BACKGROUND

In the production of linear alpha olefins, distillation columns are used to separate light hydrocarbons, for example, ethylene and butane, from heavier hydrocarbons. These separation processes present many engineering challenges. For example, the more demands that are put on a particular distillation column, the more difficult it can be to control the process parameters for that column. These process parameters can include temperature, pressure, and fluid level.

Unique process conditions place a large demand on column performance while also making column processing parameters difficult to control. For example, fixed reflux flow rates can be required to maintain efficient column operation. Constant distillate flow rates from reflux drums can also be required to service downstream processes. Furthermore, reflux drums can be used during intermittent intervals to supply on-demand liquid condensate to other process equipment. Accordingly, under these conditions, the fluid levels within the reflux drum can become difficult to control by standard means. Column pressure can also become difficult to control when demands on the column are high. For example, when condenser coolant must be re-purposed for the maintenance of other process equipment, it cannot be used to control column pressure and an alternative means of control must be used.

Thus, there is a need for an efficient method of column control that can allow for the maintenance and control of important process parameters, such as pressure and reflux drum level, despite the placement of high performance demands and restrictions on the column.

SUMMARY

Disclosed, in various embodiments, are methods of column control.

A method of column control, comprises: passing a feed stream and a make-up stream through a column; withdrawing an overhead fraction from the column; purging at least a portion of the overhead fraction; cooling at least a portion of the overhead fraction in a heat exchanger and passing it through a reflux drum; withdrawing a purge stream and a distillate stream from the reflux drum, wherein the distillate stream has a constant flow rate; recycling at least a portion of the distillate stream back to the column; and passing at least a portion of the distillate stream to a downstream process.

A method of column control, comprises: passing a feed stream comprising C2-C20 linear alpha olefins, solvent, spent catalyst, and catalyst deactivation agent, and a make-up stream comprising C4 linear alpha olefins through a C4/C6 distillation column; withdrawing an overhead fraction comprising C4− linear alpha olefins from the column, wherein the overhead fraction is in communication with a split-range controller; purging at least a portion of the overhead fraction, wherein the purged portion of the overhead fraction comprises C4− linear alpha olefins; cooling at least a portion of the overhead fraction in a heat exchanger and then passing it through a reflux drum, wherein the heat exchanger comprises a coolant fluid; withdrawing a purge stream comprising C4− linear alpha olefins and a distillate stream from the reflux drum, wherein the distillate stream has a constant flow rate; recycling at least a portion of the distillate stream back to the column; intermittently using at least a portion of the distillate stream as a liquid condensate supply for downstream equipment; and withdrawing a bottoms fraction comprising C6+ linear alpha olefins, solvent, spent catalyst and catalyst deactivation agent from the column.

These and other features and characteristics are more particularly described below.

