PTQ Gas 2022 Issue

Ceramic coating application in a refinery steammethane reformer furnace Increase an SMR’s thermal efficiency by applying a high emissivity ceramic coating on the furnace boxwalls

YAHYA AKTAS, MUAMMER SEVER and METIN BECER Tüpras, Izmir refinery

C eramic nowadays is a very popular material, thanks to its heat and corrosion-resistant properties. Ceramic material is inor- ganic and in the form of non-metal- lic oxide, nitride, or carbide. In the 20th century, new ceramic mate- rials were developed for usage in advanced ceramic engineering, such as in semiconductors and space technology. Ceramic coating has a well-known thickness, emissiv- ity, and heat transfer coefficient. Ceramic coatings can be applied to both tubes (preventing oxidation and scale information) and refrac- tory (maximising heat transfer to the process) surfaces. I-Ceramic technology By increasing the emissivity – a material’s ability to absorb and rera- diate energy – of a refractory lin- ing in a furnace, these specialised ceramic coatings can provide energy savings depending on zthe fuel being used. High emissivity ceramic coatings in industrial furnaces are widely used for this purpose.¹ Ceramic coating applications are one of the best ways to improve radiant and conductive heat trans- fer efficiency in high temperature industrial furnaces. Benefits of the application can be listed as: • Increased efficiency, leading to energy savings • Reduced stack gas emissions of NOx and CO 2 • Preventing oxidation, carburisa- tion, and various types of corrosion • Extended equipment life General information In a refinery with a hydrogen pro -

duction unit, most of the hydrogen production takes place on the nickel based catalyst in the steam meth- ane reformer (SMR) furnace tubes. The reactions inside the 188 vertical catalytic tubes in two rows (94+94) in the SMR furnace are endother- mic. Continuous and homoge- neous heat flow is critical for the reaction kinetics. The SMR heater is a terrace-wall type SMR furnace with two radi- ant chambers. The heat required for the endothermic reactions is pro- vided by 144 burners on two floors (72 burners each) and on both sides of the tubes. The fuel sources in the furnace are the off-gas mixture from the pressure swing adsorption (PSA) system and the refinery fuel gas. The hydrocarbon feed mixture (natural gas and/or LPG and/or light naphtha) combined with high pres- sure (HP) steam is separated into two and enters the SMR furnace tubes from the upper region. During the downward flow, CxHy and H 2 O react on the catalyst sur- face and turn into H 2 , CO, and CO 2 . The heat required for the reactions is transferred continuously from the combustion chamber to the catalyt- ical tubes. The hydrogen-rich high temperature process gas leaves the tubes at the bottom through hairpins and is routed down to the transfer line to downstream equipment, a waste heat boiler. The furnace operates with a nat- ural draft, and the airflow in the combustion chamber is regulated by the stack damper opening. While the hot combustion gas in the radi- ant region transfers its heat to the catalytic tubes, some of the heat is absorbed by the refractory sur-

face and reflected to the tubes. The combustion gas leaves some of its heat in the radiant zone and flows towards the convection zone. In the convection zone, it passes through the preheat and economiser coils, transferring its heat energy to the unit feed, boiler feed water, and steam streams. The thermal efficiency of the furnace box can be increased by applying a high emissivity ceramic coating on the furnace walls, which enhances the radiative heat transfer contribution from the hot surface walls to the catalyst tubes. 2 Thanks to the high emissivity coating mate- rial to be applied to the refrac- tory surface, it aims to increase the amount of heat absorbed in the radi- ant region and reflected to the tube surfaces. In this way, while the heat transferred from the combustion gas to the radiant zone increases, the heat transferred to the convection decreases, and therefore the steam production decreases. In this way, it aims to achieve the same production capacity with less fuel consumption values or to increase the production amount with the same fuel con- sumption values. Application The application was discussed with a company experienced in this field. In line with the information received about the application, it was decided to make the refractory coating dur- ing the unit planned turnaround. The application was conducted by company employees, with the chem- icals provided by them. Floor-to-ceiling scaffolding was installed in the two radiant cham- bers of the SMR furnace for the

26 Gas 2022