Method for treating flue gas denitration and capturing gold by activated carbon

Abstract

The application discloses a method for treating flue gas denitration and capturing gold by activated carbon, comprising the following steps: firstly, high-temperature flue gas is introduced into the inside of a pre-washing tower, a high-pressure fan of the pre-washing tower extracts the flue gas from the bottom of the inner cavity of the pre-washing tower to the top of the inner cavity of the pre-washing tower, in the process of flowing in the inside of the pre-washing tower, the spraying water in the pre-washing tower is sprayed into the filler layer, the flue gas contacts the spraying water after passing through the filler layer, the spraying water cools the flue gas and adsorbs the particulate matters in the flue gas, the spraying water reacts with the nitrogen oxide compounds in the flue gas to perform primary denitration, and the flue gas enters the inside of an activated carbon tower after primary treatment. The application has the advantages of good recovery effect, solves the problems that the recovery effect of noble metals in flue gas is poor during the treatment of the flue gas of a kiln, and the problems of easy environmental pollution and increased loss of noble metals.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas treatment, in particular to a method for treating flue gas with activated carbon for denitrification and gold capture. Background Art

[0002] Flue gas is a mixture of gas and smoke, and is the main cause of air pollution in residential areas. The composition of flue gas is very complex, including water vapor, SO2, N2, O2, CO, CO2 hydrocarbons, precious metals and nitrogen oxides. Flue gas treatment is to effectively treat the toxic and harmful substances contained in the flue gas to below the specified concentration to prevent the flue gas from polluting the air environment.

[0003] A large part of the gold in the kiln flue gas is fine particles. These fine gold particles are not easy to recover and will be discharged into the atmosphere with the flue gas, causing environmental pollution and loss of precious metals. At present, most of the industry uses wet electrostatic spray dust collectors to treat the flue gas. The loss of gold in the flue gas accounts for a large proportion, which has a great impact on the recovery rate. In this case, the use of activated carbon to treat the flue gas, capture the gold in the flue gas, and capture the saltpeter in the flue gas at the same time, which will greatly improve the recovery rate of gold in the flue gas and become a more ideal treatment method.

[0004] After using activated carbon to denitrify and capture gold in flue gas, the activated carbon is then de-metallized and re-processed, which allows the activated carbon to be recycled multiple times, reducing the amount of activated carbon used and the cost of flue gas treatment. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for treating flue gas with activated carbon for denitrification and capturing gold, which has the advantage of good recovery effect and solves the problem that the current kiln flue gas treatment process has poor recovery effect on precious metals in the flue gas, easily causes environmental pollution and increases the loss of precious metals.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for treating flue gas with activated carbon for denitrification and capturing gold, comprising the following steps:

[0007] 1) First, high-temperature flue gas is introduced into the interior of the pre-scrubber. The high-pressure fan of the pre-scrubber draws the flue gas from the bottom of the pre-scrubber cavity to the top of the pre-scrubber cavity. As the flue gas flows inside the pre-scrubber, the spray water in the pre-scrubber is sprayed into the packing layer. The flue gas passes through the packing layer and comes into contact with the spray water. The spray water cools the flue gas and absorbs particulate matter in the flue gas. The spray water reacts with nitrogen oxides in the flue gas to perform primary denitrification. After the initial treatment, the flue gas enters the interior of the activated carbon tower;

[0008] 2) After the flue gas enters the inside of the activated carbon tower, the activated carbon granular material is added to the inside of the activated carbon tower through the feed valve of the activated carbon tower, and the washing water is added through the water inlet valve of the activated carbon tower. After the activated carbon enters the inner container of the activated carbon tower, it is contacted with the flue gas in the inside of the activated carbon tower. A blocking framework is arranged in the inside of the activated carbon tower, so that the activated carbon is divided into multiple layers in the activated carbon tower. The number of layers is determined according to the amount of flue gas and the content of noble metal in the flue gas. The layered activated carbon can reduce the falling speed of the activated carbon, so that the activated carbon and the flue gas can be fully contacted. The activated carbon adsorbs nitrogen oxides and noble metals in the flue gas. The activated carbon after adsorption is discharged through the discharge valve of the activated carbon tower. The purified flue gas is discharged through the smoke outlet channel.

[0009] 3) The discharged activated carbon is sampled and detected. When the noble metal content change value decreases, the opening angle of the feed valve and the discharge valve is reduced to reduce the flow rate of the activated carbon, so that the activated carbon can be fully contacted with the flue gas. When the washing water enters the activated carbon tower, the dust on the surface of the activated carbon is washed, so that the activated carbon can better adsorb nitrogen oxides and noble metals. The washing water entering the activated carbon tower is discharged into the hollow cavity of the activated carbon tower through the through hole on the inner container of the activated carbon tower, and is discharged into the sewage collection equipment through the drain pipe at the bottom of the activated carbon tower for treatment.

[0010] 4) The activated carbon discharged from the activated carbon tower is collected and transported into the inside of the gold removal tank. A certain amount of hydrochloric acid solution is added into the inside of the activated carbon, and the activated carbon is stirred to mix the activated carbon and the hydrochloric acid solution, so as to avoid that the thiourea solution is unstable in the alkaline solution. After the adjustment is completed, the thiourea solution and the oxidizing agent which are matched with the amount of the activated carbon are added, and the activated carbon is stirred again to desorb the noble metal in the activated carbon. The noble metal enters the desorption solution to form a noble metal solution. After the desorption is completed, the activated carbon is taken out, and the noble metal solution is extracted subsequently.

[0011] 5) After the activated carbon is removed from the gold, the activated carbon is denitrified and treated to make the activated carbon be recycled. The activated carbon is immersed in ultrapure water, and after the immersion is completed, the activated carbon is transferred to the inner tank of the reactor, and then triethylenetetramine is added. The triethylenetetramine has many amino groups. Here, nucleophilic reaction occurs between the amino groups on the surface of the activated carbon and the epoxy groups. The adsorption sites are added to enhance the adsorption capacity. The activated carbon is denitrified and the pH value is adjusted by using ammonium hydroxide. The inner tank is placed in a stainless steel hydrothermal reactor to heat the activated carbon. Then the inner tank is taken out and cooled to room temperature. Then the activated carbon is washed with ultrapure water three times. The prepared activated carbon is freeze-dried in a freezing device to produce dry and loose porous activated carbon powder. The activated carbon powder is granulated to prepare activated carbon particles which can work in the inside of the activated carbon tower.

[0012] In order to facilitate the avoidance of thiourea solution in the basic solution is not stable, as a preferred method for treating flue gas denitration and gold capture of activated carbon of the present application, the step 4) after adding hydrochloric acid solution, the pH value of the activated carbon is 1.5-3.0.

[0013] In order to facilitate the cleaning of activated carbon, as a preferred method for treating flue gas denitration and gold capture of activated carbon of the present application, the step 5) in the activated carbon is immersed in ultrapure water for 30-60 min.

[0014] In order to facilitate the activated carbon for denitration, as a preferred method for treating flue gas denitration and gold capture of activated carbon of the present application, the step 5) after adding ammonium hydroxide, the pH value of the activated carbon is 10-11.

[0015] In order to facilitate the regeneration of activated carbon, as a preferred method for treating flue gas denitration and gold capture of activated carbon of the present application, the step 5) in the activated carbon is heated to 170-190 DEG C, and the heating time is 20-30 h.

[0016] In order to facilitate the uniform mixing of activated carbon and solution, as a preferred method for treating flue gas denitration and gold capture of activated carbon of the present application, the step 4) in the stirring time is 30-40 min, and the oxidizing agent is one of manganese dioxide, dithiocarbamate, high valence iron salt and dissolved oxygen.

[0017] In order to facilitate the prevention of corrosion damage to the reactor tank, as a preferred method for treating flue gas denitration and gold capture of activated carbon of the present application, the step 5) in the reactor tank is made of polytetrafluoroethylene.

[0018] In order to facilitate the discharge of washing water, as a preferred method for treating flue gas denitration and gold capture of activated carbon of the present application, the step 3) in the inner liner of the activated carbon tower is provided with a plurality of through holes, and the top of the drain pipe is communicated with the hollow cavity.

[0019] Compared with the prior art, the present application has the following advantages:

[0020] The present application is provided with the flowing activated carbon to absorb the nitrogen oxide compounds in the flue gas and capture the noble metals in the flue gas, solves the problem that the noble metals in the flue gas are recovered with poor effect during the treatment of the current kiln flue gas, causes environmental pollution and increases the loss of noble metals, and can be used for gold removal and utilization of activated carbon, reduces the cost of flue gas treatment. DETAILED DESCRIPTION

[0021] Embodiment:

[0022] A method for treating flue gas denitration and gold capture of activated carbon, comprising the following steps:

[0023] 1) First, the high-temperature flue gas is introduced into the inside of the pre-washing tower, and the high-pressure fan of the pre-washing tower extracts the flue gas from the bottom of the inner cavity of the pre-washing tower to the top of the inner cavity of the pre-washing tower. During the flow of the flue gas in the pre-washing tower, the spray water in the pre-washing tower is sprayed into the filler layer, the flue gas passes through the filler layer and contacts the spray water, the spray water cools and adsorbs the particulate matter in the flue gas, the spray water reacts with the nitrogen oxides in the flue gas to perform primary denitrification, and the flue gas after the primary treatment enters the inside of the activated carbon tower;

[0024] 2) After the flue gas enters the inside of the activated carbon tower, activated carbon particles are added to the inside of the activated carbon tower through the feed valve of the activated carbon tower, and washing water is added through the water inlet valve of the activated carbon tower. After the activated carbon enters the inner bag of the activated carbon tower, it contacts the flue gas inside the activated carbon tower. A blocking framework is arranged inside the activated carbon tower, so that the activated carbon is divided into multiple layers in the activated carbon tower. The number of layers is determined according to the flue gas amount and the noble metal content in the flue gas. Layering the activated carbon can reduce the falling speed of the activated carbon, so that the activated carbon and the flue gas can be fully contacted. The activated carbon adsorbs the nitrogen oxides and noble metals in the flue gas. The activated carbon after adsorption is discharged through the discharge valve of the activated carbon tower, and the purified flue gas is discharged through the smoke outlet channel;

[0025] 3) The discharged activated carbon is sampled and detected. When the noble metal content change value decreases, the opening angle of the feed valve and the discharge valve is reduced to reduce the flow rate of the activated carbon, so that the activated carbon can be fully contacted with the flue gas. When the washing water enters the activated carbon tower, it washes the dust on the surface of the activated carbon, so that the activated carbon can better adsorb the nitrogen oxides and noble metals. The washing water entering the activated carbon tower is discharged into the hollow cavity of the activated carbon tower through the through hole on the inner bag of the activated carbon tower, and is discharged into the sewage collection equipment through the drain pipe at the bottom of the activated carbon tower for treatment;

[0026] 4) The activated carbon discharged from the activated carbon tower is collected and transported into the inside of the gold removal tank. A certain amount of hydrochloric acid solution is first added to the inside of the activated carbon, and the activated carbon is stirred to mix the activated carbon and the hydrochloric acid solution. The thiourea solution is not stable in the alkaline solution, so the adjustment is completed. The amount of thiourea solution and oxidizing agent suitable for the amount of activated carbon is added, and the noble metal in the activated carbon is desorbed by stirring again. The noble metal enters the desorption solution to form a noble metal solution. After desorption, the activated carbon is taken out, and the noble metal solution is extracted subsequently;

[0027] 5) After the activated carbon is removed of gold, the activated carbon is removed of nitrogen oxide and is treated, so that the activated carbon can be recycled, the activated carbon is immersed in ultrapure water, after the immersion is completed, the activated carbon is transferred to an inner tank of a reactor, then triethylenetetramine is added, the triethylenetetramine has many amino groups, at this time, nucleophilic reaction occurs between the amino groups on the surface of the activated carbon and the epoxy groups, the adsorption sites are added to enhance the adsorption capacity, the activated carbon is removed of nitrogen oxide by using ammonium hydroxide and the pH value of the activated carbon is adjusted, the inner tank is placed in a stainless steel hydrothermal reactor to heat the activated carbon, then the inner tank is taken out and cooled to room temperature, then the activated carbon is washed with ultrapure water three times, the prepared activated carbon is freeze-dried in a freezing device, dry and loose porous activated carbon powder is generated, the activated carbon powder is granulated to prepare activated carbon particles that can work in an activated carbon tower.

[0028] In the embodiment, the flue gas is washed in advance to remove dust and particulate matters in the flue gas, and the flue gas is initially removed of nitrogen oxide, so that the activated carbon can capture gold and be removed of nitrogen oxide again, after the flue gas is washed, the temperature of the flue gas is reduced, the flue gas after the temperature is reduced is introduced into the inside of the activated carbon tower, the activated carbon particles are introduced into the activated carbon tower, the flue gas is removed of nitrogen oxide and gold is captured, the washing water introduced into the inside of the activated carbon tower can flush the dust in the activated carbon particles, the treatment effect of the activated carbon is increased, the activated carbon discharged from the activated carbon tower is introduced into the inside of the gold removal tank, the activated carbon is removed of gold by using hydrochloric acid solution, thiourea solution and oxidizing agent, and the activated carbon is treated, so that the activated carbon can be recycled.

[0029] As a technical optimization scheme of the present application, the pH value of the activated carbon after the hydrochloric acid solution is added in step 4) is 1.5-3.0.

[0030] In the embodiment, the pH value of the activated carbon after the hydrochloric acid solution is added is 1.5-3.0, so that the thiourea solution is not unstable in the alkaline solution and is not decomposed into sulfide and amino blue.

[0031] As a technical optimization scheme of the present application, the time for which the activated carbon is immersed in the ultrapure water in step 5) is 30-60 min.

[0032] In the embodiment, the activated carbon is immersed in the ultrapure water, so that the activated carbon can be cleaned and the subsequent treatment of the activated carbon is facilitated.

[0033] As a technical optimization scheme of the present application, the pH value of the activated carbon after the ammonium hydroxide is added in step 5) is 10-11.

[0034] In the embodiment, the ammonium hydroxide is added to the activated carbon, so that the pH value of the activated carbon is adjusted, the activated carbon can neutralize nitrogen oxide compounds, and the flue gas is removed of nitrogen oxide.

[0035] As a technical optimization scheme of the present application, the heating temperature of the activated carbon in step 5) is 170-190°C, and the heating time is 20-30h.

[0036] In this embodiment: by heating the activated carbon, the activated carbon can be made in.

[0037] As a technical optimization scheme of the present application, the stirring time in step 4) is 30-40min, and the oxidant is one of manganese dioxide, disulfiram, high-valent iron salt and dissolved oxygen.

[0038] In this embodiment: the stirring time of the activated carbon is 30-40min, which can make the activated carbon fully mixed with the solution.

[0039] As a technical optimization scheme of the present application, the material of the reactor inner tank in step 5) is polytetrafluoroethylene.

[0040] In this embodiment: the material of the reactor inner tank is polytetrafluoroethylene, which prevents the solution from corroding the reactor inner tank and reduces the service life of the reactor inner tank.

[0041] As a technical optimization scheme of the present application, the inner liner of the activated carbon tower in step 3) is provided with a plurality of through holes, and the top of the drain pipe is communicated with the hollow cavity.

[0042] In this embodiment: by opening a plurality of through holes, the washing water after washing the activated carbon can be discharged, and the sewage can enter the hollow cavity and the drain pipe.

[0043] In summary: the method for treating flue gas denitration and capturing gold by activated carbon, by setting the flow of activated carbon to absorb nitrogen oxides in flue gas, and to capture noble metals in flue gas, solves the problem that the current kiln flue gas is treated, the recovery effect of noble metals in flue gas is poor, which easily causes environmental pollution and increases the loss of noble metals, and can be used for gold and in the use of activated carbon, reduces the cost of flue gas treatment.

Claims

1. A method for treating flue gas denitration and capturing gold by activated carbon, characterized in that, The following steps are involved: 1) First, high-temperature flue gas is introduced into the interior of the pre-scrubber. The high-pressure fan of the pre-scrubber draws the flue gas from the bottom of the pre-scrubber cavity to the top of the pre-scrubber cavity. As the flue gas flows inside the pre-scrubber, the spray water in the pre-scrubber is sprayed into the packing layer. The flue gas passes through the packing layer and comes into contact with the spray water. The spray water cools the flue gas and absorbs particulate matter in the flue gas. The spray water reacts with nitrogen oxides in the flue gas to perform primary denitrification. After the initial treatment, the flue gas enters the interior of the activated carbon tower; 2) After the flue gas enters the activated carbon tower, activated carbon particles are added to the activated carbon tower through the feed valve of the activated carbon tower, and washing water is added through the water inlet valve of the activated carbon tower. After the activated carbon enters the inner liner of the activated carbon tower, it comes into contact with the flue gas inside the activated carbon tower. A barrier skeleton is provided inside the activated carbon tower, so that the activated carbon is divided into multiple layers inside the activated carbon tower. The number of layers is determined according to the flue gas volume and the precious metal content in the flue gas. Layering the activated carbon can reduce the falling speed of the activated carbon, so that the activated carbon and the flue gas are fully in contact. The activated carbon adsorbs nitrogen oxides and precious metals in the flue gas. The adsorbed activated carbon is discharged through the discharge valve of the activated carbon tower, and the purified flue gas is discharged through the smoke outlet channel; 3) Take samples of the discharged activated carbon for testing. When the change in the precious metal content decreases, reduce the opening and closing angles of the feed valve and the discharge valve to reduce the flow rate of the activated carbon so that the activated carbon can fully contact the flue gas. When the washing water enters the activated carbon tower, it washes the dust on the surface of the activated carbon so that the activated carbon can better adsorb nitrogen oxides and precious metals. The washing water entering the activated carbon tower is discharged into the hollow cavity of the activated carbon tower through the through-holes on the inner liner of the activated carbon tower, and is discharged into the sewage collection equipment through the drain pipe at the bottom of the activated carbon tower for treatment; 4) Collect the activated carbon discharged from the activated carbon tower and transfer it to the inside of the gold removal pool. First, add a certain amount of hydrochloric acid solution to the activated carbon, and then stir the activated carbon for 30-40 minutes to mix the activated carbon and the hydrochloric acid solution to prevent the thiourea solution from being unstable in the alkaline solution. After the adjustment is completed, add thiourea solution and oxidant that are compatible with the amount of activated carbon. The oxidant is one of manganese dioxide, disulfide formamidine, high-valent iron salt and dissolved oxygen. Stir again to desorb the precious metals in the activated carbon. The precious metals enter the desorption solution to form a precious metal solution. After desorption is completed, remove the activated carbon and perform subsequent extraction on the precious metal solution. 5) After the activated carbon is removed of gold, the activated carbon is treated for denitration and regeneration, so that the activated carbon can be recycled. The activated carbon is immersed in ultrapure water, the time for the activated carbon to be immersed in the ultrapure water is 30-60 min, after the immersion is completed, the activated carbon is transferred to an inner tank of a reactor, then triethylenetetramine is added, the triethylenetetramine has many amino groups, at this time, nucleophilic reaction occurs between the amino groups on the surface of the activated carbon and the epoxy groups, adsorption sites are added to enhance the adsorption capacity thereof, ammonium hydroxide is used to remove the nitrate from the activated carbon and to adjust the pH value thereof, the inner tank is placed in a stainless steel hydrothermal reactor to heat the activated carbon, the heating temperature of the activated carbon is 170-190℃, the heating time is 20-30 h, then the inner tank is taken out and cooled to room temperature, then the activated carbon is washed with ultrapure water three times, the prepared activated carbon is freeze-dried in a freezing device, dry and loose porous activated carbon powder is produced, the activated carbon powder is granulated to prepare activated carbon particles that can work in an activated carbon tower.

2. The method according to claim 1, wherein the method is characterized by: The pH value of the activated carbon after the hydrochloric acid solution is added in the step 4) is 1.5-3.

0.

3. The method according to claim 1, wherein the method is characterized by: The pH value of the activated carbon after the ammonium hydroxide is added in the step 5) is 10-11.

4. The method according to claim 1, wherein the method is characterized by: The material of the inner tank of the reactor in the step 5) is polytetrafluoroethylene.

5. The method of claim 1, wherein the method is characterized by: The inner liner of the activated carbon tower in the step 3) is provided with a plurality of through holes, the top of the drain pipe is communicated with the hollow cavity. The material of the inner tank of the reactor in the step 5) is polytetrafluoroethylene. The inner liner of the activated carbon tower in the step 3) is provided with a plurality of through holes, the top of the drain pipe is communicated with the hollow cavity.