triple effect evaporator control?


Thread Starter

sergio pino

i am a student of chemical engineering that is making the project and had doubts on

I want to design the control for a system of evaporators to triple effecto in paralelo. the process is in natural circulation and problem at the time of controlling the process is to know if this circulation is fulfilled at any moment by increase of pressure between the evaporators. In principle the evaporators are not but that heat exchangers where is created I the phase steam and after arrive at I deposit separator. there I control the level and the pressure of evaporador.for differentiate if reduccion of the level is not by the excess of heat but because my natural circulation is not sufficient, as I can control it?

I thought to measure the evaporated steam feed to make a cascade control connected to the providing source of heat.
it is correct?
could i control the feed in the circulation of the two phases?
could i control the composition?
Control of composition can be effected using an inline density transmitter or an inline viscosity transmitter. Either will suffice in this instance as the variation of density and viscosity with temperature and with composition are both well defined and hence can be readily resolved.
The instrument will firstly measure the density (or viscosity) at the process temperature and then compute the density (or viscosity) at a reference temperature. This value may then be used to compute the %composition. This can be output as a 4-20mA for input to the controller.
For further information i would suggest a web search for density and viscosity transducers and seek the advise of the manufacturers relative to their own technologies. web site will provide data on both density and viscosity transducers. The search should show up a number of mainstream instrument suppliers who can also help.