CN108793498A - A kind of sulfate radical removal precipitating reagent circulation utilization method - Google Patents

Abstract

The invention relates to a method for recycling a sulfate radical removal precipitant, which comprises the following steps: (a) passing sulfate radical-containing waste water into a sulfur removal tank (1), adding medicament A to make it react to form ettringite precipitation, muddy water After adding coagulant A, the mixed liquid settles for solid-liquid separation, and the precipitate A is sent to the precipitant separation tank (3); (b) Add recovery agent B, react, add coagulant B, and separate solid and liquid, The separated precipitate B is sent to the sulfur removal tank (1) and reused as a sulfate precipitation agent; the supernatant B enters the induced crystallization tank (4); (c) dosing agent C to convert sulfate into gypsum precipitation , part of the gypsum is refluxed into the induced crystallization pool (4) for reuse as induced seed crystals, and the supernatant C is supplemented into the sulfur removal pool (1) as a calcium source for sulfate radical removal. Compared with the prior art, the invention realizes the source reduction of the sulfate radical precipitation sludge while reducing the cost of the agent.

Description

A kind of sulfuric acid radical removes precipitating agent recycling method

technical field

The invention relates to the technical field of environmental protection and rational utilization of water resources, in particular to a new technology for the precipitation and removal of sulfate radicals in wastewater and the recycling of precipitating agents.

Background technique

In the production process of petrochemical, printing and dyeing, electric power, pharmaceutical and other industries, a large amount of industrial wastewater containing SO42- will be produced, collectively referred to as sulfate-containing wastewater. In recent years, the discharge of sulfate-containing wastewater has increased year by year with the rapid development of these industries. Sulfate-containing wastewater is toxic, and if it is discharged directly without treatment, it will pollute the water environment and destroy the ecological balance. Sulfate in wastewater will be converted into toxic and corrosive hydrogen sulfide in the reduced state, which will affect the normal operation of wastewater treatment equipment and facilities to varying degrees during the treatment process, threatening the safety of operation and management personnel. Under this high concentration condition, sulfate radicals in wastewater will also combine with calcium ions to form permanent calcium scale, resulting in scaling of equipment and a decrease in heat transfer efficiency. Therefore, it is necessary to develop efficient methods for the removal of sulfate to control its pollution.

The sulfate content in wastewater will vary greatly depending on the producing industry, resulting in different treatment methods. At present, domestic and foreign methods for treating sulfate-containing wastewater mainly include membrane separation, ion exchange, and anaerobic biological treatment. However, in the actual application process, it often faces many problems such as high cost, difficult operation, strict equipment material requirements, and limited desulfurization efficiency. In the prior art, the ettringite precipitation method has many advantages such as high removal efficiency, low cost, simple equipment and easy operation, etc., but there are problems such as high cost of dosing chemicals and large sediment output, and the alkaline ettringite Facing the difficult problem of dehydration treatment and disposal outlet.

Therefore, the development of sulfate ettringite precipitation removal and precipitant recycling technology in wastewater can reduce the cost of chemicals and at the same time realize the source reduction of sulfate precipitated sludge, which is of great significance to the treatment of wastewater containing sulfate radicals and the resource utilization of sludge. important practical value.

Contents of the invention

The object of the present invention is to provide a method for recycling the sulfate radical removal precipitant in order to overcome the above-mentioned defects in the prior art.

The object of the present invention can be achieved through the following technical solutions: a sulfate radical removal precipitation agent recycling method is characterized in that, comprising the following steps:

(a) Pass the pretreated sulfate-containing wastewater into the desulfurization tank (1), add agent A through the first dosing box (2) to make it react to generate ettringite precipitation, and add the mud-water mixture to aid After the coagulant A settles for solid-liquid separation, the supernatant A is discharged into the subsequent unit for advanced treatment or discharged up to the standard, and the sediment A is sent to the precipitant separation tank (3) for subsequent treatment;

(b) Add recovery agent B to the precipitant separation tank (3) by the second dosing box (5) to make it react; ) into the coagulant B to separate the solid from the liquid, and the separated precipitate B is sent to the desulfurization tank (1) for reuse as a sulfate precipitant; the supernatant B enters the induced crystallization tank (4) for next step;

(c) Dosing agent C into the induced crystallization pool (4) through the third dosing box (7), converting the sulfate radical into gypsum precipitation, and part of the gypsum is reflowed into the induced crystallization pool (4) for reuse as the induced crystal seed, The remaining gypsum is dehydrated and transported for comprehensive utilization; the supernatant C is supplemented as a calcium source for sulfate radical removal into the desulfurization pool (1).

The agent A is a conventional agent used in the ettringite precipitation method, including a compound of calcium salt and aluminum salt, and its dosage is 0.01-20g/L.

The drug A is preferably a compound of calcium salt and aluminum salt in a mass ratio of 1:1 to 5, wherein the calcium salt includes calcium chloride, calcium nitrate, calcium chlorate, calcium perchlorate, calcium bicarbonate or diphosphate Calcium hydrogen, aluminum salts include aluminum chloride, aluminum sulfate or aluminum nitrate.

The coagulant aid A is polydimethyldiallylammonium chloride, polyacrylamide or a compound of the two, and its dosage is 0.01-1g/L.

The recovering agent B is hydrochloric acid, nitric acid or a compound of the two, and its dosage is 0.01-10g/L.

The recovery agent B is preferably a compound of hydrochloric acid and nitric acid in a mass ratio of 1:1-5.

The coagulant aid B is polydimethyldiallylammonium chloride, polyacrylamide or a compound of the two, and its dosage is 0.01-1g/L.

The agent C is one or more of calcium chloride, calcium oxide, calcium hydroxide, calcium carbonate, and calcium bicarbonate, and its dosage is 0.01-10g/L.

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

(1) Recovering the precipitant from the sulfate precipitate for the removal of sulfate radicals greatly reduces the dosage of the precipitant in the desulfurization tank, which is both practical and economical;

(2) Transform ettringite into gypsum through crystallization transformation, and increase the economic value of the sediment while reducing the source of sludge;

(3) The calcium-sulfur ratio of the supernatant during the ettringite crystallization conversion process is significantly higher than that of the raw water, which can be used as an auxiliary precipitant to return to the sulfur removal tank for sulfate radical removal, realizing the complete separation and resource utilization of sewage and sludge (That is, zero emissions in the true sense).

Description of drawings

Fig. 1 is a schematic diagram of the process flow of the present invention;

In the figure, 1-desulfurization tank, 2-first dosing tank, 3-precipitant separation tank, 4-induced crystallization tank, 5-second dosing tank, 6-first coagulation aid dosing tank, 7- The third medicine box.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1

As shown in Figure 1, the sulfate radical precipitation removal and precipitant recycling method in wastewater, the specific steps are as follows:

(1) Sulphate-containing wastewater flows into the desulfurization tank 1 after pretreatment, and the agent A is added through the first dosing box 2 to make it react to generate ettringite precipitation, and the mud-water mixture is added with coagulant A After sedimentation, solid-liquid separation is carried out to achieve the purpose of removing sulfate radicals. The supernatant is discharged into the subsequent unit for advanced treatment or discharged up to the standard, and the sediment is sent to the precipitant separation tank 3. The medicament A is a compound of calcium chloride and aluminum chloride in a mass ratio of 1:2; the input amount is 1g/L, and the coagulant aid A is polydimethyldiallylammonium chloride, and its input The dosage is 1g/L;

(2) Add recovery agent B to the precipitant separation tank 3 by the second dosing box 5 to make it react; add the coagulant in the precipitant separation tank 3 by the first coagulation aid dosing box 6, The solid-liquid is separated, and the separated precipitate is sent to the sulfur removal tank 1 for reuse as a sulfate precipitation agent; the supernatant enters the induced crystallization tank 4 . The recovering agent B is a compound of hydrochloric acid and nitric acid in a mass ratio of 1:2, and its dosage is 1 g/L. The coagulant aid B is polydimethyldiallylammonium chloride, and its dosage is 1g/L.

(3) Dosing agent C into the induced crystallization pool 4 through the third chemical dosing box 7 to convert the sulfate radical into gypsum precipitation, and part of the gypsum is refluxed into the induced crystallization pool 4 for reuse as induced crystal seeds, and the remaining gypsum is dehydrated and shipped out Comprehensive utilization; the supernatant is supplemented into the sulfur removal pool 1 as a calcium source for sulfate radical removal. Described medicament C is calcium chloride, and its dosage is 1g/L.

In this example, the power plant wastewater contains 4704mg/L of sulfate. Remove sulfate radicals by ettringite precipitation method and use precipitant recycling technology to process and reuse sedimentation sludge. The process is cycled five times, and the sulfate radical removal rates are 98.9%, 93.2%, 91.3%, 95.1%, and 91.9% % and 92.6%. The recoveries of precipitant were 91%, 72.9%, 72.3%, 84.3% and 82.9%. Compared with when the precipitant was not reused, the precipitant dosage was reduced by 82.2%, 67.8%, 72.2%, 75.5% and 85% in turn. After the third recycling, the overall operation effect of the process tends to be stable, the reuse rate of precipitant is continuously improved, the amount of dosing is gradually reduced, and the treatment cost per ton of water is reduced by 29.6 yuan.

Example 2

For the specific steps of the method for removing sulfate radicals in wastewater and recycling the precipitating agent, see Example 1. The nanofiltration concentrate of a waste incineration plant contains 5071 mg/L of sulfate radicals. Remove sulfate radicals by ettringite precipitation method and use precipitant recycling process technology to process and reuse sedimentation sludge. The process is cycled five times, and the sulfate radical removal rates are 98.3%, 91.6%, 89.2%, 95.1% and 90.1% respectively. %, 93.9%. The recoveries of precipitant were 90.2%, 73.7%, 70.1%, 79.2 and 81.7%. Compared with when the precipitation agent was not reused, the dosage of the precipitation agent was reduced by 81.9%, 69.9%, 71.5%, 72.4% and 83.3%. After the third precipitant recycling, the overall operation effect of the process tends to be stable, the reuse rate of precipitant continues to increase, the amount of dosing gradually decreases, and the cost per ton of water treatment is reduced by 31.6 yuan.

Example 3

For the specific steps of the method for removing sulfate radicals in wastewater and recycling the precipitant, refer to Example 1. Coal chemical industry wastewater contains sulfate radicals of 2184 mg/L. The sulfate radical was removed by ettringite precipitation method and the precipitated sludge was treated and reused by using the precipitant recycling process technology. The process cycled five times, and the sulfate radical removal rate was 98.3%, 91.6%, 89.2%, 86.3%, 91.9% % and 93.6%. The recoveries of precipitant were 90.2%, 83.7%, 80.1%, 86.7% and 90.5%. Compared with when the precipitant was not reused, the dosage of precipitant was reduced by 81.7%, 68.8%, 65.9%, 73.8% and 87.4% in turn. After the fourth recycling, the overall operation effect of the process tends to be stable, the reuse rate of the precipitant is continuously improved, the amount of dosing is gradually reduced, and the treatment cost per ton of water is reduced by 15.2 yuan.

Example 4

For the specific steps of the method for removing sulfate radicals in wastewater and recycling the precipitant, refer to Example 1. The reverse osmosis wastewater of a waste incineration plant contains 954.45 mg/L of sulfate radicals. Remove sulfate radicals by ettringite precipitation and use precipitant recycling process technology to process and reuse sedimentation sludge. The process cycle is five times, and the sulfate radical removal rates are 93.9%, 86.7%, 85.1%, 87.2% and 90.5% %, 93.7%. The recoveries of precipitant were 83.2%, 81.7%, 84.2%, 86.6% and 91.7%. Compared with the time when the precipitant was not reused, the dosage of precipitant was reduced by 74.2%, 66.8%, 71.7%, 72.3% and 80.1%. After the third recycling, the overall operation effect of the process tends to be stable, the reuse rate of precipitant is continuously improved, the amount of dosing is gradually reduced, and the treatment cost per ton of water is reduced by 6.3 yuan.

Example 5

A kind of sulfate radical removes precipitation agent recycling method, comprises the following steps:

(a) Pass the pretreated sulfate-containing wastewater into the desulfurization tank (1), add agent A through the first dosing box (2) to make it react to generate ettringite precipitation, and add the mud-water mixture to aid After the coagulant A settles for solid-liquid separation, the supernatant A is discharged into the follow-up unit for advanced treatment or discharged up to the standard, and the sediment A is sent to the precipitant separation tank (3) for subsequent treatment; the medicament A is calcium nitrate and The compound of aluminum nitrate according to the mass ratio of 1:1, the dosage is 0.01g/L. The coagulant aid A is polydimethyldiallylammonium chloride, polyacrylamide or a compound of the two, and its dosage is 0.01g/L.

(b) Add recovery agent B to the precipitant separation tank (3) by the second dosing box (5) to make it react; ) into the coagulant B to separate the solid from the liquid, and the separated precipitate B is sent to the desulfurization tank (1) for reuse as a sulfate precipitant; the supernatant B enters the induced crystallization tank (4) for The next step is to process; the recovery agent B is a compound of hydrochloric acid and nitric acid in a mass ratio of 1:1, and its dosage is 0.01g/L. The coagulant aid B is polydimethyldiallylammonium chloride, and its dosage is 0.01g/L.

(c) Dosing agent C into the induced crystallization pool (4) through the third dosing box (7), converting the sulfate radical into gypsum precipitation, and part of the gypsum is reflowed into the induced crystallization pool (4) for reuse as the induced crystal seed, The remaining gypsum is dehydrated and transported for comprehensive utilization; the supernatant C is supplemented as a calcium source for sulfate radical removal into the desulfurization pool (1). The agent C is calcium oxide, and its dosage is 0.01g/L.

Example 6

A kind of sulfate radical removes precipitation agent recycling method, comprises the following steps:

(a) Pass the pretreated sulfate-containing wastewater into the desulfurization tank (1), add agent A through the first dosing box (2) to make it react to generate ettringite precipitation, and add the mud-water mixture to aid After the coagulant A settles for solid-liquid separation, the supernatant A is discharged into the follow-up unit for advanced treatment or discharged up to the standard, and the sediment A is sent to the precipitant separation tank (3) for subsequent treatment; the medicament A is calcium nitrate and The compound of aluminum nitrate according to the mass ratio of 1:5, the dosage is 20g/L. The coagulant aid A is polyacrylamide, and its dosage is 1g/L.

(b) Add recovery agent B to the precipitant separation tank (3) by the second dosing box (5) to make it react; ) into the coagulant B to separate the solid from the liquid, and the separated precipitate B is sent to the desulfurization tank (1) for reuse as a sulfate precipitant; the supernatant B enters the induced crystallization tank (4) for The next step is to process; the recovery agent B is a compound of hydrochloric acid and nitric acid in a mass ratio of 1:5, and its dosage is 10g/L. The coagulant aid B is polyacrylamide, and its dosage is 1g/L.

(c) Dosing agent C into the induced crystallization pool (4) through the third dosing box (7), converting the sulfate radical into gypsum precipitation, and part of the gypsum is reflowed into the induced crystallization pool (4) for reuse as the induced crystal seed, The remaining gypsum is dehydrated and transported for comprehensive utilization; the supernatant C is supplemented as a calcium source for sulfate radical removal into the desulfurization pool (1). Described medicament C is calcium bicarbonate, and its dosage is 10g/L.

Claims (8)

1. a kind of sulfate radical removes precipitating reagent circulation utilization method, which is characterized in that include the following steps：

(a) it will be passed through in sulphur removal pond (1) by pretreated containing sulfate radicals waste water, adding medicament A by the first dosing tank (2) makes It, which is reacted, generates entringite precipitation, and muddy water mixed solution is added to settle after flocculation aid A and is separated by solid-liquid separation, and supernatant A is discharged into subsequently Unit carries out advanced treating or qualified discharge, and sediment A is sent into precipitating reagent separate tank (3) and carries out subsequent processing；

(b) recovery catalyst B is added into precipitating reagent separate tank (3) by the second dosing tank (5), brings it about reaction；Pass through first It helps solidifying dosing tank (6) to add flocculation aid B into precipitating reagent separate tank (3), its separation of solid and liquid, isolated sediment B is made to send Enter and is used as sulfate precipitation agent reuse in sulphur removal pond (1)；Supernatant B enters induction crystallizing pond (4) and is further processed；

(c) medicament C is added into induction crystallizing pond (4) by third dosing tank (7), converts sulfate radical to gypsum deposition, portion Divide gypsum to flow back into induction crystallizing pond (4) as crystal seed reuse is induced, transports outward and comprehensively utilize after remaining gypsum dehydration；Supernatant C is supplemented into as the calcium source of sulfate radical removal in sulphur removal pond (1).

2. a kind of sulfate radical according to claim 1 removes precipitating reagent circulation utilization method, which is characterized in that the medicine Agent A is the conventional dose that the entringite precipitation method use, and includes the compound of calcium salt and aluminium salt, dosage 0.01-20g/L.

3. a kind of sulfate radical according to claim 1 removes precipitating reagent circulation utilization method, which is characterized in that the medicine Agent A preferred calcium salts and aluminium salt in mass ratio 1:1~5 compound, wherein calcium salt include calcium chloride, calcium nitrate, calcium chlorate, high chlorine Sour calcium, calcium bicarbonate or calcium dihydrogen phosphate, aluminium salt include aluminium chloride, aluminum sulfate or aluminum nitrate.

4. a kind of sulfate radical according to claim 1 removes precipitating reagent circulation utilization method, which is characterized in that described helps Agent A is coagulated for polydimethyl diallyl ammonium chloride, the compound of polyacrylamide or the two, dosage 0.01-1g/L.

5. a kind of sulfate radical according to claim 1 removes precipitating reagent circulation utilization method, which is characterized in that described returns Receive the compound that agent B is hydrochloric acid, nitric acid or the two, dosage 0.01-10g/L.

6. a kind of sulfate radical according to claim 5 removes precipitating reagent circulation utilization method, which is characterized in that described returns Receive the preferred hydrochloric acid of agent B, nitric acid in mass ratio 1:1~5 compound.

7. a kind of sulfate radical according to claim 1 removes precipitating reagent circulation utilization method, which is characterized in that described helps Agent B is coagulated for polydimethyl diallyl ammonium chloride, the compound of polyacrylamide or the two, dosage 0.01-1g/L.

8. a kind of sulfate radical according to claim 1 removes precipitating reagent circulation utilization method, which is characterized in that the medicine Agent C is that calcium chloride, calcium oxide, calcium hydroxide, calcium carbonate, calcium bicarbonate are one such or several, dosage 0.01- 10g/L。