Method for carbon formation free operation of reformers

A method of operating a top-fired steam reformer furnace, the furnace comprising (i) an upper half and a bottom half, (ii) a plurality of burners, (iii) a plurality of reformer tubes disposed vertically within the furnace, each reformer tube having a section located in the upper half of the furnace and a section located in the bottom half of the furnace, (iv) the plurality of burners, each burner having a burner valve with an adjustable position for controlling the fuel flow and associated heat release to the furnace in the vicinity of that burner, the method comprising:

• (a) obtaining, for at least a portion of the reformer tubes, the outside tube wall temperature at one or more elevations in the bottom half of the furnace, and, for that same portion of reformer tubes, obtaining the outside tube wall temperature at one or more elevations in the upper half of the furnace;
• (b) calculating, using (i) a Reformer Model or (ii) a combination of a Reformer Model and the outside tube wall temperatures obtained in step (a), the inside wall temperature at the one or more elevations in the bottom half of the furnace, and at the one or more elevations in the upper half of the furnace, for one or more reformer tubes located in the same portion of reformer tubes as in step (a);
• (c) calculating, using (i) a Reformer Model or (ii) a Reforming Catalyst Carbon Formation Model, the temperature for carbon formation under then-existing process conditions at the one or more elevations in the bottom half of the furnace, and at the one or more elevations in the upper half of the furnace, for the same one or more reformer tubes in step (b);
• (d) calculating Carbon Margin at the one or more elevations in the bottom half of the furnace, and at the one or more elevations in the upper half of the furnace, by subtracting the inside wall temperature calculated for the one or more reformer tubes in step (b), from the carbon formation temperature calculated for the one or more reformer tubes in step (c);
• (e) calculating the maximum allowable operating temperature for the reformer tube section located in the upper half of the furnace by adding the Carbon Margin calculated in step (d) for the one or more elevations in the upper half of the furnace to the outside tube wall temperature at the one or more elevations in the upper half of the furnace obtained in step (a);
• (f) determining, from the maximum allowable operating temperature calculated in step (e), a temperature balance for the furnace;
• and
• (g) adjusting the burner valve positions to implement the temperature balance of the furnace.