A method for treating leachate in a cold and arid region
Patent Information
- Application Number
- CN202611147466.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-30
- Publication Date
- 2026-09-25
AI Technical Summary
[0002]目前，渗滤液处理技术主要分为生物法、物化法及热解等工艺，其中生物法（厌氧/好氧工艺）运行成本较低，但对高浓度、高盐度、含有毒有机物的渗滤液适应性较差，微生物易受抑制失活；膜分离技术虽能高效去除污染物，但设备投资与运维成本高，且产生的浓缩液需进一步处置，存在二次污染风险；常规热解工艺需较高温度，能耗大，且未针对寒旱区低温环境进行适配优化
[0034]1、本发明的复合絮凝剂采用寒旱区就地易得的粉煤灰、高岭土与凹凸棒土作为功能组分。其中，粉煤灰富含铝、铁、硅氧化物，低温条件下可辅助电荷中和，同时作为刚性骨架增大絮体密度、提升沉降性能；高岭土与凹凸棒土具备丰富孔隙结构，可吸附乳化胶体颗粒，强化破乳脱稳。四种组分复配，聚合硫酸铁完成主絮凝，粉煤灰辅助絮凝并提供骨架支撑，高岭土和凹凸棒土强化吸附破乳，在-5℃~10℃低温区间内协同发挥絮凝、吸附及共沉淀作用，有效解决寒旱区低温预处理效率低下的问题。
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of leachate treatment technology, specifically relating to a leachate treatment method for special environmental conditions such as low temperature, energy shortage, and ecological fragility in cold and arid regions. Background Technology
[0002] Currently, leachate treatment technologies are mainly divided into biological methods, physicochemical methods, and pyrolysis processes. Among them, biological methods (anaerobic / aerobic processes) have lower operating costs, but they are less adaptable to leachates with high concentrations, high salinity, and toxic organic matter, and microorganisms are easily inhibited and inactivated. Membrane separation technology can efficiently remove pollutants, but the equipment investment and maintenance costs are high, and the resulting concentrate needs further treatment, posing a risk of secondary pollution. Conventional pyrolysis processes require high temperatures, consume a lot of energy, and have not been adapted and optimized for the low-temperature environment of cold and arid regions.
[0003] For the specific application scenario of cold and arid regions, existing technologies mainly suffer from the following technical problems: The freezing period in these regions lasts for 4-6 months, with winter temperatures consistently below 0°C. Low temperatures significantly increase leachate viscosity and reduce the collision frequency of colloidal particles, severely inhibiting the hydrolysis reaction of conventional flocculants and drastically reducing flocculation efficiency, making it difficult to effectively remove suspended solids, colloids, and recalcitrant organic matter. Furthermore, these regions are geographically remote and face energy supply difficulties, making conventional high-energy-consuming processes unsuitable. Simultaneously, the ecological environment in these areas is fragile and has poor self-repair capabilities; improper disposal of pollutants remaining in the treated residue and wastewater can easily cause irreversible damage to the regional soil, groundwater, and surrounding ecosystems.
[0004] To address the aforementioned shortcomings of existing technologies, this invention provides a method for treating leachate in arid and cold regions. By employing a composite flocculant and a stepwise dosing process, it achieves efficient low-temperature pretreatment and constructs a synergistic control system for low-temperature pretreatment and pyrolysis processes. This effectively solves the problems of low pretreatment efficiency, high energy consumption, and incomplete pollutant degradation in leachate under low-temperature conditions in arid and cold regions. It is adapted to the special needs of energy shortages and ecological fragility in arid and cold regions, effectively reducing operating costs and minimizing secondary pollution. Summary of the Invention
[0005] To achieve the above-mentioned objective, a first aspect of the present invention provides a method for treating leachate in arid and cold regions, comprising the following steps:
[0006] Step 1: Introduce the leachate from the cold and arid region into a low-temperature pretreatment reactor, add a composite flocculant at -5℃ to 10℃, and carry out low-temperature flocculation to obtain the pretreated liquid.
[0007] The composite flocculant comprises the following components in parts by weight: 60-80 parts polyferric sulfate, 15-25 parts fly ash, 5-10 parts kaolin, and 3-8 parts attapulgite.
[0008] The fly ash comprises a first particle size component and a second particle size component; the particle size of the first particle size component is 100-150 mesh, and the particle size of the second particle size component is 40-80 mesh; the particle size of the kaolin and attapulgite is 150-250 mesh.
[0009] Preferably, the mass ratio of the first particle size component to the second particle size component is (1.5-3):1.
[0010] Preferably, the composite flocculant is added at -5℃ to 5℃ to carry out a low-temperature flocculation reaction.
[0011] In the composite flocculant of the present invention, fly ash is taken from the solid waste of coal combustion in local thermal power plants in cold and arid regions, and kaolin and attapulgite are taken from the natural clay minerals on the surface of deserts in cold and arid regions. After grinding and sieving, they are used directly, which greatly reduces the cost of raw material procurement and transportation.
[0012] In this composite flocculant, polyferric sulfate serves as the primary flocculant, promoting colloidal particle aggregation and flocculation through adsorption, cross-linking, and bridging of polynuclear hydroxyl complexes. Addressing the issue of inhibited hydrolysis of polyferric sulfate at low temperatures, this invention utilizes the release of cations from surface-active metal oxides in fly ash to assist flocculation. Simultaneously, fly ash increases floc density and improves settling performance, compensating for the low flocculation efficiency and loose, floating flocs of polyferric sulfate at low temperatures. Furthermore, kaolin and attapulgite possess abundant microporous channels, enabling them to adsorb emulsified organic matter and fine colloids in leachate under low-temperature aquatic conditions, accelerating demulsification. The four components work synergistically to achieve a demulsification-flocculation-sedimentation synergistic effect within the -5℃ to 10℃ low-temperature range.
[0013] Preferably, the composite flocculant is added in stages, specifically as follows:
[0014] S1. Add kaolin and attapulgite to the leachate and stir for 5-10 minutes.
[0015] This stage utilizes the microporous channels of clay minerals to adsorb emulsified organic matter and fine colloids, achieving pre-adsorption and demulsification, and disrupting the stability of the leachate emulsion system.
[0016] S2. Add polyferric sulfate and the first particle size component of fly ash (100-150 mesh), and stir for 8-12 minutes.
[0017] During this stage, polyferric sulfate destabilizes the colloid through charge neutralization, gradually forming initial flocs. At the same time, fine-particle fly ash is embedded inside the flocs to act as the initial skeleton, enhancing the structural strength of the flocs.
[0018] S3. Add the second particle size component of fly ash (40-80 mesh) and stir for 3-8 minutes.
[0019] At this stage, the flocs have initially taken shape, but the structure is still relatively loose. The coarse-grained fly ash has strong rigidity and high density, which is embedded in the periphery of the flocs, making the flocs more compact and preventing them from loosening and floating under low temperature conditions.
[0020] Preferably, during the stepwise addition process, the stirring rate is 40-100 r / min.
[0021] Preferably, the total dosage of the composite flocculant is 0.5-2 g / L of leachate.
[0022] Preferably, after low-temperature pretreatment, the leachate is filtered to remove suspended solids, colloids, and some heavy metals, yielding a pretreated solution. The filtration pressure is 0.1-0.3 MPa.
[0023] Preferably, the filtration is performed using plate and frame filtration or vacuum filtration.
[0024] Step 2: Preheat the pretreatment liquid to 100-150℃ to obtain preheated material.
[0025] Preferably, the pretreated liquid is introduced into a pyrolysis furnace, and the waste heat of the pyrolysis tail gas is used to preheat the pretreated liquid. On the one hand, this reduces the water content of the pretreated liquid and reduces the energy consumption of the subsequent pyrolysis process; on the other hand, some low-boiling-point organic pollutants (such as volatile phenols) escape with the water vapor, achieving preliminary detoxification, thereby reducing the energy consumption and coking risk of subsequent high-temperature pyrolysis.
[0026] Step 3: Pyrolyze the preheated material at 400-700℃ for 30-90 minutes to cause the recalcitrant organic matter in the preheated material to undergo a pyrolysis reaction and degrade into harmless gases (mainly CO2 and H2O), while generating pyrolysis gas and pyrolysis residue.
[0027] Preferably, the pyrolysis atmosphere is selected from an inert atmosphere, an oxidizing atmosphere, or a reducing atmosphere.
[0028] In a preferred embodiment of the present invention, the parameters between low-temperature pretreatment and pyrolysis can be dynamically matched according to the actual composition of the pretreatment liquid. For example, based on indicators such as the concentration of organic matter, salt content, and viscosity in the pretreatment liquid, the pyrolysis temperature, residence time, and atmosphere can be adjusted accordingly to better match the pretreatment liquid with the pyrolysis process, improve pollutant degradation efficiency, and reduce energy consumption. Furthermore, the waste heat from the pyrolysis tail gas can be used to replenish the insulation of the pretreatment reactor and the filtration unit, preventing the leachate from freezing at low temperatures while reducing the overall energy consumption of the process.
[0029] In a second aspect, the present invention provides a composite flocculant for treating low-temperature leachate in cold and arid regions, comprising the following components in parts by weight: 60-80 parts of polyferric sulfate, 15-25 parts of fly ash, 5-10 parts of kaolin, and 3-8 parts of attapulgite.
[0030] The fly ash comprises a first particle size component and a second particle size component; the particle size of the first particle size component is 100-150 mesh, and the particle size of the second particle size component is 40-80 mesh; the particle size of the kaolin and attapulgite is 150-250 mesh.
[0031] Preferably, the mass ratio of the first particle size component to the second particle size component is (1.5-3):1.
[0032] The component ratio of the composite flocculant and the dual-particle size classification of fly ash in this invention are as follows: Figure 1 As shown in the diagram, the fine-grained portion of fly ash (100-150 mesh) has a large specific surface area and fully exposed surface active sites. When added simultaneously with polyferric sulfate, it can rapidly release metal cations, compensating for the decreased hydrolysis rate of polyferric sulfate at low temperatures. Simultaneously, the fine particles embed themselves within the flocs, providing initial skeletal support. The coarse-grained portion (40-80 mesh) is added after the flocs have initially formed. Due to its higher density and rigidity, it embeds itself around the flocs, making the floc structure more compact and preventing the flocs from loosening and floating at low temperatures. The synergistic effect of the two particle size components overcomes the shortcomings of low flocculation efficiency and poor settling performance of polyferric sulfate alone at low temperatures.
[0033] Compared with the prior art, the present invention has the following beneficial effects:
[0034] 1. The composite flocculant of this invention uses fly ash, kaolin, and attapulgite, which are readily available in cold and arid regions, as functional components. Fly ash is rich in aluminum, iron, and silicon oxides, which can assist in charge neutralization under low-temperature conditions and simultaneously act as a rigid framework to increase floc density and improve settling performance. Kaolin and attapulgite possess abundant porous structures, which can adsorb emulsified colloidal particles and enhance demulsification and destabilization. The four components are combined: polyferric sulfate completes the main flocculation, fly ash assists flocculation and provides skeletal support, and kaolin and attapulgite enhance adsorption and demulsification. Within the low-temperature range of -5℃ to 10℃, they synergistically exert flocculation, adsorption, and co-precipitation effects, effectively solving the problem of low-temperature pretreatment efficiency in cold and arid regions.
[0035] 2. This invention separates fly ash into two particle size components: fine (100-150 mesh) and coarse (40-80 mesh), which are added stepwise at different stages of the flocculation reaction. The fine-particle-size fly ash has a large specific surface area and is added simultaneously with the main flocculant in the middle stage of flocculation, participating in the construction of the flocculation network and acting as a skeleton; the coarse-particle-size fly ash is added after the flocs have initially formed, embedding itself in the periphery to form anti-settling points, so that the flocs maintain a dense structure at low temperatures, and the settling rate is significantly improved.
[0036] 3. This invention utilizes the waste heat from pyrolysis tail gas to preheat the pretreated liquid, removing moisture and low-boiling-point organic pollutants during the preheating stage, reducing energy consumption and coking risk in subsequent high-temperature pyrolysis; simultaneously, it dynamically adjusts the pyrolysis temperature and residence time according to the composition characteristics of the pretreated leachate, ensuring precise matching between the feed and the pyrolysis process, and improving degradation efficiency; and further reduces the overall energy consumption of the process by replenishing the pretreatment unit with waste heat, making it suitable for energy-scarce areas.
[0037] 4. This invention can achieve the harmlessness, volume reduction, and resource recovery of leachate. Low-temperature pretreatment removes suspended solids, colloids, and some heavy metals, while high-temperature pyrolysis completely degrades recalcitrant organic matter. Simultaneously, the pyrolysis gas can be reused as fuel, and the pyrolysis residue can be used as building material raw material or for heavy metal recovery. The overall process has low energy consumption and minimal secondary pollution, making it suitable for the ecologically fragile environments of cold and arid regions. Attached Figure Description
[0038] Figure 1 This is a schematic diagram showing the mass ratio of composite flocculant components and the dual-size classification of fly ash.
[0039] Figure 2 This is a photograph of the appearance of the leachate to be treated. Detailed Implementation
[0040] The technical solution will now be clearly and completely described with reference to the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.
[0041] The leachate used in the following examples was taken from winter leachate from the same landfill in a cold and arid region at different times, and the water quality of each batch fluctuated to some extent.
[0042] Example 1
[0043] A method for treating leachate in a cold and arid region involves taking 1L of leachate from a landfill in a cold and arid region during winter (e.g., ...). Figure 2 As shown in the figure, the initial COD was 8500 mg / L, ammonia nitrogen was 650 mg / L, suspended solids (SS) was 1800 mg / L, and heavy metals included Pb 12 mg / L and Cd 6 mg / L.
[0044] 1) The leachate is introduced into a low-temperature pretreatment reactor, and the temperature is controlled at -2℃. The composite flocculant consists of 70 parts polyferric sulfate, 18 parts fly ash, 7 parts kaolin (200 mesh), and 5 parts attapulgite (200 mesh), with a total dosage of 1.2 g / L. The mass ratio of the first particle size component (120 mesh) to the second particle size component (60 mesh) of fly ash is 2:1.
[0045] The following steps were used: S1. Kaolin and attapulgite were added to the leachate and stirred at 80 rpm for 8 min; S2. Polyferric sulfate and the first particle size component (120 mesh) of fly ash were added and stirred at 80 rpm for 10 min; S3. The second particle size component (60 mesh) of fly ash was added and stirred at 80 rpm for 5 min. After low-temperature flocculation, the solution was filtered under 0.2 MPa pressure to obtain the pretreated solution.
[0046] 2) The pretreated liquid is introduced into the pyrolysis furnace and preheated to 120°C using the waste heat of the pyrolysis tail gas to obtain the preheated material.
[0047] 3) Pyrolyze the preheated material at 550℃ under a nitrogen atmosphere for 60 minutes to generate pyrolysis gas and pyrolysis residue.
[0048] After testing, the effluent from step 1) pretreatment had a COD of 3160 mg / L, SS of 42 mg / L, Pb of 1.4 mg / L, and Cd of 0.72 mg / L. After step 3) pyrolysis, based on the original water COD, the overall COD removal rate was 97.6%, and the overall heavy metal removal rate was >87%. The calorific value of the pyrolysis gas was 18.5 MJ / m³. 3 It can be reused as fuel.
[0049] Example 2
[0050] One liter of leachate from a landfill in a cold and arid region during winter was collected. The initial COD was 9200 mg / L, SS was 2000 mg / L, Pb was 15 mg / L, and Cd was 8 mg / L.
[0051] 1) The leachate is introduced into a low-temperature pretreatment reactor, and the temperature is controlled at -3℃. The composite flocculant consists of 60 parts polyferric sulfate, 15 parts fly ash, 5 parts kaolin (200 mesh), and 3 parts attapulgite (200 mesh), with a total dosage of 1.0 g / L. The mass ratio of the first particle size component (100 mesh) to the second particle size component (40 mesh) of fly ash is 1.5:1.
[0052] The following steps were used: S1. Kaolin and attapulgite were added to the leachate and stirred at 100 rpm for 10 min; S2. Polyferric sulfate and the first particle size component of fly ash were added and stirred at 100 rpm for 12 min; S3. The second particle size component of fly ash was added and stirred at 100 rpm for 8 min. After low-temperature flocculation, the solution was filtered under 0.15 MPa pressure to obtain the pretreated solution.
[0053] 2) The pretreated liquid is introduced into the pyrolysis furnace and preheated to 100°C using the waste heat of the pyrolysis tail gas to obtain the preheated material.
[0054] 3) The preheated material is pyrolyzed at 400℃ in an oxidizing atmosphere (air) for 90 minutes to generate pyrolysis gas and pyrolysis residue.
[0055] Testing revealed that the COD of the effluent after pretreatment in step 1) was 4270 mg / L, and the SS was 55 mg / L. After pyrolysis in step 3), the total COD removal rate was 95.2%, the comprehensive heavy metal removal rate was >84%, and the calorific value of the pyrolysis gas was 17.1 MJ / m³. 3 .
[0056] Example 3
[0057] One liter of leachate from a landfill in a cold and arid region during winter was collected. The initial COD was 11,000 mg / L, SS was 2,500 mg / L, Pb was 20 mg / L, and Cd was 10 mg / L.
[0058] 1) The leachate is introduced into a low-temperature pretreatment reactor, and the temperature is controlled at -5℃. The composite flocculant consists of 80 parts polyferric sulfate, 25 parts fly ash, 10 parts kaolin (250 mesh), and 8 parts attapulgite (250 mesh), with a total dosage of 2.0 g / L. The mass ratio of the first particle size component (150 mesh) to the second particle size component (80 mesh) of fly ash is 3:1.
[0059] The following steps were used for addition: S1. Kaolin and attapulgite were added to the leachate and stirred at 60 rpm for 5 min; S2. Polyferric sulfate and the first particle size component of fly ash were added and stirred at 60 rpm for 8 min; S3. The second particle size component of fly ash was added and stirred at 60 rpm for 3 min. After low-temperature flocculation, the solution was filtered under 0.3 MPa pressure to obtain the pretreated solution.
[0060] 2) The pretreated liquid is introduced into the pyrolysis furnace and preheated to 150°C using the waste heat of the pyrolysis tail gas to obtain the preheated material.
[0061] 3) Then, pyrolyze at 700℃ in an oxidizing atmosphere (air) for 30 minutes to generate pyrolysis gas and pyrolysis residue.
[0062] Testing revealed that the COD of the pretreated effluent was 3620 mg / L, and the SS was 38 mg / L. After pyrolysis, the total COD removal rate was 98.3% (based on raw water), and the comprehensive heavy metal removal rate was >91%. The calorific value of the pyrolysis gas was 19.4 MJ / m³. 3 .
[0063] Example 4
[0064] One liter of leachate from a landfill in a cold and arid region during winter was collected. The initial COD was 7800 mg / L, SS was 1600 mg / L, Pb was 10 mg / L, and Cd was 5 mg / L.
[0065] 1) The leachate is introduced into a low-temperature pretreatment reactor, and the temperature is controlled at 5℃. The composite flocculant consists of 70 parts polyferric sulfate, 18 parts fly ash, 7 parts kaolin (200 mesh), and 5 parts attapulgite (200 mesh), with a total dosage of 0.5 g / L. The mass ratio of the first particle size component (120 mesh) to the second particle size component (60 mesh) of fly ash is 2:1.
[0066] The leachate was added in stages: S1, kaolin and attapulgite were added to the leachate and stirred at 80 rpm for 8 min; S2, polyferric sulfate and the first particle size component (120 mesh) of fly ash were added and stirred at 80 rpm for 10 min; S3, the second particle size component (60 mesh) of fly ash was added and stirred at 80 rpm for 5 min. After low-temperature flocculation, the leachate was filtered under 0.1 MPa pressure to obtain the pretreated solution.
[0067] 2) The pretreated liquid is introduced into the pyrolysis furnace and preheated to 100°C using the waste heat of the pyrolysis tail gas to obtain the preheated material.
[0068] 3) The preheated material is pyrolyzed at 450℃ in a reducing atmosphere (H2 / N2 mixture, H2 accounting for 5v%) for 30 minutes to generate pyrolysis gas and pyrolysis residue.
[0069] Testing revealed that the COD of the pretreated effluent was 3100 mg / L, and the SS was 46 mg / L. After pyrolysis, the total COD removal rate was 92.8%, the total heavy metal removal rate was >84%, and the calorific value of the pyrolysis gas was 16.5 MJ / m³. 3 .
[0070] Comparative Example 1
[0071] Take 1L of leachate from the same source as in Example 1, taken during winter in a cold and arid region. The initial COD was 8500mg / L, ammonia nitrogen was 650mg / L, SS was 1800mg / L, and it contained 12mg / L of Pb and 6mg / L of Cd.
[0072] 1) The leachate was introduced into a low-temperature pretreatment reactor, and the temperature was controlled at -2℃. The overall composition of the composite flocculant was the same as in Example 1, including 70 parts of polyferric sulfate, 18 parts of fly ash (single 120 mesh), 7 parts of kaolin (200 mesh), and 5 parts of attapulgite (200 mesh). The four components were premixed and added to the leachate at a total dosage of 1.2 g / L, and stirred at 80 r / min for 23 min. After low-temperature flocculation, the leachate was filtered under a pressure of 0.2 MPa to obtain the pretreated liquid.
[0073] 2) The pretreatment liquid is introduced into the pyrolysis furnace and preheated to 120°C to obtain the preheated material.
[0074] 3) Pyrolysis at 550℃ under an inert atmosphere (nitrogen) for 60 minutes to generate pyrolysis gas and pyrolysis residue.
[0075] Testing revealed that the COD of the pretreated effluent was 5190 mg / L, and the SS was 181 mg / L. After pyrolysis, the total COD removal rate was 76.5%, and the total heavy metal removal rate was <62%. During flocculation, the flocs were observed to be noticeably loose, with slow settling speeds, and some flocs floated to the surface.
[0076] Comparative Example 2
[0077] Take 1L of leachate from the same source as in Example 1, taken during winter in a cold and arid region. The initial COD was 8500mg / L, ammonia nitrogen was 650mg / L, SS was 1800mg / L, and it contained 12mg / L of Pb and 6mg / L of Cd.
[0078] The composite flocculant was added directly at room temperature (approximately 20°C). The composition of the composite flocculant was the same as in Example 1 (70 parts polyferric sulfate, 18 parts fly ash, 7 parts kaolin, and 5 parts attapulgite), with a total dosage of 1.2 g / L. It was added in stages (same as in Example 1), stirred for 23 min, and after flocculation, filtered under 0.2 MPa pressure to obtain the pretreated solution.
[0079] The mixture is introduced into a pyrolysis furnace, preheated to 120°C, and then pyrolyzed at 550°C under an inert atmosphere (nitrogen) for 60 minutes.
[0080] Testing revealed that the COD of the pretreated effluent was 4360 mg / L, and the SS was 88 mg / L. After pyrolysis, the total COD removal rate was 73.5% (based on raw water), and the total heavy metal removal rate was <76%. The calorific value of the pyrolysis gas was relatively low at 13.8 MJ / m³. 3 This indicates that there is a synergistic effect between low-temperature pretreatment and pyrolysis process, and the pretreatment effect directly affects the subsequent pyrolysis efficiency and product quality.
[0081] Specific embodiments and comparative data are shown in Table 1.
[0082] Table 1
[0083]
[0084] As can be seen from Table 1, in Examples 1-4, after low-temperature pretreatment with composite flocculant, the COD of the effluent was reduced to below 4300 mg / L, the SS was reduced to below 55 mg / L, and the removal rates of heavy metals Pb and Cd were higher than 84%, indicating that the composite flocculant can still effectively remove suspended solids, colloids and heavy metals under low-temperature conditions.
[0085] Comparative Example 2, where the flocculation was directly added at room temperature (20°C), showed a COD of 4360 mg / L and SS of 88 mg / L after pretreatment, significantly worse than Example 1. This indicates that low-temperature environments are not conducive to conventional flocculation, while this application is specifically designed for low-temperature conditions. Furthermore, the calorific value of the pyrolysis gas is only 13.8 MJ / m³. 3 The problems of clogging and uneven feeding in the pyrolysis feed indicate that the synergistic effect of low-temperature pretreatment and pyrolysis is significant, and low-temperature pretreatment affects the pyrolysis efficiency and product quality.
[0086] Comparative Example 1, which pre-mixed the four components and added them all at once, had the same components and total stirring time as Example 1. However, the COD after pretreatment was 5190 mg / L and SS was 181 mg / L, which were much higher than those in Example 1. Moreover, the flocs were loose and some floated. This proves that the sequential design of the dual particle size classification of fly ash combined with the step-by-step addition has a certain impact on the low-temperature flocculation effect, and is not a simple adjustment of the operation sequence.
[0087] In summary, the composite flocculant of the present invention solves the problems of low flocculation efficiency and loose flocs floating at low temperatures by combining the dual-size classification and step-by-step addition of fly ash. At the same time, the synergistic effect of low-temperature pretreatment and pyrolysis process effectively reduces energy consumption.
Claims
1. A method for treating leachate in arid and cold regions, characterized in that, Includes the following steps: Step 1: Introduce leachate from the cold and arid region into a low-temperature pretreatment reactor, add composite flocculant at -5℃~10℃, and carry out low-temperature flocculation to obtain pretreated liquid; Step 2: Preheat the pretreatment liquid to 100-150℃ to obtain preheated material; Step 3: Pyrolyze the preheated material at 400-700℃; The composite flocculant comprises the following components in parts by weight: 60-80 parts of polyferric sulfate, 15-25 parts of fly ash, 5-10 parts of kaolin, and 3-8 parts of attapulgite. The fly ash includes a first particle size component and a second particle size component; The first particle size component has a particle size of 100-150 mesh, and the second particle size component has a particle size of 40-80 mesh.
2. The method as described in claim 1, characterized in that, The particle size of both the kaolin and attapulgite is 150-250 mesh.
3. The method according to claim 1, characterized in that, The mass ratio of the first particle size component to the second particle size component of fly ash is (1.5-3):
1.
4. The method according to claim 1, characterized in that, The first particle size component has a particle size of 100-120 mesh, and the second particle size component has a particle size of 60-80 mesh.
5. The method as described in claim 1, characterized in that, In step 1, the process of adding the composite flocculant is as follows: S1. Add kaolin and attapulgite to the leachate and stir for 5-10 minutes; S2. Add polyferric sulfate and the first particle size component of fly ash, and stir for 8-12 minutes; S3. Add the second particle size component of fly ash, stir for 3-8 minutes to obtain the pretreated solution.
6. The method as described in claim 5, characterized in that, The stirring rate is 40-100 r / min.
7. The method as described in claim 1, characterized in that, In step 1, the total dosage of the composite flocculant is 0.5-2 g / L.
8. The method as described in claim 1, characterized in that, In step 3, the pyrolysis time is 30-90 min; the pyrolysis atmosphere is selected from an inert atmosphere, an oxidizing atmosphere, or a reducing atmosphere.
9. A composite flocculant for treating low-temperature leachate in arid and cold regions, characterized in that, The components include the following parts by mass: Polyferric sulfate 60-80 parts, fly ash 15-25 parts, kaolin 5-10 parts, attapulgite 3-8 parts; Fly ash includes a first particle size component and a second particle size component; The particle size of the first particle size component is 100-150 mesh, and the particle size of the second particle size component is 40-80 mesh; The particle size of both the kaolin and attapulgite is 150-250 mesh.
10. The composite flocculant according to claim 9, characterized in that, The mass ratio of the first particle size component to the second particle size component is (1.5-3):1.