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2.2 Pollution of water environment in salt mining and countermeasures The effects of salt-water mining on the environment of the mining area are mainly as follows: the leakage of the brine to the water environment and the soil environment; the collapse of the cavity causes the ground to settle; And death. The basic way of brine leakage is mainly in three aspects:
1 The brine leakage of the halogen system is mainly due to the corrosion of the pipeline, the rupture and the tight sealing, which leads to the leakage of the brine inside the pipe;
2 The brine brine discharges waste brine;
3 The brine is leaked due to the collapse of the solution cavity, and part of the brine may be lost due to the connection with the groundwater. A part of the brine may reach the surface in the form of salt spring along the fracture channel.
The pollution of surface water in the water by brine is very serious. For example, the chloride content in some waters has exceeded the standard of agricultural irrigation water. The analysis of chloride in the water environment of the water-recovery area shows that the concentration of chloride in the contaminated zone of surface water is generally 125.25~3276.50mg/dm 3 , and in some areas it is as high as 138000mg/dm 3 . The osmotic pressure of the corresponding solution is generally 0.14×10 5 ～3.85×10 5 Pa, and the surface water with serious pollution can reach 162.4×10 5 Pa. The content of Mn in the surface water of the mining area varies greatly, which is generally higher than the content of Mn in the normal water body in the adjacent area. High, this may be caused by the pollution of easily soluble salts, which has a greater impact on the leaching of Mn in the soil.
Irrigation of rice with surface water with high salt content, even considering the role of salt such as carbonate and sulfate, only considering the osmotic pressure caused by sodium chloride can reach 2.56 × 10 5 Pa, the actual solution osmotic pressure is still To be high, it indicates that the osmotic stress of rice in this area is present, and the water absorption of rice is relatively weakened, and water absorption difficulties and physiological disorders occur. This may be the main reason for shortening the heading date, filling period and rapid yellowing and even death of rice.
There are several ways to control water pollution:
(1) For salty wastewater, if conditions permit, it can be re-injected into the ground for water-soluble mining and cannot be directly discharged. For example, the Jianghuai Refined Salt Plant in Anwei Province will use salty wastewater from the salt production plant (mainly brushed water, dust removal water, flushing water, etc., the main components of which are NaCI and a small amount of Na 2 SO 4 , CaSO 4 , MgSO 4 , etc. All of them are concentrated back into the wastewater pool, pumped to the salt mine buffer pool, and then returned to the well for brine.
(2) For wastewater with a high content of sodium chloride, the salt can be recovered by enrichment and concentration. The specific process methods are as follows:
1 reverse osmosis method, select the permeable membrane with appropriate pore size, separate the wastewater from the fresh water with a semi-permeable membrane, and pressurize at the wastewater end, due to the μ water>μ wastewater (water), when pressurized to overcome the penetration of wastewater When the pressure is still relatively large, the water at the waste end will be transferred to the water end to concentrate it;
The 2Donnan balance method separates the wastewater from the macromolecular solution with a semi-permeable membrane of a smaller pore size. Na + and CI - can enter the macromolecular solution through the semipermeable membrane, which reduces the salinity of the wastewater and is large. The inclusion of Na + and CI - in the molecular solution can simplify certain chemical production processes, such as the production of soap;
3 ion exchange resin method.
The waste brine of the salt production plant can also be used as raw material for the production of other chemical products, such as chlor-alkali by electrolysis, and the use of waste brine can reduce the amount of solid sodium chloride.
2.3 Pollution to the atmospheric environment in salt mining and countermeasures When brine is transported to salt production plants and other chemical plants, especially in the process of salt production, a large amount of salt dust is flying in the air.
After entering the human body through the respiratory tract, it will cause respiratory infections and diseases such as high blood pressure. The salt-dried exhaust gas is a salt-containing waste gas, which mainly contains a small amount of NaCI, Na 2 SO 4 , CaSO 4 , MgSO 4 and the like, and is discharged into the atmosphere by a double-stage vortex cyclone and a grit water film dust remover. Can reduce its pollution to the surrounding environment. For the sodium chloride dust in the air, in the small area of ​​the workshop, it can also be sprayed (sprayed) by mechanical means to dissolve it and land on the ground; in the surrounding area, planting plants can be tall and leafy. Plants with strong leaf surface adsorption capacity (such as corn, cotton, soybean, melon, salicaceae, long grass, sea bream and soda ash) to purify the air, and further biotechnology (such as fungal inoculation) Improve the salt tolerance of crops and expand the varieties of crops.
Rock salt deposits are often associated with natural gas , and their main components are methane and hydrogen sulfide. When mining, if it is not directly recycled, it will cause harm to the atmospheric environment: methane is a strong greenhouse effect gas, and its warm potential is 21 times that of carbon dioxide; the toxicity of pure H 2 S is close to HCN. A small amount of H 2 S in the air causes headaches, while a large amount of H 2 S causes heart and lung nerve center paralysis, causing fainting and death.
For thin-layer shallow buried rock salt deposits, due to the strong fluidity of the gas itself, it is easy to seep out of the ground during the mining process, resulting in an increase in the content of methane, hydrogen sulfide, carbon dioxide, etc. in the atmosphere; if it is halogen (black or yellow) In the event of an accident, the polluting gas entering the atmosphere is even more serious. In the production of salt mines, the deposits with a small amount of gas should be taken with the same gas and gas; while the gas is stored in a large amount, the gas can be used for air-harvesting or gas-halogen mining.
On the other hand, the associated gas of the deposit has a certain solubility in the brine (which increases with the increase of the brine pressure). If it is not purified, it not only corrodes the equipment during the salt making process, but also increases the energy consumption and escapes. It will also pollute the atmosphere. For the brine produced, multiple preheating (70-80 ° C) can be used to achieve gas-halogen separation, and the recovered gas (such as methane) can be used as an energy source.
3 Conclusions The author has studied and summarized the measures to prevent roof collapse in salt mining and the analysis and treatment of accidental accidents, and concluded that the following conclusions are made:
(1) The recovery rate of rock salt in groundwater in China is low, mainly caused by salt well accidents (such as brine leakage, ground halogen, etc.), causing serious waste of natural resources. The intelligent prediction of the roof collapse of the rock salt layer during the salt water exploitation process and the utilization of the cavity need to be studied in depth.
(2) The accumulation and disposal of dry mining residues in salt mines on the ground, the collapse of the top plate in the water-soluble mining, and the leakage of the pipe wall during the transportation of brine will cause pollution to the soil or water body, and the degree of pollution is determined by the conductivity method. According to this, it is improved by planting salt-tolerant plants, soil and deep turning, and it should also strengthen the management of salt mines.
(3) The pollution of surface water in brine is very serious. The chloride content in some waters has exceeded the standard of agricultural irrigation water, so that irrigation of rice will cause water absorption difficulties and physiological disorders. The salty wastewater can be re-injected into the ground for water-soluble mining or used as a raw material for other chemical products. For wastewater with a higher sodium chloride content, the salt can be recovered by reverse osmosis, Donnam equilibrium, ion exchange resin, and the like.
(4) The salt dust flying in the air during the salt making process can be dedusted by a two-stage vortex cyclone and a grit water film dust collector. The small area of ​​the workshop can also be sprayed with water to dissolve it and land on the ground. In the surrounding area, planting salt-tolerant plants can be used to purify the air, and biotechnology can be used to improve the salinity of crops. The rock salt deposits often have a certain solubility in the brine, and the gas-halogen separation can be achieved by multiple preheating methods, and the recovered methane can be used as an energy source.
1 The brine leakage of the halogen system is mainly due to the corrosion of the pipeline, the rupture and the tight sealing, which leads to the leakage of the brine inside the pipe;
2 The brine brine discharges waste brine;
3 The brine is leaked due to the collapse of the solution cavity, and part of the brine may be lost due to the connection with the groundwater. A part of the brine may reach the surface in the form of salt spring along the fracture channel.
The pollution of surface water in the water by brine is very serious. For example, the chloride content in some waters has exceeded the standard of agricultural irrigation water. The analysis of chloride in the water environment of the water-recovery area shows that the concentration of chloride in the contaminated zone of surface water is generally 125.25~3276.50mg/dm 3 , and in some areas it is as high as 138000mg/dm 3 . The osmotic pressure of the corresponding solution is generally 0.14×10 5 ～3.85×10 5 Pa, and the surface water with serious pollution can reach 162.4×10 5 Pa. The content of Mn in the surface water of the mining area varies greatly, which is generally higher than the content of Mn in the normal water body in the adjacent area. High, this may be caused by the pollution of easily soluble salts, which has a greater impact on the leaching of Mn in the soil.
Irrigation of rice with surface water with high salt content, even considering the role of salt such as carbonate and sulfate, only considering the osmotic pressure caused by sodium chloride can reach 2.56 × 10 5 Pa, the actual solution osmotic pressure is still To be high, it indicates that the osmotic stress of rice in this area is present, and the water absorption of rice is relatively weakened, and water absorption difficulties and physiological disorders occur. This may be the main reason for shortening the heading date, filling period and rapid yellowing and even death of rice.
There are several ways to control water pollution:
(1) For salty wastewater, if conditions permit, it can be re-injected into the ground for water-soluble mining and cannot be directly discharged. For example, the Jianghuai Refined Salt Plant in Anwei Province will use salty wastewater from the salt production plant (mainly brushed water, dust removal water, flushing water, etc., the main components of which are NaCI and a small amount of Na 2 SO 4 , CaSO 4 , MgSO 4 , etc. All of them are concentrated back into the wastewater pool, pumped to the salt mine buffer pool, and then returned to the well for brine.
(2) For wastewater with a high content of sodium chloride, the salt can be recovered by enrichment and concentration. The specific process methods are as follows:
1 reverse osmosis method, select the permeable membrane with appropriate pore size, separate the wastewater from the fresh water with a semi-permeable membrane, and pressurize at the wastewater end, due to the μ water>μ wastewater (water), when pressurized to overcome the penetration of wastewater When the pressure is still relatively large, the water at the waste end will be transferred to the water end to concentrate it;
The 2Donnan balance method separates the wastewater from the macromolecular solution with a semi-permeable membrane of a smaller pore size. Na + and CI - can enter the macromolecular solution through the semipermeable membrane, which reduces the salinity of the wastewater and is large. The inclusion of Na + and CI - in the molecular solution can simplify certain chemical production processes, such as the production of soap;
3 ion exchange resin method.
The waste brine of the salt production plant can also be used as raw material for the production of other chemical products, such as chlor-alkali by electrolysis, and the use of waste brine can reduce the amount of solid sodium chloride.
2.3 Pollution to the atmospheric environment in salt mining and countermeasures When brine is transported to salt production plants and other chemical plants, especially in the process of salt production, a large amount of salt dust is flying in the air.
After entering the human body through the respiratory tract, it will cause respiratory infections and diseases such as high blood pressure. The salt-dried exhaust gas is a salt-containing waste gas, which mainly contains a small amount of NaCI, Na 2 SO 4 , CaSO 4 , MgSO 4 and the like, and is discharged into the atmosphere by a double-stage vortex cyclone and a grit water film dust remover. Can reduce its pollution to the surrounding environment. For the sodium chloride dust in the air, in the small area of ​​the workshop, it can also be sprayed (sprayed) by mechanical means to dissolve it and land on the ground; in the surrounding area, planting plants can be tall and leafy. Plants with strong leaf surface adsorption capacity (such as corn, cotton, soybean, melon, salicaceae, long grass, sea bream and soda ash) to purify the air, and further biotechnology (such as fungal inoculation) Improve the salt tolerance of crops and expand the varieties of crops.
Rock salt deposits are often associated with natural gas , and their main components are methane and hydrogen sulfide. When mining, if it is not directly recycled, it will cause harm to the atmospheric environment: methane is a strong greenhouse effect gas, and its warm potential is 21 times that of carbon dioxide; the toxicity of pure H 2 S is close to HCN. A small amount of H 2 S in the air causes headaches, while a large amount of H 2 S causes heart and lung nerve center paralysis, causing fainting and death.
For thin-layer shallow buried rock salt deposits, due to the strong fluidity of the gas itself, it is easy to seep out of the ground during the mining process, resulting in an increase in the content of methane, hydrogen sulfide, carbon dioxide, etc. in the atmosphere; if it is halogen (black or yellow) In the event of an accident, the polluting gas entering the atmosphere is even more serious. In the production of salt mines, the deposits with a small amount of gas should be taken with the same gas and gas; while the gas is stored in a large amount, the gas can be used for air-harvesting or gas-halogen mining.
On the other hand, the associated gas of the deposit has a certain solubility in the brine (which increases with the increase of the brine pressure). If it is not purified, it not only corrodes the equipment during the salt making process, but also increases the energy consumption and escapes. It will also pollute the atmosphere. For the brine produced, multiple preheating (70-80 ° C) can be used to achieve gas-halogen separation, and the recovered gas (such as methane) can be used as an energy source.
3 Conclusions The author has studied and summarized the measures to prevent roof collapse in salt mining and the analysis and treatment of accidental accidents, and concluded that the following conclusions are made:
(1) The recovery rate of rock salt in groundwater in China is low, mainly caused by salt well accidents (such as brine leakage, ground halogen, etc.), causing serious waste of natural resources. The intelligent prediction of the roof collapse of the rock salt layer during the salt water exploitation process and the utilization of the cavity need to be studied in depth.
(2) The accumulation and disposal of dry mining residues in salt mines on the ground, the collapse of the top plate in the water-soluble mining, and the leakage of the pipe wall during the transportation of brine will cause pollution to the soil or water body, and the degree of pollution is determined by the conductivity method. According to this, it is improved by planting salt-tolerant plants, soil and deep turning, and it should also strengthen the management of salt mines.
(3) The pollution of surface water in brine is very serious. The chloride content in some waters has exceeded the standard of agricultural irrigation water, so that irrigation of rice will cause water absorption difficulties and physiological disorders. The salty wastewater can be re-injected into the ground for water-soluble mining or used as a raw material for other chemical products. For wastewater with a higher sodium chloride content, the salt can be recovered by reverse osmosis, Donnam equilibrium, ion exchange resin, and the like.
(4) The salt dust flying in the air during the salt making process can be dedusted by a two-stage vortex cyclone and a grit water film dust collector. The small area of ​​the workshop can also be sprayed with water to dissolve it and land on the ground. In the surrounding area, planting salt-tolerant plants can be used to purify the air, and biotechnology can be used to improve the salinity of crops. The rock salt deposits often have a certain solubility in the brine, and the gas-halogen separation can be achieved by multiple preheating methods, and the recovered methane can be used as an energy source.
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