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Discussion on the influence of chemical process on production safety
Article 9 (2) of the "Implementation Measures for the Safety Production License for Hazardous Chemicals Production Enterprises" (Decree No. 41 of the State Administration of Work Safety), which came into effect on December 1, 2011, stipulates that any first-time domestically adopted chemical process must undergo a safety and reliability argumentation organized by the relevant provincial government departments. As a grassroots worker involved in the safety permit process for hazardous chemicals construction projects, I would like to share some insights on how certain chemical processes can affect production safety.
First, the impact of the process route
Different chemical processes involve varying reaction equations, operating conditions, and equipment. For example, the synthesis of vinyl chloride can be achieved through acetylene hydration using calcium carbide, or via the addition of hydrogen chloride to acetylene. Another method is the oxychlorination of ethylene. Similarly, methyl chloride can be produced either through methane chlorination or by reacting methanol with HCl. Ethanol can be obtained through fermentation of starchy materials or by hydrolysis of ethylene.
While these methods are all industrially viable, their safety profiles differ significantly. The acetylene and hydrogen chloride addition process involves two relatively safe steps. However, the oxychlorination of ethylene involves multiple stages, including chlorination, cracking, and oxidation—three dangerous processes that increase the risk of side reactions and operational complexity.
In the case of methyl chloride, the chlorination of methane introduces risks such as the formation of dichloromethane, chloroform, and carbon tetrachloride, which are more hazardous. In contrast, the methanol and HCl synthesis method typically results in fewer side reactions and a simpler refining process.
Ethanol production via ethylene hydro-formation involves high temperatures and pressures, leading to potential side reactions. Meanwhile, the fermentation method, when properly managed, offers a safer and more controlled environment with fewer hazards.
For fine chemicals like pharmaceutical intermediates, the process becomes even more complex, with numerous steps and combinations that can significantly influence safety outcomes.
Second, the impact of raw material selection
Raw materials serve as the foundation of chemical production. Even with the same process, the choice of raw materials and catalysts can greatly affect both product yield and process safety. For instance, in the production of permanent violet, the alkylation of carbazole can use either ethyl bromide or ethyl chloride. Although similar in properties, their reaction conditions differ significantly.
The nature of the raw materials plays a key role in determining fire and explosion risks. Factors such as flash point, ignition temperature, and explosion limits directly affect the likelihood of accidents. The stability of the material influences storage and reaction conditions, while its toxicity and purity determine the need for additional processing steps, which may introduce more hazards.
Physical properties like state, color, and odor also matter. Solid materials may generate dust, increasing the risk of electrostatic hazards and respiratory diseases. Gaseous or liquid materials, if leaked, can spread quickly, posing greater risks of explosion or poisoning. For example, carbon monoxide and hydrogen sulfide are both flammable gases, but the latter has a distinct smell that makes it easier to detect, potentially reducing the risk of unnoticed exposure.
Catalysts also play a crucial role in determining reaction safety. Their instability can lead to unpredictable reaction rates, either causing overheating or allowing raw materials to accumulate, which may result in sudden and dangerous reactions. Selectivity of the reaction is also affected, with side reactions possibly generating harmful by-products.
Considering the complexity of chemical development, it's essential for researchers and engineers to prioritize non-toxic, stable materials, simplify process flows, and adopt advanced technologies to minimize risks. Emphasizing intrinsic safety in design and operation can significantly reduce the chances of accidents.
(Yang Jie, Haimen City, Jiangsu Province)