Oxygen Carrier Aided Combustion (OCAC) of Wood Chips in a Semi-Commercial Circulating Fluidized Bed Boiler Using Manganese Ore as Bed Material

Abstract

Abstract:Oxygen Carrier Aided Combustion (OCAC) is realized by using an active oxygen-carrying bed material in fluidized bed boilers. The active material is reduced in fuel rich parts of the boiler and oxidized in air rich parts. Advantages could be achieved such as new mechanisms for oxygen transport in space and time. Here calcined manganese ore has been used as active bed material in a 12 MW th circulating fluidized bed boiler. The fuel was wood chips and the campaign lasted more than two weeks. From an operational point of view, manganese ore worked excellently. From the temperature profile of the boiler it can be concluded that fuel conversion was facilitated, especially in the dense bottom bed. The effect did not always translate to reduced emissions, which suggests that final combustion in the cyclone outlet was also influenced. Substituting 10% of the sand bed with manganese ore made it possible to reduce the air to fuel ratio without generating large amounts of CO. The use of 100% manganese ore resulted in higher emissions of CO than the sand reference, but, when combined sulphur feeding, dramatic reductions in CO emissions, up to 90% compared to sand reference, was achieved.

The Effect of Iron‐ and Manganese‐Based Oxygen Carriers as Bed Materials in Oxygen Carrier Aided Combustion

“…It is worth noting that there is an increase in CO concentration in the effluent gas as compared to that in the reference sand case, in the fuel‐lean part (Figure ) when the ilmenite or F6MZ1100 is used as an oxygen carrier. This behavior seems somewhat strange and unintuitive but has been observed before when Mn‐based ore was investigated for OCAC purposes . In that case, the study was performed using a 12 MWth CFB, and the behavior was suggested to be attributed to lack of ash removal from the system.…”

“…However, an alternative to influence oxygen distribution within the combustion zone could be to substitute the fluidizing bed material with an oxygen‐active bed material that can contribute to the homogenization of air distribution within the boiler . Such material is generally referred to as an oxygen carrier, and the use of an oxygen‐active bed material in fluidized bed combustion is generally referred to as oxygen carrier‐aided combustion (OCAC) …”

Experimental and CFD Simulation Studies on Bell-Type Air Nozzles of CFB Boilers

“…As a mature clean coal power generation technology, the circulating fluidized bed (CFB) boiler has become increasingly applied worldwide [1][2][3][4][5]. The air nozzle is one of the main components of a CFB boiler [6,7].…”

Performance Evaluation of a Chinese Lean Iron Ore as the Oxygen Carrier in Multi and Short-Time Redox Cycles

“…Currently, many successful operations have been conducted using synthetic OCs in pilot-scale gaseous fuel CLC systems. Synthetic OCs such as NiO, CoO, CuO, Mn 3 O 4 and Fe 2 O 3 presented favorable performances with high reactivity, high mechanical strength and low agglomeration [11][12][13][14][15][16]. To further enhance the reaction and/or mechanical performances, inert materials (e.g., Al 2 O 3 , SiO 2 , TiO 2 ) were widely used as supports for the synthetic OCs [17][18][19][20][21][22].…”