CA1039863A - Method and apparatus for treating organic sludge - Google Patents
Method and apparatus for treating organic sludgeInfo
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- CA1039863A CA1039863A CA218,654A CA218654A CA1039863A CA 1039863 A CA1039863 A CA 1039863A CA 218654 A CA218654 A CA 218654A CA 1039863 A CA1039863 A CA 1039863A
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- heat
- heat exchanger
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Abstract
ABSTRACT OF THE DISCLOSURE
This invention relates to and discloses a novel method for treating organic sludge and an apparatus therefor.
The sludge to be treated is preheated in a heat exchanger by means of indirect conventional heat exchange with oxidation-treated sludge, then admixed with air of 10-30 times the amount of the sludges, the air containing isolatable oxygen which reduces the COD of the sludge by 2-4%, and with steam to heat the sludge to 130°-150°C. The admixed sludge is thereby partially oxidized in a reactor which includes an oxidizing chamber and a heat concentrating chamber which is pressurized below 10 kg/cm2 for more than 30 minutes. This method is characterized by the inclusion of the step of removing incorporated sand from the preheated sludge in the heat exchanger by a sand removing device prior to its pressure-fed travel to the reactor. This method and apparatus therefor provides an improvement over the prior art processes and is suitable for not only sewage but also for petrochemical waste water, food-processing waste water and the like. It prevents the formation of bad odours and gases from the treatment system and effectively removes the sand from sludge thereby extending considerably the life of the apparatus and producing a more efficient process.
This invention relates to and discloses a novel method for treating organic sludge and an apparatus therefor.
The sludge to be treated is preheated in a heat exchanger by means of indirect conventional heat exchange with oxidation-treated sludge, then admixed with air of 10-30 times the amount of the sludges, the air containing isolatable oxygen which reduces the COD of the sludge by 2-4%, and with steam to heat the sludge to 130°-150°C. The admixed sludge is thereby partially oxidized in a reactor which includes an oxidizing chamber and a heat concentrating chamber which is pressurized below 10 kg/cm2 for more than 30 minutes. This method is characterized by the inclusion of the step of removing incorporated sand from the preheated sludge in the heat exchanger by a sand removing device prior to its pressure-fed travel to the reactor. This method and apparatus therefor provides an improvement over the prior art processes and is suitable for not only sewage but also for petrochemical waste water, food-processing waste water and the like. It prevents the formation of bad odours and gases from the treatment system and effectively removes the sand from sludge thereby extending considerably the life of the apparatus and producing a more efficient process.
Description
~39~6;~
1 In general, treatment of organic sludge i5 the combina-tion of independent processes such as diges-tion process, concentration process, dehydrating process, combustion process and the like. ~1hese processes, however, entail various problems centering around environmen-tal pollution by combustion or digestion gas as the result of chemical pretreatment applied on the sludge-to--treat for enhancing its dewaterbility. ~uch a pretreatment is required for precluding incompleteness in the decomposing state of organic substances usual in the foregolng processes.
~ he wet oxidiza-tion method for -the treatment of sludge enables to conduct substantially the same processes from digestion to incineration by means of single equipment with a comparatively easy operation, wherein not only decomposition of the organic matter is adjustable mainly by adjusting the temperature, but also production of isolated solid matter may be minimized and obtained in a stabilized state.
~ his invention relates to improvement of the conven-tional wet oxidization method, for example, improvementof dewatering of not only sewag0 but also petrochemical waste water, foods-processing waste water and the like 7 prevention of malodor generation from the treating system, and further effectivel~ removing sands out of the sludge thereb~ obtaining the elongation of life of the apparatus for treating the organic sludge.
According to the Zimmerman method, sludge is heated to over 200C by its own calorific power within a reactor, admixed with irreducibly minimized necessary air under pressure of 100 ~g/cm2, thence being decomposed b~ o~idiza-tion in a pressure resistable vessel. In this method, however, organic material incorporated in the sludge is ~.
~39863 1 partly rendered soluble by the hi~h temperature to r~sul-t in an increase of BOD value of the isolated liquid after treatment. Consequently, when the isolated liquid is returned for treatment -to the biochemical treatment system, BOD value in said system increases thereby not only losing the treating efficiency thereof but also resulting in the development of scales at -the heat exchanging portion due to processing of the preheating oxidization u~der high temperature with the resul-t of increased loss of heat.
In this invention, the reaction temperature is set below 150C, the amount of air directly fed into the reactor being over a theoretical amount required for reducing the COD (chemical ox~gen demand) of the sludge by 2 - 4% and within the realm of 10 - 30 ti~es -the amount ~-of the sludge to be treated, and further the amount of steam for heating the sludge being varied in correspondence to reaction temperature detected b~ thermocouple and the like provided within the reactor, thereby enabling to maintain the reaction -temperature substantially a-t a predetermined level ~elow 150Co ~his invention provides a method for treating organic sludge under conditions as mentio~ed above and an apparatus for putting into force said method so that this inventio~ may give a drastic solution to the defects of conventional methods in this field as referred to alread~ hereinbefore.
A first object of this i~vention is to provide a i-method for effectively treating orga~ic sludge at com~arative-ly low temperature so as to reduce the adhesion of scales of baked sludge to the heat exchanger and also lessen the ~0 generation of sludge caused by isolated liquid.
~ second object of this in~e~tion is to provide a method for -treating organic sludge in which sand within .. ..
~l~139~63 1 the sludge-to--treat is preliminarily removed -therefrom thereby preven-ting pipes ~rom stuffing, abrasion and the like and valves from damaging.
A -third object of this invention is to provide a method for trea-ting organic sludge in which the sludge-incorporated gas is deodorized thereby precluding the ejection of malodorous gas to the atmosphere.
A fourth object of this invention is to provide a method for treating organic sludge in which heat of trea-ted sludge is available as the source of heat for preheating the sludge to be treated at the heat exchanger thereby economizing the consumption of calories for -the required treatment.
A fifth object of this invention is -to provide an ;-appara-tus for putting into force -the above-mentioned methods simpl~ and precisely.
A sixth obaect of this invention is to provide an apparatus enabling to function the sludge oxidization and heat concentration withou-t fail so that an effective sludge treatment ma~ be obtained.
In order that this invention ma-g be readily understood, reference is made hereinunder t-o the annexed drawing which illustrates7 by way of examples, preferred embodiments of this invention.
~ig. 1 is a flow sheet of a sludge treating plant ~or p~tting into force the treating method of this invention in the first embodiment.
Fig. 2 is a magnified section of a reactor in the above.
Fig. 3 is a magnlfied section of a reactor in the second embodiment.
~ig~ 4 is a magnified longitudinal section of a sand .. . ..
, I , ~ ;
. .
-~L~39~3 1 removing device ln this invention.
In ~ig. 1, s1udge taken out of an orgc~nic sewage treating system is stored in a reservoir (no-t sho~Jn) after get-ting incorpora-ted me-tal pieces and -the like removed there~rom, other forei~n materials within said sludge inside said reservoir being crushed -to ~rag~ents by a crushing device 1. ~hence the sludge is pressure-fed to a heat exchanger 3 by a high pressure pump 2 whereby it is preheated to around 120C by way of indirec-tl~ absorbing hea-t from already-oxidized high temperature sludge.
r~he preheated sludge, as shown in Fig. 4, flows into a sand removing device proper 42 through a flowing pipe 40 of a cyclone-system sand removing device 4. ~he ;~
flowed-in sludge i~ high temperature is little viscostic thereby making it easier for -the sand to separate therefrom under the effect of the specific gravity di~ference between the sand and the sludge, the heavier sand naturally precipitating to lie on a sand reservoir ~ formed at the bottom of said device 4. ~he sand removing device proper 42 has a bypass pipe 45 to use for its cleaning.
~ he sludge after ge-t-ting said sand isolated therefrom passes through a sludge supply pipe 10 and enters in a reactor 5 after admixing with steam from a boiler 6 and compressed air from a compressor 7 adjacent the inlet of said reactor 5 at the lower por-tion thereof.
~ Fig. 2 showing the first embodiment of the reactor 5, a condensed-sludge supply pipe 10 connecting afore-mentio~ed sa~d removing device 4 to the inlet of said reactor 5 at its lower portion further connects with a steam pipe 11 from the boiler 6 and an airpipe 7 from the compressor 7 thereby enabling to admix the air a~d steam with the sludge by an ejector 13. Wi-thin the reactor 5 1 are disposed numerous bubble plates 28 in tiers keeping a suitable spac~ between each other, at the upper portion of said reactor 5 being provided a partitioning plate 23 for dividing -the space -therein into a sludge oxidizing chamber 22 and a heat concentrating chamber 29, at the lower portion of said reac-tor 5 being provided a space 21 wherein to admix untreated sludge with compressed air and s-team.
In said heat concentrating chamber 29, there are a liquid level controller 26 and an automa-tic sludge exhaustion valve 18 under the control of said controller 26 thereby enabling to keep the liquid at a predetermined level. Also, a pressure indicating-recording co~troller 25 is disposed within said reactor 5 to keep pressure therein as predeter-mined.
In this embodiment, the sludge, air and steam flowed -~
into said reactor 5 through lower portion thereof combi~e to pass through every hole of the bubble plate 28 in turbulence thereby resulting in the liquid-steam contact to a satisfactory state. ~nd accordingly the oxidizing chamber 2~ is free from the generation of dead space and also short-path of organic sludge therein.
The reactor 5 in the second embodiment is shown in ~ig. 3 in which, similar -to the first embodiment, a sludge suppl~ pipe 10 connecting to the inlet of said reactor 5 at its lower portion ~urther connects to a steam pipe 11 and an airpipe 12 thereby enabling to admix said sludge wi-th said air and steam by an ejector 13 before being sent into sai~ reactor 5. In this embodiment~ however, the reactor 5 differs in internal organization from that in the first embodiment, i.e., the reac-tor in the second embodiment is divided into two compartmen-ts by a partitioning plate 32 erected from the botto~ thereof to a suitable ~391~363 1 height, one compartment being an oxidizing chamber 30 on the sludge influx side and the o-ther a heat concentrating chamber 33 on the sludge outflow side.
Within said oxidizing chamber 30 are disposed a plural number of inclined plates 31 in tiers alternately on the peripheral wall of the reactor 5 and -the afore-mentioned parti-tioning plate 32 in order -to enhance the steam-liquid contacting effect. ~nd withir. the heat concentratin~
chamber 33 are provided a liquid level controller 36, an automatic sludge ejecting valve 18 u~der the control of said controller 36, so as to maintain the liquid at a pre-determined level.
In any of the foregoing embodiments, when the liquid reaches a level higher than proper wi-thin said reactor 5, ~;
the automatic sludge exhaustion valve 18 opens in response to signals from the liquid level controller 26 and 36 thereby discharging the sludge and as a result maintaining the liquid level as predetermined. Also, when reaction pressure inside the reactor 5 drops below the predetermined ~ , pressure around 10 kg/cm2 due to the exhaustion of -the sludge therefr~m resulting in the fall of the liquid level, air may be pressure-fed therein from the compressor 7 in response to signals from the afore-mentioned pressure indicating controller 25 and 34. On -the contrary, when the reactio~ pressure rises above the predetermined level due to generation of decomposed gas from the sludge, a safety valve 17 as will be referred to later may work to set back said pressure to the predetermined one in the reactor 5.
~he slud~e flowed into the reactox 5 as described above may be oxidized through consump-tion of oxygen in the air. And the sludge makes a contact with the air fed from 98~;3 1 the compressor 7 ln the oxidizing chambers 22 and 30 with the application of temperature and pressure additionally thereto, whereas -the fed air has a capaci-ty of oxygen supply by only 2 - 4% o~ -the amount required for the perfect oxidization of said sludge. Accordingly the sludge comple-tes its oxidizing reaction as predetermined through the lapse of time as it travels through said oxidizing chambers 22 and 30. ~he sludge which overflowed over the partitioning plates 23 and 32 brings the heat concentration to a completion at the heat concentrating chambers 29 and ~3 under the influence of temperature and pressure as mentioned hereinafter.
As described hereinbefore, the sludge heat-treated in the reactor 5 has a temperature at the neighborhood of 145C. Said sludge, lowering said temperature to 50 - 60C
as it travels through -the heat exchanger ~, enters a condensing tub 19 after being controlled for its outward flowing amount by the automatic sludge exhaustion valve 18.
~he heat-treated sludge having a favorable precipitating property comes to a condensed state by way of a thermal sedimentation, isolated liquid being returned to the sewage ~ -treating system, said condensed sludge being filtered through a filter 20 such as a belt filter, filter press and the like thereby becoming cake state containing about 40% of water.
An exhaustion pipe 24 communicating with the reactor 5 at its upper portion also communicates with a deodorizing ;
device 25 thereby providing a rou-te for the escape of malodorous gas from within said reactor 5 in a deodorized state to the atmosphere. ~everal deodorizing methods such as combustion method, alkali fumigation method, water washing method and the like can be employed for this 1~398~3 1 deodorizing device 25, but the combustion me-thod may be the best suitable from a view poin~ that organic chemical compounds takes -the grea-ter portion of the source of malodor in this invention method.
The safety valve 17 as shown in Fig. 1 is operated irrespective of operation of said compressor 7 so as to maintain the gas pressure within said reactor 5 as predeter-mined (10 kg/cm2), said malodorous gas passing through said valve 17 being exhausted into the atmosphere after being deodorized by the deodorizing device 25. The air to be `
blo~n in the reactor 5 needs to be sufficient in amount so that an oxidizing rate necessary for the sludge to improve its dewaterbility may be obtained and also the generated malodorous ingredients may be stripped from said sludge, said air amount in concrete terms being required -to be around 10 - 30 -times the amount of the sludge to be treated.
Also the reaction speed varies in accordance to the kind and density of the sludge to be treated, and the steam-liquid contacting hours i.5 subject to the above but a duration longer than 30 minutes is required anyway for this process.
Furthermore, the relation between the ratio of oxygen (oxygen supply percentage) in the supplied air as against the oxygen ~mount required for the complete oxidization of the sludge and the proportional resistance designating dewaterbility of the sludge is as below: when the reac-tion temperature is 145C and the reaction duration is 30 minutes with the pressure in the reactor being 10 kg/cm2, the proportional resistance may be the lowest, that is, about 107 sec.2/g with the oxygen supply ratio at 2 - ~%, thus the sludge of substantially stabilized properties being obtainable.
As described hereinbefore, this invention enables to treat sludge at comparatively low reaction temperatures 1 ranging from 130 to 150C by adjusting the influx of ~-team in-to the reactor, consequently adhesion of scales wi-thin the heat exchan~er being less -than in case of the conven-tional method in which the sludge is treated at high temperatures. ~his invention there~ore enables to minimize the heat loss resulting from the gro~th of scales within the heat exchanger.
~his invention has further advantages in that:
solubility of the sludge is reduced with the result that BOD of the isolated liquid is reduced by about one-half and the generation of sludge from the isolated liquid i~s reduced by 20 - 3~/0 as compared with the case of the conven-tional method; since the reaction is effected at comparatively low temperatures, calories re~uired for heating may be economized by 30 - 40%; and since the increase of the BOD
in the biological treatment system resulting from the return of the isolated liquid is only about 10%~ the waste water treatment system is practically free from the effect of said increase.
Moreover, high temperature above 200C re~uired for the reaction in the conventional method results in an ;~
increase in the growth of what is known as the source of malodor within the reactor, such as amines, mercaptans, sulfides, and the like. In this invention, however, the low reaction temperature helps reduce the generation of ~-amines, mercaptans, and suhfides. Also, the gases generated in the reactor are isolated from the oxidized sludge and discharged directly from said vessel, whereby oxidized sludgR free from gases is led into the heat exchanger and utilized to preheat the sludge to be treated. ~hus, the malodorous ingredients are prevented from being trans~erred into gases, reconcentrated and admixed with the oxidized ~39863 1 sludge in the reactor as in case of the conventional method.
~herefore, malodorous gases are scarcely exhausted into the atmosphere in the subsequent processes.
~ urther in this invention, sands are removed by a sand removing device from sludge which has reduced viscosit~
through preheating treatment in a heat exchanger, this sludge condition enabling to obtain a perfect sand removal with ease. ~his invention therefore has an advantage in that it enables to preclude the risk of clogging and abrasion ~ -of the piping and wear of the valves caused by such sands in the oxidization-treating plant.
1 In general, treatment of organic sludge i5 the combina-tion of independent processes such as diges-tion process, concentration process, dehydrating process, combustion process and the like. ~1hese processes, however, entail various problems centering around environmen-tal pollution by combustion or digestion gas as the result of chemical pretreatment applied on the sludge-to--treat for enhancing its dewaterbility. ~uch a pretreatment is required for precluding incompleteness in the decomposing state of organic substances usual in the foregolng processes.
~ he wet oxidiza-tion method for -the treatment of sludge enables to conduct substantially the same processes from digestion to incineration by means of single equipment with a comparatively easy operation, wherein not only decomposition of the organic matter is adjustable mainly by adjusting the temperature, but also production of isolated solid matter may be minimized and obtained in a stabilized state.
~ his invention relates to improvement of the conven-tional wet oxidization method, for example, improvementof dewatering of not only sewag0 but also petrochemical waste water, foods-processing waste water and the like 7 prevention of malodor generation from the treating system, and further effectivel~ removing sands out of the sludge thereb~ obtaining the elongation of life of the apparatus for treating the organic sludge.
According to the Zimmerman method, sludge is heated to over 200C by its own calorific power within a reactor, admixed with irreducibly minimized necessary air under pressure of 100 ~g/cm2, thence being decomposed b~ o~idiza-tion in a pressure resistable vessel. In this method, however, organic material incorporated in the sludge is ~.
~39863 1 partly rendered soluble by the hi~h temperature to r~sul-t in an increase of BOD value of the isolated liquid after treatment. Consequently, when the isolated liquid is returned for treatment -to the biochemical treatment system, BOD value in said system increases thereby not only losing the treating efficiency thereof but also resulting in the development of scales at -the heat exchanging portion due to processing of the preheating oxidization u~der high temperature with the resul-t of increased loss of heat.
In this invention, the reaction temperature is set below 150C, the amount of air directly fed into the reactor being over a theoretical amount required for reducing the COD (chemical ox~gen demand) of the sludge by 2 - 4% and within the realm of 10 - 30 ti~es -the amount ~-of the sludge to be treated, and further the amount of steam for heating the sludge being varied in correspondence to reaction temperature detected b~ thermocouple and the like provided within the reactor, thereby enabling to maintain the reaction -temperature substantially a-t a predetermined level ~elow 150Co ~his invention provides a method for treating organic sludge under conditions as mentio~ed above and an apparatus for putting into force said method so that this inventio~ may give a drastic solution to the defects of conventional methods in this field as referred to alread~ hereinbefore.
A first object of this i~vention is to provide a i-method for effectively treating orga~ic sludge at com~arative-ly low temperature so as to reduce the adhesion of scales of baked sludge to the heat exchanger and also lessen the ~0 generation of sludge caused by isolated liquid.
~ second object of this in~e~tion is to provide a method for -treating organic sludge in which sand within .. ..
~l~139~63 1 the sludge-to--treat is preliminarily removed -therefrom thereby preven-ting pipes ~rom stuffing, abrasion and the like and valves from damaging.
A -third object of this invention is to provide a method for trea-ting organic sludge in which the sludge-incorporated gas is deodorized thereby precluding the ejection of malodorous gas to the atmosphere.
A fourth object of this invention is to provide a method for treating organic sludge in which heat of trea-ted sludge is available as the source of heat for preheating the sludge to be treated at the heat exchanger thereby economizing the consumption of calories for -the required treatment.
A fifth object of this invention is -to provide an ;-appara-tus for putting into force -the above-mentioned methods simpl~ and precisely.
A sixth obaect of this invention is to provide an apparatus enabling to function the sludge oxidization and heat concentration withou-t fail so that an effective sludge treatment ma~ be obtained.
In order that this invention ma-g be readily understood, reference is made hereinunder t-o the annexed drawing which illustrates7 by way of examples, preferred embodiments of this invention.
~ig. 1 is a flow sheet of a sludge treating plant ~or p~tting into force the treating method of this invention in the first embodiment.
Fig. 2 is a magnified section of a reactor in the above.
Fig. 3 is a magnlfied section of a reactor in the second embodiment.
~ig~ 4 is a magnified longitudinal section of a sand .. . ..
, I , ~ ;
. .
-~L~39~3 1 removing device ln this invention.
In ~ig. 1, s1udge taken out of an orgc~nic sewage treating system is stored in a reservoir (no-t sho~Jn) after get-ting incorpora-ted me-tal pieces and -the like removed there~rom, other forei~n materials within said sludge inside said reservoir being crushed -to ~rag~ents by a crushing device 1. ~hence the sludge is pressure-fed to a heat exchanger 3 by a high pressure pump 2 whereby it is preheated to around 120C by way of indirec-tl~ absorbing hea-t from already-oxidized high temperature sludge.
r~he preheated sludge, as shown in Fig. 4, flows into a sand removing device proper 42 through a flowing pipe 40 of a cyclone-system sand removing device 4. ~he ;~
flowed-in sludge i~ high temperature is little viscostic thereby making it easier for -the sand to separate therefrom under the effect of the specific gravity di~ference between the sand and the sludge, the heavier sand naturally precipitating to lie on a sand reservoir ~ formed at the bottom of said device 4. ~he sand removing device proper 42 has a bypass pipe 45 to use for its cleaning.
~ he sludge after ge-t-ting said sand isolated therefrom passes through a sludge supply pipe 10 and enters in a reactor 5 after admixing with steam from a boiler 6 and compressed air from a compressor 7 adjacent the inlet of said reactor 5 at the lower por-tion thereof.
~ Fig. 2 showing the first embodiment of the reactor 5, a condensed-sludge supply pipe 10 connecting afore-mentio~ed sa~d removing device 4 to the inlet of said reactor 5 at its lower portion further connects with a steam pipe 11 from the boiler 6 and an airpipe 7 from the compressor 7 thereby enabling to admix the air a~d steam with the sludge by an ejector 13. Wi-thin the reactor 5 1 are disposed numerous bubble plates 28 in tiers keeping a suitable spac~ between each other, at the upper portion of said reactor 5 being provided a partitioning plate 23 for dividing -the space -therein into a sludge oxidizing chamber 22 and a heat concentrating chamber 29, at the lower portion of said reac-tor 5 being provided a space 21 wherein to admix untreated sludge with compressed air and s-team.
In said heat concentrating chamber 29, there are a liquid level controller 26 and an automa-tic sludge exhaustion valve 18 under the control of said controller 26 thereby enabling to keep the liquid at a predetermined level. Also, a pressure indicating-recording co~troller 25 is disposed within said reactor 5 to keep pressure therein as predeter-mined.
In this embodiment, the sludge, air and steam flowed -~
into said reactor 5 through lower portion thereof combi~e to pass through every hole of the bubble plate 28 in turbulence thereby resulting in the liquid-steam contact to a satisfactory state. ~nd accordingly the oxidizing chamber 2~ is free from the generation of dead space and also short-path of organic sludge therein.
The reactor 5 in the second embodiment is shown in ~ig. 3 in which, similar -to the first embodiment, a sludge suppl~ pipe 10 connecting to the inlet of said reactor 5 at its lower portion ~urther connects to a steam pipe 11 and an airpipe 12 thereby enabling to admix said sludge wi-th said air and steam by an ejector 13 before being sent into sai~ reactor 5. In this embodiment~ however, the reactor 5 differs in internal organization from that in the first embodiment, i.e., the reac-tor in the second embodiment is divided into two compartmen-ts by a partitioning plate 32 erected from the botto~ thereof to a suitable ~391~363 1 height, one compartment being an oxidizing chamber 30 on the sludge influx side and the o-ther a heat concentrating chamber 33 on the sludge outflow side.
Within said oxidizing chamber 30 are disposed a plural number of inclined plates 31 in tiers alternately on the peripheral wall of the reactor 5 and -the afore-mentioned parti-tioning plate 32 in order -to enhance the steam-liquid contacting effect. ~nd withir. the heat concentratin~
chamber 33 are provided a liquid level controller 36, an automatic sludge ejecting valve 18 u~der the control of said controller 36, so as to maintain the liquid at a pre-determined level.
In any of the foregoing embodiments, when the liquid reaches a level higher than proper wi-thin said reactor 5, ~;
the automatic sludge exhaustion valve 18 opens in response to signals from the liquid level controller 26 and 36 thereby discharging the sludge and as a result maintaining the liquid level as predetermined. Also, when reaction pressure inside the reactor 5 drops below the predetermined ~ , pressure around 10 kg/cm2 due to the exhaustion of -the sludge therefr~m resulting in the fall of the liquid level, air may be pressure-fed therein from the compressor 7 in response to signals from the afore-mentioned pressure indicating controller 25 and 34. On -the contrary, when the reactio~ pressure rises above the predetermined level due to generation of decomposed gas from the sludge, a safety valve 17 as will be referred to later may work to set back said pressure to the predetermined one in the reactor 5.
~he slud~e flowed into the reactox 5 as described above may be oxidized through consump-tion of oxygen in the air. And the sludge makes a contact with the air fed from 98~;3 1 the compressor 7 ln the oxidizing chambers 22 and 30 with the application of temperature and pressure additionally thereto, whereas -the fed air has a capaci-ty of oxygen supply by only 2 - 4% o~ -the amount required for the perfect oxidization of said sludge. Accordingly the sludge comple-tes its oxidizing reaction as predetermined through the lapse of time as it travels through said oxidizing chambers 22 and 30. ~he sludge which overflowed over the partitioning plates 23 and 32 brings the heat concentration to a completion at the heat concentrating chambers 29 and ~3 under the influence of temperature and pressure as mentioned hereinafter.
As described hereinbefore, the sludge heat-treated in the reactor 5 has a temperature at the neighborhood of 145C. Said sludge, lowering said temperature to 50 - 60C
as it travels through -the heat exchanger ~, enters a condensing tub 19 after being controlled for its outward flowing amount by the automatic sludge exhaustion valve 18.
~he heat-treated sludge having a favorable precipitating property comes to a condensed state by way of a thermal sedimentation, isolated liquid being returned to the sewage ~ -treating system, said condensed sludge being filtered through a filter 20 such as a belt filter, filter press and the like thereby becoming cake state containing about 40% of water.
An exhaustion pipe 24 communicating with the reactor 5 at its upper portion also communicates with a deodorizing ;
device 25 thereby providing a rou-te for the escape of malodorous gas from within said reactor 5 in a deodorized state to the atmosphere. ~everal deodorizing methods such as combustion method, alkali fumigation method, water washing method and the like can be employed for this 1~398~3 1 deodorizing device 25, but the combustion me-thod may be the best suitable from a view poin~ that organic chemical compounds takes -the grea-ter portion of the source of malodor in this invention method.
The safety valve 17 as shown in Fig. 1 is operated irrespective of operation of said compressor 7 so as to maintain the gas pressure within said reactor 5 as predeter-mined (10 kg/cm2), said malodorous gas passing through said valve 17 being exhausted into the atmosphere after being deodorized by the deodorizing device 25. The air to be `
blo~n in the reactor 5 needs to be sufficient in amount so that an oxidizing rate necessary for the sludge to improve its dewaterbility may be obtained and also the generated malodorous ingredients may be stripped from said sludge, said air amount in concrete terms being required -to be around 10 - 30 -times the amount of the sludge to be treated.
Also the reaction speed varies in accordance to the kind and density of the sludge to be treated, and the steam-liquid contacting hours i.5 subject to the above but a duration longer than 30 minutes is required anyway for this process.
Furthermore, the relation between the ratio of oxygen (oxygen supply percentage) in the supplied air as against the oxygen ~mount required for the complete oxidization of the sludge and the proportional resistance designating dewaterbility of the sludge is as below: when the reac-tion temperature is 145C and the reaction duration is 30 minutes with the pressure in the reactor being 10 kg/cm2, the proportional resistance may be the lowest, that is, about 107 sec.2/g with the oxygen supply ratio at 2 - ~%, thus the sludge of substantially stabilized properties being obtainable.
As described hereinbefore, this invention enables to treat sludge at comparatively low reaction temperatures 1 ranging from 130 to 150C by adjusting the influx of ~-team in-to the reactor, consequently adhesion of scales wi-thin the heat exchan~er being less -than in case of the conven-tional method in which the sludge is treated at high temperatures. ~his invention there~ore enables to minimize the heat loss resulting from the gro~th of scales within the heat exchanger.
~his invention has further advantages in that:
solubility of the sludge is reduced with the result that BOD of the isolated liquid is reduced by about one-half and the generation of sludge from the isolated liquid i~s reduced by 20 - 3~/0 as compared with the case of the conven-tional method; since the reaction is effected at comparatively low temperatures, calories re~uired for heating may be economized by 30 - 40%; and since the increase of the BOD
in the biological treatment system resulting from the return of the isolated liquid is only about 10%~ the waste water treatment system is practically free from the effect of said increase.
Moreover, high temperature above 200C re~uired for the reaction in the conventional method results in an ;~
increase in the growth of what is known as the source of malodor within the reactor, such as amines, mercaptans, sulfides, and the like. In this invention, however, the low reaction temperature helps reduce the generation of ~-amines, mercaptans, and suhfides. Also, the gases generated in the reactor are isolated from the oxidized sludge and discharged directly from said vessel, whereby oxidized sludgR free from gases is led into the heat exchanger and utilized to preheat the sludge to be treated. ~hus, the malodorous ingredients are prevented from being trans~erred into gases, reconcentrated and admixed with the oxidized ~39863 1 sludge in the reactor as in case of the conventional method.
~herefore, malodorous gases are scarcely exhausted into the atmosphere in the subsequent processes.
~ urther in this invention, sands are removed by a sand removing device from sludge which has reduced viscosit~
through preheating treatment in a heat exchanger, this sludge condition enabling to obtain a perfect sand removal with ease. ~his invention therefore has an advantage in that it enables to preclude the risk of clogging and abrasion ~ -of the piping and wear of the valves caused by such sands in the oxidization-treating plant.
Claims (5)
1. A method for treating organic sludge, wherein organic sludge is partially oxidized by a heat-treating system comprising a heat exchanger and a reactor, sludge to be treated being preheated in said heat exchanger by means of indirect conventional heat exchange with oxidization-treated sludge, said preheated sludge being admixed with air of 10 - 30 times the amount of said sludge, said air containing isolatable oxygen enabling to reduce COD of said sludge by 2 - 4%, and with steam enabling to heat said sludge to 130° - 150°C in reaction temperature, said admixed sludge thereby being partially oxidized in a reactor comprising an oxidizing chamber and a heat concentrating chamber pressurized below 10 kg/cm2 for more than 30 minutes, the foregoing method further being characterized in that the sludge preheated in the heat exchanger gets incorporated sands removed therefrom by a sand removing device prior to its pressure-fed travel to said reactor.
2. A method for treating organic sludge as claimed in claim 1, wherein only the treated sludge after separating from gas ingredients generated within the reactor is employed as the source of heat for preheating the sludge to be heated in the heat exchanger.
3. An apparatus for putting into force the method for treating organic sludge as claimed in claim 1, said apparatus comprising: a heat exchanger for indirectly exchanging heat between the sludge to be treated after having been crushed to fragments by a crusher and the already-oxidized sludge; a reactor consisting of an oxidizing chamber for
3. An apparatus for putting into force the method for treating organic sludge as claimed in claim 1, said apparatus comprising: a heat exchanger for indirectly exchanging heat between the sludge to be treated after having been crushed to fragments by a crusher and the already-oxidized sludge; a reactor consisting of an oxidizing chamber for
Claim 3 continued:
oxidizing the preheated sludge and a heat concentrating chamber a sludge supply pipe communicating with said oxidizing chamber, said sludge supply pipe also communicating with an air pipe and a steam pipe for feeding air and steam, res-pectively, to the sludge to be treated, the above-mentioned apparatus further being characterized in that said sludge supply pipe is provided with a sand removing device for removing sand from said sludge preheated in the heat exchanger, and said reactor at its upper portion communicates with said air pipe at one of its end portions, the other end portion of said-air pipe leading to a deodorizing device.
oxidizing the preheated sludge and a heat concentrating chamber a sludge supply pipe communicating with said oxidizing chamber, said sludge supply pipe also communicating with an air pipe and a steam pipe for feeding air and steam, res-pectively, to the sludge to be treated, the above-mentioned apparatus further being characterized in that said sludge supply pipe is provided with a sand removing device for removing sand from said sludge preheated in the heat exchanger, and said reactor at its upper portion communicates with said air pipe at one of its end portions, the other end portion of said-air pipe leading to a deodorizing device.
4. An apparatus for treating organic sludge as claimed in claim 3, wherein the reactor is divided into a sludge oxidizing chamber and a heat concentrating chamber by a partition provided at the inside upper portion of said reactor, said oxidizing chamber having bubble plates disposed in tiers therein and said heat concentrating chamber being provided with a liquid level controller.
5. An apparatus for treating organic sludge as claimed in claim 3, wherein said reactor is divided into a sludge oxidizing chamber and a heat concentrating chamber by means of mounting a partitioning plate therein, said plate being erected from the bottom of said reactor to a suitable height.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5371974A JPS50144673A (en) | 1974-05-10 | 1974-05-10 | |
| JP13733974A JPS5162552A (en) | 1974-11-26 | 1974-11-26 | Jukiseiodeino shorihohoto sochi |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1039863A true CA1039863A (en) | 1978-10-03 |
Family
ID=26394426
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA218,654A Expired CA1039863A (en) | 1974-05-10 | 1975-01-21 | Method and apparatus for treating organic sludge |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1039863A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113402138A (en) * | 2021-07-14 | 2021-09-17 | 上海发电设备成套设计研究院有限责任公司 | Harmless treatment equipment and method for medical sludge |
-
1975
- 1975-01-21 CA CA218,654A patent/CA1039863A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113402138A (en) * | 2021-07-14 | 2021-09-17 | 上海发电设备成套设计研究院有限责任公司 | Harmless treatment equipment and method for medical sludge |
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