactors involves recognition of the many important differences between continuous stirred tank reactors (CSTR) and plug flow tubular reactors (PFR).The most important distinction is the importance of the feed conditions in tubular reactor systems, particularly the reactor inlet temperature. Reactor feed preheating becomes an important design parameter, which typically involves trades off between steady state economics and dynamiccontrollability. Reactor inlet concentrations are also more critical in tubular reactor systems, because of parametric sensitivity and the potential for complex dynamics.

Aims

Experiment 1 To examine the effect of a pulse input in a tubular flow reactor. To construct a residence time distribution (RTD) function for the tubular flow reactor.

Experiment 2 To examine the effect of a step change input in a tubular flow reactor. To construct a residence time distribution (RTD) function for the tubular flow reactor.

Theory

Residence time distribution (RTD) FunctionThe residence time distribution (RTD) of a reactor is a characteristic of the mixing that occurs in the chemical reactor. No axial mixing in a plug flow reactor (PFR). The continuous stirred tank reactor (CSTR) is thoroughly mixed. Actually, different reactors can display identical RTD. However, the RTD exhibited by a given reactor yields distinctive clues to the type ofmixing. The RTD is determined by experimentally by injecting an inert chemical called a tracer into the reactor at some time t = 0 and measuring the tracer concentration, C in the effluent stream as a function time. There are two types method of injection which are pulse input and step input.

Pulse Input An amount of tracer is suddenly injected in one shot into the feed stream entering the reactor in as short time as possible in pulse input. The outlet concentration is then measured as a function of time. The effluent concentration vs. time curve is referred to as the C(t) curve in the RTD analysis. The amount of tracer C(t) exiting between time t and (t +t) is

N=C(t) vt

Where v = the effluent volumetric flow rateIf it divided by the total amount of material that was injected into the reactor,

t

which represents the fraction of material that has residence time in the reactor between time t and (t + t).For a pulse injection,1 t

E (t) called as the residence time distribution function. It is describes how much time different fluid elements have spent in thereactor.It can be obtained from the outlet concentration measurements by summing up all the amounts of materials if is not known directly. N between time t=0 and infinity. dN=C(t) vdt

By integrating, 2

By assuming v is constant, substitute 2 into 1

The integral in the denominator is the area under the C(t) curve.

Step InputA more general relationship can bedeveloped between a time-varying tracer injection and the corresponding concentration in the effluent by understanding the pulse input. Thebelow showthe outputconcentration from thevessel is relatedto theinput concentrationby the convolution integral,

By considering a constant rate of tracer addition to a feed in order to analyze a step input in the tracer concentration withconstant volumetric flow rate thatis initiated at time t=0.

Because the inlet concentration is constant with time,,itcanbetakenoutsidethe integral sign,

By dividing with yields,

The expression differentiated to obtain the RTD function E(t),

Formula for other calculation,

Apparatus

Tubular flow reactor Model BP-101-B. Sodium chloride solution, NaCl 0.025M. Deionised water.

Procedure

General Start-up Procedure1. All valves were ensured initially closed except valve V7.2. 20 liter of saltsolution was prepared. For example, sodium chloride, NaCl (0.025M).3. The feed tank B2was filled with the NaCl solution.4. The power for thecontrol panel was turned up.5. The water deionizer was connected to the laboratory water supply. Valve V3 was opened and feed tank B1 was filled up with the deionized water. Valve V3 was closed.6. Valves V2 and V10 were opened. Pump P1 was switched on. P1 flow controller was adjusted to obtain a flow rate of approximately 700 ml/min at flow meter F1-01. The conductivity display was observed at low value then a valve V10 was closed and pump P1 was switched off.7. Valves V6 and V12 were opened. Pump P2 was switched on. P2 flow controller was adjusted to obtain a flow rate of approximately 700 ml/min at flow meter F1-02. A valve V12 was closed and pump P2 was switched off.8. The unit was ready for experiment.General Shutdown Procedures1. Both pump P1, P2 and P3 were switched off. Valves V2 and V6 were closed.2. The heaters were switched off.3. The cooling water was kept circulating through the reactor while the stirrer motor is running to allow thewater jacket to cool down toroom temperature.4. All liquid were drained from the unit by opening valves V1 and V16 if the equipment is not going to be used for long period of time. The feed tanks were rinsed with cleanwater.5. The power for thecontrol panel was turned off.

Experiment 1: Pulse Input in a Tubular Flow Reactor1. The general startup procedures are performed.2. Valve V9 is opened and pump P1 is switched.3. Pump P1 flow controller is adjusted to give a constant flow rate of deionized water into the reactor R1at approximately 700 mL/min at FI-01.4. The deionized water is left to continue flowing through the reactor until the inlet(Q1-01) and outlet (Q1-02) conductivity values are stable at lows levels. The both conductivity values are recorded.5. Valve V9 is closed and pump P1 is switch off.6. Valve V11 is opened and pump P2 is switch on. The timer is stared simultaneously.7. Pump P2 flow controller is adjusted to give a constant flow rate of salt solution into the reactor R1 at 700 mL/min at FI-02.8. The salt solution is left to flow for 1 minute, and then the timer is reset and restarted. The time is start atthe average pulse input.9. Valve V11 is closed and pump P2 is switch off. Then, quickly valve V9 is opened and pump P1 is switch on.10. The deionized water flow rate is making sure toalways maintain at 700 mL/min by adjusting the P1 flow controller.11. Both the inlet (QI-01) and outlet (QI-02) conductivity values is recorded at regular intervals of 30 seconds.12. The conductivity values is continue recorded until all the readings are almost constant and approach the stable lowlevel values.

Experiment 2: Step Change Input in a Tubular Flow Reactor1. The general startup procedures were performed.2. Valve V9 is opened and pump P1 is switched on.3. Pump P1 flow controller is adjusted to give a constant flow rate of deionized water into the reactor R1at approximately 700 ml/min at FI-01.4. The deionized water is left to continue flowing through the reactor until the inlet (QI-01) and the outlet (QI-02) conductivity values are stable at low levels. Both conductivity values are recorded.5. Valve V9 is closed and pump P1 is switched off.6. Valve V11 is opened and pump P2 is switched on. The timer is started simultaneously.7. Both the inlet (QI-01) and outlet (QI-02) conductivity values are recorded at regular intervals of 30 seconds.8. The conductivity values are continued recorded until all readings are almost constant.

Result

Experiment 1:Flow rate: 700 mL/minInput type: Pulse InputTime (min)Conductivity (mS/cm)

InletOutlet

0.00.00.0

0.50.12.1

1.00.02.2

1.50.02.2

2.00.02.1

2.50.01.0

3.00.00.3

3.50.00.0

Time , min0.00.51.01.52.02.53.03.5

Outlet Conductivity, mS/cm0.02.12.22.22.11.00.30.0

E(t), 1/min0.00000.42420.44440.44440.42420.20200.06060.0000

Figure 1: Outlet Conductivity vs Time

Figure 2: RTD function plot, the E curve

Experiment 2:Flow rate: 700 mL/minInput type: Step Change InputTime (min)Conductivity (mS/cm)

InletOutlet

0.00.00.0

0.52.90.0

1.03.20.0

1.53.30.0

2.03.30.0

2.53.30.1

3.03.31.4

3.53.31.8

4.03.41.9

4.53.32.0

5.03.32.0

5.53.32.0

6.03.32.0

6.53.32.0

7.03.32.0

7.53.32.0

Time , min0.00.51.01.52.02.53.03.54.0

Outlet Conductivity, mS/cm0.00.00.00.00.00.11.41.81.9

E(t), 1/min0.00000.00000.00000.00000.00000.01040.14580.18750.1979

Time , min4.55.05.56.06.57.07.5

Outlet Conductivity, mS/cm2.02.02.02.02.02.02.0

E(t), 1/min0.020830.020830.020830.020830.020830.020830.02083

Figure 3: Outlet conductivity vs time

Figure 4: RTD function plot, the E curve

Calculations

Experiment 1For outlet conductivity of 0.3 mS/cm:==0.5 min=(0.3+2.1+1.0+2.2+2.2+2.1) (0.5)=4.95

E (t)=E (t) =E (t) =0.0606

Mean residence timetm= =tm=tm= 0.00612

Variance = === = 0.002986

Skewnesss3 = s3 = s3= 1.47 x 10-3

Experiment 2For outlet conductivity of 0.2 mS/cm:= =0.5 min= (1.9+1.8+1.4+0.1+2.0+2.0+2.0+2.0+2.0+2.0+2.0) ( 0.5 )=9.6

E (t) = E (t) = E (t) = 0.02083

Mean residence timetm= =tm=tm= 1.085 x 10-3

Variance = === = 5.40 x 10-4

Skewnesss3 = s3 =s3= 2.69 x 10-4

Discussion

In theideal tubular reactor, the fluids flow as if they were solid plugs or pistons, and reaction time is the same for all flowing material at any given tube cross section. Tubular reactors resemble batch reactors in providing initially high driving forces, which diminish as the reactions progress down the tubes.There are two experiments for tubular reactor which are pulse input in a tubular reactor and step change input in a tubular reactor. For first experiment, it was aimed to examine the effect of a pulse input in a tubular reactor. Second experiment is to attain the effect of a step input in a tubular reactor. From the result for these two experiments, the residence time distribution (RTD) function which is E(t) as a function of time isplotted. From the both graph that has been plotted, the trend for this two graphs are different. The trend for residence time distribution (RTD) graph for first experiment for pulse input is increase and then for a few minute is decreased until the value is zero. However, the graph for second experiment the graph is increase and at time 2 min, the value of E(t) is constant. In these experiments, the mean residence time, second moment (Variance), and third moment (Skewness) are also calculated. Forexperiment 1, the mean residence time is 0.00612 min, second moment (variance) is 0.002986 and third moment (Skewness) is 1.47 x 10-3for outlet conductivity of 0.3 mS/cm. On the other hand, the mean residence time for experiment 2 is 1.085 x 10-3 min. Then, the second moment (variance) is 5.40 x 10-4 and the third moment (Skewness) is 2.69 x 10-4. This experiment shows that there are differences between pulse input and step change input in tubular reactor method. One ofthe differences is the tracer of theinput. In a pulse input, an amount of tracer substance is suddenly injected in one shot into the feed stream entering the reactor in as short times as possible. While for a step input, a constant rate of tracer addition to a feed is initiated at time t =0. Before this time no tracer was added to the feed. The tubular reactor is usually used in some of the following application which is large scale reactions, fast reactions, homogeneous or heterogeneous reactions, continuous production, and high temperature reactions.

Conclusion

The objectives of these two experiments were achieved. As a conclusion, there are differences for pulse input and step change input in a tubular reactor. The residence time distribution (RTD) function is one of the differences for pulse input and step change input. For RTD graph for pulse input experiment, the graph is increase and then decrease to the value zero.However, the RTD graph for step change input, the graph is increase then constant atcertain value before decrease rapidly due to some error. Thus, the experiment was successful.

Recommendations

There are few suggestions toget more accurate results forthis experiment, which are: Ensure that no leakage atthe valve on the unit. This toprevent the result will affect. Make sure that the valve is open or close, follow as the general startup procedure carefully. For both experiments, do more trial to get average of conductivity for both inlet (Qi-01) and outlet (QI-02) conductivity values in order toget more accurate results.

Reference

1. Fogler, H.S (2006). Elements of Chemical Reaction Engineering (3rd Edition). PrenticeHall.2. Levenspiel, O. (1999). Chemical Reaction Engineering (3rd Edition). John Wiley.3. Laboratory Manual Tubular Flow Reactor.

Appendix