A chromium plating wastewater and exhaust gas closed-circuit system

Abstract

The application discloses a chromium plating waste water and waste gas closed loop circulating system, which comprises a chromium plating device, a waste gas circulating device, a waste water circulating device and a pure water device; the waste gas circulating device comprises a wind inlet, a front filter part, an air duct, a multi-stage filter part and a wind outlet which are sequentially connected; waste gas generated by the chromium plating device enters the wind inlet, and recovered liquid collected by the waste gas circulating device is reused to the chromium plating tank; the waste water circulating device comprises a DT separation unit, an evaporator, a deionized water tank, a chromium liquid tank, a cation removal unit and a waste water treatment device. The application has the following advantages: 100% of rinsing water and chemical liquid is reused, the cost of ton water reuse is low, and the system stability is good. The closed loop unit of waste gas reuse adopts pulse cleaning and effective water mist separation, compared with a traditional chromium mist barrier, the fluorine-containing chromium mist inhibitor in the waste gas is inhibited, the chromium mist recovery concentration is high, and no chemicals are used. Technical indexes: purification effect 99.9%, system wind resistance < 300 Pa, which is not easy to scale.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of chromium plating production wastewater and waste gas treatment, and particularly relates to post-plating rinsing wastewater + fluorine-containing chromium mist inhibitor recycling of a chromium plating production line and chromium-containing waste gas purification + fluorine-containing chromium mist inhibitor recycling of the production line, so as to realize overall closed-circuit circulation operation. BACKGROUND

[0002] Chromium plating is a conventional and important process in the electroplating industry, and is widely used as an outer layer of a protective / decorative plating system and a functional plating layer.

[0003] However, during the chromium plating process, waste gas and wastewater containing perfluorooctyl sulfonic acid and its salts (PFOS) are generated. At present, PFOS can only be used for metal electroplating in a closed-loop system in the electroplating industry.

[0004] Traditional closed-loop devices generally use atmospheric evaporators, vacuum evaporators, and membrane separation devices. The atmospheric evaporator itself discharges water vapor into the atmosphere, which cannot complete closed-circuit circulation. Although the vacuum evaporator can be used, its large initial purchase cost and use cost of 200 yuan / ton of water result in a lack of economy. The membrane separation device cannot concentrate the concentrated liquid to more than 250 g / L, which results in more and more concentrated liquid in the system, and cannot complete true closed-loop.

[0005] Therefore, there is an urgent need for a system device that can stably and economically recycle fluorine-containing chromium mist inhibitors and chromic acid for a long time. SUMMARY

[0006] In view of the above technical problems, the present application provides a chromium plating wastewater and waste gas closed-circuit circulation system, which realizes overall closed-loop operation of chromic acid, fluorine-containing chromium mist inhibitors, and rinsing water in a chromium plating production line. The system ensures the reliable closed-loop operation of the device while significantly reducing the operating cost of the entire device, so that the device can be operated reliably, economically, and for a long time.

[0007] The technical scheme provided by the present application is as follows:

[0008] A chromium plating wastewater and waste gas closed-circuit circulation system, comprising a chromium plating device, a waste gas circulation device, a wastewater circulation device, and a pure water device;

[0009] The chromium plating device comprises a chromium etching tank, a chromium plating tank, a first rinsing tank, a second rinsing tank, and a hot water washing tank arranged in sequence;

[0010] The waste gas circulation device comprises an air inlet, a pre-filtering component, an air duct, a multi-stage filtering component, and an air outlet connected in sequence. The waste gas generated by the chromium plating device enters the air inlet, and the recovered liquid collected by the waste gas circulation device is recycled to the chromium plating tank;

[0011] The waste water circulating device comprises a DT separation unit, an evaporator, a deionized water tank, a chromium liquid tank, a cation removal unit and a waste water treatment device.

[0012] The first flushing tank, the DT separation unit and the evaporator are connected in sequence; the evaporator is connected to the deionized water tank and the chromium liquid tank, the deionized water tank is connected to the hot water washing tank, the chromium liquid tank is connected to the chromium etching tank and the chromium plating tank through the cation removal unit.

[0013] The pure water device is connected to the deionized water tank and the waste water treatment device respectively.

[0014] Further, the DT separation unit is a disc tube type DTRO membrane assembly, and the membrane sheet material is aromatic polyamide.

[0015] Further, the cation removal unit is a cation adsorption resin, which is used to remove iron ions and copper ions, and the concentration is controlled to be less than 8 g / L.

[0016] Further, the cation adsorption resin is a sulfonic acid cation resin. Preferably, the cation adsorption resin is Plankit C150 or the like.

[0017] Further, the pre-filtering component comprises a first shell and a pre-sprayer and a pre-filtering structure arranged in the first shell.

[0018] The multi-stage filtering component comprises a second shell and a first sprayer, a first-stage filtering structure, a second sprayer, a second-stage filtering structure, a third sprayer, a third-stage filtering structure and a mist eliminator arranged in the second shell in sequence.

[0019] Further, the pre-filtering structure and the first-stage filtering structure are both provided with a plurality of filter screens arranged in parallel along the air inlet direction; the filter screen is composed of a rhombic grid unit and a triangular grid unit, the rhombic grid unit is arranged in the middle of the filter screen, and the triangular grid unit is located at the four sides; the grid unit is provided with horizontal or vertical ribs, and the ribs of adjacent grid units are perpendicular to each other.

[0020] Further, the second-stage filtering structure and the third-stage filtering structure have the same structure, and both comprise two air-permeable baffle walls and a plurality of turbulent balls arranged and stacked between the baffle walls.

[0021] Further, the mist eliminator comprises a plurality of groups of corrugated plates and hook-shaped protrusions; the plurality of groups of corrugated plates are arranged in parallel, the corrugated plate is provided with hook-shaped protrusions, and the corrugated plate has the same corrugated fluctuation direction as the air inlet direction.

[0022] Further, the sprayer adopts pulse flushing; the particle size of the chromium-containing anhydride and the fluorine-containing chromium mist inhibitor gel particles blocked by the sprayer from the air inlet to the air outlet is 10 microns, 5 microns, 3 microns and 1 micron in sequence; the concentration of the recovered liquid collected by the waste gas circulating device is greater than 100 g / L.

[0023] Further, the sprayer is pulsed by working for 2-5 seconds and stopping for 300-500 seconds.

[0024] Further, the first shell and the second shell are both tapered cylinders with narrowed ends.

[0025] Further, the first sprayer and the pre-filter structure are arranged in sequence along the air inlet direction.

[0026] Further, the evaporator is a reduced-pressure evaporator.

[0027] The present application has the following advantages:

[0028] (1) 100% of the rinsing water and the chemical solution are reused, the cost of water reuse per ton is low, the system stability is good, the waste gas purification effect is 99.9%, the fluorine-containing chromium mist inhibitor and the chromium mist separated are all reused, the unit air resistance is less than 300 Pa, and the entire system is not easy to scale.

[0029] (2) The closed-loop unit of the rinsing water introduces a DT system, achieves 80% separation of water and (fluorine-containing chromium mist inhibitor and chromium acid), the concentrated solution containing the fluorine-containing chromium mist inhibitor and the chromium acid enters the evaporator for further concentration, completes 100% separation of the fluorine-containing chromium mist inhibitor and the chromium acid, better controls the cleanliness of the rinsing water, ensures the cleaning effect of the parts, and reliably reuses the chemical solution and the fluorine-containing chromium mist inhibitor.

[0030] (3) The closed-loop unit of the waste gas reuses adopts pulse cleaning and effective water mist separation, and adopts a pre-filter and a primary filter structure with multiple filter screens, compared with the traditional chromium mist barrier, the fluorine-containing chromium mist inhibitor and the chromium mist in the waste gas have high recovery concentration, no chemicals are used, the filter screens are arranged with mutually perpendicular ribs, which not only improves the recovery rate of liquid droplets, but also reduces the air resistance. Ultimately, the purified gas meets the national emission standard, and at the same time, long-term stable operation is ensured, thereby reducing the maintenance frequency and cost, and being conducive to ensuring the continuous operation of production. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The example process flow chart is provided for the following specific embodiments;

[0032] Figure 2 The membrane diagram of the DT device;

[0033] Figure 3 The schematic diagram of the waste gas purification unit;

[0034] Figure 4 The corrugated plate schematic diagram;

[0035] Figure 5 The diamond mesh schematic diagram:

[0036] Reference signs:

[0037] 100-inlet, 110-pre-filter component, 111-first shell, 112-pre-sprayer, 113-pre-filter structure, 120-air duct, 130-multi-stage filter component, 131-second shell, 132-first sprayer, 133-first-stage filter structure, 134-second sprayer, 135-second-stage filter structure, 136-third sprayer, 137-third-stage filter structure, 138-demister, 1381-corrugated plate, 1382-hook-shaped convex strip, 140-outlet;

[0038] 300-DT separation unit, 311-fastening bolt, 312-upper flange, 313-flow guide disc, 314-DT membrane package, 315-lip-shaped sealing ring, 316-concentrated water outlet, 317-diluted water outlet, 318-water inlet, 319-lower flange, 320-O-shaped sealing ring, 321-supporting rod, 322-fastening nut. DETAILED DESCRIPTION

[0039] In order to better explain the present application, so as to be understood, the present application is described in detail in the specific embodiments, combined with the drawings.

[0040] EMBODIMENT

[0041] As Figure 1 shown, a chromium plating wastewater and exhaust gas closed-loop circulation system comprises a chromium plating device, an exhaust gas circulation device, a wastewater circulation device and a pure water equipment;

[0042] The chromium plating device comprises a chromium etching tank, a chromium plating tank, a first rinsing tank, a second rinsing tank and a hot water washing tank arranged in sequence;

[0043] The exhaust gas circulation device comprises an inlet 100, a pre-filter component 110, an air duct 120, a multi-stage filter component 130 and an outlet 140 connected in sequence; the exhaust gas generated by the chromium plating device enters the inlet 100, and the recovered liquid collected by the exhaust gas circulation device is reused to the chromium plating tank;

[0044] The wastewater circulation device comprises a DT separation unit 300, an evaporator, a deionized water tank, a chromium liquid tank, a cation removal unit and a wastewater treatment device;

[0045] The first rinsing tank, the DT separation unit 300 and the evaporator are connected in sequence; the evaporator is connected to the deionized water tank and the chromium liquid tank, the deionized water tank is connected to the hot water washing tank, and the chromium liquid tank is connected to the chromium etching tank and the chromium plating tank after passing through the cation removal unit;

[0046] The pure water equipment is connected to the deionized water tank and the wastewater treatment device, respectively.

[0047] As a specific embodiment, the DT separation unit 300 is a disc-tube DTRO membrane module, and the membrane material is aromatic polyamide.

[0048] As a specific embodiment, the cation removal unit is cation adsorption resin, which is used to remove iron ions and copper ions, and control the concentration to be less than 8 g / L.

[0049] As an improved embodiment, the cation adsorption resin is sulfonic acid cation resin. Preferably, the cation resin is Plumbite C150 or the like.

[0050] As a specific embodiment, the pre-filter component 110 includes a first shell 111 and a pre-sprayer 112 and a pre-filter structure 113 arranged therein;

[0051] The multi-stage filter component 130 includes a second shell 131 and a first sprayer 132, a first-stage filter structure 133, a second sprayer 134, a second-stage filter structure 135, a third sprayer 136, a third-stage filter structure 137, and a demister 138 arranged therein in sequence.

[0052] As an improved embodiment, the pre-filter structure 113 and the first-stage filter structure 133 are both arranged with multiple filter screens in parallel along the air inlet direction. As shown in Figure 3 The filter screen is composed of rhombic grid units and triangular grid units, wherein the rhombic grid units are arranged in the middle of the filter screen, and the triangular grid units are located at the four sides; the grid units are provided with horizontal or vertical ribs, and the ribs of adjacent grid units are perpendicular to each other.

[0053] As an improved embodiment, the second-stage filter structure and the third-stage filter structure have the same structure, both including two air-permeable baffle walls and turbulence balls stacked between the baffle walls.

[0054] As an improved embodiment, the sprayer adopts pulse flushing; the blocking particle sizes of the sprayers from the air inlet to the air outlet are 10 microns, 5 microns, 3 microns, and 1 micron for the chromium-containing anhydride and fluorine-containing chromium mist inhibitor colloidal particles; and the concentration of the recovered liquid collected by the waste gas circulating device is greater than 100 g / L.

[0055] As an improved embodiment, the sprayer adopts pulse flushing in a manner of working for 2-5 seconds and stopping for 300-500 seconds.

[0056] As an improved embodiment, the first shell 111 and the second shell 131 are both tapered cylinders with narrowed ends.

[0057] As an improved embodiment, the first sprayer 112 and the pre-filter structure 113 are arranged in sequence along the air inlet direction.

[0058] As a specific embodiment, the demister 138 comprises a plurality of groups of corrugated plates 1381 and hook-shaped protrusions 1382; the plurality of groups of corrugated plates 1381 are arranged in parallel, the corrugated plate fluctuation direction is the same as the air inlet direction, and the hook-shaped protrusions 1382 are arranged on the corrugated plates 1381.

[0059] As an improved embodiment, the structure of the hook-shaped protrusions 1382 is an inverted C-shaped plate arranged on the outer side of the corrugated plate crest, trough and the inclined surface therebetween; the direction of the notch of the hook-shaped protrusion 1382 is opposite to the air inlet direction, so that the liquid droplets can enter and collect.

[0060] As a specific embodiment, the wastewater treatment device is used for treating waste liquid and ground collected chromium wastewater to remove harmful substances such as fluorine-containing chromium mist inhibitor.

[0061] As an example, the closed loop circulating system for chromium plating wastewater and exhaust gas provided by the embodiment comprises a first washing tank and a second washing tank of the chromium plating device, and a hot water washing tank for completing the cleaning process of the parts. The rinsing water after cleaning enters the DT separation unit from the first stage tank of the first washing tank (the tank is the dirtiest rinsing water), and the first separation of the rinsing water is performed in the unit. The unit completes about 80% of the water separation, and the separated clean water enters the deionized water tank and then enters the hot water tank to complete the recycling of the water.

[0062] The concentrated solution of the DT separation unit enters the evaporator for further concentration, and the evaporated solution generated by the evaporator enters the deionized water tank to complete the recycling of the water. The concentrated solution generated by the evaporator contains fluorine-containing chromium mist inhibitor and chromic acid, and the concentration of the concentrated solution is close to the concentration of the chromium plating tank. The concentrated solution enters the chromium liquid tank and then enters the chromium plating tank after passing through the harmful ion removal device, thereby completing the closed loop circulation of the fluorine-containing chromium mist inhibitor and the chromic acid.

[0063] The exhaust gas generated by the chromium plating tank enters the pre-filter structure after being collected by the pipeline, and more than 80% of the fluorine-containing chromium mist inhibitor and the chromium mist are recycled in this link. The structure adopts high-pressure pulse cleaning, and the concentration of the collected cleaning liquid is close to that of the chromium plating tank, so that the cleaning liquid can be directly used in the chromium plating tank, thereby reducing the use of water and being beneficial to the closed loop treatment of the system. The subsequent multi-stage filter structure successively blocks the particle size of the chromium anhydride and the fluorine-containing chromium mist inhibitor of 10 microns, 5 microns, 3 microns and 1 micron. The mist droplets larger than the specifications are blocked and retained, so that the fluorine-containing chromium mist inhibitor in the exhaust gas cannot escape, thereby completing the subsequent collection of the fluorine-containing chromium mist inhibitor and the chromium mist.

[0064] Figure 2The structure of the DT separation unit is shown, which is composed of a pressure shell, a center pull rod, a membrane pack, water passing flanges, pressure bearing flanges, etc. The membrane column structure is arranged between two flow guide discs. The membrane pack is composed of two membrane sheets which are sealed by ultrasonic welding and separated by a separation layer in the middle. The DT separation unit is the core element for separating the rinse water and the solution in this embodiment, which is made of aromatic polyamide material. The rinse liquid flows in the positive or reverse "S" direction in the disc type flow channel, and the small molecular particles and dissolved ions in the liquid are trapped on the concentrated water side, and the permeated fresh water is collected as clean filtrate. The DTRO membrane assembly is completely different from the traditional roll type membrane. The raw liquid flow channel adopts the form of disc tube type membrane assembly, forming an open flow channel. The treated liquid quickly flows through the filter membrane in the shortest distance, and then reverses by 180° to the other membrane surface, and then flows into the next flow guide disc from the slot in the center of the flow guide disc, so as to form a double "S" shape route on the membrane surface from the circumference to the center of the circle, and then to the circumference, and then to the center of the circle. The concentrated liquid finally flows out from the flange at the feed end. The surface of the flow guide disc has convex points arranged in a certain way. This special hydraulic design makes the treatment liquid flow through the filter membrane surface under the action of pressure and collide with the convex points to form turbulent flow, which increases the permeation rate and self-cleaning function, thereby effectively avoiding membrane clogging and concentration polarization phenomenon, successfully prolonging the service life of the membrane sheet. The accumulated dirt on the membrane sheet is also easy to clean during cleaning, ensuring that the disc tube type membrane assembly is suitable for harsh water conditions.

[0065] The DTRO membrane assembly is used in this embodiment for the following reasons: 1. To separate as much water as possible from the rinse liquid, combined with the later evaporator, to greatly reduce the cost of directly using the evaporator for treatment; 2. The use of DTRO membrane can realize the separation of chromium plating rinse liquid with a concentration range of 0.1-15 g / L, while resisting oxidation, realizing concentration from low concentration to high concentration, avoiding clogging and polarization, and greatly improving the stability and service life of the system.

[0066] Referring to Figure 3 , the waste gas circulating device, the chromium mist waste gas enters the front filter part 110 from the air inlet 100, is treated by shrinkage in the front filter structure 113, and then passes through the first filter structure 133, the second filter structure 135, the third filter structure 137 and the demister 138. The air outlet 140 leaves.

[0067] Referring to Figure 5The pre-filter structure 113 and the first-stage filter structure 133 include an inlet filter screen module, which is composed of multiple diamond-shaped screens with interlaced stripes. The interlaced stripes increase the effective blocking area and reduce the air flow resistance. The chromium mist exhaust gas will hit the stripes on the screens multiple times during the process of passing through the diamond-shaped screens of the pre-filter structure 113. The unblocked gas will be condensed again in the multiple filter screens of the first-stage filter structure 133. The pre-filter structure with the special design has very good purification effect. In the embodiment, more than 80% of the liquid droplets in the exhaust gas passing through the exhaust gas circulating device are removed. Through good program control, the condensed mist droplet concentration reaches more than 100 g / L, which can be directly used in the plating tank. The purification effect of the entire exhaust gas circulating device reaches more than 99.9%.

[0068] The chromium plating wastewater and exhaust gas closed-loop circulation system of the embodiment can realize the closed-loop operation of the fluorine-containing chromium mist inhibitor + chromium mist and rinsing water for a long time, reliably and economically. The cleaning period is more than 6 months, and the ton water reuse cost is less than 10 yuan.

[0069] The air resistance of the chromium plating exhaust gas reuse unit system of the embodiment is less than 300 Pa, the purification effect is more than 99.9%, the purified gas meets the national emission standard, the separated fluorine-containing chromium mist inhibitor and chromium mist are 100% reused, the entire unit does not scale, the maintenance frequency and cost are reduced, and the closed-loop operation of the system is ensured.

[0070] The closed-loop circulation system of the embodiment completes the closed-loop reuse of the water system at the front end of the production line, forms zero emission, and can greatly reduce the scale and investment of the subsequent wastewater treatment station, and protects the environment.

[0071] The above is only the preferred embodiment of the present application. For those skilled in the art, according to the idea of the present application, the specific implementation and application range can be changed. The content of the specification should not be understood as a limitation of the present application.

[0072] The above is only the preferred embodiment of the present application. For those skilled in the art, according to the idea of the present application, the specific implementation and application range can be changed. The content of the specification should not be understood as a limitation of the present application.

Claims

1. A closed-loop recirculation system for chromium plating wastewater and exhaust gas, characterized in that: This includes chrome plating equipment, exhaust gas recirculation equipment, wastewater recirculation equipment, and pure water equipment; The chromium plating apparatus includes a chromium etching tank, a chromium plating tank, a first rinsing tank, a second rinsing tank, and a hot water washing tank arranged in sequence. The exhaust gas recirculation device includes an air inlet, a pre-filter, an air duct, a multi-stage filter, and an air outlet connected in sequence. The exhaust gas generated by the chrome plating unit enters the air inlet, and the recovered liquid collected by the exhaust gas circulation device is reused in the chrome plating tank. The pre-filter component includes a first housing and a pre-sprayer and a pre-filter structure disposed therein. The multi-stage filtration component includes a second housing and a first sprayer, a primary filter structure, a second sprayer, a secondary filter structure, a third sprayer, a tertiary filter structure, and a demister disposed therein in sequence. The pre-filter structure and the primary filter structure each consist of multiple filter screens arranged parallel to each other along the air inlet direction. The filter screens are composed of diamond-shaped mesh units and triangular mesh units, wherein the diamond-shaped mesh units are located in the middle of the filter screen, and the triangular mesh units are located on the four sides. The mesh units are provided with... The grid has horizontal or vertical ribs, with the ribs of adjacent grid units perpendicular to each other; the sprayer uses pulse rinsing; the sprayer from the air inlet to the air outlet blocks chromium anhydride and fluorinated chromium mist inhibitor particles with particle sizes of 10 micrometers, 5 micrometers, 3 micrometers and 1 micrometer, respectively; the concentration of the recovered liquid collected by the waste gas recirculation device is greater than 100 g / L; the wastewater recirculation device includes a DT separation unit, an evaporator, a deionized water tank, a chromium liquid tank, a cation removal unit, and a wastewater treatment device; the DT separation unit is a disc tube type DTRO membrane module, and its membrane material is aromatic polyamide; the cation removal unit is a cation adsorption resin used to remove iron ions and copper ions, controlling their concentration to be below 8 g / L. The first rinsing tank, the cation removal unit, the DT separation unit and the evaporator are connected in sequence; the evaporator is connected to the deionized water tank and the chromium solution tank, the deionized water tank is connected to the hot water rinsing tank, and the chromium solution tank is connected to the chromium etching tank and the chromium plating tank after passing through the cation removal unit. The pure water equipment is connected to the deionized water tank and the wastewater treatment device, respectively.

2. The closed-loop circulation system for chromium plating wastewater and exhaust gas according to claim 1, characterized in that: The cation adsorption resin is a sulfonic acid cation resin.

3. The closed-loop circulation system for chromium plating wastewater and exhaust gas according to claim 1, characterized in that, The secondary and tertiary filtration structures are identical, each including two breathable baffles and turbulent spheres stacked between the baffles.

4. The closed-loop circulation system for chromium plating wastewater and exhaust gas according to claim 1, characterized in that, The demister includes multiple sets of corrugated plates and hook-shaped ridges; the multiple sets of corrugated plates are arranged in parallel, the corrugation direction is the same as the air intake direction, and hook-shaped ridges are provided on the corrugated plates.

5. The closed-loop recirculation system for chromium plating wastewater and exhaust gas according to claim 1, characterized in that, The evaporator is a reduced-pressure evaporator.

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