The proprietary Uhde cold outlet manifold system
The essential feature of Uhde's reformer outlet and manifold system is the use of standard carbon steel instead of expensive heat-resistant austenitic steels. Simply put, there is no other design which so successfully combines long service life, simple design, easy maintenance, safety, reliability, and cost effectiveness.
This is made possible by the following unique design:
A catalyst grid is arranged within each reformer tube at the level of the furnace bottom, and a thin high alloy funnel and tube are welded to the grid support, the weld being gas-tight. This tube conducts the reformed hot hydrocarbon stream down into the refractory-lined manifold. Its wall is subjected to balanced pressure (i.e. the pressure acting on the inner surface of the tube is equal to the pressure acting on its outer surface), so it can freely expand downwards under thermal load and needs only to withstand the high temperature. The funnel and tube walls can therefore be thin, i.e. about 2 mm.
The annular space between the hot gas-conducting tube and the pressure-bearing shell is filled with ring-shaped insulating bricks to protect the shell from high temperatures.
The skin temperature of the reformer tube underneath the furnace bottom rapidly drops along the tube length from approx. 900 °C to below 250 °C ("cold-type" outlet). The reformer tube ends and shell of the manifold are therefore made of carbon steel.
The manifold contains a high alloy liner to shield the refractory lining. Sufficient gas barriers are provided to prevent any small hot sidestream of the gas from reaching the pressure-bearing shell. The complete manifold system is delivered to the construction site in modules.
As a result of separating the high-temperature service from the pressure service, the tube-to-manifold connection is as reliable as any other carbon steel pipe connection in the plant.
thyssenkrupp Industrial Solution's design precludes premature failure of the components due to creep and embrittlement, and avoids the difficulties and problems associated with "hot-type" outlets outside the furnace box, i. e. the use of hot flexible tube-to-manifold connections ("pigtails"), deployed in some competing concepts.