Thermal treatment method for industrial waste salt containing aluminum chloride

Abstract

The present invention belongs to the field of waste pyrolysis technology, and particularly relates to a method for thermally treating industrial waste salt. This method involves controlling the mass fraction of aluminum chloride in the industrial waste salt to less than 4%. This mass fraction is controlled by blending the aluminum chloride-containing industrial waste salt with other industrial waste salts, and then subjecting the aluminum chloride-containing industrial waste salt to two treatment steps: an anaerobic pyrolysis step and an aerobic oxidation step. This method can significantly alleviate coking within the pyrolysis furnace, ensuring safe and stable operation of the pyrolysis process. Furthermore, the method is low-cost and simple to implement.

Description

Technical Field

[0001] The invention belongs to the technical field of waste pyrolysis, and in particular relates to a heat treatment method for industrial waste salt. Background Art

[0002] Industrial waste salt, widely produced in the chemical and pharmaceutical industries, has a complex composition and is largely organic. Existing technologies primarily treat industrial waste salt using methods such as anaerobic pyrolysis, high-temperature melting, and deep oxidation after dissolving the waste salt in water. Among these, anaerobic pyrolysis is one of the most important technologies for treating industrial waste salt. Its principle is to exploit the thermal instability of organic matter and decompose it under high-temperature, anaerobic conditions.

[0003] Industrial waste salt is typically pyrolyzed in the absence of oxygen at 400-600°C. Chinese patent document CN 109882853 A points out that high-temperature carbonization or direct high-temperature treatment of industrial waste salt can lead to issues such as salt softening, equipment sticking, uneven carbonization, and incomplete impurity removal. The patent utilizes several stages of suspended incinerators, selecting different carbonization temperatures and methods based on the critical softening and carbonization points of different waste salt residues, to address these issues. Chinese patent document CN112919500 A offers another approach to solving the problems of material compaction, blockage, and coking that occur during the pyrolysis of industrial waste salt. This approach converts organic salts, which generally have a melting point of around 350°C, into organic acids, which generally have a boiling point of around 150°C. Together with other non-salt organic matter, these organics can be completely removed by pyrolysis at relatively low temperatures, thus avoiding the problems of material compaction, blockage, and coking that can occur due to high-temperature melting and decomposition of the waste salt. The aforementioned two solutions have relatively complex process flows and increase processing costs accordingly.

[0004] The applicant has found in engineering practice that the content of aluminum chloride in industrial waste salt containing aluminum chloride has a significant impact on the degree of coking of the material at high temperature. Summary of the Invention

[0005] The purpose of the present invention is to provide a heat treatment method for industrial waste salt containing aluminum chloride, which can reduce the degree of coking of industrial waste salt during the pyrolysis process by simply controlling the raw material ratio.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] The invention discloses a heat treatment method for industrial waste salt containing aluminum chloride, characterized in that the mass fraction of aluminum chloride in the industrial waste salt is controlled to be less than 4%.

[0008] Preferably, the mass fraction of the aluminum chloride in the industrial waste salt is 2.8%.

[0009] As an improvement, the mass fraction of the aluminum chloride in the industrial waste salt is controlled by mixing other industrial waste salts into the industrial waste salt containing aluminum chloride.

[0010] As an improvement, the aluminum chloride-containing industrial waste salt undergoes two treatment steps: an anaerobic pyrolysis step and an aerobic oxidation step.

[0011] As a further improvement, the temperature of the oxygen-free pyrolysis step is 400-600° C., and the residence time is 40-60 min.

[0012] As a further improvement, the temperature of the aerobic oxidation step is 500-700° C., and the residence time is 10-30 minutes.

[0013] In summary, the present invention can alleviate the coking phenomenon in the pyrolysis furnace to a large extent, ensuring the safe and stable operation of the pyrolysis process, and the method is low in cost and simple to implement. DETAILED DESCRIPTION

[0014] The present invention will be further described in detail below with reference to the embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0015] Example 1

[0016] Characteristics of blended industrial waste salt 1: 5.2% moisture content, 2.8% insoluble matter, 4.8% total organic carbon (TOC), 49.6% sodium sulfate (Na2SO4), and 30.1% sodium chloride (NaCl). Characteristics of blended industrial waste salt 2: 4.6% moisture content, 4.4% insoluble matter, 3.4% TOC, 68.5% NaCl, and 10.3% Na2SO4. Characteristics of untreated industrial waste salt 3: 11.7% moisture content, 3.7% insoluble matter, 10.1% TOC, 62.4% NaCl, and 7.8% aluminum chloride (AlCl3).

[0017] The industrial waste salt to be treated 3 and the blended industrial waste salt 2 were mixed uniformly in a mass ratio of 1:1. The mass fraction of AlCl3 in the obtained mixture was 3.9%. The obtained mixture was anaerobic pyrolyzed at 500°C for 40 minutes, and then high-temperature oxidized at 600°C with an air flow rate of 1-1.5 kg / h for 20 minutes. The TOC of the discharge was 0.018%, and slight coking was observed in the pyrolysis furnace.

[0018] Comparative Example 1

[0019] Keeping other conditions in Example 1 unchanged, the industrial waste salt 3 to be treated was not mixed with other industrial waste salts, the TOC of the discharge was 0.032%, and there was severe coking in the pyrolysis furnace.

[0020] Comparative Example 2

[0021] Keeping the other conditions in Example 1 unchanged, the industrial waste salt to be treated 3 and the blended industrial waste salt 2 were evenly mixed in a mass ratio of 1:2. The mass fraction of AlCl3 in the obtained mixture was 5.2%, the TOC of the discharge was 0.026%, and moderate coking was observed in the pyrolysis furnace.

[0022] Example 2

[0023] Keeping the other conditions in Example 1 unchanged, the industrial waste salt to be treated 3, the blended industrial waste salt 1, and the blended industrial waste salt 2 were evenly mixed in a mass ratio of 3:1:4. The mass fraction of AlCl3 in the obtained mixture was 2.8%, the TOC of the discharge was 0.012%, and there was slight coking in the pyrolysis furnace.

[0024] Comparative Example 3

[0025] Keeping the other conditions in Example 1 unchanged, the industrial waste salt to be treated 3, the blended industrial waste salt 1, and the blended industrial waste salt 2 were evenly mixed in a mass ratio of 7:1:2. The mass fraction of AlCl3 in the obtained mixture was 5.5%, the TOC of the discharge was 0.023%, and moderate coking was observed in the pyrolysis furnace.

Claims

1. A method for thermal treatment of industrial waste salt containing aluminum chloride, characterized by: The mass fraction of aluminum chloride in industrial waste salt is controlled at less than 4%, and the industrial waste salt is sequentially subjected to an anaerobic pyrolysis step and an aerobic oxidation step; the anaerobic pyrolysis temperature is 400-600°C, and the constant temperature time is 40-60 minutes; the aerobic oxidation temperature is 500-700°C, and the constant temperature time is 10-30 minutes.

2. The heat treatment method for aluminum chloride-containing industrial waste salt according to claim 1, wherein: The mass fraction of the aluminum chloride in the industrial waste salt is 2.8%.

3. The heat treatment method for aluminum chloride-containing industrial waste salt according to claim 1, wherein: The mass fraction of aluminum chloride in industrial waste salt is controlled by mixing other industrial waste salts into the industrial waste salt containing aluminum chloride.