Pressure and temperature in process design

Borrow a book on registered chemical engineers to read.

Is it on the registration form? I’ll go look for it; I just don’t seem to be very clear about this aspect

Personally, I think it is the temperature and pressure determined based on the process conditions.

Once the process is understood, the temperature and pressure of each pipeline and device should be clear; at the very least, the operating temperature and operating pressure need to be known. The design temperature and pressure should be the extreme values corresponding to the most severe operating conditions. If the maximum operating pressure and temperature are not well known, the design temperature and pressure can be determined based on the operating temperature and pressure.

Calculate the design pressure of the equipment based on the maximum operating temperature and pressure.

The design pressure and design temperature are determined by the process flow; these cannot be calculated by referring to some book

There are several key points in a process that are dictated by the technical requirements; the other temperatures and pressures are those imposed by the equipment in order to achieve these key points. For example, the catalyst used in methanol synthesis achieves the highest yield when operating at 240–260°C and 5.5 Mpa, so the operating temperature of its feed pipe should be 240°C. The temperature of the raw gas is assumed to be 40°C, coming from the previous stage of the process. To bring the temperature up to 240°C, heating is applied via heat exchangers, which allows us to determine the temperatures of the inlet and outlet pipes of these heat exchangers. The pressure before entering the synthesis tower should be 5.5 Mpa, and subsequent pressures are calculated based on pressure drops. Finally, it is pressurized to 5.5 Mpa using a circulation pump or compressor and then returned to the raw material inlet. The discharge temperature is calculated based on factors such as the heat released during the reaction and heat losses; it is usually determined through software simulations. After that, methanol needs to be separated – at what temperature must it be cooled in order to achieve this separation? Assuming 40 degrees, the inlet and outlet temperatures of the water cooler are also determined. It’s hard to explain in just a few words; in short, in order to meet the temperature and pressure requirements at key nodes, the temperature and pressure at other nodes can vary freely.

Well, thank you for your answer. But I found that a technician here advised me to reduce the work pressure and temperature; is this the correct approach?

Well, thank you for your answer. It’s indeed a bit difficult for someone like me who is just starting out in process design. Could you give another simple example? Or a complete calculation process?