NL1034329C2 - Deposition formation preventing method for liquid food treating device, involves separating stream of liquid food from mainstream, adding calcium salt to stream of liquid food, and re-introducing stream of liquid food into mainstream - Google Patents

Abstract

The method involves separating a stream of liquid food from a mainstream of liquid food supplied to a liquid food treating device. Calcium salt is added to the stream of liquid food, and a precipitation of the calcium salt is formed. The liquid food stream is re-introduced into the mainstream of the liquid food such that the calcium precipitate floats on the mainstream of liquid food. An independent claim is also included for a device for treating a liquid food, comprising a main supply.

Description

"The integrated process to extract vanadium and nickel from fly ash and similar oil by-products"

Description

BACKGROUND OF THE INVENTION

This invention is related to waste processing, fly ash treatment and similar vanadium-containing by-products of conventional hydrometallurgical routes to recover vanadium 0 and nickel.

Several processes are known for recovering vanadium, such as the roasting of vanadium-bearing materials with sodium salt (the pyrometallurgical route). This process is known as the salt lattice process. The salt-roasted ore / ash is then leached in a basic or acidic solution to obtain an annealed substance from which the vanadium can subsequently be recovered. Other processes use the conventional hydrometallurgical route in which fly ash is leached with sodium hydroxide and then sulfuric acid to dissolve vanadium. The next step consists of cleaning and settling vanadium pentoxide. See, for example, the following patents: Canadian Pat. No. 783.006; 0 US Pat. No. 4,539,186; U.S. Pat. No. 4,640,823; U.S. Pat. No. 4,798,709; U.S. Pat. No. 4,966,761 and U.S. Pat. No. 5,277,795).

Various hydrometallurgical processes have been developed over the past decades, but none of these technologies have been implemented in a large-scale, commercial manner. Most of these technologies have remained stuck at the laboratory or pilot plant level. It is therefore important to design a further commercial implementation to extract vanadium from fly ash or other by-products such as furnace ash (boiler ash), slag (Eng. Slag) and catalysts.

The ideal process schedule must meet economic and environmental requirements. The 0 newly to be developed process scheme will use the hydrometallurgical route instead of the pyrometallurgical route. The reason for this is that the hydrometallurgical route entails lower costs. In addition, the new route will include steps that control residues and residual solution.

A new process has been found to recover vanadium and nickel from fly ash and related materials by the hydrometallurgical route. The designed process is economically I0.t4.t29 2 and environmentally satisfactory. The process has been developed as an alternative to salt roasting. The old processes lead to air pollution if emissions are not controlled and use large amounts of energy.

Summary of the invention

The invented process is called "the integrated process to extract vanadium and nickel from fly ash and similar oil by-products". It is a waste processing technology with a virtually closed material cycle. The integrated process was conceived from an environmental technical point of view. It is a sustainable process with relatively low energy consumption and controlled emissions. The process is based on conventional hydrometallurgical operations that guarantee reliability and practicability.

The most prominent operational characteristics can be summarized as follows: a three-step joint leaching process carried out at a temperature of 80 ° C using sulfuric acid under atmospheric pressure, controlled by redox potential with nitrogen or sulfur dioxide; iron is removed from the solution by pH adjustment with sodium hydroxide; nickel is recovered from the saturated solution by a cementing process with zinc grains; vanadium is precipitated in its tetravalent form and is converted to high-quality vanadium pentoxide by annealing; the used solution and emissions are controlled, reused or converted into products that can be traded on the market.

Brief description of the drawings 25 The diagrams provide a schematic illustration of “the integrated process for extracting vanadium and nickel from fly ash and similar oil by-products”.

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Detailed description

The process of the invention is explained with reference to the diagram. It comprises four basic operations: A. alkalis, B. cleaning, C. settling / precipitation and D. controlling 5 used solution and emissions.

A. The leaching process

The most important tasks of the leaching process are to dissolve vanadium and nickel. This is achieved by a continuous leaching process in three steps. The main task of the leaching process is to dissolve vanadium and nickel. The optimal leaching parameters were determined by laboratory testing.

1. First step of the leaching process: leaching with water 15

In the water leaching process fly ash is brought into contact with diluted acid, rinse water from the process, seawater, freshwater and bleed. The parameters under which work is carried out are described in Table A.l. In this phase, all phases of vanadium that are soluble in water are leached.

20 TABLE A. 1 Leaching treatment conditions of water alkalis Parameters Conditions

Temperature 80 ° C

pH of the mixture ~ 7 25 Response time (economic time limit) 1 hour

Reactor Agitated tank reactor

Mixture density (% solid) 20%

Degree of extraction ~ 55%

Lye composition (lixiviant) · Fresh / tap water (50-55% extraction) 30 · Seawater (40% extraction) • Bleeding • Rinse water 35 4 2. Second step of the leaching process: alkalis with acid

All phases that occur as water-insoluble compositions are leached using sulfuric acid (1M).

5 TABLE A.2 Leaching conditions for alkalis with sulfuric acid.

Parameters Conditions

Temperature 80 ° C

pH of the mixture> 1 10 Response time (environmental time limit) 4 hours

Reactor Agitated tank reactor

Mixture density (% solid) 20%

Degree of extraction 95%

Lye composition (lixiviant) H2SO4 (10%) 15 3. Third step of the leaching process: strong acid alkalis

The remaining part of the vanadium mixture that has not been leached in the previous two steps is dissolved in strong sulfuric acid (2M), as indicated in Table A.3.

20 TABLE A.3 Leaching conditions for alkalis with strong sulfuric acid.

Parameters Conditions

Temperature 80 ° C

pH of the mixture> 1 Response time (economic time limit) 1 hour

Reactor Agitated tank reactor

Density of the mixture (% solid) 33% Degree of removal 10%

Lye composition (lixiviant) H 2 SO 4 (18%) B. Cleaning process

After the leaching process of fly ash, the physical separation of the rich leaching moisture from the unreacted solid residues is carried out. Solid / liquid separation is carried out: in the case of fly ash (small particles), the filtration process is used (laboratory scale filtration tests are performed after leaching) to obtain a clear liquid - free from sediment. The purpose of the lye treatment is to transform the vanadium contained in the fly ash into a solution. In this treatment it is inevitable that undesired elements such as Fe, Ni, Mg, Na and others end up in the mixture; these elements may interfere with further processing, or may co-settle with vanadium, threatening unacceptable levels of contamination of the end product. That is why the following cleaning steps are carried out.

B.l. Removal of iron by potential and pH control 15

Fe (OH) 3 complexes are formed in the presence of ferric ions in the mixture. These iron complexes achieve a true equilibrium in the solution in the absence of oxygen in gas form. When the conditions of the solution are changed to obtain the Fe (OH) 3 sediment, it appears that these complexes form polymers that also sink. If the pH value is rapidly increased, these long polymers solidify by means of hydroxyl bridges and Fe (OH) 3 gel colloids form. This is an undesirable structure since the poor sedimentation properties of the iron gel make the separation of sediment and solution difficult.

The reactions are carried out in a closed vessel at N 2 atmosphere to maintain vanadium in its tetravalent state, the pH value is slowly increased from 0.4 to 2.0 and the mixture is stirred vigorously at a stirring speed of 350 rpm. The reactions are carried out at a temperature of 70 ° C. The process conditions are shown in Table II below.

30 35 6 TABLE B.1 Process conditions for the removal of iron Parameters Conditions

Process temperature ~ 70-80 ° C

Increase from pH 0.4 to 2.0 5 Processing time (economic time limit) 2 hours

Reactor Agitated tank reactor

Reagent NaOH (20%)

Removal of iron 95%

Remark · Closed vessel 10 · N2 atmosphere • S02 • Stirred vigorously 15 10: 5 o 5 7 B.2 Removal of nickel

After the iron has been removed by filtration of the iron sediment, the residual slurry (pH slurry) with a pH value of 2.0 is used for the cementation process.

Cementation is one of the technologies used to extract metal ions from the solution. This refers to the use of a solid metal to recover another type of metal from a solution through a simple redox reaction. In the present invention, the active metal zinc is added to the solution to remove the noble metal nickel. The chemistry of this process is as follows:

NiSO 4 + Zn = Ni + ZnSO 4 (1)

The equilibrium constant for this reaction at 25 ° C is 2.011 * 1019. As stated, the ions of several noble metals in a solution can simply be subjected to adhesion to less noble or more reactive metal substrates during the cementing reaction. The thermodynamic data is summarized in Table B.2.

TABLE B.2 Thermodynamic data under standard conditions Response AH (Kcal) AS (cal / K) AG (Kcal) K

20 (I) -25.270 3 ^ 61 -26.332 2.011 * 101V

The purpose of cementing in the process is to reduce unwanted elements to a low level and to produce nickel powder.

The metal zinc is oxidized and nickel is removed from the solution according to the reactions indicated below:

Ni 2+ + 2e '= Ni E0: -0.27 V (2)

Zn = Zn2 + + 2e 'Ec: +0.76 V (3) Ni2 + + Zn = Ni + Zn2 + Eo: + 0.49V (4)

Eo indicates: standard conditions of 25 ° C, a concentration of 1 mol / liter and a pressure of 1 atmosphere. The entire reaction is spontaneous, because the thermodynamic ratio between the metals is favorable, i.e. the net E0 is positive.

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The conditions for nickel cementation are shown in Table B.3. It was discovered that when zinc granules were added to the solution (pH: 2), another, unavoidable reaction of zinc solution takes place leading to the production of hydrogen.

5 TABLE B.3 Process conditions for Ni cementation

Parameters Conditions

Process temperature 25 ° C

~ pH ~ 2.0

Operation time 1 hour 10 Reactor Agitated tank reactor

Reactant Zn granules

Remark · Closed vessel • N2 atmosphere • Stirred thoroughly IS - C. Settling of vanadium

After removing nickel and subsequent filtration to separate solids from liquid parts, the residual suspension is subjected to a change in pH value with »0 NH 4 OH. The pH value of the solution is increased to pH 7. By using concentrated ammonium hydroxide, the settling starts at a pH value of about 3.5 and is ready at a pH value of 7. Annealing of the sludge at 600 ° C yields vanadium pentoxide. The conditions for settling are summarized in Table C.l.

.5 0 5 9 TABLE C.1 Operating conditions for vanadium precipitation and production of vanadium pentoxide

Parameters Conditions

Process temperature ~ 25 ° C

5 Increase from pH 3 to 7.0

Response time Fast process

Reactor Agitated tank reactor

Reactant NH 4 OH (30%)

Vanadium removal 99%

Annealing · At 600 ° C for 12 hours • NH3 is collected and reused D. Removal of zinc 15

Zinc dissolved by cementation does not interfere with the vanadium precipitation process. A solution of Na 2 CC> 3 is added to the suspension (slurry) (with a pH value of approximately 7), ZnCC> 3 is generated and precipitated from the suspension. The process conditions are shown in Table D. 1 below.

TABLE D.1 Process conditions for zinc precipitation. Parameters Conditions

Process temperature ~ 25 ° C

Increasing from pH 7.0 to 8.0 Reaction time Fast process

Reactor Agitated tank reactor

Reactant Na 2 CO 3

Zinc removal ZnCC> 3 30 034329 35

Claims (9)

A process for removing vanadium and nickel from fly ash and related by-products or residual products such as furnace ash, slag (slag) and used catalysts containing iron mixtures, silicon, magnesium and other impurities; Having the following characteristics: jq 1.1. Fly ash and related materials are leached with water, sea water and bleed followed by sulfuric acid. The leaching process is designed as a three-step continuous system. 1.2. Saturated solution is cleaned by means of pH adjustment and redox control to remove iron, followed by cementation of nickel by zinc grains. 1.3. After the removal of iron and nickel, vanadium is precipitated by means of hydrolytic settling with ammonium hydroxide. 1.4. Consumed solution and emissions are controlled, neutralized and reused in the process to close the process, hence the concept of an integrated process. A process according to claim 1, characterized in that the leaching process is carried out in a closed vessel in a nitrogen or sulfur dioxide atmosphere wherein the redox potential is controlled by keeping vanadium in its tetravalent state. A high leaching rate of 75 is obtained at an optimum temperature of 80 ° C. A process according to claim 1.2, characterized in that sulfuric acid is used as a lye composition (lixiviant) in the leaching process. jQ A process as claimed in claim 1, characterized in that the leaching process is designed in three steps: water liquor, acid liquor and strong acid liquor. A process according to claim 1, characterized in that the purification process is based on selective precipitation by pH adjustment and redox control. Iron is removed by adjusting the pH value at a temperature of about 70 ° C, 034329 from 0.6 to 2.0 by means of sodium hydroxide in an agitated closed reactor in an N2 atmosphere (SO2 as a reductant) . A process according to claim 1, characterized in that nickel is removed from the solution by cementation through zinc (Zn) grains at a pH value of about 2. A process according to claim 6, characterized in that nickel (Ni) is recovered as a nickel powder. A process according to claim 1.4, characterized in that after the removal of nickel by cementation, the pH value of the saturated solution is increased with ammonium hydroxide to a level of pH 7, wherein vanadium (IV) is obtained from the mixture by hydrolitic precipitation; the settling starts at a pH value of 3.5 and ends at a pH value of about 7. Annealing of the vanadium at 600 ° C for 12 hours yields vanadium pentoxide. 9. A process characterized in that the spent solution is controlled and reused as bleed for alkalis and emissions of ammonia are reused in the vanadium precipitation process. 20 25 30 35 034329