Original Title: Super Petrochemical Good Article: Treatment Technology for Improving Organic Wastewater Quality of Electric Desalination and Decalcification Units! Notice for reprinting: The purpose of the article is to share and forward. In order to respect the fruits of Xiaobian's labor, please mark "This article is reprinted from Super Petrochemical (ID: superpc91)" at the top of the text. Those who reprint without authorization and do not cooperate with the request for reprinting will be reported. Activity Information 1: With the strong support of Sinopec, PetroChina, CNOOC, Sinochem, ChemChina, State Energy Group and Yanchang Petroleum, as well as the equipment management departments of local oil refining, coal chemical and chemical enterprises, China Chemical Industry Society The "2021 (2nd) China Petrochemical Equipment Inspection and Maintenance Technical Conference" is planned to be held on May 12-14, 2021. The conference will provide an effective communication platform for petrochemical equipment management personnel and equipment manufacturing, inspection and maintenance technology service enterprises, and bring management innovation and research and development and application regulations of entity technology. If you are interested in participating in the exhibition, please contact Super Petrochemical. (400-600 people) Activity information 2: China Chemical Industry Society and Sinopec Electrical Design Technology Center will jointly hold the "2021 China Petrochemical Enterprise Electrical Technology Summit Forum" in Ningbo from June 2 to 4, 2021, to innovate intelligent and efficient electrical technology and ensure the high-quality development of petrochemical enterprises. If you are interested in participating in the exhibition, please contact Super Petrochemical. (Conference size 500 people) Activity Information III: China Petroleum and Petrochemical Engineering Research Association will organize CNPC/Sinopec/CNOOC/Sinochem/China Aviation Fuel Group to hold the "2021 China Petrochemical Industry Warehousing and Logistics Technology Innovation Conference" in Qingdao, Shandong Province from April 14 to 16, 2021. The persons in charge of logistics, transportation and warehousing enterprises in dangerous goods industries such as petroleum, chemical industry, natural gas, explosive products and highly toxic drugs discussed and exchanged on the development of petroleum and chemical warehousing logistics industry in the direction of scale, specialization, intensification and intellectualization. If you are interested in participating in the exhibition, please contact Super Petrochemical. (Conference size: 350 people) Activity information 4: China Chemical Industry Society organizes Sinopec, PetroChina, CNOOC, Sinochem, ChemChina, State Energy Group, Yanchang Petroleum and private petrochemical enterprises to hold the "2021 (5th) International Olefin and Polyolefin Conference" in Ningbo on May 25-27, 2021. If you are interested in participating in the exhibition, please contact Super Petrochemical. (Conference size: 350 people) Treatment Technology of Organic Wastewater Quality Improvement in Electric Desalting and Decalcification Unit Dai Min, Ma Zhongting, Sun Jinmei (PetroChina Karamay Petrochemical Co., Ltd. Refining and Chemical Research Institute) Main contents: According to the needs of crude oil processing and coke quality upgrading, the wastewater produced in the process of electric desalting and decalcification was treated by organic acid extraction, extractant regeneration, organic acid recovery and steam stripping. According to the extraction equilibrium data and physical parameters of isopropyl acetate, isobutyl acetate and ethyl acetate, isopropyl acetate was selected as the extractant for the water sample with acid mass fraction of 3. 0%. According to the treatment efficiency and acid concentration less than 0. 2%,rotary vacuum evaporator, the suitable extraction phase ratio (oil/water volume ratio) was determined as 3 ∶ 1, and the corresponding extraction stage was 6. Under this condition, the extraction rate was 95%, and the acid concentration in the lower water layer was 0. 149%. The upper extract was treated by azeotropic distillation, and the purity of the recovered acetic acid was 96. 81%. After stripping, the COD of the water phase was reduced from 29 300 mg/L to 4 710 mg/L, and the COD was reduced by 83. 9%.The water quality can meet the requirements of the influent water quality of the existing industrial wastewater treatment device, and the reuse or discharge of organic wastewater can be realized. At the same time, the economic benefit of 1.828 million yuan per year can be obtained by implementing the process.
Keyword: electric desalting, decalcification, extraction, industrial wastewater The mass fraction of calcium in Fengcheng super heavy oil produced from Xinjiang Oilfield is up to 265 μg/G. These metal calcium salts are easy to remain in coke during crude oil processing, resulting in high ash content and poor quality and grade of coke. In order to improve the quality and grade of coke and fully realize the maximum benefit, it is necessary to decalcify the heavy oil. In the industrial test of decalcification of crude oil with organic acid [1-2], there is a problem of high COD in the drainage after decalcification. The direct discharge method not only fails to recover the decalcifying agent,hemp extraction centrifuge, but also increases the raw material cost of the decalcifying process. At the same time, the sewage with high calcium and COD will cause environmental pollution. The above problems are not conducive to the smooth operation of electric desalting and decalcification units [3-6], have a certain impact on the safe production of refineries, and hinder the industrial application of crude oil desalting and decalcification processes. To solve this problem, organic acid extraction and stripping processes are used to treat the wastewater from desalination and decalcification processes, and the application and effect of the treatment technology are mainly introduced below. Expand the full text 1 Overview of wastewater 1.1 Nature of wastewater When the conventional electric desalting is carried out on the calcium-containing crude oil, the water quality is required to be directly discharged to the subsequent sewage treatment device. According to the nature of crude oil processing and production practice, the main components of industrial wastewater, especially primary drainage, are organic calcium carboxylate and some inorganic salts such as calcium chloride and sodium chloride when crude oil is desalted and decalcified by primary electric desalination. Table 1 shows the nature of the drainage. In the wastewater after decalcification, the water quality of primary drainage has changed to a certain extent, which belongs to high calcium and high COD wastewater. If the wastewater is discharged directly, it will impact the sewage treatment unit of the refinery, resulting in unqualified drainage and even environmental pollution. During the implementation of the decalcification process, the pretreatment test process for the primary electric desalting wastewater is as follows: the primary electric desalting and decalcification wastewater is solidified and regenerated by sulfuric acid, so that the organic acid calcium in the primary wastewater is converted into organic acid and calcium slag, and the organic acid-containing wastewater is obtained through solid-liquid separation. The existing industrial units of the enterprise can realize the pretreatment of primary electric desalting wastewater. The properties of the pretreated organic acid wastewater are shown in Table 1. The mass fraction of acetic acid is 1% ~ 3%, and its COD is relatively high, so it is not suitable to be discharged to the downstream sewage treatment unit. In order to carry out the decalcification process successfully, the wastewater containing organic acid needs to be further treated. Table 1 Properties of Drainage The extraction ratio is not only related to the extraction efficiency of organic acids in wastewater, but also to the subsequent recovery of extractant, the treatment of wastewater after extraction and its effect. According to the index requirements of treatment efficiency and acid mass fraction less than 0. 2%, when isopropyl acetate is used for the extraction treatment of wastewater containing 3. 01% acetic acid, the suitable extraction phase ratio is 3 ∶ 1, the corresponding extraction series is six, the extraction rate is 95%, and the acid mass fraction in the lower water after extraction is 0. 149%. 2.2 Extractant regeneration and decalcifying agent recovery process The upper layer after extraction is the oil phase extraction liquid, which mainly contains extraction agent, decalcification agent and water. In order to realize the recovery and recycling of the decalcification agent and extraction agent, decarboxylation after extraction ,50l rotovap, it is necessary to use the regeneration process to treat the material at the upper layer of extraction, so as to realize the separation of the decalicification agent and extraction agent. Therefore, the effect of extractant regeneration process is the key to the implementation of extraction process and an important link in the implementation of extraction process technology. There are two regeneration processes. One process selects the aqueous solution of inorganic alkali sodium hydroxide or sodium carbonate as the regenerant, and the extract in the oil phase reacts with the inorganic alkali to obtain a salt that is easily soluble in water, so as to realize the separation of the extractant and acetic acid. Comprehensive analysis of the implementation effect of extractant regeneration by alkali washing technology, although the extractant can be regenerated, but the sodium acetate or calcium acetate solution produced in the process has a high COD, and can not be rationalized, which brings a new problem of wastewater treatment. Therefore, combined with the actual situation of the current production, it is not feasible to use inorganic base to regenerate the extractant.
The other regeneration process is to separate the upper extract liquid by azeotropic distillation according to the different volatility of the materials, and recover the extractant and acetic acid to realize the reuse of the two materials. Azeotropic distillation is to remove water from the top of the azeotropic column and distill acetic acid from the bottom of the column by using the characteristics of heterogeneous azeotropic mixture formed by water and azeotrope. The implementation effect of this method is good, and its application in related industries in China is mature. Isopropyl acetate was selected as extractant to separate acetic acid from ester-water mixture by using the characteristic of heterogeneous azeotrope formed by water and isopropyl acetate. The extractant regeneration unit in the test is a small rectification unit, which rectifies the upper material after extraction. The test results are shown in Table 5. Table 5 Distillation Test Material Distribution w,% It can be seen from Table 5 that after the distillation of the upper extract liquid after extraction, the extractant accounts for 83.85% and water accounts for 16.14% of the material separated from the upper part. The regenerated extractant is recovered by settling and cutting water, and is collected and recycled in the extraction process; high-purity acetic acid is distilled out from the bottom of the rectification kettle, and the purity of the acetic acid is 96.81%. The experimental results show that the separation of extractant and acetic acid can be realized by rectifying the upper extract liquid after extraction. Repeatedly extract and regenerate the regenerated extractant to verify the effect of extractant recycling. The test results are shown in Figure 1. It can be seen from Figure 1 that the extraction efficiency of the extractant is maintained at 33% ~ 37% during 6 times of regeneration, and the application effect of the extractant obtained from multiple regenerations is basically equivalent to that of the fresh extractant, indicating that the extraction liquid of the upper oil phase is regenerated to recover the extractant, which can meet the quality requirements for the recycling of extractant. Fig. 1 Variation Curve of Regeneration Times and Extraction Efficiency 2.3 Steam stripping of aqueous phase after extraction The heavy phase material after extraction is treated by steam stripping technology, which is relatively mature in the industry at present, to extract the light components and realize the discharge of wastewater quality up to the standard. In the laboratory, the lower heavy phase material after extraction was treated by steam stripping, and the lower water sample containing isopropyl acetate, acetic acid and water was extracted and separated by using the different boiling points of the three. The analysis data of water samples before and after stripping are measured, and the results are shown in Table 6. It can be seen from Table 6 that the COD of the heavy phase material after industrial water extraction is reduced by 83.9% from the initial 29,300 mg/L to the stripped 4,710 mg/L. Table 6 Water Sample Analysis Data after Steam Advance Since the solubility of isopropyl acetate in water is 2.9%, the direct COD contribution value is about 27 000 mg/L, and the corresponding stripping feed water in Table 6 has higher COD due to the dissolution of isopropyl acetate. The results of gas chromatography showed that the mass fraction of isopropyl acetate in water after stripping was 0. 021 4%, and the mass fraction of acid was 0. 19%.The separated isopropyl acetate could be collected for reuse after oil-water phase separation. The experimental results show that the separation of ester and water can be realized by stripping the lower aqueous phase after extraction, and the COD of water can be greatly reduced. 2.4 Economic analysis of water treatment There are many treatment technologies for industrial wastewater, such as advanced oxidation, extraction, anaerobic or aerobic biological treatment. The advanced oxidation technologies mainly include Fenton oxidation, photocatalytic oxidation, catalytic ozonation, ultrasonic oxidation, etc. After investigation, for the industrial water with COD of about 30 000 mg/L, if the advanced oxidation process is used to treat the industrial water, the amount of chemicals used in the treatment process will be too large, and the requirements for equipment manufacturing and operation control will be high, and the investment will be large. However, catalytic ozonation and photocatalytic oxidation can be considered as pretreatment processes for removing oil and degrading macromolecular organics in wastewater. At present, some refractory organic substances and toxic substances in wastewater are usually treated by biological methods. Biological bacteria can degrade and utilize harmful substances, thus purifying the wastewater. For the refractory industrial sewage with high salinity, in order to ensure the operation of the sewage treatment unit, it is generally necessary to carry out separate treatment before the sewage treatment unit in the enterprise to degrade part of the COD in the water.
In addition to the direct use of biochemical treatment methods, it can also be combined with coagulation and sedimentation, extraction, chemical oxidation, ion exchange and other methods for pretreatment to reduce the load and difficulty of subsequent biological treatment. The wastewater after decalcification is oily, high salt and high COD wastewater. When the biological treatment process is adopted, there is a very high requirement for the bacteria in the biological treatment process. The wastewater after decalcification in the process route firstly adopts the extraction-rectification-stripping process, and then is directly discharged to the sewage treatment device. This combined process route will increase the operation cost to a certain extent, but it can provide a strong guarantee for the stable operation of the subsequent sewage treatment device. The discharge of high-calcium organic wastewater in the process of electric desalting and decalcification is estimated to be 4 m3/H. On the basis of this treatment scale, the overall economic benefit is estimated. The annual benefit of acetic acid recovery and utilization is 3.888 million yuan, and the total cost of treating decalcified acetic acid-containing wastewater is 2.06 million yuan. The specific estimation process is as follows: (1) Income from recycling of acetic acid. The treatment capacity of acetic acid wastewater is 4 m3/H, the calculation is based on 4 t/H, the mass fraction of acetic acid is 3%, the price of acetic acid is 4 500 yuan/t, the operation time of the plant is 8 000 H/a, the acetic acid recovery rate is more than 90%, and the annual benefit of acetic acids recovery and utilization is 4 × 3% × 0.9 × 8 000 × 4 500 = 3 888 thousand yuan. (2) Cost of treating acetic acid wastewater. ① Device depreciation: the estimated price of the device is 10 million yuan, the depreciation period is 10 years, and the device depreciation is 1,000/10 = 1 million yuan/a. ② Energy consumption cost: when the total power of the motor is 220 kW and the electricity charge is 0.4 yuan/ (kW · H), the electricity cost is 220 × 0.7 × 8,000 = 704,000 yuan; when the steam consumption is 0.3 t/H and the steam price is 25 yuan/t, the steam cost is 0.3 × 8,000 × 25 = 60,000 yuan. ③ Extractant cost: In the process of acetic acid wastewater treatment, the extractant consumption is less than 0. 5 kg/t wastewater, the annual consumption of extractant is 0. 5 × 4 × 8 000 = 16 t, and the cost of extractant is 16 × 8 500 = 136 000 yuan if the extractant price is 8 500 yuan/t. ④ Labor cost: Each shift of the device requires one operator, three shifts in four shifts, and four operators are required to be added in total. If the wage income of each person is calculated as 40,000 yuan/a, the labor cost is 4 × 4 = 160,000 yuan. Therefore, the total cost of treating the decalcified wastewater containing acetic acid is 100 + 70.4 + 6 + 13.6 + 16 = 2.06 million yuan. (3) Direct economic benefit. Considering the benefits and costs, the annual economic benefit is 388.8-206 = 1828000 yuan. 3 Conclusion According to the nature of organic wastewater in the electric desalting and decalcification device, the process route of organic acid extraction treatment in the wastewater was investigated. The wastewater with acetic acid mass fraction of 3% was taken as the research object, and isopropyl acetate was used as the extractant. The suitable extraction phase ratio was 3 ∶ 1, and the extraction stage was six. The acid content in the waste water was less than 0. 2%. The COD of the decalcified wastewater after treatment is reduced by 83.9%, and the target requirement for the treatment of high-calcium organic wastewater is realized. The cost of treating the decalcified wastewater containing acetic acid is estimated to be 2.06 million yuan per year and the economic benefit is 1.828 million yuan per year when the discharge of high-calcium organic wastewater in the process of electric desalting and decalcification is 4 m3/H. Thank the author for his hard work and contribution! Super petrochemical finishing release,winterization filtration, for reference and understanding, reproduced please indicate the source. If this article is helpful to you, please click below to read and leave a message! Return to Sohu to see more Responsible Editor:. toptiontech.com