CN117623555A - Flue gas desulfurization and denitrification wastewater treatment method and treatment system - Google Patents
Flue gas desulfurization and denitrification wastewater treatment method and treatment system Download PDFInfo
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- 238000006477 desulfuration reaction Methods 0.000 title claims abstract description 65
- 230000023556 desulfurization Effects 0.000 title claims abstract description 65
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 title claims abstract description 47
- 239000003546 flue gas Substances 0.000 title claims abstract description 47
- 238000004065 wastewater treatment Methods 0.000 title claims abstract description 47
- 239000002351 wastewater Substances 0.000 claims abstract description 206
- 150000002500 ions Chemical class 0.000 claims abstract description 175
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims abstract description 126
- 239000012528 membrane Substances 0.000 claims abstract description 88
- 238000000926 separation method Methods 0.000 claims abstract description 82
- 238000006386 neutralization reaction Methods 0.000 claims abstract description 51
- 239000002455 scale inhibitor Substances 0.000 claims abstract description 48
- 239000000701 coagulant Substances 0.000 claims abstract description 40
- 229910002651 NO3 Inorganic materials 0.000 claims abstract description 27
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims abstract description 27
- 238000000034 method Methods 0.000 claims abstract description 14
- 238000002425 crystallisation Methods 0.000 claims description 31
- 230000008025 crystallization Effects 0.000 claims description 29
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 24
- 239000006228 supernatant Substances 0.000 claims description 13
- 238000001556 precipitation Methods 0.000 claims description 10
- 239000008213 purified water Substances 0.000 claims description 10
- 238000004891 communication Methods 0.000 claims description 7
- 238000001728 nano-filtration Methods 0.000 claims description 6
- 238000001223 reverse osmosis Methods 0.000 claims description 6
- 150000003467 sulfuric acid derivatives Chemical class 0.000 claims description 6
- 238000012958 reprocessing Methods 0.000 claims description 2
- 239000013078 crystal Substances 0.000 claims 1
- 238000005516 engineering process Methods 0.000 abstract description 10
- 238000004064 recycling Methods 0.000 abstract description 7
- 230000007613 environmental effect Effects 0.000 abstract description 5
- 239000013043 chemical agent Substances 0.000 abstract description 3
- 239000013049 sediment Substances 0.000 abstract description 2
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 11
- 230000008901 benefit Effects 0.000 description 9
- 239000000126 substance Substances 0.000 description 7
- 238000011084 recovery Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 239000002244 precipitate Substances 0.000 description 5
- 239000007787 solid Substances 0.000 description 4
- 229910052815 sulfur oxide Inorganic materials 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- 230000001112 coagulating effect Effects 0.000 description 3
- 239000003814 drug Substances 0.000 description 3
- 238000005265 energy consumption Methods 0.000 description 3
- 239000013505 freshwater Substances 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 229920006395 saturated elastomer Polymers 0.000 description 3
- 238000004062 sedimentation Methods 0.000 description 3
- XTQHKBHJIVJGKJ-UHFFFAOYSA-N sulfur monoxide Chemical class S=O XTQHKBHJIVJGKJ-UHFFFAOYSA-N 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 230000003750 conditioning effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009297 electrocoagulation Methods 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- YPJKMVATUPSWOH-UHFFFAOYSA-N nitrooxidanyl Chemical compound [O][N+]([O-])=O YPJKMVATUPSWOH-UHFFFAOYSA-N 0.000 description 1
- 230000003204 osmotic effect Effects 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
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Abstract
The invention provides a flue gas desulfurization and denitrification wastewater treatment method, which comprises the following steps: s10: adding an ion scale inhibitor into the desulfurization and denitrification wastewater; s20: carrying out ion concentration treatment on desulfurization and denitrification wastewater by utilizing an ion concentration membrane to obtain concentrated wastewater; s30: performing ion separation treatment on the concentrated wastewater by utilizing an ion separation membrane to respectively obtain nitrate wastewater and concentrated sulfate wastewater in a supersaturated state; s40: and adding an electric neutralization coagulant into the supersaturated concentrated sulfate wastewater to crystallize and separate out sulfate in the supersaturated concentrated sulfate wastewater to obtain sulfate. The treatment method realizes the equivalent and optimal utilization of the existing common dosing treatment technology, greatly reduces the dosage of chemical agents, reduces the treatment cost, realizes the recycling of system sediment, and has environmental protection and economy. The invention also provides a flue gas desulfurization and denitrification wastewater treatment system.
Description
Technical Field
The invention relates to the technical field of wastewater treatment, in particular to a flue gas desulfurization and denitrification wastewater treatment method and a flue gas desulfurization and denitrification wastewater treatment system.
Background
The flue gas generated by burning the coal-fired boiler contains a large amount of nitrogen oxides (NOx) and sulfur oxides (SOx), and if the flue gas is directly discharged into the atmosphere without any treatment, serious pollution can be caused to the atmosphere. In order to reduce the emission of nitrogen oxides and sulfur oxides in the flue gas, a wet flue gas desulfurization and denitrification technology is generally adopted to treat the flue gas so as to remove the nitrogen oxides and the sulfur oxides in the flue gas.
SO-containing produced by wet desulfurization and denitrification of flue gas 4 2- 、NO 3 - The wastewater is difficult to treat, and is usually directly discharged after coagulating sedimentation or enters a membrane system, a biochemical system and the like for further advanced treatment. The general treatment steps of the coagulating sedimentation technology are as follows: the first step involves adding a large amount of Ca 2+ Removing SO in the wastewater 4 2- The second step of adding a large amount of CO 3 2- Removing the original Ca in the wastewater 2+ And Ca excessively added in the first step 2+ . On the one hand, ca is added 2+ 、CO 3 2- Is introduced into the process of (1) a large amount of Cl - 、OH - 、Na + And the like, thereby changing the osmotic pressure, pH value and other properties of the wastewater, and therefore, a water conditioning unit needs to be added, and the complexity of system operation is increased; and the dosage of the chemical agent is large, and the treatment cost is high. On the other hand, the coagulating sedimentation can produce CaSO 4 、CaCO 3 Iso-precipitation, large precipitation amount, and CaSO 4 The method is a slightly soluble substance, and a purer single precipitate is difficult to obtain, so that the processing load of the system and the difficulty of recycling are increased.
Disclosure of Invention
The invention aims to provide a flue gas desulfurization and denitrification wastewater treatment method, which realizes the equivalent and optimal utilization of the conventional common dosing treatment technology, greatly reduces the dosage of chemical agents, reduces the treatment cost, realizes the resource utilization of sediment in a system, and has environmental protection and economy.
The invention provides a flue gas desulfurization and denitrification wastewater treatment method, which comprises the following steps:
s10: to contain SO 4 2- And NO 3 - Adding an ion scale inhibitor into the desulfurization and denitrification wastewater;
s20: carrying out ion concentration treatment on the desulfurization and denitrification wastewater by utilizing an ion concentration membrane to obtain concentrated wastewater;
s30: ion separation treatment is carried out on the concentrated wastewater by utilizing an ion separation membrane, SO that SO in the concentrated wastewater is realized 4 2- And NO 3 - Separating to obtain nitrate wastewater and concentrated sulfate wastewater in a supersaturated state respectively; wherein the concentrated sulfate wastewater contains the ionic scale inhibitor;
s40: and adding an electric neutralization coagulant into the concentrated sulfate wastewater in a supersaturated state, so that the electric neutralization coagulant and the ion scale inhibitor perform electric neutralization reaction, and sulfate in the concentrated sulfate wastewater in a supersaturated state is crystallized and separated out to obtain sulfate.
In one implementation manner, before the step S40, the flue gas desulfurization and denitrification wastewater treatment method further includes:
detecting a TDS value of the concentrated sulfate wastewater; if the concentrated sulfate wastewater reaches a supersaturated state and the TDS value of the concentrated sulfate wastewater reaches a preset range, performing S40 step treatment on the concentrated sulfate wastewater; and if the TDS value of the concentrated sulfate wastewater is lower than the preset range, returning the concentrated sulfate wastewater to the step S10 or the step S20, performing ion concentration treatment and ion separation treatment on the concentrated sulfate wastewater again until the TDS value of the concentrated sulfate wastewater reaches the preset range, and performing the step S40 on the concentrated sulfate wastewater.
In one possible manner, the TDS value of the concentrated sulfate wastewater reaches a preset range, specifically: the TDS value of the concentrated sulfate wastewater is greater than or equal to 1.5 times the TDS value of the saturated sulfate solution.
In one implementation manner, in the step S20, after the desulfurization and denitrification wastewater is subjected to ion concentration treatment, clean water is obtained, and the clean water is used for the configuration of the ion scale inhibitor and/or the electric neutralization coagulant.
In one implementation manner, in the step S40, a supernatant is obtained after crystallization of sulfate in the supersaturated concentrated sulfate wastewater, and the supernatant is returned to the step S10 for reprocessing.
In one implementation, the ion concentrating membrane is a reverse osmosis membrane and the ion separating membrane is a nanofiltration membrane.
The invention also provides a flue gas desulfurization and denitrification wastewater treatment system which is applied to the flue gas desulfurization and denitrification wastewater treatment method, and comprises a wastewater pipeline, a booster pump, an ion concentration unit, an ion separation unit, crystallization equipment and an electric neutralization dosing unit; the electric neutralization dosing unit comprises an ion scale inhibitor dosing unit and an electric neutralization coagulant dosing unit, wherein an ion concentration membrane is arranged in the ion concentration unit, and an ion separation membrane is arranged in the ion separation unit;
the waste water pipeline is communicated with the inlet of the pressurizing pump, the outlet of the pressurizing pump is communicated with the inlet of the ion concentration unit, the concentrated wastewater outlet of the ion concentration unit is communicated with the inlet of the ion separation unit, and the concentrated sulfate wastewater outlet of the ion separation unit is communicated with the inlet of the crystallization equipment through a first pipeline; the outlet of the ionic scale inhibitor dosing unit is communicated with the waste water pipeline, and the outlet of the electric neutralization coagulant dosing unit is communicated with the inlet of the first pipeline or the crystallization equipment.
In one implementation manner, the flue gas desulfurization and denitrification wastewater treatment system further comprises a control unit and a second pipeline, wherein one end of the second pipeline is communicated with the first pipeline, and the other end of the second pipeline is communicated with the wastewater pipeline; the first pipeline is provided with a TDS detector and a first valve, the second pipeline is provided with a second valve, and the control unit is respectively connected with the TDS detector, the first valve and the second valve through electric signals.
In one implementation, the ion concentrating membrane is a reverse osmosis membrane and the ion separating membrane is a nanofiltration membrane.
In one implementation, the clean water outlet of the ion concentration unit is in communication with the electrically neutralizing dosing unit; and/or, a supernatant outlet of the crystallization device is communicated with the waste water pipeline.
The flue gas desulfurization and denitrification wastewater treatment method provided by the invention realizes the separation of sulfate, nitrate and water in desulfurization and denitrification wastewater by utilizing membrane concentration, membrane separation and electric neutralization technologies, and has the advantages that compared with the existing dosing treatment technology, the flue gas desulfurization and denitrification wastewater treatment method comprises the following steps: 1. good separation effect and high separation efficiency, and can realize SO 4 2- And NO 3 - Is separated efficiently; 2. the final treatment products can respectively obtain single substances (nitrate wastewater and sulfate), complex precipitates are avoided, the treatment load of the system is reduced, and the subsequent recycling and harmless utilization are facilitated; 3. the dosage of the system is greatly reduced, and only a proper amount of ionic scale inhibitor and electric neutralization coagulant are needed to be added, so that the medicament cost and the treatment cost are greatly saved, and good environmental benefit and economic benefit are realized; 4. equipment such as a mixing tank and a reaction tank is not required, the amount of system equipment is reduced, and the equipment cost and space are saved; 5. the sequence of ion concentration membrane treatment and ion separation membrane treatment is reasonably set, the ion separation treatment process can be completed by utilizing the pressure of the concentrated wastewater after ion concentration treatment, the intersegmental pressure lifting is not required to be set between the ion concentration membrane and the ion separation membrane, and the energy consumption is saved.
Drawings
FIG. 1 is a schematic flow chart of a flue gas desulfurization and denitrification wastewater treatment method in an embodiment of the invention.
Fig. 2 is a schematic structural diagram of a flue gas desulfurization and denitrification wastewater treatment system in an embodiment of the invention.
Detailed Description
The following describes in further detail the embodiments of the present invention with reference to the drawings and examples. The following examples are illustrative of the invention and are not intended to limit the scope of the invention.
The terms "first," "second," "third," "fourth" and the like in the description and in the claims, if any, are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order.
The terms upper, lower, left, right, front, rear, top, bottom and the like (if any) in the description and in the claims are used for descriptive purposes and not necessarily for describing relative positions of structures in the figures and in describing relative positions of structures. It should be understood that the use of directional terms should not be construed to limit the scope of the invention as claimed.
As shown in fig. 1, the flue gas desulfurization and denitrification wastewater treatment method provided by the embodiment of the invention comprises the following steps:
s10: to contain SO 4 2- And NO 3 - Adding an ion scale inhibitor into the desulfurization and denitrification wastewater; the ionic scale inhibitor is added to prevent the scaling of the wastewater in the subsequent ion concentration treatment and ion separation treatment, so as to prevent the scaling substances from adhering to the ion concentration membrane or ion separation membrane to influence the treatment effect and the service life of the membrane. The adding amount of the ion scale inhibitor is determined according to the concentration of sulfate in the wastewater, and the adding concentration of the ion scale inhibitor is generally 3-6 mg/L (namely 3-6 mg of ion scale inhibitor is added into each liter of wastewater).
S20: ion concentration treatment is carried out on desulfurization and denitrification wastewater by utilizing an ion concentration membrane, so as to obtain concentrated wastewater and purified water respectively; this step is to remove a portion of the water from the wastewater, facilitating subsequent obtaining of concentrated sulfate wastewater in a supersaturated state.
S30: ion separation treatment is carried out on the concentrated wastewater by utilizing an ion separation membrane, SO that SO in the concentrated wastewater is realized 4 2- And NO 3 - Separating to obtain nitrate waste water (containing NO) 3 - ) And concentrated sulfate wastewater (SO-containing) in supersaturated state 4 2- ) And the TDS value (Total Dissolved Solids, total solid content dissolved in water) of the supersaturated concentrated sulfate wastewater is within a preset range (namely, the larger the TDS value is, the higher the sulfate content in the concentrated sulfate wastewater is), thereby facilitating the crystallization precipitation of the sulfate in the subsequent concentrated sulfate wastewater. Wherein the concentrated sulfate wastewater contains an ion scale inhibitor (i.e. NO in the concentrated wastewater after ion separation treatment) 3 - Is separated out, SO in the wastewater 4 2- And the ionic scale inhibitor remains in the concentrated wastewater to yield concentrated sulfate wastewater containing the ionic scale inhibitor). The obtained nitrate wastewater can be further subjected to biochemical advanced treatment.
S40: and adding an electric neutralization coagulant into the supersaturated concentrated sulfate wastewater to enable the electric neutralization coagulant and the ion scale inhibitor to generate electric neutralization reaction, so that sulfate in the supersaturated concentrated sulfate wastewater is crystallized and separated out to obtain sulfate (the electric neutralization coagulant and the ion scale inhibitor have opposite charges, for example, the ion scale inhibitor has negative charges, the electric neutralization coagulant has positive charges, the electric neutralization coagulant damages the scale inhibition effect of the ion scale inhibitor through the electric neutralization reaction, and further damages the steady state of the concentrated sulfate wastewater, so that sulfate in the supersaturated concentrated sulfate wastewater is crystallized and separated out to obtain sulfate solid). Wherein, the dosage of the electric neutralization coagulant is determined according to the dosage of the ionic scale inhibitor, and the dosage of the electric neutralization coagulant is generally 0.2 to 0.5 times of the dosage of the ionic scale inhibitor.
The flue gas desulfurization and denitrification wastewater treatment method provided by the embodiment realizes the separation of sulfate, nitrate and water in the desulfurization and denitrification wastewater by utilizing the technologies of membrane concentration, membrane separation and electric neutralization, and has the advantages that compared with the existing chemical dosing treatment technology, the flue gas desulfurization and denitrification wastewater treatment method comprises the following steps: 1. good separation effect and high separation efficiency, and can realize SO 4 2- And NO 3 - Is separated efficiently; 2. the final treated product can obtain single substances (nitrate waste water and sulfate) respectively, and has no complex precipitationThe system processing load is reduced, and the subsequent recycling and harmless utilization are facilitated; 3. the dosage of the system is greatly reduced, and only a proper amount of ionic scale inhibitor and electric neutralization coagulant are needed to be added, so that the medicament cost and the treatment cost are greatly saved, and good environmental benefit and economic benefit are realized; 4. equipment such as a mixing tank and a reaction tank is not required, the amount of system equipment is reduced, and the equipment cost and space are saved; 5. the ion separation treatment process can be completed by reasonably setting the sequence of ion concentration membrane treatment and ion separation membrane treatment and utilizing the pressure of the concentrated wastewater after ion concentration treatment, and the energy consumption is saved without setting inter-stage pressure elevation between the ion concentration membrane and the ion separation membrane (specifically, because the operating pressure of the ion concentration membrane is larger than that of the ion separation membrane, for example, the operating pressure of the ion concentration membrane is 1.9-2.0MPa, and the operating pressure of the ion separation membrane is 1.7-1.8MPa, the pressure of the concentrated wastewater after ion concentration treatment is larger than that of the ion separation membrane, so that a pressurizing device such as a pump is not required to be arranged between the ion concentration membrane and the ion separation membrane for pressurizing, and if the ion concentration membrane and the ion separation membrane are exchanged, namely, the ion separation treatment is carried out firstly, then the pressure of the wastewater after ion separation treatment cannot reach the operating pressure required by the ion concentration membrane, and at the moment, the pressurizing device is required to be arranged between the ion separation membrane and the ion concentration membrane for pressurizing.
As an embodiment, before the step S20, the desulfurization and denitrification wastewater is pressurized by a pressurizing pump so that the pressure of the desulfurization and denitrification wastewater reaches the operation pressure required by the ion concentration membrane.
As an embodiment, before the step S40, the flue gas desulfurization and denitrification wastewater treatment method further includes:
detecting a TDS value of the concentrated sulfate wastewater; if the concentrated sulfate wastewater reaches a supersaturated state and the TDS value of the concentrated sulfate wastewater reaches a preset range, performing S40 step treatment on the concentrated sulfate wastewater so that sulfate in the subsequent concentrated sulfate wastewater can be better crystallized and separated out; if the TDS value of the concentrated sulfate wastewater is lower than the preset range (for example, the concentrated sulfate wastewater does not reach the saturated state, or has reached the saturated state but does not reach the supersaturated state), the concentrated sulfate wastewater is returned to step S10 or step S20, the concentrated sulfate wastewater is subjected to ion concentration treatment and ion separation treatment again until the TDS value of the concentrated sulfate wastewater reaches the preset range, and then the concentrated sulfate wastewater is subjected to step S40.
As an embodiment, the TDS value of the concentrated sulfate wastewater reaches a preset range, specifically: the TDS value of the concentrated sulfate wastewater is more than or equal to 1.5 times of the TDS value of the saturated sulfate solution (under the same temperature condition); i.e. the preset range is 1.5 times greater than or equal to the TDS value of the saturated sulfate solution. Specifically, if the concentrated sulfate wastewater in the step S30 has reached a saturated state but has not reached a supersaturated state, the content of sulfate in the concentrated sulfate wastewater is insufficient, and the amount of sulfate obtained in the subsequent crystallization process is smaller, so that the separation efficiency is lower, and more wastewater needs to be subjected to reflux and repeated treatment at this time, thereby increasing the system treatment load and reducing the treatment efficiency.
Preferably, the TDS value of the concentrated sulfate wastewater reaches a preset range, specifically: the TDS value of the concentrated sulfate wastewater is 2-3 times of that of the saturated sulfate solution; the preset range is 2-3 times of the TDS value of the saturated sulfate solution, so that more sulfate can be obtained in the subsequent crystallization and precipitation process, the separation efficiency is improved, and the premature precipitation of sulfate in supersaturated concentrated sulfate wastewater due to the too high concentration is avoided.
In the step S20, the purified water obtained by ion concentration treatment of the desulfurization and denitrification wastewater is used for preparing an ion scale inhibitor and/or an electric neutralization coagulant, so that the purified water is recycled, and the resource utilization rate is improved.
In one embodiment, in the step S40, the sulfate in the supersaturated concentrated sulfate wastewater is crystallized to obtain a supernatant (i.e., the concentrated sulfate wastewater is crystallized to obtain sulfate solids in the lower layer of the wastewater and the supernatant in the upper layer of the wastewater), and SO is contained in the supernatant 4 2- Failure toThe supernatant liquid is returned to the step S10 for re-treatment (i.e. the steps of adding ion scale inhibitor, ion concentration, ion separation, adding electric neutralization coagulant and crystallizing precipitation are repeatedly performed) SO as to lead SO in the wastewater 4 2- The crystallization is separated out in the repeated treatment process.
As an implementation mode, the ion concentration membrane is a reverse osmosis membrane so as to realize concentration of ions in desulfurization and denitrification wastewater. The ion separation membrane is a nanofiltration membrane, so that the separation of sulfate and nitrate in the wastewater is realized, and nitrate wastewater and further concentrated sulfate wastewater are obtained. Of course, in other embodiments, the ion concentrating and ion separating membranes may be other types of membranes.
As shown in fig. 2, the embodiment of the invention also provides a flue gas desulfurization and denitrification wastewater treatment system, which is applied to the flue gas desulfurization and denitrification wastewater treatment method. The flue gas desulfurization and denitrification wastewater treatment system comprises a wastewater pipeline 1, a booster pump 2, an ion concentration unit 3, an ion separation unit 4, crystallization equipment 5 and an electric neutralization dosing unit 6. The waste water pipeline 1 is used for conveying the waste water containing SO 4 2- And NO 3 - The pressurizing pump 2 is used for pressurizing the wastewater; an ion concentration membrane is arranged in the ion concentration unit 3, and an ion separation membrane is arranged in the ion separation unit 4; the electric neutralization dosing unit 6 comprises an ionic scale inhibitor dosing unit 61 and an electric neutralization coagulant dosing unit 62, wherein the ionic scale inhibitor dosing unit 61 is used for adding an ionic scale inhibitor into the system, and the electric neutralization coagulant dosing unit 62 is used for adding an electric neutralization coagulant into the system.
The waste water pipeline 1 is communicated with the inlet of the pressurizing pump 2, the outlet of the pressurizing pump 2 is communicated with the inlet of the ion concentration unit 3, the concentrated waste water outlet of the ion concentration unit 3 is communicated with the inlet of the ion separation unit 4, and the concentrated sulfate waste water outlet of the ion separation unit 4 is communicated with the inlet of the crystallization equipment 5 through the first pipeline 41. The outlet of the ionic scale inhibitor dosing unit 61 is in communication with the waste water line 1 and the outlet of the electrocoagulation coagulant dosing unit 62 is in communication with the inlet of the first line 41 or the crystallization apparatus 5.
As shown in fig. 2, as an embodiment, the flue gas desulfurization and denitrification wastewater treatment system further includes a control unit 7 and a second pipeline 42, wherein one end of the second pipeline 42 is communicated with the first pipeline 41 (specifically, is communicated with the first pipeline 41 before the first valve 82), and the other end of the second pipeline 42 is communicated with the wastewater pipeline 1 (the second pipeline 42 may be communicated with the wastewater pipeline 1 before the dosing point of the ion scale inhibitor dosing unit 61 or communicated with the wastewater pipeline 1 after the dosing point of the ion scale inhibitor dosing unit 61). The first pipeline 41 is provided with a TDS detector 81 and a first valve 82, and the second pipeline 42 is provided with a second valve 83; the TDS detector 81 is an online TDS detector, the TDS detector 81 is used for detecting the TDS value of the wastewater, and the first valve 82 and the second valve 83 are all electrically controlled valves. The control unit 7 is electrically connected with the TDS detector 81, the first valve 82 and the second valve 83, and the control unit 7 is used for controlling the opening and closing of the first valve 82 and the second valve 83 according to the TDS value detected by the TDS detector 81.
Specifically, the TDS detector 81, the first valve 82, and the second valve 83 are automatically controlled by interlocking. When the TDS detector 81 detects that the TDS value of the concentrated sulfate wastewater from the ion separation unit 4 reaches a preset range (the preset range is shown in the above description), the control unit 7 controls the first valve 82 to be opened and the second valve 83 to be closed, so that the concentrated sulfate wastewater enters the crystallization device 5 for crystallization precipitation of sulfate after the subsequent addition of the electro-neutralization coagulant; when the TDS detector 81 detects that the TDS value of the concentrated sulfate wastewater from the ion separation unit 4 is lower than the preset range, the control unit 7 controls the first valve 82 to be closed and the second valve 83 to be opened, so that the concentrated sulfate wastewater is returned to the ion concentration unit 3 and the ion separation unit 4 to repeat the ion concentration process and the ion separation process.
As shown in fig. 2, as an embodiment, the purified water outlet of the ion concentration unit 3 is communicated with the electric neutralization dosing unit 6, so that purified water obtained after ion concentration treatment is used for the configuration of the ion scale inhibitor and/or the electric neutralization coagulant, thereby realizing the recycling of the purified water.
As shown in FIG. 2, as an embodiment, the supernatant outlet of the crystallization apparatus 5 is communicated with the wastewater line 1 through a return line 51(specifically, the return line 51 communicates with the wastewater line 1 before the dosing point of the ion scale inhibitor dosing unit 61) to re-treat the supernatant produced in the crystallization apparatus 5 (i.e., repeatedly perform the steps of ion scale inhibitor addition, ion concentration treatment, ion separation treatment, electro-neutralization coagulant addition, and crystallization precipitation) to cause SO in the wastewater 4 2- The crystallization is separated out in the repeated treatment process.
As one embodiment, the ion concentration membrane is a reverse osmosis membrane and the ion separation membrane is a nanofiltration membrane.
As one embodiment, the pressurizing pump 2 is a variable-frequency high-pressure pump.
As an embodiment, the crystallization apparatus 5 may be a crystallizer, a general precipitation apparatus, a storage container (e.g., a tank), or the like, and since the concentrated sulfate wastewater in a supersaturated state is crystallized and precipitated in the crystallization apparatus 5, the crystallization process does not require an external force, and thus the demand on the crystallization apparatus 5 is low. The outlet of the electrocoagulation-coagulant dosing unit 62 may be in communication with the first line 41, i.e. the electrocoagulation-coagulant is dosed into the first line 41 (in which case the dosing point of the electrocoagulation-coagulant dosing unit 62 is required to be close to the inlet of the crystallisation apparatus 5 to prevent crystallisation out in the first line 41); the outlet of the charge unit 62 for the electro-neutralization coagulant may also be in communication with the inlet of the crystallization apparatus 5, i.e. the electro-neutralization coagulant is directly fed into the crystallization apparatus 5.
As shown in fig. 2, as an embodiment, the flue gas desulfurization and denitrification wastewater treatment system further includes a nitrate wastewater treatment line 43, the nitrate wastewater treatment line 43 being in communication with the nitrate wastewater outlet of the ion separation unit 4, the nitrate wastewater treatment line 43 being connectable to a wastewater tank, a nitrate wastewater treatment device (e.g., a biochemical treatment device), or the like.
As an implementation mode, the treatment flow of the flue gas desulfurization and denitrification wastewater treatment system is as follows:
(1) The desulfurization and denitrification wastewater enters the wastewater pipeline 1, and the ion scale inhibitor is added into the desulfurization and denitrification wastewater in the wastewater pipeline 1 through the ion scale inhibitor dosing unit 61 so as to prevent the wastewater from scaling in advance.
(2) The desulfurization and denitrification wastewater in the wastewater pipeline 1 enters a booster pump 2, is pressurized to the operation pressure required by an ion concentration unit 3 by the booster pump 2, and enters the ion concentration unit 3; under the action of an ion concentration membrane, separating desulfurization and denitrification wastewater into purified water (pure water) and concentrated wastewater; the purified water enters the electric neutralization dosing unit 6 to be used for the configuration of the ionic scale inhibitor and/or the electric neutralization coagulant, thereby realizing the recycling of the purified water.
(3) Under the action of self pressure, the concentrated wastewater enters an ion separation unit 4 without additional pressurization; separating sulfate from nitrate under the action of an ion separation membrane to obtain nitrate wastewater and sulfate wastewater which is further concentrated; nitrate waste water enters a waste water storage tank for temporary storage or a nitrate waste water treatment device for further treatment through a nitrate waste water treatment pipeline 43.
(4) The concentrated sulfate wastewater enters the first pipeline 41, and the TDS detector 81 detects the TDS value of the concentrated sulfate wastewater. When the TDS detector 81 detects that the TDS value of the concentrated sulfate wastewater is lower than the preset range, the control unit 7 controls the first valve 82 to be closed and the second valve 83 to be opened, so that the concentrated sulfate wastewater is returned to the ion concentration unit 3 and the ion separation unit 4 to repeatedly perform ion concentration treatment and ion separation treatment. When the TDS detector 81 detects that the TDS value of the concentrated sulfate wastewater reaches a preset range, the control unit 7 controls the first valve 82 to be opened and the second valve 83 to be closed, and simultaneously, an electric neutralization coagulant is added into the concentrated sulfate wastewater through the electric neutralization coagulant adding unit 62, and the stable state of the wastewater is destroyed through electric neutralization reaction, so that the concentrated sulfate wastewater enters the crystallization equipment 5 to crystallize and separate sulfate, and sulfate is obtained; while the excess supernatant is returned to the waste line 1 through the return line 51 for repeated treatment.
The flue gas desulfurization and denitrification wastewater treatment method provided by the embodiment of the invention realizes the separation of sulfate, nitrate and water in the desulfurization and denitrification wastewater by utilizing the technologies of membrane concentration, membrane separation and electric neutralization, and has the advantages that compared with the existing chemical dosing treatment technology, the flue gas desulfurization and denitrification wastewater treatment method comprises the following steps: 1. good separation effect and high separation efficiency, and can realize SO 4 2- And NO 3 - Is separated efficiently; 2. the final treatment products can respectively obtain single substances (nitrate wastewater and sulfate), complex precipitates are avoided, the treatment load of the system is reduced, and the subsequent recycling and harmless utilization are facilitated; 3. the dosage of the system is greatly reduced, and only a proper amount of ionic scale inhibitor and electric neutralization coagulant are needed to be added, so that the medicament cost and the treatment cost are greatly saved, and good environmental benefit and economic benefit are realized; 4. equipment such as a mixing tank and a reaction tank is not required, the amount of system equipment is reduced, and the equipment cost and space are saved; 5. the sequence of ion concentration membrane treatment and ion separation membrane treatment is reasonably set, the ion separation treatment process can be completed by utilizing the pressure of the concentrated wastewater after ion concentration treatment, the intersegmental pressure lifting is not required to be set between the ion concentration membrane and the ion separation membrane, and the energy consumption is saved.
Example 1
Desulfurization and denitrification wastewater is 50t/h, sulfate radical is 7000mg/L, nitrate radical is 40mg/L, and TDS=10.5 g/L. The adding amount of the wastewater ion scale inhibitor is 4.5mg/L, then the wastewater ion scale inhibitor enters an ion concentration membrane, the operating pressure of the ion concentration membrane is 1.9-2.0MPa, the recovery rate is controlled at 50%, and 25t/h of fresh water and 25t/h of concentrated wastewater are obtained. The concentrated wastewater enters an ion separation membrane, the operating pressure of the ion separation membrane is 1.7-1.8MPa, the recovery rate is controlled at 40%, and 10t/h of nitrate wastewater and 15t/h of further concentrated sulfate wastewater are obtained. Concentrated sulfate wastewater tds=34 g/L, in a supersaturated state under working conditions; addition of an electroneutralizing coagulant (Fe) to concentrated sulfate wastewater 3+ High molecular polymer) 1.0mg/L to give sulfate precipitate.
Example two
Desulfurization and denitrification wastewater 30t/h, sulfate 5000mg/L, nitrate 70mg/L and TDS=7.5 g/L. The adding amount of the wastewater ion scale inhibitor is 4.0mg/L, then the wastewater ion scale inhibitor enters an ion concentration membrane, the operating pressure of the ion concentration membrane is 1.5-1.6Mpa, the recovery rate is controlled at 45%, the fresh water is 13.5t/h, and the concentrated wastewater is 16.5t/h. The concentrated wastewater enters an ion separation membrane, the operation pressure of the ion separation membrane is 1.1-1.2MPa, the recovery rate is controlled at 40%, and 6.5t/h of nitrate wastewater and 10t/h of further concentrated sulfate wastewater are obtained. Concentrated sulfuric acidThe salt wastewater TDS=22.2 g/L is in an unsaturated state under the working condition, returns to the water inlet, enters the ion concentration membrane again along with the water inlet, has the operating pressure of 2.4-2.5Mpa, and has the recovery rate controlled at 45% to obtain 18t/h of fresh water and 22t/h of concentrated wastewater. The concentrated wastewater enters an ion separation membrane, the operation pressure of the ion separation membrane is 1.9-2.0MPa, the recovery rate is controlled at 40%, and 8.5t/h of nitrate wastewater and 13.5t/h of further concentrated sulfate wastewater are obtained. Concentrated sulfate wastewater tds=34.5 g/L, in supersaturated state under working conditions; addition of an electroneutralizing coagulant (Fe) to concentrated sulfate wastewater 3+ High molecular polymer) 1.0mg/L to give sulfate precipitate.
The foregoing is merely illustrative embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily think about variations or substitutions within the technical scope of the present invention, and the invention should be covered. Therefore, the protection scope of the invention is subject to the protection scope of the claims.
Claims (10)
1. The flue gas desulfurization and denitrification wastewater treatment method is characterized by comprising the following steps of:
s10: to contain SO 4 2- And NO 3 - Adding an ion scale inhibitor into the desulfurization and denitrification wastewater;
s20: carrying out ion concentration treatment on the desulfurization and denitrification wastewater by utilizing an ion concentration membrane to obtain concentrated wastewater;
s30: ion separation treatment is carried out on the concentrated wastewater by utilizing an ion separation membrane, SO that SO in the concentrated wastewater is realized 4 2- And NO 3 - Separating to obtain nitrate wastewater and concentrated sulfate wastewater in a supersaturated state respectively; wherein the concentrated sulfate wastewater contains the ionic scale inhibitor;
s40: and adding an electric neutralization coagulant into the concentrated sulfate wastewater in a supersaturated state, so that the electric neutralization coagulant and the ion scale inhibitor perform electric neutralization reaction, and sulfate in the concentrated sulfate wastewater in a supersaturated state is crystallized and separated out to obtain sulfate.
2. The flue gas desulfurization and denitrification wastewater treatment method according to claim 1, wherein prior to the step S40, the flue gas desulfurization and denitrification wastewater treatment method further comprises:
detecting a TDS value of the concentrated sulfate wastewater; if the concentrated sulfate wastewater reaches a supersaturated state and the TDS value of the concentrated sulfate wastewater reaches a preset range, performing S40 step treatment on the concentrated sulfate wastewater; and if the TDS value of the concentrated sulfate wastewater is lower than the preset range, returning the concentrated sulfate wastewater to the step S10 or the step S20, performing ion concentration treatment and ion separation treatment on the concentrated sulfate wastewater again until the TDS value of the concentrated sulfate wastewater reaches the preset range, and performing the step S40 on the concentrated sulfate wastewater.
3. The flue gas desulfurization and denitrification wastewater treatment method according to claim 2, wherein the TDS value of the concentrated sulfate wastewater reaches a preset range, specifically: the TDS value of the concentrated sulfate wastewater is greater than or equal to 1.5 times the TDS value of the saturated sulfate solution.
4. The method for flue gas desulfurization and denitrification wastewater treatment according to claim 1, wherein in the step S20, clean water is obtained after the desulfurization and denitrification wastewater is subjected to ion concentration treatment, and the clean water is used for the configuration of the ion scale inhibitor and/or the electrolytic neutralization coagulant.
5. The method for flue gas desulfurization and denitrification wastewater treatment according to claim 1, wherein in the step S40, a supernatant is obtained after precipitation of sulfate crystals in the supersaturated concentrated sulfate wastewater, and the supernatant is returned to the step S10 for reprocessing.
6. The flue gas desulfurization and denitrification wastewater treatment method according to any one of claims 1 to 5, wherein the ion concentration membrane is a reverse osmosis membrane and the ion separation membrane is a nanofiltration membrane.
7. A flue gas desulfurization and denitrification wastewater treatment system, which is characterized by being applied to the flue gas desulfurization and denitrification wastewater treatment method according to any one of claims 1-6, and comprises a wastewater pipeline, a booster pump, an ion concentration unit, an ion separation unit, crystallization equipment and an electric neutralization dosing unit; the electric neutralization dosing unit comprises an ion scale inhibitor dosing unit and an electric neutralization coagulant dosing unit, wherein an ion concentration membrane is arranged in the ion concentration unit, and an ion separation membrane is arranged in the ion separation unit;
the waste water pipeline is communicated with the inlet of the pressurizing pump, the outlet of the pressurizing pump is communicated with the inlet of the ion concentration unit, the concentrated wastewater outlet of the ion concentration unit is communicated with the inlet of the ion separation unit, and the concentrated sulfate wastewater outlet of the ion separation unit is communicated with the inlet of the crystallization equipment through a first pipeline; the outlet of the ionic scale inhibitor dosing unit is communicated with the waste water pipeline, and the outlet of the electric neutralization coagulant dosing unit is communicated with the inlet of the first pipeline or the crystallization equipment.
8. The flue gas desulfurization and denitrification wastewater treatment system according to claim 7, further comprising a control unit and a second pipeline, wherein one end of the second pipeline is communicated with the first pipeline, and the other end of the second pipeline is communicated with the wastewater pipeline; the first pipeline is provided with a TDS detector and a first valve, the second pipeline is provided with a second valve, and the control unit is respectively connected with the TDS detector, the first valve and the second valve through electric signals.
9. The flue gas desulfurization and denitrification wastewater treatment system according to claim 7, wherein the ion concentration membrane is a reverse osmosis membrane and the ion separation membrane is a nanofiltration membrane.
10. The flue gas desulfurization and denitrification wastewater treatment system according to any one of claims 7 to 9, wherein a purified water outlet of the ion concentration unit is in communication with the electric neutralization dosing unit; and/or, a supernatant outlet of the crystallization device is communicated with the waste water pipeline.
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