Application of the method of electric heating on the skin effect in the oil pipeline
The electric heating method of oil-seam pipeline can be divided into surface effect electric heating method and electric heating method. The skin effect electric heating technology is a new type of pipeline heating technology. The skin-effect electric heating method has become widespread abroad and has become the first choice for heating oil over the past 20 years.
The principle of skin-effect electric heating is to use AC electromagnetic induction to generate joules heat, as shown in Figure 1. The far end of the ordinary cable is short-circuited through the pipe with the heating steel pipe, and alternating current is passed between the near end of the cable through the pipe and the steel pipe, And an alternating magnetic field is set at the far end. Steel pipe. Under the action of a magnetic field, vortex currents are generated inside the wall of the steel pipe, with vortex currents close to short circuit, releasing a large amount of joules of heat. It can be seen that the skin-effect electric heating body is a steel electric heating pipe, not a cable. Electric heating with a skin effect can be divided into two methods: internal heating and external heating.
The heat transfer effect from the heater in the pipe is good, but the design and maintenance are complicated; the heat transfer effect from the heater outside the pipe is worse than that of the steel pipe heater, but the design and maintenance are more convenient. The heating system using surface effect electric heating technology has simple design, safety and reliability, long service life, simple automatic temperature control, high thermal efficiency and low design cost. The following advantages:
(1) The process is simplified, the design is convenient, and the construction cost is low. Electricity skin effect.
In electric heating technology, only one pipe is used, and the project cost is 20% lower than the three-pipe process.
(2) The temperature is adjusted automatically and the worker's work intensity is low.
(3) High heating efficiency and low power consumption.
(4) The whole pipeline line is heated, so no need to worry about condensation on the pipeline.
Once the skin effect electric heating technology is promoted and applied in remote well stations, it can replace the three-pipe process, reduce energy consumption, reduce costs, obtain obvious economic benefits, and raise the technical level of crude oil collection and transportation to a new stage.
Electric heating cable is a heating method that uses insulation resistance or resistance heating wire to create a temperature after power supply. It can automatically adjust the output temperature and reasonably maintain the process temperature requirements to keep warm, raise the temperature and protect the heating equipment from freezing. The insulation and antifreeze effect of the container is very good.
Transport of heavy oil through the pipeline over long distances and long-term retention in the pipeline will result in a drop in temperature due to heat dissipation and increased viscosity, which will cause the pipeline to be blocked by freezing or condensation-related accidents. Electric heating is widely used as effective insulation of pipelines and anti-freeze protection.
According to the statistics of the Hydrometeorological Center, the average daily minimum temperature at the location of the CNPC tank farm is 5 ° C, and the average daily maximum temperature is 14 ° C. Since the freezing point of the PX is about 15 °C, the supply pipeline needs heat preservation and heating. The oil depot has been in operation for many years without a stable source of steam, therefore, this project is considering the use of electric heating technology.
Long-distance crude oil pipelines with a high paraffin content with freezing temperatures above 50 °C. According to the requirements of the production plan of the plant, the volume of oil transportation through the pipeline is 150 thousand rubles. Tons per year, maximum-200 thousand. Tons per year.. According to the thermodynamic analysis of the pipeline, the initial supply temperature of the pipeline is 80 ° C (TN), and the temperature of the end entering the tank is 60 ° C (Tu). Since the transportation temperature needs to be adjusted according to the time of year, it sometimes needs to be transported by heat.
In petrochemical engineering, trunk infusion pipelines are the lifeblood of the factories. The temperature in the northern region is too low in winter and the pipeline needs to be insulated to compensate for the heat loss due to the low temperature in winter to ensure the normal operation of the pipeline.
The toughness of the asphalt is greatly affected by the temperature. When the temperature decreases, the toughness of the asphalt increases, and the drop in resistance of the asphalt during pipeline transportation increases; when the temperature falls below the freezing point, the asphalt solidifies, causing the pipeline to clog and the conveyor belt to come to trouble. Therefore, electric heating and heat preservation during the transportation of asphalt are very important.
To solve many problems in the "three high levels" crude oil extraction process, the thermal energy generated by the electric heating is used to heat the crude oil in the oil pipe throughout the process to improve the fluidity of the crude oil. Effectively solve various technical problems encountered in the operation of high-condensation, high-viscosity and high-paraffin crude oil, and achieve the goal of improving the productivity and efficiency of oil wells.