Is it normal for the pressure and temperature inside the cylinder to be higher than those in the jacket?
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Today, I saw the design drawings, which indicate that the design pressure for the cylinder of the heating vessel is 0.66, and the design temperature is 168. Jacket design pressure: 0.54, design temperature: 162. From a functional perspective, steam is introduced into the jacket to heat the cylinder, so the temperature of the cylinder will not exceed that of the jacket. Pressure and temperature are related, and the pressure inside the cylinder will not exceed that in the jacket. So why are the design pressure and design temperature of the cylinder higher than those of the jacket?
If this is a reactor, it’s normal: there is steam pressure in the jacket, while the pressure inside the reactor chamber is determined by the saturated vapor pressure of the liquid inside the reactor, as well as by the gases released during the reaction. These factors operate independently of each other and do not conflict with one another. As for temperature, initially it is the steam that provides the heat; later, as the reaction releases heat, the internal temperature rises above that of the jacket
Let’s take the example of a sulfur jacketed tube. The pressure of the steam in the jacket is 3–4 kg/cm2. Under normal conditions, there is little pressure inside the inner tube, but this is different at the pump outlet; it is normal for the pressure inside the inner tube to be higher than that of the steam in the jacket.
Check: The temperature of saturated water vapor at 0.54 MPa(g) is 161.4 degrees, and at 0.66 MPa(g) it is 168.3 degrees, which are roughly consistent with the design temperature; the operating temperature will be slightly lower. It can be seen that once the jacket steam heats the reactants in the reactor to below the reaction initiation temperature of 161 degrees, a liquid-phase reaction begins in the reaction solution. The heat of reaction further raises the temperature of the solution to slightly below 168 degrees; at this temperature, the water in the solution continues to vaporize until it reaches saturation, with no other gases being produced. There may be valves to control the pressure inside the tank, or the pressure can also be controlled by adjusting the flow rate of hot water in the jacket. The jackets of many reaction vessels have both heating and cooling functions.