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Fluidised-Bed Combustion Reactor and Coal Gasification; Hot Gas Generator (HGG) and Organic Rankine Cycle (ORC) Generator

 

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Overview


The Fluidised-Bed Combustion Reactor system (FBCR) utilises high moisture, low grade fuels such as low grade coal or other solid waste (such as Biomass, Agricultural Green/Wood Waste, MSW and Effluent Sludge) to produce environmentally clean hot gas for generating process steam and/or power steam, or for product drying applications. The FBCR process includes low-temperature gasification followed by high-temperature combustion in one reactor, which has been commercially verified by independent experts as meeting the world's best practice for power generation. It has also been tested and proven as being suitable for a low-emission coal liquefaction.

 

The key innovations in the FBCR system, initiated and invented by James Kwok, have been widely adopted and commercialized in the designs of Fluidised-Bed Combustion systems around the world. More than a decade after their initial implementation in the proprietary Fluidised-Bed Combustion Reactor, the technology continues to be considered cutting-edge.

 

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Typical arrangement of a Fluidised-Bed Combustion Reactor

 

A fluidised bed is a bed of hot inert particles suspended in thin air. The bed is maintained at a temperature between 750 and 950 degrees Celsius, at which temperature fuels will ignite rapidly and burn. The fluidising air is the air in which the particles are suspended and is also the combustion air for fuel. Combustion occurs in two stages: in the bed and above in the freeboard of the furnace. Following low-temperature gasification, the gas is oxygenated firing at the reactor freeboard and releasing thermal heat at 1200 degrees Celsius.

 

In 1998 James Kwok initiated and co-developed with Prof Dr Udo Hellwig of ERK Germany the unique integrated 'shell-tubes', rated at 35t/h superheated steam generator at 400 degrees Celsius and 40Bar pressure, to power a 7MWt steam-turbine which was incorporated in the 25m high proprietary and patented Energy Equipment Fluidised-Bed Combustion Reactor (FBCR).

 

Patents that were held by James Kwok include key elements in project fuel-handling and feeding, being one of the main items that was resolved in all constructed FBCR installations world wide, including the use of CO2, a by-product of combustion recycled from the stack, to control critical bed temperatures. The basis of the FBCR principles were further developed and adopted as an HGG operating and ORC system to drive an expander turbo generator.

The benefits are:


1. Steam-cycle is completely avoided. Water resources are saved, where traditionally it is consumed in processing and cooling.
2. Cooling-cycle is done based on ambient and air-cooling augmentation.
3. HGG is well suited for brown coal fuels with high moisture and is capable of being fed-in on an 'as arrives' basis, meaning no bricking and/or palletising.
4. HGG suppresses emissions of SOx, NOx and VOx; as well as dust emissions as the cyclonic system is possible for adaptation.
5. HGG can be retrofitted to the existing coal fired plants without the removal of the existing structures and installations.
6. HGG can produce 3MWt of thermal energy at 13GJ/ton of brown coal at 40-45% moisture.

 

 

 

Installations


There are currently many FBCR units around Australia that have been built and are in commercial operation, with two also having been built in PRChina. A large-scale (5MWe) renewable power generating plant, using 70,000 t/yr of biomass (garden waste) as fuel, was designed and constructed using the latest Energy Equipment FBCR technology and completed at Stapylton, Queensland in 2001, attaining successful commercial operation. This plant produced 30tph super heated steam at 400 degrees Celsius and 40Bar pressure, and was amongst Australia’s first using a multi-stage air condenser system for cooling (instead of water). The plant was constructed as an embedded generator for an Industrial complex in South East Queensland, Australia and operated until 2005 when prolonged drought halted the supply of biomass.

 

Completed in 1999 was a HGG plant at Subiaco Waste Treatment plant, using 25tp/d of sewer sludge to produce bio-diesel. The typical feed of biomass was at 30-40% moisture with CV at ~8GJ/ton.

 

In 2002 the Stapylton plant was granted with Australia’s first renewable energy generation and transmission license and renewable energy certification from the Australian Greenhouse Office (AGO) in Canberra. In 2003 the plant was successfully commissioned with independent expert verification from Burns Roe Worley (Melbourne, Australia). Other verifications were also conducted by Sinclair Knight Mertz (SKM, Sydney Australia); GHD Black & Veatch (Sydney, Australia and USA); and the Queensland State and Environmental Protection Authority; to confirm meeting designed performance, operational and emissions abatements.

 

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Completed green waste to energy plant in Stapylton, Queensland


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FBCR installed on green waste to energy site

 

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James Kwok on site in Stapylton, Queensland

 

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Turbine rotor on site

 

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Turbine stator on site

 

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Standard 10-30MW thermal FBCR Steam Generator, pressure up to 40Bar

 

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Coal Gasification under construction in PRChina

 

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FBCR Effluent Sludge to Energy installation - processing 100t per day

 

 

Also in 2002 James Kwok and Dr Rajinder Malik (previously with The University of Sydney, Chemical Engineering Faculty) developed, designed and documented the process for ethanol production using 85kT/yr of cellulose as feed stock from agriculture waste, in a proposed project in Trangie District, Dubbo City, Central New South Wales of Australia. This project was planned to feature a 10MW capacity FBCR as a co-generation system for the 30ML/yr ethanol plant. With a dedicated bio-farm to be located adjacent to the plant, the proposed project was granted with Australia’s first EPA approvals. The Australian Federal Government’s anticipated ethanol legislation was not passed at that time and the project was shelved. However in the latter part of 2010, mandatory 10% ethanol-mix legislation has since been passed and E10 fuel has now been introduced to replace the fuel previously known as unleaded. Click the schematic below for a larger image.

 

 

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