CN222007534U

CN222007534U - A wastewater pretreatment system for shutdown and maintenance of a refinery

Info

Publication number: CN222007534U
Application number: CN202420612892.XU
Authority: CN
Inventors: 陈春茂; 陈霖; 张鑫倩; 刘浩威; 李琢宇; 詹亚力; 王庆宏
Original assignee: China University of Petroleum Beijing
Current assignee: China University of Petroleum Beijing
Priority date: 2024-03-27
Filing date: 2024-03-27
Publication date: 2024-11-15
Anticipated expiration: 2034-03-27

Abstract

The utility model provides a wastewater pretreatment system for shutdown and maintenance of a refinery, the pretreatment system comprising a homogenizing device, a flotation device, a pH adjusting device, a filtering device, and an ozone catalytic oxidation device connected in sequence through pipelines; the ozone catalytic oxidation device is filled with a natural ore catalyst, the natural ore catalyst is selected from one of magnetite, dolomite, chalcopyrite and chalcocite; the pH adjusting device is used to make the pH value of the wastewater to be oxidized entering the ozone catalytic oxidation device 10 to 12. The pretreatment system of the utility model can effectively pretreat wastewater from shutdown and maintenance of a refinery, remove characteristic organic pollutants in the wastewater, reduce the biological toxicity of the water body, significantly improve the biodegradability of the water body, and avoid impact on downstream sewage fields.

Description

Sewage pretreatment system for parking and overhauling of refining device

Technical Field

The utility model relates to a sewage pretreatment system for shutdown maintenance of a refining device, and belongs to the technical field of sewage treatment.

Background

Sulfur, nitrogen, heavy metals in crude oil and pollutants such as high-temperature high-pressure steam, high-concentration alkali liquor, free ammonia and the like generated in the refining process are easy to corrode equipment and pipelines, and after a production device runs for a certain period, dirt such as oil sludge, ferrous sulfide, oil scale, salt scale and the like can be attached to the inside of equipment such as a tray, a tower wall, a heat exchanger and the like, so that the efficiency of the tray is reduced and the energy consumption of the device is increased.

In order to ensure safe and stable operation and product quality of the refining device, the refining enterprises can carry out comprehensive shutdown and large maintenance every 3-5 years, and the equipment such as a tower, a container and the like is cleaned so as to ensure safe and stable production in the next period. During the large overhaul period, tens of refining devices are stopped to carry out operations such as depressurization, cooling, emptying, material returning, passivation, cleaning and the like, at the moment, the pollutants such as metal rust, dirt, organic solvent, alkaline residue and the like stored in the devices and the towers are eluted in a short time, and a large amount of pollutants are transferred from gas phase to liquid phase, so that a special high-concentration polluted water body is formed.

Part of production devices and equipment mainly produce chemical cleaning sewage during shutdown maintenance of a refining enterprise, and the other part of production devices need to be deodorized, cleaned and passivated, so that mixed sewage for deodorization, cleaning and passivation is mainly produced. The sewage for parking and maintenance contains a large amount of chemical cleaning and deodorizing auxiliary agents, and the direct discharge to a sewage treatment system can cause irreversible impact on a biochemical unit, so that the sludge is blacked, smelled and dead in a large amount in a short time, and great trouble is caused to the environmental management of a refining enterprise.

The suspended state and colloid state pollutant content of the overhauling sewage is high, the dissoluble organic pollution load is high, the COD and DOC load is extremely high, the characteristic organic pollutant in the sewage is mainly alcohol ethers, hydrocarbons and phenols, the alcohol ethers are mainly dipropylene glycol butyl ether and homologs, and the alcohol ethers are mainly derived from surface active substances added in the overhauling process, such as water-based cleaning agents; the hydrocarbon material originates from petroleum pollutants remaining in equipment, trays and piping; the phenolic substances are derived from crude oil and organic intermediate products generated in the crude oil refining process, and the characteristic organic pollutants are strong in biotoxicity, poor in biodegradability, difficult to biodegrade and easy to impact a biochemical system. At present, aiming at large overhauling sewage, domestic refining enterprises do not have a targeted pretreatment means, partial refining enterprises adopt a slow dilution mode to treat, however, the toxicity of high-concentration overhauling sewage is extremely high, once the dilution operation is problematic, the impact on a biochemical system is extremely easy, forced recovery is not adopted, the duration is often required, and the normal standard emission of the enterprises is seriously influenced. In addition, the slow dilution mode can occupy accident pools and accident tanks of refining enterprises for a long time. The reservoir capacity of the accident pool and the accident tank of the part of the refinery is insufficient, and the accident pool and the accident tank in the rainy season also need to take the role of intercepting the initial rainwater in the factory, so that the accident pool or the accident tank is occupied for a long time, and great environmental risks, social risks and potential safety hazards exist. Further, although the concentration of the contaminants can be reduced by the dilution treatment, some contaminants with strong biotoxicity remain in the water body, and even the dilution treatment inevitably affects the sewage treatment biological system. The emission standard of industrial pollutants for petroleum refining is implemented in 2017 by all refining enterprises in China, the requirement of the discharge amount of ton oil is increased, and the mode of diluting and treating overhauling sewage is further restricted.

Therefore, how to pretreat the sewage generated during the shutdown and maintenance of the refining device, reduce the pollution load and the total amount of characteristic pollutants, reduce the biotoxicity and improve the biodegradability, avoid the irreversible damage to the sewage treatment system, and ensure the stable operation of the sewage treatment system is a technical problem to be solved in the field.

Disclosure of utility model

The utility model provides a sewage pretreatment system for shutdown overhaul of a refining device, which is used for pretreating the sewage for shutdown overhaul of the refining device by adopting a pretreatment system comprising a homogenizing device, a flotation device, a pH adjusting device, a filtering device and an ozone catalytic oxidation device, aiming at the characteristics of the sewage for shutdown overhaul of the refining device, so that the removal of organic pollutants and biotoxicity in the sewage is enhanced, and the stable standard reaching operation of a sewage treatment system is more effectively supported.

The utility model provides a sewage pretreatment system for shutdown maintenance of a refining device, which comprises a homogenizing device, a flotation device, a pH adjusting device, a filtering device and an ozone catalytic oxidation device which are sequentially communicated through pipelines;

the ozone catalytic oxidation device is filled with a natural ore catalyst, wherein the natural ore catalyst is selected from one of magnetite, dolomite, chalcopyrite and chalcocite;

The pH adjusting device is used for enabling the pH value of the sewage to be oxidized entering the ozone catalytic oxidation device to be 10-12.

In an alternative embodiment, the natural ore catalyst has a particle size of 20 to 80 mesh.

In an alternative embodiment, the ozone catalytic oxidation device comprises an inlet and an outlet, wherein the inlet is communicated with an ozone adding device, and the ozone adding device is used for adding ozone into the ozone catalytic oxidation device.

In an alternative embodiment, a first dosing device and a second dosing device are also communicated with the pipeline of the homogenizing device communicated with the flotation device;

Coagulant is filled in the first dosing device, and flocculant is filled in the second dosing device.

In an alternative embodiment, the coagulant comprises 20-25% of polyaluminum sulfate or polyaluminum ferric chloride according to the mass percentage, and the adding amount of the coagulant is 2.0-2.5 kg/ton of sewage to be treated.

In an alternative embodiment, the flocculant comprises 1.5-2.0 per mill of cationic polyacrylamide according to the mass percentage, and the adding amount of the flocculant is 0.020-0.025 kg/ton of sewage to be treated.

In an alternative embodiment, the cationic polyacrylamide has a molecular weight of 600 to 1800 tens of thousands and a charge density of 10 to 40%.

In an alternative embodiment, the outlet of the ozone catalytic oxidation unit is in communication with a water storage tank.

In an alternative embodiment, the outlet of the water storage tank is in communication with the inlet of the ozone catalytic oxidation device and the inlet of the filtration device, respectively.

In an alternative embodiment, the filter device is selected from a multi-media filter, and the filter layer of the multi-media filter comprises a quartz sand filter layer and an anthracite filter layer which are distributed from bottom to top.

The implementation of the utility model has at least the following technical effects:

According to the sewage pretreatment system for shutdown overhaul of the refining device, provided by the utility model, the homogenizing device, the flotation device, the pH adjusting device, the filtering device and the ozone catalytic oxidation device which are sequentially communicated are adopted to respectively carry out homogenizing treatment, flotation treatment, pH adjusting treatment, filtering treatment and ozone catalytic oxidation treatment on the sewage for shutdown overhaul of the refining device, so that the COD content and biotoxicity in water can be effectively reduced, the organic load, biotoxicity and biodegradability in the discharged water can be effectively improved, and the water inlet requirement of a downstream sewage treatment system is met.

Drawings

FIG. 1 is a schematic diagram of a sewage pretreatment system for shutdown maintenance of a refining apparatus according to an embodiment of the present utility model;

FIG. 2 is a schematic view of a pretreatment system for wastewater from a shutdown of a refining apparatus according to yet another embodiment of the present utility model;

Fig. 3 is a schematic diagram of a pretreatment process of sewage for shutdown maintenance of a refining apparatus according to an embodiment of the present utility model.

Reference numerals illustrate:

10: a homogenizing device; 20: a flotation device; 30: a filtering device; 40: an ozone catalytic oxidation device; 50: a first dosing device; 60: a second dosing device; 70: and a pH adjusting device.

Detailed Description

The following description of the embodiments of the present utility model will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present utility model, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.

The utility model provides a sewage pretreatment system for shutdown overhaul of a refining device, and fig. 1 is a schematic diagram of the sewage pretreatment system for shutdown overhaul of the refining device according to an embodiment of the utility model, and as shown in fig. 1, the pretreatment system comprises a homogenizing device 10, a flotation device 20, a pH adjusting device 70, a filtering device 30 and an ozone catalytic oxidation device 40 which are sequentially communicated through pipelines;

Wherein the ozone catalytic oxidation unit 40 is filled with a natural ore catalyst selected from one or more of magnetite, dolomite, chalcopyrite and chalcocite;

By adopting the pretreatment system, the sewage pretreatment system for shutdown maintenance of the refining device can be sequentially subjected to homogenization treatment, flotation treatment, pH adjustment treatment, filtration treatment and ozone catalytic oxidation treatment;

After homogenization treatment, floatation treatment and filtration treatment, the organic pollution load in the overhauling sewage can be obviously reduced, most suspended pollutants and emulsified oil in the sewage are removed, and the organic pollution load in the sewage is greatly reduced. The flotation treatment has excellent effect on removing colloidal and suspended pollutant particles in sewage, and the chromaticity, petroleum substances and COD can be obviously reduced after the flotation treatment;

When ozone catalytic oxidation treatment is carried out, the natural ore catalyst filled in the ozone catalytic oxidation device 40 can adsorb organic pollutants in a water body, free OH ^- in the water body induces ozone to generate hydroxyl free radicals under the condition of a pH value of 10-12, so that degradation of the organic pollutants is promoted, and the natural ore surface is subjected to alkali activation treatment, so that the porosity of the ore is enhanced, the specific surface area is increased, and meanwhile, hydroxyl groups (-OH) on the ore surface are enriched, so that adsorption and degradation of the organic pollutants are more facilitated, the residual solubility characteristic organic pollutants in sewage are effectively removed, COD in the sewage is greatly reduced, the biotoxicity of the water body is reduced, and the biodegradability of the water body is improved.

In conclusion, the organic load, biotoxicity and biodegradability of the pretreated effluent obtained by the pretreatment system can be effectively improved, and the water inlet requirement of a downstream sewage treatment system can be met.

In the present utility model, the ozone catalytic oxidation device 40 may be selected from an acid-resistant and alkali-resistant ozone catalytic oxidation tower or an ozone catalytic oxidation tank. The utility model does not limit the number of the ozone catalytic oxidation devices 40, and can select one or more ozone catalytic oxidation devices 40 to treat the sewage to be treated according to the treatment difficulty, and the treatment efficiency can be obviously improved by connecting the ozone catalytic oxidation devices in series or in parallel.

In a specific embodiment, when the loading amount of the catalyst in the ozone catalytic oxidation device 40 is 8% -10% of the mass of sewage to be treated per hour, a better sewage treatment effect can be obtained.

In addition, when the inlet-outlet pressure difference DeltaP of the ozone catalytic oxidation device 40 is more than or equal to 0.1Mpa, excessive mechanical impurities possibly trapped in the filler layer affect the normal operation of the device, the device can be cleaned by adopting a back flushing method, and the specific back flushing process comprises the following steps: the reverse water is fed into the ozone catalytic oxidation device 40, so that the filler layer in the ozone catalytic oxidation device is loosened, and the retentate (such as sediment and suspended matters) adhered to the surface of the filler is carried away by the backwash water, so that the catalytic ozone oxidation capability is fully recovered.

The ozone catalytic oxidation unit 40 is subjected to the exhaust of the unit and the pipeline before being put into operation. When the exhaust is completed after the exhaust pipeline discharges water, the water inlet valve and the exhaust valve of the ozone catalytic oxidation device 40 are firstly opened to enable water to flow in from the upper port, at the moment, the water inlet valve is adjusted to control the water inlet flow, the normal washing drain valve is opened, and the exhaust valve is closed to enable sewage to flow out from the normal washing drain valve. After the forward washing is finished when the forward washing water is discharged until the discharged water is clear and transparent, the water inflow is regulated, so that the ozone catalytic oxidation device 40 enters a pre-working state, then the forward washing water discharging valve is closed, the water discharging valve is opened, and meanwhile, the ozone air inlet valve and the ozone tail gas valve are opened, so that the ozone catalytic oxidation device 40 enters an operating state.

Furthermore, the natural ore catalyst is preferably magnetite, and compared with other natural ores, the surface of the magnetite has more abundant hydroxyl groups (-OH), can be combined with ozone molecules to form a five-membered ring structure, and can generate OH and O ₂ ^·- under the action of water molecules to accelerate the degradation of organic pollutants; in addition, magnetite contains Fe ²⁺ and Fe ³⁺ in two valence states, and the electron transfer process generated in the oxidation-reduction process between Fe ²⁺/Fe³⁺ can activate ozone molecules to generate OH, so that the degradation of organic pollutants is accelerated. Thus, magnetite can obtain a more excellent ozone catalytic oxidation effect than other natural ores.

Further, the particle size of the natural ore catalyst packed in the ozone catalytic oxidation apparatus 40 is 20 to 80 mesh. When the particle size is too large, the specific surface area of the catalyst is low, the contact area of the catalyst and soluble pollutants in sewage is reduced, the activity of the catalyst is influenced, and the reaction speed is low; the particle size of the natural ore catalyst is too small, so that the catalyst is easy to deactivate, the bed resistance of the ore catalyst with small particle size is increased, the power consumption is increased, and the equipment backwashing is not facilitated.

The natural ore catalyst having the above particle size can be obtained by crushing and sieving commercially available natural ores. After crushing and sieving, the particles can be washed with 50 times of mass of ultrapure water to remove dust on the surface and impurities adsorbed inside the ore.

Furthermore, when the loading of the natural ore catalyst is 8-10% of the sewage to be treated per hour, a better sewage treatment effect can be obtained.

In a specific embodiment, the ozone catalytic oxidation device 40 includes an inlet and an outlet, wherein the inlet is in communication with an ozone dosing device for dosing ozone into the ozone catalytic oxidation device 40.

Further, the ratio of the mass of ozone added by the ozone adding device to the mass of sewage to be treated in the ozone catalytic oxidation device is (80-100) g:1 ton. The ozone adding amount is controlled within the range, so that the degradation efficiency of pollutants such as phenols, benzene series, surface active substances, heterocycles and the like can be enhanced, most of biotoxic substances such as phenols, benzene series and the like in the water body can be effectively degraded in a short time, and part of polycyclic and heterocyclic compounds can be degraded. In addition, in the range of the above adding mass ratio, the ozone catalytic oxidation treatment process can be completed within 60-90 min when the temperature of the ozone catalytic oxidation treatment is controlled to be 30-40 ℃ and the pressure is normal pressure.

The sewage to be treated in the utility model refers to the sewage for stopping and overhauling the refining device to be treated.

Further, the ozone adding device can be an ozone generator. The main structure of the ozone generator comprises an air compressor, a cold dryer, an oxygen generator, an air storage tank, a gas-water separator and the like.

The outlet of the ozone catalytic oxidation device 40 may be further communicated with a water storage tank, and the discharged pretreated effluent may be collected by the water storage tank.

In a preferred embodiment, the outlet of the water storage tank communicates with the inlet of the ozone catalytic oxidation unit 40 and the inlet of the filtration unit 30, respectively. By the arrangement, the pretreated effluent stored in the water storage tank can be used as the backwash water inlet of the filtering device 30 and the ozone catalytic oxidation device 40, and the two water inlet are backwashed, so that the recycling of the pretreated effluent is realized.

An ozone tail gas destructor may be further connected to the outlet of the ozone catalytic oxidation device 40 to treat the discharged ozone tail gas. The ozone tail gas destructor mainly removes redundant ozone in the tail gas through catalytic decomposition, and the main structure of the ozone tail gas destructor comprises a stainless steel catalytic groove, a stainless steel net-shaped partition plate, a supporting grid plate and the like.

Fig. 2 is a schematic diagram of a pretreatment system for wastewater from shutdown and overhaul of a refining apparatus according to another embodiment of the present utility model, and as shown in fig. 2, a first chemical adding device 50 and a second chemical adding device 60 are further connected to a pipeline between the homogenizing device 10 and the flotation device 20; wherein the first dosing device 50 is filled with coagulant and the second dosing device 60 is filled with flocculant.

Further, pipeline mixers are respectively arranged at the junctions of the pipelines communicated with the homogenizing device 10 and the flotation device 20 and the pipelines of the first dosing device 50 and the second dosing device 60, so that the hydrolysis efficiency of the coagulant and the full contact of the flocculant and the flocs can be ensured by using the pipeline mixers, the adsorption bridging and net capturing effects are exerted, and the aggregation destabilization of the flocs is promoted.

The flotation device 20 of the present utility model may be selected from flotation devices conventionally used in the art, and further, the flotation of the wastewater may be accomplished in the flotation device 20 using a partial reflux pressurized dissolved air flotation process.

In a preferred embodiment, when the reflux ratio of the partial reflux pressurized dissolved air flotation process is 30% -50%, the air/reflux water mixing ratio is 10vol%, and the average diameter of dissolved air releasing air bubbles is less than 30 μm, the suspended matters in sewage can be subjected to efficient flotation.

In the utility model, the reflux ratio refers to the mass ratio of the dissolved air water quantity to the sewage to be treated, the air/reflux water mixed transmission ratio refers to the volume ratio of air and reflux water pumped by the air-liquid mixed transmission pump, and the dissolved air release air bubbles refer to air released by air dissolved in the sewage after decompression.

Further, the coagulant comprises 20-25% of polyaluminium sulfate and/or polyaluminium ferric chloride according to the mass percentage, and the adding amount of the coagulant is 2.0-2.5 kg/ton of sewage to be treated.

After the polyaluminum sulfate and polyaluminum ferric chloride are hydrolyzed, a series of polynuclear hydroxyl complexes are generated, and aggregation of colloid-state and suspended-state pollutants is promoted through adsorption and electric neutralization, so that floccules which are favorable for removal through flotation are formed.

The coagulant includes not only the active components such as polyaluminium sulfate and/or polyaluminium ferric chloride which play a role of coagulation, but also auxiliary agents such as aluminum oxide, aluminum hydroxide and the like.

Further, the flocculant comprises 1.5 to 2.0 per mill of cationic polyacrylamide according to the mass percentage, and the addition amount of the flocculant is 0.020 to 0.025 kg/ton of sewage to be treated. The cationic polyacrylamide can generate a long-chain macromolecular polymer after hydrolysis, has obvious adsorption and bridging effects on flocs, and improves the separation performance of the flocs through adsorption.

Further, the molecular weight of the cationic polyacrylamide is 600-1800 ten thousand, and the charge density is 10-40%. In the above molecular weight and charge density ranges, the flocculant can have a better flocculation effect.

More preferably, the molecular weight of the cationic polyacrylamide is 600 to 1800 ten thousand, and the charge density is 10 to 40 percent.

The first and second dosing devices 50, 60 may be in communication with the pipeline via a metering pump so that the amount of coagulant and flocculant added is regulated via the metering pump.

The homogenizing device 10 can be a regulating water tank, sewage to be treated is introduced into the regulating water tank for accumulation, and then a metering pump is used for controlling constant outflow quantity, so that the fluctuation range of the pollutant concentration of the effluent is within +/-5%, and the purpose of homogenization is achieved.

The main structure of the flotation device 20 comprises a pressure pump, a dissolved air tank, a dissolved air releaser and an air floatation tank, wherein the dissolved air tank utilizes a gas-liquid mixing and conveying pump to carry out efficient dissolved air, and the gas-liquid mixing and conveying pump has a special impeller structure, so that gas-liquid two phases are fully dissolved and saturated at high pressure, and high-dispersivity micro-nano bubbles are generated after decompression release, and flocs are adhered, thereby realizing separation.

The flotation device 20 can be further connected with a water storage tank, so that sewage after flotation treatment is homogenized and regulated again, the uniformity and stability of subsequent treatment are ensured, and a certain buffering effect is achieved.

Further, the filtering device 30 is selected from a multi-media filter, and the filtering layer of the multi-media filter comprises a quartz sand filtering layer and an anthracite filtering layer which are distributed from bottom to top. Under a certain pressure, the pH-adjusted anhydrous water passes through the filter material layer, and residual flocs and suspended pollutants in the sewage can be effectively removed by utilizing the principle of filtration interception.

In addition, during the filtration process, it is necessary to pay attention to the pressure of the filtration device 30 regularly to avoid excessive mechanical impurities remaining during filtration from affecting the proper operation of the filter.

Specifically, when the inlet-outlet pressure difference DeltaP of the filter device 30 is more than or equal to 0.1MPa, the filter device needs to be backwashed to remove impurities. Specifically, the back flushing process comprises the following steps: the reverse water inflow is utilized to loosen the filter material layer in the filter device 30, so that the trapped matters adhered to the surface of the filter material are stripped and taken away by the back flush water flow, thereby removing sediment, suspended matters and the like in the filter material layer, preventing the filter material from hardening and fully recovering the dirt-intercepting capability.

The pretreatment system for the shutdown overhaul sewage of the refining device and the operation process thereof provided by the utility model are described below by specific embodiments.

In the following examples, reference is made to the prior art for operations not mentioned in detail, and the devices and apparatuses not mentioned in detail may employ devices existing in the art.

Example 1

Fig. 3 is a schematic diagram of a pretreatment system for shutdown maintenance sewage of a refining device according to still another embodiment of the present utility model, where the pretreatment system shown in fig. 3 is used for pretreatment operation, and as shown in fig. 3, the pretreatment system in this embodiment includes a regulating water tank, a flotation device, a first water storage tank, a multi-medium filter, an ozone catalytic oxidation tower, and a second water storage tank which are sequentially connected through pipes, where a coagulant dosing device and a flocculant dosing device are further connected to a connecting pipe line of the regulating water tank and the flotation device, a pH adjusting device is further connected to a connecting pipe line of the first water storage tank and the multi-medium filter, the ozone catalytic oxidation tower adopts a parallel connection mode of an ozone catalytic oxidation tower 1# and an ozone catalytic oxidation tower 2#, and inlets of the two are further respectively connected to an ozone generator, and outlets of the two are further respectively connected to the second water storage tank. The dimensions and operating parameters of the above devices are as follows:

The size of the water tank is regulated to be phi 1400 multiplied by 2700mm, and the volume is regulated to be 4m ³;

The size of the flotation device is 6260mm multiplied by 2600mm;

The size of the multi-medium filter is phi 1400mm multiplied by 2400mm, the equipment treatment capacity is 15m ³/h, the equipment working pressure is less than or equal to 0.6Mpa, the equipment working temperature is 5-50 ℃, the supporting layer of the multi-medium filter is cobblestone, the grain size specification is 8-16 mm, the arrangement height is 200mm, the filtering layer comprises two filtering materials including quartz sand and anthracite, the quartz sand is used as a lower filtering material, the grain size specification is 1-2 mm, the arrangement height is 400mm, the anthracite is used as an upper filtering material, the grain size specification is 1-1.5 mm, and the arrangement height is 400mm;

The volumes of the ozone catalytic oxidation towers 1# and 2# are 7m ³, the equipment size is phi 2100mm multiplied by 2700mm, the equipment working pressure is less than or equal to 0.6Mpa, and the equipment working temperature is normal temperature;

The second tank had dimensions Φ1400mm×2000mm and an effective volume of 3m ³.

The pretreatment system shown in fig. 3 is adopted to pretreat the shutdown overhaul sewage of the refining device, and the pretreatment process comprises the following steps:

1) Introducing the sewage from the shutdown of the refining device into an adjusting water tank to separate and float the floating oil, the coarse dispersion oil and the water body to the upper part of the adjusting water tank for recycling, separating and settling the granular pollutants with larger specific gravity from the water body to the bottom of the tank body for removing, and settling to remove the large granular pollutants;

2) Coagulant and flocculant are respectively introduced into the pipeline through a coagulant dosing device and a flocculant dosing device, so that the coagulant and the flocculant are fully mixed with the effluent of the regulating water tank in a pipeline static mixer and then enter a flotation device;

Wherein, the coagulant comprises 20 percent of PAS and PAFC mixture according to the mass percent, and the adding amount of the coagulant is 2 kg/ton of sewage to be treated; the flocculant comprises 2 per mill of CPAM (molecular weight is 1500 ten thousand, charge density is 30%) according to the mass percentage, and the dosage of the flocculant is 0.025 kg/ton of sewage to be treated;

3) The flotation device adopts a partial reflux pressurized air dissolving process, air is dissolved in water under the pressurized condition to form an air supersaturated state, then water is reduced to normal pressure through a releaser, so that the air is separated out, part of the treated air floatation tank water flows back, pressurized air dissolving is carried out, the reflux quantity is 30-50% of water inflow, the dissolved air water is released in the air floatation tank to generate micro-nano bubbles with the average diameter smaller than 30 mu m, insoluble pollutants in sewage take the micro-bubbles as carriers, aggregate and combine to form floccules with smaller apparent density, the floccules enter a separation area, most of the floccules are rapidly lifted to a slag collecting area to be discharged by a slag scraping machine, and part of floccules and suspended matters with larger apparent density are separated and removed after settling to the bottom of the device. The scum and bottom mud generated by the flotation device are directly discharged into skid-mounted equipment of the stacked spiral sludge dehydrator for treatment, a part of the water discharged by the flotation device is lifted by a gas-liquid mixing pump and enters a pressure dissolved air tank, the air/backflow water mixing and conveying ratio is 10vol%, the water discharged by the pressure dissolved air tank flows back into the flotation device for dissolved air release, and a part of the water flows into a first water storage tank automatically;

4) Homogenizing and adjusting the floating effluent which is automatically introduced into the first water storage tank again, and lifting the sewage after homogenizing and adjusting into a multi-medium filter through a lifting pump of the first water storage tank; adding sodium hydroxide into a water inlet pipeline of the multi-medium filter through a metering pump outlet pipeline of the pH adjusting device, so that the sodium hydroxide and the water discharged from the first water storage tank are fully mixed in a pipeline static mixer to adjust the pH value of the sewage water body to 11, and the sewage flows through a filter layer in the multi-medium filter from top to bottom at an operation flow rate of 8-12 m/h;

5) Introducing effluent water of a multi-medium filter into an ozone catalytic oxidation tower 1# and an ozone catalytic oxidation tower 2# respectively in a self-flowing manner for ozone catalytic oxidation treatment, wherein magnetite catalysts with the particle size of 20 meshes are filled in the ozone catalytic oxidation tower 1# and the ozone catalytic oxidation tower 2#, the filling amount of the magnetite catalysts is 10% of the sewage treatment mass per hour, in the ozone catalytic oxidation treatment, the ozone adding amount is 2000g/t of sewage to be treated, the total hydraulic retention time is 1h, and the treatment temperature is 25 ℃ at room temperature;

6) Introducing the treated effluent of the ozone catalytic oxidation tower 1# and the ozone catalytic oxidation tower 2# into a second water storage tank, wherein the water in the second water storage tank is the pretreated effluent.

Example 2

In this example, the pretreatment system consistent with example 1 was used to pretreat the sewage from the shutdown of the refining apparatus, and the pretreatment method was substantially consistent with example 1, except that the ozone catalytic oxidation column 1# and the ozone catalytic oxidation column 2# were packed with dolomite catalyst.

Example 3

In this example, the pretreatment system consistent with example 1 was used to pretreat the sewage from the shutdown of the refining apparatus, and the pretreatment method was substantially consistent with example 1, except that the ozonation catalytic oxidation column # 1 and the ozonation catalytic oxidation column # 2 were filled with chalcopyrite catalyst.

Example 4

In this example, the pretreatment system consistent with example 1 was used to pretreat the sewage from the shutdown of the refining apparatus, and the pretreatment method was substantially consistent with example 1, except that the ozonation catalytic oxidation tower # 1 and the ozonation catalytic oxidation tower # 2 were packed with chalcocite catalysts.

Example 5

The pretreatment system consistent with the embodiment 1 is adopted for pretreatment of the shutdown overhaul sewage of the refining device, and the pretreatment method is basically consistent with the embodiment 1, except that in the step 4), the pH value of the sewage body is regulated to be 10.

Example 6

In this example, the pretreatment system consistent with example 1 was used to pretreat the wastewater from the shutdown of the refinery apparatus, and the pretreatment method was substantially consistent with example 1, except that in step 4), the pH of the wastewater body was adjusted to be 12.

Example 7

In this example, the pretreatment system consistent with example 1 was used to pretreat the wastewater from the shutdown of the refinery apparatus, and the pretreatment method was substantially consistent with example 1, except that in step 4), the pH of the wastewater body was adjusted to 13.

Example 8

In this example, the pretreatment system consistent with example 1 was used to pretreat the refinery off-line wastewater, and the pretreatment method was substantially consistent with example 1, except that in step 5), the total hydraulic retention time was 0.5h.

Example 9

The pretreatment system consistent with the embodiment 1 is adopted for pretreatment of the sewage for shutdown maintenance of the refining device, and the pretreatment method is basically consistent with the embodiment 1, except that in the step 5), the ozone addition amount is 1kg/t of the sewage to be treated.

Example 10

In this example, the pretreatment system consistent with example 1 was used to pretreat the sewage from the shutdown of the refining apparatus, and the pretreatment method was substantially consistent with example 1, except that in step 2), the mixture of PAS and PAFC was replaced with PAC (polyaluminum chloride).

Example 11

In this example, the pretreatment system consistent with example 1 was used to pretreat the sewage from the shutdown of the refining apparatus, and the pretreatment method was substantially consistent with example 1, except that in step 2), the mixture of PAS and PAFC was replaced with FeCl ₃ (ferric chloride).

Example 12

In this example, the pretreatment system consistent with example 1 was used to pretreat the sewage from the shutdown of the refining apparatus, and the pretreatment method was substantially consistent with example 1, except that in step 2), CPAM (molecular weight 1500 ten thousand, charge density 30%) was replaced with anionic polyacrylamide (PAM, molecular weight 1500 ten thousand, charge density 30%).

Example 13

In this example, the pretreatment system consistent with example 1 was used to pretreat the sewage from the shutdown of the refining apparatus, and the pretreatment method was substantially consistent with example 1, except that in step 2), CPAM (molecular weight: 1500 ten thousand and charge density: 30%) was replaced with nonionic polyacrylamide (NPAM, molecular weight: 1500 ten thousand).

Example 14

The pretreatment system consistent with the embodiment 1 is adopted for pretreatment of the sewage for shutdown maintenance of the refining device, and the pretreatment method is basically consistent with the embodiment 1, except that in the step 2), the molecular weight of CPAM is 1000 ten thousand and the charge density is 20%.

Comparative example 1

This comparative example uses a pretreatment system consistent with example 1 to pretreat the refinery off-line service wastewater, and the pretreatment method is substantially consistent with example 1, except that the ozone catalytic oxidation tower 1# and the ozone catalytic oxidation tower 2# are filled with a conventional ceramic-based ozone catalyst having a particle size of 3-5 mm.

Comparative example 2

The comparative example adopts a pretreatment system consistent with the embodiment 1 to pretreat the shutdown overhaul sewage of the refining device, and the pretreatment method is basically consistent with the embodiment 1, except that in the step 4), the pH value of the sewage body is regulated to 7.

Test case

The pretreatment effluent obtained in the above examples and comparative examples was subjected to measurement of the following parameters:

1、COD

The measuring method comprises the following steps: COD measurement is described in "method for measuring chemical oxygen demand of Water quality", potassium dichromate (HJ 828-2017).

2. OUR inhibition of activated sludge

The measuring method comprises the following steps: OUR inhibition experiments refer to chemical activated sludge respiratory inhibition experiments (GB/T21796-2008).

The index is used for measuring the biotoxicity of toxic substances in the water body to activated sludge of a biochemical unit of the sewage treatment system, and the greater the OUR inhibition rate, the more obvious the inhibition effect of the toxic substances in the water body to the activated sludge is, namely the stronger the toxicity of sewage is.

3. Biochemical availability (BOD ₅/COD)

The measuring method comprises the following steps: BOD ₅ measurement reference "dilution for determination of five-day oxygen demand of Water quality", inoculation method (HJ 505-2009); COD measurement is described in "method for measuring chemical oxygen demand of Water quality", potassium dichromate (HJ 828-2017).

The higher BOD ₅/COD is used for representing the biodegradability of the water body, which indicates that the more organisms in the sewage can be utilized by organisms, the more easily the organisms are biochemically degraded.

4. Total soluble organic carbon (Dissolved Organic Carbon, DOC)

The measuring method comprises the following steps: DOC measurement is referred to technical requirement of automatic analysis of Total organic carbon Water quality (HJ/T104-2003)

5. Petroleum products

The measuring method comprises the following steps: petroleum detection refers to infrared spectrophotometry for detection of oil quality, petroleum and animal and vegetable oils (HJ 637-2018)

6. Chromaticity of

The measuring method comprises the following steps: the measurement of chromaticity is described in "measurement of chromaticity of Water quality" (GB 11903-1989).

7. Acute biotoxicity (EC ₅₀)

The measuring method comprises the following steps: the measurement of sewage EC ₅₀ is referred to the standard ISO 11348-3.

The index is used for measuring the biotoxicity of toxic substances in water to the Vibrio freudenreichii, and the smaller EC ₅₀ (%), the more obvious the luminous inhibition effect of the toxic substances in the water to the Vibrio freudenreichii is, namely the stronger the toxicity of sewage is.

8. Turbidity degree

The measuring method comprises the following steps: turbidity determination reference standard ISO 7027-1984 determination of Water quality-turbidity.

The water quality data of the raw sewage (i.e., untreated sewage) is shown in table 1, and the water quality data of the pretreated effluent of each of the above examples and comparative examples is shown in table 2.

The COD removal rate, DOC removal rate, petroleum removal rate, and chromaticity removal rate of each example and comparative example were calculated from the detection data, respectively, and the calculation results are shown in table 2.

COD removal rate= (untreated sewage COD-pretreated effluent COD)/untreated sewage COD×100%;

DOC removal = (untreated sewage DOC-pretreated effluent DOC)/untreated sewage doc×100%;

Petroleum removal rate= (untreated sewage petroleum concentration-pretreated effluent petroleum concentration)/untreated sewage petroleum concentration x 100%.

Chromaticity removal = (untreated sewage chromaticity-pretreated effluent chromaticity)/untreated sewage chromaticity x 100%.

Turbidity removal = (untreated sewage turbidity-pretreated effluent turbidity)/untreated sewage turbidity x 100%.

TABLE 1

TABLE 2

From Table 2, the following conclusions can be analytically drawn:

1) As can be seen from comparative examples 1 to 4 and comparative example 1, the natural ore catalyst of the utility model is adopted for ozone catalytic oxidation, and the COD removal rate, OUR inhibition rate, BOD ₅/COD, petroleum removal rate and EC ₅₀ of the sewage are all obviously higher than those of the common ceramic-based ozone catalyst adopted in comparative example 1, so that the organic pollution load and acute biotoxicity of the sewage can be obviously reduced, and the biodegradability of the sewage is improved; as can be seen from the comparison of examples 1 to 4, the magnetite catalyst has more excellent ozone catalytic oxidation effect than dolomite, chalcopyrite and chalcocite catalysts, and has better effects in reducing the organic pollution load of sewage, reducing the acute biotoxicity of sewage and improving the biodegradability of sewage.

2) As is clear from comparative examples 1, 5, 6, 7 and comparative example 2, when the ozone catalytic oxidation is carried out at a pH of 10 to 13, the ozone treatment effect is significantly better than that when the pH of the water body is neutral.

3) As is clear from comparative examples 1, 8 and 9, the addition amount of ozone and the time of ozone catalytic treatment also have significant influence on the treatment effect, and too small addition amount of ozone and too short treatment time affect the catalytic efficiency and the contact reaction efficiency, and also cannot obtain excellent sewage treatment effect.

4) As is clear from comparative examples 1, 10 and 11, the use of polyaluminum sulfate and polyaluminum ferric chloride as the coagulant can obtain more excellent sewage treatment effect than polyaluminum chloride and ferric chloride, and the polyaluminum chloride and ferric chloride as the coagulant have poorer COD removal rate, OUR inhibition rate, biodegradability, DOC removal rate, chromaticity removal rate, turbidity removal rate and other parameters, and the EC ₅₀ value is also higher, especially the petroleum removal rate, chromaticity removal rate and turbidity removal rate are different from those of example 1 significantly, which indicates that polyaluminum chloride and ferric chloride are difficult to effectively adsorb suspended pollutants in sewage as the coagulant.

5) As can be seen from comparative examples 1 and 12-13, the types of the flocculant have obvious influence on the sewage treatment effect, and compared with anionic polyacrylamide and nonionic polyacrylamide, the cationic polyacrylamide can obtain better sewage treatment effect, and the anionic polyacrylamide and the nonionic polyacrylamide are used as the flocculant, so that COD removal rate, OUR inhibition rate, biodegradability, DOC removal rate, chromaticity removal rate and other parameters are poor, EC ₅₀ value is also high, and especially, the difference from example 1 is obvious in petroleum removal rate, chromaticity removal rate and turbidity removal rate value, so that the anionic polyacrylamide and the nonionic polyacrylamide are used as the flocculant and are difficult to effectively adsorb suspended pollutants and flocs in sewage, and the adsorption bridging effect is difficult to be exerted;

As is apparent from comparative examples 1 and 14, the molecular weight and charge density of the cationic polyacrylamide also have an effect on the sewage treatment effect, which is generally more excellent when the molecular weight of CPAM is 1500 ten thousand and the charge density is 30%.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present utility model, and not for limiting the same; although the utility model has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the utility model.

Claims

1. The sewage pretreatment system for shutdown maintenance of the refining device is characterized by comprising a homogenizing device, a flotation device, a pH adjusting device, a filtering device and an ozone catalytic oxidation device which are sequentially communicated through pipelines;

2. The pretreatment system of claim 1, wherein the natural ore catalyst has a particle size of 20 to 80 mesh.

3. The pretreatment system of claim 1, wherein the ozone catalytic oxidation device comprises an inlet and an outlet, the inlet in communication with an ozone dosing device for dosing ozone into the ozone catalytic oxidation device.

4. The pretreatment system of claim 1, wherein a first dosing device and a second dosing device are further in communication with the homogenizing device in sequence on a conduit in communication with the flotation device;

5. The pretreatment system of claim 4, wherein the coagulant comprises 20-25% of polyaluminum sulfate or polyaluminum ferric chloride according to mass percent, and the adding amount of the coagulant is 2.0-2.5 kg/ton of sewage to be treated.

6. The pretreatment system of claim 4, wherein the flocculant comprises 1.5-2.0 per mill cationic polyacrylamide by mass, and the flocculant is added in an amount of 0.020-0.025 kg/ton of sewage to be treated.

7. The pretreatment system of claim 6, wherein the cationic polyacrylamide has a molecular weight of 600 to 1800 tens of thousands and a charge density of 10 to 40%.

8. A pretreatment system according to claim 3, wherein the outlet of the ozone catalytic oxidation unit is in communication with a water storage tank.

9. The pretreatment system of claim 8, wherein the outlet of the water storage tank is in communication with the inlet of the ozone catalytic oxidation unit and the inlet of the filtration unit, respectively.

10. The pretreatment system of claim 1, wherein the filtration device is selected from the group consisting of a multi-media filter having a filter layer comprising a quartz sand filter layer and an anthracite filter layer distributed from bottom to top.