Please teach me how to control the heating rate of multiple equipment through steam stop valve
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Thank you all for reading this post. To be honest, this is my first time coming into contact with steam, so I have been browsing the forum for two months and combined various opinions to boldly draw a flow chart. I hope I can get help from my friends. Thank you very much. I am not a chemical major, so I can only reach out for help. The first is the process requirements: Simply put, it involves the control of the evaporation rate, which is the amount of heat input. That is, the steam generator generates steam, and then the steam is split into two cooking pots for heating respectively. At the same time, the amount of heating needs to be controlled at different stages. The liquid in the boiler passes through the steam jacket and heat exchange coil, and is heated from 65 degrees Celsius to nearly 100 degrees Celsius. During this period, slower heating is required in the early stage and faster heating in the later stage. I have been using natural gas for heating before, so it is relatively intuitive to control the heating speed, just like cooking at home. When the fire is low, turn it up, and when the fire is high, turn it down. But after switching to steam, I got confused. After reading a lot of information, I roughly understood that the generator generates saturated steam and then uses it under reduced pressure. But how should steam usage be controlled? At the same time, what method can be used to better record each steam, that is, heat input, so that it can be calibrated to the same heating rate next time.
suggestion: 1. Add a steam flow meter to each branch to facilitate visual statistics of steam flow usage. 2. Replace the manual stop valve with an automatic regulating valve to observe changes in opening. 3. Add a remote thermometer to the heating tank, so that steam can be controlled in a chain. The above are personal suggestions and are for reference only!
Thanks for the advice, seniors. There is a problem here that the application of automatic regulating valve may not work, because the heat energy input during the heating process needs to be changed. If it is automatically adjusted, it may not be controllable. My understanding here is that the function of the manual stop valve is similar to our previous valve for adjusting the natural gas fire and the small fire. I don't know if this understanding is correct. The function of pressure reduction is to facilitate the rapid condensation of steam and discharge through the trap, preventing pressure from building up in the heat exchange jacket and coil. Then can I just choose an ordinary pressure reducing valve for the pressure reducing valve? Just like a faucet, it ensures that decompressed steam is continuously input into the heat exchange jacket. Thanks for your suggestion.
If it is more advanced, you can consider adding a temperature element to the tank and linking it to the regulating valve. For period control, you can choose software control such as PLC. The simple method is to control the temperature and pressure of your steam delivery at a constant level. If the requirements are not very high, you can choose a superheat higher than 100°C. It can be controlled manually in the early stage and can be fully opened in the later stage. The larger the heat exchanger area in the tank, the easier it is to control. If the steam trap works well, the steam usage rate can still be guaranteed. As for the rate, it is necessary to increase the heat exchange area and increase the steam pressure. As for the steam generator, a steam drum is set up, the steam heats the water, and the water is evaporated to produce steam, so that it can be transported stably. Oh, in order to increase the heating rate evenly, relevant stirring must also be set. It seems that you can use this stop valve to operate and control it just like using gas. For reference.
http://imgeditor.ybzhan.cn/MTEditor/20120608/634747451160828750.jpg What you want to control is the temperature after heating, and the steam flow rate is just a reference parameter, so the above control loop mode is enough for you to achieve the target control!
Thank you for the teacher's advice. My current goal is to manually control the amount of steam and thereby control the evaporation of the liquid in the pot. It is a change, and it is not expected to keep the temperature in the pot constant. In fact, because the inside of the boiler is an azeotrope, the temperature continues to rise as low-boiling substances evaporate. I also have a question: after the saturated steam with a pressure of 0.7MPa transmitted from the steam generator is decompressed to 0.2MPa, will the steam temperature not decrease and become superheated steam? So in this case, is it necessary to have a larger internal heat exchange area of the boiler so that sensible heat can be transferred faster and become latent heat transfer? After the steam flow rate of 0.7MPa -- 300KG is reduced to 0.2MPa, will the flow rate increase? Can you calculate the flow rate after decompression?
Thank you teacher! What actually needs to be controlled here is not the temperature after heating, but the amount of heat energy input. The heat exchange area in the boiler is much larger than the maximum amount of steam that the generator can provide, so what is desired is to control the flow of steam through a hand valve.
Then the steam drum mentioned by the teacher is not very clear. Is it a steam-water separator or a water tank? The decompressed steam is superheated steam, and then it is blown directly into the tank with water to heat the water in the tank into steam. In this way, the decompressed superheated steam becomes saturated steam as much as possible to increase the latent heat ratio?
If you want to understand this knowledge in detail, it is recommended to get a copy of "Principles of Chemical Engineering". It is not difficult, so you might as well give it a try. According to your needs, if you do not consider the connection with the steam supply, just use it directly. No complicated additional considerations are required. If the steam pressure is unstable, you can consider using superheated steam to heat the water. The steam produced is relatively stable. For reference.