CN114291930A - Treatment method of boiler washing wastewater of sulfate pulping alkali recovery boiler - Google Patents
Treatment method of boiler washing wastewater of sulfate pulping alkali recovery boiler Download PDFInfo
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Abstract
The invention provides a method for treating boiler washing wastewater of an alkali recovery boiler for sulfate pulping, which adopts a strong agent to replace a common wastewater treating agent and then is matched with polyaluminium chloride for use in the physicochemical treatment of the boiler washing wastewater, meanwhile, part of chemical sludge added with polyferric sulfate flows back to a radial flow sedimentation tank, and the wastewater subjected to the physicochemical treatment in the invention does not pass through a biological system, so that the treatment method has the advantages of practical operation, wide application, more economy and more conformity with the environmental protection concept than the traditional process.
Description
Technical Field
The invention relates to the field of pulping wastewater treatment, in particular to a treatment method of boiler washing wastewater of a sulfate pulping alkali recovery boiler.
Background
The alkali recovery boiler is the necessary industrial equipment for all large pulping and papermaking enterprises at present, and uses the concentrated black liquor after pulping and pulp washing as fuel, i.e. the black liquor provides steam required by the enterprises, and can reduce alkali from the black liquor, thus meeting the requirements of the pulping and papermaking industries on circular economy and environmental protection of the enterprises.
After the alkali recovery boiler operates for a period of time, boiler coking inevitably exists, and then boiler efficiency is reduced. The only way to restore boiler efficiency is chemical cleaning with chemicals such as acids, bases, detergents, etc. The concentration of the pollutants in the furnace washing wastewater generated by the method is high (high pH, high COD, high alkalinity and high conductivity), the variation range is large (the difference between the initial stage, the middle stage and the later stage of furnace washing is large), and the components are complex (containing metal salts, nitrates, silicon, sulfides, mercaptan, phenols, amines and other substances).
The traditional method for treating the furnace washing wastewater is characterized in that the wastewater is mixed into a wastewater treatment system and is directly discharged into each level of wastewater treatment system after being adjusted by simple acid and alkali, but most of processes in the pulping wastewater treatment system are biochemical systems, so that in actual application, due to the particularity and complexity of the furnace washing wastewater, physicochemical flocculation effect is poor, a biological system is collapsed, the dosage of an advanced treatment agent is increased, the sludge dewatering effect is reduced, and finally the quality of discharged water is over standard. This problem has become the operational bottleneck in all pulp wastewater treatment plants.
Disclosure of Invention
In view of the above, the invention provides a method for treating boiler washing wastewater of an alkali recovery boiler for sulfate pulping, which screens out important influence factors by long-term tracking and analysis of the boiler washing wastewater, and finds a better treatment scheme by combining with an actual treatment process of a sewage plant so as to stabilize the treatment efficiency of each working section and reduce the consumption of chemicals, thereby obtaining the purposes of ensuring that the effluent is discharged after reaching the standard and saving the treatment cost compared with the traditional treatment mode. Therefore, the technical scheme of the invention is more environment-friendly and economical, and has wider application prospect.
The technical scheme of the invention is realized as follows:
a method for treating boiler washing wastewater of an alkali recovery boiler for sulfate pulping comprises the following steps:
(1) the system used by the treatment method comprises a recovery tank, an adjusting tank, a coagulation reaction tank, a radial flow sedimentation tank, a neutralization tank, a folded plate reactor and a reaction flocculation tank, wherein the coagulation reaction tank comprises a coagulation tank and a flocculation reaction tank;
(2) collecting the furnace washing wastewater into a recovery tank, pumping the furnace washing wastewater into an adjusting tank through a centrifugal pump, adding a pH regulator into the adjusting tank, fully stirring and uniformly mixing the materials, and adjusting the pH value of the furnace washing wastewater to 7.0-8.0 to prepare pre-coagulation wastewater;
(3) introducing the pre-coagulation wastewater treated in the step (2) into a coagulation reaction tank, adding 6-10mg/L of a strong agent for mixing, simultaneously adding 300-400mg/L of polyaluminum chloride (PAC), reacting for 8-12 minutes under the stirring condition, then entering a flocculation tank, adding 2-4ppm of anionic PAM, and reacting for 15-20 minutes to form alum floc;
(4) enabling the wastewater treated in the step (3) to flow into a radial flow type sedimentation tank, mixing the wastewater with the chemical sludge refluxed in the subsequent step (7), allowing the mixture to stay for 50-70 minutes under hydraulic power, settling the sludge, and collecting supernatant to obtain materialized wastewater;
(5) introducing the materialized wastewater and the normal wastewater after pretreatment in the step (4) into a neutralization tank together, wherein the materialized wastewater is 1.8-2.2% of the normal wastewater by volume percent, stirring and mixing, and then adjusting the pH value of the wastewater to 6.3-6.8 to prepare advanced wastewater;
the pretreatment refers to the pretreatment of normal wastewater by a traditional method, and comprises the following steps: adding hydrochloric acid or sodium hydroxide solution into the adjusting tank when normal wastewater enters the adjusting tank, and adjusting the pH value of the wastewater to 7.0-8.0 to prepare pre-coagulation wastewater; introducing the pre-coagulation wastewater into a coagulation reaction tank, adding 8mg/L wastewater treatment agent (purchased from Bakman laboratories, chemical industry and Co., Ltd., product model number BLX14397) for rapid mixing, and simultaneously adding 350mg/L polyaluminium chloride, wherein the polyaluminium chloride is prepared into a solution with the mass concentration of 10% before use; reacting for 10 minutes under the condition of stirring; then, the mixture enters a flocculation tank, and 3ppm of anionic PAM is added to react for 15 minutes to form alum floc; then the normal wastewater after pretreatment is obtained after biological system treatment.
(6) Introducing the wastewater subjected to advanced treatment in the step (5) into a folded plate reactor, adding polyferric sulfate (PFS) according to the addition amount of 1100-1800mg/L, controlling the pH value to react for 30-40 minutes under the condition of 3.5-4.0, then feeding the wastewater into a reaction flocculation tank, adding 2.5-4mg/L cationic PAM, stirring the wastewater for reaction for 15-20 minutes, and feeding the wastewater into a sedimentation tank;
(7) after 4-6 hours of sedimentation in the sedimentation tank, discharging most of the settled chemical sludge, and refluxing a small part of the chemical sludge to the step (4), wherein the reflux amount of the chemical sludge is 0.08-0.1% of the volume of the treated wastewater in the step (4); collecting supernatant, adjusting pH to 6.2-6.5, and discharging.
Further, in the step (2), the furnace washing wastewater is the furnace washing wastewater of a sulfate pulping alkali recovery boiler. Further, in the step (2), indexes of the furnace washing wastewater are as follows: pH is more than 11.0, alkalinity is more than 800mg/L, conductance is 10-70ms/cm, and COD is more than 2000 mg/L. The normal wastewater index pH6.0-7.0, alkalinity 400-.
Further, in the step (3), the reaction time after adding the polyaluminium chloride is 10 minutes, and the reaction time after adding the anionic PAM is 15 minutes; in the step (6), the reaction time after adding the polymeric ferric sulfate is 35 minutes, and the reaction time after adding the cationic PAM is 15 minutes.
Further, in the step (7), the precipitation time is 4 hours.
Further, in the step (2), the hydraulic retention time is 60 minutes.
Further, in the step (3), the strength agent is a strength agent produced by Sichuan Baocheng corporation, model number BCWC-A1#, and the appearance is black powder.
Further, hydrochloric acid (HCl) having a mass concentration of 32% or sodium hydroxide (NaOH) solution having a mass concentration of 31% was used for pH adjustment.
Further, in the step (3), the polyaluminium chloride is prepared into a solution with the mass concentration of 10% before use; in the step (6), the total iron content of the polymeric ferric sulfate is 11%.
Further, in the steps (4) and (7), the settled sludge is pumped into a sludge storage tank through a bottom sludge discharge pump, and a centrifugal dehydrator is utilized to prepare a sludge cake.
Compared with the prior art, the invention has the beneficial effects that:
1) the invention separately collects the physicochemical treatment of the furnace washing wastewater, and adopts a strong agent to replace the common wastewater treatment agent and then to be matched with polyaluminium chloride for use. The absorption and sedimentation assisting effects of the strong agent are utilized to further improve the compactness of flocs after the coagulation reaction of the polyaluminium chloride, improve the sludge sedimentation performance, reduce the adding amount of the polyaluminium chloride and the sludge generation amount, and further reduce the subsequent sludge treatment pressure. Meanwhile, the strong agent can also effectively remove soluble COD in the wastewater.
2) According to the invention, the chemical sludge added with the polymeric ferric sulfate is refluxed to the water inlet of the radial flow type sedimentation tank according to the volume of 0.08-0.1% of the treatment amount of the furnace washing wastewater, so that the alkalinity of the furnace washing wastewater is reduced, and the sedimentation performance of the sludge in the radial flow type sedimentation tank is promoted.
3) The wastewater subjected to physicochemical treatment does not pass through a biological system, and is mixed with the normal operation wastewater according to the volume of about 2% of the normal operation wastewater through the variable frequency control of the flow, so that the pre-advanced treatment wastewater is prepared and is directly treated by an advanced treatment system, and the impact of the high-alkalinity and high-conductivity furnace washing wastewater on the biological system is avoided. And the dosage of the polymeric ferric sulfate agent in the advanced treatment section is greatly reduced, so that the wastewater treatment cost is reduced.
Drawings
FIG. 1 shows a conventional method for treating wastewater from a furnace washing.
FIG. 2 is a method for treating wastewater from washing a furnace according to the present invention.
Detailed Description
In order to better understand the technical content of the invention, specific examples are provided below to further illustrate the invention.
The experimental methods used in the examples of the present invention are all conventional methods unless otherwise specified.
The materials, reagents and the like used in the examples of the present invention can be obtained commercially without specific description.
The invention uses the 'strength agent' as a commercial product, is produced by Sichuan Baocheng limited company and has the model number BCWC-A1#, and the appearance is black powder.
The invention aims to optimize the treatment method for the boiler washing wastewater of the sulfate pulping alkali recovery boiler and simultaneously treat normal wastewater. The water quality indexes of the normal wastewater to be treated and the furnace washing wastewater are as follows:
TABLE 1 comparison table of water quality of normal wastewater and furnace washing wastewater
The traditional method for treating the waste water from the furnace washing (as shown in figure 1) comprises the following steps:
(1) the method comprises the following steps of (1): 100, sending the wastewater to an adjusting tank, adding hydrochloric acid or sodium hydroxide solution into the adjusting tank, and adjusting the pH value of the wastewater to 7.0-8.0 to prepare pre-coagulation wastewater;
(2) introducing the pre-coagulation wastewater obtained in the step (1) into a coagulation reaction tank, adding 8mg/L wastewater treatment agent (purchased from Bakman laboratory chemical industry Co., Ltd., product model number BLX14397) for quick mixing, and simultaneously adding 350mg/L polyaluminium chloride, wherein the polyaluminium chloride is prepared into a solution with the mass concentration of 10% before use; reacting for 10 minutes under the condition of stirring; then, the mixture enters a flocculation tank, and 3ppm of anionic PAM is added to react for 15 minutes to form alum floc;
(3) pretreating the wastewater treated in the step (2) by a biological system;
(4) introducing the mixture obtained in the step (3) into a coagulation reaction tank, adding hydrochloric acid with the mass concentration of 32%, adjusting the pH value of the wastewater to be 6.3-6.8, adding polymeric ferric sulfate according to the adding amount of 1400mg/L, controlling the total iron content of the polymeric ferric sulfate to be 11%, and controlling the pH value to be 3.5-4.0 for reacting for 35 minutes; adding 3.0mg/L cationic PAM, and stirring for reaction for 15 minutes; entering a sedimentation tank;
(5) and after 4 hours of sedimentation in the sedimentation tank, sending the settled chemical sludge to a sludge storage tank through a bottom sludge pump, preparing a mud cake by using a centrifugal dehydrator, collecting supernatant, adding a sodium hydroxide solution with the mass concentration of 31%, adjusting the pH value to 6.2-6.5, and discharging.
Example 1
As shown in figure 2, the method for treating the boiler washing wastewater of the soda recovery boiler for sulfate pulping comprises the following steps:
(1) a treatment system is arranged and comprises a recovery tank, an adjusting tank, a coagulation reaction tank (divided into two grids, namely a coagulation tank 1 and a flocculation reaction tank 1), a radial flow sedimentation tank, a neutralization tank, a folded plate reactor, a high-efficiency reaction flocculation tank and a matched medicament adding system;
(2) collecting the boiler washing wastewater of the sulfate pulping alkali recovery boiler into a recovery tank, pumping the boiler washing wastewater into an adjusting tank through a centrifugal pump, adding hydrochloric acid with the mass concentration of 32% into the adjusting tank, fully stirring and uniformly mixing, and adjusting the pH value of the boiler washing wastewater to 7.0-8.0 to prepare pre-coagulation wastewater;
(3) introducing the pre-coagulation wastewater treated in the step (2) into a coagulation reaction tank, adding 8mg/L of a strong agent for quick mixing, and simultaneously adding 350mg/L of polyaluminium chloride, wherein the polyaluminium chloride is prepared into a solution with the mass concentration of 10% before use; reacting for 10 minutes under the condition of stirring; then, the mixture enters a flocculation tank, and 3ppm of anionic PAM is added to react for 15 minutes to form alum floc;
(4) enabling the wastewater treated in the step (3) to flow into a radial flow type sedimentation tank, mixing the wastewater with the chemical sludge refluxed in the subsequent step (7), enabling the mixture to stay for 60 minutes by waterpower, pumping the settled sludge into a sludge storage tank by a bottom sludge pump, preparing a sludge cake by using a centrifugal dehydrator, and collecting supernatant to obtain materialized wastewater;
(5) introducing the materialized wastewater in the step (4) and the pretreated normal wastewater into a neutralization tank together, adding the materialized wastewater to the normal wastewater by the volume percentage of 2.0%, stirring and mixing, adding hydrochloric acid with the mass concentration of 32%, and adjusting the pH value of the wastewater to 6.3-6.8 to obtain the pretreated advanced wastewater;
(6) introducing the wastewater subjected to the advanced treatment in the step (5) into a folded plate reactor, adding polymeric ferric sulfate according to the adding amount of 1400mg/L, controlling the total iron content of the polymeric ferric sulfate to be 11%, and reacting for 35 minutes under the condition that the pH value is controlled to be 3.5-4.0; then the mixture enters a high-efficiency reaction flocculation tank, and then cationic PAM of 3.0mg/L is added, and the mixture is stirred and reacts for 15 minutes; entering a sedimentation tank;
(7) after 4 hours of sedimentation in the sedimentation tank, most of the settled chemical sludge is pumped to a sludge storage tank through a bottom sludge discharge pump, a mud cake is prepared by using a centrifugal dehydrator, a small part of the chemical sludge flows back to the step (4), and the backflow amount of the chemical sludge is 0.1 percent of the volume of the wastewater treatment amount in the step (4); collecting supernatant, adding 31% sodium hydroxide solution, adjusting pH to 6.2-6.5, and discharging.
The stirring is mechanical stirring with adjustable rotating speed.
The step (5) of pretreating the normal wastewater introduced into the neutralization tank by a conventional method comprises the following steps:
1) adding hydrochloric acid or sodium hydroxide solution into the adjusting tank when normal wastewater enters the adjusting tank, and adjusting the pH value of the wastewater to 7.0-8.0 to prepare pre-coagulation wastewater;
2) introducing the pre-coagulation wastewater obtained in the step 1) into a coagulation reaction tank, adding 8mg/L wastewater treatment agent (which is purchased from Bakman laboratory chemical industry Co., Ltd., product model number BLX14397) for quick mixing, and simultaneously adding 350mg/L polyaluminium chloride, wherein the polyaluminium chloride is prepared into a solution with the mass concentration of 10% before use; reacting for 10 minutes under the condition of stirring; then, the mixture enters a flocculation tank, and 3ppm of anionic PAM is added to react for 15 minutes to form alum floc;
3) pretreating the wastewater treated in the step 2) by a biological system.
The indexes before and after the pretreatment of normal wastewater are as follows:
comparative experiment 1-comparison of Experimental results of Replacing wastewater treatment agent with Strength agent
On the basis of the embodiment 1, the dosage of the pretreatment reagent in the step (3) is adjusted according to the inflow water quality with different COD values, and the effluent water quality results are as follows:
TABLE 2 comparison table of experimental results of pretreatment of washing furnace wastewater by strong agent instead of wastewater treatment agent
The results show that the use of the strong agent to replace a wastewater treatment agent for pretreating the furnace washing wastewater greatly improves the removal rate of COD and reduces the generation amount of sludge. In the physicochemical treatment, the strength agent is used for replacing a common wastewater treatment agent and then part of the polyaluminium chloride is matched, so that the compactness of a coagulation reaction floc is improved, the sludge settling property is improved, the adding amount of the polyaluminium chloride is reduced, the sludge generation amount is reduced, and the subsequent sludge treatment pressure is reduced. Meanwhile, the strong agent can also effectively remove soluble COD in the wastewater.
Comparative experiment 2-comparison of Water sample alkalinity before and after refluxing chemical sludge with materialized wastewater
Based on example 1, for the furnace washing wastewater with different alkalinity before materialization, a comparative test is carried out between before the materialized wastewater is not refluxed with the chemical sludge and after the materialized wastewater is refluxed with the chemical sludge, and the results are as follows:
TABLE 3 comparison table of alkalinity of water sample before and after the return of physicochemical wastewater to chemical sludge
The results show that the treatment effect is better after the physicochemical wastewater refluxes part of the chemical sludge. The invention recycles the chemical sludge added into the polyferric sulfate reaction in the advanced treatment section, not only achieves the purpose of reducing the alkalinity of the wastewater, but also is beneficial to the sedimentation of sludge flocs in the radial flow sedimentation tank.
Comparative experiment 3-comparison of the results of the experiment of the furnace washing wastewater in the biological system and the biological system
On the basis of example 1, the comparison experiment between the "furnace washing wastewater enters the biological system" and the "furnace washing wastewater does not enter the biological system" shows the following results:
table 4: experimental result of furnace washing wastewater entering biological system
Table 5: experimental result of furnace washing wastewater without entering biological system
The results show that compared with the traditional method for treating the waste water from the furnace washing and the normal waste water entering the biological system together, the method for treating the waste water from the furnace washing does not enter the biological system, thereby not only improving the treatment effect, but also reducing the cost.
By adopting the treatment method, the treatment of the furnace washing wastewater avoids a biological system, and breaks through the original traditional treatment mode in the pulping and papermaking industry, namely, the wastewater is subjected to physical and chemical treatment by the strong agent and then is merged into the advanced treatment section according to the accurate set amount, so that the impact of the high-alkalinity and high-conductivity furnace washing wastewater on the biological system is avoided, the adding amount of a chemical agent polymeric ferric sulfate agent in the advanced treatment section is greatly reduced, and the treatment cost of ton wastewater is reduced. In addition, the treatment amount of the waste water of the washing furnace is 10m of the traditional treatment mode3Lifting to 50m of the scheme about/h3And about/h, the treatment progress of the abnormal waste water of the furnace washing is accelerated.
Example 2-treatment method of boiler washing wastewater of sulfate pulping alkali recovery boiler
(1) Setting a processing system consistent with example 1;
(2) collecting furnace washing wastewater with the source consistent with that of the embodiment 1 into a recovery tank, pumping the furnace washing wastewater into an adjusting tank through a centrifugal pump, adding hydrochloric acid with the mass concentration of 32% into the adjusting tank, fully stirring and uniformly mixing the hydrochloric acid and the adjusting tank, and adjusting the pH value of the furnace washing wastewater to 7.0-8.0 to prepare pre-coagulation wastewater;
(3) introducing the pre-coagulation wastewater treated in the step (2) into a coagulation reaction tank, adding 8mg/L of a strong agent for quick mixing, and simultaneously adding 350mg/L of polyaluminium chloride, wherein the polyaluminium chloride is prepared into a solution with the mass concentration of 10% before use; reacting for 8 minutes under the condition of stirring; then, the mixture enters a flocculation tank, and 3ppm of anionic PAM is added to react for 15 minutes to form alum floc;
(4) enabling the wastewater treated in the step (3) to flow into a radial flow type sedimentation tank, mixing the wastewater with the chemical sludge refluxed in the subsequent step (7), enabling the mixture to stay for 50 minutes in a hydraulic mode, pumping the settled sludge into a sludge storage tank through a bottom sludge discharge pump, preparing a sludge cake by using a centrifugal dehydrator, and collecting supernatant to obtain materialized wastewater;
(5) introducing the materialized wastewater and the normal wastewater in the step (4) into a neutralization tank together, adding the materialized wastewater to the normal wastewater by the volume percentage of 1.8%, stirring and mixing, adding hydrochloric acid with the mass concentration of 32%, and adjusting the pH value of the wastewater to 6.3-6.8 to prepare pre-deep treatment wastewater;
(6) introducing the wastewater subjected to the advanced treatment in the step (5) into a folded plate reactor, adding polymeric ferric sulfate according to the addition amount of 1100mg/L, controlling the total iron content of the polymeric ferric sulfate to be 11%, and reacting for 30 minutes under the condition that the pH value is controlled to be 3.5-4.0; then the mixture enters a high-efficiency reaction flocculation tank, and then cationic PAM of 3mg/L is added, and the mixture is stirred and reacts for 15 minutes; entering a sedimentation tank;
(7) after 3.5 hours of sedimentation in the sedimentation tank, most of the settled chemical sludge is pumped to a sludge storage tank through a bottom sludge discharge pump, a mud cake is prepared by using a centrifugal dehydrator, a small part of the chemical sludge flows back to the step (4), and the backflow amount of the chemical sludge is 0.08 percent of the volume of the wastewater treatment amount in the step (4); collecting supernatant, adding 31% sodium hydroxide solution, adjusting pH to 6.2-6.5, and discharging. The treated wastewater meets the discharge requirement.
Example 3-treatment of boiler washing wastewater of soda recovery boiler for sulfate pulping
(1) Setting a processing system consistent with example 1;
(2) collecting furnace washing wastewater with the source consistent with that of the embodiment 1 into a recovery tank, pumping the furnace washing wastewater into an adjusting tank through a centrifugal pump, adding hydrochloric acid with the mass concentration of 32% into the adjusting tank, fully stirring and uniformly mixing the hydrochloric acid and the adjusting tank, and adjusting the pH value of the furnace washing wastewater to 7.0-8.0 to prepare pre-coagulation wastewater;
(3) introducing the pre-coagulation wastewater treated in the step (2) into a coagulation reaction tank, adding 8mg/L of a strong agent for quick mixing, and simultaneously adding 350mg/L of polyaluminium chloride, wherein the polyaluminium chloride is prepared into a solution with the mass concentration of 10% before use; reacting for 12 minutes under the condition of stirring; then, the mixture enters a flocculation tank, and 3ppm of anionic PAM is added to react for 20 minutes to form alum floc;
(4) enabling the wastewater treated in the step (3) to flow into a radial flow type sedimentation tank, mixing the wastewater with the chemical sludge refluxed in the subsequent step (7), allowing the mixture to stay for 70 minutes hydraulically, pumping the settled sludge into a sludge storage tank through a bottom sludge pump, preparing a sludge cake by using a centrifugal dehydrator, and collecting supernatant to obtain the physicochemical wastewater;
(5) introducing the materialized wastewater and the normal wastewater in the step (4) into a neutralization tank together, adding the materialized wastewater to the normal wastewater by the volume percentage of 2.2%, stirring and mixing, adding hydrochloric acid with the mass concentration of 32%, and adjusting the pH value of the wastewater to 6.3-6.8 to prepare pre-deep treatment wastewater;
(6) introducing the wastewater subjected to the advanced treatment in the step (5) into a folded plate reactor, adding polymeric ferric sulfate according to the addition amount of 1800mg/L, controlling the total iron content of the polymeric ferric sulfate to be 11%, and reacting for 40 minutes under the condition of controlling the pH value to be 3.5-4.0; then the mixture enters a high-efficiency reaction flocculation tank, and then cationic PAM of 3.0mg/L is added, and the mixture is stirred and reacts for 20 minutes; entering a sedimentation tank;
(7) after 5.0 hours of sedimentation in the sedimentation tank, most of the settled chemical sludge is pumped to a sludge storage tank through a bottom sludge discharge pump, a mud cake is prepared by using a centrifugal dehydrator, a small part of the chemical sludge flows back to the step (4), and the backflow amount of the chemical sludge is 0.1 percent of the volume of the wastewater treatment amount in the step (4); collecting supernatant, adding 31% sodium hydroxide solution, adjusting pH to 6.2-6.5, and discharging. The treated wastewater meets the discharge requirement.
In conclusion, compared with the traditional process, the treatment method has the advantages of practical operation, wide application, economy and environmental protection.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A treatment method of boiler washing wastewater of an alkali recovery boiler for sulfate pulping is characterized by comprising the following steps:
(1) the system used by the treatment method comprises a recovery tank, an adjusting tank, a coagulation reaction tank, a radial flow sedimentation tank, a neutralization tank, a folded plate reactor and a reaction flocculation tank, wherein the coagulation reaction tank comprises a coagulation tank and a flocculation reaction tank;
(2) collecting the furnace washing wastewater into a recovery tank, pumping the furnace washing wastewater into an adjusting tank through a centrifugal pump, adding a pH regulator into the adjusting tank, fully stirring and uniformly mixing the materials, and adjusting the pH value of the furnace washing wastewater to 7.0-8.0 to prepare pre-coagulation wastewater;
(3) introducing the pre-coagulation wastewater treated in the step (2) into a coagulation reaction tank, adding 6-10mg/L of a strong agent for mixing, simultaneously adding 300-400mg/L of polyaluminium chloride, reacting for 8-12 minutes under the stirring condition, then entering a flocculation tank, adding 2-4ppm of anionic PAM, and reacting for 15-20 minutes to form alum blossom;
(4) enabling the wastewater treated in the step (3) to flow into a radial flow type sedimentation tank, mixing the wastewater with the chemical sludge refluxed in the subsequent step (7), allowing the mixture to stay for 50-70 minutes under hydraulic power, settling the sludge, and collecting supernatant to obtain materialized wastewater;
(5) introducing the materialized wastewater and the normal wastewater after pretreatment in the step (4) into a neutralization tank together, wherein the materialized wastewater is 1.8-2.2% of the normal wastewater by volume percent, stirring and mixing, and then adjusting the pH value of the wastewater to 6.3-6.8 to prepare advanced wastewater;
(6) introducing the wastewater subjected to advanced treatment in the step (5) into a folded plate reactor, adding polymeric ferric sulfate according to the addition amount of 1100 plus 1800mg/L, controlling the pH value to be 3.5-4.0, reacting for 30-40 minutes, then feeding the wastewater into a reaction flocculation tank, adding 2.5-4mg/L cationic PAM, stirring and reacting for 15-20 minutes, and feeding the wastewater into a sedimentation tank;
(7) after 4-6 hours of sedimentation in the sedimentation tank, discharging most of the settled chemical sludge, and refluxing a small part of the chemical sludge to the step (4), wherein the reflux amount of the chemical sludge is 0.08-0.1% of the volume of the treated wastewater in the step (4); collecting supernatant, adjusting pH to 6.2-6.5, and discharging.
2. The treatment method according to claim 1, wherein in the step (2), the furnace washing wastewater is furnace washing wastewater of a kraft pulping soda recovery boiler.
3. The treatment method according to claim 1, wherein in the step (2), the indexes of the furnace washing wastewater are as follows: pH is more than 11.0, alkalinity is more than 800mg/L, conductance is 10-70ms/cm, and COD is more than 2000 mg/L.
4. The processing method according to claim 1,
in the step (3), the reaction time after adding the polyaluminium chloride is 10 minutes, and the reaction time after adding the anionic PAM is 15 minutes;
in the step (6), the reaction time after adding the polymeric ferric sulfate is 35 minutes, and the reaction time after adding the cationic PAM is 15 minutes.
5. The process of claim 1, wherein in step (7), the precipitation time is 4 hours.
6. The process of claim 1, wherein in step (2), the hydraulic retention time is 60 minutes.
7. The treatment method according to claim 1, wherein in the step (3), the strength agent is a strength agent manufactured by Sichuan Baocheng corporation, model number BCWC-A1 #.
8. The treatment method according to claim 1, wherein the pH is adjusted by using hydrochloric acid having a mass concentration of 32% or sodium hydroxide solution having a mass concentration of 31%.
9. The processing method according to claim 1,
in the step (3), the polyaluminium chloride is prepared into a solution with the mass concentration of 10% before use;
in the step (6), the total iron content of the polymeric ferric sulfate is 11%.
10. The process according to claim 1, wherein in the steps (4) and (7), the settled sludge is pumped to a sludge storage tank through a bottom sludge pump, and a sludge cake is obtained by a centrifugal dehydrator.
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| CN113044942A (en) * | 2021-03-15 | 2021-06-29 | 武汉工程大学 | Bentonite coagulant and application thereof in wastewater treatment |
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| CN115434178A (en) * | 2022-08-23 | 2022-12-06 | 天津科技大学 | Chemical alkali recovery treatment process for chemi-mechanical pulp waste liquid |
| CN115434178B (en) * | 2022-08-23 | 2023-09-01 | 天津科技大学 | Chemical alkali recovery treatment process for chemical mechanical pulp waste liquid |
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