A device for neutralizing free acid in by-product ammonium sulfate product of ammonia desulfurization
By introducing a neutralizing agent silo and a metering feeder into the ammonium sulfate post-treatment system of the ammonia desulfurization unit, the problem of excessive free acid in the ammonium sulfate by-product of ammonia desulfurization is solved by using solid-liquid phase reaction to neutralize wet ammonium sulfate. This achieves low-cost and efficient neutralization, ensuring that the product quality meets the standards.
Patent Information
- Application Number
- CN202520699743.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-14
- Publication Date
- 2026-07-03
- Estimated Expiration
- 2035-04-14
Smart Images
Figure CN224442975U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of ammonium sulfate post-treatment technology in ammonia desulfurization, specifically to a device for neutralizing free acid in ammonium sulfate by-products of ammonia desulfurization. Background Technology
[0002] Ammonia desulfurization is a desulfurization technology with independent intellectual property rights in my country and is among the world's leading technologies. Since 2003, the ammonia desulfurization process with ammonium sulfate recovery has been rapidly promoted in the field of flue gas treatment for coal-fired boilers in my country. To date, more than 200 units have been put into operation, with an annual by-product ammonium sulfate production exceeding 2 million tons. Ammonia desulfurization uses ammonia as raw material to recover SO2 from flue gas and produce ammonium sulfate as a by-product, without generating secondary pollution. The equipment has high operational flexibility and low operating costs. Therefore, it has been rapidly promoted and applied from the field of flue gas desulfurization for thermal power boilers to the desulfurization of tail gas in the steel and metallurgical industries. In the past five years, coal chemical enterprises have also used it for the deep treatment of CLAUS sulfur recovery tail gas.
[0003] Since 2003, ammonium sulfate produced as a byproduct of ammonia desulfurization has been subject to the DL / T 808-2002 power industry standard, which had relatively low quality requirements, with free acid (calculated as H2SO4 content) not exceeding 2% (w). This standard was abolished in December 2014, and since then, most enterprises have formulated their own enterprise standards based on DL / T 808-2002. Currently, the applicable standards for byproduct ammonium sulfate are the group standard T / CPCIF 0006-2017 "Ammonium Sulfate Produced as a Byproduct of Ammonia Desulfurization" and the national standard GB / T 535-2020 "Fertilizer Grade Ammonium Sulfate". The group standard requires free acid content not to exceed 0.3% (w), while the national standard requires that the free acid content for Type II products not exceed 0.2% (w).
[0004] The capacity for producing ammonium sulfate as a byproduct in ammonia desulfurization units is designed based on the boiler's maximum load and the highest designed sulfur content of the coal. However, the actual operating output is only about 40-50% of the unit's capacity, or even as low as 30%. Secondly, the dust content in the flue gas entering the desulfurization tower can be as high as 50 mg / Nm3. Most ammonia desulfurization processes use an in-tower saturated crystallization process without a slurry filtration stage, resulting in poor quality of the byproduct ammonium sulfate. Generally, the purity of ammonium sulfate is less than 97%, the nitrogen content is less than 20.5%, and the free acid content is mostly between 0.3% and 0.5%, and in some cases, it can even be as high as 1% or more.
[0005] Modern power plants, steel and metallurgical enterprises, and coal chemical enterprises are all equipped with wastewater treatment facilities. Na₂CO₃ is generally used in wastewater treatment to adjust the alkalinity of activated sludge during the denitrification process. Therefore, it is possible to consider using Na₂CO₃ (solid powder) to neutralize the excess free acid in the wet ammonium sulfate after centrifugation and control the free acid content of the finished ammonium sulfate product to 0.10%–0.15%, thereby fundamentally solving the problem of excessive free acid in the ammonium sulfate byproduct of ammonia desulfurization. Utility Model Content
[0006] To achieve the above objectives, this utility model provides the following technical solution: a free acid neutralization device for ammonium sulfate byproduct of ammonia desulfurization, comprising a hydrocyclone, a centrifuge, a neutralizing agent silo, a metering feeder, a feeding screw, a dryer and dust removal equipment, and a finished product storage silo. A centrifuge is located on one side of the hydrocyclone, and a neutralizing agent silo is located on the other side. A metering feeder is located on one side of the neutralizing agent silo, a feeding screw is located on one side of the centrifuge, a dryer and dust removal equipment are located on one side of the feeding screw, and a finished product storage silo is located on one side of the dryer and dust removal equipment.
[0007] As a preferred technical solution of this utility model, the ammonium sulfate slurry from the concentration section of the desulfurization tower is dehydrated by a hydrocyclone and a centrifuge and then fed into a dryer and dust removal equipment by a feeding screw. After being dried by the dryer and dust removal equipment, the ammonium sulfate enters the finished product storage silo by its own weight.
[0008] As a preferred embodiment of this utility model, the neutralizing agent in the neutralizing agent silo is added to the centrifuge via a metering feeder.
[0009] As a preferred embodiment of this invention, the dilute slurry separated by the hydrocyclone and the centrifuge filtrate are returned to the lower concentration section of the desulfurization tower.
[0010] As a preferred technical solution of this utility model, the wet washing liquid of the dryer and dust removal equipment is sent to the upper absorption section of the desulfurization tower.
[0011] Compared with the prior art, the beneficial effects of this utility model are:
[0012] 1. The free acid neutralization device for the ammonium sulfate by-product of ammonia desulfurization makes full use of the existing equipment of the ammonium sulfate post-treatment system of the ammonia desulfurization unit. Only a neutralizing agent silo and a metering feeder are added. The process is simple, the equipment investment is low, the neutralizing agent is widely available, and the operating cost is negligible.
[0013] 2. The free acid neutralization device for the ammonium sulfate byproduct of the ammonia desulfurization process does not affect the operation of the ammonia desulfurization unit and the ammonium sulfate post-treatment system, and has the characteristics of low failure rate and safety and reliability.
[0014] 3. The free acid neutralization device for the ammonium sulfate by-product of ammonia desulfurization involves adding the neutralizing agent to the wet ammonium sulfate after centrifugation and then feeding it into the dryer via a feeding screw. Compared to adding the neutralizing agent to the finished product, theoretically the consumption of neutralizing agent is the same, but the neutralization reaction occurs between the solid and liquid phases. The reaction process is well agitated, has a long residence time, high neutralization efficiency, and good reaction effect, ensuring that the free acid of the by-product ammonium sulfate product can stably meet the standards. Attached Figure Description
[0015] The accompanying drawings are provided to further understand this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof.
[0016] Figure 1 This is a flowchart illustrating the process of this utility model.
[0017] In the diagram: 1. Hydrocyclone; 2. Centrifuge; 3. Neutralizing agent silo; 4. Metering feeder; 5. Feeding screw; 6. Dryer and dust removal equipment; 7. Finished product storage silo. Detailed Implementation
[0018] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0019] 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 application, unless otherwise stated, "multiple" means two or more.
[0020] Example 1
[0021] Please see Figure 1 This utility model provides a technical solution: a free acid neutralization device for ammonium sulfate byproduct of ammonia desulfurization, comprising a hydrocyclone 1, a centrifuge 2, a neutralizing agent silo 3, a metering feeder 4, a feeding screw 5, a dryer and dust removal equipment 6, and a finished product storage silo 7. The neutralizing agent silo 3 and the metering feeder 4 are new additions, while the neutralizing agent silo 3, the metering feeder 4, the feeding screw 5, the dryer and dust removal equipment 6, and the finished product storage silo 7 are existing equipment utilizing the ammonium sulfate post-treatment system of the ammonia desulfurization unit. The ammonium sulfate slurry in the concentration section of the tower is dehydrated by hydrocyclone 1 and centrifuge 2 to form wet ammonium sulfate with a moisture content of about 5%. It is then fed into dryer and dust removal equipment 6 via feed screw 5. After drying, the ammonium sulfate enters the finished product storage silo 7 by its own weight. The neutralizing agent in the neutralizing agent silo 3 is added to the wet ammonium sulfate drop pipe after centrifuge 2 via metering feeder 4. In the dryer of feed screw 5 and dryer and dust removal equipment 6, the neutralizing agent reacts with the wet ammonium sulfate to neutralize part of the free acid, so that the finished ammonium sulfate meets the relevant national product quality requirements.
[0022] The dilute slurry separated by hydrocyclone 1 and the filtrate from centrifuge 2 are returned to the lower concentration section of the desulfurization tower. The wet washing liquid from the dryer and dust removal equipment 6 is sent to the upper absorption section of the desulfurization tower. The neutralizing agent is preferably sodium carbonate in powder form, followed by ammonium bicarbonate or sodium bicarbonate, and quicklime powder can also be used. The neutralizing agent silo 3 and the metering feeder 4 can be independent equipment or a combined equipment. The metering feeder 4 can be set as a star feeder, screw feeder, disc feeder, belt or scraper feeder, electromagnetic vibrating feeder, or mechanical feeding equipment with weighing and metering, which is controlled by simple speed. The principle and application of neutralization and acid reduction are not only applicable to the by-product ammonium sulfate of ammonia desulfurization units, but also applicable to coking plants and caprolactam and other chemical by-product ammonium sulfate production units.
[0023] Specifically, sodium carbonate is selected as the neutralizing agent. The volume of neutralizing agent silo 3 is determined based on adding 2 bags, totaling 100 kg, each time. Under the conditions of 5% (w) moisture content of wet ammonium sulfate, 3000 kg hourly output of finished ammonium sulfate, 0.5% (w) moisture content of finished product, and 0.4% (w) free acid of the original finished product, neutralization is implemented to reduce the free acid of the finished product to 0.12%. Based on the above conditions, the total amount of free acid in the finished ammonium sulfate is calculated to be 3000 × 0.4% = 12 kg / h. If the free acid of the finished ammonium sulfate is to be controlled to 0.12%, the amount of free sulfuric acid to be neutralized is 12 - 3000 × 0.12% = 8.4 kg / h. Therefore, the sodium carbonate reagent consumption is 8.4 × 106 / 98 = 9.0857 kg / h.
[0024] Practical Application: The metering feeder 3 uses a low-speed, small-dosage mechanical feeding device to quantitatively add 8.5–9.5 kg / h of sodium carbonate solid powder to wet ammonium sulfate. In the feed screw 5 and the dryer and dust removal equipment 6, a neutralization reaction occurs, and sodium carbonate reacts with free sulfuric acid to produce sodium sulfate. The trace amounts of moisture and CO2 gas produced by the neutralization reaction are completely volatilized during the drying process. Therefore, the total amount of ammonium sulfate in the finished product increases slightly after drying, but will not exceed 3004 kg / h. The impact on the nitrogen content of the finished product is negligible. It can be seen that the neutralizing agent consumption is very small, and two bags of sodium carbonate (100 kg) can be continuously discharged for about 10 hours.
[0025] Working principle: The wet ammonium sulfate product typically contains about 5% (w) of water. Besides ammonium sulfate, it also contains trace amounts of salt-forming components such as ammonium chloride and ammonium bisulfate. These salt-forming components reach dissociation equilibrium with water. Ammonium sulfate and ammonium chloride are strong acid-weak base salts; their aqueous solutions are weakly acidic, but their dissociation products are only stable ions such as SO42-, NH4+, H3O+, and OH-. Ammonium bisulfate, however, dissociates into sulfuric acid and ammonium sulfate. This is the source of free acid in ammonium sulfate products. Therefore, weak acid salts or bases can be used to neutralize the free acid in ammonium sulfate products. Sodium carbonate, ammonium bicarbonate, sodium bicarbonate, and even quicklime powder can all be used as neutralizing agents.
[0026] Drying wet ammonium sulfate is a concentration and recrystallization process. During this process, the total amount of free acid does not decrease. After drying, the finished product typically has a water content of 0.5% (w) and a free acid content of 0.3%–0.5% (w). When adding neutralizing agents to the finished ammonium sulfate product, the solvent (water) is very small, and the reaction is essentially a solid-solid reaction, resulting in a slow neutralization process and difficulty in ensuring a consistent level of free acid in the finished product. However, when the neutralizing agent is added to the wet ammonium sulfate product after centrifugation and then fed into a dryer (usually a fluidized bed dryer) via a feeding screw, the neutralization reaction occurs between the solid and liquid phases. The reaction mixture is well-disturbed and has a long residence time, resulting in high neutralization efficiency and a better reaction effect. This ensures that the free acid content of the finished ammonium sulfate product consistently meets the standards.
[0027] In the embodiments provided in this application, it should be understood that the disclosed systems, modules, and methods can be implemented in other ways. For example, the module embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, or indirect coupling or communication connection between modules or units, and may be electrical, mechanical, or other forms.
[0028] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. This application is not limited to the exact structures described above and illustrated in the accompanying drawings, and it should not be considered that the specific implementation of this application is limited to these descriptions. For those skilled in the art, various changes and modifications made without departing from the concept of this application should be considered to fall within the protection scope of this application.
Claims
1. An apparatus for neutralizing free acid in an ammonium sulfate product produced as a byproduct of an ammonia process for desulfurization, characterized by: The system includes ammonium sulfate slurry from the concentration section of the desulfurization tower, a hydrocyclone (1), a centrifuge (2), a neutralizing agent silo (3), a metering feeder (4), a feeding screw (5), a dryer and dust removal equipment (6), and a finished product storage silo (7). The hydrocyclone (1) is equipped with a centrifuge (2) on one side and a neutralizing agent silo (3) on the other side. The neutralizing agent silo (3) is equipped with a metering feeder (4) on one side. The centrifuge (2) is equipped with a feeding screw (5) on one side. The dryer and dust removal equipment (6) is equipped with a dryer and dust removal equipment (6) on one side. The finished product storage silo (7) is equipped with a dryer and dust removal equipment (6).
2. The free acid neutralization device for ammonium sulfate by-product of ammonia desulfurization according to claim 1, characterized in that: The ammonium sulfate slurry from the concentration section of the desulfurization tower is dehydrated by a hydrocyclone (1) and a centrifuge (2) and then fed into a dryer and dust removal equipment (6) by a feeding screw (5). After drying by the dryer and dust removal equipment (6), the ammonium sulfate enters the finished product storage silo (7) by its own weight.
3. The device for neutralizing free acid in the by-product of ammonium sulfate produced by the ammonia desulfurization method according to claim 1, characterized in that: The neutralizing agent in the neutralizing agent silo (3) is added to the centrifuge (2) via the metering feeder (4).
4. The device for neutralizing free acid in the by-product of ammonium sulfate produced by the ammonia desulfurization method according to claim 1, characterized in that: The thin slurry separated by the hydrocyclone (1) and the filtrate from the centrifuge (2) are returned to the lower concentration section of the desulfurization tower.
5. The device for neutralizing free acid in the by-product of ammonium sulfate produced by the ammonia desulfurization method according to claim 1, characterized in that: The wet washing liquid from the dryer and dust removal equipment (6) is sent to the upper absorption section of the desulfurization tower.