Systems and methods for operating candle filters to recover glycols from drilling operations

A method of operating a candle filter system for removing solids from monoethylene glycol (MEG) recovered from drilling fluids, the method comprising:

• passing an MEG rich stream to a candle filter system comprising a plurality of candle filter units operated in parallel and a slurry vessel disposed downstream of the candle filter system, wherein the MEG rich stream comprises at least the MEG and dissolved solids and each of the plurality of candle filter units comprises a vessel, a register, and a plurality of filter candles fluidly coupled to the register;
• determining a concentration of total dissolved solids in the MEG rich stream;
• determining whether to operate the candle filter system in a low TDS mode or a high TDS mode based on the concentration of total dissolved solids (TDS) in the MEG rich stream;
• filtering the MEG rich stream in the plurality of candle filter units to produce a filtrate and a filter cake deposited on outer surfaces of the filter candles of the candle filter units;
• determining to conduct a cleaning cycle for one or more of the plurality of candle filter units based on a pressure differential across the plurality of candle filter units;
• and
• conducting a cleaning cycle to remove the filter cake from the outer surfaces of the filter candles, where conducting the cleaning cycle comprises:
• reducing a pressure in the one or more candle filter units;
• draining a residual volume of the MEG rich stream all the way to the slurry vessel disposed downstream of the candle filter system;
• after the draining, pulsing the plurality of filter candles with a compressed gas, where the pulsing causes separation of the solid filter cake from the outer surfaces of the filter candles;
• allowing solids from the solid filter cake to settle in a bottom of the vessel for a sedimentation duration;
• and
• removing the solids from the vessel;
• and
• resuming filtering operation of the one or more candle filter units.