Zero-emission treatment system for electrolytic aluminum flue gas and application of zero-emission treatment system

Abstract

The invention relates to the technical field of energy conservation and environmental protection, in particular to an electrolytic aluminum flue gas zero emission treatment system and application. The system comprises an electrolytic aluminum flue gas purification device, a desulfurization device, a pretreatment device, a reverse osmosis device and an evaporative crystallization device, and a first outlet of the electrolytic aluminum flue gas purification device, the desulfurization device, the pretreatment device, the reverse osmosis device and the evaporative crystallization device are sequentially connected; the evaporative crystallization device comprises an atomization unit, an evaporative crystallization tower, a dust remover and a trough; the atomization unit, a first inlet of the evaporative crystallization tower, an outlet of the evaporative crystallization tower, an inlet of the efficient dust remover, a first outlet of the efficient dust remover and the trough are connected in sequence; a second outlet of the electrolytic aluminum flue gas purification device is connected with a second inlet of the evaporative crystallization tower; and a second outlet of the high-efficiency dust remover is connected with a second inlet of the electrolytic aluminum flue gas purification device. The objective situation that wastewater discharge in the electrolytic aluminum industry does not reach the standard at present is thoroughly solved through the wastewater zero discharge treatment process.

Description

Technical Field

[0001] The present invention relates to the technical field of energy conservation and environmental protection, and in particular to a zero-emission treatment system for electrolytic aluminum fume and its application. Background Art

[0002] At present, there are more than 10 relatively mature and economical and scientific process technologies for industrial flue gas desulfurization, among which the limestone-gypsum wet desulfurization process technology is the most widely used. The electrolytic aluminum limestone-gypsum wet desulfurization process will produce desulfurization wastewater. For areas where desulfurization wastewater can be discharged, the current treatment technologies mainly include the three-unit process or the wastewater integration process. The above two technical routes can only treat wastewater that meets the second period and first level standard of the "Comprehensive Sewage Discharge Standard" (GB8978-1996) and the "Water Quality Control Index of Limestone-Gypsum Wet Desulfurization Wastewater from Thermal Power Plants" (DL / T997) before discharge; for areas where the discharge of desulfurization wastewater is prohibited, the current treatment technologies mainly include the single-effect MVR forced circulation crystallization method wastewater zero discharge process. The single-effect MVR forced circulation crystallization method wastewater zero discharge process uses electric heating to generate steam and then evaporates the wastewater, which has high power consumption and high operating costs. Summary of the invention

[0003] In order to solve the above problems, the present invention provides a zero-emission treatment system for electrolytic aluminum fume and its application. The present invention provides the following technical solutions:

[0004] The present invention provides a zero-emission treatment system for electrolytic aluminum fume, which comprises an electrolytic aluminum fume purification device, a desulfurization device, a pretreatment device, a reverse osmosis device and an evaporation crystallization device, wherein:

[0005] The first outlet of the electrolytic aluminum fume purification device, the desulfurization device, the pretreatment device, the reverse osmosis device and the evaporation crystallization device are connected in sequence;

[0006] The evaporation crystallization device comprises an atomization unit, an evaporation crystallization tower, a dust collector and a material trough.

[0007] The atomizing unit, the first inlet of the evaporation crystallization tower, the outlet of the evaporation crystallization tower, the inlet of the high-efficiency dust collector, the first outlet of the high-efficiency dust collector and the material trough are connected in sequence;

[0008] The second outlet of the aluminum electrolysis fume purification device is connected to the second inlet of the evaporation crystallization tower;

[0009] The second outlet of the high-efficiency dust collector is connected to the second inlet of the electrolytic aluminum fume purification device.

[0010] Specifically, the second outlet of the high-efficiency dust collector is connected to the second inlet of the electrolytic aluminum fume purification device through a fan.

[0011] Specifically, the reverse osmosis device includes a pipe network reverse osmosis membrane concentration unit, a concentrate pump and a water outlet pump, wherein:

[0012] The first outlet of the net-type reverse osmosis membrane concentration unit is connected to the atomization unit through a concentrate pump;

[0013] The second outlet of the mesh reverse osmosis membrane concentration unit is connected to the desulfurization device through a water outlet pump.

[0014] Specifically, a reverse osmosis module assembly and an ultrafiltration module are arranged inside the pipe network type reverse osmosis membrane concentration unit.

[0015] Specifically, the reverse osmosis module assembly is a tubular module assembly.

[0016] Specifically, the reverse osmosis module assembly includes a pipe network type reverse osmosis membrane.

[0017] Specifically, the ultrafiltration module is one of submerged ultrafiltration, column ultrafiltration, tubular ultrafiltration, scroll ultrafiltration or plate ultrafiltration.

[0018] Specifically, the pretreatment device includes a pre-sedimentation tank, a magnesium removal reaction tank, a calcium removal reaction tank, a neutralization tank, a homogenization tank, a flocculation tank and a sedimentation tank which are connected in sequence.

[0019] Specifically, the pretreatment device also includes a pre-sedimentation tank sludge pump, a sedimentation tank sludge pump and a dewatering machine, wherein:

[0020] The bottom of the pre-sedimentation tank is connected to the dewatering machine via a pre-sedimentation tank sludge pump;

[0021] The bottom of the sedimentation tank is connected with a dewatering machine through a sedimentation tank sludge pump.

[0022] Also provided is the application of the zero-emission treatment system for electrolytic aluminum fume as described above in treating electrolytic aluminum fume.

[0023] Technical effects and advantages of the present invention:

[0024] (1) Through the zero-discharge wastewater treatment process, the current objective situation of substandard wastewater discharge in the electrolytic aluminum industry can be completely resolved.

[0025] (2) Fill the gap in the research and application of zero-emission technology of flue gas evaporation and crystallization of desulfurization wastewater in the electrolytic aluminum industry.

[0026] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a diagram of a preprocessing device provided in an embodiment of the present application;

[0028] Figure 2 is a diagram of a reverse osmosis device provided in an embodiment of the present application;

[0029] Figure 3 This is a diagram of the evaporation crystallization device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In order to solve the shortcomings of the prior art, the present invention discloses a zero-emission treatment system for electrolytic aluminum fume, which includes an electrolytic aluminum fume purification device, a desulfurization device, a pretreatment device, a reverse osmosis device and an evaporation crystallization device, wherein the first outlet of the electrolytic aluminum fume purification device, the desulfurization device, the pretreatment device, the reverse osmosis device and the evaporation crystallization device are connected in sequence.

[0032] In a specific embodiment of the present invention, Figure 1 As shown, the pretreatment device includes a pre-sedimentation tank, a magnesium removal reaction tank, a calcium removal reaction tank, a neutralization tank, a homogenization tank, a flocculation tank, a sedimentation tank, a clean water tank, a pre-sedimentation tank sludge pump, a sedimentation tank sludge pump and a dewatering machine, wherein the pre-sedimentation tank, the magnesium removal reaction tank, the calcium removal reaction tank, the neutralization tank, the homogenization tank, the flocculation tank, the sedimentation tank and the clean water tank are connected in sequence; the bottom of the pre-sedimentation tank is connected to the dewatering machine through the pre-sedimentation tank sludge pump; the bottom of the sedimentation tank is connected to the dewatering machine through the sedimentation tank sludge pump.

[0033] The desulfurization wastewater flowing out of the desulfurization device enters the pre-precipitation tank for pre-precipitation. The upper clear liquid after pre-precipitation enters the magnesium removal reaction tank, and the reagent NaOH is added to generate Mg(OH)2 solid precipitation to remove Mg. 2+ ; The clear liquid from the magnesium removal reaction tank enters the calcium removal reaction tank, where the reagent Na2CO3 is added to generate CaCO3 solid precipitation to remove Ca 2+The upper clear liquid of the decalcification reaction tank enters the neutralization tank. Due to the addition of NaOH and Na2CO3 reagents upstream, the pH value of the wastewater is relatively high, and H2SO4 needs to be added to neutralize the pH value; the upper clear liquid of the neutralization tank enters the equalization tank, and a coagulant is added to enlarge the solid particles; the effluent from the equalization tank enters the flocculation tank, and a flocculant is added to enlarge the alum flowers, and at the same time, it is slowly stirred to allow the solid particles to grow fully; the upper clear liquid of the flocculation tank enters the sedimentation tank, and after free sedimentation, the upper clear liquid enters the clean water tank. The sludge at the bottom of the pre-sedimentation tank is transferred to the vacuum belt dehydrator by the pre-sedimentation tank sludge pump for dehydration and discharge. The sludge at the bottom of the sedimentation tank is transferred to the vacuum belt dehydrator by the sedimentation tank sludge pump for dehydration and discharge. This step can remove most of the suspended matter in the desulfurization wastewater, and the upper clear liquid meets the "Comprehensive Sewage Discharge Standard" after treatment.

[0034] (GB8978-1996) the second period first level standard, and the "Water Quality Control Index for Limestone-Gypsum Wet Fluoride Desulfurization Wastewater from Thermal Power Plants" (DL / T997) standard.

[0035] In a specific embodiment of the present invention, Figure 2 As shown, the reverse osmosis device includes a pipe network reverse osmosis membrane concentration unit, a concentrate pump and a water outlet pump, wherein the first outlet of the network reverse osmosis membrane concentration unit is connected to the atomization unit through the concentrate pump; the second outlet of the network reverse osmosis membrane concentration unit is connected to the desulfurization device through the water outlet pump.

[0036] The pipe network type reverse osmosis membrane concentration unit is internally provided with a reverse osmosis module assembly and an ultrafiltration module.

[0037] The reverse osmosis module assembly is a tubular module assembly, and the reverse osmosis module assembly includes a tubular network reverse osmosis membrane;

[0038] The ultrafiltration module is one of immersed ultrafiltration, column ultrafiltration, tubular ultrafiltration, scroll ultrafiltration or plate ultrafiltration.

[0039] The treated upper clear liquid (wastewater) collected in the clean water tank is pumped into the reverse osmosis system for concentration through a clean water pump. The reverse osmosis system is equipped with an ultrafiltration pretreatment device to remove larger solid particles, and then a high-pressure pump is used to pass the wastewater through a pipe network membrane column. The clean water produced accounts for 75%, and the concentrated wastewater produces accounts for 25%, which greatly reduces the amount of wastewater. For example, 1t of water is taken in, 0.75t of clean water is reused, and 0.25t of concentrated wastewater is further treated. The clean water is also recycled to the desulfurization system to reduce the water consumption of the desulfurization system.

[0040] In a specific embodiment of the present invention, Figure 3As shown, the evaporation crystallization device includes an atomization unit, an evaporation crystallization tower, a high-efficiency dust collector and a material trough, wherein the atomization unit, the first inlet of the evaporation crystallization tower, the outlet of the evaporation crystallization tower, the inlet of the high-efficiency dust collector, the first outlet of the high-efficiency dust collector and the material trough are connected in sequence; the second outlet of the electrolytic aluminum fume purification device is connected to the second inlet of the evaporation crystallization tower; the second outlet of the high-efficiency dust collector is connected to the second inlet of the electrolytic aluminum fume purification device through a fan.

[0041] The reverse osmosis concentrate is pumped into the atomizing device of the evaporation and crystallization system. Compressed air is introduced into the atomizing device, and the wastewater is atomized by a dual-fluid spray gun and then sprayed into the evaporation and crystallization tower. In addition, high-temperature flue gas (90-110℃) is drawn out from the electrolytic aluminum flue gas purification device and introduced into the evaporation and crystallization tower to evaporate and crystallize the atomized wastewater through high-temperature flue gas. The dry flue gas after evaporation and crystallization of the wastewater contains solid crystalline salt, which is then separated by a high-efficiency dust collector. The clean flue gas is pressurized by a fan and then connected back to the electrolytic aluminum flue. The separated solid crystalline salt is disposed of together with the solid waste of the aluminum plant.

[0042] The present invention also provides an application of the zero-emission treatment system for electrolytic aluminum fume as described above in treating electrolytic aluminum fume.

[0043] The zero emission treatment system for electrolytic aluminum fume includes the following methods for treating electrolytic aluminum fume:

[0044] Step 1: The aluminum electrolysis flue gas is sequentially processed through an aluminum electrolysis flue gas purification device and a desulfurization device to obtain aluminum electrolysis desulfurization wastewater;

[0045] Step 2: pre-treating the electrolytic aluminum desulfurization wastewater to obtain the upper clear liquid and the bottom sediment;

[0046] Step 3: The upper clear liquid after sedimentation in the pre-sedimentation tank is treated in the clean water tank and then enters the reverse osmosis device for concentration to obtain clean water and concentrated wastewater; the clean water is returned to the desulfurization system for recycling;

[0047] Step 4: The concentrated wastewater enters an evaporation crystallization device for treatment to obtain water and solid crystalline salt.

[0048] In step 2, pre-treating the aluminum electrolytic desulfurization wastewater to obtain the upper clear liquid and the bottom sediment comprises the following steps:

[0049] First, the electrolytic aluminum desulfurization wastewater is pre-precipitated in a pre-precipitation tank to obtain a first clear liquid and a first precipitate;

[0050] The first clear liquid enters the magnesium removal reaction tank, and the reagent NaOH is added to generate Mg(OH)2 solid precipitation to remove Mg 2+ The upper clear liquid of the magnesium removal reaction tank enters the calcium removal reaction tank, and the reagent Na2CO3 is added to generate CaCO3 solid precipitation to remove Ca2+ , obtaining a second clear solution;

[0051] The second clear liquid enters the neutralization tank. Because the reagents NaOH and Na2CO3 are added upstream, the pH value of the wastewater is relatively high, and H2SO4 needs to be added to neutralize the pH value; the upper clear liquid of the neutralization tank enters the homogenization tank, and a coagulant is added to enlarge the solid particles; the effluent of the homogenization tank enters the flocculation tank, and a flocculant is added to enlarge the alum flowers, and slowly stirred to make the solid particles grow fully; the upper clear liquid of the flocculation tank enters the sedimentation tank, and after free sedimentation, the upper clear liquid enters the clean water tank. The sludge at the bottom of the pre-sedimentation tank is conveyed to the vacuum belt dehydrator by the pre-sedimentation tank sludge pump for dehydration and discharge. The sludge at the bottom of the sedimentation tank and the magnesium hydroxide precipitate and calcium hydroxide precipitate are all conveyed to the vacuum belt dehydrator by the sedimentation tank sludge pump for dehydration and discharge. Most of the suspended matter in the desulfurization wastewater can be removed in this step, and the upper clear liquid after treatment meets the "Water Quality Control Index of Limestone-Gypsum Wet Desulfurization Wastewater in Thermal Power Plants" (DL / T997) standard.

[0052] In a specific embodiment of the present invention, for step 3: the upper clear liquid after precipitation in the pre-sedimentation tank is treated in a clean water tank and then enters a reverse osmosis device for concentration to obtain clean water and concentrated wastewater, wherein the treated upper clear liquid (wastewater) collected in the clean water tank is pumped into a reverse osmosis system for concentration through a clean water pump, and an ultrafiltration pretreatment device is provided in the reverse osmosis system to remove larger particles of solids, and then a high-pressure pump is used to pass the wastewater through a pipe network membrane column, and the clean water produced accounts for 75%, and the concentrated wastewater produced accounts for 25%, which greatly reduces the amount of wastewater, and also recycles the clean water to the desulfurization system to reduce the water consumption of the desulfurization system.

[0053] In a specific embodiment of the present invention, for step 4: the concentrated wastewater enters an evaporation crystallization device for treatment to obtain water and solid crystalline salt, comprising the following steps:

[0054] Step 401: using a dual-fluid spray gun, spraying compressed air and concentrated wastewater into an atomization unit at a predetermined pressure for atomization;

[0055] Step 402: the atomized wastewater enters an evaporation crystallization tower, and is evaporated and crystallized with the flue gas of a predetermined temperature from the electrolytic aluminum flue gas purification device in the evaporation crystallization tower. The evaporation and crystallization temperature of the flue gas in the evaporation crystallization tower is 90-110°C, and dry flue gas and solid crystalline salt are obtained. In this process, the flue gas temperature in the electrolytic aluminum industry is relatively low (90-110°C), and there is no other heat source such as steam, but the discharge of wastewater from wet desulfurization of electrolytic aluminum is small (the discharge of wastewater from each desulfurization device is generally less than 1t / h), and the required heat is correspondingly small. At present, there is no engineering application that uses flue gas evaporation to achieve zero discharge of flue gas wastewater from electrolytic aluminum.

[0056] Step 403: The dry flue gas is pressurized by a fan and returned to the electrolytic aluminum flue gas purification device to recover the solid crystals. The dry flue gas after evaporation of the crystallization wastewater contains solid crystalline salt, which is then separated by a high-efficiency dust collector. The clean flue gas is pressurized by a fan and returned to the electrolytic aluminum flue. The separated solid crystalline salt is disposed together with the solid waste of the aluminum plant.

[0057] The traditional thermal power plant desulfurization wastewater zero discharge treatment process adopts flue evaporation technology. The evaporation flue gas is taken from the high-temperature flue gas (about 300-380℃) before the air preheater. It has high heat, short evaporation time, and large amount of evaporation wastewater. The flue gas temperature of the electrolytic aluminum industry is relatively low (90-110℃), and there is no other heat source such as steam. However, the discharge of electrolytic aluminum wet desulfurization wastewater is small (the discharge of wastewater from each desulfurization device is generally less than 1t / h), and the required heat is relatively small. At present, there is no engineering application that uses flue gas evaporation to achieve zero discharge of electrolytic aluminum flue gas wastewater.

[0058] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A zero-emission treatment system for electrolytic aluminum fume, characterized in that: The system includes an aluminum electrolytic fume purification device, a desulfurization device, a pretreatment device, a reverse osmosis device and an evaporation crystallization device, wherein: The first outlet of the electrolytic aluminum fume purification device, the desulfurization device, the pretreatment device, the reverse osmosis device and the evaporation crystallization device are connected in sequence; The evaporation crystallization device comprises an atomization unit, an evaporation crystallization tower, a dust collector and a material trough. The atomization unit, the first inlet of the evaporation crystallization tower, the outlet of the evaporation crystallization tower, the inlet of the high-efficiency dust collector, the first outlet of the high-efficiency dust collector and the material trough are connected in sequence; The second outlet of the electrolytic aluminum fume purification device is connected to the second inlet of the evaporation crystallization tower; The second outlet of the high-efficiency dust collector is connected to the second inlet of the electrolytic aluminum fume purification device.

2. The zero-emission treatment system for electrolytic aluminum fume according to claim 1 is characterized in that: The second outlet of the high-efficiency dust collector is connected to the second inlet of the electrolytic aluminum fume purification device through a fan.

3. The zero-emission treatment system for electrolytic aluminum fume according to claim 1 is characterized in that: The reverse osmosis device includes a pipe network reverse osmosis membrane concentration unit, a concentrate pump and a water outlet pump, wherein: The first outlet of the net-type reverse osmosis membrane concentration unit is connected to the atomization unit through a concentrate pump; The second outlet of the mesh reverse osmosis membrane concentration unit is connected to the desulfurization device through a water outlet pump.

4. The zero-emission treatment system for electrolytic aluminum fume according to claim 3 is characterized in that: The pipe network type reverse osmosis membrane concentration unit is internally provided with a reverse osmosis module assembly and an ultrafiltration module.

5. The zero-emission treatment system for electrolytic aluminum fume according to claim 1 is characterized in that: The reverse osmosis module assembly is a tubular module assembly.

6. The zero-emission treatment system for electrolytic aluminum fume according to claim 5 is characterized in that: The reverse osmosis module assembly includes a pipe network type reverse osmosis membrane.

7. The zero-emission treatment system for electrolytic aluminum fume according to claim 1 is characterized in that: The ultrafiltration module is one of immersed ultrafiltration, column ultrafiltration, tubular ultrafiltration, scroll ultrafiltration or plate ultrafiltration.

8. The zero-emission treatment system for electrolytic aluminum fume according to claim 1 is characterized in that: The pretreatment device comprises a pre-sedimentation tank, a magnesium removal reaction tank, a calcium removal reaction tank, a neutralization tank, a homogenization tank, a flocculation tank and a sedimentation tank which are connected in sequence.

9. The zero-emission treatment system for electrolytic aluminum fume according to claim 8 is characterized in that: The pretreatment device also includes a pre-sedimentation tank sludge pump, a sedimentation tank sludge pump and a dewatering machine, wherein: The bottom of the pre-sedimentation tank is connected to the dewatering machine via a pre-sedimentation tank sludge pump; The bottom of the sedimentation tank is connected with a dewatering machine through a sedimentation tank sludge pump.

10. Application of the zero-emission treatment system for electrolytic aluminum fume as described in any one of claims 1 to 9 in treating electrolytic aluminum fume.

Images