Boiler make-up water treatment system and treatment method

Abstract

The invention discloses a boiler make-up water treatment system and method, and belongs to the technical field of water treatment systems. Comprising the following steps: S1, pre-oxidation treatment; s2, flocculent precipitation; s3, primary filtering; s4, preparing biological activated carbon; s5, performing secondary filtration; s6, carrying out desalting treatment; and S7, TOC analysis. Through synergistic catalytic oxidation of ferrate and ozone, organic matters in a water source are degraded, and the biodegradability is further improved. Meanwhile, the final product ferric ions of the ferrate serve as a coagulant and are matched with an organic-inorganic composite flocculant to perform coagulation treatment on the pre-oxidized effluent, and under the action of pre-oxidation, the effect of coagulating and clarifying the effluent is improved, and meanwhile, the removal efficiency of micromolecule TOC is improved by strengthening the coagulation process. And carrying out deep adsorption and biodegradation on pre-oxidized effluent organic matters through biological activated carbon. TOC analysis is carried out on the effluent of the desalination unit, and when the TOC exceeds a threshold value, the ultraviolet advanced oxidation treatment unit is automatically started to carry out post-oxidation treatment on the effluent of the desalination unit, so that the TOC reaches the effluent index.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment systems, and in particular relates to a boiler feed water treatment system and a treatment method. Background Art

[0002] Boilers play a key role in thermal power generation. After a long period of theoretical and practical experience, people have come to realize that the quality of boiler feed water is a key factor in ensuring its safe and economical operation. Boilers usually use two water sources: one is untreated natural water, such as groundwater, mountain spring water or reservoir water; the other is wastewater treated by industrial reuse water stations. Although the latter has been treated, it still contains a high concentration of salt, especially chloride ions, sodium ions, ammonium ions, a certain amount of organic matter, and a small amount of calcium ions and magnesium ions. At the same time, untreated natural water contains a variety of impurities. Poor water quality for boiler water will lead to widespread scaling and corrosion problems on the heating surface. If the salt content of treated water is still high, it may cause steam to carry water and steam-water co-boiling, which will not only increase the amount of sewage discharged, but also affect the safe and economical operation of the boiler. Therefore, it is of great practical significance and urgency to effectively treat the boiler water quality to ensure that it meets the appropriate standards.

[0003] Traditional boiler feed water treatment processes mainly include coagulation, sedimentation, ultrafiltration pretreatment units, and reverse osmosis and ion exchange resin desalination units. The purpose of pretreatment is to remove large particles, suspended matter and some dissolved solids in the water to protect subsequent equipment. The coagulation unit adds iron or aluminum coagulants, and under the action of double layer compression, adsorption neutralization, adsorption bridging, and net capture and sweeping, the suspended particles in the raw water and some organic matter form larger flocs, which are then removed by gravity clarification. Reverse osmosis treatment, which is a highly efficient desalination technology, separates salts and other dissolved substances in the water by applying pressure to force water molecules through a semipermeable membrane. Reverse osmosis can significantly reduce the total dissolved solids (TDS) and total organic carbon (TOC) in water and improve water quality. Finally, resin treatment, also known as ion exchange, is used to remove the remaining hardness ions (such as calcium and magnesium) in the water, as well as some dissolved salts. The resin bed can adsorb these ions, thereby softening the water and reducing the risk of boiler scaling. The entire treatment process needs to be precisely controlled to ensure that the final feed water meets the safe and economical operation requirements of the boiler.

[0004] The traditional boiler feed water treatment process of thermal power plants can ensure that its salt content meets the national standard requirements, but as the organic components in the water source become increasingly complex, the traditional boiler feed water treatment process often has the problem of excessive organic concentration in the effluent. After the organic matter enters the boiler, it changes under high temperature and high pressure, and produces some substances that can cause corrosion of the metal materials of the boiler and steam turbine unit.

[0005] Traditional boiler feed water treatment processes are prone to microbial contamination, which can cause fouling of ultrafiltration and reverse osmosis membranes, increase operating costs, and deteriorate effluent quality.

[0006] Generally, reverse osmosis membranes have a relatively high removal rate for organic matter, but their ability to remove small molecular organic matter is relatively poor. Therefore, as the concentration of organic matter in the influent increases, the complexity of the pollutant composition often leads to the inability of the effluent TOC to meet the standard.

[0007] In addition, as the concentration of organic matter in the water source increases, the pollution of the reverse osmosis membrane becomes increasingly serious. Frequent membrane cleaning leads to the degradation of membrane performance and the increase of the TOC index of the effluent, which cannot meet the water quality requirements of the feed water. Frequent replacement of reverse osmosis membranes greatly increases the cost of boiler feed water treatment. Summary of the invention

[0008] Aiming at the problems that TOC of produced water in traditional boiler feed water treatment process often exceeds standard and reverse osmosis membrane is seriously polluted, the present invention provides a boiler feed water treatment system and method which combines organic matter pre-treatment of "organic-inorganic composite coagulant + ozone ferrate pre-oxidation + biological activated carbon" with organic matter post-treatment of "ultraviolet lamp oxidation" to solve the problem that TOC concentration of effluent in traditional boiler feed water treatment process exceeds standard.

[0009] The technical solution adopted by the present invention is:

[0010] A boiler feed water treatment system, comprising

[0011] A pre-oxidation reaction unit, connected to the quick mixing unit, is used for pre-oxidation treatment of boiler feed water;

[0012] A quick mixing unit, connected to the flocculation unit, is used for mixing water;

[0013] A flocculation unit, connected to the sedimentation unit, for flocculating water;

[0014] A sedimentation unit, connected to the primary filtration unit, for performing sedimentation treatment on water;

[0015] A primary filtration unit, connected to the biological activated carbon unit, for performing primary filtration treatment on water;

[0016] A biological activated carbon unit, connected to the secondary filtration unit, is used for adsorption and degradation treatment of water;

[0017] A secondary filtration unit is connected to the desalination treatment unit and is used for performing secondary filtration treatment on water;

[0018] A desalination treatment unit, connected to the ultraviolet oxidation unit, is used to desalinate water;

[0019] UV oxidation unit for post-oxidation treatment of water.

[0020] A method for treating boiler feed water comprises the following steps:

[0021] S1. Pre-oxidation treatment: adding ferrate and ozone to the raw water to be treated;

[0022] S2. Flocculation and sedimentation: Flocculation and gravity clarification treatment using the final product of ferrate and an organic-inorganic composite flocculant;

[0023] S3. Primary filtration: Filter the effluent from the sedimentation tank using a sand filter;

[0024] S4. Bioactivated carbon: Use bioactivated carbon to adsorb and degrade organic matter;

[0025] S5. Secondary filtration: filtration using ultrafiltration membrane;

[0026] S6. Desalination treatment: two-stage desalination treatment is carried out by reverse osmosis and resin; S7. TOC analysis: TOC analysis is carried out on the desalination effluent; if TOC < 0.2 mg / L, the desalination effluent is sent to the production water tank; if TOC > 0.2 mg / L, the desalination effluent is sent to the ultraviolet oxidation treatment device for post-oxidation treatment, and the post-oxidation effluent is sent to the production water tank.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention can achieve deep removal of organic matter in water sources, inhibit bacterial growth in the system, reduce reverse osmosis membrane pollution, and ensure stable operation of the membrane system; through the synergistic catalytic oxidation of ferrate and ozone, the organic matter in the water source is degraded, and the biodegradability is further improved. At the same time, the final product of ferrate, trivalent iron ions, is used as a coagulant to cooperate with an organic-inorganic composite flocculant to coagulate the pre-oxidation effluent. Under the action of pre-oxidation, while improving the coagulation and clarification effect of the effluent, the removal efficiency of small molecule TOC is improved by strengthening the coagulation process. The organic matter in the pre-oxidation effluent is deeply adsorbed and biodegraded by biological activated carbon. The effluent of the desalination unit is subjected to TOC analysis. When the TOC exceeds the threshold, the ultraviolet advanced oxidation treatment unit is automatically started, and the effluent of the desalination unit is post-oxidized to make the TOC reach the effluent index. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the structure of the processing system of the present invention;

[0030] Figure 2 It is a schematic diagram of the structure of the pre-oxidation reaction unit of the present invention;

[0031] Figure 3is a flow chart of the processing method of the present invention;

[0032] Wherein: 1. pre-oxidation reaction unit; 2. fast mixing unit; 3. flocculation unit; 4. precipitation unit; 5. primary filtration unit; 6. biological activated carbon unit; 7. secondary filtration unit; 8. desalination treatment unit; 9. ultraviolet oxidation unit; 11. pre-oxidation reaction device cavity; 12. ferrate dosing component; 13. ozone dosing component; 14. mixing component; 121. dosing ring; 122. agent water outlet; 123. ferrate dosing pump; 131. ozone air distribution pipe; 132. ozone dissolved air pump; 141. agitator. DETAILED DESCRIPTION

[0033] In order to better understand the purpose, structure and function of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings.

[0034] The present invention provides a boiler feed water treatment method and a treatment system using the method, which realizes deep removal of organic matter in water source by "ferrate + ozone" pre-oxidation method, degrades organic matter in water source by synergistic catalytic oxidation of ferrate and ozone, and further improves biodegradability. The organic matter in pre-oxidation effluent is deeply adsorbed and biodegraded by biological activated carbon (i.e., ferrate and ozone pre-oxidation are coupled with biological activated carbon to remove organic matter before desalination), and at the same time, the final product of ferrate, trivalent iron ions, is used as a coagulant in combination with an organic-inorganic composite flocculant to coagulate the pre-oxidation effluent. Under the action of pre-oxidation, while improving the coagulation and clarification effect of effluent, TOC is further removed by strengthening the coagulation process.

[0035] The effluent from the desalination unit is subjected to TOC analysis. When the TOC exceeds the threshold, the UV advanced oxidation treatment unit is automatically started to perform post-oxidation treatment on the effluent from the desalination unit to make the TOC reach the effluent index.

[0036] like Figure 1 , Figure 2 As shown, the present invention provides a boiler feed water treatment system, comprising

[0037] The pre-oxidation reaction unit 1 is connected to the fast mixing unit 2 and is used for pre-oxidation treatment of boiler feed water;

[0038] The quick mixing unit 2 is connected to the flocculation unit 3 and is used for mixing the water;

[0039] The flocculation unit 3 is connected to the sedimentation unit 4 and is used for flocculating the water;

[0040] The sedimentation unit 4 is connected to the primary filtration unit 5 and is used for sedimentation treatment of water;

[0041] The primary filtration unit 5 is connected to the biological activated carbon unit 6 and is used for primary filtration treatment of water;

[0042] The biological activated carbon unit 6 is connected to the secondary filtration unit 7 and is used for adsorption and degradation of water;

[0043] The secondary filtering unit 7 is connected to the desalination treatment unit 8 and is used for performing secondary filtering treatment on water;

[0044] The desalination treatment unit 8 is connected to the ultraviolet oxidation unit 9 and is used to desalinate water;

[0045] The ultraviolet oxidation unit 9 is used for post-oxidation treatment of water.

[0046] The pre-oxidation reaction unit 1 includes a pre-oxidation reaction device chamber 11, a ferrate dosing component 12, an ozone dosing component 13 and a mixing component 14;

[0047] The ferrate dosing component 12 is a dosing ring 121 arranged in the middle of the pre-oxidation reaction device cavity 11. The dosing ring 121 has holes uniformly opened on the inner side toward the center of the circle as a reagent water outlet 122. The inlet of the dosing ring 121 is connected to the outlet of the ferrate dosing pump 123.

[0048] The ozone dosing component 13 is an ozone air distribution pipe 131 arranged at the bottom of the pre-oxidation reaction device cavity 11, and the inlet of the ozone air distribution pipe 131 is connected to the outlet of the ozone dissolved air pump 132;

[0049] The mixing assembly 14 is an agitator 141 arranged on the central axis of the pre-oxidation reaction device cavity 11 and passing through the dosing ring 121, and the blades of the agitator 141 are above the ozone dosing assembly 13;

[0050] The blades of the stirrer 141 are double-layer blades, wherein the distance between the lower blade and the ozone distribution pipe 131 is 10-50 cm, and the upper blade and the dosing ring 121 are in the same plane.

[0051] The fast mixing unit 2 is a complete mixing reactor, equipped with a stirring device, and the speed gradient of the fast mixing unit 2 is 800-1500s -1 , residence time 30s-180s.

[0052] Flocculation unit 3 uses one of the mechanical stirring flocculation tank, folded plate flocculation tank or grid flocculation tank, and the GT value is 0.5*10 5 -1.5*10 5 .

[0053] The biological activated carbon unit 6 uses coconut shell granular activated carbon with an activated carbon size of 0.1-0.2 mm. The biofilm on the surface of the coconut shell granular activated carbon is domesticated during the debugging stage using the effluent from the previous treatment system (i.e., the primary filtration unit 5). The formed microbial colony has a specific adaptability to the residual organic matter formed after the water source organic matter has been previously treated.

[0054] The secondary filtration unit 7 adopts one of submerged ultrafiltration and column ultrafiltration, wherein the molecular weight cutoff of the ultrafiltration membrane is 10,000-100,000.

[0055] The ultraviolet oxidation unit 9 uses one of a low-pressure mercury lamp, a medium-pressure mercury lamp, and an ultraviolet LED.

[0056] like Figure 3 As shown, the present invention provides a method for treating boiler feed water, comprising the following steps:

[0057] S1. Pre-oxidation treatment: adding ferrate and ozone to the raw water to be treated;

[0058] The raw water is pre-oxidized by adding ferrate and ozone to obtain pre-oxidized effluent;

[0059] Ferrate is one of sodium ferrate and potassium ferrate or a combination of the two, and the ferrate dosage T1 is 1-20 mg / L (in terms of Fe);

[0060] Ozone is mixed and added by an ejector, wherein the ozone dosage T2 is 1-10 mg / L.

[0061] S2. Flocculation and precipitation: the organic-inorganic composite flocculant is added to the quick mixing unit 2, and the final product of ferrate is used for flocculation and gravity clarification. The dosage of the organic-inorganic composite flocculant is 0.1-5 mg / L;

[0062] Control the GT value of the reaction tank to promote the flocculation reaction of the pre-oxidation effluent. The large-sized flocs obtained are removed under the gravity clarification of the sedimentation tank to obtain flocculated effluent;

[0063] S3. Primary filtration: Filter the effluent from the sedimentation tank using a sand filter;

[0064] The flocculation sedimentation effluent is subjected to sand filtration to further remove suspended solid particles and obtain primary filtration effluent;

[0065] S4. Bioactivated carbon: Use bioactivated carbon to adsorb and degrade organic matter;

[0066] The primary filtered water is treated with biological activated carbon to further remove organic matter and obtain biological activated carbon effluent, wherein the microorganisms on the surface of the activated carbon are biofilms formed on the surface of the activated carbon after domestication;

[0067] S5. Secondary filtration: filtration using ultrafiltration membrane;

[0068] S6. Desalination: Two-stage desalination using reverse osmosis and resin;

[0069] The biological activated carbon effluent is subjected to reverse osmosis desalination treatment, and the obtained reverse osmosis produced water is subjected to ion exchange treatment to obtain desalinated effluent;

[0070] S7.TOC analysis: Perform TOC analysis on the desalination effluent; if TOC < 0.2 mg / L, send the desalination effluent to the production water tank; if TOC > 0.2 mg / L, send the desalination effluent to the ultraviolet oxidation treatment device for post-oxidation treatment, and send the post-oxidation effluent to the production water tank.

[0071] S7 uses a controller to achieve automatic post-oxidation control. By collecting TOC online detection signals, it controls the switching valve to directly send the desalinated water into the water production tank or into the ultraviolet oxidation unit 9 for treatment.

[0072] Example 1

[0073] This embodiment provides the treatment method and effect of boiler feed water disclosed in the present invention. The raw water volume of boiler feed water is 50t / h, and the main water quality is shown in Table 1.

[0074] project Detection value <![CDATA[Total silicon Si02 (mg / L)]]> 14.39 TOC(mg / L) 56 Turbidity (NTU) 1.58 Total hardness (mg / L, in CaCO3) 51.9 pH 7.22 Conductivity (μS / cm) 150.5

[0075] The raw water is pre-oxidized by adding 10 mg / L ferrate and 5 mg / L ozone to the raw water to be treated to obtain pre-oxidized effluent.

[0076] Add organic-inorganic composite flocculant to fast mixing unit 2, and use the final product of ferrate for flocculation and gravity clarification. The dosage of organic-inorganic composite flocculant is 2 mg / L. The organic-inorganic composite flocculant adopts NALCO-3108 model flocculant. After flocculation and clarification, flocculation precipitation effluent is obtained. The flocculation precipitation effluent is further removed from the sand filter tank to remove suspended solid particles, and then COD is removed by biological activated carbon. The biological activated carbon effluent is filtered through the secondary ultrafiltration membrane. The ultrafiltration membrane adopts a column ultrafiltration membrane, model SFP-2660, with a design flux of 35LMH. The secondary filtered effluent is desalinated by two-stage reverse osmosis membranes. The design flux of the first reverse osmosis membrane is 20LMH, and the design flux of the second reverse osmosis membrane is 35LMH. The concentrated water of the desalination treatment unit is sent to the subsequent concentrated brine disposal workshop. The TOC of the water produced by the desalination treatment unit is tested to be 0.23 mg / L, and the ultraviolet oxidation treatment device is started. After being treated by the ultraviolet oxidation treatment device, the effluent TOC is 0.18 mg / L, meeting the make-up water quality standard.

[0077]

[0078] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A boiler feed water treatment system, characterized in that: include A pre-oxidation reaction unit (1) is connected to the fast mixing unit (2) and is used for pre-oxidation treatment of boiler feed water; The quick mixing unit (2) is connected to the flocculation unit (3) and is used for mixing water; A flocculation unit (3) connected to the sedimentation unit (4) for flocculating water; A sedimentation unit (4) connected to the primary filtration unit (5) for performing sedimentation treatment on water; A primary filtration unit (5) is connected to the biological activated carbon unit (6) and is used to perform primary filtration treatment on water; The biological activated carbon unit (6) is connected to the secondary filtration unit (7) and is used for adsorption and degradation treatment of water; A secondary filtering unit (7) is connected to the desalination treatment unit (8) and is used to perform secondary filtering treatment on water; A desalination treatment unit (8) is connected to the ultraviolet oxidation unit (9) and is used to desalinate water; The ultraviolet oxidation unit (9) is used for post-oxidation treatment of water.

2. A boiler feed water treatment system according to claim 1, characterized in that: The pre-oxidation reaction unit (1) comprises a pre-oxidation reaction device chamber (11), a ferrate dosing component (12), an ozone dosing component (13) and a mixing component (14); The ferrate dosing component (12) is a dosing ring (121) arranged in the middle of the pre-oxidation reaction device cavity (11), the dosing ring (121) has holes uniformly opened on the inner side toward the center of the circle as a medicine water outlet (122), and the inlet of the dosing ring (121) is connected to the outlet of the ferrate dosing pump (123); The ozone dosing component (13) is an ozone air distribution pipe (131) arranged at the bottom of the pre-oxidation reaction device cavity (11), and the inlet of the ozone air distribution pipe (131) is connected to the outlet of the ozone dissolved air pump (132); The mixing assembly (14) is an agitator (141) arranged on the central axis of the pre-oxidation reaction device cavity (11) and passing through the dosing ring (121), and the blades of the agitator (141) are above the ozone dosing assembly (13); The blades of the stirrer (141) are double-layer blades, the lower blades are 10-50 cm away from the ozone distribution pipe (131), and the upper blades are in the same plane as the dosing ring (121).

3. A boiler feed water treatment system according to claim 1, characterized in that: The fast mixing unit (2) is a complete mixing reactor with a speed gradient of 800-1500s -1 , residence time 30s-180s.

4. A boiler feed water treatment system according to claim 1, characterized in that: The flocculation unit (3) adopts one of a mechanical stirring flocculation tank, a folded plate flocculation tank or a grid flocculation tank, and the GT value is 0.5*10 5 -1.5*10 5 .

5. A boiler feed water treatment system according to claim 1, characterized in that: The biological activated carbon unit (6) uses coconut shell granular activated carbon with a size of 0.1-0.2 mm. The biofilm on the surface of the coconut shell granular activated carbon is domesticated using the effluent from the primary filtration unit (5) during the debugging stage.

6. A boiler feed water treatment system according to claim 1, characterized in that: The secondary filtration unit (7) adopts one of submerged ultrafiltration and column ultrafiltration.

7. A boiler feed water treatment system according to claim 1, characterized in that: The ultraviolet oxidation unit (9) adopts one of a low-pressure mercury lamp, a medium-pressure mercury lamp, and an ultraviolet LED.

8. A treatment method using the boiler feed water treatment system according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Pre-oxidation treatment: adding ferrate and ozone to the raw water to be treated; S2. Flocculation and sedimentation: Flocculation and gravity clarification treatment using the final product of ferrate and an organic-inorganic composite flocculant; S3. Primary filtration: Filter the effluent from the sedimentation tank using a sand filter; S4. Bioactivated carbon: Use bioactivated carbon to adsorb and degrade organic matter; S5. Secondary filtration: filtration using ultrafiltration membrane; S6. Desalination: Two-stage desalination using reverse osmosis and resin; S7.TOC analysis: Perform TOC analysis on the desalination effluent; if TOC < 0.2 mg / L, send the desalination effluent to the production water tank; if TOC > 0.2 mg / L, send the desalination effluent to the ultraviolet oxidation treatment device for post-oxidation treatment, and send the post-oxidation effluent to the production water tank.

9. A method for treating boiler feed water according to claim 8, characterized in that: The ferrate in S1 is one of sodium ferrate and potassium ferrate or a combination of the two, and the ferrate dosage T1 is 1-20 mg / L; The ozone in S1 is mixed and added by an ejector, and the ozone dosage T2 is 1-10 mg / L.

10. A method for treating boiler feed water according to claim 8, characterized in that: The S7 uses a controller to realize post-oxidation automatic control, collects TOC online detection signals, controls the switching valve, and directly sends the desalination treatment effluent into the water production tank or into the ultraviolet oxidation unit (9) for treatment.

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