Patent ID: 8469081
Filing Date: 2013-06-25
Classification: F28F,Y10T

Abstract:
1. A method of reducing fouling in a heat exchanger for crude oil, wherein the heat exchanger having a plurality of existing heat exchanger tubes, the method comprising: removing at least a portion of the plurality of existing heat exchanger tubes from the heat exchanger; installing a plurality of replacement heat exchanger tubes, wherein each of the plurality of replacement heat exchanger tubes having a surface roughness of less than 40 micro inches (1.1 μm), wherein each of the plurality of replacement heat exchanger tubes being formed from a steel composition comprising X, Y, and Z, wherein X is a metal selected from the group consisting of Fe, Ni, Co and mixtures thereof, wherein is Y is Cr, and wherein Z is at least one alloying element selected from the group consisting of Si, Al, Mn, Ti, Zr, Hf, V, Nb, Ta, Mo, W, Sc, Y, La, Ce, Pt, Cu, Ag, Au, Ru, Rh, Ir, Ga, In, Ge, Sn, Pb, B, C, N, O, P, and S, wherein each of the plurality of replacement heat exchanger tubes having a Cr-enriched layer formed on at least one of an inner surface or an exterior surface of the tube, wherein the Cr-enriched layer also being formed from the steel composition X, Y, and Z, wherein the ratio of Y to X in the Cr-enriched layer being greater than the ratio of Y to X in the remaining portion of the tube; and forming a protective layer on an outer surface of the Cr-enriched layer, wherein the protective layer comprises a material selected from the group consisting of a magnetite, an iron-chromium spinel, a chromium oxide, oxides of the same and mixtures thereof.