Falling film evaporator and method of use and application thereof

Abstract

The application discloses a falling film evaporator and a use method and application thereof. The method comprises the following steps: an upper pipe header, a shell side cylinder, a lower pipe header, a pipe bundle connecting the upper pipe header and the lower pipe header, and at least one steam distribution control unit arranged outside the shell side cylinder. The steam distribution control unit comprises a steam main pipe and at least two steam branch pipes connected with the steam main pipe, and the steam branch pipes are connected with steam inlets on the shell side cylinder. The steam distribution control unit can make the steam in the shell side more uniformly distributed, improve the heating state of the pipe bundle, avoid the occurrence of dry pipe and scaling phenomena, and improve the efficiency of the falling film evaporator and prolong the service life.

Description

Technical Field

[0001] This invention relates to the field of petrochemical technology, and in particular to a falling film evaporator and its usage and application. Background Technology

[0002] In the petrochemical, salt production, and environmental protection industries, falling film evaporators are commonly used in the concentration stage. The feed liquid is added from the upper tube box of the falling film evaporator. Under the action of gravity, the feed liquid flows from top to bottom in a film form along the inner wall of each heat exchange tube. During the flow, it is heated and vaporized by the shell-side heating medium, thus achieving the concentration function. Summary of the Invention

[0003] The inventors of this application have discovered that currently used falling film evaporators typically employ a single, large-diameter steam pipeline as the steam inlet on the shell side. This easily leads to uneven heating between the heat exchange tubes at the steam inlet and the back-side heat exchange tubes, causing overheating and scaling near the inlet, resulting in reduced tube efficiency or tube failure. The tube drying and scaling phenomena gradually worsen and spread within the tube bundle, ultimately reducing the overall efficiency of the falling film evaporator, making it difficult to meet production demands, and even causing serious consequences such as production shutdowns for maintenance.

[0004] In view of the above problems, the present invention is proposed to provide a falling film evaporator and its method of use and application that overcome or at least partially solve the above problems.

[0005] This invention provides a falling film evaporator, comprising: an upper tube box, a shell-side cylinder, a lower tube box, a tube bundle connecting the upper tube box and the lower tube box, and at least one steam distribution control unit disposed outside the shell-side cylinder;

[0006] The steam distribution control unit includes a main steam pipe and at least two steam branch pipes connected to the main steam pipe, wherein the steam branch pipes are connected to the steam inlet on the shell side.

[0007] In some optional embodiments, the main steam pipe is annular, the steam branch pipes are evenly distributed along the circumference of the main steam pipe, the steam branch pipes are connected to the main steam pipe through branch pipe connectors, and the steam branch pipes are provided with steam flow regulating valves to regulate the steam flow rate entering the steam inlet.

[0008] In some alternative embodiments, the number of steam branch pipes is 2, 3, 4, 6, or 8.

[0009] In some optional embodiments, the steam distribution control unit further includes a pipe support member, the lower end of which is fixed to the outside of the shell-side cylinder, and the upper end of which is used to support and fix the steam main pipe.

[0010] In some optional embodiments, the falling film evaporator described above further includes: a steam distribution plate;

[0011] The steam distribution disk includes annular distribution disks and circular distribution disks alternately arranged along the tube bundle;

[0012] The annular distribution plate is an annular plate with a central through hole. The annular plate has through holes corresponding to the positions of some heat exchange tubes in the tube bundle. The annular distribution plate allows steam in the shell side to pass through the central through hole of the annular distribution plate.

[0013] The circular distribution plate is a circular flat plate with through holes corresponding to the positions of some heat exchange tubes in the tube bundle. The circular distribution plate allows steam in the shell side to pass through the outside of the circular distribution plate.

[0014] In some alternative embodiments, adjacent steam distribution discs are connected by connectors, and the top steam distribution disc is connected to the upper tube sheet by connectors, the upper tube sheet being located between the upper tube box and the shell-side cylinder.

[0015] In some optional embodiments, a spacer tube is provided between adjacent steam distribution discs to make the spacing between the steam distribution discs uniform.

[0016] In some optional embodiments, the diameter of the central through hole of the annular distribution disk is not greater than the diameter of the circular distribution disk; the through holes on the annular distribution disk and the through holes on the circular distribution disk are clearance-fitted with the heat exchange tubes in the tube bundle.

[0017] In some alternative embodiments, the steam distribution control unit is arranged at predetermined intervals along the shell-side cylinder axis.

[0018] In some optional embodiments, the falling film evaporator described above further includes:

[0019] Multiple steam distribution rods are arranged on the tube bundle at the steam inlet of the steam branch pipe connection and fixed to the upper tube sheet and the annular distribution plate at the top.

[0020] In some optional embodiments, the falling film evaporator described above further includes:

[0021] The observation sight glass is located on the side wall of the lower pipe box and is positioned corresponding to the steam branch pipe.

[0022] A rinsing device is provided on one side of the viewing mirror to spray liquid onto the viewing mirror and rinse it.

[0023] This invention also provides a method for using the above-mentioned falling film evaporator, including:

[0024] The material to be concentrated is injected into the liquid inlet of the upper tube box, and the material to be concentrated forms a thin film along the inner wall of the heat exchange tube in the tube bundle and flows from top to bottom;

[0025] Steam is injected through the steam inlet of the main steam pipe, and the steam enters the shell-side cylinder through the steam branch pipe to heat the material to be concentrated in the tube bundle;

[0026] The concentrated liquid and gas separated from the material to be concentrated after flowing through the tube bundle are respectively output from the outlet of the lower tube box.

[0027] In some optional embodiments, after steam is injected from the steam inlet of the steam main pipe, the water outlet condition at the bottom of the heat exchange tube is observed through a sight glass, and the opening of the steam flow control valve is adjusted according to the water outlet condition to regulate the steam flow rate entering the steam inlet.

[0028] This invention also provides an application of the above-mentioned falling film evaporator in the evaporation and concentration process.

[0029] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following:

[0030] The falling film evaporator provided in this invention uses the steam main pipe and steam branch pipe in the steam distribution control unit to ensure that the steam injected into the shell side is evenly distributed into the shell side space. By setting up a multi-layer steam distribution control unit, the steam distribution can be made more uniform, improving the heating state of the tube bundle. This ensures that the tube bundle is heated evenly, effectively reducing the dry tubes and scaling phenomena on the inlet side heat exchange tubes caused by uneven steam distribution, slowing down the scaling rate of the heat exchange tubes, extending the operation and service life of the falling film evaporator, improving the efficiency of the falling film evaporator, and reducing the tube bundle vibration generated during equipment operation.

[0031] The aforementioned falling film evaporator is equipped with a steam flow regulating valve on the steam branch pipe, which controls the steam flow control valve on the same side to regulate the steam flow, further improving the heating state of the tube bundle and preventing dry pipe and scaling phenomena. The lower tube box is equipped with an observation window, which allows observation of the water outlet status at the bottom of the heat exchange tubes. This enables real-time observation of the liquid flow status in the lower tube box, and the flow rate of the corresponding steam branch pipe is adjusted according to the flow status at the bottom of the heat exchange tubes, achieving real-time and interactive regulation and improving the operating status of the falling film evaporator in real time.

[0032] The secondary distribution of steam after it enters the shell-side space can be achieved by setting up steam distribution rods and steam distribution discs, making the heat exchange tubes more uniformly heated and further solving the problem of uneven heating of heat exchange tubes in the prior art.

[0033] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.

[0034] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0035] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0036] Figure 1 This is a schematic diagram of the falling film evaporator in an embodiment of the present invention;

[0037] Figure 2 This is a schematic diagram of the steam distribution control unit in an embodiment of the present invention;

[0038] Figure 3 This is a schematic diagram of the structure of the annular distribution disk in an embodiment of the present invention;

[0039] Figure 4 This is a schematic diagram of the circular distribution disk in an embodiment of the present invention;

[0040] Figure 5 This is a schematic diagram of the structure of the lower tube box sight glass and flushing pipe in an embodiment of the present invention.

[0041] Explanation of reference numerals in the attached figures:

[0042] 1000-Upper tube box, 2000-Steam distribution control unit, 3000-Tube bundle, 4000-Shell side shell, 5000-Lower tube box, 6000-Upper tube sheet, 7000-Lower tube sheet;

[0043] 1001 - Liquid Inlet;

[0044] 2001-Pipe rack support, 2002-Main steam pipe, 2003-Steam flow regulating valve, 2004-Steam branch pipe;

[0045] 3001 - Annular distribution disc, 3002 - Circular distribution disc, 3003 - Steam distribution rod;

[0046] 5001 - Observation scope, 5002 - Rinse tube, 5003 - Liquid outlet, 5004 - Gas outlet. Detailed Implementation

[0047] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0048] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0049] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0050] To address the problems of uneven heating of heat exchange tubes, leading to tube dryness and scaling, and consequently reduced efficiency in existing falling film evaporators, this invention provides a falling film evaporator with the following structure: Figure 1 As shown, the evaporator includes: an upper tube box 1000, a shell-side cylinder 4000, a lower tube box 5000, a tube bundle 3000 connecting the upper tube box 1000 and the lower tube box 5000, and at least one steam distribution control unit 2000 disposed outside the shell-side cylinder 4000. The steam distribution control unit 2000 includes a main steam pipe 2002 and at least two steam branch pipes 2004 connected to the main steam pipe 2002. The steam branch pipes 2004 are connected to steam inlets on the shell-side cylinder 4000. The upper tube box 1000 of the falling film evaporator is provided with a liquid inlet 1001, and the lower tube box is provided with two outlets. The two outlets include a liquid outlet 5003 and a gas outlet 5004.

[0051] The aforementioned falling film evaporator can be equipped with a tube support structure and a steam distribution control unit on the main steam pipe, and a steam flow control valve can be installed on the steam branch pipe, which is connected to the steam inlet on the shell side. The tube bundle can be arranged in a ring and equipped with a steam distribution rod, a circular steam distribution plate, and an annular steam distribution plate. The lower tube box can include multiple observation mirrors and a flushing device. The observation mirrors can be used to observe the water outlet status at the bottom of the heat exchange tubes, control the steam flow control valve on the same side, adjust the steam flow, improve the heating status of the tube bundle, avoid the occurrence of dry tubes and scaling, improve the efficiency of the falling film evaporator, and extend its service life.

[0052] Figure 1 The diagram illustrates the structure of a falling film evaporator only, with some sections represented by lines. This is merely to show that the structure exists in the falling film evaporator and does not imply that its actual shape is also a line shape. Furthermore, in the falling film evaporator, the upper tube box 1000, the tube bundle 3000, and the lower tube box 5000 form the tube side, while the shell side is formed within the shell-side cylinder 4000.

[0053] In some optional embodiments, the vapor distribution control unit 2000 in the above-described falling film evaporator has the following structure: Figure 2 As shown, it may include an annular steam main pipe 2002, steam branch pipes 2004, steam flow regulating valves 2003 on the steam branch pipes, and connecting parts between the steam main pipe and the steam branch pipes. The steam main pipe 2002 has a main pipe inlet as the total inlet for steam entry. After entering the steam main pipe 2002, the steam is distributed to each steam branch pipe and enters the shell side through the steam inlet connected to the steam branch pipe 2004.

[0054] In the aforementioned falling film evaporator, the main steam pipe 2002 is installed outside the shell-side cylinder 4000, surrounding it. It can be designed in different shapes; optionally, the main steam pipe 2002 is annular, and the steam branch pipes 2004 are evenly distributed along the circumference of the main steam pipe 2002. The steam branch pipes 2004 are connected to the main steam pipe 2002 via branch pipe connectors. A steam flow regulating valve 2003 is installed on each steam branch pipe 2004 to regulate the steam flow rate entering through the steam inlet. The branch pipe connectors can be custom-designed or standard pipe connectors can be used; for example, a tee connector can be used to connect the steam branch pipes 2004 and the main steam pipe 2002. The steam branch pipes can be evenly or unevenly distributed; even distribution is more conducive to uniform steam diffusion within the shell-side cylinder. The number of steam branch pipes 2004 can be set as needed; preferably, there are 2, 3, 4, 6, or 8. The steam flow rate of each branch pipe can be controlled by the steam flow regulating valve 2003.

[0055] The steam distribution control unit 2000 also includes a tube rack support 2001. The lower end of the tube rack support 2001 is fixed to the outside of the shell-side cylinder 4000, and the upper end is used to support and fix the steam main pipe 2002. Depending on the size of the falling film evaporator and the required steam volume, multiple steam distribution control units 2000 can be arranged in a single layer or multiple layers along the shell-side axis. When multiple steam distribution control units 2000 are installed, they are spaced apart along the axis of the shell-side cylinder 4000, and adjacent steam distribution control units 2000 can be arranged at a set distance. The steam distribution control units 2000 can be arranged in a slightly upper-middle position to facilitate steam diffusion, and can be arranged at equal or unequal intervals starting from the top. Each steam distribution control unit 2000 is supported by a tube rack support 2001. The tube rack support 2001 can include multiple support rods, each support rod having one end connected to the shell-side cylinder 4000 and the other end connected to the steam main pipe 2002.

[0056] The aforementioned falling film evaporator further includes an upper tube sheet 6000 and a lower tube sheet 7000; the tube bundle 3000 is fixed to the shell-side cylinder 4000 via the upper tube sheet 6000 and the lower tube sheet 7000; the upper tube box 1000 is connected to the shell-side cylinder 4000 via the upper tube sheet 6000; and the lower tube box 5000 is connected to the shell-side cylinder 4000 via the lower tube sheet 7000. Figure 1 As shown, the upper tube sheet is located between the upper tube box 1000 and the shell-side cylinder 4000. The upper tube box 1000 has a liquid inlet 1001. Additionally, a film distributor is installed inside the upper tube box. At least one layer of the film distributor can be installed; the example shown has two layers, located between the liquid inlet 1001 and the upper tube sheet 6000. The film distributor ensures that the liquid injected from the liquid inlet 1001 is evenly distributed and enters each heat exchange tube in the tube bundle. The heat exchange tubes in the tube bundle are connected between the upper tube sheet 6000 and the lower tube sheet 7000. The liquid can also flow downwards along each heat exchange tube into the lower tube box 5000. The lower tube box 5000 has a liquid outlet 5003 and a gas outlet 5004. A shell outlet is also provided below the shell-side cylinder 4000 to discharge the steam condensate.

[0057] The aforementioned falling film evaporator also includes multiple steam distribution rods 3003, which are arranged on the tube bundle at the steam inlet connected to the steam branch pipe 2004 and fixed on the upper tube plate 6000 and the annular distribution plate 3001 at the top.

[0058] The aforementioned falling film evaporator further includes a steam distribution plate, comprising annular distribution plates 3001 and circular distribution plates 3002 alternately arranged along the tube bundle 3000; as shown Figure 3As shown, the annular distribution plate 3001 is an annular flat plate with a central through hole. The annular flat plate has through holes corresponding to the positions of some heat exchange tubes in the tube bundle. The annular distribution plate 3001 allows steam in the shell side to pass through the central through hole; as shown... Figure 4 As shown, the circular distribution plate 3002 is a circular flat plate with through holes corresponding to the positions of some heat exchange tubes in the tube bundle 3000. The circular distribution plate 3002 allows steam in the shell side to pass through the outside of the circular distribution plate 3002. Several steam distribution rods are set at the inlet of the steam branch pipe, and multiple annular and circular steam distribution plates are arranged along the tube bundle axis to achieve secondary distribution of steam within and between the tube bundle layers, thereby achieving more uniform steam distribution and improving heat transfer efficiency.

[0059] Adjacent annular distribution discs 3001 and circular distribution discs 3002 are connected by connectors. The top annular distribution disc 3001 or circular distribution disc 3002 is connected to the upper tube sheet 6000 by connectors, and the bottom annular distribution disc 3001 or circular distribution disc 3002 is connected to the lower tube sheet 7000 by connectors. A spacer tube is provided between adjacent annular distribution discs 3001 and circular distribution discs 3002 to ensure uniform spacing between them.

[0060] The diameter of the central through hole of the annular distribution plate 3001 is no larger than the diameter of the circular distribution plate 3002. Both the annular distribution plate 3001 and the circular distribution plate 3002 have several through-holes, the positions of which are determined by the positions of the heat exchange tubes in the tube bundle, allowing the heat exchange tubes to pass through. The through-holes on the annular distribution plate 3001 and the circular distribution plate 3002 are clearance-fitted with the heat exchange tubes in the tube bundle 3000.

[0061] The aforementioned falling film evaporator also includes a sight glass 5001, located on the side wall of the lower tube box 5000, corresponding to the position of the steam branch pipe 2004. In other words, by arranging the same number and orientation of sight glasses as the steam branch pipes 2004 along the circumference of the shell-side cylinder 4000, the need for real-time observation of the liquid outflow status at the bottom of the heat exchange tubes can be met. Adjusting the steam flow regulating valve on the corresponding steam branch pipe based on the observation results increases or decreases the amount of steam flowing into the shell side, thus improving the heating condition of the heat exchange tubes. The sight glass 5001 includes two fixed plates with holes in the middle and a light-transmitting plate located between the fixed plates; the two fixed plates are connected by screws, with one fixed plate fixed in a mounting hole on the side wall of the lower tube box 5000. The light-transmitting plate can be a flat glass plate.

[0062] The aforementioned falling film evaporator also includes a rinsing device 5002, disposed on one side of the viewing mirror 5001, for spraying liquid onto the viewing mirror to rinse it. Optionally, the rinsing device 5002 can be a rinsing pipe, located on one side of the viewing mirror 5001, with one end inside the lower tube box 5000, for spraying liquid onto the viewing mirror 5001 to rinse it. Figure 1 and Figure 5 As shown, a flushing pipe 5002 is provided below the observation lens 5001. Each observation lens 5001 can be provided with at least one flushing pipe 5002. The end of the observation lens 5001 outside the lower tube box 5000 can be injected with flushing fluid. The flushing fluid is sprayed from the end located inside the lower tube box 5000 onto the observation lens 5001 to flush the observation lens 5001. The end of the flushing pipe located inside the lower tube box 5000 can have a certain degree of curvature. The bending angle can be designed and adjusted according to the position of the observation lens 5001 and the flushing pipe 5002 so that the flushing fluid can be accurately sprayed onto the observation lens 5001.

[0063] The falling film evaporator described in this embodiment of the invention has a steam distribution control function and mainly consists of a shell-side steam distribution control unit, a steam distribution rod at the steam inlet, and multiple layers of steam distribution discs arranged along the tube bundle axis. The shell-side steam distribution control unit of the falling film evaporator uses a ring-shaped pipeline as the main steam pipe, with several steam branch pipes evenly arranged around the circumference of the ring main pipe. Each steam branch pipe is equipped with a steam flow regulating valve, which can adjust the flow rate of the corresponding steam branch pipe according to the flow rate at the bottom of the heat exchange tubes. The ends of the steam branch pipes are connected to the shell-side cylinder of the falling film evaporator. The steam distribution rod at the steam inlet is arranged on the tube bundle at the inlet of the branch pipe of the steam distribution control unit and is connected to the upper tube sheet and adjacent steam distribution discs using fasteners. The steam distribution discs are evenly arranged along the tube bundle axis, with uniform spacing achieved using spacer pipes, and are connected to the upper and lower tube sheets using connectors. The falling film evaporator has sight glasses and flushing devices arranged around the lower tube box in the same number and orientation as the branch pipes of the steam distribution control unit. The steam distribution control unit ensures uniform steam distribution along the circumference of the falling film evaporator shell side, effectively reducing scaling and fouling on the inlet-side heat exchange tubes caused by uneven steam distribution, and minimizing tube bundle vibration during operation. The steam distribution control unit can be arranged in a single layer or multiple layers along the axial direction of the falling film evaporator, depending on the evaporator's size and required steam volume. Each branch of the steam distribution control unit has independent adjustment capabilities, allowing for online adjustment of the corresponding branch's steam supply by observing the heat exchange tube outlet water status through the lower tube box sight glass, thus improving the evaporator's operating condition. The steam distribution rods and steam distribution discs installed on the falling film evaporator tube bundle enable secondary distribution of shell-side steam within the tube bundle and between layers, resulting in more uniform heating of the heat exchange tubes. The falling film evaporator achieves uniform distribution of heating steam in the shell side through an innovative structure, and adjusts the steam flow on the supply side through real-time monitoring function of upper and lower linkage. This solves the scaling problems commonly found in existing falling film evaporators caused by dry tubes or easily scaled water due to fluctuations in inlet water and uneven heating of heat exchange tubes. It can effectively reduce the occurrence of local dry tube phenomenon in falling film evaporators, slow down the scaling rate of heat exchange tubes, and extend the operating cycle of falling film evaporators.

[0064] Based on the same inventive concept, this invention also provides a method for using the aforementioned falling film evaporator, comprising: injecting the material to be concentrated into the liquid inlet of the upper tube box, the material to be concentrated forming a thin film flowing from top to bottom along the inner wall of the heat exchange tubes in the tube bundle; injecting steam into the steam inlet of the steam main pipe, the steam entering the shell-side cylinder through the steam branch pipe to heat the material to be concentrated in the tube bundle; the concentrated liquid and gas separated after the material to be concentrated flows through the tube bundle are respectively output from the outlet of the lower tube box. Optionally, after injecting steam into the steam inlet of the steam main pipe, the water outlet condition at the bottom of the heat exchange tubes is observed through a sight glass, and the opening of the steam flow control valve is adjusted according to the water outlet condition to regulate the steam flow rate entering the steam inlet.

[0065] During operation, the material to be concentrated enters from the inlet of the upper tube box and is evenly distributed onto the upper tube sheet by the distributor. The material forms a thin film along the inner wall of the heat exchange tubes and flows from top to bottom. Heating steam enters from the main steam pipe of the steam distribution control unit and enters the shell-side cylinder through the steam branch pipe to heat the material to be concentrated. As the material to be concentrated flows through the heat exchange tubes in the tube bundle, it is continuously evaporated and concentrated. The water outlet condition at the bottom of the heat exchange tubes is observed by observing the sight glass of the lower tube box. The steam flow control valve on the same side is controlled to adjust the steam flow, improve the heating condition of the tube bundle, and avoid the occurrence of dry tubes and scaling.

[0066] During use, the liquid flow state inside the lower tube box can be observed through the sight glass. Based on the liquid flow state, it can be determined whether the steam inlet volume needs to be adjusted and which steam branch pipe needs to be adjusted. The corresponding steam flow regulating valve can be adjusted to adjust the steam inlet volume of the steam branch pipe. The steam inlet volume of the steam branch pipe can be closed, opened, increased, or decreased to adjust the amount of steam entering the corresponding side of the shell.

[0067] When the viewing mirror needs cleaning, flushing fluid is injected through the flushing tube.

[0068] Based on the same inventive concept, this embodiment of the invention also provides an application of the above-mentioned falling film evaporator in the slurry evaporation and concentration process.

[0069] The falling film evaporator with steam distribution control function provided by this invention can be used in the concentration section of petrochemical, salt production, and environmental protection industries. It is particularly suitable for devices in these fields where the tube-side medium is prone to scaling, requires high operational flexibility, and has long operating cycles. This falling film evaporator is equipped with a steam distribution control unit. By uniformly arranging steam branch pipes along the circumference of the annular steam main pipe, steam can be evenly distributed within the shell side of the falling film evaporator. This effectively reduces localized scaling and dry-tube phenomena caused by uneven steam distribution and minimizes tube bundle vibration during equipment operation. Each branch pipe of the falling film evaporator has an independent adjustment function. The lower tube box is equipped with a sight glass and a flushing device, enabling real-time observation. The steam supply to the corresponding branch pipe can be adjusted by observing the liquid flow status at the bottom of the heat exchange tubes through the sight glass located in the lower tube box, thereby improving the operating status of the falling film evaporator. The steam distribution rods and steam distribution discs installed on the tube bundle of the falling film evaporator enable secondary distribution of shell-side steam within and between the tube bundle layers, making the heat exchange tubes more uniformly heated, improving the operating condition of the falling film evaporator, enhancing the heat transfer effect, effectively reducing the occurrence of local dry tube phenomena in the falling film evaporator, slowing down the scaling rate of the heat exchange tubes, and extending the operating cycle of the falling film evaporator.

[0070] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process may be rearranged without departing from the scope of this disclosure. The appended method claims provide elements of various steps in an exemplary order and are not intended to limit the scope to the specific order or hierarchy described.

[0071] In the detailed description above, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the invention is presented with fewer features than all of the features in a single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, with each claim representing a separate preferred embodiment of the invention.

[0072] The foregoing description includes examples of one or more embodiments. It is certainly impossible to describe all possible combinations of components or methods in order to describe the above embodiments, but those skilled in the art will recognize that further combinations and arrangements of the various embodiments are possible. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims. Furthermore, the term "comprising" as used in the specification or claims is interpreted in a manner similar to the term "including," as interpreted when used as a conjunction in the claims. Additionally, the use of any term "or" in the specification of the claims is intended to mean "non-exclusive or."

Claims

1. A falling film evaporator, characterized in that, include: The upper tube box, the shell-side cylinder, the lower tube box, the tube bundle connecting the upper tube box and the lower tube box, at least one steam distribution control unit disposed outside the shell-side cylinder, multiple steam distribution rods, and multi-layer steam distribution disks spaced apart along the axial direction of the tube bundle; The steam distribution control unit includes an annular steam main pipe arranged around the outer side of the shell-side body and at least two steam branch pipes connected to the steam main pipe. The steam branch pipes are evenly distributed along the circumference of the steam main pipe. The steam branch pipes are connected to the steam inlet on the shell-side body and enter the shell-side body through the steam inlet. Multiple steam distribution rods are arranged on the tube bundle at the steam inlet where the steam branch pipe is connected; The steam distribution plate includes annular and circular distribution plates alternately arranged along the tube bundle. The annular distribution plate has a central through hole. The diameter of the central through hole of the annular distribution plate is not greater than the diameter of the circular distribution plate.

2. The falling film evaporator as described in claim 1, characterized in that, The steam branch pipe is connected to the main steam pipe via a branch pipe connector, and a steam flow regulating valve is provided on the steam branch pipe to regulate the steam flow rate entering the steam inlet.

3. The falling film evaporator as described in claim 2, characterized in that, The number of steam branch pipes is 2, 3, 4, 6 or 8.

4. The falling film evaporator as described in claim 1, characterized in that, The steam distribution control unit also includes a pipe support component, the lower end of which is fixed to the outside of the shell-side cylinder, and the upper end of which is used to support and fix the steam main pipe.

5. The falling film evaporator as described in claim 1, characterized in that, Also includes: Steam distribution plate; The annular distribution plate is an annular plate with a central through hole. The annular plate has through holes corresponding to the positions of some heat exchange tubes in the tube bundle. The annular distribution plate allows steam in the shell side to pass through the central through hole of the annular distribution plate. The circular distribution plate is a circular flat plate with through holes corresponding to the positions of some heat exchange tubes in the tube bundle. The circular distribution plate allows steam in the shell side to pass through the outside of the circular distribution plate.

6. The falling film evaporator as described in claim 5, characterized in that, Adjacent steam distribution plates are connected by connectors, and the top steam distribution plate is connected to the upper tube sheet by connectors; the upper tube sheet is located between the upper tube box and the shell-side cylinder.

7. The falling film evaporator as described in claim 5, characterized in that, A spacer tube is installed between adjacent steam distribution discs to ensure uniform spacing between the discs.

8. The falling film evaporator as described in claim 5, characterized in that, The through holes on the annular distribution plate and the through holes on the circular distribution plate are fitted with the heat exchange tubes in the tube bundle with clearance.

9. The falling film evaporator as described in claim 1, characterized in that, The steam distribution control unit is arranged at predetermined intervals along the shell-side cylinder axis.

10. The falling film evaporator as claimed in claim 1, characterized in that, The plurality of steam distribution rods are fixed to the upper tube sheet and the annular distribution plate at the top.

11. The falling film evaporator according to any one of claims 1-10, characterized in that, Also includes: The observation sight glass is located on the side wall of the lower pipe box and is positioned corresponding to the steam branch pipe. A rinsing device is provided on one side of the viewing mirror to spray liquid onto the viewing mirror and rinse it.

12. A method of using the falling film evaporator according to any one of claims 1-11, characterized in that, include: The material to be concentrated is injected into the liquid inlet of the upper tube box, and the material to be concentrated forms a thin film along the inner wall of the heat exchange tube in the tube bundle and flows from top to bottom; Steam is injected through the steam inlet of the main steam pipe, and the steam enters the shell-side cylinder through the steam branch pipe to heat the material to be concentrated in the tube bundle; The concentrated liquid and gas separated from the material to be concentrated after flowing through the tube bundle are respectively output from the outlet of the lower tube box.

13. The method as described in claim 12, characterized in that, Also includes: After steam is injected into the steam inlet of the main steam pipe, the water outlet condition at the bottom of the heat exchange tube is observed through the sight glass. The opening of the steam flow control valve is adjusted according to the water outlet condition to regulate the steam flow rate entering the steam inlet. The steam flow control valve is installed on the steam branch pipe, and the sight glass is located on the side wall of the lower pipe box, corresponding to the orientation of the steam branch pipe.

14. The application of the falling film evaporator according to any one of claims 1-11 in the evaporation and concentration process.

Images