Garbage leachate treatment method based on pyrolysis

Abstract

The invention belongs to the technical field of landfill leachate treatment, and discloses a landfill leachate treatment method based on pyrolysis. Firstly, filtration is performed, and then Fenton oxidation is performed, so that the colloid stability can be broken, the subsequent pyrolysis temperature is reduced, and the pyrolysis efficiency is improved; then evaporation and concentration are carried out, and waste heat of generated steam is reused for the evaporation and concentration process through heat exchange so as to provide part of heat; and then pyrolysis is conducted, heat of generated pyrolysis gas is reused for the evaporation and concentration process through heat exchange so as to provide part of heat, the pyrolysis gas is subjected to purification treatment after being subjected to heat exchange and cooling to serve as pyrolysis fuel, and generated pyrolysis residues are subjected to activation treatment to serve as an adsorbent. By means of pyrolysis, zero emission of the landfill leachate is achieved, gas and solid generated by pyrolysis can be recycled, the resource recycling rate is increased, heat of gas generated in the evaporation concentration and pyrolysis process can be subjected to waste heat recycling through heat exchange, and energy consumption is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of landfill leachate treatment, and in particular to a landfill leachate treatment method based on pyrolysis. Background Art

[0002] Landfill leachate is a highly concentrated organic wastewater generated during landfill or dumping. Its composition is complex and poses significant risks. It contains high concentrations of chemical oxygen demand (COD), ammonia nitrogen (NH3-N), heavy metal ions (such as Pb, Cd, and Cr), refractory organic matter (such as polycyclic aromatic hydrocarbons and halogenated hydrocarbons), and high salinity. If not properly handled, it can cause severe pollution to soil, groundwater, and the surrounding ecosystem.

[0003] At present, the treatment technologies for landfill leachate are mainly divided into biological methods and physicochemical methods, but both have certain limitations. For example, although the operating cost of biological treatment methods (such as anaerobic / aerobic processes) is relatively low, they have poor adaptability to leachates with high concentrations, high salinity, and those containing toxic organic matter. Microorganisms are easily inhibited or even inactivated by poisoning, resulting in low treatment efficiency. The removal of ammonia nitrogen often requires additional deep denitrification units, which increases the process cost. Although membrane separation technologies (such as reverse osmosis and nanofiltration) can efficiently remove pollutants and produce high-quality effluent, the equipment investment and operation and maintenance costs are high, and the concentrated liquid produced still needs further disposal, which poses a risk of secondary pollution. To summarize the problems of the existing technology, it is difficult for traditional methods to balance the relationship between treatment efficiency, treatment cost, secondary pollution, and resource recovery. Therefore, the development of a landfill leachate treatment method that can efficiently and thoroughly degrade pollutants, minimize the generation of secondary waste, and achieve resource recovery at the same time is a problem that needs to be solved urgently. Summary of the Invention

[0004] The purpose of the present invention is to provide a landfill leachate treatment method based on pyrolysis to solve the above-mentioned problems existing in traditional treatment methods.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for treating landfill leachate based on pyrolysis, comprising the following steps:

[0007] filtering the landfill leachate to obtain a filtrate and a solid;

[0008] The filtrate is adjusted to a pH of 4 to 4.5, and ferric sulfate and hydrogen peroxide are added to perform Fenton oxidation treatment to obtain a treated liquid;

[0009] heating the treated liquid to evaporate and concentrate it to obtain a concentrated liquid;

[0010] The concentrated liquid is pyrolyzed to obtain pyrolysis gas and pyrolysis residue;

[0011] Purify the pyrolysis gas and use it as fuel for pyrolysis;

[0012] The pyrolysis residue is activated and used as an adsorbent.

[0013] Preferably, in the above-mentioned method for treating landfill leachate based on pyrolysis, the molar ratio of ferric sulfate to hydrogen peroxide is 1:2-6; and the concentration of hydrogen peroxide in the filtrate is 10-20 mL / L.

[0014] Preferably, in the above-mentioned method for treating landfill leachate based on pyrolysis, the time of the Fenton oxidation treatment is 2 to 4 hours.

[0015] Preferably, in the above-mentioned method for treating landfill leachate based on pyrolysis, the temperature of the evaporation and concentration is 180-220° C.; the evaporation and concentration is carried out until the volume of the treated liquid is reduced by 60-80%.

[0016] Preferably, in the above-mentioned landfill leachate treatment method based on pyrolysis, the pyrolysis temperature is 600-700°C.

[0017] Preferably, in the above-mentioned landfill leachate treatment method based on pyrolysis, the waste heat of the steam generated by the evaporation and concentration is recycled for evaporation and concentration through heat exchange.

[0018] Preferably, in the above-mentioned landfill leachate treatment method based on pyrolysis, the waste heat of the pyrolysis gas is reused for evaporation and concentration through heat exchange.

[0019] Preferably, in the above-mentioned landfill leachate treatment method based on pyrolysis, the activation is steam activation.

[0020] It can be seen from the above technical solutions that compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention first pre-treats landfill leachate by mechanically filtering to remove suspended matter and large particles, then performs Fenton oxidation, which can break the colloid stability, reduce the temperature of subsequent pyrolysis, and improve pyrolysis efficiency. Evaporation and concentration are then performed, and the waste heat of the steam generated by evaporation and concentration is reused in the evaporation and concentration process through heat exchange to provide a portion of the heat. Pyrolysis is then performed, and the heat of the generated pyrolysis gas is reused in the evaporation and concentration process through heat exchange to provide a portion of the heat. The pyrolysis gas is cooled by heat exchange and then subjected to purification treatments such as dust removal and desulfurization, and can be used as fuel in the pyrolysis process. The generated pyrolysis residue is activated and used as an adsorbent. Through pyrolysis treatment, the present invention achieves zero emission of landfill leachate. The gas, solid, and other products generated by pyrolysis can also be reused, thereby improving resource recycling efficiency. The heat of the gas generated during evaporation and concentration and pyrolysis can be recycled as waste heat through heat exchange, reducing energy consumption. DETAILED DESCRIPTION

[0022] The present invention provides a method for treating landfill leachate based on pyrolysis, comprising the following steps:

[0023] filtering the landfill leachate to obtain a filtrate and a solid;

[0024] The filtrate is adjusted to a pH of 4 to 4.5, and ferric sulfate and hydrogen peroxide are added to perform Fenton oxidation treatment to obtain a treated liquid;

[0025] heating the treated liquid to evaporate and concentrate it to obtain a concentrated liquid;

[0026] The concentrated liquid is pyrolyzed to obtain pyrolysis gas and pyrolysis residue;

[0027] Purify the pyrolysis gas and use it as fuel for pyrolysis;

[0028] The pyrolysis residue is activated and used as an adsorbent.

[0029] In the present invention, the solid obtained by filtration is mixed with domestic waste for treatment.

[0030] In the present invention, the molar ratio of ferric sulfate to hydrogen peroxide is preferably 1:2-6, more preferably 1:3-6, and more preferably 1:5; the concentration of hydrogen peroxide in the filtrate is preferably 10-20 mL / L, more preferably 13-17 mL / L, and more preferably 15 mL / L.

[0031] In the present invention, the Fenton oxidation treatment time is preferably 2 to 4 hours, more preferably 2.5 to 4 hours, and more preferably 3 hours.

[0032] In the present invention, the Fenton oxidation treatment process further includes stirring; the stirring speed is preferably 500 to 800 rpm, more preferably 600 to 800 rpm, and more preferably 800 rpm.

[0033] In the present invention, the Fenton oxidation treatment further includes homogenization; the homogenization time is preferably 30 to 60 minutes, more preferably 35 to 50 minutes, and even more preferably 40 minutes. The present invention does not limit the homogenization equipment, and a conventional homogenization tank in the art can be used.

[0034] In the present invention, the temperature of the evaporation concentration is preferably 180-220°C, more preferably 190-220°C, and more preferably 200°C; the evaporation concentration is preferably carried out until the volume of the treatment liquid is reduced by 60-80%, more preferably 70-80%, and more preferably 75%.

[0035] In the present invention, the pyrolysis temperature is preferably 600-700°C, more preferably 610-650°C, and even more preferably 620°C.

[0036] In the present invention, the pyrolysis is preferably carried out in the absence of air.

[0037] In the present invention, the waste heat of the steam generated by the evaporation and concentration is reused for evaporation and concentration through heat exchange.

[0038] In the present invention, the waste heat of the pyrolysis gas is recycled for evaporation and concentration through heat exchange.

[0039] In the present invention, the heat exchange method is preferably to use heat transfer oil as the medium and perform heat exchange through a heat exchanger.

[0040] In the present invention, the purification treatment preferably includes dust removal and desulfurization. The present invention does not limit the dust removal and desulfurization methods, and conventional flue gas dust removal and desulfurization operations in the art can be used.

[0041] In the present invention, the activation is preferably steam activation. The present invention does not limit the method of steam activation, and conventional steam activation operations in the art can be used.

[0042] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0043] Example 1

[0044] This embodiment provides a method for treating landfill leachate based on pyrolysis, comprising the following steps:

[0045] (1) Pretreatment: Filter the landfill leachate through a filter to obtain a filtrate and solids; mix the solids with domestic waste and perform corresponding treatment;

[0046] The pH of the filtrate was adjusted to 4.2 with acid, and then ferric sulfate and hydrogen peroxide were added at a molar ratio of 1:5 to make the concentration of hydrogen peroxide in the filtrate 15 mL / L. Fenton oxidation treatment was performed at a speed of 800 rpm for 3 hours to obtain a treated liquid;

[0047] Homogenize the treated liquid in a homogenizing tank for 40 min;

[0048] (2) Evaporation concentration and pyrolysis: The homogenized treated liquid is evaporated and concentrated at 200°C until the volume of the treated liquid is reduced by 75% to obtain a concentrated liquid;

[0049] The concentrated liquid is pyrolyzed at 620°C in an airtight condition to obtain pyrolysis gas and pyrolysis residue;

[0050] (3) Recycling: The waste heat of the steam generated by evaporation and concentration is exchanged with heat transfer oil as the medium, and the recovered heat is reused to provide part of the heat for the evaporation and concentration process;

[0051] The waste heat of the pyrolysis gas generated by pyrolysis is exchanged with heat transfer oil as the medium, and the recovered heat is reused to provide part of the heat for the evaporation and concentration process;

[0052] The pyrolysis gas after heat exchange is subjected to dust removal and desulfurization purification treatment and then collected as fuel for the pyrolysis process;

[0053] The pyrolysis residue produced by pyrolysis is steam activated and then recovered as an adsorbent.

[0054] Example 2

[0055] This embodiment provides a method for treating landfill leachate based on pyrolysis, comprising the following steps:

[0056] (1) Pretreatment: Filter the landfill leachate through a filter to obtain a filtrate and solids; mix the solids with domestic waste and perform corresponding treatment;

[0057] The pH of the filtrate was adjusted to 4.5 with acid, and then ferric sulfate and hydrogen peroxide were added at a molar ratio of 1:3 to make the concentration of hydrogen peroxide in the filtrate 20 mL / L. Fenton oxidation treatment was performed at a speed of 500 rpm for 2 hours to obtain a treated liquid;

[0058] Homogenize the treated liquid in a homogenizing tank for 60 min;

[0059] (2) Evaporation concentration and pyrolysis: The homogenized treated liquid is evaporated and concentrated at 220°C until the volume of the treated liquid is reduced by 80% to obtain a concentrated liquid;

[0060] The concentrated liquid is pyrolyzed at 650°C in an airtight condition to obtain pyrolysis gas and pyrolysis residue;

[0061] (3) Recycling: The waste heat of the steam generated by evaporation and concentration is exchanged with heat transfer oil as the medium, and the recovered heat is reused to provide part of the heat for the evaporation and concentration process;

[0062] The waste heat of the pyrolysis gas generated by pyrolysis is exchanged with heat transfer oil as the medium, and the recovered heat is reused to provide part of the heat for the evaporation and concentration process;

[0063] The pyrolysis gas after heat exchange is subjected to dust removal and desulfurization purification treatment and then collected as fuel for the pyrolysis process;

[0064] The pyrolysis residue produced by pyrolysis is steam activated and then recovered as an adsorbent.

[0065] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for treating landfill leachate based on pyrolysis, characterized in that: The following steps are involved: filtering the landfill leachate to obtain a filtrate and a solid; The filtrate is adjusted to a pH of 4 to 4.5, and ferric sulfate and hydrogen peroxide are added to perform Fenton oxidation treatment to obtain a treated liquid; heating the treated liquid to evaporate and concentrate it to obtain a concentrated liquid; The concentrated liquid is pyrolyzed to obtain pyrolysis gas and pyrolysis residue; Purify the pyrolysis gas and use it as fuel for pyrolysis; The pyrolysis residue is activated and used as an adsorbent.

2. The method for treating landfill leachate based on pyrolysis according to claim 1, characterized in that: The molar ratio of the ferric sulfate to the hydrogen peroxide is 1:2-6; and the concentration of the hydrogen peroxide in the filtrate is 10-20 mL / L.

3. The method for treating landfill leachate based on pyrolysis according to claim 2, characterized in that: The Fenton oxidation treatment time is 2 to 4 hours.

4. The method for treating landfill leachate based on pyrolysis according to claim 1 or 2, characterized in that: The temperature of the evaporation and concentration is 180-220° C.; the evaporation and concentration is performed until the volume of the treated liquid is reduced by 60-80%.

5. The method for treating landfill leachate based on pyrolysis according to claim 1, characterized in that: The pyrolysis temperature is 600-700°C.

6. The method for treating landfill leachate based on pyrolysis according to claim 4, characterized in that: The waste heat of the steam generated by the evaporation and concentration is reused for evaporation and concentration through heat exchange.

7. The method for treating landfill leachate based on pyrolysis according to claim 6, characterized in that: The waste heat of the pyrolysis gas is recycled for evaporation and concentration through heat exchange.

8. The method for treating landfill leachate based on pyrolysis according to claim 1, characterized in that: The activation is steam activation.