A method for recovering ammonium chloride from an ammonia process desulfurization slurry
By adding ammonium sulfate to the ammonia desulfurization slurry to promote the precipitation of ammonium chloride, the problem of equipment corrosion caused by chloride ions was solved, the separation and recovery of ammonium chloride and the stable operation of the system were achieved, and the economic benefits were improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XIAN THERMAL POWER RES INST CO LTD
- Filing Date
- 2024-01-04
- Publication Date
- 2026-07-07
AI Technical Summary
The high chloride ion content in the ammonia desulfurization slurry leads to equipment corrosion and a decrease in the purity of ammonium sulfate products, affecting the stable operation of the system and economic benefits.
By adding ammonium sulfate to the ammonia desulfurization slurry, ammonium chloride is precipitated and salted out, thus separating and recovering ammonium chloride, reducing the risk of equipment corrosion, and returning ammonium sulfate to the absorption tower to form a closed loop.
It achieves effective separation and recovery of chloride ions, reduces equipment corrosion, ensures stable system operation, increases the purity and economic benefits of ammonium chloride, and requires no additional heat source or waste treatment.
Smart Images
Figure CN117819569B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of desulfurization technology, and in particular to a method for recovering ammonium chloride from ammonia desulfurization slurry. Background Technology
[0002] The large-scale emission of SO2 has caused significant harm to my country's ecological environment, making the control of industrial SO2 emissions imperative. In my country, ammonia-based desulfurization technology exhibits unique advantages compared to other desulfurization methods. This technology uses ammonia water (NH3·H2O) or liquid ammonia of a certain concentration as an absorbent to wash SO2 in the flue gas within the absorption tower, achieving flue gas purification. This technology allows for the resource utilization of SO2, with the resulting desulfurization byproduct being ammonium sulfate, which can be used as agricultural fertilizer, and produces no wastewater or other waste. The ammonia-based desulfurization reaction process is a gas-liquid phase reaction, offering advantages such as low energy consumption, fast reaction rate, high absorbent utilization, and high desulfurization efficiency. Furthermore, ammonia-based desulfurization technology is highly adaptable to coal sulfur content, suitable for coals with sulfur content of 0.3-8% or even higher. Its economic advantages are even more pronounced when applied to medium- and high-sulfur coals; the higher the sulfur content of the coal, the greater the yield of the byproduct ammonium sulfate, and the lower the operating cost per unit of SO2 removed. Simultaneously, boiler costs are reduced due to the use of medium- and high-sulfur coal, resulting in both environmental and economic benefits. However, in ammonia desulfurization processes, there is usually no wastewater discharge outlet. Chlorine from coal combustion and makeup water will remain in the ammonium sulfate slurry as Cl-. - The form of [acid] continuously accumulates and enriches, reaching concentrations of tens of thousands or even over 100,000 mg / L. Under the weakly acidic conditions of ammonia-based desulfurization slurry, high Cl content [is a significant contributor to this process]. - It not only causes severe uniform corrosion of equipment, but also produces localized corrosion such as pitting corrosion and crevice corrosion. At the same time, it reduces the crystallinity of ammonium sulfate and makes the crystal particles smaller. In addition, chloride ions usually precipitate out in the form of ammonium chloride and mix into the ammonium sulfate product, affecting its purity.
[0003] Therefore, Cl in the desulfurization slurry is separated and recovered. - This is of great significance for the efficient, safe and stable operation of ammonia desulfurization systems, as well as for the further promotion and application of this technology. Summary of the Invention
[0004] In view of this, this application aims to provide a method for recovering ammonium chloride from ammonia desulfurization slurry. The method involves adding ammonium sulfate, a byproduct of the ammonia desulfurization process, to the ammonia desulfurization slurry, and obtaining ammonium chloride through salting-out and other processes. This achieves the separation and recovery of chloride ions in the ammonia desulfurization slurry, reducing its corrosion of the desulfurization equipment, and thus ensuring the efficient, safe, and stable operation of the ammonia desulfurization system. Simultaneously, the generated ammonium chloride can be sold as a byproduct, increasing production profits.
[0005] Therefore, a first aspect of this application provides a method for recovering ammonium chloride from an ammonia-based desulfurization slurry, wherein the ammonia-based desulfurization slurry is a saturated solution of ammonium chloride and ammonium sulfate, comprising:
[0006] Ammonium sulfate, a byproduct of the ammonia desulfurization process, is added to the ammonia desulfurization slurry for dissolution to obtain a suspension.
[0007] The suspension was stirred to allow ammonium chloride to fully salt out, resulting in a mixed solution containing ammonium chloride crystals;
[0008] The mixed solution containing ammonium chloride crystals was subjected to solid-liquid separation to obtain a saturated ammonium sulfate solution and ammonium chloride crystals;
[0009] After drying the ammonium chloride crystals, the ammonium chloride product is obtained.
[0010] In some embodiments, the amount of ammonium sulfate product added is 1-5 wt% of the mass of the ammonia desulfurization slurry.
[0011] In some embodiments, the stirring speed is 200-800 r / min, and the stirring time is 0.5-3 h.
[0012] In some embodiments, the temperature of the ammonia desulfurization slurry is 45-55°C.
[0013] In some embodiments, the solid-liquid separation method includes at least one of centrifugal separation and filtration.
[0014] In some embodiments, the drying temperature is 105-120°C, and the drying time is 0.5-3 hours.
[0015] In some embodiments, the drying method includes at least one of vacuum drying, spray drying, and fluidized bed drying.
[0016] In some embodiments, the method for recovering ammonium chloride from ammonia desulfurization slurry further includes: refluxing the saturated ammonium sulfate solution obtained from the solid-liquid separation to the concentration section of the absorption tower in the ammonia desulfurization process.
[0017] In some embodiments, the purity of the ammonium chloride product is 80-95 wt%.
[0018] In some embodiments, the mass ratio of ammonium chloride to ammonium sulfate in the ammonia desulfurization slurry is 1:(30-120).
[0019] The method for recovering ammonium chloride from ammonia desulfurization slurry according to the embodiments of this application can bring at least the following beneficial effects:
[0020] 1. Ammonium sulfate, a byproduct of the ammonia desulfurization process, is added to the ammonia desulfurization slurry. Ammonium chloride is obtained through salting out and other processes. This achieves the separation and recovery of chloride ions in the ammonia desulfurization slurry, reduces its corrosion of the desulfurization equipment, and ensures the efficient, safe and stable operation of the ammonia desulfurization system.
[0021] 2. Ammonium chloride products can be disposed of and sold flexibly. Depending on the N, S, Cl and other element requirements of different types of ammonium sulfate products (GB / T 535-2020), NH4Cl products can be disposed of and sold separately as nitrogen fertilizer or mixed with ammonium sulfate products for disposal and sale together.
[0022] 3. The saturated (NH4)2SO4 liquid is returned to the absorption tower to form a closed loop, eliminating the need for a solidification process.
[0023] 4. The process is short, with no heat or cold loss, and does not require changing the temperature of the operating unit. It is low-cost and easy to implement.
[0024] 5. No secondary wastewater, waste gas, or waste residue is generated, making it environmentally friendly and clean.
[0025] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description
[0026] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings.
[0027] in:
[0028] Figure 1 The flowchart illustrates a method for recovering ammonium chloride from ammonia desulfurization slurry, which is an exemplary embodiment of this application. Detailed Implementation
[0029] The embodiments of this application are described in detail below, with examples of these embodiments illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.
[0030] In the application, the disclosure of the numerical range includes all values throughout the range and the disclosure of further subdivisions of the range, including the endpoints and subranges given for these ranges.
[0031] Unless otherwise specified, all raw materials and equipment involved in the application are those that can be manufactured commercially or by known methods; and all methods involved are conventional methods unless otherwise specified.
[0032] The following describes a method for recovering ammonium chloride from ammonia desulfurization slurry according to an embodiment of this application, with reference to the accompanying drawings.
[0033] This embodiment describes a method for recovering ammonium chloride from ammonia desulfurization slurry, wherein the ammonia desulfurization slurry is a saturated solution of ammonium chloride and ammonium sulfate. For example... Figure 1 As shown, the method includes the following steps:
[0034] S101. The ammonium sulfate product, a by-product of the ammonia desulfurization process, is added to the ammonia desulfurization slurry for dissolution to obtain a suspension.
[0035] In the embodiments of this application, ammonium sulfate is added to the ammonia desulfurization slurry. The purpose is that ammonium chloride has lower solubility than ammonium sulfate. Adding a small amount of ammonium sulfate to the slurry can increase the concentration of ammonium ions in the desulfurization slurry, so that the product of the concentration of ammonium ions and the concentration of chloride ions first exceeds its solubility product, reaching a supersaturated state and thus precipitating out.
[0036] In some embodiments, the mass ratio of ammonium chloride to ammonium sulfate in the ammonia desulfurization slurry is 1:(30-120), including but not limited to 1:30, 1:60, 1:90 or 1:120.
[0037] In some embodiments, the amount of ammonium sulfate added is 1-5 wt% of the mass of the ammonia desulfurization slurry, including but not limited to 1 wt%, 2 wt%, 3 wt%, 4 wt%, or 5 wt%. When the amount of ammonium sulfate added is 1-5 wt% of the mass of the ammonia desulfurization slurry, it effectively promotes the precipitation of ammonium chloride. When it is less than 1%, the ammonium sulfate content in the suspension is too low, and its ability to promote salting out is insufficient; when it is greater than 5%, the ammonium sulfate content in the suspension is too high, which will promote the precipitation of ammonium sulfate and affect the purity of the ammonium chloride product.
[0038] In some embodiments, the temperature of the ammonia desulfurization slurry is 45-55°C, including but not limited to 45°C, 48°C, 50°C, 53°C, or 55°C. Maintaining the temperature of the ammonia desulfurization slurry within this range can accelerate the dissolution of ammonium sulfate, a byproduct of the ammonia desulfurization process, in the slurry. It also provides the necessary salting-out temperature for subsequent salting-out, avoiding the potential increase in energy consumption that might result from introducing additional heat sources.
[0039] S102. Stir the suspension to allow ammonium chloride to fully salt out, resulting in a mixed solution containing ammonium chloride crystals.
[0040] In some embodiments, the stirring speed is 200-800 r / min, including but not limited to 200 r / min, 400 r / min, 600 r / min or 800 r / min. If the stirring speed is too fast, it will not be conducive to the nucleation and growth of ammonium sulfate crystals; if the stirring speed is too slow, it will not be conducive to the dissolution of the added ammonium sulfate.
[0041] In some embodiments, the stirring time is 0.5-3 hours, including but not limited to 0.5 hours, 1 hour, 2 hours or 3 hours.
[0042] S103. The mixed solution containing ammonium chloride crystals is subjected to solid-liquid separation to obtain a saturated ammonium sulfate solution and ammonium chloride crystals.
[0043] In some embodiments, the solid-liquid separation method includes, but is not limited to, at least one of centrifugal separation and filtration.
[0044] S104. After drying the ammonium chloride crystals, the ammonium chloride product is obtained.
[0045] In some embodiments, the drying temperature is 105-120°C, including but not limited to 105°C, 110°C, 115°C, or 120°C.
[0046] In some embodiments, the drying time is 0.5-3 hours, including but not limited to 0.5 hours, 1 hour, 2 hours or 3 hours.
[0047] In some embodiments, the drying method includes at least one of vacuum drying, spray drying, and fluidized bed drying.
[0048] In some embodiments, the method for recovering ammonium chloride from ammonia desulfurization slurry further includes: refluxing the saturated ammonium sulfate solution obtained from solid-liquid separation to the concentration section of the absorption tower in ammonia desulfurization.
[0049] In some embodiments, the purity of the ammonium chloride product is 80-95 wt%, including but not limited to 80 wt%, 85 wt%, 90 wt%, or 95 wt%.
[0050] This application describes a method for recovering ammonium chloride from ammonia desulfurization slurry. Ammonium sulfate, a byproduct of the ammonia desulfurization process, is added to the slurry. After salting out, ammonium chloride is obtained, achieving the separation and recovery of chloride ions in the slurry, reducing its corrosion of the desulfurization equipment, and ensuring the efficient, safe, and stable operation of the ammonia desulfurization system. Simultaneously, the disposal and sale of the ammonium chloride product are flexible. Depending on the N, S, and Cl element requirements (GB / T 535-2020) of different ammonium sulfate products, NH4Cl can be disposed of and sold separately as a nitrogen fertilizer or mixed with ammonium sulfate for disposal and sale together. The saturated (NH4)2SO4 solution is returned to the absorption tower, forming a closed loop, eliminating the need for a solidification process. The entire method is short, with no heat or cold consumption, does not require changes to the operating unit temperature, is low-cost, easy to implement, and generates no secondary wastewater, waste gas, or waste residue, making it environmentally friendly and clean.
[0051] The following non-limiting embodiments further illustrate certain features of the present technology.
[0052] Example 1
[0053] A method for recovering ammonium chloride from ammonia-based desulfurization slurry, wherein the ammonia-based desulfurization slurry is a saturated solution of ammonium chloride and ammonium sulfate, wherein the mass ratio of ammonium chloride to ammonium sulfate is 1:35; and the temperature of the ammonia-based desulfurization slurry is 50°C. The method includes the following steps:
[0054] (1) 1.5g of ammonium sulfate by-product produced by the ammonia desulfurization process (product test composition: N content 20.8wt%, sulfur content 24.2wt%, chlorine content 0.9wt%, the remainder is ammonium sulfate) was added to 100g of ammonia desulfurization slurry for dissolution to obtain a suspension.
[0055] (2) Stir the suspension obtained in step (1) at a speed of 300 r / min for 2 h to allow ammonium chloride to be fully salted out, and obtain a mixed solution containing ammonium chloride crystals.
[0056] (3) Centrifuge the mixed solution containing ammonium chloride crystals obtained in step (2) at a speed of 6000 r / min for 1 min to obtain a saturated ammonium sulfate solution and ammonium chloride crystals.
[0057] (4) The ammonium chloride crystals obtained in step (3) are vacuum dried at 105°C for 0.5 h to obtain the ammonium chloride product.
[0058] The purity of the ammonium chloride product recovered in this embodiment was tested to be 95 wt%.
[0059] Example 2
[0060] This embodiment is basically the same as embodiment 1, except that:
[0061] Methods for recovering ammonium chloride from ammonia desulfurization slurry also include:
[0062] Step (5): The ammonium sulfate saturated solution obtained by centrifugation in step (3) is refluxed to the concentration section of the absorption tower for ammonia desulfurization.
[0063] Example 3
[0064] This embodiment is basically the same as embodiment 1, except that:
[0065] In step (1), the amount of ammonium sulfate, a byproduct of the ammonia desulfurization process, added is 1g.
[0066] The purity of the ammonium chloride product recovered in this embodiment was tested to be 92.7 wt%.
[0067] Example 4
[0068] This embodiment is basically the same as embodiment 1, except that:
[0069] In step (1), the amount of ammonium sulfate, a byproduct of the ammonia desulfurization process, added is 5g.
[0070] The purity of the ammonium chloride product recovered in this embodiment was tested to be 87.2 wt%.
[0071] Example 5
[0072] This embodiment is basically the same as embodiment 1, except that:
[0073] The mass ratio of ammonium chloride to ammonium sulfate in the ammonia desulfurization slurry is 1:120.
[0074] The purity of the ammonium chloride product recovered in this embodiment was tested to be 80 wt%.
[0075] Example 6
[0076] This embodiment is basically the same as embodiment 1, except that:
[0077] The mass ratio of ammonium chloride to ammonium sulfate in the ammonia desulfurization slurry is 1:30.
[0078] The purity of the ammonium chloride product recovered in this embodiment was tested to be 91.1 wt%.
[0079] Example 7
[0080] This embodiment is basically the same as embodiment 1, except that:
[0081] The temperature of the ammonia desulfurization slurry is 45℃.
[0082] The purity of the ammonium chloride product recovered in this embodiment was tested to be 93.6 wt%.
[0083] Example 8
[0084] This embodiment is basically the same as embodiment 1, except that:
[0085] The temperature of the ammonia desulfurization slurry is 55℃.
[0086] The purity of the ammonium chloride product recovered in this embodiment was tested to be 94.1 wt%.
[0087] Example 9
[0088] This embodiment is basically the same as embodiment 1, except that:
[0089] In step (2), the suspension obtained in step (1) is stirred at a speed of 200 r / min for 3 h.
[0090] The purity of the ammonium chloride product recovered in this embodiment was tested to be 90 wt%.
[0091] Example 10
[0092] This embodiment is basically the same as embodiment 1, except that:
[0093] In step (2), the suspension obtained in step (1) is stirred at a speed of 800 r / min for 0.5 h.
[0094] The purity of the ammonium chloride product recovered in this embodiment was tested to be 91.5 wt%.
[0095] In this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.
[0096] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.
Claims
1. A method for recovering ammonium chloride from ammonia desulfurization slurry, wherein the ammonia desulfurization slurry is a saturated solution of ammonium chloride and ammonium sulfate, characterized in that, include: Ammonium sulfate, a byproduct of the ammonia desulfurization process, is added to the ammonia desulfurization slurry for dissolution to obtain a suspension. The suspension was stirred to allow ammonium chloride to fully salt out, resulting in a mixed solution containing ammonium chloride crystals; The mixed solution containing ammonium chloride crystals was subjected to solid-liquid separation to obtain a saturated ammonium sulfate solution and ammonium chloride crystals; After drying the ammonium chloride crystals, an ammonium chloride product is obtained; The amount of ammonium sulfate added is 1-5 wt% of the mass of the ammonia desulfurization slurry; The temperature of the ammonia desulfurization slurry is 45-55℃; In the ammonia desulfurization slurry, the mass ratio of ammonium chloride to ammonium sulfate is 1:(30-120).
2. The method according to claim 1, characterized in that, The stirring speed is 200-800 r / min, and the stirring time is 0.5-3 h.
3. The method according to claim 1, characterized in that, The solid-liquid separation method includes at least one of centrifugal separation and filtration.
4. The method according to claim 1, characterized in that, The drying temperature is 105-120℃, and the drying time is 0.5-3h.
5. The method according to claim 1, characterized in that, The drying method includes at least one of vacuum drying, spray drying, and fluidized bed drying.
6. The method according to any one of claims 1 to 5, characterized in that, The method for recovering ammonium chloride from ammonia desulfurization slurry further includes: The saturated ammonium sulfate solution obtained from the solid-liquid separation is refluxed to the concentration section of the absorption tower for ammonia desulfurization.
7. The method according to claim 1, characterized in that, The purity of the ammonium chloride product is 80-95 wt%.