PROCESS FOR PRODUCING A HYDROGEN-RICH GAS STREAM FROM ALUMINIUM WASTE

Abstract

A process for the obtention of a hydrogen-rich gas stream from aluminium waste by obtaining a process water resulting from contacting aluminium salt slag with tap water, adding the process water of the previous step to an aluminium waste in a solution, and the hydrolysis of that solution to obtain the gas stream. The process is capable to obtain a yield of reaction close to 100% in higher reaction times.

Claims

1. A process for obtaining a hydrogen-rich gas stream from aluminium waste comprising: a) obtaining a process water resulting from contacting aluminium salt slag with tap water in a relation of 1:2 by weight during a time of reaction of 60-120 minutes, b) adding the process water from step a) to an aluminium waste consisting of particles of 1 mm size or less, in a solution, and c) conducting a hydrolysis of the solution obtained in step b) to obtain the hydrogen-rich gas stream.

2. The process according to claim 1, wherein said process comprises a further step c) of purifying the resulting gas stream.

3. The process according to claim 1, wherein said aluminium waste comprises salt slag.

4. The process according to claim 1, wherein said aluminium waste comprises aluminium dross.

5. The process according to claim 1, wherein step a) is performed at room temperature.

6. The process according to claim 1, wherein said hydrolysis of step c) is performed at room temperature.

7. The process according to claim 1, wherein a catalyst is incorporated in the hydrolysis of step c).

8. The process according to claim 7, wherein said catalyst is NaOH+KOH.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0046] .circle-solid. M1, M2, .box-tangle-solidup. M3, M4, applying to all figures.

[0047] FIG. 1. Shows the variation of the generated gas stream in time of the process water of the present invention with respect to distilled water (M2 vs. M1) in the hydrolysis of salt slag, and the same process with a mixture of NaOH and KOH as catalyst (M4 vs. M3).

[0048] FIG. 2. Shows the variation of the generated gas stream (expressed in conversion percentage) in time of the process water of the present invention with respect to catalyzed distilled tap water (M1 vs. M2) in the hydrolysis of salt slag of Example 1.

[0049] FIG. 3. Shows the variation of the generated gas stream (expressed in conversion percentage) in time of the process water of the present invention with respect to catalyzed distilled tap water (M1 vs. M2) in the hydrolysis of salt slag in Example 2.

[0050] FIG. 4. Shows the variation of the generated gas stream (expressed in conversion percentage) in time of the process water of the present invention with respect to catalyzed distilled tap water (M1 vs. M2) in the hydrolysis of white aluminium dross in Example 3.

[0051] FIG. 5. Shows the variation of the generated gas stream (expressed in conversion percentage) in time of the process water of the present invention with respect to catalyzed distilled tap water (M1 vs. M2) in the hydrolysis of black aluminium dross in Example 4.

EXAMPLES

Example 1. Grinding the Aluminium Waste

[0052] The wastes, salt slags or dross, were crushed in a laboratory rod mill filled with 12 rods, during 15 minutes, in order to activate the reaction surface of aluminium waste particles. The resulting particles were screened using vibrational sieving device submitting the sample to three dimensional movements. This mechanism causes the particles to be evenly distributed over the entire sieving surface. Different sieves with meshes less than or equal to 1 millimeter were used to determine their weighted particle size distributions. The number of sieves and the size depends on the sample quality and on the approximate particle size distribution.

[0053] The weighted particle size distributions of salt slags and dross used in the next examples are gathered in Table 5.

TABLE-US-00005 TABLE 5 Particle % weight % weight % weight % weight size Salt slag Salt slag White dross Black dross (microns) Example 3 Example 4 Example 5 Example 6 1000-710  9.99% 2.44% 7.81% 9.38% 710-500 11.78% 5.01% 11.03% 9.79% 500-300 16.39% 13.44% 15.54% 14.69% 300-200 9.91% 10.61% 9.64% 9.28% 200-100 16.73% 18.78% 18.09% 16.71% <100 35.19% 49.72% 37.88% 40.15%

Example 2. Performance of Process Water Versus Tap Water in the Hydrolysis Reaction

[0054] The starting material was salt slag comprising 3.5% metallic aluminium determined by alkaline gas test, 11.2% (w/w) elemental sodium and 5.5% (w/w) elemental potassium analyzed by X Ray fluorescence, grinded as explained in Example 1. 100 g of starting material were mixed with: [0055] Test M1: 200 ml distilled water. [0056] Test M2: 200 g process water (1,803 ppm of Al, 29,445 ppm of Na and 18,103 ppm of K determined by ICP-OES). [0057] Test M3: 200 ml of distilled water with added catalyst (a mixture of 3.7 g pure NaOH and 15.3 g of 85% purity KOH) [0058] Test M4: 200 g process water (1,789 ppm of Al, 47,228 ppm of Na and 16,768 ppm of K determined by ICP-OES with added catalyst (a mixture of 3.7 g pure NaOH and 15.3 g of 85% purity KOH).

[0059] FIG. 1 shows the improvement of the use of a process water according to the present invention (sample M2 or M4) vs. the processes of the prior art based on water with or without catalyst (sample M3 or M1), by showing the gas conversion versus time in a hydrolysis of the salt slag.

[0060] The reaction with process water without catalyst starts after a contact time of 42 minutes, whereas, with distilled water, the contact time is much higher, 75 minutes until it begins to produce gas. Once both reactions have started, the slope of the curve for process water is much higher than for water without a catalyst, which means that the gas production flow rate is higher in the procedure of the present invention. The procedure using process water achieves 97% of gas conversion along time, whereas the reaction with non-catalyzed distilled water reveals that the hydrogen production peak has been reached close to 50% of conversion.

[0061] In any case, although not essential, the use of an additional catalyst in the hydrolysis procedure (samples M3 and M4) is beneficial. Particularly, adding a mixture of NaOH and KOH in distilled water (Sample M3) can be compared to the incorporation of said additional catalysts with process water, described in sample M4. During the first moments of the reaction, the evolution of the conversion versus time for two tests are similar, but in the catalyzed water the gas production stops suddenly before the reaction finishes (conversion close to 80%), because the amount of sodium and potassium is limited conditioning the aluminate formation and hence the hydrogen generation. However, the gas production with process water continues gradually until achieves almost the total conversion.

Example 3. Hydrolysis of Salt Slags

[0062] The starting material was salt slag comprising 3.5% metallic aluminium determined by alkaline gas test, 11.2% (w/w) elemental sodium and 5.5% (w/w) elemental potassium analyzed by X Ray fluorescence, grinded as explained in Example 1. Tables 6 and 7 show the composition of the salt slag and the water process used in the present Example.

TABLE-US-00006 TABLE 6 Salt slag F Na2O MgO Al2O3 SiO2 P2O5 SO3 Cl K2O CaO TiO2 2.5 15.17 3.58 37.82 7.95 0.06 0.32 19.09 6.62 2.51 0.65 Cr2O3 MnO Fe2O3 NiO CuO ZnO SrO ZrO2 BaO P2O5 LOI 0.10 0.20 1.49 0.04 0.29 0.08 0.03 0.04 0.16 2.42

TABLE-US-00007 TABLE 7 Process water Na K Al S Si P Fe Ni Ca 29445 18103 1803 25 37 3 5 <0.5 1 As Ba Mn Co Cr Hg Mg <0.5 <0.5 <0.5 <0.5 <0.5 <0.002 <0.5

[0063] 100 g of starting material were mixed with 200 g process water (1,803 ppm of Al, 29,445 ppm of Na and 18,103 ppm of K determined by ICP-OES) in test M1; Independently, 100 g of starting material were mixed with 200 ml distilled water with added catalyst (a mixture of 2.91 g pure NaOH and 12.13 g of 85% purity KOH) in test M2. The ratio of Na+K/Al in both cases resulted identical and of value 6.8. The reaction takes place in continuous stirring at room temperature.

[0064] The pressure produced by the generated hydrogen-rich gas stream pushes a water volume that is determined using weight and density. The volume of displaced water is considered the generated hydrogen-rich gas stream (Nm.sup.3) and was expressed as conversion percentage. The conversion percentage is calculated as a proportion between generated hydrogen-rich gas stream (Nm.sup.3) and theorical gas volume using the stoichiometric ratio.

[0065] When the hydrolysis was carried out with catalyzed distilled water (sample M2) the hydrogen production was adjacent and increased quicker for a high gas production flow rate, reaching 80% of conversion in a few minutes. However, in the next minutes the climax of the reaction was achieved, and the hydrogen production stopped.

[0066] The hydrolysis process for the M1 sample with process water started after 42 minutes, and its slope reported a slow growth until reached 80% of conversion in 435 minutes. Contrary to sample M2, the hydrogen production continued, achieving more than 95% of conversion in 500 minutes (FIG. 2).

[0067] Both experiments start at the reaction of metallic aluminium with alkaline water, whereby sodium and potassium aluminates are formed together with the evolution of hydrogen. When the reaction takes place with catalyzed water (M2), the hydrogen evolution is roughly stopped due to the high sodium and potassium concentration where no further aluminate formation and hence hydrogen generation occurs. On the contrary, the aluminates formation and hydrogen production continue until maximal performance when process water (M1) is used, acting as a catalyst for the reaction.

[0068] The hydrolysis of this salt slag with process water without additional catalysts produces 4.5 l of hydrogen-rich gas stream. The analysis of the composition of the gas resulting from this process is shown in Table 8.

TABLE-US-00008 TABLE 8 Component Abundance range Hydrogen 78.8% v/v Methane 13.7% v/v Ammonia 5.5% v/v Phosphine 8 ppm H.sub.2S 1.3% v/v Total siloxanes 3.2 mg/Nm.sup.3 Total silicon 1.11 mg/Nm.sup.3 PCl 3,030.6 kCal/Nm.sup.3

Example 4. Hydrolysis of Salt Slags

[0069] The starting material was salt slag comprising 12.1% metallic aluminium determined by alkaline gas test, 12.0% elemental sodium and 3.6% elemental potassium analyzed by X Ray fluorescence, grinded as explained in Example 1. Tables 9 and 10 show the composition of the salt slag and the water process used in the present Example.

TABLE-US-00009 TABLE 9 Salt slag F Na2O MgO Al2O3 SiO2 P2O5 SO3 Cl K2O CaO TiO2 0.42 16.25 2.87 39.94 7.95 0.67 20.32 4.33 3.90 0.43 Cr2O3 MnO Fe2O3 NiO CuO ZnO SrO ZrO2 BaO P2O5 LOI 0.10 0.20 1.41 0.04 0.57 0.19 0.03 0.09 0.18 0.11

TABLE-US-00010 TABLE 10 Process water Na K Al S Si P Fe Ni Ca 47228 16768 1789 686 59 6 6 <0.5 1 As Ba Mn Co Cr Hg Mg <0.5 <0.5 <0.5 <0.5 <0.5 <0.002 <0.5

[0070] 100 g of starting material were mixed with 200 g process water (1,789 ppm of Al, 47,228 ppm of Na and 16,768 ppm of K determined by ICP-OES) in test M1; Independently, 20 g of starting material were mixed with 200 ml distilled water with added catalysts (a mixture of 1.06 g pure NaOH and 4.40 g of 85% purity KOH) in test M2. The ratio of Na+K/Al in both cases resulted identical and of value 2.4. The reaction takes place in continuous stirring at room temperature.

[0071] The hydrolysis with catalyzed distilled water (M2) started the hydrogen production in few seconds and the gas production flow rate is high, achieving quickly the culmination, but after 100 minutes the reaction finishes, and the hydrogen generation presents a plateau. On the contrary, the hydrolysis of sample M1 with process water requires more than 100 minutes to arise with slow gas production but always increasing, accomplishing higher conversion than catalyzed water after 1000 minutes (FIG. 3).

[0072] The hydrolysis of this salt slag with process water without catalyst produces 11.1 l of hydrogen-rich gas stream. The analysis of the composition of the gas resulting from this process is shown in Table 11.

TABLE-US-00011 TABLE 11 Component Abundance range Hydrogen 88.6% v/v Methane 10.3% v/v Ammonia 7.2% v/v Phosphine 10 ppm H.sub.2S 2.6% v/v Total siloxanes 11.8 mg/Nm.sup.3 Total silicon 4.09 mg/Nm.sup.3 PCl 2,954.1 kCal/Nm.sup.3

Example 5. Hydrolysis of White Aluminum Dross

[0073] The starting material was white aluminium dross comprising 25% metallic aluminium determined by alkaline gas test, 0.1% elemental sodium and 0.1% elemental potassium analyzed by X Ray fluorescence, grinded as explained in Example 1. Tables 12 and 13 show the composition of the salt slag and the water process used in the present Example.

TABLE-US-00012 TABLE 12 White aluminium dross BaO CaO Cl Cr2O3 CuO Fe2O3 K2O MgO — 1.38 0.85 <0.10 <0.10 0.21 <0.10 2.75 MnO Na2O SiO2 SO3 TiO2 ZnO Al <0.10 0.17 1.52 0.56 0.94 <0.10 87.76

TABLE-US-00013 TABLE 13 Process water Na K Al S Si P Fe Ni Ca 47228 16768 1789 686 59 6 6 <0.5 1 As Ba Mn Co Cr Hg Mg <0.5 <0.5 <0.5 <0.5 <0.5 <0.002 <0.5

[0074] 100 g of starting material were mixed with 200 g process water (1,789 ppm of Al, 47,228 ppm of Na and 16,768 ppm of K determined by ICP-OES) in test M1; Independently, 20 g of starting material were mixed with 200 ml distilled water with added catalysts (a mixture of 1.1 g pure NaOH and 4.6 g of 85% purity KOH) in test M2. The ratio of Na+K/Al in both cases resulted identical and of value 0.5. The reaction takes place in continuous stirring at room temperature.

[0075] The M2 hydrolysis show a very productive formation of the aluminate and hydrogen generation in a short period of time but in 80 minutes reached its maximal and remains stand since then. As for M1, the gas generation continues in the time until higher conversion values (FIG. 4). Thus, the production of a hydrogen-rich gas stream from an aluminium waste consisting of aluminium dross is achieved highly efficient.

[0076] The hydrolysis of this white dross with process water produces 27.4 l of hydrogen-rich gas stream. The analysis of the composition of the gas resulting from the process is shown in Table 14.

TABLE-US-00014 TABLE 14 Component Abundance range Hydrogen 91.3% v/v Methane 7.5% v/v Ammonia 2.1% v/v Phosphine 9 ppm H.sub.2S 3.5% v/v Total siloxanes 5.6 mg/Nm.sup.3 Total silicon 1.9 mg/Nm.sup.3 PCl 2,798.7 kCal/Nm.sup.3

Example 6. Hydrolysis of Black Aluminium Dross

[0077] The starting material was black aluminium dross comprising 26.1% metallic aluminium determined by alkaline gas test, 3.6% elemental sodium and 1.2% elemental potassium analyzed by X Ray fluorescence, grinded as explained in Example 1. Tables 15 and 16 show the composition of the salt slag and the water process used in the present Example.

TABLE-US-00015 TABLE 15 Black aluminium dross BaO CaO Cl Cr2O3 CuO Fe2O3 K2O MgO — 1.37 4.71 <0.10 0.85 1.09 1.49 4.33 MnO Na2O SiO2 SO3 TiO2 ZnO P2O5 Al 0.14 4.87 8.73 0.44 0.40 0.30 <0.10 65.00

TABLE-US-00016 TABLE 16 Process water Na K Al S Si P Fe Ni Ca 47228 16768 1789 686 59 6 6 <0.5 1 As Ba Mn Co Cr Hg Mg <0.5 <0.5 <0.5 <0.5 <0.5 <0.002 <0.5

[0078] 100 g of starting material were mixed with 200 g process water (1,789 ppm of Al, 47,228 ppm of Na and 16,768 ppm of K determined by ICP-OES) in test M1; Independently, 20 g of starting material were mixed with 200 ml distilled water with added catalysts (a mixture of 1.1 g pure NaOH and 4.6 g of 85% purity KOH) in test M2. The ratio of Na+K/Al in both cases resulted identical and of value 0.7. The reaction takes place in continuous stirring at room temperature.

[0079] The profile of hydrogen production followed a similar pattern as for the previous examples both for M1 and M2. Remarkable is that the M1 the hydrolysis took almost 200 minutes to start but then progressed with time (1200 minutes) to a final conversion close to 100% (FIG. 5).

[0080] The hydrolysis of this black dross with process water produced a 31.3 l of hydrogen-rich gas stream. The analysis of the composition of the gas resulting from this process is shown in Table 17.

TABLE-US-00017 TABLE 17 Component Abundance range Hydrogen 87.0% v/v Methane 8.7% v/v Ammonia 6.9% v/v Phosphine 9 ppm H.sub.2S 0.3% v/v Total siloxanes 3.8 mg/Nm.sup.3 Total silicon 1.0 mg/Nm.sup.3 PCl 3,035.4 kCal/Nm.sup.3