Method and device for regenerating a platinum bath

Abstract

A method of regenerating a platinum bath by flow reaction, the method comprising the successive steps of: drawing off fluid from the platinum bath by means of a draw-off flow; complexing platinum by mixing together the draw-off flow and a regeneration solution flow containing platinum, mixing taking place in an intensified reactor; and feeding the platinum bath with the mixture resulting from the platinum complexing step, by means of a regenerated bath flow; all of these steps being performed as a continuous flow.

Claims

1. A method of regenerating a platinum bath by flow reaction, the method comprising the successive steps of: drawing off fluid from the platinum bath by means of a draw-off flow; complexing platinum by mixing together the draw-off flow and a regeneration solution flow containing platinum, mixing taking place in an intensified reactor, wherein the step of complexing in the reactor comprises the steps of: preheating the draw-off flow and the regeneration solution flow so that their respective temperatures are equal to a predetermined temperature higher than the temperature of the platinum bath; mixing the draw-off flow with the regeneration solution flow so as to form a platinum complex; and feeding the platinum bath with the mixture resulting from the platinum complexing step, by means of a regenerated bath flow; all of these steps being performed as a continuous flow.

2. A method according to claim 1, further comprising: thermal monitoring, for a predetermined time, of the mixture formed in the complexing step in order to ensure that the temperature of the mixture is equal to the predetermined temperature during the complexing step.

3. A method according to claim 2, wherein, after the step of thermal monitoring, the mixture is returned to a temperature of 64 C. in a tank located downstream from the reactor.

4. A method according to claim 1, wherein the rate at which the reactor is fed with the draw-off flow is 80 g/min, and the rate at which the reactor is fed with the regeneration solution flow is 10 g/min.

5. A method according to claim 1, wherein the concentration of platinum in the platinum bath is maintained continuously at a value lying in an interval of 1 g/L.

6. A method according to claim 1, wherein the temperature of the platinum bath is maintained at a value lying in an interval of 4 C.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The invention and its advantages can be better understood on reading the following description of various implementations of the invention given as non-limiting examples. The description refers to the accompanying sheet of figures, in which:

(2) FIG. 1 is a block diagram of a device in accordance with the present disclosure for regenerating a platinum bath;

(3) FIG. 2 is a block diagram of an intensified reactor in accordance with the present disclosure; and

(4) FIG. 3 shows the various steps of a method of the present disclosure for regenerating a platinum bath.

DETAILED DESCRIPTION OF EMBODIMENTS

(5) FIG. 1 is a block diagram of a device 100 of the present disclosure for regenerating a platinum bath. The device 100 comprises a platinum bath B filled at least in part with a fluid including one or more platinum complexes suitable for forming a metal underlayer. Under the effect of the electric current passing through the bath, the platinum complexes become deposited on the metal part, e.g. a turbine engine blade part, so as to form the metal underlayer.

(6) For example, in order to fabricate one liter of platinum bath B having 8 g/L of platinum, the procedure is as follows:

(7) Preparing a solution B: in 300 milliliters (mL) of distilled water (<500 ohms (0)) at 30 C., adding 44.0 grams (g) of diammonium hydrogen phosphate having the chemical formula (NH.sub.4).sub.2HPO.sub.4 (i.e. 0.33 moles) and 75.0 g of ammonium dihydrogen phosphate of chemical formula NH.sub.4H.sub.2PO.sub.4 (i.e. 0.65 moles). The molar ratio between the quantity of ammonium dihydrogen phosphate and the quantity of diammonium hydrogen phosphate is 2. Once the salts have dissolved, covering the solution and raising it to 50 C. over 4 h 30 min.

(8) Preparing a solution A: in 300 mL of distilled water at 45 C., adding 5 g of sodium hydroxide of chemical formula NaOH (i.e. 0.080 moles) and 18.3 g of diammonium hexachloroplatinate platinum salt of formula (NH.sub.4).sub.2PtCl.sub.6 (i.e. 0.040 moles). The molar ratio between the quantity of sodium hydroxide and the diammonium hexachloro-platinate salt is 2. Allowing the platinum salts to dissolve within solution A.

(9) Once the solution B is ready and hot, preparing the solution A and adding it to the solution B previously raised to 60 C.

(10) To finish, taking the mixture A+B (of pH previously adjusted to 6.3 by adding a basic solution, such as, for example, sodium hydroxide, potassium hydroxide, or sodium triphosphate) and raising it to 85 C. over 3 h. All of the solutions are covered throughout the heating steps.

(11) More generally, with this solution B containing diammonium hydrogen phosphate of chemical formula (NH.sub.4).sub.2HPO.sub.4 and ammonium dihydrogen phosphate of chemical formula NH.sub.4H.sub.2PO.sub.4, setting the pH of the mixture of solutions A+B to lie in the range 6 to 10, and preferably in the range 6 to 7.

(12) The device 100 also has a draw-off flow 1 flowing in a first pipe, a regeneration solution flow 2 flowing in a second pipe, and an intensified reactor R. The platinum bath B and the intensified reactor R are connected together by the draw-off flow 1. The draw-off flow 1 takes a portion of the platinum bath B for regenerating and conveys it to the intensified reactor R, e.g. at a rate of 80 g/min. A bath of regeneration solution S is connected to the intensified reactor R by the regeneration solution flow 2. The regeneration solution bath S has platinum at a concentration of 10.5 g/L. This concentration corresponds to the regeneration solution flowing at 10 g/min. The regeneration solution flow 2 takes a portion of the regeneration solution bath S and conveys it to the intensified reactor R. The draw-off flow 1 and the regeneration solution flow 2 then mix in the intensified reactor R.

(13) A regenerated bath flow 3 flows in a third pipe, and connects the intensified reactor R to the platinum bath B. The mixture of the draw-off flow 1 mixed with the regeneration solution flow 2 and coming from the intensified reactor R, is then conveyed to the platinum bath B.

(14) The assembly constituted by the platinum bath B, the draw-off flow 1, the intensified reactor R, and the regenerated bath flow 3 forms a loop for circulating the platinum bath, going from a bath for regeneration state in the draw-off flow 1, to a regenerated bath state in the regenerated bath flow 3.

(15) The regeneration of the platinum bath B takes place outside the bath, during the step S2 in the intensified reactor R, with its operating principles shown diagrammatically in FIG. 3.

(16) The intensified reactor R may be an intensified reactor made up in particular of a plurality of modules. Each of the modules has four glass plates that are superposed on one another, and brazed together, for example, with the various flows, including a heating fluid flow, flowing separately between them. The channels formed between the plates, in which the various flows flow, possess flow diameters in the range 0.5 mm to 20 mm. This serves in particular to enable heat to be transferred effectively. The intensified reactor R thus has a first preheater module 10a for preheating the draw-off flow 1, and a second preheater module 10b for preheating the regeneration solution flow 2. The preheater modules 10a and 10b each have an inlet and an outlet.

(17) In this example, in order to optimize formation of the platinum complex, the mixing temperature between the flows is set at 80 C., the flow rate of the draw-off flow 1 feeding the first preheater module 10a is set at 80 g/min, and the flow rate of the regeneration solution flow 2 feeding the second preheater module 10b is set at 10 g/min. The first preheater module 10a thus serves to preheat the draw-off flow 1 so as to raise its temperature to at least 80 C., while remaining below 90 C. The second preheater module 10b serves to preheat the regeneration solution flow 2 so as to raise its temperature to at least 80 C., while remaining below 90 C. A heating fluid flows between the plates of the first and second modules 10a and 10b in order to raise the mixing temperature to this value lying in the range 80 C. to 90 C.

(18) The outlets from the first and second preheater modules 10a and 10b are connected to a mixer 20 in which the draw-off flow 1 and the regeneration solution flow 2 are mixed together, thereby forming the platinum complex. In this example, the mixer 20 is a module comprising four plates of glass brazed together with the two flows flowing in particular between them and mixing together, the module having two inlets and one outlet. The first inlet of the mixer 20 is fed with the preheated draw-off flow 1 and the second inlet of the mixer 20 is fed with the preheated regeneration solution flow 2. The outlet from the mixer 20 delivers the resulting mixture. A heating fluid also flows between those plates, so as to maintain the temperature of the mixture at a value higher than 80 C. and lower than 90 C.

(19) Alternatively, the mixer 20 may be a continuous mixer, e.g. a T-coupling, having a flow diameter of one-quarter of an inch, and in which a first inlet is fed with the preheated draw-off flow 1, a second inlet is fed with the preheated regeneration solution flow 2, and an outlet delivers the resulting mixture.

(20) The mixture leaving the mixer 20 thus includes the reformed platinum complex. The transit time through the reactor R for the mixture leaving the mixer 20 is set to a predetermined value, e.g. 6 seconds (s). In FIG. 2, the reactor R has one or two control modules 30, analogous to the preheater modules 10a and 10b and connected in series, through which the mixture coming from the mixer 20 flows. These control modules 30 serve to increase the transit time of the mixture at 80 C. through the reactor R, thereby finishing off the complexing of the mixture, where necessary. The reactor could equally well not have any control module 30, or it could have only one or it could have more than two.

(21) The reactor R also has temperature-measuring means 50, possibly being thermocouples, arranged at the outlets from the first and second preheater modules 10a and 10b, from the mixer 20, and from each pipe module 30. These temperature-measuring means 50 serve to monitor the temperature of the fluid at various points. In particular, the temperature-measuring means 50 located downstream from the mixer 20 in the flow direction of the fluid serve to ensure that the temperature of the mixture is a temperature of 80 C., so that the platinum complex is properly formed. A thermostat may also be arranged at the outlet from the mixer, in order to regulate the temperature of the mixture.

(22) A tank 40 in which the mixture is stored temporarily is located downstream from the reactor R. Since the formation of the platinum complex has been completed, this tank serves, e.g. by means of a cooling thermostat, to readjust the temperature of the mixture to the temperature of the platinum bath B. Thus, the flow of regenerated bath 3 leaving the reactor R passing through the tank 40 and feeding the platinum bath B is at the optimum temperature for depositing a platinum underlayer on the metal parts. The temperature of the platinum bath B for forming the underlayers lies in the range 62 C. to 66 C., and preferably in the range 63 C. to 65 C., more preferably in the range 63.5 C. to 64.5 C. In this example, the temperature of the regenerated bath flow in the tank 40 is lowered from 80 C. to 64 C. The tank 40 may also include a mixer 42 for making the temperature of the mixture uniform. Temperature-measuring means 50 such as a thermocouple may also be arranged in the tank 40 in order to monitor the temperature of said tank.

(23) Furthermore, any evaporation from the platinum bath B is compensated by the fluid coming from the regeneration solution bath S or by adding water to the platinum bath B. The method of regenerating the platinum bath by flow reaction, using the device 100, is described below with reference to FIG. 3.

(24) The method comprises a step S1 of drawing off fluid from the platinum bath B, a complexing step S2, by mixing together the draw-off flow 1 and the regeneration solution flow 2 in the reactor R, and a step S3 of feeding the platinum bath B with the mixture coming from the complexing step S2.

(25) Furthermore, the complexing step S2 comprises various substeps performed in the reactor R. A preheating step S2-1 in which the draw-off flow 1 and the regeneration solution flow 2 are preheated to 80 C. independently of each other in the respective preheater modules 10a and 10b. A mixing step S2-2 in which the draw-off flow 1 and the regeneration solution flow 2 are mixed together in the mixer 20. A thermal monitoring step S2-3 in which the temperature of the mixture resulting from step S2-2 is controlled so as to ensure that it is equal to 80 C.

(26) In this example, in order to deposit underlayers of platinum on metal parts, the concentration of platinum in the platinum bath B is maintained overall in the range 7.5 g/L to 8.5 g/L, i.e. within an interval of 1 g/L, preferably in the range 7.7 g/L to 8.3 g/L, more preferably in the range 7.9 g/L to 8.1 g/L. The above-described method is performed so that the concentration of platinum remains within this range of values. Thus, the method can be performed simultaneously with depositing platinum underlayers, such that production is thus not interrupted while regeneration is taking place, or the method can be performed while no deposition of platinum underlayers is taking place. The method may equally well be interrupted depending on production requirements. Furthermore, since the concentration of platinum is generally constant within the platinum bath, the time and the rate of platinum underlayer deposition can also be constant.

(27) Although the present invention is described with reference to specific embodiments, it is clear that modifications and changes may be carried out on those examples without going beyond the general ambit to the invention as defined by the claims. In particular, individual characteristics of the various embodiments shown and/or mentioned may be combined in additional embodiments. Consequently, the description and the drawings should be considered in a sense that is illustrative rather than restrictive. For example, it is possible to omit the tank 40.

(28) It is also clear that all of the characteristics described with reference to a method are transposable, singly or in combination, to a device, and conversely that all of the characteristics described with reference to a device can be transposed, singly or in combination, to a method.