Patent ID: 8355891

Claim:
A method for the maintenance of a furnace for the catalytic steam reforming of a hydrocarbon reaction mixture, the furnace comprising tubes filled with catalyst, a first portion of the tubes T(j) being equipped with a thermocouple attached to a wall of said tube at a point Y t (j), the other tubes T(i) being free thereof, the method comprising at least the following steps: 1) measuring periodically, for each tube, a temperature θp of the wall of the tube using a remote temperature measurement means; 2) measuring and recording continuously, for each of the tubes T(j), a second temperature θt(j) of the wall of the tube using a thermocouple attached to the lower portion of said tubes and connected to a data acquisition system capable of storing data for a time at least equal to the service life of the furnace, to establish a curve θt(j) as a function of the time; 3) calculating Δθ(j)=θp(j)−θt(j), for each tube T(j) and for each measurement θp(j); 4) establishing a virtual curve θt(i) virtual , for each tube T(i), as a function of the time such that: the virtual curve θt(i) virtual passes through the ordinate points θp(i) 1 −Δθ(j) for which Δθ(j) is the value calculated during step 3) for a chosen neighboring tube T(j); and the virtual curve θT(j) results from the translation of the curve for said neighboring tube T(j), passing through the ordinate points θp(i) 1 −Δθ(j); 5) determining the hottest point of the tube and estimating the temperature difference Δθ max between the temperature θ max at said hottest point and the temperature θt measured at the same time under the conditions of step 2), for at least one tube; 6) establishing a curve θmax(i) as a function of the time starting from the virtual curve θt(i) virtual established in step 4) and from Δθ max from step 5), for each tube T(i), and for each tube T(j) establishing the curve θ max (j) starting from the curve established in step 2) and from the estimated Δθ max , so as to establish a temperature history for each tube T(i); 7) deducing, in real time, and using the Larson-Miller relation, a remaining service life for each tube T(i), from the curve θ max (i) and for each tube T(j) from the curve θ max (j); 8) comparing the remaining service life for each of the tubes with the time remaining before the next programmed shutdowns of the furnace; and 9) replacing the tubes that need replacing during each programmed shutdown.