A ferric nitrate solution evaporation system and evaporation process thereof

Abstract

The present invention belongs to the technical field of lithium iron phosphate preparation, and specifically relates to an evaporation system for an iron nitrate solution and an evaporation process thereof. The technical key points are as follows: a preheating unit, an evaporation unit and a product collection unit connected in sequence; the evaporation unit includes a two-stage falling film evaporation and a transition falling film evaporation; the two-stage falling film evaporation is composed of a first-stage falling film heater, a second-effect falling film heater and a second-effect falling film separation chamber connected in series in sequence; the transition falling film evaporation is composed of a transition falling film heat exchanger, a transition falling film evaporation chamber and a second-stage compression connected in series in sequence; the discharge port of the second-effect falling film separation chamber is connected to the shell-side feed port of the transition falling film heat exchanger, the tube-side discharge port of the transition falling film heat exchanger is connected to the feed port of the transition falling film evaporation chamber, the discharge port of the transition falling film evaporation chamber is connected to the second-stage compression, and the second-stage compression is connected to the shell-side feed port of the second-effect falling film heater.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to a ferric nitrate solution evaporation system and an evaporation process thereof. Background Art

[0002] In industrial production, in order to strengthen the recycling of industrial water, improve water efficiency and prevent industrial pollution, the problem of treating saline wastewater is often encountered, such as treating ferric nitrate wastewater. In the process of treating ferric nitrate wastewater, it is necessary to concentrate the ferric nitrate wastewater to reduce the cost of subsequent crystallization, salt separation or storage.

[0003] Since ferric nitrate is acidic, ordinary evaporation and concentration processes are prone to cause equipment corrosion, explosion and other problems. In addition, conventional evaporators use fresh steam produced by boilers as a heat source, and heat the solution to boiling point through a heat exchanger and continue to heat the solution to boil and evaporate to produce secondary steam. The water in the solution turns into water vapor and evaporates from the solution, and the solution itself is concentrated. The secondary steam generated during the evaporation process is then condensed into condensed water using cooling water. The heat energy in the secondary steam is transferred to the cooling water and then diffused into the air, causing heat energy waste and cooling water consumption. The MVR evaporator uses a compressor to compress the secondary steam generated by the evaporator to increase its pressure and temperature, and then use it as the heat source of the evaporator to replace fresh steam. The heat energy in the secondary steam is reused, and the heat energy of the evaporator is recycled.

[0004] However, due to the large boiling point rise of the ferric nitrate solution, the overall efficiency of the overall evaporation process of the MVR evaporator is too low to meet the needs of industrial production.

[0005] In view of the defects in the existing ferric nitrate wastewater treatment technology, the inventor, based on many years of rich practical experience and professional knowledge in the design and manufacture of such materials, and in conjunction with the application of theory, actively conducts research and innovation in order to create a ferric nitrate solution evaporation system and evaporation process. After continuous research and design, and repeated trial samples and improvements, the present invention with real practical value was finally created. Summary of the invention

[0006] The first object of the present invention is to provide a ferric nitrate solution evaporation system, which effectively improves the overall efficiency of the evaporator and reduces the cost.

[0007] The above technical objectives of the present invention are achieved through the following technical solutions:

[0008] The present invention provides a ferric nitrate solution evaporation system, comprising a preheating unit, an evaporation unit and a product collection unit connected in sequence;

[0009] The evaporation unit includes two-stage falling film evaporation and transition falling film evaporation;

[0010] The 2-stage falling film evaporation is composed of a first-stage falling film heater, a second-effect falling film heater and a second-effect falling film separation chamber connected in series;

[0011] The transition falling film evaporation is composed of a transition falling film heat exchanger, a transition falling film evaporation chamber and a secondary compression in series;

[0012] The discharge port of the II effect falling film separation chamber is connected to the shell side feed port of the transition falling film heat exchanger, the tube side discharge port of the transition falling film heat exchanger is connected to the feed port of the transition falling film evaporation chamber, the discharge port of the transition falling film evaporation chamber is connected to the secondary compression, and the secondary compression is connected to the shell side feed port of the II effect falling film heater.

[0013] Furthermore, the preheating unit includes a first-stage plate preheater, a second-stage plate preheater and a third-stage plate preheater. The tube-side discharge port of the first-stage plate preheater is connected to the tube-side feed port of the second-stage plate preheater, the tube-side discharge port of the second-stage plate preheater is connected to the tube-side feed port of the third-stage plate preheater, and the tube-side discharge port of the third-stage plate preheater is connected to the tube-side feed port of the first-stage falling film heater.

[0014] Furthermore, the tube-side discharge port of the first-effect falling film heater is connected to the tube-side feed port of the II-effect falling film heater, and the tube-side discharge port of the II-effect falling film heater is connected to the product collection unit; the tube-side discharge ports of the first-effect falling film heater and the II-effect falling film heater are connected to the feed port of the II-effect falling film separation chamber.

[0015] Furthermore, the shell side feed port of the first-stage falling film heater is connected to the external fresh steam.

[0016] Furthermore, the tube-side feed port of the transition falling film heat exchanger is connected to the discharge port of the condensate tank, and the shell-side discharge port of the transition falling film heat exchanger is connected to the feed port of the condensate tank.

[0017] Furthermore, the shell side outlets of the first-stage falling film heater and the second-effect falling film heater are connected to the feed inlet of the condensed water tank.

[0018] The second object of the present invention is to provide a ferric nitrate solution evaporation process, which has the same technical effect.

[0019] The above technical objectives of the present invention are achieved through the following technical solutions:

[0020] The present invention provides a ferric nitrate solution evaporation process, comprising the following steps:

[0021] S1, heating the ferric nitrate solution to boiling point through a preheating unit;

[0022] S2, passing the ferric nitrate solution heated to boiling point into an evaporation unit to obtain a concentrated solution;

[0023] S3. The concentrated liquid enters the product collection unit.

[0024] Further, the ferric nitrate solution evaporation process comprises the following steps:

[0025] In step S2, the ferric nitrate solution heated to the boiling point first enters the first-stage falling film heater for heating to obtain the first-stage concentrated solution; the first-stage concentrated solution enters the second-effect falling film heater for heating by the pressure difference to obtain the concentrated solution.

[0026] Furthermore, in the evaporation process of the ferric nitrate solution of the present invention, in step S2, the ferric nitrate solution heated to the boiling point enters the first-effect falling film heater, the raw material in the tube of the first-effect falling film heater exchanges heat with the heating steam outside the tube to make the raw material boil and evaporate, the concentrated liquid enters the second-effect falling film heater by pressure difference, the water vapor generated by evaporation of the first-effect falling film heater and the second-effect falling film heater entrains part of the droplets and enters the second-effect falling film separation chamber, the second-effect falling film separation chamber separates and removes the droplets in the water vapor from the steam to form secondary steam a, the secondary steam enters the transition falling film heat exchanger, the pure water in the tube of the transition falling film heat exchanger is heated and vaporized, generating secondary steam b which enters the secondary compression, the saturation temperature of the steam increases after the secondary compression, and enters the shell of the second-effect falling film heater to heat the material.

[0027] Further, in the ferric nitrate solution evaporation process of the present invention, the temperature of the secondary steam b is determined by the following calculation model:

[0028] T1=(W1 / W2)·(C2 / C1)·T;

[0029] Wherein, T1 is the temperature of secondary steam b, in °C, W1 and W2 are the concentration of iron ions in the raw material and the concentration of iron ions in the discharge, in %, C1 and C2 are the boiling points of the raw material and the discharge, in °C, and T is the temperature of secondary steam a, in °C.

[0030] In the evaporation process provided by the present invention, after the heat of the secondary steam a is recovered by transition falling film evaporation, a large amount of secondary steam b is generated. However, the temperature of the secondary steam b will drop. If the temperature of the secondary steam b is too low, the burden of the secondary compression will be too heavy, thereby increasing energy consumption. If the temperature of the secondary steam b is too high, the purpose of obtaining a large amount of steam cannot be achieved, thereby also increasing energy consumption.

[0031] Therefore, in the present invention, the boiling point rise of the ferric nitrate solution and the feed and discharge amounts of ferric nitrate are used to limit the temperature of the secondary steam b, thereby providing more steam while reducing the burden of the secondary compression, thereby further reducing energy consumption and improving the overall efficiency of evaporation.

[0032] In summary, the present invention has the following beneficial effects:

[0033] The evaporation system provided by the present invention is composed of two-stage falling film plus transition falling film evaporation, and adopts two-stage compression steam compression heating, which is suitable for the concentration or crystallization of materials with high boiling points. At the same time, due to the high concentration and high biological toxicity of industrial wastewater such as ferric nitrate wastewater, it is difficult for general biochemical and chemical methods to meet the emission standards or the treatment cost is too high. The more reasonable process also requires high concentration. The evaporation process provided by the present invention can not only meet the emission standards but also recycle some valuable components to treat industrial wastewater, and can meet the requirements of zero-emission clean production. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the structure of the evaporation system of the present invention.

[0035] Reference numerals

[0036] 11. Primary plate preheater, 12. Secondary plate preheater, 13. Third stage plate preheater, 2. Primary falling film heater, 3. II effect falling film heater, 4. II effect falling film separation chamber, 5. Transition falling film heat exchanger, 6. Transition falling film evaporation chamber, 7. Primary compressor, 8. Secondary compressor, 9. Concentration tank, 10. Condensate tank. DETAILED DESCRIPTION

[0037] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, a ferric nitrate solution evaporation system and evaporation process thereof proposed in accordance with the present invention, its specific implementation method, characteristics and effects are described in detail as follows.

[0038] Example 1: A ferric nitrate solution evaporation system and evaporation process thereof

[0039] A ferric nitrate solution evaporation system, such as Figure 1 As shown, it includes a preheating unit, an evaporation unit and a product collection unit connected in sequence;

[0040] Among them, the preheating unit includes a first-stage plate preheater 11, a second-stage plate preheater 12 and a third-stage plate preheater 13. The tube-side discharge port of the first-stage plate preheater 11 is connected to the tube-side feed port of the second-stage plate preheater 12, the tube-side discharge port of the second-stage plate preheater 12 is connected to the tube-side feed port of the third-stage plate preheater 13, and the tube-side discharge port of the third-stage plate preheater 13 is connected to the tube-side feed port of the first-stage falling film heater 2.

[0041] The evaporation unit includes a two-stage falling film evaporation and a transition falling film evaporation; the two-stage falling film evaporation is composed of a first-stage falling film heater 2, a second-effect falling film heater 3 and a second-effect falling film separation chamber 4 connected in series in sequence; the transition falling film evaporation is composed of a transition falling film heat exchanger 5, a transition falling film evaporation chamber 6 and a second-stage compression connected in series in sequence.

[0042] The tube-side discharge port of the first-stage falling film heater 2 is connected to the tube-side feed port of the II-effect falling film heater 3, and the tube-side discharge port of the II-effect falling film heater 3 is connected to the product collection unit; the shell-side feed port of the first-stage falling film heater 2 is connected to the external fresh steam, and the tube-side discharge ports of the first-stage falling film heater 2 and the II-effect falling film heater 3 are connected to the feed port of the II-effect falling film separation chamber 4; the shell-side discharge ports of the first-stage falling film heater 2 and the II-effect falling film heater 3 are connected to the feed port of the condensed water tank 10.

[0043] The discharge port of the II effect falling film separation chamber 4 is connected to the shell side feed port of the transition falling film heat exchanger 5, the tube side discharge port of the transition falling film heat exchanger 5 is connected to the feed port of the transition falling film evaporation chamber 6, the discharge port of the transition falling film evaporation chamber 6 is connected to the secondary compression, and the secondary compression is connected to the shell side feed port of the II effect falling film heater 3. Specifically, the secondary compression includes a primary compressor 7 and a secondary compressor 8 connected in series.

[0044] The product collection unit comprises three concentration tanks 9 connected in series.

[0045] The present embodiment provides a ferric nitrate solution evaporation process, comprising the following steps:

[0046] S1, 70℃ concentration of Fe 3+ The 9% iron nitrate solution is filtered by the previous process pump and sent to the feed tank. It is pressurized by the feed pump and then enters the preheating unit to be heated to 96°C. The feed rate is 11.255 t / h.

[0047] S2, the ferric nitrate solution obtained in step S1 enters the first-stage falling film heater 2, the raw material in the tube of the first-stage falling film heater 2 exchanges heat with the heating steam outside the tube to make the raw material boil and evaporate, the boiling point of the concentrated liquid increases by 2.5°C, and enters the second-effect falling film heater 3 by pressure difference, the water vapor generated by the evaporation of the first-stage falling film heater 2 and the second-effect falling film heater 3 entrains part of the droplets into the second-effect falling film separation chamber 4, the second-effect falling film separation chamber 4 separates and removes the droplets in the water vapor from the steam to form secondary steam a with a temperature of 60°C, the secondary steam a enters the transition falling film heat exchanger 5, the pure water in the tube side of the transition falling film heat exchanger 5 is heated and vaporized to generate secondary steam b with a temperature of 56°C, and enters the second-stage compression, the steam saturation temperature after the second-stage compression is increased to 108°C, and enters the shell layer of the second-effect falling film heater 3 to heat the material;

[0048] S3, the concentrated liquid enters the product collection unit, and the Fe 3+ The content is 13.45%, the output is 9.17 t / h, and the boiling point of the solution increases by 22°C.

[0049] Example 2: A ferric nitrate solution evaporation system and evaporation process thereof

[0050] The ferric nitrate solution evaporation system provided in this embodiment is the same as that in embodiment 1.

[0051] The ferric nitrate solution evaporation process provided in this embodiment includes the following steps:

[0052] S1, 70℃ concentration of Fe 3+ The 9% iron nitrate solution is filtered by the previous process pump and sent to the feed tank. It is pressurized by the feed pump and then enters the preheating unit to be heated to 96°C. The feed rate is 11.255 t / h.

[0053] S2, the ferric nitrate solution obtained in step S1 enters the first-stage falling film heater 2, the raw material in the tube of the first-stage falling film heater 2 exchanges heat with the heating steam outside the tube to make the raw material boil and evaporate, the boiling point of the concentrated liquid increases by 2.5°C, and enters the second-effect falling film heater 3 by pressure difference, the water vapor generated by the evaporation of the first-stage falling film heater 2 and the second-effect falling film heater 3 entrains part of the droplets into the second-effect falling film separation chamber 4, the second-effect falling film separation chamber 4 separates and removes the droplets in the water vapor from the steam to form secondary steam a with a temperature of 60°C, the secondary steam a enters the transition falling film heat exchanger 5, the pure water in the tube side of the transition falling film heat exchanger 5 is heated and vaporized to generate secondary steam b with a temperature of 58°C, and enters the second-stage compression, the steam saturation temperature after the second-stage compression is increased to 108°C, and enters the shell layer of the second-effect falling film heater 3 to heat the material;

[0054] S3, the concentrated liquid enters the product collection unit, and the Fe 3+ The content is 13.45%, the output is 9.17 t / h, and the boiling point of the solution increases by 22°C.

[0055] Among them, the temperature of secondary steam b is calculated by the formula T1=(W1 / W2)·(C2 / C1)·T, where T1 is the temperature of secondary steam b, the unit is ℃, W1 and W2 are the concentration of iron ions in the raw material and the concentration of iron ions in the discharge, respectively, the unit is %, C1 and C2 are the boiling points of the raw material and the discharge, respectively, the unit is ℃, and T is the temperature of secondary steam a, the unit is ℃.

[0056] Comparative Example 1: A ferric nitrate solution evaporation system and evaporation process thereof

[0057] A ferric nitrate solution evaporation system comprises a preheating unit, an evaporation unit and a product collection unit which are connected in sequence;

[0058] Among them, the preheating unit includes a first-stage plate preheater 11, a second-stage plate preheater 12 and a third-stage plate preheater 13. The tube-side discharge port of the first-stage plate preheater 11 is connected to the tube-side feed port of the second-stage plate preheater 12, the tube-side discharge port of the second-stage plate preheater 12 is connected to the tube-side feed port of the third-stage plate preheater 13, and the tube-side discharge port of the third-stage plate preheater 13 is connected to the tube-side feed port of the first-stage falling film heater 2.

[0059] The evaporation unit comprises a two-stage falling film evaporation, which is composed of a first-stage falling film heater 2, a second-effect falling film heater 3 and a second-effect falling film separation chamber 4 connected in series in sequence.

[0060] The tube-side discharge port of the first-stage falling film heater 2 is connected to the tube-side feed port of the II-effect falling film heater 3, and the tube-side discharge port of the II-effect falling film heater 3 is connected to the product collection unit; the shell-side feed port of the first-stage falling film heater 2 is connected to the external fresh steam, and the shell-side discharge ports of the first-stage falling film heater 2 and the II-effect falling film heater 3 are connected to the feed port of the II-effect falling film separation chamber 4; the shell-side discharge ports of the first-stage falling film heater 2 and the II-effect falling film heater 3 are connected to the feed port of the condensed water tank 10.

[0061] The discharge port of the II effect falling film separation chamber 4 is connected to the secondary compressor, and the secondary compressor is connected to the shell side feed port of the II effect falling film heater. Specifically, the secondary compressor includes a primary compressor 7 and a secondary compressor 8 connected in series.

[0062] The product collection unit comprises three concentration tanks 9 connected in series.

[0063] S1, 70℃ concentration of Fe 3+ The 9% iron nitrate solution is filtered by the previous process pump and sent to the feed tank. It is pressurized by the feed pump and then enters the preheating unit to be heated to 96°C. The feed rate is 11.255 t / h.

[0064] S2, the ferric nitrate solution obtained in step S1 enters the first-stage falling film heater 2, the raw material in the tube of the first-stage falling film heater 2 exchanges heat with the heating steam outside the tube to make the raw material boil and evaporate, the boiling point of the concentrated liquid increases by 2.5°C, and enters the second-effect falling film heater 3 by pressure difference, the water vapor generated by the evaporation of the first-stage falling film heater 2 and the second-effect falling film heater 3 entrains part of the droplets into the second-effect falling film separation chamber 4, the second-effect falling film separation chamber 4 separates and removes the droplets in the water vapor from the steam to form secondary steam a, the temperature of which is 60°C, the secondary steam a enters the second-stage compression, the steam saturation temperature after the second-stage compression increases to 108°C, and enters the shell layer of the second-effect falling film heater 3 to heat the material;

[0065] S3, the concentrated liquid enters the product collection unit, and the Fe 3+The content is 13.45%, the output is 9.17 t / h, and the boiling point of the solution increases by 22°C.

[0066] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been presented as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A ferric nitrate solution evaporation system, characterized in that: It includes a preheating unit, an evaporation unit and a product collection unit connected in sequence; The evaporation unit comprises a two-stage falling film evaporation and a transition falling film evaporation; The two-stage falling film evaporation is composed of a first-stage falling film heater, a second-effect falling film heater and a second-effect falling film separation chamber connected in series; The transition falling film evaporation is composed of a transition falling film heat exchanger, a transition falling film evaporation chamber and a secondary compression in series; The discharge port of the II effect falling film separation chamber is connected to the shell side feed port of the transition falling film heat exchanger, the tube side discharge port of the transition falling film heat exchanger is connected to the feed port of the transition falling film evaporation chamber, the discharge port of the transition falling film evaporation chamber is connected to the secondary compression, and the secondary compression is connected to the shell side feed port of the II effect falling film heater; The tube side discharge port of the primary falling film heater is connected to the tube side feed port of the II effect falling film heater, and the tube side discharge port of the II effect falling film heater is connected to the product collection unit; the tube side discharge ports of the primary falling film heater and the II effect falling film heater are connected to the feed port of the II effect falling film separation chamber; The shell side feed port of the first-stage falling film heater is connected to the external fresh steam; The tube-side feed port of the transition falling film heat exchanger is connected to the discharge port of the condensed water tank, and the shell-side discharge port of the transition falling film heat exchanger is connected to the feed port of the condensed water tank.

2. A ferric nitrate solution evaporation system according to claim 1, characterized in that: The preheating unit comprises a primary plate preheater, a secondary plate preheater and a tertiary plate preheater, the tube side discharge port of the primary plate preheater is connected to the tube side feed port of the secondary plate preheater, the tube side discharge port of the secondary plate preheater is connected to the tube side feed port of the tertiary plate preheater, and the tube side discharge port of the tertiary plate preheater is connected to the tube side feed port of the primary falling film heater.

3. A ferric nitrate solution evaporation system according to claim 1, characterized in that: The shell side outlets of the first-stage falling film heater and the second-effect falling film heater are connected to the feed inlet of the condensed water tank.

4. A ferric nitrate solution evaporation process, using the ferric nitrate solution evaporation system according to any one of claims 1 to 3, characterized in that: The steps are as follows: S1, heating the ferric nitrate solution to boiling point through a preheating unit; S2, passing the ferric nitrate solution heated to boiling point into an evaporation unit to obtain a concentrated solution; S3. The concentrated liquid enters the product collection unit.

5. A ferric nitrate solution evaporation process according to claim 4, characterized in that: The steps are as follows: In step S2, the ferric nitrate solution heated to the boiling point first enters the first-stage falling film heater for heating to obtain the first-stage concentrated solution; the first-stage concentrated solution enters the second-effect falling film heater for heating by the pressure difference to obtain the concentrated solution.

6. A ferric nitrate solution evaporation process according to claim 5, characterized in that: In step S2, the ferric nitrate solution heated to the boiling point enters the first-stage falling film heater, the raw material in the tube of the first-stage falling film heater exchanges heat with the heating steam outside the tube to make the raw material boil and evaporate, and the concentrated liquid enters the second-effect falling film heater by pressure difference, and the water vapor generated by evaporation of the first-stage falling film heater and the second-effect falling film heater carries part of the droplets into the second-effect falling film separation chamber, and the second-effect falling film separation chamber separates and removes the droplets in the water vapor from the steam to form secondary steam a, and the secondary steam a enters the transition falling film heat exchanger, and the pure water in the transition falling film heat exchanger tube is heated and vaporized to generate secondary steam b which enters the secondary compression, and the saturation temperature of the steam increases after the secondary compression, and enters the shell of the second-effect falling film heater to heat the material.

7. A ferric nitrate solution evaporation process according to claim 6, characterized in that: The temperature of the secondary steam b is determined by the following calculation model: T1=(W1 / W2)·(C2 / C1)·T; Wherein, T1 is the temperature of secondary steam b, in °C, W1 and W2 are the concentration of iron ions in the raw material and the concentration of iron ions in the discharge, in %, C1 and C2 are the boiling points of the raw material and the discharge, in °C, and T is the temperature of secondary steam a, in °C.

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