Pressure responsive fractionation control

Apparatus comprising:

• fractionation column means for receiving at least one feed material stream and delivering an overhead product stream from the top portion thereof and a bottom product stream from the bottom portion thereof;
• heating means for providing heat to said bottom portion of said fractionation column means;
• pressure transducer means for sensing the pressure at a preselected location within said fractionation column means and delivering a column pressure signal representative of the thus sensed pressure;
• a first signal conversion means for accepting said column pressure signal and delivering in response thereto a temperature requirement signal representative of the value of a column bottom temperature for said fractionation column means required to provide a preselected value of a constituent ratio in said bottom product stream at the column pressure represented by said column pressure signal;
• a second signal conversion means for accepting said temperature requirement signal and delivering in response thereto a required heat signal representative of the direction and magnitude of the change in heat input to said fractionation column means required to provide the column bottom temperature required to provide said preselected value of said constituent ratio in said bottom product stream at the column pressure represented by said column pressure signal;
• temperature transducer means for sensing a column bottom temperature within said fractionation column means adjacent the bottom thereof and delivering a bottom temperature signal representative of the thus sensed temperature;
• temperature controller means for delivering a required heat correction signal in response to a comparison of said bottom temperature signal with a bottom temperature set point signal;
• analyzer means for analyzing said bottom product stream and delivering an analysis signal representative of the analyzed value of said constituent ratio within said bottom product stream;
• analysis controller means for delivering, in response to comparison of said analysis signal with a constituent ratio set point signal, a temperature requirement adjustment signal representative of the adjustment of said temperature requirement signal necessary to compensate for the difference between said preselected value of said constituent ratio and the analyzed value of said constituent ratio;
• a first correction means for applying said temperature requirement adjustment signal to said temperature requirement signal to produce said bottom temperature set point signal;
• a second correction means for applying said required heat correction signal to said required heat signal to produce a corrected required heat signal;
• and
• means for controlling the amount of heat flow delivered to said bottom portion of said fractionation column means by said heating means in response to said corrected required heat signal.