Up to now, the discussion on environmental protection cable technology in the cable industry has almost all focused on the use performance of cable products, that is, the friendly relationship between cable products and the ecological environment, but rarely on the pollution of the cable product manufacturing process to the human ecological environment. How to control the environmental pollution caused by cable manufacturing should be put on the agenda.

In the process of rapid industrial development, if environmental pollution is not strictly controlled, it will cause devastating ecological problems. In the 1980s, when we attacked the environmental pollution in the industrial developed countries, it was also the time when China's industrial development started and the industrial developed countries were considering transferring pollution to developing countries. Over the past 20 years, with the rapid development of China's industry, it has also caused more and more serious pollution.

We have always said that the cable industry is an industry that does not produce environmental pollution. Every factory has been recognized by the Environmental Protection Bureau, and many factories have also obtained ISO14001 environmental protection certification. However, according to thorough and careful understanding, environmental pollution exists in almost every process in the cable manufacturing factory, but the form, way and degree of pollution are different. The greening, tree planting, grass planting, flower planting, rockery building, bonsai building, and the construction of a "garden factory" in the plant area can only give people a visual impression, but it does not help to deal with the "three wastes" generated in the production process, which can only be a kind of external decoration. In recent years, some experts and scholars have discussed the environmental pollution of the cable industry, but they are still limited to the composition of cable materials, not the environmental pollution caused by the cable manufacturing process.

The environmental pollution of several main processes in the cable manufacturing process is discussed below.

Copper rod manufacturing:

Copper is an essential trace element for life, but excessive copper is harmful to people, animals and plants. In the process of copper smelting and processing, if appropriate smoke suppression and dust removal measures are not taken, black smoke will occur and pollution will be serious. The smoke and dust of copper and its compounds enter the atmosphere, causing air pollution. During copper smelting and processing, copper acid wastewater will be produced, with the maximum copper content of tens to hundreds of milligrams per liter of wastewater. The soil near the copper smelting plant contains high concentration of copper. If the wastewater is discharged without treatment, the water quality will be affected.

It is understood that some small copper rod factories are full of thick smoke and stink. A large amount of sewage and waste gas are directly discharged without any treatment, which seriously pollutes the water quality, severely damages crops, and even refuses to harvest. Many residents around have experienced chest tightness, headache, vomiting and other diseases.

The waste gas generated is mainly the flue gas generated by the melting furnace, copper particles and SO2 gas generated in the gas furnace, which shall be discharged after being dedusted by the bag filter in series. The process wastewater generated in the continuous casting and rolling process shall be cooled and recycled. The waste oil and waste emulsion of the rolling mill lubrication system shall be properly treated.

China stipulates that the maximum allowable discharge concentration of copper and its compounds in industrial wastewater is 1 mg/L (calculated as per copper). Some factories still use the pyrometallurgical copper smelting process, which is backward in technology. Countless local copper smelters cause serious environmental pollution. The state is making greater efforts to inspect copper processing plants with serious pollution, so as to control material utilization and pollution discharge from the production process, reduce pollution from the source, and comprehensively utilize or recycle waste water, waste heat, etc. generated in the production process, so as to improve resource utilization efficiency and reduce or eliminate hazards to human health and the environment.

Aluminum rod manufacturing:

Many cable plants have their own ability to process aluminum rods. Fuel for aluminum melting heat source mainly includes producer gas and heavy oil. If the heavy oil has poor atomization and incomplete combustion, it will produce black smoke. If the gas generator is improperly configured or out of repair, CO gas leakage will poison the environment. In the smelting process, the solvent used also produces a large amount of harmful flying dust. If the smoke suppression and dust removal measures are not effective, dense smoke will be generated and the atmosphere will be polluted. Non polluting and toxic auxiliary materials shall be used, and the generated flue gas shall be discharged at high altitude after being treated by dry flue gas purification technology. The cooling liquid for aluminum rod continuous casting and rolling can only be discharged after careful treatment. First adjust the PH value of the waste emulsion (to 6.5-7.5), and then add 2~5% sodium chloride of the total waste liquid for mixing. After two hours of dissolution, add 1~3% potassium aluminum sulfate of the waste oil, stir slightly, and then stand still for 24 hours. After it is condensed and stratified, separate the upper floats and discharge the lower wastewater. Some small factories use indigenous equipment to manufacture aluminum rods, without any treatment measures for flue gas, flying dust and waste water, causing serious environmental pollution.

Rubber processing:

Cable manufacturers generally use small and medium-sized internal mixers. Due to the cost problem, they generally use manual batching, manual feeding, and manual rubber mixing. The labor intensity of workers is high, and the workshop and the surrounding environment are seriously polluted.

Henan Medical University and other units have investigated the skin diseases of rubber mixing workers in cable plants, and found that the prevalence of skin diseases among rubber mixing workers was 68.7%; Patch test was carried out on 12 rubber ingredients, among which 8 ingredients, including antioxidant (DNP and D), accelerator (DM, M, CZ, DPTT), antioxidant 1246 and sun fast dark red, showed positive reactions to varying degrees. Through diagnosis and investigation, it is proved that the skin diseases of rubber processing workers are mainly caused by dust pollution.

At present, the internal mixer adopts the feeding system of the upper auxiliary machine, which realizes mechanization and automation. Compared with manual batching and feeding, it does reduce labor intensity and environmental pollution. However, the raw materials have to go through the process of unpacking, putting into the storage hopper, automatically weighing according to the formula requirements, and putting into the intermediate hopper. Dust is flying in these processes. After the workers who unpack and pour carbon black finish their work, their bodies are all black except for their eyes and teeth.

In addition, the wastewater and waste oil discharged from the rubber processing process will also cause serious public pollution if they are discharged into the sewer without treatment.

wire drawing:

Copper wire drawing oil is composed of basic lubricating oil, emulsifier and stabilizer. The main pollution source of wire drawing process is wire drawing oil. The treatment of copper wire drawing oil waste liquid mainly includes two steps: demulsification and water purification. Demulsification is mainly to separate oil and water phases. Its principle is to add salt compounds containing Ca2+, Na+, Al3+and other metal ions to the emulsion, so that the surfactant in the emulsion can generate insoluble soaps with it, thus causing condensation.

Some chemical substances, such as sodium tripolyphosphate or sodium ethylenediaminetetraacetate, need to be added when the drawing oil is prepared. The drawing oil will produce foam in the process of use, and defoamer needs to be added. Since the lotion contains a variety of oils and fats and is prone to bacteria, it is necessary to add an appropriate amount of antioxidants and bactericides. After the emulsion is eroded by microorganisms (such as bacteria, molds and algae), the unsaturated fatty acids and other compounds in the lotion are decomposed by microorganisms, which destroys the balance of the lotion, produces oil and soap evolution, and increases the acid value, resulting in the deterioration of the emulsion and odor. All these factors decide that the wire drawing oil cannot be discharged randomly, and it is better to recycle it after filtering. It is better to use deionized water to reduce the influence of water hardness on wire drawing oil and the corrosion of Cl - in water on copper wire. The pH value should not be lower than 6.5. Properly control the temperature of lotion. The system shall be equipped with a filtering device to filter copper powder and copper mud in time to keep the wire drawing oil clean. When replacing waste oil, a special recycling company shall be entrusted to take away the waste oil. The environmental protection of some cable plants cannot meet the standard, among which the use of drawing oil and improper treatment of waste liquid and waste residue are also important reasons.

Some small wire drawing plants scattered in villages and towns still use the old water tank wire drawing machine, which uses soapy water for single machine dead water lubrication, has no wastewater treatment capacity at all, and discharges at will, causing water pollution around the plant. Waste wire drawing lubricant usually contains more than 90% water, and the rest is copper soap, fat and oil. The copper content of this waste is very high. Like pesticides, it cannot be discharged into the sewer.

Tinning:

Tin plating is recognized as one of the environmental pollution industries. At present, the copper wire tin plating methods widely used in the wire and cable industry are still hot tin plating and electrolytic tin plating. The traditional open hot tin plating method is still used in many small and medium-sized enterprises. The main pollution sources of the hot tin plating process are the acid of the copper wire cleaner, the acid vapor emitted from the tin pot and the process wastewater. The traditional high temperature hot dip tin process is expensive, energy and tin consumption is wasteful and unsafe, which is very harmful to the environment and the health of operators. Attention should be paid to ventilation, exhaust, ground pollution, wastewater discharge, workers' labor protection, etc. in the workshop. Although the improved hot tin plating equipment and process have improved the environmental pollution, even called "pollution-free tin plating", it is necessary to strictly control the workshop ventilation and wastewater discharge.

Electrotinning is generally considered as a non polluting tin plating process. In fact, the pollution of electroplating tin process mainly depends on the composition of electroplating solution and process control. China's wire and cable industry has some imported wire electrotinning units. Some of these imported tin electroplating machines are in normal operation, and it is said that they do not produce pollution; Some have been banned from use due to the environmental protection department's investigation of water pollution. Even in some normal use factories, electroplating waste liquid and sludge are secretly transported to remote areas to be thrown away, rather than being placed in disorder.

Facts have proved that both hot tin plating and electrolytic tin plating have made great improvements in the equipment itself, tin plating solution and additives, but people can only minimize their pollution to the environment, and it is impossible to completely eliminate the pollution. Tin plating process is still a process highly concerned by environmental protection departments.

Painting:

As early as 20 years ago, the United States had listed a "chimney industry" blacklist, in which the electromagnetic wire industry was listed, which attracted the attention of all countries.

Especially since the use of varnish to manufacture enamelled wire, this industry has brought vexing environmental pollution control problems. Phenol, aromatic hydrocarbon and cresol are usually used as solvent carriers for enamelled wires. The harmful gases generated during the burning of these materials will be discharged into the atmosphere, which will seriously pollute the air and endanger human health. In order to eliminate pollution and improve the environment, catalytic combustion and incineration combustion devices were later installed on the enamelled furnace. Old enamelled stoves all have incinerators, some use catalysts, and some are equipped with internal combustion incinerators. The practice shows that the efficiency of the thermal incineration combustion device can reach 90-99%, while the efficiency of the catalyst is 90-95% at the beginning, but its efficiency decreases as the device gets dirty. According to foreign data, the validity of the catalyst in the enamelled furnace is about 10000 hours at most, while the validity of the new ceramic catalyst can reach more than one year. As for the exhaust gas emitted from the enamelled furnace, high solid content paint and water-soluble paint are now being used to solve the problem.

The wastes generated by the enamelled wire factory include wire drawing lubricant, waste paint, waste solvent, waste water and exhaust gas, which are harmful to the environment and cannot be discharged randomly.

Extrusion:

PVC and PE can produce various toxic or corrosive products such as methyl chloride, hydrogen chloride, benzene, carbon monoxide, carbon dioxide, etc. when they are decomposed, oxidized and burned in a fire, causing harm to people.

The environmental pollution in PVC extrusion stage is caused by the thermal decomposition of PVC. The thermal decomposition of PVC first emits HCL, as well as some heavy metals such as lead and chromium. At the normal extrusion temperature (160-180 ℃) of PVC cable material, thermal decomposition starts to occur, and strong white smoke is generated (Fig. 5). The PVC wire and cable extrusion workshop is full of this harmful gas smell, and the control instrument shell beside the extruder is black and rusty due to HCL gas corrosion. People who have been in contact with PVC extrusion working environment for a long time will have nausea, dizziness, nerve numbness and other symptoms, and will cause other diseases. Some factories have installed air suction and exhaust devices above the PVC extrusion head, while others have not. It is extremely harmful to the health of operators to let harmful gases escape. The discharged gas causes serious pollution to the atmosphere. The acid PH value of the water in the cooling water tank of the extrusion production line is higher than that of the normal tap water due to HCL decomposed from PVC, so it cannot be discharged arbitrarily and should be recycled.

Extrusion vulcanization:

The rubber raw materials can only be changed into rubber with different functions after proper compounding agent is added, fully mixed and vulcanized. When the mixed rubber is extruded, whether it is hot feed or cold feed, it will emit a strong smell. In addition to the smell of rubber itself, it mainly comes from various ingredients. Some of these smells can be eliminated, while others cannot. As mentioned above, the dust of these compounding agents is very harmful to the operators, and their decomposition products at the extrusion temperature are harmful to human health in the form of gas. The gas generated during rubber extrusion and vulcanization is discharged into the atmosphere, which will pollute the air. All residents living around the rubber products factory complain about this. In addition, the waste water generated in the vulcanization process of rubber cables contains rubber and various ionized harmful substances, which cannot be discharged into the sewer without treatment.

Crosslinking:

People always think that XLPE is a non-toxic and harmless material. In the project proposal and feasibility report, the chemical cross-linked cable project is also described as a project without environmental pollution. Actually not.

XLPE material is made of polyethylene added with cross-linking agent, antioxidant and voltage stabilizer, which is used to manufacture medium and high voltage cross-linked cables on CCV and VCV production lines. When XLPE undergoes chemical crosslinking reaction at high temperature, it will also decompose into cumyl alcohol, acetylbenzene, methane and other by-products. Especially when the CCV production line is used to manufacture the cross-linked cable, the cross-linked tube must be cleaned every 3 months to remove the cross-linked by-product dirt accumulated in the tube. According to field observation, the by-product dirt is as viscous as asphalt and has a bad smell. Some crosslinking by-products exist in liquid form. After they are discharged from the cross-linked pipe, they should be collected for proper treatment and not discharged at will. According to British experts, some by-products of polyethylene chemical crosslinking are extremely toxic and carcinogenic. China has 235 CCV cross-linked cable production lines distributed throughout the country. If the cross-linking process wastewater discharge is not strictly controlled, the consequences can be imagined.

Countermeasures for environmental protection in cable manufacturing plants

From the above description of environmental pollution of cable factories, it can be seen that the cable industry is not an industry without pollution, but an industry with serious pollution. Appropriate countermeasures should be taken and implemented.

(1) Factory operators should effectively improve their awareness of environmental protection, understand the national environmental protection laws and regulations, and make the factory construction and human social ecology develop harmoniously.

(2) Increase investment in environmental protection, eliminate old equipment with high pollution and high energy consumption, try to use new technologies, new equipment and new processes, reduce pollution generated in the production process, strengthen the treatment of waste gas, waste water and waste residue, and control the waste discharge at the lowest level allowed by the state.

(3) Strengthen the environmental supervision of major pollution processes such as wire drawing, tin plating, enameling, extrusion, rubber mixing, rubber extrusion, vulcanization and cross-linking, and implement the ISO14001 system certification.

(4) People first, care about the health of workers, and improve the working environment and labor protection conditions.