Alternative additives to enhance slurry dewatering

Abstract

The invention provides methods and compositions for improving dewatering of Bayer Process alumina trihydrate slurry. The method comprises adding an R-Succinic Compound (such as octadecenyl succinic acid, hexadecenyl succinic acid, and/or dodecenyl succinic acid) to the slurry. The R-Succinic Compound removes water that would otherwise be trapped within the filtered slurry cake and therefore reduces the energy needed to calcine the resulting solids.

Claims

1. A method comprising: adding a wash fluid to an alumina trihydrate bearing slurry comprising alumina trihydrate and caustic-soluble aluminate liquor; adding to the alumina trihydrate bearing slurry or to the wash fluid a composition comprising at least one R-succinic compound having a structure selected from formula (I) or formula (II), a conjugate acid-base of the R-succinic compound having a structure selected from formula (I) or formula (II), and combinations thereof; wherein formula (I) is ##STR00005## and formula (II) is ##STR00006## and wherein R and R are independent, distinct, and represent alkyl, alkenyl, or aromatic hydrocarbon groups containing 1-30 carbon atoms.

2. The method of claim 1, wherein the R-succinic compound is selected from octadecenyl succinic acid, hexadecenyl succinic acid, dodecenyl succinic acid, or any combination thereof.

3. The method of claim 1 wherein the composition further comprises a base.

4. The method of claim 1, further comprising in order: preparing an aqueous slurry of pulverized bauxite ore and caustic solution; digesting, comprising extracting alumina from the bauxite ore as a caustic-soluble aluminate liquor; clarifying, comprising removing solid particles from the liquor; precipitating, comprising forming the alumina trihydrate bearing slurry from the liquor, and classifying, comprising separating alumina trihydrate seeds from the liquor.

5. The method of claim 1, further comprising: removing liquor and water from the alumina trihydrate bearing slurry to give alumina trihydrate.

6. The method of claim 5, further comprising calcining the alumina trihydrate.

7. The method of claim 1, wherein the R-succinic compound forms in situ within the alumina trihydrate bearing slurry or the wash fluid by opening the ring of an R-succinic anhydride compound.

8. The method of claim 7 in which the R-succinic compound forms from an anhydride added to the alumina trihydrate bearing slurry or the wash fluid.

9. The method of claim 1, wherein the wash fluid comprises water.

10. The method of claim 1, wherein the wash fluid consists essentially of water.

11. The method of claim 1, wherein the composition is added to the slurry alongside the wash fluid, before the wash fluid, after the wash fluid, or combinations thereof.

12. The method of claim 1, wherein the composition is added to the wash fluid.

13. The method of claim 5, wherein the removing liquor and water from the alumina trihydrate bearing slurry comprises filtration.

14. The method of claim 5, wherein the wash fluid is added to the slurry before the removing, during the removing, after the removing, or combinations thereof.

15. The method of claim 5, wherein the removing liquor and water from the alumina trihydrate bearing slurry comprises gravity separation, pressure separation, vacuum separation, or combinations thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) A detailed description of the invention is hereafter described with specific reference being made to the drawings in which:

(2) FIG. 1 is an illustration of the application of the invention in the Filtration Stage of a Bayer Process.

(3) FIG. 2 is an illustration of the synthesis of an R-Succinic Compound.

(4) For the purposes of this disclosure, like reference numerals in the figures shall refer to like features unless otherwise indicated. The drawings are only an exemplification of the principles of the invention and are not intended to limit the invention to the particular embodiments illustrated.

DETAILED DESCRIPTION OF THE INVENTION

(5) The following definitions are provided to determine how terms used in this application, and in particular how the claims, are to be construed. The organization of the definitions is for convenience only and is not intended to limit any of the definitions to any particular category.

(6) R-Succinic Compound means any one or more molecule(s) (including but not limited to octadecenyl succinic acid, hexadecenyl succinic acid, and/or dodecenyl succinic acid), whose structure conforms to the generalized structure of: Formula 1, Formula 2, conjugate acid-bases thereof, and any combination thereof, wherein Formula 1 and Formula 2 are:

(7) ##STR00001##
where R and R are independent, distinct, and represent alkyl, alkenyl, or aromatic hydrocarbon groups containing 1-30 carbon atoms

(8) Octadecenyl Succinic Acid means a molecule and acid-base conjugates thereof having a structure of:

(9) ##STR00002##

(10) Hexadecenyl Succinic Acid means a molecule and acid-base conjugates thereof having a structure of:

(11) ##STR00003##

(12) Dodecenyl Succinic Acid means a molecule and acid-base conjugates thereof having a structure of:

(13) ##STR00004##

(14) Consisting Essentially of means that the methods and compositions may include additional steps, components, ingredients or the like, but only if the additional steps, components and/or ingredients do not materially alter the basic and novel characteristics of the claimed methods and compositions.

(15) Filter means a structure constructed and arranged to remove suspended materials from within a liquid that is passed through it, more detailed descriptions of filters and filtration are described in The Nalco Water Handbook (3rd Edition), by Daniel Flynn, McGraw Hill (2009) in general and in particular pp. 6.1-8.30.

(16) Filter Cake means the accumulation of solid matter that is retained on a filter, it increases in the course of filtration and becomes thicker as more particulate matter is retained, with increasing layer thickness the flow resistance of the filter cake increases, and if not removed soon enough, eventually thick filter cake can disrupt filtration because the flow resistance of the filter cake gets so high that too little of the liquid from the slurry being filtered can pass through the filter cake and the filter plugs.

(17) Liquor or Bayer liquor means a caustic, liquid medium that has run through a Bayer process in an industrial facility.

(18) Membrane means a structure having lateral dimensions much greater than its thickness though which a mass transfer may occur, membranes may be used to filter liquids.

(19) Separation and Separation Method means a mass transfer process that converts a mixture of substances into two or more distinct product mixtures, at least one of which is enriched in one or more of the mixture's constituents, it includes but is not limited to such processes as: Adsorption, Centrifugation, cyclonic separation, density based separation, Chromatography, Crystallization, Decantation, Distillation, Drying, Electrophoresis, Elutriation, Evaporation, Extraction, Leaching extraction, Liquid-liquid extraction, Solid phase extraction, Flotation, Dissolved air flotation, Froth flotation, Flocculation, Filtration, Mesh filtration, membrane filtration, microfiltration, ultrafiltration, nanofiltration, reverse osmosis, Fractional distillation, Fractional freezing, Magnetic separation, Precipitation, Recrystallization, Sedimentation, Gravity separation, Sieving, Stripping, Sublimation, Vapor-liquid separation, Winnowing, Zone refining, and any combination thereof.

(20) Slurry means a mixture comprising a liquid medium within which finely divided solids are dispersed or suspended, the liquid medium may be entirely water, partially water, or may not contain any water at all.

(21) Surfactant is a broad term which includes anionic, nonionic, cationic, and zwitterionic surfactants. Enabling descriptions of surfactants are stated in Kirk-Othmer, Encyclopedia of Chemical Technology, Third Edition, volume 8, pages 900-912, and in McCutcheon's Emulsifiers and Detergents, both of which are incorporated herein by reference.

(22) Thickener or Settler means a vessel used to effect a solid-liquid separation of a slurry, often with the addition of flocculants, the vessel constructed and arranged to receive a slurry, retain the slurry for a period of time sufficient to allow solid portions of the slurry to settle downward (underflow) away from a more liquid portion of the slurry (overflow), decant the overflow, and remove the underflow. Thickener underflow and thickener overflow are often passed on to filters to further separate solids from liquids.

(23) Water Soluble means materials that are soluble in water to at least 3%, by weight, at 25 degrees C.

(24) In the event that the above definitions or a description stated elsewhere in this application is inconsistent with a meaning (explicit or implicit) which is commonly used, in a dictionary, or stated in a source incorporated by reference into this application, the application and the claim terms in particular are understood to be construed according to the definition or description in this application, and not according to the common definition, dictionary definition, or the definition that was incorporated by reference. In light of the above, in the event that a term can only be understood if it is construed by a dictionary, if the term is defined by the Kirk-Othmer Encyclopedia of Chemical Technology, 5th Edition, (2005), (Published by Wiley, John & Sons, Inc.) this definition shall control how the term is to be defined in the claims. All illustrated chemical structures also include all possible stereoisomer alternatives.

(25) At least one embodiment of the invention is directed towards the addition of a dewatering composition to precipitated alumina trihydrate in the filtration stage of a Bayer Process. The composition comprises at least one R-succinic compound. The R-succinic compound may be one item selected from: octadecenyl succinic acid, hexadecenyl succinic acid, dodecenyl succinic acid, and any combination thereof.

(26) As previously mentioned and as described in U.S. Pat. Nos. 7,771,681, 7,976,820, 7,976,821, and Published Patent Application 2007/0172405, generally the Bayer Process is a sequential loop through which alumina bearing liquor passes. The process comprises: a digestion stage where alumina is extracted from Bauxite ore, a clarification stage where red mud is removed, a precipitation stage where alumina trihydrate is formed, and a classification stage where precipitated alumina trihydrate seeds of various sizes are separated out of the liquor. After classification the liquor may be reintroduced into the digestion stage and the precipitated alumina trihydrate (in the form of a slurry) passes on to a filtration stage and then to a calcination stage where the final alumina product is formed.

(27) In the filtration stage the water and alumina trihydrate bearing slurry is acted on to remove as much liquor and water as possible. The better the water removal, the lower the energy required to complete the subsequent calcination stage. As a result any number of separation methods can be applied. These methods include but are not limited to gravity separation, pressure separation, vacuum separation and any combination thereof. In at least one embodiment the composition is added before the slurry is separated, while the slurry is separated, and/or after the slurry is separated.

(28) As illustrated in FIG. 1, in at least one embodiment wash fluid is added to the slurry before, during, and/or after the separation. The wash fluid may comprise water and/or may consist essentially of water. The composition may be added to the wash fluid, may be added to the slurry alongside wash fluid, may be added to the slurry before the wash fluid, may be added to the slurry after the wash fluid, and any combination thereof.

(29) The effectiveness of this composition is quite unexpected. As described in such references as U.S. Pat. Nos. 5,011,612, 5,454,329, and 5,167,831, US Published Patent Application 2012/0288438 A1, and European Patent Documents EP0417360B1, EP0672620B1, EP1406711B1, EP0460811A1, EP0286034A1, fatty acids such as oleic acid and alkylsulfosuccinate compounds such as dioctylsulfosuccinate are known to be effective dewatering agents. The effectiveness of this composition however is in contrast to previous expectations. In prior art compositions it was assumed that a strong carboxylic acid was needed to grasp the water molecules and the fatty region was to address steric and lipophilic obstacles the acid faced. In contrast the structure of the open ring, and in particular the presence of two reflection carboxyl groups results in an acid that has an overall pKa which is lower than those of the prior art yet which is more effective than the prior art. In addition because of its lower pKa, R-succinic compounds have fewer unwanted downstream reactions than prior art fatty acid dewatering agents. In at least one embodiment the composition comprises an R-succinic compound with a lower pKa than dioctylsulfosuccinate and/or oleic acid yet is more effective as a dewatering agent.

(30) Without being limited by a particular theory or design of the invention or of the scope afforded in construing the claims, it is believed that the unique structure of the R-succinic compound is what causes exceptionally effective dewatering effects. The R-succinic compound comprises an open ring which contains carbonyl and hydroxide groups whose unique charge distribution may be able to grasp and pull water molecules that would otherwise remain hydrogen bonded to the alumina trihydrate. The ring structure and two-headed nature of the acid site therefore works better than would be expected by the lower pKa.

(31) In at least one embodiment the composition also comprises a ring opening agent. Under certain chemical conditions the open ring of the R-succinic compound could close by the formation of an anhydride bond between the hydroxide groups. The ring opening agent acts to prevent such ring closings. In at least one embodiment the ring opening agent is a base. The base may be selected from the list consisting of; potassium hydroxide, sodium hydroxide, sodium bicarbonate, sodium carbonate, ammonia, organic bases (including but not limited to triethylamine), and any combination thereof. The ring opening agent may be a catalyst and/or may be a reactive composition. In at least one embodiment the composition comprises an R-succinic compound in equilibrium between being open ringed and close ringed and the ring opening agent favorably shifts the equilibrium to favor the open ringed configuration. In at least one embodiment if in excess the ring opening agent would hydrolyze at least part of the ring and the dosage of the agent is sufficient to favorably shift the equilibrium to favor the open ringed configuration but not substantially hydrolyze any part of the ring.

(32) In at least one embodiment the R-succinic compound is formed by opening the ring of an R-succinic anhydride compound. For example as illustrated in FIG. 2 dodecenyl succinic anhydride (which is representative of any C1-C100 succinic anhydride) can be used to make the R-succinic compound. The R-succinic compound may be formed as a result of a base driven reaction.

(33) In at least one embodiment the R-succinic compound is stored in an anhydride form and its ring is opened immediately prior to or simultaneous to its introduction into the slurry or into the wash fluid.

(34) In at least one embodiment the composition reduces the amount of wash fluid required to remove the same amount of water from the slurry relative to use of a prior art dewatering agent.

(35) In at least one embodiment the composition reduces the amount of energy required to calcine the solids relative to use of a prior art dewatering agent.

(36) In at least one embodiment a lower dosage of the composition (and/or of the R-succinic compound) is required to remove the same amount of water from the slurry relative to use of a prior art dewatering agent.

(37) In at least one embodiment the composition reduces the amount of water remaining with the filter cake resulting from a separation method that the slurry goes through, relative to use of a prior art dewatering agent.

EXAMPLES

(38) The foregoing may be better understood by reference to the following examples, which are presented for purposes of illustration and are not intended to limit the scope of the invention. In particular the examples demonstrate representative examples of principles innate to the invention and these principles are not strictly limited to the specific condition recited in these examples. As a result it should be understood that the invention encompasses various changes and modifications to the examples described herein and such changes and modifications can be made without departing from the spirit and scope of the invention and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.

(39) A number of formulations were prepared to simulate the dewatering effectiveness of prior art fatty acid dewatering agents and the inventive composition. Table 1 summarizes the formulations.

(40) TABLE-US-00001 TABLE 1 Other Formulation Active Type Active % Water/KOH % Components % A* Fatty Acid 25 35 40 B* Fatty Acid 25 0 75 C ODSA 25 58 17 D DSA 25 60 15 E Fatty Acid 5 95 0 F ODSA 5 95 0 G HDSA 5 95 0 *Commercially available product DSA = Dodecenyl succinic acid prepared from dodecenyl succinic anhydride HDSA = Hexadecenyl succinic acid prepared from hexadecenyl succinic anhydride ODSA = Octadecenyl succinic acid prepared from octadecenyl succinic anhydride

(41) The test procedure that the samples underwent was as follows: Filtered alumina refinery spent liquor (200 mL) and alumina trihydrate (80 g) was added to 250 mL Nalgene bottles to prepare the slurry. De-ionised water (200 mL), for use as the wash water, was added to separate 250 mL Nalgene bottles. All of the bottles were then placed in a rotating water bath at 65 C. for a minimum period of 2 hours. A bottle of slurry was poured into a Buchner funnel (130 mm diam., Whatman 540 filter paper) and allowed to settle for 20 seconds then a vacuum was applied. (During this time the appropriate quantity of dewatering aid was added to the wash water (5-80 mg)). The solution was then shaken for a period of 30 seconds. After 30 seconds the vacuum was removed, the wash water/dewatering aid solution added onto the cake and the vacuum re-applied for a period of 80 sec. The cake was then sampled from the centre of the cake and the moisture content was determined gravimetrically by drying in an oven at 110 C.

(42) The results of the tests were as follows:

(43) Dewatering Aid Tests

(44) TABLE-US-00002 TABLE 2 DSA product formulation vs commercially available formulation Actives Dose % Reduction in Cake Formulation Used (g/T of alumina trihydrate) Moisture A (Fatty Acid) 14 4.2 28 16.5 D (DSA) 14 5.8 28 18.6

(45) TABLE-US-00003 TABLE 3 ODSA product formulation vs commercially available formulation Actives Dose % Reduction in Cake Formulation Used (g/T of alumina trihydrate) Moisture B (Fatty Acid) 37.5 11.0 B (Fatty Acid) 50 20.9 C (ODSA) 37.5 15.1 C (ODSA) 50 29.8

(46) TABLE-US-00004 TABLE 4 ODSA and HDSA product formulations vs equivalent fatty acid based formulation Actives Dose % Reduction in Cake Treatment (g/T of alumina trihydrate) Moisture E (Fatty Acid) 50 24.6 F (ODSA) 50 32.0 G (HDSA) 50 26.6

(47) The data demonstrates that all things equal, the inventive composition provides superior performance than would be expected for a fatty acid dewatering agent with its properties.

(48) While this invention may be embodied in many different forms, there are described in detail herein specific preferred embodiments of the invention. The present disclosure is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated. All patents, patent applications, scientific papers, and any other referenced materials mentioned herein are incorporated by reference in their entirety. Furthermore, the invention encompasses any possible combination of some or all of the various embodiments mentioned herein, described herein and/or incorporated herein. In addition the invention encompasses any possible combination that also specifically excludes any one or some of the various embodiments mentioned herein, described herein and/or incorporated herein.

(49) The above disclosure is intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the claims where the term comprising means including, but not limited to. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims.

(50) All ranges and parameters disclosed herein are understood to encompass any and all subranges subsumed therein, and every number between the endpoints. For example, a stated range of 1 to 10 should be considered to include any and all subranges between (and inclusive of) the minimum value of 1 and the maximum value of 10; that is, all subranges beginning with a minimum value of 1 or more, (e.g. 1 to 6.1), and ending with a maximum value of 10 or less, (e.g. 2.3 to 9.4, 3 to 8, 4 to 7), and finally to each number 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 contained within the range. All percentages, ratios and proportions herein are by weight unless otherwise specified.

(51) This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art may recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto.