What is a hot-wall reactor, what are its characteristics, and what are its main uses?

From Baidu: Hydrocracking reactors can be divided into two types based on the temperature of their shell – one type is called a “hot-wall” reactor； Another type is called a “cold-wall” reactor. In a hot-wall reactor, there is no internal insulation layer, so the temperature of the reactor wall is not much different from the temperature of the reaction taking place inside ； A cold-wall reactor is lined with a thermal insulation layer; thanks to this insulation, the temperature of the reactor wall is much lower than the temperature of the reaction taking place inside. In cold-wall reactors, the corrosion rates of H2 and H2S decrease due to the lower temperature of the reactor walls (below 250°C); as a result, the requirements for the steel material are not as high as those in hot-wall reactors. However, construction is more complex, and it is difficult to inspect the inner walls. In hot-wall reactors, local overheating is less likely to occur on the reactor walls, which enhances safety during operation. In the cold-wall structure, the thermal insulation lining is prone to damage during the production process; hot fluids seep into the walls, causing the wall temperatures to rise excessively, which threatens safe operation or forces shutdowns. Hot-wall reactors can make full use of the reactor’s volume; their effective volume utilization rate (which is the ratio of the volume occupied by the catalyst in the reactor to the total volume of the reactor) can reach 80%–90%, whereas cold-wall reactors generally have only a rate of 50%–65%. Hot-wall reactors have a shorter construction period and are easier to produce and maintain. However, since the \"hot wall\" operates under harsh conditions, high requirements are placed on the steel material.

So here’s the question: with such high temperatures in a hot-wall reactor, what is used to heat it? Steam? Still heat transfer oil? Is it a jacketed device, or a semi-tube heat tracing device?

I don’t understand; I’ve come to learn from all of you experts*.

Still worried about a lack of high-temperature heat source for hydrocracking reactions? It’s a exothermic reaction anyway!

I see, now I understand------A cold-wall reactor has a thermal insulation layer lining it, and thanks to this insulation layer, the temperature of the reactor wall is much lower than the temperature of the reaction taking place inside. In cold-wall reactors, the corrosion rates of H2 and H2S are **reduced** due to the lower temperature of the reactor wall (below 250°C); therefore, the requirements for the steel material are not as high as those in hot-wall reactors. However, construction is more complex, and it is also difficult to inspect the inner wall.--------------------------

A hot wall means that the container walls are exposed to heat directly, without any insulation layer; this simplifies the structure inside the container. More importantly, it relies on the material’s ability to withstand high temperatures

In cold-wall reactors, a non-metallic insulation layer is installed on the inner wall of the equipment; in some cases, a stainless steel lining is also added to this insulation layer. This allows the design wall temperature of the reactor to be reduced to below 300°C, making it possible to use 15CrMoR or carbon steel. There is also no need to weld stainless steel onto the inner wall, thereby **reducing the complexity of manufacturing. However, since the insulation layer of the cold-wall reactor occupies space within the inner shell, it reduces the utilization rate of the reactor’s volume and results in material waste. Moreover, the non-metallic insulation layer in cold-wall reactors is prone to damage due to the scouring by the flowing medium or changes in temperature; it may need to be repaired or replaced after operation for some time, and the costs associated with installation and repair are high. If the lining comes off during operation, the reactor wall near the area where the lining has fallen off will exceed the design temperature; visually, the paint in that area will change color. As a result, the safety risks associated with the reactor **increase**, and in severe cases it can even lead to the forced shutdown of the facility.