NO20220405A1

NO20220405A1 - Continuous dissolution reactor

Info

Publication number: NO20220405A1
Application number: NO20220405A
Authority: NO
Inventors: Ole Morten Dotterud; Finn Stålesen; Therese Amili
Original assignee: Glencore Nikkelverk As
Priority date: 2022-04-01
Filing date: 2022-04-01
Publication date: 2023-10-02
Also published as: WO2023187107A1

Description

CONTINUOUS DISSOLUTION REACTOR

The present invention relates to a method and apparatus for continuous dissolution of a substance in a solvent.

Background

There is present an increasing focus on mitigating climate change and reducing emissions of greenhouse gases. A vital part to achieve these goals is the electrifying of sectors presently applying fossil fuels as energy source. Many sectors involve mobility such that successful electrification of these sectors relies on access to high capacity and high energy density batteries enabling them to carry along their need for electric energy.

A secondary battery converts chemical energy stored in its electrochemical cell(s) to electric energy when being discharged, and stores imposed electrical energy as chemical energy in its electrochemical cell(s) when being charged. The cyclability, power delivering capacity, charging capacity, and especially the energy density both by mass and volume, are essential factors determining the applicability and usefulness of a secondary battery. Presently, secondary lithium ion batteries (LIB) deliver the best compromise on these parameters and are subject to an intense interest from the market. The cathode of secondary lithium ion batteries often applies mixed oxides containing nickel and/or cobalt, such as e.g. LiCoO2, LiNixMnyCozO2, LiNiCoAlO2, as the electrode active material.

According the S&P Global Market Intelligence, the global production of LIB is expected to more than triple from the present (2020) annual level of 455 GWh to nearly 1500 GWh in 2025. China and Europe is expected to be the largest contributors to this growth. The expected growth in the production of LIB will thus induce a comparable growth in the battery manufactures demand for high purity nickel and/or cobalt sulphate.

Prior art

Nickel and cobalt metal may be made from a solution of the metal by electroplating to produce a plate, typically a few mm up to a few centimetres thick, of high purity nickel or cobalt as a deposit on the cathode. Nickel and cobalt made by electroplating, often denoted as electrolytic nickel or electrolytic cobalt, have in general very high purity making them suitable for use as raw material for LIB manufacturing without need for refining/purification.

However, the battery manufacturers utilise high purity aqueous solutions of Ni or Co sulphates in their manufacturing process such that the electrolytic nickel or electrolytic cobalt need to be dissolved in sulphuric acid to be applicable for the lithium ion battery industry. The dissolution of solid nickel or cobalt in sulphuric acid is however a rather slow process making it relatively costly to scale up the dissolution capacity to large scale industrial production volumes.

WO 2020/129396 discloses a production method and a production device which increase the processing amount per device of nickel sulfate. A first dissolving step I and a second dissolving step II are performed in order, the first dissolving step I comprising placing nickel briquettes, sulfuric acid, and water in a leaching tank and dissolving the nickel briquettes to obtain a primary nickel sulfate solution, and the second dissolving step II comprising placing the primary nickel sulfate solution and additional nickel briquettes in a leaching adjusting tank and dissolving the additional nickel briquettes with free sulfuric acid in the primary nickel sulfate solution to obtain a nickel sulfate solution. Continuous dissolution can be achieved without increasing retention time and without unnecessarily enlarging the device by making the leaching adjusting tank serve as a concentration adjusting tank in which nickel concentration is increased and free sulfuric acid concentration is reduced and by supplying sulfuric acid and water in addition to the nickel briquettes to the leaching tank.

There is a need for a relatively rapid dissolution process for dissolving metals such as e.g. Co, Fe, Mn, or Ni in a mineral acid to make electroplated high purity metals an asset for the battery industry.

Objective of the invention

The main objective of the invention is to provide an apparatus and method for producing a rich solvent containing an intended level of solute.

A further objective of the invention is to provide an apparatus and method for producing a rich solvent containing an intended level of a dissolved metal.

It is further an objective of the invention to provide a dissolution reactor for dissolving a metal having a self-drainage of hydrogen gas which may develop.

Description of the invention

The objectives of the invention may be obtained by serially enriching successive volumes of solvent with solute by circulating one volume of solvent between a dissolution reactor containing the solid substance to be dissolved and a storage container until said volume of solvent is made rich by reaching its intended solute concentration, and then switch to enriching a new volume of (lean) solvent supplied from another storage container by circulating the new volume of solvent between the dissolution reactor and said another storage container. The process of enriching one volume of solvent in this manner is herein referred to as one dissolution cycle.

By serially performing successive dissolution cycles, it becomes possible to obtain a semi-continuous production of rich solvent by alternately switching between at least two storage containers, one being engaged in enriching its solvent content and the other being prepared for a coming dissolution cycle by being emptied of rich solvent and re-filled with lean solvent and vice-versa. This arrangement makes the dissolution process in the dissolution reactor run practically continuously and uninterrupted, while the production of rich solvent becomes a batch-resembling process since each successive volume of solvent under enrichment is not emptied from the storage container before reaching its intended concentration level of solute.

Thus, in a first aspect, the invention relates to a method for producing a rich solvent containing a dissolved compound at an intended concentration level, wherein the method comprises:

filling one of two storage containers with lean solvent and fluidly connecting said storage container to a dissolution reactor containing the compound to be dissolved,

characterised in that the method further comprises:

i) enriching the lean solvent in the storage container being fluidly connected to the dissolution reactor by circulating the lean solvent between the dissolution reactor and said storage container,

ii) emptying, if present, rich solvent from one of the two storage containers not fluidly connected to the dissolution reactor to a product handling facility, and then filling said storage container with lean solvent, and

iii) when the solvent in step i) has reached the predetermined concentration level of dissolved compound, fluidly disconnecting said storage container in step i) from the dissolution reactor and fluidly connecting the dissolution reactor to the said storage container in step ii) being filled with lean solvent,

and then

go to step i).

The method according to the invention may be made fully continuous in the sense that also the production of rich solvent may made continuous by applying at least three storage containers for each dissolution reactor.

Thus, in a second aspect, the invention relates to a method for producing a rich solvent containing a dissolved compound at an intended concentration level, characterised in that the method comprises:

applying three storage containers labelled as no. 1, 2 and 3, respectively, and one dissolution reactor containing the compound to be dissolved,

set index n=1,

filling the storage container labelled no. 1 with a volume of lean solvent and fluidly connecting it to the dissolution reactor,

characterised in that the method further comprises the following steps:

i) enriching the solvent in the no.1 labelled storage container by circulating it between the dissolution reactor and said storage container, ii) if index n=1 go to step iii) or else:

emptying the no. 2 labelled storage container’s content of a rich solvent to a product handling facility,

iii) filling the no. 3 labelled storage container with a volume of lean solvent, and

iv) when the solvent in step i) has reached the intended concentration level of dissolved compound, fluidly disconnecting the no.1 labelled storage container from the dissolution reactor and fluidly connecting the no. 3 labelled storage container to the dissolution reactor, and

v) relabel the storage containers such that the no. 1 storage becomes labelled the no. 2 storage container, the no. 2 storage container becomes labelled the no. 3 storage container, and the no. 3 storage container becomes labelled the no. 1 storage container, set index n=n+1, and go to step i).

In one example embodiment, the steps i) to iii) in the method according to the second aspect of the invention may advantageously be executed simultaneously such that one storage container is engaged in enriching its content of solvent by solute, one storage container is being emptied of rich solvent (enriched in the previous dissolution cycle, and one storage container is being filled with lean solvent to be enriched in the next dissolution cycle. In a further example embodiment, the production of rich solvent may become practically continuous and uninterrupted by adapting the flow rate of rich solvent exiting the no. 2 labelled storage container such that it takes equally long time to empty the no. 2 labelled storage container for its rich solvent as it takes to arrive at the predetermined level of solute in the no. 1 labelled storage container. The adaption of the flow rate to make the emptying of the no. 2 labelled storage container to take equally long time as the enrichment of the solvent circulating between the dissolution reactor and the no. 1 labelled storage container may be obtained by simple trial and error attempts or by estimates/calculations of the reaction kinetics between the compound to be dissolved and the solvent. Both are within the ordinary skills of a person skilled in the art.

The term “rich solvent containing a dissolved compound at an intended concentration level” as used herein refers to the level of dissolved compound as specified by a customer, as requested from process considerations of a downstream handling of the solvent and its solute, or any other downstream consideration which may affect the intended concentration level of solute in the rich solvent produced by the method. The term “dissolved compound” and “solute” are interchangeably herein.

The method according to the first and second aspect of the invention is not tied to dissolution of any specific chemical compound but may be applied to dissolve any (solid) chemical compound in any liquid solvent. One advantage of the method of the first or second aspect of the invention is that it is versatile in the sense that it may easily produce solvent solution containing any level of solute from zero to a saturated solution by simply varying the cut-off threshold value (i.e. the intended concentration level) which terminates the enrichment of a volume of solvent being and initiates a new cycle of solvent enrichment. This makes the present method suited to serve several customers having different desires for solute level.

The term “compound to be dissolved” as used herein encompasses any chemical compound being soluble in a suitable solvent. In one example embodiment, the compound to be dissolved may be a metal, such as e.g. cobalt, copper, iron, manganese, nickel, zinc, or alloys thereof. An especially preferred compound to be dissolved is electrolytic nickel or electrolytic cobalt. In one example embodiment, the compound to be dissolved may advantageously be in the form of solid particulates/pieces, or alternatively briquettes of pressed particulates of the compound. The solid particulates/pieces, or alternatively briquettes, may have characteristic dimensions of a thickness from 1 to 20 mm, preferably from 3 to 15 mm, more preferably from 4 to 10 mm, and most preferably from 5 to 7 mm, a length in the range of from 1 to 10 cm, and a width in the range of from 1 to 10 cm. In one especially preferred embodiment, the compound to be dissolved is cathode deposited electrolytic nickel or electrolytic cobalt of 1 – 10 mm thickness cut into pieces of a width & length of 1x1 ̈ (2.5x2.5 cm<2>), preferably of 2x2 ̈ (5.1x5.1 cm<2>), and most preferably of 4x4 ̈ (10.2x10.2 cm<2>). However, the invention is not tied to any specific shape or dimensions of the solid compound to be dissolved. It is also envisioned dissolving plates and/or larger pieces.

The term “solvent” as used herein encompasses any liquid capable of dissolving a compound. In one example embodiment, the solvent may be an acid solvent, e.g. a mineral acid such as e.g. hydrochloric acid (HCl), nitric acid (HNO3), or sulphuric acid (H2SO4), or a mixture thereof. The solvent may in one embodiment contain additives such as e.g. hydrogen peroxide (H2O2). An especially preferred solvent is a mixture of sulphuric acid, water and hydrogen peroxide. The peroxide enhances the dissolution rate of the metallic compounds and supresses the formation of hydrogen gas. Even though the present invention is described herein by way of an example of a dissolution process and apparatus/plant for dissolving a metal in a mineral acid, the method and apparatus/plant according to the invention may be applied for dissolving practically any solid material in any solvent.

In one example embodiment applying a mineral acid as the solvent, the strength of the lean acid solvent may advantageously be adapted such that most or nearly all mineral acid is consumed when the intended concentration level of metal is obtained. This embodiment has the advantage of forming a product, rich solvent, containing relatively little of the highly corrosive mineral acid alleviating downstream handling of the rich acid solvent and its solute. In one especially preferred embodiment, the lean solvent is sulphuric acid diluted with water to an acid concentration corresponding to having less than 50 g/l (0.51 molar), preferably less than 25 g/l (0.25 molar), more preferably less than 10 g/l (0.11 molar), preferably less than 7.5 g/l (0.08 molar), more preferably less than 5 g/l (0.05 molar), and most preferably less than 2.5 g/l (0.03 molar) of sulphuric acid per litre solvent remaining after finishing a dissolution cycle. The adaption of the acid strength of the lean acid solvent to reach an intended maximum level of remaining acid in the rich acid solvent is a matter of basic stoichiometric considerations/calculations within the common general knowledge of a person skilled in the art. For example, since the mole weight of Ni is 58.7 g and the mole weight of H2SO4 is 98.1 g, and the molar ratio nickel : sulphuric acid in the dissolution reaction is 1 : 1, dissolution of 1.0 g Ni-metal in an aqueous sulphuric acid solution consumes close to 1.7 g sulphuric acid. Thus, as an example, when the intended rich solvent shall contain 100 g Ni<2+ >ions per litre rich solvent and about 10 g/l remaining sulphuric acid, the amount of sulphuric acid in the lean (no dissolved Ni) solvent should be approx. 180 g/l (1.8 molar). The loss of water by evaporation and added volume of eventual additives such as e.g. H2O2 may also be taken into consideration.

In one embodiment, in the case of dissolving Ni or Co in an aqueous sulphuric acid solution, the intended concentration level of solute in the enriched solvent may preferably be from 10 to 200 g/l, more preferably from 50 to 150 g/l, and most preferably from 80 to 120 g/l.

In one embodiment, the method according to the invention may further comprise tempering the solvent to an intended temperature which may be in the range of from 20 to 105 °C, preferably from 70 to 100 °, more preferably from 60 to 85 °C, and most preferably from 70 to 80 °C. The tempering may in one embodiment be obtained by passing the circulating solvent through a heat exchanger. In the case of employing a mineral acid, and especially sulphuric acid, the heating may be obtained by e.g. diluting the acid with water to the intended acid concentration such as e.g. specified above.

In one example embodiment, the method according to the first and second aspects of the invention may further comprise applying a vertically oriented counter-current dissolution reactor where compound to be dissolved is entering the dissolution reactor at the top and the solvent is entering at the bottom of the dissolution reactor and wherein the circulating solvent exits the dissolution reactor via an outlet at the upper part of the dissolution reactor.

In a third aspect, the invention relates to a process plant, comprising:

- a dissolution reactor 1 comprising a first dissolution chamber 60-1 having a lower inlet 2-1 for a solvent, an upper inlet 3-1 for solid compound, and an outlet 4-1 for solvent located below the inlet 3-1 and above the inlet 2-1,

- a first storage container 5,

- a second storage container 6,

- a first liquid conduit 10 fluidly connecting a lower end of the first 5 and the second 6 storage containers to the inlet 2-1 of the first dissolution chamber 60, wherein the first liquid conduit 10 comprises a first solvent pump 11, a first valve 12 regulating the flow of solvent from the first storage container 5 into the first liquid conduit 10, and a second valve 13 regulating the flow of solvent from the second storage container 6 into the first liquid conduit 10,

- a second liquid conduit 20 fluidly connecting the outlet 4-1 of the first dissolution chamber 60 an upper end of the first 5 and the second 6 storage containers, where the second liquid conduit 20 comprises a third valve 21 regulating the flow of solvent from the second liquid conduit 20 into the first storage container 5 and a fourth valve 22 regulating the flow of solvent from the second liquid conduit 20 into the second storage container 6,

- a third liquid conduit 30 fluidly connecting the lower end of the first 5 and the second 6 storage containers to a downstream product handling facility 9, where the third liquid conduit 30 comprises a fifth valve 31 regulating the flow of solvent from the first storage container 5 to the downstream product handling facility 9, and a sixth valve 32 regulating the flow of solvent from the second storage container 6 to the downstream product handling facility 9, and

- a fourth liquid conduit 40 fluidly connecting the upper end of the first 5 and the second 6 storage containers to an upstream supply of lean solvent 8, where the fourth liquid conduit 40 comprises a seventh valve 41 regulating the flow of solvent from the upstream supply of lean solvent 8 to the first storage container 5, and an eight valve 42 regulating the flow of solvent from the upstream supply of lean solvent 8 to the second storage container 6.

An example embodiment of a process plant is shown schematically in figure 1. As seen on the figure, the example embodiment contains two storage containers 5, 6 being fluidly connected to the inlet 2-1 and the outlet 4-1 of the first dissolution chamber 60-1 of the dissolution reactor 1 by a first 10 and a second 20 liquid conduit, respectively. The first liquid conduit 10 has a first 12 and a second 13 valve to regulate the flow of solvent out of the first 5 or second 6 storage container, respectively, and the second liquid conduit 20 has a third 21 and a fourth 22 valve to regulate the flow of solvent into the first 5 or second 6 storage container, respectively. A pump 11 is located in the first liquid conduit to create a pressure setting up a circulation of solvent through the storage container 5, 6 being applied in the dissolution cycle, the first liquid conduit 10, the dissolution reactor 1, and the second liquid conduit 20. Lean solvent is supplied to the storage container 5, 6 not being engaged in the present dissolution cycle from a supply 8 via a fourth liquid conduit 40. The fourth liquid conduit 40 has a seventh valve 41 and an eight valve 42 regulating the flow of lean solvent into the first 5 or the second 6 storage container, respectively. Rich solvent produced in the previous dissolution cycle is emptied from the storage container 5, 6 not being engaged in the present dissolution cycle to a downstream product handling facility 9 via a third liquid conduit 30 having a fifth valve 31 and a sixth valve 32 regulating the flow of rich solvent out of the first 5 or the second 6 storage container, respectively. A logical control unit 53 regulates the action of the first to the eight valves and pump 11.

As mentioned above, it may be advantageous to apply at least three storage containers to make the production of rich solvent fully continuous. Thus in one example embodiment, shown schematically in figure 2, the process plant according to the third aspect of the invention may further comprise a third storage container 7, wherein:

the first liquid conduit 10 further fluidly connects a lower end of the third 7 storage container to the inlet 2-1 of the first dissolution chamber 60-1 of the dissolution reactor 1 and comprises a ninth valve 14 regulating the flow of solvent from the third storage container 7 into the first liquid conduit 10,

the second liquid conduit 20 further fluidly connects the outlet 4-1 of the first dissolution chamber 60-1 of the dissolution reactor 1 to an upper end of the third 7 storage container and comprises a tenth valve 23 regulating the flow of solvent from the second liquid conduit 20 into the third storage container 7,

the third liquid conduit 30 further fluidly connects the lower end of the third 7 storage container to the downstream product handling facility 9, where the third liquid conduit 30 comprises an eleventh valve 33 regulating the flow of solvent from the third storage container 7 to the downstream product handling facility 9, and

the fourth liquid conduit 40 further fluidly connects the upper end of the third 7 storage container to the upstream supply of lean solvent 8, where the fourth liquid conduit 40 comprises a twelfth valve 43 regulating the flow of solvent from the upstream supply of lean solvent 8 to the third storage container 7.

It may be advantageous for large scale production that the dissolution reactor comprises a plurality of dissolution chambers to increase the volume rates of produced rich solvent. This may be envisioned both for serially connected dissolution reactors or parallel connected dissolution chambers, or a combination thereof. An example embodiment comprising two serially connected dissolution chambers is schematically shown in figure 3.

Thus, in one embodiment, the process plant according to the third aspect of the invention, the dissolution reactor 1 may further comprise:

- a second dissolution chamber 60-2 comprising a lower inlet 2-2 for a solvent, an upper inlet 3-2 for solid compound, and an outlet 4-2, for solvent located below the inlet 3-2 and above the inlet 2-2,

wherein

- the inlet 2-1 of the first dissolution chamber 60-1 is fluidly connected to the first liquid conduit 10,

- the outlet 4-1 of the first dissolution chamber 60-1 is fluidly connected to the inlet 2-2 of the second dissolution chamber 60-2, and

- the outlet 4-2 of the second dissolution chamber 60-2 is fluidly connected to the second liquid conduit 20.

In a further embodiment, the process plant according to the third aspect of the invention may further comprise:

- a second dissolution chamber 60-2 comprising a lower inlet 2-2 for a solvent, an upper inlet 3-2 for solid compound, and an outlet 4-2, for solvent located below the inlet 3-2 and above the inlet 2-2, and

- a third dissolution chamber 60-3 comprising a lower inlet 2-3, for a solvent, an upper inlet 3-3 for solid compound, and an outlet 4-3, for solvent located below the inlet 3-3 and above the inlet 2-3,

and wherein

- the outlet 4-1 of the first dissolution chamber 60-1 is fluidly connected to the inlet 2-2 of the second dissolution chamber 60-2,

- the outlet 4-2 of the second dissolution chamber 60-2 is fluidly connected to the inlet 2-3 of the third dissolution chamber 60-3, and

- the outlet 4-3 of the third dissolution chamber 60-3 is fluidly connected to the second liquid conduit 20.

In one embodiment, the process plant according to the third aspect of the invention may further comprise a series of four, five, six, seven or eight dissolution chamber, each having a lower inlet for a solvent, an upper inlet for solid compound, and an outlet for solvent located below the inlet and above the inlet as described above, and which is serially interconnected by having the outlet of each dissolution chamber except the last of the series fluidly connected to the inlet of the next dissolution chamber, and where the inlet of the first dissolution chamber of the series is fluidly connected to the first liquid conduit and the outlet of the last dissolution chamber of the series is fluidly connected to the second liquid conduit.

An example embodiment of a process plant according to the third aspect of the invention applying two serially connected dissolution chambers 60-1, 60-2 is shown schematically in figure 3. As seen on the figure, the solvent being passed from the first 5 or the second 6 storage container enters the “first” dissolution chamber 60-1 via its inlet 2-1 and exits via its outlet 4-1, and then passes to the inlet 2-2 of the “second” dissolution chamber 60-2 and exits via its outlet 4-2 and then enters the second liquid conduit 20. Otherwise, the process plant is identical to the example embodiment shown in figure 1.

Without being bound by theory, it is believed that the dissolution of a solid compound in a solvent is a surface reaction being rate controlled by diffusive mass transfer of solute across the solid-liquid boundary layer, which according to Fick’s first law of diffusion, is proportional to the concentration difference of solute over the boundary layer. This concentration difference is sometimes denoted as the driving force of the mass diffusion. Solvent present at the surface of the solid compound will constantly be saturated by solute since the chemical dissolution reaction rate is more than adequate to keep up with the mass diffusion controlled removal of solute. The flux of solute through the solid-liquid boundary will therefore be controlled by the concentration level of solute in the bulk solvent.

Thus, the mass flux of solute passing through the solid-liquid boundary layer into the bulk solvent is highest at the initial phase of a dissolution cycle when there is no or only little solute in the bulk solvent and then slows down gradually as the solute concentration builds up in the bulk solvent. Consequently, the dissolution rate is considerably slower towards the end of a dissolution cycle as compared to the initial phase. However, the total surface area of the particles/pieces of solid compound to be dissolved may also influence the dissolution rate since the total mass transfer of solute from the solid phase into the bulk solvent equals the mass flux across the boundary layer times the total surface area of the particles/pieces of solid compound. Thus, the dissolution rate is expected, and observed to be increased by increasing the surface to volume ratio of the particles/pieces of solid compound, i.e. decreasing the particle sizes.

Furthermore, for exothermic dissolution processes, it may be advantageous to apply relatively large particulates/pieces of solid compound in the initial phase of a dissolution cycle when the driving force of the mass diffusion is relatively large to avoid excessive heat development, and then switch to smaller particulates/pieces of solid at a later stage of the dissolution cycle to maintain a relatively high dissolution rate when the driving force becomes lower. In the example embodiment with two or more serially connected dissolution reactors, this effect may simply be obtained by loading at least the first dissolution reactor with the relatively largest particulates/-pieces of solid compound to be dissolved and then loading at least the last dissolution reactor of the plurality with the relatively finest particulates/pieces of solid compound to be dissolved.

wherein

- the inlet 2-1 of the first dissolution chamber 60-1 is fluidly connected to the first liquid conduit 10 and the outlet 4-1 of the first dissolution chamber 60-1 is fluidly connected to the second liquid conduit 20,

- the inlet 2-2 of the second dissolution chamber 60-2 is fluidly connected to the first liquid conduit 10 and the outlet 4-2 of the second dissolution chamber 60-2 is fluidly connected to the second liquid conduit 20,

and wherein

- the first liquid conduit further comprises a thirteenth valve 15 regulating the flow of solvent from the first liquid conduit 10 into the first dissolution chamber 60-1, and a fourteenth valve 16 regulating the flow of solvent from the first liquid conduit 10 into the second dissolution chamber 60-2.

wherein

- the inlet 2-3 of the third dissolution chamber 60-3 is fluidly connected to the first liquid conduit 10 and the outlet 4-3 of the third dissolution chamber 60-3 is fluidly connected to the second liquid conduit 20,

and wherein

- the first liquid conduit further comprises a thirteenth valve 15 regulating the flow of solvent from the first liquid conduit 10 into the first dissolution chamber 60-1, a fourteenth valve 16 regulating the flow of solvent from the first liquid conduit 10 into the second dissolution chamber 60-2, and an fifteenth valve 17 regulating the flow of solvent from the first liquid conduit 10 into the third dissolution chamber 60-3.

In one embodiment, the process plant according to the third aspect of the invention may further comprise a second solvent pump 24 located in the second 20 liquid conduit for pumping solvent between the dissolution reactor 1 and one of the first 5, second 6, or if present, the third 7 storage container.

In one example embodiment, the process plant according to the third aspect of the invention may further comprise a solvent strength monitoring unit 52 located in either the first 10 or in the second 20 liquid conduit and being adapted to measure the acid strength and/or the solute concentration level in the solvent. The invention is not tied to any specific method to measure the concentration of a solvent, but may apply any method known to be suited by the person skilled in the art. In the case of applying an acid solvent, the monitoring of the acid strength may be obtained by e.g. measuring the pH, by titration, by spectrophotometry, etc.

In one embodiment, the process plant according to the third aspect of the invention may further comprise an inlet 51 located either in the first 10, second 20 or the fourth 40 liquid conduit, or in the first 5, second 6, or the third 7 storage container, or in the first 60-1, second 60-2 or the third 60-3 dissolution chamber for adding additives to the solvent, such as e.g. hydrogen peroxide.

In one example embodiment, the process plant according to the third aspect of the invention may further comprise a heat exchanger 50 located either in the first 10 or the second 20 liquid conduit for tempering the solvent being enriched. Depending on the compound to be dissolved and solvent being applied, the solvent may advantageously be heated or cooled by the heat exchanger. For example, exothermic dissolution of metals may require cooling the solvent passing through the heat exchanger.

In one embodiment, the process plant according to third aspect of the invention, each of the first to the twelfth valves may advantageously be actuator controlled valves regulated by a logical controller unit 53 loaded with logic commands which, when executed, controls and regulates the actuators of the first to the twelfth valves such that the process plant is made to execute the method according to the first or the second aspect of the invention.

In one embodiment, the first 12, second 13, third 21, fourth 22, fifth 31, sixth 32, seventh 41 and the eighth 42, and if present, the ninth 14, tenth 23, eleventh 33, twelfth 43, thirteenth 15, fourteenth 16, and the fifteenth 17 valves are actuator controlled valves, and the first 11, and if present, the second 24 solvent pumps are actuator controlled pumps. The term “actuator controlled valve” as used herein encompasses any known and conceivable valve comprising an actuator enabling automatically shutting-off and opening a conduit from zero to full through-flow of fluid in the conduit. The valve may advantageously e.g. be a throttle valve. The actuator may advantageously be electrically driven. The term “actuator controlled pump” as used herein encompasses any known and conceivable pump able to pump a liquid in a liquid conduit.

In one embodiment, the process according to the third aspect of the invention may further comprise a logic controller unit 53 comprising a processor loaded with a logic commands which when executed regulates the actuators of the first 12, second 13, third 21, fourth 22, fifth 31, sixth 32, seventh 41 and the eighth 42, and if present, the ninth 14, tenth 23, eleventh 33, twelfth 43, thirteenth 15, fourteenth 16, and the fifteenth 17 valves and the first 11, and if present, the second 24 solvent pumps such as to executing the method according to the first or the second aspect of the invention. The term “logic control unit” as applied herein, encompasses any known and conceivable control unit able to engage the above described actuators. Examples of suited logic control unit includes but is not limited to; a PID-controller, a feed-forward (open loop) controller, a fuzzy logic controller, a processmodel based controller, or combinations thereof.

In a fourth aspect, the invention relates to a dissolution reactor, wherein the dissolution reactor comprises:

a container 100 having a wall 101 and a bottom plate 102 but being open in its upper end 111,

an abrasive and corrosion resilient basket 103 constituting a dissolution chamber 60 located inside the container 100 such that it rests on the inner surface of the bottom plate 102 and extends a first distance upwards inside the container 100, wherein the basket 103 comprises a perforated plate 104 covering its horizontal cross-sectional area and which is located a second distance above its lover end, and where the second distance is less than the first distance,

a fluid inlet 105 adapted to inject a liquid into the dissolution chamber 60 of the container 100 from below and into a space confined between the bottom plate 102, a lower part of the basket 103, and the perforated plate 104,

a fluid outlet 106 adapted to extract liquid from the dissolution chamber 60 of the container 100 through the wall 101 at a height being at least the same height at which the upper end 108 of the basket 103 extends inside the container,

a funnel 107 adapted to be suspended from the upper end of the container 100 and being tapered and pointing towards the bottom plate 102, and which extends a third distance downwards into the container such that the narrow lower end 109 of the funnel 107 is below the upper end 108 of the basket 103, and

a removable lid 110 adapted to cover the upper end 111 of the container 100 and wherein the lid is adapted to be fluidly connected to a gas evacuation 112 for extracting eventual gases being formed inside the dissolution reactor.

In one embodiment, the container 100 is made of a metal, preferably a stainless steel alloy. However, any material having the mechanical strength to carry and hold the solid to be dissolved and the solvent may be applied. In one embodiment, the inner wall of the container 100 may be lined with a corrosion resistant lining, such as e.g. a rubber, a polyethylene, a polytetrafluoroethylene, or a vinyl ester.

In one embodiment, the abrasive and corrosion resistant basket 103 and the perforated bottom plate 104 is made of a polyethylene, a polyvinyl, a vinyl ester, or a polypropylene.

In one embodiment, the lid 110 and/or the upper part 111 of the container 100 may comprise one or more openings allowing false air to enter inside the lid and dilute eventual gases developed inside the dissolution reactor.

I one embodiment, the plant according to the third aspect of the invention or the method according to the first or second aspect of the invention may apply the reactor according to the fourth aspect of the invention.

List of figures

Figure 1 is a drawing schematically illustrating an example embodiment of a process plant according to the third aspect of the invention utilising one dissolution chamber and two storage containers.

Figure 2 is a drawing schematically illustrating another example embodiment of a process plant according to the third aspect of the invention utilising one dissolution chamber and three storage containers.

Figure 3 is a drawing schematically illustrating another example embodiment of a process plant according to the third aspect of the invention utilising two dissolution chambers connected in series and two storage containers.

Figure 4 is a drawing schematically illustrating another example embodiment of a process plant according to the third aspect of the invention utilising two dissolution chambers connected in parallel and two storage containers.

Figure 5 is a drawing schematically illustrating an example embodiment of a process plant according to the second aspect of the invention.

Example embodiments of the invention

The invention will be described in more detail by way of an example embodiment of a process plant according to the third aspect of the invention intended for dissolving cuttings of electrolytic nickel in sulphuric acid.

The example embodiment is illustrated schematically in figure 1. As seen on the figure, the process plant applies to storage containers 5, 6 being connected to a dissolution reactor. The dissolution reactor is similar to the dissolution reactor 100 shown in figure 5. In this example embodiment, the container 101 is shaped into a vertically standing cylinder made of S325 structural steel having an inner diameter of 70 cm and a total inner height of 2 m (from the inner side of the bottom 102 to the top end 111). The inner wall of the steel container is coated with a 3-4 mm thick layer of rubber. A cylindrical basket 103 of outer diameter 65 cm and height of 160 cm is placed coaxially inside the container 101. The basket 103 is made of a 1 cm thick polyester polymer and has a perforated, with a plurality of 1 mm ϕ throughgoing holes, plate 104 covering the horizontal inner cross-section of the basket at 5 cm up from its lower end, and thus forming a relatively small chamber confined between the inner surface of the bottom 102 of the container 101, the lower surface of the perforated plate 104 and the lower part of the inner wall of the basket 103. A fluid inlet 105 penetrates the bottom plate 102 and is adapted to inject acid solvent into the said chamber where it will fill the chamber and flow through the perforations and further upwards in the gasket 103. The basket 103 provides the advantage that metal cuttings will be prevented from coming in mechanical contact with the inner surface/lining of the steel container 101 and will thus represent no danger of abrasive wear on the container.

A funnel 107 having 10 mm thick wall of polyester polymer with an inner diameter of 60 cm at its upper end and an inner diameter of 40 cm at its lower end, is suspended coaxially from the top end 111 of the container 101 and protrudes downward a distance of 55 cm into the inner space of the cylindrical container 101. This makes the lower end 109 of the funnel to downwardly protrude approx. 5 cm into the upper part 108 of the basket 103. This has the advantage that metal cuttings fed through the funnel will enter and fall into the basket 103 without being in mechanical contact with the steel container.

The dissolution reactor will typically be made ready for a series of dissolution cycles by filling the entire inner space of the basket and funnel with metal cuttings. The metal cuttings may e.g. be 1 about cm thick and a few cm of length and width and will fill the inner section of the cylindrical container from bottom to top. A fluid outlet 106 is located at a height of 160 cm (from the bottom plate 102) and will make acid solvent flowing up through the container 101 to exit the dissolution reactor at about the upper end 108 of the basket 103. Thus, metal cuttings being inside the funnel being above the upper end of the basket being dry. They will only be exposed to the acid solvent when sinking below the fluid level of the solvent.

The dissolution of nickel in an aqueous sulphuric acid solution produces hydrogen. This is potentially hazardous. Hydrogen gas is highly explosive at certain stoichiometric ratios with oxygen gas (in the air). The dissolution reactor is therefore equipped with a pivotally hinged lid 110 which covers the upper end of the cylindrical container 101 and is in fluid connection with a fan operated gas evacuation 112. The lid 100 may be opened to allow filling of metal cuttings.

If the plant is to produce solved nickel at a solute level of 100 g Ni per litre solvent, the lean acid solution (no dissolved nickel) may advantageously have a sulphuric acid concentration of 170 - 175 g per litre. This corresponds to a 1.75 – 1.80 molar sulphuric acid solution. When the solvent is enriched to its intended solute level of 100 g/l, the rest concentration of the sulphuric acid will be approx. 0.1 molar.

The operation of the process plant may be as follows: At start up, the dissolution chamber 113 is filled with nickel cuttings and both storage containers 5, 6 and the dissolution chamber 113 may be empty of solvent. In this case, the dissolution process may be initiated by the logical controller opening e.g. the seventh valve 41 to fill the first storage container 5 with lean acid solvent (sulphuric acid) from the acid supply 8, and then closing the seventh valve 41 and opening the first 12 and the third valves 21 and engage pump 11 to circulate the acid solvent through the nickel cuttings filled space of the dissolution reactor. The acid solvent is circulated through the dissolution chamber 113 until the solvent strength monitoring unit 52 reports that the acid solvent has reached its intended solute level of 100 g nickel per litre solvent. Then the first dissolution cycle is terminated by the logical controller unit 53 shutting valves 12 and 21 to disengage the first storage container.

In the meantime, the logical controller unit 53 has prepared the second storage container by opening valve 42 to fill the storage container with lean acid solvent and then close valve 42. The second storage container is therefore ready to start the second dissolution cycle the moment the first dissolution cycle terminates by simultaneously opening valves 13 and 22 when valves 12 and 21 are being closed. In this manner, the flow of acid solvent through the dissolution reactor is made continuous.

While the second storage container 6 is occupied with executing the second dissolution cycle, the first storage container 5 is made ready for the third dissolution cycle by the logical controller unit 53 opening valve 31 to empty the first storage container for rich solvent which is passed to a downstream product handling facility 9, and then closing valve 31 and opening valve 41 to refill the first storage container with lean acid solvent and then closing valve 41.

In this manner the dissolution process is made continuous by interchanging between applying the first and second storage container to enrich the acids solvent.

List of reference numbers

1 dissolution reactor

2-1 lower inlet for solvent to the dissolution reactor

3-1 upper inlet for solid compound

4-1 outlet for solvent located below the upper inlet and above the lower inlet 5 first storage container

6 second storage container

7 third storage container

8 supply of lean solvent

9 product handling facility

10 first liquid conduit

11 first solvent pump

12 first valve

13 second valve

14 ninth valve

15 thirteenth valve

16 fourteenth valve

17 fifteenth valve

20 second liquid conduit

21 third valve

22 fourth valve

23 tenth valve

24 second solvent pump

30 third liquid conduit

31 fifth valve

32 sixth valve

33 eleventh valve

40 fourth liquid conduit

41 seventh valve

42 eighth valve

43 twelfth valve

50 heat exchanger

51 inlet for adding additives

52 solvent strength monitoring unit 53 logical control unit

60-1 dissolution chamber

100 container

101 container wall

102 container bottom plate

103 corrosion resilient basket

104 perforated plate

105 fluid inlet

106 fluid outlet

107 funnel

108 upper end of the basket

109 lower end of the funnel

110 lid

111 upper end of the container 112 gas evacuation 113 dissolution chamber

Claims

1. A method for producing a rich solvent containing a dissolved compound at a intended end concentration level, wherein the method comprises:

characterised in that the method further comprises the following steps:

and then

go to step i).

2. A method for producing a rich solvent containing a dissolved compound at a intended end concentration level, characterised in that the method comprises:

set index n=1,

characterised in that the method further comprises the following steps:

i) enriching the solvent in the no.1 labelled storage container by circulating it between the dissolution reactor and said storage container,

ii) if index n=1 go to step iii) or else:

iv) when the solvent in step i) has reached the intended end concentration level of dissolved compound, fluidly disconnecting the no.1 labelled storage container from the dissolution reactor and fluidly connecting the no. 3 labelled storage container to the dissolution reactor, and

3. The method according to claim 2, wherein steps i) to iii) are executed simultaneously.

4. The method according to claim 2 or 3, wherein the emptying of rich solvent from the no. 2 labelled storage container to the product handling facility is adapted to take equally long time to empty the no. 2 labelled storage container as it takes to enrich the solvent in the no. 1 labelled storage container from lean solvent to rich solvent containing the intended end concentration level of dissolved compound.

5. The method according to any preceding claim, wherein the lean solvent is a mineral acid, preferably a hydrochloric acid (HCl), nitric acid (HNO3), sulphuric acid (H2SO4), or a mixture thereof, and most preferably a solution of sulphuric acid, water and hydrogen peroxide (H2O2).

6. The method according to claim 5, wherein the compound to be dissolved is a metal, preferably a metal chosen from; cobalt, copper, iron, manganese, nickel, zinc, or alloys thereof, and most preferably electrolytic nickel or electrolytic cobalt, optionally having a characterising dimensions in the range of a thickness from 1 to 20 mm, preferably from 3 to 15 mm, more preferably from 4 to 10 mm, and most preferably from 5 to 7 mm, a length in the range of from 1 to 10 cm, and a width in the range of from 1 to 10 cm.

7. The method according to claim 6, wherein the concentration of sulphuric acid in the lean solvent is adapted such that when the lean solvent is enriched to rich solvent containing the intended end concentration level of the dissolved compound, the sulphuric acid concentration of the rich solvent is less than 0.100 molar, preferably less than 0.075 molar, more preferably less than 0.050 molar, and most preferably less than 0.025 molar.

8. A process plant, comprising:

- a dissolution reactor (1) comprising a first dissolution chamber (60) comprising a lower inlet (2) for a solvent, an upper inlet (3) for solid compound, and an outlet (4) for solvent located below the upper inlet (3) and above the lower inlet (2),

- a first storage container (5),

- a second storage container (6),

- a first liquid conduit (10) fluidly connecting a lower end of the first (5) and the second (6) storage containers to the inlet (2) of the first dissolution chamber (60), wherein the first liquid conduit (10) comprises a first pump (11), a first valve (12) regulating the flow of solvent from the first storage container (5) into the first liquid conduit (10), and a second valve (13) regulating the flow of solvent from the second storage container (6) into the first liquid conduit (10),

- a second liquid conduit (20) fluidly connecting the outlet (4) of the first dissolution chamber (60) to an upper end of the first (5) and the second (6) storage containers, where the second liquid conduit (20) comprises a third valve (21) regulating the flow of solvent from the second liquid conduit (20) into the first storage container (5) and a fourth valve (22) regulating the flow of solvent from the second liquid conduit (20) into the second storage container (6),

- a third liquid conduit (30) fluidly connecting the lower end of the first (5) and the second (6) storage containers to a downstream product handling facility (9), where the third liquid conduit (30) comprises a fifth valve (31) regulating the flow of solvent from the first storage container (5) to the downstream product handling facility (9), and a sixth valve (32) regulating the flow of solvent from the second storage container (6) to the downstream product handling facility (9), and

- a fourth liquid conduit (40) fluidly connecting the upper end of the first (5) and the second (6) storage containers to an upstream supply of lean solvent (8), where the fourth liquid conduit (40) comprises a seventh valve (41) regulating the flow of solvent from the upstream supply of lean solvent (8) to the first storage container (5), and an eight valve (42) regulating the flow of solvent from the upstream supply of lean solvent (8) to the second storage container (6).

9. The process plant according to claim 8, further comprising a third storage container (7), and wherein:

the first liquid conduit (10) further fluidly connects a lower end of the third (7) storage container to the inlet (2) of the first dissolution chamber (60) and comprises a ninth valve (14) regulating the flow of solvent from the third storage container (7) into the first liquid conduit (10),

the second liquid conduit (20) further fluidly connects the outlet (4) of the first dissolution chamber (60) to an upper end of the third (7) storage container and comprises a tenth valve (23) regulating the flow of solvent from the second liquid conduit (20) into the third storage container (7),

the third liquid conduit (30) further fluidly connects the lower end of the third (7) storage container to the downstream product handling facility (9), where the third liquid conduit (30) comprises an eleventh valve (33) regulating the flow of solvent from the third storage container (7) to the downstream product handling facility (9), and

the fourth liquid conduit (40) further fluidly connects the upper end of the third (7) storage container to the upstream supply of lean solvent (8), where the fourth liquid conduit (40) comprises a twelfth valve (43) regulating the flow of solvent from the upstream supply of lean solvent (8) to the third storage container (7).

10. The process plant according to claim 8 or 9, wherein the dissolution reactor (1) further comprises:

- a second dissolution chamber (60-2) comprising a lower inlet (2-2) for a solvent, an upper inlet (3-2) for solid compound, and an outlet (4-2), for solvent located below the inlet (3-2) and above the inlet (2-2),

wherein

- the inlet (2-1) of the first dissolution chamber (60-1) is fluidly connected to the first liquid conduit (10),

- the outlet (4-1) of the first dissolution chamber (60-1) is fluidly connected to the inlet (2-2) of the second dissolution chamber (60-2), and

- the outlet (4-2) of the second dissolution chamber (60-2) is fluidly connected to the second liquid conduit (20).

11. The process plant according to claim 8 or 9, wherein the dissolution reactor (1) further comprises:

- a second dissolution chamber (60-2) comprising a lower inlet (2-2) for a solvent, an upper inlet (3-2) for solid compound, and an outlet (4-2), for solvent located below the inlet (3-2) and above the inlet (2-2), and

- a third dissolution chamber (60-3) comprising a lower inlet (2-3), for a solvent, an upper inlet (3-3) for solid compound, and an outlet (4-3), for solvent located below the inlet (3-3) and above the inlet (2-3),

and wherein

- the outlet (4-1) of the first dissolution chamber (60-1) is fluidly connected to the inlet (2-2) of the second dissolution chamber (60-2),

- the outlet (4-2) of the second dissolution chamber (60-2) is fluidly connected to the inlet (2-3) of the third dissolution chamber (60-3), and

- the outlet (4-3) of the third dissolution chamber (60-3) is fluidly connected to the second liquid conduit (20).

12. The process plant according to claim 8 or 9, wherein the dissolution reactor (1) further comprises:

wherein

- the inlet (2-1) of the first dissolution chamber (60-1) is fluidly connected to the first liquid conduit (10) and the outlet (4-1) of the first dissolution chamber (60-1) is fluidly connected to the second liquid conduit (20),

- the inlet (2-2) of the second dissolution chamber (60-2) is fluidly connected to the first liquid conduit (10) and the outlet (4-2) of the second dissolution chamber (60-2) is fluidly connected to the second liquid conduit (20),

and wherein

- the first liquid conduit further comprises a thirteenth valve (15) regulating the flow of solvent from the first liquid conduit (10) into the first dissolution chamber (60-1), and a fourteenth valve (16) regulating the flow of solvent from the first liquid conduit (10) into the second dissolution chamber (60-2).

13. The process plant according to claim 8 or 9, wherein the dissolution reactor (1) further comprises:

wherein

- the inlet (2-3) of the third dissolution chamber (60-3) is fluidly connected to the first liquid conduit (10) and the outlet (4-3) of the third dissolution chamber (60-3) is fluidly connected to the second liquid conduit (20),

and wherein

- the first liquid conduit further comprises a thirteenth valve (15) regulating the flow of solvent from the first liquid conduit (10) into the first dissolution chamber (60-1), and a fourteenth valve (16) regulating the flow of solvent from the first liquid conduit (10) into the second dissolution chamber (60-2), and a fifteenth valve (17) regulating the flow of solvent from the first liquid conduit (10) into the third dissolution chamber (60-3).

14. The process plant according to anyone of claims 8 to 13, further comprising a second solvent pump (24) located in the second liquid conduit (20).

15. The process plant according to anyone of claims 8 to 14, further comprising a heat exchanger (50) located in one of the first (10), second (20), third (30) or the fourth liquid conduit (40).

16. The process plant according to anyone of claims 8 to 15, further comprising an inlet (51) located either in the first (10), second (20), or the fourth (40) liquid conduit, or in the first (5), second (6), or the third (7) storage container, or in the first (60-1), second (60-2) or the third (60-3) dissolution chamber for adding additives to the solvent.

17. The process plant according to anyone of claims 8 to 16, further comprising a solvent strength monitoring unit (52) located in either the first (10) or in the second (20) liquid conduit.

18. The process plant according to anyone of claims 8 to 17, wherein

- the first (12), second (13), third (21), fourth (22), fifth (31), sixth (32), seventh (41) and the eighth (42), and if present, the ninth (14), tenth (23), eleventh (33), twelfth (43), thirteenth (15), the fourteenth (16), and the fifteenth (17) valves are actuator controlled valves, and the first (11), and if present, the second (24) solvent pumps are actuator controlled pumps, and

- wherein the process plant further comprises a logic controller unit (53) comprising a processor loaded with a logic commands which when executed regulates the actuators of the first (12), second (13), third (21), fourth (22), fifth (31), sixth (32), seventh (41) and the eighth (42), and if present, the ninth (14), tenth (23), eleventh (33), twelfth (43), thirteenth (15), the fourteenth (16) valves, and the fifteenth (17) valves, and the first (11), and if present, the second (24) solvent pumps such as to executing the method according to anyone of claims 1 to 7.

19. A dissolution reactor,

characterised in that the dissolution reactor comprises:

a container (100) having a wall (101) and a bottom plate (102) but being open in its upper end (111),

a corrosion resilient lining covering an inner surface of the wall (101) and bottom plate (102) of the container (100),

a corrosion resilient basket (103) being open at its bottom end and at its top end, and being located inside the container (100) such that it rests on the inner surface of the bottom plate (102) and extends a first distance upwards inside the container (100), wherein the basket (103) comprises a perforated plate (104) covering its horizontal cross-sectional area and which is located a second distance above its lover end, and where the second distance < the first distance,

a fluid inlet (105) adapted to inject a liquid into the container (100) from below and into a space confined between the bottom plate (102), a lower part of the basket (103), and the perforated plate (104),

a fluid outlet (106) adapted to extract liquid from the container (100) through the wall (101) at a height being at least the same height at which the upper end (108) of the basket (103) extends inside the container,

a funnel (107) adapted to be suspended from the upper end of the container (100) and being tapered and pointing towards the bottom plate (102), and which extends a third distance downwards into the container such that the narrow lower end (109) of the funnel (107) is below the upper end (108) of the basket (103), and a lid (110) adapted to cover the upper end (111) of the container (100) and wherein the lid is adapted to be fluidly connected to a gas evacuation (112) for extracting eventual gases being formed inside the dissolution reactor.

20. The dissolution reactor according to claim 19, wherein the container (100) is made of a metal, preferably a stainless steel alloy, and where the inner wall of the container (100) is lined with a corrosion resistant lining chosen from one of; a rubber, a polyethylene, a polytetrafluoroethylene, or a vinyl ester.

21. The dissolution reactor according to claim 19 or 20, wherein the corrosion resistant basket (103) and the perforated bottom plate (104) is made of a polyethylene, a polyvinyl, a vinyl ester, or a polypropylene.

22. The dissolution reactor according to any one of claims 19 to 21, wherein the lid (110) and/or the upper part (111) of the container (100) may comprise one or more openings allowing false air to enter inside the lid.

23. The process plant according to any one of claims 8 to 18, wherein the dissolution reactor (1) is a dissolution reactor according to any one of claims 19 to 22.