PROCESS FOR THE DESULPHURIZATION OF MATERIALS AND/OR RESIDUES CONTAINING LEAD SULPHATE EMPLOYING AN AMINO COMPOUND

Abstract

The present invention claims a process for the desulphurization of materials and/or residues containing lead sulphate, carried out in one or more stages. The main characteristic of this process is that the only desulphurising agent is an amino compound selected among urea, guanidine, guanine, arginine or another similar amino compound.

Claims

1. A process for the desulphurization of materials and/or residues containing lead sulphate, carried out in one or more stages, wherein the only desulphurising agent is an amino compound selected among urea, guanidine, guanine or arginine.

2. The process according to claim 1, where the amino compound is urea.

3. The process according to claim 1, where the process occurs in a single stage in a closed reactor where the amino compound in an aqueous solution between 20% and 50% m/v, reacts directly with the material that has to be desulphurised with the following operational conditions: temperature between 50 and 190° C.; pressure between 1 and 12 atmospheres (atm); reaction time between 5 and 120 minutes (min); and liquid/solid ratio m/m between 0.5 and 4.

4. The process according to claim 3, where operational conditions are: temperature between 90 and 190° C., pressure between 2 and 12 atm; reaction time between 10 and 100 min; and liquid/solid ratio between 1 and 4.

5. The process according to claim 1, where the process is carried out in more stages where the amino compound, before reacting with the material that has to be desulphurised, is activated through a distillation or a flash.

6. The process according to claim 5, where the activated amino compound is mixed with one or more other amino compounds, the resulting mixture of the above mentioned amino compounds being activated through a distillation or a flash before its reaction with the material to be desulphurised.

7. The process according to claim 5, where the amino compound, or the mixture of the amino compounds, is activated through a distillation or a flash in presence of an adjuvant substance, in quantities below 20% of the weight mass of the amino compound itself.

8. The process according to claim 5, where the amino compound, or the mixture of the amino compounds, is activated through distillation, comprising: preparing a solution with variable concentration between 40 and 60% m/v of amino compound, or of the mixture of the amino compounds, and feeding it into a distiller; separately preparing a lead paste suspension with water, with a liquid/solid ratio m/m between 0.5 and 2 and feeding it to a reactor; starting a distillation of the amino compound solution or of the mixture of the amino compounds, at a temperature between 140° C. and 190° C. and pressure between 4 and 10 atm; and conveying the obtained distillate, optionally condensed, into the reactor containing the lead paste suspension to finalize the desulphurization reaction initially at ambient temperature and atmospheric pressure.

9. The process according to claim 8, where the desulphurization reaction is carried out up to half an hour after the end of the distillation of the amino compound or of the mixture of the amino compounds in stoichiometric quantity compared to lead sulphate.

10. The process according to claim 6, where the amino compound or the mixture of the amino compounds is activated through flash, comprising: preparing a solution with concentration between 40 and 60% m/v of the amino compound, or of the mixture of the amino compounds, and feeding it into a closed reactor without headspace heated to a temperature between 170 and 190° C. and pressure between 8 and 12 atm. separately preparing a lead paste suspension with water with a liquid/solid ratio m/m between 0.5 and 2 and feeding it to a reactor; feeding further fresh amino compound solution, optionally pre-heated, at the same concentration, into the closed reactor, forcing part of the solution already heated to come out of the reactor itself; and conveying the solution coming out of the closed reactor into the reactor where the lead paste suspension is contained, at a non-controlled temperature and under pressure, causing these conditions the flash of the heated solution of the amino compound or of the mixture of the amino compounds and the desulphurization reaction.

11. The process according to claim 1, where lead sulphate residue is made of a lead paste fraction separated from exhausted lead acid batteries, or at least scrapped, having a paste with a lead sulphate content between 10 and 80% in weight.

12. The process according to claim 1, where the suspension obtained at the end of the desulphurization reaction is filtered to separate the solid phase from the liquid one; the liquid phase, once filtered and deprived of any suspension, is sent to a concentration and crystallization system of salts, mainly represented by ammonium sulphate, or it is used as such, after pH correction, in fertirrigation plants.

Description

[0051] In relation to the present invention, the two diagrams represented in FIGS. 1 and 2, which cannot be considered a limitation of the invention itself, are described as follows.

[0052] In FIG. 1, the desulphurization process is illustrated in one single stage.

[0053] The desulphurization stage is carried out by charging both the paste containing lead sulphate (1) and the amino compound (2) in aqueous solution inside a reactor (R). The suspension obtained after the desulphurization process (3) is composed of a solution containing ammonium sulphate and ammonium carbonate traces, and carbonated paste mainly composed of lead carbonate and lead oxides, which do not react with urea.

[0054] Via a solid/liquid (S/L) filtration, the two main resulting products are separated: lead carbonate (insoluble) (4) and ammonium sulphate (soluble) in a solution (5).

[0055] The ammonium sulphate solution, once filtered and deprived of any suspension, can be sent to a concentration and salts crystallization system, mainly ammonium sulphate. As an alternative, after pH correction, the solution can be used as such in agriculture for fertirrigation techniques.

[0056] In FIG. 2, the desulphurization process is represented in multi-stage with pre-activation of the amino compound.

[0057] The amino compound (2) in an aqueous solution, before being sent to the desulphurization reactor (R), is “activated” through distillation or flash in a previous stage (M).

[0058] The activated amino compound (6) is fed to a desulphurising reactor (R), in which also a water suspension of lead paste (containing lead sulphate) (1) is charged.

[0059] The resulting suspension (3), composed of a solution containing ammonium sulphate and ammonium carbonate traces and carbonated paste, will be processed as in FIG. 1.

[0060] Hereinafter, some examples are provided in order to better understand the surprising simplicity and effectiveness of the present invention, and they cannot be considered a limitation of the invention itself.

EXAMPLE 1

[0061] The desulphurization operation is carried out, according to the diagram in FIG. 1, on lead paste extracted from exhausted lead acid batteries, with a 58% amount of lead sulphate.

[0062] 1000 grams of lead paste, 130 grams of urea and 1.5 liters of water are charged into the reactor. The reactor is sealed and heated to a temperature of 150° C. ca.

[0063] At this temperature, pressure is 4.7 absolute atmospheres ca. The liquid/solid ratio m/m is 1.6 ca. When these conditions are fulfilled, the reaction is protracted for about one hour under the same conditions and, at the end of it, the reactor heating is turned off.

[0064] The resulting suspension is composed of a solution containing ammonium sulphate and ammonium carbonate traces, and carbonated paste mainly composed of lead carbonate and lead oxides which do not react with urea.

[0065] Only little traces of the initial lead sulphate will still result among the products. The conversion, and consequently the reaction yield, is higher than 95%, giving a greater added value to the lead paste compared to the original composition.

[0066] The solution, once filtered and deprived of any suspension, is sent to a concentration and crystallization system of salts, mainly represented by ammonium sulphate, or it is used as such, after PH correction, in fertirrigation plants.

EXAMPLE 2

[0067] The desulphurization operation is carried out, according to the diagram in FIG. 1, on lead paste extracted from exhausted lead acid batteries containing 65% amount of lead sulphate.

[0068] 1000 grams of lead paste, 140 grams of urea and 1.5 liters of water are charged into a reactor. The reactor is closed and set up as described in example 1. Reaction conditions are maintained for 4 hours and, at the end, the suspension is extracted and filtered in order to separate the solid phase from the liquid one.

[0069] The resulting desulphurised lead paste has a level of sulphates below 1%; as a consequence, the desulphurization yield is above 99%.

[0070] The liquid phase, once filtered and deprived of any suspension, is sent to a concentration and crystallization system of salts, mainly represented by ammonium sulphate, or it is used as such, after PH correction, in fertirrigation plants.

EXAMPLE 3

[0071] The desulphurization operation is carried out, according to the diagram in FIG. 2, on lead paste extracted from exhausted lead acid batteries with 58% amount of lead sulphate.

[0072] Differently from previous examples, the distillation of urea solution at 50% m/v occurs at a temperature of 150° C. and a pressure of 4.7 absolute atmospheres.

[0073] The condensed distillate is conveyed into a second reactor containing a water suspension of lead paste.

[0074] 130 grams of urea are dissolved in 130 milliliters of water and poured into a distiller. 1000 grams of lead paste with 58% amount of lead sulphate are instead suspended in 850 milliliters ca. of water.

[0075] The distillate of urea solution is conveyed towards the lead paste suspension. Operative conditions of this reactor are free, meaning ambient temperature and atmospheric pressure. Liquid/solid ration m/m is 1 ca.

[0076] The reaction continues until the whole urea solution is distilled.

[0077] At the end of the distillation, the suspension agitation persists for about half an hour and it is eventually filtered.

[0078] The solid phase consists of desulphurised paste. Desulphurization yield is above 99%.

[0079] The solution, once filtered and deprived of any suspension, is sent to a concentration and crystallization system of salts, mainly represented by ammonium sulphate, or it is used as such, after PH correction, in fertirrigation plants. Thanks to this setup, it is possible to have a continuous-operating system configuration.

EXAMPLE 4

[0080] As in example 1 above, 1000 grams of lead paste with 58% amount of lead sulphate, 130 grams of urea and 1.5 liters of water are charged into the reactor.

[0081] The reactor is sealed and heated to a temperature of 180° C. ca. At this temperature, pressure is 10 absolute atmospheres ca. Liquid/solid ratio m/m is 1.6 ca. Once these conditions are fulfilled, the reaction is protracted for about 1 hour under the same conditions and, at the end, the reactor heating is turned off. After filtering the suspension and measuring the amount of sulphate residues in the lead paste, the desulphurization yield is above 99%.

[0082] The liquid phase, once filtered and deprived of any suspension, is sent to a concentration and crystallization system of salts, mainly represented by ammonium sulphate, or it is used as such, after PH correction, in fertirrigation plants.

EXAMPLE 5

[0083] As in Example 2 above, 1000 grams of lead paste with 65% level of lead sulphate, 140 grams of Urea and 1.5 liters of water are charged into the reactor. The reactor is sealed and heated to a temperature of 180° C. ca. At this temperature, the pressure is 10 absolute atmospheres ca. Liquid/solid ratio m/m is 1.6 ca. Once these conditions are fulfilled, the reaction is protracted for about one hour under the same conditions and, at the end, the reactor heating is turned off.

[0084] After filtering the suspension and measuring the amount of sulphate residues in the paste, the desulphurization yield is above 99%.

[0085] The liquid phase, once filtered and deprived of any suspension, is sent to a concentration and crystallization system of salts, mainly represented by ammonium sulphate, or it is used as such, after PH correction, in fertirrigation plants.

EXAMPLE 6

[0086] As in example 3 above, the lead paste suspension is not directly in contact with the solution containing dissolved urea, but it is placed into a different reactor.

[0087] A 50% urea solution is contained in a closed reactor without headspace, heated to a temperature of 180° C. ca and pressures of 10 atm ca. By feeding the “fresh” solution, part of the heated solution is forced to come out of the reactor.

[0088] This solution is conveyed into a reactor where the lead paste suspension is contained, at non-controlled temperature and under pressure.

[0089] Under these conditions, the flash of the heated urea solution occurs and the desulphurization reaction takes place. Once 130 grams of urea in solution are spilled, the reaction can be considered completed. After filtering the suspension and measuring the amount of sulphate residues in the lead paste, the calculated desulphurization yield is above 99%.

[0090] The liquid phase, once filtered and deprived of any suspension, is sent to a concentration and crystallization system of salts, mainly represented by ammonium sulphate, or it is used as such, after PH correction, in fertirrigation plants.

EXAMPLE 7

[0091] The desulphurization operation is carried out, according to the diagram in FIG. 2, on lead paste extracted from exhausted lead acid batteries with 58% amount of lead sulphate.

[0092] Differently from previous examples, the distillation of urea solution at 50% m/v occurs at a temperature of 150° C. and a pressure of 4.7 absolute atmospheres, in presence of an adjuvant substance, ammonium bicarbonate, in a quantity equal to 5% of the mass of urea.

[0093] The condensed distillate is conveyed into a second reactor containing a water suspension of lead paste.

[0094] 130 grams of urea are dissolved in 130 milliliters of water and poured into a distiller. 1000 grams of lead paste with 58% amount of lead sulphate are instead suspended in 850 milliliters ca. of water.

[0095] The distillate of urea solution is conveyed towards the lead paste suspension. Operative conditions of this reactor are free, meaning ambient temperature and atmospheric pressure. Liquid/solid ration m/m is 1 ca.

[0096] The reaction continues until the whole urea solution is distilled.

[0097] At the end of the distillation, the suspension agitation persists for about half an hour and it is eventually filtered.

[0098] The solid phase consists of desulphurised paste. Desulphurization yield is above 99%.

[0099] The solution, once filtered and deprived of any suspension, is sent to a concentration and crystallization system of salts, mainly represented by ammonium sulphate, or it is used as such, after PH correction, in fertirrigation plants. Thanks to this setup, it is possible to have a continuous-operating system configuration.

EXAMPLE 8

[0100] As in example 3 above, the lead paste suspension is not directly in contact with the solution containing dissolved urea, but it is placed into a different reactor.

[0101] The urea solution at 50% m/v, in presence of an adjuvant substance, ammonium carbonate, in a quantity equal to 5% of the mass of urea, is contained in a closed reactor without headspace, heated to a temperature of 180° C. ca and pressures of 10 atm ca. By feeding the “fresh” solution, the heated part of the solution is forced to come out of the reactor.

[0102] This solution is conveyed into a reactor where the lead paste suspension is contained, at non-controlled temperature and under pressure.

[0103] Under these conditions, the flash of the heated urea solution occurs and the desulphurization reaction takes place. Once 130 grams ca. of urea in solution are spilled, the reaction can be considered completed. After filtering the suspension and measuring the amount of sulphate residues in the lead paste, the calculated desulphurization yield is above 99%.

[0104] The liquid phase, once filtered and deprived of any suspension, is sent to a concentration and crystallization system of salts, mainly represented by ammonium sulphate, or it is used as such, after PH correction, in fertirrigation plants.