High-efficiency boiling and washing tank for nitrocellulose production

Abstract

The application relates to the technical field of chemical production equipment, in particular to a high-efficiency cooking and washing tank for producing nitrocellulose. The cooking and washing tank comprises a tank body serving as a closed pressure container, and the inner surface of the tank body is covered with a ceramic coating to enhance corrosion resistance and wear resistance. A half-pipe type jacket is arranged outside the tank body, the half-pipe type jacket is formed by helically winding and welding a metal pipe with a semicircular cross section along the outer wall of the tank body, and constitutes a continuous channel for the circulation of heating medium. The cooking and washing tank solves the problems of the existing equipment in mixing efficiency, heat exchange performance and automatic control through integrated design, and realizes energy saving and consumption reduction and quality improvement in the production process.

Description

Technical Field

[0001] This application relates to the field of chemical production equipment technology, and in particular to a high-efficiency boiling tank for nitrocellulose production. Background Technology

[0002] In the production process of nitrocellulose, the boiling and washing process is a crucial step in removing residual acid and impurities from the fibers and improving product purity. Its effectiveness directly determines the quality and performance of the final product. Currently, the industry commonly uses traditional boiling and washing tanks, which typically consist of an open or closed tank, a heating unit via steam coils or a jacket, a simple mechanical stirring system driven by a motor, and corresponding feed and discharge ports. This type of equipment repeatedly washes the nitrocellulose at a specific temperature and time by injecting hot water and agitation, thus basically meeting the production process requirements. However, this technology system, originating from early industrial levels, is gradually revealing its inherent limitations when facing modern production processes that demand higher efficiency, energy consumption, and product quality.

[0003] Specifically, the shortcomings of existing technologies are mainly reflected in several aspects, including production efficiency, energy consumption, and process control. Firstly, because their stirring systems often use a single type of blade (such as anchor or paddle), the stirring flow pattern is fixed and the range of action is limited, easily creating fluid dead zones within the tank, leading to uneven fiber dispersion and low mass and heat transfer efficiency. To ensure washing effectiveness, the washing time for a single batch of material must be significantly extended, severely restricting the equipment's production capacity and pace. Secondly, the thermal system design is rudimentary, typically relying on direct steam heating or indirect heat exchange, resulting in low heat exchange efficiency and poor temperature uniformity within the tank, with obvious localized overheating or underheating. This not only wastes energy but may also lead to over-reaction of some materials or incomplete cleaning, affecting the uniformity and stability of product quality. Furthermore, existing equipment generally has a low level of automation, lacking online monitoring and closed-loop control functions. Process parameters mainly rely on manual experience for setting and adjustment, resulting in poor reproducibility. Simultaneously, equipment cleaning mostly requires manual completion after shutdown, which is not only labor-intensive and time-consuming but also carries the risk of cross-contamination due to incomplete cleaning. The root cause of these defects lies in the fact that the structural design of traditional equipment fails to comprehensively optimize fluid dynamics and thermodynamic efficiency, the control system lacks intelligence, and there is a lack of consideration for resource recycling and life cycle costs.

[0004] Therefore, there is an urgent need and significant value in developing a new and efficient boiling and washing technology to address the above problems. Utility Model Content

[0005] The purpose of this application is to overcome at least one deficiency of the prior art and provide a high-efficiency boiling tank for nitrocellulose production. This boiling tank solves the shortcomings of existing equipment in terms of mixing efficiency, heat exchange performance and automated control through integrated design, thereby achieving energy saving, consumption reduction and quality improvement in the production process.

[0006] To achieve the above objectives, this application discloses a high-efficiency boiling tank for nitrocellulose production, which includes a tank body serving as a closed pressure vessel, the inner surface of which is covered with a ceramic coating to enhance corrosion resistance and wear resistance.

[0007] The tank body is provided with a semi-tube jacket, which is formed by spirally winding and welding a metal tube with a semi-circular cross-section along the outer wall of the tank body, forming a continuous channel for the flow of heating medium. The tank is equipped with a multi-stage stirring device, which consists of a high-shear dispersion disk located at the bottom of the tank, an axial flow oblique blade turbine located in the upper part of the tank, and two drive units that drive the high-shear dispersion disk and the axial flow oblique blade turbine respectively. The high-shear dispersion disk is responsible for breaking up fiber agglomerates and preventing solid sedimentation, while the axial flow oblique blade turbine dominates the formation of a strong overall circulating flow field.

[0008] Furthermore, four longitudinal baffles are evenly distributed around the inner wall of the tank to convert tangential flow into axial flow, eliminate vortices and enhance turbulence intensity, thereby ensuring that the material remains uniformly dispersed and at a consistent temperature throughout the entire washing process.

[0009] Furthermore, to further reduce energy consumption, a waste heat recovery unit is installed outside the tank. The waste heat recovery unit is connected to the tank's inlet and outlet. The waste heat recovery unit includes at least one plate heat exchanger. The high-temperature wastewater discharged after the tank is boiled and washed undergoes countercurrent heat exchange with the freshly injected cold water in the plate heat exchanger, effectively preheating the process water and thus significantly reducing the steam consumption of subsequent heating units.

[0010] Furthermore, a rotating spray ball is installed at the top of the tank, which is connected to an external cleaning fluid supply pipeline through a pipe. This spray ball is used to perform tank cleaning after boiling and washing, thereby achieving thorough cleaning of the inner surface and internal components of the tank.

[0011] Furthermore, the outer circumferential edge of the high-shear dispersion disk is provided with several sets of circumferentially evenly distributed sharp serrations to generate extremely high local shear rates at the tooth tips during high-speed rotation. Simultaneously, multiple concentric rings of through holes with sharp edges are formed on the disk surface.

[0012] Compared with the prior art, this application has at least the following beneficial technical effects: 1. The multi-stage stirring device, consisting of a high-shear dispersion disc and an axial flow inclined blade turbine, combined with the internal baffle design, effectively eliminates the fluid dead zone, achieves uniform material dispersion and temperature field uniformity, significantly improves mass and heat transfer efficiency, and shortens the boiling and washing time.

[0013] 2. The combination of a semi-tube jacketed heating structure and an integrated waste heat recovery unit significantly improves heat exchange efficiency and energy utilization, reduces steam consumption, and avoids local overheating or underheating, thus ensuring product quality stability.

[0014] 3. By integrating a rotary spray online cleaning system with a modular design, automated cleaning and efficient maintenance of the production process are achieved, effectively reducing manual intervention, eliminating the risk of cross-contamination, and improving the reliability of continuous equipment operation.

[0015] The beneficial effects listed above are not exhaustive of all advantages. Other potential beneficial effects and detailed technical implementation methods will be further disclosed in the embodiments or other descriptive sections of this application. Attached Figure Description

[0016] A better understanding of various aspects of this disclosure will be achieved by reading the following detailed description in conjunction with the accompanying drawings. The positions, dimensions, and extents of the structures shown in the drawings, etc., do not always represent actual positions, dimensions, and extents. In the drawings: Figure 1 This is a schematic diagram of the structure of one embodiment disclosed in this application. Detailed Implementation

[0017] The present disclosure will now be described with reference to the accompanying drawings, which illustrate several embodiments of the present disclosure. However, it should be understood that the present disclosure can be presented in many different ways and is not limited to the embodiments described below; in fact, the embodiments described below are intended to make the disclosure more complete and to fully illustrate the scope of protection of the present disclosure to those skilled in the art. It should also be understood that the embodiments disclosed herein can be combined in various ways to provide further additional embodiments.

[0018] It should be understood that the same reference numerals denote the same elements in all the accompanying drawings. For clarity, the dimensions of certain features may be modified in the drawings.

[0019] It should be understood that the terminology used in this specification is for describing specific embodiments only and is not intended to limit this disclosure. All terms used in this specification (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. For the sake of brevity and / or clarity, techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail; however, where appropriate, such techniques, methods, and apparatus should be considered part of this specification.

[0020] Unless otherwise specified, the singular forms “a,” “the,” and “the” used in this specification include the plural forms. The terms “comprising,” “including,” and “containing” used in this specification indicate the presence of the claimed feature but do not exclude the presence of one or more other features. The term “and / or” used in this specification includes any and all combinations of one or more of the relevant listed items.

[0021] See attached document Figure 1 The high-efficiency boiling and washing tank system of this embodiment consists of a closed pressure vessel tank 1, a semi-tube jacket heat exchange structure 2, a multi-stage stirring device 3, a waste heat recovery unit 9, and an online cleaning system. The tank 1 serves as the core reaction vessel, and its inner wall ceramic coating provides corrosion-resistant protection. The outer semi-tube jacket 2 achieves efficient heating, the internal multi-stage stirring device 3 ensures uniform material dispersion, and the waste heat recovery unit 9 and the external cleaning system respectively realize energy recycling and automated cleaning. Each subsystem is integrated and works collaboratively through pipelines and the control system.

[0022] Furthermore, the tank body 1 is formed by rolling and welding duplex stainless steel, with a design pressure of not less than 0.6 MPa. Its inner surface is coated with an alumina-based ceramic coating through a thermal spraying process, with a preferred coating thickness of 0.3-0.5 mm. This structural design aims to resist the erosion of acidic media and fiber friction loss generated during the boiling and washing of nitrocellulose. Based on this, a semi-tube jacket 2 is welded to the outer wall of the tank body 1 in a spiral winding manner. The ratio of the jacket diameter to the diameter of the tank body 1 is controlled between 1:8 and 1:12, and the winding spacing ensures that the gap between adjacent tube walls is not greater than 0.5 times the tube diameter, thereby forming a continuous and uniform heating medium flow channel. This design significantly improves heat transfer efficiency by increasing the heat exchange area and medium flow velocity.

[0023] Subsequently, the multi-stage stirring device 3 installed inside the tank 1 includes an independently driven high-shear dispersion disc 4 and an axial flow inclined blade turbine 6. The high-shear dispersion disc 4 is located in the central area of ​​the tank bottom and is connected to the output shaft of the reducer of the first drive unit 5 via a coupling. The outer circumference of the disc has 48-60 evenly distributed serrated protrusions with the tooth tip angle controlled between 30° and 45°. Simultaneously, 3-5 rings of annular array through holes are opened on the disc surface, and the edges of the through holes are chamfered to form sharp cutting edges. This structure utilizes the centrifugal pumping effect and local shear force field generated by high-speed rotation to achieve physical breaking of fiber clumps. The axial flow inclined blade turbine 6, installed in conjunction with this device, is located in the middle of the tank 1. Its blades adopt a backward-curved design with an inclination angle adjusted within the range of 45°-60°. Driven by the second drive unit 7, it generates a downward-flowing axial mainstream, forcing the material to circulate within the tank.

[0024] Understandably, the high-shear dispersion disk 4 is driven by its drive unit to rotate at high speed. When the disk rotates, the multiple concentric rings of through holes on its surface generate a strong centrifugal pumping effect, continuously drawing in the material from the bottom of the tank and forcing it through the through holes. The sharp edges of the through holes exert an initial shearing and tearing effect on the fiber clusters in the fluid. At the same time, the sharp serrations evenly distributed around the outer circumference of the disk form an extremely high linear velocity and shear stress gradient at the tooth tips under high-speed rotation. When the material is ejected from the through holes and impacts the tooth tip area, it is further broken and dispersed. This dual-action mechanism effectively solves the problems of fiber agglomeration and sedimentation, ensuring that the nitrocellulose fibers are fully exposed to the washing medium in the form of single fibers or small clusters during the washing process, thus laying the foundation for subsequent efficient mass transfer and uniform reaction.

[0025] Furthermore, four longitudinal baffles, evenly distributed at 90° circumference, are welded to the inner wall of tank 1. The width of the baffles is 1 / 10 to 1 / 12 of the diameter of tank 1, and their height extends through the entire liquid layer. This arrangement is used to disrupt tangential flow and transform it into radial and axial turbulence, thereby eliminating mixing dead zones. Based on this, the inlet and outlet pipes of tank 1 are connected to plate heat exchangers to form waste heat recovery unit 9. The high-temperature wastewater inlet and the cold water outlet are arranged diagonally to form countercurrent heat exchange. The plate gap is controlled at 3-5mm and is made of 316L stainless steel. This known heat exchange structure achieves heat recovery through temperature gradient.

[0026] Understandably, the rotating spray ball 8 installed at the center of the tank top is connected to the cleaning fluid supply pipeline via a flange. The fan-shaped nozzles on the surface of the spray ball are arranged alternately at an angle of 15°-30°. During operation, it relies on the fluid reaction force to achieve 360° rotating spray. This known cleaning device can cover all surfaces inside the tank. Preferably, the drive units of the high-shear dispersion disk 4 and the axial flow inclined blade turbine 6 are both combinations of variable frequency motors and planetary reducers, with their output speeds adjustable in the ranges of 0-3000 rpm and 0-500 rpm, respectively. This configuration allows for precise control of shear intensity and circulation flow rate according to material characteristics.

[0027] It is understood that, in this embodiment, structural components, connections, or control logic not described in detail, such as the selection of the coupling between the drive unit and the stirring shaft, the specific structural form of the mechanical seal, and the valve configuration and automation control program implementation of the system pipeline, are all common knowledge or existing technology in the field of art and need not be elaborated upon. This embodiment is only used to assist in illustrating the technical solution of this application, and its specific implementation details are not intended to limit the scope of protection of this application. Any equivalent substitutions or reasonable improvements made based on the core concept of this application should be covered within the scope of the claims of this application.

[0028] While exemplary embodiments of this disclosure have been described, those skilled in the art will understand that various changes and modifications can be made to the exemplary embodiments of this disclosure without departing from the spirit and scope thereof. Therefore, all changes and modifications are included within the scope of protection of this disclosure as defined by the claims. This disclosure is defined by the appended claims, and equivalents of those claims are also included.

Claims

1. A high-efficiency boiling tank for nitrocellulose production, characterized in that, The washing tank includes a tank body that serves as a closed pressurized container, with the inner surface of the tank covered with a ceramic coating to enhance corrosion resistance and abrasion resistance. The tank body is provided with a semi-tube jacket, which is formed by spirally winding and welding a metal tube with a semi-circular cross-section along the outer wall of the tank body, forming a continuous channel for the flow of heating medium. The tank is equipped with a multi-stage stirring device, which consists of a high-shear dispersion disk located at the bottom of the tank, an axial flow oblique blade turbine located in the upper part of the tank, and two drive units that drive the high-shear dispersion disk and the axial flow oblique blade turbine respectively. The high-shear dispersion disk is responsible for breaking up fiber agglomerates and preventing solid sedimentation, while the axial flow oblique blade turbine dominates the formation of a strong overall circulating flow field.

2. The high-efficiency boiling tank for nitrocellulose production as described in claim 1, characterized in that, The inner wall of the tank is provided with four longitudinal baffles evenly distributed around its circumference.

3. The high-efficiency boiling tank for nitrocellulose production as described in claim 1, characterized in that, A waste heat recovery unit is installed outside the tank, and the waste heat recovery unit is connected to the tank's inlet and outlet.

4. The high-efficiency boiling tank for nitrocellulose production as described in claim 1, characterized in that, A rotating spray ball is installed at the top of the tank, and the spray ball is connected to an external cleaning fluid supply pipeline through a pipeline.

5. The high-efficiency boiling tank for nitrocellulose production as described in claim 1, characterized in that, The high-shear dispersion disk has several sets of sharp serrations evenly distributed around its outer circumference, which generate extremely high local shear rates at the tooth tips when rotating at high speed. At the same time, multiple concentric ring-shaped through holes with sharp edges are opened on the surface of the disk.

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