A method for harmless treatment of industrial saline wastewater and salt ion solidification for mixing mine filling / void grouting materials

Abstract

A method for harmless treatment of industrial saline wastewater and salt ion solidification for mixing mine filling / void grouting materials, comprising the following steps: pretreating the industrial saline wastewater through a reverse osmosis device to obtain reverse osmosis industrial high-salt wastewater; mixing the reverse osmosis industrial high-salt wastewater with solid waste to form a mixture for mine filling / void grouting materials; adopting a pumping grouting method to transport the mixture for mine filling / void grouting materials to the filling working face or grouting void of the mine, and curing for several days to achieve the solidification of salt ions. The salt ion solidification method for mixing mine filling / void grouting materials of the present invention can achieve 100% treatment of industrial saline wastewater, realize large-scale, high-efficiency and harmless treatment of industrial saline wastewater, has a good solidification effect on salt ions in reverse osmosis industrial high-salt wastewater, and the leaching concentration of heavy metal elements is lower than the leaching limit of groundwater (Class III water quality), meeting the requirements of environmental safety.

Description

Technical Field

[0001] The invention relates to the technical fields of water disposal, industrial waste disposal, mine filling and void grouting, and in particular to a harmless disposal of industrial saline wastewater and a salt ion solidification method for mixing mine filling / void grouting materials. Background Art

[0002] Industrial saline wastewater mainly includes coal chemical saline wastewater, coal-fired power plant saline wastewater and saline mine water, which cannot be discharged directly. In recent years, with the rapid development of social economy, the demand for resources such as coal, oil and metallurgy has been increasing day by day, which has led to an increase in the amount of industrial wastewater, circulating sewage and process drainage in related fields with complex salt components year by year, which has also led to widespread attention on the treatment of industrial saline wastewater.

[0003] At present, industrial saline wastewater is generally concentrated by membrane method based on reverse osmosis, resulting in the generation of a large amount of reverse osmosis industrial high-salt wastewater (the disposal capacity of reverse osmosis equipment: about 75% of system water and about 25% of concentrated high-salt wastewater). According to statistics, domestic industrial high-salt wastewater is mainly treated by evaporation and crystallization, but there is still a direct discharge disposal method, which seriously threatens the local ecological environment and groundwater resources (disposal methods for industrial high-salt wastewater: about 60% is evaporation and crystallization, about 27% is direct discharge, and about 13% is sewage treatment plants). The scale of disposal, disposal cost and salt separation technology are the bottleneck problems of evaporation and crystallization treatment of industrial high-salt wastewater. At this stage, industrial high-salt wastewater lacks large-scale, efficient and harmless disposal methods.

[0004] Low carbon, green and low cost have become the vane of development in various fields. However, due to the resource endowment pattern of "rich in coal, poor in oil and little gas" in my country, the situation of coal as the dominant energy source is difficult to change in the short term, and it accounts for more than half of the one-time energy consumption. As a result, there are serious ecological problems such as coal mining subsidence, groundwater resource loss and coal-based solid waste storage. Factors such as large output, low activity and unclear environmental stability of coal-based solid waste also urgently need large-scale, efficient and harmless disposal methods. Summary of the invention

[0005] Aiming at the technical problems existing in the prior art: industrial saline wastewater and coal-based solid waste lack large-scale, efficient and harmless disposal methods, and the existing disposal methods have certain bottleneck problems in terms of disposal scale, disposal cost and technical process. The present invention proposes a harmless disposal of industrial saline wastewater and a salt ion solidification method for mixing mine filling / void grouting materials, which realizes chemical solidification of salt ions through the hydration reaction of mine filling / void grouting cementitious materials, while ensuring environmental stability.

[0006] To achieve the above object, the present invention provides a method for harmless treatment of industrial saline wastewater and salt ion solidification for mixing mine filling / void grouting materials, which includes the following steps:

[0007] S1. Concentrate and reduce the amount of industrial saline wastewater through a reverse osmosis device to obtain reverse osmosis industrial high-salt wastewater containing salt ions Na + , K + , Cl － , SO 2 4 － ;

[0008] S2. Mix and stir the reverse osmosis industrial high-salt wastewater and solid waste evenly at a mass concentration of 60-70% to form a mixed mine filling / void grouting material, where the solid waste is composed of 10-20 parts by weight of modified magnesium slag, 10-30 parts by weight of fly ash, and 50-80 parts by weight of coal gasification slag. The solid waste contains active particles C3A, C2S, and C3S;

[0009] S3. Adopt the pumping grouting method to transport the mixed mine filling / void grouting material to the filling working face or grouting void of the mine, and cure it for 3-30 days under the conditions of a temperature of 15-35°C and a humidity of 80-90% to achieve the solidification of salt ions.

[0010] The modified magnesium slag of the present invention is prepared by adding stabilizers (such as Fe3O2, Al2O3, Na2O, K2O, BaO, Cr3O2, and P2O3) at the source of magnesium smelting, and stabilizing the C2S crystal phase in the magnesium slag in the β phase during the high-temperature magnesium smelting process, aiming to solve the problems of easy pulverization and low hydration activity of magnesium slag. For the specific preparation method, reference can be made to the Chinese patent with the application number CN202111309926.5, or the literature: Liu Lang, Ruan Shishan, Fang Zhiyu, Hou Dongzhuang, Zhang Bo, Sun Weiji. Modification of magnesium slag and its application exploration in the field of mine filling. Journal of China Coal Society. Network first release date: 2021-08-18.

[0011] As a further preferred technical solution of the present invention, in step S3, the mixed mine filling / void grouting material is transported to the filling working face or grouting void of the mine through a slurry machine, a filling pump, and a conveying pipeline.

[0012] As a further preferred technical solution of the present invention, in step S3, an artificial water barrier is constructed on the top and bottom plates of the filling working face or grouting void to prevent the seepage effect of groundwater from affecting the solidification effect of salt ions in the reverse osmosis industrial high-salt wastewater.

[0013] As a further preferred technical solution of the present invention, an artificial water barrier is formed on the top and bottom plates of the filling working face or grouting void by using a quickly hardening concrete slurry.

[0014] The present invention proposes a green, efficient and resource-based disposal method for industrial high-salt wastewater and multi-source coal-based solid wastes. The fresh mixed mine filling / void grouting material in slurry state is composed of modified magnesium slag, fly ash, coal gasification slag and reverse osmosis industrial high-salt wastewater. Its solidification / hardening process is fundamentally the hydration reaction of active particles (such as C3A, C2S and C3S). Using industrial high-salt wastewater as an activator, the activation of the hydration activity of the mixed mine filling / void grouting material by industrial high-salt wastewater is fundamentally the combined action of sulfate and chloride salts, which makes a large number of hexagonal plate-like hydration products (Ca(OH)2 crystals), needle-like hydration products (AFt) and flocculent hydration products (C-S-H) randomly interpenetrate the particle gaps, which promotes the development of the mechanical properties of the mixed mine filling / void grouting material.

[0015] The harmless disposal of the industrial saline wastewater of the present invention and the salt ion solidification method for use in the mixed mine filling / void grouting material. By adopting the above technical solutions, the following beneficial effects can be achieved:

[0016] The mixed mine filling / void grouting material of the present invention has good fluidity, mechanical properties and environmental stability, and is suitable for the technical requirements of mine filling. Among them, reverse osmosis industrial high-salt wastewater can be used as a hydration activity activator for the mixed mine filling / void grouting material, realizing a resource-based consumption method of "treating waste with waste", achieving 100% disposal of industrial saline wastewater, and realizing large-scale, efficient and harmless disposal of industrial saline wastewater. It has a good solidification effect on the salt ions in reverse osmosis industrial high-salt wastewater, and the leaching concentration of heavy metal elements is lower than the leaching limit of groundwater (Class III water quality), meeting the environmental safety requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0018] Figure 1 It is the EDS spectrum (surface scan, cured for 28 days) of the sample of the mixed mine filling / void grouting material in Example 6 of the present invention.

[0019] Figure 2 It is the EDS spectrum (point scan, cured for 28 days) of the sample of the mixed mine filling / void grouting material in Example 6 of the present invention.

[0020] The realization of the object of the present invention, functional characteristics and advantages will be further described in conjunction with the embodiments with reference to the drawings. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for the purpose of illustration and explanation of the present invention, and are not intended to limit the present invention.

[0022] Unless otherwise defined, the technical terms used in the following examples have the same meanings as commonly understood by those skilled in the art to which the present invention pertains. The test reagents used in the following examples are all conventional biochemical reagents unless otherwise specified; the experimental methods are all conventional methods unless otherwise specified.

[0023] Example 1

[0024] First, the industrial saline wastewater is pretreated by a reverse osmosis device to preliminarily achieve the reduction treatment of the industrial saline wastewater, and the reverse osmosis industrial high-salt wastewater is obtained.

[0025] Then, the reverse osmosis industrial high-salt wastewater and the solid waste are mixed and stirred evenly by a mixer to form a mixed mine filling / void grouting material (abbreviated as MCBM or MCBM slurry) with a mass concentration of 64 wt%, wherein the modified magnesium slag in the solid waste accounts for 20%, the fly ash accounts for 30%, and the coal gasification slag accounts for 50%; the modified magnesium slag is obtained by adding stabilizers (such as Fe3O2, Al2O3, Na2O, K2O, BaO, Cr3O2, and P2O3, etc.) at the source of magnesium smelting, and stabilizing the C2S crystal phase inside the magnesium slag in the β-phase during the high-temperature magnesium smelting process at 1100 - 1300 °C, aiming to solve the problems of easy pulverization and low hydration activity of the magnesium slag.

[0026] Finally, the fresh mixed mine filling / void grouting material is transported to the grouting void through a slurry machine, a filling pump, and a conveying pipeline, and cured / hardened by curing for several days, thereby realizing the solidification of salt ions; preferably, considering the seepage effect of groundwater, a concrete slurry that can be quickly hardened is used to construct an artificial impermeable thin layer on the top and bottom plates of the filling working face / grouting void to prevent the migration of salt ions in the mine filling / void grouting material caused by the seepage effect of groundwater, thereby reducing the solidification effect of salt ions.

[0027] Examples 2, 3, and 6

[0028] The same method as in Example 1 is adopted, except that the mixing ratio of the reverse osmosis industrial high-salt wastewater and the solid waste is different, and the mass concentrations of the obtained mixed mine filling / void grouting materials are 64 wt%, 68 wt%, and 70 wt% respectively.

[0029] Example 4

[0030] As a control experimental group for Example 6, the same method as in Example 6 was used, except that the reverse osmosis industrial high-salt wastewater was completely replaced (the proportion of reverse osmosis industrial high-salt wastewater was 0%) with water (such as tap water), and the water and solid waste were mixed to form a slurry, with the mass concentration maintained at 70 wt%.

[0031] Example 5

[0032] As a control experimental group for Example 6, the same method as in Example 6 was used, except that water was added to the reverse osmosis industrial high-salt wastewater (the proportion of reverse osmosis industrial high-salt wastewater was 50%), and the diluted reverse osmosis industrial high-salt wastewater and solid waste were mixed to form a slurry, with the mass concentration maintained at 70 wt%.

[0033] The component ratios in the above Examples 1-6 are shown in Table 1:

[0034] Table 1

[0035]

[0036] The following tests were respectively carried out on the above Examples 1-6:

[0037] 1) Salt ion solidification effect test:

[0038] For Example 6, the leachate of the mixed mine filling / void grouting material transported to the grouting void area with different curing ages (3 days, 28 days) was tested. Taking the reverse osmosis industrial high-salt wastewater used in Example 6 as a reference, the conventional physical and chemical properties of the reverse osmosis industrial high-salt wastewater and the leachate of the samples with different curing ages are shown in Table 2:

[0039] Table 2

[0040]

[0041] It can be seen from Table 2 that the total dissolved solids, total chlorine and sulfate in the industrial high-salt wastewater are 8750.00 mg / L, 1.514 mg / L and 5754.060 mg / L respectively. When the MCBM was cured for 3 days, the leaching concentrations of total dissolved solids, total chlorine and sulfate were 970.00 mg / L, 0.024 mg / L and 187.719 mg / L respectively. When the MCBM was cured for 28 days, the leaching concentrations of total dissolved solids, total chlorine and sulfate were 910.00 mg / L, 0.018 mg / L and 136.887 mg / L respectively. Therefore, the MCBM slurry has a significant consolidation effect on the salt ions in the industrial high-salt wastewater, and can achieve 100% disposal of the industrial saline wastewater.

[0042] 2) Microstructural analysis

[0043] Figure 1Shows the EDS spectrum of the mixed mine filling / void grouting material MCBM after 28 days of curing. It can be seen that Na + 、K + 、Cl － and SO 2 4 － are evenly distributed inside the MCBM. This is because Na + 、K + 、Cl － and SO 2 4 － all participated in the hydration reaction of the MCBM and exist in the MCBM in the form of hydration products. This chemically solidified Na + 、K + 、Cl － and SO24 － and also promoted the uniaxial compressive strength of the MCBM, realizing the sustainable development idea of "turning waste into useful materials".

[0044] The pore characteristics of the MCBM are important structural characteristics of the hardened paste, and the pore structure can reflect the degree of hydration reaction of the MCBM. Figure 2 Describes the pore characteristics of the MCBM after curing. It can be clearly observed that the pore size distribution is mainly concentrated in the range of 10 - 10000 nm. There are two forms of the pore size distribution curve, single-peak and double-peak, with the single-peak curve being the main one, and the peak of the pore size distribution characteristic is around 1000 nm. When the mass concentration of the MCBM is fixed, with the increase of the industrial high-salt wastewater content (0%, 50%, and 100%), the cumulative pore volume gradually decreases, the peak of the pore size distribution characteristic gradually shifts to the right, and the roughness gradually decreases.

[0045] 3) Flow characteristics and mechanical property tests:

[0046] Conducted the flow characteristics test of the 1 - 6 mixed mine filling / void grouting materials, and the mechanical property tests of the samples after different curing ages (3 days, 7 days, 28 days) after filling. The test results are shown in Table 3:

[0047] Table 3

[0048]

[0049] The slump and spread can reflect the flow characteristics of the mixed mine filling / void grouting material. From the data in Table 3, it can be seen that when the proportion of reverse osmosis industrial high-salt wastewater is 100%, with the increase of the mass concentration of the mixed mine filling / void grouting material (64%, 66%, 68% and 70%), or when the mass concentration of the mixed mine filling / void grouting material (70%) remains unchanged and the water addition amount of reverse osmosis industrial high-salt wastewater (0%, 50% and 100%) increases, both the slump and spread gradually decrease, the shear yield stress and plastic viscosity between the solid and liquid phases in the slurry gradually increase, and the resistance of the slurry to slump and spread under the action of gravity gradually increases, resulting in the gradual deterioration of the fluidity of the fresh MCBM slurry. The slump and spread tests show that the salt ions in industrial high-salt wastewater accelerate the early hydration reaction of MCBM and rapidly form a network structure, leading to the gradual deterioration of fluidity (Mini-slump: 1356 mm → 134.5 mm, Mini-spread: 148.0 mm → 139.0 mm). The fresh MCBM slurry of the present invention meets the fluidity technical requirements for mine filling, and can be used for filling grouting by combining a filling pump and a pipeline. When the mass concentration of the mixed mine filling / void grouting material (new MCBM slurry) exceeds 70%, the fluidity becomes significantly worse and it is not suitable for grouting filling. When the mass concentration exceeds 40%, although the fluidity is good, the solidification efficiency of salt ions will become low.

[0050] The uniaxial compressive strength of the fresh MCBM slurry gradually increases with the curing days. Taking the curing of MCBM for 28 days as an example, when the proportion of reverse osmosis industrial high-salt wastewater is 100%, with the increase of the mass concentration of the mixed mine filling / void grouting material (64%, 66%, 68% and 70%), the uniaxial compressive strength gradually increases; when the mass concentration of the mixed mine filling / void grouting material (70%) remains unchanged and the water addition amount of reverse osmosis industrial high-salt wastewater (0%, 50% and 100%) increases, the uniaxial compressive strength gradually decreases. After curing the mixed mine filling / void grouting material for 28 days, through the uniaxial compressive strength test, it shows that industrial high-salt wastewater (proportion 0 - 100%) has a promoting effect on the development of the mechanical properties of MCBM (mass concentration of 70%: 4.741 MPa → 6.181 MPa; mass concentration of 68%: 3.940 MPa → 4.994 MPa; mass concentration of 66%: 2.025 MPa → 4.599 MPa; mass concentration of 64%: 2.464 MPa → 4.143 MPa), indicating that industrial high-salt wastewater accelerates the hydration reaction of MCBM, resulting in the generation of a large amount of hydration products, which has a promoting effect on the improvement of the uniaxial compressive strength, and the MCBM slurry of the present invention meets the mechanical strength technical requirements for mine filling.

[0051] 4) Environmental stability test

[0052] The solid waste of the present invention is prepared by mixing different types of bulk solid wastes (10-20 parts by weight of modified magnesium slag, 10-30 parts by weight of fly ash, 50-80 parts by weight of coal gasification slag). Its main environmental problem is that harmful chemical elements seep into groundwater at a certain concentration, causing potential harm to human health and the natural environment.

[0053] Therefore, the present invention also evaluated the leaching effect of heavy metal elements in the mixed mining filling / void grouting material. The test results are shown in Table 4. According to the heavy metal leaching limit of GB / T 14848-2007 "Groundwater Quality Standard - Class III Water Quality", the leaching toxicity of MCBM at different curing ages was evaluated. It is not difficult to find that the leaching concentration of heavy metal elements in MCBM is lower than the leaching limit of groundwater (Class III water quality), indicating that it meets the environmental safety requirements.

[0054]

[0055] Although the specific implementation manners of the present invention have been described above, those skilled in the art should understand that these are only examples, and various changes or modifications can be made to this implementation manner without departing from the principle and essence of the present invention. The protection scope of the present invention is only defined by the appended claims.

Claims

1. A method for the harmless treatment of industrial saline wastewater and the salt ion solidification method for mixing mine filling / void grouting materials, characterized in that, It includes the following steps: S1. Pretreat industrial saline wastewater through a reverse osmosis device to obtain reverse osmosis industrial high-salt wastewater containing salt ions Na + , K + , Cl － , ; S2. Mix the reverse osmosis industrial high-salt wastewater and the solid waste evenly at a mass concentration of 60-70% to form a slurry-like mine filling / void grouting material, where the solid waste is composed of 10-20 parts by weight of modified magnesium slag, 10-30 parts by weight of fly ash, and 50-80 parts by weight of coal gasification slag; Modified magnesium slag is prepared by adding a stabilizer at the source of magnesium smelting to stabilize the C2S crystal phase in magnesium slag during the high-temperature magnesium smelting process at 1100-1300 °C phase; the stabilizer includes Fe3O2, Al2O3, Na2O, K2O, BaO, Cr3O2, and P2O3; S3. Adopt the pumping grouting method to transport the mixed mine filling / void grouting material to the filling working face or grouting void of the mine, and cure for several days to achieve the solidification of salt ions.

2. The method for harmless treatment of industrial saline wastewater and salt ion solidification method for mixing mine filling / void grouting materials according to claim 1, characterized in that, In step S3, the mixed mine filling / void grouting material is transported to the filling working face or grouting void of the mine through a slurry machine, a filling pump, and a conveying pipeline.

3. The method for harmless treatment of industrial saline wastewater and salt ion solidification method for mixing mine filling / void grouting materials according to claim 1, characterized in that, In step S3, an artificial water barrier is constructed on the roof and floor of the filling working face or grouting void.

4. The method for harmless treatment of industrial saline wastewater and salt ion solidification method for mixing mine filling / void grouting materials according to claim 3, characterized in that, An artificial water barrier is formed on the roof and floor of the filling working face or grouting void by using a quickly hardening concrete slurry.

5. The method for harmless treatment of industrial saline wastewater and salt ion solidification method for mixing mine filling / void grouting materials according to claim 1, characterized in that, In step S3, the curing conditions are: temperature: 15-35°C, humidity: 80-90%.

Images