I. Industry Challenge: Frequent Cracking of Evaporators

In alumina plant production, the cracking of evaporators is a common occurrence, severely affecting production efficiency and equipment lifespan. This has become a major problem hindering the development of the industry. What lies behind this persistent issue? Let’s delve into an in - depth exploration.

 II. Classification of Evaporators: Different Types for Distinct Application Scenarios

Alumina evaporators are mainly categorized into high - concentration evaporators and low - concentration evaporators. High - concentration evaporators are predominantly used in the high - temperature digestion process of domestic bauxite ores. Due to the characteristics of this process, they require a higher concentration of mother liquor. In contrast, low - concentration evaporators are suitable for the low - temperature digestion of foreign bauxite ores, especially三水软铝石 (gibbsite). These two types of evaporators each play a specific role in the alumina production process. However, the cracking and corrosion problems primarily occur in high - concentration evaporators.

 III. The Root Cause of Cracking: In - Depth Analysis of the "Alkali Embrittlement" Phenomenon

In the alumina industry, the cracking of high - concentration evaporators is referred to as "alkali embrittlement," which is essentially stress corrosion. During the manufacturing process of evaporators, processing techniques such as cold deformation and welding inevitably generate internal stresses within the equipment. When these stressed devices come into contact with high - concentration alkali liquor, the interaction between stress and the alkali liquor triggers stress corrosion. As time passes, this ultimately leads to the cracking of the evaporators.

 IV. Material Selection Strategy: Mitigating Cracking Risks at the Source

The key to solving the problem of evaporator cracking lies in reducing the stress generated during the manufacturing process, and material selection is a crucial first step. It is essential to choose materials that generate less stress during deformation or welding. Among them, 245R and 345R are excellent choices. Although the 245R material has relatively lower strength and requires thicker plates for equipment manufacturing, it exhibits excellent resistance to alkali embrittlement and is soft in texture. Equipment manufactured from 245R can effectively reduce internal stress, minimize the occurrence of stress corrosion, and thereby alleviate the alkali embrittlement phenomenon. It is particularly worth noting that in the past, some people mistakenly thought that using 245R instead of 345R was an act of cutting corners. In fact, the cost of 245R is slightly higher than that of 345R, and the choice of 245R is based on its superior alkali - embrittlement resistance.

 V. Stress Elimination: The Crucial Role of the Annealing Process

In addition to material selection, stress elimination is also a vital aspect of addressing evaporator cracking, and the annealing process in heat treatment is the most effective method. Precise control of temperature and time is of utmost importance during the annealing process. Only by scientifically and reasonably regulating the parameters of the annealing process and eliminating at least 97% of the stress can the occurrence of alkali embrittlement in equipment be effectively avoided at the root, ensuring the stable operation of the evaporators.

 VI. Technological Breakthrough: Bringing Multiple Benefits to the Industry
The effective solution to the problem of evaporator cracking represents a significant core technological breakthrough for evaporator manufacturers. For alumina plant users, this means a reduction in equipment failures, lower equipment maintenance costs, and guaranteed production continuity. As a result, production efficiency is significantly improved, bringing tangible economic benefits and social value to the enterprises.