1. Dust hazard
The dust produced in the production process of aluminum plant mainly includes alumina dust, petroleum coke dust and asphalt dust. Alumina dust mainly exists in electrolysis workshop and alumina storage and transportation system; The feeding system, discharging system, kneader, preheating screw machine and grinding system of calcination section produce dust and asphalt smoke; The molding section also produces asphalt smoke; Dust is produced in the process of coarse crushing, batching and screening in the residual electrode treatment section. Crane drivers, electrolytic workshop workers, workers in positions such as powder crushing and screening are greatly endangered by dust. According to TJ36-79 Hygienic Standard for the Design of Industrial Enterprises, the maximum allowable concentration of harmful substances in the air of the workshop is that the alumina dust in the productive dust shall not exceed 6 mg/m3; Other dust (when the content of free silica is lower than 10%) shall not exceed 10mg/m3.
2. Poison hazards
The main toxicants exposed to workers are fluoride, sulfide, asphalt smoke and carbon monoxide. Poisons mainly exist near electrolytic cells and flue gas purification systems.
Aluminum electrolysis takes cryolite-alumina-aluminum fluoride melt as electrolyte and carbon material as electrode. In the process of electrolysis, liquid aluminum precipitates at the cathode and gas is generated at the anode. At the same time, it also emits electrolytic flue gas mainly containing fluoride, dust and other pollutants. At the temperature of 400℃ ~ 600℃, alumina can still contain 0.2% ~ 0.5% moisture. Water in raw materials can react with solid fluoride salt at high temperature, and water entering molten electrolyte can also react with liquid fluoride salt to generate harmful hydrogen fluoride.
Inhalation of excessive fluoride often leads to skeletal fluorosis such as osteoporosis, hyperosteogeny, tooth mottle, etc., and severe cases lose the ability to work. Fluoride also has a strong stimulating and corrosive effect on respiratory mucosa and skin. According to China's health standards, the maximum allowable concentration of fluoride in the air of workplace is 0.5mg/m3. According to the principle of toxicity classification in the current national standard "Classification of Occupational Exposure Poisons", fluoride is Grade II, which is highly harmful.
Asphalt smoke mainly comes from the kneader, grinding system and molding section of the raw anode section of this process. The softening point of coal tar pitch is 100℃ ~ 1 10℃, which belongs to high temperature pitch. There are two main hazards of asphalt to human body: first, because asphalt contains anthracene and other photosensitive substances, long-term exposure to the sun will cause dermatitis; The second is the stimulating effect of asphalt smoke on skin and mucosa. According to the principle of toxicity classification in the current national standard "Classification of Hazard Degree of Occupational Exposure Poisons", asphalt smoke is Grade III, which belongs to moderate hazard.
Carbon monoxide is produced in the anode of electrolytic cell, which is a colorless and odorless gas. It combines with hemoglobin in the blood, resulting in tissue hypoxia. Patients with mild poisoning have headache, dizziness, tinnitus, palpitation, nausea, vomiting, fatigue, rapid pulse, irritability and shallow to moderate coma; In severe cases, there are deep coma, pupil contraction, increased muscle tension, frequent convulsions, incontinence, pulmonary edema and serious myocardial damage. The maximum allowable concentration of carbon monoxide in workplace air in China is 30mg/m3. According to the principle of poison classification in the current national standard "Classification of Occupational Exposure Poisons", carbon monoxide is Grade II, which is highly dangerous.
Sulfides are also produced during electrolysis. Sulfur dioxide is a colorless gas, which has a strong stimulating effect on eyes and respiratory mucosa. In mild poisoning, skin or eye contact can cause inflammation or burns; Severe poisoning can cause pulmonary edema, laryngeal edema, vocal cord spasm and suffocation within a few hours. The maximum allowable concentration of sulfur dioxide in workplace air in China is 15mg/m3. According to the principle of poison classification in the current national standard "Classification of Hazard Degree of Toxic Occupational Exposure", sulfur dioxide can be classified as grade VI, which is a mild hazard.
3. High temperature hazards
According to the current national standard "Classification of High Temperature Work", the work with an average WBGT index equal to or greater than 25℃ is high temperature work. The electrolysis temperature of aluminum reduction cell is as high as 940℃ ~ 960℃, which is the main production heat source. Production equipment such as calcination, roasting, continuous kneading, preheating screw and asphalt melting in carbon section are all productive heat sources. The data show that when the ambient temperature reaches 28℃, people's reaction speed, calculation ability, sensory sensitivity and sensory motor coordination function decrease obviously. High temperature reduces labor efficiency and increases operation error rate. Mainly reflected in the body's temperature regulation, water and salt metabolism and circulatory system. High temperature can also inhibit the central nervous system, so that workers' attention is distracted during operation and their muscle working ability is reduced, which leads to injury accidents.
4. Noise hazards
The equipment that produces noise mainly includes purification system fan, carbon system crusher, ball mill, molding machine, feeder, vibrating screen, conveyor, roasting flue gas purification system fan and dust removal fan. In the ball mill workshop, the noise level caused by coke grinding is as high as 100dB(A). The noise level generated by using pneumatic slag shell crusher near the electrolyzer in the electrolysis workshop reaches 100dB(A). Noise can lead to hearing loss or even deafness, or neurasthenia, cardiovascular diseases and digestive system diseases. Noise affects information exchange and promotes misoperation.
As long as it is silicosis, the occupational prevention and treatment institute must have a compulsory physical examination every year, and the company should also have practical occupational disease prevention and control measures, otherwise it will do great harm to the health of workers.