System and method for drying raffinate acid sludge

Abstract

The invention provides a raffinate acid sludge drying system and method.The method specifically comprises the following steps that 1, raffinate acid sludge is sampled and analyzed, and the content of all components in the raffinate acid sludge is measured; step 2, adding ammonium bicarbonate according to the phosphoric acid content of the raffinate acid sludge in the result of the content of each component in the raffinate acid sludge measured in the step 1, and fully stirring and mixing; 3, after full mixing and stirring, the raffinate acid sludge and ammonium bicarbonate are subjected to a full reaction, phosphoric acid in the raffinate acid sludge is completely neutralized, the raffinate acid sludge is subjected to primary crushing through a crusher till the diameter is smaller than 100 mm, and then the raffinate acid sludge is spread in a reaction field to be aired and dried; 4, after the water content of the dried slag obtained through airing is reduced to 5% or below, crushing is conducted again, and particles with the finer particle size are obtained; and 5, the dried slag is screened. According to the method, ammonium bicarbonate is adopted as a drying agent, and the raffinate acid sludge is dried, so that batch utilization of the raffinate acid sludge can be realized.

Description

Technical Field

[0001] The invention relates to the technical field of wet-process phosphoric acid purification, and in particular to a system and method for drying raffinate slag. Background Art

[0002] The residual acid residue is the solid material after the residual acid, a byproduct of phosphoric acid purification, is physically squeezed. At present, it is re-pulped with pool water and sent to the phosphogypsum yard for storage. After a long period of enrichment, the amount of mixed oxides in the pool water of the yard continues to increase, affecting the production of phosphoric acid and the extraction rate of phosphoric acid purification. The separated residual acid residue contains 20%-25% of phosphorus pentoxide, which is not effectively utilized, and phosphorus resources are wasted. The free phosphoric acid and the associated oxides in the residue will cause the quality of phosphogypsum to deteriorate, and the disposal of phosphogypsum becomes more difficult. Therefore, it is urgent to find a way to dispose of the residual acid residue. The residual acid residue after filtration also contains a lot of free acid and metal oxides, which cause compaction and cannot be directly added to the production of phosphate fertilizers and taken away with phosphate fertilizer products.

[0003] Acid slag is a product of the development of phosphoric acid purification technology. It is the same substance as phosphogypsum. In comparison, the phosphorus content and metal oxide content in acid slag are increased exponentially, and there are also organic solvents, so the acid slag has high viscosity and is hardened. The free acid is mostly moist and cannot be dried directly. Traditionally, quicklime and acid slag are mixed and fermented. After adjusting the pH of the acid slag, low-end fertilizers such as calcium sulfate can be made. The product value is low, and quicklime reacts with phosphoric acid to generate calcium hydrogen phosphate precipitate (chemical reaction equation GaO+H 3 PO 4 =GaHPO 4 +H 2 O), reducing the activity of phosphoric acid and fertilizer efficiency. The mixing and dispersion of the residual acid residue and quicklime is uneven, and the quicklime will absorb water and dry to produce slaked lime, which will then react with the free acid in the residual acid residue. The cycle is long and the reaction is slow. Summary of the invention

[0004] The object of the present invention is to provide a system and method for drying raffinate slag, which adopts ammonium bicarbonate as a drying agent to dry the raffinate slag, thereby realizing batch utilization of the raffinate slag.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method for drying raffinate residues, comprising the following steps:

[0007] Step 1: sampling and analyzing the residual acid residue, and measuring the content of each component in the residual acid residue;

[0008] Step 2: according to the content of each component in the raffinate slag measured in step 1, add ammonium bicarbonate and stir and mix thoroughly;

[0009] Step 3: After sufficient mixing and stirring, the raffinate residue and ammonium bicarbonate are fully reacted to completely neutralize the phosphoric acid in the raffinate residue, and then the residue is crushed into a diameter of less than 100 mm by a crusher, and then spread out on the reaction site for drying in the sun;

[0010] Step 4: After the moisture content of the dried slag is reduced to less than 5% after drying, it is crushed again to obtain particles with finer particle size;

[0011] Step 5: The dried slag is screened, and particles with a particle size less than 2 mm are qualified particles, and particles with a particle size greater than 2 mm are returned to step 4 for re-crushing.

[0012] Furthermore, in some preferred embodiments, in step 2, ammonium bicarbonate is added to the raffinate slag at a phosphoric acid content of 1:1-1.2 and the mixture is stirred and mixed thoroughly.

[0013] In the present invention, ammonium bicarbonate is used instead of quicklime as a drying agent, which can increase the reaction rate, quickly complete the neutralization reaction, and neutralize the free acid in the residual acid slag. The product is monoammonium phosphate, which is a soluble acidic fertilizer, consistent with the product category of existing phosphate fertilizer devices, and is convenient for later use.

[0014] In the present invention, the raffinate is quantitatively analyzed, and after the content of each component is clarified, ammonium bicarbonate is added according to the calculated amount to ensure that all free acids in the raffinate residue are neutralized into monoammonium phosphate. The gas generated during the neutralization process promotes the expansion and loosening of the raffinate residue, thereby reducing the viscosity of the residue. The neutralized residue is turned over and dried naturally to reduce the moisture in the residue and further improve the dispersibility of the residue. The dried raffinate residue is crushed and screened, and qualified fine particles can be directly used. The coarse particles are again subjected to the drying, crushing and screening process, and the raffinate residue that is screened and qualified is sent to the production device for use. The effective utilization of phosphorus pentoxide in the raffinate residue is achieved.

[0015] Furthermore, in some preferred embodiments, in step 2, ammonium bicarbonate is used to neutralize free acid in the raffinate slag, so that phosphoric acid in the slag is neutralized into monoammonium phosphate, and the carbon dioxide released in the reaction is used to promote the expansion and loosening of the raffinate slag, and the raffinate slag no longer contains acid after neutralization.

[0016] Furthermore, in some preferred embodiments, in step 3, the water in the slag is evaporated at ambient temperature.

[0017] The present invention also discloses a system for drying raffinate slag, which comprises a feeding device, a stirring device, a drying device, a crushing device and a screening device. The feeding device is used for feeding, the stirring device is used for fully stirring the mixed raffinate slag and ammonium bicarbonate, the drying device is used for drying the stirred raffinate slag and ammonium bicarbonate, the crushing device is used for crushing the dried material, the screening device is used for screening the crushed material, and a material return mechanism is provided between the screening device and the crushing device, and the material return mechanism is used for sending the screened large-particle material to the crushing device for re-crushing.

[0018] Furthermore, in some preferred embodiments, the feeding device includes a feeding funnel and a screw feeder, the feeding funnel is connected to the screw feeder, the feeding funnel is used to mix the raffinate slag and ammonium bicarbonate, and the screw feeder is used to mix the mixed raffinate slag and bicarbonate again and send them to the stirring device for stirring reaction.

[0019] Furthermore, in some preferred embodiments, the diameter of the discharge end of the screw feeder gradually decreases.

[0020] Furthermore, in some preferred embodiments, the discharge end of the screw feeder is arranged at the end of the barrel of the screw feeder, and a plurality of discharge holes are arranged at the end, and the first rotating shaft of the screw feeder is connected to the cutting unit after extending out of the end of the barrel.

[0021] Further, in some preferred embodiments, the cutting unit includes a mounting screw and a cutter, and the mounting screw is used to fix the cutter to the end of the first rotating shaft after being connected to the first rotating shaft.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention adopts ammonium bicarbonate instead of quicklime as a drying agent, which can improve the reaction rate, quickly complete the neutralization reaction, and neutralize the free acid in the residual acid slag. The product is monoammonium phosphate, which is a soluble acidic fertilizer, consistent with the category of existing phosphate compound fertilizer products, and convenient for later use. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 It is the overall principle diagram of the present invention.

[0026] Figure 2It is a schematic diagram of the overall structure of the feeding device of the present invention.

[0027] Figure 3 For the present invention Figure 2 A partial enlarged schematic diagram in the middle.

[0028] Figure 4 For the present invention Figure 2 A partial enlarged schematic diagram of point B in the middle.

[0029] Reference numerals:

[0030] 101 feeding funnel, 102 spiral feeder, 103 discharge hole, 104 cutting unit, 105 mounting screw, 106 cutter, 107 discharge port, 108 first rotating shaft, 109 rotating shaft, 110 first driving unit, 111 fixed cutter, 112 rotating cutter, 113 first funnel, 114 rotating shaft, 115 first spiral blade, 116 second spiral blade, 117 mounting plate, 118 first motor, 119 fixed box, 120 second motor, 121 transmission mechanism, 122 closing plate. DETAILED DESCRIPTION

[0031] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the embodiments of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0032] In the description of the embodiments of the present invention, it should be understood that the terms "length", "vertical", "horizontal", "top", "bottom", etc. indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present invention.

[0033] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0034] In the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0035] In the embodiments of the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0036] The disclosure below provides many different embodiments or examples to implement different structures of the embodiments of the present invention. In order to simplify the disclosure of the embodiments of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the embodiments of the present invention. In addition, the embodiments of the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed.

[0037] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0038] Embodiment 1

[0039] This embodiment discloses a method for drying raffinate residue, which specifically comprises the following steps:

[0040] Step 1: Sampling and analyzing the residual acid slag, and measuring the content of each component in the residual acid slag; the residual acid slag mainly contains 20-25% phosphorus pentoxide, about 15% metal cations such as iron, magnesium, and aluminum, and the rest is mostly phosphogypsum.

[0041] Step 2: according to the content of each component in the raffinate slag measured in step 1, add ammonium bicarbonate and stir and mix thoroughly;

[0042] Step 3: After sufficient mixing and stirring, the raffinate residue and ammonium bicarbonate are fully reacted to completely neutralize the phosphoric acid in the raffinate residue, and then the residue is crushed into a diameter of less than 100 mm by a crusher, and then spread out on the reaction site for drying in the sun;

[0043] Step 4: After the moisture content of the dried slag is reduced to less than 5% after drying, it is crushed again to obtain particles with finer particle size;

[0044] Step 5: The dried slag is screened, and particles with a particle size less than 2 mm are qualified particles, and particles with a particle size greater than 2 mm are returned to step 4 for re-crushing.

[0045] Furthermore, in actual use, in step 2, the content of phosphoric acid in the raffinate slag is 1:1-1.2 and ammonium bicarbonate is added and fully stirred and mixed. In actual use, 1:1.1 is preferred to ensure sufficient reaction and reduce the residual amount of ammonium bicarbonate.

[0046] Among them, in step 2, ammonium bicarbonate is used to neutralize the free acid in the raffinate slag, so that the phosphoric acid in the slag is neutralized into monoammonium phosphate, and the carbon dioxide released in the reaction is used to promote the expansion and loosening of the raffinate slag. After neutralization, the raffinate slag no longer contains acid.

[0047] Furthermore, in step 3, the water in the slag is evaporated using the ambient temperature, and in actual use, a drying device may also be used to achieve the purpose of rapid drying.

[0048] See also Figure 1-Figure 4 In addition, the present invention also discloses a system for drying raffinate slag, which comprises a feeding device, a stirring device, a drying device, a crushing device and a screening device. The feeding device is used for feeding, the stirring device is used for fully stirring the mixed raffinate slag and ammonium bicarbonate, the drying device is used for drying the stirred raffinate slag and ammonium bicarbonate, the crushing device is used for crushing the dried material, the screening device is used for screening the crushed material, and a material return mechanism is provided between the screening device and the crushing device, and the material return mechanism is used for sending the screened large-particle material to the crushing device for re-crushing.

[0049] In actual use, since the residual acid slag is formed by physical plate and frame extrusion, the residual phosphoric acid content is about 20%. Due to the presence of phosphoric acid, the residual acid slag is usually a paste-like and block-like semi-solid material. Strong stirring is required when mixing the residual acid slag with ammonium bicarbonate. When the residual acid slag and ammonium bicarbonate are directly placed in a stirring device for stirring, it is difficult to mix the paste-like and block-like semi-solid residual acid slag with ammonium bicarbonate, and long-term strong stirring is required to achieve effective mixing.

[0050] Therefore, in actual use, it is necessary to mix the residual acid slag with ammonium bicarbonate before stirring to reduce the subsequent stirring time while ensuring the mixing effect.

[0051] The structure of the feeding device is improved as follows:

[0052] The feeding device includes a feeding hopper 101 and a screw feeder 102. The feeding hopper 101 is connected to the screw feeder 102. The feeding hopper 101 is used to mix the raffinate slag and ammonium bicarbonate. The screw feeder 102 is used to mix the mixed raffinate slag and bicarbonate again and send them to the stirring device for stirring reaction.

[0053] In actual use, the raffinate residue and ammonium bicarbonate are mixed in the feeding hopper 101, and the automatic feeding is realized under the action of the screw conveyor. The raffinate residue and ammonium bicarbonate will be preliminarily mixed in the screw conveyor; since carbon dioxide gas will be generated after the raffinate residue and ammonium bicarbonate are mixed, an exhaust port can be provided on the screw conveyor as needed.

[0054] The discharge end of the screw feeder 102 is arranged at the end of the cylinder of the screw feeder 102, and a plurality of discharge holes 103 are arranged at the end. The first rotating shaft 108 of the screw feeder 102 extends out of the end of the cylinder and is connected to a cutting unit 104.

[0055] As the diameter of the discharge end gradually decreases, the raffinate slag has undergone a preliminary mixing reaction in the spiral feeding device. When the mixed material passes through the discharge port 107, the mixed material is cut and dispersed under the action of the cutting unit 104, so that the mixed raffinate slag and ammonium bicarbonate can enter the stirring device in a dispersed state.

[0056] The cutting unit 104 includes a mounting screw 105 and a cutter 106. The mounting screw 105 is used to connect with the first rotating shaft 108 to fix the cutter 106 to the end of the first rotating shaft 108. The mounting screw 105 is used to install the cutter 106, and the rotating shaft 109 is used to drive the cutter 106, so that the cutter 106 cuts and breaks up the mixed material.

[0057] Furthermore, in actual use, since the raffinate slag added to the feeding hopper 101 is in the form of solid blocks, the premixing effect in the spiral feeding device is limited. Therefore, in actual use, a crushing mechanism is provided in the feeding hopper 101, and the crushing mechanism includes a rotating shaft 109, a first driving unit 110, a fixed cutter 111 and a rotating cutter 112. The fixed cutter 111 is provided in the feeding hopper 101, and the rotating cutter 112 is provided on the rotating shaft 109. The rotating shaft 109 is rotatably mounted on the feeding hopper 101. The first driving unit 110 is connected to the rotating shaft 109 after being installed on the feeding hopper 101; the fixed cutter 111 and the rotating cutter 112 are arranged alternately.

[0058] When in use, the fixed cutter 111 and the rotating cutter 112 are provided to achieve preliminary crushing and cutting of the residual acid slag, so as to improve the subsequent mixing effect.

[0059] Furthermore, in actual use, the rotating shaft 109 is a hollow shaft, a rotating shaft 114 is disposed inside the rotating shaft 109, a first funnel 113 is connected to the rotating shaft, a first spiral blade 115 is disposed on the rotating shaft 114, and a second spiral blade 116 is disposed on the outer wall of the rotating shaft 109;

[0060] A mounting plate 117 is rotatably provided at the upper end of the rotating shaft, the mounting plate 117 is fixedly connected to the feeding funnel 101 , and a first motor 118 connected to the rotating shaft is provided on the mounting plate 117 .

[0061] A fixed box 119 is provided on the feeding funnel 101 , the rotating shaft 109 passes through the fixed box 119 and is rotatably connected to the fixed box 119 , the first driving unit 110 includes a second motor 120 and a transmission mechanism 121 , and the second motor 120 drives the rotating shaft 109 to rotate through the transmission mechanism 121 .

[0062] In this way, in actual use, the mixing ratio of the raffinate slag and ammonium bicarbonate can be accurately controlled, two independent feeding mechanisms are formed in the feeding funnel 101, and after mixing, they enter the spiral feeding device, thereby achieving proportional mixing of the raffinate slag and ammonium bicarbonate.

[0063] During use, the first drive motor drives the rotating shaft to rotate, thereby realizing quantitative feeding of ammonium bicarbonate; at the same time, the first drive unit 110 drives the rotating shaft 109 to rotate, thereby realizing quantitative feeding of the crushed residual acid slag. Since the rotating shaft 109 will rotate in actual time, the rotation speed of the rotating shaft 109 is different from that of the rotating shaft to ensure normal feeding.

[0064] Furthermore, in actual use, a closing plate 122 is provided at the lower end of the rotating shaft 109, and the rotating shaft is rotatably mounted on the closing plate 122. A plurality of discharge ports 107 are provided at the side of the rotating shaft 109 near the closing plate 122. This arrangement can achieve the purpose of side discharge, and the ammonium bicarbonate can be mixed with the raffinate slag after the side discharge. In this way, the raffinate slag and the ammonium bicarbonate can be quantitatively mixed, and the raffinate slag and the ammonium bicarbonate can be preliminarily mixed, and they can be mixed again under the action of the feeding device, and they can be crushed again under the action of the cutting unit 104, so that the raffinate slag and the ammonium bicarbonate entering the stirring device are smaller in volume and in a more dispersed state, so as to facilitate a sufficient neutralization reaction.

[0065] In actual use, the gas produced during the neutralization process promotes the expansion and loosening of the acid residue, reducing the viscosity of the residue. After mixing, it is dried to reduce the moisture in the residue and further improve the dispersibility of the residue. The dried acid residue is crushed and screened, and the qualified fine particles can be used directly, and the coarse particles are dried, crushed and screened again. The dried and qualified acid residue is sent to the production device for use.

[0066] In the prior art, lime and acid residue are mixed and reacted, and then the pH value of the acid residue is adjusted to make low-end fertilizers such as calcium sulfate. The product value is low, and calcium hydrogen phosphate precipitation is generated after the quicklime reacts with phosphoric acid. The chemical reaction equation is GaO+H 3 PO 4 =GaHPO 4 +H 2 O, reduce the activity of phosphoric acid and reduce the fertilizer efficiency.

[0067] In the present invention, ammonium bicarbonate is used to mix and react with the raffinate slag, and the slag phosphoric acid is neutralized and then air-dried and dehydrated, and the dried slag is finely crushed and added to the phosphate compound fertilizer product by metering to form a high-end phosphate compound fertilizer product, thereby improving the value of the raffinate slag. The phosphorus in the raffinate slag is recycled, and the large amount of elements such as calcium, magnesium, and iron enriched in the raffinate slag provide more comprehensive nutrition for plants, thereby improving the application effect of the phosphate compound fertilizer product.

[0068] More importantly, in the present invention, the drying path can prevent phosphorus pentoxide from forming citrate-soluble phosphorus and reducing its activity.

[0069] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for drying raffinate residue, characterized in that: The specific steps include: Step 1: sampling and analyzing the residual acid residue, and measuring the content of each component in the residual acid residue; Step 2: according to the content of each component in the raffinate slag measured in step 1, add ammonium bicarbonate and stir and mix thoroughly; Step 3: After sufficient mixing and stirring, the raffinate residue and ammonium bicarbonate are fully reacted to completely neutralize the phosphoric acid in the raffinate residue, and then the residue is crushed into a diameter of less than 100 mm by a crusher, and then spread out on the reaction site for drying in the sun; Step 4: After the moisture content of the dried slag is reduced to less than 5% after drying, it is crushed again to obtain particles with finer particle size; Step 5: The dried slag is screened, and particles with a particle size less than 2 mm are qualified particles, and particles with a particle size greater than 2 mm are returned to step 4 for re-crushing.

2. The method for drying raffinate slag according to claim 1, characterized in that: In step 2, ammonium bicarbonate is added to the raffinate slag at a phosphoric acid content of 1:1-1.2 and the mixture is stirred and mixed thoroughly.

3. The method for drying raffinate slag according to claim 1, characterized in that: In step 2, ammonium bicarbonate is used to neutralize the free acid in the raffinate slag, so that the phosphoric acid in the slag is neutralized into monoammonium phosphate. The carbon dioxide released in the reaction is used to promote the expansion and loosening of the raffinate slag. After neutralization, the raffinate slag no longer contains acid.

4. The method for drying raffinate slag according to claim 1, characterized in that: In step 3, the water in the slag is evaporated using ambient temperature.

5. A system for drying acid residue, characterized in that: The raffinate slag drying system is applied to the raffinate slag drying method described in claims 1-4; Among them, the acid residue drying system includes a feeding device, a stirring device, a drying device, a crushing device and a screening device. The feeding device is used for feeding, the stirring device is used for fully stirring the mixed acid residue and ammonium bicarbonate, the drying device is used for drying the stirred acid residue and ammonium bicarbonate, the crushing device is used for crushing the dried material, the screening device is used for screening the crushed material, and a return mechanism is arranged between the screening device and the crushing device, and the return mechanism is used for sending the screened large-particle material to the crushing device for re-crushing.

6. The system for drying raffinate residue according to claim 5, characterized in that: The feeding device includes a feeding funnel and a screw feeder. The feeding funnel is connected to the screw feeder. The feeding funnel is used to mix the raffinate slag and ammonium bicarbonate. The screw feeder is used to mix the mixed raffinate slag and bicarbonate again and send them to the stirring device for stirring reaction.

7. The system for drying raffinate residue according to claim 6, characterized in that: The diameter of the screw feeder discharge end gradually decreases.

8. The system for drying raffinate residue according to claim 6, characterized in that: The discharge end of the screw feeder is arranged at the end of the cylinder of the screw feeder, and a plurality of discharge holes are arranged at the end. The first rotating shaft of the screw feeder is connected with a cutting unit after extending out of the end of the cylinder.

9. The system for drying the residual acid residue according to claim 8, characterized in that: The cutting unit comprises a mounting screw and a cutting knife. The mounting screw is used to fix the cutting knife to the end of the first rotating shaft after being connected with the first rotating shaft.

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