How should the heating and cooling rates for different processes be determined?
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How should the heating and cooling rates for different processes be determined? For the newly developed process packages, such as hydrogenation processes, what determines the speed at which the system’s temperature and pressure are increased or decreased? Is it the selected material? Is it a requirement of the process reaction? Generally, the rate in distillation towers is 15–25°C/h, while in reactors and similar vessels it is often less than 50°C. Where do these values come from?
The speed at which the system’s temperature and pressure can be increased or decreased should depend on several factors: first, the material chosen for the relevant equipment, as it is generally not acceptable for pressures and temperatures to rise excessively； Secondly, it depends on the size of the system; when the system is large, it is necessary to take into account the delays associated with operational conditions, to ensure that the increase in pressure and temperature – especially the increase in temperature – spreads throughout the entire system and reaches a dynamic equilibrium ； Thirdly, in terms of process conditions and the properties of the materials, when deviating significantly from normal operating conditions, large changes in pressure and temperature have little impact; however, when approaching normal operating conditions, temperature fluctuations become much more significant, and this is also closely related to the properties of the reactant materials. It should also be noted that most reactions are exothermic; once the system releases heat as a result of being heated, the cumulative effect of this heat must be taken into account. In practice, it is necessary to ensure that all the heat released by the system has been completely absorbed before raising the temperature again.
Are there any books or standards that discuss system heating and cooling?
There are relevant regulations in the specifications for heating and pressurization of pressure vessels! It is more based on the tolerance of the equipment!