CN114956502B - A method and system for two-stage thermal hydrolysis of municipal sludge - Google Patents
A method and system for two-stage thermal hydrolysis of municipal sludge Download PDFInfo
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- 239000010802 sludge Substances 0.000 title claims abstract description 128
- 238000009283 thermal hydrolysis Methods 0.000 title claims abstract description 50
- 238000000034 method Methods 0.000 title claims abstract description 21
- 238000006460 hydrolysis reaction Methods 0.000 claims abstract description 73
- 230000007062 hydrolysis Effects 0.000 claims abstract description 71
- ZCCIPPOKBCJFDN-UHFFFAOYSA-N calcium nitrate Chemical compound [Ca+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ZCCIPPOKBCJFDN-UHFFFAOYSA-N 0.000 claims abstract description 34
- 239000007788 liquid Substances 0.000 claims abstract description 30
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 28
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims abstract description 22
- 239000003337 fertilizer Substances 0.000 claims abstract description 20
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims abstract description 19
- 229910017604 nitric acid Inorganic materials 0.000 claims abstract description 19
- 238000000926 separation method Methods 0.000 claims abstract description 17
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 16
- 235000012255 calcium oxide Nutrition 0.000 claims abstract description 11
- 239000000292 calcium oxide Substances 0.000 claims abstract description 11
- 239000002689 soil Substances 0.000 claims abstract description 9
- 230000002378 acidificating effect Effects 0.000 claims abstract description 8
- 238000005903 acid hydrolysis reaction Methods 0.000 claims abstract description 6
- 239000000706 filtrate Substances 0.000 claims abstract description 5
- 238000003756 stirring Methods 0.000 claims description 11
- 230000018044 dehydration Effects 0.000 claims description 8
- 238000006297 dehydration reaction Methods 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 6
- 230000035484 reaction time Effects 0.000 claims description 5
- 239000002002 slurry Substances 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 3
- 229920006395 saturated elastomer Polymers 0.000 claims description 3
- 239000005909 Kieselgur Substances 0.000 claims 4
- 239000003153 chemical reaction reagent Substances 0.000 claims 2
- 238000007865 diluting Methods 0.000 claims 1
- 239000002893 slag Substances 0.000 abstract description 10
- 238000004064 recycling Methods 0.000 abstract description 8
- 230000000694 effects Effects 0.000 abstract description 7
- 230000001105 regulatory effect Effects 0.000 abstract description 4
- 235000015097 nutrients Nutrition 0.000 abstract description 3
- 238000003825 pressing Methods 0.000 description 7
- 239000003814 drug Substances 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 4
- 229910001424 calcium ion Inorganic materials 0.000 description 4
- 238000006386 neutralization reaction Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 230000035699 permeability Effects 0.000 description 3
- 238000004537 pulping Methods 0.000 description 3
- 238000005086 pumping Methods 0.000 description 3
- QJZYHAIUNVAGQP-UHFFFAOYSA-N 3-nitrobicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid Chemical compound C1C2C=CC1C(C(=O)O)C2(C(O)=O)[N+]([O-])=O QJZYHAIUNVAGQP-UHFFFAOYSA-N 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 2
- DHMQDGOQFOQNFH-UHFFFAOYSA-N Glycine Chemical compound NCC(O)=O DHMQDGOQFOQNFH-UHFFFAOYSA-N 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 229910052783 alkali metal Inorganic materials 0.000 description 2
- 150000001340 alkali metals Chemical class 0.000 description 2
- 235000001014 amino acid Nutrition 0.000 description 2
- 150000001413 amino acids Chemical class 0.000 description 2
- 229910052791 calcium Inorganic materials 0.000 description 2
- 239000011575 calcium Substances 0.000 description 2
- 238000010668 complexation reaction Methods 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 239000012065 filter cake Substances 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 238000005189 flocculation Methods 0.000 description 2
- 230000016615 flocculation Effects 0.000 description 2
- 239000004021 humic acid Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 230000002209 hydrophobic effect Effects 0.000 description 2
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 2
- 230000003472 neutralizing effect Effects 0.000 description 2
- 239000005416 organic matter Substances 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 235000018102 proteins Nutrition 0.000 description 2
- 102000004169 proteins and genes Human genes 0.000 description 2
- 108090000623 proteins and genes Proteins 0.000 description 2
- 239000010865 sewage Substances 0.000 description 2
- 230000008093 supporting effect Effects 0.000 description 2
- WHUUTDBJXJRKMK-UHFFFAOYSA-N Glutamic acid Natural products OC(=O)C(N)CCC(O)=O WHUUTDBJXJRKMK-UHFFFAOYSA-N 0.000 description 1
- 239000004471 Glycine Substances 0.000 description 1
- QNAYBMKLOCPYGJ-REOHCLBHSA-N L-alanine Chemical compound C[C@H](N)C(O)=O QNAYBMKLOCPYGJ-REOHCLBHSA-N 0.000 description 1
- WHUUTDBJXJRKMK-VKHMYHEASA-N L-glutamic acid Chemical compound OC(=O)[C@@H](N)CCC(O)=O WHUUTDBJXJRKMK-VKHMYHEASA-N 0.000 description 1
- 235000004279 alanine Nutrition 0.000 description 1
- 244000052616 bacterial pathogen Species 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 235000013922 glutamic acid Nutrition 0.000 description 1
- 239000004220 glutamic acid Substances 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 239000000413 hydrolysate Substances 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 244000005700 microbiome Species 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 235000016709 nutrition Nutrition 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000004016 soil organic matter Substances 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/10—Treatment of sludge; Devices therefor by pyrolysis
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
- C02F11/121—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
- C02F11/122—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering using filter presses
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
- C02F11/121—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
- C02F11/123—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering using belt or band filters
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
- C02F11/121—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
- C02F11/127—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering by centrifugation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
- C02F11/14—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents
- C02F11/143—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents using inorganic substances
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
- C02F11/14—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents
- C02F11/143—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents using inorganic substances
- C02F11/145—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents using inorganic substances using calcium compounds
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A40/00—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production
- Y02A40/10—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production in agriculture
- Y02A40/20—Fertilizers of biological origin, e.g. guano or fertilizers made from animal corpses
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/20—Sludge processing
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Mechanical Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Treatment Of Sludge (AREA)
- Fertilizers (AREA)
Abstract
The invention relates to the related technical field of sludge treatment and disposal, and provides a municipal sludge two-stage thermal hydrolysis method and a system thereof, which can solve the technical problems of incomplete municipal sludge hydrolysis and poor solid-liquid separation effect, improve the fertilizer efficiency of subsequent liquid fertilizers, reduce the water content of dry slag and realize the recycling utilization of sludge, and are characterized in that the method comprises the following steps of: step 2, outputting the sludge to a first hydrolysis device, adding a dilute nitric acid solution containing calcium nitrate into the first hydrolysis device, regulating the pH of the sludge to be acidic, and performing thermal acid hydrolysis at high temperature, step 3, outputting the sludge to a second hydrolysis device, adding industrial diatomite into the second hydrolysis device, regulating the pH of the sludge to be weak alkaline by using quicklime, performing low-temperature thermal hydrolysis, step 4, outputting the sludge to a solid-liquid separation device, collecting filtrate by the solid-liquid separation device, recovering nutrient components in the sludge, and simultaneously taking dry slag as landfill cover soil to realize the recycling of the sludge.
Description
Technical Field
The invention relates to the technical field related to sludge treatment, in particular to a municipal sludge two-stage thermal hydrolysis method and a municipal sludge two-stage thermal hydrolysis system
Background
With the rapid development of the number and scale of cities in the world, the discharge amount of municipal sewage is also rapidly increased, and continuously municipal sludge is generated in the sewage purification process, so that how to scientifically and effectively treat the amount of sludge has become a new problem of urban development. Municipal sludge not only has extremely complex components and extremely high water content, but also contains a large amount of nutrient substances, pathogenic bacteria microorganisms, heavy metals and other toxic and harmful substances, and most of sludge is often accompanied with malodorous smell, so that the air quality is affected. If the sludge is not scientifically treated and is randomly piled up on the land, under the flushing of rainwater, pollutants in the sludge can permeate into underground water and soil, so that the national water and soil safety and the physical health of people are directly affected, and the reduction and resource utilization of the sludge become an urgent problem in China and even worldwide.
The thermal hydrolysis technology of sludge is a common technology for sludge treatment at present. In the thermal hydrolysis process, sludge floc decomposition, cell disruption and organic matter release can be realized, the sludge is harmless, the sludge volume is reduced, the dehydration performance is improved, and meanwhile, the content of volatile organic matters in the sludge is reduced, so that the stabilization of the sludge is realized. However, the prior thermal hydrolysis technology is faced with the problems of incomplete hydrolysis, poor solid-liquid separation effect and dispersed utilization of heat in the industrialized scale popularization, so that the fertilizer efficiency of the follow-up liquid fertilizer is low, and the water content of dry slag is high, thereby influencing the follow-up recycling.
Disclosure of Invention
The invention provides a municipal sludge two-stage thermal hydrolysis method and a municipal sludge two-stage thermal hydrolysis system, which can solve the technical problems of incomplete municipal sludge hydrolysis and poor solid-liquid separation effect, improve the fertilizer efficiency of a subsequent liquid fertilizer, reduce the water content of dry slag and realize the recycling of sludge.
The technical scheme is as follows:
a municipal sludge two-stage thermal hydrolysis method is characterized in that:
step 1, slurrying sludge;
Step 2, outputting the sludge to a first hydrolysis device, adding a dilute nitric acid solution containing calcium nitrate into the first hydrolysis device, adjusting the pH of the sludge to be acidic, and performing thermal acid hydrolysis at a high temperature;
step3, outputting the sludge to a second hydrolysis device, adding industrial diatomite into the second hydrolysis device, adjusting the pH of the sludge to be alkalescent by using quicklime, and performing low-temperature thermal hydrolysis;
And step 4, outputting the sludge to a solid-liquid separation device, collecting filtrate through the solid-liquid separation device, recovering the nutritional ingredients in the sludge, and simultaneously taking dry slag as landfill covering soil to realize the recycling of the sludge.
Further, in the step 1, the municipal dewatered sludge with the water content of 80-85% is diluted to 88-90% by adding water in a slurrying tank, and is homogenized and stirred.
Further, the step 2 specifically comprises the steps of pumping the homogenized sludge slurry in the step 1 into a first hydrolysis device through a plunger pump, adding a dilute nitric acid solution containing calcium nitrate into the first hydrolysis device to adjust the pH of the sludge, maintaining the thermal hydrolysis temperature at 120-220 ℃, and maintaining the thermal hydrolysis reaction time at 30-120 min.
Further, the step 3 specifically comprises the steps of conveying the sludge hydrolyzed in the step 2 to a second hydrolysis device through self positive pressure in the first hydrolysis device, adding industrial diatomite into the second hydrolysis device, adjusting the pH of the sludge by using quicklime, maintaining the thermal hydrolysis temperature at 80-100 ℃, and enabling the thermal hydrolysis reaction time to be 30-60 min.
In the step 2, the mass fraction of the dilute nitric acid in the dilute nitric acid solution is 30%, the pH of the sludge is adjusted to 3-5, and the addition amount of the calcium nitrate accounts for 10% -25% of the dry weight of the sludge.
In step 3, the adding amount of the industrial diatomite accounts for 10% -25% of the dry weight of the sludge, and the pH=7-8 of the sludge is adjusted by using quicklime.
The invention also comprises a municipal sludge two-stage thermal hydrolysis system based on the method, which is characterized by comprising a slurrying tank, a first hydrolysis device, a second hydrolysis device, a solid-liquid separation device, a liquid fertilizer collecting device and a dry residue collecting device which are sequentially connected through pipelines, wherein the first medicament tank is connected with the first hydrolysis device through a pipeline, the second medicament tank is connected with the second hydrolysis device through a pipeline, and a negative pressure fan and a condenser are sequentially connected on a branch pipeline connected with an air outlet port of the second hydrolysis device and the slurrying tank for recovering heat and recycling reclaimed water.
Further, the slurrying tank is used for adding water to dilute municipal dewatered sludge with the water content of 80% -85% to 88% -90%, and homogenizing and stirring the municipal dewatered sludge.
Further, the first hydrolysis device is used for adding a dilute nitric acid solution containing calcium nitrate, adjusting the pH of the sludge to be acidic, and then carrying out high-temperature thermal acid hydrolysis on the sludge.
Further, the first hydrolysis device is provided with a heating jacket, wherein the heating medium is saturated steam or heat conducting oil.
Further, the second hydrolysis device is used for adding industrial diatomite, and low-temperature thermal hydrolysis is carried out on the sludge after the pH value of the sludge is adjusted to be alkalescent by adopting quicklime.
Furthermore, the second hydrolysis device is a normal pressure container, and the outer wall of the second hydrolysis device is provided with a cooling jacket, so that the hydrolysis reaction is ensured to be carried out at a proper temperature.
Further, the solid-liquid separation device is a plate-frame filter pressing device or a centrifugal dehydration device or a belt filter pressing device.
Further, the slurrying tank, the first hydrolysis device and the second hydrolysis device are all provided with variable frequency stirring devices, and the stirring rotating speed is set to be 50-75 rpm.
The method has the beneficial effects that:
According to the invention, through setting two-stage hydrolysis, high-temperature thermal hydrolysis is performed in a first hydrolysis device, calcium nitrate is utilized to have strong oxidability under an acidic condition, the sludge floc can be effectively destroyed under a hot acid condition, so that an extracellular polymer is shed and dissolved in a water phase, because the surface of the sludge is negatively charged, divalent calcium ions can play a role in bridging flocculation and electric neutralization on sludge cells, meanwhile, calcium ions have an alkali metal chelating property and carry out complexation reaction with proteins, the dehydration performance of the sludge is improved through hydrophobic effect and hydrogen bonding, calcium nitrate is used as a common agricultural fertilizer, the fertilizer efficiency of the liquid fertilizer can be improved, meanwhile, calcium-containing dry slag can be used for improving alkalized soil, then the low-temperature thermal hydrolysis is performed in a second hydrolysis device, the industrial diatomite contains a small amount of substances such as Al 2O3、Fe2O3, caO and MgO, and the like, the effect of electric neutralization is achieved in the process of neutralizing nitric acid, meanwhile, the specific surface area of the diatomite in a dilute nitric acid environment is improved, a loose porous structure is modified in the filter pressing process, the skeleton supporting effect is achieved, the water permeability of the sludge cake is improved, the water-permeable property is further improved, the dry slag is further improved, the water-free of the sludge is further improved, the dry sludge is not separated from the water-containing sludge is thoroughly solved, and the technical problem of the dry sludge is thoroughly solved.
Drawings
FIG. 1 is a schematic diagram of the overall structure of the system of the present invention.
Detailed Description
For a better description of the objects, technical solutions and advantages of the present invention, the present invention will be further described with reference to the following specific examples.
Example 1
A municipal sludge two-stage thermal hydrolysis system comprises a slurrying tank, a first hydrolysis device, a second hydrolysis device, a solid-liquid separation device, a liquid fertilizer collection device and a dry residue collection device which are sequentially connected through pipelines, wherein a first medicament tank is connected with the first hydrolysis device through a pipeline, a second medicament tank is connected with the second hydrolysis device through a pipeline, and an air outlet port of the second hydrolysis device is connected with a negative pressure fan and a condenser which are sequentially connected to a branch pipeline of the slurrying tank and used for recovering heat and recycling reclaimed water.
The slurrying tank is used for adding water into municipal dewatered sludge with the water content of 80-85% to dilute the municipal dewatered sludge to 88-90%, and homogenizing and stirring the municipal dewatered sludge.
The first hydrolysis device is provided with a heating jacket, wherein the heating medium is saturated steam or heat conducting oil. The first hydrolysis device is used for adding a dilute nitric acid solution containing calcium nitrate, adjusting the pH value of the sludge to be acidic, and then carrying out high-temperature hot acid hydrolysis on the sludge.
The second hydrolysis device is a normal pressure container, and the outer wall of the second hydrolysis device is provided with a cooling jacket to ensure that the hydrolysis reaction is carried out at a proper temperature. The second hydrolysis device is used for adding industrial diatomite, and low-temperature thermal hydrolysis is carried out on the sludge after the pH value of the sludge is regulated to be slightly alkaline by adopting quicklime.
The solid-liquid separation device is a plate-frame filter pressing device, a centrifugal dehydration device or a belt filter pressing device.
The pulping tank, the first hydrolysis device and the second hydrolysis device are all provided with variable frequency stirring devices, and the stirring rotating speed is set to be 50-75 rpm.
Example 2
A method for two-stage thermal hydrolysis of municipal sludge, comprising the steps of:
(1) Pulping sludge, namely adding water into municipal dewatered sludge with the water content of 80% -85% in a pulping tank to dilute the sludge to 90%, and homogenizing and stirring the sludge.
(2) The first thermal hydrolysis of sludge, namely pumping the homogenized sludge slurry into a first hydrolysis device through a plunger pump, respectively storing dilute nitric acid and calcium nitrate in a first medicament tank, and feeding the calcium nitrate and a dilute nitric acid solution into the first hydrolysis device through pipeline transportation, wherein the mass fraction of the dilute nitric acid is 30%, the pH of the sludge is regulated to 3, the calcium nitrate addition amount accounts for 25% of the dry weight of the sludge, the thermal hydrolysis temperature is maintained at 120 ℃, the thermal hydrolysis reaction time is maintained at 120min,
(3) And (3) carrying out second thermal hydrolysis on the sludge, conveying the sludge after the first thermal hydrolysis into a second hydrolysis device through self positive pressure, adding industrial-grade diatomite into the second hydrolysis device, wherein the adding amount of the diatomite accounts for 10% of the dry weight of the sludge, adjusting the pH to about 7 by using quicklime, maintaining the thermal hydrolysis temperature at 90 ℃, and carrying out thermal hydrolysis reaction for 60min.
(4) Pumping the sludge after the second thermal hydrolysis into a diaphragm type plate-and-frame filter press through a plunger pump for solid-liquid separation, wherein the feeding pressure is 1.0Mpa, the feeding time is 40min, the squeezing pressure is 1.0Mpa, the squeezing time is 60min, after the filter pressing liquid passes through a filtering device, water insoluble matters in filtrate are removed, the obtained filtrate passes through an MVR evaporation concentration device, the evaporation temperature is 95 ℃ and is concentrated by 20 times, the obtained concentrated solution is used as a liquid fertilizer, and a filter cake is used as landfill covering soil.
The main realization principle of the system and the method is that the high-temperature thermal hydrolysis is firstly carried out in a first hydrolysis device, calcium nitrate is utilized to have strong oxidability under the acidic condition, the sludge floc can be effectively destroyed under the thermal acid condition, the extracellular polymer is shed and dissolved in a water phase, because the surface of the sludge is negatively charged, divalent calcium ions can play the roles of bridging flocculation and electric neutralization on sludge cells, meanwhile, calcium ions have the alkali metal chelating property and carry out complexation reaction with proteins, the dehydration performance of the sludge is improved through the hydrophobic effect and the hydrogen bonding, calcium nitrate is used as a common agricultural fertilizer, the fertilizer efficiency of the liquid fertilizer can be improved, meanwhile, calcium-containing dry slag can be used for improving alkalized soil, then the low-temperature thermal hydrolysis is carried out in a second hydrolysis device, the industrial diatomite contains a small amount of substances such as Al 2O3、Fe2O3, caO and MgO, and the like, the effect of electric neutralization is achieved in the process of neutralizing nitric acid, meanwhile, the specific surface area of the diatomite is improved in the dilute nitric acid environment, the porous structure is modified in the filter pressing process, the skeleton supporting effect is achieved, the water permeability of the sludge cake is improved, and the water permeability of the sludge is further improved.
The experimental data are as follows, the sludge hydrolysate and the dry slag after press filtration in the second hydrolysis device are detected, wherein the capillary water absorption time (CST) is 20.4s, the water content of a filter cake is stabilized below 40%, the dehydration performance is greatly improved, the dehydration is very easy, the component detection is carried out on the obtained liquid fertilizer, the free amino acid is more than or equal to 100g/L, wherein the free amino acid is mainly alanine, glutamic acid and glycine, the organic matter is more than or equal to 200g/L, the humic acid is more than or equal to 50g/L, the soil organic matter can be increased when the liquid fertilizer is applied into soil, the cultivated land quality is improved, the crop root system environment is improved, the humic acid promotes the growth and development of crops, stimulates the root system activity of the crops, and is beneficial to promoting the absorption and utilization of the crops to nutrients. Therefore, the invention solves the technical problems of incomplete municipal sludge hydrolysis and poor solid-liquid separation effect, and achieves the beneficial effects of improving the fertilizer efficiency of the liquid fertilizer, reducing the water content of dry slag and realizing the recycling of sludge.
While the invention has been described in detail in connection with specific embodiments thereof, it is to be understood that the invention is not limited to the precise embodiments, and that various changes and modifications can be effected therein without departing from the scope of the invention as defined by the appended claims.
Claims (10)
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| CN202210357196.4A CN114956502B (en) | 2022-04-07 | 2022-04-07 | A method and system for two-stage thermal hydrolysis of municipal sludge |
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| CN202210357196.4A CN114956502B (en) | 2022-04-07 | 2022-04-07 | A method and system for two-stage thermal hydrolysis of municipal sludge |
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| CN114956502A CN114956502A (en) | 2022-08-30 |
| CN114956502B true CN114956502B (en) | 2025-01-07 |
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| JP2000197899A (en) * | 1999-01-07 | 2000-07-18 | Kankyo Biken:Kk | Agent and method for purification treatment of lake, marsh, and the like |
| JP2001104998A (en) * | 1999-10-05 | 2001-04-17 | Kankyo Biken:Kk | Fluid mud immediate effect solidifying agent |
| JP2005161253A (en) * | 2003-12-04 | 2005-06-23 | Osaka Industrial Promotion Organization | Bio-flocculant of sludge and method and apparatus for treating sludge |
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