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The slurry-bed residue reaction system belongs to the category of liquid-phase hydrogenation; it features large reactor volumes and high liquid holdup. When the system is subjected to emergency pressure relief, liquid phase must be discharged. The characteristics of high temperature, short residence time, and low investment mean that downstream there must be equipment capable of allowing the liquid phase to cool down rapidly (below 380°C) and facilitating the buffering and transition of the slurry – and this is what is referred to as low-temperature fractionation. The characteristics of low temperature and high pressure in heat-based fractionation determine the structural features of its equipment – namely, a slender and tall design. Normal production requires a slurry retention time of 5 to 10 minutes, and it is the self-flowing hydrostatic pressure difference that results in a large height-to-diameter ratio in the lower part of the heat-based fractionation unit ； The slurry buffer volume reserved for emergency pressure relief (30–45 minutes) determines the sufficient space that needs to be provided below the feed inlet ； The gas-phase suspension of the reactor product coke powder and catalyst particles, along with a high vaporization rate, determine the large diameter and high height at the upper part of the feed inlet ； Parameters such as the 60° conical design to prevent accumulation at the bottom of the slurry determine a structure with a high height, narrow width, and large diameter variation, thereby meeting both normal operating conditions and emergency scenarios while also minimizing the overall height of the heat low-sulfur fraction. At present, the heat low-pressure section still faces design challenges related to the feed piping system. The high-temperature slurry passes from the bottom of the heat high-pressure section, where its pressure is reduced via angle valves, before entering the spiral-plate steam generator. There, heat is transferred through spiraling motion, causing the slurry to cool down to 370°C. The pressure is then reduced from 2.0 MPa to 1.0 MPa using primary and secondary pressure control valves. As the fluid moves upward toward the heat low-pressure section, it passes through horizontal and vertical piping sections, undergoing repeated changes in direction; during this process, the pressure decreases while vaporization increases, resulting in various two-phase flow patterns such as initial bubble flow in horizontal pipes, plug flow with increasing gas flow during vaporization, stratified flow, and mist flow ； In vertical pipes, bubble flow, slug flow, foam flow, and annular flow occur; as a result, pipe vibration and abnormal noises often arise. Inspections reveal coking on the outside of the vertical pipes, as well as coking in the lower 1/3 of horizontal pipes. When the thermal load is reduced, the amount of vaporized coke particles carried along increases significantly, indicating that the design of the two-phase flow in the inlet pipes for thermal low-pressure systems is unreasonable. In my personal analysis, the reason why the amount of coke powder entrained increases as the load rises in hot low-temp fractions is that the horizontal feed pipe, due to the gas flow velocity exceeding the maximum flow velocity for a misty flow, results in the formation of a mist that cannot settle or separate within the horizontal pipe and the internal distributor. This leads to the creation of a \"haze\" composed of coke powder, catalyst, and gas above the hot low-temp fractions, thereby rapidly reducing the separation efficiency of these fractions. To address vibration, abnormal noises, and tube wall coking, the upstream piping system should be optimized in design; the initial flow velocity in the pipes should be increased. By raising the pressure drop, the gasification rate of the oil and gas at the front end can be reduced. The diameter of the horizontal pipes before they enter the thermal cracker should be increased gradually to facilitate progressive gasification. At the same time, the inclination angle of these horizontal pipes as they lead into the thermal cracker should be increased, and the direct-inlet design approach should be modified.