CN101186423A - Heat treatment-dehydration-fertilizer making method for town sewage and sludge - Google Patents

Heat treatment-dehydration-fertilizer making method for town sewage and sludge Download PDF

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Publication number
CN101186423A
CN101186423A CNA2007103020149A CN200710302014A CN101186423A CN 101186423 A CN101186423 A CN 101186423A CN A2007103020149 A CNA2007103020149 A CN A2007103020149A CN 200710302014 A CN200710302014 A CN 200710302014A CN 101186423 A CN101186423 A CN 101186423A
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China
Prior art keywords
sludge
treatment
dehydration
composting
mud
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CNA2007103020149A
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Chinese (zh)
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金宜英
李欢
聂永丰
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Tsinghua University
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Tsinghua University
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Priority to CNA2007103020149A priority Critical patent/CN101186423A/en
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    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02ATECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A40/00Adaptation technologies in agriculture, forestry, livestock or agroalimentary production
    • Y02A40/10Adaptation technologies in agriculture, forestry, livestock or agroalimentary production in agriculture
    • Y02A40/20Fertilizers of biological origin, e.g. guano or fertilizers made from animal corpses
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02WCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00Technologies for solid waste management
    • Y02W30/40Bio-organic fraction processing; Production of fertilisers from the organic fraction of waste or refuse

Abstract

A heat treatment-dehydration-making fertilizer method of urban sewage and sludge is provided, which pertains to the treatment filed of solid waste. Sodium hydroxide is added into dewatered sludge and stirred, hypoxic steam with temperature and pressure more than 250 DEG C and 4MPa is input, the temperature is raised to 120-140 DEG C for 40-100 min; the temperature is reduced to less than 100 DEG C, dehydrated liquid and dehydrated sludge cake with amount decreased are obtained after dehydration; the dehydrated liquid is treated by sand filtration and microfiltration, then whole filtration is carried out and the concentrated solution with humic acid more than 3wt percent is obtained; the humic acid liquid fertilizer is obtained after the concentrated solution is added with additive. The invention can greatly reduce the expenses of sludge heat treatment; water content of the obtained dehydrated sludge cake is less than 60 percent and the total solid reduces by 35 percent; the heavy mental content of the obtained humic acid liquid fertilizer is low, the pH value keeps in the range of weak alkaline and the pathogen is inactivated; the method is safe and efficient, complies with Fertilizer Application Guideline of National Ministry of Agriculture and can be widely applied to harmless, quantitative reduction and resource utilization treatment of urban sewage and sludge.

Description

Thermal treatment-the dehydration of treatment of town sewage and sludge-composting method
Technical field
The present invention relates to that treatment of town sewage and sludge after heat treatment dewaters, a kind of method of composting, belong to the solid waste process field.
Background technology
The most of city domestic sewages of China adopt activated sludge process to handle, the a large amount of excess sludge of annual generation, by 30,000,000,000 tons of sanitary sewage quantity dischargeds in 2006, processing rate 40%, mud (water ratio 99%) generation is 1% of a sewage load, then produce about 1.2 hundred million tons of excess sludge, convert to dehydrated sludge cake (water ratio 80%) and be about 6,000,000 tons.Along with the increase of China's city domestic sewage quantity discharged and the raising of processing rate, the mud generation also will constantly increase.Dehydrated sludge cake not only generation is big, and water ratio and organic content are very high, is difficult to satisfy the requirement that follow-up landfill, compost, burning etc. are handled, and has brought a difficult problem also for the conveying of mud and secondary pollution control.
In order to reduce the dehydrated sludge cake water ratio, can before sludge dewatering, introduce pretreatment process, improve the degree of dehydration of mud.The most frequently used pretreatment process is thermal treatment, at first excess sludge is heated to 135~165 ℃ of (low-temperature heat treatment methods, need oxygenation) or 180~220 ℃ (high-temperature heat treatment method), utilize heat effect to destroy the mud colloidal structure, discharge combination water, make the cohesion of part flco, directly dewater after the processing, moisture content of the cake can reach below 60%.(water ratio was reduced to 60% o'clock from 80% because the decline of moisture percentage in sewage sludge and the removal amount of actual moisture are also disproportionate, moisture promptly removes 63%), therefore the tupe of thermal treatment+dehydration can effectively reduce the expense that the mud subsequent disposal is disposed, and the dehydrated sludge cake of water ratio 60% also can directly carry out landfill or compost, satisfies the technical requirements of subsequent disposal.
Though the development of many decades has been passed through in thermal treatment, technology is constantly improved, and itself some problem of inherent has restricted its widespread use in the sludge dewatering field.On the one hand, no matter be high-temperature heat treatment, or low-temperature heat treatment, all needing under high pressure the large quantity of moisture in the excess sludge (water ratio is more than 95%) to be heated to relevant temperature, energy expenditure is very big, and processing costs is very high.On the other hand, mud thermal treatment also can produce the liquid of deviating from of high density, because the most of organism in the mud is dissolved, it is dense to deviate from liquid BOD, COD, can increase the load of Waste Water Treatment, and deviate from liquid and contain and be difficult for biodegradable humic acid material in a large number, being dark brown, conventional biological treatment process is difficult to satisfy the requirement of deviating from the liquid decolouring.The humic acid of deviating from the liquid derives from two portions, a part is the humic acid that itself contains in the mud, organic content generally accounts for dried solid more than 60% in the mud, wherein based on larger molecular organicses such as protein (about 46-52%), humic acid (about 18-23%), polysaccharide (about 7%), nucleic acid and fat; Another part is that the mud organic matter forms in heat treatment process, when larger molecular organics is decomposed into small organic molecule, also has the polymerization of part small molecules to generate humic acid organic substances.
Summary of the invention
The present invention is directed to the problem that the existing heat treatment technics of mud exists, proposed a kind of new mud heat treating method, one side as heat treatment object, significantly reduces the required energy consumption of sludge water content heating with dehydrated sludge cake; The humic acid that utilizes membrane separation technique to extract in the liquid is on the other hand produced liquid fertilizer, solves the processing difficult problem that high density is deviate from liquid.This method can realize the reinforcement dehydration and the composting utilization of mud synchronously.
Thermal treatment-the dehydration of treatment of town sewage and sludge-composting method, this method may further comprise the steps:
(1) NaOH of adding 0.08~0.16wt% in dehydrated sludge cake (water ratio 80%) to reduce thermal treatment temp, promotes the stripping of humic acid in the mud and the precipitation of heavy metal;
(2) this mud be transported in the horizontal spiral thermal treater stir, import simultaneously high pressure steam (250 ℃, more than the 4MPa, anaerobic or hypoxemia), mud is heated to 120~140 ℃, the residence time 40~100min, mud is effectively cracked, and organic stripping enters liquid phase;
(3) reacted mud enters water cooler, is cooled to below 100 ℃ (to prevent mud decompression back vaporization, take away heat);
(4) cooled mud enters water extracter dehydration, obtains the dehydrated sludge cake after the decrement;
(5) deviate from liquid through sand filtration (1~2mm quartz sand) and micro-filtration (alkaline-resisting mineral membrane, aperture 0.1~1 μ m, mould difference 0.3MPa) handles, remove suspended particle, filter entirely then, carry out ultrafiltration and concentration after promptly adding water, always add 3~5 times in water, adopt the inorganic ultra-filtration membrane of molecular weight cut-off 2500, working pressure 0.5MPa, 3~6 times of total cycles of concentration obtain to contain the above concentrated solution of humic acid 3wt%.
(6) concentrated solution is a humic acid stoste, can be made into different types of humic acid liquid fertilizer after adding different additives.
Described additive is nitrogen, phosphorus, potassium (deciding on primary sludge character).
(7) liquid that sees through that ultrafiltration produces adopts conventional activated sludge process to handle or be back to the sewage treatment plant inflow end.
The present invention has the following advantages:
(1) with the dehydrated sludge cake is process object, adapts to the present situation that the most of cities of China focus on dehydrated sludge cake.
(2) compare with existing mud heat treatment technics, the present invention has realized the recycling of mud.Because heavy metal mainly remains in the dehydrated sludge cake with precipitation forms under the alkaline condition, the heavy metal content of deviating from the liquid is few, deviate from liquid again through heavy metal there not being the ultrafiltration membrane treatment of the effect held back, heavy metal content is extremely low in the humic acid concentrated solution that finally obtains, and the pH value remains on the weakly alkaline scope, meet the national Ministry of Agriculture " fertilizer usage criteria ", can satisfy general humic acid liquid fertilizer standard (as " the containing humic acid dissolved fertilizer standard DB240-2003 " of Hubei Province Department of Agriculture promulgation) behind the interpolation nitrogen phosphorus potassium additive.
(3) compare with existing mud heat treatment technics, the present invention can significantly reduce the heat treated expense of mud.For water ratio is that 98% thickened sludge and water ratio are for 80% the dehydrated sludge cake, and when their contained dried solid masses were identical, the moisture among the former was more than 12 times of the latter, was that process object can reduce the thermal treatment energy consumption with the dehydrated sludge cake therefore.Add small amount of N aOH in the dehydrated sludge cake, can reduce thermal treatment temp, and not need aerating oxygen.Deviate from liquid behind larger molecular organicses such as extraction humic acid, only contain the small organic molecule of readily biodegradable, the long-time aeration that needn't adopt is handled, and the liquid waste disposal time obviously shortens, and processing costs obviously reduces.
(4) the present invention has tangible mud decrement effect.Present method not only can make the dehydrated sludge cake water ratio be reduced to 40~60%, and total solids is reduced more than 35%, so total mass compares former dehydrated sludge cake and reduce more than 65%, and this can significantly reduce the mummification of mud subsequent thermal and other treatment and disposal expense.The present invention is innoxious at treatment of town sewage and sludge, have more by force in the processing of minimizing, resource utilization and use.
Description of drawings
Fig. 1 is the schematic flow sheet of the inventive method.
Embodiment
Further specify the present invention below in conjunction with embodiment.
Fig. 1 is the schematic flow sheet of the inventive method.The processing unit that the inventive method adopts can be divided into three processing units: thermal treatment unit, dewatering unit and liquid waste disposal unit, and each unitary equipment and technological process are respectively described below:
(1) thermal treatment unit: this unit main body is horizontal spiral thermal reactor and water cooler.
NaOH with common dehydrated sludge cake adding 0.08~0.16wt% sends into thermal reactor through spiral pump, and the mud temperature is increased to 120~140 ℃ under the high pressure steam effect, reaction times 40~100min.Under this temperature condition, mud granule disintegrates, and cell rupture, cell organic matter discharge.Reacted mud enters dewatering unit after the water cooler cooling.
High pressure steam also can utilize near thermal source (as power plant) to provide, or the dehydrated sludge cake (Lower heat value is higher than self-supporting incendiary lower limit 3500KJ/kg) that is produced by dewatering unit provides in the burning boiler internal combustion.
(2) dewatering unit: this unit main body is a water extracter.
Dewatering performance of sludge after the thermal treatment is good, enters dewatering unit and can dewater under the condition that does not add flocculation agent to water ratio and be lower than 60%.
(3) liquid waste disposal unit: this unit main body is sand filter, micro-filtration and ultrafiltration apparatus.
The liquid (waste liquid) of deviating from that sludge dewatering produces is at first removed fine particle through sand filtration and micro-filtration, the full filtration purification of utilization concentrates the larger molecular organicses such as humic acid in the liquid again, in concentrated solution, add proper N, phosphorus, potassium additive (deciding), make liquid fertilizer on primary sludge character; Ultrafiltration produces sees through the small-molecule substance that liquid only contains readily biodegradable, can adopt conventional activated sludge process to handle, and also can be back to sewage work's front end.
Embodiment 1:
The dehydrated sludge cake water ratio that certain urban wastewater treatment firm produces is 81%, and organic content is 74% in the dried solid.
In dehydrated sludge cake, add the sodium hydroxide of 0.16wt%, utilize spiral pump that it is delivered in the horizontal spiral thermal treater then, and the feeding high pressure steam (250 ℃, 4MPa) be heated to 140 ℃, the residence time is 40min; Sludge reaction is laggard goes into water cooler, carries out mechanical dehydration after the cooling.Reaction result, before handling, dried solid masses reduces 40%, dehydrated sludge cake water ratio 47%; Chemical oxygen demand (COD) in the waste liquid (COD) is 103.0g/L, and content of humic acid is 31.0g/L, and content of humic acid is 3.1wt% after full filtration is purified, heavy metal content Cd≤0.01wt%, As≤0.002wt%, Pb≤0.002wt% meets the national Ministry of Agriculture " fertilizer usage criteria "; It is transparent, colourless that ultrafiltration sees through liquid, can be back to sewage work's front end.
Embodiment 2:
The dehydrated sludge cake water ratio that certain urban wastewater treatment firm produces is 80%, and organic content is 61% in the dried solid.
In dehydrated sludge cake, add the sodium hydroxide of 0.08wt%, utilize spiral pump that it is delivered in the horizontal spiral thermal treater then, and the feeding high pressure steam (250 ℃, 4MPa) be heated to 120 ℃, the residence time is 100min; Sludge reaction is laggard goes into water cooler, carries out mechanical dehydration after the cooling.Reaction result, before handling, dried solid masses reduces 35%, dehydrated sludge cake water ratio 56%; COD is 99.7g/L in the waste liquid, and content of humic acid is 22.2g/L, and content of humic acid is 4.4wt% after full filtration purification concentrates 2 times, heavy metal content Cd≤0.01wt%, As≤0.002wt%, Pb≤0.002wt% meets the national Ministry of Agriculture " fertilizer usage criteria "; It is transparent, colourless that ultrafiltration sees through liquid, can be back to sewage work's front end.

Claims (7)

1. thermal treatment-the dehydration of treatment of town sewage and sludge-composting method at dewatered sludge, is characterized in that, this method may further comprise the steps:
(1) in dewatered sludge, adds sodium hydroxide;
(2) step (1) is added the mud that sodium hydroxide obtains and stir, import simultaneously that 250 ℃, 4MPa are above, anaerobic or hypoxemia steam, mud is heated to 120~140 ℃, 40~100 minutes residence time;
(3) the reacted mud of step (2) is cooled to below 100 ℃;
(4) the cooled mud of step (3) is dewatered, obtain the dehydrated sludge cake after liquid and the decrement;
(5) step (4) being deviate from liquid handles through sand filtration processing and micro-filtration, filter entirely then, carry out ultrafiltration and concentration after promptly adding water, always add 3~5 times in water, adopt the inorganic ultra-filtration membrane of molecular weight cut-off 2500, working pressure 0.5MPa, 3~6 times of total cycles of concentration obtain containing the above concentrated solution of humic acid 3wt%;
(6) step (5) gained concentrated solution is added additive, promptly make humic acid liquid fertilizer.
2. thermal treatment-the dehydration of treatment of town sewage and sludge according to claim 1-composting method is characterized in that, described sodium hydroxide weight ratio is 0.08~0.16wt%.
3. thermal treatment-the dehydration of treatment of town sewage and sludge according to claim 1-composting method is characterized in that, described being stirred in the horizontal spiral thermal treater carried out.
4. thermal treatment-the dehydration of treatment of town sewage and sludge according to claim 1-composting method is characterized in that, described cooling is carried out in water cooler.
5. thermal treatment-the dehydration of treatment of town sewage and sludge according to claim 1-composting method is characterized in that, described sand filtration is treated to 1~2mm quartz sand.
6. thermal treatment-the dehydration of treatment of town sewage and sludge according to claim 1-composting method is characterized in that, described micro-filtration is treated to alkaline-resisting mineral membrane, aperture 0.1~1 μ m, mould difference 0.3MPa.
7. thermal treatment-the dehydration of treatment of town sewage and sludge according to claim 1-composting method is characterized in that, described additive is that described additive is one or more in nitrogen, phosphorus, the potassium.
CNA2007103020149A 2007-12-19 2007-12-19 Heat treatment-dehydration-fertilizer making method for town sewage and sludge Pending CN101186423A (en)

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101905994A (en) * 2010-06-22 2010-12-08 山东省科学院新材料研究所 Method for extracting humic acid liquid fertilizer with rich trace elements from sludge
CN101913921A (en) * 2010-09-06 2010-12-15 长沙洁湘环保工程有限公司 Method for preparing compound fertilizer from sludge produced by treatment of town sewage
CN101935141A (en) * 2010-07-30 2011-01-05 浙江捷丰环保技术工程有限公司 Method for removing water from sludge in sewage treatment
CN101987772A (en) * 2010-11-23 2011-03-23 北京机电院高技术股份有限公司 Method for improving sludge dewatering performance through thermal conditioning of sludge
CN101402492B (en) * 2008-11-19 2011-06-29 北京桑德环境工程有限公司 Wastewater treatment system and method for improving coefficient of recovery
CN102167490A (en) * 2011-05-23 2011-08-31 江苏恒亮离心机制造有限公司 Integrated treatment method for thickening, drying and purifying municipal sludge
CN102849910A (en) * 2012-10-10 2013-01-02 清华大学深圳研究生院 Method for recovering humic acid from sludge and improving anaerobic digestion of sludge
CN104478190A (en) * 2014-11-04 2015-04-01 清华大学深圳研究生院 Method for recovering humic acid from sludge
CN108033818A (en) * 2017-12-13 2018-05-15 北京环清环境科技有限公司 A kind of organic fertilizer production method

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101402492B (en) * 2008-11-19 2011-06-29 北京桑德环境工程有限公司 Wastewater treatment system and method for improving coefficient of recovery
CN101905994A (en) * 2010-06-22 2010-12-08 山东省科学院新材料研究所 Method for extracting humic acid liquid fertilizer with rich trace elements from sludge
CN101905994B (en) * 2010-06-22 2013-05-01 山东省科学院新材料研究所 Method for extracting humic acid liquid fertilizer with rich trace elements from sludge
CN101935141A (en) * 2010-07-30 2011-01-05 浙江捷丰环保技术工程有限公司 Method for removing water from sludge in sewage treatment
CN101913921A (en) * 2010-09-06 2010-12-15 长沙洁湘环保工程有限公司 Method for preparing compound fertilizer from sludge produced by treatment of town sewage
CN101987772A (en) * 2010-11-23 2011-03-23 北京机电院高技术股份有限公司 Method for improving sludge dewatering performance through thermal conditioning of sludge
CN102167490A (en) * 2011-05-23 2011-08-31 江苏恒亮离心机制造有限公司 Integrated treatment method for thickening, drying and purifying municipal sludge
CN102849910A (en) * 2012-10-10 2013-01-02 清华大学深圳研究生院 Method for recovering humic acid from sludge and improving anaerobic digestion of sludge
CN104478190A (en) * 2014-11-04 2015-04-01 清华大学深圳研究生院 Method for recovering humic acid from sludge
CN108033818A (en) * 2017-12-13 2018-05-15 北京环清环境科技有限公司 A kind of organic fertilizer production method

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Open date: 20080528