Method and apparatus for maximizing the productivity of a natural gas liquids production plant

A method for maximizing the production of natural gas liquids (liquid high-molecular weight fractions) from natural gas using a recompressor having a compressor antisurge controller and a compressor antisurge valve, the method comprising:

• (a) measuring appropriate parameters in the vicinity of the recompressor;
• (b) determining a recompressor operating point location relative to a high-flow limit;
• and
• (c) using the relative location of the recompressor's operating point to the high-flow limit to modulate the compressor antisurge valve to maintain the location at a predetermined value.

An apparatus for maximizing the production of natural gas liquids (liquid high-molecular weight fractions) from natural gas using equipment comprising a turboexpander with adjustable nozzles, a recompressor, a turboexpander speed controller, a flow-rate control, a compressor antisurge controller, and a compressor antisurge valve, the apparatus comprising:

• (a) means for measuring a rotational speed, N, of the turboexpander;
• (b) means for calculating a deviation, N-Nsp, of the turboexpander rotational speed, N, from a limiting set point, Nsp;
• (c) means for controlling the rotational speed of the turboexpander when the deviation is positive by modulating the compressor antisurge valve to return and maintain the deviation to a value less than or equal to zero;
• and
• (d) means for limiting the opening of the compressor antisurge valve when further opening results in a decrease in compressor power.

An apparatus for maximizing the production of natural gas liquids (liquid high-molecular weight fractions) from natural gas using a recompressor having a compressor antisurge controller and a compressor antisurge valve, the apparatus comprising:

• (a) means for measuring appropriate parameters in the vicinity of the recompressor;
• (b) means for determining a recompressor operating point location relative to a high-flow limit;
• and
• (c) means for using the relative location of the recompressor's operating point to the high-flow limit to modulate the compressor antisurge valve to maintain the location at a predetermined value.