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CN-121990722-A - Industrial wastewater hardness removal method and system based on pH and medicament cooperative control

CN121990722ACN 121990722 ACN121990722 ACN 121990722ACN-121990722-A

Abstract

The invention is suitable for the technical field of industrial wastewater treatment, and provides an industrial wastewater hardness removal method and system based on pH and medicament cooperative control, wherein the hardness removal method comprises water quality analysis and parameter setting, accurate pH value regulation and control, carbonate precipitation stage, flocculation stage and solid-liquid separation, the hardness removal system comprises a water quality on-line monitoring unit, a parallel reaction tank unit, a medicament accurate adding unit and an intelligent control unit, and the hardness removal method and system provide a set of process control logic which can be quantitatively and automatically executed, so that the traditional empirical operation is converted into accurate engineering control based on a clear chemical reaction mechanism.

Inventors

  • WANG HAORAN
  • ZHAO TING
  • LIU JING
  • XU NA

Assignees

  • 内蒙古大全新能源有限公司

Dates

Publication Date
20260508
Application Date
20260309

Claims (10)

  1. 1. The industrial wastewater hardness removal method based on pH and medicament cooperative control is characterized by comprising the following steps of: S1, acquiring water quality parameters of wastewater to be treated, including magnesium ion concentration, setting a target pH value, an upper limit value of the addition amount of polyaluminium chloride (PAC), the addition sequence of each medicament and the minimum time interval between adjacent steps in a control system according to the water quality parameters; s2, accurately regulating and controlling the pH value, namely introducing wastewater into a reaction tank, adding an alkaline agent into the reaction tank, and rapidly lifting and stably maintaining the pH value of a reaction system within a range of 11.3-11.7 through stirring and real-time monitoring; S3, carbonate precipitation, namely adding sodium carbonate solution into the reaction tank after the pH value reaches and is stabilized in a target range through a first preset time delay, so that the sodium carbonate solution reacts with calcium ions in the wastewater to generate calcium carbonate precipitation, and the calcium carbonate precipitation and the magnesium hydroxide precipitation which is formed under alkaline conditions coexist; s4, a flocculation stage, namely after the sodium carbonate solution is fully added, adding a polyaluminium chloride (PAC) solution into the reaction tank through a second preset time delay, wherein the adding concentration of PAC is not more than 1.25 g/L of wastewater calculated by commodity solids; s5, solid-liquid separation, namely adding coagulant aid into the reaction tank to enable the formed floccules to be coagulated into compact floccules, and then carrying out precipitation separation on the mixed solution to obtain softened effluent.
  2. 2. The method for hardness removal of industrial wastewater based on pH cooperative control with a chemical according to claim 1, wherein the target pH is preferably 11.5 in step S2.
  3. 3. The method for removing hardness from industrial wastewater based on cooperative control of pH and chemicals as set forth in claim 1, wherein the first predetermined time delay is 1 to 2 minutes to ensure that hydroxide ions and magnesium ions are sufficiently reacted to form magnesium hydroxide nuclei.
  4. 4. The method for removing hardness from industrial wastewater based on cooperative control of pH and medicament according to claim 1, wherein the second preset time delay is at least 1 minute to ensure that carbonate ions remained in water fully react with calcium and magnesium ions and avoid interfering reaction with aluminum ions in PAC (aluminum chloride) added subsequently.
  5. 5. The industrial wastewater hardness removal method based on pH and medicament cooperative control of claim 1, wherein in step S4, the adding amount of PAC is dynamically adjusted according to the concentration of magnesium ions in water to be treated, and the calculating formula is PAC adding amount (g/L) =min (kxMg2+ ], 1.25), wherein k is a coefficient, the value range is 0.01-0.015L/Mg, and Mg2+ ] is the concentration of magnesium ions in water, and the unit is Mg/L.
  6. 6. The method for removing hardness from industrial wastewater based on cooperative control of pH and medicament according to claim 1, wherein in step S3, when the concentration of calcium ions in the wastewater to be treated is lower than a set threshold value, carbon dioxide gas is introduced into a reaction system, and bicarbonate ions formed in water are utilized to generate calcium carbonate precipitation under the condition that the pH value is 9-10, so as to replace or partially replace the addition of sodium carbonate solution.
  7. 7. The method for removing hardness from industrial wastewater based on cooperative control of pH and chemicals according to any one of claims 1 to 6, wherein steps S1 to S5 are intermittently or continuously performed in one or more reaction tanks arranged in parallel, and inflow water is dynamically distributed in real time according to the outflow water quality of each reaction tank by an intelligent control unit.
  8. 8. A hardness removal system for implementing the hardness removal method according to any one of claims 1 to 7, comprising: the water quality on-line monitoring unit is used for monitoring the hardness, the pH value and the flow of the inlet water and the outlet water in real time; the parallel reaction tank unit comprises at least two independent reaction tanks, and each reaction tank is internally provided with a stirring device and a high-precision pH sensor; The accurate dosing unit of the medicament comprises an independent medicament storage tank for respectively storing an alkaline medicament, a sodium carbonate solution, a PAC solution and a coagulant aid, and a metering pump communicated with a corresponding reaction tank through a pipeline; The intelligent control unit is in signal connection with the water quality on-line monitoring unit, the sensor in the parallel reaction tank unit and the metering pump in the accurate dosing unit of medicament, and the intelligent control unit is configured to: (a) Controlling the adding amount of the alkaline medicament according to the set target pH value and the feedback signal of the high-precision pH sensor; (b) According to the irreversible adding sequence of the preset alkaline medicament, sodium carbonate solution, PAC solution and coagulant aid and the minimum time interval between the adjacent steps, sequentially starting and stopping metering pumps of the corresponding medicaments; (c) Calculating and controlling the addition amount of PAC solution according to the formula of claim 5 according to the concentration of magnesium ions in inlet water measured by the water quality on-line monitoring unit, so as to ensure that the upper limit value is not exceeded; and the high-efficiency solid-liquid separation unit is used for receiving and processing the mixed liquid from the parallel reaction tank units to realize rapid sedimentation and sludge concentration of the flocs.
  9. 9. The hardness removal system of claim 8, wherein when said parallel reaction tank unit has a plurality of reaction tanks, the flow rate of wastewater entering each reaction tank is dynamically optimized according to the hardness data of the effluent of each reaction tank.
  10. 10. The hardness removal system as set forth in claim 8, wherein said high-efficiency solid-liquid separation unit is a high-density sedimentation tank with inclined pipe or inclined plate packing.

Description

Industrial wastewater hardness removal method and system based on pH and medicament cooperative control Technical Field The invention relates to the technical field of industrial wastewater treatment, in particular to an industrial wastewater hardness removal method and system based on pH and medicament cooperative control. Background The treatment of high hardness industrial wastewater (such as wastewater produced by photovoltaic, chemical, electrical, etc. industries) is a worldwide problem. The high concentration of calcium and magnesium ions in the wastewater is easy to cause the problems of scaling of a subsequent membrane treatment system, efficiency reduction of heat exchange equipment, pipeline blockage and the like, so that effective softening pretreatment is required. The main current high-hardness wastewater treatment technology mainly comprises a chemical precipitation method and an improvement route thereof, and alternative technologies such as ion exchange, membrane separation and the like, but the main current high-hardness wastewater treatment technology has respective limitations: the traditional chemical precipitation method (such as lime-soda ash method) is to add lime and soda ash to form calcium carbonate and magnesium hydroxide precipitate. The method has wide application, but has the inherent defects that (1) the treatment efficiency is unstable, organic matters and scale inhibitors in the wastewater are complexed with calcium and magnesium ions to seriously inhibit precipitation reaction, (2) a large amount of chemical sludge with high water content is generated, the treatment cost is high, (3) magnesium hydroxide is colloid precipitation, the sedimentation performance is poor, effluent is easy to cause 'muddy', and (4) the pH control is rough, generally only an alkaline condition is required, and the accurate control on an optimal reaction pH interval is lacked, so that the precipitation thoroughness is influenced. The improved route of chemical precipitation (such as 'oxidation decomplexing + optimizing agent') is to increase advanced oxidation pretreatment or develop compound agent aiming at complex interference. The route increases the complexity of the process flow and the operation cost, possibly introduces new sludge or secondary pollution, and fails to fundamentally solve the problems of cooperation and interference among agents in the chemical precipitation process. Alternative softening techniques (such as ion exchange, nanofiltration, electrochemical methods, etc.) which have better effluent quality but generally have the problems of high cost, limited applicability, etc. For example, the regeneration of ion exchange resin consumes a large amount of salt and produces high-salt wastewater, the membrane method is easy to pollute, the investment and maintenance cost is high, and the electrochemical method has high energy consumption. They are difficult to treat complex industrial wastewater with high hardness, high suspended matters and high organic matters economically and efficiently alone. In practice, it has been found that when polyaluminium chloride is used as a flocculant to improve the conventional chemical precipitation process, there are two key problems that can easily lead to system failure: (1) The reaction interference among the medicaments is usually supplemented with sodium carbonate for improving the hardness removing effect. If the adding sequence or timing of PAC and sodium carbonate is improper, carbonate ions can react with aluminum ions in PAC preferentially to generate aluminum carbonate complex without flocculation, so that PAC is completely deactivated, and the flocculation capacity of the system is lost. (2) The secondary pollution is introduced by the dosing, and the commodity PAC itself contains a certain amount of calcium and magnesium impurities. When the hardness of the inlet water is not extremely high, PAC is added excessively empirically, hardness ions introduced by the PAC can offset the treatment effect, and even the hardness of the outlet water is higher than that of the inlet water. Therefore, the prior art lacks a deep hardness removal systemization scheme capable of fundamentally preventing the interference factors and realizing efficient cooperation and quantitative and precise control of the medicament under the strong alkaline condition. Disclosure of Invention Aiming at the defects existing in the prior art, the invention aims to provide a high-hardness industrial wastewater deep hardness removal system and method which are stable in operation, low in medicament consumption, good in sludge sedimentation performance and capable of thoroughly avoiding mutual medicament interference and secondary pollution. In order to achieve the above purpose, the present invention provides the following technical solutions: An industrial wastewater hardness removal method based on pH and medicament cooperative control comprises the following steps: