Method of drying sludge and apparatus for carrying out the method

The present invention relates to a method for drying sludge and an apparatus used to carry out this method, and more particularly, a method for drying industrial sludge, mixed sludge, or urban waste and an apparatus thereof. Regarding.

The problems posed by the treatment of sewage sludge are those that are very seriously distracted by national and local governments. In fact, the amount of sludge is constantly increasing, and the risk of toxic, bacterial and olfactory contamination of soil, groundwater, and the environment also tends to increase. Therefore, in all cases it is necessary to have the best technology for treating and reusing these sludges, which are reliable, sustainable, ecological, economical and applicable. Is.

Currently, there are several solutions for sludge disposal to address these issues.

In particular, the principle is convection processing based on heat transfer. The drawback of this technique is that it is very expensive.

The other solution consists of a first step of drying the sludge and then a step of converting the sludge into a storable granule form.

Generally, the drying step is carried out by placing the still moist sludge on the drying floor, after which the sludge is then washed away with a stream of heated air. At the end of this stage, sludge is converted into granular form.

The disadvantage of this type of treatment is that this drying step of sludge with a heated air stream is too long.

Patent Document 1 proposes a device capable of solving the problem of excessively long drying time, and this device is used for dry food type products for animals and fertilizers, and these products are first used. After being made into the form of crushed sludge, these products are used to sterilize. This device includes a worm feed in the form of a tube capable of transporting crushed sludge. The transport device includes an axis containing vanes that are axially placed and spirally arranged with respect to the tube. The carrier must move the sludge forward towards the area where the shattered sludge is processed by microwaves, for its sole purpose. The function of the microwave is to sterilize the debris and complete the drying step by releasing residual water from the crushed sludge. A large amount thus dried exits the device and is collected for packaging.

The disadvantage of this device is that it requires several steps to complete the drying of the product, especially the step of crushing the sludge to be dried. These various stages require more complex and bulkier equipment.

Another drawback of these desiccants is that in certain cases there can be a risk of fire or explosion. The danger of explosion exists in the presence of three factors: high dust content, high oxygen content, and ignition source. Therefore, it is important to avoid the presence of any one of these three factors.

Moreover, equipment that utilizes these technologies is expensive and energy costs are high when using this equipment.

If the drying step is done correctly, the dried sludge can become hot, resulting in a spontaneous source of ignition. Therefore, this ignition factor is often present during the sludge drying step. Therefore, it is necessary to take steps to avoid the presence of two other factors: dust content and oxygen content.<patcit num="1"><text>French Patent No. 2115951</text></patcit>

<p> An object of the present invention is a method and a method that can be used to optimize the sludge drying step without the risk of explosion and at the same time to achieve a complete sludge drying step very quickly and thus reduce energy consumption. To provide a device.</p>

<p> The purpose of this is the sludge drying method used for sewage sludge, liquid fertilizer, or output from septic tanks. --At least the step of raising the sealed enclosure to a set pressure by injecting saturated water vapor and holding this pressure for a given period of time, --At the stage of loading sludge into a tank far away from the wall of the enclosure using the loading means that guarantees the sustainability of the above pressure, --The stage of injecting superheated steam into the sludge by a mixer operating near the wall of the tank farthest from the microwave source, including the injection means, --The stage of heating to the center of the sludge by emitting microwaves at frequencies between 400MHz and 2450MHz in the direction of the tank while the sludge is being mixed and executed. --The stage of removing the water collected by condensing on the wall of the enclosure toward the bottom of the enclosure by a valve leading to the outside and running-off, Satisfied with the fact that it contains.</p><p> According to another special feature, during the entire drying period, sludge is a mixer to achieve more pronounced uniformity of the drying process and at the same time significantly aid the transmission of microwaves into the material. Is mixed with.</p><p> According to another special feature, the saturation pressure of water vapor is in the range between 1 bar and 3 bar.</p><p> According to another special feature, the saturation pressure of water vapor is 1 bar.</p><p> According to another special feature, the superheated vapor pressure is between 1 bar and 5 bar.</p><p> According to another special feature, the superheated vapor pressure is 3 bar.</p><p> According to another special feature, the temperature of the enclosure must be lower than the temperature of the sludge to allow evaporation.</p><p> According to another special feature, microwave irradiation is performed when the sludge temperature is between 110 ° C and 140 ° C.</p><p> According to another special feature, microwave irradiation is performed when the sludge temperature is 130 ° C.</p><p> Another object of the present invention is to provide a device used to carry out this method.</p><p> The purpose of this is for the equipment used to carry out this method to include a closed tank, withstand the pressures mentioned above, and to be used in crystals or in microwaves with at least one microwave generator. It consists of an enclosure that communicates with any other suitable material by at least one window, which communicates with the saturated steam arrival path and the input side of the sludge to be dried, and the mixer passes the overheated steam placed in the enclosure. Satisfied by the fact that it includes a means for injecting and an opening for lowering the dried sludge.</p><p> According to another special feature, at its bottom, the device is on the ground, controlled by a valve and used to remove dripping water due to gravity, or to regulate the internal pressure of the enclosure. Includes an orifice directed towards.</p><p> According to another special feature, the enclosure includes a freezing means placed at its bottom to cool its inner wall in contact with the pressurized atmosphere, which means is part of the enclosure. Arranged to cool only.</p><p> According to another special feature, the freezing means is used to cool between 1/2 and 3/4 of the enclosure.</p><p> According to another special feature, the mixer is formed from a tube containing at least one vane-shaped mixer element mounted around it, and the injection means is placed on this element.</p><p> According to another special feature, the tube is connected to a superheated steam generator, and the steam generated by the generator flows through the tube until it reaches the mixer element and is then injected by the infusion means.</p><p> According to another special feature, the injection means is formed by the openings formed in the mixer element.</p><p> According to another special feature, all openings in the enclosure can be closed by plug means to adjust the seal against pressure and microwaves.</p><p> According to another special feature, the enclosure includes a freezing means used to cool a portion of its inner surface to help condense the water that evaporates during the drying process.</p><p> According to another special feature, the device includes at least one end that can be closed by an automatic door to adjust the seal against the pressure and microwaves mentioned above.</p><p> According to another special feature, the microwave generator communicates with the drying enclosure via a microwave coupler / adapter.</p><p> According to another special feature, the enclosure includes a safety valve.</p><p> According to another special feature, the tank is separated from the enclosure wall by a perforated support to allow condensed water to drip.</p>

Other special features and advantages of the present invention will become more apparent when reading the instructions that follow with reference to the accompanying drawings.

As shown in FIGS. 1, 2 and 3, the device consists of a preferably cylindrical and elongated enclosure (1) made of a metal material with a double wall, the double wall of which is the first. First, it allows both good insulation and sealing against steam pressure, and second, it allows sealing against microwaves. The enclosure (1) includes at least one end that is open to the outside and can be closed by a door (10) or lid (10). In a preferred embodiment of the invention, the enclosure (1) comprises one end that can be sealed. The door (10) used to close the opening is designed so that the enclosure (1) is completely airtight to electromagnetic waves such as air, vapor pressure, and microwaves when the door (10) is closed. Will be done. Thus, the door (10) includes a Teflon® or silicone gasket (102) for sealing against pressure, and a metal gasket (101) for sealing against microwaves. In the embodiment shown in FIG. 2, the door (10) can be slid by a mobile system (152) including wheels (151) connected to the door. Therefore, this system allows the door to move axially with respect to the enclosure (1). In this embodiment, sludge is loaded through an opening that is formed when the door is open.

Generally, the enclosure (1) is placed on the ground and held in place by the foot (15), which portion of the ground forms the bottom of the enclosure (1).

On the inside, the enclosure (1) contains an additional wall at its bottom, which bottom forms a spherical tank (7) loaded with sludge (5) to be dried. This tank (7) includes an upper ridge (71) that is attached to the enclosure (1) and has a small opening formed therein. These openings allow the water condensed on the inner wall of the enclosure (1) to slowly dissipate towards the bottom of the enclosure (1).

In the embodiment shown in FIG. 1, the material (5) to be dried is loaded into the enclosure (1) via the material input side (8). This destination (8) is located on one outer surface of the enclosure (1) at the latter mid-height.

In the embodiment shown in FIG. 2, the loading of the material (5) to be dried can be achieved by a tank that is placed on the mobile trolley (151) and the mobile trolley (152) and can be moved laterally. , Its unloading is achieved by tilting the tank.

The sludge (5) treated by the present invention is of the kind such as sewage sludge, liquid fertilizer, or output from septic tanks.

The enclosure (1) also includes at least one rounded or rectangular opening (2) that makes up the window (2). In one embodiment of the invention, the enclosure (1) includes several windows (2). These windows (2) are made of a material that is sealed to steam but allows microwave radiation to pass through. In one embodiment, the window (2) is made of quartz. In another embodiment, the window (2) is made of Teflon® or any other material that is capable of passing electromagnetic radiation and sealing against vapors. These pressurized windows (2) are used to send microwaves (23) towards the interior of the enclosure (1) and are referred to as transmission windows (2). Thus, they allow the microwave (23) to pass through, which in turn acts on the sludge (5) to be dried. The microwave (23) is carried by the waveguide (24) to at least one window (2). The waveguide (24) is communicated via an impedance coupler / adapter (21) and a microwave generator (22). Thus, the wave generator (22) and the wave generator (23) are used to process the sludge (5) to be dried. The window (2) is located at the top of the enclosure (1), which means the opposite part to the ground.

In the first embodiment shown in FIG. 1, the enclosure (1) is vertical. In this case, it is taller than wide. In this embodiment, the enclosure (1) includes an opening at the end opposite to the one resting on the ground. The window (2) is then placed at the top, below the opening and, as a result, just below the lid (10). In this case, as the microwave exits the window, it is perpendicular to the bottom of the tank and then redirected to reach the material (5) to be dried perpendicular.

In another embodiment, the window (2) is placed on the lid (10), thus allowing direct radiation, which reaches perpendicular to the material (5) to be dried.

In the second embodiment shown in FIG. 2, the tanks are arranged horizontally. That is, it is wider than it is tall. In this case, the opening, also at one end, would be located on the opposite side of the power supply. The window (2) is then placed at the top of the enclosure (1), which also means the part opposite to the part resting on the ground.

In any embodiment, if the windows (2) are rectangular, they are arranged to be reversed relative to each other, which means that one window is lengthwise, as shown in FIG. It means that they are arranged and another window is arranged side by side in the height direction.

Enclosure (1) communicates through at least two tubes with at least two steam-generating systems.

The first generator (9) generates saturated steam. This vapor is injected into all of the enclosure (1) before loading the material (5) to be dried.

The second generator (32) generates superheated steam. This superheated steam is injected directly into the material (5) to be dried.

The mixer (3) is located inside the enclosure (1). This mixer (3) is formed from a tube (31) and a tube (31') that pass through the enclosure (1). The pipe (31) and the pipe (31') are connected to a superheated steam generator (32). Tube (31) and tube (31') include at least one mixer element (35) and mixer element (35'). The mixer element (35) and the mixer element (35') possess means (33) and means (33') for injecting superheated steam. The injection means (33) and the injection means (33') are formed by the openings (33) and openings (33') formed in the mixer element (35) and the mixer element (35'). The steam generated by the generator (32) flows through the pipe until it reaches the mixer element (35) and the mixer element (35'), then the injection means (33) and the center of the material (5) to be dried. It is injected by the injection means (33').

In a first embodiment, the mixer element (35) is formed by a vane attached to the end of a tube (31) that reaches the bottom of the enclosure (1). The mixer is driven by a motor (34) located outside the enclosure (1). The vane follows the shape of a sphere or ellipse at the bottom of the tank (7).

The tube is offset with respect to the tank's axis of symmetry (A), which means near a wall away from the microwave source.

In a second embodiment, the mixer element (35') is formed by a rectangular vane mounted around the tube (31'), preferably in a spiral form and offset from each other. The tube is rotated by a motor (34) and functions as an endless screw.

In both cases, the vanes are fixed to reach as close as possible to the bottom of the tank (7) to mix the maximum amount of material (5) to be dried. The material used for the vane is a material that can withstand microwaves. This material can be, for example, Pyrex® or Teflon®.

The vanes are fixed so that they do not pass outside the material (5) that should be dried before drying, and the amount of material (5) is that the vanes are placed at the end of the drying process to avoid problems due to microwave impact. Selected so that it does not protrude excessively.

The role of the mixer is, firstly, to mix the sludge (5) to achieve homogeneous drying, and secondly, to increase the transmission of microwaves into the sludge (5) and to carry out the drying process. To help. In practice, in the absence of sludge (5) mixing, a dry crust forms rapidly on its surface, thus blocking the proper transmission of microwaves and thus providing effective and homogeneous drying. Deter.

Condensed water is removed via a pipe (4), which is controlled by a water removal valve (41) and is located at the bottom of the enclosure.

This water vent valve (41) keeps the enclosure (1) at the desired pressure, to relieve the pressure if the latter is too high, and finally to the atmosphere when the drying process is complete (1). ) Is used to release.

The top of the enclosure (1) includes a safety valve (12) set by the required pressure, which additionally requires a pressure to be adjusted other than using the water removal valve (41). Works only if. Therefore, this valve (12) is never used during normal operation of the device.

The enclosure (1) also includes a freezing means (203) within its double wall. These freezing means (203) are arranged to allow cooling of the bottom of the enclosure (1) and thus condensation of evaporated water. The freezing means (203) can be, for example, a coil through which the refrigerant gas flows.

These cooling means (203) form a cold zone (200) and a hot zone (300) in the enclosure. The partition (202) between the two zones is located between 1/2 and 3/4 from the bottom of the enclosure.

At its bottom, the enclosure (1) contains a door (6) that is used to remove the drying material when the drying cycle is over. Also, in the embodiment shown in FIG. 1, the door (6) includes a guide that can keep the mixer (3) straight and stop the mixer (3) from tipping over during the mixing process.

The enclosure (1) includes means (11) for measuring temperature and pressure to adjust these parameters during drying.

The open assembly of the enclosure (1) is a valve system (91), valve system (81), valve system (61), and valve system that allows the enclosure (1) to remain sealed and thus prevent microwave leakage. Including (41).

All of the pressures and temperatures used in the context of the present invention are calculated specifically from the Moriel diagram.

The drying method using the equipment just described includes the following operations. That is, --The step of pressurizing the enclosure (1) by sending the saturated steam into the enclosure (1) until a pressure corresponding to the desired operating temperature of the saturated steam is reached. For example, pressures can be selected from 1 bar for a temperature of 100 degrees Celsius for saturated steam to 3 bar for a temperature of 130 degrees Celsius for saturated steam. --Steps to introduce the material to be dried (5) in the form of sludge. At this stage, sludge (5) contains between 70% and 80% water. --Simultaneously mixing sludge (5) and sending superheated steam to the center of the sludge (5) to be dried by the tube (31) and tube (31') and the mixer element (35) and mixer element (35'). Step. Mixing is very important as it allows for even drying. The superheated steam is injected at a pressure from 1 bar to 5 bar, at 3 bar in one embodiment. This results in a sludge (5) temperature near 130 ° C. This step is used to pre-dry the material. --- When the temperature reaches 130 ° C, the step of passing microwaves to accelerate the drying of the material. Microwave frequencies are between 400MHz and 2450MHz.

Therefore, there is a pressure difference between the top of the enclosure (1) and the bottom of the enclosure (1) where the sludge (5) is located. This pressure difference will help remove water outwards from the sludge (5). The power of the microwave generator is calculated to reach the temperature of sludge (5), which is higher than the temperature of saturated steam.

In the presence of saturated vapor pressure, therefore, the dampness released by the sludge during its processing drips through the cold wall due to gravity and below the grill (71) via the water removal valve (41). Will be recovered. The opening of the valve (41) is activated at regular intervals by the monitoring system each time its level approaches the grill. The enclosure (1) includes a level detector capable of automatically opening the valve (41).

After a period of time, when the sludge dries, the microwave generator is also shut down and the pressure is gradually reduced to reach atmospheric pressure.

By saturating the ambient environment around the sludge (5) and using the power of the microwave wisely, the interior of the sludge (5) consumes much less energy than is normally used in the prior art. The process for removing dampness can be accelerated to achieve faster drying with less energy consumption.

In addition, when operating under saturated pressure, the explosion phenomenon is eliminated by preventing the presence of oxygen.

It will be apparent to those skilled in the art that the present invention allows many other specific embodiments without departing from the scope of the invention described in the claims. As a result, the present embodiment should be understood only as an example, but may be modified within the scope of the appended claims, limiting the invention to the detailed description described above. It doesn't become.

<figref num="1">It is a longitudinal sectional view of one embodiment of the apparatus according to this invention.</figref><figref num="2">FIG. 5 is a longitudinal sectional view of another embodiment of the apparatus according to the present invention.</figref><figref num="3">It is a cross-sectional view of the embodiment shown in FIG.</figref>

Code description

1 Enclosure, Chamber, 2 Windows, Opening, 3 Mixer, 4 Gasket, Pipe, 5 Sludge, Material to be dried, 6 Valve, Door, 7 Tank, 8 Input side, Reach point, 9 First generator, 11 Means for measuring temperature and pressure, 12 safety valves, 15 feet, 21 microwave couplers / adapters, 22 microwave generators, 23 microwaves, wave generators, 23 waveguides, 31,31'tubes, 32 saturated steam Generator, 33,33'injection means, 34 motor, 35,35' mixer element, 41 water removal valve, 71 grill, upper ridge, 41,61,81,91 valve system, 101 metal gasket, 102 silicone gasket, 151 Wheels, mobile trolleys, 152 mobile systems, mobile trolleys, 200 cold zones, 202 dividers, 203 refrigeration means, 300 hot zones