Thread Content
The success of converting slurry-bed residue hydrodesulfurization products from high boiling points to low boiling points depends entirely on the steam generator used; the unique properties of the slurry introduce many difficulties and uncertainties regarding the selection and use of such steam generators. “Slurry circuits featuring a short process flow, isothermal quenching, seamless flow, and countercurrent upward movement impose almost stringent requirements on steam generators. A \"large-scale\" design necessarily brings about significant differences; the key difference lies in the fact that supercooling must be strictly avoided, as it would cause the slurry to lose its fluidity, leading to local condensation, deposition, and coking ； The difference lies in the fact that the slurry must maintain laminar flow within the push-pipe, thereby enabling self-cleaning of the flow field ； The difference is that the degree of vaporization of the feed to the vacuum tower must be adjustable ； The difference lies in the two-phase flow that involves receiving three streams of hot high-viscosity oil while simultaneously dealing with the reactor’s slag discharge at any time ； The difference lies in the utilization of high-temperature sites responsible for the heat generated by high-temperature reactions ； The difference lies in the design with one active and one hot standby unit, where downtime is inevitable in case of a failure ； The difference lies in the strict procedures for introducing preheated, pressurized exhaust gas (equipped with a dedicated electric heating system for preheating the wax oil) ； The difference lies in the special design of the spiral plate heat exchanger with a simple structure ； The biggest difference is that the slurry outlet channel naturally bends upward to the highest point of the unit—the heat low-pressure section. Of course, where there are significant differences, there must also be aspects that are not so different. In an isothermal cycle on the water side, the sudden vaporization of hot water causes water hammer effects of varying intensity at different times, leading to fatigue and welding stresses as well as other damages. Internal leakage is only a matter of time; moreover, fluctuations in load, instability in water circulation, and inaccurate steam backpressure further exacerbate the faults in this steam generator. Another reason it’s not \"great\" is that there are significant considerations regarding the installation method of the generator; different schools of thought have varying opinions on this matter – it’s problematic to fire at it while it’s \"lying down,\" and it’s impractical to disassemble it when it’s \"standing up.\" The slurry bed process technology indeed has many remarkable aspects; looking back at it, one truly feels as if they were unaware of the essence of it at first hearing, but after listening again, it seems as though one has become part of that process.