Tube bundle, fixed-bed converter

The tubes in that tubular converter are joined by plate expansion joints. Given that the tubes expand due to the exothermic reaction, how is this issue addressed in the case of a fixed-bed reactor? I don’t quite understand – if expansion leads to a tighter connection, what’s wrong with that? By DN2400 and DN3000, people are referring to the outer diameter of the reactor, right? I think so; generally, 2400 was the type commonly used in old factories in the past. Approximately 4 units are needed per 10,000 tons of PVC. For new plants, about 2 units are required per 10,000 tons. I’ve heard that there are improved versions as well, with 1.5 units needed per 10,000 tons in those cases. I’m not sure if it refers to Haji. I heard that Haji’s converters have a capacity of 12,000 tons per year each. The reason for choosing 3000 at present is mainly the increasing scale of operations; using smaller units would result in excessive land usage. (It’s easy to imagine how impressive it would be to use a 2400 converter in a plant with an annual production capacity of 500,000 tons.) In the future, converters will definitely move in the direction of larger sizes, assuming no breakthroughs are made in boiling bed converters. The reason for not producing larger sizes such as 4000 or 5000 is mainly due to transportation issues (I’m not sure if my factory is capable of handling that). This post was last edited by shizhiyong001 on 2009-3-16 09:39.]

Our converters are joined by expansion welding; the tube material is 16MN. When selecting the number of converters, the space flow rate of acetylene gas is taken into account, with a value of 25–40 m3/catalyst·m3·h. If the flow rate is too high, the acetylene does not convert completely; if it is too low, the level of the by-product dichloroethane increases.

The sizes of conventional converters using mercury-containing catalysts are 2400, 3000, 3200, etc., with the tube sizes being DN50, DN40, and other specifications. For converters of size 2400, the tube sheet is usually joined by expansion fitting; larger converters employ both expansion fitting and TIG welding (in one layer). This is because vibrations that occur during transportation and lifting of large tube-based converters can cause the expansion fitings to loosen, leading to leaks, damage to the tube sheet, and significant losses. Argon arc welding has a minor impact on converter overhauls.

Answer to the original poster’s first question: During the design and calculation of the reactor, the pulling stress on the tubes is calculated based on the most severe operating conditions of the reactor. If this pulling stress is unacceptable, expansion joints must be added to the reactor’s shell to absorb the stress. Second question: The numbers 2400, 3000, and 3200 mentioned usually refer to the inner diameter of the converter.

The tubes in that tubular converter are joined by plate expansion joints. Given that the tubes expand due to the exothermic reaction, how is this issue addressed in the case of a fixed-bed reactor? Since both the tube sheet and the tubes are made of carbon steel, and the elastic changes resulting from thermal expansion and contraction of both in a certain temperature range are effective, no leakage will occur. By checking the performance curves and temperature range of the tube sheet and tube materials, one can determine the maximum temperature that the converter can withstand. Generally, there is a range on the design drawings. By DN2400 and DN3000, people are referring to the outer diameter of the reactor, right? It refers to the inner diameter of the cylinder.

The heat exchange tubes of the DN3200 converter are welded entirely by TIG welding, so transportation and installation have little impact on the welds. The equipment from Xinjiang Tianye has been in use for 2 years.