Treatment of sludges and flocculants using insoluble mineral colloidal suspensions

Abstract

A method of separating sludge which involves adding an insoluble mineral colloidal suspension into an industrial sludge to destabilize the industrial sludge and separating destabilized components of the industrial sludge. The insoluble mineral colloidal suspension includes magnesium hydroxide. In an alternative embodiment dry finely divided magnesium hydroxide can be added and then dispersed into an industrial sludge. Conventional flocculants and/or coagulants can also be added. Conventional physical separation processes can be used to separate the destabilized industrial sludge.

Claims

1. A method of separating sludges which comprises: obtaining an industrial sludge, wherein the industrial sludge comprises DNF bottom sludge and top float; adding an insoluble magnesium hydroxide colloidal suspension into the industrial sludge to destabilize the industrial sludge; and separating destabilized components of the industrial sludge.

2. A method of separating sludges according to claim 1, wherein a flocculant and/or coagulant is added to the industrial sludge to aid in the separation of the destabilized components of the industrial sludge.

3. A method of separating sludges according to claim 1, wherein the industrial sludge is refinery sludge.

4. A method of separating sludges according to claim 1, wherein the insoluble magnesium hydroxide colloidal suspension has a solids percent by weight of at least 25%.

5. A method of separating sludges according to claim 1, wherein the insoluble magnesium hydroxide colloidal suspension has a solids percent of up to 65%.

6. A method of separating sludges according to claim 1, wherein the insoluble magnesium hydroxide colloidal suspension has a solids percent by weight that ranges from 25% to 65%.

7. A method of separating sludges according to claim 1, the method further comprising heating the combined mixture comprising industrial sludge and insoluble magnesium hydroxide colloidal suspension to 170° F. from ambient temperature.

8. A process for physically separating components of an industrial sludge, wherein the industrial sludge comprises DNF bottom sludge and top float, the improvement comprising adding an insoluble mineral colloidal suspension into the sludge prior to physically separating components of the sludge.

9. A process for physically separating components of an industrial sludge according to claim 8, wherein the process for physically separating the components of the sludge includes at least one of gas-assisted flotation, gravity separation and centrifugal separation.

10. A process for physically separating components of an industrial sludge according to claim 8, wherein the process for physically separating the components of the sludge comprises one of dissolved nitrogen floatation and dissolved air flotation.

11. A process for physically separating components of an industrial sludge according to claim 8, wherein the process for physically separating the components of the sludge comprises the use of an American Petroleum Institute Separator.

12. A process for physically separating components of an industrial sludge according to claim 8, wherein the insoluble mineral colloidal suspension has a solids percent by weight of at least 25%.

13. A process for physically separating components of an industrial sludge according to claim 8, wherein the insoluble mineral colloidal suspension has a solids percent of up to 65%.

14. A process for physically separating components of an industrial sludge according to claim 8, wherein the insoluble mineral colloidal suspension has a solids percent that ranges from 25% to 65%.

Description

DETAILED DESCRIPTION OF THE DRAWINGS AND THE PRESENTLY PREFERRED EMBODIMENTS

(1) The present invention relates generally to separating sludges and more particularly to the addition of insoluble magnesium hydroxide colloidal suspensions to DNF, DAF, and API sludges, and other sludge wastes for purposes of separation and component recovery.

(2) The insoluble colloidal magnesium hydroxide suspension used in the present invention can be obtained from mined sources or formed by precipitation and added as a colloidal suspension to sludges and/or floats. Those familiar with the art will understand the benefits of using these materials to destabilize various types of sludge including DNF, DAF, API, and other sludge and/or float wastes.

(3) According to one aspect the present invention involves the introduction of magnesium hydroxide to process sludges which acts to inhibit the effect of accumulated spent flocculent and increase the density of new flocculent such that traditional processing equipment can be used to more effectively process sludges.

(4) The use of magnesium hydroxide allows the introduction and/or formation of stable and pumpable, high concentration suspensions without detrimentally altering pH or significantly increasing total solids content. The low solubility results in a diffuse solids component with suitable charge that adds density to the floc and allows for easy settling or centrifugation from the water and oil components of the sludges.

(5) Adding an insoluble colloidal magnesium hydroxide suspension into an industrial sludge according to the present invention causes colloidal particles and very fine solid suspensions initially present in the industrial sludge to combine into larger agglomerates that can be separated by means of sedimentation, flocculation, filtration, centrifugation, or other separatory methods.

(6) The insoluble colloidal magnesium hydroxide suspensions of the present invention can include mined material suspended in an aqueous solution or precipitated from soluble compounds to yield suspended solids.

(7) The insoluble colloidal mineral suspensions used in the present invention can have as little of 25% percent solids by weight and up to 65% percent solids by weight with about 50-60% solids by weight being generally suitable for purposes of the present invention. In an alternative embodiment to adding an insoluble colloidal mineral suspension to a sludge dry solids of finely divided magnesium hydroxide can be added to the sludge and then dispersed. However this alternative does not afford the ease of addition or certainty of thorough solids distribution.

(8) While the insoluble colloidal magnesium hydroxide suspension used according to the present invention causes colloidal particles and very fine solid suspensions initially present in an industrial sludge to combine into larger agglomerates, it can be understood that the addition of other known coagulants and/or flocculants can also be used to aid and improve agglomeration and clumping for separation purposes

(9) According to the present invention exemplary sludges include industrial wastewater sludges in general, refinery sludges and in particular sludges from processes such as DNF, DAF, API separators, and tank clean-out sludges.

(10) For purposes of the present invention conventional flocculants/coagulants can also be used including mineral, natural and synthetic materials as well as those listed above.

EXAMPLES

(11) The following non-limited Examples are provided to illustrate various features and characteristics of the present invention which are not intended to be specifically limited thereto.

Example 1

(12) In this example DNF sludge and float were transferred from a DNF tank to a smaller tank where a 50-60% solids by weight suspension of magnesium hydroxide was added at 1.75% by volume of the DNF sludge and float. A coagulant (water soluble cationic polymer) was added at 500 parts per million to aid in separation. The combined mixture was heated from ambient temperature to 170° F. The heated material was then fed to a three phase centrifuge to separate clean water (centrate), oils and solids. The centrate had the characteristic of having less than 1% particulate solids and could be sent back (recovered and recycled) to the DNF or sent on to wastewater treatment. The oil could be recovered (and recycled) and the solids could be disposed of.

Example 2

(13) In this example the same procedure in Examples 1 above was followed except 200 ppm of water soluble anionic was added to the sludge and float. The combined mixture was heated from ambient temperature to 170° F. The heated material was then fed to a three phase centrifuge to separate clean water (centrate), oils and solids. The centrate had the characteristic of having less than 1% particulate solids and could be sent back (recovered and recycled) to the DNF or sent on to wastewater treatment. The oil could be recovered (and recycled) and the solids could be disposed of.

(14) Although the present invention has been described with reference to particular means, materials and embodiments, from the foregoing description, one skilled in the art can easily ascertain the essential characteristics of the present invention and various changes and modifications can be made to adapt the various uses and characteristics without departing from the spirit and scope of the present invention as described above and set forth in the attached claims.