1 Function definition for the function
psat() for calculating saturation temperature by using Antonie equation :
function[prhex,prhept,proct]=psat(t)
hexa=13.8193;hexb=2696.04;hexc=-48.833;
hepta=13.8622;heptb=2910.26;heptc=-56.718;
octa=13.9346;octb=3123.13;octc=-63.515;
prhex=exp(hexa-((hexb/(t+hexc))));
prhept=exp(hepta-((heptb/(t+heptc))));
proct=exp(octa-((octb/(t+octc))));
end
2 The main body of the programme where the
function psat() has been called is:
xihex=input('enter the
composition of hexane');
xihept=input('enter the composition of
heptane');
xioct=input('enter the composition of
octane');
pt=input('enter the total pressure');
mlkd=(0.98*xihex)/((0.98*xihex)+(0.01*xihept));
disp('the mole fraction of hexane in
distillate is');
disp(mlkd);
mhkd=(0.01*xihept)/((0.98*xihex)+(0.01*xihept));
disp('the
composition of heptane in distillate is:');
disp(mhkd);
moctd=0;
mlfrhex=((0.02*xihex)/((0.02*xihex)+(0.99*xihept)+(1*xioct)));
mlfrhept=((0.99*xihept)/((0.02*xihex)+(0.99*xihept)+(1*xioct)));
mlfroct=((1*xioct)/((0.02*xihex)+(0.99*xihept)+(1*xioct)));
for t=250:0.1:423
[p,q,r]=psat(t);
kihex1=p/pt;
kihept1=q/pt;
kioct1=r/pt;
sumkixi=(kihex1*mlkd)+(kihept1*mhkd)+(kioct1*moctd);
if(sumkixi>0.99 &&
sumkixi<1)
disp('temp of condenser')
disp(t)
break
end
end
disp('the value of equilibrium constant of
light key at bubble point is:');
disp(kihex1);
disp('the value of equilibrium constant of
heavy key at bubble point is:');
disp(kihept1);
for temp=250:0.1:573
[a,b,c]=psat(temp);
kihex=a/pt;
kihept=b/pt;
kioct=c/pt;
sumy=(mlfrhex/kihex)+(mlfrhept/kihept)+(mlfroct/kioct);
if(sumy>0.99 && sumy<1)
disp('temp of reboiler')
disp(temp)
break
end
end
alpha=kihex1/kihept1;
disp('the
value of relative volatility is');
disp(alpha);
s=mlkd+mhkd+moctd;
disp('now
the minimum number of stages by Fenske equation is calculated');
sum=mlfrhex+mlfrhept+mlfroct;
nmin=(log(((mlkd/mhkd)/(mlfrhex/mlfrhept)))/log(alpha))-1;
disp('the minimum
number of trays required are')
disp(nmin)
disp('minimum
number of stages including reboiler are')
nminn=nmin+1;
disp(nminn)
disp('now
the calculation of minimum reflux by undrewood method is done:')
alpha1=kihex1/kihept1;
alpha2=kihept1/kihept1;
alpha3=kioct1/kihept1;
for
phi=alpha2:0.01:alpha1
sumf=((alpha1*xihex)/(alpha1-phi))+((alpha2*xihept)/(alpha2-phi))+((alpha3*xioct)/(alpha3-phi));
if(sumf>-0.1&sumf<0.2)
disp('the value of phi is')
disp(phi)
break;
end;
end;
disp('the
moles of all the four components in distillate are calculated below by simple
material balnce calculations:')
summoles=(0.98*xihex*100)+(0.01*xihept*100)
disp('the
total moles in distillate are')
disp(summoles)
sumrd=(((alpha1*mlkd)/(alpha1-phi))+((alpha2*mhkd)/(alpha2-phi))+((alpha3*moctd)/(alpha3-phi)))-1;
disp('minimum
reflux ratio is')
disp(sumrd);
disp('now
the calculations will be done on the basis of Gilliland corelations for
claculating actual number of stages')
disp('actual
reflux ration is taken as 1.5 times the minimum reflux ratio')
rd=1.5*sumrd;
x=(rd-sumrd)/(rd+1);
y=1-exp(((1+(54.4*x))/(11+(117.2*x)))*((x-1)/(x.^0.5)));
n=round((y+nminn)/(1-y));
disp('required
number of stages are')
disp(n)
mlbottom=(0.02*xihex*100)+(0.99*xihept*100)+(1*xioct*100);
rationrns=[(xihept/xihex)*((mlfrhex/mhkd)^2)*(mlbottom/summoles)]^0.206;
ns=round((rationrns/(rationrns+1))*n);
nr=n-ns;
disp('stages
in stripping section')
disp(ns);
disp('stages
in rectifying section')
disp(nr);
for
i=340:0.1:450
[x,y,z]=psat(i);
khex=x/pt;
khept=y/pt;
koct=z/pt;
summation=(khex*mlfrhex)+(khept*mlfrhept)+(koct*mlfroct);
if(summation>0.99 &&
summation<1)
ftemp=i;
disp('temp and composition and at tray
1 is')
disp(ftemp)
break
end
end
v=(summoles)*(rd+1)
l=summoles*rd
lbar=l+100
yhex1=(x/pt)*mlfrhex;
yhept1=(y/pt)*mlfrhept;
yoct1=(z/pt)*mlfroct;
x1=(yhex1+(mlbottom/v)*mlfrhex)/(lbar/v);
x2=(yhept1+(mlbottom/v)*mlfrhept)/(lbar/v);
x3=(yoct1+(mlbottom/v)*mlfroct)/(lbar/v);
k=[yhex1,yhept1,yoct1,x1,x2,x3];
disp(k);
nt=n;
for i=2:1:nt
if(i~=2)
x1=xnewhex;
x2=xnewhept;
x3=xnewoct;
end
xbnrhex=x1/(x1+x2+x3);
xbnrhept=x2/(x1+x2+x3);
xbnroct=x3/(x1+x2+x3);
for j=250:0.1:450
[x,y,z]=psat(j);
khex=x/pt;
khept=y/pt;
koct=z/pt;
summation=(khex*xbnrhex)+(khept*xbnrhept)+(koct*xbnroct);
if(summation>0.99 &&
summation<1)
ftemp=j;
disp('temp and composition at tray');
disp(i); disp('is');
disp(ftemp)
break
end
end
yhex1=(x/pt)*xbnrhex;
yhept1=(y/pt)*xbnrhept;
yoct1=(z/pt)*xbnroct;
xnewhex=(yhex1+((mlbottom/v)*mlfrhex))/(lbar/v);
xnewhept=(yhept1+((mlbottom/v)*mlfrhept))/(lbar/v);
xnewoct=(yoct1+((mlbottom/v)*mlfroct))/(lbar/v);
t=[yhex1,yhept1,yoct1,xnewhex,xnewhept,xnewoct];
disp(t);
if(i==ns)
disp('the feed plate location is');
disp(ns);
nf=i+1;
for j=250:0.1:450
[x,y,z]=psat(j);
khex=x/pt;
khept=y/pt;
koct=z/pt;
summation=(khex*xnewhex)+(khept*xnewhept)+(koct*xnewoct);
if(summation>0.99 &&
summation<1)
yhex1=(x/pt)*xnewhex;
yhept1=(y/pt)*xnewhept;
yoct1=(z/pt)*xnewoct;
break
end
end
break
end
end
for i=nf:1:n
if(i~=nf)
yhex1=ynewhex;
yhept1=ynewhept;
yoct1=ynewoct;
end
xhexr=(yhex1-(mlkd/(rd+1)))/(rd/(rd+1));
xheptr=(yhept1-(mhkd/(rd+1)))/(rd/(rd+1));
xoctr=(yoct1-(moctd/(rd+1)))/(rd/(rd+1));
xnrhex=xhexr/(xhexr+xheptr+xoctr);
xnrhept=xheptr/(xhexr+xheptr+xoctr);
xnroct=xoctr/(xhexr+xheptr+xoctr);
for j=150:0.1:450
[x,y,z]=psat(j);
khex=x/pt;
khept=y/pt;
koct=z/pt;
summation=(khex*xnrhex)+(khept*xnrhept)+(koct*xnroct);
if(summation>0.99 &&
summation<1)
ftemp=j;
disp('temp and composition at tray');
disp(i); disp('is');
disp(ftemp)
break
end
end
ynewhex=(x/pt)*xnrhex;
ynewhept=(y/pt)*xnrhept;
ynewoct=(z/pt)*xnroct;
w=[ynewhex,ynewhept,ynewoct,xnrhex,xnrhept,xnroct];
disp(w);
end
coded by: Ravisha Goswami, Mamta Nainwal & group; Chemical Batch 2010-14, BTKIT Dwarahat
Hi, What kind of rigurous method are you using in your code?
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