Wastewater treatment
For the chemical industry, especially for the coking and petrochemical wastewater, the low concentration coking and petrochemical wastewater has been treated by the former physical-chemical method, cod is generally over 100 mg/L. The treatment of this kind of wastewater is extremely difficult. When the granular activated carbon adsorption method is used for treatment, only when the absorber design is reasonable can the pollutant control effect be achieved (the COD of drainage water is reduced to the target control value of 30-50 mg/L) .
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The design of liquid flow rate and empty tower contact time
Ideally, the carbon adsorber is required to be designed in the“Shortest possible mass transfer zone (Mtz)” type to avoid excessive“Penetration” and ensure the reliable operation of the adsorbent. To achieve the operational goal of shortening the mass transfer zone, the optional measures are: reducing the empty column rate (or the linear velocity of the fluid in the activated carbon bed) , and/or designing a higher adsorption bed, to extend the residence time of the fluid in the adsorber. Figure 1 shows the effect of the linear velocity of the fluid on the mass transfer band in the activated carbon bed.
Figure 1: effect of the linear velocity of liquid in the bed on the mass transfer band (Source: CHEMVIRON method for laboratory evaluation of liquid-phase adsorption of activated carbon)
From Fig. 1, it can be seen that the higher the linear velocity of the fluid in the carbon bed, the smaller the slope of the“Adsorption wave” and the larger/wider the mass transfer region, and the easier the adsorption penetration occurs, the absorption wave becomes steeper, the mass transfer area shortens, and the utilization ratio of carbon bed is higher, the adsorption removal effect of pollutants is more stable.
Depending on the type and nature of the contaminant components, the performance of the adsorbent activated carbon, and the concentration of the contaminant components, for general wastewater treatment, the“Empty tower contact time (EBCT, which represents the flow rate, the slower the flow, the longer the contact time)” design values for wastewater in the activated carbon bed range from 20 to 120 minutes (information: Calgon Absorber Design Guide) , in order to ensure the effect of wastewater treatment and the stability of effluent quality, the EBCT of 20-30 minutes is used to design the adsorption device for wastewater advanced treatment project.
2.The design of pulsating bed adsorber is recommended
From the point of view of mass transfer zone, the ideal“Adsorption wave” is a vertical line (see Figure 1) , but in actual operation, especially for the refractory coking and petrochemical industrial wastewater to be treated by this project, as the uniformity of activated carbon particles in the adsorbent can not reach an ideal distribution, the uniformity of the loading of the adsorbent can not be controlled to an ideal level, and the composition and concentration of pollutants inevitably fluctuate, the mass transfer zone in the adsorber will become“Flat” gradually or suddenly, and the mass transfer zone will become longer. If a fixed-bed carbon adsorber design is used, and if the thickness of the unsaturated carbon layer is insufficient, should appear at any time“Adsorption penetration” phenomenon, resulting in unqualified effluent.
The pulsating bed adsorber adopts the reverse movement mode of the carbon layer and the fluid, and the saturated carbon layer is removed intermittently from the adsorber and regenerated, in theory, pollutants are always exposed to a layer of“Fresh” activated carbon, which has the same adsorption properties as the original carbon, as the whole bed height is“Fresh carbon layer”, and will not occur“Adsorption penetration” phenomenon, to ensure that the effluent quality is still in a stable state.
Figure 2 shows a comparison of the operating principles of a fixed-bed adsorber and a pulsating-bed adsorber, and figure 3 shows the variation of effluent quality with the operation of different adsorbers.
Fig. 2: Schematic diagram of fixed-bed adsorber (left) and pulsating-bed adsorber (right)(source: design of Calgon Liquid adsorption system)
Figure 3: the relationship between product quality and the number of switching operations of the fixed bed adsorber (left) and the pulsatile frequency of the pulsatile adsorber (right)(source: design of the CALGON liquid phase adsorption technology system)
Compared with the effluent quality of fixed-bed adsorber, the fluctuation of effluent quality is much smaller when the pulsating bed is used.
In addition, when there is a certain concentration of suspended particles in the influent or entrainment with a gas component, due to the inherent mechanism of the pulsating bed adsorber, can effectively avoid the occurrence of increased bed resistance, the occurrence of“Gas resistance” and other operational failures. This is another inherent advantage of the pulsating bed adsorber.
The pulsatile bed adsorber can obtain the effluent with stable quality, which can be reused to reduce the amount of wastewater discharged and save the cost of water consumption.
Therefore, we recommend that the pulsed bed absorber design be preferred.
3. Comparison of pulsating bed adsorber and fixed bed adsorber
Fixed bed type adsorption device
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the building height is smaller and the area is larger
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there is no need for a dedicated operator
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the system has the function of“Self-filtration”, but when the suspended matter is too much, the bed will be blocked
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it is easy to check the inside of the adsorber, and the faults in the adsorber can be found in time
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the inlet pressure can be controlled at a relatively low value to overcome the resistance of the whole bed
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larger flow design and operation value can be adopted
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the backwash/backwash design and backwash operation system can be adopted
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need to design more auxiliary operating space area
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when the same liquid is treated with activated carbon and the same efficiency is achieved, the total investment of fixed bed adsorption system is higher than that of pulsating bed adsorption system
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if the single-adsorber design is adopted, the outlet quality will change gradually with the prolongation of the operation time of the adsorber (outlet quality is unstable)
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when the effluent quality of an adsorption device reaches the preset target value, the device should be immediately disconnected from the system for subsequent disposal
Advantages
Disadvantages
Pulsating bed type adsorption device
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there is almost no need to design the auxiliary operating space area
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the effluent quality can be accurately controlled to the set required value
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having a long mass transfer band, the amount of activated carbon can be minimized in practical application
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when the product in saturated activated carbon is recovered, there is no requirement of“Peak value” of water consumption
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if there is gas in the liquid or gas products can be formed in the activated carbon bed, the upflow pulsating bed adsorber design is most suitable
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the non-expandable pulsating bed adsorber is not suitable to deal with the liquid containing more suspended solid particles, when the expandable pulsating bed adsorber is used, it can effectively overcome the resistance problem caused by suspended particles
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internal inspection and/or maintenance operations can only be carried out after the adsorbent is disconnected from the system and all activated carbon is removed from it
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a certain amount of activated carbon powder will be contained in the effluent after each pulsating operation, which needs subsequent filtration treatment
Engineering performance of Yangzhou in advanced treatment of chemical wastewater
The latest engineering performance of Shangding Company in the field of advanced treatment and reuse of industrial wastewater in Chinese mainland areas
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“Sandy Wetland Ecological Garden of Yulin Energy and Chemical Co. , Ltd.” and “Jingbian Energy and chemical comprehensive utilization project Sandy Wetland”
1.1 Owner: Yulin Energy and Chemical Co. , Ltd.
1.2 General design and construction contract unit: Shaanxi Research and Design Institute of Petrochemical Industry
1.3 The scope and objectives of the subcontract project
Shangding furnaces technology (Yangzhou) Co. , Ltd. won the tender for the advanced treatment of wastewater by granular activated carbon adsorption process between the front catalytic oxidation wastewater treatment system, the back-end reverse osmosis wastewater treatment system, the back-end MBR wastewater treatment system (three different COD concentrations of wastewater) and the RO reverse osmosis treatment system and the MBR treatment system (two wastewater secondary advanced treatment systems, the final product water is reused as process source water) .
The main installations in the scope of the project include: the pulsating bed type granular activated carbon adsorption tower and its auxiliary equipment system, the new carbon storage tank and preparation/transportation equipment system, the saturated carbon storage tank and the disposal equipment system.
Objectives of the project:
The advanced treatment of the mixed“After half-treatment wastewater” with COD concentration of 80 something 120 mg/l in the effluent of the front-end catalytic oxidation system, 120 something 150 mg/l in the concentrated water of the back-end RO reverse osmosis system and 60 something 80 mg/l in the concentrated water of the back-end MBR system was carried out, the total effluent COD was reduced to ≤40mg/L. Activated carbon adsorbent water or send to follow-up RO unit or MBR unit after the second deep treatment, reuse as process source water, or directly meet the standard discharged to the central water supply station into the pool.
The total capacity of the activated carbon unit is 270 m3/h.
1.4 Project profile
Shanbei energy and chemical industry base Jingbian Energy and chemical industry comprehensive utilization park's major industrial projects include: using Yulin's kerosene gas field, residual oil, etc. as raw materials, in the first phase of the project, 1.8 million tons/year methanol unit, 1.5 million tons/year residue catalytic pyrolysis unit, 600,000 tons/year DMTO unit, 600,000 tons/year PE unit, 600,000 tons/year PP unit and associated public works and auxiliary facilities will be built. The project is a centralized wastewater treatment project for these industrial projects. According to the design plan, all wastewater must be treated to meet the targets of reclaimed water reuse and process source water reuse, achieve“Zero emission” technical requirements.
Two sets of pulsating bed type granular activated carbon adsorption tower systems were designed and manufactured. The total volume of a single unit is 120 cubic meters, and the designed treatment load of a single unit is 135 cubic meters per hour, the maximum design load of COD is 15kg/h, and the design value of consumption quota of granular activated carbon is ≤0.85 kg/T effluent. The project was put into field operation in September 2013, trial operation in July 2014 and continuous operation in September 2014. The design goal was fully achieved.
1.5 Project site photos
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“Tianjin Lugang Petroleum Rubber Co. , Ltd. . Sewage Treatment Project” project
2.1 Owner: Tianjin Lugang Petroleum Rubber Co. , Ltd.
2.2 The scope and objectives of the subcontract project
Shangding Furnace Technology (Yangzhou) Co. , Ltd. won the tender for the third stage, namely “Advanced treatment” process of petrochemical wastewater “Granular activated carbon adsorption wastewater advanced treatment process system”.
The main installations in the scope of the project include: the pulsating bed type granular activated carbon adsorption tower and its auxiliary equipment system, the new carbon storage tank and preparation/transportation equipment system, the saturated carbon storage tank and the disposal equipment system.
Objectives of the project:
The petrochemical wastewater with COD concentration of 100 something 120 mg/L (designed to take the highest possible value of 150 mg/L) , which has been treated by the first and second stages of the existing wastewater, was treated by three stages of the granular activated carbon adsorption method, the total effluent COD can be reduced to ≤50 mg/L (the design value is 30 mg/L) . The effluent of activated carbon adsorber reaches the standard and is discharged directly into the water inlet pool of the intermediate water centralized supply station.
The total capacity of the activated carbon unit is 100 m3/h.
2.3 Project profile
A set of pulsating bed type granular activated carbon adsorption tower system was designed and manufactured. The total volume of a single unit is 120 cubic meters, and the designed treatment load of wastewater is 100 cubic meters per hour, the maximum design load of COD is 12kg/h.
The project was put into operation in November 2013, and started continuous operation in December 2014. The design goal was fully achieved.
2.4 Project site photos
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“China-france Advanced Water Treatment Project of Chongqing Changshou Industrial Park”
3.1 Owner: Sino-french Water Company of Chongqing Changshou Industrial Park (PPP is the regional public-private partnership model for this project)(Sino-french Water Company is part of the Suez Environnement)
3.2 The scope and objectives of the subcontract project
Shangding Furnace Technology (Yangzhou) Co. , Ltd. won the tender for the third stage, namely “Advanced treatment” process of petrochemical wastewater “Granular activated carbon adsorption wastewater advanced treatment process system”.
The main installations in the scope of the project include: fixed-bed granular activated carbon adsorption tower and its auxiliary equipment system, new carbon/regenerated carbon storage tank and preparation/transportation equipment system, saturated carbon storage tank and disposal equipment system (the project will build the on-line granular activated carbon regeneration process system) , backwashing equipment system, etc. .
Objectives of the project:
The concentration wastewater of chemical industrial park with COD concentration of 100MG/L (design value) , which has been treated by the first and second stage wastewater, was treated by granular activated carbon adsorption method, the total effluent COD was reduced to ≤50mg/L (design value) . Activated carbon adsorber discharge directly up to the standard.
The total capacity of the activated carbon unit is 30000 m3/day.
3.3 Project profile
A total of 12 fixed-bed granular activated carbon adsorption tower systems were designed and manufactured. Each of the four adsorption units (one for three uses) formed a wastewater treatment line, the capacity of each treatment line unit is 10000 tons/day, and the total design capacity is 30000 tons/day.
The design load of wastewater treatment is 140 cubic meters per hour, and the maximum design load of COD is 7 kg per hour.
The project was put into operation in late February 2015, and the first treatment line was put into trial operation on March 25,2015. The remaining two processing lines are scheduled to be fully operational by April 30,2015.
3.4 Project related pictures
The existing engineering performance of Shangding and its predecessors in the advanced treatment/reuse technology of industrial wastewater in Taiwan, China
1、Qimei petrifaction
Project: three-stage advanced treatment of wastewater
Project Outline: The designed wastewater treatment capacity is 4000 tons/day. The whole equipment system consists of two groups of activated carbon continuous running pulsating bed adsorption tower and a group of ø2.1 × 6-layer MHF furnace for activated carbon regeneration.
2、Runtai group
Project: three-stage advanced treatment of wastewater
Project Outline: The designed wastewater treatment capacity is 4000 tons/day. The whole equipment system consists of two groups of activated carbon continuous running pulsating bed adsorption tower and a group of ø2.3 × 6-layer MHF furnace for activated carbon regeneration.
3、China Steel
Project: three-stage advanced treatment of wastewater
Project Outline: The designed wastewater treatment capacity is 6000 tons/day. The whole equipment system consists of two groups of activated carbon continuous running pulsating bed adsorption tower and one group of ø2.8 × 6-layer MHF furnace for activated carbon regeneration.
4、Taiwan plastic six light
Project: three-stage advanced treatment of wastewater
Project Outline: The designed wastewater treatment capacity is 40000 t/D, which consists of 20 groups of activated carbon continuous running fixed-bed adsorption tower and a group of ø5.1 × 6-layer MHF furnace for activated carbon regeneration.
