Selection of hydrophobic scheme
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This post was last edited by The wise are not confused on 2010-10-28 at 13:38. We are facing significant difficulties with the use of a strainer in our company; it belongs to a gap-type purification system that involves processes such as feeding auxiliary materials (at room temperature), heating and reflux, feeding raw material 1, feeding raw material 2, depressurization, removing auxiliary materials, further depressurization, removing light components, removing the finished product, additional depressurization, removing heavy components, venting air, adding water, and heating the tank for cleaning. Among them, after being treated with auxiliary materials, the composition of Raw Material 1 becomes identical to that of Raw Material 2. Two reboilers are installed inside the kettle, each with a heat exchange area of 365 square meters. The heat source used is 15 KG of steam, and the total steam inlet flow rate ranges from 0 to 12,000 KG/HR (the steam flow varies at different operating stages). To make full use of energy, the outlet of the trap is connected to a flash tank with a lift height of 8 M; the pressure in this flash tank is 4 KG. The normal temperature inside the kettle is 140–170 degrees; during cleaning, the temperature is 105 degrees (water temperature, with slight positive pressure). During use, the lifespan of steam traps is generally short, and poor steam drainage often occurs; sometimes there is inadequate drainage of steam and at other times steam leakage takes place, which severely affects the yield of the product. When selecting traps, we have used 1. Domestic free-floating ball traps ； 2. Imported free-floating ball hydrophoger ； 3. Imported inverted bucket traps do not yield satisfactory results. I would like to ask the experts among you all – is there a better hydrophobic treatment solution available for our operating conditions?
Have you tried an orifice-type trap? It’s simple and efficient.
The steam used by the poster has a pressure of 1.5 MPa; after passing through the reboiler, the vapor produced has a pressure of 0.4 MPa. Given that the flow rate of steam used is fairly high, it is recommended to direct the steam directly from the reboiler’s outlet into the flash tank, eliminating the need for a drain valve. The vapor at the top of the flash tank can be reused, while the condensed water at the bottom can be utilized for other purposes. I once encountered a chemical processing unit that was operated in this way, with very satisfactory results.
It seems that there might also be an issue with the selection of the steam trap; could you take a look at the piping layout for your steam trap? Study it in detail.
This post was last edited by chinazwr on 2009-6-7 09:55. It is quite difficult to choose a steam trap with high flow rates and large capacity; even if one is selected, it may not function properly due to the frequent changes in operating conditions as well as variations in the amount of steam released. Consider that a steam trap with a large capacity will have a relatively high air leakage rate when the amount of steam used is low. It is recommended to use a steam-water separator instead of a conventional drain valve; this is what we do in our several distillation towers and evaporators that require large amounts of steam, and the results are excellent – the drainage function works properly and there is no leakage at all. The specific working process of the steam-water separator is as follows: The diameter of the steam-water separator is approximately 500 mm, and its height is around 1500 mm. It is important that the separator be installed at a lower level than the heating equipment; in other words, the condensate water enters the upper middle part of the separator, and this inlet should be below the heating equipment. At the top, there are gas equilibrium pipes that connect to the gas phases of heating devices such as distillation towers and evaporators. This allows for communication between the gas and liquid phases in the heating equipment and the steam-water separator. Thanks to the difference in pressure, the condensate water from the heating equipment can flow smoothly into the separator, preventing any issues with poor flow of the condensate. The function of these gas connection pipes is not only to maintain gas phase pressure balance but also to prevent the accumulation of non-condensable gases inside the separator. Once connected, these gases can be discharged along with the non-condensable gases from the heating equipment. The pressure of the soda separator is the same as that of the heating equipment, which is usually a pressure vessel. A self-controlled level gauge is installed in the steam-water separator; it is generally recommended to use an electric remote-transmission external float level gauge. The liquid level should be maintained between 1/3 and 2/3 of its maximum capacity, and this level can be displayed and adjusted from the control room. Upper and lower limit alarms for the liquid level can also be set – too low a level can lead to steam leakage, while too high a level hinders the entry of condensate water into the steam-water separator. If the liquid level rises above the inlet pipe for condensate water, water hammer may occur. In addition, a glass-level gauge is usually installed on the steam-water separator for on-site monitoring, as well as for verifying the readings of the self-controlled level gauge. A condensate outlet is provided at the bottom of the steam-water separator, and a control valve is installed on the discharge pipeline; this control valve is used to regulate the liquid level in the steam-water separator. The liquid level in the separator is kept at a stable value of 1/2 to 2/3, which ensures that the steam remains trapped inside the separator and does not escape. The gas phase from the separator is connected to the heating equipment, so all of the steam is utilized for heating purposes. The condensed water discharged from the steam-water separator is sent back to the flash tank for use. Due to the very low back pressure in the steam-water separator, there is almost no pressure loss, allowing this steam-condensed water to be utilized to the fullest extent in the flashing process within the flash tank. The minimal energy loss of this condensed water facilitates its reuse later on.
There seems to be an issue with the selection of the steam trap; some steam traps have a minimum drainage volume, and leakage occurs when the flow rate falls below this level.
1# YBHX: Based on what the poster has described, I am pretty sure that there is a problem of stagnant condensate in your reactor. If the steam valve is opened too quickly at the start of intermittent operation, water hammer may still occur. Due to the presence of chemical reactions, whose heat of reaction is unknown, and the volume of the reactor being unknown, it is not possible to calculate the heat and determine the steam pressure inside the reboiler. However, during the boiler cleaning phase (which is a purely heat exchange phase), the water temperature is 105 degrees. Ignoring the heat exchange resistance, the steam pressure at 105 degrees (primary pressure) is only 0.2 Kg, whereas the back pressure of the steam trap (secondary pressure) is 4.8 Kg. Such a situation cannot be made hydrophobic. Condensate water accumulates in the reboiler, reducing the heat exchange area and causing the temperature to rise very slowly. If there is a temperature control system, the steam valve should be gradually opened at this point; once it reaches a certain position, the steam pressure in the boiler becomes sufficient to overcome the backpressure from the drain valve, causing the temperature of the material to rise rapidly again, at which point the steam control valve is closed. Such a process repeats itself. The poster can observe this, especially during the pot cleaning process; by checking whether the temperature trend and the opening/closing pattern of the control valve are fluctuating, they can gain an understanding. Additionally, a pressure gauge can be installed after the control valve to check whether the steam pressure in the reboiler is lower than the back pressure. Such stagnant flow conditions can only be resolved by using a steam trap pump. Under a condition where the primary pressure is greater than the secondary pressure, the normal function of the trap is to drain water ； Under a condition where the pressure is lower than the secondary pressure, hydrophobicity is removed using the function of a hydrophobic pump. Here is the structure diagram: http://home.hcbbs.com/attachment/200906/9/351338_1244522985gXxg.jpg If you need my assistance, please contact me. 13050523351
We also made some attempts during actual production by installing two traps at the outlet of the reboiler, one large and one small, to adjust according to different steam inlet volumes. The effect was slight but not significant; however, the service life of the traps was increased.
There is now a type of venturi-type hydrophoger that might work better; you could give it a try.
The analysis on the fifth floor is very professional; it is recommended to use a soda separator together with a lever-operated float-type steam trap, which will ensure a long service life