1 Introduction Iron and steel enterprises have a large volume of steel rolling wastewater, and the oil contained in the wastewater and impurities such as iron sheet, mud sand, etc., form sludge with a large viscosity, which greatly harms the operation of water equipment and pipelines and water treatment systems, and affects normal production. And the quality of the product, the workshop was discontinued when serious. Masteel's three-roll strip steel plant sewage treatment system is not good because of the degreasing effect, sludge adheres to the water treatment equipment, the magnetic filter is idle due to the filter material is blocked by the sludge, the cooling tower due to the impact of sludge, the filler often fall off The system water quality is poor and the equipment cannot be put into operation normally. This increases production stoppage time and maintenance workload. In addition, the adjustment capacity of hot and cold water pools is relatively small, resulting in unbalanced water quantity, large amounts of sewage being discharged, and polluting the environment; the content of suspended solids/oil in the discharged effluent exceeds the national environmental discharge standards. The process flow is shown in Figure 1. Application of Chemical Deoiling Technology in Oil-containing Water Treatment of Steel Rolling For this reason the company decided to modify the system, due to the physical method of oil removal equipment such as pipe degreasing machine \ scraping scraper \ floater oil collector \ oil recovery type \ belt degreasing machine, can only remove part Floating oil can't remove emulsified oil. Air floatation can remove floating oil and emulsified oil, but it has large power consumption, complicated equipment, and it is difficult to implement when the amount of water is large. Therefore, the use of chemical degreasing techniques jointly developed with the relevant scientific research departments to transform existing water treatment systems. 2 Chemical method of degreasing The chemical degreasing process adopts the process of dosing coagulation, chemical flocculation, reaction, and sedimentation. The process is shown in Figure 2. Application of Chemical Deoiling Technology in Oil-containing Water Treatment of Steel Rolling The flocculating agent is a dielectric coagulant with a strong demulsification effect. The flocculating agent is an oil flocculant. The mechanism of oil removal is: After adding coagulant, it can neutralize the surface electricity of the colloidal particles in the water and reduce the thickness of the diffusion layer. Eliminate or reduce the E-potential of the colloidal particles to make the colloids destabilize and coalesce with each other, which is the agglomeration effect. The flocculant is added to the oily sewage, which can destabilize and coalesce the colloid formed by the emulsified oil/suspension. The oil flocculant is a linear polymer with many branches and contains a large number of suitable ionic groups and active groups. It has strong adsorption and bridging capacity for solid suspended particles and emulsified oil beads in sewage, making The particles formed by the agglomeration are bridged by a polymer and the particles gradually become larger. Finally, a dense, coarse floc cluster is formed and settled to achieve the purpose of purifying water quality. 3 Reform Program Maanshan Steel's three rolling tropical wastewater recycling capacity is 0.9~1. 1 km3/h9 SS of imported suspension is 200~400mg/19 oil content of 20~40mg/1O. The content of the transformation of this system and the objectives to be achieved. The values ​​are as follows. 3. 1 Renovation content: A new steel chemical sedimentation tank with a treatment capacity of 300m3/h was newly constructed, and the sludge discharged from the chemical sedimentation tank was subjected to filter press dehydration tests to find the preferred equipment for sludge dewatering and related technical parameters. 3. 2 target value: treated water volume: 300m3/h; effluent oil content: <10mg/1; effluent suspended substance content: <40mg/1O filter cake produced mud cake can be directly loaded into the car and shipped without secondary pollution. 3. 3 Addition of major equipment: MHCY I type chemical degreasing device 1 device length 12. 5m9 wide 3. 3m9 high 4. 5m9 set 3kW electric mixer 1 set, inclined zone 35mm inclined pipe in sedimentation area, length of inclined pipe The 836mm9 installation angle 60 MY0. 8 0 200 type dosing device 2 sets of 9 each set with 0. 8m3 drug solution barrel. 10m2 double diaphragm box high efficiency frame filter press 1 electrical control cabinet 1 set of 3. 4 transformation process flow after transformation of the process shown in Figure 3 Application of Chemical Deoiling Technology in Oil-containing Water Treatment of Steel Rolling 4 System Operation and Effect Analysis 4.1 Selection of pharmaceuticals and determination of dosing amount: The system-injected pharmaceuticals are composite polyaluminium and polymer oil flocculants; the concentration of the formulated pharmaceuticals is 3%; Dosage is determined according to laboratory and semi-industrial tests. 10~20mg/1. 4. 2 Water sample monitoring: On November 4, 1999, the system began commissioning and running. On 24th September, the continuous operation began on 24 hours. On September 8th, sampling monitoring began. On December 8th, a total of 35 consecutive days were taken before and after, taking a total of 60 Group 120 water samples (In and out water is a set of D, each sample was measured PH value \ SS \ oil 3 items O and the water sample was analyzed 5 times, 5 times for the moisture content of mud \ mud cake Detection, the composition and particle size of the mud cake were analyzed three times.From the test results, the target value determined before the transformation was completely achieved, that is, the average content of the influent oil was 27.94 mg/1, and the average oil content of the outflow was 2. 88%。 88mg / 1; Into the water content of suspended solids average 233. 23mg / 1, effluent was 22. 53mg / 1; sludge pressure filtered by the frame, the moisture content from the original 94.72% reduced to 35. 04% It can be directly transported without secondary pollution. 4. 3 The effect of water quantity change on the treatment effect: The project transformation is carried out on-line. The amount of sewage into the chemical degreasing device is controlled by the valve. Due to the restriction of production conditions, the fluctuation of the water volume is large, and the fluctuation range is 18O. ~ OO m3/h. When the amount of water exceeds 3OO m3/h, it is clearly seen that the floc is flushed out of the inclined pipe. This phenomenon is particularly evident when the water volume suddenly increases. According to the scavenge water load, it is considered that when the circulating water suspended matter is controlled at 0~5O mg/1, the treatment load in the inclined pipe sedimentation zone is not more than 1O m3/< m2 - hD, and when the circulating water quality SS is controlled at 25 mg/ Below 1 the processing load is not more than 8m3/< m2 - hD. 4. 4 The effect of dosing amount on the treatment effect: The adjustment range of the dosing amount is controlled at 1O~2O mg/1. It is finally determined that when the dosing amount at 15mg/1G is small, the quality of the effluent is obvious, especially when the oil flocculant is added. When the amount is small, slicks appear in the clear water zone; Because the amount of drug is large, the formed floc is large and loose, the specific gravity is light, and it is not easy to settle 9 to affect the water quality. If the system can be operated in a closed circuit, the dosage can be further reduced. 4. 5 The influence of the mixture of medicines on the treatment effects: The uniformity of the medicine-water mixture has a great influence on the treatment effect. Evenly mixed, the chance of colliding with the drug-water increases, the ability to capture suspended matter increases, and the treatment effect is good. On the contrary, the effect is poor. But machine
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Application of Chemical Deoiling Technology in Oil-containing Water Treatment of Steel Rolling