HP耐热钢结焦、渗碳的原因分析

ANALYSIS OF COKING AND CABURIZING OF HP HEAT-RESISTANT STEEL

对退役HP耐热钢裂解炉管结焦、渗碳状况进行了分析 ,藉加速结焦实验研究了耐热钢的初期结焦行为 ,推断出催化结焦促进结焦和渗碳的机制 .

This paper deals with the coking and caburizing of the used cracking tube made by HP heat-resistant steel.The experiments show that the structure on the cross-section of the used cracking tube is consisted of the oxide and coking layer,the chromium depletion layer,and the inner carburized layer due to serious carburizing.It is found that there is filamentary coke near the surface of the tube but the spherical coke exists far from the surface of the tube.The initial coking behaviour of HP heat-resistant steel is investigated by quick coking experiment.During the initial coking stage,the filamentary is formed under the catalytic action of nickel or iron elements in the steel,although there is a Cr 2O 3 film on the surface of the steel.The hydrocarbon cracking intermediates can permeate the Cr 2O 3 film and combine with the nickel or iron elements in the steel,which arouses the catalytic coking,and causes the destruction of the Cr 2O 3 film and serious coking and carburizing.With increasing of the cracking time,the spherical coke begins to develop instead of the catalytic filamentary coke.