CA1036721A - Method for treating organic sludge - Google Patents
Method for treating organic sludgeInfo
- Publication number
- CA1036721A CA1036721A CA218,653A CA218653A CA1036721A CA 1036721 A CA1036721 A CA 1036721A CA 218653 A CA218653 A CA 218653A CA 1036721 A CA1036721 A CA 1036721A
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- CA
- Canada
- Prior art keywords
- sludge
- reactor
- air
- steam
- heated
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Treatment Of Sludge (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
This invention relates to and discloses a novel process for the treatment of organic sludge. The sludge is pre-heated in a heat exchanger by means of indirect conventional heat exchange from previously oxidized sludge and the heated sludge is then admixed with about 10 to 30 times of air which contains isolatable oxygen and steam. The sludge, which is heated to about 130°C to 150°C, is treated in a reactor under a pressure of less than 10 Kg/cm2 for more than 30 minutes and the gaseous ingredients produced in the reactor are then separated from the sludge. The sludge may be filtered prior to preheating, prior to the admixing with air and steam or after treatment. This method is applicable for not only sewage but also for petrochemical waste water, food-processing wastes and the like. Bad odors may be easily removed from the treatment system and by filtering effectively, the life of the apparatus may be significantly prolonged. In addition to these advantages, the process also provides for effective treatment of the sludge at relatively low temperatures thereby reducing the adhesion of scales of baked sludge to the heat exchanger.
This invention relates to and discloses a novel process for the treatment of organic sludge. The sludge is pre-heated in a heat exchanger by means of indirect conventional heat exchange from previously oxidized sludge and the heated sludge is then admixed with about 10 to 30 times of air which contains isolatable oxygen and steam. The sludge, which is heated to about 130°C to 150°C, is treated in a reactor under a pressure of less than 10 Kg/cm2 for more than 30 minutes and the gaseous ingredients produced in the reactor are then separated from the sludge. The sludge may be filtered prior to preheating, prior to the admixing with air and steam or after treatment. This method is applicable for not only sewage but also for petrochemical waste water, food-processing wastes and the like. Bad odors may be easily removed from the treatment system and by filtering effectively, the life of the apparatus may be significantly prolonged. In addition to these advantages, the process also provides for effective treatment of the sludge at relatively low temperatures thereby reducing the adhesion of scales of baked sludge to the heat exchanger.
Description
10367~1 1 In general, treatment of organic sludge is the combination of independent processes such as digestion process, concentration process, dewatering process, combus-tion process and the like. ~hese processes, however, entail various probl~ms centering around environmental pollution by combustion or digestion gas as the result of chemical pretreatment applied on the sludge-to-treat for enhancing its dewaterbility. Such a pretreatment is required for precluding incompleteness in the decomposing state of organic substances usual in the foregoing processes.
~ he wet oxidization 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, improvement of dewatering of not only sewage but also petrochemical waste water, foods-processing waste water and the like, prevention of malodor generation from the treating system, and further effectively remov~ng sands out of the sludge thereby 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 kg/cm2, thence being decomposed by oxidiza-tion in a pressure resistable vessel. In this method,however, organic material incorporated in the sludge is partly rendered soluble by the high temperature to result ~L
--2-- ~
~()367Zl 1 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 exc~anging portion due to processing of the preheating oxidization under high temperature with the result 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 oxigen demand) of the sludge b~ 2 - 4% and within the realm of 10 - ~0 times 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 at a predetermined level below 150C. ~his invention provides a method for treating organic sludge under conditions as mentioned above so that this invent~on may give a drastic solution to the defects of conventional methods in this field as referred to alread~
hereinbefore.
A first object of this invention is to provide a method for effectively treating organic sludge at comparatively low temperature so as to reduce the adhesion of scales of baked sludge to the heat exchanger and also lessen the generation of sludge caused by isolated liquid.
A second object of this invention is to provide a method ~0 for treating organic sludge in which sand within the sludge-to-treat is preliminarily removed therefrom thereb~
preventing pipes from stuffing, abrasion and the like and 1o~36 7 1 valves from damaging.
In order that this invention may be readily understood, reference is made hereinunder to the a~nexed drawing which illustrates, by way of examples, preferred embodiments of this invention.
Fig. 1 is a flow sheet of a sludge treating plant for putting 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 magnified section of a reactor in the second embodiment.
Fig. 4 is a magnified longitudinal section of a sand removing device in this invention.
In Fig. 1, sludge taken out of an organic sewage treating system is stored in a reservoir (not shown) after getting incorporated metal pieces and the like removed therefrom, other foreign materials within said sludge inside said reservoir being crushed to fragments by a crushing device 1.
~hence the sludge is pressure-fed to a heat exchanger 3 b~ a high pressure pump 2 whereby it is preheated to around 120C by wa~ of indirectly absorbi~g heat from already-oxidized high temperature sludge.
~ 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 in high temperature is little viscostic thereby making it easier for the sand to separate therefrom under the effect of the specific gravity difference between the sand and the sludge, the heavier sand naturally precipitating to lie on a sand reservoir 44 formed at the bottom of said device 4. ~he sand removing device proper 42 has a bypass pipe 45 to use for its cleaning.
~U3~7~,1 1 ~he sludge after getting 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 portion thereof.
In Fig. 2 showing the first embodiment of the reactor 5, a condensed-sludge supply pipe 10 connecting afore-mentioned sand removing device 4 to the inlet of said reactor 5 at its lower portion further con~ects with a steam pipe 11 from the boiler 6 and an airpipe 7 from the compressor 7 thereby enabling to admix the air and steam with the sludge b~ an ejector 13. Within the reactor 5 are disposed numerous bubble plates 28 in tiers keeping a suitable space between each other, at the upper portion of said reactor 5 being provided a partitioning plate 2 for dividing the space therein into a sludge oxidizing chamber 22 and a heat concentrating chamber 29, at the lower portion of said reactor 5 being provided a space 21 wherein to admix untreated sludge with compressed air and steam. In said heat concentrating chamber 29, there are a liquid level controller 26 and an automatic sludge exhaustion valve 18 under the control of said controller 26 th~reby enabling to keep the liquid at a predetermined level.
~lso, a pressure indicating-recording controller 25 is disposed within said reactor 5 to keep pressure therein as predetermined.
In this embodiment, the sludge, air and steam flowed into said reactor 5 through lower portion thereof Gombine to pass through every hole of the bubble plate 28 in turbulence thereby resulting in the liquid-vapor contact to a ~atisfactory state. And accordingly the oxidizing chamber 22 is free from the generation of dead space and 103ti7~21 1 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 supply pipe 10 connecting to the inlet of said reactor 5 at its lower portion further connects to a steam pipe 11 and an airpipe 12 thereby enabling to admix said sludge with said air and steam by an ejector 13 before being sent into said reactor 5. In this embodiment, however, the reac~or 5 differs in internal organization from that in the first embodiment, i.e., the reactor in the second embodiment is divided into two compartments by a partitionin~
plate 32 erected from the bottom thereof to a suitable height, one compartment being an oxidizing chamber 30 on the sludge in~lux side and the other 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 partitioning plate 32 in order to enhance the steam-liquid contacting effect. And within the heat concentrating chamber 33 are provided a liquid level control-ler 36, an automatic sludge ejecting valve 18 under the control of said controller 36, so as to maintain the liquid at a predetermined level.
In any of the foregoing embodiments, when the liquid reaches a level higher than proper within 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 1 therefrom resulting in the fall of t~e li~uid level, air may be pressure-fed therein from the compressor 7 in response to signals from the afore-mentioned pressure îndicating controller 25 and 34.
On the contrary, when the reaction 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.
The sludge flowed into the reactor 5 as described above may be oxidized through consumption of oxygen in the air. And the sludge makes a contact with the air fed from the compressor 7 in the oxidizing chamber 22 and 30 with the application of tempera-ture and pressure additionally thereto, whereas the fed air has a capacity of oxygen supply by only 2-4~ of the amount required for the perfect oxidization of said sludge. Accordingly the sludge completes its oxidizing reaction as predetermined through the lapse of time as it travels through said oxidizing chambers 22 and 30. The sludge which overflowed over the partitioning plates 23 and 32 brings the heat concentration to a completion at the heat concentrating chambers 29 and 33 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 3, enters a condensing tub 19 after being controlled for its outward flowing amount by the àutomatic sludge exhaustion valve 18. The heat-treated sludge having a favorable precipitating property comes to a condensed state by ~ay o~ a thermal sedimentation, 103tj7;~1 1 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 4~,b 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 route ~or 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 fumiga~ion method, water washing method and the like can be employed for this deodorizing device 25, but the combustion method may be the best suitable from a view point that organic chemical compounds takes the greater portion of the source of malodor in this invention method.
The safety valve 17 as shown in ~ig. 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 val~e 17 being exhausted into the atmosphere after being deodorized by the deodorizing device 25. The air to be blown in the reactor 5 needs to be sufficient in amount so that an oxidizing rate necessary for the sludge to improve its dewaterbility ma~ be obtained and also the generated malodorous ingredie~ts 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.
~lso the reaction speed varies in accordance to the kind and density of the sludge to be treated, and the steam-liquid contacting hours is subject tG the above but a duration longer than ~0 minutes is required anyway for this process.
Furthermore, the relation between the ratio of oxygen 103~7Zl 1 (oxygen supply percentage) in the supplied air as against the oxygen amount required for the complete oxidization of the sludge and the proportional resistance desig~ating dewaterbility of the sludge is as below: when the reaction temperature is 145C and the reaction duration is 30 minutes with the pressure in the reactor being 10 kg/cm2, the proportional resista~ce may be the lowest, that is, about 107 sec.2/g with the o~ygen supply ratio at 2 - ~%, thus th~ sludge of substantially stabilized properties being obtainable.
As described hereinbefore, this inven*ion enables to treat sludge at comparatively low reaction temperatures ranging from 130 to 150C by adjusting the influx of steam into the reactor, consequently adhesion of scales within the heat exchanger being less than in case of the conventional method in which the sludge is treated at high temperatures.
~his invention therefore enables to minimize the heat loss resulting from the growth of scales within the heat exchanger.
~ his invention has further advantages in that:
solubility of the sludge is reduced with the result that ~OD of the isolated liquid is reduced by about one-half and the generation of sludge from the isolated liquid is reduced by 20 - 30% as compared with the case of the conven-tional method; since the reaction is effected at comparatively low temperatures, calories required for heating may be economized by 30 - 40Yo; and since the increase of the BOD
in the biological treatment system resulting from the return of the isolated liquid is only about 1~/o~ the waste water treatment system is practically free from the effect of said increase.
Moreover, high temperature above 200C required for the reaction in the conventional method results in an 103ti~/21 1 increase in the growth of what is known as the source of malodor within the reactor, such as amines, mercaptans, sul~ides, and the like. In this invention, however, the low reaction temperature helps reduce the generation of amines, mercaptans, and sulfides. Also, the gase~ generated in the reactor are isolated from the oxidized sludge and discharged directly from said vessel, whereby oxidized sludge free from gases is led into the heat exchanger and utilized to pre~eat the sludge to be treated. ~hus, the malodorous ingredients are prevented from being transferred into gases, reconcentrated and admixed with the oxidized sludge in the reactor as in case of the conventional method.
~herefore, malodorous gases are scarcely exhausted into the atmosphere in the subsequent processes.
Further in this invention, sands are removed by a sand removing device from sludge which has reduced viscosity through preheating treatment in a heat exchanger, this sludge condition enabling to obtain a perfect sand removal with ease. ~his in~ention 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.
~ he wet oxidization 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, improvement of dewatering of not only sewage but also petrochemical waste water, foods-processing waste water and the like, prevention of malodor generation from the treating system, and further effectively remov~ng sands out of the sludge thereby 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 kg/cm2, thence being decomposed by oxidiza-tion in a pressure resistable vessel. In this method,however, organic material incorporated in the sludge is partly rendered soluble by the high temperature to result ~L
--2-- ~
~()367Zl 1 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 exc~anging portion due to processing of the preheating oxidization under high temperature with the result 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 oxigen demand) of the sludge b~ 2 - 4% and within the realm of 10 - ~0 times 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 at a predetermined level below 150C. ~his invention provides a method for treating organic sludge under conditions as mentioned above so that this invent~on may give a drastic solution to the defects of conventional methods in this field as referred to alread~
hereinbefore.
A first object of this invention is to provide a method for effectively treating organic sludge at comparatively low temperature so as to reduce the adhesion of scales of baked sludge to the heat exchanger and also lessen the generation of sludge caused by isolated liquid.
A second object of this invention is to provide a method ~0 for treating organic sludge in which sand within the sludge-to-treat is preliminarily removed therefrom thereb~
preventing pipes from stuffing, abrasion and the like and 1o~36 7 1 valves from damaging.
In order that this invention may be readily understood, reference is made hereinunder to the a~nexed drawing which illustrates, by way of examples, preferred embodiments of this invention.
Fig. 1 is a flow sheet of a sludge treating plant for putting 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 magnified section of a reactor in the second embodiment.
Fig. 4 is a magnified longitudinal section of a sand removing device in this invention.
In Fig. 1, sludge taken out of an organic sewage treating system is stored in a reservoir (not shown) after getting incorporated metal pieces and the like removed therefrom, other foreign materials within said sludge inside said reservoir being crushed to fragments by a crushing device 1.
~hence the sludge is pressure-fed to a heat exchanger 3 b~ a high pressure pump 2 whereby it is preheated to around 120C by wa~ of indirectly absorbi~g heat from already-oxidized high temperature sludge.
~ 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 in high temperature is little viscostic thereby making it easier for the sand to separate therefrom under the effect of the specific gravity difference between the sand and the sludge, the heavier sand naturally precipitating to lie on a sand reservoir 44 formed at the bottom of said device 4. ~he sand removing device proper 42 has a bypass pipe 45 to use for its cleaning.
~U3~7~,1 1 ~he sludge after getting 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 portion thereof.
In Fig. 2 showing the first embodiment of the reactor 5, a condensed-sludge supply pipe 10 connecting afore-mentioned sand removing device 4 to the inlet of said reactor 5 at its lower portion further con~ects with a steam pipe 11 from the boiler 6 and an airpipe 7 from the compressor 7 thereby enabling to admix the air and steam with the sludge b~ an ejector 13. Within the reactor 5 are disposed numerous bubble plates 28 in tiers keeping a suitable space between each other, at the upper portion of said reactor 5 being provided a partitioning plate 2 for dividing the space therein into a sludge oxidizing chamber 22 and a heat concentrating chamber 29, at the lower portion of said reactor 5 being provided a space 21 wherein to admix untreated sludge with compressed air and steam. In said heat concentrating chamber 29, there are a liquid level controller 26 and an automatic sludge exhaustion valve 18 under the control of said controller 26 th~reby enabling to keep the liquid at a predetermined level.
~lso, a pressure indicating-recording controller 25 is disposed within said reactor 5 to keep pressure therein as predetermined.
In this embodiment, the sludge, air and steam flowed into said reactor 5 through lower portion thereof Gombine to pass through every hole of the bubble plate 28 in turbulence thereby resulting in the liquid-vapor contact to a ~atisfactory state. And accordingly the oxidizing chamber 22 is free from the generation of dead space and 103ti7~21 1 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 supply pipe 10 connecting to the inlet of said reactor 5 at its lower portion further connects to a steam pipe 11 and an airpipe 12 thereby enabling to admix said sludge with said air and steam by an ejector 13 before being sent into said reactor 5. In this embodiment, however, the reac~or 5 differs in internal organization from that in the first embodiment, i.e., the reactor in the second embodiment is divided into two compartments by a partitionin~
plate 32 erected from the bottom thereof to a suitable height, one compartment being an oxidizing chamber 30 on the sludge in~lux side and the other 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 partitioning plate 32 in order to enhance the steam-liquid contacting effect. And within the heat concentrating chamber 33 are provided a liquid level control-ler 36, an automatic sludge ejecting valve 18 under the control of said controller 36, so as to maintain the liquid at a predetermined level.
In any of the foregoing embodiments, when the liquid reaches a level higher than proper within 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 1 therefrom resulting in the fall of t~e li~uid level, air may be pressure-fed therein from the compressor 7 in response to signals from the afore-mentioned pressure îndicating controller 25 and 34.
On the contrary, when the reaction 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.
The sludge flowed into the reactor 5 as described above may be oxidized through consumption of oxygen in the air. And the sludge makes a contact with the air fed from the compressor 7 in the oxidizing chamber 22 and 30 with the application of tempera-ture and pressure additionally thereto, whereas the fed air has a capacity of oxygen supply by only 2-4~ of the amount required for the perfect oxidization of said sludge. Accordingly the sludge completes its oxidizing reaction as predetermined through the lapse of time as it travels through said oxidizing chambers 22 and 30. The sludge which overflowed over the partitioning plates 23 and 32 brings the heat concentration to a completion at the heat concentrating chambers 29 and 33 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 3, enters a condensing tub 19 after being controlled for its outward flowing amount by the àutomatic sludge exhaustion valve 18. The heat-treated sludge having a favorable precipitating property comes to a condensed state by ~ay o~ a thermal sedimentation, 103tj7;~1 1 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 4~,b 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 route ~or 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 fumiga~ion method, water washing method and the like can be employed for this deodorizing device 25, but the combustion method may be the best suitable from a view point that organic chemical compounds takes the greater portion of the source of malodor in this invention method.
The safety valve 17 as shown in ~ig. 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 val~e 17 being exhausted into the atmosphere after being deodorized by the deodorizing device 25. The air to be blown in the reactor 5 needs to be sufficient in amount so that an oxidizing rate necessary for the sludge to improve its dewaterbility ma~ be obtained and also the generated malodorous ingredie~ts 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.
~lso the reaction speed varies in accordance to the kind and density of the sludge to be treated, and the steam-liquid contacting hours is subject tG the above but a duration longer than ~0 minutes is required anyway for this process.
Furthermore, the relation between the ratio of oxygen 103~7Zl 1 (oxygen supply percentage) in the supplied air as against the oxygen amount required for the complete oxidization of the sludge and the proportional resistance desig~ating dewaterbility of the sludge is as below: when the reaction temperature is 145C and the reaction duration is 30 minutes with the pressure in the reactor being 10 kg/cm2, the proportional resista~ce may be the lowest, that is, about 107 sec.2/g with the o~ygen supply ratio at 2 - ~%, thus th~ sludge of substantially stabilized properties being obtainable.
As described hereinbefore, this inven*ion enables to treat sludge at comparatively low reaction temperatures ranging from 130 to 150C by adjusting the influx of steam into the reactor, consequently adhesion of scales within the heat exchanger being less than in case of the conventional method in which the sludge is treated at high temperatures.
~his invention therefore enables to minimize the heat loss resulting from the growth of scales within the heat exchanger.
~ his invention has further advantages in that:
solubility of the sludge is reduced with the result that ~OD of the isolated liquid is reduced by about one-half and the generation of sludge from the isolated liquid is reduced by 20 - 30% as compared with the case of the conven-tional method; since the reaction is effected at comparatively low temperatures, calories required for heating may be economized by 30 - 40Yo; and since the increase of the BOD
in the biological treatment system resulting from the return of the isolated liquid is only about 1~/o~ the waste water treatment system is practically free from the effect of said increase.
Moreover, high temperature above 200C required for the reaction in the conventional method results in an 103ti~/21 1 increase in the growth of what is known as the source of malodor within the reactor, such as amines, mercaptans, sul~ides, and the like. In this invention, however, the low reaction temperature helps reduce the generation of amines, mercaptans, and sulfides. Also, the gase~ generated in the reactor are isolated from the oxidized sludge and discharged directly from said vessel, whereby oxidized sludge free from gases is led into the heat exchanger and utilized to pre~eat the sludge to be treated. ~hus, the malodorous ingredients are prevented from being transferred into gases, reconcentrated and admixed with the oxidized sludge in the reactor as in case of the conventional method.
~herefore, malodorous gases are scarcely exhausted into the atmosphere in the subsequent processes.
Further in this invention, sands are removed by a sand removing device from sludge which has reduced viscosity through preheating treatment in a heat exchanger, this sludge condition enabling to obtain a perfect sand removal with ease. ~his in~ention 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 (6)
1. A method of treating organic sludge comprising:
(a) preheating said sludge in a heat exchanger by means of indirect conventional heat exchange from previously oxidized sludge;
(b) admixing said heated sludge with air and steam, said air being present in an amount of about 10 to 30 times the amount of sludge present and containing isolatable oxygen thereby reducing the chemical oxygen demand of said sludge by two to four per cent, said sludge being heated to from about 130°C - 150°C;
(c) treating said sludge in a reactor which includes an oxidizing chamber and a heat concentrating chamber under a pressure of less than 10 Kg/cm2 for more than 30 minutes;
(d) separating from said sludge gaseous ingredients produced in said reactor.
(a) preheating said sludge in a heat exchanger by means of indirect conventional heat exchange from previously oxidized sludge;
(b) admixing said heated sludge with air and steam, said air being present in an amount of about 10 to 30 times the amount of sludge present and containing isolatable oxygen thereby reducing the chemical oxygen demand of said sludge by two to four per cent, said sludge being heated to from about 130°C - 150°C;
(c) treating said sludge in a reactor which includes an oxidizing chamber and a heat concentrating chamber under a pressure of less than 10 Kg/cm2 for more than 30 minutes;
(d) separating from said sludge gaseous ingredients produced in said reactor.
2. A method as claimed in claim 1 wherein said sludge is filtered to remove metallic pieces therefrom prior to preheating said sludge.
3. A method as claimed in claim 1 wherein said preheated sludge is filtered prior to admixing said preheating sludge with air and steam to remove sand therefrom.
4. A method as claimed in claim 1 further including the step of filtering said treated sludge.
5. A method as claimed in claim 1 wherein said gaseous ingredients are removed from said reactor by means of an air pipe extending from the inner area of the reactor, through the upper portion thereof and into the atmosphere.
6. A method as claimed in claim 5 wherein said gaseous ingredients are deodorized prior to their escape to the atmosphere through said air pipe.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1398574A JPS50108175A (en) | 1974-02-02 | 1974-02-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1036721A true CA1036721A (en) | 1978-08-15 |
Family
ID=11848506
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA218,653A Expired CA1036721A (en) | 1974-02-02 | 1975-01-21 | Method for treating organic sludge |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS50108175A (en) |
| CA (1) | CA1036721A (en) |
-
1974
- 1974-02-02 JP JP1398574A patent/JPS50108175A/ja active Pending
-
1975
- 1975-01-21 CA CA218,653A patent/CA1036721A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS50108175A (en) | 1975-08-26 |
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