Co-processing method and system for carbon alkali waste residues and aluminum ash hazardous waste

Abstract

The invention provides a carbon alkali waste residue and aluminum ash hazardous waste cooperative treatment method and system. Sodium aluminate is obtained from waste residues and aluminum ash generated in the salt discharging process of an aluminum oxide factory through the processes of raw material compatibility, high-temperature sintering, detoxification treatment and the like, and then the sodium aluminate is returned to the aluminum oxide process, so that a full-process scheme of resource circulation is formed. According to the method, the production cost can be reduced by more than 20%, the sodium recovery rate is more than or equal to 95%, the aluminum recovery rate is more than or equal to 90%, the yield in the rotary kiln is 70-80%, the aluminum oxide dissolution rate is more than 80%, the energy consumption is reduced by 30-40% compared with that of a traditional sintering method, and ammonia gas pollution is eliminated.

Description

TECHNICAL FIELD

[0001] The application relates to a recycling method of industrial waste, in particular to a synergic treatment method and system of carbon-alkali waste residue and aluminum ash hazardous waste. BACKGROUND

[0002] The carbon-alkali waste residue (containing Na2CO3 30-50%) generated in the salt discharge process of an alumina plant and the aluminum ash (containing Al 15-40%) generated in the electrolytic aluminum industry are both difficult-to-treat hazardous waste.

[0003] In addition, the existing sintering method for producing sodium aluminate needs to purchase pure alkali raw materials, and has high energy consumption and is only suitable for treating difficult-to-dissolve ores, and the byproduct red mud is mainly calcium-silicon slag. SUMMARY

[0004] The application aims at the deficiencies in the prior art, and provides a synergic treatment method and system of carbon-alkali waste residue and aluminum ash hazardous waste.

[0005] The application is implemented by the following technical scheme: a synergic treatment method of carbon-alkali waste residue and aluminum ash hazardous waste, comprising the following steps:

[0006] (1) the carbon-alkali waste residue of the salt discharge process of an alumina plant, the hazardous aluminum ash of the electrolytic aluminum or casting process and limestone are mixed in a mass ratio of (30-50):(20-40):(20-30) and then are uniformly mixed in a ball mill;

[0007] (2) the mixed material is put into a rotary kiln, the temperature is controlled to be 1180 DEG C + / - 30 DEG C, and high-temperature sintering is performed for 30 min-1 h;

[0008] (3) the sintered clinker is crushed, and then is dissolved by using dilute alkali solution, and sodium aluminate is put into the solution;

[0009] (4) the dissolved solution is treated by adding lime milk to remove silicon, soluble silicon is removed by precipitation, and refined sodium aluminate solution is obtained, which is returned to the alumina process in step (1) as an intermediate product for producing alumina.

[0010] Further, in step (1), the mass ratio of the carbon-alkali waste residue to the aluminum ash is (38-42):(28-32).

[0011] Further, in step (2), the temperature is controlled to be 1180 DEG C, and high-temperature sintering is performed for 45 min.

[0012] Further, in step (1), the mixture is pressed into a block and then sintered.

[0013] Further, it comprises a ball mill, a bin pump, a mixing bin, a spiral scale, a bucket elevator, a semi-finished product bin, a spiral scale, a rotary kiln, a cooler, a vibrating screen, a bucket elevator and a finished product bin connected in sequence.

[0014] The core innovation of the present application is:

[0015] (1) synergistic utilization of waste residues: carbon-alkali waste residues replace purchased pure alkali, and aluminum ash provides active aluminum source, reducing production cost by more than 20%.

[0016] (2) synergistic effect of raw materials: NaCl in carbon-alkali waste residues promotes the oxidation of metallic aluminum in aluminum ash, the sodium recovery rate is ≥95%, and the aluminum recovery rate is ≥90%.

[0017] (3) high-temperature sintering: high-temperature reaction window 1180℃±30℃ interval realizes efficient synthesis of sodium aluminate, relies on aluminum ash fluxing, and fluorinated salt (such as Na3AlF6) in aluminum ash reduces the reaction activation energy. The fluxing effect of fluorinated salt (Na3AlF6) in aluminum ash is fully manifested in the interval of 1180℃±30℃, and the decomposition rate of Na2CO3 and the reaction rate of Al2O3 reach a dynamic balance. When the temperature is lower than 1150℃, the conversion rate of sodium aluminate decreases to below 70%. When the temperature exceeds 1210℃, sodium volatilization loss will also cause the conversion rate to decrease. The energy consumption is reduced by 30-40% compared with the traditional sintering method, and the yield in the rotary kiln is between 70-80%.

[0018] (4) integration of detoxification treatment: high-temperature decomposition of aluminum nitride (AlN+H2O→Al(OH)3+NH3↑) in aluminum ash, ammonia gas concentration less than 5ppm, compared with the ammonia gas concentration (600-1000ppm) generated by wet treatment of aluminum ash, the ammonia gas concentration is reduced by 20 times, and the ammonia gas pollution is eliminated.

[0019] (5) salt removal and carbon-alkali recycling: high-temperature removal of organic matter in salt removal carbon-alkali, and the carbon-alkali components return to the alumina process, and the alumina leaching rate is more than 80%. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The figure is a process flow diagram of the present application. DETAILED DESCRIPTION

[0021] The present application will be further described in detail below in conjunction with examples.

[0022] Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in the field or according to the product instructions. Materials or equipment whose manufacturers are not specified are all conventional products that can be obtained by purchase.

[0023] Example 1

[0024] This embodiment provides a method for the co-treatment of carbon-alkali waste residue and aluminum ash hazardous waste, including the following steps:

[0025] (1) Carbon-alkali waste residue (byproduct of the salt discharge process of alumina plant, including Na2CO3 30-50%, NaCl 5-10%, red mud and ash residue), aluminum ash (hazardous waste from electrolytic aluminum or casting process, containing Al 15-80%, Al2O3 40-70%, aluminum nitride and salt residue), and limestone (CaCO3 ≥ 95%, particle size ≤ 100 μm) are mixed in a mass ratio of (30-50): (20-40): (20-30) and fed into a ball mill for uniform mixing (particle size ≤ 20 μm).

[0026] (2) The mixture enters the rotary kiln, and the temperature is controlled at 1180℃±30℃. High-temperature sintering is carried out for 30min-1h.

[0027] (3) The carbon-alkali components are returned to the alumina process. XRD analysis shows that the sodium aluminate crystal phase content in the carbon-alkali components is ≥85%, and the alumina dissolution rate is ≥80%.

[0028] Example 2

[0029] Based on Example 1, the sintered clinker is crushed and then dissolved in a dilute alkaline solution (NaOH alkaline solution with a molar concentration of less than 0.1 mol / L), and sodium aluminate enters the solution; the dissolved solution is subjected to desilication treatment with lime milk under pressure, and soluble silicon is removed by precipitation to obtain a refined sodium aluminate solution, which is returned to the alumina process in step (1) as an intermediate product for the production of alumina.

[0030] Example 3

[0031] Based on Example 1 or 2, as the optimal example, the mass ratio of carbon-alkali waste residue to aluminum ash is selected as (38-42):(28-32). Sintering process: The temperature-time parameter combination is selected as 1180℃ / 45min. Under these conditions, Na2CO3 will not encapsulate the particles, and the aluminum ash is at a relatively low melting point, simultaneously achieving a high conversion rate of 95% sodium aluminate crystalline phase content and 89% alumina dissolution rate, along with low energy consumption.

[0032] Example 4

[0033] Based on Example 1, 2 or 3:

[0034] (1) When carbon-alkali waste residue is insufficient: supplement with some soda ash residue (byproduct of chlor-alkali industry, containing 40-60% Na2CO3);

[0035] (2) When aluminum ash is in short supply: use secondary aluminum ash (after ammonia removal treatment) as a substitute, and adjust the ratio to carbon-alkali waste residue, hazardous waste aluminum ash, limestone (50-70): (10-20): (20-30).

[0036] Example 5

[0037] Non-sintering method: In step (2), the mixture is directly reacted with concentrated alkaline solution (NaOH 30%) in a high-pressure reactor at 200℃, but the purity of the product is low (requiring subsequent purification);

[0038] Example 6

[0039] Dry briquetting: The mixed raw materials in step (1) are pressed into briquettes and then sintered to reduce dust (suitable for small equipment).

[0040] Example 7

[0041] This invention also provides a co-treatment system for carbon-alkali waste residue and aluminum ash hazardous waste, such as... Figure 1 As shown, the system includes a ball mill, a silo pump, a mixing silo, a screw conveyor, a bucket elevator, a semi-finished product silo, a screw conveyor, a rotary kiln, a cooler, a vibrating screen, a bucket elevator, and a finished product silo, connected in sequence. The ball mill is connected to an aluminum ash silo, an alkali silo, and a limestone silo.

[0042] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for the co-treatment of carbon-alkali waste residue and aluminum ash hazardous waste, characterized in that, Includes the following steps: (1) The carbon-alkali waste residue from the salt discharge process of the alumina plant, the hazardous aluminum ash from the electrolytic aluminum or casting process, and limestone are mixed in a mass ratio of (30-50):(20-40):(20-30) and fed into the ball mill for uniform mixing. (2) The mixture enters the rotary kiln, and the temperature is controlled at 1180℃±30℃. High-temperature sintering is carried out for 30min-1h. (3) After the sintered clinker is crushed, it is dissolved in dilute alkali solution, and sodium aluminate enters the solution; (4) The leachate is subjected to desilication treatment with lime milk under pressure, and soluble silicon is removed by precipitation to obtain a refined sodium aluminate solution, which is returned to the alumina process in step (1) as an intermediate product for the production of alumina.

2. The method for co-treating carbon-alkali waste residue and aluminum ash hazardous waste according to claim 1, characterized in that, In step (1), the mass ratio of carbon-alkali waste residue to aluminum ash is (38-42):(28-32).

3. The method for co-treating carbon-alkali waste residue and aluminum ash hazardous waste according to claim 1, characterized in that, In step (2), the temperature is controlled at 1180℃ and sintered at high temperature for 45 minutes.

4. The method for co-treating carbon-alkali waste residue and aluminum ash hazardous waste according to claim 1, characterized in that, In step (1), the mixture is pressed into blocks and then sintered.

5. A co-treatment system for carbon-alkali waste residue and aluminum ash hazardous waste, characterized in that, It includes a ball mill, a silo pump, a mixing silo, a screw conveyor, a bucket elevator, a semi-finished product silo, a screw conveyor, a rotary kiln, a cooler, a vibrating screen, a bucket elevator, and a finished product silo, connected in sequence.

Images