New trends

Microencapsulated drag reducing agent (mdra) is prepared by encapsulating high concentration of drag reducing polymer particles in the shell composed of some inert substances. The successful development of microcapsule drag reducer is a new trend in the development of drag reducer.

There are many ways to produce microcapsule drag reducing agent, including static extrusion, centrifugal extrusion, vibrating nozzle method, rotating disk method, interfacial polymerization, multi-component condensation, suspension polymerization, etc. To produce microcapsule drag reducer, polymerization monomer, catalyst and shell material are added from the central hole and outer ring sleeve respectively, and extruded from the lower end of the device at a certain speed to form microcapsule drag reducing agent particles. The extrusion speed is very important. When the extrusion speed is slow, the appearance of microcapsules is regular and the size is uniform; on the contrary, if the extrusion speed is fast, the microcapsule particles will adhere, resulting in abnormal shape and different sizes of microcapsules. It is beneficial to control the particle size of microcapsules by keeping a certain frequency of vibration in the production process.    

Because the monomer is polymerized in the closed microcapsules, the reaction scale is very small for a single microcapsule, so the reaction conditions can be well controlled, especially the reaction heat can be released in time. If the monomer is σ - olefin, Ziegler Natta catalyst is usually used and added before the formation of microcapsules. Because the catalyst of Ziegler Natta system will lose efficacy quickly when encountering oxygen, there is no oxygen in the reaction system. Some monomers can be polymerized using ultraviolet rays, but the ultraviolet rays must be able to penetrate the microcapsule shell.

The shell of microcapsule is an important part of drag reducing agent, and the reactants in the inner core of microcapsules can not react with each other or mix with each other. If the inner core of the microcapsules is a σ - olefin polymerization system, in order to avoid catalyst failure, there is no oxygen in the microcapsule shell, but a small amount of hydroxyl and carboxyl groups have little effect on the polymerization. The suitable shell materials are polybutylene, polymethacrylate, polyethylene glycol, wax, stearic acid, etc. However, the polymer microcapsules can not be formed in the process of polymer coating polymerization. In addition, the performance of microcapsule shell is required to be stable during transportation and storage, and its broken or dissolved residue has no effect on the physical and chemical properties of crude oil or petroleum products and the oil processing process. The microcapsule shell can be removed by dissolving in the injection medium or pipeline fluid, mechanical crushing, melting, photochemical crushing, biodegradation and chemical combination. As the microcapsule drag reducer is stored and transported in the form of solid particles, the cost of transporting solvent, slurry or other carriers is saved. If solvent or other carrier (i.e. injection medium) is needed for injection into oil pipeline, it can be purchased at low price locally and mixed on site instead of complex post-treatment process.

Application examples

First of all, take a look at the examples of drag reduction agents used in oil pipelines abroad. For the trans Alaska crude oil pipeline in the United States, the original design of 12 pumping stations was reduced to 10, and the daily oil transportation capacity increased from 22.26 × 10 m to 38.16 × 10 m. The diameter of a pipeline in the North Sea oil field of England was 1066 mm in the original design scheme. After comparison and selection of schemes, the scheme of adding drag reducing agent at peak time was adopted. The pipe diameter was changed to 914.4mm, which greatly reduced the investment. A 200 mm diameter product oil pipeline in the southwest of the United States once had a neck jam problem when gasoline throughput increased in summer. After using drag reducing agent, the problem is solved quickly and economically. The friction resistance of the pipeline decreases by 40% and the throughput increases by 28%. A 93km long oil pipeline with a diameter of 200 mm in the Midwest of the United States requires synchronous transportation of diesel and gasoline, and the flow rate of diesel oil should be increased by 20%. The friction resistance of diesel oil decreased by 38% after using drag reducing agent.

In China, ZODR-G350, produced by Zoranoc company, was first used in Tieda line, Donghuang line and Pulin line, and achieved success. For example, after the successful field test in 1986, drag reducing agent was put into use intermittently for 79 days and 97m in Shenyang, Xiongyue and Fuxian stations and sections, and 17.667 × 10t crude oil was transported along the whole line, which eased the tense situation of Tieda line's export, gained large export exchange rate, and created higher economic benefits for the country. In 1987, the world oil price fell and the national export decreased. The pipeline resumed normal operation. It was very flexible and convenient to stop injecting drag reducer.

The original design oil transportation capacity of Huatugou Golmud oil pipeline in Qinghai Oilfield was 100 × 10 tons per year. Later, the oil field production increased, and the pipeline transportation capacity was required to be increased to 150 × 10 tons per year. According to the traditional method of increasing mechanical power, the original 4 pumping stations need to be transformed into heat pump stations, and the original 3 heat pump stations need to be reconstructed and expanded. Not only time is not allowed, but also the investment is large. They cooperated with Beck pipeline chemicals company in the United States to carry out drag reduction additive test. The test results show that the annual throughput of 150 × 10t can be easily achieved without adding any oil pump, and the cost is much lower than the investment of the expansion pump station.