CONTINUOUS DISSOLUTION REACTOR

Abstract

A method for producing a rich solvent containing a dissolved compound at an intended concentration level includes 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. The method further includes the following steps: 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).

Claims

1. 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, wherein the method further comprises the following steps: 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).

2. A method for producing a rich solvent containing a dissolved compound at an intended concentration level, wherein 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, wherein 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).

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

4. The method according to claim 2, 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 concentration level of dissolved compound.

5. The method according to claim 1, wherein the lean solvent is a mineral acid, preferably a hydrochloric acid (HCl), nitric acid (HNO.sub.3), sulphuric acid (H.sub.2SO.sub.4), or a mixture thereof, and most preferably a solution of sulphuric acid, water and hydrogen peroxide (H.sub.2O.sub.2).

6. The method according to claim 5, wherein the compound to be dissolved is a metal.

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 concentration level of the dissolved compound, the sulphuric acid concentration of the rich solvent is less than 0.100 molar.

8. A process plant, comprising: a dissolution reactor comprising a first dissolution chamber comprising a lower inlet for a solvent, an upper inlet for solid compound, and an outlet for solvent located below the upper inlet and above the lower inlet, a first storage container, a second storage container, a first liquid conduit fluidly connecting a lower end of the first and the second storage containers to the inlet of the first dissolution chamber, wherein the first liquid conduit comprises a first pump, a first valve regulating the flow of solvent from the first storage container into the first liquid conduit, and a second valve regulating the flow of solvent from the second storage container into the first liquid conduit, a second liquid conduit fluidly connecting the outlet of the first dissolution chamber to an upper end of the first and the second storage containers, where the second liquid conduit comprises a third valve regulating the flow of solvent from the second liquid conduit into the first storage container and a fourth valve regulating the flow of solvent from the second liquid conduit into the second storage container, a third liquid conduit fluidly connecting the lower end of the first and the second storage containers to a downstream product handling facility, where the third liquid conduit comprises a fifth valve regulating the flow of solvent from the first storage container to the downstream product handling facility, and a sixth valve (32) regulating the flow of solvent from the second storage container to the downstream product handling facility, and a fourth liquid conduit (40) fluidly connecting the upper end of the first and the second storage containers to an upstream supply of lean solvent, where the fourth liquid conduit comprises a seventh valve regulating the flow of solvent from the upstream supply of lean solvent to the first storage container, and an eight valve regulating the flow of solvent from the upstream supply of lean solvent to the second storage container.

9. The process plant according to claim 8, further comprising a third storage container, and wherein: the first liquid conduit (10) further fluidly connects a lower end of the third storage container to the inlet of the first dissolution chamber and comprises a ninth valve regulating the flow of solvent from the third storage container into the first liquid conduit, the second liquid conduit (20) further fluidly connects the outlet of the first dissolution chamber to an upper end of the third storage container and comprises a tenth valve regulating the flow of solvent from the second liquid conduit into the third storage container, the third liquid conduit (30) further fluidly connects the lower end of the third storage container to the downstream product handling facility, where the third liquid conduit comprises an eleventh valve regulating the flow of solvent from the third storage container to the downstream product handling facility, and the fourth liquid conduit further fluidly connects the upper end of the third storage container to the upstream supply of lean solvent, where the fourth liquid conduit comprises a twelfth valve regulating the flow of solvent from the upstream supply of lean solvent to the third storage container.

10. The process plant according to claim 8, wherein the dissolution reactor further comprises: a second dissolution chamber comprising 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, wherein the inlet of the first dissolution chamber is fluidly connected to the first liquid conduit, the outlet of the first dissolution chamber is fluidly connected to the inlet of the second dissolution chamber, and the outlet of the second dissolution chamber is fluidly connected to the second liquid conduit.

11. The process plant according to claim 8, wherein the dissolution reactor further comprises: a second dissolution chamber comprising 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, and a third dissolution chamber comprising 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, and wherein the inlet of the first dissolution chamber is fluidly connected to the first liquid conduit, the outlet of the first dissolution chamber is fluidly connected to the inlet of the second dissolution chamber, the outlet of the second dissolution chamber is fluidly connected to the inlet of the third dissolution chamber, and the outlet of the third dissolution chamber is fluidly connected to the second liquid conduit.

12. The process plant according to claim 8, wherein the dissolution reactor further comprises: a second dissolution chamber comprising 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, wherein the inlet of the first dissolution chamber is fluidly connected to the first liquid conduit and the outlet of the first dissolution chamber is fluidly connected to the second liquid conduit, the inlet of the second dissolution chamber is fluidly connected to the first liquid conduit and the outlet of the second dissolution chamber is fluidly connected to the second liquid conduit, and wherein the first liquid conduit further comprises a thirteenth valve regulating the flow of solvent from the first liquid conduit into the first dissolution chamber, and a fourteenth valve regulating the flow of solvent from the first liquid conduit into the second dissolution chamber.

13. The process plant according to claim 8, wherein the dissolution reactor further comprises: a second dissolution chamber comprising 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, and a third dissolution chamber comprising 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, wherein the inlet of the first dissolution chamber is fluidly connected to the first liquid conduit and the outlet of the first dissolution chamber is fluidly connected to the second liquid conduit, the inlet of the second dissolution chamber is fluidly connected to the first liquid conduit and the outlet of the second dissolution chamber is fluidly connected to the second liquid conduit, the inlet of the third dissolution chamber is fluidly connected to the first liquid conduit and the outlet of the third dissolution chamber is fluidly connected to the second liquid conduit, and wherein the first liquid conduit further comprises a thirteenth valve regulating the flow of solvent from the first liquid conduit into the first dissolution chamber, and a fourteenth valve regulating the flow of solvent from the first liquid conduit into the second dissolution chamber, and a fifteenth valve regulating the flow of solvent from the first liquid conduit into the third dissolution chamber.

14. The process plant according to claim 8, further comprising a second solvent pump located in the second liquid conduit.

15. The process plant according to claim 8, further comprising a heat exchanger located in one of the first, second, third or the fourth liquid conduit.

16. The process plant according to claim 8, further comprising an inlet located either in the first, second, or the fourth liquid conduit, or in the first, second, or the third storage container, or in the first, second or the third dissolution chamber for adding additives to the solvent.

17. The process plant according to claim 8, further comprising a solvent strength monitoring unit located in either the first or in the second liquid conduit.

18. The process plant according to claim 8, wherein the first, second, third, fourth, fifth, sixth, seventh and the eighth, and if present, the ninth, tenth, eleventh, twelfth, thirteenth, the fourteenth, and the fifteenth valves are actuator controlled valves, and the first, and if present, the second solvent pumps are actuator controlled pumps, and wherein the process plant further comprises a logic controller unit comprising a processor loaded with a logic commands which when executed regulates the actuators of the first, second, third, fourth, fifth, sixth, seventh and the eighth, and if present, the ninth, tenth, eleventh (33), twelfth, thirteenth, the fourteenth valves, and the fifteenth valves, and the first, and if present, the second solvent pumps so as to execute a method for producing a rich solvent containing a dissolved compound at a 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, wherein the method further comprises the following steps: 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).

19. A dissolution reactor, wherein the dissolution reactor comprises: a container having a wall and a bottom plate but being open in its upper end, a corrosion resilient lining covering an inner surface of the wall and bottom plate of the container, a corrosion resilient basket being open at its bottom end and at its top end, and being located inside the container such that it rests on the inner surface of the bottom plate and extends a first distance upwards inside the container, wherein the basket comprises a perforated plate 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 adapted to inject a liquid into the container from below and into a space confined between the bottom plate, a lower part of the basket, and the perforated plate, a fluid outlet adapted to extract liquid from the container through the wall at a height being at least the same height at which the upper end of the basket extends inside the container, a funnel adapted to be suspended from the upper end of the container and being tapered and pointing towards the bottom plate, and which extends a third distance downwards into the container such that the narrow lower end of the funnel is below the upper end of the basket, and a lid adapted to cover the upper end of the container and wherein the lid is adapted to be fluidly connected to a gas evacuation for extracting eventual gases being formed inside the dissolution reactor.

20. The dissolution reactor according to claim 19, wherein the container is made of a metal, preferably a stainless steel alloy, and where the inner wall of the container 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, wherein the corrosion resistant basket and the perforated bottom plate is made of a polyethylene, a polyvinyl, a vinyl ester, or a polypropylene.

22. The dissolution reactor according to claim 19, wherein the lid and/or the upper part of the container may comprise one or more openings allowing false air to enter inside the lid.

23. The process plant according to claim 8, wherein the dissolution reactor is a dissolution reactor according to comprises: a container having a wall and a bottom plate but being open in its upper end, a corrosion resilient lining covering an inner surface of the wall and bottom plate of the container, a corrosion resilient basket being open at its bottom end and at its top end, and being located inside the container such that it rests on the inner surface of the bottom plate and extends a first distance upwards inside the container, wherein the basket comprises a perforated plate 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 adapted to inject a liquid into the container from below and into a space confined between the bottom plate, a lower part of the basket, and the perforated plate, a fluid outlet adapted to extract liquid from the container through the wall at a height being at least the same height at which the upper end of the basket extends inside the container, a funnel adapted to be suspended from the upper end of the container and being tapered and pointing towards the bottom plate, and which extends a third distance downwards into the container such that the narrow lower end of the funnel is below the upper end of the basket, and a lid adapted to cover the upper end of the container and wherein the lid is adapted to be fluidly connected to a gas evacuation for extracting eventual gases being formed inside the dissolution reactor.

Description

LIST OF FIGURES

[0100] FIG. 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.

[0101] FIG. 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.

[0102] FIG. 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.

[0103] FIG. 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.

[0104] FIG. 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

[0105] 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.

[0106] The example embodiment is illustrated schematically in FIG. 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 FIG. 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 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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

[0115] 1 dissolution reactor [0116] 2-1 lower inlet for solvent to the dissolution reactor [0117] 3-1 upper inlet for solid compound [0118] 4-1 outlet for solvent located below the upper inlet and above the lower inlet [0119] 5 first storage container [0120] 6 second storage container [0121] 7 third storage container [0122] 8 supply of lean solvent [0123] 9 product handling facility [0124] 10 first liquid conduit [0125] 11 first solvent pump [0126] 12 first valve [0127] 13 second valve [0128] 14 ninth valve [0129] 15 thirteenth valve [0130] 16 fourteenth valve [0131] 17 fifteenth valve [0132] 20 second liquid conduit [0133] 21 third valve [0134] 22 fourth valve [0135] 23 tenth valve [0136] 24 second solvent pump [0137] 30 third liquid conduit [0138] 31 fifth valve [0139] 32 sixth valve [0140] 33 eleventh valve [0141] 40 fourth liquid conduit [0142] 41 seventh valve [0143] 42 eighth valve [0144] 43 twelfth valve [0145] 50 heat exchanger [0146] 51 inlet for adding additives [0147] 52 solvent strength monitoring unit [0148] 53 logical control unit [0149] 60-1 dissolution chamber [0150] 100 container [0151] 101 container wall [0152] 102 container bottom plate [0153] 10.3 corrosion resilient basket [0154] 104 perforated plate [0155] 105 fluid inlet [0156] 106 fluid outlet [0157] 107 funnel [0158] 108 upper end of the basket [0159] 109 lower end of the funnel [0160] 110 lid [0161] 111 upper end of the container [0162] 112 gas evacuation [0163] 113 dissolution chamber