System and method for improving quality of ammonia desulphurization byproduct ammonium sulfate product

Abstract

The invention relates to the field of flue gas desulfurization, in particular to a system and a method for improving the quality of ammonium sulfate as a byproduct of ammonia desulfurization. The system comprises a desulfurization tower, a delivery pump, an oxidation circulation tank and a post-treatment device, two layers of sprayers are arranged in the desulfurization tower, and an ion exchange column is arranged in the oxidation circulation tank. The method comprises the following steps: (S1) reacting boiler flue gas with a lower spraying absorbent to obtain crude ammonium sulfite I and desulfurized flue gas; (S2) carrying out reaction on the desulfurized flue gas and the upwards sprayed circulating material to obtain crude ammonium sulfite II and purified flue gas; (S3) converting the crude ammonium sulfite I and the crude ammonium sulfite II into crude ammonium sulfate in an oxidation tank; (S4) in the presence of an absorbent and an oxidant, removing impurities from the crude ammonium sulfate in an oxidation circulation tank to obtain an ammonium sulfate solution; and (S5) taking part of the ammonium sulfate solution as a circulating material, and carrying out post-treatment on the rest to obtain an ammonium sulfate product. The carbon steel pipelines are adopted for conveying materials among the devices, and linings of the desulfurizing tower and the carbon steel pipelines are made of fluorine-containing materials, so that corrosion of the linings and the spraying devices can be reduced, and the quality of ammonium sulfate is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas desulfurization, and in particular to a system and method for improving the quality of ammonium sulfate by-product produced by ammonia-based desulfurization. Background Art

[0002] As an important nitrogen fertilizer, ammonium sulfate is widely used in agriculture to increase crop yields. With the rise of lower-cost by-product ammonium sulfate processes, especially in the coking and chemical industries, the traditional method of directly synthesizing ammonium sulfate from sulfuric acid and ammonia has gradually been replaced. At present, ammonia desulfurization technology is an important production method for by-product ammonium sulfate. Liquid nitrogen, ammonia water, etc. are used as absorbents to absorb SO from the flue gas of coal-fired boilers. 2 , which reduces SO 2 The byproduct ammonium sulfate can be used as fertilizer, which has significant economic benefits and environmental advantages.

[0003] However, with the growing market demand for high-quality ammonium sulfate, the existing ammonia desulfurization process is mainly used to meet the emission standards of flue gas desulfurization in coal chemical enterprises. Its production equipment and process are significantly different from professional ammonium sulfate production. Coal dust and metal impurities in the production environment are easily left in the product, seriously affecting the quality of ammonium sulfate. The existing ammonia desulfurization process lacks the design for this special working condition, resulting in unstable quality of by-product ammonium sulfate and high impurity content. Therefore, it is urgent to optimize the production process equipment to reduce impurities in the product and improve product quality.

[0004] In the ammonia desulfurization process, the desulfurization tower is the core equipment, and the selection of its lining material is crucial. It must have the characteristics of corrosion resistance, high temperature resistance and wear resistance. At present, most desulfurization towers have the following problems:

[0005] 1. The desulfurization tower usually adopts the anti-corrosion process of carbon steel lining glass flakes, but this lining has problems such as poor thermal shock resistance and easy falling off, which may cause secondary pollution of ammonium sulfate mother liquor and affect product quality.

[0006] 2. The spray devices in the desulfurization tower are mostly made of metal, which is prone to rust or corrosion after long-term use, and eventually falls off and contaminates the product. In addition, the spray device cannot flexibly control the spray volume and spray angle to adapt to different working conditions;

[0007] 3. Existing material conveying pipelines are mostly made of fiberglass, which have problems such as high cost, low strength, easy corrosion, easy damage, etc. Long-term use will also produce impurities and pollute the product;

[0008] Therefore, it is particularly important to improve the system and process of the ammonia-based desulfurization by-product ammonium sulfate unit to ensure product quality and production stability. Summary of the invention

[0009] The purpose of the present invention is to solve the problems in the above-mentioned ammonia flue gas desulfurization by-product ammonium sulfate process device, and to provide a system and method for improving the quality of the ammonia flue gas desulfurization by-product ammonium sulfate product.

[0010] In order to achieve the above-mentioned object, the first aspect of the present invention provides a system for improving the quality of ammonium sulfate by-product of ammonia desulfurization, the system comprising the following devices: a desulfurization tower, an oxidation circulation tank, a post-treatment device, a first delivery pump, a second delivery pump, and a third delivery pump; wherein,

[0011] A spray device is provided inside the desulfurization tower, and the spray device comprises a lower spray layer and an upper spray layer; wherein,

[0012] The lower spray layer is provided with a first absorbent inlet for spraying out the absorbent to convert the boiler flue gas entering the desulfurization tower into desulfurized flue gas, and at the same time obtain a crude ammonium sulfite solution I;

[0013] The upper spraying layer is provided with a circulating material inlet for spraying out circulating materials to convert the desulfurized flue gas into clean flue gas, and simultaneously obtain a crude ammonium sulfite solution II;

[0014] The crude ammonium sulfite solution I and the crude ammonium sulfite solution II fall into the oxidation tank at the bottom of the desulfurization tower by gravity, and the clean flue gas is discharged from the clean flue gas outlet arranged at the top of the desulfurization tower;

[0015] The oxidation tank is located at the bottom of the desulfurization tower, and is provided with a first oxidant inlet and a crude ammonium sulfate solution outlet. The oxidation tank is used to convert the crude ammonium sulfite solution I and the crude ammonium sulfite solution II falling into the oxidation tank by gravity into a crude ammonium sulfate solution;

[0016] The oxidation circulation tank is located outside the desulfurization tower, and includes a tank body and an ion exchange column arranged in the tank body, and the outside of the ion exchange column is wrapped with a detachable impurity removal net, wherein the side of the tank body is also provided with a crude ammonium sulfate solution inlet, a circulating material outlet, and a product material outlet; the bottom of the tank body is also provided with an absorbent second inlet and an oxidant second inlet for introducing absorbent and oxidant into the circulation oxidation tank;

[0017] The ion exchange column is used to remove metal ions in the crude ammonium sulfate solution; the impurity removal net is used to remove water-insoluble substances in the crude ammonium sulfate solution;

[0018] The first delivery pump is used to deliver the crude ammonium sulfate solution from the oxidation tank to the oxidation circulation tank through the crude ammonium sulfate solution outlet;

[0019] The second delivery pump is used to deliver part of the processed liquid in the oxidation circulation tank as circulating material from the circulating material outlet to the upper spray layer of the spray device;

[0020] The third delivery pump is used to deliver part of the processed liquid in the oxidation circulation tank as product material from the product material outlet to the post-processing device;

[0021] The post-processing device is used to post-process the product material to obtain an ammonium sulfate product.

[0022] A second aspect of the present invention provides a method for the system, the method comprising the following steps:

[0023] (S1) passing the boiler flue gas into a desulfurization tower to react with the absorbent sprayed from the lower spray layer of the spray device to obtain desulfurized flue gas and crude ammonium sulfite solution I; preferably, the absorbent is ammonia water and / or liquid ammonia;

[0024] (S2) the desulfurized flue gas reacts from bottom to top with the circulating material sprayed from the upper spray layer of the spray device to obtain clean flue gas and crude ammonium sulfite solution II;

[0025] (S3) the crude ammonium sulfite solution I and the crude ammonium sulfite solution II fall into an oxidation tank by gravity, and an oxidant is introduced to oxidize the crude ammonium sulfite solution I and the crude ammonium sulfite solution II to obtain a crude ammonium sulfate solution; preferably, the oxidant is at least one of air, oxygen and hydrogen peroxide;

[0026] (S4) delivering the crude ammonium sulfate solution to an oxidation circulation tank by a first delivery pump, and introducing an excess of the absorbent and the oxidant in the presence of an ion exchange column wrapped with a decontamination net to remove impurities from the crude ammonium sulfate solution to obtain an ammonium sulfate solution;

[0027] (S5) A portion of the ammonium sulfate solution is delivered to the upper spray layer of step (S2) by a second delivery pump as a circulating material, and the remaining portion is delivered to a post-processing device by a third delivery pump as a product material for post-processing to obtain an ammonium sulfate product.

[0028] Compared with the prior art, the present invention aims at the problem of insufficient product quality control in the existing ammonia flue gas desulfurization by-product ammonium sulfate device system, and proposes a boiler flue gas ammonia desulfurization by-product ammonium sulfate device system and its use method. The system improves the quality of by-product ammonium sulfate products and ensures the stability of product quality through the updated design of key components and overall system improvement, as follows:

[0029] 1. Optimization of desulfurization tower lining: The lining material of the desulfurization tower is replaced from traditional glass flakes to high-performance fluorine-containing materials such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and polyperfluoroethylene propylene (FEP). These materials have excellent corrosion resistance and high temperature resistance, effectively extending the life of the equipment and ultimately improving the quality of by-product ammonium sulfate.

[0030] 2. Optimization of material transportation pipelines: Use carbon steel pipelines with fluorine-containing materials (PTFE, PVDF, FEP) as lining materials to replace fiberglass pipelines to enhance the corrosion resistance of pipelines and adapt to high temperature and high pressure environments. The inner surface of the pipeline is smooth to reduce material adhesion and ensure that the ammonium sulfate product is not contaminated.

[0031] 3. Optimization of the spray device: Replace the material of the spray head and pipeline from traditional metal materials to fluorine-containing materials (PTFE, PVDF, FEP) to avoid rusting of the spray head due to long-term use, thereby reducing impurities introduced into the ammonium sulfate product.

[0032] 4. Combination of ion exchange column and impurity removal net: An ion exchange column based on chelating resin is added to the oxidation circulation tank, and the impurity removal net is wrapped around the ion exchange column to achieve efficient stirring and impurity removal through the rotation of the shaft. This system can effectively remove various impurities in the crude ammonium sulfate solution and improve the quality of ammonium sulfate products. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A system for improving the quality of ammonium sulfate by-product of ammonia desulfurization and a schematic diagram of a process for processing using the system provided by the present invention; wherein:

[0034] 1- desulfurization tower, 2- spray device, 3- oxidation tank, 4- first delivery pump, 5- oxidation circulation tank, 6- second delivery pump, 7- third delivery pump, 8- post-processing device;

[0035] 11-absorbent first inlet, 12-oxidant first inlet, 13-circulating material inlet, 14-clean flue gas outlet, 15-crude ammonium sulfate solution outlet;

[0036] 51 - tank body, 52 - ion exchange column, 53 - crude ammonium sulfate solution inlet, 54 - circulating material outlet, 55 - product material outlet, 56 - absorbent second inlet, 57 - oxidant second inlet.

[0037] Figure 2 for Figure 1 The schematic diagram of the structure of the spray device 2; wherein,

[0038] 2a-fixed pipe, 2b-delivery pipe, 2c-spherical nozzle. DETAILED DESCRIPTION

[0039] Typical embodiments that embody the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various changes in different embodiments without departing from the scope of the present invention, and the descriptions therein are essentially used as illustrations rather than to limit the present invention.

[0040] like Figure 1-2 As shown, the first aspect of the present invention provides a system for improving the quality of ammonium sulfate by-product of ammonia-based desulfurization, the system comprising the following devices: a desulfurization tower 1, a first delivery pump, an oxidation circulation tank 5, a second delivery pump 6, a third delivery pump 7 and a post-treatment device 8.

[0041] In the present invention, a spray device 2 is provided inside the desulfurization tower 1, and the spray device 2 includes a lower spray layer and an upper spray layer.

[0042] In some embodiments, the upper spray layer and the lower spray layer each include a fixed pipe 2a, a plurality of parallel spherical nozzles 2c, and a delivery pipe 2b (used to connect the fixed pipe 2a and the spherical nozzles 2c).

[0043] Preferably, the spherical nozzle 2c is configured to be rotatable at multiple angles to achieve multi-angle spraying.

[0044] Preferably, the spherical nozzle 2c is made of a fluorine-containing material, for example, at least one fluorine-containing material selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and polyperfluoroethylene propylene (FEP).

[0045] The inventors have found that the use of metal materials such as carbon steel will cause the nozzle to rust after long-term use, and impurities such as rust will be brought in during the spraying process to contaminate the ammonium sulfate product. The use of the fluorine-containing material can avoid this situation and enhance the durability and chemical stability of the nozzle. In some embodiments, the lining material of the fixed pipe 2a and the delivery pipe 2b can be independently selected from the fluorine-containing material.

[0046] In the present invention, the lower spray layer is provided with a first absorbent inlet 11, which is used to spray out the absorbent to convert the boiler flue gas entering the desulfurization tower 1 into desulfurized flue gas, and at the same time obtain a crude ammonium sulfite solution I;

[0047] Preferably, the absorbent is aqueous ammonia and / or liquid ammonia.

[0048] In some embodiments, the absorbent enters the lower spraying layer of the spraying device 2 from the absorbent first inlet 11. Then, the absorbent is distributed from one side of the fixed pipe 2a to each spherical spray head 2c via the delivery pipe 2b for spraying.

[0049] In the present invention, the upper spray layer is provided with a circulating material inlet 13 for spraying out circulating materials, converting the desulfurized flue gas from the lower spray layer from bottom to top into clean flue gas (i.e., the circulating material sprayed out by the upper spray layer is used to further absorb ammonium sulfite, sulfur dioxide and ammonia entrained in the desulfurized flue gas), and obtaining a crude ammonium sulfite solution II at the same time.

[0050] Furthermore, the circulating material from the oxidation circulation tank 5 is delivered to the circulating material inlet 13 of the upper spraying layer through the circulating material outlet 54 by the second delivery pump 6. Subsequently, the circulating material is distributed to each spherical nozzle 2c for spraying from one side of the fixed pipe 2a through the delivery pipe 2b.

[0051] In the present invention, the crude ammonium sulfite solution I and the crude ammonium sulfite solution II respectively fall into the oxidation tank 3 at the bottom of the desulfurization tower 1 by gravity; the clean flue gas is discharged through the clean flue gas outlet 14 arranged at the top of the desulfurization tower 1, and is discharged to the chimney after defoaming.

[0052] In the present invention, the oxidation tank 3 is located at the bottom of the desulfurization tower 1, and the oxidation tank 3 is provided with a first oxidant inlet 12 and a crude ammonium sulfate solution outlet 15. The oxidation tank 3 is used to convert the crude ammonium sulfite solution I and the crude ammonium sulfite solution II falling into the oxidation tank 3 by gravity into a crude ammonium sulfate solution. Among them, the oxidant entering the oxidation tank 3 from the first oxidant inlet 12 has a slower flow rate, and can fully oxidize the crude ammonium sulfite solution to ensure the subsequent output of ammonium sulfate.

[0053] Preferably, the oxidant entering the oxidation tank 3 from the first oxidant inlet 12 is at least one of air, oxygen and hydrogen peroxide.

[0054] In the present invention, the crude ammonium sulfate solution from the oxidation tank 3 is delivered to the oxidation circulation tank 5 through the crude ammonium sulfate solution outlet 15 by the first delivery pump 4 .

[0055] In the present invention, the oxidation circulation tank 5 is located outside the desulfurization tower 1, and includes a tank body 51 and an ion exchange column 52 arranged in the tank body 51, and the outside of the ion exchange column 52 is wrapped with a detachable impurity removal net (not marked in the figure), wherein the side of the tank body 51 is also provided with a crude ammonium sulfate solution inlet 53, a circulating material outlet 54, and a product material outlet 55; the bottom of the tank body 51 is also provided with a second absorbent inlet 56 and a second oxidant inlet 57, which are used to introduce absorbent and oxidant into the circulating oxidation tank 5.

[0056] Preferably, the absorbent is aqueous ammonia and / or liquid ammonia, and the oxidant is at least one of air, oxygen and hydrogen peroxide.

[0057] In the present invention, the ion exchange mechanism inside the ion exchange column 52 can effectively remove metal impurities in the crude ammonium sulfate solution.

[0058] In some embodiments, the ion exchange column 52 uses a chelating resin made of macroporous cross-linked polystyrene resin as a core material. This chelating resin can efficiently remove metal ions in water by virtue of its unique adsorption, ion exchange and chelation mechanisms, thereby ensuring the purity of the ammonium sulfate solution. At the same time, the internal structure of the chelating resin contains many channels with ion exchange groups, which can efficiently adsorb and exchange ions in the crude ammonium sulfate solution, further improving the impurity removal effect.

[0059] In some embodiments, the functional groups of the chelating resin are selected from iminodiacetic acid and / or a specific type of tertiary amine (e.g., tert-amylamine, tert-hexylamine), and these functional groups cover two major categories: strong acid cation resin and weak acid cation resin. Both types of resins can be regenerated by strong acid treatment to extend the service life of the resin.

[0060] It is known to those skilled in the art that, although the working capacity of weak acid cation exchange resin is lower than that of strong acid type, it can maintain stable operation in a wider pH range. However, weak acid type resins are relatively weak in acid resistance and easily lose activity in a strong acidic environment. Therefore, when selecting resins, it is necessary to weigh the different fields and specific conditions to ensure the stability and efficiency of the system.

[0061] In some embodiments, a rotating shaft is provided on the top of the oxidation circulation tank 5 to drive the ion exchange column 52 to rotate.

[0062] Preferably, the rotation speed of the rotating shaft is 100-800 rpm.

[0063] Preferably, a plurality of ion exchange columns 52 are provided and symmetrically arranged around the central axis where the rotating shaft is located, so that the ion exchange columns 52 can be rotated by the rotating shaft, stirring and removing impurities from the ammonium sulfate solution in the oxidation circulation tank 5, and efficiently removing metal ion impurities therein.

[0064] In some embodiments, the impurity removal net wrapped around the outside of the ion exchange column 52 also plays an indispensable role. The impurity removal net is a stainless steel net with a mesh size of 1-500 μm. The impurity removal net can not only intercept water-insoluble impurities in the crude ammonium sulfate solution, but also ensure the stability and durability of the impurity removal effect through its detachable design and the selection of stainless steel material.

[0065] In the present invention, a second absorbent inlet 56 and a second oxidant inlet 57 are provided at the bottom of the oxidation circulation tank 5. These two inlets allow the absorbent and the oxidant to be conveniently introduced during the stirring process, which can not only further remove impurities such as sulfur dioxide and ammonium sulfite entrained in the crude ammonium sulfate solution, but also promote the removal of impurities in the solution and the purification of the solution through chemical reactions.

[0066] In the present invention, a portion of the ammonium sulfate solution that has been treated with impurities removal and purification is used as a circulating material and is delivered to the circulating material inlet 13 of the upper spray layer through the circulating material outlet 54 by the second delivery pump 6. These circulating materials have been described above and will not be described in detail.

[0067] In the present invention, the remaining part of the ammonium sulfate solution is used as a product material and is delivered to a post-processing device 8 through a product material outlet 55 by a third delivery pump 7. In the post-processing device 8, the ammonium sulfate solution is further processed and purified to obtain a high-quality ammonium sulfate product.

[0068] In some embodiments, the pipelines used for transportation in the system are all carbon steel pipelines, and these transportation pipelines at least involve material transportation between the spray device 2, the oxidation tank 3, the first delivery pump 4, the oxidation circulation tank 5, the second delivery pump 6, the third delivery pump 7 and the post-processing device 8.

[0069] Preferably, the desulfurization tower 1 and the carbon steel pipeline are both provided with inner liners, and the inner liners of the desulfurization tower 1 and the carbon steel pipeline are independently selected from at least one fluorine-containing material selected from polytetrafluoroethylene, polydiethylene fluoride, and polyperfluoroethylene propylene.

[0070] More preferably, the lining thickness of the carbon steel pipeline is 0.5-3 mm, and the lining thickness of the desulfurization tower 1 is 3-5 mm.

[0071] The inventors have found that the use of the fluorine-containing material as the lining material of the carbon steel pipeline and the desulfurization tower 1 can significantly improve their ability to resist acid and alkali corrosion during the ammonia desulfurization process. This innovation enables the carbon steel pipeline and the desulfurization tower 1 to have the characteristics of corrosion resistance, sealing, high temperature resistance, wear resistance and aging resistance. In addition, the self-lubricity and non-stickiness of the fluorine-containing material effectively prevent the material from sticking and extend the service life of the internal components. Compared with traditional glass flake materials and fiberglass pipes, the use of the fluorine-containing material avoids the mother liquor contamination caused by the shedding of the lining of the desulfurization tower 1 and the transmission pipeline and the secondary contamination of the solution during transportation.

[0072] In some embodiments, the inner lining of the desulfurization tower and the inner lining of the carbon steel pipeline are attached to the inner wall of the desulfurization tower and the carbon steel pipeline respectively by electrostatic spraying and sintering. This allows the fluorine-containing material of the inner wall and the inner lining to be completely combined into a whole, while also significantly reducing the amount of fluorine-containing material used and greatly reducing costs. This method not only consolidates the industrial application status of fluorine-containing materials as the inner lining material of the desulfurization tower 1 and the carbon steel pipeline, but also effectively solves the problem of weak bonding with substrates such as the desulfurization tower 1 and the carbon steel pipeline and the selection of adhesives in traditional applications.

[0073] In some embodiments, the desulfurization tower 1 is also provided with a smoke dust SO 2 Detector, used to detect SO in the desulfurization tower in real time 2 concentration, which is tested in real time by electrical signals 2 The concentration signal is transmitted back to the control center to adjust the spraying amount and spraying angle of the spherical nozzle 2c.

[0074] In some embodiments, a mesh electric signal detection system is provided between the inner lining and the outer wall of the carbon steel pipe to detect the use status of the carbon steel pipe in real time. Once the carbon steel pipe is worn, leaked, etc., the integrated electric signal detection system can timely obtain the leakage point location information through the electric signal change and alarm.

[0075] A second aspect of the present invention provides a method for the system, the method comprising the following steps:

[0076] (S1) passing the boiler flue gas into the desulfurization tower 1 to react with the absorbent sprayed from the lower spray layer of the spray device 2 to obtain desulfurized flue gas and crude ammonium sulfite solution I;

[0077] (S2) the desulfurized flue gas reacts from bottom to top with the circulating material sprayed from the upper spray layer of the spray device 2 to obtain clean flue gas and crude ammonium sulfite solution II;

[0078] (S3) the crude ammonium sulfite solution I and the crude ammonium sulfite solution II fall into the oxidation tank 3 by gravity, and an oxidant is introduced to oxidize the crude ammonium sulfite solution I and the crude ammonium sulfite solution II to obtain a crude ammonium sulfate solution;

[0079] (S4) delivering the crude ammonium sulfate solution to an oxidation circulation tank 5 by using a first delivery pump 4, and introducing an excess of the absorbent and the oxidant in the presence of an ion exchange column 52 wrapped with a decontamination net to remove impurities from the crude ammonium sulfate solution to obtain an ammonium sulfate solution;

[0080] (S5) A portion of the ammonium sulfate solution is delivered to the upper spray layer of step (S2) by a second delivery pump 6 as a circulating material, and the remaining portion is delivered to a post-processing device 8 by a third delivery pump 7 as a product material for post-processing to obtain an ammonium sulfate product.

[0081] In some embodiments, in step (S1), the boiler flue gas may be pre-treated, such as cooling and dust removal, before entering the desulfurization tower 1. Preferably, the absorbent is aqueous ammonia and / or liquid ammonia.

[0082] In some embodiments, in step (S2), the oxidant is at least one of air, oxygen and hydrogen peroxide.

[0083] In some embodiments, in step (S5), since the absorbent and the oxidant are in excess, the ammonium sulfate solution also contains some absorbent and oxidant. Because of this, the circulating material can be returned to the upper spray layer of step (S2) to further convert the desulfurized flue gas into clean flue gas. The excess absorbent and oxidant in the product material can also be easily removed in the post-treatment in step (S5), for example, by heating.

[0084] Furthermore, the post-treatment may include methods commonly used in the art, such as subjecting the product material to cyclone and centrifugal separation to obtain wet ammonium sulfate, and then drying and packaging the wet ammonium sulfate to obtain an ammonium sulfate product.

[0085] The present invention will be further described in detail below through specific examples. In the following examples and comparative examples,

[0086] The contents of fluoride, arsenic, cadmium, lead and chromium are measured as described in GB / T 535-2020 Fertilizer-grade ammonium sulfate;

[0087] The ignition residue is measured as described in GB / T 23951-2009 General method for determination of ignition residue of inorganic chemical products;

[0088] The water insoluble matter is measured as described in Appendix D of GB / T 535-2020 Fertilizer Grade Ammonium Sulfate.

[0089] The boiler flue gas comes from the coal-fired boiler of the State Energy Xinjiang Chemical Company.

[0090] Example 1

[0091] (S1) The boiler flue gas after dust removal is passed into the desulfurization tower 1, and then reacts with the ammonia water (25wt%) sprayed from the lower spray layer of the spray device 2 to obtain desulfurized flue gas and crude ammonium sulfite solution I; wherein,

[0092] The inner lining of the desulfurization tower 1 is made of polytetrafluoroethylene, and the thickness of the inner lining is 3 mm.

[0093] (S2) the desulfurized flue gas reacts from bottom to top with the circulating material sprayed from the upper spray layer of the spray device 2 to obtain clean flue gas and crude ammonium sulfite solution II;

[0094] The inner lining material of the fixed pipe 2a, the delivery pipe 2b and the spherical nozzle 11c of the upper spray layer and the lower spray layer is polytetrafluoroethylene;

[0095] The clean flue gas is discharged from the clean flue gas outlet 14 and discharged to the chimney after being defoamed.

[0096] (S3) Crude ammonium sulfite solution I and crude ammonium sulfite solution II fall into the oxidation tank 3 by gravity, and air is blown into the first oxidant inlet 12 to oxidize the crude ammonium sulfite solutions to obtain crude ammonium sulfate solutions.

[0097] (S4) The crude ammonium sulfate solution is delivered to the oxidation circulation tank 5 by the first delivery pump 4. Driven by the rotating shaft at the top of the oxidation circulation tank 5, the ion exchange column 52 wrapped with a stainless steel mesh rotates accordingly to adsorb or remove metal ions and water-insoluble impurities in the crude ammonium sulfate solution to obtain an ammonium sulfate solution; wherein,

[0098] During the stirring process of the rotating shaft, excess ammonia water (25 wt%) and air are introduced into the absorbent second inlet 56 and the oxidant second inlet 57 at the bottom of the oxidation circulation tank 5 respectively;

[0099] The material of the ion exchange column is macroporous cross-linked polystyrene resin, and the functional group is iminodiacetic acid;

[0100] The rotation speed of the stirring process is 500r / min.

[0101] (S5) A portion of the ammonium sulfate solution is used as a circulating material and is delivered to the circulating material inlet 13 of the upper spray layer by the second delivery pump 6; the remaining portion of the ammonium sulfate solution is used as a product material and is delivered to the post-processing device 8 by the third delivery pump 7. In the post-processing device 8, the product material is subjected to cyclone and centrifugal separation to obtain wet ammonium sulfate, and then the wet ammonium sulfate is dried and packaged to obtain an ammonium sulfate product.

[0102] In the above steps, the pipes involved in material transportation are all carbon steel pipes with linings, and the linings are made of polytetrafluoroethylene with a thickness of 2 mm.

[0103] Example 2

[0104] Refer to Example 1, the only difference is:

[0105] In step (S1), the inner lining material of the desulfurization tower 1 is polyvinylidene fluoride, and the inner lining thickness is the same.

[0106] The pipelines involved in material transportation are all carbon steel pipelines with linings, and the linings are made of polyvinylidene fluoride with a thickness of 1 mm.

[0107] Example 3

[0108] Refer to Example 1, the only difference is:

[0109] In step (S1), the inner lining material of the desulfurization tower 1 is polyperfluoroethylene propylene, and the thickness of the inner lining is 5 mm.

[0110] In step (S4), the functional group of the ion exchange column is tert-amylamine, and the stirring speed is 400 r / min.

[0111] The pipes involved in material transportation are all carbon steel pipes with linings, and the linings are made of polytetrafluoroethylene propylene with a thickness of 2 mm.

[0112] Comparative Example 1

[0113] Refer to Example 1, the only difference is:

[0114] In step (S1), the inner lining material of the desulfurization tower 1 is glass flakes, and the inner lining thickness is the same.

[0115] Comparative Example 2

[0116] Refer to Example 2, the only difference is:

[0117] In step (S4), the interior of the oxidation circulation tank 5 contains only the impurity removal net, no ion exchange column, and only the impurity removal net that can be stirred with the rotating shaft.

[0118] All pipes involved in material transportation are made of fiberglass.

[0119] Comparative Example 3

[0120] Refer to Example 3, the only difference is:

[0121] In step (S1), the inner lining material of the fixed pipe 2a, the delivery pipe 2b and the spherical nozzle 11c of the upper spray layer and the lower spray layer is carbon steel.

[0122] The technical indicators of the ammonium sulfate products obtained in the above Examples 1-3 and Comparative Examples 1-3 were tested, and the results are shown below.

[0123] Table 1: Technical indicators of ammonium sulfate products in Examples 1-3 and Comparative Examples 1-3

[0124]

[0125]

[0126] Table 2: Mass fraction of each element in the water-insoluble matter of the ammonium sulfate product in Example 2 and Comparative Example 2

[0127] Si element Al element Fe element S element Ca Zn element Comparative Example 2 21.34％ 12.31％ 16.34％ 28.84％ 5.42％ 6.78％ Example 2 13.71％ 8.37％ 1.83％ 23.42％ 3.55％ 0.43％

[0128] From the comparison between Example 1 and Comparative Example 1, it can be seen that replacing the inner lining material of the desulfurization tower from the traditional glass flakes with the fluorine-containing material of the present invention can significantly improve the various technical indicators of the ammonium sulfate product.

[0129] From the comparison between Example 2 and Comparative Example 2, it can be seen that replacing the material of the material conveying pipeline from the traditional glass fiber reinforced plastic to the fluorine-containing material in the present invention can significantly improve the various technical indicators of the ammonium sulfate product. In addition, when the oxidation circulation tank does not contain an ion exchange column, the impurity removal effect of the oxidation circulation tank is poor, resulting in a significant reduction in the various technical indicators of the obtained ammonium sulfate product.

[0130] In particular, compared with Comparative Example 2, the content of impurities and heavy metal elements such as As, Cd, Pb, and Cr in the ammonium sulfate product of Example 2 is significantly reduced. At the same time, the content of water-insoluble matter in the ammonium sulfate product of Comparative Example 2 is relatively high, and it is found that the content of Si, Al, and Fe elements is relatively high. The high content of Fe element is due to the corrosion and shedding of the inner wall of the delivery pipeline of Comparative Example 2, resulting in a high content of Fe element in the ammonium sulfate product. After the inner lining of the delivery pipeline is replaced with the fluorine-containing material of the present invention, the content of Fe element is significantly reduced, indicating that the present invention has a significant effect on improving the quality of ammonium sulfate products.

[0131] From the comparison between Example 3 and Comparative Example 3, it can be seen that replacing the material of the pipe and the spray head of the spray device from the traditional metal material to the fluorine-containing material of the present invention can significantly improve the various technical indicators of the ammonium sulfate product.

[0132] In summary, the content of impurities and various metal ions in the ammonium sulfate product obtained by the present invention is significantly reduced, and various technical indicators meet the requirements of GB / T 535-2020 fertilizer-grade ammonium sulfate. Therefore, the device of the present invention can be used to improve the production device of the enterprise, and the quality of the obtained ammonium sulfate product is significantly improved, and a higher standard product is obtained, and its market price will also be correspondingly increased, which has a broad market application prospect.

[0133] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A system for improving the quality of ammonium sulfate by-product of ammonia desulfurization, the system comprising the following devices: a desulfurization tower, an oxidation circulation tank, a post-treatment device, a first delivery pump, a second delivery pump and a third delivery pump, characterized in that: A spray device is provided inside the desulfurization tower, and the spray device comprises a lower spray layer and an upper spray layer; wherein, The lower spray layer is provided with a first absorbent inlet for spraying out the absorbent to convert the boiler flue gas entering the desulfurization tower into desulfurized flue gas, and at the same time obtain a crude ammonium sulfite solution I; The upper spraying layer is provided with a circulating material inlet for spraying out circulating materials to convert the desulfurized flue gas into clean flue gas, and simultaneously obtain a crude ammonium sulfite solution II; The crude ammonium sulfite solution I and the crude ammonium sulfite solution II fall into the oxidation tank at the bottom of the desulfurization tower by gravity, and the clean flue gas is discharged from the clean flue gas outlet arranged at the top of the desulfurization tower; The oxidation tank is located at the bottom of the desulfurization tower, and is provided with a first oxidant inlet and a crude ammonium sulfate solution outlet. The oxidation tank is used to convert the crude ammonium sulfite solution I and the crude ammonium sulfite solution II falling into the oxidation tank by gravity into a crude ammonium sulfate solution; The oxidation circulation tank is located outside the desulfurization tower, and includes a tank body and an ion exchange column arranged in the tank body, and the outside of the ion exchange column is wrapped with a detachable impurity removal net, wherein the side of the tank body is also provided with a crude ammonium sulfate solution inlet, a circulating material outlet, and a product material outlet; the bottom of the tank body is also provided with an absorbent second inlet and an oxidant second inlet for introducing absorbent and oxidant into the circulation oxidation tank; The ion exchange column is used to remove metal ions in the crude ammonium sulfate solution; the impurity removal net is used to remove water-insoluble matter in the crude ammonium sulfate solution; The first delivery pump is used to deliver the crude ammonium sulfate solution from the oxidation tank to the oxidation circulation tank through the crude ammonium sulfate solution outlet; The second delivery pump is used to deliver part of the processed liquid in the oxidation circulation tank as circulating material from the circulating material outlet to the upper spray layer of the spray device; The third delivery pump is used to deliver part of the processed liquid in the oxidation circulation tank as product material from the product material outlet to the post-processing device; The post-processing device is used to post-process the product material to obtain an ammonium sulfate product.

2. The system according to claim 1, characterized in that The pipes used for material transportation in the system are all carbon steel pipes; The desulfurization tower and the carbon steel pipeline are both provided with inner liners, and the inner liners of the desulfurization tower, the nozzles of the spraying device and the inner liners of the carbon steel pipeline are independently selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride and polyperfluoroethylene propylene.

3. The system according to claim 2, characterized in that The inner lining of the desulfurization tower and the inner lining of the carbon steel pipeline are respectively attached to the inner wall of the desulfurization tower and the carbon steel pipeline by electrostatic spraying and sintering; A mesh electrical signal detection system is arranged between the inner lining and the outer wall of the carbon steel pipeline, for detecting the use status of the inner wall of the carbon steel pipeline in real time.

4. The system according to claim 2 or 3, characterized in that: The thickness of the inner lining of the desulfurization tower is 3-5 mm, and the thickness of the inner lining of the carbon steel pipe is 0.5-3 mm.

5. The system according to any one of claims 1 to 4, characterized in that The upper spray layer and the lower spray layer each include a fixed pipe, a plurality of parallel spherical nozzles and a delivery pipe for connecting the fixed pipe and the spherical nozzles; wherein, The absorbent enters the lower spray layer of the spray device from one side of the fixed pipe and is distributed to each spherical nozzle for spraying through the delivery pipe. The circulating material absorbent enters the upper spraying layer of the spraying device from one side of the fixed pipe and is distributed to each spherical sprinkler head for spraying through the conveying pipe; Preferably, the spherical nozzle is configured to be rotatable at multiple angles.

6. The system according to any one of claims 1 to 5, wherein the ion exchange column uses a chelating resin made of macroporous cross-linked polystyrene resin as a core material, and the functional group of the chelating resin is at least one of iminodiacetic acid, tert-amylamine and tert-hexylamine; The impurity removal net is a stainless steel net, and the mesh size of the impurity removal net is 1-500 μm.

7. The system according to any one of claims 1 to 6, characterized in that A rotating shaft is provided on the top of the oxidation circulation tank for driving the ion exchange column to rotate; Preferably, the rotation speed of the rotating shaft is 100-800 rpm; Preferably, the ion exchange columns are provided in plurality and are symmetrically arranged around the central axis where the rotating shaft is located, so that the ion exchange columns can be rotated by the rotating shaft to stir and remove impurities from the ammonium sulfate solution in the oxidation circulation tank.

8. The system according to any one of claims 1 to 7, characterized in that The absorbent is aqueous ammonia and / or liquid ammonia; the oxidant is at least one of air, oxygen and hydrogen peroxide.

9. The system according to any one of claims 1 to 8, characterized in that A smoke SO2 detector is also provided inside the desulfurization tower for real-time detection of the SO2 concentration in the desulfurization tower so as to adjust the spraying amount and spraying angle of the spherical nozzle.

10. A method for use in the system of any one of claims 1 to 9, the method comprising the steps of: (S1) passing the boiler flue gas into a desulfurization tower to react with the absorbent sprayed from the lower spray layer of the spray device to obtain desulfurized flue gas and crude ammonium sulfite solution I; preferably, the absorbent is ammonia water and / or liquid ammonia; (S2) the desulfurized flue gas reacts from bottom to top with the circulating material sprayed from the upper spray layer of the spray device to obtain clean flue gas and crude ammonium sulfite solution II; (S3) the crude ammonium sulfite solution I and the crude ammonium sulfite solution II fall into an oxidation tank by gravity, and an oxidant is introduced to oxidize the crude ammonium sulfite solution I and the crude ammonium sulfite solution II to obtain a crude ammonium sulfate solution; preferably, the oxidant is at least one of air, oxygen and hydrogen peroxide; (S4) delivering the crude ammonium sulfate solution to an oxidation circulation tank by a first delivery pump, and introducing an excess of the absorbent and the oxidant in the presence of an ion exchange column wrapped with a decontamination net to remove impurities from the crude ammonium sulfate solution to obtain an ammonium sulfate solution; (S5) A portion of the ammonium sulfate solution is delivered to the upper spray layer of step (S2) by a second delivery pump as a circulating material, and the remaining portion is delivered to a post-processing device by a third delivery pump as a product material for post-processing to obtain an ammonium sulfate product.

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