The use of electric heating when not freezing a ditch at the entrance to the tunnel of an expressway
For the Fushui Tunnel project located in the Alpine region, usually due to the low daytime temperature in the geographic location of the tunnel and the high wind speed at the tunnel entrance, subject to extreme winter weather conditions, drainage ditches on both sides of the tunnel entrance can freeze. As a result, seeping water in the tunnel cannot be released unhindered and eventually overflows through the ditch, enters the ballast layer and forms ice, affecting traffic safety and creating huge safety threats. Therefore, the prevention of drainage and freezing of ditches at the entrance to tunnels in the highlands is an important issue that requires attention in the construction of tunnels in the highlands.
In our country, the following types of drainage ditches are mainly used at the entrance section of the tunnel in the highland region: deep buried in the center, thermal insulation, warming, as well as a combination of thermal insulation and warming ditches. As a rule, after the completion of the tunnel, there are two remedial measures. The details are as follows:
After the ice in the cuvette is cleaned, the concrete at the bottom of the ditch will be removed with a pickaxe within 50 m of the mouth of the ditch on both sides, the slope at the bottom of the ditch will be heated, and will be connected to the inspection well on the hole through the thermal insulation pipe at the hole; The construction team installed a self-regulating non-freezing electric heating system at the bottom of the ditch on both sides and laid a heating cable on each side of the ditch, and the installation range was within 1 km from the entrance to the tunnel.
The key to non-freezing tunnels in alpine regions is good drainage work The isolation part of the ditch, especially the part of the tunnel entrance, should be well insulated to avoid freezing and expansion of the layout causing serious illness. When installing a thermal insulation ditch, you should pay attention to the moisture-proof treatment of the cold insulation material, t. The ditch should be weakened as much as possible in terms of design to reduce convection caused by convection heat losses.
Reliable measures should be put in place in tunnel ditches in the highlands to prevent flowing water from freezing. Taking into account comprehensively, a single insulation of the gutters on both sides cannot guarantee the occurrence of ice in the winter. To prevent cold and keep warm, a combination of passive protection from cold and active insulation in thermal insulation ditches is used. Method, Which consists in installing an electric heating system in trenches in which insulation measures are taken, can effectively solve the problem of freezing dains at the entrance to the cave.
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.