CN112807601A - Organic pollutant environment-friendly pyrolysis treatment method - Google Patents

Abstract

The invention proposes a method for the environmental protection pyrolysis treatment of organic pollutants. A tank-type ultrasonic generator is used to perform ultrasonic anaerobic pretreatment on the organic pollutants, and the original organic pollutants are taken and placed in the reaction tank of the tank-type ultrasonic generator. Add NaOH under stirring to decompose the organic pollutants by ultrasonic, and put the organic pollutants after ultrasonic decontamination into the anaerobic digestion reactor, and the organic pollutants react with ozone and defoaming. After the ultrasonic anaerobic pretreatment is completed, use The pyrolysis unit performs the pyrolysis process of polluted organics, collects the solid residues and weighs them, and calculates the efficiency of pyrolysis.

Description

Organic pollutant environment-friendly pyrolysis treatment method

Technical Field

The invention relates to a method for degrading pollutants, in particular to a method for carrying out environment-friendly pyrolysis treatment on organic pollutants.

Background

The persistent organic pollutants enter the urban sewage treatment system along with industrial wastewater and domestic sewage, and due to lipophilicity, hydrophobicity and difficult degradability of the persistent organic pollutants, besides a small amount of the persistent organic pollutants are decomposed and utilized by microorganisms, the persistent organic pollutants are mostly adsorbed and enriched in sludge, so that the persistent organic pollutants seriously affect the agricultural safety and effectiveness of the sludge and become a sludge land utilization limiting factor which is in proportion to heavy metals.

Disclosure of Invention

In order to solve the technical problems in the prior art, the invention provides an organic pollutant environment-friendly pyrolysis treatment method, which adopts a groove type ultrasonic generator to carry out ultrasonic anaerobic pretreatment on organic pollutants: placing the original machine pollutants in a reaction tank of a tank type ultrasonic generator, adding NaOH under stirring to keep the pH value stable for 4min, placing in a refrigerator at 2 ℃ for 5-7h, taking out from the refrigerator, and placing to room temperature; setting acoustic energy density of 0.2W/mL, O.5W/mL, 1.0W/mL and 2.0W/mL to carry out ultrasonic cracking on the organic pollutants, wherein 6 cracking times are respectively set under each acoustic energy density: 5min, 10min, 20min, 40min and 60 min; putting the organic pollutants subjected to ultrasonic cracking into an anaerobic digestion reactor, inputting ozone at a gas flow of 5L/min, reacting the organic pollutants with the ozone and defoaming, collecting tail gas, adopting a 20% iodine solution, and titrating the ozone concentration in the tail gas by an iodometry method;

after ultrasonic anaerobic pretreatment is finished, a pyrolysis process of polluting organic matters is carried out by adopting a pyrolysis device, organic pollutants are added through a feed inlet at the top of the pyrolysis device, nitrogen is introduced into the pyrolysis device at a flow rate of 0.8L/min, 20min is kept to remove air in the device, the pyrolysis device is heated to a target temperature, the nitrogen flow rate is adjusted to 0.2L/min, after pyrolysis is finished, the pyrolysis device is naturally cooled to the room temperature, solid residues are collected and weighed, the solid residues are condensed in glacial ethanol at the temperature of-20 ℃, volatile components are condensed into liquid phase products to be collected for characterization analysis, and the pyrolysis efficiency is calculated by measuring the weight difference of the pyrolysis device before and after pyrolysis.

Further, the method also comprises a step of verifying the pyrolysis sufficiency, which comprises the following steps:

step 1, placing about 5g of a sample of the solid residue after the reaction in a mortar, pouring liquid nitrogen, and quickly grinding the sample to be powder;

step 2, placing the sample powder in the step 1 in a freeze dryer, and freeze-drying at 63Pa and-25 ℃ for about 24 hours;

and 3, putting 2g of the sample in the step 2 into a filter cylinder, putting the filter cylinder into an extraction tube, pouring n-hexane with the volume of about 2/3 distillation flasks, adjusting the temperature to 70 ℃, controlling the siphoning rate to reflux for 5-10 times per hour for 8-12 hours, collecting the refluxed n-hexane droplets by using filter paper, after the n-hexane volatilizes, if no trace is left, the pyrolysis is proved to be sufficient, otherwise, the pyrolysis time is continuously prolonged.

Furthermore, the method also comprises a sampling test for verifying the pretreatment effect, wherein the gas production amount and the pH value of the anaerobic digestion reactor are measured once a day, VS, VSS, TCOD, SCOD, TKN, total carbohydrate, soluble protein, VFA and ammonia nitrogen parameters generated by anaerobic digestion are measured three times a week, and simultaneously the content of methane in the produced gas is measured in a stable operation stage.

Detailed Description

The biodegradation process of the organic pollutants is long, and on one hand, macromolecular organic matters in the organic pollutants cannot directly enter cells to be decomposed and utilized because the macromolecular organic matters are blocked by cell walls and cell membranes of microorganisms; on the other hand, the organic pollutants have stable chemical structures, and the degradation difficulty is increased along with the increase of the molecular weight and the number of aromatic hydrocarbon rings, so that the biological treatment efficiency is low. Therefore, the organic pollutants need to be pretreated before pyrolysis, so that the cell walls of the organic pollutant microorganisms are accelerated to be damaged, the substances in the cells are fully released, the organic pollutants are promoted to be hydrolyzed and acidified, the decomposition and absorption capacity of the microorganisms on the organic matters is improved, and the organic matters enter the cells and the discharge of metabolites in the cells is promoted.

The pretreatment process of the ultrasonic anaerobic treatment device adopts ultrasonic anaerobic treatment, and the ultrasonic generator adopts a groove type ultrasonic generator which is a multi-frequency multi-power ultrasonic device. Placing original organic pollutants in a reaction tank of an ultrasonic generator, cooling to room temperature, adding a certain volume of 4mol/L NaOH under stirring to keep the pH value stable for 2min, pretreating organic pollutants, and placing at 4 deg.C iceStoring for 5-7h, taking out from the refrigerator, and cooling to room temperature. Under the frequency of 20KHz, the power of 160W, 400W, 800W and 1600W, namely the acoustic energy density of 0.2W/mL, O.5W/mL, 1.0W/mL and 2.0W/mL are respectively selected to carry out ultrasonic crack on the organic pollutants. The total 6 cracking times are set under each sound energy density as follows: 5min, 10min, 20min, 40min and 60 min. Samples were taken for measurement after the end of each irradiation time. Adding 200g of organic pollutants into a 250mL conical bottle with a plug, adding a certain amount of alkali into the organic pollutants by using 4mol/L of NaOH to control the adding amount of the alkali to be 0.02, 0.04, 0.09, O.25, O.75, 1.00, 1.25 and 1.59NaOH/gTS, uniformly mixing, and then introducing N into the conical bottle₂About 4min to drive off residual air, adding stopper, shaking and stirring on an air bath shaker (25 + -2) deg.C, and sampling at 0.5, 1.0, 5.0, 10, 24h for analysis.

Putting the organic pollutants subjected to ultrasonic cracking into an anaerobic digestion reactor, wherein the anaerobic digestion reactor is an air source generator, the maximum ozone amount is 10g/h, the ozone gas production concentration is 33mg/L, and the organic pollutants enter an ozone contact column from the bottom of the ozone contact column through an Qinzhen alloy micropore aeration disc with the diameter of 8cm at the gas flow rate of 5L/min; the height of the ozone contact column is 1m, the effective volume is 5L, and the volume of the actual reaction polluted organic matter is 3L; after the reaction starts, a large amount of foam is generated due to the interaction of ozone and the polluted organic matters, ozone gas carrying a large amount of polluted organic matter particles enters a reaction device with the height of 0.3m and the diameter of 12cm from the top of a contact column for further reaction and defoaming, and is pumped back into the contact column from the bottom of a reactor through a peristaltic pump, so that the contact time of the ozone and the polluted organic matters is circularly increased, and the polluted organic matters and the ozone are fully reacted; and collecting tail gas by adopting 20% KI solution, and titrating the concentration of ozone in the tail gas by adopting an iodometry method so as to accurately calculate the actual ozone consumption of the organic pollutants. The ozone utilization efficiency in the reaction process is more than 90 percent.

To verify the effect of the pretreatment, a sampling test was performed: the test is carried out in two batches, the first batch of test runs 6 sets of anaerobic reactors in total, one reactor treats the original non-pretreated polluted organic matter, the retention time of the polluted organic matter is 20d, the other 5 reactors treat the pretreated polluted organic matter, the retention time of the polluted organic matter is respectively set to be 20, lO, 8, 5 and 2d, and the retention time is respectively marked as P.1, P.2, P.3, P.4 and P.5. The initial inoculation amount of the 6 sets of reactors is 760g, the residence time (SRT) of organic pollutants in the 6 sets of reactors is 20d at the beginning stage of the test, after a period of time, the SRT of the 3 rd to 6 th sets of reactors is gradually shortened to 10 d, 8d, 5d and 2d respectively, the gas production rate and the pH value of the organic pollutants are measured every day during the period, VS, TS, VSS, TSS, TCOD, VFA and alkalinity are measured twice every week, and the reactors are considered to reach a stable state when all indexes are basically stable. In the stable operation stage of each reactor, the gas production amount and the pH value of the digestion reactor are measured once a day, VS, VSS, TCOD, SCOD, TKN, total carbohydrate, soluble protein, VFA, ammonia nitrogen and the like generated by anaerobic digestion are measured three times every week, and simultaneously, the content of methane in the produced gas is measured in the stable operation stage. In the second run, 2 reactors were run in parallel, all processing the non-pretreated original contaminated organics, with the SRT set to 8d and 5d, respectively, and the test procedure was as above.

In the dynamic test, after the reactors are operated for a period of time to reach a stable state, the microbial biomass and activity of the digestion pollution organic matters in the reactors are considered to be stable, and the pollution organic matters are taken as static inoculation pollution organic matters. In the completely mixed anaerobic digestion reactor, the residence time of the contaminated organic matter and the dosage rate of the contaminated organic matter are in inverse relation, namely, when the residence time of the contaminated organic matter is 20 days, 10 days, 8 days, 5 days and 2 days, the corresponding dosage rates are 5 percent, 10 percent, 12.5 percent, 20 percent and 50 percent respectively. In order to investigate the influence of the retention time of the polluted organic matter on the degradation process of the organic matter, the polluted organic matter is put into an anaerobic digestion reactor at one time according to the dosing rate corresponding to the retention time of the polluted organic matter in the original reactor, samples are taken from the reactor at fixed time every day for measurement, the test period is set to 5d, and samples are taken at intervals of 2h for measurement in the first 8 hours when the digestion reaction is started. The measurement items mainly include: soluble proteins, soluble carbohydrates, ammonia nitrogen and VFA.

After the pyrolysis pretreatment reaction is finished, a pyrolysis device is adopted to carry out the pyrolysis process of the polluted organic matters, and the pyrolysis device comprises a nitrogen generator, a feeding hole, a reactor and a solid residue collecting part.

After organic pollutants are added into a pyrolysis device with an effective volume of 2L through a top feeding hole, the feeding hole is closed, a nitrogen gas inlet valve is opened, nitrogen gas is introduced into the pyrolysis device at a flow rate of 0.8L/min, air in the device is removed by keeping for 20min, and meanwhile, a pyrolysis tube is heated to a target temperature (250 ℃ and 600 ℃). Then, the nitrogen flow rate was adjusted to 0.2L/min and maintained until the end. The contaminated organics are subjected to fast pyrolysis at the target temperature and held for a period of time to ensure adequate pyrolysis.

After pyrolysis, the pyrolysis apparatus was cooled naturally to room temperature, and the solid residue was collected and weighed. After the reaction in the reactor is completed for a certain time, opening a little outlet valve, slowly releasing the pressure of the device to be below 3Pa, and then quickly opening the outlet valve to enable the solid residue in the reactor to enter a solid residue collecting device. Finally, the solid residue after the reaction was taken out. Condensing most of volatile components into liquid phase products under the condition of-20 ℃ of ice ethanol condensation, and collecting the liquid phase products for characterization and analysis; after the temperature of the fast pyrolysis device is reduced to the room temperature, the pyrolysis efficiency is calculated by measuring the weight difference of the pyrolysis device before and after pyrolysis. The pyrolysis gas was collected with a gas collection bag and its composition was determined by gas chromatography.

Verification of the completeness of pyrolysis:

step 1, taking about 5g of a sample of the solid residue after the reaction, putting the sample into a mortar, pouring liquid nitrogen into the mortar, and quickly grinding the sample into powder.

And 2, placing the sample powder obtained in the step 1 in a freeze dryer, and freeze-drying at 63Pa and 25 ℃ for about 24 hours. The ground sample powder should be sent to a freeze dryer for drying, otherwise, a large amount of moisture in the air is condensed on the sample, so that the moisture content in the sample is measured to be higher.

And 3, putting 2g of the sample in the step 2 into a filter cartridge, putting the filter cartridge into an extraction tube, and pouring about 2/3 volumes of n-hexane in a distillation flask. Regulating the temperature to 70 ℃, controlling the siphoning rate to reflux for 5-10 times per hour, and controlling the duration to be 8-12 h. And collecting the reflowed n-hexane liquid drops by using filter paper, after the n-hexane volatilizes, if no trace is left, the pyrolysis is sufficient, and otherwise, the pyrolysis time is continuously prolonged.

The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are merely illustrative of the principles of the present invention, but that various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined by the appended claims and their equivalents.

Claims (3)

1. An environment-friendly pyrolysis treatment method for organic pollutants,

carrying out ultrasonic anaerobic pretreatment on organic pollutants by adopting a groove type ultrasonic generator: placing the original machine pollutants in a reaction tank of a tank type ultrasonic generator, adding NaOH under stirring to keep the pH value stable for 4min, placing in a refrigerator at 2 ℃ for 5-7h, taking out from the refrigerator, and placing to room temperature; setting acoustic energy density of 0.2W/mL, O.5W/mL, 1.0W/mL and 2.0W/mL to carry out ultrasonic cracking on the organic pollutants, wherein 6 cracking times are respectively set under each acoustic energy density: 5min, 10min, 20min, 40min and 60 min; putting the organic pollutants subjected to ultrasonic cracking into an anaerobic digestion reactor, inputting ozone at a gas flow of 5L/min, reacting the organic pollutants with the ozone and defoaming, collecting tail gas, adopting a 20% iodine solution, and titrating the ozone concentration in the tail gas by an iodometry method;

after ultrasonic anaerobic pretreatment is finished, a pyrolysis process of polluting organic matters is carried out by adopting a pyrolysis device, organic pollutants are added through a feed inlet at the top of the pyrolysis device, nitrogen is introduced into the pyrolysis device at a flow rate of 0.8L/min, 20min is kept to remove air in the device, the pyrolysis device is heated to a target temperature, the nitrogen flow rate is adjusted to 0.2L/min, after pyrolysis is finished, the pyrolysis device is naturally cooled to the room temperature, solid residues are collected and weighed, the solid residues are condensed in glacial ethanol at the temperature of-20 ℃, volatile components are condensed into liquid phase products to be collected for characterization analysis, and the pyrolysis efficiency is calculated by measuring the weight difference of the pyrolysis device before and after pyrolysis.

2. The method for the environmental protection pyrolysis treatment of organic pollutants according to claim 1, further comprising a step of verifying the sufficiency of pyrolysis, comprising:

step 1, placing about 5g of a sample of the solid residue after the reaction in a mortar, pouring liquid nitrogen, and quickly grinding the sample to be powder;

step 2, placing the sample powder in the step 1 in a freeze dryer, and freeze-drying at 63Pa and 25 ℃ for about 24 hours;

and 3, putting 2g of the sample in the step 2 into a filter cylinder, putting the filter cylinder into an extraction tube, pouring n-hexane with the volume of about 2/3 distillation flasks, adjusting the temperature to 70 ℃, controlling the siphoning rate to reflux for 5-10 times per hour for 8-12 hours, collecting the refluxed n-hexane droplets by using filter paper, after the n-hexane volatilizes, if no trace is left, the pyrolysis is proved to be sufficient, otherwise, the pyrolysis time is continuously prolonged.

3. The environmental protection pyrolysis treatment method for organic pollutants according to claim 1, further comprising a sampling test for verifying the pretreatment effect, wherein the gas production and the pH value of the anaerobic digestion reactor are measured once a day, VS, VSS, TCOD, SCOD, TKN, total carbohydrate, soluble protein, VFA and ammonia nitrogen parameters generated by anaerobic digestion are measured three times a week, and the content of methane in the produced gas is measured in a stable operation stage.