High-concentration iron-based coagulant and method of manufacturing the same

Abstract

A super-high concentration polyferric sulfate solution, which could not be produced by conventional manufacturing methods due to the long reaction time, is manufactured continuously. Ferrous sulfate, sulfuric acid, and oxygen gas are used as raw materials, and a raw material liquid containing ferrous sulfate and sulfuric acid satisfying the following relationship, along with oxygen gas, is supplied into a high-temperature, high-pressure reaction vessel to continuously extract a polyferric sulfate solution. The molar ratio of total iron to sulfate ions (SO42- / T-Fe) is 1.2 or higher, and when the weight concentration of sulfate ions is [SO42-], [SO42-] is 35 wt% or lower.

Description

Technology Field

[0001] The present invention relates to a high-concentration iron-based coagulant used in wastewater treatment and a method for manufacturing the same. Background Technology

[0002] The applicant of the present patent conducts sales of wastewater treatment agents centered on the independently developed iron-based inorganic polymer coagulant "Polytetsu" (registered trademark) and holds several patents related thereto.

[0003] Among these patents, Patent Document 1 describes adding sodium nitrite and an oxidizing agent as catalysts to a solution of ferrous sulfate (FeSO4), an iron-based raw material, and carrying out an oxidation reaction at room temperature and pressure for about 10 hours to produce ferric polysulfate ([Fe2(OH) n (SO4) 3-n / 2 〕 m Only 0 <n≤2, m은 자연수) 용액을 얻는 방법이 기재되어 있다.

[0004] However, since this method requires a long time for the reaction, it was required to shorten the reaction time by some method.

[0005] In addition, the method for manufacturing an iron-based inorganic coagulant described in Patent Document 2 is a method of using magnetite (Fe3O4) as an iron-based raw material, adjusting the molar ratio of sulfate ions and iron ions, and then reacting them in a reaction vessel at a temperature of 120 to 180°C. This method aims to shorten the reaction time by carrying out the reaction under high temperature and high pressure, but it still required a reaction time of 0.8 to 1.5 hours.

[0006] Patent document 3 discloses a method for manufacturing an iron-based coagulant by dissolving iron-based raw material, ferric oxide (Fe2O3), in excess sulfuric acid to produce ferric sulfate (Fe2(SO4)3) and partially neutralizing it with hydrated iron-based oxide.

[0007] However, this method has a difficulty in that it cannot efficiently produce a polyferric sulfate solution because the manufacturing process becomes complex, as it includes two processes: dissolving ferric oxide in sulfuric acid and partially neutralizing the generated ferric sulfate. In the example, it is stated that the reaction must be carried out by maintaining the temperature at 100°C for about 3 hours. Prior art literature

[0008] Patent Document 1: Japanese Patent Publication No. Showa 51-17516 Patent Document 2: Japanese Patent Publication No. 3379204 Patent Document 3: Japanese Patent Publication No. 2741137 The problem to be solved

[0009] As mentioned above, in conventional technology, attempts have been made to produce a polyferric sulfate solution by selecting various types of iron compounds as iron-based raw materials and reacting them in various reaction forms; however, in addition to problems such as the generation of free sulfuric acid and reaction residues, there remained the problem of the manufacturing time being prolonged to produce a polyferric sulfate solution suitable for practical use.

[0010] In addition, although details will be provided later, it is stated that in the case of iron-based coagulants, the higher the total iron concentration, the higher the characteristics as a coagulant. Furthermore, the applicant of this patent manufactures and sells the iron-based inorganic polymer coagulant "Polytets" (trademark registered), and its total iron concentration is approximately 11.0 to 12.5% ​​(referred to as "commercial product"). Since iron-based inorganic polymer coagulants possess high coagulation ability and dewatering properties when their total iron concentration is high, recently, products with a total iron concentration of 12.5% ​​or higher have been manufactured and sold as "high-concentration products."

[0011] However, even if a coagulant with a high total iron concentration is manufactured, the total iron concentration was limited to at most 12.7% (less than 13%) due to the problem of the aforementioned manufacturing time being prolonged.

[0012] Furthermore, in the present invention, concentration refers to weight% unless molar concentration is specified, and [T-Fe] is the total weight concentration of iron, [SO4 2- ] represents the weight concentration of sulfate ions.

[0013] Here, the total iron concentration refers to the concentration that includes not only the iron dissolved in the raw material but also the iron present in the raw material solution as a solid (powder, etc.) that is not dissolved. Since even iron-based powders present in the raw material solution contribute to the reaction for manufacturing the ferric polysulfate solution, it is reasonable to include iron-based components that are not dissolved in the solution in the iron concentration.

[0014] However, even in the polyferric sulfate solution prepared in the present invention, although the concentration is indicated as the total iron concentration, it is natural that all the iron is dissolved.

[0015] The present invention was made to solve these problems and aims to provide a manufacturing method capable of continuously producing a polyferric sulfate solution with a high total iron concentration compared to conventional products. The present invention aims to provide a high-concentration polyferric sulfate solution at a low cost by continuously manufacturing it under pressure using a reaction vessel. means of solving the problem

[0016] In order to solve these problems, the present invention is composed of the following technical means.

[0017] (1) A method for continuously producing an iron-based coagulant containing a polyferric sulfate solution, characterized by using ferrous sulfate, sulfuric acid, and oxygen gas as raw materials, continuously supplying a raw material liquid containing ferrous sulfate and sulfuric acid satisfying the following conditions and oxygen gas into a reaction vessel, and continuously removing a polyferric sulfate solution produced by carrying out a reaction at high temperature and high pressure from the reaction vessel.

[0018] Molar ratio of total iron to sulfate ions (SO42- / T-Fe) is 1.2 or higher

[0019] The weight concentration of sulfate ions [SO4 2- When set to ], [SO4 2- ] is 35 weight% or less

[0020] (2) A continuous method for producing an iron-based coagulant of (1) characterized by adding nitric acid or nitrite as a catalyst into the reaction vessel.

[0021] (3) A continuous method for manufacturing an iron-based coagulant of (1) or (2), characterized by high temperature and high pressure reaction conditions of 100°C or higher and 0.3 MPa or higher.

[0022] (4) A method for continuously manufacturing any one of (1) to (3) an iron-based coagulant, characterized by filling 9 liters of a polyferric sulfate solution into a reaction vessel and heating a raw material solution containing ferrous sulfate and sulfuric acid supplied into the reaction vessel to 55 to 70°C.

[0023] (5) A continuous method for manufacturing an iron-based coagulant as described in any one of (1) to (4), characterized by the residence time being within 10 minutes.

[0024] (6) A continuous method for manufacturing an iron-based coagulant as described in any one of (1) to (5), characterized by maintaining the temperature inside the reaction vessel at 100°C to 150°C through the reaction. Effects of the invention

[0025] The ultra-high concentration iron-based coagulant of the present invention is characterized by having a high concentration even when compared to the high concentration iron-based coagulant commercially available to the applicant of the present invention, and possesses high coagulation ability and dewatering properties. In addition, since it contains less moisture compared to conventional products, product transportation costs can be reduced.

[0026] In addition, according to the method for manufacturing an iron-based coagulant of the present invention, continuous production can be achieved by significantly reducing the manufacturing time, which required more than 10 hours in conventional methods, and efficient manufacturing of an iron-based coagulant can be performed. Brief explanation of the drawing

[0027] Figure 1 shows the region where ferric polysulfate can be produced by high temperature and high pressure reaction. Figure 2 is a flowchart of a continuous manufacturing method. Specific details for implementing the invention

[0028] Here, before describing the technical features of the method for manufacturing an iron-based coagulant according to the present invention, first, an inorganic coagulant is described.

[0029] Generally, in sewage sludge treatment, solid-liquid separation is performed by coagulating suspended particles or colloidal particles in the sludge with a coagulant and dewatering them. The surfaces of suspended particles or colloidal particles in sewage sludge are usually negatively charged and remain in a stable state due to repulsive forces caused by surface charges and hydration. A coagulant is an agent that adsorbs to the surface of these particles, neutralizes the surface charges, and weakens the repulsive forces between the particles, thereby causing them to coagulate.

[0030] Iron-based coagulants are representative inorganic coagulants that perform coagulation by neutralizing the negative surface charge of suspended substances, such as suspended particles or colloidal particles, with positively charged iron ions. For this reason, iron-based coagulants always exhibit coagulation whenever iron ions are present; as the coagulation ability of suspended substances increases with higher iron ion concentrations, the amount of coagulant added can be reduced.

[0031] Furthermore, for iron ions in the coagulant to exist stably, a certain amount of negative ions must be present. In the case of iron-based coagulants, sulfate ions typically fulfill this role. Iron-based coagulants are stable when the amount of negative ions is in an appropriate molar ratio with the amount of iron ions; however, if the amount of negative ions is excessive or insufficient, the coagulant becomes unstable and precipitates out as crystals.

[0032] In addition, when sewage sludge is treated using such iron-based coagulants, iron ions are adsorbed onto the surface of suspended particles or colloidal particles and are separated and recovered as solids, but sulfate ions remain in the treated water.

[0033] For this reason, since the treated water becomes highly acidic, it needs to be neutralized with a large amount of neutralizing agent before being discharged into rivers, and it is said that this is one of the factors increasing the cost of sewage sludge treatment. In other words, as a characteristic required of iron-based coagulants, the total iron concentration ([T-Fe]) contained in the coagulant is high, and the sulfate ion concentration ([SO4) 2- It was required that ]) be low.

[0034] (Ingredients used)

[0035] In the preparation of a polyferric sulfate solution using ferrous sulfate as a raw material, the following chemical reaction is believed to proceed.

[0036] m[2FeSO4+(1-n / 2)H2SO4+1 / 2O2+(n-1)H2O]

[0037] → 〔Fe2(OH) n (SO4) 3-n / 2 〕 m

[0038] Only 0 <n≤2, m은 자연수

[0039] The present invention provides a method for continuously forming a solution with high [T-Fe] for an iron-based coagulant comprising the above-described polyferric sulfate solution, and an iron-based coagulant produced thereby.

[0040] In the present invention, first, when an oxidation reaction is carried out under high temperature and high pressure conditions using a raw material solution containing ferrous sulfate (FeSO4) and sulfuric acid as raw materials and oxygen gas, the relationship between the total iron concentration and the sulfate ion concentration of the input raw material solution is set to a specific range. The present invention relates to the molar ratio of total iron to sulfate ions (SO4 2- / T-Fe) is above a specific value, and [SO4 2- By making ] below a specific value, continuous manufacturing that cannot be predicted from conventional technology can be performed, and furthermore, a particularly remarkable effect is achieved in that the manufactured ferric polysulfate solution can be produced with an ultra-high total iron concentration ([T-Fe]) that cannot be produced from conventional technology.

[0041] That is, the first feature of the present invention is to react a raw material solution containing ferrous sulfate and sulfuric acid satisfying the following conditions with oxygen gas under high temperature and high pressure.

[0042] Molar ratio of total iron to sulfate ions (SO4 2- / T-Fe) is 1.2 or higher

[0043] The weight concentration of sulfate ions [SO4 2- When set to ], [SO4 2- ] is 35 weight% or less

[0044] It is a new finding discovered by the inventors that when the total iron concentration of ferrous sulfate and the sulfate ion concentration are in this relationship, an ultra-high concentration polyferric sulfate solution can be obtained in a short time without generating a precipitate.

[0045] This area was established by the following experiment.

[0046] The inventors of the present invention set the reaction conditions for high temperature and high pressure to (1) a reaction temperature of 110°C, a reaction pressure of 0.3 MPa, and a reaction time of 10 minutes, and (2) a reaction temperature of 120°C, a reaction pressure of 10 MPa, and a reaction time of 10 minutes, and adjusted the raw material solution containing ferrous sulfate and sulfuric acid to various concentrations. Nitric acid was added as a catalyst to this, and a high temperature and high pressure reaction was carried out in batch mode. Then, after the reaction time had elapsed, they examined whether a precipitate was formed.

[0047] The results are summarized in the table below. It was found that the same results were obtained when performed under either condition (1) or (2) above. That is, the total iron concentration [T-Fe] and total sulfuric acid concentration [SO4] shown in Table 1 2- In the case of ], no precipitate was formed and a ferric polysulfate solution was formed, and in the case shown in Table 2, the occurrence of a precipitate was confirmed.

[0048]

[0049]

[0050] (Specific area)

[0051] The results of these are summarized in FIG. 1. The area marked with a circle in the figure is the area where a ferric polysulfate solution was formed without the formation of a precipitate. This is the area defined in the present invention and is referred to as the "specific area" hereinafter. The [T-Fe] and [SO4] indicated by the white circle included in this specific area 2- ] is a raw material composition that can stably produce a polyferric sulfate solution in continuous manufacturing according to the present invention. By reacting this composition under high temperature and high pressure conditions, a reddish-brown solution of polyferric sulfate can be obtained.

[0052] Meanwhile, when a reaction is carried out under high temperature and high pressure using the raw material composition indicated by the ▲ symbol outside the specific region, the occurrence of precipitates is confirmed in all cases, and the molar ratio of iron and sulfate ions (SO4 2- In samples in the region where / T-Fe) is lower than 1.2, the precipitate is confirmed to be hydronium jarcite.

[0053] The inventors have defined this specific region from the following two perspectives.

[0054] First, the upper limit of this region is the weight concentration of sulfate ions [SO4 2- ] can be set to 35 weight% or less.

[0055] Next, the lower limit of this region can be defined by an oblique straight line that rises toward the right. This oblique straight line represents the molar ratio of total iron to sulfate ions (SO4 2- The straight line representing the relationship where / T-Fe) is 1.2 or higher was converted into a diagram where the vertical axis and horizontal axis represent the weight concentration of sulfate ions and the weight concentration of total iron, and recorded.

[0056] The [T-Fe] and [SO4] specified in the present invention as described above 2- The specific region regarding the raw material composition of ] can be said to represent a region in which the production of a ferric polysulfate solution can be stably carried out in a short time under high temperature and high pressure conditions.

[0057] (Continuous manufacturing)

[0058] A second feature of the present invention is that the preparation of a polyferric sulfate solution is carried out continuously.

[0059] The specific region shown in FIG. 1 above is the result of a batch-type high-temperature, high-pressure reaction using an autoclave, but since the reaction is carried out under high-temperature, high-pressure conditions, it is a region that can be applied to the adjustment of the raw material composition in the continuous manufacturing of the present invention. Since it became clear that a ferric polysulfate solution can be produced in a short time by carrying out an oxidation reaction under high-temperature, high-pressure conditions using the raw material of the specific region above, the inventors examined manufacturing conditions for continuous manufacturing in order to transition from batch to continuous.

[0060] Since the manufacturing reaction of ferric polysulfate involves carrying out an oxidation reaction under high temperature and high pressure conditions using ferrous sulfate (FeSO4) as a raw material, it is necessary to adjust several conditions when manufacturing it continuously.

[0061] (Setting of manufacturing conditions)

[0062] First, since this reaction involves an exothermic reaction due to the dissolution of the raw material ferrous sulfate and the oxidation of divalent iron ions, temperature control within the reaction vessel is required when carrying out a continuous reaction. In addition, it is necessary to secure sufficient reaction time for the production of polyferric sulfate within the reaction vessel by adjusting the input rate of the raw material and the output rate of the reaction product, the polyferric sulfate solution.

[0063] By adjusting their reaction conditions, the inventors were able to succeed in the continuous production of a ferric polysulfate solution, which was previously unthinkable.

[0064] (Flow of the manufacturing method)

[0065] FIG. 2 illustrates the flow of a continuous manufacturing method for high-concentration polyferric sulfate employed in the present invention. The reaction vessel is equipped with a heating device for startup.

[0066] A device for supplying raw materials is connected to this reaction vessel, and water, iron sulfate, sulfuric acid, and oxygen are supplied, and a catalyst is supplied as needed. The manufactured ferric polysulfate solution is stored in a product tank.

[0067] (Input materials)

[0068] As raw materials, a raw material liquid containing ferrous sulfate and sulfuric acid, and oxygen gas are supplied. In batch type, the supply of oxygen gas is unnecessary, but in continuous type, oxygen is consumed in the reaction, so it is necessary to continuously supply it into the reaction vessel. In addition, if necessary, nitric acid may be added as a catalyst.

[0069] The reaction vessel is filled with preheated final product, ferric polysulfate, and when continuous manufacturing is initiated, the process is set to a high temperature and high pressure state. These raw materials are heated and introduced into the reaction vessel at a constant flow rate. Simultaneously, the reaction product, a ferric polysulfate solution, is discharged at a constant flow rate.

[0070] To promote the reaction for the formation of the above-mentioned ferric polysulfate solution, it is desirable to use a catalyst. Preferred catalysts for promoting the reaction include nitric acid and nitrites, and nitrites include sodium or potassium salts of nitrite. Nitric acid is preferred in terms of reaction-promoting function and cost.

[0071] (Reaction temperature)

[0072] It is necessary to adjust the temperature inside the reaction vessel to a range of 100 to 150°C.

[0073] It has been confirmed that if the reaction temperature is less than 100°C, the oxidation reaction of ferrous sulfate does not proceed sufficiently, and if it exceeds 150°C, a yellow precipitate remains, and this precipitate has been identified as Fe(OH)SO4 by X-ray analysis. Therefore, it is desirable to adjust the temperature inside the reaction vessel to a range of 110°C to 130°C, and furthermore, to a range of 115°C to 125°C.

[0074] In addition, by preheating the input raw materials using the heat generated by the reaction, the reaction heat can be recovered to produce ferric polysulfate at a low cost.

[0075] (enter)

[0076] The pressure inside the reaction vessel must be 0.3 MPa or higher.

[0077] In the method for manufacturing an iron-based coagulant according to the present invention, since the reaction proceeds by the solid raw material ferrous sulfate (FeSO4·7H2O) being dissolved and oxidized in sulfuric acid, the dissolution of ferrous sulfate proceeds under high temperature conditions, and the oxidation reaction is promoted by increasing the partial pressure of oxygen under high pressure conditions. For this reason, theoretically, higher pressure is preferable from the perspective of promoting the reaction.

[0078] However, from the perspective of industrial production, it is natural that low pressure is desirable. In the present invention, the lower limit of the pressure is set to 0.3 MPa. If the reaction is carried out at a lower pressure than this, the oxidation reaction of the solution is suppressed, normal reaction conditions are disrupted, and stable continuous operation cannot be performed. In addition, by setting the pressure inside the reaction vessel to about 5.0 MPa, the manufacturing efficiency of polyferric sulfate can be significantly improved.

[0079] (Time of stay)

[0080] In the continuous production of ferric polysulfate solutions, the time from when the raw material liquid introduced into the reaction vessel and the separately supplied oxygen gas undergo a chemical reaction within the reaction vessel until the ferric polysulfate solution is withdrawn from the reaction vessel (here, this time is referred to as the residence time) becomes important.

[0081] In the present invention, the residence time is defined as follows. That is, if the amount of liquid filled in the reaction vessel in advance before starting the manufacturing reaction is M[L], and the amount of raw material liquid input and reaction liquid output is Q[L / min], the residence time t[min] is expressed by the following formula.

[0082] t=M / Q

[0083] In the case of batch manufacturing, the raw material introduced can be kept in the reaction vessel until the oxidation reaction is completed. However, in the case of continuous manufacturing, if a long time is required until the reaction is completed, the introduction of the raw material liquid and the extraction of the reaction product are carried out continuously, so it becomes necessary to take measures such as increasing the size of the reaction vessel or slowing down the rate of introduction of the raw material and extraction of the product.

[0084] For this reason, securing an appropriate residence time is a major issue in order to enable continuous industrial manufacturing. On the other hand, it is natural that a short residence time in the reaction vessel is desirable for efficient manufacturing.

[0085] In particular, regarding the production of ferric polysulfate solution, since it took at least several hours to complete the reaction in conventional technology, continuous production was unthinkable in conventional technology.

[0086] As described above, the inventors succeeded in significantly shortening the reaction time in a batch process by using ferrous sulfate and sulfuric acid as raw materials and reacting them under high temperature and high pressure conditions. However, even in that case, a reaction time of within 10 minutes was required when the total iron concentration of the raw materials was less than 13%, and within 30 minutes when the total iron concentration of the raw materials was high, ranging from 13% to 16%.

[0087] However, surprisingly, by transitioning the production of the polyferric sulfate solution from batch to continuous production, it was experimentally confirmed that even when using a 20-liter capacity reaction vessel, the time required for the reaction, i.e., the residence time, was about 8 minutes when the reaction was carried out under pressure conditions of 0.3 MPa and 5.0 MPa.

[0088] Although no theoretical explanation has been provided regarding the reduction of reaction time (residence time) by performing the continuous production of a ferric polysulfate solution, the inventors believe that this may be due to the following reference. However, the technical content of the present invention should not be interpreted based on the following assumptions.

[0089] That is, in continuous manufacturing, the raw material solution containing ferrous sulfate and sulfuric acid is introduced together with a catalyst into a polyferric sulfate solution maintained at the high temperature and high pressure required for the reaction, and since the reaction is initiated in the polyferric sulfate solution, it is thought that the reaction is accelerated compared to the batch method in which the reaction is initiated from an environment of only the raw material solution.

[0090] In addition, it is technically obvious that the residence time can be further shortened by devising various means to promote the oxidation reaction of ferrous sulfate. For example, it is thought that the residence time can be shortened by adopting stricter high-temperature and high-pressure conditions, highly active catalysts, and efficient stirring methods. Considering the economic feasibility of industrial operations, it is desirable that the residence time be within 10 minutes.

[0091] Furthermore, it goes without saying that continuous production of ferric polysulfate is possible even when the residence time is set to a long duration by disregarding economic efficiency, such as by using a larger reaction vessel or performing the input of raw materials and the extraction of products at a low flow rate.

[0092] Table 3 summarizes the extent to which efficiency can be improved by continuously producing a polyferric sulfate solution compared to the conventional batch method.

[0093]

[0094] The conventional method by batch processing is the conventional method for manufacturing a polyferric sulfate solution proposed by the applicant of this application in Patent Document 1. In the batch process, since it is necessary to sequentially carry out the processes of raw material input, oxidation reaction, and product extraction, it was necessary to take a long time to manufacture. Specifically, in order to manufacture 1,000 tons of polyferric sulfate solution per month, it was necessary to use a large reaction vessel with a capacity of 45 m³ and continue operation for 12 hours a day for 20 days.

[0095] However, according to the continuous manufacturing method of the present invention, since the above-mentioned manufacturing process can be carried out simultaneously, it is possible to shorten the manufacturing time, increase the manufacturing volume, and miniaturize the reaction vessel.

[0096] Specifically, by using a 0.6 m³ vessel, which is about 1 / 10 the capacity of the reaction vessel used in the conventional method, and operating continuously for 24 hours, it is possible to produce three times the amount of polyferric sulfate solution as in the conventional method in 20 days. In addition, even if the reaction vessel is miniaturized to a capacity of 0.2 m³, an amount of polyferric sulfate solution equivalent to that of the conventional method can be produced.

[0097] This effect brings immeasurable economic benefits to factory production.

[0098] Examples

[0099] The embodiments of the present invention are summarized below. However, the present invention is not limited to these embodiments.

[0100] Example 1

[0101] 9 liters of ferric polysulfate solution were filled into a 20-liter capacity autoclave, and the temperature inside the vessel was adjusted to 120°C and the pressure to 0.3 MPa. The filled ferric polysulfate solution had the total iron concentration [T-Fe] and sulfate ion concentration [SO4] at an elapsed time of 0 minutes as shown in Table 4 below. 2- It is to have ].

[0102] To this, ferrous sulfate heated to 60°C, sulfuric acid, sodium nitrite, and oxygen gas were added. The total iron concentration [T-Fe] and sulfate ion concentration [SO4] of the raw material solution containing the added ferrous sulfate and sulfuric acid 2- ] were 12.7 wt% and 32.5 wt%, respectively. In addition, the molar ratio of total iron to sulfate ions (SO4 2- / T-Fe) was 1.49.

[0103] The feed solution containing ferrous sulfate and sulfuric acid was added at a rate of 1.2 liters per minute. Upon adding the feed solution, the reaction for the formation of polyferric sulfate was initiated, and although the temperature inside the reaction vessel rose, the temperature inside the vessel was maintained within the range of 110 to 130°C through cooling operations. The reaction product was discharged at a rate of 1.2 liters per minute. Since 1.2 liters of the feed solution was added per minute to 9 liters of polyferric sulfate solution inside the reaction vessel, the residence time was 8 minutes.

[0104] By regularly chemically analyzing the product solution discharged from the reaction vessel and checking the levels of divalent iron, it was confirmed that ferric polysulfate was produced.

[0105] Example 2

[0106] Except for adjusting the pressure inside the reaction vessel to 5.0 MPa, the reaction was carried out under the same conditions as in Example 1 regarding the composition of the raw materials to be introduced, the rate of introduction of the raw materials, the rate of release of the reaction products, the residence time, etc.

[0107] As in Example 1, the reaction product was periodically sampled and extracted, and chemical analysis was performed. As in Example 1, it was confirmed that ferric polysulfate was produced.

[0108] The results of sampling the reaction product at set intervals and investigating changes in the component concentrations are summarized in Table 4.

[0109]

[0110] As is evident from Table 4, a high-concentration ferric polysulfate solution with a total iron concentration of 12.5% ​​or higher could be stably prepared over a period of approximately 100 minutes from the start of the reaction. In addition, Fe 2+ Since the concentration was below the detection limit, it was confirmed that there were no unreacted residues.

[0111] In Example 2, considering the safety of the experimental results, conditions such as the input rate of raw materials, the output rate of reaction products, and the residence time were set to be the same as in Example 1. However, since the pressure inside the reaction vessel is overwhelmingly higher compared to Example 1, it is possible to shorten the residence time inside the reaction vessel by increasing the input rate of raw materials and the output rate of reaction products. Then, it is believed that the manufacturing efficiency of polyferric sulfate can be significantly improved. Industrial applicability

[0112] This invention relates to a coagulant used in the treatment of wastewater such as sewage. Since a coagulant with high coagulation performance can be manufactured in a short time, it can be widely used in the field of wastewater treatment.

Claims

Claim 1 A continuous manufacturing method of an iron-based coagulant containing a polyferric sulfate solution, characterized by using ferrous sulfate, sulfuric acid, and oxygen gas as raw materials, supplying a raw material solution containing ferrous sulfate and sulfuric acid satisfying the following conditions and oxygen gas into a reaction vessel, and carrying out a reaction at high temperature and high pressure to continuously extract the polyferric sulfate produced from the reaction vessel. The molar ratio of total iron to sulfate ions (SO4 2- / T-Fe) is 1.2 weight concentration of ion-12 ions [SO4 2- When set to ], [SO4 2- ] is 35 wt% or less, and the total iron concentration in the raw material solution is 13 wt% or more. Claim 2 A continuous method for producing an iron-based coagulant according to claim 1, characterized by further adding nitric acid or nitrite as a catalyst into the reaction vessel. Claim 3 A continuous manufacturing method for an iron-based coagulant according to claim 1 or 2, characterized in that the high temperature and high pressure reaction conditions are 100°C or higher and 0.3 MPa or higher. Claim 4 A continuous method for manufacturing an iron-based coagulant according to claim 1 or 2, characterized by filling a reaction vessel with 9 liters of a polyferric sulfate solution and heating a raw material solution containing ferrous sulfate and sulfuric acid supplied to the reaction vessel to 55 to 70°C. Claim 5 A continuous manufacturing method of an iron-based coagulant according to claim 1 or 2, characterized in that the residence time is within 10 minutes. Claim 6 A continuous manufacturing method of an iron-based coagulant according to claim 1 or 2, characterized in that the temperature inside the reaction vessel is maintained at 100℃ to 150℃ through the reaction. Claim 7 A continuous manufacturing method of an iron-based coagulant according to claim 1 or 2, characterized in that the total iron concentration in the raw material liquid is 13% by weight or more and 16% by weight or less.

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