Chromium-containing waste liquid treatment process

Abstract

The invention relates to the technical field of wastewater treatment, in particular to a chromium-containing waste liquid treatment process which comprises the following steps: A, injecting chromium-containing waste liquid into a treatment tank, and injecting an organic reducing agent into the treatment tank to reduce hexavalent chromium in the chromium-containing waste liquid into a trivalent chromium solution; b, the gas inlet end of a gas inlet pipe of the treatment tank communicates with a gas inlet pipe for heat discharged after galvanization is completed, high-temperature flue gas enters a heating cavity through the gas inlet pipe, and the trivalent chromium solution is evaporated and concentrated; c, the gas subjected to heating and heat exchange enters a filtering tank through a filtering pipe, and nitric oxide and other impurities in the gas are filtered out through the filtering tank; d, solid chromium obtained after evaporation and concentration is discharged out of the treatment tank; the heat generated after galvanization can be used for treating the chromium-containing waste liquid, so that the chemical electroplating cost can be reduced, the heat generated after galvanization can be fully utilized, hot gas pollution caused by the heat can be avoided, and the device has great significance in energy conservation and environmental protection.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, in particular to a process for treating chromium-containing waste liquid. Background Art

[0002] On the one hand, the chemical electroplating industry requires or produces chromium (hexavalent chromium), which will produce a large amount of chromium-containing (Cr) waste liquid. Chromium is one of the highly toxic elements. Direct discharge will cause serious pollution to the environment. Human contact or ingestion will cause skin ulcers, respiratory inflammation, anemia, neuritis and other serious injuries, and the cost of treating chromium-containing (Cr) waste liquid is required separately; on the other hand, in the galvanizing process, the galvanized parts need to be blown zinc after galvanizing is completed to remove excess zinc on the surface of the galvanized parts at the outlet of the zinc pot. The zinc dissolving furnace of each production line consumes about 4,000 cubic meters of natural gas every day. The normal working temperature of the furnace is 750°C. The temperature of the high-temperature flue gas discharged after combustion at the end of the furnace body is about 200°C. There is a large amount of heat energy waste in the high-temperature flue gas, which will also cause thermal pollution.

[0003] To sum up, on the one hand, directly discharging chromium waste liquid will cause serious pollution and increase the cost of treating chromium (Cr) waste liquid. On the other hand, the heat generated after galvanizing is wasted and will cause thermal pollution. If the heat generated after galvanizing is used to treat chromium waste liquid, the chromium waste liquid can be evaporated and concentrated into solid, which is of great significance to energy saving and environmental protection. Summary of the invention

[0004] The purpose of the present invention is to provide a chromium-containing waste liquid treatment process in view of the above-mentioned shortcomings, which can use the heat generated after galvanizing to treat the chromium-containing waste liquid, thereby reducing the cost of chemical electroplating and making full use of the heat generated after galvanizing to avoid the hot air pollution caused by it, which is of great significance to energy saving and environmental protection.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A chromium-containing waste liquid treatment process, characterized in that it comprises the following steps:

[0007] Step A: injecting the chromium-containing waste liquid into a treatment tank, and injecting an organic reducing agent into the treatment tank to reduce the hexavalent chromium in the chromium-containing waste liquid into a trivalent chromium solution;

[0008] Step B: connecting the air inlet end of the air inlet pipe of the treatment tank to the heat air inlet pipe exhausted after the galvanizing is completed, and the high-temperature flue gas enters the heating chamber through the air inlet pipe to evaporate and concentrate the trivalent chromium solution;

[0009] Step C: The gas after heating and heat exchange enters the filter tank through the filter tube, and the nitrogen oxides and other impurities in the gas are filtered out by the filter tank;

[0010] Step D: Discharge the evaporated and concentrated solid chromium from the treatment tank.

[0011] Furthermore, the organic reducing agent is an alcohol having 1 to 3 carbon atoms.

[0012] Furthermore, the processing tank includes an outer tank body, an inner tank body is arranged inside the outer tank body, the heating chamber is formed between the outer tank body and the inner tank body, the air outlet end of the air inlet pipe and the air inlet end of the filter tube are both connected to the heating chamber, and the top of the processing tank is provided with an air outlet pipe and a feed pipe connected to the inside of the inner tank body.

[0013] Furthermore, a spiral partition is provided in the heating chamber, and a spiral heat exchange channel is formed between the spiral partition, the outer wall of the inner tank body, and the inner wall of the outer tank body. The air outlet end of the air inlet pipe and the air inlet end of the filter tube are respectively connected to the bottom and top of the spiral heat exchange channel.

[0014] Furthermore, a rotating shaft is rotatably connected to the inner tank body, and a rotating vane is provided on the rotating shaft. The end of the rotating vane away from the rotating shaft scrapes along the inner wall of the inner tank body. A motor is fixed to the top of the outer tank body. The top of the rotating shaft passes through the outer tank body and is connected to the output shaft of the motor. A funnel-shaped discharge port connected to the outside of the processing tank is provided at the bottom of the inner tank body, and a valve body is provided at the funnel-shaped discharge port.

[0015] Furthermore, a smoke filter and an air pump are provided on the air inlet pipe.

[0016] Furthermore, a partition mesh plate is fixed in the middle of the filter tank, and the partition mesh plate divides the filter tank into a nitrogen oxide filter area and other impurity filter areas from bottom to top. Urea is provided in the nitrogen oxide filter area, and activated carbon is provided in the other impurity filter area. An air vent is provided on the top of the filter tank, and one end of the air inlet pipe extends into the urea.

[0017] The beneficial effects of the present invention are:

[0018] It can be seen from the above technical scheme that the hexavalent chromium in the chromium-containing waste liquid is reduced to a trivalent chromium solution by an organic reducing agent, and the trivalent chromium solution is heated by the heat generated after the galvanizing is completed, so that the trivalent chromium solution is evaporated and concentrated, and the solid chromium can be recovered. The nitrogen oxides and other impurities in the gas are filtered out by a filter tank, and the gas after heat exchange can be discharged. The present invention can use the heat generated after the galvanizing is completed to treat the chromium-containing waste liquid, which can not only reduce the cost of chemical electroplating, but also make full use of the heat generated after the galvanizing is completed to avoid the hot gas pollution caused by it, which is of great significance to energy saving and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the description of the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual scale.

[0020] Figure 1 It is a process step diagram of the present invention;

[0021] Figure 2 It is a structural schematic diagram of the processing tank in the present invention;

[0022] Figure 3 It is a right side view of the filter tank in the present invention.

[0023] Figure numerals: outer tank body 11; inner tank body 12; air outlet pipe 13; feed pipe 14; rotating shaft 15; rotating vane 16; motor 17; air inlet pipe 2; filter tube 3; spiral separator 4; filter tank 5; separator mesh plate 51; nitrogen oxide filter area 52; other impurities filter area 53. DETAILED DESCRIPTION

[0024] The following is a detailed description of a chromium-containing waste liquid treatment process technology scheme according to the present invention in conjunction with embodiments.

[0025] Embodiment 1:

[0026] like Figure 1-3 As shown, the following steps are included:

[0027] Step A: injecting the chromium-containing waste liquid into a treatment tank, and injecting an organic reducing agent into the treatment tank to reduce the hexavalent chromium in the chromium-containing waste liquid into a trivalent chromium solution;

[0028] Step B: connecting the air inlet end of the air inlet pipe 2 of the treatment tank to the heat air inlet pipe 2 exhausted after the galvanizing is completed, and the high-temperature flue gas enters the heating chamber through the air inlet pipe 2 to evaporate and concentrate the trivalent chromium solution;

[0029] Step C: The gas after the heating and heat exchange enters the filter tank 5 through the filter tube 3, and the nitrogen oxides and other impurities in the gas are filtered out by the filter tank 5;

[0030] Step D: Discharge the evaporated and concentrated solid chromium from the treatment tank.

[0031] like Figure 1-3 As shown, the organic reducing agent is an alcohol having 1 to 3 carbon atoms; in this embodiment, the alcohol having 1 to 3 carbon atoms can reduce hexavalent chromium to trivalent chromium.

[0032] like Figure 1-3As shown, the processing tank includes an outer tank body 11, an inner tank body 12 is arranged in the outer tank body 11, and the heating chamber is formed between the outer tank body 11 and the inner tank body 12. The outlet end of the air inlet pipe 2 and the air inlet end of the filter tube 3 are both connected to the heating chamber, and the top of the processing tank is provided with an outlet pipe 13 and a feed pipe 14 connected to the inside of the inner tank body 12; in this embodiment, the high-temperature gas discharged after the galvanizing is completed enters the heating chamber through the air inlet pipe 2, and heat is exchanged with the inner tank body 12 in the heating chamber to heat the inside of the inner tank body 12. The gas after the heat exchange enters the filter tank 5 through the filter tube 3 and is filtered and then discharged.

[0033] like Figure 1-3 As shown, a spiral partition plate 4 is provided in the heating chamber, and a spiral heat exchange channel is formed between the spiral partition plate 4, the outer wall of the inner tank body 12, and the inner wall of the outer tank body 11, and the air outlet end of the air inlet pipe 2 and the air inlet end of the filter tube 3 are respectively connected to the bottom and top of the spiral heat exchange channel; in this embodiment, a spiral heat exchange channel is formed between the spiral partition plate 4, the outer wall of the inner tank body 12, and the inner wall of the outer tank body 11, so as to extend the heat exchange time of the high-temperature flue gas in the heating chamber and achieve a better heating effect.

[0034] like Figure 1-3 As shown, a rotating shaft 15 is rotatably connected in the inner tank body 12, and a rotating vane 16 is provided on the rotating shaft 15. The end of the rotating vane 16 away from the rotating shaft 15 scrapes along the inner wall of the inner tank body 12, and a motor 17 is fixed to the top of the outer tank body 11. After the top of the rotating shaft 15 passes through the outer tank body 11, it is connected to the output shaft of the motor 17. A funnel-shaped discharge port connected to the outside of the processing tank is provided at the bottom of the inner tank body 12, and a valve body is provided at the funnel-shaped discharge port. In this embodiment, the rotating shaft 15 is driven by the motor 17 to drive the spiral scraper to rotate, so as to stir the liquid in the inner tank body 12, so as to heat it more evenly, and to assist in discharging the evaporated and concentrated solid chromium from the processing tank, so as to prevent the solid chromium from adhering to and accumulating on the inner wall of the processing tank.

[0035] like Figure 1-3 As shown, a smoke filter and an air pump are provided on the air inlet pipe 2; in this embodiment, the smoke filter can filter large particle impurities in the high-temperature smoke, and the air pump provides a power source for the high-temperature smoke.

[0036] like Figure 1-3As shown, a partition mesh plate 51 is fixed in the middle of the filter tank 5, and the partition mesh plate 51 divides the filter tank 5 into a nitrogen oxide filter area 52 and other impurities filter area 53 from bottom to top. The nitrogen oxide filter area 52 is provided with urea, and the other impurities filter area 53 is provided with activated carbon. A vent pipe is provided on the top of the filter tank 5, and one end of the intake pipe 2 extends into the urea. In this embodiment, nitrogen oxides in the gas can be removed by urea, and small particle impurities in the gas can be adsorbed by activated carbon, so that the gas meets the national emission standards.

[0037] The specific embodiments described herein are merely examples of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways without departing from the scope of the present invention.

Claims

1. A process for treating chromium-containing waste liquid, characterized in that: Step A: injecting the chromium-containing waste liquid into a treatment tank, and injecting an organic reducing agent into the treatment tank to reduce the hexavalent chromium in the chromium-containing waste liquid into a trivalent chromium solution; Step B: connecting the air inlet end of the air inlet pipe (2) of the treatment tank to the heat air inlet pipe (2) discharged after the galvanizing is completed, and the high-temperature flue gas enters the heating chamber through the air inlet pipe (2), so that the trivalent chromium solution evaporates and concentrates; Step C: the gas after the heating and heat exchange enters the filter tank (5) through the filter tube (3), and the nitrogen oxides and other impurities in the gas are filtered out by the filter tank (5); Step D: Discharge the evaporated and concentrated solid chromium from the treatment tank.

2. A chromium-containing waste liquid treatment process according to claim 1, characterized in that: The organic reducing agent is an alcohol having 1 to 3 carbon atoms.

3. A chromium-containing waste liquid treatment process according to claim 1, characterized in that: The processing tank comprises an outer tank body (11), an inner tank body (12) is arranged inside the outer tank body (11), a heating chamber is formed between the outer tank body (11) and the inner tank body (12), the air outlet end of the air inlet pipe (2) and the air inlet end of the filter pipe (3) are both connected to the heating chamber, and an air outlet pipe (13) and a feed pipe (14) connected to the interior of the inner tank body (12) are arranged at the top of the processing tank.

4. A chromium-containing waste liquid treatment process according to claim 3, characterized in that: A spiral partition (4) is provided in the heating chamber, and a spiral heat exchange channel is formed between the spiral partition (4), the outer wall of the inner tank body (12), and the inner wall of the outer tank body (11); the air outlet end of the air inlet pipe (2) and the air inlet end of the filter pipe (3) are respectively connected to the bottom end and the top end of the spiral heat exchange channel.

5. A chromium-containing waste liquid treatment process according to claim 3, characterized in that: A rotating shaft (15) is rotatably connected inside the inner tank body (12), and a rotating vane (16) is arranged on the rotating shaft (15). The end of the rotating vane (16) away from the rotating shaft (15) scrapes along the inner wall of the inner tank body (12). A motor (17) is fixed to the top end of the outer tank body (11). The top end of the rotating shaft (15) passes through the outer tank body (11) and is connected to the output shaft of the motor (17). A funnel-shaped discharge port communicating with the outside of the treatment tank is arranged at the bottom of the inner tank body (12), and a valve body is arranged at the funnel-shaped discharge port.

6. A chromium-containing waste liquid treatment process according to claim 1, characterized in that: The air inlet pipe (2) is provided with a smoke filter and an air pump.

7. A chromium-containing waste liquid treatment process according to claim 1, characterized in that: A partitioning mesh plate (51) is fixed in the middle of the filter tank (5), and the partitioning mesh plate (51) divides the filter tank (5) into a nitrogen oxide filtering area (52) and a other impurity filtering area (53) from bottom to top. Urea is arranged in the nitrogen oxide filtering area (52), and activated carbon is arranged in the other impurity filtering area (53). A venting pipe is arranged at the top of the filter tank (5), and one end of the air inlet pipe (2) extends into the urea.

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