WO2018214350A1

WO2018214350A1 - Wet desulfurization wastewater resource processing system and processing method therefor

Info

Publication number: WO2018214350A1
Application number: PCT/CN2017/102654
Authority: WO
Inventors: 唐坚; 陈振宇; 陈鸥; 钟洪玲; 劳俊; 姚宣; 彭光军; 褚玥
Original assignee: 北京国电龙源环保工程有限公司
Priority date: 2017-05-25
Filing date: 2017-09-21
Publication date: 2018-11-29
Also published as: CN107082523B; CN107082523A

Abstract

A wet desulfurization wastewater resource processing system, comprising: a desulfurization wastewater preprocessing system, a primary tempering system, a deep modulation system, and a solid calcium chloride generation system which are sequentially connected. The desulfurization wastewater preprocessing system comprises a concentration tower (1), and a front desulfurization flue (2) and a desulfurization wastewater storage tank (3) which are connected to the concentration tower (1); the primary tempering system comprises a thick slurry discharge pump (4), a primary tempering box (10), and a solid-liquid separation device I (11) which are sequentially connected along the water direction; the deep modulation system comprises a deep modulation box (13), a clarifioccuiation pool (14), and a solid-liquid separation device II (15) which are sequentially connected along the water direction; the deep modulation box (13) is simultaneously connected to the solid-liquid separation device I (11) and a dosing device II (21); the clarifioccuiation pool (14) and the solid-liquid separation device II (15) are both connected to a collecting tank II (17); and the solid calcium chloride generation system comprises a dryer (18), a drying fan (19), and a collecting tank III (20). Also provided is a processing method for the wet desulfurization wastewater resource processing system. The wet desulfurization wastewater resource treatment system is safe and applicable, has good promotion and practical value, and would produce good economic benefits after being widely popularized and used.

Description

Wet desulfurization wastewater resource treatment system and treatment method thereof

Technical field

The invention relates to the field of wastewater for wet desulfurization of a thermal power plant, in particular to a wet desulfurization wastewater resource treatment system and a treatment method thereof.

Background technique

The thermal desulfurization of thermal power plants produces a large amount of wastewater. The cost of wastewater is relatively complicated. The main solid components in wastewater are dust and gypsum. The liquid phase is mainly magnesium sulfate, magnesium chloride, calcium sulfate and calcium chloride. Due to the complicated changes in coal-fired conditions, the difference in the composition of wastewater from wet desulfurization is also large. The existing wastewater treatment technology is mainly pretreated by triple tank, and then advanced treatment through reverse osmosis membrane, multi-effect evaporation, MVR evaporation, etc., to achieve zero discharge of desulfurization wastewater.

The triple tank is added with slaked milk, sodium carbonate, flocculant and other drugs in the desulfurization wastewater to adjust the pH of the wastewater to neutral. The pretreated wastewater is treated by reverse osmosis membrane, multi-effect evaporation and MVR evaporation. Advanced processing. The dosing cost, reverse osmosis membrane cost, and steam consumption of such technology are relatively high, and the economy is poor. The treated wastewater cannot be utilized for resource utilization, and a large amount of magnesium ions and chloride ions in the wastewater are not effectively recycled. .

Calcium chloride and magnesium hydroxide are two important chemical synthesis products. Calcium chloride is mainly used as a desiccant and a snow melting agent. Magnesium hydroxide is mainly used as a fire retardant and has a huge use. At present, the domestic calcium chloride production adopts the method of neutralizing hydrochloric acid + limestone (slaked lime) to form a calcium chloride solution, and then drying to obtain a finished calcium chloride product; the production of magnesium hydroxide mainly uses magnesium oxide ore as a raw material, and the alkali is used after dissolution. Liquid production. Both of them require a certain amount of raw materials to be produced, so the current market price is higher.

The wastewater from the limestone-gypsum wet desulfurization process contains a large amount of chloride and magnesium ions, and is treated according to conventional wastewater. After that, both chlorine and magnesium ions in the wastewater are directly discharged, causing water pollution and waste. In view of the above problems, this patent proposes a wet desulfurization wastewater resource treatment system, which uses the flue gas from the desulfurization inlet as a drying medium to concentrate and reduce the desulfurization wastewater to obtain a concentrated solution of strong acidity and high chloride ion, and then utilize Low-cost slaked lime dosing, solid-liquid separation, flocculation and sedimentation process, calcium chloride clear liquid and magnesium hydroxide solid are obtained. After drying, calcium chloride and magnesium hydroxide products can be separately produced to realize waste turning into treasure and solve desulfurization at the same time. The problem of wastewater discharge.

Summary of the invention

The object of the present invention is to provide a wet desulfurization wastewater resource treatment system and a treatment method thereof, which solve the technical problem that the prior art is easy to cause water pollution and waste; and solve the complicated technical process and high operation cost of the prior art. technical problem.

To achieve the above object, the present invention adopts the following technical solutions:

A wet desulfurization wastewater resource treatment system, comprising: a sequential desulfurization wastewater pretreatment system, a primary quenching and tempering system, a depth modulation system and a solid calcium chloride production system, wherein the desulfurization wastewater pretreatment system comprises a concentration tower and a desulfurization front flue and a desulfurization waste water storage tank respectively connected to the concentration tower, wherein the lower part of the concentration tower is connected to the pre-desulfurization flue through a booster fan, and the flue-before-extracting flue is connected to the pre-desulfurization flue The upper part is connected to the top of the concentration tower through a pipeline, and the desulfurization waste water storage tank and the lower tower body of the concentration tower are connected by a transfer pump, and the upper tower body of the concentration tower is provided with a mist eliminator and a spray layer from top to bottom. The spray layer is connected to the lower tower body of the concentration tower through a circulation pump disposed outside the concentration tower;

The primary quenching and tempering system comprises a thick slurry discharge pump, a first-stage tempering tank and a solid-liquid separation device connected in sequence according to the direction of the water flow, and the thick slurry discharge pump is connected to the bottom of the concentration tower, the first-stage tempering box Connected to the dosing device, the solid-liquid separating device is connected to the collecting tank;

The depth modulation system includes a depth modulation tank, a clarification flocculation tank and a solid-liquid separation device which are sequentially connected in accordance with the direction of the water flow. Secondly, the depth modulation tank is simultaneously connected to the solid-liquid separation device and the dosing device 2, and the clarification flocculation tank and the solid-liquid separation device 2 are both connected to the collection tank 2;

The solid calcium chloride production system comprises a dryer, a drying fan and a collecting tank 3. The dryer is connected to a depth modulation system through a solid-liquid separation device 2, and the dryer and the collecting tank 3 are both connected to the dryer.

Further preferably, the spray layer is at least two layers, and a single-phase hollow cone pressure nozzle is disposed thereon, and the spray droplet size is 1500-1400 micrometers.

Further, the mist eliminator is at least one layer and is a mechanical defogger.

In addition, the dosing device is internally provided with slaked lime, and the dosing device 2 is a multi-stage series dosing device, which is provided with slaked lime and a flocculating agent.

More preferably, the collection tank one is a primary waste collection tank, the collection tank two is a magnesium hydroxide collection tank, and the collection tank three is a calcium chloride collection tank.

A method for treating a wet desulfurization wastewater resource treatment system, comprising the steps of:

Step 1: Pretreatment of desulfurization wastewater: The desulfurization wastewater in the desulfurization wastewater storage tank is pumped into the concentration tower through the transfer pump, and the high temperature flue gas in the flue before desulfurization is pumped into the concentration tower through the booster fan, and the high temperature flue gas is sequentially After passing through the spray layer and the demister in the concentration tower, the flue gas is returned to the pre-desulfurization flue through the pipeline disposed at the top of the concentration tower. After the desulfurization waste water is sprayed through the spray layer, the high-temperature flue gas evaporates the desulfurization waste water into a concentrated waste liquid;

Step 2: Primary quenching and tempering of desulfurization wastewater: After the pretreatment of the desulfurization wastewater is carried out in step 1, the concentrated waste liquid is discharged into the first-stage tempering tank through the thick slurry discharge pump, and the slaked lime contained in the dosing device is adjusted to the first stage. The desulfurization waste water in the mass box is quenched and tempered, and after being treated by the solid-liquid separation device, the first-stage filtration liquid and the first-stage waste residue are separated;

Step 3: Deep quenching and tempering of desulfurization wastewater: after the first stage of quenching and smelting treatment of the desulfurization wastewater, the first-stage filtration liquid Entering the depth modulation box, using the slaked lime and flocculating agent in the dosing device 2 for quenching and tempering, after quenching and tempering, the calcium chloride clear liquid is separated from the magnesium hydroxide solid by the solid-liquid clarification flocculation tank and the separating device;

Step 4: Solid calcium chloride formation: After the desulfurization waste water is subjected to the deep quenching and tempering treatment in the third step, the calcium chloride clear liquid enters the desiccator, and the calcium chloride clear liquid is dried by hot air through a drying fan to form a calcium chloride salt. At this point, the desulfurization wastewater resource treatment is completed.

Further preferably, in the first step, the temperature of the high-temperature flue gas is 100-150 ° C, the flow rate in the tower is 2-5 m/s; the spray liquid-gas ratio of the spray layer is 1-10 L/M ³ The concentrated waste liquid has a pH value of 0.2 to 2.0 and a chloride ion concentration of 50,000 mg/L to 250,000 mg/L, and is a strongly acidic and highly corrosive liquid.

In addition, the primary filtration liquid in the second step has a pH of 4-6.

More preferably, in the third step, the primary filtration liquid is tempered by the slaked lime and the flocculating agent in the dosing device 2, and the pH is 9 to 11.5.

Compared with the prior art, the present invention has the following characteristics and beneficial effects:

The invention utilizes waste heat of flue gas to realize evaporation of waste water, completes the concentration process of desulfurization waste water without additional heat source, and solves the technical problem of the influence of complex and variable waste water components on the process technology.

The invention utilizes chlorine ions and magnesium ions in the waste water to be medicated and tempered by low-cost slaked lime, and finally forms calcium chloride and magnesium hydroxide products, thereby realizing the resource utilization of the waste water.

The process of the invention is simple, the running cost is far lower than the conventional wastewater treatment process such as membrane treatment and multi-effect evaporation, and the pure water in the wastewater can be recovered, and the water consumption of the subsequent desulfurization system is reduced.

The invention has the characteristics of safety, application, etc., and has good promotion and practical value, and will have good economic benefits after extensive application and application.

DRAWINGS

1 is a schematic structural view of a wet desulfurization wastewater resource treatment system according to the present invention;

Fig. 2 is a flow chart showing the operation of the present invention for the desulfurization wastewater resource treatment.

LIST OF REFERENCE NUMERALS: 1-concentration tower; 2-desulfurization front flue; 3-desulfurization wastewater storage tank; 4-booster fan; 5-feed pump; 6-demister; 7-spray layer; 8-cycle pump ; 9 - thick slurry discharge pump; 10 - first-grade conditioning box; 11 - solid-liquid separation device 1; 12 - dosing device 1; 13 - depth modulation box; 14 - clarification flocculation tank; 15 - solid-liquid separation device ; 16 - collection tank one; 17 - collection tank two; 18 - dryer; 19 - drying fan; 20 - collection tank three; 21 - dosing device two.

detailed description

The present invention will be further described in conjunction with the accompanying drawings in order to facilitate the understanding of the technical means, the innovative features, and the objects and advantages of the present invention.

The embodiments described herein are illustrative of specific embodiments of the invention, and are intended to be illustrative of the embodiments of the invention. In addition to the implementations described herein, those skilled in the art will be able to devise other obvious technical solutions based on the disclosure of the present application and the specification, which includes any obvious use of the embodiments described herein. Replacement and modification of the technical solution.

A wet desulfurization wastewater resource treatment system, as shown in Fig. 1, comprises a sequential desulfurization wastewater pretreatment system, a primary quenching and tempering system, a depth modulation system and a solid calcium chloride production system, and the desulfurization wastewater pretreatment system includes The concentration tower 1 and the desulfurization front flue 2 and the desulfurization waste water storage tank 3 connected to the concentration tower 1 are connected to the desulfurization front flue 2 through the booster fan 4, and the flue gas before desulfurization and the flue gas before desulfurization The upper part of the connecting portion of the channel 2 is connected to the top of the concentration tower 1 through a pipeline, and the desulfurized wastewater storage tank 3 and the lower tower body of the concentration tower 1 are connected by a transfer pump 5, and the upper tower body of the concentration tower 1 is from the upper The demister 6 and the spray layer 7 are provided in sequence, and the demister 6 is at least one layer, which is a mechanical demister, and the spray layer 7 passes through the circulation pump 8 and the concentration tower 1 which are disposed outside the concentration tower 1. The lower tower body is connected, and the spray layer 7 is at least two layers, and a single-phase hollow cone pressure nozzle is arranged thereon, and the spray droplet size is 1500-1400 micrometers.

The first-stage quenching and tempering system comprises a thick slurry discharge pump 9, a first-stage tempering tank 10 and a solid-liquid separation device 11 connected in sequence according to the direction of the water flow, and the thick slurry discharge pump 9 is connected to the bottom of the concentration tower 1, and the first-stage tempering tank 10 Connected to the dosing device 12, the solid-liquid separating device 11 is connected to the collecting tank 16 and the collecting trough 16 is a primary waste collecting tank, and the dosing device 12 is provided with slaked lime.

The depth modulation system includes a depth modulation tank 13 connected in sequence with the flow direction, a clarification flocculation tank 14 and a solid-liquid separation device 2, and the depth modulation tank 13 is simultaneously connected to the solid-liquid separation device 11 and the dosing device 21, and the clarification flocculation tank 14 and the solid-liquid separation device 2 are connected to the collecting tank 2, and the dosing device 21 is a multi-stage series dosing device, which is provided with slaked lime and flocculating agent, and the collecting trough 21 is a magnesium hydroxide collecting trough.

The solid calcium chloride generating system comprises a dryer 18, a drying fan 19 and a collecting tank 30, and the dryer 18 is connected to the depth modulation system through a solid-liquid separating device 2, and the dryer 18 and the collecting tanks 30 are connected to the dryer 18. The collection tank three 20 is a calcium chloride collection tank.

The utility model also relates to a processing method of a wet desulfurization wastewater resource treatment system, which is characterized in that, as shown in FIG. 2, the following steps are included:

Step 1: Pretreatment of desulfurization wastewater: The desulfurization wastewater in the desulfurization wastewater storage tank 3 is pumped into the concentration tower 1 through the transfer pump 5, and the high temperature flue gas in the flue gas 2 before desulfurization is pumped into the concentration tower through the booster fan 4. In the middle, the high-temperature flue gas passes through the spray layer 7 and the demister 8 in the concentration tower 1 and then returns to the pre-desulfurization flue 2 through the pipeline disposed at the top of the concentration tower 1, and the desulfurized waste water is sprayed through the spray layer 7, The high-temperature flue gas evaporates the desulfurization wastewater into a concentrated waste liquid, wherein the temperature of the high-temperature flue gas is 100-150 ° C, and the flow rate in the tower is 2-5 m/s; the spray liquid gas of the spray layer (7) The ratio is 1 to 10 L/M ³ ; the concentrated waste liquid has a pH of 0.2 to 2.0, and the chloride ion concentration is 50,000 mg/L to 250,000 mg/L, which is a strongly acidic and highly corrosive liquid.

Step 2: Primary quenching and tempering of desulfurization wastewater: After the pretreatment of the desulfurization wastewater is carried out in step 1, the concentrated waste liquid passes through the thick slurry discharge pump 9 and enters the primary tempering tank 10, and the slaked lime pair installed in the dosing device 12 is used. The desulfurization waste water in the first-stage tempering tank 10 is quenched and tempered, and after being tempered and tempered, the first-stage filtration liquid and the first-stage waste slag are separated by the solid-liquid separation device 11 , and the pH of the first-stage filtration liquid is 4 ～. 6.

Step 3: Deep quenching and tempering of the desulfurization wastewater: after the desulfurization waste water is subjected to the first-stage quenching and tempering treatment in the second step, the first-stage filtration liquid enters the depth modulation tank 13 and is tempered by the slaked lime and the flocculating agent in the dosing device 21; The pH after quenching and tempering is 9 to 11.5. After the quenching and tempering, the calcium chloride clear liquid is separated from the magnesium hydroxide solid by the solid-liquid clarification flocculation tank 14 and the separation device 2, and the magnesium hydroxide solid enters the collecting tank 2-17.

Step 4: Solid calcium chloride formation: After the desulfurization waste water is subjected to the deep quenching and tempering treatment in the third step, the calcium chloride clear liquid enters the dryer 11 , and the calcium chloride clear liquid is dried by hot air through the drying fan 19 to form calcium chloride. The salt and calcium chloride salt enter the collection tank 30, and the desulfurization wastewater treatment is completed.

The following three examples were used to treat the desulfurization wastewater by the treatment method of the present invention, and the specific results are as follows:

Embodiment 1: The desulfurization device of a 1000 MW coal-fired thermal power plant has a wastewater output of 15 t/h, wherein the wastewater components are as follows:

Table 1. Desulfurization wastewater components in Example 1.

pH值pH value	5.395.39
含固量 Solid content	5％5%
Ca(mg/L)Ca(mg/L)	13141314
Mg(mg/L)Mg(mg/L)	93189318
Fe(mg/L)Fe(mg/L)	00
Na(mg/L)Na(mg/L)	166166
K(mg/L)K (mg/L)	186186
B(mg/L)B (mg/L)	772772

Mn(mg/L)Mn (mg/L)	8585
F^-(mg/L)F ^- (mg/L)	--
Cl^-(mg/L)Cl ^- (mg/L)	25144.1525,144.15
SO₄ ^2-(mg/L)SO ₄ ^2- (mg/L)	4780.134780.13

The flue gas of 120 °C is used as the concentration medium, and the flue gas volume is 360,000 NM ³ /h. The concentrated water is concentrated in the flue gas concentration tower, and the designed concentration ratio is 1:10. The concentration tower has a diameter of 6.5 meters and a height of 30 meters. After concentration, the continuous slurry discharge amount is 1.5t/h. The concentration of concentrated slurry is 1.0, the chloride ion concentration is 120,000mg/L, and the magnesium ion concentration is 40000mg/L. It has strong acid corrosion characteristics.

The concentrated slurry is adjusted to a pH of 7.0 by a first-stage slaked lime addition, and a large amount of calcium sulfate is precipitated to form a sludge; after passing through the solid-liquid separation device, the filtrate is subjected to deep dosing treatment, and the pH is slowly controlled to rise to 10.0, and a large amount of hydroxide is used. Magnesium precipitates and simultaneously forms a calcium chloride serum. After the flocculation precipitation and solid-liquid separation device, the calcium chloride solution and the solid magnesium hydroxide are respectively obtained, and the calcium chloride solution is evaporated by a drier to obtain a calcium chloride solid.

The purity of the final product calcium chloride product is 85% (calculated as anhydrous calcium chloride); the purity of magnesium hydroxide is 81% (dry basis).

The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalents, improvements, etc., which are within the spirit and scope of the present invention, should be included in the protection of the present invention. Within the scope.

Claims

A wet desulfurization wastewater resource treatment system, comprising: a sequential desulfurization wastewater pretreatment system, a primary quenching and tempering system, a depth modulation system and a solid calcium chloride production system, wherein the desulfurization wastewater pretreatment system comprises a concentration tower (1) and a pre-desulfurization flue (2) and a desulfurization waste water storage tank (3) both connected to the concentration tower (1), and the lower part of the concentration tower (1) passes through the booster fan (4) and the pre-desulfurization smoke The road (2) is connected, and the upper portion of the pre-desulfurization flue (2) and the portion adjacent to the pre-desulfurization flue (2) are connected to the top of the concentration tower (1) through a pipeline, and the desulfurization wastewater storage tank (3) is The lower tower body of the concentration tower (1) is connected by a transfer pump (5), and the upper tower body of the concentration tower (1) is provided with a mist eliminator (6) and a spray layer (7) from top to bottom. The spray layer (7) is connected to the lower tower body of the concentration tower (1) through a circulation pump (8) disposed outside the concentration tower (1); the primary quenching and tempering system includes a thick slurry discharged in sequence in accordance with the direction of the water flow. a pump (9), a primary tempering tank (10) and a solid-liquid separation device (11), the thick slurry discharge pump (9) is connected to the bottom of the concentration tower (1), the primary tempering tank (10) ) and dosing device (12) connected, the solid-liquid separation device (11) is connected to the collection tank one (16); the depth modulation system comprises a depth modulation tank (13), a clarification flocculation tank (14) and a condensing flocculation tank (14) which are sequentially connected in accordance with the direction of the water flow. a solid-liquid separation device (15), the depth modulation tank (13) is simultaneously connected to the solid-liquid separation device (11) and the dosing device (21), the clarification flocculation tank (14) and the solid-liquid separation device The two (15) are all connected to the collecting tank two (17); the solid calcium chloride generating system comprises a dryer (18), a drying fan (19) and a collecting tank three (20), and the dryer (18) passes The solid-liquid separation device (15) is connected to a depth modulation system, and the dryer (18) and the collection tank three (20) are both connected to the dryer (18).
A wet desulfurization wastewater resource treatment system according to claim 1, characterized in that the spray layer (7) is at least two layers, and a single-phase hollow cone pressure nozzle is arranged thereon, and the spray droplets are sprayed. The diameter is 1500 ~ 1400 microns.
A wet desulfurization wastewater resource treatment system according to claim 1, wherein the mist eliminator (6) is at least one layer and is a mechanical mist eliminator.
A wet desulfurization wastewater resource treatment system according to claim 1, wherein said dosing device (12) is provided with slaked lime, and said dosing device (21) is a multi-stage series dosing The device is equipped with slaked lime and flocculant.
A wet desulfurization wastewater resource treatment system according to claim 1, wherein said collection tank (16) is a primary waste collection tank, and said collection tank two (17) is hydrogen hydroxide. A magnesium collection tank, the collection tank three (20) being a calcium chloride collection tank.
The method for processing a wet desulfurization wastewater resource treatment system according to any one of claims 1 to 5, comprising the steps of:

Step 1: Pretreatment of desulfurization wastewater: The desulfurization wastewater in the desulfurization wastewater storage tank (3) is pumped into the concentration tower (1) through the transfer pump (5), and the flue gas before desulfurization is passed through the booster fan (4) (2) High-temperature flue gas is pumped into the concentration tower (1), high The warm flue gas passes through the spray layer (7) and the demister (8) in the concentration tower (1), and then returns to the pre-desulfurization flue (2) through a pipe disposed at the top of the concentration tower (1), and the desulfurized waste water is sprayed. After the shower layer (7) is sprayed, the high-temperature flue gas evaporates the desulfurization waste water into a concentrated waste liquid;

Step 2: Primary quenching and tempering of the desulfurization wastewater: after the pretreatment of the desulfurization wastewater is carried out in step 1, the concentrated waste liquid passes through the thick slurry discharge pump (9) to enter the first-stage tempering tank (10), and is installed in the dosing device ( 12) The slaked lime in the first-grade tempering tank (10) is quenched and tempered, and after being tempered, the first-stage filtering liquid and the first-stage slag are separated after being treated by the solid-liquid separation device (11);

Step 3: Deep quenching and tempering of desulfurization wastewater: After the desulfurization wastewater is treated by the first-stage quenching and tempering treatment in step two, the first-stage filtration liquid enters the depth modulation tank (13), and the slaked lime and flocculant in the dosing device (21) are utilized. After quenching and tempering, after the quenching and tempering, the calcium chloride clear liquid is separated from the magnesium hydroxide solid by the solid-liquid clarification flocculation tank (14) and the separation device two (15);

Step 4: Solid calcium chloride formation: After the desulfurization waste water is subjected to the deep quenching and tempering treatment in the third step, the calcium chloride clear liquid enters the dryer (11), and the calcium chloride clear liquid is dried by hot air through a drying fan (19). The calcium chloride salt is formed, and the desulfurization wastewater is recycled to this point.
The method for processing a wet desulfurization wastewater resource treatment system according to claim 6, wherein the temperature of the high temperature flue gas in the step 1 is 100 to 150 ° C, and the flow rate in the tower is 2 to 5m / s; the spray layer (7) spray liquid gas ratio of 1 ~ 10L / M3; the concentrated waste liquid PH value of 0.2 ~ 2.0, chloride ion concentration of 50000mg / L ~ 250,000mg / L, is strong acid high Corrosive liquid.
The method for treating a wet desulfurization wastewater resource treatment system according to claim 6, wherein the pH of the primary filtration liquid in the second step is 4-6.
The method for treating a wet desulfurization wastewater resource treatment system according to any one of claims 7 or 8, wherein in the step (3), the first-stage filtration liquid is used in the dosing device (21). After slaked lime and flocculant are tempered, the pH is 9 to 11.5.