What is the specific content of the technical case of oil production wastewater reuse treatment? The following is the answer from Zhongda Consulting.
1. Reuse technology of dilute oil wastewater for industry and irrigation water treatment
1.1. Technical principle and characteristics
After advanced treatment, the discharged wastewater can be reused for industrial production, agricultural irrigation and even domestic water, which is also one of the important ways to effectively alleviate the water crisis. At present, in addition to recycling ion exchange technology of steam injection boiler, effective advanced treatment methods include freezing, distillation, oil film and so on.
The methods of advanced treatment of oily sewage in oil fields by oil film include ultrafiltration, microfiltration, electrodialysis, reverse osmosis and nanofiltration. Among them, the treatment principle of ultrafiltration and microfiltration is to intercept micron-sized emulsified oil, suspended solids and dissolved substances in oily sewage by oil film, and the treated water is mostly used for oilfield reinjection or further nanofiltration and reverse osmosis treatment. Electrodialysis and reverse osmosis treatment methods are mostly used to filter and remove low-quality ions or compounds in sewage.
Distillation can generally be divided into compressed air distillation, multi-effect distillation and multi-stage evaporation, etc. In the Netherlands, the Middle East and Germany, this method is widely used to treat oilfield sewage, so as to further realize sewage reuse.
freezing refers to the desalination process by using the characteristic that the freezing point of brine is higher than that of pure water. At first, the water temperature of the extracted pure water is lowered below 1℃, at this time, thin ice will be formed on the surface of the water body, and then, when the ambient temperature is higher than 1℃, the ice will melt into water for use. Natural freezing is usually used in oil fields.
1.2 case analysis
Dagang Oilfield Group Company's sewage advanced treatment and reuse project is used to solve the water problem of the company's thermal power plant, calcined coke and polypropylene construction projects. After the treatment of oil production sewage reaches the standard, it is mixed with domestic sewage, pretreated by hydrolysis-biological aerated filter-coagulation sedimentation filtration process, and then advanced sewage treatment technology of "double membrane method" is adopted. The effluent can be used for boiler make-up water of thermal power plant, calcined coke and process water of polypropylene project.
C. Murray-Gulde has treated the oil field recovery water with high salt concentration by combining wetland construction with reverse osmosis. The general process is as follows: the mined water passes through a polyethylene filtering device to soften the exchanged ions, then passes through a polyethylene filtering device with a filter membrane of 1.45μm, completes the reaction in a reverse osmosis treatment device, combines with the construction of a wetland, and finally finishes the effluent. The toxicity of sewage treated by this process is obviously reduced, the salt content is reduced by 96%, and the conductivity is reduced by 98%, which basically meets the relevant indicators of discharge and irrigation, and also provides a feasible way to treat oilfield effluent.
GE water treatment technology enterprise made a pilot comprehensive analysis on the treatment of oilfield effluent by oil film method, and the results met the relevant indexes of federal drainage and reuse. The site of the experiment is located in a heavy oil field in Kern County, California, USA. The effluent water temperature of the oil field is about 85℃, the oil density is 11 mg/L ~ 41 mg/L, the content concentration is 11111mg/L, the concentration of solid suspended solids is high, and it contains saturated Si, Fe and B. The analysis has been carried out for five months, and the * * * has been running for 71 days, and the sewage treatment rate is 4.5m? /h。 The application of primary ion exchange technology combined with tertiary membrane treatment technology fully meets the standard of farmland irrigation water.
2 treatment technology of steam injection boiler for heavy oil wastewater reuse
2.1 water quality conditions of steam injection boiler
The steam injection water should meet the requirements of "Design Code for Water Treatment of Steam Generator with Produced Water from Heavy Oil Field" SY/T 1197-2111. In petroleum industry, steam generator is also called steam injection boiler. Different from other boilers, the steam quality produced by steam injection boilers is low, generally about 81%, and the steam pressure is about 31MPa. In order to verify whether the silicon content standard of produced water can be relaxed when it is used as the water source of steam injection boiler, some industrial-scale experiments have been carried out at home and abroad, and the basic conclusion is that when the iron concentration and hardness in water are low, salt accumulation will not occur in high sulfur dioxide and high water quality monitoring equipment. However, so far, there is no recognized conclusion that has been verified by production operation.
2.2 technical features and principles
according to the damage of heavy oil water to boilers, different treatment methods are adopted for different types of pollutants according to the standards of water quality of oil field steam equipment. Including: priority strengthening and subsection strengthening. Priority strengthening refers to deoiling in the front stage and filtering in the back stage. Generally, inclined plate oil separation tank, regulating tank and air flotation tank are used in the pre-stage oil removal treatment, and a certain amount of treatment chemicals are added to remove a large number of suspended solids, oil, chemical oxygen demand, etc., and some sulfides and ferrous ions can be removed; Sectional strengthening is to further remove oil, suspended matter and total iron on the basis of front oil removal. In addition, because resin exchange ions have weak treatment performance on SiO _ 2, the concentration of SiO _ 2 should be reduced to 45mg/L before resin exchange. Therefore, before resin ion exchange, the standards of iron concentration, suspended solids and oil should be ensured to meet the water supply requirements of steam equipment.
In recent years, the multi-effect evaporation process is mostly used to treat highly mineralized oilfield sewage. In Binnan Station of Shengli Oilfield, China, the multi-effect evaporation process was first applied to treat heavy oil sewage, and the treated water quality basically meets the water consumption index of thermal recovery boiler, and also meets the water quality index of industrial cold water and mother liquor configuration. However, because the steam discharged from the tail end can not be recovered, it consumes heat energy and has a high investment in operation.
2.3 case analysis
At present, there are 7 sewage reuse boiler treatment projects in Liaohe Oilfield, with a total design scale of 8.1×114m3/d, and there are ***161 sewage reuse thermal recovery boilers, with a steam injection capacity of * * * 4.5× 114m3/d.. According to the characteristics of its own heavy oil sewage, Liaohe Oilfield has determined the typical process of advanced sewage treatment.
Because the operation cost of chemical desilication is high and it is easy to cause scaling in the subsequent process, Liaohe Oilfield began to try the technology of reusing the sewage without desilication. Firstly, the boiler pressure, temperature and dryness are ensured to be stable through the boiler stable operation control technology, and then the secondary macroporous weak acid resin is replaced by a new resin by using the water quality control technology, and the trace scaling ions such as divalent/trivalent calcium, magnesium and iron are deeply removed, and the effluent concentration is controlled below 21ppb. On the premise of safe operation of the boiler, the concentration of silicon dioxide in the sewage reuse boiler can be increased, even without silicon removal. Since August 1, 2111, the desilication process has been stopped in Huansilian Sewage Advanced Treatment Station. On the basis of regular cleaning of the boiler, the process runs normally, and the treatment cost of adding chemicals and silicon sludge is saved.
In addition, the large-scale application of membrane technology has brought development prospects to the water treatment industry, and the "combination of ultrafiltration and reverse osmosis" is used as the center of "dual-mode" treatment, replacing the previous mode of ion exchange. The treatment rate of Shengli Oilfield is 2511m? /d, * * * invested more than 4.2 million yuan, and the operating cost was 2.3 yuan /m? . After advanced treatment, excess oily sewage can be reused as feed water for steam injection boiler to realize water recycling.
A large amount of oil production wastewater can be reused after being treated to meet the technological requirements, which not only avoids the unnecessary impact of ineffective recharge on the stratum and underground water system and reduces environmental pollution, but also can use the heat energy in the sewage to reduce the energy consumption of boilers and reduce the consumption of water resources, which is helpful to delay the shortage of local water supply.
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