Stabilizing agent and process for reducing pollution and carbon reduction for old landfill sites

Abstract

The application provides a stabilizing agent and a pollution-reducing and carbon-reducing process for an aged landfill site. The stabilizing agent comprises magnesium chloride, calcium oxide, polyacrylamide, calcium salt and iron oxide. The pollution-reducing and carbon-reducing process for the aged landfill site comprises the following steps: firstly, mixing the leachate of the aged landfill site with the stabilizing agent uniformly to obtain a spraying mixed solution; secondly, delineating the pressure field inside the stack of the aged landfill site; and finally, spraying the spraying mixed solution on the stack according to the distribution of the pressure field and assisting aeration so as to reduce the settlement of the stack of the aged landfill site and the leachate yield of the aged landfill site. The application can effectively realize the pollution-reducing and carbon-reducing effect of the aged landfill site by simple equipment and materials without interfering with the normal operation of the landfill site, and has the advantages of simple implementation, low cost and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of pollution reduction and carbon reduction, and particularly relates to a stabilizing agent and a pollution reduction and carbon reduction process for an aged landfill site. BACKGROUND

[0002] Landfilling is still an important end-of-life waste disposal method. Although more and more regions have begun to implement zero landfilling of primary waste, the existing stock of waste has occupied a large amount of land resources and continuously releases greenhouse gases and leachate to the outside world.

[0003] With the increase of landfill time, the easily degradable organic matter in the waste has been basically converted into landfill gas, and most of the remaining refractory organic matter has been highly humified. The pollutant load in the leachate also decreases, but the heap has not yet reached stabilization, the pollutants and greenhouse gases continue to be discharged, and the settlement is still developing, which makes the site utilization impossible.

[0004] The aged landfill site usually faces the problems of low landfill gas resourceization potential and difficult leachate treatment, which is related to the unbalanced carbon-nitrogen-phosphorus ratio and mineralization of organic matter in the heap. For this stage of landfill site, the conventional repair methods such as leachate recirculation and aeration are limited in diffusion in the heterogeneous heap, and cannot achieve uniform distribution, which may lead to less expected repair effect and increase additional energy consumption cost.

[0005] Considering the poor biodegradability of the heap at this stage, the landfill site at this time is regarded as a carbon sink to reduce the biochemical reaction activity in the heap, reduce the water content, limit the carbon emission under mineralization, and reduce the biological degradation compression and the migration ability of pollutants, thereby reducing the settlement of the heap and the leachate production, and realizing the carbon reduction and pollution reduction of the landfill site. SUMMARY

[0006] The present application is made to solve the above problems, and aims to provide a stabilizing agent and a carbon reduction and pollution reduction process for an aged landfill site.

[0007] The present application provides a stabilizing agent, which has the following characteristics: magnesium chloride, calcium oxide, polyacrylamide, calcium salt and iron oxide, wherein the stabilizing agent is used to be put into the heap of the aged landfill site to reduce the biochemical reaction activity in the heap, thereby reducing the settlement of the heap and the leachate production of the aged landfill site.

[0008] In the stabilizing agent provided by the application, the magnesium chloride can account for 10-12% by mass in the stabilizing agent, the calcium oxide can account for 15-18% by mass in the stabilizing agent, the polyacrylamide can account for 5-7% by mass in the stabilizing agent, the calcium salt includes calcium chloride and calcium nitrate, the calcium salt can account for 65-68% by mass in the stabilizing agent, the iron element in the iron oxide is +2 valence, the iron oxide can account for 4-5% by mass in the stabilizing agent, and the mass ratio of the calcium chloride to the calcium nitrate in the calcium salt is (8-8.5):2.

[0009] The application further provides a pollution reduction and carbon reduction process for an aged landfill site, which has the characteristics of reducing the settlement of a heap of the aged landfill site and the leachate yield of the aged landfill site, and comprises the following steps: S10, mixing the leachate of the aged landfill site with the stabilizing agent of any one of the above to obtain a spraying mixed solution; S20, depicting a pressure field inside the heap of the aged landfill site; and S30, spraying the spraying mixed solution on the heap according to the distribution of the pressure field, and simultaneously assisting aeration.

[0010] In the pollution reduction and carbon reduction process for the aged landfill site provided by the application, the pH of the spraying mixed solution in step S10 can be 10.5-13.

[0011] In the pollution reduction and carbon reduction process for the aged landfill site provided by the application, the depicting method of the pressure field in step S20 can be as follows: pressure sensors are arranged in the heap to measure the pressure therein, and the pressure sensors include pore pressure sensors, liquid pressure sensors and gas pressure sensors, which are respectively used to measure the pore pressure, the liquid pressure and the gas pressure in the heap.

[0012] In the pollution reduction and carbon reduction process for the aged landfill site provided by the application, the region selected for spraying in the heap in step S30 can have a liquid pressure and a gas pressure that are both less than 3 / 4 of the slope safety limit of the heap before spraying, and the liquid pressure and the gas pressure in the heap are controlled to be less than the slope safety limit of the heap during the auxiliary aeration process.

[0013] In the process for reducing pollution and carbon provided by the application for the aged landfill, the process can have the following features: in step S30, the control method of the spraying speed is: according to the pressure field described in step S20, the CFD module is mobilized by computer simulation, the permeability coefficient in the heap under a specific pore pressure is simulated, and the spraying speed is determined according to the Darcy formula; the control method of the spraying amount is: the amount of the spraying mixed solution is adjusted so that the mass ratio of the stabilizing agent in the heap to the dry garbage is greater than or equal to 5 mg / g; the spraying is stopped immediately after the pore pressure in the heap rises by 10-15%; and the aeration is stopped immediately after the air pressure in the heap rises by 7-10%.

[0014] In the process for reducing pollution and carbon provided by the application for the aged landfill, the process further comprises the following step: S40, during each rainfall process, the heap is additionally supplemented with spraying of the spraying mixed solution, and the parameters of the aeration are adjusted according to the rainfall amount and the aeration is additionally performed.

[0015] In the process for reducing pollution and carbon provided by the application for the aged landfill, the process can have the following features: in step S30, the control method of the spraying speed is: according to the pressure field described in step S20, the CFD module is mobilized by computer simulation, the permeability coefficient in the heap under a specific pore pressure is simulated, and the spraying speed is determined according to the Darcy formula; the control method of the spraying amount is: the amount of the spraying mixed solution is adjusted so that the mass ratio of the stabilizing agent in the heap to the dry garbage is greater than or equal to 5 mg / g; the spraying is stopped immediately after the pore pressure in the heap rises by 10-15%; and the aeration is stopped immediately after the air pressure in the heap rises by 7-10%.

[0016] In the process for reducing pollution and carbon provided by the application for the aged landfill, the process can have the following features: in step S30, the control method of the spraying speed is: according to the pressure field described in step S20, the CFD module is mobilized by computer simulation, the permeability coefficient in the heap under a specific pore pressure is simulated, and the spraying speed is determined according to the Darcy formula; the control method of the spraying amount is: the amount of the spraying mixed solution is adjusted so that the mass ratio of the stabilizing agent in the heap to the dry garbage is greater than or equal to 5 mg / g; the spraying is stopped immediately after the pore pressure in the heap rises by 10-15%; and the aeration is stopped immediately after the air pressure in the heap rises by 7-10%.

[0017] Effects of the application

[0018] According to the stabilizing agent and the process for reducing pollution and carbon for the aged landfill provided by the application, because the stabilizing agent comprises magnesium chloride, calcium oxide, polyacrylamide, calcium salt and iron oxide, the process for reducing pollution and carbon for the aged landfill sprays the stabilizing agent on the heap and assists the aeration, so the application can effectively realize the effect of reducing pollution and carbon for the aged landfill by simple equipment and materials without interfering with the normal operation of the landfill, and has the advantages of simple implementation, low cost and the like. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a flowchart of a process for reducing pollution and carbon for the aged landfill in an embodiment of the application. DETAILED DESCRIPTION

[0020] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the following embodiments will be specifically described in combination with the drawings.

[0021] Embodiment

[0022] The embodiment provides a stabilizing agent for being put into a stack of an aged landfill site to reduce biochemical reaction activity in the stack, so as to reduce settlement of the stack and leachate production of the aged landfill site, and the stabilizing agent comprises: magnesium chloride, which is used for inhibiting disordered mineralization of microorganisms in the stack and reacting with excessive ammonia nitrogen in the stack to generate struvite, so as to limit migration of pollutants in the stack; calcium oxide, which is used for adjusting pH in the stack, reducing migration ability of heavy metal pollutants, and can be used as a filler to enhance structural stability of the stack; polyacrylamide, which is used for increasing a proportion of bound water in the stack to improve water retention of the stack, and increasing viscosity of leachate to reduce flowability of the leachate; calcium salt, comprising calcium chloride and calcium nitrate, which is used for inhibiting disordered mineralization of microorganisms and reducing activity of water in the stack; and iron oxide, which is ferrous oxide, and is used as a cementing agent to promote organic matter to form aggregates to realize physical protection of organic carbon, and can form a mineral-organic carbon complex with characteristic organic matters (especially lignin and humus) through physical and chemical action to reduce biological availability.

[0023] In the embodiment, the mass ratio of the magnesium chloride, the calcium oxide, the polyacrylamide, the calcium salt and the iron oxide is 2:3:1:13:1, and the mass ratio of the calcium chloride to the calcium nitrate in the calcium salt is (8-8.5):2.

[0024] Figure 1 is a flow chart of a leachate reduction and carbon reduction process for an aged landfill site in the embodiment of the present application.

[0025] As shown in Figure 1 The embodiment further provides a leachate reduction and carbon reduction process for an aged landfill site, which is used for reducing settlement of a stack of the aged landfill site and leachate production of the aged landfill site, and comprises the following steps:

[0026] S10, the magnesium chloride, the calcium oxide, the polyacrylamide, the calcium salt and the iron oxide are mixed in a mass ratio of 2:3:1:13:1 to obtain the stabilizing agent in the embodiment, and the leachate of the aged landfill site is mixed with the stabilizing agent in a reaction kettle and heated and stirred at 37 DEG C for 1 h, and then the pH is adjusted to 12-13 to obtain a spraying mixed solution.

[0027] The calcium salt includes calcium chloride and calcium nitrate, and the mass ratio is 8:2, the iron oxide is ferrous oxide, the mass ratio of the leachate to the stabilizing agent is 5:1 for the heap with a landfill age greater than 2 years, and the mass ratio of the leachate to the stabilizing agent can be appropriately reduced for the heap with a landfill age greater than 10 years, but is not less than 8:1.

[0028] S20, in combination with the ground penetrating radar technology, the pore pressure sensor, the liquid pressure sensor and the gas pressure sensor are arranged at the predetermined heap detection points, one detection point every 5m depth, so that the continuous pore pressure, liquid pressure and gas pressure data are obtained.

[0029] The mechanical pressure is calculated according to the measured pore pressure, and the calculation method of the mechanical pressure is:

[0030] .

[0031] wherein, BD SD is the mechanical pressure, IBD is the initial bulk density of the heap, OP is the pressure applied by the overlying garbage (measured pore pressure), a (m 3 / m 2 ) and b (m 3 / kg) are both empirical constants which can be obtained by referring to the Handbook of solid Waste Management, 2nd Edition (Frank Kreith, George Tchobanoglous, McGraw Hill, ISBN-13: 978-0071356237).

[0032] Finally, the pressure field inside the heap of the old landfill is depicted by relying on the calculated mechanical pressure, the measured liquid pressure and the gas pressure.

[0033] S30, the area in the heap where the liquid pressure and the gas pressure do not exceed 3 / 4 of the slope safety limit is selected for spraying the spraying mixture, the spraying process relies on the computer simulation to mobilize the CFD module to simulate the permeability coefficient in the heap under a specific pore pressure in the area, so as to calculate the spraying speed according to the Darcy formula, and at the same time, the amount of the spraying mixture is adjusted so that the mass ratio of the stabilizing agent in the spraying mixture to the dry garbage in the heap is ≥5mg / g, and finally, auxiliary aeration is performed in the heap, and the liquid pressure and the gas pressure in the heap during the whole process do not exceed the slope safety limit of the heap.

[0034] In order to ensure the safety of the spraying process, the spraying is stopped immediately after the pore pressure in the heap rises by 10-15% during the spraying.

[0035] For the safety of the aeration process, the pressure value of the aeration well is controlled not to exceed 30 kPa during aeration, and the aeration is stopped immediately when the gas pressure in the pile body rises by 7-10% during aeration. In order to ensure the uniform distribution of oxygen in the pile body during aeration, at least one aeration well should be provided every 20m on the pile body.

[0036] S40, before each precipitation forecast, preferably at least once spray the spray mixture, so that after precipitation, the stabilizing agent in the spray mixture can be transported to all parts of the pile by the infiltrating water, so as to promote its uniform distribution in the pile and reduce the active pile moisture replenishment, after the end of the rainfall, adjust the parameters of the aeration according to the size of the rainfall and carry out the supplementary aeration.

[0037] Wherein, when the single precipitation of rainfall is greater than 100mm, after the end of rainfall, the oxygen content in the air corresponding to each gram of dry weight of the garbage in the pile during the supplementary aeration process is ≥0.09mol.

[0038] Wherein, the duration of the supplementary aeration t≥0.018514*total mass of garbage in the pile, t is in min, and the total mass of garbage in the pile is in wet weight, kg.

[0039] Effects of the embodiment

[0040] The embodiment is different from the method of accelerating the degradation of organic matter in the conventional garbage landfill pile treatment method, the embodiment adds a large amount of industrial salt, metal oxide and high molecular polymer as stabilizing agent, so that the mineralization of microorganisms in the aged pile of the aged garbage landfill is weakened by 80-85%, the disordered mineralization of organic matter is inhibited, the directional production of quinone substances is guided, and the protection of humus is played.

[0041] The embodiment reduces the water content in the pile by adding stabilizing agent and aeration means, so that the water activity is reduced to below 0.6, the proportion of free water is reduced to 50% of the original, and the migration ability of pollutants is reduced, and the passivation effect is produced, so that the concentration of heavy metals in the leachate is reduced by 90%.

[0042] The scheme provided by the embodiment can reduce 60% of the carbon emissions of the aged garbage landfill, reduce 50% of the leachate of the pile of the aged garbage landfill, and shorten the maintenance period of the aged garbage landfill by 50%.

[0043] Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only to illustrate the principles of the present application, and various changes and improvements can be made without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A pollution and carbon reduction process for an aged landfill site, characterized in that, A method for reducing the settlement of a heap of an aged landfill and the leachate production of the aged landfill, comprising the following steps: S10, mixing the leachate of the aged landfill with a stabilizing agent to obtain a spraying mixture, wherein the stabilizing agent comprises magnesium chloride, calcium oxide, polyacrylamide, calcium salt and iron oxide; S20, characterizing the pressure field inside the heap of the aged landfill; S30, spraying the spraying mixture on the heap according to the distribution of the pressure field, while assisting aeration, wherein the control method of the spraying speed is: according to the pressure field characterized in step S20, relying on the CFD module of computer simulation to simulate the permeability coefficient in the heap under a specific pore pressure, so as to determine the spraying speed according to Darcy's formula, the control method of the spraying amount is: adjusting the amount of the spraying mixture so that the mass fraction of the stabilizing agent in the dry garbage of the heap is ≥5 mg / g, wherein the spraying is stopped immediately after the pore pressure in the heap rises by 10-15% during the spraying process; the aeration is stopped immediately after the gas pressure in the heap rises by 7-10%.

2. The pollution reduction and carbon reduction process for the aged landfill according to claim 1, characterized in that: wherein in step S10, the mass fraction of magnesium chloride in the stabilizing agent is 10%-12%, the mass fraction of calcium oxide in the stabilizing agent is 15%-18%, the mass fraction of polyacrylamide in the stabilizing agent is 5%-7%, the calcium salt comprises calcium chloride and calcium nitrate, and the mass fraction of the calcium salt in the stabilizing agent is 65%-68%, the iron element in the iron oxide is +2 valence, and the mass fraction of the iron oxide in the stabilizing agent is 4-5%, the mass ratio of calcium chloride to calcium nitrate in the calcium salt is (8-8.5):

2.

3. The pollution reduction and carbon reduction process for the aged landfill according to claim 1 or 2, characterized in that: wherein in step S10, the pH of the spraying mixture is 10.5-13.

4. The pollution reduction and carbon reduction process for the aged landfill according to claim 1 or 2, characterized in that: wherein in step S20, the characterization method of the pressure field is: setting pressure sensors in the heap to measure the pressure therein, the pressure sensors comprise pore pressure sensors, liquid pressure sensors and gas pressure sensors, which are used to measure the pore pressure, liquid pressure and gas pressure in the heap, respectively.

5. The pollution reduction and carbon reduction process for the aged landfill according to claim 4, characterized in that: wherein in step S30, the area selected for spraying in the heap has a liquid pressure and a gas pressure before spraying, both of which do not exceed 3 / 4 of the slope safety limit of the heap, the liquid pressure and the gas pressure in the heap are controlled to be less than or equal to the slope safety limit of the heap during the auxiliary aeration process.

6. The pollution and carbon reduction process for old landfill sites according to claim 4, characterized in that, Further comprising the following steps: S40, accompanying each rainfall process, additionally supplementing the spraying of the spraying mixture on the heap, and adjusting the parameters of the aeration and supplementing the aeration according to the size of the rainfall.

7. The pollution reduction and carbon reduction process for old landfill sites according to claim 6, characterized in that: wherein The adjustment method of the parameters is: when the single rainfall of rainfall is greater than 100 mm, the oxygen content in the air of the supplementary aeration process corresponding to each gram of dry garbage of the pile is greater than or equal to 0.09 mol after the rainfall ends.

8. The pollution reduction and carbon reduction process for old landfill sites according to claim 6, characterized in that: wherein, The duration t of the supplementary aeration is greater than or equal to 0.018514*total mass of garbage in the pile, The unit of the duration t of the supplementary aeration is min, and the total mass of garbage in the pile is measured in wet weight, kg.

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