Utilizing STAR-CCM+ to advance the South African Power Generation - PowerPoint PPT Presentation

Utilizing STAR-CCM+ to advance the South African Power Generation Industry The advantages of incorporating Computational Fluid Dynamics (CFD) analysis in power plant management and optimization

Who is Aerotherm • Aerotherm Computational Dynamics is a well established consulting firm with a vast amount of experience in the application of Computational Fluid Dynamics (CFD) in industry. • Aerotherm has been applying CFD since 1995, to solve numerous fluid flow and heat transfer related problems to improve plant efficiency, reliability and maintainability. • Aerotherm is unique in that it specialises only in CAE simulation and has therefore developed a highly specialised consulting experience in a wide variety of application areas. Our Mission Statement: To assist our clients in finding cost effective practical engineering solutions through CAE simulation of components, systems and/or entire plant.

Focus on Coal Fired Power Plant • Aerotherm has in the past 16 years placed a lot of focus on fault finding and optimization in Coal Fired Power Plants (CFPP). • Approximately 60% of or work experience is related to CFPP due to the following reasons: • Approximately 77% of the power generated in SA is via CFPP • CFD was not used in the original design of any of the CFPP currently in operation in SA today (not even Majuba – commissioned 1996-2001). • There exists large room for improvement in: • Air flow control and measurement • Coal combustion optimisation • Emissions reduction • Boiler tube leak reduction etc.

Example application areas • Primary and secondary air flow measurement • Calibration of flow measurement devices (venturi’s / orifice plates) • General flow optimisation in ducting to reduce pressure drops and erosion • PF milling & classification process • PF distribution & transport • Air flow distribution & control • Gas flow in furnace and convective gas pass • Burner optimisation / NOx Reduction • Combustion Modelling – Coal quality variations • SOx reduction

Holistic approach to combustion modeling • Input Airflow : Optimisation of the secondary air windbox which supplies combustion air to the burners in order to evenly distribute the secondary air supply to each individual burner • Calibrate burners: Use mapped data from secondary air windbox model on single burner sub-model and characterise burner for different swirler settings • Characterise Coal: Generate a simple drop tube furnace model (DTF) and calibrate the model to specific coal data for input to full furnace model • Furnace Combustion: Generate of a model of the furnace area starting at the burner mouth and ending at the outlet of the furnace and run combustion simulations • Optimisation: Use the full boiler model, using mapped data and calibrated input data from the single burner and DTF models, to evaluate the effect of different swirler settings, coal types etc. • Erosion Modelling: Use mapped data at outlet of furnace model in boiler tube erosion model

Secondary air windbox optimisation • Secondary air windbox supplies combustion air to the burners • Optimise geometry to evenly distribute the secondary air supply to each individual burner

Single burner sub-model • Highly detailed single burner model • Results from the secondary air windbox model simulations mapped as inlet boundary condition to single burner sub-model • The single burner sub-model is used to characterise the burner for different swirler settings • The results are exported and mapped as boundary conditions in the full boiler model

Single burner sub-model maps

Simple drop tube furnace model Simplified DTF CFD Model centre of model Cell refinement towards

Simple drop tube furnace model • The DTF model is used to calibrate the CFD model to laboratory rate data for the specific coals and test conditions. (activation energy, CV, Arinius factor for burnout rate) • Calibration used as input data in full burner model to accurately model specific coals

Full furnace model • The combustion models, calibrated for specific coals using the DTF model, is applied in the full furnace model • The secondary air flow field, relating to specific swirler and damper settings are extracted from the single burner sub-model solution and mapped as inlet boundary condition in the full furnace model Input Boundary Areas Secondary Air Mapping Area Refined Burner and Furnace Section

Full furnace model High swirl Low swirl CO contours O2 contours Temperature contours

Boiler tube erosion • Extract the solution from the full furnace model and apply as inlet boundary condition to the boiler tube erosion/boiler aerodynamics model • In these analysis, all the tubes are modelled explicitly • A Legrangian multiphase model is used to track particles through the domain and evaluate the resultant erosion

Boiler tube erosion Slotted Screens Expanded metal screen

Boiler tube erosion Explicit modelling (Meshing of screens)

Boiler tube erosion High erosion areas

PF Milling

PF Classification • Modelling of Classifiers to optimise throughput and particle size distribution to boilers

Other Power Plant Specific Areas • Fan modelling and optimisation • ACC modelling & performance prediction

Centrifugal Flow – FD & ID fans • Fan flow induced vibration root cause analysis • Fan Stress analysis & vibration modes

Hydro / Pumped Storage • Design of intakes, outlets, spillways, surge towers etc. • Calculation of hydrostatic and dynamic forces • Transient predictions of water hammers and other transient responses Closing of valve

Hydro / Pumped Storage Stilling pond outlet Inlet structure Surge Tower

Pollution control Fabric filter plant Detailed bags are individually modelled

Valve characterisation / Optimisation • Single components such as valves can be characterised and/or optimised

Cavitation prediction • Many piping systems suffer from cavitation patches which erode and eventually destroy valves and measurement equipment

Explosion modelling • Evaluation of work site safety in the vicinity of high risk explosive storage and/or systems.

Summary • As can be seen there exist a multitude of applications for CFD in the power generation industry. • Most existing Coal Fired Power Plants have been designed before the advent of commercial CFD. CD-adapco’s products therefore provides an understanding of where problem areas originate and it therefore offers a unique opportunity to address the root cause for problems. • Evaluation of general flow systems also provides a birds eye view of where losses occur and therefore CFD is opens the door to efficiency improvements in almost all areas of CFPP. • The incredible robustness, efficiency and advanced capabilities of STAR- CCM+ has made CFD a tool that provides extremely fast turnaround times and therefore it offers a cost effective route for problem solving, design and optimisation.