Continuous Online Monitoring of Fireside Tube Skin Temperature in a Depropanizer Reboiler

Paper from the AFRC 2015 conference titled Continuous Online Monitoring of Fireside Tube Skin Temperature in a Depropanizer Reboiler

Continuous monitoring of the fireside skin temperature of process tubes is a difficult but desired objective for the safe and efficient operation of many process heaters and boilers. A new measurement technology has been developed for providing local skin temperatures in such furnaces. With this paper we present the development of this technology on a refinery process heater serving as a reboiler for the bottoms of a; depropanizer tower. The cylindrical, vertical type furnace is operated by a refinery in North Salt Lake, Utah. It is fired from four floor-fired, staged fuel gas burners with individual gas pilots. There are 40 radiant tubes which are arranged vertically around the wall of the furnace. The technology for online monitoring of the maximum fireside skin temperatures takes advantage of the existing continuous measurements of the process side fluid temperature at the inlet and outlet of each coil in the heater. High performance computing simulations were performed to map out the operational space of the furnace. Surrogate models were constructed for the local skin temperatures as a function of operating parameters. Thus the skin temperature is correlated through the non-linear detailed model of the combustion process to the continuous measurements of the outlet process temperature of each of the coils. This model is calibrated and updated through continuous feedback through remote monitoring of the furnace operating conditions. The first phase of deployment of this technology was to develop the instrument model and demonstrate proof-of-concept. This phase is presented in this paper. The final three stages, yet to be completed, are to validate the instrument model then deploy it, first offline, then online for continuous tube skin temperature monitoring.