How to prevent gas pipelines from freezing in Chongqing and other southwestern regions

Published on:

2023-01-31 14:47

Part of gas production and transportation pipelines at the gas mine in Chongqing are prone to being clogged by hydrated ice in winter to varying degrees. One of the measures to prevent the pipeline from clogging with ice in the winter is the injection into the pipeline of antifreeze, such as ethylene glycol, within 2-3 months of winter. The filling method generally uses intermittent filling, which has problems such as long-term, simple equipment, drug storage, and high labor intensity of workers. For pipelines with ice jams, measures are also taken to free and eliminate blockages. This method is fraught with hidden dangers such as safety and pollution.

There are many factors for the formation of gas hydrates, but the latest manifestation is the effect of temperature. When the temperature of natural gas transportation through the pipeline exceeds the temperature at which hydrates are formed, changes in the water and sulfur content of natural gas components, as well as changes in the environment, do not produce He Hewu and do not cause the pipeline to be blocked by ice. Based on studies on the electric heating of offshore oil pipelines, the use of electric heating technology to increase the temperature of pipelines for collecting and transporting natural gas in order to prevent the formation of hydrates in pipelines and clogging them with ice is considered.

The SECT principle is based on the AC "skin effect" and "proximity effect" Due to the strong magnetic permeability of the steel pipe, even

A significant skin effect also occurs at the industrial frequency voltage. The so-called skin-effect is a phenomenon in which an alternating current passes through a carbon steel conductor, a current gradually becomes splashed on the surface of the conductor, and the proximity effect is an electromagnetic phenomenon between a pair of electrical bodies with opposite currents, in the heating tube When the current passes between the cable and the heat pipe, The current on the heating pipe gradually tends to the inner wall of the heating pipe, and this is the joule heat generated by this thin inner wall to meet the needs of electric heating. The Joule heat generated by the surface effect electric heating system mainly comes from three parts:

When the leather cable is energized, the heat emitted by the carbon steel pipe is the main heat source of the skin electric heating system.

Heat generated by cables inside carbon steel pipes.

Hysteresis loss in carbon steel pipe emits some of the heat.

In a skin-effect device, an insulated wire (SECT wire) passes through a strong magnetism steel pipe and connects to the end of the steel pipe. Or medium-frequency variable voltage, current passes through the wire and steel pipe to form a loop to generate joule heat. Since there is a certain relationship between the size, material, and frequency of the steel pipe, the alternating current does not flow uniformly across the cross section of the steel pipe, but flows concentratingly to a certain depth from its inner surface, and the current density decreases exponentially the voltage and current on the outer surface are practically zero, which is very safe.

Thus, the SECT tube can be welded directly to the feed tube, making it an efficient heat source. The heat generated by the SECT pipe is quickly transferred to the transport pipe through a weld and heat-conducting cement, which plays the role of electric heating.

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