CN112811551A - Electroplating and precious metal smelting wastewater treatment method - Google Patents

Abstract

The invention belongs to a method for treating waste water from electroplating and precious metal smelting, which comprises the steps of obtaining sludge containing complex-state metals with the water content of 85 percent and partial waste water through chelating, precipitating and separating the waste water; dehydrating and drying the sludge until the water content is 30-50%, and pouring the sludge into a sludge storage tank; heating the sludge with the metal content exceeding 5% in the sludge storage tank; incinerating sludge with the metal content lower than 5%, detecting whether fly ash generated in the incineration process contains heavy metals and whether the heavy metals exceed the standard, and if so, chelating the fly ash; if not, the subsequent resource utilization is carried out. The invention can well solve the problems of harmlessness and reduction in the wastewater treatment process in the electroplating industry and the precious metal smelting industry, direct reduction of the sludge production by more than 30 percent through the chelating process, resource utilization, reduction of secondary pollution generated in the sludge treatment process and the like. The technical scheme, the process flow, the system equipment and the like have stable and reliable performance, are suitable for centralized disposal, and have high disposal capability and lower cost.

Description

Electroplating and precious metal smelting wastewater treatment method

Technical Field

The invention relates to the field of treatment of sludge generated in the treatment processes of electroplating wastewater and precious metal smelting wastewater, in particular to a treatment method of smelting wastewater containing heavy metals and precious metals.

Background

According to the relevant data, the electroplating industry/precious metal smelting industry is rapidly enlarged, so that a large amount of harmful substances are contained in the water body, the water resource is polluted in a large area, and the electroplating industry/precious metal smelting industry is selected as one of the industries with serious global pollution. The pollutants in the electroplating wastewater/precious metal smelting wastewater are complex, and the water quality and components are not easy to control, but generally, the pollutants can be divided into heavy metal ion wastewater, acid and alkali wastewater, grease-containing wastewater and the like, and the expressed components often contain a plurality of pollutants at the same time. The toxic and harmful substances include cadmium, lead, chromium, nickel, tin, zinc, acid, alkali, suspended substances, petroleum substances, nitrogen-containing compounds, surfactant, phosphate and the like. In recent years, under the environmental protection policy of governments, the domestic electroplating industry/precious metal smelting industry carries out upgrading and transformation of wastewater treatment, the wastewater reaches the standard and is discharged with remarkable effect, but a large amount of hazardous waste sludge containing heavy metals and precious metals is generated in the wastewater treatment process.

At present, in the aspect of treating electroplating wastewater/precious metal smelting wastewater in China, the treatment cost is high, the energy consumption is high, the treatment is not thorough, and even the problem of secondary pollution exists, and the treatment capability is low, so that the centralized treatment cannot be realized.

Disclosure of Invention

In order to solve the problems in the background technology, the invention provides a method for treating electroplating and precious metal smelting wastewater.

The technical problem solved by the invention is realized by adopting the following technical scheme:

the method for treating the electroplating and precious metal smelting wastewater is characterized by comprising the following steps of:

step S10, chelating, precipitating and separating waste water

Raw water of electroplating and precious metal smelting wastewater enters a reaction tank, 0.2-1% of chelating agent and 1% of magnetic powder are added and stirred to form a solid-liquid separation state;

obtaining sludge containing complex state metal with the water content of 85 percent and partial wastewater; the chelating process can directly reduce the sludge production by more than 30 percent;

step S20, dewatering and drying

Dehydrating and drying the sludge containing the complex metal generated after the separation, wherein the water content of the dehydrated and dried sludge is between 30 and 50 percent, and pouring the sludge into a sludge storage tank;

step S30 incineration

Picking up sundries in the sludge storage pool;

detecting whether the metal content in the sludge storage tank exceeds 5%, if so, heating the sludge in the sludge storage tank in a heating furnace at a heating temperature of at least 300 ℃ to generate oxidized metal, and treating other flue gas generated in the heating process to reach the standard and discharging; if not, burning the sludge in the sludge storage tank in a burning furnace at 850-950 ℃;

discharging fly ash generated in the incineration process into a fly ash bin, and discharging the flue gas generated in the incineration process up to the standard;

detecting whether fly ash in a fly ash bin contains heavy metal and whether the heavy metal exceeds the standard, and if the fly ash contains the heavy metal and the heavy metal exceeds the standard, chelating the fly ash; if not, performing subsequent resource utilization;

chelating step S40

And (3) conveying the fly ash to a mixing stirrer, adding 20-30% of water and 3% of chelating agent, reacting for 10-30 minutes, discharging into a ton bag, reacting for 24 hours, and conveying to a landfill.

Preferably, the wastewater generated in the wastewater sequestration precipitation separation process enters a water system for system recovery.

Preferably, the magnetic powder can be recycled after being extracted.

Preferably, in the step S20, the dewatering is to mechanically dewater the sludge with the water content of 85% by using a high-pressure membrane filter press until the water content is 65% -75%, and the drying is to reduce the wet sludge dewatered by using a disc type drying machine through a heat source drying mode from 65% -75% to 30% -50%.

Preferably, the specific method of incineration is as follows:

step S301, reserving slag generated in the incineration process at the bottom of an incineration hearth, wherein the slag can be used for resource utilization, and in the incineration process, air required by sludge incineration is heated to 200-400 ℃ through an air preheater under the action of an air blower and then is fed into a fluidized bed hearth to participate in combustion;

step S302, detecting whether the flue gas and the fly ash in the incineration process in the step S301 are fully combusted, and if not, entering the step S303; if the combustion is sufficient, the process proceeds to step S304;

step S303, the flue gas and fly ash generated by incineration in the incinerator enter a secondary combustion chamber for secondary combustion, the combustion temperature is 1100 ℃, and the residence time of the flue gas is more than 2S;

step S304, fly ash and smoke generated in the process enter the waste heat boiler through a high-temperature smoke pipeline, and the fly ash and the smoke can provide heat for the waste heat boiler;

s305, discharging part of fly ash and flue gas in the waste heat boiler to the atmosphere after passing through a high-temperature air preheater, an SNCR and SCR denitration device, an economizer, an electrostatic precipitator, an activated carbon ejector, a bag-type dust remover and a desulfurization device in sequence and reaching the standard;

step S306, the rest fly ash left in the waste heat boiler, the fly ash generated by the electrostatic dust collector and the bag-type dust collector enter a fly ash bin, whether the fly ash in the fly ash bin contains heavy metal and whether the heavy metal exceeds the standard is detected, and if the fly ash contains the heavy metal and the heavy metal exceeds the standard, the fly ash is chelated; if not, the subsequent resource utilization is carried out.

Preferably, the chelating agent is a thiourea aldehyde resin.

The invention has the beneficial effects that the invention can well solve the problems of harmlessness, reduction and resource in the wastewater treatment process in the electroplating industry and the precious metal smelting industry, and the like, and can reduce the secondary pollution generated in the sludge treatment process as much as possible. The technical scheme, the process flow, the system equipment and the like have stable and reliable performance, are suitable for centralized disposal, and have high disposal capability and lower cost.

Detailed Description

The present invention is further described below.

The method for treating the electroplating and precious metal smelting wastewater is characterized by comprising the following steps of:

step S10, chelating, precipitating and separating the waste water;

raw water of electroplating and precious metal smelting wastewater enters a reaction tank of a wastewater chelating, precipitating and separating system, 0.2-1% of chelating agent and 1% of magnetic powder are added and stirred to form a solid-liquid separation state, and sludge containing complexing metal with the water content of 85% is obtained; the chelating process can directly reduce the sludge production by more than 30 percent;

in the embodiment, the wastewater generated in the process of chelating, precipitating and separating the wastewater enters a water system for system recovery; the magnetic powder can be recycled after being extracted.

The wastewater chelating, precipitating and separating system in the embodiment has the existing equipment, which is not described in detail herein, and can fully react without adjusting the pH value of raw water in the separation process, but the pH value of the wastewater is adjusted to 6-9 before the wastewater is discharged, so that the wastewater can be discharged after reaching the standard.

Step S20, dewatering and drying

Dehydrating and drying the mixture containing the complex metal sludge with the water content of 85 percent after separation, pouring the dehydrated and dried sludge with the water content of 30 to 50 percent into a sludge storage tank;

in the embodiment, the dehydration drying is to adopt a high-pressure membrane filter press to perform mechanical dehydration, and a disc type drying machine is used to reduce the moisture content of wet sludge dehydrated by the mechanical filter press from 85% to 30% -50% in a heat source drying mode.

The high-pressure membrane filter press in the embodiment is intermittent pressurizing and filtering equipment, is the existing equipment, is used for solid-liquid separation of suspension, and is characterized in that a pressing device is used for pressing a filter plate, then the suspension is pressed into a filter chamber by a pump, the purpose of separating solid particles from liquid materials is achieved through filter cloth, the water content of the suspension is reduced to 65-75%, and waste water generated in the process is recycled after entering a water treatment system for treatment, and a small amount of waste water is discharged after reaching standards.

The disc type drying machine in the embodiment is the existing equipment, the wet sludge subjected to mechanical filter pressing and dehydration can be reduced to 30% -50% from 65% -75% of water content in a heat source drying mode, and then the wet sludge enters the sludge storage tank.

Step S30 incineration

Picking up sundries in the sludge storage pool;

detecting whether the content of metal in the sludge storage tank exceeds 5%, if so, heating the sludge in the sludge storage tank in a heating furnace at a heating temperature of at least 300 ℃ to generate oxidized metal, wherein the oxidized metal generated in the process can be recycled, and other flue gas generated in the heating process is treated and then is discharged after reaching the standard; if not, burning the sludge in the sludge storage tank in a burning furnace at 850-950 ℃;

the fly ash generated in the incineration process is discharged into a fly ash bin, and the smoke generated in the incineration process is discharged up to the standard, and the specific method comprises the following steps:

step S301, reserving slag generated in the incineration process at the bottom of an incineration hearth, wherein the slag can be used for resource utilization, and in the incineration process, air required by sludge incineration is heated to 200-400 ℃ through an air preheater under the action of an air blower and then is fed into a fluidized bed hearth to participate in combustion;

in this embodiment, if the combustion value is too low, the intelligent afterburner in the furnace will automatically supplement a proper amount of natural gas to maintain the stable operation of the incineration system, and generally, after-combustion is needed when the system is started.

Step S302, detecting whether the flue gas and the fly ash in the incineration process in the step S301 are fully combusted, and if not, entering the step S303; if the combustion is sufficient, the process proceeds to step S304;

step S303, the flue gas and fly ash generated by incineration in the incinerator enter a secondary combustion chamber for secondary combustion, the combustion temperature is 1100 ℃, and the residence time of the flue gas is more than 2S;

step S304, the fly ash and the flue gas generated in the process enter a waste heat boiler through a high-temperature flue gas pipeline;

and S305, sequentially passing part of fly ash and flue gas in the waste heat boiler through a high-temperature air preheater, an SNCR and SCR denitration device (reducing the content of NOx in the flue gas emission of an incinerator), an economizer, an electrostatic precipitator, an activated carbon injector (removing harmful substances such as heavy metals and dioxin in the flue gas), a bag-type dust remover (reducing the content of smoke dust in the flue gas and the temperature of inlet smoke to be about 150 ℃) and a desulfurization device (reducing the content of SO2, HCl and HF in the sludge incineration flue gas), and then discharging the part of fly ash and the flue gas to the atmosphere after reaching the standard, wherein the discharge standard meets the No. 1 modification list of DB31/768-2013 'emission standard of domestic garbage incineration atmospheric pollutants'.

The waste heat boiler water firstly enters the economizer for heating, then enters the waste heat boiler tube bundle for exchanging heat with high-temperature flue gas to form steam, and the generated steam can be recycled by a system and used for heat supply or power generation;

steam generated in the waste heat boiler firstly enters a cyclone separator to remove dry sludge particles carried by the steam, then enters a cooling device to be condensed into wastewater, condensed water and desalted water are recycled, non-condensable gas and the dry sludge particles are sent into a fluidized bed again to be directly incinerated, and a small amount of wastewater reaches the standard and is sent into a sewage pipe network to be treated;

step S306, the rest fly ash left in the waste heat boiler, the fly ash generated by the electrostatic dust collector and the bag-type dust collector enter a fly ash bin, whether the fly ash in the fly ash bin contains heavy metal and whether the heavy metal exceeds the standard is detected, and if the fly ash contains the heavy metal and the heavy metal exceeds the standard, the fly ash is chelated; if not, the subsequent resource utilization is carried out.

In the embodiment, before heating or incineration, sludge in the sludge storage tank is conveyed to a stokehole storage bin through a spiral pipeline or a belt, and then is uniformly, quantitatively and continuously conveyed into a heating furnace or a fluidized bed through a feeding device for heating or combustion;

the sludge storage and conveying system in the embodiment needs to be matched with a necessary control and monitoring system; the accurate measurement and control of the comprehensive sludge are completed by a weighing system of a dry sludge buffer bin in front of the furnace and a variable frequency conveying device together, the rotating speed of the variable frequency conveying device is controlled according to the setting, and the sludge enters the furnace according to the quantitative and stable flow. The speed of the sludge fed into the stokehole bin can be controlled through adjustment; the gate is arranged at the outlet, and the maintenance and replacement operation of the stator or the rotor can be carried out without emptying the system; when the system stops running, pipeline sludge does not need to be removed in a short time; stopping the operation for a long time, and cleaning the pipeline by using water;

and S308, the rest fly ash in the waste heat boiler, the fly ash generated by the electrostatic dust collector and the bag-type dust collector enter a fly ash bin, whether the fly ash in the fly ash bin contains heavy metal is detected, and if the fly ash contains the heavy metal, chelating treatment is carried out.

Chelating process S40

Conveying the fly ash to a mixing stirrer, adding 20-30% of water and 3% of chelating agent, reacting for 10-30 minutes, discharging into a ton bag, reacting for 24 hours, and conveying to a landfill; in this example, the chelating agent is thiourea aldehyde resin, and the chelating agent in this example is an invention patent with the patent name of 201910930712.6, which is published on the days of 2019.09.29 and 2019.12.20, of "application of thiourea aldehyde resin in inhibiting urease in soil", and is a stabilizing agent with broad spectrum.

In this embodiment, the amount of cement component can be reduced by 10% with or without adding cement component during the chelating process.

In the incineration process, a sludge fluidized bed incineration system is adopted, and a fluidized bed low-temperature and multi-stage incineration technology is adopted for the existing equipment. The fluidized bed incinerator has simple structure, simple maintenance and long service life, the lower part of the hearth is provided with the air distribution plate for evenly distributing fluidized air, and the hearth is filled with a certain amount of heat-resistant granular bed materials. The movement is violent, the gas and the solid are uniformly mixed, and the device is insensitive to the fluctuation of the quality of the fuel, so that the fuel is well burnt out in the furnace, and secondary pollution is avoided. Simultaneously reduces the generation amount of nitrogen oxides, and can also control SO by adopting a desulfurization technology in the furnace₂ And the generation of harmful gases, the clean treatment and the resource utilization of the comprehensive sludge at lower cost are realized. The circulating combustion temperature of the comprehensive sludge in the hearth isAnd (3) rapidly completing the processes of water analysis, volatile component precipitation and ignition and coke formation under the high-strength heating of the hot fluidized bed material at 850-950 ℃, further crushing the hot fluidized bed material into finer particles in a fluidized state, and vitrifying heavy metal components in the comprehensive sludge to be fixed in ash. The combined high-temperature vortex burnout technology in the furnace separates and captures the inert materials and larger sludge particle clusters brought out by hot flue gas by a vortex separator arranged at the top of a hearth, and returns to a dense-phase region through a feedback channel at the lower part of the separator, thereby not only reducing the loss of the inert materials, but also realizing the circular combustion of the sludge particle clusters, further increasing the retention time of solid particles in a bed and realizing the high-efficiency combustion of the sludge. The incinerator shell is provided with a remote pressure gauge for measuring the pressure in the incinerator, and the pressure is controlled by the opening degree of a baffle of a draught fan at the tail part, so that the pressure in the incinerator is maintained within a specified range. In order to prevent the incinerator body from being damaged by deflagration (sudden expansion of gas volume) caused by improper operation in the incineration process, the top of the incinerator is provided with an explosion door.

The air distribution of the fluidized bed ignition burner is supplied by a primary air branch, and a regulating valve is arranged on the branch and is matched with the temperature of the hearth for regulation.

In the embodiment, the disc dryer can also guide a steam heat source generated in the heating or burning process into the disc dryer, wet sludge continuously enters the second layer of drying disc from the first layer of drying disc through the horizontal disc, sludge on the surface of the small drying disc in the horizontal disc rotating and turning process enters the second layer of drying disc, the sludge rotates from outside to inside and moves from the middle leakage port into the second small drying disc and then enters the third layer of drying disc, the sludge is discharged after the three layers of drying discs contain the large drying disc and the small drying disc in an alternating arrangement mode, and steam evaporated in the process is discharged through the moisture discharging port.

In this embodiment, in the incineration process, the steam that mud heat drying produced gets into cyclone earlier and gets into the dry oil mud granule that carries, and the condensation is waste water in getting into cooling device afterwards, and comdenstion water and demineralized water recycle use, and noncondensable gas and granule are sent into the sled dress formula fluidized bed once more and are directly burned, and a small amount of waste water is up to standard and is sent into the sewage pipe network and handle. Air required by sludge incineration is heated to 200-400 ℃ by an air preheater under the action of an air blower, and then is sent into a fluidized bed hearth for combustion.

The waste heat boiler water firstly enters the economizer to be heated, and then enters the waste heat boiler tube bundle to exchange heat with high-temperature flue gas to form steam, and the generated steam can be recycled by a system.

Although the embodiments of the present invention have been described in detail, the description is only a preferred embodiment of the present invention, and should not be considered as limiting the scope of the invention, and all equivalent changes and modifications made within the scope of the present invention should be covered by the claims of the present invention.

Claims (6)

1. The method for treating the electroplating and precious metal smelting wastewater is characterized by comprising the following steps of:

step S10, chelating, precipitating and separating waste water

Raw water of electroplating and precious metal smelting wastewater enters a reaction tank, 0.2-1% of chelating agent and 1% of magnetic powder are added and stirred to form a solid-liquid separation state;

obtaining sludge containing complex state metal with the water content of 85 percent and partial wastewater;

step S20, dewatering and drying

Dehydrating and drying the sludge containing the complex metal generated after the separation, wherein the water content of the dehydrated and dried sludge is between 30 and 50 percent, and pouring the sludge into a sludge storage tank;

step S30 incineration

Picking up sundries in the sludge storage pool;

detecting whether the metal content in the sludge storage tank exceeds 5%, if so, heating the sludge in the sludge storage tank in a heating furnace at a heating temperature of at least 300 ℃ to generate oxidized metal, and treating other flue gas generated in the heating process to reach the standard and discharging; if not, burning the sludge in the sludge storage tank in a burning furnace at 850-950 ℃;

discharging fly ash generated in the incineration process into a fly ash bin, and discharging the flue gas generated in the incineration process up to the standard;

detecting whether fly ash in a fly ash bin contains heavy metal and whether the heavy metal exceeds the standard, and if the fly ash contains the heavy metal and the heavy metal exceeds the standard, chelating the fly ash; if not, performing subsequent resource utilization;

chelating step S40

And (3) conveying the fly ash to a mixing stirrer, adding 20-30% of water and 3% of chelating agent, reacting for 10-30 minutes, discharging into a ton bag, reacting for 24 hours, and conveying to a landfill.

2. The method for treating wastewater from electroplating and precious metal smelting according to claim 1, wherein part of the wastewater generated in the process of chelating, precipitating and separating wastewater enters a water system for systematic recovery.

3. The method for treating wastewater from electroplating and precious metal smelting according to claim 1, wherein the magnetic powder is extracted and reused.

4. The method for treating electroplating and precious metal smelting wastewater according to claim 1, wherein in step S20, the dehydration is that a high-pressure membrane filter press is used to mechanically dehydrate the sludge with the water content of 85% to the water content of 65% -75%, and the drying is that a disc type drying machine is used to reduce the water content of the wet sludge dehydrated by the mechanical filter press from 65% -75% to 30% -50% by means of heat source drying.

5. The method for treating the electroplating and precious metal smelting wastewater according to claim 1, wherein the incineration specifically comprises the following steps:

step S301, reserving slag generated in the incineration process at the bottom of an incineration hearth, wherein the slag can be used for resource utilization, and in the incineration process, air required by sludge incineration is heated to 200-400 ℃ through an air preheater under the action of an air blower and then is fed into a fluidized bed hearth to participate in combustion;

step S302, detecting whether the flue gas and the fly ash in the incineration process in the step S301 are fully combusted, and if not, entering the step S303; if the combustion is sufficient, the process proceeds to step S304;

step S303, the flue gas and fly ash generated by incineration in the incinerator enter a secondary combustion chamber for secondary combustion, the combustion temperature is 1100 ℃, and the residence time of the flue gas is more than 2S;

step S304, the fly ash and the flue gas generated in the process enter a waste heat boiler through a high-temperature flue gas pipeline;

s305, discharging part of fly ash and flue gas in the waste heat boiler to the atmosphere after passing through a high-temperature air preheater, an SNCR and SCR denitration device, an economizer, an electrostatic precipitator, an activated carbon ejector, a bag-type dust remover and a desulfurization device in sequence and reaching the standard;

step S306, the rest fly ash left in the waste heat boiler, the fly ash generated by the electrostatic dust collector and the bag-type dust collector enter a fly ash bin, whether the fly ash in the fly ash bin contains heavy metal and whether the heavy metal exceeds the standard is detected, and if the fly ash contains the heavy metal and the heavy metal exceeds the standard, the fly ash is chelated; if not, the subsequent resource utilization is carried out.

6. The method for treating wastewater from electroplating and precious metal smelting according to claim 1, wherein the chelating agent is thiourea aldehyde resin.