Combustion characteristics and pollution minimum technology for VR (Vacuum Residue) fired boiler

An experimental study on the combustion of extra heavy oil has been performed using a cylindrical test furnace. Recently, light oil such as gasoline is almost exclusively demanded as liquid fuel made from petroleum. In order to produce light oil in a high yield, extra heavy oil, which is called as VR(Vacuum Residue), remains after refinement under reduced pressure. VR features extremely high viscosity, as well as high percentages of sulfur, nitrogen, heavy metals, and resident carbon in fuel. Regarding the use of VR as a fuel for actual commercial boilers, a number of serious problems must be overcome. These include high- and low-temperature corrosion of metal materials, and the need to meet environmental regulations calling for low NOx and a low unburned carbon ratio in exhaust gas. In the present study, accordingly, a firing test has been conducted to accumulate the basic characteristics of VR combustion. From the test results, stable ignitability was ascertained, and both NOx emission and the unburned carbon ratio in exhaust gas were found to be at the same level as for bituminous coal combustion. Also, the reactivity and the carbon structure of the sampled soot and char were chemically examined in detail, and the reaction rate with oxygen was formulated. Furthermore, numerical simulation of combustion in one-dimensional furnace was conducted, and the calculated results were compared with the experimental data.