A kind of ladder drying process and protective drying tray for the corrosion prevention of cobalt nickel salt dehydration

Abstract

This invention discloses a stepped drying process and a protective drying tray for dehydration and corrosion prevention of cobalt-nickel salts, belonging to the field of cobalt-nickel salt deep processing technology. The process uses a specially designed protective drying tray with a PTFE protective pad laid on the bottom surface of a stainless steel tray. The process includes: spreading the cobalt-nickel salt material containing crystal water flat in the drying tray and performing two-stage drying: first drying at 120-140℃ for 1-3 hours, then raising the temperature to 200-280℃ for 1-4 hours until complete dehydration. The core of this invention lies in the combination of a "protective drying tray" and a "stepped drying process," utilizing the chemical inertness and high-temperature resistance of the PTFE protective pad to effectively isolate the stainless steel tray from corrosion during high-temperature dehydration. This significantly extends the service life of the equipment and prevents metal impurities from contaminating the product due to tray corrosion. Ultimately, it improves the purity and yield of anhydrous cobalt-nickel salt products while reducing production costs. The equipment is simple, easy to operate, and suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of cobalt-nickel salt deep processing technology, specifically to a dehydration and drying process for producing anhydrous cobalt salts and anhydrous nickel salts, and the special equipment used in this process. Background Technology

[0002] Cobalt and nickel salts (such as cobalt chloride and nickel sulfate) are important chemical raw materials and battery material precursors. In their numerous applications, particularly in high-end catalysis, electronics, and new energy fields, anhydrous compounds are frequently required. Therefore, converting water-containing cobalt and nickel salts (hereinafter collectively referred to as cobalt-nickel salts) into anhydrous forms is a crucial production step.

[0003] Currently, the most commonly used dehydration methods in industry are spray drying and oven drying. While spray drying produces products with uniform particle size, it suffers from drawbacks such as high equipment investment, high energy consumption, and poor adaptability to heat-sensitive materials. Furthermore, controlling the purity of certain hygroscopic or sticky cobalt-nickel salts is challenging. In contrast, oven drying offers simpler equipment, easier operation, and greater adaptability, making it a popular choice for small- to medium-scale and multi-variety production.

[0004] However, oven drying methods face a significant technical bottleneck in practical applications: corrosion. Cobalt-nickel salts, especially their halides (such as cobalt chloride), readily release corrosive gases (such as hydrogen chloride) during high-temperature dehydration, or the materials themselves exhibit strong corrosiveness to metals in their molten state. Currently, the support trays used in ovens are mostly made of stainless steel. Under long-term, high-temperature, and corrosive environments, stainless steel trays suffer severe pitting and rusting, significantly shortening equipment lifespan and increasing production costs. More seriously, the iron, chromium, and nickel ions produced by corrosion directly contaminate the product, leading to a decrease in the purity of the final anhydrous cobalt-nickel salt, making it difficult to meet the quality requirements of high-end applications.

[0005] Chinese patent CN102357308B discloses a spray drying method for directly preparing anhydrous cobalt chloride powder from a cobalt chloride solution. While this method avoids the problem of tray corrosion, it introduces new problems such as complex equipment, high energy consumption, and difficulty in controlling product batch stability. Furthermore, it is not suitable for technical modifications to existing drying oven equipment.

[0006] Therefore, how to fundamentally solve the core defects of oven drying, such as easy equipment corrosion and easy product contamination, while retaining the advantages of oven drying method such as "simple equipment, convenient operation and strong adaptability", has become an urgent technical problem to be solved in this field. Summary of the Invention

[0007] (I) Purpose of the Invention

[0008] This invention aims to overcome the technical shortcomings of existing oven drying methods in the production of anhydrous cobalt-nickel salts, such as easy equipment corrosion and low product purity, and provides an innovative solution. Specifically, the objectives of this invention include:

[0009] 1. A special device that can effectively prevent the drying tray from being corroded is provided – a protective drying tray.

[0010] 2. A stepped drying process that is compatible with the protective drying tray and can efficiently and stably remove the crystal water of cobalt nickel salts is provided.

[0011] 3. By combining the above processes and equipment, we can achieve the comprehensive effects of extending equipment life, improving product purity and yield, and reducing production costs.

[0012] (II) Technical Solution

[0013] To achieve the above objectives, the present invention adopts the following technical solution:

[0014] On the one hand, the present invention provides a stepped drying process for dehydration and corrosion prevention of cobalt-nickel salts, which includes the following steps:

[0015] Material loading: Cobalt salt and / or nickel salt containing water of crystallization are spread evenly in a protective drying tray, which includes a stainless steel tray body and a PTFE protective pad laid on the bottom surface of the tray body.

[0016] Step drying: Place the drying trays containing the material in the drying equipment, first dry at a first temperature of 120-140℃ for 1-3 hours, then raise the temperature to a second temperature of 200-280℃ and continue drying for 1-4 hours until the crystal water of the material is removed.

[0017] On the other hand, the present invention provides a protective drying tray for the above-mentioned stepped drying process, comprising:

[0018] Stainless steel disc for holding materials;

[0019] A PTFE protective pad is laid on the bottom surface of the stainless steel pan to form an isolation and protective layer between the material and the pan.

[0020] As a further improvement of the present invention, before the material is loaded onto the tray, a pretreatment step of screening and removing impurities from the material may be included to improve the uniformity of the raw materials.

[0021] As a further improvement of the present invention, after the step drying process, the method may further include: cooling and pulverizing the dehydrated material until it passes through a 150-mesh sieve to meet the particle size requirements of downstream applications.

[0022] As a further improvement of the present invention, after the pulverization, it may further include a step of magnetic separation of the obtained powder to further remove trace magnetic metal impurities that may be introduced and improve the product purity.

[0023] As a further improvement of the present invention, the tetrafluoro protection pad is preferably a polytetrafluoroethylene (PTFE) gasket. Polytetrafluoroethylene has excellent chemical inertness, a wide temperature resistance range (-180°C to 250°C), and excellent non-stick properties, making it an ideal isolation and protection material.

[0024] As a further improvement of the present invention, the stainless steel disc body is preferably made of 316 stainless steel. 316 stainless steel has better pitting corrosion resistance than ordinary 304 stainless steel in a chloride environment. Combined with the tetrafluoro protection pad, it can provide double protection.

[0025] (III) Beneficial effects

[0026] Compared with the prior art, the stepped drying process and the protective drying disc provided by the present invention have the following remarkable advantages:

[0027] 1. Excellent anti-corrosion effect and significantly extended equipment life: The core innovation of the present invention is to add a tetrafluoro protection pad inside the drying disc. This gasket forms a permanent physical and chemical isolation barrier between the corrosive cobalt-nickel salt material and the stainless steel disc body, fundamentally preventing the direct contact and corrosion of the material and its decomposition products to the metal disc body. Experiments show that after using the protective drying disc of the present invention, the service life of the disc body can be extended by more than 5 times, greatly reducing the equipment depreciation and maintenance costs.

[0028] 2. Simultaneous improvement of product purity and yield: Since the corrosion of the disc body is effectively prevented, the content of metal impurities such as iron, chromium, and nickel introduced due to corrosion in the product is greatly reduced, ensuring the high purity of anhydrous cobalt-nickel salt. At the same time, the non-stick property of the polytetrafluoroethylene gasket enables the dried material to be easily and completely taken out of the disc, with very little material residue, thereby improving the actual yield of the product.

[0029] 3. Process optimization and better dehydration effect: The "stepped drying process" supporting the present invention is not simply a temperature segmentation. First, dehydration is carried out at a relatively low temperature (120 - 140°C), which can gently and stably remove most of the free water and part of the crystal water, avoiding premature hardening of the material surface; then it is raised to a high temperature (200 - 280°C) to completely remove the remaining crystal water. This stepped heating strategy helps the material to dehydrate evenly inside and outside, preventing agglomeration, melting, or local overheating decomposition. The obtained anhydrous product is more porous and uniform, facilitating subsequent pulverization.

[0030] 4. Good compatibility, low modification cost, and suitable for large-scale production: The protective drying tray of this invention has a simple structure and can directly replace the ordinary trays in existing drying ovens without any complex modifications to the main drying equipment. The entire process is based on conventional drying oven operation, which is easy to master and control, making it very suitable for low-cost technical transformation of existing production lines and also facilitating large-scale, continuous, and stable production.

[0031] In summary, this invention systematically solves the inherent problems of the traditional oven drying method for producing anhydrous cobalt nickel salts through an ingenious combination of "equipment + process", achieving significant progress in both technical effectiveness and economic benefits. Attached Figure Description

[0032] Figure 1 This is a flowchart of the stepped drying process of the present invention.

[0033] Figure 2 This is a schematic diagram of the structure of the protective drying tray of the present invention.

[0034] Explanation of markings in the diagram:

[0035] 1-Stainless steel disc; 2-PTFE protective pad; 3-Materials. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0037] Example 1: Production of anhydrous cobalt chloride

[0038] Reference Figure 1 and Figure 2 The process and equipment of this invention are used to produce anhydrous cobalt chloride (CoCl2), and the steps are as follows:

[0039] 1. Pretreatment: The raw material cobalt chloride hexahydrate (CoCl2·6H2O) is sieved through a 20-mesh sieve to remove any possible lumps or foreign matter.

[0040] 2. Loading: Spread the sieved raw material evenly in a protective drying tray. This drying tray is a square shallow tray 1 welded from 1mm thick 316 stainless steel plate (size can be customized according to the drying oven). A 1.5mm thick polytetrafluoroethylene (PTFE) soft pad is laid and pasted on the inner bottom surface of the tray as a PTFE protective pad 2. The thickness of the pad is about 1-2cm.

[0041] 3. Step-by-step drying: Place multiple drying trays filled with materials into a preheated electric forced-air drying oven. Set the drying program: First stage, dry at a constant temperature of 130℃ for 2 hours; Second stage, raise the temperature to 260℃ and continue drying at a constant temperature for 2.5 hours. The forced-air system is turned on throughout the drying process to ensure uniform temperature within the oven. The dehydration endpoint is determined by monitoring the material's weight loss rate (approaching the theoretical water loss rate of 48.7%).

[0042] 4. Cooling and Post-processing: After drying, remove the material and allow it to cool naturally to room temperature in a dry environment. Transfer the slightly agglomerated blue anhydrous cobalt chloride to a pulverizer and pulverize it using a 150-mesh sieve. Subsequently, pass the powder through a permanent magnet separator with a magnetic field strength of 300mT for magnetic separation.

[0043] 5. Testing and Packaging: Sampling and testing are conducted. The anhydrous cobalt chloride content of the product is ≥43% (theoretical value 45.39%), iron content ≤30ppm, and moisture content ≤0.5%. After passing the tests, the product is vacuum-packed in aluminum foil bags lined with plastic bags, with a net weight of 25kg per bag.

[0044] Comparative Example 1

[0045] All other conditions were identical to those in Example 1, except that the protective drying tray was replaced with a standard 316 stainless steel tray without a PTFE pad. After three batches were produced, obvious brown corrosion spots appeared on the bottom of the tray. Product testing showed that the iron content had increased to over 150 ppm. After five batches were produced, the corrosion of the tray worsened, necessitating its replacement.

[0046] Example 2: Production of anhydrous nickel sulfate

[0047] Anhydrous nickel sulfate (NiSO4) is produced using the process and equipment of this invention.

[0048] 1. The raw material is nickel sulfate hexahydrate (NiSO4·6H2O), which is pretreated by sieving.

[0049] 2. Use a protective drying tray with the same structure as in Example 1.

[0050] 3. The tiered drying program is adjusted as follows: the first stage is dried at 125℃ for 2.5 hours, and the second stage is dried at 240℃ for 3 hours.

[0051] 4. After cooling, crush and pass through a 150-mesh sieve, then perform magnetic separation.

[0052] 5. Finally, a light yellow powder of anhydrous nickel sulfate is obtained, with a nickel content ≥33%, low impurity content, and good fluidity.

[0053] Effect Analysis:

[0054] A comparison of the embodiments and comparative examples clearly demonstrates that the protective drying tray of the present invention plays a decisive role in corrosion prevention. During long-term use, the tray remains intact, eliminating product contamination caused by equipment corrosion at the source. Simultaneously, the stepped drying process ensures that different cobalt-nickel salts can be fully and uniformly dehydrated under suitable temperature profiles. Combined with the non-stick properties of the PTFE pad, the product yield remains stable at over 98.5%, and the purity is significantly higher than that of traditional methods.

Claims

1. A step drying process for the preservation of cobalt nickel salts from corrosion by dehydration, characterized by, The method comprises the following steps: Material traying: the cobalt salt and / or nickel salt material containing crystal water is laid flat in a protective drying tray, which comprises a stainless steel tray body and a Teflon protective pad laid on the inner bottom surface of the tray body; Stepwise drying: the material tray is placed in a drying device, and the material is dried at a first temperature of 120-140 ℃ for 1-3 hours, and then the temperature is increased to a second temperature of 200-280 ℃ for continuous drying for 1-4 hours until the crystal water of the material is removed.

2. The step drying process for the preservation of cobalt nickel salts from corrosion by dehydration as claimed in claim 1 wherein, The step of material traying further comprises a pretreatment step of screening and removing impurities from the material before the step.

3. The step drying process for the preservation of cobalt nickel salts from corrosion by dehydration as claimed in claim 1 wherein, The step of stepwise drying further comprises the steps of cooling the dehydrated material and crushing the material to pass through a 150-mesh screen.

4. The step drying process for the preservation of cobalt nickel salts from corrosion by dehydration as claimed in claim 3 wherein, After the crushing, the obtained powder is subjected to magnetic separation.

5. The step drying process for the preservation of cobalt nickel salts from corrosion by dehydration as claimed in claim 1 wherein, The Teflon protective pad is a polytetrafluoroethylene pad.

6. The step drying process for the preservation of cobalt nickel salts from corrosion by dehydration as claimed in claim 1 wherein, The stainless steel tray body is made of 316 stainless steel.

7. A guard drying tray for use in the step drying process according to any one of claims 1-6, characterized in that The method comprises: a stainless steel tray body for carrying the material; a Teflon protective pad laid on the inner bottom surface of the stainless steel tray body for forming an isolation protective layer between the material and the tray body.

8. The guarded drying tray of claim 7, wherein, The Teflon protective pad is a polytetrafluoroethylene pad.

9. The guarded drying tray of claim 7, wherein, The stainless steel tray body is made of 316 stainless steel.

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