Efficient ammonia nitrogen stripping process system

Abstract

The invention relates to an efficient ammonia-nitrogen stripping process system, aiming at solving the problems that the existing high-ammonia-nitrogen wastewater treatment process generally neglects precipitation control of metal ions in alkali adjustment reaction, and long-term operation causes hardening of a filler layer, so that pressure loss is increased and stripping efficiency is attenuated; in order to solve the problems of low ammonia nitrogen removal efficiency and low ammonia nitrogen removal efficiency in a single air stripping process, a precipitation unit is additionally arranged between an alkali adjusting unit and a high-efficiency ammonia nitrogen circulating air stripping unit, so that a large amount of precipitates generated in the alkali adjusting process are prevented from blocking a filler in the air stripping unit; meanwhile, a backflow device is additionally arranged in the ammonia nitrogen stripping link, circulation of the water to be treated in the ammonia nitrogen stripping link is enhanced, the ammonia nitrogen stripping reaction is repeatedly carried out, and the ammonia nitrogen removal efficiency is high and the ammonia nitrogen removal is more thorough. The invention has the advantages of good treatment effect, stable process system operation, low failure rate, low operation cost, small influence of water quality and water quantity change of water to be treated, and stable effluent quality.

Description

Technical Field

[0001] The invention belongs to the field of water treatment, and in particular relates to an ammonia nitrogen efficient stripping process system. Background Art

[0002] In recent years, with the development of industrial scale and the acceleration of urbanization, high-ammonia nitrogen wastewater generated by industries such as petrochemicals, landfill leachate, and coking has become a global environmental governance problem. According to statistics, my country produces more than 2 billion tons of such wastewater each year (China Water Pollution Prevention and Control Blue Book 2023), of which nearly 40% fails to meet discharge standards. This type of wastewater not only contains high concentrations of ammonia nitrogen, but is often accompanied by high salt, heavy metals, and difficult-to-degrade organic matter, and traditional treatment technologies face severe challenges.

[0003] First, the existing gas stripping process generally ignores the precipitation control of metal ions in the alkali adjustment reaction, resulting in insoluble substances such as CaCO3 and Mg(OH)2 directly entering the stripping tower, causing the packing layer to compact after long-term operation, resulting in increased pressure loss and reduced stripping efficiency. In the technical solution disclosed in CN110627299A (a high-ammonia nitrogen wastewater treatment system), although the pH adjustment operation is mentioned, no dedicated precipitation unit is set, resulting in the stripping tower packing in the patent embodiment requiring acid washing and maintenance every 3 months of operation, with a downtime of 36 hours / time. CN113698026A (high-salt wastewater deammonification device) also has technical defects, and its specification clearly admits in paragraph

[0024] : "During the operation of the system, the porosity of the packing gradually decreases with the accumulation of scale, and the deammonification efficiency fluctuates periodically."

[0004] In addition, traditional stripping technology mostly adopts a one-way design, and the ammonia nitrogen mass transfer efficiency is limited by the gas-liquid contact time. In order to solve the efficiency problem, CN113636705A (multi-stage gas stripping deammonification device) adopts a three-stage stripping tower in series, which leads to a 42% increase in system footprint and a 67% increase in energy consumption. Claim 1 of the patent clearly defines: "At least two stages of stripping towers are connected in sequence." CN114105241A (a method for improving the efficiency of stripping towers) attempts to improve efficiency by modifying the internal components of the tower, but its specification paragraph

[0038] points out: "The maximum ammonia nitrogen removal rate under single tower operation is only 83.7%, which requires subsequent biochemical process supplementation treatment." Furthermore, paragraph

[0015] of the CN110627299A specification states: "The wastewater after stripping still contains about 20% of residual ammonia nitrogen that needs further treatment", highlighting the limitations of a single stripping process.

[0005] Based on the above analysis, the present invention creatively reconstructs the ammonia nitrogen stripping process: a precipitation unit is added between the alkali adjustment unit and the high-efficiency ammonia nitrogen circulation stripping unit to avoid clogging of the filler in the stripping unit by a large amount of precipitate generated during the alkali adjustment process; at the same time, a reflux device is added to the ammonia nitrogen stripping link to strengthen the circulation of the water to be treated in the ammonia nitrogen stripping link, and the ammonia nitrogen stripping reaction is repeatedly performed, so that the ammonia nitrogen removal efficiency is higher and the removal is more thorough under the premise of similar costs, which fundamentally solves the technical barriers that have plagued the industry for many years. Summary of the invention

[0006] The present invention increases the circulation of the water to be treated in the ammonia nitrogen stripping link by adding a reflux device, repeatedly performs the ammonia nitrogen stripping reaction, and makes the ammonia nitrogen removal efficiency high and more thorough; at the same time, the present invention increases the precipitation unit between the alkali adjustment unit and the high-efficiency ammonia nitrogen circulation stripping unit, thereby avoiding the blockage of the filler in the stripping unit by a large amount of precipitation generated during the alkali adjustment process. The present invention has good treatment effect, stable operation of the process system, low failure rate, low operation cost, little influence by the changes in the water quality and quantity of the water to be treated, and stable effluent water quality.

[0007] As conceived above, the technical solution adopted by the present invention to solve the above problems is: An ammonia nitrogen efficient air stripping process system, characterized in that the ammonia nitrogen efficient air stripping process system comprises: a pH adjustment module, a circulation enhanced air stripping module and a pH callback module connected in sequence; The pH adjustment module comprises an alkali adjustment unit 1 and a pre-precipitation tank 16, wherein the alkali adjustment unit 1 comprises an automatic alkali solution dosing system 6 and an alkalinity detection control device 11; the circulation enhanced stripping module comprises a stripping tower 35 and a reflux water tank 37 connected in parallel therewith, wherein the stripping tower 35 has a packing layer and a support structure composed of multiple layers of packing 35b, and is externally configured with a gas booster 24, an aeration system and a reflux pump 38; the pH callback module comprises an automatic acid solution dosing system 29 and an acidity detection control device 32; The operation method of the ammonia nitrogen efficient stripping process system is as follows: S1. Dynamic alkali adjustment reaction: The pH of the water to be treated is controlled in the range of 8-12 and maintained for ≥0.5h. PID intelligently adjusts the alkali addition flow rate to achieve closed-loop control of alkali solution addition; S2. Separation by sedimentation: chemical precipitation is first performed in the pre-sedimentation tank 16, and the precipitate is collected for solid waste treatment; S3 enhanced cycle stripping: in the stripping tower 35 is implemented simultaneously: through the gas booster 24 to inject gas water ratio 1000-8000 times the air flow; using the reflux pump 38 so that the treatment liquid cycle frequency of 3-8 times; S4. Dynamic acid addition callback: adjust the outlet water pH to 5-9, and PID intelligently adjusts the acid addition flow to achieve closed-loop control of acid dosage.

[0008] The alkali adjustment unit 1 is connected to the pre-sedimentation tank 16 .

[0009] The stripping tower 35 comprises: a gas-liquid mixing chamber 35a at the bottom of the tower body, with a gas booster 24 configured externally; fillers 35b are arranged in layers in the middle, with a spacing of 0.5-2.0m between each layer; a spray water distribution device 35c is arranged at the top of the tower, and the stripping tower 35 is externally connected to a waste gas treatment pipeline.

[0010] Compared with the prior art, the present invention has the following beneficial effects: A reflux device is added to the ammonia nitrogen stripping step to strengthen the circulation of the water to be treated in the ammonia nitrogen stripping step, and the ammonia nitrogen stripping reaction is repeated to make the ammonia nitrogen removal efficiency high and more thorough.

[0011] The present invention adds a precipitation unit between the alkali adjustment unit and the high-efficiency ammonia nitrogen circulation stripping unit, thereby preventing a large amount of precipitation generated during the alkali adjustment process from clogging the filler in the stripping unit.

[0012] The invention has good treatment effect, stable operation of the process system, low failure rate, low operation cost, little influence by changes in water quality and quantity of water to be treated, and stable effluent water quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The invention discloses a process flow chart of an ammonia nitrogen efficient stripping process system.

[0014] Figure 2 The present invention is a schematic diagram of system connection of an ammonia nitrogen efficient stripping process system. DETAILED DESCRIPTION

[0015] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Specific implementation method 1

[0016] Combination Figure 1~Figure 2 This embodiment will be described.

[0017] In a sewage treatment center of a chemical park, the initial ammonia nitrogen concentration of wastewater is 450 mg / L, and the daily processing capacity is 1,500 tons.

[0018] System configuration: The ammonia nitrogen efficient stripping process system of the present invention is adopted, including a pH adjustment module, a circulation enhanced stripping module and a pH callback module which are connected in sequence.

[0019] The system operates as follows: 1. Dynamic alkaline adjustment reaction (pH adjustment module): Alkali adjustment unit 1: NaOH solution is added through the alkali solution automatic dosing system 6, and combined with the real-time data of the alkalinity detection and control device 11, the PID intelligently adjusts the alkali addition flow rate to 80 L / h, stabilizes the pH to 10.5±0.2 and maintains it for 1.2 hours, and the closed-loop control error is <3%; Pre-sedimentation tank 16: After alkali adjustment, the wastewater enters the sedimentation tank, and the moisture content of the sedimentation sludge is ≤35%, which is transported out as solid waste; 2. Enhanced circulation stripping (circulation enhanced stripping module): Stripping tower 35: 4 layers of ball ring packing 35b are set, with a layer spacing of 1.2 m; the gas booster device 24 introduces air into the gas-liquid mixing chamber 35a at a gas-water ratio of 6000:1, and the tower top spray water distribution device 35c evenly distributes the wastewater flow rate; Reflux water tank 37 and reflux pump 38: the treated liquid circulates 5 times (total residence time 45 minutes), the ammonia nitrogen concentration drops to 18 mg / L after stripping, and the waste gas at the top of the tower is treated by activated carbon adsorption to meet the emission standards; 3. Dynamic acid addition callback (pH callback module): Automatic acid dosing system 29: Add dilute sulfuric acid (H2SO4) to the outlet water. Based on the feedback from the acidity detection control device 32, the PID adjustment consumption is 15 L / ton of water, and the final pH = 6.5 ± 0.3. Specific implementation method 2

[0020] Combination Figure 1~Figure 2 This embodiment will be described.

[0021] The ammonia nitrogen content of the digestate of a municipal sewage treatment plant is 1200 mg / L, and the treatment scale is 800 tons / day.

[0022] System configuration: The ammonia nitrogen efficient stripping process system of the present invention is adopted, including a pH adjustment module, a circulation enhanced stripping module and a pH callback module which are connected in sequence.

[0023] The system operates as follows: 1. Dynamic alkali adjustment (pH adjustment module): Alkali adjustment unit 1: adding Ca(OH)2 slurry, the alkalinity detection and control device 11 dynamically corrects the pH to 11.8±0.1 for 1 hour, the PID response time is ≤5 seconds, and the alkali solution addition speed is 120 L / h; Pre-sedimentation tank 16: PAC is added to remove Ca²⁺ and Mg²⁺. The moisture content of the mud cake after plate and frame filter pressing is ≤40%, which is used as raw material for building materials; 2. Enhanced stripping (circulation enhanced stripping module): Stripping tower 35: multi-layer ceramic corrugated packing 35b is arranged in layers with a spacing of 0.8 m; the gas booster 24 inputs superheated steam with a gas-water ratio of 2500:1 from the bottom of the tower to improve the ammonia nitrogen desorption efficiency; Reflux pump 38: forced circulation 7 times (total time 60 minutes), ammonia nitrogen concentration dropped from 1200 mg / L to 85 mg / L, removal rate 92%; 3. pH callback (pH callback module): Acid dosing system 29: Add HCl in a closed loop to control pH to 7.0±0.2, and the acid dosing error is ≤2%. Specific implementation method three

[0024] Combination Figure 1~Figure 2 This embodiment will be described.

[0025] A semiconductor factory produces ammonia-containing cleaning wastewater with an initial ammonia nitrogen concentration of 2100 mg / L and a treatment capacity of 200 tons / day.

[0026] System configuration: The ammonia nitrogen efficient air stripping process system of the present invention is adopted, including a pH adjustment module, a circulation enhanced air stripping module and a pH callback module which are connected in sequence.

[0027] The system operates as follows: 1. Alkali adjustment and precipitation (pH adjustment module): Alkali adjustment unit 1: KOH solution is added by PID intelligently (rate 50 L / h), pH is controlled to 9.5±0.3 and maintained for 2 hours; Pre-sedimentation tank 16: for sedimentation, and for transporting out the solid waste generated after centrifugal dehydration; 2. Circulation stripping (circulation enhanced stripping module): Stripping tower 35: equipped with 5 layers of multi-faceted hollow ball fillers 35b, with a layer spacing of 1.5 m; the gas-liquid mixing chamber 35a inputs air with a gas-water ratio of 8000:1 through the gas booster 24, and the ozone-ultraviolet light combined treatment of the tower top exhaust gas; Reflux pump 38 and reflux water tank 37: the treated liquid is forced to circulate 8 times (staying for 75 minutes), and the final ammonia nitrogen concentration is ≤10mg / L; 3. pH callback (pH callback module): Automatic acid dosing system 29: Based on the signal of the acidity detection control device 32, HNO3 is added to adjust the pH to 5.8±0.2, with a consumption of 8 L / ton of water.

Claims

1. An efficient ammonia nitrogen stripping process system, characterized in that: The ammonia nitrogen efficient air stripping process system comprises: a pH adjustment module, a circulation enhanced air stripping module and a pH callback module which are connected in sequence; The pH adjustment module comprises an alkali adjustment unit (1) and a pre-precipitation tank (16), wherein the alkali adjustment unit (1) comprises an automatic alkali solution dosing system (6) and an alkalinity detection control device (11); the circulation enhanced stripping module comprises a stripping tower (35) and a reflux water tank (37) connected in parallel therewith, wherein the stripping tower (35) has a packing layer and a support structure composed of multiple layers of packing (35b) built in, and is externally equipped with a gas booster (24), an aeration system and a reflux pump (38); the pH readjustment module comprises an automatic acid solution dosing system (29) and an acidity detection control device (32); The operation method of the ammonia nitrogen efficient stripping process system is as follows: S1. Dynamic alkali adjustment reaction: The pH of the water to be treated is controlled in the range of 8-12 and maintained for ≥0.5h. PID intelligently adjusts the alkali addition flow rate to achieve closed-loop control of alkali solution addition; S2. Sedimentation and separation: chemical precipitation is first performed in the pre-sedimentation tank (16), and the precipitate is collected for solid waste treatment; S3. Enhanced cycle stripping: Simultaneously implemented in the stripping tower (35): injecting a gas-water ratio of 1000-8000 times of air through a gas booster (24); using a reflux pump (38) to circulate the treated liquid 3-8 times; S4. Dynamic acid addition callback: adjust the outlet water pH to 5-9, and PID intelligently adjusts the acid addition flow to achieve closed-loop control of acid dosage.

2. The ammonia nitrogen efficient stripping process system according to claim 1 is characterized in that: The alkali adjustment unit (1) is connected to the pre-sedimentation tank (16).

3. The ammonia nitrogen efficient stripping process system according to claim 1, characterized in that: The stripping tower (35) comprises: a gas-liquid mixing chamber (35a) at the bottom of the tower body, with a gas booster device (24) arranged outside; fillers (35b) arranged in layers in the middle, with a spacing of 0.5-2.0 m between each layer; a spray water distribution device (35c) arranged at the top of the tower, and the stripping tower (35) is externally connected to a waste gas treatment pipeline.

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