Reduced-Order Modeling of a Commercial-Scale Gasifier Using a Multielement Injector Feed System

Abstract

This study presents a reduced order model (ROM) that describes the behavior of a commercial-scale short-residence gasifier which uses a multielement injector feed system. The state-of-the-art injection technology disperses the feed across the crosssection of the gasifier to enhance the mixing efficiency, thereby allowing a reduction in the reactor size and capital cost. A reactor network is integrated into the ROM to capture the laminar and mixing zones formed by each nozzle and subsequently the merging point of the multiphase flow coming from all of the nozzles. The results of the ROM are in reasonable agreement with the limited data reported for a short-residence time commercial-scale gasifier, that is, residence time, carbon conversion, and cold gas efficiency. Moreover, the performance of the gasifier is examined under changes in the operating pressure, number of injectors, flow nonuniformity, and plugging in the fuel's injection tubes. The ROM provides valuable insights on the operation of the commercial-scale gasifier and potential safety concerns that can be used to design suitable and safe operation policies for the system. Furthermore, sensitivity analyses on the model, design, and operational parameters are performed to assess the suitability of the model assumptions and identify the most important factors influencing carbon conversion, particle residence time, and temperature profiles.

Modelling and optimization of a pilot-scale entrained-flow gasifier using artificial neural networks

“…27,28,29 Therefore, IGCC plants need to have high flexibility to change the feed flowrate when combined with alternative energy sources and being able to maintain continuous operation with different solid fuels to meet the targets of compensating for variable electricity supply. 13 However, it is relatively challenging to achieve flexibility and incorporate variability for an IGCC plant due to the high complexity and interconnectivity of the different units involved in this process. As a result, there is a need to study the transient behaviour of each component of the IGCC in order to gain insight into the dynamic response of the units under different disturbances, such as changes to the fuel load and variability in feed composition.…”

“…That model was developed based on the streamlines of multi-phase flow via conservation equations describing the momentum, heat and mass transfer inside the gasifier. 13 With regards to the computational cost, the ROM model required on average about 257 s of CPU time per simulation (Intel® Core™ i7-4770 CPU @ 3.40Hz, 3392 Mhz, 4 Core(s), 8 Logical Processor(s)). 42 However, even though the ROMs require substantially lower computational costs compared to CFD models, they still require considerable numerical analysis and thus they are still computationally expensive for optimization, online monitoring and control purposes.…”

“…Each ANN was trained using data obtained from the ROM reported previously in Section 3.1. 13 The following sections will provide a brief overview of the ANN methodology implemented in this work. A general overview of the feedforward ANN structure and its backpropagation algorithm is provided, followed by a brief description of the gasifier variables that serve as the input and output parameters to the ANNs.…”

“…Reduced order models (ROMs) are an alternative approach that can capture the essential features of multi-phase flow structure inside the gasifier at reduced computational costs. 12,13 However, although ROMs require substantially lower computational costs compared to CFD models, they are still computationally expensive and may not be applied for process optimization, monitoring and on-line control purposes.…”

“…Sahraei et al 13 The performance of a gasifier can be described by the conversion of its reactants, the concentration of its desired products at the outlet, and the temperature distribution throughout the unit. 25 In the ROM model, the carbon conversion is the main important output parameter for characterizing the gasifier performance, as it serves to measure the fraction of solid coal converted into the more useful syngas form.…”