Contacting of heavy hydrocarbon liquids with circulating coke particles can provide a cost effective mechanism for converting residual hydrocarbon molecules into useful products and minimize hazardous disposal. For success of this processing step it is important to achieve homogeneous mixing of liquid on solid surfaces in a short residence time. Since by-product coke can deposit indiscriminately anywhere including metal surfaces, scraping of such deposits is necessary to prevent equipment fouling. Co-Rotating Twin-Screw Mixer technology can deliver such demanding mixing result with self-cleaning mechanism.

This paper discusses several experimental techniques useful for characterizing the design of Twin-Screw Mixers. These techniques provide the necessary data for capacity limits, residence time and residence time distribution, and efficiency of solid/liquid contacting. The objective is to screen several designs of mixer internals based on process needs. An optimum design selection can be made using these measurements, and operating guidelines can be defined for the desired process result.

Various scale-up strategies will be discussed that are commonly used in the industry. These strategies will be summarized into three different scale-up rules and respective impacts on the mixer design will be presented. For the process under consideration it is proposed to use a different scale-up rule emerging from a combination in order to ensure full contacting before the material exits the mixer.