CA2992657C - Method and facility for the semi-continuous thermal hydrolysis of sludge - Google Patents
Method and facility for the semi-continuous thermal hydrolysis of sludge Download PDFInfo
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- CA2992657C CA2992657C CA2992657A CA2992657A CA2992657C CA 2992657 C CA2992657 C CA 2992657C CA 2992657 A CA2992657 A CA 2992657A CA 2992657 A CA2992657 A CA 2992657A CA 2992657 C CA2992657 C CA 2992657C
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/18—Treatment of sludge; Devices therefor by thermal conditioning
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2209/00—Controlling or monitoring parameters in water treatment
- C02F2209/02—Temperature
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2209/00—Controlling or monitoring parameters in water treatment
- C02F2209/03—Pressure
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2303/00—Specific treatment goals
- C02F2303/06—Sludge reduction, e.g. by lysis
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- Hydrology & Water Resources (AREA)
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- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Treatment Of Sludge (AREA)
Abstract
Method for the thermal hydrolysis of sludges comprising: the pressurizing of sludges to be treated at a reference pressure of 2 bar a to 16 bar a, the injection of live steam into said pressurized sludges so as to carry the temperature of these sludges to 120°C to 200°C, the application to said pressurized and heated sludges of a cycle of thermal hydrolysis treatment comprising the steps consisting in: a) conveying a batch of heated and pressurized sludges into a reaction space, b) maintaining said batch of sludges in said reaction space for a duration sufficient for its thermal hydrolysis, c) draining said reaction space of said batch of sludges, the cooling of said hydrolyzed sludges, the depressurizing of said hydrolyzed sludges, and their removal, the application to said sludges of a cycle of thermal hydrolysis treatment that is conducted in parallel in at least three reaction spaces in each of which a succession of treatment cycles is implemented, each of said reaction spaces being dedicated to the treatment of distinct batches of sludges, said steps a), b) and c) of said treatment cycles being staggered in time from one reaction space to the other, a gas atmosphere common to at least three reaction spaces being prepared and the pressure prevailing in said common gas atmosphere being measured and maintained so as to be essentially constant at said reference pressure.
Description
METHOD AND FACILITY FOR THE SEMI-CONTINUOUS THERMAL HYDROLYSIS OF
SLUDGE
Field of the Invention The invention relates to the field of the treatment of effluents constituted by or highly charged with fermentable organic matter and especially the treatment of sludge obtained from processes for the depollution of urban or industrial waste-water or sludges from the treatment of industrial or agricultural bio-wastes.
Here below, these effluents are generally called "sludges".
Prior Art At present, a part of the sludges produced by purification stations is recycled in the agricultural sector and another part is incinerated or treated in other ways.
However, these sludges are increasingly being treated in specific sub-sectors.
Since the production of these sludges is increasingly great, it is indeed necessary that they entail no danger to the environment and to human health.
In fact, these sludges contain germs, some of which (coliform bacteria, salmonella, helminth eggs, etc.) are pathogenic. In addition, they are highly fermentable and cause the production of gases (amines, hydrogen sulfide, mercaptans, etc.) which cause olfactory nuisance. These considerations explain the need, in the above-mentioned sludge treatment sub-sectors, to apply at least one step for stabilizing these sludges in order to obtain sludges that no longer evolve or evolve slowly, both biologically and at the physical/chemical level.
A major concern is to reduce the volume of these sludges and/or recycle them in the form of biogas.
The methods proposed in the prior art to treat these sludges include thermal hydrolysis which is considered to be a particularly promising method.
The thermal hydrolysis of sludges consists in treating them at a high temperature and under pressure so as to make them hygienic (i.e. to greatly reduce their content in microorganisms, especially pathogenic microorganisms), solubilize a major part of the particulate matter and convert the organic matter that they contain into easily soluble matter that is biodegradable (into volatile fatty acids for example).
Such thermal hydrolysis of sludges could be planned upstream to or even downstream from a step of anaerobic digestion.
A technique described in FR2820735 has been proposed for the hydrolysis of sludges. This technique implements at least two reactors working in parallel.
In each of these reactors, batches of sludges undergo a full cycle of thermal hydrolysis. Each of the cycles of thermal hydrolysis implemented in a reactor comprises steps for feeding the sludges to be treated in the reactor, injecting recovered steam (flash steam) therein in order to recover heat in the sludges, injecting live steam therein in order take them to a pressure P and a temperature T enabling hydrolysis, keeping .. them at this pressure P and at this temperature T for a certain period of time, bringing the sludges to a pressure close to atmospheric pressure by releasing flash steam that is recycled to pre-heat the sludges to be treated from the reactor in parallel, and draining the reactor of the sludges thus hydrolyzed.
According to this technique, it is planned that the cycle will be staggered in time from one reactor to the next to use the flash steam produced from a reactor to inject it into the other reactor. Such an implementation makes it possible to make use of the flash steam produced in one of the reactors to feed the other reactor with steam.
Such a method can be implemented in facilities that are simple to use, the steps of filling, hydrolysis, depressurizing and draining being carried out in the same reactor. The method thus minimizes the speed at which these facilities get clogged, minimizes odors when there is no passage of sludges from reactor to another and reduces live steam requirements.
It can be noted that, according to this technique, the injection of flash steam is done via a steam injector for injecting steam into the reactor sludge blanket. Such a configuration leads to major load losses, on the one hand because of the configuration of the steam injector and on the other hand because of the height of the sludges in the reactor above the injector. In order to minimize these load losses, it is necessary in practice to use reactors having great height provided with several injectors distributed across this height. The steam can thus be distributed at several points in the sludge column through these different injectors. As a corollary, the
SLUDGE
Field of the Invention The invention relates to the field of the treatment of effluents constituted by or highly charged with fermentable organic matter and especially the treatment of sludge obtained from processes for the depollution of urban or industrial waste-water or sludges from the treatment of industrial or agricultural bio-wastes.
Here below, these effluents are generally called "sludges".
Prior Art At present, a part of the sludges produced by purification stations is recycled in the agricultural sector and another part is incinerated or treated in other ways.
However, these sludges are increasingly being treated in specific sub-sectors.
Since the production of these sludges is increasingly great, it is indeed necessary that they entail no danger to the environment and to human health.
In fact, these sludges contain germs, some of which (coliform bacteria, salmonella, helminth eggs, etc.) are pathogenic. In addition, they are highly fermentable and cause the production of gases (amines, hydrogen sulfide, mercaptans, etc.) which cause olfactory nuisance. These considerations explain the need, in the above-mentioned sludge treatment sub-sectors, to apply at least one step for stabilizing these sludges in order to obtain sludges that no longer evolve or evolve slowly, both biologically and at the physical/chemical level.
A major concern is to reduce the volume of these sludges and/or recycle them in the form of biogas.
The methods proposed in the prior art to treat these sludges include thermal hydrolysis which is considered to be a particularly promising method.
The thermal hydrolysis of sludges consists in treating them at a high temperature and under pressure so as to make them hygienic (i.e. to greatly reduce their content in microorganisms, especially pathogenic microorganisms), solubilize a major part of the particulate matter and convert the organic matter that they contain into easily soluble matter that is biodegradable (into volatile fatty acids for example).
Such thermal hydrolysis of sludges could be planned upstream to or even downstream from a step of anaerobic digestion.
A technique described in FR2820735 has been proposed for the hydrolysis of sludges. This technique implements at least two reactors working in parallel.
In each of these reactors, batches of sludges undergo a full cycle of thermal hydrolysis. Each of the cycles of thermal hydrolysis implemented in a reactor comprises steps for feeding the sludges to be treated in the reactor, injecting recovered steam (flash steam) therein in order to recover heat in the sludges, injecting live steam therein in order take them to a pressure P and a temperature T enabling hydrolysis, keeping .. them at this pressure P and at this temperature T for a certain period of time, bringing the sludges to a pressure close to atmospheric pressure by releasing flash steam that is recycled to pre-heat the sludges to be treated from the reactor in parallel, and draining the reactor of the sludges thus hydrolyzed.
According to this technique, it is planned that the cycle will be staggered in time from one reactor to the next to use the flash steam produced from a reactor to inject it into the other reactor. Such an implementation makes it possible to make use of the flash steam produced in one of the reactors to feed the other reactor with steam.
Such a method can be implemented in facilities that are simple to use, the steps of filling, hydrolysis, depressurizing and draining being carried out in the same reactor. The method thus minimizes the speed at which these facilities get clogged, minimizes odors when there is no passage of sludges from reactor to another and reduces live steam requirements.
It can be noted that, according to this technique, the injection of flash steam is done via a steam injector for injecting steam into the reactor sludge blanket. Such a configuration leads to major load losses, on the one hand because of the configuration of the steam injector and on the other hand because of the height of the sludges in the reactor above the injector. In order to minimize these load losses, it is necessary in practice to use reactors having great height provided with several injectors distributed across this height. The steam can thus be distributed at several points in the sludge column through these different injectors. As a corollary, the
2 injectors must be equipped with as many passageways as there are levels of steam injection in order to ensure the maintenance of these injectors, and this makes their construction complex and increases their cost.
In order to limit steam consumption while at the same time improving the efficiency of the thermal hydrolysis of the sludges, especially those with high dry content, another method of thermal hydrolysis has been proposed and is described in FR2990429. Such a method is carried out in at least two reactors working in parallel, in each of which the sludges undergo a full thermal hydrolysis cycle, said cycle being staggered in time from one reactor to another to use the flash steam produced from one reactor to inject it into other reactor. The method comprises a step for extracting a part of the sludges contained in a thermal hydrolysis reactor and then reintroducing them into this reactor (i.e. this is a method in which a part of the content of a thermal hydrolysis reactor is recirculated within itself).
Such a method does not however give full satisfaction. Indeed, it lengthens the time spans of the cycles and therefore entails increases in the size of the facilities that implement it. In addition, it introduces flash steam into the non-preheated sludges, and this does not favor the thermal transfer of steam towards the sludges.
In practice, it is necessary to maintain a leftover quantity (a basic residual quantity) of hot sludges in each thermal hydrolysis reactor, these sludges representing about 10% of the volume of the reactor and limit the filling of these reactors.
Under heat, the reactors cannot be filled beyond 70% of their volume capacity. Finally, the dry content of the sludges that can be treated by this process remains in practice limited to 18% of dry matter.
Although these techniques implement cycles of treatment by thermal hydrolysis of batches of sludges using several thermal hydrolysis reactors, they also provide for a feeding with sludges to be treated and for a draining of the sludges that can be continuous. They are thus called semi-continuous methods or again "serial continuous" methods. These methods ensure that each batch of sludges undergoes a given thermal hydrolysis time.
There also is a known method in the prior art, according to FR3010403, for the treatment of sludges by thermal hydrolysis which is an entirely continuous
In order to limit steam consumption while at the same time improving the efficiency of the thermal hydrolysis of the sludges, especially those with high dry content, another method of thermal hydrolysis has been proposed and is described in FR2990429. Such a method is carried out in at least two reactors working in parallel, in each of which the sludges undergo a full thermal hydrolysis cycle, said cycle being staggered in time from one reactor to another to use the flash steam produced from one reactor to inject it into other reactor. The method comprises a step for extracting a part of the sludges contained in a thermal hydrolysis reactor and then reintroducing them into this reactor (i.e. this is a method in which a part of the content of a thermal hydrolysis reactor is recirculated within itself).
Such a method does not however give full satisfaction. Indeed, it lengthens the time spans of the cycles and therefore entails increases in the size of the facilities that implement it. In addition, it introduces flash steam into the non-preheated sludges, and this does not favor the thermal transfer of steam towards the sludges.
In practice, it is necessary to maintain a leftover quantity (a basic residual quantity) of hot sludges in each thermal hydrolysis reactor, these sludges representing about 10% of the volume of the reactor and limit the filling of these reactors.
Under heat, the reactors cannot be filled beyond 70% of their volume capacity. Finally, the dry content of the sludges that can be treated by this process remains in practice limited to 18% of dry matter.
Although these techniques implement cycles of treatment by thermal hydrolysis of batches of sludges using several thermal hydrolysis reactors, they also provide for a feeding with sludges to be treated and for a draining of the sludges that can be continuous. They are thus called semi-continuous methods or again "serial continuous" methods. These methods ensure that each batch of sludges undergoes a given thermal hydrolysis time.
There also is a known method in the prior art, according to FR3010403, for the treatment of sludges by thermal hydrolysis which is an entirely continuous
3 method. This method includes the steps for injecting recovered steam into the sludges and mixing them with these sludges by means of a primary dynamic mixer-injector device in order to obtain a uniform primary mixture; injecting and mixing live steam into this primary uniform mixture by means of a secondary dynamic mixer-injector device so as to obtain a uniform secondary mixture; conveying the uniform secondary mixture to a pressurized tubular reactor and prompting the flow, essentially a plug flow, of this secondary uniform mixture into said reactor for a residence time that is sufficient and at a temperature that is sufficient to enable the thermal hydrolysis of the organic matter present in this secondary uniform mixture;
producing said recovered steam within means for the production of recovered steam from said secondary uniform mixture obtained at exit of said tubular reactor;
cooling said uniform secondary mixture at its exit from said means for the production of recovered steam at a temperature enabling the subsequent digestion of the hydrolyzed organic matter that it contains.
Such a technique, which is very promising, however implies the need to sometimes install several treatment lines to meet the demand for sludge treatment.
All the techniques described here above have the advantage of implementing recovered steam produced by depressurization of a thermal hydrolysis reactor.
The piping and pumps provided for this purpose are, however, subject to pressure and temperature constraints that necessitate maintenance and supervision and can ultimately make them fragile. They therefore make the structure of the facilities and their maintenance somewhat complex.
Goals of the invention It is a goal of the invention to propose a method for the semi-continuous thermal hydrolysis of sludges, offering an alternative to the known prior-art methods art described here above.
It is a goal of the present invention thus to describe such a method that has the advantages of:
- treating the sludges by thermal hydrolysis in batches (i.e. without risks of migration of particles from one batch to another) while at the same time being capable of being implemented in facilities that receive sludges to be
producing said recovered steam within means for the production of recovered steam from said secondary uniform mixture obtained at exit of said tubular reactor;
cooling said uniform secondary mixture at its exit from said means for the production of recovered steam at a temperature enabling the subsequent digestion of the hydrolyzed organic matter that it contains.
Such a technique, which is very promising, however implies the need to sometimes install several treatment lines to meet the demand for sludge treatment.
All the techniques described here above have the advantage of implementing recovered steam produced by depressurization of a thermal hydrolysis reactor.
The piping and pumps provided for this purpose are, however, subject to pressure and temperature constraints that necessitate maintenance and supervision and can ultimately make them fragile. They therefore make the structure of the facilities and their maintenance somewhat complex.
Goals of the invention It is a goal of the invention to propose a method for the semi-continuous thermal hydrolysis of sludges, offering an alternative to the known prior-art methods art described here above.
It is a goal of the present invention thus to describe such a method that has the advantages of:
- treating the sludges by thermal hydrolysis in batches (i.e. without risks of migration of particles from one batch to another) while at the same time being capable of being implemented in facilities that receive sludges to be
4 hydrolyzed continuously and that remove the hydrolyzed sludges also continuously;
- ensuring that each particle of the sludge undergoes thermal hydrolysis during a sufficient pre-determined time.
It is another goal of the invention to propose such a method that can be implemented in facilities that are less complex to make than those used for the methods of the prior art. In particular, it is the goal of the invention to describe a facility which, for substantially equal treatment capacity, has fewer passageways, fewer pipes, fewer valves and a smaller footprint than facilities implementing the semi-continuous methods of the prior art described here above.
It is a goal of the present invention especially to disclose such a method capable of being implemented in at least certain embodiments, in facilities that do not implement steam injectors in the hydrolysis thermal reactor.
Summary of the Invention These goals, as well as others that shall appear here below, are achieved by means of the invention which relates to a method for the thermal hydrolysis of sludges characterized in that it comprises:
the pressurizing of sludges to be treated at a reference pressure of 2 bar a to 16 bar a, the injection of live steam into said pressurized sludges so as to carry the temperature of these sludges to 120 C to 200 C, the application to said pressurized and heated sludges of a cycle of thermal hydrolysis treatment comprising the steps consisting of:
a) conveying a batch of heated and pressurized sludges into a reaction space, b) maintaining said batch of sludges in said reaction space for a duration sufficient for its thermal hydrolysis, c) draining said reaction space of said batch of sludges, the cooling of said hydrolyzed sludges, the depressurizing of said hydrolyzed sludges, the removal of said hydrolyzed sludges,
- ensuring that each particle of the sludge undergoes thermal hydrolysis during a sufficient pre-determined time.
It is another goal of the invention to propose such a method that can be implemented in facilities that are less complex to make than those used for the methods of the prior art. In particular, it is the goal of the invention to describe a facility which, for substantially equal treatment capacity, has fewer passageways, fewer pipes, fewer valves and a smaller footprint than facilities implementing the semi-continuous methods of the prior art described here above.
It is a goal of the present invention especially to disclose such a method capable of being implemented in at least certain embodiments, in facilities that do not implement steam injectors in the hydrolysis thermal reactor.
Summary of the Invention These goals, as well as others that shall appear here below, are achieved by means of the invention which relates to a method for the thermal hydrolysis of sludges characterized in that it comprises:
the pressurizing of sludges to be treated at a reference pressure of 2 bar a to 16 bar a, the injection of live steam into said pressurized sludges so as to carry the temperature of these sludges to 120 C to 200 C, the application to said pressurized and heated sludges of a cycle of thermal hydrolysis treatment comprising the steps consisting of:
a) conveying a batch of heated and pressurized sludges into a reaction space, b) maintaining said batch of sludges in said reaction space for a duration sufficient for its thermal hydrolysis, c) draining said reaction space of said batch of sludges, the cooling of said hydrolyzed sludges, the depressurizing of said hydrolyzed sludges, the removal of said hydrolyzed sludges,
5 the application to said sludges of a cycle of thermal hydrolysis treatment that is conducted in parallel in at least three reaction spaces, in each of which a succession of treatment cycles is implemented, each of said reaction spaces being dedicated to the treatment of distinct batches of sludges, said steps a), b) and c) of said treatment cycles being staggered in time from one reaction space to the other, a gas atmosphere common to at least three reaction spaces being prepared and the pressure prevailing in said common gas atmosphere being measured and kept essentially constant at said reference pressure.
The method according to the invention therefore proposes not to isolate the .. gas atmospheres in the different reaction spaces. Thus, the common gas atmosphere serves as a chamber for re-balancing the pressures of these reaction spaces during the steps of a) filling one reaction space and c) draining another reaction space. In practice, the draining of one reaction space enables the concomitant filling of another reaction space.
In order to prepare such a gas atmosphere common to all the reaction spaces, it is possible to do away with the implementation of valves isolating the gas atmosphere of each reaction space. This simplifies the design and construction or at least the use of facilities for implementing such a method.
Besides, the injection of live steam upstream to the reaction spaces makes .. the use of live steam injectors not indispensable. It is thus possible to reduce the number of passageways serving these reaction spaces and enable the facility and maintenance of such injectors.
It can also be noted that the method according to the invention does not implement any depressurizing of sludges within reaction spaces. Indeed, the sludges are depressurized after having undergone a processing cycle in one of these spaces and after having been drained from this cycle.
Preferably, the method according to the invention comprises a step for adjusting the pressure prevailing in said common gas atmosphere, said step for adjusting the pressure comprising the injection of a gas into said common gas atmosphere when said pressure prevailing in this gas atmosphere is below a predetermined lower threshold and/or the removal of a part of the gas present in
The method according to the invention therefore proposes not to isolate the .. gas atmospheres in the different reaction spaces. Thus, the common gas atmosphere serves as a chamber for re-balancing the pressures of these reaction spaces during the steps of a) filling one reaction space and c) draining another reaction space. In practice, the draining of one reaction space enables the concomitant filling of another reaction space.
In order to prepare such a gas atmosphere common to all the reaction spaces, it is possible to do away with the implementation of valves isolating the gas atmosphere of each reaction space. This simplifies the design and construction or at least the use of facilities for implementing such a method.
Besides, the injection of live steam upstream to the reaction spaces makes .. the use of live steam injectors not indispensable. It is thus possible to reduce the number of passageways serving these reaction spaces and enable the facility and maintenance of such injectors.
It can also be noted that the method according to the invention does not implement any depressurizing of sludges within reaction spaces. Indeed, the sludges are depressurized after having undergone a processing cycle in one of these spaces and after having been drained from this cycle.
Preferably, the method according to the invention comprises a step for adjusting the pressure prevailing in said common gas atmosphere, said step for adjusting the pressure comprising the injection of a gas into said common gas atmosphere when said pressure prevailing in this gas atmosphere is below a predetermined lower threshold and/or the removal of a part of the gas present in
6 said common gas atmosphere when said pressure prevailing in it is above a predetermined upper threshold.
The upper and lower pressure thresholds will be determined around said reference pressure desired for the thermal hydrolysis of sludges, itself varying as a function of the nature and/or composition of the sludges to be treated.
It will be noted that the gas in question could advantageously be live steam.
It could also be another gas, such as an inert gas, nitrogen (N2), carbon dioxide (CO2), or air especially.
In either case, means will be provided for injecting this gas into said common gas atmosphere.
Although, said step for adjusting the pressure prevailing in the common gas atmosphere could be done manually, using measurements of pressure made, this adjustment will preferably be implemented automatically.
Equally preferably, the injection of live steam into said pressurized sludges is .. done so as to carry said sludges to a temperature of 140 C to 180 C. This temperature of thermal hydrolysis could be chosen as a function especially of the nature of the sludges and of the final purpose of the method (hygienization or sanitization, solubilization etc.).
Equally preferably, said reference pressure will range from 3.5 bar a to 10 bar a.
Equally, according to an advantageous variant, the injection of live steam is done using means included in the group constituted by dynamic mixer-injector devices and inline steam injection heaters. It will be noted that the following are the meanings of some of the terms used in the present description:
- Dynamic mixer-injector: any mixer constituted by a chamber receiving a steam injector and means used to cause a stirring operation, using motor-driven mechanical elements, of the different phases entering this chamber in order to obtain a uniform mixture at output; such motor-driven mechanical elements can for example be constituted by blades or screws moved by a rotor or any other type of .. mixture also moved by a rotor; advantageously, the chamber is cylindrical and provided with rotary blades having appropriate geometry mounted on a shaft
The upper and lower pressure thresholds will be determined around said reference pressure desired for the thermal hydrolysis of sludges, itself varying as a function of the nature and/or composition of the sludges to be treated.
It will be noted that the gas in question could advantageously be live steam.
It could also be another gas, such as an inert gas, nitrogen (N2), carbon dioxide (CO2), or air especially.
In either case, means will be provided for injecting this gas into said common gas atmosphere.
Although, said step for adjusting the pressure prevailing in the common gas atmosphere could be done manually, using measurements of pressure made, this adjustment will preferably be implemented automatically.
Equally preferably, the injection of live steam into said pressurized sludges is .. done so as to carry said sludges to a temperature of 140 C to 180 C. This temperature of thermal hydrolysis could be chosen as a function especially of the nature of the sludges and of the final purpose of the method (hygienization or sanitization, solubilization etc.).
Equally preferably, said reference pressure will range from 3.5 bar a to 10 bar a.
Equally, according to an advantageous variant, the injection of live steam is done using means included in the group constituted by dynamic mixer-injector devices and inline steam injection heaters. It will be noted that the following are the meanings of some of the terms used in the present description:
- Dynamic mixer-injector: any mixer constituted by a chamber receiving a steam injector and means used to cause a stirring operation, using motor-driven mechanical elements, of the different phases entering this chamber in order to obtain a uniform mixture at output; such motor-driven mechanical elements can for example be constituted by blades or screws moved by a rotor or any other type of .. mixture also moved by a rotor; advantageously, the chamber is cylindrical and provided with rotary blades having appropriate geometry mounted on a shaft
7 rotating at a rotation speed preferably ranging from 200 rpm to 4000 rpm, corresponding to a speed of 1 m/s to 94 m/s;
- In-line steam injection heater: any means for injecting or distributing steam in a network of tubes without motor-driven mechanical stirring.
Such equipment makes it possible to obtain essentially homogenous sludges at exit. The residence time of these sludges in such equipment is very short:
second to a maximum of 5 minutes. The dynamic injector/mixer devices can, in addition, be used to lower the viscosity of the sludges and thus favor their mixing with steam.
Advantageously, the method comprises a step for the pre-heating of said incoming sludges upstream to the injection of live steam.
Equally advantageously, the cooling of the hydrolyzed sludges produces recovered steam and the method comprises the mixing of recovered steam with said incoming sludges for their pre-heating.
Preferably, the recovered steam is injected into said sludges upstream to said step for injecting live steam through at least one means included in the group constituted by dynamic mixer-injector devices, inline steam injection heater and pulper-mixer devices It will be noted that in the present description the term "pulper/mixer" is understood to mean any mixer constituted by a mixing vessel with a steam injection heater integrated into the vessel or a recirculation loop, the stirring means of which are mechanical and internal (blades, submerged pumps etc.) or external (a pump in a recirculation loop).
Preferably, each of said steps a), b) and c) of said cycle has a duration ranging from 10 mn to 120 mn, advantageously from 15 mn to 30 mn. According to the invention, said steps a), b) and c) are conducted concomitantly in said at least three reaction spaces.
It will be noted that in the context of the present invention, the method according to this invention could implement more than three reaction spaces.
Advantageously, said batch of sludges to be treated has a dry content of 10%
to 40% by weight of dry matter. In order to show the desired dry content for
- In-line steam injection heater: any means for injecting or distributing steam in a network of tubes without motor-driven mechanical stirring.
Such equipment makes it possible to obtain essentially homogenous sludges at exit. The residence time of these sludges in such equipment is very short:
second to a maximum of 5 minutes. The dynamic injector/mixer devices can, in addition, be used to lower the viscosity of the sludges and thus favor their mixing with steam.
Advantageously, the method comprises a step for the pre-heating of said incoming sludges upstream to the injection of live steam.
Equally advantageously, the cooling of the hydrolyzed sludges produces recovered steam and the method comprises the mixing of recovered steam with said incoming sludges for their pre-heating.
Preferably, the recovered steam is injected into said sludges upstream to said step for injecting live steam through at least one means included in the group constituted by dynamic mixer-injector devices, inline steam injection heater and pulper-mixer devices It will be noted that in the present description the term "pulper/mixer" is understood to mean any mixer constituted by a mixing vessel with a steam injection heater integrated into the vessel or a recirculation loop, the stirring means of which are mechanical and internal (blades, submerged pumps etc.) or external (a pump in a recirculation loop).
Preferably, each of said steps a), b) and c) of said cycle has a duration ranging from 10 mn to 120 mn, advantageously from 15 mn to 30 mn. According to the invention, said steps a), b) and c) are conducted concomitantly in said at least three reaction spaces.
It will be noted that in the context of the present invention, the method according to this invention could implement more than three reaction spaces.
Advantageously, said batch of sludges to be treated has a dry content of 10%
to 40% by weight of dry matter. In order to show the desired dry content for
8 treatment through the method according to the invention, the sludges to be treated could be preliminarily diluted, especially with hot water.
The invention also relates to any facility characterized in that it comprises:
means for conveying sludges;
means for pressurizing said sludges;
means for conveying live steam and means for mixing said live steam with said sludges;
means for distributing batches of sludges from said mixing means alternately into at least three reaction spaces for the thermal hydrolysis of said sludges;
means for removing said batches of hydrolyzed sludges alternately from each of said at least reaction spaces to means for cooling and means for depressurizing said hydrolyzed sludges;
means for removing depressurized hydrolyzed sludges;
said at least three reaction spaces having a common gas atmosphere and said common gas atmosphere being provided with means for removing gas and means for measuring the pressure prevailing therein.
The common gas atmosphere with which the facility is provided enables the pressures in the different reaction spaces to be balanced with the reference pressure desired for thermal hydrolysis. The means for measuring pressure in this gas atmosphere are used to supervise the maintaining of this pressure at the right level.
The means for removing gas, apart from removing non-condensable gases, for their part are used to lower this pressure if the pressure thus measured is excessively high.
According to one variant, said means for mixing said live steam with said .. sludges include at least one dynamic mixer/injector (as defined here above) and/or at least one inline steam injection heater (as defined here above) connected to said live steam inlet means.
According to one variant, said gas atmosphere common to the reaction spaces is provided with not only gas-removal means but also gas-injection means.
Thus, the pressure measured in said common gas atmosphere is below a lower
The invention also relates to any facility characterized in that it comprises:
means for conveying sludges;
means for pressurizing said sludges;
means for conveying live steam and means for mixing said live steam with said sludges;
means for distributing batches of sludges from said mixing means alternately into at least three reaction spaces for the thermal hydrolysis of said sludges;
means for removing said batches of hydrolyzed sludges alternately from each of said at least reaction spaces to means for cooling and means for depressurizing said hydrolyzed sludges;
means for removing depressurized hydrolyzed sludges;
said at least three reaction spaces having a common gas atmosphere and said common gas atmosphere being provided with means for removing gas and means for measuring the pressure prevailing therein.
The common gas atmosphere with which the facility is provided enables the pressures in the different reaction spaces to be balanced with the reference pressure desired for thermal hydrolysis. The means for measuring pressure in this gas atmosphere are used to supervise the maintaining of this pressure at the right level.
The means for removing gas, apart from removing non-condensable gases, for their part are used to lower this pressure if the pressure thus measured is excessively high.
According to one variant, said means for mixing said live steam with said .. sludges include at least one dynamic mixer/injector (as defined here above) and/or at least one inline steam injection heater (as defined here above) connected to said live steam inlet means.
According to one variant, said gas atmosphere common to the reaction spaces is provided with not only gas-removal means but also gas-injection means.
Thus, the pressure measured in said common gas atmosphere is below a lower
9 threshold. A gas can be injected enabling this pressure to be made to rise to the height of the reference pressure.
According to one variant of the invention, said reaction spaces are each demarcated by a reactor structure.
In such an example, the common gas atmosphere is advantageously constituted by a set of upper parts of the reactor structures not filled with sludges and by all the pipes going from each reactor structure to said gas-removal means.
According to another variant, said reaction spaces are grouped together in a single reactor structure, each of said reaction spaces constituting a compartment of said single reactor structure. This reactor structure could be cylindrical and the compartments could advantageously take the form of a cylinder portion. Such a configuration of reaction spaces optimizes the footprint of the reactor structure.
In such an example, said common gas atmosphere is advantageously constituted by a space provided in the upper part of the reactor common to the compartments forming it and by all the pipes going from each reactor structure to said gas-removal means.
Equally, according to one variant of the invention, the facility comprises a standby vessel sized to receive at least one batch of sludges and means for dispensing batches of sludges from said at least one dynamic mixer-injector device or inline steam injection heater or pulper-mixer towards said standby vessel Such a standby vessel could be used for the application of one or more batches of sludges of the thermal hydrolysis processing cycles during periods when one of the reaction spaces will be under maintenance. In practice, the reaction space under maintenance will then be isolated by the closing off of a set of valves and this standby vessel will be used by the opening of another set of valves.
In the context of the present invention, the means for cooling the hydrolyzed sludges could be planned in different shapes. Preferably, these means will be chosen from the group constituted by heat exchangers, means for diluting hydrolyzed sludges with industrial-use water, means for injecting fresh sludges into said hydrolyzed sludges, means for generating recovered steam.
When a heat exchange is implemented, it is possible to use an exchanger comprising an inlet for the treatment for sludges to be heated and an inlet for the hydrolyzed sludges to be cooled. This type of heat exchanger is called a sludge-sludge heat exchanger.
When these cooling means include at least one heat exchanger, the heat recovered through the heat exchanger could be used to heat buildings or for other treatment operations such as a digestion of the sludges.
The means for generating recovered steam could be constituted by a waste steam boiler or could advantageously include a flash tank. It will be noted that in the .. present description the term 'flash tank' is understood to mean a tank in which the pressure of the hydrolyzed sludges is suddenly lowered, giving rise concomitantly to the cooling of the sludges and to the emission of steam under high pressure.
Such a tank therefore constitutes both the cooling means and the depressurizing means.
When the facility comprises means for generating recovered steam, it will preferably include at least one piping for conveying said recovered steam upstream to said mixing means for mixing live steam with the sludges and means for putting said recovered steam into contact with said sludges to be treated. This putting into contact will then enable the preheating of the sludges at reduced cost. In order to favor this putting into contact, the plant will preferably include at least one of the means chosen from among a pulper-mixer, a dynamic mixer-injector device, an in-line steam injector and a pulper-mixer device (as defined here above).
List of figures The invention, as well as its different advantages will be understood more easily from the following description of four non-exhaustive embodiments given with .. reference to the appended drawings of which:
figure 1 schematically represents a first embodiment of a facility according to the invention in which the reaction spaces are each demarcated by a reactor structure;
figure 2 schematically represents a second embodiment of a facility according to the invention in which the reaction spaces are grouped together in a single reactor structure;
figure 3 schematically represents a third embodiment of a facility according to the invention in which the reaction spaces are each demarcated by a reactor structure, the facility comprising in addition a standby vessel to ensure the maintenance of the reaction spaces;
figure 4 schematically represents a fourth embodiment of a facility according to the invention.
Description of embodiments Referring to figure 1, the facility comprises sludge-conveying means 1 comprising a main piping having two bypasses la, lb. The main piping and its bypasses are each equipped with, on the one hand, means 2, 2a, 2b for pressurizing the sludges, each including a pump, and on the other hand mixer means 4, 4a, 4b for mixing the pressurized sludges with the live "water" steam each including a dynamic mixer-injector 18, 18a, 18b. It will noted that in other embodiments, the mixing means could include an inline steam dispenser or inline steam injection heater (as defined here above). Such distributors are especially commercially distributed by the ProSonix firm under the name "inline direct steam injection heater".
In order to enable the mixing of the pressurized sludges with the steam, the facility comprises live steam conveying means 3 comprising a main piping having two bypasses 3a and 3b respectively serving the dynamic mixer-injectors 18, 18a, 18b.
These live steam conveying means 3 are connected to a steam production unit (not shown in figure 1).
The facility also comprises means of distribution 5 of batches of sludges from said dynamic mixer-injectors 18, 18a, 18b in alternation in at least three reaction spaces 7a, 7b, 7c for the application of thermal hydrolysis cycles which shall be described here below in detail.
In this embodiment, each reaction space 7a, 7b, 7c is individualized by a reactor structure 19a, 19b, 19c respectively. In other words, each reaction space is demarcated by the walls of a reactor independent of the other reactors demarcating the other reaction spaces.
The distribution means 5 comprise three distribution lines 5a, 5b, 5c each equipped with a sludge feeder valve 6a, 6b, 6c respectively and enabling the distribution of the batches of pressurized sludges pressurized and heated in alternation in the three reaction spaces 7a, 7b, 7c.
The facility further comprises means 8 for removing batches of hydrolyzed sludges in alternation from each of the three reaction spaces 7a, 7b, 7c to depressurizing means 10, 10a, 10b each comprising a pump.
These removal means 8 comprise three removal lines 8a, 8b, 8c each equipped with a draining valve 9a, 9b, 9c enabling the distribution of the batches of hydrolyzed sludges respectively to the depressurizing means 10, 10a, 10b.
The facility also comprises removal means 11, 11a, 11b for removing the hydrolyzed sludges. Each of the removal means 18comprise a piping.
A heat exchanger 20 is provided on these removal means in order to recover and/or remove a part of the heat from the removed hydrolyzed sludges, the heat being possibly re-routed towards a steam production unit or else used to heat buildings or for another processing such as a digestion.
The installation also comprises a water system 21 used to dilute the sludges at the exit from the reaction spaces.
The heat exchanger 20 and the water system 21 constitute means of cooling hydrolyzed sludges. As specified here above, other means of cooling could be used in the context of the present invention such as especially an injection of fresh sludges.
In accordance with the present invention, the three reaction spaces 7a, 7b, 7c demarcated by the walls of the reactors 19a, 19b, 19c respectively have a common gas atmosphere 12. This common gas atmosphere is provided with means 13 for removing the gas present in it including a valve 14, and means 16 for injecting a gas in it including an injection lance and a valve 17. The common gas atmosphere 12 is further provided with means 15 for measuring the pressure of the gas prevailing in it.
It will be noted that the common gas atmosphere is represented schematically in figure 1 as a set capping the three reactors 19a, 19b, 19c.
In practice, it is constituted by the set of upper parts of the three reactors 19a, 19b, 19c not filled with sludges and by the set of piping systems going from these reactors up to the valve 14.
The working of this installation shall now be described. On this subject, it will be noted that, when the elements are represented in dotted lines, it means that their use is optional.
Sludges to be treated, possibly diluted and/or pre-heated, are raised to an absolute pressure ranging from 2 bar to 16 bar, preferably 3.5 bar to 12 bar using the pumps 2, 2a, 2b and then heated to a temperature of 120 C to 200 C, preferably 140 C to 180 C through mixer-injector devices 18, 18a, 18b. Through such equipment, the sludges are intimately mixed with the steam and their viscosity is lowered, thus facilitating their subsequent processing.
One batch of these sludges (i.e. a given volume) is then distributed through the means 5 to one of the reaction spaces where they undergo a full cycle of thermal hydrolysis comprising the steps of:
a) routing the batch of heated and pressurized sludges into this reaction space, b) keeping said batch of sludges in said reaction space for a duration sufficient for its thermal hydrolysis, c) draining said reaction space of said sludges through draining means.
Following this full cycle of thermal hydrolysis, the hydrolyzed sludges are cooled (here through the heat exchanger 20 and the input of water by the water system 21 and then possibly by other means in the context of other embodiments), and then depressurized through the depressurizing means and removed.
According to the invention, the cycles of thermal hydrolysis processing are conducted in parallel with the three reaction spaces, the steps a), b) and c) of these cycles being staggered in time from one reaction space to the other.
According to such a cycle, a batch of pressurized and heated sludges is conveyed during the step a), called a filling step, into the reaction space 7a. To this end, the valve 6a serving the reaction space 7a is opened and the draining valve 9a is closed.
In this filling step a), the reactor 19a demarcating the reaction space 7a is filled up to between 70% and 95% of its total volume capacity. The volume of the interior of the reactor not occupied by the sludges is occupied by a gas atmosphere planned in the upper part of the reactor during the step a).
In the present example, this step a) lasts 20 minutes.
During a step b), called a thermal hydrolysis reaction step which, in this example, also lasts 20 minutes, the thermal hydrolysis of the sludges takes place, while the supply valve 6a and draining valve 9a remain closed.
At the end of this step b), the valve 9a is open causing, during a step c), the draining of the content of the batch of hydrolyzed sludges contained in the reaction space 7a towards the heat exchange at 20 and then towards the depressurizing means 10, 10a, 10b before they are removed through pipings of the removal means 11, 11a, 11b. Upstream to the exchanger 20 and downstream from this exchanger 20, water is conveyed to take part in the cooling of the sludges hydrolyzed by the water system 21.
The step c) also lasts 20 minutes.
In the present embodiment, the steps a), b) and c) each have a duration of 20 minutes and constitute a 60-minute processing cycle.
This cycle is immediately repeated for one and then other batches of sludges to be processed in the reaction space 7a. The operations for treating different batches of sludges therefore succeed one another in a succession of 60-minute cycles during which these different batches of sludges travel in transit through the reaction space 7a.
Identical successions of processing cycles are implemented for other batches of sludges by means of the reaction spaces 7b and 7c. The description of these successions of cycles is identical to that made here above with reference to the reaction space 7a, except that it is the valves associated with the reaction spaces 7b and 7c that are actuated, namely:
- the sludge feeder valve 6b and the draining valve 9b for the treatment cycle implemented in the reaction space 7h;
- the sludge feeder valve 6c and the draining valve 9c for the treatment cycle implemented in the reaction space 7c.
According to the invention, the starting points of the cycles of these different successions of cycles are staggered in time so that the steps a) of a succession of cycles carried out in a first reaction space are concomitant with the steps b) of another succession of cycles conducted in a second reaction space and with the steps c) of another succession of cycles conducted in a third reaction space.
In the present example, this staggering between the cycle starting points of each succession of cycles is 20 minutes.
The feeding of sludges into the installation and the discharging of sludges from the installation is thus continuous.
Through the common gas atmosphere 12, the pressure prevailing in the different reaction spaces 7a, 7b, 7c is balanced in these spaces.
If the means 15 for measuring the pressure prevailing in the gas atmosphere 12 show that the pressure prevailing in this gas atmosphere 12 is above a pre-determined upper threshold, the valve 14 can be open for a certain period of time in order to lower this pressure and bring it into the region of the reference pressure.
If, on the contrary, these means 15 for measuring pressure prevailing in the gas atmosphere 12 show that the pressure prevailing the gas atmosphere 12 is below a pre-determined lower threshold, the valve 17 can be open for a certain period of time to convey a gas (for example an inert gas or live steam) into this gas atmosphere to increase this pressure and bring it to the reference pressure or into the region of this reference pressure.
The embodiment described with reference to figure 2 does not differ from that made with reference to figure 1 except by the characteristic according to which the reaction spaces 7a, 7b, 7c are grouped into a single reactor structure 19 of which they constitute portions and by the fact that the inline steam injection heaters 22, 22a, 22b are used instead of the mixer-injector devices. In this embodiment, the common gas atmosphere is constituted by the upper part of the reactor. It will be noted that in this embodiment, the reactor has a vertical shape. In other embodiments, it could however have a horizontal shape.
The embodiment described with reference to figure 3 does not differ from that described with reference to figure 1 except by the characteristic according to which a standby vessel 7d is provided to act as a reaction space during maintenance of one of the reaction spaces 7a, 7b and 7c. This vessel 7d can also be used to temporarily store sludges.
In the embodiment according to figure 4, the hydrolyzed sludges are depressurized and cooled concomitantly in a flash tank 23 provided at the exit from the reaction spaces 7a, 7b and 7c. The cooling of the sludges is completed by the injection of water into the sludges exiting this flash tank through the water system 21 before they are removed by a piping of removal means 11.
The flash steam emitted is routed via a piping 25 towards a pulper-mixer 24 also receiving the incoming sludges. Thus, the incoming sludges can be pre-heated to a temperature ranging for example from 50 to 100 C and preferably from 80 to 95 C. The pre-heated incoming sludges are then routed by a pipe 25a to mixing means 4, 4a, 4b for mixing these sludges with live steam. The rest of the installation is compliant with the embodiment given with reference to figure 1.
It will be noted that, in other embodiments, the means for placing the recovered steam into contact with the incoming sludges could include other items of equipment than a pulper-mixer. In particular, in this context it is possible to envisage the implementing of mixer-injector devices or inline steam injection heaters as described here above.
It will also be noted that, in other embodiments, the recovered steam production means could be means other than a flash tank. In particular, it could be a simple waste steam boiler.
According to one variant of the invention, said reaction spaces are each demarcated by a reactor structure.
In such an example, the common gas atmosphere is advantageously constituted by a set of upper parts of the reactor structures not filled with sludges and by all the pipes going from each reactor structure to said gas-removal means.
According to another variant, said reaction spaces are grouped together in a single reactor structure, each of said reaction spaces constituting a compartment of said single reactor structure. This reactor structure could be cylindrical and the compartments could advantageously take the form of a cylinder portion. Such a configuration of reaction spaces optimizes the footprint of the reactor structure.
In such an example, said common gas atmosphere is advantageously constituted by a space provided in the upper part of the reactor common to the compartments forming it and by all the pipes going from each reactor structure to said gas-removal means.
Equally, according to one variant of the invention, the facility comprises a standby vessel sized to receive at least one batch of sludges and means for dispensing batches of sludges from said at least one dynamic mixer-injector device or inline steam injection heater or pulper-mixer towards said standby vessel Such a standby vessel could be used for the application of one or more batches of sludges of the thermal hydrolysis processing cycles during periods when one of the reaction spaces will be under maintenance. In practice, the reaction space under maintenance will then be isolated by the closing off of a set of valves and this standby vessel will be used by the opening of another set of valves.
In the context of the present invention, the means for cooling the hydrolyzed sludges could be planned in different shapes. Preferably, these means will be chosen from the group constituted by heat exchangers, means for diluting hydrolyzed sludges with industrial-use water, means for injecting fresh sludges into said hydrolyzed sludges, means for generating recovered steam.
When a heat exchange is implemented, it is possible to use an exchanger comprising an inlet for the treatment for sludges to be heated and an inlet for the hydrolyzed sludges to be cooled. This type of heat exchanger is called a sludge-sludge heat exchanger.
When these cooling means include at least one heat exchanger, the heat recovered through the heat exchanger could be used to heat buildings or for other treatment operations such as a digestion of the sludges.
The means for generating recovered steam could be constituted by a waste steam boiler or could advantageously include a flash tank. It will be noted that in the .. present description the term 'flash tank' is understood to mean a tank in which the pressure of the hydrolyzed sludges is suddenly lowered, giving rise concomitantly to the cooling of the sludges and to the emission of steam under high pressure.
Such a tank therefore constitutes both the cooling means and the depressurizing means.
When the facility comprises means for generating recovered steam, it will preferably include at least one piping for conveying said recovered steam upstream to said mixing means for mixing live steam with the sludges and means for putting said recovered steam into contact with said sludges to be treated. This putting into contact will then enable the preheating of the sludges at reduced cost. In order to favor this putting into contact, the plant will preferably include at least one of the means chosen from among a pulper-mixer, a dynamic mixer-injector device, an in-line steam injector and a pulper-mixer device (as defined here above).
List of figures The invention, as well as its different advantages will be understood more easily from the following description of four non-exhaustive embodiments given with .. reference to the appended drawings of which:
figure 1 schematically represents a first embodiment of a facility according to the invention in which the reaction spaces are each demarcated by a reactor structure;
figure 2 schematically represents a second embodiment of a facility according to the invention in which the reaction spaces are grouped together in a single reactor structure;
figure 3 schematically represents a third embodiment of a facility according to the invention in which the reaction spaces are each demarcated by a reactor structure, the facility comprising in addition a standby vessel to ensure the maintenance of the reaction spaces;
figure 4 schematically represents a fourth embodiment of a facility according to the invention.
Description of embodiments Referring to figure 1, the facility comprises sludge-conveying means 1 comprising a main piping having two bypasses la, lb. The main piping and its bypasses are each equipped with, on the one hand, means 2, 2a, 2b for pressurizing the sludges, each including a pump, and on the other hand mixer means 4, 4a, 4b for mixing the pressurized sludges with the live "water" steam each including a dynamic mixer-injector 18, 18a, 18b. It will noted that in other embodiments, the mixing means could include an inline steam dispenser or inline steam injection heater (as defined here above). Such distributors are especially commercially distributed by the ProSonix firm under the name "inline direct steam injection heater".
In order to enable the mixing of the pressurized sludges with the steam, the facility comprises live steam conveying means 3 comprising a main piping having two bypasses 3a and 3b respectively serving the dynamic mixer-injectors 18, 18a, 18b.
These live steam conveying means 3 are connected to a steam production unit (not shown in figure 1).
The facility also comprises means of distribution 5 of batches of sludges from said dynamic mixer-injectors 18, 18a, 18b in alternation in at least three reaction spaces 7a, 7b, 7c for the application of thermal hydrolysis cycles which shall be described here below in detail.
In this embodiment, each reaction space 7a, 7b, 7c is individualized by a reactor structure 19a, 19b, 19c respectively. In other words, each reaction space is demarcated by the walls of a reactor independent of the other reactors demarcating the other reaction spaces.
The distribution means 5 comprise three distribution lines 5a, 5b, 5c each equipped with a sludge feeder valve 6a, 6b, 6c respectively and enabling the distribution of the batches of pressurized sludges pressurized and heated in alternation in the three reaction spaces 7a, 7b, 7c.
The facility further comprises means 8 for removing batches of hydrolyzed sludges in alternation from each of the three reaction spaces 7a, 7b, 7c to depressurizing means 10, 10a, 10b each comprising a pump.
These removal means 8 comprise three removal lines 8a, 8b, 8c each equipped with a draining valve 9a, 9b, 9c enabling the distribution of the batches of hydrolyzed sludges respectively to the depressurizing means 10, 10a, 10b.
The facility also comprises removal means 11, 11a, 11b for removing the hydrolyzed sludges. Each of the removal means 18comprise a piping.
A heat exchanger 20 is provided on these removal means in order to recover and/or remove a part of the heat from the removed hydrolyzed sludges, the heat being possibly re-routed towards a steam production unit or else used to heat buildings or for another processing such as a digestion.
The installation also comprises a water system 21 used to dilute the sludges at the exit from the reaction spaces.
The heat exchanger 20 and the water system 21 constitute means of cooling hydrolyzed sludges. As specified here above, other means of cooling could be used in the context of the present invention such as especially an injection of fresh sludges.
In accordance with the present invention, the three reaction spaces 7a, 7b, 7c demarcated by the walls of the reactors 19a, 19b, 19c respectively have a common gas atmosphere 12. This common gas atmosphere is provided with means 13 for removing the gas present in it including a valve 14, and means 16 for injecting a gas in it including an injection lance and a valve 17. The common gas atmosphere 12 is further provided with means 15 for measuring the pressure of the gas prevailing in it.
It will be noted that the common gas atmosphere is represented schematically in figure 1 as a set capping the three reactors 19a, 19b, 19c.
In practice, it is constituted by the set of upper parts of the three reactors 19a, 19b, 19c not filled with sludges and by the set of piping systems going from these reactors up to the valve 14.
The working of this installation shall now be described. On this subject, it will be noted that, when the elements are represented in dotted lines, it means that their use is optional.
Sludges to be treated, possibly diluted and/or pre-heated, are raised to an absolute pressure ranging from 2 bar to 16 bar, preferably 3.5 bar to 12 bar using the pumps 2, 2a, 2b and then heated to a temperature of 120 C to 200 C, preferably 140 C to 180 C through mixer-injector devices 18, 18a, 18b. Through such equipment, the sludges are intimately mixed with the steam and their viscosity is lowered, thus facilitating their subsequent processing.
One batch of these sludges (i.e. a given volume) is then distributed through the means 5 to one of the reaction spaces where they undergo a full cycle of thermal hydrolysis comprising the steps of:
a) routing the batch of heated and pressurized sludges into this reaction space, b) keeping said batch of sludges in said reaction space for a duration sufficient for its thermal hydrolysis, c) draining said reaction space of said sludges through draining means.
Following this full cycle of thermal hydrolysis, the hydrolyzed sludges are cooled (here through the heat exchanger 20 and the input of water by the water system 21 and then possibly by other means in the context of other embodiments), and then depressurized through the depressurizing means and removed.
According to the invention, the cycles of thermal hydrolysis processing are conducted in parallel with the three reaction spaces, the steps a), b) and c) of these cycles being staggered in time from one reaction space to the other.
According to such a cycle, a batch of pressurized and heated sludges is conveyed during the step a), called a filling step, into the reaction space 7a. To this end, the valve 6a serving the reaction space 7a is opened and the draining valve 9a is closed.
In this filling step a), the reactor 19a demarcating the reaction space 7a is filled up to between 70% and 95% of its total volume capacity. The volume of the interior of the reactor not occupied by the sludges is occupied by a gas atmosphere planned in the upper part of the reactor during the step a).
In the present example, this step a) lasts 20 minutes.
During a step b), called a thermal hydrolysis reaction step which, in this example, also lasts 20 minutes, the thermal hydrolysis of the sludges takes place, while the supply valve 6a and draining valve 9a remain closed.
At the end of this step b), the valve 9a is open causing, during a step c), the draining of the content of the batch of hydrolyzed sludges contained in the reaction space 7a towards the heat exchange at 20 and then towards the depressurizing means 10, 10a, 10b before they are removed through pipings of the removal means 11, 11a, 11b. Upstream to the exchanger 20 and downstream from this exchanger 20, water is conveyed to take part in the cooling of the sludges hydrolyzed by the water system 21.
The step c) also lasts 20 minutes.
In the present embodiment, the steps a), b) and c) each have a duration of 20 minutes and constitute a 60-minute processing cycle.
This cycle is immediately repeated for one and then other batches of sludges to be processed in the reaction space 7a. The operations for treating different batches of sludges therefore succeed one another in a succession of 60-minute cycles during which these different batches of sludges travel in transit through the reaction space 7a.
Identical successions of processing cycles are implemented for other batches of sludges by means of the reaction spaces 7b and 7c. The description of these successions of cycles is identical to that made here above with reference to the reaction space 7a, except that it is the valves associated with the reaction spaces 7b and 7c that are actuated, namely:
- the sludge feeder valve 6b and the draining valve 9b for the treatment cycle implemented in the reaction space 7h;
- the sludge feeder valve 6c and the draining valve 9c for the treatment cycle implemented in the reaction space 7c.
According to the invention, the starting points of the cycles of these different successions of cycles are staggered in time so that the steps a) of a succession of cycles carried out in a first reaction space are concomitant with the steps b) of another succession of cycles conducted in a second reaction space and with the steps c) of another succession of cycles conducted in a third reaction space.
In the present example, this staggering between the cycle starting points of each succession of cycles is 20 minutes.
The feeding of sludges into the installation and the discharging of sludges from the installation is thus continuous.
Through the common gas atmosphere 12, the pressure prevailing in the different reaction spaces 7a, 7b, 7c is balanced in these spaces.
If the means 15 for measuring the pressure prevailing in the gas atmosphere 12 show that the pressure prevailing in this gas atmosphere 12 is above a pre-determined upper threshold, the valve 14 can be open for a certain period of time in order to lower this pressure and bring it into the region of the reference pressure.
If, on the contrary, these means 15 for measuring pressure prevailing in the gas atmosphere 12 show that the pressure prevailing the gas atmosphere 12 is below a pre-determined lower threshold, the valve 17 can be open for a certain period of time to convey a gas (for example an inert gas or live steam) into this gas atmosphere to increase this pressure and bring it to the reference pressure or into the region of this reference pressure.
The embodiment described with reference to figure 2 does not differ from that made with reference to figure 1 except by the characteristic according to which the reaction spaces 7a, 7b, 7c are grouped into a single reactor structure 19 of which they constitute portions and by the fact that the inline steam injection heaters 22, 22a, 22b are used instead of the mixer-injector devices. In this embodiment, the common gas atmosphere is constituted by the upper part of the reactor. It will be noted that in this embodiment, the reactor has a vertical shape. In other embodiments, it could however have a horizontal shape.
The embodiment described with reference to figure 3 does not differ from that described with reference to figure 1 except by the characteristic according to which a standby vessel 7d is provided to act as a reaction space during maintenance of one of the reaction spaces 7a, 7b and 7c. This vessel 7d can also be used to temporarily store sludges.
In the embodiment according to figure 4, the hydrolyzed sludges are depressurized and cooled concomitantly in a flash tank 23 provided at the exit from the reaction spaces 7a, 7b and 7c. The cooling of the sludges is completed by the injection of water into the sludges exiting this flash tank through the water system 21 before they are removed by a piping of removal means 11.
The flash steam emitted is routed via a piping 25 towards a pulper-mixer 24 also receiving the incoming sludges. Thus, the incoming sludges can be pre-heated to a temperature ranging for example from 50 to 100 C and preferably from 80 to 95 C. The pre-heated incoming sludges are then routed by a pipe 25a to mixing means 4, 4a, 4b for mixing these sludges with live steam. The rest of the installation is compliant with the embodiment given with reference to figure 1.
It will be noted that, in other embodiments, the means for placing the recovered steam into contact with the incoming sludges could include other items of equipment than a pulper-mixer. In particular, in this context it is possible to envisage the implementing of mixer-injector devices or inline steam injection heaters as described here above.
It will also be noted that, in other embodiments, the recovered steam production means could be means other than a flash tank. In particular, it could be a simple waste steam boiler.
Claims (27)
1. A method for the thermal hydrolysis of sludges wherein the method comprises:
- the pressurizing of sludges to be treated at a setpoint pressure of 2 bar absolute to 16 bar absolute, - the injection of live steam into said pressurized sludges so as to carry the temperature of these sludges to 120°C to 200°C, - the application to said pressurized and heated sludges of a cycle of thermal hydrolysis treatment to yield hydrolyzed sludges, said cycle comprising steps of:
a) conveying a batch of the heated and pressurized sludges into a reaction space, b) maintaining said batch of sludges in said reaction space for a duration sufficient for thermal hydrolysis of said batch of sludges, and c) draining said reaction space of said batch of sludges, - cooling and depressurizing said hydrolyzed sludges, and - removing said hydrolyzed sludges from a location where said hydrolyzed sludges were depressurized, wherein the application to said sludges of said cycle of thermal hydrolysis treatment is conducted in parallel in at least three reaction spaces in each of which a succession of said treatment cycles is implemented, each of said reaction spaces being dedicated to the treatment of distinct batches of sludges, said steps a), b) and c) of said treatment cycles being staggered in time from one of said reaction spaces to the other, a gas atmosphere common to said reaction spaces being provided and the pressure prevailing in said common gas atmosphere being measured and maintained so as to be substantially constant at said setpoint pressure.
- the pressurizing of sludges to be treated at a setpoint pressure of 2 bar absolute to 16 bar absolute, - the injection of live steam into said pressurized sludges so as to carry the temperature of these sludges to 120°C to 200°C, - the application to said pressurized and heated sludges of a cycle of thermal hydrolysis treatment to yield hydrolyzed sludges, said cycle comprising steps of:
a) conveying a batch of the heated and pressurized sludges into a reaction space, b) maintaining said batch of sludges in said reaction space for a duration sufficient for thermal hydrolysis of said batch of sludges, and c) draining said reaction space of said batch of sludges, - cooling and depressurizing said hydrolyzed sludges, and - removing said hydrolyzed sludges from a location where said hydrolyzed sludges were depressurized, wherein the application to said sludges of said cycle of thermal hydrolysis treatment is conducted in parallel in at least three reaction spaces in each of which a succession of said treatment cycles is implemented, each of said reaction spaces being dedicated to the treatment of distinct batches of sludges, said steps a), b) and c) of said treatment cycles being staggered in time from one of said reaction spaces to the other, a gas atmosphere common to said reaction spaces being provided and the pressure prevailing in said common gas atmosphere being measured and maintained so as to be substantially constant at said setpoint pressure.
2. The method according to claim 1 wherein the method comprises a step of adjusting the pressure prevailing in said common gas atmosphere, said step of adjusting comprising the injection of a gas into said common gas atmosphere when said pressure prevailing in said common gas atmosphere is below a predetermined lower threshold and/or the removal of a part of the gas present in said common gas atmosphere when said pressure prevailing in said common gas atmosphere is above a predetermined upper threshold.
3. The method according to claim 2, wherein said gas is chosen from the group consisting of live steam and inert gas.
4. The method according to any one of claims 2 to 3, wherein said step of adjusting is automatic.
5. The method according to any one of claims 1 to 4, wherein the injection of live steam into said pressurized sludges is done so as to heat the sludges to a temperature of 140°C to 180°C.
6. The method according to any one of claims 1 to 5, wherein said setpoint pressure is in the range of 3.5 bar absolute to 10 bar absolute.
7. The method according to any one of claims 1 to 6, wherein the injection of live steam is done using means selected from the group consisting of: dynamic mixer-injector devices and inline steam injection heaters.
8. The method according to any one of claims 1 to 7 wherein the method comprises pre-heating of said incoming sludges upstream of the injection of live steam.
9. The method according to claim 8 wherein the cooling of the hydrolyzed sludges produces recovery steam and the method comprises mixing the recovery steam with said incoming sludges for their pre-heating.
10. The method according to claim 9 wherein the recovery steam is injected into said sludges upstream to the injection of live steam.
11. The method according to any one of claims 1 to 10 wherein the injection of live steam is performed using at least one of: dynamic mixer-heater devices, inline steam injection heaters or pulper-mixer devices.
12. The method according to any one of claims 1 to 10 wherein the duration of the step a) ranges from 10 to 120 min, the duration of the step b) ranges from 10 to 120 min, and the duration of the step c) ranges from 10 to 120 min.
13. The method according to any one of claims 1 to 12 wherein said batch of sludges to be treated has a dryness of 10% to 40% by weight of dry matter.
14. A plant for implementing the method according to any one of claims 1 to wherein the plant comprises:
means for conveying sludges;
means for pressurizing said sludges;
means for conveying live steam;
means for mixing said live steam with said sludges;
means for distributing batches of sludges from said means for mixing said live steam with said sludges alternately into at least three reaction spaces for the thermal hydrolysis of said sludges;
means for removing said batches of hydrolyzed sludges alternately from each of said at least three reaction spaces to means for cooling and means for depressurizing said hydrolyzed sludges;
means for discharging depressurized hydrolyzed sludges;
said at least three reaction spaces having a common gas atmosphere and said common gas atmosphere being provided with means for removing gas and means for measuring the pressure prevailing therein.
means for conveying sludges;
means for pressurizing said sludges;
means for conveying live steam;
means for mixing said live steam with said sludges;
means for distributing batches of sludges from said means for mixing said live steam with said sludges alternately into at least three reaction spaces for the thermal hydrolysis of said sludges;
means for removing said batches of hydrolyzed sludges alternately from each of said at least three reaction spaces to means for cooling and means for depressurizing said hydrolyzed sludges;
means for discharging depressurized hydrolyzed sludges;
said at least three reaction spaces having a common gas atmosphere and said common gas atmosphere being provided with means for removing gas and means for measuring the pressure prevailing therein.
15. The plant according to claim 14, wherein said means (4, 4a, 4b) for mixing said live steam with said sludges comprise at least one dynamic mixer-injector device (18, 18a, 18b) or at least one inline steam injection heater (22, 22a, 22b) connected to said means for conveying live steam.
16. The plant according to claim 14 or 15 wherein said common gas atmosphere (12) is provided with gas injection means (16).
17. The plant according to any one of claims 14 to 16 wherein said reaction spaces (7a, 7b, 7c) are each demarcated by a reactor structure (19a, 19b, 19c).
18. The plant according to any one of claims 14 to 16 wherein said reaction spaces (7a, 7b, 7c) are grouped together in a single reactor structure (19), each of said reaction spaces (7a, 7b, 7c) comprising a compartment of said single reactor structure (19).
19. The plant according to any one of claims 14 to 18 wherein the plant comprises a standby tank sized to receive at least one batch of sludges and means for dispensing batches of sludges from said means for mixing said live steam with said sludges towards said standby tank (7d).
20. The plant according to any one of claims 14 to 19 wherein said means for cooling hydrolyzed sludges comprise one or more heat exchangers (20).
21. The plant according to any one of claims 14 to 20 wherein said means for cooling hydrolyzed sludges comprise means for diluting hydrolyzed sludges with industrial-use water.
22. The plant according to any one of claims 14 to 21 wherein said means for cooling hydrolyzed sludges comprise means for injecting fresh sludges into said hydrolyzed sludges.
23. The plant according to any one of claims 14 to 22 wherein said means for cooling hydrolyzed sludges comprise means for generating recovered steam.
24. The plant according to claim 23, wherein the plant comprises at least one flash tank (23) producing recovered steam.
25. The plant according to any one of claims 20 to 24 wherein the plant comprises at least one conveying pipe (25, 25a) for conveying said recovered steam, placed upstream to said means (4, 4a, 4b) for mixing live steam with the sludges and means for putting said recovered steam into contact with said sludges to be treated.
26. The plant according to claim 25 wherein said means for putting into contact include at least one means chosen from among dynamic mixer-injector devices, inline steam injection heaters and pulper-mixer devices (24).
27. The plant according to claim 20 wherein said means for cooling hydrolyzed sludges include a sludge/sludge exchanging type of heat exchanger.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR1557397 | 2015-07-31 | ||
| FR1557397A FR3039533B1 (en) | 2015-07-31 | 2015-07-31 | METHOD AND INSTALLATION FOR SEMI-CONTINUOUS THERMAL HYDROLYSIS OF SLUDGE |
| PCT/EP2016/066255 WO2017021097A1 (en) | 2015-07-31 | 2016-07-08 | Process and facility for semi-continuous thermal hydrolysis of sludge |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2992657A1 CA2992657A1 (en) | 2017-02-09 |
| CA2992657C true CA2992657C (en) | 2019-08-20 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2992657A Active CA2992657C (en) | 2015-07-31 | 2016-07-08 | Method and facility for the semi-continuous thermal hydrolysis of sludge |
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| Country | Link |
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| EP (1) | EP3328802B1 (en) |
| CN (1) | CN107848853B (en) |
| CA (1) | CA2992657C (en) |
| DK (1) | DK3328802T3 (en) |
| FR (1) | FR3039533B1 (en) |
| HK (1) | HK1254616B (en) |
| PL (1) | PL3328802T3 (en) |
| WO (1) | WO2017021097A1 (en) |
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| NZ777258A (en) | 2018-12-17 | 2024-03-22 | Cambi Tech As | Thermal hydrolysis methods and plants |
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| NO310717B1 (en) * | 1999-05-31 | 2001-08-20 | Cambi As | Process and apparatus for continuous hydrolysis of wastewater |
| FR2820735B1 (en) | 2001-02-14 | 2004-05-14 | Vivendi Water Systems | PROCESS AND PLANT FOR THE THERMAL HYDROLYSIS OF SLUDGE |
| NO330122B1 (en) * | 2009-07-13 | 2011-02-21 | Cambi As | Process and apparatus for thermal hydrolysis of biomass and steam explosion of biomass |
| CN102417285B (en) * | 2011-10-20 | 2013-05-01 | 同济大学 | Continuous pyrohydrolysis device and method for high-solid-content biological sludge |
| CN102424508A (en) * | 2011-10-28 | 2012-04-25 | 广西博世科环保科技股份有限公司 | Sludge pyrolytic digestion process for efficiently recovering heat energy and equipment thereof |
| FR2990429B1 (en) | 2012-05-10 | 2014-06-13 | Veolia Water Solutions & Tech | METHOD AND INSTALLATION FOR THERMAL HYDROLYSIS OF SLUDGE |
| CN102775031B (en) * | 2012-06-26 | 2015-02-25 | 深圳市环源科技发展有限公司 | Treating method of sludge through catalysis and double thermal hydrolysis by adding alkali and acid |
| FR3010403B1 (en) | 2013-09-06 | 2017-01-13 | Veolia Water Solutions & Tech | METHOD AND DEVICE FOR CONTINUOUS THERMAL HYDROLYSIS WITH RECIRCULATION STEAM RECIRCULATION |
| FR3015971B1 (en) * | 2013-12-26 | 2016-01-01 | Veolia Water Solutions & Tech | METHOD FOR CONTINUOUS THERMAL HYDROLYSIS OF HIGH SICCITE SLUDGE. |
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2015
- 2015-07-31 FR FR1557397A patent/FR3039533B1/en not_active Expired - Fee Related
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2016
- 2016-07-08 WO PCT/EP2016/066255 patent/WO2017021097A1/en active Application Filing
- 2016-07-08 CN CN201680044991.0A patent/CN107848853B/en active Active
- 2016-07-08 EP EP16736199.7A patent/EP3328802B1/en active Active
- 2016-07-08 CA CA2992657A patent/CA2992657C/en active Active
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- 2016-07-08 DK DK16736199.7T patent/DK3328802T3/en active
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2018
- 2018-10-23 HK HK18113582.7A patent/HK1254616B/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| EP3328802A1 (en) | 2018-06-06 |
| HK1254616B (en) | 2020-03-27 |
| FR3039533B1 (en) | 2017-08-11 |
| CA2992657A1 (en) | 2017-02-09 |
| EP3328802B1 (en) | 2018-10-03 |
| FR3039533A1 (en) | 2017-02-03 |
| CN107848853B (en) | 2019-07-16 |
| PL3328802T3 (en) | 2019-04-30 |
| DK3328802T3 (en) | 2019-01-28 |
| CN107848853A (en) | 2018-03-27 |
| WO2017021097A1 (en) | 2017-02-09 |
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