Airco, Inc.

Bradley S Kirk

Raymond M Chappel

Mark J Kirschner

In a process for delignifying wood pulp with oxygen, a pulp slurry and oxygen are introduced into an elongated reactor having a plurality of gravitational fall zones at which oxygen is dissolved in the liquid phase of the slurry. The length of the reactor is sufficient to provide the residence time required for delignification reactions. Alkali is added in controlled quantities along the reactor length in response to sensed slurry pH to maintain a predetermined slurry pH throughout the reactor. The oxygen treated slurry discharged from the reactor is separated into pulp and hot recycle liquor, the latter being utilized to effect thermal, chemical and water economies.

Oxygen delignification of wood pulp

This invention provides improved methods and apparatus for dissolving oxygen in wastewater treatment processes such as is required to satisfy the biological oxygen demand in the activated sludge process for the biodegradation of organic impurities. The invention enables attainment of high concentrations of dissolved oxygen with minimum consumption of oxygen and power. Wastewater with the high concentration of dissolved oxygen may be mixed with a larger volume of untreated wastewater to achieve the desired oxygen concentration and maintain volatile solids in suspension in the bulk liquid for optimum efficiency of purification.

Methods and apparatus for treating wastewater

The supply of a gas to be dissolved in a liquid is controlled by initially sensing the concentration of dissolved gas in the liquid under treatment and subsequently producing appropriate control signals for adjusting the setting of a valve in the gas supply line. A dissolution device emplaceable in the liquid under treatment includes a liquid inlet and outlet and a static liquid-gas mixing means therebetween. The device is adapted to receive supplied gas whereby a gas space in the upper reaches of the device is established. The gas space is also maintained in communication with a dip tube disposed exteriorly of the device in the body of liquid with the lower extremity of the dip tube establishing the maximum height of the gas space within the dissolution device. The static mixing means comprises a gravitational fall device such that upon detecting an increase or decrease in the concentration of gas dissolved in the body of liquid, the supply of gas to the fall zone is reduced or increases, respectively, thereby decreasing or increasing the rate of gas dissolution. Upon reducing the supply of gas the electrical power necessary to pump liquid through the dissolution device is also conserved. In this manner, the supply of gas is correlated to the demand of the liquid therefor and wastage of electrical power necessary to effect the gas-liquid mixing within the dissolution device is substantially avoided.

Methods and apparatus for controlling the supply of a feed gas to

Methods and apparatus for treating a liquid with a gas wherein a liquid feed is introduced to the initial stage of a multi-stage device for dissolving the gas in the liquid. Efficient mass transfer is achieved by effecting a gas-liquid counter flow in serial stages of the dissolution device. The effluent from the dissolution device exhibits a relatively high dissolved gas concentration which gas is subsequently consumed by the liquid in a reaction tank. A liquid recycle line is provided for returning and combining treated liquid with the incoming feed thereby enabling further dissolution of the gas in the liquid. In the course of treating wastewater with ozone, a flotation clarifier may be provided with the initial stage of the dissolution device to enable the surface coagulation of impurities in the wastewater feed. The coagulants may be skimmed prior to introducing wastewater into subsequent stages of the dissolution device, thereby substantially reducing the ultimate ozone demand of the wastewater.

Methods and apparatus for treating a liquid with a gas

Methods and apparatus for treating wastewater, such as municipal sewage, are provided in which an oxygen enriched feed gas is supplied to an oxygenation chamber wherein oxygen is efficiently dissolved in wastewater (mixed liquor) by means of a static mixing device. The chamber is preferably submerged in a large body of wastewater being treated, such as is commonly found in the secondary stage of an activated sludge wastewater treatment system with the chamber being adapted to receive such wastewater from a location slightly below the surface thereof. Oxygenated wastewater is discharged from the chamber in either a radial or multi-directional pattern at a sufficient velocity to effect a thorough mixing of the oxygenated wastewater and the large body of wastewater contained in the secondary stage treatment tank. The overall concentration of dissolved oxygen in the wastewater is maintained throughout the tank to a level sufficient to sustain microbial digestion of organic waste while providing the requisite stirring necessary to preclude settling of solids from the wastewater.

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North Plainfield, NJ, United States of America

Bradley S Kirk