AU2012203902A1

AU2012203902A1 - Metal hydroxide formulation

Info

Publication number: AU2012203902A1
Application number: AU2012203902A
Authority: AU
Inventors: Gary Ernest James
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-07-02
Filing date: 2012-07-02
Publication date: 2014-01-30
Anticipated expiration: 2032-07-02
Also published as: AU2012203902B2

Abstract

A method for the manufacture of a stabilised metal hydroxide slurry is described. A pre-cursor formulation comprising a mixture of the metal oxide such as magnesium oxide, a monohydroxyalkanol such as methanol and a 5 dihydroxyalkanol such as ethylene glycol is prepared. This formulation can be transported to a site for use where it is added to an aqueous medium to generate the metal hydroxide slurry. The aqueous medium can be the waste liquid from a sewerage well of a sewerage lift station and the resultant slurry finds use to reduce the levels of obnoxious gases in the waste liquid within the 10 sewerage well

Description

1 TITLE: METAL HYDROXIDE FORMULATION THIS INVENTION relates to a metal hydroxide formulation. In particular, it is directed to, although not limited to, a metal hydroxide formulation, such as a magnesium hydroxide slurry, which is stable for an extended period. 5 Throughout this specification., unless the contrary is expressly stated, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was, at the priority date, publicly available, known to the public, part of the common general knowledge, or known to be relevant 10 to an attempt to solve any problem with which this specification is concerned. Magnesium hydroxide, as an aqueous slurry, is used in various chemical processes, including for pH adjustment in the treatment of waste water and sewage, scrubbing and neutralization of acidic vapours in flue gases, and in the production of other specific magnesium-containing compounds such as 15 magnesium sulphate, magnesium nitrate and magnesium chloride. With particular reference to the waste water / sewerage industry, a magnesium hydroxide slurry is used to raise the pH of the sewage to inhibit the formation of the obnoxious gas hydrogen sulphide. A typical rate of addition is 100 gallons of slurry per 100,000 gallons of waste water / sewage. This slurry is 20 preferred as, presently, it represents the safest and most effective commercially available product. Commercially, magnesium hydroxide is manufactured by hydrating magnesium oxide and then transporting the resultant slurry for on-site use.

2 Currently, a magnesium hydroxide slurry is derived from three basic sources 0 cawater, well brines and magnesite ore. Typically, a magnesium hydroxide aqueous slurry is obtained containing 40-55% solids and having a relatively high viscosity as much as between 3,000 and 4,000 centipoise. 5 One advantage of such a magnesium slurry is that a reliable and accurate dosing in its subsequent use can be ensured. Further, by undertaking the hydration off-site, the potential danger of the exothermic reaction of magnesium oxide with water can be reduced. Nevertheless, there remain significant disadvantages to the prior art production 10 of a magnesium hydroxide slurry which include (i) production is limited to close proximity to sources of brine or seawater which may be remote from the intended use of the slurry; (ii) the cost of subsequently transporting (usually by road or rail) a product which is at least 50% water is relatively high; (iii) such a slurry requires relatively frequent agitation to prevent the settling out and 15 agglomeration of the suspended solids; if settling and agglomeration occurs, the resultant mass is extremely hard which, after a period of time, is virtually impossible to re-suspend; consequently, customers for the slurry, rarely being aware of the date of initial production of any particular slurry, only hold relatively small supplies of the slurry to avoid this agglomeration which leads 20 to a greater than ideal frequency of delivery which, in turn, raises the cost of the treatment; and (iv) in industries such as waste water and sewage treatment, these imported slurries are adding extra water to a process where the disposal of unwanted water from that site is already a significant major aim of the industries. 25 It is thus a general object of the present invention to overcome, or at least ameliorate, one or more of the above-mentioned disadvantages to provide a 3 stable, high solid content metal hydroxide slurry, especially a magnesium hydroxide slurry, that can readily be prepared at the site of its intended use. According to a first aspect of the present invention, there is provided a process for the production of a slurry of a hydroxide of a required metal, said process 5 including: agitating a mixture of an oxide of said metal in alcohol to form a substantially uniform suspension of said oxide in said alcohol; adding a first quantity of a first aqueous medium while maintaining said agitation for a first period until a substantially uniform suspension forms, 10 if necessary raising temperature of said suspension while undertaking said agitation; adding a second quantity of a second aqueous medium while maintaining said agitation for a second period until a substantially uniform suspension forms; 15 if necessary, allowing the subsequent suspension to cool to ambient temperature; if required, filtering said suspension to eliminate any particulate matter of unwanted size; and if required, homogenising the resultant slurry to a required particle size. 20 Said metal may be selected from Group 2a of the Periodic Table. Prefera $y, said Metal ii magnesium.

4 Said alcohol may be at least one alkanol. Preferably, said alkanol is at least two of said alkanol. When said alkanol is at least two of said a[kanol, a first said alkanol is a monohydroxyalkanol and a second said alkanol is a dihydroxyalkanol. 5 When said a first said alkanol is a monohydroxyalkanol and a second said alkanol is a dihydroxyalkanol, the ratio of monohydroxyalkanol dihydroxyalkanol is preferably approximately 1.5:1. When a first said alkanol is a monohydroxyalkanol and a second said alkanol is a dihydroxyalkanol, the ratio of oxide : monohydroxyalkanol : 10 dihydroxyalkanol: first and second aqueous media is preferably approximately 60 : 1.5 :1 : 140. Preferably, said monohydroxyalkanol is methanol. Preferably, said dihydroxyalkanol is ethylene glycol. Said first and second aqueous media may be from the same or different 15 source. Preferably, each said first and second aqueous media is sourced from a site at which said slurry is to be used. When said raising temperature of said suspension is required, said temperature is preferably raised to approximately 500C.

5 The instant inventor has determined that, if a said slurry is prepared as hereinbefore described, said slurry resists agglomeration for an extended period of several weeks, has a relatively low viscosity and maintains a high pH for an equally extended period. 5 Therefore, a second aspect of the present invention is a stabilised slurry prepared by the process as hereinbefore described. As hereinbefore described, the slurry of the present invention finds particular use at sites which can readily access and utilise said aqueous media, such as council-operated sewage treatment sites. At such sites, there is already 10 available the required said aqueous media in the form of treated or untreated waste water. Further, if said raising temperature is required, such sites can utilise the waste gases, such as methane, which are generated thereat to supply the required heat. Therefore, as a third aspect of the present invention, there is provided a 15 method for the production of a slurry of a hydroxide of a required metal at a site of intended use of said slurry, said method including: delivering an oxide of said metal to said site; agitating a mixture of said oxide in alcohol to form a substantially uniform suspension of said oxide in said alcohol in a first container; 20 adding a first quantity of a first aqueous medium from said site while maintaining said agitation for a first period until a substantially uniform suspension forms, if necessary raising temperature of said suspension while undertaking said agitation using waste combustible gaseous material from said site; 6 adding a second quantity of-a second aqueous medium from said site while maintaining said agitation for a second period until a substantially uniform suspension forms; if necessary, allowing the subsequent suspension to cool to ambient 5 temperature; if required, filtering said suspension to eliminate any particulate matter of unwanted size; if required, homogenising the resultant slurry to a required particle size; and 10 either storing said slurry in a second container for subsequent use and/or directly using said slurry at said site. Said first and second aqueous media of said method may each be treated or untreated waste liquid from a sewerage well of a sewerage lift station. Said method may be used to reduce the levels of at least one obnoxious gas 15 in waste liquid within a sewerage well of a sewerage lift station. The instant inventor has also determined that a pre-cursor to said slurry can be prepared off-site which reduces the workload required by a user of said slurry while still offering one or more advantages of the present invention. Therefore, as a fourth aspect of the present invention, there is provided a 20 formulation for use in the production of a slurry of a hydroxide of a required metal, said formulation including: 7 an oxide of said metal; a said first alkanol; and a said second alkanol. Preferred embodiments of the present invention will now be described with 5 reference to the following examples. EXAMPLE 1 Bagged magnesium oxide is delivered to a sewage treatment site. Typically, the magnesium oxide is technical grade readily available in the art and comprises approximately 97% by weight oxide, with the balance essentially 1o being oxides of calcium, silica, iron and aluminium. Supplies of methanol and ethylene glycol are also delivered to the site. Readily available technical grade methanol and ethylene glycol solvents are sufficient for the present invention. These supplies are stored at the site by any convenient means known in the art until required for use. 15 For every 15 litres of magnesium hydroxide slurry required: 360 mis of methanol and 128 mis of ethylene glycol are mixed together to a homogenous solution; 25g of magnesium oxide is added to the solution and agitation continued until a substantially uniform suspension is obtained; 20 7.5 litres of water is added to the suspension; (conveniently, this water is that reclaimed from the sewage treatment facility) 8 the temperature of the suspension is monitored while agitating; if the temperature fails to reach 70'C before the uniform suspension is obtained, heat is applied to the suspension (from the burning of the methane gas in the digesters of the sewage treatment facility), stirring 5 the suspension until the temperature is reached; agitation is continued for a further 1 hour; a further 7.5 litres of water is added to the suspension; (conveniently, this water is that reclaimed from the sewage treatment facility) agitation is continued for a further 30 minutes; 10 remove heat if applied, maintain agitation and allow the slurry to cool to ambient temperature; if required, dependent on the grade of reagents used, it may be necessary to filter the slurry to remove any particulate matter of unwanted size; 15 if it is necessary to use a slurry of a required particulate size, pass through a homogeniser; and the slurry is either pumped to a storage tank for later use or is passed to one or more sewerage wells of a sewerage lift station for use in the reduction of obnoxious gases such as hydrogen sulphide in the waste 20 liquid within the well(s). Typically, the viscosity of the slurry is 50 to 400 centipoise with a particulate size of 1 to 3 microns.

9 The slurry of the typically maintains a pH of 10.8 for at least four (4) weeks and also remains stable, and thus pumpable, for at least four (4) weeks. EXAMPLE 2 For every 100 kgs of magnesium hydroxide slurry to be prepared 5 subsequently: 71 Og of methanol and 540g of ethylene glycol are mixed together to a homogenous solution; and 30kg of magnesium oxide is added to the solution and agitation continued until a substantially uniform suspension is obtained. 10 The present invention thus provides a number of advantages which include (i) can be manufactured partially or entirely at the site of intended use of the slurry; (ii) the expected life time of the slurry is known directly by the user; (iii) can be manufactured as required in the quantities required thus saving on transport costs; and (iv) when used in waste water and sewage treatment 15 facilities or similar, it can use the onsite treated water rather than adding an outside water source. It will be appreciated that the above described embodiments are only exemplifications of the various aspects of the present invention and that modifications and alterations can be made thereto without departing from the 20 inventive concept as defined in the following claims.

Claims

1. A process for the production of a slurry of a hydroxide of a required metal, said process including: agitating a mixture of an oxide of said metal in alcohol to form a 5 substantially uniform suspension of said oxide in said alcohol; adding a first quantity of a first aqueous medium while maintaining said agitation for a first period until a substantially uniform suspension forms, if necessary raising temperature of said suspension while undertaking said agitation; 10 adding a second quantity of a second aqueous medium while maintaining said agitation for a second period until a substantially uniform suspension forms; if necessary, allowing the subsequent suspension to cool to ambient temperature; 15 if required, filtering said suspension to eliminate any particulate matter of unwanted size; and if required, homogenising the resultant slurry to a required particle size.

2. A process as defined in Claim 1 wherein said metal is selected from 20 Group 2a of the Periodic Table.

3. A process as defined in Claim 2 wherein said metal is magnesium. 11

4. A process as defined in any one of Claims I to 3 wherein said alcohol is at least one alkanol.

5. A process as defined in Claim 4 wherein said alkanol is at least two of said alkanol. 5

6. A process as defined in Claim 5 wherein a first said alkanol is a monohydroxyalkanol and a second said alkanol is a dihydroxyalkanol.

7. A process as defined in Claim 6 wherein the ratio of said monohydroxyalkanol said dihydroxyalkanol is approximately 1.5:1.

8. A process as defined in Claim 7 wherein the ratio of said oxide : said 10 monohydroxyalkanol : said dihydroxyalkanol : said first and second aqueous media is approximately 60: 1.5 :1 :140.

9. A process as defined in any one of Claims 6 to 8 wherein said monohydroxyalkanol is methanol.

10. A process as defined in any one of Claims 6 to 9 wherein said 15 dihydroxyalkanol is ethylene glycol.

11. A process as defined in any one of Claims 1 to 10 wherein said first aqueous medium is from the same source as said second aqueous medium.

12. A process as defined in any one of Claims 1 to 10 wherein said first 20 aqueous medium is from a different source as said second aqueous medium. 12

13. A process as defined in Claim 11 wherein each said first and second aqueous media is sourced from a site at which said slurry is to be used.

14. A process as defined in any one of Claims I to 13 wherein ifs aid raising temperature of said suspension is required, said temperature is raised 5 to approximately 5 0 0C.

15. A stabilised slurry prepared by a process as defined in any one of Claims 1 to 14.

16. A method for the production of a slurry of a hydroxide of a required metal at a site of intended use of said slurry, said method including: 10 delivering an oxide of said metal to said site; agitating a mixture of said oxide in alcohol to form a substantially uniform suspension of said oxide in said alcohol in a first container; adding a first quantity of a first aqueous medium from said site 15 while maintaining said agitation for a first period until a substantially uniform suspension forms, if necessary raising temperature of said suspension while undertaking said agitation using waste combustible gaseous material from said site; adding a second quantity of a second aqueous medium from said 20 site while maintaining said agitation for a second period until a substantially uniform suspension forms; 13 if necessary, allowing the subsequent suspension to cool to ambient temperature; if required, filtering said suspension to eliminate any particulate matter of unwanted size; 5 if required, homogenising the resultant slurry to a required particle size; and either storing said slurry in a second container for subsequent use and/or directly using said slurry at said site.

17. A method as defined in Claim 16 wherein each of said first and second 10 aqueous media is treated or untreated waste liquid from a sewerage well of a sewerage lift station.

18. A method as defined in Claim 17 when used to reduce the levels of at least one obnoxious gas in waste liquid within a sewerage well of a sewerage lift station. 15

19. A formulation for use in the production of a slurry of a hydroxide of a required metal, said formulation including: an oxide of said metal; a said first alkanol; and a said second alkanol. 14

20. A formulation as defined in Claim 19 wherein said metal is selected from Group 2a of the Periodic Table.

21. A formulation as defined in Claim 20 wherein said metal is magnesium.

22. A formulation as defined in Claim 20 or Claim 21 wherein said first 5 alkanol is a monohydroxyalkanol.

23. A formulation as defined in Claim 22 wherein said monohydroxyalkanol is methanol.

24. A formulation as defined in any one of Claims 20 to 23 wherein said second alkanol is a dihydroxyalkanol. 10

25. A formulation as defined in Claim 24 wherein said dihydroxyalkanol is ethylene glycol.

26. A process for the production of a slurry of a hydroxide substantially as herein described with reference to the examples.

27. A method for the production of a slurry of a hydroxide of a required metal 15 substantially as herein described with reference to the examples.

28. A formulation for use in the production of a slurry of a hydroxide of a required metal substantially as herein described with reference to the examples.