Regarding the high tank pressure when propylene is fed into the spherical tank, can it be handled in this way?
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This post was last edited by alongtcl00 on 2019-3-5 at 10:55. When propane needs to be fed into the spherical tank, once a certain liquid level is reached and external temperature conditions come into play, the pressure inside the tank becomes very high. This results in a slower feeding rate as well as increased energy consumption. Currently, the tank is equipped with a liquid-phase temperature transmitter and a gas-phase temperature transmitter, and there is a significant difference between these two temperatures; for example, the liquid-phase temperature might be 2 degrees, while the gas-phase temperature could be around 50 degrees. To address this issue, it is possible to install a pipe along the feeding line that leads from the top of the tank, thereby reducing the gas-phase temperature and also the pressure, and thus increasing the feeding rate. What impact will this have on the tank? Can it be done this way? How to control it when feeding is required from the top of the spherical tank? (Can we control it based on the saturated vapor pressure of the material? That is, when the vapor phase pressure reaches 11 kilograms, the saturated temperature is around 31°C; by introducing propane with a lower temperature from the top, can this help reduce the saturated vapor pressure?) Have you ever seen natural gas tankers being filled? There are types of such tankers with liquid inlet at the top and another at the bottom; when filling them, the top inlet is used first, followed by the bottom inlet. Sometimes, if the temperature of the tanker is low, both inlets are used simultaneously. It was from here that I thought of the method for replenishing material in spherical tanks.)
1. How is the pressure control of the spherical tank managed? Why does the pressure increase during the feeding process? 2. Doesn’t the spherical tank have insulation? Why can the gas phase temperature reach 50°C?
The storage capacity of propane spheres has reached the threshold considered a major hazard source; it’s not something that can be simply discussed on forums based on one’s own ideas. Technical modifications must be designed by qualified professionals. I’ve seen nitrogen filling processes, where material is added from below; when filling a 175L Dewar vessel, the nitrogen inside is first emptied before filling begins, and filling does not take place from the gas phase
The storage capacity of propane spheres has reached the threshold considered a major hazard source; it’s not something that can be simply discussed on forums based on one’s own ideas. Technical modifications must be designed by qualified professionals. I’ve seen nitrogen filling processes, where material is added from below; when filling a 175L Dewar vessel, the nitrogen inside is first emptied before filling begins, and filling does not take place from the gas phase
Even when feeding from the top of the tank, it needs to be inserted at the bottom of the tank as well; it’s the same
Regarding the high temperature in the gas phase, I have an idea – I’m not sure if it’s correct, so I’d like to share it and ask the experts for their feedback: Before entering the tank, propane is in liquid form; once it enters the tank, due to the low pressure inside, part of the liquid propane vaporizes, absorbing heat and thereby lowering the temperature of the liquid phase； As charging continues and gas-liquid equilibrium is gradually reached, more propane in the gas phase liquefies, the heat released increases, which leads to a rise in the temperature of the gas phase.
This understanding is a theoretical speculation based on books, far from reality; those with practical experience would not think in this way. Storage inside the tank is a long-term process, and the low temperature of the liquid phase is due to the heat absorbed during vaporization. The gas that has already entered the gas phase no longer cools down through vaporization; its temperature gradually approaches the ambient temperature, with the final temperature depending on the amount of gas used, as well as the insulation properties and the location of the sensing points
Is the feed pumped directly or using a compressor? If it is pumped, the power of the pump is converted into heat and enters the propane storage system; the same applies to compressors. It has been noted that for butadiene and propylene, compressors are used for unloading, and there are coolers after the butadiene is compressed. The gas-phase operating temperature of the propylene storage tank at 50 degrees is a bit too high; this is something that needs to be taken into account.
Aren’t the gas phases of the spherical tank and the tank truck connected?
No, that’s not allowed. Hazardous chemicals must be handled in accordance with the designed procedures; making unauthorized changes can result in imprisonment
The production and transportation of hazardous chemicals cannot be changed just by having an idea