CN117661534A - Method for in-situ inhibition of acid production by oxidation of acidic coal gangue hill - Google Patents
Method for in-situ inhibition of acid production by oxidation of acidic coal gangue hill Download PDFInfo
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- CN117661534A CN117661534A CN202311390035.6A CN202311390035A CN117661534A CN 117661534 A CN117661534 A CN 117661534A CN 202311390035 A CN202311390035 A CN 202311390035A CN 117661534 A CN117661534 A CN 117661534A
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Abstract
The invention relates to a method for in-situ inhibition of acid production by oxidation of acidic coal gangue dump. The oxygen control and acid control materials are uniformly arranged in the acidic coal gangue hill; the oxygen control and acid control material comprises sulfate reducing bacteria and sodium dodecyl sulfate; covering an oxygen-isolation acid-control material layer above the gangue layer of the acid coal gangue hill; the oxygen-isolation acid-control material layer comprises 100-70 parts of powder clay and 0-30 parts of fly ash; the thickness of the oxygen-isolation and acid-control material layer is not less than 15cm, and the compactness of the oxygen-isolation and acid-control material layer reaches more than 85 percent; a transverse ecological drainage ditch is arranged on one side of the top platform and the horse road platform along the slope toe; the sloping surfaces are provided with longitudinal flexible drainage devices; a rigid drainage ditch, a stilling pool and a three-dimensional baffle wall are sequentially arranged at the junction of the acidic gangue hill of the mountain foot and the natural mountain body; the acid yield can be fundamentally reduced, the pollution of the gangue storage yard to the atmosphere, surface water, underground water and surrounding soil can be effectively inhibited, and the release of acidic gangue pollutants to the surrounding environment can be effectively controlled for a long time.
Description
Technical Field
The invention belongs to the technical field of ecological restoration of mine abandoned land, and particularly relates to a method for in-situ inhibition of acid production by oxidation of acidic coal gangue hill.
Background
Coal is the most important primary energy source in China, and the energy structure is not changed in a quite long time. The development of coal resources plays an important supporting role in the economic construction and social development of China. The gangue is solid waste discharged in the coal mining process and the coal washing process, and comprises tunneling gangue in the tunnel tunneling process, gangue clamped in the roof and the floor and the coal seam in the mining process and gangue discharged in the coal washing process. Generally, the coal gangue accounts for about 15% of the total coal yield, and the coal gangue yield changes in a floating way between 10% and 15% according to different mining modes and geological conditions. Limited to the national conditions of coal extensive exploitation in China, the productivity of the gangue is higher, and the highest productivity can be about 30% of the yield of raw coal.
As an inevitable product in the coal exploitation and processing process, coal gangue is one of the largest amount of solid wastes discharged by the current industry in China, and is also one of main reasons for environmental pollution and ecological deterioration in mining areas. At present, the existing gangue hill of coal mines in China is increased at a speed of 3-7 hundred million t each year, wherein the self-ignition gangue hill is about 1700 seats, the accumulation amount is more than 50 hundred million t, and the accumulation amount accounts for more than 40% of the total national industrial solid waste discharge amount. Coal gangue is piled up under natural conditions, and under the comprehensive actions of air oxidation, rain leaching, microorganisms and the like, acid mine wastewater (AMD) which is low in pH value, high in sulfate content and rich in a large amount of harmful heavy metal ions is extremely easy to form, so that serious environmental influence and ecological hazard can be caused to surrounding and downstream aquatic ecosystems and agricultural ecosystems. The carbon dioxide, sulfur dioxide, nitrogen oxide, hydrogen sulfide, smoke dust and the like discharged in the coal gangue oxidation process seriously pollute the atmosphere, and secondary pollution is generated to the surrounding environment through the atmospheric sedimentation effect, so that the mining area and the surrounding ecological environment are seriously damaged, and the method has become a great hidden trouble for restricting the sustainable development of the coal mining area and even the ecological safety of the area.
Compared with other coal gangue hills, the acidic coal gangue hills have larger harm to the ecological environment and higher restoration difficulty. Firstly, the catalyst is extremely easy to react with water and oxygen, and is rapidly oxidized under the catalysis of microorganisms to release heat, so that the risk of spontaneous combustion and explosion is huge; secondly, the increase of the environmental acidity of the coal gangue hill promotes the dissolution and release of toxic and harmful substances such as heavy metals in minerals, and serious pollution is caused to the environment (soil, surface water and underground water); in addition, the coal gangue hill has poor water retention, so that the water loss and soil loss are serious, the organic matter content is low, and the vegetation is difficult to survive. The acid gangue hill is treated and repaired more difficult than the neutral and alkaline gangue hill due to various factors, and specific problems such as surface and deep temperature monitoring, fire prevention, fire extinguishment, vegetation planting and the like exist. Therefore, the environmental pollution generated by the acid gangue storage yard is the most serious and difficult to treat, and is the current worldwide difficult problem. The generation of environmental problems and disasters such as spontaneous combustion, explosion, landslide and pollution to the atmosphere, soil and water of many gangue hillocks are related to the acidity of the gangue. Traditional gangue pollution control is mostly terminal treatment technology, such as acid mine wastewater treatment.
In the treatment of repairing the gangue hill, the conventional methods for inhibiting the acid production include a mixed neutralization treatment technology, a cover rolling isolation technology, a surface passivation technology, a bactericide technology, a dredging and cooling technology, a grouting technology, an inert gas technology, a biotechnology, a spray blocking isolation layer technology and the like, but most of the technologies are not suitable for the acidic gangue hill, or the single technology has very little use effect.
(1) And (5) mixing and neutralizing. The mixing neutralization treatment is to mix or jointly treat the coal gangue and the alkaline material to improve the buffer capacity of the coal gangue mountain to acidic substances, and is toA direct and effective method for in-situ control of acid production by oxidation of coal gangue dump. Common alkaline materials are limestone, quicklime, sodium carbonate, sodium bicarbonate, phosphate minerals (e.g. quicklime Ca 5 (PO 4 ) 3 F) Etc. A great deal of alkaline industrial byproducts (such as fly ash, desulfurized gypsum, fly ash, red gypsum, sugar foam, biomass combustion ash, green liquor slag, fly ash, table lime, argon oxygen decarburization slag, cement kiln ash, red mud bauxite and the like) generated by coal-fired power plants, pulp mills, steel plants and the like can be used for achieving the purpose of comprehensively utilizing wastes. However, in order to effectively perform co-processing or mixing operations, the correct stoichiometric balance between acid-producing and acid-consuming materials must be used. For example, the lack of acid consuming substances will not neutralize the acidic leachate, while an excess of alkaline material may form a strong alkaline leachate, thereby increasing the solubility of some hazardous metals (e.g., al, cu, ni, pb and Zn).
(2) And (5) covering and rolling an isolation method. The surface of the gangue hill is covered with loess, fly ash and other inert substances with the thickness of 0.8-1.2 m, and compacted to isolate the external air from entering and prevent oxidation. The method is economical and is widely used at home and abroad. The choice of the covering laminate material should be based on studying the permeability on the basis of taking into account economic and environmental benefits as appropriate, and the air permeability of the composite covering material consisting of natural materials and industrial waste is significantly reduced under the action of the laminate technology. The surface coating must remain airtight throughout the construction and use process. However, the properties of surface coverings are affected by critical parameters such as material height, initial moisture, saturated moisture, performance control, construction quality, etc., and under the alternating effects of sedimentation, shrinkage, drying, precipitation, fire and root intrusion, it is difficult for practical engineering applications to maintain the covering in a highly saturated state and ensure its integrity, presenting significant challenges to its sustainability and oxygen barrier efficiency.
(3) Surface passivation techniques. The passivation coating is constructed on the surface of the gangue pyrite to inhibit chemical reactions such as surface oxidation, surface dissolution, surface adsorption and the like, so that the oxidation reaction of sulfur-containing minerals can be effectively inhibited, and acid production is inhibited. Studies have shown that at pH >Under the condition of 6The pyrite surface can be passivated, and in dynamic leaching experiments and sequencing batch leaching experiments, the oxidation rate can be reduced by about 95%, and the oxidation inhibition efficiency is remarkable. The passivating agents commonly used at present mainly comprise: carbonate (limestone) and silicate (NaSiO) 3 ) Microorganisms, 8-hydroxyquinline, triethylenetetramine (TETA), sodium triethylenetetramine bis-dithiocarbamate (DTC-TETA), organosilanes (gamma-aminopropyl trimethoxysilane (APS), vinyltrimethoxysilane (VTMS), gamma-mercaptopropyl trimethoxysilane (PropS-SH) (oxidation reduced by 89.2%), n-propyl trimethoxysilane (NPS) (total iron reduced by 96% for 70 hours), tetraethylorthosilicate (TEOS), polysiloxanes) and the like. However, this technique adds a large amount of chemical agents to the gangue, which on the one hand costs a large amount of money, and on the other hand introduces additional chemicals, which may cause secondary pollution to the surrounding environment.
(4) Germicide technology. Autotrophic or heterotrophic archaebacteria, prokaryotic microorganisms, eukaryotic microorganism communities in mine environments can promote oxidation of iron and sulfur in sulfur-containing minerals, and release of metal ions and sulfate into the environment is significantly affected. The bactericide can obviously influence the activity of environmental microorganisms and the behavior of the bactericide in the environment, and previous researches show that the bactericide can inhibit the activity of oxidizing bacteria in coal gangue, weaken the biocatalysis in the oxidation process, inhibit the oxidation of sulfur-containing minerals in the coal gangue and the generation of acidic substances, and meanwhile, the sterilization treatment can effectively inhibit the oxidation of ferrous ions in the solution, so that the heat generated in the reaction is reduced, and the acid production of the coal gangue is prevented from the source. Although the bactericide shows excellent oxidation inhibition performance in indoor experiments, the shorter action time restricts popularization and use on site, and the expected effect is difficult to achieve on site as a single technology.
(5) And (5) a cooling method is excavated. The main process is to find the fire source, then dig out the coal gangue which fires and heats, cool or naturally cool with water, then backfill to the original place. The cooling method is simple to apply, and the principle is that the heat preservation capability of a high-temperature area in the gangue is destroyed, so that the gangue rapidly releases heat to the environment, the temperature is rapidly reduced, and the condition of oxidation reaction is lost. The biggest shortcoming of this method is the safety problem, and the waste dump that is uncovered has a large amount of air to get into, easily causes inside combustible gas to reach the explosion limit, causes the explosion. Secondly, the pollution problem is that the excavated coal gangue releases a large amount of high-concentration gaseous pollutants in a short time, and the pollution is caused to the surrounding atmospheric environment. In addition, this method has problems thoroughly, and oxidation reaction may continue after the treatment.
(6) Grouting method. The grouting fire extinguishing method achieves the aim of inhibiting oxidation by the combined action of cooling and oxygen isolation, is a fire extinguishing technology widely adopted at home and abroad at present, and achieves good effect in many hillocks. The process flow is as follows: firstly, preparing the material into slurry with a certain concentration and proportion, then drilling a series of drilling holes in a fire area, and injecting the slurry into the coal gangue by using a grouting pump. After the slurry is contacted with the high-temperature coal gangue, the moisture in the slurry is rapidly evaporated under the action of high temperature, so that a large amount of heat is taken away, and the temperature of the coal gangue is reduced. The rest solid matters in the slurry are covered on the surface of the coal gangue or filled in gaps among the gangue, so that the effect of blocking air is achieved. If the fire-extinguishing slurry contains alkaline substances, a certain amount of sulfide gas released by combustion of the gangue can be absorbed, and the pollution of the gangue to the atmosphere is reduced. The method has the greatest advantages that the method can quickly cool the burnt coal gangue, has a good oxygen isolation effect, and achieves a good practical effect in the practice of the fire extinguishing engineering of the gangue dump. The disadvantage of this method is that it is difficult to drill holes in fire areas, as the ignition of the gangue hill mainly occurs in the slope part, and the slope length of some large gangue hill often exceeds hundred meters. After the gangue mountain burns in a large area, the operation of entering a fire area is quite difficult, the concentration of harmful gas and the ambient temperature are high, the rolling stones above the gangue are prevented from injuring people, and operators have certain dangers.
(7) Inert gas method. The method is based on the principle that a mixture of dry ice and liquid nitrogen is injected into a high-temperature area of the coal gangue hill, the material undergoes phase change to cause volume expansion, and the material can be rapidly diffused to other areas from an injection point to rise to the surface of the coal gangue to extrude low-density air to the ground surface, so that the air is isolated from combustible substances in the coal gangue hill, and the coal gangue hill is synchronously subjected to the process ofCooling and inhibiting oxidation of gangue hill to produce acid. The low-temperature inert gas can keep the inside of the coal gangue hill at a low temperature for a long time, and the final temperature is reduced below the critical temperature. However, inert gas fire extinguishing is currently less common in engineering applications because: (1) the fire extinguishing materials such as liquid nitrogen and dry ice are used under severe transportation and use conditions, and the transportation cost is high; (2) compared with grouting fire extinguishing method, the method has insufficient persistence and stability, N in the pore space of the gangue dump 2 And CO 2 Gradually replaced by air, so that the coal gangue is continuously oxidized; (3) when liquid nitrogen or dry ice undergoes phase change expansion or the pores of the gangue are enlarged, the specific surface area of the gangue is increased, and the oxidization is further accelerated.
(8) Biological methods. The sulfate is reduced into hydrogen sulfide through the action of sulfate reducing bacteria, the pH value of the environment of the coal gangue is improved, meanwhile, heavy metals are precipitated, and the activity of oxidizing bacteria is inhibited due to the change of the living environment. The biological method for inhibiting the oxidation and acid production of the coal gangue hill is a hot spot in the current research, but the biological method for inhibiting the oxidation and acid production of the coal gangue hill is not promoted on a large scale because the large-scale breeding is difficult, target bacteria are not easy to become dominant strains on the coal gangue hill, and the actual application effect is difficult to quantitatively describe.
(9) And (5) a spray blocking isolation layer method. Is a common acid production inhibiting technology for acidic coal gangue hill, and can realize the purposes of long-acting oxygen inhibition and stopping reoxidation to produce acid. The spraying and blocking isolating layer process includes mixing glass fiber, adhesive, ash (lime, loess, flyash, etc.) and water in certain proportion, stirring in slurry sprayer, and adding fireproof fiber and polyacrylamide inhibitor to raise fireproof effect. On the basis of ensuring the flame-retardant effect, the blocking isolation layer can adapt to the settlement deformation of the waste dump to a certain extent. However, this method uses a large amount of glass fiber, binder, lime, refractory fiber, polyacrylamide, and the like, and lacks certain advantages as compared with the method using solid waste as a surface covering material.
Disclosure of Invention
Technical problems:
the method for in-situ inhibition of acid production by oxidation of the acidic coal gangue is environment-friendly, so that the performance of inhibiting acid production of the acidic coal gangue is improved, and the treatment cost is reduced.
The technical conception is as follows:
the inventor has found through a great deal of intensive research on the acid production mechanism of the oxidation of the acid gangue dump that: the combined action of oxygen, water and microorganisms promotes the oxidation reaction of the coal gangue. Based on this, the inventors consider that inhibition of acid production by oxidation of acidic coal gangue hill can be started from the aspects of isolating oxygen infiltration, blocking water infiltration from falling, inhibiting activity of oxidizing bacteria, enhancing activity of reducing bacteria, and the like. Therefore, the method combines a drainage system for blocking and reducing rainfall infiltration, and simultaneously couples an oxygen control (controlling oxidation) acid control (controlling acid production) process for inhibiting oxidation bacterial oxidation acid production, an oxygen isolation (isolating oxygen) acid control process for blocking oxygen infiltration and a vertical blocking process for preventing acid leaching liquor from releasing to the periphery of a storage yard, so that the method can cooperatively inhibit the oxidation acid production of the acid gangue hill in multiple ways, reduces the potential safety hazard of the acid gangue hill and the pollution risk to the environment from the source, provides a feasible solution for the safety management and treatment of the acid gangue hill, and is beneficial to realizing the win-win of safe production, environmental protection and economic development of mining areas.
The technical scheme is as follows:
in one aspect, a comprehensive treatment structure for in-situ inhibition of acid production by oxidation of an acidic coal gangue dump is provided, wherein the acidic coal gangue dump is formed with a top platform, a plurality of horse way platforms, a plurality of slopes and mountainous feet; the top platform is connected with the pavement platform through the slope, the two pavement platforms are connected with each other through the slope, and the pavement platform is connected with the mountain foot through the slope; the inside of the acid coal gangue hill is uniformly provided with an oxygen control and acid control material; the oxygen control and acid control material comprises sulfate reducing bacteria and sodium dodecyl sulfate; an oxygen-isolation acid-control material layer and a soil covering layer are sequentially covered above the gangue layer of the acid coal gangue hill from bottom to top; the oxygen-isolation acid-control material layer comprises, by weight, 100-70 parts of powder clay and 0-30 parts of fly ash; the thickness of the oxygen-isolation and acid-control material layer is not less than 15cm, and the compactness of the oxygen-isolation and acid-control material layer reaches more than 85%; the top platform is provided with a first transverse ecological drainage ditch; a second transverse ecological drainage ditch is arranged on one side of the horse road platform along the slope toe; a plurality of sloping surfaces are provided with longitudinal flexible drainage devices; a hard drainage ditch and a stilling pool are sequentially arranged at the junction of the acidic coal gangue hill and the natural mountain along the terrain from high to low; the first transverse ecological drainage ditch, the second transverse ecological drainage ditch and the hard drainage ditch are communicated through the longitudinal flexible drainage device along the topography of the acidic coal gangue hill from high to low; the hard drainage ditch is communicated with the stilling pool through a pipeline; the first transverse ecological drainage ditch, the second transverse ecological drainage ditch, the hard drainage ditch and the longitudinal flexible drainage device are all formed in the soil covering layer; a three-dimensional barrier wall is further arranged at the lowest position of the land form of the junction of the acidic coal gangue hill and the natural mountain body of the mountain foot; the three-dimensional baffle wall is buried in the natural mountain, and the top end of the three-dimensional baffle wall is level with the surface layer of the natural mountain; the three-dimensional baffle wall comprises a filler pool, a water distribution wall, a reaction wall, a water outlet wall and a crushed stone layer; the water distribution wall, the reaction wall and the water outlet wall are sequentially formed in the filler pool along the direction away from the acidic coal gangue hill; the top parts of the water distribution wall, the reaction wall and the water outlet wall are respectively provided with the gravel layer; the filler of the reaction wall is limestone; the fillers of the water distribution wall and the water outlet wall are crushed stone and quartz sand.
In some embodiments, the oxygen barrier acid control material layer is replaced with a composition of: according to the weight portions, the powder soil comprises 100 to 50 portions of powder soil and 0 to 50 portions of fly ash; the thickness of the oxygen-isolation and acid-control material layer is not lower than 75cm, and the compactness of the oxygen-isolation and acid-control material layer reaches more than 85%.
In some embodiments, the oxygen control and acid control material is obtained by mixing sulfate reducing bacteria liquid and sodium dodecyl sulfate aqueous solution with the concentration of 50mg/L according to the volume ratio of 1:20; wherein sulfurAs the acid salt-reducing bacterial solution, bacterial solution (OD) 600 0.6 to 0.8).
In some embodiments, the oxygen barrier acid control material layer has a moisture content of 18% to 22%.
In some embodiments, the cross sections of the first and second lateral ecological drains are inverted trapezoids; the first transverse ecological drainage ditch and the second transverse ecological drainage ditch are respectively provided with a multi-layer seepage-proofing structure; the multi-layer seepage-proofing structure sequentially comprises a water stabilizing layer, a main material layer, a bentonite layer, a composite geomembrane layer and an ecological bag layer from bottom to top; the material composition of the water stabilization layer comprises graded broken stone, fly ash, cement and water; the paving thickness of the water stabilization layer is 3-5 cm; the paving thickness of the main material layer is 4cm; the main material layer comprises the following materials: a mixture of steel slag, fly ash and desulphurized ash; or a mixture of slag, fly ash and desulphurized ash; the paving thickness of the bentonite layer is 1cm, and the bentonite layer accounts for 5% -25% of the total weight of the bentonite layer and the main material layer; the composite geomembrane layer is laid above the bentonite layer, on each side surface of the first transverse ecological drainage ditch and on each side surface of the second transverse ecological drainage ditch; the cloth surface of the composite geomembrane layer faces downwards and contacts with the bentonite layer; the ecological bag layer is arranged above the composite geomembrane layer and is used for pressing.
In some embodiments, in the water stable layer: the maximum grain size of the graded broken stone is not more than 30mm; the weight ratio of cement to pulverized fuel ash to graded broken stone is 4:10:86, and the water-cement ratio is 0.4.
In some embodiments, in the primary material layer: the weight ratio of the steel slag to the fly ash to the desulfurized fly ash is 60:30:10; or the weight ratio of slag, fly ash and desulfurized ash is 60:30:10.
In some embodiments, the longitudinal flexible drain comprises a bellows, a screw steel, and an ecological bag layer; the middle part of the bent screw thread steel surrounds the corrugated pipe, and two ends of the screw thread steel sequentially extend into the earthing layer and the gangue layer, so that the corrugated pipe is fixed on the acid coal gangue dump; and pressing the ecological bag layer above the corrugated pipe.
In some embodiments, the bellows has a diameter of 300mm and a burial depth of 400mm.
In some embodiments, the spacing between two adjacent longitudinal flexible drains on the same slope is 100m.
In another aspect, a method for in situ inhibition of acid production by oxidation of acidic coal gangue dump is provided, comprising the steps of:
(1) Spraying oxygen-control acid-control material: spraying oxygen-controlling and acid-controlling materials at intervals before the coal gangue is piled up to the surface covering construction of the acid coal gangue dump; the oxygen control and acid control material comprises sulfate reducing bacteria and sodium dodecyl sulfate; the working temperature of the oxygen control and acid control material is 10-40 ℃;
(2) Covering an oxygen-isolation acid-control material: after the acid coal gangue hill is shaped and prepared, covering an oxygen-isolation and acid-control material above a gangue layer of the acid coal gangue hill, carrying out layered rolling, and covering a soil covering layer above the oxygen-isolation and acid-control material; the oxygen-isolation acid-control material layer comprises, by weight, 100-70 parts of powder clay and 0-30 parts of fly ash; the thickness of the oxygen-isolation and acid-control material layer is not less than 15cm, and the compactness of the oxygen-isolation and acid-control material layer reaches more than 85%;
(3) And (3) arranging a drainage system: the acidic coal gangue hill is formed with a top platform, a plurality of pavement platforms, a plurality of slopes and hill feet; the top platform is connected with the pavement platform through the slope, the two pavement platforms are connected with each other through the slope, and the pavement platform is connected with the mountain foot through the slope; the top platform is provided with a first transverse ecological drainage ditch; a second transverse ecological drainage ditch is arranged on one side of the horse road platform along the slope toe; a plurality of sloping surfaces are provided with longitudinal flexible drainage devices; a hard drainage ditch and a stilling pool are sequentially arranged at the junction of the acidic coal gangue hill and the natural mountain along the terrain from high to low; the first transverse ecological drainage ditch, the second transverse ecological drainage ditch and the hard drainage ditch are communicated through the longitudinal flexible drainage device along the topography of the acidic coal gangue hill from high to low; the hard drainage ditch is communicated with the stilling pool through a pipeline; the first transverse ecological drainage ditch, the second transverse ecological drainage ditch, the hard drainage ditch and the longitudinal flexible drainage device are all formed in the soil covering layer;
(4) Setting a three-dimensional baffle wall: a three-dimensional barrier wall is further arranged at the lowest position of the land form of the junction of the acidic coal gangue hill and the natural mountain body of the mountain foot; the three-dimensional baffle wall is buried in the natural mountain, and the top end of the three-dimensional baffle wall is level with the surface layer of the natural mountain; the three-dimensional baffle wall comprises a filler pool, a water distribution wall, a reaction wall, a water outlet wall and a crushed stone layer; the water distribution wall, the reaction wall and the water outlet wall are sequentially formed in the filler pool along the direction away from the acidic coal gangue hill; the top parts of the water distribution wall, the reaction wall and the water outlet wall are respectively provided with the gravel layer; the filler of the reaction wall is limestone; the fillers of the water distribution wall and the water outlet wall are crushed stone and quartz sand.
In some embodiments, the oxygen barrier acid control material layer is replaced with a composition of: according to the weight portions, the powder soil comprises 100 to 50 portions of powder soil and 0 to 50 portions of fly ash; the thickness of the oxygen-isolation and acid-control material layer is not lower than 75cm, and the compactness of the oxygen-isolation and acid-control material layer reaches more than 85%.
In some embodiments, before step (1), further comprising the steps of: diagnosis of coal gangue hill acidity: oxidizing coal gangue samples with hydrogen peroxide to accelerate the simulated long-term natural oxidation process with net acid yield w (NAG, kg/t, H) 2 SO 4 Meter) the net acid production during the chemical oxidation of the coal gangue, in determining the w (NAG) of the coal gangue sample>50, then the acid coal gangue hill is diagnosed.
The beneficial effects are that:
1. the invention provides a method for in-situ inhibition of acid production by oxidation of an acidic coal gangue hill, which combines a drainage system for blocking rainfall infiltration, and simultaneously couples an oxygen control and acid control process for inhibiting oxidation and acid production by oxidizing bacteria, an oxygen isolation and acid control process for blocking oxygen infiltration and a vertical blocking process for preventing release of acidic leachate to the periphery of a storage yard, and the method cooperatively inhibits the acid production by oxidation of the acidic coal gangue hill in multiple ways, so that the potential safety hazard of the acidic coal gangue hill and the pollution risk to the environment are reduced from the source, a feasible solution is provided for safety management and treatment of the acidic coal gangue hill, and the win-win effect of realizing safe production, environmental protection and economic development of a mining area is facilitated. Compared with the existing terminal treatment technology, the method greatly reduces the difficulty of pollutant treatment, reduces the treatment cost, and can effectively control the release of acidic gangue pollutants to the surrounding environment for a long time.
2. The method for in-situ inhibition of acid production by oxidation of the acidic coal gangue hill improves the performance of inhibiting acid production of the acidic coal gangue hill and reduces the treatment cost. The method has the advantages of wide sources of materials, simple construction process, strong operability and low cost, can radically reduce the acid yield, effectively inhibit pollution of the gangue storage yard to the atmosphere, surface water, underground water and surrounding soil, and has remarkable effect.
Drawings
FIG. 1 is a schematic illustration of a synthetic abatement structure for inhibiting acid production from acidic coal gangue dump oxidation in situ, as provided in some embodiments;
FIG. 2 is an effect of oxygen control acid control material on sulfate concentration, with or without some embodiments;
FIG. 3 is an effect of oxygen and acid control materials on pH with or without some embodiments;
FIG. 4 is a cross-sectional view of a lateral ecological drain provided by some embodiments;
FIG. 5 is a cross-sectional view of a longitudinally flexible drain provided by some embodiments;
fig. 6 is a schematic structural view of a three-dimensional barrier wall provided in some embodiments.
Detailed Description
In one aspect, a comprehensive treatment structure for in-situ inhibition of acid production by oxidation of an acidic coal gangue dump is provided, as shown in fig. 1, the acidic coal gangue dump 1 is formed with a top platform 10, a plurality of horse road platforms 20, a plurality of sloping surfaces 30 and mountain feet 40; the top platform 10 is connected with the pavement platform 20 through a slope 30, the two pavement platforms 20 are connected through a slope 30, and the pavement platform 20 is connected with the mountain feet 40 through a slope 30; the inside of the acid coal gangue hill 1 is uniformly provided with oxygen control and acid control materials; the oxygen control and acid control material comprises sulfate reducing bacteria 3 and sodium dodecyl sulfate 2; an oxygen-isolation acid-control material layer 4 and a soil covering layer 50 are sequentially covered above the gangue layer of the acid coal gangue hill 1 from bottom to top; the oxygen-isolation acid-control material layer 4 comprises 100-70 parts of powder clay and 0-30 parts of fly ash according to parts by weight; the thickness of the oxygen-isolation and acid-control material layer 4 is not less than 15cm, and the compactness of the oxygen-isolation and acid-control material layer 4 is more than 85%; the top platform 10 is provided with a first lateral ecological drain 51; a second transverse ecological drainage ditch 52 is arranged on one side of the catwalk platform 20 along the slope toe; the plurality of slopes 30 are provided with longitudinal flexible drainage means 6; a rigid drainage ditch 7 and a stilling basin 8 are sequentially arranged at the junction of the acidic coal gangue hill 1 of the mountain foot 40 and the natural mountain 60 along the terrain from high to low; the first transverse ecological drainage ditch 51, the second transverse ecological drainage ditch 52 and the hard drainage ditch 7 are communicated through the longitudinal flexible drainage device 6 along the topography of the acid coal gangue hill 1 from high to low; the hard drainage ditch 7 is communicated with the stilling pool 8 through a pipeline; the first lateral ecological drainage ditch 51, the second lateral ecological drainage ditch 52, the hard drainage ditch 7 and the longitudinal flexible drainage device 6 are all formed in the soil covering layer 50; a three-dimensional barrier wall 9 is arranged at the lowest position of the land pattern at the junction of the acidic coal gangue hill 1 and the natural mountain 60 of the mountain foot 40; the three-dimensional baffle wall 9 is buried in the natural mountain 60, and the top end of the three-dimensional baffle wall 9 is level with the surface layer of the natural mountain 60; as shown in fig. 6, the three-dimensional barrier wall 9 includes a filler pool, a water distribution wall 91, a reaction wall 92, a water outlet wall 93, and a crushed stone layer; the water distribution wall 91, the reaction wall 92 and the water outlet wall 93 are sequentially formed in the filler pool along the direction away from the acid coal gangue hill 1; the tops of the water distribution wall 91, the reaction wall 92 and the water outlet wall 93 are respectively provided with a gravel layer; the filler of the reaction wall 92 is limestone; the fillers of the water distribution wall 91 and the water outlet wall 92 are crushed stone and quartz sand.
In some embodiments, the oxygen barrier acid control material layer 4 is replaced with a composition of: according to the weight portions, the powder soil comprises 100 to 50 portions of powder soil and 0 to 50 portions of fly ash; the thickness of the oxygen-isolation and acid-control material layer 4 is not less than 75cm, and the compactness of the oxygen-isolation and acid-control material layer 4 is more than 85%.
In some embodiments, the oxygen control and acid control material is obtained by mixing sulfate reducing bacteria liquid and dodecyl sodium sulfate aqueous solution with the concentration of 50mg/L according to the volume ratio of 1:20; among them, sulfate-reducing bacteria liquid (OD) in the logarithmic growth phase was used 600 0.6 to 0.8).
In some embodiments, the oxygen barrier acid control material layer 4 has a moisture content of 18% to 22%.
In some embodiments, as shown in fig. 4, the cross sections of the first and second lateral ecological drains 51 and 52 are inverted trapezoids; the first and second lateral ecological drainage ditches 51 and 52 are respectively provided with a multi-layer seepage-proofing structure; the multi-layer seepage-proofing structure sequentially comprises a water stabilizing layer 511, a main material layer 512, a bentonite layer 513, a composite geomembrane layer 514 and an ecological bag layer 515 from bottom to top; the material composition of the water stabilization layer 511 comprises graded broken stone, fly ash, cement and water; the paving thickness of the water stabilization layer 511 is 3-5 cm; the main material layer 512 was laid to a thickness of 4cm; the main material layer 512 has a material composition of: a mixture of steel slag, fly ash and desulphurized ash; or a mixture of slag, fly ash and desulphurized ash; the paving thickness of the bentonite layer 513 is 1cm, and the bentonite layer 513 accounts for 5% -25% of the total weight of the bentonite layer 513 and the main material layer 512; the composite geomembrane layer 514 is laid above the bentonite layer 513, on each side of the first lateral ecological drain 51 and on each side of the second lateral ecological drain 52; and the cloth surface of the composite geomembrane layer 514 faces downwards and contacts the bentonite layer 513; the ecological bag layer 515 is disposed above the composite geomembrane layer 514 for capping.
In some embodiments, in the water stabilization layer 511: the maximum grain size of the graded broken stone is not more than 30mm; the weight ratio of cement to pulverized fuel ash to graded broken stone is 4:10:86, and the water-cement ratio is 0.4.
In some embodiments, in the primary material layer 512: the weight ratio of the steel slag to the fly ash to the desulfurized fly ash is 60:30:10; or the weight ratio of slag, fly ash and desulfurized ash is 60:30:10.
In some embodiments, as shown in fig. 5, the longitudinal flexible drain 6 comprises a bellows 61, a screw steel 62, and an ecological bag layer 63; the middle part of the bent screw steel 62 surrounds the corrugated pipe 61, and both ends of the screw steel 62 sequentially extend into the overburden layer 50 and the gangue layer, so that the corrugated pipe 61 is fixed on the acid gangue dump 1; the roof is pressed by providing an ecological bag layer 63 above the bellows 61.
In some embodiments, the bellows 61 has a diameter of 300mm and a burial depth of 400mm.
In some embodiments, the spacing between two adjacent longitudinal flexible drains 6 on the same slope is 100m.
In another aspect, a method for in situ inhibition of acid production by oxidation of acidic coal gangue dump is provided, comprising the steps of:
(1) Spraying oxygen-control acid-control material: spraying oxygen-controlling and acid-controlling materials at intervals before the coal gangue is piled up to the surface covering construction of the acid coal gangue dump; the oxygen control and acid control material comprises sulfate reducing bacteria and sodium dodecyl sulfate; the working temperature of the oxygen control and acid control material is 10-40 ℃;
(2) Covering an oxygen-isolation acid-control material: after the acid coal gangue hill is shaped and prepared, covering an oxygen-isolation and acid-control material above a gangue layer of the acid coal gangue hill, carrying out layered rolling, and covering a soil covering layer above the oxygen-isolation and acid-control material; the oxygen-isolation acid-control material layer comprises, by weight, 100-70 parts of powder clay and 0-30 parts of fly ash; the thickness of the oxygen-isolation and acid-control material layer is not less than 15cm, and the compactness of the oxygen-isolation and acid-control material layer reaches more than 85 percent;
(3) And (3) arranging a drainage system: the acidic coal gangue hill is formed with a top platform, a plurality of horse road platforms, a plurality of slopes and hill feet; the top platform is connected with the pavement platform through a slope surface, the two pavement platforms are connected through a slope surface, and the pavement platform is connected with the mountain foot through a slope surface; the top platform is provided with a first transverse ecological drainage ditch; a second transverse ecological drainage ditch is arranged on one side of the horse road platform along the slope toe; the sloping surfaces are provided with longitudinal flexible drainage devices; a rigid drainage ditch and a stilling pool are sequentially arranged at the junction of the acidic gangue hill of the mountain foot and the natural mountain body along the topography from high to low; the first transverse ecological drainage ditch, the second transverse ecological drainage ditch and the hard drainage ditch are communicated through a longitudinal flexible drainage device along the topography of the acidic coal gangue hill from high to low; the hard drainage ditch is communicated with the stilling pool through a pipeline; the first transverse ecological drainage ditch, the second transverse ecological drainage ditch, the hard drainage ditch and the longitudinal flexible drainage device are all formed in the soil covering layer;
(4) Setting a three-dimensional baffle wall: a three-dimensional barrier wall is arranged at the lowest position of the land at the junction of the acidic gangue hill of the mountain foot and the natural mountain body; the three-dimensional baffle wall is buried in the natural mountain body, and the top end of the three-dimensional baffle wall is level with the surface layer of the natural mountain body; the three-dimensional baffle wall comprises a filler pool, a water distribution wall, a reaction wall, a water outlet wall and a crushed stone layer; the water distribution wall, the reaction wall and the water outlet wall are sequentially formed in the filler pool along the direction away from the acid gangue hill; the tops of the water distribution wall, the reaction wall and the water outlet wall are respectively provided with a rubble layer; the filler of the reaction wall is limestone; the fillers of the water distribution wall and the water outlet wall are crushed stone and quartz sand.
In some embodiments, the oxygen barrier acid control material layer is replaced with a composition of: according to the weight portions, the powder soil comprises 100 to 50 portions of powder soil and 0 to 50 portions of fly ash; the thickness of the oxygen-isolation and acid-control material layer is not less than 75cm, and the compactness of the oxygen-isolation and acid-control material layer reaches more than 85%.
In some embodiments, before step (1), further comprising the steps of: diagnosis of coal gangue hill acidity: oxidizing coal gangue samples with hydrogen peroxide to accelerate the simulated long-term natural oxidation process with net acid yield w (NAG, kg/t, H) 2 SO 4 Meter) the net acid production during the chemical oxidation of the coal gangue, in determining the w (NAG) of the coal gangue sample>50, then the acid coal gangue hill is diagnosed.
Example 1
In order to overcome the defects of poor effect and high terminal treatment cost of the existing single repair method, and effectively inhibit acid production of acidic coal gangue. The method for inhibiting the oxidation and acid production of the acid gangue hill is formed by combining an oxygen control and acid control process for inhibiting the oxidation and acid production of oxidizing bacteria, an oxygen isolation and acid control process for inhibiting the oxygen infiltration and a three-dimensional blocking process for preventing the release of acid leachate to the periphery of a storage yard from being carried out by starting with the acid diagnosis of the gangue hill and combining a drainage system for blocking the rainfall infiltration, and the method for inhibiting the oxidation and acid production of the acid gangue hill in situ is formed by multiple paths of cooperation.
1. Acid diagnosis of gangue hill (gangue yard)
The coal gangue can be divided into acidic coal gangue and non-acidic gangue according to the acid production characteristic of the coal gangue. Previous researches show that the components of the coal gangue are complex, the pH value is only used for reflecting the acidity and alkalinity of the coal gangue, and the real acid yield of each component of the coal gangue cannot be really obtained. In order to improve the accuracy of the acid diagnosis result of the gangue storage yard, the invention calculates the net acid yield w (NAG, kg/t, H) of the gangue through the net acid yield experiment 2 SO 4 Meter). Criteria for determining whether ore is acid producing or not using w (NAG): when w (NAG)>At 50, minerals have extremely strong acidogenic potential; when w (NAG) =2-50, minerals have a certain acid potential; when w (NAG) =0 to 2, minerals generally do not cause acidic contamination. Thus, in the present invention, w (NAG) of a coal refuse sample is determined>50, then the acid coal gangue hill is diagnosed.
Net acid yield experiments with strong oxidizer hydrogen peroxide (H 2 O 2 ) Oxidizing gangue samples to accelerate the simulated long-term natural oxidation process with a net acid yield w (NAG, kg/t, H) 2 SO 4 Meter) measures the net acid production in the chemical oxidation process of the gangue, thereby comprehensively judging the acid production condition of the gangue. The specific method for the net acid yield experiment is as follows:
randomly taking 4 samples at 20cm of the surface layer of each sampling point of the waste dump, and mixing the samples into one sample; the sample is air-dried and then is sieved by a 1mm sieve; a sample of 2.5g was taken and added to a 500mL Erlenmeyer flask, followed by 250mL of 15% hydrogen peroxide (H 2 O 2 ) Covering the glass cover with the aqueous solution, and placing the aqueous solution in a fume hood for 24 hours; then heating by using an electric hot plate to remove residual H 2 O 2 Stopping adding until boiling or bubbling is stoppedHeat, taking care that a small amount of distilled water is added to the flask as appropriate to prevent boiling dry, and cooling to room temperature. Measuring pH of the material in the conical flask by acid-base neutralization titration to obtain NAG-pH, and calculating net acid yield w (NAG, kg/t, in H) 2 SO 4 Meter). Wherein:
acid-base neutralization titration: titration of the flask contents to pH 7 with 0.1mol/L NaOH solution, recording of the volume v of 0.1mol/L NaOH solution used for the acid-base titration, and calculation of the net acid yield w (NAG, kg/t, in H) according to the following formula 2 SO 4 Meter):
w(NAG)＝(0.1×v×49)/m
wherein:
v-the volume of 0.1mol/L NaOH solution used for acid-base titration in milliliters (mL);
m-coal gangue sample mass, the unit is gram (g); where m=2.5.
2. Oxygen control and acid control procedure-spraying oxygen control and acid control material (SDS+SRB)
When the acid gangue is diagnosed as the acid gangue hill, the gangue is piled up from the beginning to the end of soil preparation and shaping, and then the oxygen control and acid control material is sprayed at intervals before the surface covering construction, so that the oxidation and acid production of the gangue are controlled in a short period of time.
Screening oxygen-control acid-control materials:
the acidophilic ferrous oxide thiobacillus (Acidithiobacillus ferrooxidans, A.f bacteria) in the acid coal gangue hill plays a catalytic role in the acidogenesis reaction, and can increase the acidogenesis reaction rate by about 10 6 Multiple times. The proper environment-friendly organic bactericide is selected to inhibit the growth of A.f bacteria, which has great significance for controlling the acid production by oxidation. The inventor screens out A.f bacteria from acid gangue hill leaching water, and tests and compares the sterilizing effect of three environment-friendly organic bactericides of Sodium Dodecyl Sulfate (SDS), triclosan and pinocembrin on A.f bacteria. The research results show that: all three bactericides can maintain the bacteriostasis rate of more than 80 percent and can effectively inhibit the oxidation and acid production. The minimum inhibitory concentrations of SDS, triclosan and pinus koraiensis on A.f bacteria are 10mg/L, 16mg/L and 30mg/L, respectively (the minimum inhibitory concentration means the minimum concentration which can effectively inhibit the activity of A.f bacteria, and sterilize)The concentration of the agent is continuously increased, and the antibacterial effect is not obviously improved).
The inventor separates Sulfate Reducing Bacteria (SRB) from acid gangue, and researches show that the SRB contains SO in a culture solution within 10 days 4 2- The removal rate reaches 73.41%, the pH of the culture solution is raised from 6.83 to 7.86, and the culture solution is kept stable, so that the acid production performance is well controlled.
In order to explore the formula of oxygen-controlling acid-controlling material which can effectively kill A.f bacteria and does not affect the normal growth of SRB, SDS, triclosan and pinocembrin are respectively used for acting on SRB, and the minimum antibacterial concentration of the material is studied. The research results show that: the minimum inhibitory concentrations of SDS, triclosan and pinocembrane on SRB are respectively: 15mg/L, 8mg/L and 15-30 mg/L. As can be seen, SRB is best resistant to SDS, and SDS solutions at concentrations below 15mg/L do not inhibit the normal growth of SRB. Thus, SDS may be combined with SRB to form an oxygen and acid control material to which SDS is coupled with SRB.
SRB artificial domestication:
SRB was inoculated by artificial acclimation to a medium containing SDS alone as a single carbon source to increase the tolerance of SRB to SDS to 50mg/L.
The ability and efficiency of SRB to degrade SDS in solution was investigated. The research results show that: SRB can decompose SDS to meet the requirement of self-growth on energy and electron donor, and the degradation rate of SDS can reach 86.90% after 7 d.
The oxygen-controlling acid-controlling material in this example mainly includes an organic bactericide and sulfate-reducing bacteria (SRB) that inhibit the activity of oxidizing bacteria. Wherein the organic bactericide is Sodium Dodecyl Sulfate (SDS). The oxygen control and acid control material is in a solution form and is prepared by mixing Sodium Dodecyl Sulfate (SDS), sulfate Reducing Bacteria (SRB) and water. Specifically, the oxygen control and acid control material is prepared by mixing SRB bacterial liquid and SDS aqueous solution with the concentration of 50mg/L according to the volume ratio of 1:20; among them, bacterial solutions in the logarithmic phase (OD 600 of 0.6 to 0.8) were used as SRB bacterial solutions.
It should be noted that: the SRB has higher activity at 10-40 ℃, so that the working temperature of the oxygen control and acid control material is 10-40 ℃; it is forbidden to mix with other bactericides. In order to ensure the effect of controlling the oxidation and acid production of the gangue, the oxygen-control acid-control material needs to be stored in a sealed way at normal temperature in a dark place and is uniformly shaken before use. In preparing the oxygen control and acid control material, the adopted device is clean and the water temperature is not higher than 40 ℃.
Frequency and amount of application: for acid coal gangue hill with stacking time estimated to be longer than 30 days, the oxygen and acid control material should be sprayed once every 10-15 days to ensure that a proper amount of SDS kills oxidizing bacteria and that SRB has enough carbon source for growth and reproduction. The dosage of the oxygen-control acid-control material sprayed each time is 3-4L/m 2 。
The application method comprises the following steps: and according to the area size of the acid coal gangue hill, a watering can or a watering cart is selected for spraying.
Performance test:
the oxygen control and acid control material is used for verifying the use effect in a laboratory by using a leaching column. The diameter of the leaching column is 10cm, and the height is 40cm. And (3) air-drying the coal gangue, crushing and sieving. The lower end 20cm of the leaching column is filled with coal gangue with the particle size smaller than 5mm, and the upper end 20cm of the leaching column is filled with coal gangue with the particle size of 5-10 mm.
Spraying oxygen-control acid-control material: 10mL of the oxygen control and acid control material of the previous embodiment is added into the leaching column every day, the leaching solution is collected, and the sulfate ion concentration and the pH value of the leaching solution are tested;
oxygen and acid control materials were not used (control): adding 10mL of water into another leaching column every day, collecting leaching solution, and testing the sulfate ion concentration and pH value;
as a result, as shown in fig. 2 and 3, the spray of the oxygen-controlling acid-controlling material (SDS and SRB) was superior in oxygen-controlling acid-controlling effect compared to the case where the oxygen-controlling acid-controlling material was not used: on the fifth day, the concentration of sulfate ions in the leaching solution obtained by the experimental group using the oxygen control and acid control material is as low as 94.5mg/L, the concentration of sulfate ions in the leaching solution of the control group is 709.5mg/L, and the acid production inhibition rate reaches the maximum value of 86.68%. The pH was raised from 5.12 to 6.06 in the short term (2 d) and remained relatively stable for at least 9 d. In addition, the inventors have found through research that the oxygen and acid control effect of the oxygen and acid control material containing SDS and SRB is significantly better than that of SDS alone and SRB alone.
3. Oxygen-isolation and acid-control procedure-surface covering oxygen-isolation and acid-control material and rolling
After the coal gangue hill is shaped and prepared, the surface of the coal gangue hill is covered with oxygen-isolation and acid-control materials (loess, lime, fly ash, powder clay, silt and the like) and rolled to achieve low enough permeability to inhibit oxygen infiltration.
The oxygen-isolation acid-control material adopts the following formula A or formula B, and the weight parts are as follows:
A. 100-70 parts of powdery clay and 0-30 parts of fly ash;
B. 100-50 parts of silt and 0-50 parts of fly ash;
the water content of the oxygen-isolation and acid-control material is kept between 18% and 22%.
When the oxygen-isolation and acid-control material of the formula A is adopted, the covering thickness of the oxygen-isolation and acid-control material is 15cm;
when oxygen-barrier acid-controlling material of formula B is used, the covering thickness of the oxygen-barrier acid-controlling material is 75cm.
And (5) layering and rolling during rolling. When the loose paving thickness is 30 cm-40 cm, the roller with the weight of 4t is used for flat rolling for 3-5 times, so that the compactness reaches more than 85%. For the coal gangue hill with strong oxidation phenomenon and tendency, the rolling of the top surface and the slope surface is enhanced, for example, the important rolling is needed for increasing the covering thickness and the rolling strength.
And (3) performance optimization test of the oxygen-isolation acid-control material:
air permeabilities of different oxygen barrier acid control materials were tested under laboratory conditions using an air permeameter.
According to the research of the invention, the following is found:
(1) The air permeability of the oxygen-isolating and acid-controlling material increases with the increase of the content of the fly ash in the oxygen-isolating and acid-controlling material, namely the oxygen-isolating performance of the oxygen-isolating and acid-controlling material gradually decreases with the increase of the content of the fly ash in the oxygen-isolating and acid-controlling material.
(2) When the oxygen-insulating and acid-controlling material of the formula A is adopted, namely, the fly ash content in the oxygen-insulating and acid-controlling material of the formula A is 30 parts, the permeability of the oxygen-insulating and acid-controlling material is 3.14X10 -15 m 2 The method comprises the steps of carrying out a first treatment on the surface of the When the oxygen-isolating and acid-controlling material of the formula B is adopted, namely, the content of the fly ash in the oxygen-isolating and acid-controlling material of the formula B is 50 partsThe permeability of the oxygen-isolation acid-control material is 4.49 multiplied by 10 -14 m 2 . The air permeability of the oxygen-isolation and acid-control material adopting the formula A and the formula B is smaller than the air permeability requirement (2 multiplied by 10) of oxygen-isolation and flame-proofing of a coal gangue storage yard -13 m 2 ). And when the content of the fly ash in the oxygen-isolation and acid-control material of the formula A is more than 30 parts, or the content of the fly ash in the oxygen-isolation and acid-control material of the formula B is more than 50 parts, the air permeability of the oxygen-isolation and acid-control material is obviously increased.
(3) After determining the formulation of the oxygen barrier acid control material based on the target air permeability of the oxygen barrier acid control material, the coverage thickness is calculated using the darcy formula.
Wherein:
l' —the theoretically calculated coverage thickness in centimeters (cm);
K-permeability of different oxygen-barrier acid-controlling materials (covering materials), unit is square meter (m) 2 ) The method comprises the steps of carrying out a first treatment on the surface of the The K value of the formula A in the invention is 3.14X10 -15 m 2 The K value of the formula B is 4.49 multiplied by 10 -14 m 2 ；
Mu-dynamic viscosity coefficient of air, the unit is Pa.s;
P limiting the limit The assumed high-limit pressure difference takes the value of 10KPa;
v critical of The critical speed of spontaneous combustion of gangue hill is 4.4 multiplied by 10 -5 m·s -1 。
Darcy's law states that: the air permeation velocity v in the cover layer is related to the permeability K of the cover material (oxygen barrier acid control material), the cover thickness L, and the internal and external pressure difference Δp of the gangue hill. Under certain conditions, the covering thickness L (air seepage distance) is increased, and the change of the pressure gradient can be reduced, so that the seepage speed is effectively reduced. Therefore, in order to ensure that the air seepage velocity in the oxygen-separation acid-control material layer and the coal gangue hill does not exceed the spontaneous combustion critical velocity, a certain covering thickness is ensured.
Air permeation according to oxygen barrier acid control materialThe test result of the rate, the critical seepage velocity is selected to be 4.4x10 -5 m·s -1 The Darcy formula calculates the necessary thickness (thickness after compaction) of the oxygen barrier acid control material at a high differential pressure of 10 KPa. The research finds that:
the single powder clay is used as an oxygen-isolation and acid-control material, and the covering thickness is at least 15cm; when the oxygen-isolation and acid-control material of the formula A is adopted, namely, when the content of the fly ash in the oxygen-isolation and acid-control material of the formula A is 30 parts, the covering thickness of the oxygen-isolation and acid-control material is at least 15cm; therefore, compared with single powder clay, the oxygen-isolation and acid-control material of the formula A can save 30% of powder clay.
The single silt is used as an oxygen-isolation and acid-control material, and the covering thickness is at least 60cm; when the oxygen-isolation and acid-control material of the formula B is adopted, namely, when the content of the fly ash in the oxygen-isolation and acid-control material of the formula B is 50 parts, the covering thickness of the oxygen-isolation and acid-control material is at least 75cm; therefore, compared with single silt, the oxygen-isolation and acid-control material in the formula B can save 37.5% of silt.
4. Drainage system
4.1 setting a transverse ecological drainage ditch
After the oxygen isolation and acid control process is finished, a first transverse ecological drainage ditch is arranged on a top platform of the coal gangue dump; a second transverse ecological drainage ditch is arranged on the catwalk platform along the slope toe; and digging a transverse ecological drainage ditch with a proper size on the earthing layer.
As shown in fig. 4, the cross section of the lateral ecological drainage ditch is in an inverted trapezoid shape. The bottom and the side of the transverse ecological drainage ditch are respectively provided with an anti-seepage structure so as to prevent rainwater from penetrating into the acidic coal gangue hill from the transverse ecological drainage ditch. The seepage-proofing structure at the bottom of the transverse drainage ditch comprises a water stabilizing layer 511, a mixed material layer, a composite geomembrane layer 514 and an ecological bag layer 515 from bottom to top. The seepage-proofing structure of the lateral side of the transverse drainage ditch is sequentially provided with a composite geomembrane layer 514 and an ecological bag layer 515 from bottom to top.
Water stabilization layer 511: the water-stable layer material mainly comprises graded broken stone, fly ash, cement and water. Wherein: the cement for the water stabilization layer is selected from cement with the mark less than or equal to 42.5 and the final setting time less than or equal to 3 hours. The graded broken stone adopts artificial graded broken stone, and the maximum grain diameter of the broken stone is not more than 30mm; cement in the water stabilization layer 511: fly ash: the weight ratio of the artificial graded broken stone is 4:10:86, and the water-cement ratio is 0.4. The paving thickness of the water stabilization layer 511 is 3-5 cm, and the water stabilization layer is timely rolled and formed by vibration equipment in the paving and shaping process.
Mixing material layers: the mixed material layer is a main material layer 512 and a bentonite layer 513 sequentially from bottom to top. The primary material layer 512 may be a mixture of steel slag, fly ash and desulfurized ash, or a mixture of slag, fly ash and desulfurized ash, steel slag (or slag): fly ash: the mass ratio of the desulfurization ash is 60:30:10; the paving thickness of the main material layer 512 is 4cm; the components in the primary material layer 512 are uniformly mixed. The bentonite layer 513 accounts for 5% -25% of the total weight of the mixed material layers, and the paving thickness of the bentonite layer 513 is 1cm. And (5) after the mixed material layer is paved, rolling and forming by using vibration equipment.
Composite geomembrane layer 514: a composite geomembrane layer 514 (a cloth membrane) is laid above the mixed material layer and on the side surface of the transverse ecological drainage ditch, wherein the cloth surface of the composite geomembrane layer 514 faces downwards and contacts with the bentonite layer 513.
Ecological bag layer 515: an ecological bag layer 515 is arranged on the upper side of the composite geomembrane layer 514 and the side surface of the transverse ecological drainage ditch to press the roof.
4.2 longitudinal Flexible drainage device
A longitudinal flexible drainage device 6 is arranged at each grade slope of the acidic coal gangue dump 1. As shown in fig. 5, the longitudinal flexible drain 6 includes a bellows 61, a screw steel 62, and an ecological bag layer 63. During construction, firstly, excavating an overburden layer above the acid coal gangue hill 1, and paving a corrugated pipe 61 in the overburden layer, wherein the diameter of the corrugated pipe 61 is 300mm, and the burial depth is 400mm; the middle part of the bent threaded steel 62 with the diameter of 12mm surrounds the corrugated pipe 61, and both ends of the threaded steel 62 sequentially extend into the overburden layer 50 and the gangue layer, so that the corrugated pipe 61 is fixed on the acid gangue dump; the upper part of the corrugated pipe 61 is pressed by an ecological bag layer 63; and finally backfilling the overburden 50. The longitudinal flexible drainage devices of the slope surfaces of all levels are distributed in a staggered way; the distance between the two longitudinal flexible drainage devices on the slope surface is 100m.
4.3 setting hard drainage ditch
As shown in fig. 1, a hard drainage ditch 7 is provided at the junction of an acidic coal gangue dump and a natural mountain. The size of the hard drainage ditch is determined according to technical Specification for conservation of Water and soil of Water conservancy and hydropower engineering SL575, and the local flood control standard is met. The section of the hard drainage ditch 7 is rectangular, the bottom width of the hard drainage ditch 7 is 1.0m, and the depth of the hard drainage ditch 7 is 0.6m;
because the gradient of the position where the hard drainage ditch 7 is arranged is larger than 40 degrees, the hard drainage ditch belongs to a steeper side slope and is seriously washed by water power, the hard drainage ditch is poured by C20 reinforced concrete, and the roughness rate is 0.012; double-layer bidirectional ribs are arranged, the longitudinal ribs phi 12@200, the transverse ribs phi 10@200, the lining thickness of the side wall is 20cm, and the thickness of the bottom plate is 25cm. According to the actual slope vertical height and projection length, the drain ditch slope drop is calculated, and the drain ditch slope drop of the embodiment is 0.147.
4.4 setting the stilling pool
In order to prevent the catchment of the hard drainage ditch from directly flushing the natural ditch, a stilling pool is arranged at the tail end of the hard drainage ditch; the dimensions of the stilling pool of this embodiment: length x width x depth = 4.1m x 2.6m. When the stilling pool is excavated, the bearing capacity of the foundation is required to be not less than 120kPa, and if the bearing capacity of the foundation after excavation is insufficient, the foundation is treated by adopting a gray soil foundation (the gray soil thickness is 500mm, and the gray soil is 3:7); the stilling pool is built by adopting reinforced concrete materials, the reinforcing steel bars are HRB335, and the thickness of the protective layer is 30mm; backfilling the periphery of the stilling pool with plain soil, and tamping in layers, wherein the compaction coefficient is not less than 0.85.
5. Three-dimensional separation procedure-setting three-dimensional separation wall
On the basis of inhibiting the oxidation and acid production of the acid gangue storage yard by controlling the infiltration of oxygen and precipitation and weakening the activity of oxidizing bacteria, a three-dimensional barrier wall 9 is arranged at the lowest position of the land form of the junction of the acid gangue storage yard and a natural mountain body in order to further prevent the acid gangue storage yard from releasing acid pollutants to the surrounding environment. The three-dimensional barrier wall is a permeable reaction wall filled with alkaline medium, and can enable acid pollutants generated by leaching of the gangue storage yard to be subjected to neutralization reaction with the alkaline medium in the three-dimensional barrier wall so as to achieve the purpose of removing the acid pollutants.
The three-dimensional barrier wall used in this embodiment includes a filler pool and a filler. The main filler of the three-dimensional baffle wall is limestone, the front end (one end close to the acid coal gangue hill) and the tail end (one end far away from the acid coal gangue hill) of the limestone filler of the three-dimensional baffle wall are filled with crushed stone and quartz sand, and the top of the three-dimensional baffle wall is paved with crushed stone; and the filler pool is poured by reinforced concrete. Thus, the excellent property of the limestone for neutralizing acidic pollutants can be utilized, and the limestone has a better removal effect on Fe, al, zn, mn. The broken stone and quartz sand can play a role in fixing the reaction medium limestone and preventing the blockage of the three-dimensional baffle wall. Broken stone is paved at the top of the three-dimensional baffle wall, so that the effect of fixing the reaction medium limestone can be achieved.
The dimensions of the packing pool of this embodiment are: length x width x height = 4m x 4.5m x 2.6m; the filling pool of the embodiment adopts reinforced concrete casting, the side wall thickness is 25cm, and the bottom plate thickness is 30cm.
As shown in fig. 6, the filler part of the present embodiment has a total length of 4m, a total width of 4m, and a height of 2.3m. The filler part comprises 4 regions: a water distribution wall 91, a reaction wall 92, a water outlet wall 93 and a crushed stone layer. The water distribution wall 91 at the front end is filled with broken stone and quartz sand, and the filling length is 1m; the reaction wall 92 in the middle is filled with limestone with a filling length of 2.5m; the water outlet wall 93 at the tail end is filled with crushed stone and quartz sand, and the filling length is 0.5m; the filling thickness of the filler of the water distribution wall 91, the reaction wall 92 and the water outlet wall 93 is 2m, and the upper parts of the water distribution wall and the reaction wall are paved with 30cm gravel layers so as to play a role of fixing. The packing of the stereoscopic barrier wall of this embodiment has a service life of 1 year, and the packing needs to be replaced after 1 year.
The research results of the embodiment show that the method for in-situ inhibition of acid production by oxidation of the acid gangue dump can fundamentally reduce the acid production, effectively inhibit pollution of the gangue dump to the atmosphere, surface water, underground water and surrounding soil, and effectively control release of acid gangue pollutants to the surrounding environment for a long time.
Claims (10)
1. The comprehensive treatment structure for in-situ inhibition of acid production by oxidation of the acid coal gangue hill is characterized in that the acid coal gangue hill is formed with a top platform, a plurality of horse way platforms, a plurality of slopes and mountainous feet; the top platform is connected with the pavement platform through the slope, the two pavement platforms are connected with each other through the slope, and the pavement platform is connected with the mountain foot through the slope;
the inside of the acid coal gangue hill is uniformly provided with an oxygen control and acid control material; the oxygen control and acid control material comprises sulfate reducing bacteria and sodium dodecyl sulfate;
an oxygen-isolation acid-control material layer and a soil covering layer are sequentially covered above the gangue layer of the acid coal gangue hill from bottom to top; the oxygen-isolation acid-control material layer comprises, by weight, 100-70 parts of powder clay and 0-30 parts of fly ash; the thickness of the oxygen-isolation and acid-control material layer is not less than 15cm, and the compactness of the oxygen-isolation and acid-control material layer reaches more than 85%;
the top platform is provided with a first transverse ecological drainage ditch; a second transverse ecological drainage ditch is arranged on one side of the horse road platform along the slope toe; a plurality of sloping surfaces are provided with longitudinal flexible drainage devices; a hard drainage ditch and a stilling pool are sequentially arranged at the junction of the acidic coal gangue hill and the natural mountain along the terrain from high to low; the first transverse ecological drainage ditch, the second transverse ecological drainage ditch and the hard drainage ditch are communicated through the longitudinal flexible drainage device along the topography of the acidic coal gangue hill from high to low; the hard drainage ditch is communicated with the stilling pool through a pipeline; the first transverse ecological drainage ditch, the second transverse ecological drainage ditch, the hard drainage ditch and the longitudinal flexible drainage device are all formed in the soil covering layer;
A three-dimensional barrier wall is further arranged at the lowest position of the land form of the junction of the acidic coal gangue hill and the natural mountain body of the mountain foot; the three-dimensional baffle wall is buried in the natural mountain, and the top end of the three-dimensional baffle wall is level with the surface layer of the natural mountain; the three-dimensional baffle wall comprises a filler pool, a water distribution wall, a reaction wall, a water outlet wall and a crushed stone layer; the water distribution wall, the reaction wall and the water outlet wall are sequentially formed in the filler pool along the direction away from the acidic coal gangue hill; the top parts of the water distribution wall, the reaction wall and the water outlet wall are respectively provided with the gravel layer; the filler of the reaction wall is limestone; the fillers of the water distribution wall and the water outlet wall are crushed stone and quartz sand.
2. The comprehensive treatment structure for in-situ inhibition of acid production by oxidation of acidic coal gangue hill of claim 1, wherein the oxygen-barrier acid-controlling material layer is replaced with the following composition: according to the weight portions, the powder soil comprises 100 to 50 portions of powder soil and 0 to 50 portions of fly ash; the thickness of the oxygen-isolation and acid-control material layer is not lower than 75cm, and the compactness of the oxygen-isolation and acid-control material layer reaches more than 85%.
3. The comprehensive treatment structure for in-situ inhibition of acid production by oxidation of acidic coal gangue hill according to claim 1 or 2, wherein the oxygen control and acid control material is obtained by mixing sulfate reducing bacteria liquid and sodium dodecyl sulfate aqueous solution with the concentration of 50mg/L according to the volume ratio of 1:20; wherein the sulfate reducing bacterial liquid is bacterial liquid in logarithmic phase.
4. The comprehensive treatment structure for in-situ inhibition of acid production by oxidation of acidic coal gangue dump according to claim 1 or 2, wherein the cross sections of the first transverse ecological drainage ditch and the second transverse ecological drainage ditch are inverted trapezoids; the first transverse ecological drainage ditch and the second transverse ecological drainage ditch are respectively provided with a multi-layer seepage-proofing structure; the multi-layer seepage-proofing structure sequentially comprises a water stabilizing layer, a main material layer, a bentonite layer, a composite geomembrane layer and an ecological bag layer from bottom to top;
the material composition of the water stabilization layer comprises graded broken stone, fly ash, cement and water; the paving thickness of the water stabilization layer is 3-5 cm;
the paving thickness of the main material layer is 4cm; the main material layer comprises the following materials:
a mixture of steel slag, fly ash and desulphurized ash;
or,
a mixture of slag, fly ash and desulphurized ash;
the paving thickness of the bentonite layer is 1cm, and the bentonite layer accounts for 5% -25% of the total weight of the bentonite layer and the main material layer;
the composite geomembrane layer is laid above the bentonite layer, on each side surface of the first transverse ecological drainage ditch and on each side surface of the second transverse ecological drainage ditch; the cloth surface of the composite geomembrane layer faces downwards and contacts with the bentonite layer; the ecological bag layer is arranged above the composite geomembrane layer and is used for pressing.
5. The in situ inhibition acidic gangue hill oxidation acidogenesis integrated remediation structure of claim 4 wherein in the water stable layer:
the maximum grain size of the graded broken stone is not more than 30mm; the weight ratio of cement to pulverized fuel ash to graded broken stone is 4:10:86, and the water-cement ratio is 0.4.
6. The in situ inhibition acid production by oxidation of acidic coal gangue hill integrated treatment structure of claim 4, wherein in the primary material layer:
the weight ratio of the steel slag to the fly ash to the desulfurized fly ash is 60:30:10;
or alternatively, the first and second heat exchangers may be,
the weight ratio of slag, fly ash and desulfurized ash is 60:30:10.
7. The in situ inhibition acid production by oxidation of acidic coal gangue hill comprehensive treatment structure of claim 1 or 2, wherein the longitudinal flexible drainage device comprises a corrugated pipe, a screw thread steel and an ecological bag layer; the middle part of the bent screw thread steel surrounds the corrugated pipe, and two ends of the screw thread steel sequentially extend into the earthing layer and the gangue layer, so that the corrugated pipe is fixed on the acid coal gangue dump; and pressing the ecological bag layer above the corrugated pipe.
8. The comprehensive treatment structure for in-situ inhibition of acid production by oxidation of acidic coal gangue hill of claim 7, wherein the distance between two adjacent longitudinal flexible drainage devices on the same slope is 100m.
9. The method for in-situ inhibition of acid production by oxidation of acidic coal gangue dump is characterized by comprising the following steps:
(1) Spraying oxygen-control acid-control material: spraying oxygen-controlling and acid-controlling materials at intervals before the coal gangue is piled up to the surface covering construction of the acid coal gangue dump; the oxygen control and acid control material comprises sulfate reducing bacteria and sodium dodecyl sulfate; the working temperature of the oxygen control and acid control material is 10-40 ℃;
(2) Covering an oxygen-isolation acid-control material: after the acid coal gangue hill is shaped and prepared, covering an oxygen-isolation and acid-control material above a gangue layer of the acid coal gangue hill, carrying out layered rolling, and covering a soil covering layer above the oxygen-isolation and acid-control material; the oxygen-isolation acid-control material layer comprises, by weight, 100-70 parts of powder clay and 0-30 parts of fly ash; the thickness of the oxygen-isolation and acid-control material layer is not less than 15cm, and the compactness of the oxygen-isolation and acid-control material layer reaches more than 85%;
(3) And (3) arranging a drainage system: the acidic coal gangue hill is formed with a top platform, a plurality of pavement platforms, a plurality of slopes and hill feet; the top platform is connected with the pavement platform through the slope, the two pavement platforms are connected with each other through the slope, and the pavement platform is connected with the mountain foot through the slope; the top platform is provided with a first transverse ecological drainage ditch; a second transverse ecological drainage ditch is arranged on one side of the horse road platform along the slope toe; a plurality of sloping surfaces are provided with longitudinal flexible drainage devices; a hard drainage ditch and a stilling pool are sequentially arranged at the junction of the acidic coal gangue hill and the natural mountain along the terrain from high to low; the first transverse ecological drainage ditch, the second transverse ecological drainage ditch and the hard drainage ditch are communicated through the longitudinal flexible drainage device along the topography of the acidic coal gangue hill from high to low; the hard drainage ditch is communicated with the stilling pool through a pipeline; the first transverse ecological drainage ditch, the second transverse ecological drainage ditch, the hard drainage ditch and the longitudinal flexible drainage device are all formed in the soil covering layer;
(4) Setting a three-dimensional baffle wall: a three-dimensional barrier wall is further arranged at the lowest position of the land form of the junction of the acidic coal gangue hill and the natural mountain body of the mountain foot; the three-dimensional baffle wall is buried in the natural mountain, and the top end of the three-dimensional baffle wall is level with the surface layer of the natural mountain; the three-dimensional baffle wall comprises a filler pool, a water distribution wall, a reaction wall, a water outlet wall and a crushed stone layer; the water distribution wall, the reaction wall and the water outlet wall are sequentially formed in the filler pool along the direction away from the acidic coal gangue hill; the top parts of the water distribution wall, the reaction wall and the water outlet wall are respectively provided with the gravel layer; the filler of the reaction wall is limestone; the fillers of the water distribution wall and the water outlet wall are crushed stone and quartz sand.
10. The method of claim 9, further comprising, prior to step (1), the steps of:
diagnosis of coal gangue hill acidity: the method comprises the steps of oxidizing a coal gangue sample by using hydrogen peroxide to accelerate a long-term natural oxidation process, metering the net acid production in the chemical oxidation process of the coal gangue by using the net acid production w (NAG), and diagnosing the coal gangue as acidic coal gangue under the condition that the w (NAG) of the coal gangue sample is determined to be more than 50.
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