A method for synergic treatment of desulfurization wastewater and sintering dust

Abstract

The application discloses a kind of desulfurization wastewater and sintering dust's collaborative processing method, including s1, after mixing stirring of sintering dust and desulfurization wastewater, solid-liquid separation is carried out, and supernatant separated is treated to remove hardness;S2, after treating to remove hardness, flocculation, precipitation treatment is carried out, and the filtrate of the sludge of precipitation and the supernatant of precipitation unit are filtered and then treated by brine conditioning tank, then enter pH adjusting tank, finally, evaporation crystallization is carried out to obtain potassium chloride and sodium chloride crystalline salt, the reagent of the reagent for treating to remove hardness is prepared into solution using water in brine conditioning tank;Flocculation treatment is prepared into solution using condensate produced by evaporation crystallization;Calcium hydroxide solution and sodium carbonate solution are prepared using water in brine conditioning tank, and flocculant solution is prepared using condensate in evaporation crystallization unit, not only save the use of fresh water, but also use the residual alkalinity generated by the excess of dosing amount of hardening-removing reagent, and the dosing amount of hardening-removing reagent is further saved by pH feedback control.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of industrial wastewater treatment, in particular to a method for co-processing desulfurization wastewater and sintering dust. BACKGROUND

[0002] At present, the most advanced technology for treating water-washed sintering dust at home and abroad is the potassium chloride recovery process of water-washing potassium removal-solid-liquid separation-impurity removal and purification-solid-liquid separation-evaporation crystallization, which can produce high-quality potassium chloride from sintering dust. This method can leach potassium, sodium, chlorine and other elements from the dust to improve the quality of the dust. The sintering wet desulfurization wastewater and sintering dust are in the same production unit, which can be used to treat the wastewater with the dust, i.e. using the desulfurization wastewater to wash the sintering dust. However, the wet desulfurization wastewater contains a large amount of magnesium hardness and calcium hardness, which requires a large amount of calcium hydroxide and sodium carbonate as hardening removal agents. If new water is used to prepare the solvent, a large amount of new water will be consumed, and the water treatment capacity of the subsequent evaporation crystallization will also increase, resulting in an increase in the operation cost of the evaporation crystallization. At the same time, the unit price of sodium carbonate is relatively high, and how to reduce the addition of sodium carbonate as much as possible also relates to the operation cost of the entire process.

[0003] Therefore, in order to solve the above problems, there is an urgent need for a method for co-processing desulfurization wastewater and sintering dust that can effectively utilize the desulfurization wastewater and sintering dust and optimize the desulfurization wastewater and sintering dust treatment unit. SUMMARY

[0004] Therefore, the present application provides a method for co-processing wet desulfurization wastewater and sintering dust, which solves the problem of high operation cost of the existing wet desulfurization wastewater and sintering dust co-processing technology.

[0005] The method for co-processing desulfurization wastewater and sintering dust of the present application comprises the following steps:

[0006] s1, mixing and stirring the sintering dust and the desulfurization wastewater, and then performing solid-liquid separation, and performing hardening removal treatment on the separated supernatant;

[0007] s2, performing flocculation and sedimentation treatment after the hardening removal treatment, filtering the sedimentation sludge filtrate and the supernatant of the sedimentation unit, and then treating them in a concentrated brine adjustment tank, and then treating them in a pH adjustment tank, and finally performing evaporation crystallization to obtain potassium chloride and sodium chloride crystalline salt, wherein the hardening removal treatment agent is prepared into a solution by using the water in the concentrated brine adjustment tank, and the flocculant used in the flocculation treatment is prepared into a solution by using the condensate water produced in the evaporation crystallization;

[0008] Further, in step s1, magnesium hardness removal treatment is performed first, and then calcium hardness removal treatment is performed.

[0009] Further, in step s1, the water in the concentrated brine adjusting pool is adjusted with calcium hydroxide to prepare a magnesium-removing hard agent solution, and the water in the concentrated brine adjusting pool is adjusted with sodium carbonate to prepare a calcium-removing hard agent solution;

[0010] Further, in step s2, a flocculating agent is used for flocculation treatment, and the flocculating agent is prepared into a solution with condensed water generated by the evaporation crystallization;

[0011] Further, the variable frequency pump is used to add the calcium hydroxide solution and the sodium carbonate solution, a pH meter is installed in the concentrated brine adjusting pool, and a pH initial threshold value of the concentrated brine adjusting pool is set, the variable frequency pump and the pH meter are both controlled by a PLC control system, and the residual alkalinity generated by the excess of the calcium hydroxide solution and the sodium carbonate solution is used to adjust the adding amount of the hard-removing agent through the pH feedback and the PLC control system;

[0012] Further, the control of the PLC control system comprises the following steps:

[0013] 1) The initial adding amount of calcium hydroxide and the adding amount of sodium carbonate are calculated according to the calcium hardness and the magnesium hardness of the wet desulfurization wastewater to ensure that the total hardness and the calcium hardness entering the evaporation crystallization are less than the allowable value of the evaporation crystallization;

[0014] 2) When the pH of the concentrated brine adjusting pool exceeds the threshold value, the adding amount of sodium carbonate is reduced by the PLC control system until the pH of the concentrated brine adjusting pool is lower than the threshold value, while ensuring that the total hardness and the calcium hardness entering the evaporation crystallization are lower than the allowable value of the evaporation crystallization, and if the total hardness and the calcium hardness are higher than the allowable value of the evaporation crystallization, the initial threshold value of the pH of the concentrated brine adjusting pool is reset;

[0015] 3) The threshold value of the pH of the concentrated brine adjusting pool is further reduced, and step (2) is repeated.

[0016] The wet desulfurization wastewater and sintering dust collaborative disposal process method has the advantages that the calcium hydroxide solution and the sodium carbonate solution are prepared with the water in the concentrated brine adjusting pool, the flocculating agent solution is prepared with the condensed water of the evaporation crystallization unit, new water is saved, the residual alkalinity generated by the excess of the adding amount of the hard-removing agent is used, the adding amount of the hard-removing agent is adjusted through the pH feedback, and the adding amount of the hard-removing agent is further saved. In addition, since no new water is introduced, there is no dilution phenomenon in the whole process, and the cost of the subsequent evaporation crystallization is saved. BRIEF DESCRIPTION OF DRAWINGS

[0017] The application will be further described below in combination with the drawings and examples:

[0018] Figure 1 The wet desulfurization wastewater and sintering dust collaborative disposal process method has the advantages that the calcium hydroxide solution and the sodium carbonate solution are prepared with the water in the concentrated brine adjusting pool, the flocculating agent solution is prepared with the condensed water of the evaporation crystallization unit, new water is saved, the residual alkalinity generated by the excess of the adding amount of the hard-removing agent is used, the adding amount of the hard-removing agent is adjusted through the pH feedback, and the adding amount of the hard-removing agent is further saved. In addition, since no new water is introduced, there is no dilution phenomenon in the whole process, and the cost of the subsequent evaporation crystallization is saved. DETAILED DESCRIPTION

[0019] The synergistic treatment method of the desulfurization wastewater and the sintering dust removal ash of the embodiment comprises the following steps:

[0020] s1, after mixing and stirring the sintering dust removal ash and the desulfurization wastewater, solid-liquid separation is carried out, and the supernatant separated is subjected to hardness removal treatment; first magnesium hardness removal treatment is carried out, and then calcium hardness removal treatment is carried out; after mixing the sintering machine head ash and the desulfurization wastewater according to a certain solid-liquid ratio, stirring for several hours, and solid-liquid separation, the supernatant is introduced into a first hardness removal unit, calcium hydroxide is added, magnesium hardness is removed, then a second hardness removal unit is entered, sodium carbonate is added, and calcium hardness is removed;

[0021] s2, after the hardness removal treatment, flocculation and sedimentation treatment are carried out, the sedimentation sludge filtrate and the supernatant of the sedimentation unit are filtered, treated by a concentrated brine adjusting tank, then introduced into a pH adjusting tank, and finally subjected to evaporation crystallization to obtain potassium chloride and sodium chloride crystalline salt; the reagent for the hardness removal treatment is prepared into a solution by using water in the concentrated brine adjusting tank; the flocculant for the flocculation treatment is prepared into a solution by using condensed water generated by the evaporation crystallization; after the hardness removal treatment, a flocculation unit is entered, polyacrylamide (PAM) is added, then a sedimentation tank is entered, solid-liquid separation is carried out on the bottom sediment, the filtrate and the supernatant of the sedimentation tank are introduced into a filtration unit to remove suspended solids, then introduced into the concentrated brine adjusting tank, part of the water is backflowed to a reagent dissolving barrel to be used for preparation of the calcium hydroxide solution and the sodium carbonate solution; then introduced into the pH adjusting tank, hydrochloric acid is added until the pH is 6.5 to 7, and finally introduced into an evaporation crystallization system to obtain potassium chloride and sodium chloride crystalline salt, part of the condensed water is backflowed to the reagent dissolving barrel to be used for preparation of the PAM solution.

[0022] In the embodiment, the variable frequency pump is used to add the calcium hydroxide solution and the sodium carbonate solution, the concentrated brine adjusting tank is installed with a pH meter and provided with a concentrated brine adjusting tank pH initial threshold value, and the variable frequency pump and the pH meter are both controlled by a PLC control system; the control of the PLC control system comprises the following steps:

[0023] 1) The initial calcium hydroxide addition amount and the sodium carbonate addition amount are calculated according to the calcium hardness and the magnesium hardness of the wet desulfurization wastewater to ensure that the total hardness and the calcium hardness when entering the evaporation crystallization are both less than the evaporation crystallization allowable value; for example, the total hardness and the calcium hardness are both less than 200 mg / L;

[0024] 2) When the pH of the concentrated brine adjusting tank exceeds the threshold value, the sodium carbonate addition amount is reduced by the PLC control system until the pH of the concentrated brine adjusting tank is lower than the threshold value, while ensuring that the total hardness and the calcium hardness when entering the evaporation crystallization are both less than the evaporation crystallization allowable value, if higher than the evaporation crystallization allowable value, the concentrated brine adjusting tank pH initial threshold value is reset;

[0025] 3) The concentrated brine adjusting tank pH threshold value is further reduced, and step (2) is repeated.

[0026] Since the market price of sodium carbonate is about 3000 yuan per ton. The market price of calcium hydroxide is about 500 yuan per ton. And the magnesium hardness of the wet desulfurization wastewater accounts for a large proportion in the total hardness, with the order of magnitude of ten thousand mg / L, so it is necessary to reduce the dosage of sodium carbonate as much as possible to save the cost of reagent, and calcium hydroxide can be excessive. Excessive calcium hydroxide can reduce the sulfate and ammonia nitrogen of the desulfurization wastewater.

[0027] Example one

[0028] The wet desulfurization wastewater from the desulfurization wastewater conditioning tank enters the water washing unit through the self-priming pump, and the sintering dust from the dust storage bin enters the water washing unit through the pneumatic diaphragm pump. The first-stage water washing is adopted, and the water and dust are washed and stirred for 3 hours according to the water-dust ratio of 6 to 1, and then the supernatant (also known as eluent) is placed for 24 hours. The supernatant enters the water quantity conditioning tank, and the sludge at the bottom is discharged into the ton bag in the ton barrel through the electric gate valve. About 130 L / h of eluent from the water quantity conditioning tank enters the first-stage hardness removal unit to add about 45 L / h of calcium hydroxide (mass concentration 5%) to remove magnesium hardness, enters the second-stage hardness removal unit to add about 36 L / h of calcium hydroxide (mass concentration 10%) to remove calcium hardness, enters the flocculation unit to add about 10 L / h of PAM (mass concentration 0.5%) for flocculation reaction, enters the sedimentation unit to remove suspended solids, and the sludge in the sedimentation tank is discharged and then filtered through the plate and frame filter press to recover the filtrate. The filtrate and the supernatant in the sedimentation tank enter the filtration unit together to further remove suspended solids, and enter the concentrated brine conditioning tank. Part of the water in the concentrated brine conditioning tank is returned to the medicine dissolving barrel to prepare calcium hydroxide solution and sodium carbonate solution, and the rest of the water enters the ph conditioning tank, and hydrochloric acid is added to the ph of 6.5-7. It enters the evaporation and crystallization unit, and the condensed water is returned to the medicine dissolving barrel to prepare PAM solution. The produced potassium chloride and sodium chloride crystalline salt both reach the industrial first-class standard and can be sold.

[0029] Finally, it should be pointed out that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the purpose and scope of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A method for synergistic treatment of desulfurization wastewater and sintering dust, characterized in that: It comprises the following steps: s1, after mixing and stirring the sintered fly ash and desulfurization wastewater, solid-liquid separation is carried out, the supernatant is separated, magnesium hardness removal treatment is carried out again, and calcium hardness removal treatment is carried out; The water in the concentrated brine adjusting pool is used to prepare a magnesium hardness removal agent solution with calcium hydroxide, and the water in the concentrated brine adjusting pool is used to prepare a calcium hardness removal agent solution with sodium carbonate; The variable frequency pump is used to add calcium hydroxide solution and sodium carbonate solution, the concentrated brine adjusting pool is installed with a pH meter and set with a concentrated brine adjusting pool pH initial threshold value, the variable frequency pump and the pH meter are controlled by a PLC control system, the excess alkalinity generated by the addition amount of calcium hydroxide solution and sodium carbonate solution is used to adjust the addition amount of the hardness removal agent through the PLC control system combined with pH feedback, and the control of the PLC control system comprises the following steps: 1) The initial calcium hydroxide addition amount and sodium carbonate addition amount are calculated according to the calcium hardness and magnesium hardness of the wet desulfurization wastewater to ensure that the total hardness and calcium hardness entering the evaporation crystallization are less than the evaporation crystallization allowable value; 2) When the pH of the concentrated brine adjusting pool exceeds the threshold value, the sodium carbonate addition amount is reduced by the PLC control system until the pH of the concentrated brine adjusting pool is lower than the threshold value, while ensuring that the total hardness and calcium hardness entering the evaporation crystallization are lower than the evaporation crystallization allowable value, if higher than the evaporation crystallization allowable value, the initial pH threshold value of the concentrated brine adjusting pool is reset; 3) Further reduce the pH threshold value of the concentrated brine adjusting pool, repeat step (2); s2, after the hardness removal treatment, flocculation and sedimentation treatment are carried out, the sedimentation sludge filtrate and the supernatant of the sedimentation unit are filtered and then treated by the concentrated brine adjusting pool, then treated by the pH adjusting pool, and finally evaporated and crystallized to obtain potassium chloride and sodium chloride crystalline salt, the agent for hardness removal treatment is prepared into a solution with water in the concentrated brine adjusting pool; The flocculant used in flocculation treatment is prepared into a solution with condensate water generated from evaporation crystallization.

2. The method for synergic treatment of desulfurization wastewater and sintering dust ash according to claim 1, characterized in that: In step s2, flocculation treatment is carried out with a flocculant prepared into a solution with condensate water generated from evaporation crystallization. In step s2, flocculation treatment is carried out with a flocculant prepared into a solution with condensate water generated from evaporation crystallization.

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