| In recent years, domestic crude oil is getting heavier and lower quality along with the application of the tertiary recovery technique. At the same time, calcium content in some domestic crude oil has been increasing quickly, which has bad effects on the desalter and FCC’s daily operation. Currently, marketed decalcifying agents are mainly strongly acidic of serious equipment corrosion, containing eutrophication elemental phosphorus which can cause serious environmental pollution. The existing decalcification techniques are not optimal, especially when they encounter some crude oil which has higher quantity of oil-soluble calcium. Therefore, it is necessary and urgent to select a highly efficient decalcification technique which bears good removal ability for oil-soluble calcium and to improve the processing technique for heavy oil. With the enhancement of the environmental consciousness, the research of decalcifying agent which is non-toxic, pollution-free has become an important research aspect.In order to solve the hazardous problems on pipelines and refinery catalyst by high calcium, allyl polyoxyethylene ether (APEG), asparagine, acrylic acid (AA) and hydroxyethyl acrylate (HEA) were chosen as raw materials to synthesis of environmentally friendly green decalcifying. Luning pipeline oil and Yichang pipeline oil were used as target oil to conducted removal of calcium and other metals. And terpolymers were mixed with other agents such as HPMA, PAA, CH4O3S, C6H8O7, (NH4)2C2O4, DTAB and C4H10O2 to prepare a series of environment-friendly decalcifying agents, and the preferred complex-type decalcifying agent product was used in pilot scale and industrial application test. The main research contents are exhibited as follows:(1) Luning and Yichang pipeline oil were chosen as the research object, using Vista AX full spectrum direct-reading inductively coupled plasma atomic emission spectrometer (ICP-AES) analyzed the element content in crude oil. The results showed that the calcium content in Luning pipeline oil metal element oil of is 67.0μg/g, nickel, iron, sodium are 17.1μg/g,14.7μg/g and 29.3μg/g, respectively.Yichang pipeline oil content of calcium in 23.1μg/g, nickel, vanadium, iron, sodium are 6.01μg/g and 3.82p.g/g,2.67μg/g and 6.44μg/g, respectively. Method of solvent extraction was used to analysis state of metal elements Luning and Yichang pipe line oil. The results in Luning pipeline oil accounted for 42.1% of water-soluble inorganic calcium salt, calcium petroleum accounted for 24.0%; 83.2% of water-soluble inorganic salt; 14.5% of porphyrin Ni, accounting for the non-porphyrin Ni 77.7%; inorganic ferric iron salt and oil accounted for 64.0% acid, a porphyrin iron and non-iron porphyrin compound 36.0%; 13.7% of water-soluble vanadium salts, porphyrin and non-porphyrin compounds of vanadium is 86.3%. Yichang pipeline oil have water-soluble inorganic calcium salt oil accounted for 25.5%,48.8% of the calcium in the form of oil and salt; porphyrin and non-porphyrin compounds mainly in the form of nickel, a nickel porphyrin accounted for 11.8%, non-porphyrin Nickel accounting for 72.6%; water-soluble inorganic iron salts accounted for 19.9%, non-iron porphyrin compound represents 38.2%; 15.3% water-soluble salts of vanadium, vanadium porphyrins and porphyrin non-vanadium 18.7% and 66.0%, respectively.From the above results, Luning pipeline oil contain more water-soluble calcium and easy to remove. However, Yichang pipeline oil containshigher proportion of oil-soluble organic calcium, thus its difficult than Luning pipeline oil to remove calcium from it. Therefore, it should be directed of development an efficient decalcifying agent for removing oil-soluble organic calcium.(2) Water-soluble monomer APEA was produced from APEG and L-asparagine by esterification via the microwave technique rout. Phosphorous free copolymer of AA-APEA was synthesized with different molar ratios in this study and the synthesized copolymers were characterized by FT-IR and further conformed by H-NMR. The best synthesis process is as following:microwave radiation power is 500 W, radiation time is 10 min, n(APEG):n(L-Asparagine) of 1:1.4. Yield of 78.3%. A series of copolymers as decalcifying agent were prepared through free radical polymeric reaction in aqueous solution by using of AA as small molecule monomers and APEA as macromonomers and the TGA results indicated that APEA-AA copolymer has better heat stable property. The best synthesis process is as following: monomer ratio AA:APEA=2:1,5% initiator amount, drop for 1.0 h, reaction temperature is 85℃, reaction time is 2 h and 3% chain transfer agent. Best desalting process is as follows:6% of the water injection,200 times mixing intensity, the total dose rate of agent:calcium is 4:1, the first step electric desalting temperature is 135℃ and the second step is 130℃ and stand reaction time is 20 min, Luning pileline oil using 50 ppm water-soluble R1-02 demulsifier and Yichang pipeline oil with 20 ppm oil soluble demulsifier DCR-168. Under the best conditions, the calcium removal efficiency of Luning pipeline oil and Yichang pipeline oil by water soluble copolymer APEA-AA is 79.2% and 70.4%, respectively.(3) Amphipathicity terpolymer AA-APEA-HEA was prepared with APEA macromolecular monomer, acrylic acid (AA) and hydroxyl ethyl acrylate (HEA) hrough the water phase free radical copolymerization. And the Fourier infrared spectrum (FT-IR), nuclear magnetic resonance hydrogen spectrum (’H-NMR), thermogravimetric (TGA) and bromine value results indicated the polymerization monomer copolymerization reaction completely and have good thermal stability. The best synthesis process is as following:monomer ratio AA:APEA:HEA=2:1:1,7% initiator amount, drop time is 1.0 h, reaction temperature is 85℃, reaction time is3h andchain transfer agent is 5%. Best desalting conditions are as follows:6% of the water injection,200 times mixing intensity, the total dose rate of agent:calcium is 3:1, the first step electric desalting temperature is 125℃ and the second step is 120℃ and stand reaction time is 10 min. Under the best conditions, the calcium removal efficiency of Luning pipeline oil and Yichang pipeline oil by amphipathicity terpolymer AA-APEA-HEA decalcifying agent is 90.7% and 90.4%, respectively. Meanwhile, iron removal rate is about 60% and Na, Mg, Al removal rate are over 80%, which are better than water soluble copolymer APEA-AA. The research results on the recycle use of amphipathicity terpolymer AA-APEA-HEA decalcifying agent showed that it can remove about 70% calcium from crude oil based on the addition of 50% fresh decalcifying agent. And electric conductivity method was used to research the mechanism between amphipathicity terpolymer AA-APEA-HEA decalcifying agent and calcium in crude oil.(4) In order to enhance the calcium remove property of amphipathicity terpolymer, several complex monomer including HPMA, PAA, CH4O3S, C6H8O7, (NH4)2C2O4, HCOOH and C4H10O2 were introduced to form series efficient environment-friendly decalcifying agents. The result showed that the B-7 decalcifying agent exhibit best calcium remove property in Luning (98.1%) and Yichang (99.2%) pipeline oil when the monomers in accordance with the ratio of quality:terpolymer (20%), PAA (15%), HPMA (15%), C6H8O7(10%), (NH4)2C2O4 (20%), CH4O3S (15%) and C4H10O2(5%). In addition, the compound decalcifying agent has low corrosion of 20# carbon steel.Pilot test was carried out for optimization of environment-friendly compound decalcifying agentof B-3 and B-7, the results show that B-3 and B-7 decalcifying agent can reach about 94.5% and 96.7% calcium removal efficiency, respectively, in the following conditions:processing crude oil quantity of 5 kg/h, ratio of agent: calcium is 4:1. This is superior to the decalcifying agent which used in field (72.6%) under the same conditions. Environmental-friendly decalcifying agent of B-7 was carried out on an industrial scale production, and provides five tons of B-7 products for the completion of the industrial application test. The result showed that the environmental friendly decalcifying agent of B-7 can reach 74.3% calcium removal efficiency at first step electric-desalting. The decalcification effect increased by 15 to 20% compared with the current decalcifying agent in site. The environmentally-friendly decalcifying agent of B-7 doesn’t contain phosphorus elemental and also odorless, thus make the production environment significantly improved and fulfill the requirements of industrial application and now realize the large-scale production and use. |
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