exaust & contineous application of chemicals calculations
Post on 22-Nov-2014
75 Views
Preview:
TRANSCRIPT
CHEMICALS CALCULATIONS IN EXHAUST AND CONTINUOUS PROCESS
EXAUST APPLICATION OF CHEMICALS
A cycle comprises one complete circulation of the complete volume of the dyebath
All the chemicals are added into the bath step by step after some intervals
Two main factors which are important in exhaust process i.e.,
1. Main component %age on the fabric
2. Liquor to goods ratio (L:R)
All chemicals quantity depends upon these two things
Let’s assume the following bleaching recipe
L:R = 1:50H2O2 = 4% o.w.fCaustic Soda = 4% o.w.fWetting Agent = 1g/lSquestering Agent = 1g/l
Assume that fabric weight = 2.15gTotal liquor = 2.15*50 = 107.5 mlQuantity of H2O2 = 4*2.15/100Caustic soda = 4*2.15/100
Wetting agent:
1000ml require = 1 g1 ml require = 1/1000107.5ml require = 1/1000*107.5 = .1075g
Squestering agent:
1000ml require = 1 g1 ml require = 1/1000107.5ml require = 1/1000*107.5 = .1075g
PAD APPLICATION OF CHEMICALS
Two types of pad applications:
Application of chemicals to dry fabric i.e., Wet on Dry. e.g, in finishing and dyeing process
Application of chemicals to wet fabric i.e., Wet on Wet. e.g., in bleaching process
The following conditions should be met to obtain consistent chemical application:
Uniform nip pressureUniform initial moisture contentConstant saturator levelConstant fabric speedConstant temperatureGood liquor penetration and interchange
PAD APPLICATION OF CHEMICALS TO DRY FABRIC
The amount of liquor taken up by the fabric is often described as the mangle expression i.e., ‘pick up’
Dry fabric is passed through the chemical solution and this process is called a ‘wet on dry’ process
Factors affecting fabric wet pickup
Factor Effect on wet pickupFiber type Higher wet pickup with hydrophilic fibersYarn construction Higher wet pickup with low twistFabric construction Higher wet pickup with loose constructionWettability Higher wet pickup with more easily wetted fabricPressure of squezz rolls Higher pressure will lead to low pickupNature and hardness of squezz rolls Harder coveribgs lead to low pickupLength of immersion time Higher wet pickup with longer immersion timeViscosity of solution Higher wet pickup with higher viscositySurface tension of solution Higher wet picup with faster wetting solutions
Temperature of solutionViscosity and surface tension changes with temp, changing pickup
Concentration of solution Change the conc. Change the pickup
Wet pickup of the fabric can be calculated by the following equation
%wpu = wt of solution applied*100/wt of dry fabric……(A)
amount of supplied chemical added to the fabric is calculated by
%add-on = %conc in sol(wt/wt)*%wpu/100………..(B)
Where %conc is the concentration of the chemical in the applied solution expressed as percentage by weight
Pick-up can also be calculated as
Pick-up(E) = Wet wt after pad-air dry wt/air dry wt*100……(C)
PAD APPLICATION OF CHEMICALS TO WET FABRIC
In scouring and bleaching chemicals are applied to wet fabric i.e., undried from preceding washers
Water is added to the saturator chemicals by the fabric
Let assume that the entry expression of the fabric is Ei and exit expression is Eo
if Ei>Eo…….then
if Ei<Eo…….then
The minimum difference in these entries is 10% adopted by most industries
In wet on wet case the effective pick-up is calculted
effective pick-up = (Eo-Ei)+(Ei*F)
F= interchange factor or fracrion by which the incoming water is exchanged
The value of F is usually about 0.7-0.8
CHEMICAL FEED SYSTEMSFor wet on dry application, the feed
sol. is made at same concentration as the saturator
For wet on wet padding, more concentrated chemical feed will be required
Concentrated chemical feed liqour will be 5-8 times the strength of saturator liquor
There are five basic systems available
1.Manual control2.Rotameter flow meters3.Metering pumps4.Proportioning cylinders, e.g. Texicon5.Fully automated units, e.g. Polymetron
MANUAL CONTROL SYSTEM
ROTAMETER FLOW METERS
METERING PUMPS
PROPROTIONING CYLINDERS
FULLY AUTOMATED UNITS
CONCENTRATION OF FEED LIQUOR CALCULATION
Let,exit mangle expression = Eo%entry mangle expression = Ei%percentage chemicals on the fabric = Xweight of fabric per minute = W kg/min
X = saturator conc(K1)*epu/1000
By putting the value of epu
X = K1*[(Eo-Ei)+(Ei*F)]/1000…….(A)
The volume change (V) per minute in the saturator is
V = W*(Eo-Ei)/SG*100 = W*(Eo-Ei)/100 l/min, assuming SG = 1
And the weight of chemical (w) used per min is
w = W*X/100 kg/min = W*X*1000/100 g/min
This then is the feed liquor concentration (K2)
K2 = w/V = W*X/100*1000*100/W*(Eo-Ei)
K2 = 1000*X/Eo-Ei g/l
or X = K2*(Eo-Ei)/1000……(B)
equating A and B, we have
K2 = K1[(Eo-Ei)+(E*F)]/Eo-Ei
THANK YOU
top related