System Hydrodynamics of a 1 MWth Dual Circulating Fluidized Bed Chemical Looping Gasifier

Abstract

Highlights: What are the main findings? A holistic dataset covering the hydrodynamic behavior of a 1 MWth coupled dual-fluidized bed reactor system, encompassing more than 100 h of hot chemical looping gasification operation, is presented. Using data collected during more than 50 h of operation of a downscaled cold flow model (CFM), the hydrodynamic behavior of the hot 1 MWth setup is predicted and further evaluated. A novel and robust method to calculate solids entrainment from a circulating fluidized bed (CFB) system, relying solely on pressure and temperature measurements, developed using the CFM data and validated using live data from the 1 MWth chemical looping gasifier, is presented. What is the implication of the main finding? Data from the cold flow model and the 1 MWth pilot plant show that free variations of all underlying hydrodynamic boundary conditions are viable in a given range, each resulting in a characteristic response of the dual-fluidized bed reactor system. These findings are formalized in a set of operating ground rules, applicabale to similar dual-fluidized bed systems of any scale. The novel calculation approach for the solid entrainment from the CFB(s) can be applied to any fluidized bed setup, allowing for accurate determination of this crucial parameter in any process configuration. Chemical looping gasification (CLG) is a novel dual-fluidized bed gasification technology that allows for the production of high-calorific syngas from various solid feedstocks (e.g., biomass). Solid circulation between the two coupled fluidized bed reactors, serving the purpose of heat and oxygen transport, is a key parameter for the CLG technology, making system hydrodynamics the backbone of the gasification process. This study serves the purpose to provide holistic insights into the hydrodynamic behavior of the dual-fluidized bed reactor system. Here, special focus is placed on the operational principles of the setup as well as the entrainment from the circulating fluidized bed (CFB) reactors, the latter being the driving force for the solid circulation inside the entire reactor system. Using an elaborate dataset of over 130 operating periods from a cold flow model and 70 operating periods from a 1 MWth CLG pilot plant, a holistic set of ground rules for the operation of the reactor setup is presented. Moreover, a novel easily-applicable approach, solely relying on readily-available live data, is presented and validated using data from the 1 MWth chemical looping gasifier. Thereby, a straightforward estimation of solid entrainment from any CFB setup is facilitated, thus closing a crucial research gap.