Method and arrangement for process water treatment

Patent metadata

Field	Value
Publication number	US-2021379605-A1
Application number	US-201817288975-A
Country	US
Kind code	A1
Filing date	Oct 29, 2018
Priority date	Oct 29, 2018
Publication date	Dec 9, 2021
Grant date	—

Abstract

A method for treating process water of a flotation arrangement is disclosed. The process comprising the steps of a) dewatering overflow of a mineral flotation circuit in a gravitational solid-liquid separator to separate a sediment from a supernatant comprising water, silica-containing particles and soluble SiO2, fine particles, microbes, and residual flotation chemicals; b) subjecting the supernatant to cleaning flotation, in which at least 90% of the flotation gas bubbles have a size from 0.2 to 250 μm, in a cleaning flotation unit for collecting at least silica-containing particles, for separating at least silica-containing particles from the supernatant into cleaning flotation overflow, and for forming purified process water as cleaning flotation underflow; c) removing cleaning flotation overflow as tailings; and d) recirculating purified process water into the mineral flotation circuit. A process water treatment arrangement is also disclosed.

First claim

1 . A method for treating process water of a flotation arrangement comprising a mineral flotation circuit arranged to treat ore particles comprising Fe suspended in slurry by reverse flotation for the separation of slurry into underflow and overflow, and a process water treatment arrangement for treating overflow of the mineral flotation circuit; the process comprising the steps of:
a) dewatering overflow of the flotation circuit in a gravitational solid-liquid separator to separate a sediment from a supernatant comprising water, silica-containing particles and soluble SiO2, fine particles, microbes, and residual flotation chemicals, b) subjecting the supernatant to cleaning flotation, in which at least 90% of the flotation gas bubbles have a size from 0.2 to 250 μm, in a cleaning flotation unit for collecting at least silica-containing particles, for separating at least silica-containing particles from the supernatant into cleaning flotation overflow, and for forming purified process water as cleaning flotation underflow, c) removing cleaning flotation overflow as tailings, and d) recirculating purified process water into the mineral flotation circuit.

2 . The method according to claim 1 , wherein the cleaning flotation unit is a dissolved gas flotation unit.

3 . The method according to claim 1 wherein prior to step b), the temperature of the supernatant is 2 to 70° C.

4 . The method according to claim 1 wherein prior to step b), the pH of the supernatant is 5 to 14.

5 . The method according to claim 1 wherein in step a), the residence time of overflow in the gravitational solid-liquid separator is under 10 hours, preferably 2 to 8 hours.

6 . The method according to claim 1 wherein the solids content of the sediment of the gravitational solid-liquid separator is at least 80 w-%.

7 . The method according to claim 1 wherein after step a), the supernatant is led into a separator overflow tank.

8 . The method according to claim 1 wherein prior to step b), the supernatant is chemically conditioned in a mixing unit by adding a coagulant and/or a flocculant to flocculate silica-containing particles in the supernatant.

9 . The method according to claim 8 , wherein the coagulant is chosen from a group comprising: inorganic collector, aluminium salts, iron salts, organic coagulants.

10 . The method according to claim 8 wherein a coagulant is added into the supernatant in an amount of 20 to 2000 ppm.

11 . The method according to claim 8 wherein the flocculant is chosen from a group comprising: natural polymers, synthetic flocculants.

12 . The method according to claim 8 wherein a flocculant is added into the supernatant in an amount of 2 to 100 ppm.

13 . The method according to claim 1 wherein in step b), at least 90% of the SiO2 of overflow from the flotation circuit is removed.

14 . The method according to claim 1 wherein in step b), at least 70% of soluble SiO2 of overflow from the flotation circuit is removed.

15 . The method according to claim 1 wherein prior to step d), the purified process water is subjected to filtration for removing chemicals promoting microbiological growth.

16 . The method according to claim 15 , wherein in filtration, a filtering unit comprising a ceramic filter is used.

17 . The method according to claim 1 wherein hardness of the purified process water is unaffected by the process water treatment arrangement.

18 . A process water treatment arrangement for treating overflow of a mineral flotation circuit arranged to treat ore particles comprising Fe suspended in slurry by reverse flotation, wherein the arrangement comprises
a gravitational solid-liquid separator for dewatering overflow to separate a sediment from a supernatant comprising water, silica-containing particles and soluble SiO2, fine particles, microbes and residual flotation chemicals; and a cleaning flotation unit employing flotation gas bubbles of which at least 90% have a size from 0.2 to 250 μm, operationally connected to the gravitational solid-liquid separator for receiving the supernatant, and arranged to collect at least silica-containing particles, to separate at least silica-containing particles from the supernatant into cleaning flotation overflow, and to form purified process water as cleaning flotation underflow configured to be led back into the mineral flotation circuit.

19 . The process water treatment arrangement according to claim 18 , wherein the cleaning flotation unit is a DAF unit.

20 . The process water treatment arrangement according to claim 18 wherein it further comprises a mixing unit after the gravitational solid-liquid separator, the mixing unit configured to chemically condition the supernatant to flocculate silicate-containing particles in the supernatant.

21 . The process water treatment arrangement according to claim 18 wherein it further comprises a separator overflow tank after the gravitational solid-liquid separator.

22 . The process water treatment arrangement according to claim 18 wherein it further comprises a filtering unit for removing chemicals promoting microbiological growth from the purified process water after the cleaning flotation unit.

23 . The process water treatment arrangement according to claim 22 , wherein the filtering unit comprises a ceramic filter.

Assignees

• Metso Outotec Finland Oy

Inventors

• Jansson Kaj

Classifications

• B03D1/082

  of the froth product, e.g. washing · CPC title

• B03D1/08

  Subsequent treatment of concentrated product (froth dispersion B01D19/02) · CPC title

• C02F2101/10

  Inorganic compounds · CPC title

• B03D1/02

  Froth-flotation processes · CPC title

• C02F1/24

  by flotation (C02F1/465 takes precedence) · CPC title