Process and apparatus for oxidizing industrial spent caustic and effecting gas-liquid mass transfer and separation

Apparatus for the oxidation of industrial spent caustic and for effecting gas-liquid mass transfer and gas-liquid separation which comprises a unitary processing tower having:

• a lower chamber divided into four compartments vertically superposed in the chamber wherein oxidizing gas and spent caustic are mixed and communicated through the compartments using a redistributor positioned in a partition separating adjacent compartments, each compartment forming an oxidation zone, said chamber further having:
• an inlet adjacent to the bottom of the chamber for introducing spent caustic to the chamber;
• an injector for introducing the gas into the chamber near the bottom of the chamber, said injector connected to a flow distributor positioned in the bottom of the chamber;
• and
• a chimney tray defining the upper limit of the lower chamber;
• a middle chamber forming a gas-liquid separation zone communicating with the lower chamber through the chimney tray, wherein the chimney of the chimney tray defines a liquid collection zone in the lower part of the middle chamber with a gas phase zone above the liquid collection zone, said middle chamber having an outlet for removing caustic from the liquid collection zone;
• and
• an outlet for removing gas from the gas phase zone;
• an upper chamber comprising:
• means for introducing to the upper chamber cooled oxidized caustic from an upper recycle conduit and gas from the middle chamber, said means comprising a mass transfer apparatus having a conduit extending into the upper chamber with inlets for introducing the gas and caustic and an outlet for the release of the gas and caustic from the conduit, said conduit containing a plurality of fibers positioned longitudinally within the conduit to allow a downstream end of the fibers to extend out of the conduit making contact with oxidized caustic in a liquid collection zone of the upper chamber;
• a gas-liquid separation zone;
• an outlet in the chamber for removing the oxidized caustic;
• and
• means for removing the gas from the chamber, wherein a gas conduit in communication with the means for removing gas from the upper chamber has a back pressure control valve connected therein for controlling the transport of gas from the upper chamber, said means for removing gas also including a demister pad and a second conduit for removal of gas in over-pressure situations that is controlled by a pressure relief valve;
• a spent caustic conduit communicating with the lower chamber for introducing spent caustic into the chamber;
• a second spent caustic conduit communicating with the lower chamber for introducing cooled oxidized caustic to the chamber, connected thereto at a second compartment from the bottom of the chamber, having a temperature control valve connected therein that allows release of the cooling caustic into the lower chamber from a lower recycle conduit when gas and,caustic in the lower chamber reach a specified temperature level;
• a gas conduit communicating with the lower chamber to introduce the oxidizing gas into the spent caustic;
• a conduit connecting the outlet for removing the gas from the middle chamber to the inlet for introducing gas to the upper chamber;
• a conduit in fluid communication with the liquid collection zone of the middle chamber through the outlet for removing liquids, said conduit connected to the lower recycle conduit;
• a liquid level control system connected to the middle chamber that releases oxidized caustic from the lower recycle conduit to an offloading conduit when the caustic capacity level of the middle chamber is reached;
• a conduit communicating with the upper chamber;
• for introducing cooled caustic from the lower recycle conduit into the chamber, said conduit connected to the upper recycle conduit;
• a conduit in fluid communication with the outlet for removing liquid from the upper chamber, said conduit connected to the upper recycle conduit;
• a liquid level control system connected to the upper chamber that allows release of cooled oxidized caustic from the upper recycle conduit into the lower recycle conduit;
• a gas conduit in communication with the means for removing cooled, clean gas from the upper chamber;
• and
• caustic/cooling water exchangers in fluid communication with each of the recycle conduits.

Apparatus for the oxidation of industrial spent caustic and for effecting gas-liquid mass transfer and gas-liquid separation which comprises a unitary processing tower having:

• a lower chamber providing an oxidation zone wherein the spent caustic is contacted with an oxidizing gas, said chamber having:
• an inlet adjacent to the bottom of the chamber for introducing the spent caustic to the chamber;
• and
• means for introducing the gas to the chamber to contact the caustic near the bottom of the chamber;
• a middle chamber forming a gas-liquid separation zone in fluid communication with the lower chamber, wherein the lower part of the middle chamber defines a liquid collection zone with a gas phase zone above the liquid collection zone, said middle chamber having an outlet for removing caustic from the liquid collection zone and an outlet for removing gas from the gas phase zone;
• and
• an upper chamber comprising:
• means for introducing oxidized caustic and gas from the middle chamber to the upper chamber, wherein said caustic has been cooled by means for cooling caustic after transport from the middle chamber, said means for introducing providing for contact between the caustic and gas to allow for cooling and cleaning of the gas;
• a gas-liquid separation zone;
• an outlet in the chamber for removing the caustic;
• and
• means for removing the gas from the chamber.