Method for treating a fluid containing salts and device for implementing the method

Abstract

The invention relates to a method for treating a fluid, comprising the steps of: introducing the fluid to be treated into a cavity (225) of a dryer (220) (S31); drying the fluid in the cavity (225), comprising a first phase (B) during which the weight of the cavity decreases, and a second phase (C) during which the weight of the cavity decreases, the drying step further comprising a step of refilling the cavity until the weight of the cavity reaches an upper threshold value when the weight of the cavity reaches a lower threshold value or the rate of change of the weight of the cavity is less than a first predetermined value; and a step of extracting the solid residue in powder form (S33) when the rate of change of the weight is less than a second predetermined value. The invention also relates to a device for implementing the method.

Description

Technical Field

[0001] The present invention relates to a fluid treatment method, particularly for fluids containing salts, referred to as "salt solutions", especially in the case of low to medium concentrations of salts, i.e., for example, salt content below 500 g / L or possibly above 300 g / L.

[0002] This method is specifically designed for the recovery of waste liquids, such as those generated by salt bath treatment lines.

[0003] The present invention also relates to an apparatus capable of carrying out the method. Background Technology

[0004] For example, in the field of nitriding, steel parts are usually processed in batches of several parts on a nitriding production line, also known as batch processing.

[0005] For this purpose, the parts to be treated are degreased, then rinsed and dried in an oven.

[0006] The dried parts are then immersed in a nitriding bath placed in a container (also called a crucible) at a high temperature (e.g., 500–650°C). This nitriding bath is generally composed mainly of molten nitride salts.

[0007] For example, nitriding is performed to increase the surface hardness of steel or steel parts and improve their mechanical properties through the diffusion of nitrogen in the steel or steel parts.

[0008] After nitriding, the parts may optionally be immersed in an oxidation bath placed in a container (also called a crucible) at a temperature of, for example, about 450°C. This oxidation bath typically consists mainly of molten oxidizing salts.

[0009] For example, oxidation is performed to improve the corrosion resistance of parts, which usually gives them a conventional black appearance.

[0010] After nitriding, or, depending on the circumstances, oxidation, the parts undergo a quenching process, for example, in a water bath at a temperature much lower than the bath temperature, i.e., a relatively cold water bath.

[0011] However, in the continuous process, each bath became contaminated.

[0012] The water used for rinsing or quenching tanks (also known as "eaude claquage") is also rich in oxidizing salts and / or nitrifying salts, such as nitrates and nitrites.

[0013] This quenching water is a hazardous waste liquid and needs to be treated by a company specializing in such waste. Generally, treatment methods include incineration.

[0014] In addition, it is necessary to store the quenching water before sending it for treatment.

[0015] Meanwhile, continuous batches through nitriding and / or oxidation tanks can generate sludge, which also contains nitrides and / or oxides.

[0016] Therefore, these different forms of waste need to be stored before they are sent for processing.

[0017] However, the storage and processing operations are not only costly, but also harmful to the environment.

[0018] Therefore, it is necessary to be able to process these wastes to some extent, especially to be able to recover the salts they contain.

[0019] The particle size of the recycled salt must not be too fine to avoid powder volatilization, nor too coarse (e.g., greater than 1 cm), because larger particle sizes are more likely to retain residual moisture. Moreover, using this salt, for example, in a molten salt bath, may be dangerous, as the instantaneous evaporation of water during the melting of the salt may cause molten salt to splash.

[0020] Drying techniques for nitriding and / or oxidizing quenching water were tested on a "semi-industrial" scale for the purpose of recovering salts, particularly evaporation concentration methods or spray atomization methods.

[0021] The test was conducted under vacuum using a scraped evaporator-concentrator. This method yields a concentrate with a moisture content of approximately 30%, which is unsuitable for nitriding / oxidation production lines. An additional drying step is necessary to obtain a powder with a dryness of at least 95%, and ideally at least 98%. However, centrifugation tests did not achieve the required dryness. Therefore, this two-step method was not selected.

[0022] Atomization involves drying the solution introduced into the nozzle through a hot airflow in an atomization tower. The droplets are dried instantly, and the powder is collected in a cyclone separator.

[0023] The particle size of the powder produced by the single-effect atomizer test was 30μm to 50μm, which is too fine for the application goals pursued by this invention.

[0024] Other experiments using the "multi-effect" atomizer yielded coarser powder particles, but did not achieve the desired result: in fact, some salts did not reach the target dryness, and the particle size distribution of other salts obtained did not match the required distribution.

[0025] In addition, the equipment required to implement the above methods is relatively bulky and complex, and auxiliary equipment (evaporation and concentration and vibratory fluidizer) is also required, so the cost is relatively high.

[0026] The "hybrid" version (flash atomizer) has also been tested on pilot devices.

[0027] Flash atomization is based on the same principle as atomizing towers, but it features a more integrated and visible annular drying device, which makes it possible to accelerate particle drying.

[0028] However, the experiment could not be concluded because the powder agglomerated prematurely in the annular container.

[0029] There are also crystallization methods that control particle size and are implemented in crystallizers, but these have proven difficult to use or ineffective for multi-component solutions or highly soluble salts.

[0030] Therefore, known methods produce powders that are either too fine, too moist, too expensive, or unsuitable for processing multi-component salts.

[0031] Therefore, it is necessary to develop an alternative treatment method to recover and recycle residual salts in salt solutions, especially for waste liquids containing nitrides and / or oxidized salts.

[0032] Therefore, the present invention aims to overcome, at least partially overcome, the above-mentioned defects, and further has other advantages. Summary of the Invention

[0033] Therefore, according to a first aspect of the present invention, a method for treating a fluid containing salts (e.g., particularly nitrides and / or oxidized salts) is provided, the method comprising:

[0034] - The step of introducing the fluid to be treated into the dryer cavity;

[0035] - A step of drying fluid in a chamber by placing it at a temperature of 30–90°C and a pressure of 10–900 mbars, the drying step including sub-steps of evaporating at least a portion of the fluid and generating at least water vapor, and sub-steps of increasing the salt concentration of the fluid contained in the chamber, the drying step including:

[0036] In the first stage, during which the weight of the cavity decreases, when the weight of the cavity reaches a lower threshold or the rate of change of the cavity weight is less than a first predetermined value, the drying step includes replenishing the cavity until the weight of the cavity reaches an upper threshold; and

[0037] In the second stage, during which the weight of the cavity decreases, when the rate of change of weight is less than a second predetermined value, the method includes:

[0038] - The steps for extracting powdery solid residues.

[0039] Therefore, this method can recover nitrides and / or oxidized salts, as well as salts produced by heat treatment, or salts produced by seawater desalination, for example.

[0040] For example, the fluid to be dried can come from a salt solution in a tank (e.g., a quenching tank) of a nitriding production line.

[0041] In addition, the fluid to be processed, i.e., the salt solution, may have multiple components and contain highly soluble salts.

[0042] For example, the initial salt concentration of the fluid to be dried is less than 500 g / L, such as 50 to 500 g / L, or even 300 to 400 g / L.

[0043] Therefore, this method can recover salts contained in fluids from nitriding production lines (e.g., quenching water and / or sludge), thereby reducing waste; incidentally, some processing costs are also controlled as a result.

[0044] This method can remove large amounts of waste liquid because the waste liquid is recycled, at least partially or even completely recovered to the extent possible, to extract the salts contained in the fluid, which can then flow from the tank from which it originated to the continuous channels of the parts.

[0045] Furthermore, it can limit the waste of non-renewable resources and recycle raw materials.

[0046] For example, this method is particularly effective for oxidizing and / or nitriding quenching water, allowing the desired particle size, composition, and dryness for salt recovery to be achieved in a single drying step with potentially relatively short drying times.

[0047] For example, the chamber of the dryer is kept under vacuum.

[0048] Here, vacuum refers to pressures of approximately 10–900 mbars (millibars), such as 20–500 mbars, or even 20–100 mbars.

[0049] This vacuum allows salt solutions to evaporate at relatively low temperatures (e.g., 35–90°C). It can also be used to transport fluids to be treated via suction.

[0050] Therefore, supplemental filling during the drying step enables the chamber to be filled semi-continuously, that is, filling is performed so that the fluid to be treated is added to the chamber of the dryer while the chamber is being emptied due to processing.

[0051] Therefore, the first stage of the drying step includes at least one cycle during which the fluid is compressed and the vapor is evaporated until the weight of the cavity reaches a lower threshold or its rate of change is less than a first predetermined value, and then replenishment filling is performed.

[0052] In fact, during the processing, specifically during the drying step and especially the concentration stage, some fluid, particularly water in the fluid, evaporates, thus reducing the weight of the cavity contents.

[0053] At the same time, the salt concentration of the fluid contained in the cavity increases.

[0054] For example, the dryer includes a pressure sensing element system configured to detect the weight of the fluid contained in the chamber.

[0055] In the first stage of the drying process, for example, when the chamber weight reaches a certain threshold (called the lower threshold), or when the rate of change of the chamber weight is less than a first predetermined value (i.e., the rate of change of weight decreases within a given time), the valve is opened to introduce the fluid to be treated. The chamber is considered fully filled and evaporation continues until the weight exceeds the threshold or the rate of change exceeds the first predetermined value.

[0056] The lower threshold is chosen so that the addition of fluid has a small effect on the temperature of the cavity contents (e.g., the temperature change is less than 20%, or possibly less than 15%, or even less than 10%, or even less than 5%, or even less than 3%, relative to the average temperature of the cavity contents before the addition of fluid); for example, the lower threshold is chosen to represent approximately 85% of the maximum cavity volume.

[0057] For example, a threshold is determined for each replenishment fill to represent a substantially constant fill volume. In reality, as the drying process continues, the salt concentration in the fluid within the chamber increases. Therefore, the same volume weighs increasingly more. Consequently, the threshold may vary from one replenishment fill operation to another.

[0058] Therefore, for example, the method includes the step of detecting the weight of the cavity, and when the weight reaches a lower threshold limit or the rate of change of the cavity weight is less than a first predetermined value, the method includes the step of opening a filling valve and the step of replenishing the cavity with the fluid to be processed.

[0059] In addition, for example, when the weight of the cavity reaches a threshold limit, the method includes the step of closing the filling valve.

[0060] For example, the pressure-sensing element system is also configured to detect the end of drying at the end of the second stage. For example, when the weight of the container remains relatively constant over time (i.e., the change in the weight of the cavity over time is less than a second predetermined value), it is considered that all the water has evaporated and the product is "dry" (the target degree of dryness has been achieved).

[0061] The first predetermined value and the second predetermined value may be the same or different. For example, the second predetermined value may be less than the first predetermined value; for example, the second predetermined value may be close to zero.

[0062] For example, a second stage can be carried out after a predetermined number of replenishment filling operations, or when the cavity reaches a certain weight.

[0063] For example, repeat the first stage of replenishment filling operation until the salt concentration of the fluid contained in the cavity reaches the target value; for example, at least 400 g / L for oxidized salts and / or nitride salts, preferably at least 500 g / L, but the target value depends on the nature of the salts and / or the required application.

[0064] In one embodiment, the drying step is set such that the moisture content of the resulting solid residue is 0.5–5% by weight, or even 0.5–3%, or even 1–2%.

[0065] For example, moisture content is detected by thermogravimetric analysis, such as when sampling solid residues.

[0066] In one embodiment, the drying step is used to produce a solid residue with a specific particle size.

[0067] For example, the solid residue is in the form of powder with an average particle size of 100–1000 μm, such as 200–500 μm.

[0068] To avoid powder evaporation, the particle size cannot be too fine or too coarse (e.g., greater than 1 cm), because larger particles are more likely to retain moisture.

[0069] With this drying method, using a dryer as described below in the context of this invention, it is possible to obtain the desired particle size.

[0070] In one embodiment, the drying step includes breaking up clumps.

[0071] This step is to limit (or even prevent) the formation of lumps within the cavity.

[0072] In one embodiment, the method includes the step of condensing steam from a dryer to produce condensate.

[0073] In addition, this method can reduce water consumption by reusing condensate.

[0074] For example, the method includes the step of introducing condensate into a tank (e.g., a tank for rinsing water).

[0075] For example, the obtained condensate can then be used as rinsing water.

[0076] For example, the step of condensing water is performed by a condenser.

[0077] According to the implementation scheme, the method includes the step of absorbing and neutralizing the gas generated in the steam condensation step by means of an absorber-neutralizer (also known as a scrubber).

[0078] In a preferred embodiment, the method includes the step of extracting the fluid to be treated from a tank (or even a storage tank, for example) in the nitriding production line.

[0079] For example, the method includes a step of filtering the fluid to be treated before introducing the fluid into the cavity of the dryer.

[0080] For example, the filtration step includes passing the fluid through a sieve with a sieve aperture size of less than 50 μm (e.g., 2–50 μm).

[0081] The filtration process includes, for example, removing particles using a magnetic rod.

[0082] For example, this magnetic rod can trap magnetic particles, especially iron oxide.

[0083] The present invention also relates to an apparatus for carrying out a method comprising at least some of the steps described above.

[0084] Therefore, the device includes at least one dryer configured to perform at least a drying step.

[0085] The dryer mainly consists of a cavity.

[0086] For example, the cavity is typically cylindrical.

[0087] For example, the cavity is a non-rotational cavity.

[0088] For example, the cavity includes at least one inlet for the fluid to be dried, configured to introduce the fluid to be dried into the cavity.

[0089] For example, the cavity includes at least one outlet for discharging solid residues.

[0090] For example, the cavity includes at least one steam outlet.

[0091] In a preferred embodiment, the dryer includes a mixer, particularly a heated spiral mixer, which is heated, for example, by circulating a heat-conducting fluid.

[0092] For example, the mixer is set to rotate within the chamber, for example at a medium speed, such as a maximum of 100 rpm, such as 1 to 100 rpm (revolutions per minute), such as 1 to 25 rpm, so that the fluid to be dried can be mixed thoroughly and evenly, and its contact with the chamber wall can be improved.

[0093] For example, to avoid scraping the inner wall of the chamber and thus reduce wear on the mixer, the mixer operates at a certain distance from the chamber wall.

[0094] In other words, the spiral mixer is heated and extended near the cavity wall to ensure the uniformity of the mixture and the uniformity of temperature within the cavity.

[0095] In a preferred embodiment, the cavity includes a tapered bottom.

[0096] Such a conical bottom facilitates the discharge of any solid residue.

[0097] For example, solid residues (e.g., in powder form) are discharged from the dryer cavity by gravity.

[0098] For example, the bottom of the cone includes an outlet for the discharge of solid residues.

[0099] In addition, conventional dryers are typically used for batch operations to dry paste-like products, with a filling rate of 60 to 100% of the chamber volume during drying.

[0100] Here, considering the fluid to be processed, this batch operation mode will significantly limit the productivity and recovery rate of the method. For example, the dried residue obtained after drying 2000L of fluid will only account for about 20% of the dryer cavity volume according to the invention.

[0101] Therefore, the dryer according to the present invention can operate in a "semi-continuous" mode.

[0102] Therefore, it includes a pressure sensing element system.

[0103] The pressure sensing element system is configured to weigh the cavity (potentially continuously) and, incidentally, the contents of the cavity.

[0104] For example, the pressure sensing element system includes at least one weight sensor.

[0105] To accurately measure the weight of the cavity, it is preferable that the cavity is not mechanically connected to other parts of the device, for example, by using flexible tubing at the inlet and outlet.

[0106] The weight loss of the cavity contents can then be compensated by adding the fluid to be treated, for example, weight loss due to the evaporation of water in the fluid. This further allows the salt concentration of the fluid contained in the cavity to be gradually increased as the drying operation proceeds.

[0107] The volume of the dried residue obtained in this way is approximately 50-75% of the cavity volume, or possibly greater than 80%, and ideally greater than 90%.

[0108] This "semi-continuous" filling operation can be fully automated; for example, the number of additions and the amount of fluid added each time can be set. Fluid is added during the drying process: the fluid is "sucked," for example, through a pressure difference between a tank (e.g., a storage tank or buffer tank) connected to the dryer, without releasing the vacuum within the chamber.

[0109] For this purpose, for example, the dryer includes at least one filling valve.

[0110] For example, the filling valve is set to open when the weight of the cavity reaches a lower threshold or when the rate of change of the cavity weight is less than a first predetermined value, and to close when the weight of the cavity reaches an upper threshold or when the cavity is filled to its maximum water level.

[0111] For example, the weight measured by the pressure sensing element system is related to the filling rate of the cavity.

[0112] For example, the device includes a control system configured to control the opening or closing of at least one filling valve based on the chamber weight measured by the pressure sensor system.

[0113] In a preferred embodiment, the cavity includes a wall formed by a double-layered jacket.

[0114] For example, the double jacket is configured to allow the heat transfer fluid to circulate within it.

[0115] For example, the heat transfer fluid is configured to maintain a temperature of 30–90°C in the cavity where the fluid is processed.

[0116] For example, the same heat-conducting fluid circulates in the cavity walls and the spiral mixer.

[0117] For example, a dryer is a vertical dry-mixer that is stirred in a vacuum.

[0118] In one embodiment, the drying chamber includes an agglomerator configured to reduce the formation of agglomerates in the fluid being processed within the chamber.

[0119] For example, the agglomeration crusher is a blade-type agglomeration crusher, located at the bottom of the cavity.

[0120] For example, this type of agglomerator can reach speeds of up to 1500 rpm.

[0121] In one embodiment, the apparatus includes an extraction system configured to deliver the fluid to be treated from a storage tank (e.g., a tank in a nitriding production line) to a dryer.

[0122] For example, the extraction system includes a filtration system.

[0123] The filtration system includes screens with mesh sizes of less than 50 μm, such as 2–50 μm, or possibly 5–10 μm.

[0124] For example, the filtration system also includes magnetic rods configured to remove magnetic particles that may be contained in the fluid being treated.

[0125] For example, the steam outlet of the dryer is equipped with a filter.

[0126] For example, the filter is configured to filter steam. To do this, for example, the filter includes a filter cartridge that is cleared by compressed air.

[0127] For example, filters retain ultrafine powder. Unclogging can cause the powder to fall out and restore the filter's efficiency.

[0128] According to the implementation plan, the cleared powder falls into the drying chamber due to gravity.

[0129] According to the implementation plan, the device includes a boiler configured to maintain the dryer cavity at the desired temperature.

[0130] For example, the boiler is configured to heat the heat transfer fluid circulating in the double-layered jacket of the cavity to about 130°C, and the same applies to the spiral mixer.

[0131] The boiler is configured to have both heating and cooling modes to reduce the temperature of the solid residues produced.

[0132] In one embodiment, the device includes a vacuum module.

[0133] For example, the vacuum module is configured to generate a medium vacuum within the dryer cavity, i.e., a pressure of 10–900 mbars, such as 20–500 mbars, or even 20–100 mbars.

[0134] For example, the vacuum module is configured to generate a pressure of approximately 10 mbar during the drying process.

[0135] For example, the vacuum module is configured to generate a pressure of approximately 50 mbar during the evaporation process.

[0136] This vacuum-like pressure makes it possible to evaporate water from a fluid at low temperatures, specifically 30–90°C.

[0137] For example, the vacuum module is connected to the steam outlet of the dryer.

[0138] For example, the vacuum module includes at least one vacuum pump.

[0139] In one embodiment, the device also includes a condenser.

[0140] For example, the condenser is configured to condense steam coming from the dryer through the steam outlet and produce condensate.

[0141] For example, the condenser is connected to the steam outlet of the dryer.

[0142] For example, the condenser is a tubular condenser.

[0143] Therefore, the device can recycle water, which can be reused.

[0144] In one embodiment, the device also includes a cooler.

[0145] For example, a tubular heat exchanger is connected to a cooler.

[0146] For example, the device includes a condensate storage tank configured to collect condensed steam.

[0147] In one embodiment, the device includes a condensate supply pipe configured to extract condensate from the condenser and potentially return it to a tank, such as a flushing tank.

[0148] According to a preferred example, the condensate supply pipe includes a filter.

[0149] According to a preferred example, the device also includes an absorber-neutralizer, commonly referred to as a scrubber.

[0150] For example, a scrubber connected to a condenser can reduce or even eliminate any toxic or corrosive gases that may be present in the condensate (such as nitrogen in nitriding).

[0151] According to the embodiments, the present invention will be properly understood and its advantages will be more clearly appreciated through the following detailed description, which is given with reference to the accompanying drawings as illustrative examples and not as limiting. Attached Figure Description

[0152] Figure 1 This is a flowchart of a conventional nitriding production line.

[0153] Figure 2 A processing apparatus according to an embodiment of the present invention is shown, the apparatus being coupled with (e.g., as...) Figure 1 The nitriding production lines shown are arranged in parallel.

[0154] Figure 3 This is a schematic diagram of the dryer according to the implementation plan;

[0155] Figure 4 A diagram illustrating a processing method according to an embodiment of the present invention is shown; and

[0156] Figure 5 A diagram showing fluid processing via semi-continuous filling within the cavity 225 of the dryer 220 is displayed. Detailed Implementation

[0157] Figure 1 This is an example of a nitriding production line 10.

[0158] Parts (e.g., steel) are placed in cage 11 for batch processing of multiple parts, also known as batch processing.

[0159] For this purpose, cage 11 is, for example, soaked in a first tank 12 containing a degreasing bath.

[0160] Then rinse, for example, by immersing the cage 11 in a rinsing water bath 13 in sequence, or even in several rinsing water baths in succession, 13a, 13b, 13c.

[0161] Then put them in oven 14 to dry.

[0162] The cage 11 is then immersed in at least one nitriding bath 15, or even two consecutive baths 15a and 15b, as shown in the diagram. The nitriding bath 15 is generally composed mainly of molten nitride salts, and its temperature is approximately 500–650°C.

[0163] After nitriding, the parts can be selectively immersed in an oxidation bath 16. This oxidation bath 16 is generally composed mainly of molten oxide salts at a temperature of approximately 450°C.

[0164] After nitriding or oxidation, depending on the actual situation, the parts will undergo a quenching step, for example in a quenching water tank 17, where the temperature is much lower than that of the bath, i.e., relatively cold.

[0165] Subsequently, the parts are rinsed in a post-treatment rinsing tank 18 or multiple consecutive tanks 18a, 18b, 18c.

[0166] Other treatment procedures may also be employed, such as infiltration. For example, the cage may then be immersed in infiltration bath 19.

[0167] However, during the continuous passage, each tank became contaminated.

[0168] For example, sludge is secreted into nitrification and / or oxidation baths 15 and 16 containing nitrides and / or oxidants.

[0169] The water in the rinse or quench tanks 18 and 17 after treatment (also known as "expend water") is also rich in oxidized and / or nitrated salts, such as nitrates and nitrites.

[0170] This quenching water 17 is a hazardous waste liquid and needs to be treated by a company that specializes in handling such waste.

[0171] Therefore, these different forms of waste need to be stored before they are sent for processing.

[0172] Figure 2 An example of device 200 is shown, which can process at least part of the waste by recycling the salts contained therein.

[0173] In this example, a fluid containing salt was extracted from the quenching tank 17, but it could of course be any other tank containing a liquid that constitutes a salt solution.

[0174] Therefore, the device 200 mainly includes a dryer 220, in Figure 3 More detailed illustrations are shown in the diagrams.

[0175] In order to transport the fluid to be treated from the tank (here, the quenching tank 17) to the dryer 220, the apparatus first includes an extraction system 201.

[0176] In this document, the extraction system 201 includes, for example, a buffer tank 203 and at least one upstream pipe 202 leading from the tank from which the fluid to be processed is extracted to the buffer tank 203.

[0177] For example, the upstream pipe 202 in this paper includes a filtration system 205.

[0178] For example, the filtration system 205 includes a sieve with a mesh size of less than 50 μm, such as 2 to 50 μm, or possibly 5 to 10 μm.

[0179] In this document, the filtration system 205 also includes a magnetic rod, for example, which is configured to remove magnetic particles that may be contained in the particles to be treated.

[0180] Downstream of the buffer tank 203, the extraction system 201 includes, for example, at least one downstream conduit 204 leading from the buffer tank 203 to the dryer 220, particularly to the inlet 221 of the dryer 220, to dry the fluid.

[0181] The dryer 220 described herein includes at least two outlets 222 and 223: one outlet for discharging solid residue 222 and one steam outlet 223.

[0182] The steam outlet 223 has two parallel pipes, both of which are connected to the vacuum module 207.

[0183] For example, the first of the two pipes extending from the steam outlet 223 is equipped with a filter 224.

[0184] For example, filter 224 is configured to filter steam. To this end, filter 224 includes, for example, a filter cartridge that is unclogged by compressed air.

[0185] For example, as long as the contents of the dryer are sufficiently liquid, the steam will condense directly without passing through filter 224, i.e., through the second of the two pipes leading from steam outlet 223 to vacuum module 207.

[0186] However, when the contents are relatively dry, for example during stage C of the method described below, dust may be entrained by steam, in which case it is preferable to pass through filter 224, i.e., through the first of the two pipes from steam outlet 223.

[0187] Therefore, filter 224 is activated during phase C of the method.

[0188] For example, the device also includes a boiler 206, configured to maintain the cavity of the dryer at the desired temperature.

[0189] For example, boiler 206 is configured to heat the heat transfer fluid to about 130°C, and the heat transfer fluid is configured to maintain the interior of the cavity at the desired temperature.

[0190] Boiler 206 can be switched to heating or cooling mode to reduce the temperature of solid residue generated in the cavity and discharged through outlet 222, which is configured to discharge solid residue during the discharge stage.

[0191] Downstream of the dryer, the device also includes a vacuum module 207, which is connected to a steam outlet 223.

[0192] For example, the vacuum module includes at least one vacuum pump configured to generate a medium vacuum, i.e., a pressure of 10 to 900 mbars, within the cavity of the dryer 220.

[0193] For example, a vacuum module may include two pumps that can be used in series or individually (depending on the application and required efficiency), such as a Roots pump and a liquid ring pump.

[0194] The apparatus may also include a condenser 208 configured to condense steam from the dryer 220 via steam outlet 223. The condenser is, for example, a tubular condenser. For instance, condenser 208 may include a tubular heat exchanger.

[0195] Therefore, the device may further include a cooler 209.

[0196] For example, tubular heat exchanger 208 is connected to cooler 209.

[0197] Condensed steam can be collected in a condensate storage tank.

[0198] Here, downstream of condenser 208, the device includes a condensate supply pipe 210, configured to extract condensate from the condenser and possibly return it to a flushing tank, such as flushing tank 18c here.

[0199] It should be noted that the condensate here includes liquid water produced by the condensation of water vapor from the dryer.

[0200] In this embodiment, the condensate supply pipe 210 may optionally include a filter 211.

[0201] According to a preferred embodiment, the device here also includes an absorber-neutralizer 212, commonly referred to as a scrubber 212. Here, the scrubber 212 is connected to the condenser, enabling the reduction or even elimination of any toxic or corrosive gases that may be present.

[0202] These gases (such as nitrogen) may be contained in the condensate.

[0203] Dryer 220 Figure 3 There are more detailed illustrations inside.

[0204] Dryer 220 is configured to dry fluids containing salt, whether liquids or sludge, in a vacuum. These fluids are also referred to as salt solutions.

[0205] Dryer 220 is a vacuum dryer, specifically a heated vertical mixer that rotates at a medium speed, causing the product to flow radially upward and renew itself upon contact with the heated walls of the chamber.

[0206] Therefore, the dryer mainly includes a cavity 225, which has an inlet 221 configured for the fluid to be dried, an outlet 222 configured for discharging solid residues, and a steam outlet 223.

[0207] The cavity 225 here is fixed because it cannot rotate and is secured by the bracket 228.

[0208] The cavity 225 here includes a conical bottom, which facilitates the discharge of any solid residues obtained.

[0209] Therefore, the outlet 222 for discharging solid residue is preferably located at the end of the conical bottom, at the bottom of the cavity.

[0210] For example, outlet 222 for discharging solid residues includes a ball valve with metal-to-metal contact.

[0211] Depending on the desired characteristics, the cavity 225 includes a double-layered jacket, namely an outer wall and an inner wall, with a space between them for the circulation of heat-conducting fluid.

[0212] For example, the heat transfer fluid is heated to, for example, 130°C by electric heating (e.g., boiler 206).

[0213] For example, the heat transfer fluid includes oil.

[0214] In this embodiment, the inner wall thus forms an internal groove, the material of which is Hastelloy C22 or other equivalent material.

[0215] In cavity 225, the dryer includes a mixer 226 configured to mix and dry the contents of the cavity (i.e., the fluid to be treated).

[0216] For example, the mixer includes helical blades heated by circulating heat-conducting fluid.

[0217] For example, mixer 226 is configured to rotate at a variable speed as needed, such as up to 100 rpm.

[0218] There is a certain distance between the mixer 226 and the inner wall of the cavity 225 to avoid scratching the inner wall, thereby reducing wear on the mixer.

[0219] According to a preferred embodiment of the invention, the dryer includes an agglomerator (cutter) 230 in a cavity 225, which is configured, for example, to rotate at a speed of up to 1500 rpm to break up any possible agglomerates.

[0220] For semi-continuous filling, the dryer includes a filling valve 227.

[0221] In this embodiment of the invention, the filling valve 227 is connected to the dryer inlet 221 of the fluid to be dried.

[0222] For example, filling valve 227 is located between the storage tank and the dryer of the fluid to be treated.

[0223] The filling valve 227 opens or closes according to the weight of the cavity.

[0224] When the filling valve 227 is opened, the fluid to be processed is introduced into the cavity through the inlet 221 of the fluid to be dried by the vacuum module 207.

[0225] To determine the weight of the chamber, the dryer includes a pressure sensing element system 229.

[0226] This allows us to understand the filling status of the cavity and introduce the fluid to be processed accordingly.

[0227] In this embodiment, the pressure sensing element system 229 includes at least two, preferably three, weight sensors regularly distributed around the cavity. For example, the measured values ​​are then averaged (or summed) to determine the weight of the cavity, thereby indicating its filling status.

[0228] The weight sensor is schematically located here between the shoulder of the cavity and the bracket 228.

[0229] Figure 4 An embodiment of the invention is described (in such a way as...) Figure 2 (In the case of the apparatus shown), the main steps of a method for treating a fluid containing salt.

[0230] For example, the method may include a series of steps as follows.

[0231] First, the method includes step S1 of extracting the fluid to be treated from the tank (here, the quenching tank 17 of the nitriding production line).

[0232] The fluid to be treated (followed by quenching water containing salts from the prior bath used for nitriding and oxidation) is conveyed through extraction system 201.

[0233] For example, the method includes step S2 of filtering the fluid to be treated (e.g., through a filtration system 205). Here, the filtration step S2 also includes step S21 of passing the fluid through a screen of the filtration system 205, and step S22 of removing magnetic particles (such as iron oxides) by a magnetic rod.

[0234] The method then includes step S3, which involves processing the fluid.

[0235] - Step S31: The fluid to be treated is introduced into the cavity 225 of the dryer 220 through the inlet 221 for the fluid to be dried;

[0236] - Step S32, drying the fluid in chamber 225 by placing it at a temperature of 30–90°C and a pressure of 10–900 mbars; and

[0237] - Step S33, extract the powdered solid residue, which is, for example, the solid residue recovered through outlet 222 for discharging solid residue.

[0238] Drying step S32 includes two steps performed simultaneously:

[0239] Sub-step S321 involves evaporating at least a portion of the fluid, generating at least water vapor, which is extracted from cavity 225 through steam outlet 223; and

[0240] Sub-step S322 increases the salt concentration of the fluid contained in cavity 225.

[0241] Such as combination Figure 5 To describe in more detail, the drying process here includes two stages:

[0242] Phase 1 (e.g.) Figure 5 (As shown in "B"), during this period, the weight of the cavity decreases. When the cavity weight reaches the lower threshold or the rate of change of the cavity weight is less than a first predetermined value, the drying step includes replenishing the cavity until the cavity weight reaches the upper threshold; and

[0243] Phase Two (e.g.) Figure 5(As shown in "C"), during this period the weight of the cavity decreases, and when the rate of weight change is less than a second predetermined value, step S33 of extracting solid residue is performed.

[0244] For semi-continuous filling, the method includes step S4, which involves detecting the weight of the cavity 225, for example, using a pressure sensing element system 229. When the weight reaches a lower threshold (corresponding to a lower filling threshold) or when the rate of change of the cavity weight is less than a second predetermined value, the method includes step S51, which involves opening the filling valve 227 and adding the fluid to be processed into the cavity 225. When the cavity weight reaches an upper threshold (corresponding to an upper filling threshold), the method includes step S52, which involves closing the filling valve 227.

[0245] At the same time, the cavity is kept in a vacuum state, which allows the fluid to be processed to be drawn into the cavity when the filling valve 227 is opened.

[0246] The method further includes step S6: condensing the steam discharged from the dryer 220 through the steam outlet 223 by the condenser 208, thereby generating condensate.

[0247] According to one example of the invention, the method includes step S7 of steam scrubbing via a scrubber 212.

[0248] Next, condensate is supplied by, for example, condensate supply pipe 210.

[0249] According to another example of the invention, the method includes step S8: filtering condensate through filter 211 of condensate supply pipe 210.

[0250] The method then includes step S9: injecting condensate into the rinsing tank 18c.

[0251] Figure 5 A diagram showing the processing of fluid in cavity 225 of dryer 220 using a semi-continuous filling method.

[0252] This figure shows more specifically the change in cavity filling rate (in %) along the y-axis, which varies with time along the x-axis, with the unit of time being arbitrary.

[0253] The figure shows four stages over time: stage “A” corresponds to step S31 (introducing the fluid to be treated into the initially empty cavity 225 of the dryer 220), stage “B” corresponds to the first stage of drying step S32, during which the contents of the cavity are mainly concentrated salts, stage “C” corresponds to the second stage of drying step S32, and the last stage “D” corresponds to step S33, which extracts solid residues, for example, through outlet 222 for discharging solid residues.

[0254] Filling is typically done using a water pump (not shown). The completion of filling can be detected by weighing or volume measurement.

[0255] After filling in step S31 (e.g., via vacuum module 207) by introducing the fluid to be processed, the cavity is placed under vacuum.

[0256] In the first stage "B", the weight of the chamber is monitored, for example, continuously; when the lower threshold is reached, or until it decreases to a first predetermined value, the filling valve 227 is triggered to open, and fluid is subsequently drawn in by vacuum; when the upper threshold is reached, the filling valve 227 is triggered to close again. As fluid is added, the salt content in the chamber gradually increases. During the filling operation, the upper and lower thresholds can change, especially to maintain a constant fill rate in terms of volume. In fact, the density of salt may differ from that of water, and the weight depends on the salt content.

[0257] The number of filling operations and the variation of thresholds can be pre-programmed or determined entirely by measurements of weight, flow rate, or salt content.

[0258] Once the desired concentration is reached, Phase 1 "B" terminates, and Phase 2 "C" begins immediately, during which no more fluid is added.

[0259] In this step, pump suction can be enhanced, for example, by using a rotary compressor (Roots pump) upstream of the vacuum pump in a vacuum module, to achieve a higher degree of dryness. Weight is also continuously monitored during this step. The weight loss per unit time (equivalent to the evaporation rate) can be used to estimate the remaining water content and determine the end time of drying.

[0260] Preferably, the agglomerator is operated in the second stage "C", either from the beginning or when a certain water content is reached.

[0261] Finally, empty the dryer.

[0262] In this example, oxidizing quenching water from a nitriding production line was dried. The average concentration of the solution to be treated was 225 g / L. An initial weight of 2324 kg (volume 1857 L) of solution was introduced into the drying chamber. The chamber was brought under vacuum (approximately 50 mbars) using a liquid ring pump. The solution was heated to 38°C.

[0263] The evaporation / concentration cycle then begins. 3397 kg of quenching water is added in ten steps over 2421 minutes (the duration of phase B) (i.e., an average of 377 kg added each time) until a concentration of 52% by mass is reached.

[0264] Then, the final drying stage (stage C) is triggered, and a liquid-solid phase transition is observed after 21 hours of drying. The dry residue analysis shows a dryness of 91.67%. The steam filtration mode is then switched on, the agglomerator is started, and a vacuum of 10 mbars is obtained after activating the Roots pump.

[0265] After drying at 85°C for 6 hours, 1217 kg of powder was extracted from the dryer, with a dry extract purity of 99.09%, and was then reused on the nitriding production line without affecting quality. The drying operation generated 4335 kg of condensate, which was reused for rinsing operations on the nitriding production line.

Claims

1. A method for treating a fluid, the method comprising: - Step (S31): Introduce the fluid to be treated into the cavity (225) of the dryer (220); - Step (S32): The fluid in the drying chamber (225) is dried by placing it at a temperature of 30 to 90°C and a pressure of 10 to 900 mbars. The drying step includes a sub-step (S321) of evaporating at least a portion of the fluid and generating at least water vapor, and a sub-step (S322) of increasing the salt concentration of the fluid contained in the chamber (225). The drying step includes: o First stage (B): During the first stage, the weight of the cavity decreases. When the weight of the cavity reaches a lower threshold or the rate of change of the cavity weight is less than a first predetermined value, the drying step includes replenishing the cavity until the weight of the cavity reaches an upper threshold; and o Second stage (C): During the second stage, the weight of the cavity decreases, and when the rate of change of weight is less than a second predetermined value, the method includes: - Step (S33): Extract the powdery solid residue.

2. The method according to claim 1, characterized in that, The method includes the step (S4): detecting the weight of the cavity (225), when the weight reaches a lower threshold limit or when the rate of change of the cavity weight is less than a first predetermined value, the method includes the step of opening the filling valve (227) (S51) and performing a supplementary filling step, when the weight of the cavity reaches an upper threshold limit, the method includes the step of closing the filling valve (227) (S52).

3. The method according to claim 1, characterized in that, The drying step is set such that the moisture content of the resulting solid residue is 0.5 to 5% by weight.

4. The method according to claim 1, characterized in that, The drying step (S32) is set to produce a powdery solid residue with an average particle size of 100 to 1000 μm.

5. The method according to claim 1, characterized in that, The method includes step (S6): condensing steam from the dryer (220) to produce condensate.

6. The method according to claim 5, characterized in that, The method includes step (S9): introducing condensate into a rinsing water tank (18).

7. The method according to any one of claims 1-6, characterized in that, The fluid is a fluid containing salts.

8. An apparatus (200) configured for carrying out the method of any one of claims 1-7, the apparatus (200) comprising at least: a dryer (220), the dryer (220) comprising at least: One cavity (225); At least one inlet (221) for the fluid to be dried; Outlet (222) for discharging solid residues; Steam outlet (223); Pressure measuring element system (229) for weighing the cavity (225); At least one filling valve (227) is configured to open when the cavity weight reaches a lower threshold or when the rate of change of the cavity weight is less than a first predetermined value, and to close when the cavity weight reaches an upper threshold. and A mixer (226) is configured to rotate within a cavity (225) at a speed of 1 to 100 rpm; A control system configured to control the opening or closing of at least one filling valve (227) based on the weight of the cavity (225) measured by the pressure sensing element system (229); Boiler (206), the boiler (206) being configured to maintain the cavity of the dryer at a desired temperature of 30 to 90°C; as well as Vacuum module (207) is configured to generate a pressure of 10 to 900 mbars in the cavity (225) of the dryer (220).

9. The apparatus (200) according to claim 8, characterized in that, The dryer cavity includes an agglomerator (230) configured to reduce the formation of agglomerates in the fluid being processed in the cavity, the agglomerator being configured to rotate at a speed of 1500 rpm.

10. The apparatus (200) according to claim 8, characterized in that, The cavity (225) includes a wall formed by a double-layered jacket configured to circulate a heat-conducting fluid within the jacket.

11. The apparatus (200) according to claim 10, characterized in that, The heat-conducting fluid is configured to maintain a temperature of 30 to 90°C in the cavity (225), and the fluid is processed in the cavity (225).

12. The apparatus (200) according to claim 8, characterized in that, The device includes a condenser (208) connected to the steam outlet (223) of the dryer (220), the condenser (208) being configured to condense steam from the dryer (220) through the steam outlet (223) and produce condensate, and the device (200) includes a condensate supply pipe (210) configured to extract condensate from the condenser (208) and return it to the flushing tank (18).

13. The apparatus (200) according to any one of claims 8 to 12, characterized in that, The cavity (225) is a non-rotating cavity, and / or the mixer (226) is a heated spiral mixer.

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