Systematized method and control of fractionation heat balance

Claim 1

In a fractionation column containing a plurality of spaced-apart trays or decks, and wherein (i) a feed stream is introduced through a locus intermediate the top and bottom thereof; (ii) liquid bottoms material is recovered from the lower end of said column, and at least a portion thereof partially vaporized and returned to the reboiler section; and, (iii) overhead material is recovered from the upper end of said column, condensed and at least a portion thereof returned to the rectification section as a reflux stream, the control system which comprises, in cooperative combination: a. a first pair of vertically-spaced temperature sensors below and proximate to said feed locus, said pair separated by a first plurality of trays, and a first differential-temperature measuring device communicating with said first pair of temperature sensors; b. a second pair of vertically-spaced temperature sensors below said feed locus and separated by a second plurality of trays which are greater than said first plurality of trays, and a second differential-temperature measuring device communicating with said second pair of temperature sensors; c. first differential-temperature computing means communicating with a selected one of said first and second differential-temperature measuring devices to determine a first differential communicating output, said output being a function of the ratio of said second and said first plurality of trays; d. second differential temperature computing means communicating with said first computing means and the non-selected differential temperature measuring device, and co-acting with first control means for regulating the degree of vaporization of said liquid bottoms material returned to said reboiler section; e. a third pair of vertically-spaced temperature sensors above said feed locus; and, f. a third differential-temperature measuring device communicating with said third pair of temperature sensors and co-acting with second control means for regulating the quantity of reflux returned to said rectification section.

Claim 8

A method for controlling a fractionation column, wherein (i) a feed stream is introduced through a locus intermediate the top and bottom thereof; (ii) liquid bottoms material is recovered from the lower end of said column, and at least a portion thereof is partially vaporized and returned to the reboiler section; and, (iii) vaporous overhead material is recovered from the upper end of said column, condensed and at least a portion thereof returned to the rectification section as a reflux stream, which method comprises the steps of: a. sensing a first temperature differential between two vertically-spaced temperature sensing points below said feed locus, separated by a first plurality of trays, measuring the resulting first differential-temperature and generating a first signal representative thereof; b. sensing a second temperature differential between two vertically-spaced temperature sensing points below said feed locus, separated by a second plurality of trays which is greater than said first plurality of trays, measuring the resulting second differential temperatue and generating a second signal representative thereof; c. multiplying a selected one of said first and second differential temperature signals by a multiplier representing the ratio of the number of trays between the sensors supplying the non-selected differential temperature signal to the number of trays between the sensors supplying said selected differential temperature signal, and generating a third signal representing the resulting product; d. obtaining a computed relationship of said third signal and said non-selected signal, and generating a fourth signal representative of the resulting computed relationship; e. regulating the degree to which said liquid bottoms material is vaporized in response to said fourth signal; f. sensing a third temperature differential between two vertically-spaced temperature sensing points above said feed locus, measuring the resulting third differential temperature and generating a fifth signal representative thereof; and, g. regulating the quantity of said returned reflux stream responsive to said fifth signal.

Claim 9

A method for controlling a fractionation column, wherein (i) a feed stream is introduced through a locus intermediate the top and bottom thereof; (ii) liquid bottoms material is recovered from the lower end of said column, and at least a portion thereof is partially vaporized and returned to the reboiler section; and, (iii) vaporous overhead material is recovered from the upper end of said column, condensed and at least a portion thereof returned to the rectification section as a reflux stream, which method comprises the steps of: a. sensing a first temperature differential between two vertically-spaced temperature sensing points below said feed locus, separated by a first plurality of trays, measuring the resulting first differential-temperature and generating a first signal representative thereof; b. sensing a second temperature differential between two vertically-spaced temperature sensing points below said feed locus, separated by a second plurality of trays which is greater than said first plurality of trays, measuring the resulting second differential temperatue and generating a second signal representative thereof; c. multiplying a selected one of said first and second differential temperature signals by a multiplier representing the ratio of the number of trays between the sensors supplying the non-selected differential temperature signal to the number of trays between the sensors supplying said selected differential temperature signal, and generating a third signal representing the resulting product; d. obtaining a computed relationship of said third signal and said non-selected signal, and generating a fourth signal representative of the resulting computed relationship; e. regulating the degree to which said liquid bottoms material is vaporized in response to said fourth signal; f. sensing a third temperature differential between two vertically-spaced temperature sensing points above said feed locus, measuring the resulting third differential temperature and generating a fifth signal representative thereof; and, g. regulating the quantity of said returned reflux stream responsive to said fifth signal.