Pharmaceutical and Chemical Process Technology
LABORATORY MANUAL
September 2008
CONTENTS
1. Filtration at constant pressure.
2. Aspen Plus tutorials (version 11):
Separation Processes (I and II)
3. Drying of solids – (i) tray drying
(ii) spray drying
(iii) fluid bed drying
4. Heat Transfer – double tube and shell and tube heat exchangers.
5. Reactor experiments: Batch reactor
6. Distillation: Vapour – liquid equilibrium curve and application.
7. Fluid flow: Flowmeter demonstration
Energy losses in pipes
8. Continuous column extraction
9. GMP 1/2
10. PID control
11. Membrane separation - pervaporation
12. Pharmaceutical Plant visit.
Introduction
Students are required to complete practicals from the list provided.
Ensure that you read through each experiment prior to commencement and discuss with the laboratory supervisor.
Laboratory reports must be written following the completion of each experiment and handed into the laboratory supervisor for assessment.
Laboratory reports should be written using the following format:
· Title
· Introduction (statement of objectives, theory, background)
· Experimental methods (a concise account of all experimental methods used including equipment, materials)
· Results (tabulation of results, figures, calculations etc)
· Discussion (of results)
· Conclusions
· References
Reports should be contained in plastic envelopes and folders.
All reports must be written using Microsoft Word/Excel.
Filtration at Constant Pressure
Safety information
Refer to CRA and MSDS
Hazard identification and risk assessment
Chemical / Hazard class / Hazard identification and risks / Risk phrasesCalcium carbonate / Xi / Xi / R 37/38, 41
Precautions
· Avoid inhalation of dust
Waste
· Calcium carbonate must be dried and reused.
Spillage
· Clear up and dispose of as non-hazardous waste
1. Introduction
The integrated form of the filtration equation for constant pressure filtration (assuming an incompressible filter cake) gives:
V2 + AVL = A2 DPt
2 v rmv
i.e. V = 2A2D Pt - 2AL
rm v V v (V is linear with t/v)
where
V = volume of filtrate (m3)
A = filter area (m2)
r = specific resistance of filter cake
m = filtrate viscosity (Nsm-2)
v = Volume of cake
Volume of filtrate
L = filter cake equivalent thickness to cloth or paper (m)
DP = pressure drop (Nm-2)
t = filtration time (s)
The terms L and rmv are termed the filtration constants and may be determined by
v
obtaining values for V and t, plotting V versus t and
V
obtaining slope and intercept. Having obtained these, the values can be used to scale-up a filtration. If the viscosity of the filtrate is known and a value for v obtained, then values for r and L may be obtained also. The viscosity at any temperature may be obtained by using the attached nomograph.
Another parameter of interest is the fractional porosity of the cake, e, and this may be obtained from measuring cake volume and calculating particle volume from specific gravity. In summary, the objective of the experiment is to operate a laboratory scale filtration at constant pressure, estimate the filtration constants, calculate r, L and use the filtration constants to carry out a preliminary design for a filter press.
2. Experimental Procedure
2.1 Equipment
As assembled.
2.2 Method
Make up a suspension of 5%w/w CaCO3 (or CaSO4. 2H2O as available) in water and place in reservoir. Start the stirrer motor. Start the vacuum pump with stopcock A closed and using stopcock B obtain a steady pressure reading of between 50 and 60 cm Hg (i.e. between 67,763 and 78,947 Nm-2) to give a steady filtrate flowrate. Use safety screen provided. Maintain this pressure at a steady reading. Fill the funnel about half-way, at the same time opening A fully. Adjust B to obtain a steady pressure reading as before. Maintain the level in the funnel as constant as possible and take filtrate volume readings at suitable time intervals i.e. try and include at least five readings for each run. Do not exceed the capacity of the filtrate vessel. Record final filtrate volume. Repeat the experiment twice more, for each run changing the DP to give sensible filtrate flowrates. Record DP values Dry filter cakes in drying oven to constant weight. Record weight, diameter and thickness of each filter cake.
Retain filter cakes for further use.
3. Calculations
3.1 Plot V against t/V for the separate DP runs and
calculate rmv, L, r and L. Compare values.
v
Use the rmv, and L average values obtained to carry out design calculation in 3.2
v
3.2 Filter Design
A filter press consisting of 12 frames is to be operated on a 15 minute cycle using the slurry above. It is required that the volume of filtrate processed on each cycle should be 80.0 litres. If the pressure drop across the filter is maintained at 4.0 X 105 Nm-2, what is the required area of each frame? (Note: A filter frame contains two filtration areas).
4. Report
The following should be included:
4.1 Comments on control of process, appearance of filter cake etc.
4.2 Tabulation of rm v and L results.
v
4.3 r and L values.
4.4 e values for each filtration.
4.5 The calculated filter-frame area in scale-up.
Note: (i) All calculations and units of measurement are to be clearly shown.
(ii) S.I. units are to be used throughout.
Modelling of Chemical Processes – Separation Processes (I)
Introduction
This practical is concerned with the use of Aspen Plus as a modeling tool for the operation of continuous fractional distillation.
Objectives
1. To obtain operating results for a continuous fractional distillation system.
2. To perform a sensitivity analysis for a continuous fractional distillation system.
3. To develop a process flowsheet.
4. To meet a process design specification.
Method
Complete the tutorials in ‘Building and running a process model version 11’ as follows:
Ch.1 Aspen plus basics (20 min.)
Ch.2 Building and running a process simulation model (50 min.)
Ch. 3 Performing a sensitivity analysis (20 min.)
Ch.4 Meeting process design specifications (20 min.)
Ch.5 Creating a process flow diagram (20 min.)
When the tutorials have been completed build and run a process simulation model using the following process parameters/system specification:
Feed: 10 kmol h-1 benzene/toluene
Feed composition: 60 mol %toluene/40 mol % benzene (xf = 0.4)
Reflux ratio (R): 4
Feed temperature: 95oC
Theoretical plates: 7 (N)
Distillate flow: 3.75 kmol h-1
Feed stage: 4
Pressure: 1 atm.
Obtain operating results for the above system. Choose ‘Template’/’Metric units’ for your model. Use the RadFrac unit operation model and the UNIFAC activity coefficient model or IDEAL model. Obtain operating results for a system with 12 stages instead of 7 (N = 12).
Perform a sensitivity analysis on the above system (variation of xd, distillate composition, with R)
Develop the process flowsheet as described in the tutorial.
Meet a process design specification (say xd = 0.90).
Save results on disc. Print results and include with your report.
Reference
Building and Running a Process Model Version 11.
Modeling of Industrial Chemical Processes – Separation Processes (II)
Introduction
This practical is concerned with the use of Aspen Plus as a modeling tool for the operation of liquid-liquid extraction.
Objectives: To obtain operating results for a liquid-liquid extraction system.
1 3
L2
48 kmol s-1 water
4 2 7.69 kmol s-1 benzene
2.31 kmol s-1 acetone
Method
Complete the tutorials in ‘Building and running a process model version 11’ as follows:
Ch.1 Aspen plus basics (20 min.)
Ch.2 Building and running a process simulation model (50 min.)
Ch.3 Performing a sensitivity analysis (20 min.)
Ch.4 Meeting process design specifications (20 min.)
Ch.5 Creating a process flow diagram (20 min.)
When the tutorials have been completed build and run a process simulation model using the following process parameters/system specification:
Continuous counter-current liquid – liquid extraction
Use Type-Column and Model-EXTRACT. Use UNIQUAC activity coefficient model.
System specifications.
solvent: 48 kmol s-1 water.
feed: 7.69kmol s-1 benzene/2.31kmol s-1 acetone.
T: 298 K
P: 101325 Pa. (1 atm)
N (stages): 3
Vary N (say N = 2, 4, 5, 6) and examine the effect on the raffinate composition.
Print results.
Reference
Building and Running a Process Model Version 11.
Drying of solids – tray drying
Safety information
Hazard identification and risk assessment
Precautions
· sand is used in this experiment
· oven and contents are hot!
Waste
· Sand must be dried and reused.
Spillage
· Sweep up and dispose of as non-hazardous waste
Oven
· Avoid direct contact with any hot item, use tong to manipulate hot apparatus or use special gloves.
Objectives
Experimental determination of the rate of drying curve for solid, at constant drying conditions (constant air flow, temperature and humidity).The experiment is carried out in a batch dryer and heat is supplied by direct contact with heated air at atmospheric pressure. The drying oven is operated at three temperatures – 100, 110 and 120 deg. cent.
Important Definitions
· Humidity of an air-water vapor mixture (H):
H = Mass of Water (kg) / Mass of Dry Air (kg)
· Moisture content of a solid (X):
X = Mass of Water (kg) / Mass of Dry Solid (kg)
· Equilibrium Moisture Content of a Solid (Xe): Is the final moisture content of a solid after being brought into contact with a stream of air (having humidity “H” and temperature “T”) long enough, for equilibrium to be reached. Is expressed in the same way as X.
· Free Moisture Content of a solid: Is the moisture above the equilibrium moisture content. Is the only moisture that can be removed by drying under the given drying conditions.
· Critical Moisture Content of a solid (Xc): Is the solid moisture content attained, during the drying process, when the entire surface of the solid is no longer wetted.
Experimental Determination of the Rate of Drying Curve
The rate of drying “R” is defined as the mass of liquid evaporated by unit time and by unit of exposed surface area for drying. It can be mathematically expressed by
S dX
R = - ¾ ¾¾¾ (1)
A dt
Where
R = drying rate (kg H2O/sm2)
S = weight of dry solid (kg)
A = exposed surface area for drying (m2)
X = solid moisture content (kg H2O/kg dry solid)
t = time (s)
To experimentally determine the rate of drying for a given material (case study sand), a sample is placed in a dryer and under constant drying conditions, the loss in weight of moisture during the drying process is determined at constant time intervals.
With the data obtained from the batch experiment, a plot of the solid moisture content “X” versus time can be made (Figure 1). From this plot, the rate of drying curve can be obtained by measuring the slopes of the tangents drawn to the curve, which give the values of dX/dt at given values of t. The drying rate “R” is calculated for each point using equation (1). The drying rate curve is obtained by plotting R versus the solid moisture content “X” as in figure 2.
The plot of the rate of drying curve can presents several shapes but generally the two major points – constant and falling rate period – are present. At time zero the initial moisture content of the solid is shown at point A or A’ depending on the solid temperature. At point B the surface temperature as attained its equilibrium value and the constant rate period starts. This period continues as long as the water is supplied to the surface as fast as it evaporates. At point C, the solid critical moisture content “Xc” is attained. At this point there is no insufficient water on the surface to maintain a continuous film of water and the first falling rate period starts. The wetted area of the solid continually decreases until the surface is totally dry at point D. At this point begins the second falling rate period, that continues until the equilibrium moisture content of the solid is reached, at point E.
Figure1: solid moisture content “X” versus time for constant drying conditions
Figure2: drying rate “R“ versus solid moisture content “X” for constant drying conditions
Date : ………/………./
Weight of dry solid ………………………………….. kg
Weight of added water……………………………….. kg
Initial moisture content……………………………….. %
Total sample weight (tray + solid + water)……………. kg
Air temperature………………………………………… oC
Air velocity…………………………………………….. m/s
Surface area…………………………………………….. m2
Time (s) / Weight of solid (kg)Time (s) . / X (kg H2O/kg dry solid) . / dX/dt . / R (kg/s m2)
Calculations
· Plot experimental X versus time t
· Plot experimental R versus experimental X
Practical Formulas
W - Ws
X = ¾¾¾¾¾¾ I
Ws
Ws dX
R = - ¾¾ ¾¾ II
A dt
where
W = weight of total solid (kg)
Ws = weight of dry solid (kg)
References
Geankoplis, Christie, J (1983). Transport Processes and Unit Operations, 2nd ed. Massachusetts, Allyn and Bacon. Inc., pg 508-552
Spray drying
The aims of this experiment are:
· To investigate the performance of the spray drier
· To investigate parameters that control the spray drying process
· To examine and study spray dried product properties e.g. particle size and shape
See operating manual for experimental details.
Drying of solids – fluid bed drying
Introduction: When a stream of gas is passed upwards through a bed of material at a certain velocity the bed will first expand, then become suspended and agitated by the gas stream to form a fluidised bed. This has the appearance of boiling liquid due to the formation of many small bubbles-the so-called ‘bubbling fluidisation’.
At higher gas velocity, larger bubbles and plugs of material are formed resulting in a more violent type of fluidisation called slugging or spouting. The optimum operating gas velocity for bubbling fluidisation lies above the minimum fluidising velocity but below the velocity of entrainment of the material.