In the furnace, the reforming of steam-hydrocarbon mixtures is accomplished in catalyst-filled tubes. The reformer reaction is endothermic, requiring high level heat input. For a safe, reliable and efficient operation, we design our Terrace Wall™ reformers to control the heat transfer to the tubes, considering:
- The process heat demand of the catalyst tubes varies significantly from inlet to outlet
- Requirement for uniformity of heat distribution along the length of the furnace
- Use of low-BTU and low-pressure PSA off-gas for the majority of the burner firing.
The inclined firing walls of our Terrace Wall reformers are uniformly heated by a number of flat flame burners laid out on both sides of the tubes at two terrace levels. Each terrace is capable of being independently fired to provide the particular heat flux desired in its zone. This allows the operator to match the vertical flux to the process heat demand within the catalyst tube thereby avoiding hot spots and prolonging catalyst and tube lives. The countercurrent flue gas to process flow provides a predictable steady tube metal temperature increase and eliminates intense heat flux at tube inlets when catalyst degradation occurs.
The burners are selected to spread the flames both horizontally and vertically along the brick firing wall for a planar heat flux pattern. Low-BTU, low-pressure PSA off-gas is combusted and stabilised on the brick firing walls, preventing instability or flame impingement common in top-fired designs.
Our more recent Terrace Wall reformers have modifications in the terrace location that significantly lower the bridge wall temperature. This allows several cost savings over other designs:
- Less fuel use for the process production
- Lower material cost of convection section tube supports
- Less heat to recover in the convection section
- Lower horsepower on fans due to lower volumes.