A salt-containing wastewater drying device and a salt-containing wastewater zero-discharge system

Abstract

The invention discloses a salt-containing wastewater drying device and a zero-emission system thereof, comprising a spouted bed, a three-dimensional air distribution device, a liquid distribution pipe and a wastewater circulation device. The lower part of the spouted bed is a tapered bed area that tapers from top to bottom, and the inclination angle of the wall of the tapered bed area is 65° to 85°. The liquid distribution pipe is arranged in a surrounding manner at the upper part of the tapered bed area and is arranged close to the wall. A plurality of liquid spray holes are arranged on the liquid distribution pipe. The three-dimensional air distribution device comprises a bottom air distribution plate and a drying air chamber, and a peripheral air distribution plate surrounding the bottom air distribution plate and an annular wind box outside thereof. The peripheral air distribution plate is arranged in an inclined manner, and the inclination angle is 65° to 85°. The bottom air distribution plate comprises a high-density hole area and a low-density hole area arranged from inside to outside, and the area of ​​the high-density hole area accounts for 8% to 20% of the total area of ​​the bottom air distribution plate. A plurality of side air distribution holes with opening angles inclined downward are provided on the peripheral air distribution plate. The invention has the advantages of high heat exchange coefficient, long residence time, good drying effect, stable flow field, and no adhesion of bed material particles into blocks.

Description

Technical Field

[0001] The invention relates to a salt-containing wastewater drying device and a salt-containing wastewater zero-discharge system, belonging to the technical field of environmental protection. Background Art

[0002] Some industrial production processes will discharge industrial wastewater containing salt, such as desulfurization wastewater from thermal power plants, which has a salt content of tens of thousands of mg / L or even hundreds of thousands of mg / L. These salt-containing wastewaters discharged into natural water bodies will pollute the water environment. In order to prevent and control environmental pollution, it is necessary to separate the salt in the wastewater to achieve zero discharge of salt-containing wastewater. The existing process routes include chemical method and thermal method. Among them, the thermal method usually atomizes the salt-containing wastewater into fine droplets and sprays them into hot flue gas or hot air, and uses the heat of hot flue gas or hot air to dry the droplets into water vapor and solid particles. However, in these methods, the heat exchange between the droplets and the hot flue gas or hot air is a gas-liquid two-phase heat exchange, and the heat exchange coefficient is relatively low. Moreover, for the atomized droplets, if the droplet diameter is large, the drying time is long and the equipment volume is large; and if the atomized droplets are too small, it is easy to scale at the nozzle and block the nozzle, resulting in a high equipment failure rate, low reliability, and a large workload for inspection and maintenance. Summary of the invention

[0003] The present invention aims to provide a drying device and a zero-emission system capable of efficiently drying saline wastewater. The device utilizes the characteristics of a spouted bed with a high heat transfer coefficient and a long residence time, and through technical solutions such as annular liquid distribution and three-dimensional air distribution, the device can achieve rapid drying of saline wastewater while avoiding problems such as bed material adhesion, agglomeration and "defluidization".

[0004] The present invention is achieved through the following technical solutions:

[0005] A device for drying salt-containing wastewater comprises a spouted bed, a three-dimensional air distribution device arranged at the bottom of the spouted bed, and a liquid distribution pipe arranged at the lower part of the spouted bed; the lower part of the spouted bed is a tapered bed area that tapers from top to bottom, and the liquid distribution pipe is arranged in a surrounding manner at the upper part of the tapered bed area and is arranged close to the wall; the liquid distribution pipe is provided with a plurality of liquid spray holes, and the liquid spray holes are opened downward and / or obliquely downward; the three-dimensional air distribution device comprises a bottom air distribution plate and a drying air chamber arranged at the bottom of the bottom air distribution plate, as well as a peripheral air distribution plate surrounding the bottom air distribution plate and an annular wind box outside thereof; the peripheral air distribution plate is arranged in an inclined manner, and the peripheral air distribution plate is arranged at the lower part of the wall of the tapered bed area; a plurality of side air distribution holes are opened on the peripheral air distribution plate, and the opening angles of the side air distribution holes are inclined downward.

[0006] Optionally, according to an embodiment of the present invention, in the aforementioned technical solution, the inclination angle between the wall surface of the conical bed area and the horizontal plane is 65°~85°; the inclination angle between the peripheral side air distribution plate and the horizontal plane is 65°~85°.

[0007] Optionally, according to an embodiment of the present invention, in the aforementioned technical solution, the bottom air distribution plate includes a high-density hole area and a low-density hole area arranged from the inside to the outside, the high-density hole area refers to an air distribution hole area with an opening rate of 10% to 20% on the bottom air distribution plate, and the low-density hole area refers to an air distribution hole area with an opening rate of 5% to 10% on the bottom air distribution plate, the area of ​​the high-density hole area accounts for 8% to 20% of the total area of ​​the bottom air distribution plate, and the opening rate of the high-density hole area is more than twice the opening rate of the low-density hole area.

[0008] Optionally, according to an embodiment of the present invention, in the aforementioned technical solution, the peripheral side air distribution plates are arranged in more than two layers along the height and each layer has a plurality of side air distribution holes.

[0009] Optionally, according to an embodiment of the present invention, in the aforementioned technical solution, the inclination angle of the side air distribution holes is 30°~40°.

[0010] Optionally, according to an embodiment of the present invention, in the aforementioned technical solution, the conical bed area also includes inert bed material, and the side air distribution holes are arranged according to a wind speed of 0.4 to 0.6 times the terminal velocity of the inert bed material particles.

[0011] A zero-discharge system for salt-containing wastewater comprises the aforementioned drying device and a wastewater circulation device, wherein the wastewater circulation device comprises a wastewater circulation tank, a wastewater circulation pump and a wastewater circulation main pipe, the wastewater circulation tank is connected to the liquid distribution pipe via the wastewater circulation main pipe to form a circulation connection; the wastewater circulation tank is also provided with a wastewater inlet pipe.

[0012] The advantages and outstanding effects of the present invention include:

[0013] 1) The gas-liquid-solid three-phase contact heat exchange is adopted, and its heat transfer coefficient is much higher than the conventional gas-liquid two-phase contact heat exchange, with high heat transfer efficiency and good heat transfer effect, so that the droplets can be completely evaporated in the dryer.

[0014] 2) A three-dimensional air distribution device is used. By arranging high-density air distribution holes and low-density air distribution holes in different areas on the bottom air distribution plate, and arranging side air distribution holes inclined downward on the surrounding side air distribution plates, the fluidization dead zone at the corner can be eliminated, the macroscopic internal circulation of the bed material particles can be strengthened, and the agglomeration phenomenon caused by low flow rate can be avoided.

[0015] 3) By adopting a surrounding liquid distribution pipe and multi-point liquid distribution method, the liquid is evenly distributed in the annular gap area, effectively avoiding the phenomenon of sticking together caused by excessive local salt-containing wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of a salt-containing wastewater drying device involved in the present invention.

[0017] Figure 2 A schematic diagram of a bottom air distribution plate according to one embodiment of the present invention.

[0018] Figure 3 It is a schematic diagram of the structure of the peripheral air distribution plate involved in the present invention.

[0019] Figure 4 Schematic diagram of the arrangement of the liquid distribution pipe involved in the present invention: a) circular surround; b) circular evenly divided surround; c) rectangular evenly divided surround.

[0020] Figure 5 This is a schematic diagram of the salt-containing wastewater drying system involved in the present invention.

[0021] In the figure: 1-sprayed bed; 2-three-dimensional air distribution device; 3-liquid distribution pipe; 4-inert bed material; 5-discharge pipe; 6-separator; 7-wastewater circulation water tank; 8-wastewater circulation main pipe; 9-wastewater circulation pump; 10-wastewater bypass pipe; 11-wastewater circulation main valve; 12-bypass valve; 201-bottom air distribution plate; 202-side air distribution plate; 203-side air distribution hole; 204-drying air chamber; 205-annular bellows. DETAILED DESCRIPTION

[0022] The specific implementation manner and working process of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0023] The terms such as up, down, left, right, front and back in this application document are based on the positional relationships shown in the drawings. If the drawings are different, the corresponding positional relationships may also change accordingly, so they cannot be understood as limiting the scope of protection.

[0024] Salty wastewater includes wet desulfurization wastewater, circulating cooling water concentrated wastewater, and acid-base neutralization wastewater after chemical workshop treatment. The salt content in the wastewater ranges from tens of thousands of mg / L to hundreds of thousands of mg / L, and during the drying process, the salt will only crystallize and precipitate, and its chemical composition will not decompose under heat. Inert bed materials are solid particles that do not chemically react with any component in the salty wastewater under the temperature and pressure of the operating conditions, and do not decompose or deteriorate themselves.

[0025] like Figure 1As shown, a salt-containing wastewater drying device includes a spouted bed 1, a three-dimensional air distribution device 2, a liquid distribution pipe 3 and an inert bed material 4. The spouted bed 1 includes a conical bed area and a columnar bed area. The conical bed area is arranged at the bottom and is arranged in a tapered manner from top to bottom, and the bottom cross-sectional area is the smallest. The cross-section of the columnar bed area is circular, square or rectangular. An exhaust pipe is arranged on the top or the side of the upper part of the spouted bed near the top, which can be connected to the separator 6 or directly to the dust removal system (for example, when used in a thermal power plant, the original dust removal system of the thermal power plant can be directly used). The inclination angle β between the wall of the conical bed area and the horizontal plane is 65°~85°. For a bed body with a circular cross-section, the inclination angle is the angle between the generatrix of the conical platform and the horizontal plane. A bed material discharge port is arranged on the wall of the conical bed area close to the bottom air distribution plate, and the bed material discharge port is inclined downward by 15°~30°. The bed material discharge port is connected to a discharge pipe 5 to facilitate the discharge of inert bed material particles.

[0026] A three-dimensional air distribution device 2 is provided at the bottom of the conical bed area. The three-dimensional air distribution device 2 includes a bottom air distribution plate 201 and a drying air chamber 204 provided at the bottom of the bottom air distribution plate, and a peripheral air distribution plate 202 surrounding the bottom air distribution plate and an annular wind box 205 outside the peripheral air distribution plate. The peripheral air distribution plate 202 is arranged in an inclined manner and is provided at the lower part of the wall surface of the conical bed area, close to the bottom. The inclination angle α of the peripheral air distribution plate 202 to the horizontal plane is 65°~85°.

[0027] There are several air distribution holes on the bottom air distribution plate, with an opening rate of 5% to 20%. Dry air (usually hot air >250°C) enters the bottom of the spouted bed from the drying air chamber through the air distribution holes. The bottom air distribution plate 201 includes a high-density hole area and a low-density hole area arranged from the inside to the outside. The high-density hole area refers to the area with an opening rate of 10% to 20% on the air distribution plate, and the low-density hole area refers to the area with an opening rate of 5% to 10% on the air distribution plate, and the opening rate of the high-density hole area is 2 times or more than 2 times the opening rate of the low-density hole area. The area of ​​the high-density hole area accounts for 8% to 20% of the total area of ​​the bottom air distribution plate. The empty tower flow velocity in the upper space of the high-density hole area reaches 1.2 to 1.5 times the terminal velocity of the bed material particles, and then the upward and downward zones are formed in the bed to form a macro internal circulation. In fact, it is through the distributed arrangement of high-density hole areas and low-density hole areas that the dry wind forms a high-speed airflow area (i.e., the ejection area) in the upper space of the high-density hole area, and a low-speed airflow area in the upper space of the low-density hole area, thereby forming an internal circulation flow state in the annular gap area around the central ejection area. One implementation method is as follows Figure 2 For the rectangular bottom air distribution plate, similar implementation methods can also be adopted (including circular, elliptical, and quasi-rectangular, so that the inner and outer sides form a spraying area and an annular gap area respectively), which can be understood and imagined by ordinary technicians in this field and will not be described in detail here.

[0028] like Figure 3As shown, a number of side air distribution holes are provided on the peripheral air distribution plate. Generally speaking, the thickness of the air distribution plate can be directly utilized to directly provide side air distribution holes with opening angles inclined downward on the peripheral air distribution plate. If necessary, the inclined air distribution can also be strengthened by means of air distribution ducts. The inclination angle θ of the side air distribution holes is 30°~40°. And the side air distribution holes are set according to the wind speed of 0.4~0.6 times the terminal velocity of the inert bed material particles, thereby eliminating the fluidization dead zone of the cone section, and generating a lateral driving force at the same time, strengthening the macroscopic internal circulation, and avoiding the defluidization phenomenon caused by the bed material particles sticking together at the corners. A connecting pipe or a connecting port is provided between the drying air chamber and the annular bellows to connect the two, or the two are independently supplied with air. During implementation, the three-dimensional air distribution device can usually be deployed through three implementation methods: 1) the bottom air distribution plate and the surrounding air distribution plates are arranged in an integrated manner; 2) the bottom air distribution plate and the surrounding air distribution plates are arranged independently, and the surrounding air distribution plates and the conical bed area are also independent of each other. At this time, the inclination angle of the surrounding air distribution plate and the inclination angle of the conical bed area are also independently set within their ranges; 3) the wall surface close to the bottom of the conical bed area is used as the surrounding air distribution plate, and side air distribution holes are directly opened on it. At this time, the inclination angle of the surrounding air distribution plate is consistent with that of the conical bed area.

[0029] During the drying and crystallization process of salty wastewater, if the bed material particle flow rate is low, the salt and bed material particles will stick together and defluidization will occur at the corners of the bed space. The three-dimensional air distribution structure of the side wall + bottom can strengthen the flow of bed material particles at the corners, prevent defluidization in the corners, strengthen the internal circulation of bed material particles, and effectively reduce the risk of bed material particles sticking together.

[0030] The liquid distribution pipe 3 is arranged at the upper part of the conical bed area, preferably, close to the top of the conical bed area. Figure 4 Several embodiments of the liquid distribution pipe arrangement are shown. The liquid distribution pipe 3 is arranged around the spouted bed body 1 (such as Figure 4 a), and is usually arranged in the conical bed area and close to the wall. Preferably, in order to achieve uniform liquid distribution as much as possible, the liquid distribution pipe 3 is arranged in a two-stage symmetrical surrounding manner. According to the cross-sectional arrangement of the conical bed area, a circular surrounding ( Figure 4 b) or rectangular surround ( Figure 4 c) or even polygonal surrounding. And according to the scale, three to four sections can also be evenly arranged. At the same time, a number of liquid spray holes are evenly arranged on the liquid distribution pipe 3 to form a uniform liquid distribution. The liquid spray holes are tilted downward so that the salt-containing wastewater is sprayed to the descending area of ​​the inert bed material particles rather than the ascending area, that is, sprayed to the annular gap area.

[0031] The airflow velocity in the spouting zone is high and the kinetic energy is large. It carries the inert bed material particles upward, exceeds the height of the inert bed material particles in the surrounding annular gap zone, and enters or approaches the bottom of the cylindrical bed zone. Since the cross-section of the conical bed zone is a structure with a small bottom and a large top, as the cross-sectional area increases, the gas velocity decreases. When it decreases to a certain level, the airflow velocity in the spouting zone can no longer carry the inert bed material particles upward, and the inert bed material particles fall to the annular gap zones on both sides. The airflow velocity in the annular gap zone is lower than the terminal velocity of the inert bed material particles, and it cannot carry the inert bed material particles upward, but can only blow the inert bed material particles to roll and translate. In this way, the inert bed material particles in the annular gap zone violently collide and rub against each other in the space of the annular gap zone, and heat and mass transfer are carried out. As the number of inert bed material particles in the spouting zone decreases, they are transported to the spouting zone under the dual effects of pressure and lateral wind. In this way, the inert bed material particles form a circular motion in the conical bed area: they are carried up by the high-speed airflow in the ejection area, and spray out of the liquid surface like a "fountain", then fall to the surroundings, fall into the annular gap area, slowly fall in the annular gap area, violently collide and rub with the surrounding inert bed material particles, transfer heat and mass, and then are blown to the middle ejection area for a new round of circulation. The inert bed material particles can only circulate in the conical bed area, and the airflow velocity at the outlet section of the conical bed area is not enough to carry the inert bed material particles upward. The setting of the upper cylindrical bed area also allows the tiny droplets that may be carried in the upward gas to be further dried.

[0032] like Figure 5 As shown, a zero discharge of salty wastewater includes Figure 1 The drying device shown in the figure, and the wastewater circulation device. The wastewater circulation device includes a wastewater circulation water tank 7, a wastewater circulation pump 9 and a wastewater circulation main pipe 8. The wastewater circulation water tank 7 is connected to the liquid distribution pipe 3 through the wastewater circulation main pipe 8 to form a circulation connection. A wastewater bypass pipe 10 is arranged on the wastewater circulation main pipe 8, so that the saline wastewater can be short-circuited during the startup process or shutdown and maintenance process of the drying device. At this time, the wastewater circulation main pipe 8 and the wastewater bypass pipe 10 are respectively provided with a wastewater circulation main valve 11 and a bypass valve 12, and the wastewater circulation main valve 11 is arranged near one end of the drying device. The wastewater circulation main valve can also include a circulating wastewater inlet valve and an outlet valve, etc. The wastewater circulation water tank is also provided with a wastewater inlet pipe, and the saline wastewater to be dried enters the wastewater circulation water tank through the wastewater inlet pipe. The drying device can be provided with multiple sets, which are connected to the wastewater circulation water tank in parallel. At this time, each set of drying device is correspondingly provided with a trunk line, and each trunk line is provided with a control valve. In this regard, those skilled in the art can understand and imagine it, and will not be described in detail here.

[0033] The saline wastewater is dried in the drying device, and the salt is precipitated in solid form. After friction and collision between the bed material particles, it is broken into fine particles ranging from several microns to tens of microns, which are blown out together with the hot air and exhaust gas. Gas-solid separation is achieved in the subsequent separation or dust removal device (such as separator 6), thereby achieving zero discharge of saline wastewater.

[0034] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A salt-containing wastewater drying device, characterized in that: The invention comprises a spouting bed (1), a three-dimensional air distribution device (2) arranged at the bottom of the spouting bed (1), and a liquid distribution pipe (3) arranged at the bottom of the spouting bed (1); the bottom of the spouting bed (1) is a tapered bed area that tapers from top to bottom, and the liquid distribution pipe (3) is arranged in a surrounding manner at the upper part of the tapered bed area and close to the wall surface; a plurality of liquid spray holes are arranged on the liquid distribution pipe (3); the three-dimensional air distribution device (2) comprises a bottom air distribution plate and a drying air chamber arranged at the bottom of the bottom air distribution plate, and a peripheral air distribution plate surrounding the bottom air distribution plate and an annular wind box outside the bottom air distribution plate; the peripheral air distribution plate is arranged in an inclined manner and is arranged at the lower part of the wall surface of the tapered bed area; a plurality of side air distribution holes are opened on the peripheral air distribution plate, and the opening angles of the side air distribution holes are inclined downward; the bottom air distribution plate comprises a high-density hole area and a low-density hole area arranged from the inside to the outside.

2. The drying device according to claim 1, characterized in that: The inclination angle of the wall surface of the conical bed area is 65° to 85°; the inclination angle of the peripheral air distribution plate is 65° to 85°.

3. The drying device according to claim 1, characterized in that The area of ​​the high-density hole zone accounts for 8% to 20% of the total area of ​​the bottom air distribution plate, and the opening rate of the high-density hole zone is more than twice the opening rate of the low-density hole zone.

4. The drying device according to claim 1, characterized in that: The peripheral side air distribution plate is provided with more than two layers of side air distribution holes along the height.

5. The drying device according to claim 1, characterized in that: The inclination angle of the side air distribution holes is 30° to 40°.

6. A zero-discharge system for saline wastewater, characterized in that: It comprises a drying device as described in any one of claims 1 to 5, and a wastewater circulation device, wherein the wastewater circulation device comprises a wastewater circulation tank, a wastewater circulation pump and a wastewater circulation main pipe, the wastewater circulation tank is connected to the liquid distribution pipe through the wastewater circulation main pipe to form a circulation connection; the wastewater circulation tank is also provided with a wastewater inlet pipe.

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