Waste heat utilization system for black liquor of paper mill

Abstract

A paper mill black liquor waste heat utilization system belongs to the technical field of energy conservation and environmental protection. The utility model solves the problem that the residual heat cannot be effectively utilized due to environmental pollution caused by direct flash evaporation of the black liquor in the existing paper mill. Comprising a reboiler, a demineralized water system, a black liquor system and a positive pressure steam preparation system, the two ends of a heat release pipe in the reboiler are connected with the black liquor system through a liquid supply pipe and a liquid return pipe respectively, a steam-water side inlet in the reboiler is connected with the demineralized water system, and the positive pressure steam preparation system comprises a steam-water separator and a steam compressor. A steam inlet end and a steam outlet end of the steam-water separator are respectively connected with a steam-water side outlet of the reboiler and a steam inlet of the steam compressor through a negative pressure steam pipeline, and a steam outlet of the steam compressor is connected to a process demand point through a positive pressure steam pipeline. According to the utility model, the waste heat of the black liquor in the paper mill can be utilized, high-quality steam is prepared, the waste heat in the black liquor is recovered, and clean steam is generated and applied to the technological process.

Description

Technical Field

[0001] The utility model relates to a black liquor waste heat utilization system for a paper mill, belonging to the technical field of energy conservation and environmental protection. Background Art

[0002] The pulping process of paper mills produces a large amount of medium-temperature (60-90°C) black liquor, which has a huge amount of heat. However, due to its low thermal quality and the particularity of black liquor (such as high concentration, high viscosity, dark color, low pH value, etc., which has certain pollution to the environment), the conventional flash evaporation method is not suitable for the waste heat utilization of black liquor, which will cause the flash steam of black liquor to carry a lot of pollution, and this part of heat cannot be well utilized in other processes of the paper mill. Therefore, there is an urgent need for a waste heat utilization system to better utilize the waste heat of black liquor in paper mills and reduce the pollution to the environment caused by the waste heat utilization process. Utility Model Content

[0003] The utility model is to solve the above technical problems and further provide a system for utilizing waste heat of black liquor in a paper mill.

[0004] The technical solution adopted by the utility model to solve the above technical problems is:

[0005] A paper mill black liquor waste heat utilization system comprises a reboiler, a desalted water system, a black liquor system and a positive-pressure steam production system, wherein both ends of a heat release tube in the reboiler are connected to the black liquor system via a liquid supply pipe and a liquid return pipe respectively, a steam-water side inlet in the reboiler is connected to the desalted water system, and the positive-pressure steam production system comprises a steam-water separator and a steam compressor, the steam inlet and steam outlet of the steam-water separator are respectively connected to the steam-water side outlet of the reboiler and the steam inlet of the steam compressor via a negative-pressure steam pipeline, and the steam outlet of the steam compressor is connected to a process demand point via a positive-pressure steam pipeline.

[0006] Furthermore, a desalted water pump group is provided on the connecting pipeline between the desalted water system and the steam-water side inlet of the reboiler.

[0007] Furthermore, an automatic constant pressure regulating valve is provided on the connecting pipeline between the desalted water pump group and the steam-water side inlet of the reboiler.

[0008] Furthermore, a first pressure gauge is provided on the connecting pipeline between the desalted water pump group and the steam-water side inlet of the reboiler.

[0009] Furthermore, a steam buffer tank is connected to the positive pressure steam pipeline.

[0010] Furthermore, a second pressure gauge is provided on the positive pressure steam pipeline between the steam compressor and the steam buffer tank.

[0011] Furthermore, a third pressure gauge is provided on the negative pressure steam pipeline between the steam-water separator and the steam compressor.

[0012] Furthermore, thermal resistors are respectively arranged on the connecting pipeline between the desalted water pump group and the steam-water side inlet of the reboiler, on the negative pressure steam pipeline between the steam-water separator and the steam compressor, and on the positive pressure steam pipeline.

[0013] Furthermore, a steam inlet valve is provided on the negative pressure steam pipeline between the steam-water side outlet of the reboiler and the steam-water separator.

[0014] Furthermore, a main steam valve and a one-way valve are provided on the positive-pressure steam pipeline between the steam buffer tank and the process demand point.

[0015] Compared with the prior art, the utility model has the following effects:

[0016] Through the paper mill black liquor waste heat utilization system of the utility model, after desalted water and black liquor are used for heat exchange, flash evaporation occurs in a negative pressure environment maintained by a steam compressor, and positive pressure steam is formed after multi-stage compression by the steam compressor. While realizing the waste heat utilization of the paper mill black liquor, high-quality steam can be produced, the waste heat in the black liquor can be recovered and clean steam can be generated for use in the process flow. Compared with the existing technology, the effective recovery and application of the waste heat of the black liquor is better realized, and the economic benefits of the paper mill are effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the system composition of the utility model.

[0018] In the figure:

[0019] 1. Reboiler; 2. Desalted water system; 3. Black liquor system; 4. Positive pressure steam production system; 4-1. Steam-water separator; 4-2. Steam compressor; 5. Liquid supply pipe; 6. Liquid return pipe; 7. Process demand point; 8. Desalted water pump group; 9. Automatic constant pressure regulating valve; 10. First pressure gauge; 11. Steam buffer tank; 12. Second pressure gauge; 13. Third pressure gauge. DETAILED DESCRIPTION

[0020] Specific implementation method 1: Combination Figure 1 This implementation mode is explained by clearly and completely describing the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, rather than all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the utility model.

[0021] It should be noted that the descriptions of the present invention regarding directions such as "left", "right", "left side", "right side", "upper", "lower", "top", "bottom", etc. are all defined based on the relationship between the orientations or positions shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the structure described must be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention. In the description of the present invention, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0022] In the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0023] A paper mill black liquor waste heat utilization system comprises a reboiler 1, a desalted water system 2, a black liquor system 3 and a positive-pressure steam production system 4, wherein both ends of the heat release tube in the reboiler 1 are connected to the black liquor system 3 through a liquid supply pipe 5 and a liquid return pipe 6 respectively, the steam-water side inlet in the reboiler 1 is connected to the desalted water system 2, the positive-pressure steam production system 4 comprises a steam-water separator 4-1 and a steam compressor 4-2, the steam inlet and steam outlet of the steam-water separator 4-1 are respectively connected to the steam-water side outlet of the reboiler 1 and the steam inlet of the steam compressor 4-2 through a negative-pressure steam pipeline, and the steam outlet of the steam compressor 4-2 is connected to a process demand point 7 through a positive-pressure steam pipeline.

[0024] Through the paper mill black liquor waste heat utilization system of the utility model, after desalted water and black liquor are used for heat exchange, flash evaporation occurs in the negative pressure environment maintained by the steam compressor 4-2, and positive pressure steam is formed after multi-stage compression by the steam compressor. It can realize the waste heat utilization of the black liquor in the paper mill, produce high-quality steam, recover the waste heat in the black liquor and generate clean steam for use in the process flow. Compared with the existing technology, it better realizes the effective recovery and application of the waste heat of the black liquor, and effectively improves the economic benefits of the paper mill.

[0025] The desalted water system 2 and the black liquor system 3 are both prior art and will not be described in detail here.

[0026] The process flow of the paper mill black liquor waste heat utilization system described in the utility model is as follows:

[0027] 1. Black liquor process:

[0028] The medium-low temperature black liquor from the evaporation tower in the black liquor system 3 enters the heat release pipe in the reboiler 1 through the liquid supply pipe 5, exchanges heat with the cold water on the other side of the heat exchange surface, that is, with the demineralized water on the steam-water side, and then the temperature is reduced and flows back to the black liquor system 3 through the liquid return pipe 6;

[0029] 2. Desalted water and negative pressure steam process:

[0030] The desalted water from the desalted water system 2 enters the steam-water side of the reboiler 1, flashes through the negative pressure environment generated by the steam compressor 4-2, and the desalted water generates negative pressure steam. The negative pressure steam after steam-water separation in the steam-water separator 4-1 enters the steam compressor 4-2;

[0031] 3. Positive pressure steam process:

[0032] After the negative pressure steam enters the steam compressor 4-2, it is compressed in multiple stages to continuously increase the saturation point of the negative pressure steam to positive pressure steam, and then transported to the process demand point 7 as production steam.

[0033] A desalted water pump group 8 is provided on the connecting pipeline between the desalted water system 2 and the steam-water side inlet of the reboiler 1. Such a design facilitates the delivery of desalted water to the steam-water side of the negative pressure reboiler 1. The specific structure of the desalted water pump group 8 is prior art and will not be described in detail here.

[0034] An automatic constant pressure regulating valve 9 is provided on the connecting pipeline between the desalted water pump group 8 and the steam-water side inlet of the reboiler 1. With such a design, the water pressure entering the steam-water side of the negative pressure reboiler 1 is strictly controlled.

[0035] A first pressure gauge 10 is also provided on the connecting pipeline between the desalted water pump group 8 and the steam-water side inlet of the reboiler 1. Such a design facilitates monitoring of the water pressure entering the steam-water side of the reboiler 1, and further facilitates strict control of the water pressure entering the steam-water side of the negative pressure reboiler 1.

[0036] The positive pressure steam pipeline is connected with a steam buffer tank 11. In this design, by setting the steam buffer tank 11 on the positive pressure steam pipeline sent to the process demand point 7, the pressure stabilization and steam storage of the positive pressure steam are achieved, which is further convenient for subsequent production steam.

[0037] A second pressure gauge 12 is provided on the positive pressure steam pipeline between the steam compressor 4-2 and the steam buffer tank 11. Such a design facilitates monitoring the pressure of the positive pressure steam discharged from the steam compressor 4-2.

[0038] A third pressure gauge 13 is provided on the negative pressure steam pipeline between the steam-water separator 4-1 and the steam compressor 4-2. Such a design facilitates monitoring the negative pressure steam pressure entering the steam compressor 4-2.

[0039] Thermal resistors are provided on the connecting pipeline between the desalted water pump group 8 and the steam-water side inlet of the reboiler 1, on the negative pressure steam pipeline between the steam-water separator 4-1 and the steam compressor 4-2, and on the positive pressure steam pipeline. Such a design enables the temperature monitoring of the desalted water, negative pressure steam or positive pressure steam in each pipeline.

[0040] A steam inlet valve is provided on the negative pressure steam pipeline between the steam-water side outlet of the reboiler 1 and the steam-water separator 4-1. Such a design facilitates the control of the steam inlet of the negative pressure steam in the steam-water separator 4-1.

[0041] A main steam valve and a one-way valve are provided on the positive pressure steam pipeline between the steam buffer tank 11 and the process demand point 7. Such a design facilitates the control of the positive pressure steam inlet in the process demand point 7.

[0042] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes within the technical scope disclosed by the present invention according to the technical scheme and the utility model concept of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A paper mill black liquor waste heat utilization system, characterized by: The invention comprises a reboiler (1), a desalted water system (2), a black liquor system (3) and a positive pressure steam production system (4), wherein the two ends of the heat release pipe in the reboiler (1) are respectively connected to the black liquor system (3) through a liquid supply pipe (5) and a liquid return pipe (6), and the steam-water side inlet in the reboiler (1) is connected to the desalted water system (2). The positive pressure steam production system (4) comprises a steam-water separator (4-1) and a steam compressor (4-2), wherein the steam inlet and the steam outlet of the steam-water separator (4-1) are respectively connected to the steam-water side outlet of the reboiler (1) and the steam inlet of the steam compressor (4-2) through a negative pressure steam pipeline, and the steam outlet of the steam compressor (4-2) is connected to a process demand point (7) through a positive pressure steam pipeline.

2. A paper mill black liquor waste heat utilization system according to claim 1, characterized in that: A desalted water pump group (8) is provided on the connecting pipeline between the desalted water system (2) and the steam-water side inlet of the reboiler (1).

3. The paper mill black liquor waste heat utilization system according to claim 2, characterized in that: An automatic constant pressure regulating valve (9) is provided on the connecting pipeline between the desalted water pump group (8) and the steam-water side inlet of the reboiler (1).

4. The paper mill black liquor waste heat utilization system according to claim 3, characterized in that: A first pressure gauge (10) is also provided on the connecting pipeline between the desalted water pump group (8) and the steam-water side inlet of the reboiler (1).

5. The paper mill black liquor waste heat utilization system according to claim 1, characterized in that: A steam buffer tank (11) is connected to the positive pressure steam pipeline.

6. The paper mill black liquor waste heat utilization system according to claim 5, characterized in that: A second pressure gauge (12) is provided on the positive pressure steam pipeline between the steam compressor (4-2) and the steam buffer tank (11).

7. The paper mill black liquor waste heat utilization system according to claim 1, characterized in that: A third pressure gauge (13) is provided on the negative pressure steam pipeline between the steam-water separator (4-1) and the steam compressor (4-2).

8. The paper mill black liquor waste heat utilization system according to claim 2, characterized in that: Thermal resistors are respectively arranged on the connecting pipeline between the desalted water pump group (8) and the steam-water side inlet of the reboiler (1), on the negative pressure steam pipeline between the steam-water separator (4-1) and the steam compressor (4-2), and on the positive pressure steam pipeline.

9. The paper mill black liquor waste heat utilization system according to claim 1, characterized in that: A steam inlet valve is provided on the negative pressure steam pipeline between the steam-water side outlet of the reboiler (1) and the steam-water separator (4-1).

10. The paper mill black liquor waste heat utilization system according to claim 5, characterized in that: A main steam valve and a one-way valve are provided on the positive pressure steam pipeline between the steam buffer tank (11) and the process demand point (7).

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