What are the dangers of exchanging LNG for water at 15 degrees Celsius using a heat exchanger?
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Could you analyze in detail the reasons and the consequences? Thank you
What is the temperature of LNG? Can it freeze water into ice? When water turns to ice, its volume expands and this can cause the container to burst, leading to an LNG leakage accident
The storage temperature for LNG is generally -162 degrees; an increase in temperature causes it to vaporize into natural gas. For gasification, air-temperature gasification is generally considered; it’s not clear whether heat exchange with water is possible.
Just install more fin-type carburetors; it requires no energy, and there’s no need for water circulation or measures to prevent freezing
The main topics discussed in the slides didn’t cover removal. First, is LNG in liquid or gas form? Second, the operating temperature, pressure, and flow rate. Third, what is used for heating (hot water/steam?). ---------------------------------------- The simplest aspect related to the first point is the concern over leaks; the second concern is volume expansion
LNG exchanges heat directly with water, with a temperature difference of 178 degrees – this represents a significant risk. Theoretically, an adequate amount of water can be used for heat exchange, but who can guarantee that there will be enough water? If something goes wrong, it will cause problems
1. The temperature difference is too large, making it difficult to put the equipment into operation (the greater the temperature difference, the higher the heat transfer efficiency); either the water freezes instantly or the LNG vaporizes instantly. 2. If water freezes, it can block the equipment, and the increase in volume may cause the equipment to crack. 3. If LNG vaporizes suddenly, the resulting rise in pressure can damage the equipment.
This post was last edited by Tanran_VRPN on 2018-9-5 at 15:46. LNG vaporization can be achieved using hot water vapor; this method is known as a \"water bath vaporizer.\" In this approach, water is heated first by an electric heater inside a water bath tube, thereby vaporizing the LNG. There will be no issue of tank expansion and leakage, as the LNG is contained within the tank; it exits through low-temperature pipes and then goes directly into the vaporizer, where it is vaporized into a gas and sent out.
I am currently working on a project for an LNG gasification station, and the design temperature for the water bath gasifier is -40°C. Under normal circumstances, the air-cooled vaporizer is first cooled to ambient temperature; if it falls below 5°C, a water-bath vaporizer is used.
If the water flow is insufficient, it will freeze and the equipment will be damaged
After passing through the air-temperature vaporizer, LNG usually reaches a temperature of around (ambient temperature – 15°C). At this point, LNG has turned into cryogenic natural gas and is no longer in a liquid state. If the temperature is too low to meet the requirements, a water bath reheater must be used in series. If the utility conditions permit, hot water circulation can be used for heating; otherwise, an electrically heated water bath regenerator can be used. When a water-bath type reheat apparatus is used, it is required that the equipment be equipped with a temperature interlock; when the outlet gas temperature drops to 5°C, the interlock shuts down the upstream LNG pump, which generally prevents freezing.