CN111196659A - Industrial cleaning waste liquid treatment method - Google Patents

Abstract

The invention discloses a method for treating industrial cleaning waste liquid, which comprises a step of mixing alkali cleaning waste liquid and acid cleaning waste liquid, a step of adding hydrogen peroxide and calcium hypochlorite, a step of adding passivating solution, a step of adding medicament sodium hydroxide solution and polyacrylamide, and a step of flocculating settling, membrane treatment and desalting treatment. The treatment method of the invention has the advantages of convenient and fast treatment of the cleaning waste liquid, high efficiency and low cost, realizes the recycling of the cleaning liquid, reduces the treatment cost of enterprises, and simultaneously promotes the development of chemical cleaning.

Description

Industrial cleaning waste liquid treatment method

Technical Field

The invention belongs to the technical field of waste liquid treatment, and particularly relates to a system and a method for treating industrial cleaning waste liquid.

Background

The chemical cleaning is mainly divided into alkaline cleaning, water washing after alkaline cleaning, acid cleaning, water washing after acid cleaning and passivation, and the generated waste liquid is mainly alkaline cleaning waste liquid, acid cleaning waste liquid, passivation waste liquid and water washing waste liquid after acid cleaning and alkaline cleaning. The main agents for alkali washing are various alkalis and surfactants, such as caustic soda, trisodium phosphate and the like. The pollution to the environment mainly comprises strong alkaline pH of more than 9, Chemical Oxygen Demand (COD) of 0-50000 mg/L and oily sewage. The pickling process is mainly used for treating various iron rust, welding oxides in newly built equipment or devices and scale, rust scale, copper scale and the like formed by using the equipment or devices in the production process for various reasons through acidity and coordination. Common acids are hydrochloric acid, hydrofluoric acid, sulfuric acid, phosphoric acid, EDTA, and the like. The main waste liquid is: strong acid pH is less than 1, COD is 500-5000 mg/L; other harmful substances, fluorine ions, iron ions, etc. And passivation is carried out by oxidation and precipitation of the chemical, so that a layer of protective film combining a compact oxide film and a precipitation film is formed on the metal surface in an active state after acid cleaning, and the metal surface is protected from secondary rust. Sodium nitrite, trisodium phosphate and the like are commonly used as passivating agents. The main environmental pollution produced is: strong alkaline pH is greater than 9, nitrite, high phosphorus content, etc.

Along with the deterioration of global environment, the environmental protection consciousness of people is gradually strengthened, the requirement on the environmental protection aspect of the cleaning industry is higher and higher, the chemical cleaning has the advantages of high cleanliness, thorough cleaning, corrosion resistance and the like, and is popular with enterprises, but the cleaning waste liquid is difficult to treat, the cost is high, and a plurality of enterprises and construction units are forbidden to go by the treatment, and the development of the chemical cleaning is also restricted. Most of cleaning enterprises are disposed by a third party during actual treatment, and the disposition by the third party is high in cost and has risks of transportation leakage, stealing and the like; some enterprises can carry out self-treatment, but most of treatment means can not meet the technical requirements of cleaning waste liquid treatment; in addition, a plurality of enterprises only simply neutralize and dilute the waste water and directly discharge the waste water, so that serious environmental pollution is caused, and irreparable harm is caused to the local environment.

In view of the above, there is an urgent need for a method for treating industrial cleaning waste liquid effectively, with low cost and high efficiency, and reducing the burden of enterprises.

Disclosure of Invention

The invention aims to provide a method for effectively treating industrial cleaning waste liquid so as to solve the problems in the prior art.

The invention is realized by the following technical scheme: a method for treating industrial cleaning waste liquid is characterized by comprising the following steps: the method comprises the following steps:

s1, mixing the alkali washing waste liquid and the acid washing waste liquid according to the ratio of 1: (1.2-1.8), mixing, controlling the pH value to be 3-4 after mixing, and reacting for 10-15 minutes after mixing;

s2, adding hydrogen peroxide and calcium hypochlorite into the mixed liquid obtained in the step 1 in sequence, wherein the adding amount of the hydrogen peroxide is 1-2.7% of the total mass of the mixed liquid, and the adding amount of the hydrogen peroxide is as follows: the proportion of calcium hypochlorite is (2-5): 1, and the mixture is kept stand for 15-40 minutes until no precipitate is generated;

s3, adding a passivation solution into the mixed solution obtained in the step 2 for reaction, wherein the mixing ratio of the mixed solution to the passivation solution is 1 (1-3), and the reaction time is 15-30 minutes;

s4, adding a sodium hydroxide solution and polyacrylamide after the reaction is finished, wherein the adding mass percentage of the sodium hydroxide solution is 1.2-5%, the adding concentration of polyacrylamide is 0.1-5 mg/L, and stirring at a constant speed, wherein the stirring is controlled at 0-200 r/min;

and S5, performing flocculation sedimentation on the mixed solution, treating the mixed solution in a membrane treatment system after the flocculation sedimentation, and desalting the high-salinity water after the membrane treatment in an MVR system, namely finishing the treatment.

Further: the passivation solution is sodium nitrite or trisodium phosphate aqueous solution.

The invention has the advantages that: the treatment method of the invention has the advantages of convenient and fast treatment of the cleaning waste liquid, high efficiency and low cost, realizes the recycling of the cleaning liquid, reduces the treatment cost of enterprises, and simultaneously promotes the development of chemical cleaning.

Detailed Description

The invention discloses a method for treating industrial cleaning waste liquid, which is used for treating and recycling the cleaning waste liquid and comprises the following steps:

s1, mixing the alkali washing waste liquid and the acid washing waste liquid according to the mol ratio of 1: (1.2-1.8), mixing, controlling the pH value to be 3-4 after mixing, and reacting for 10-15 minutes after mixing;

s2, adding hydrogen peroxide and calcium hypochlorite into the mixed liquid obtained in the step 1 in sequence, wherein the adding amount of the hydrogen peroxide is 1-2.7% of the total mass of the mixed liquid, and the adding amount of the hydrogen peroxide is as follows: the mass ratio of the calcium hypochlorite to the calcium hypochlorite is (2-5): 1, and the calcium hypochlorite is kept still for 15-40 minutes until no precipitate is generated;

s3, adding a passivation solution into the mixed solution obtained in the step 2 for reaction, wherein the volume ratio of the mixed solution to the passivation solution is 1 (1-3), and the reaction time is 15-30 minutes;

s4, adding a sodium hydroxide solution and polyacrylamide after the reaction is finished, wherein the adding mass of the sodium hydroxide solution accounts for 1.2-5% of the total amount of the mixed solution, the adding amount of the polyacrylamide is 0.1-5 mg/L, and stirring at a constant speed, and the stirring is controlled to be 0-200 r/min;

and S5, performing flocculation sedimentation on the mixed solution, treating the mixed solution in a membrane treatment system after the flocculation sedimentation, and desalting the high-salinity water after the membrane treatment in an MVR system, namely finishing the treatment.

The passivation solution is a passivation solution commonly used in the field, such as an aqueous solution of sodium nitrite or trisodium phosphate.

Specifically, according to the types of chemical substances contained in the cleaning waste liquid, a proper medicament is added to perform a synergistic reaction with the chemical substances under certain conditions, so that the purposes of treating other pollutants by using the pollutants in the cleaning waste liquid, and effectively converting and removing the pollutants are achieved. Mixing the alkaline cleaning waste liquid and the acidic cleaning waste liquid in proportion, adjusting the pH value by utilizing the alkalinity and the acidity of the alkaline cleaning waste liquid and the pickling waste liquid, adjusting the pH value to 3-4 after mixing, adding hydrogen peroxide and calcium hypochlorite, wherein ferrous ions are generated in the pickling process, the ferrous ions and the hydrogen peroxide form a Fenton reagent, and COD generated in the alkaline cleaning and pickling processes is oxidized to reduce COD. The calcium hypochlorite precipitates fluoride ions in a system in a calcium fluoride form, meanwhile, COD (chemical oxygen demand) is oxidized by hypochlorite radicals to reduce the COD content, then the calcium hypochlorite precipitates and is mixed with passivation waste liquid according to a certain proportion, the mixing proportion is 1: 1-1: 3, after mixing, alkali neutralization alkali washing and acid washing mixed liquid of the passivation waste liquid is obtained, unreacted oxidant oxidizes nitrite radicals to form nitrate ions, meanwhile, calcium ions react with phosphate radicals to produce calcium phosphate precipitates, divalent iron ions in the mixed liquid are oxidized to form ferric iron ions, the ferric iron ions exist in a ferric chloride form and form a flocculation settling agent with added polyacrylamide, and insoluble substances in the mixed liquid are effectively flocculated and settled. The main pollutant after the mixed solution is flocculated and settled is nitrate ions, the mixed solution enters a membrane treatment system, clean water is directly discharged after membrane filtration, the part containing high-concentration medicament nitrate ions enters MVR for treatment, the nitrate separation is realized after treatment, and the separated waste liquid finally meets the standard after the treatment of the cleaning waste liquid.

The modular treatment equipment for the cleaning waste liquid comprises a PLC (programmable logic controller), a cleaning waste liquid storage tank, a reactor, a water quality monitor, an inclined plate type sedimentation tank, a filter, an adsorber, a membrane treatment device, a reduced pressure distillation device, a clear water storage tank and the like, and is characterized in that a corresponding program is set in a vehicle-mounted container according to the PLC, the cleaning waste liquid firstly enters the cleaning waste liquid storage tank for storage and then enters a primary reactor according to a set amount, the PLC controls chemical agents in a chemical agent storage tank to be quantitatively injected into the primary reactor, the pH value of the cleaning waste liquid is adjusted, the cleaning waste liquid is fed into the primary reactor by a pump after being adjusted to a proper pH value, the PLC controls the chemical agents in the chemical agent storage tank to be quantitatively injected into the primary reactor, substances (COD, metal ions and acid radical ions) in the cleaning waste liquid react in the reactor, wherein the COD is subjected to oxidative decomposition, and, the method comprises the steps of enabling the waste liquid to enter a secondary reactor again after full reaction, adding a settling agent after full reaction, fully mixing, enabling the mixture to enter an inclined plate settling tank for settling, enabling the sediment to be filter-pressed by a filter press to become a filter cake, enabling filtrate to enter the reactor, enabling a PLC (programmable logic controller) to control chemical agents in an agent storage tank to be quantitatively injected into the reactor, adjusting the pH value of the filtrate, enabling the cleaning waste liquid to continue to enter a membrane processor under the control of the PLC, enabling the cleaning waste liquid to be directly discharged or recycled when ions such as nitrate radicals and other organic acid radicals are contained, needing to pass through the membrane processor, filtering through a membrane, enabling the water quality to be directly discharged or recycled, and.

Example 1

Hydrofluoric acid is used as a cleaning main agent, the generated cleaning waste liquid is treated, the cleaning waste liquid is connected to a sewage storage tank after cleaning is finished, alkaline cleaning waste liquid and acid cleaning waste liquid in the cleaning waste liquid are quantitatively input into a primary reactor according to the ratio of 1:1.4 for mixing reaction for 12 minutes, hydrogen peroxide and calcium hypochlorite are added, the adding concentration of the hydrogen peroxide is 2.4%, and hydrogen peroxide: the ratio of calcium hypochlorite is 2: 1; after reacting for 18 minutes, mixing the passivation waste liquid and the mixed liquid according to the proportion of the passivation waste liquid to the mixed liquid of 1:2, and reacting for 22 minutes; adding polyacrylamide with the adding concentration of 2.8 mg/L. The mixed liquor enters an inclined plate sedimentation tank, the separated mixed liquor enters a membrane treatment system, the part of water not containing nitrate ions can be directly discharged after membrane filtration, the part of water containing high-concentration nitrate ions enters MVR (mechanical vapor recompression) for distillation, the separation of nitrate ions and water is realized, and the separated water can be directly discharged.

Example 2

EDTA is adopted as a cleaning main agent, the generated cleaning waste liquid is treated, after cleaning is finished, the cleaning waste liquid is connected to a sewage storage tank, alkali cleaning waste liquid and acid cleaning waste liquid are quantitatively input into a primary reactor according to the ratio of 1:1.2 for mixing reaction for 13 minutes, a sulfuric acid solution is quantitatively input into the primary reactor through a pump by a medicament storage tank, after the reaction is carried out to the required pH value, solutions such as hydrogen peroxide, calcium hypochlorite and the like are quantitatively input into the reactor through the pump in the medicament storage tank, after the reaction is carried out for 26 minutes, a passivation waste liquid is input into the reactor according to the ratio of 3:1 for mixing reaction for 19 minutes, a polyacrylamide solution is quantitatively input into the reactor through the medicament storage tank, the cleaning waste liquid is input into an inclined plate sedimentation tank through the pump, supernatant is input into the value reactor through the pump, hydrochloric acid is quantitatively input into the reactor through the pump by the medicament storage tank, the pH value is adjusted, the supernatant of the cleaning waste, the separated water part can be directly reused, the higher concentration department enters a reduced pressure distiller to completely separate nitrate radicals, and the treated water can be reused.

The method has the advantages of simple treatment process, small addition amount of the medicament, low treatment cost and high efficiency. The method can realize the recycling of the cleaning liquid, reduce the treatment cost of enterprises and promote the development of chemical cleaning.

Claims (2)

1. A method for treating industrial cleaning waste liquid is characterized by comprising the following steps: the method comprises the following steps:

s1, mixing the alkali washing waste liquid and the acid washing waste liquid according to the ratio of 1: (1.2-1.8), mixing, controlling the pH value to be 3-4 after mixing, and reacting for 10-15 minutes after mixing;

s2, adding hydrogen peroxide and calcium hypochlorite into the mixed liquid obtained in the step 1 in sequence, wherein the adding amount of the hydrogen peroxide is 1-2.7% of the total mass of the mixed liquid, and the adding amount of the hydrogen peroxide is as follows: the proportion of calcium hypochlorite is (2-5): 1, and the mixture is kept stand for 15-40 minutes until no precipitate is generated;

s3, adding a passivation solution into the mixed solution obtained in the step 2 for reaction, wherein the mixing ratio of the mixed solution to the passivation solution is 1 (1-3), and the reaction time is 15-30 minutes;

s4, adding a sodium hydroxide solution and polyacrylamide after the reaction is finished, wherein the adding mass percentage of the sodium hydroxide solution is 1.2-5%, the adding concentration of polyacrylamide is 0.1-5 mg/L, and stirring at a constant speed, wherein the stirring is controlled at 0-200 r/min;

and S5, performing flocculation sedimentation on the mixed solution, treating the mixed solution in a membrane treatment system after the flocculation sedimentation, and desalting the high-salinity water after the membrane treatment in an MVR system, namely finishing the treatment.

2. The method for treating an industrial cleaning waste liquid according to claim 1, characterized in that: the passivation solution is sodium nitrite or trisodium phosphate aqueous solution.