Distillation

Distillation separates  two  or more liquid components in  a  mixture using the

principle of relative volatility or boiling points. The greater the difference in relative

volatility the greater the nonlinearity  and  the easier it  is  to separate the mixture

using  distillation. The process involves production of vapour by  boiling the liquid

mixture in a  still and removal of  the vapour  from the still by condensation. Due  to

differences in relative volatility or boiling points, the vapour is rich  in  light

components and the liquid is rich in heavy components. 

Batch Processes

In  the 1950s, chemical engineers might have the impression that  the  ultimate 

mission  of  the engineers  was  to transform old-fashioned batch processes into 

modern continuous ones (Rippin, 1983). With  such a perspective it is surprising to 

find  that, today, fifty years later  a  significant proportion  of  the world’s chemical 

production by volume and a much  larger proportion by  value is still made in batch 

plants  and  it is unlikely that this proportion  will  decline in  the  near  future. 

Parakrama  (1985)  reported  that  99  batch  processes  were  in operation  in  74 UK 

manufacturing companies. Among these, 80% plants were producing chemicals  in 

steady  or  growing markets. Moreover,  many  more products, which could  be 

manufactured continuously,  are in  fact made in batch plants on economic grounds.