System for secondary steam volatilization, black liquid concentration and condensed water recovery of black liquid

Abstract

The utility model discloses a system for secondary steam volatilization, black liquid concentration and condensate water recovery of black liquid. The system comprises a digester, an evaporator, a steam generating device and a condensate water collecting device, the evaporator is provided with a black liquor channel and a steam channel, and the black liquor channel and the steam channel are arranged in the evaporator at intervals and do not communicate with each other. The steam generating device is communicated with the input end of the steam channel through a first steam pipe, and the output end of the steam channel is connected with the condensate water collecting device through a first condensate water pipe. The black liquor output end of the digester is communicated with the input end of the black liquor channel through a first black liquor pipe, the steam output end of the black liquor channel is connected with the steam input end of the digester through a second steam pipe, and the black liquor output end of the black liquor channel is connected with a black liquor discharging system. According to the scheme, the digester produces the black liquor under the action of the digesting heat source, so that the utilization rate of steam is greatly improved, and the problem of large steam consumption in a traditional black liquor production system is solved.

Description

Technical Field

[0001] This utility model relates to the field of cooking pot technology, specifically a system for secondary steam volatilization, black liquor concentration, and condensate recovery of black liquor. Background Technology

[0002] In traditional digester processes, a large amount of steam is typically required as a heating and reaction medium to effectively separate cellulose and lignin. During this process, the steam not only heats the materials in the digester to the required high temperatures but also participates in the chemical reactions, promoting the deconstruction and dissolution of the lignin structure.

[0003] Because the cooking process is a continuous and large-scale heat input process, high-temperature steam needs to be constantly injected into the cooker to maintain the temperature and pressure conditions required for the reaction. This not only increases the consumption of energy (such as coal, natural gas, or biomass fuels) but may also impose a certain burden on the environment, especially as greenhouse gases may be released during the energy conversion process.

[0004] Secondly, traditional cooking methods produce black liquor with a relatively low concentration. The large amount of steam injected directly not only participates in the reaction but also increases the total volume of the black liquor, thereby diluting the effective components. Low-concentration black liquor is not only less efficient in subsequent treatments (such as concentration, combustion, or chemical recovery) but also increases processing costs and complexity.

[0005] In addition, directly injecting high-pressure steam into the cooking pot causes large pressure fluctuations inside the cooking pot, which leads to fluctuations in the black liquor concentration process within the evaporator, further affecting the consistency of product quality. Utility Model Content

[0006] To address the aforementioned shortcomings, this invention proposes a system for secondary steam volatilization, black liquor concentration, and condensate recovery in black liquor production. Under the influence of the secondary steam heat source, the pressure in the cooking pot becomes more stable, increasing the concentration of the discharged black liquor. This reduces steam consumption in subsequent processes, lowers energy costs, and solves the problems of unstable pressure, low discharged black liquor concentration, and high steam consumption in subsequent processes inherent in traditional black liquor production systems. Furthermore, the spaced arrangement of the steam channel and black liquor channel allows for efficient heat transfer from the steam to the black liquor, enabling the black liquor to fully absorb the heat and become concentrated, thus improving the overall thermal efficiency of the system and resolving the problem of low black liquor concentration in traditional black liquor production systems.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] A system for secondary steam volatilization, black liquor concentration and condensate recovery of black liquor includes a cooking pot, an evaporator, a steam generating device and a condensate collection device;

[0009] The evaporator is provided with a black liquor channel and a steam channel, which are spaced apart and not connected to each other within the evaporator.

[0010] The steam generator is connected to the input end of the steam channel via a first steam pipe, and the output end of the steam channel is connected to the condensate collection device via a first condensate pipe.

[0011] The black liquor output end of the cooking pot is connected to the input end of the black liquor channel through a first black liquor pipe. The steam output end of the black liquor channel is connected to the steam input end of the cooking pot through a second steam pipe. The black liquor output end of the black liquor channel is connected to the black liquor discharge system.

[0012] The input end of the first steam pipe is connected to the steam generating device, the first output end of the first steam pipe is connected to the input end of the steam channel, and the second output end of the first steam pipe is connected to the steam input end of the cooking pot.

[0013] The inlet of the first condensate pipe is connected to the outlet of the steam channel, the first outlet of the first condensate pipe is connected to the inlet of the first steam pipe, and the second outlet of the first condensate pipe is connected to the condensate collection device.

[0014] The input end of the second steam pipe is connected to the steam output end of the black liquor channel, and the output end of the second steam pipe is connected to the second output end of the first steam pipe.

[0015] The first input end of the first black liquor pipe is connected to the black liquor output end of the cooking pot, the second input end of the first black liquor pipe is connected to the black liquor output end of the black liquor channel, the first output end of the first black liquor pipe is connected to the black liquor input end of the black liquor channel, and the second output end of the first black liquor pipe is connected to the black liquor discharge system.

[0016] The first black liquor pipe is equipped with a circulation pump.

[0017] The evaporator includes multiple interconnected heat sink fin groups, the gap between any two adjacent heat sink fin groups is the black liquid channel, and the internal space of the heat sink fin group is the steam channel.

[0018] The heat sink assembly includes two heat sinks that are attached to each other and arranged opposite each other. Each heat sink includes a plurality of regularly arranged welded portions and protrusions. The welded portions of two adjacent heat sinks are fixedly connected. The protrusions of two adjacent heat sinks form the steam channel.

[0019] The black liquor output end of the cooking pot is equipped with a black liquor discharge pipe, and the output end of the black liquor discharge pipe is connected to the black liquor discharge system.

[0020] The technical solution of this utility model can include the following beneficial effects:

[0021] 1. The cooking pot produces black liquor under the action of this cooking heat source, which greatly increases the operating pressure of the cooking pot and is beneficial to the stability of the system; it significantly increases the concentration of discharged black liquor and efficiently reduces the amount of steam required for concentration in subsequent stages; the recovered high-temperature clean condensate effectively saves boiler water treatment costs.

[0022] 2. The steam channel and the black liquor channel are set apart, which allows the heat of the steam to be efficiently transferred to the black liquor. The black liquor can fully absorb the heat of the steam and be concentrated, which improves the thermal efficiency of the entire system and solves the problem of low black liquor concentration in traditional black liquor production systems. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a black liquor production and concentration system according to one embodiment of this utility model;

[0024] Figure 2 This is a cross-sectional view of a heat sink assembly according to one embodiment of this utility model;

[0025] The components include: 1. Cooking pot; 2. Evaporator; 21. Heat sink assembly; 22. Heat sink; 23. Welding part; 24. Protrusion; 3. Steam generating device; 4. Condensate collection device; 5. Black liquor discharge system; 01. First steam pipe; 02. First condensate pipe; 03. First black liquor pipe; 04. Second steam pipe; 05. Circulation pump; 06. Black liquor discharge pipe. Detailed Implementation

[0026] The technical solution of this utility model will be further described below with reference to the accompanying drawings and specific embodiments.

[0027] In the description of this utility model, it should be understood that the terms "length", "middle", "upper", "lower", "left", "right", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and 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 this utility model.

[0028] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0029] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "assembly," and "connection" 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 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 utility model based on the specific circumstances.

[0030] The following is combined Figures 1 to 2 This invention describes a system for secondary vapor evaporation, black liquor concentration, and condensate recovery of black liquor according to an embodiment of the present invention.

[0031] A system for secondary steam volatilization, black liquor concentration and condensate recovery of black liquor includes a cooking pot 1, an evaporator 2, a steam generating device 3 and a condensate collection device 4;

[0032] The evaporator 2 is provided with a black liquor channel and a steam channel, which are spaced apart and not connected to each other within the evaporator 2.

[0033] The steam generator 3 is connected to the input end of the steam channel via the first steam pipe 01, and the output end of the steam channel is connected to the condensate collection device 4 via the first condensate pipe 02.

[0034] The black liquor output end of the cooking pot 1 is connected to the input end of the black liquor channel through the first black liquor pipe 03. The steam output end of the black liquor channel is connected to the steam input end of the cooking pot 1 through the second steam pipe 04. The black liquor output end of the black liquor channel is connected to the black liquor discharge system 5.

[0035] Steam generated by steam generator 3 enters the steam channel of evaporator 2 through first steam pipe 01. After releasing heat in the steam channel, the steam turns into condensate and flows into condensate collection device 4 through first condensate pipe 02. Meanwhile, the black liquor in the black liquor channel of evaporator 2 exchanges heat with the steam in the steam channel, heating the black liquor in the black liquor channel to form secondary steam and concentrated black liquor. The secondary steam generated in the black liquor channel flows back to the cooking pot 1 through second steam pipe 04 as a cooking heat source. Under the action of this cooking heat source, cooking pot 1 produces black liquor, greatly increasing the concentration of discharged black liquor, reducing the overall steam consumption of the system, increasing the steam buffer space, stabilizing the pressure inside the cooking pot, stably recovering clean condensate, reducing energy costs, and solving the problem of high steam consumption in traditional black liquor production systems.

[0036] It is worth noting that the steam channel and the black liquor channel are spaced apart, allowing the heat from the steam to be efficiently transferred to the black liquor. The black liquor can fully absorb the heat from the steam and be concentrated, improving the overall thermal efficiency of the system and solving the problem of low black liquor concentration in traditional black liquor production systems. Moreover, the steam channel and the black liquor channel are not interconnected, which avoids the problem of impurities being introduced due to direct mixing of steam and black liquor.

[0037] The input end of the first steam pipe 01 is connected to the steam generating device 3, the first output end of the first steam pipe 01 is connected to the input end of the steam channel, and the second output end of the first steam pipe 01 is connected to the steam input end of the cooking pot 1.

[0038] In the initial stage of black liquor production and concentration, when the digester 1 requires a large amount of steam to start the initial heating and reaction process of the black liquor, more steam can be directly allocated to the digester 1 to ensure that it quickly reaches the appropriate operating temperature and pressure conditions, enabling efficient black liquor production. Once the reaction inside the digester 1 stabilizes, as the black liquor is transported to the evaporator 2, more steam can be directed through the steam channel at the first output end for use in the black liquor concentration process. This dynamic steam allocation method, based on the needs of different production stages, avoids excessive steam supply and waste, improves the overall steam utilization efficiency, and saves a significant amount of steam energy compared to a fixed steam allocation mode, thus significantly reducing production costs.

[0039] Traditional high-pressure steam conveying puts the cooker under the dual pressure impact of steam pressure and material fluctuations. The new system, with its secondary steam being closer to the usage requirements and evaporator 2 increasing the steam buffer space, makes the pressure more stable, resulting in more stable pressure operation of the cooker.

[0040] The input end of the first condensate pipe 02 is connected to the output end of the steam channel, the first output end of the first condensate pipe 02 is connected to the input end of the first steam pipe 01, and the second output end of the first condensate pipe 02 is connected to the condensate collection device 4.

[0041] After the steam releases heat in the steam channel, a portion of the condensate is returned to the inlet of the first steam pipe 01 through the diversion design of the first condensate pipe 02. This portion of condensate mixes with the fresh steam, effectively absorbing the excess heat of the fresh steam and gradually reducing the superheat of the fresh steam until it approaches saturation.

[0042] The pressure and flow rate of superheated steam are significantly affected by temperature changes. In black liquor production concentration systems, unstable steam pressure and flow rate can lead to fluctuations in the black liquor concentration process within evaporator 2, affecting the consistency of product quality. Therefore, saturated steam has better heat exchange performance than superheated steam during black liquor concentration. Saturated steam releases a large amount of latent heat upon condensation, which can be transferred to the black liquor more efficiently, promoting the evaporation of water and thus improving concentration efficiency.

[0043] Furthermore, when superheated steam comes into contact with equipment surfaces, the high temperature can easily cause scaling and corrosion, especially in critical equipment such as steam channels and evaporators. When the steam superheat decreases and becomes saturated, the moisture content in the steam becomes relatively stable, reducing the likelihood of scale formation caused by impurities left behind due to rapid evaporation of moisture at high temperatures.

[0044] The input end of the second steam pipe 04 is connected to the steam output end of the black liquor channel, and the output end of the second steam pipe 04 is connected to the second output end of the first steam pipe 01.

[0045] The second steam pipe 04 connects the steam output end of the black liquor channel to the second output end of the first steam pipe 01, enabling the secondary steam generated during the heating and concentration of black liquor in the black liquor channel of the evaporator 2 to be effectively collected and reintroduced into the system's steam cycle. Previously, direct discharge of this secondary steam would have resulted in heat waste; now, it can participate again in the heating process of the cooking pot 1 as supplementary steam, reducing reliance on the fresh steam generated by the steam generator 3.

[0046] Steam recycling is achieved through the second steam pipe 04, which reduces the system's need for large and frequent inputs of fresh steam, thereby avoiding drastic changes in equipment thermal stress caused by frequent introduction of fresh steam.

[0047] The first input end of the first black liquor pipe 03 is connected to the black liquor output end of the cooking pot 1, the second input end of the first black liquor pipe 03 is connected to the black liquor output end of the black liquor channel, the first output end of the first black liquor pipe 03 is connected to the black liquor input end of the black liquor channel, and the second output end of the first black liquor pipe 03 is connected to the black liquor discharge system 5.

[0048] A portion of the black liquor can flow back from the black liquor outlet to the black liquor inlet, forming an internal circulation path for the black liquor. This circulation mechanism allows the black liquor to undergo multiple concentration processes in evaporator 2, making full use of the heat resources in evaporator 2 and the heat exchange conditions between steam and black liquor to maximize the extraction of useful components and remove moisture from the black liquor, achieving a more efficient concentration effect.

[0049] In traditional black liquor production and concentration systems, if the black liquor is not sufficiently concentrated and is directly discharged into the black liquor discharge system 5, a large amount of usable components in the black liquor will be wasted, and the subsequent treatment of this insufficiently concentrated black liquor is also relatively costly. However, in this system, by rationally controlling the flow direction of the black liquor through the first black liquor pipe 03, the black liquor has the opportunity to circulate within the system, maximizing the utilization of the heat energy in the black liquor, reducing the amount of black liquor directly discharged into the black liquor discharge system 5, reducing the waste of black liquor resources, improving the overall utilization rate of black liquor, and helping enterprises to obtain more valuable products from the black liquor, thereby improving economic benefits.

[0050] The first black liquor pipe 03 is equipped with a circulation pump 05.

[0051] The circulation pump 05 is installed on the first black liquor pipe 03, providing additional power for the flow of black liquor. During the recycling of black liquor, especially when the black liquor output from the black liquor channel is returned to the input end for multiple concentrations, relying solely on gravity or conventional conveying pressure is often insufficient to ensure a stable and efficient circulation. The circulation pump 05 overcomes the effects of pipe resistance and the black liquor's own gravity, allowing the black liquor to circulate smoothly within the system. This ensures that the black liquor undergoes multiple passes through the evaporator 2 for sufficient heat exchange, maximizing the removal of water and achieving a more efficient concentration effect.

[0052] The evaporator 2 includes multiple heat sink groups 21 that are spliced ​​together. The gap between any two adjacent heat sink groups 21 is the black liquid channel, and the internal space of the heat sink group 21 is the steam channel.

[0053] Compared to the relatively simple pipe or cavity structure of traditional evaporators 2, the heat sink assembly 21 of this solution has a large surface area. When steam flows in the steam channel inside the heat sink assembly 21, it can come into contact with the heat sink 22 over a large area. The black liquid flows in the gap between adjacent heat sink assemblies 21 (i.e., the black liquid channel), which also has a sufficient contact area with the heat sink 22, effectively improving the heat dissipation efficiency.

[0054] The heat sink 22 is typically made of a material with excellent thermal conductivity, enabling it to rapidly transfer the heat carried by the steam in the steam channel to the black liquor in the black liquor channel. Furthermore, the close-fitting arrangement of adjacent heat sink assemblies 21 ensures uniform heat transfer throughout the entire evaporator 2 structure, preventing localized heat accumulation or poor conduction. This allows the black liquor to receive heat evenly from the steam as it flows through the black liquor channels, achieving a more stable and efficient heat exchange process, further improving the concentration quality and overall concentration effect of the black liquor.

[0055] The heat sink assembly 21 includes two heat sinks 22 that are attached to each other and arranged opposite each other. Each heat sink 22 includes a plurality of regularly arranged welded portions 23 and protrusions 24. The welded portions 23 of two adjacent heat sinks 22 are fixedly connected. The protrusions 24 of two adjacent heat sinks 22 form the steam channel.

[0056] Reference Figure 2 A steam channel is formed between the two protrusions 24, with the blue arrow indicating the flow direction of the condensate; a black liquor channel is formed between the two heat sinks 22, with the red arrow indicating the flow direction of the secondary steam and the black arrow indicating the flow direction of the concentrated black liquor.

[0057] The presence of the protrusion 24 creates localized narrow spaces and velocity variation zones within the steam channel. When steam flows through these zones, strong thermal convection occurs. This convection allows for a more uniform distribution of heat within the steam, preventing the formation of localized overheated or undercooled areas and ensuring that heat is transferred more comprehensively and stably to the entire surface of the heat sink 22. Simultaneously, this thermal convection further enhances heat exchange between the steam and the heat sink 22, enabling the black liquor to absorb sufficient heat in a shorter time, increasing the evaporation rate of the black liquor, and thus improving the concentration efficiency while reducing the time and energy consumption required for concentration.

[0058] Furthermore, adjacent heat sinks 22 are fixedly connected by multiple regularly arranged welded joints 23. This multi-welded connection method makes the structure of the heat sink assembly 21 more stable. Compared with traditional single continuous welding or simple connection methods, multiple dispersed welded joints 23 can better withstand external forces such as steam pressure, black liquor flow impact, and vibration during equipment operation. Under long-term high temperature, high pressure, and high flow rate operating environments, the heat sink assembly 21 is less prone to loosening, deformation, or cracking, ensuring the structural integrity and stability of the evaporator 2, extending the service life of the equipment, reducing the number of production interruptions caused by equipment failure, and improving the continuity and reliability of production.

[0059] The black liquid flows between the two heat exchangers in a planar thin film falling film flow, which has a low probability of scaling. If scaling does occur after long-term operation, it is easy to fall off on its own. Because the black liquid flow channel has a planar structure, cleaning is very convenient.

[0060] The black liquor output end of the cooking pot 1 is provided with a black liquor discharge pipe 06, and the output end of the black liquor discharge pipe 06 is connected to the black liquor discharge system 5.

[0061] On the one hand, the black liquor discharged from the digester 1 can be used as needed, ensuring continuous and orderly production processes and facilitating subsequent black liquor treatment operations. On the other hand, the evaporator 2 can be cleaned as needed at any time without affecting the operation of the digester 1, maintaining a stable internal production environment, reducing interference between systems, and improving the reliability and economy of the black liquor production system.

[0062] The technical principles of this utility model have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of this utility model and should not be construed as limiting the scope of protection of this utility model in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of this utility model without any inventive effort, and these embodiments will all fall within the scope of protection of this utility model.

Claims

1. A system for secondary vapor volatilization, black liquor concentration, and condensate recovery of black liquor, characterized in that, Includes a cooking pot, evaporator, steam generator, and condensate collection device; The evaporator is provided with a black liquor channel and a steam channel, which are spaced apart and not connected to each other within the evaporator. The steam generator is connected to the input end of the steam channel via a first steam pipe, and the output end of the steam channel is connected to the condensate collection device via a first condensate pipe. The black liquor output end of the cooking pot is connected to the input end of the black liquor channel through a first black liquor pipe. The steam output end of the black liquor channel is connected to the steam input end of the cooking pot through a second steam pipe. The black liquor output end of the black liquor channel is connected to the black liquor discharge system.

2. The system for secondary steam volatilization, black liquor concentration, and condensate recovery of black liquor according to claim 1, characterized in that, The input end of the first steam pipe is connected to the steam generating device, the first output end of the first steam pipe is connected to the input end of the steam channel, and the second output end of the first steam pipe is connected to the steam input end of the cooking pot.

3. The system for secondary steam volatilization, black liquor concentration, and condensate recovery of black liquor according to claim 1, characterized in that, The inlet of the first condensate pipe is connected to the outlet of the steam channel, the first outlet of the first condensate pipe is connected to the inlet of the first steam pipe, and the second outlet of the first condensate pipe is connected to the condensate collection device.

4. The system for secondary steam volatilization, black liquor concentration, and condensate recovery of black liquor according to claim 1, characterized in that, The input end of the second steam pipe is connected to the steam output end of the black liquor channel, and the output end of the second steam pipe is connected to the second output end of the first steam pipe.

5. The system for secondary steam volatilization, black liquor concentration, and condensate recovery of black liquor according to claim 1, characterized in that, The first input end of the first black liquor pipe is connected to the black liquor output end of the cooking pot, the second input end of the first black liquor pipe is connected to the black liquor output end of the black liquor channel, the first output end of the first black liquor pipe is connected to the black liquor input end of the black liquor channel, and the second output end of the first black liquor pipe is connected to the black liquor discharge system.

6. The system for secondary steam volatilization, black liquor concentration, and condensate recovery of black liquor according to claim 1, characterized in that, The first black liquor pipe is equipped with a circulation pump.

7. The system for secondary steam volatilization, black liquor concentration, and condensate recovery of black liquor according to claim 1, characterized in that, The evaporator includes multiple interconnected heat sink fin groups, the gap between any two adjacent heat sink fin groups is the black liquid channel, and the internal space of the heat sink fin group is the steam channel.

8. The system for secondary steam volatilization, black liquor concentration, and condensate recovery of black liquor according to claim 7, characterized in that, The heat sink assembly includes two heat sinks that are attached to each other and arranged opposite each other. Each heat sink includes a plurality of regularly arranged welded portions and protrusions. The welded portions of two adjacent heat sinks are fixedly connected. The protrusions of two adjacent heat sinks form the steam channel.

9. The system for secondary steam volatilization, black liquor concentration, and condensate recovery of black liquor according to claim 5, characterized in that, The black liquor output end of the cooking pot is equipped with a black liquor discharge pipe, and the output end of the black liquor discharge pipe is connected to the black liquor discharge system.

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