250kW Air Combustion Plant

Overview

The Air Combustion Plant (ACP) is a cylindrical design, 250kWth down fired pulverised fuel combustion system with interchangeable coal/biomass burners, fuel (coal/biomass) feeding system, a dedicated air metering skid, flue gas filter, heat exchanger and temperature and flow monitored water cooling system for the combustion vessel and flue ducts. The plant is operated and monitored using a dedicated control system connected to an industry standard SCADA system in a central control room for system monitoring, operation and data acquisition.

Upper floor of the rig (from left: gas heaters and steam skid, Combustion vessel with burner on top, Flue gas duct to heat exchanger, connection to central flu gas duct to stack)

Lower floor of the rig (from left: oxyfuel skid, air skid, gas heater controllers, bottom of combustion vessel, fuel feeding system. control PLC)

Example applications

  • Conventional combustion research with state of the art analytical capability to enable flame visualisation and modelling for combustion system design, development and optimisation.
  • Fuel testing and system optimisation for different types of fuels and fuel combinations coal, co-firing and biomass combustion.
  • Post Combustion Capture research: the rig flue gas is connected to a 1tonne/day (150kW equivalent) Solvent-based Carbon Capture Plant enabling post-combustion capture research with different fuels and under different combustion conditions. 
  • Air to oxy firing: the rig enables conventional air firing as well as research into  O2 enriched air combustion for example for more difficult samples such as biomass; in combination with a dedicated gas mixing facility the rig can also be operated  in simulated and full oxyfuel mode with Exhaust gas recirculation as a 250kW Oxyfuel Combustion Plant

System description

Main Fuels: Coal, biomass, co-firing, and natural gas (primarily for pre-heating).
Combustion vessel: Down fired, 2.5m3 cylindrical design rig with eight sections of approximately 0.5m in height and total height of nearly 4m; rig sections are double skinned and water cooled.
Burner: The rig is equipped with two dedicated interchangeable burners for biomass and coal respectively. The burners have an internal air split system providing both secondary and tertiary air feeds from one air supply (tertiary).
Fuel feeding system: The plant has two solid fuel feeding systems: one for biomass and one for coal (with an option of mixing of up to 10% biomass). The feeding system is installed over two levels with a hopper on the upper floor and fuel metering through a vibrating tray on the lower floor. Measured quantities of fuel are fed to the primary line where the fuel is mixed with the air and carried over as a mixture to the burner.
Combustion air supply: The plant is equipped with high precision PLC controlled air feed system, optional gas heaters and steam injection system for wet gas operation. Combustion air for the rig is supplied by a dedicated air compressor with a backup air fan. The air is fed through three dedicated lines via a dedicated air metering skid. From the air skid the individual air lines can be optionally preheated with dedicated gas heaters. The primary air line is connected to a coal/biomass feeding system to pick up solid fuel; the mixed air and fuel are fed directly to the burner. The tertiary line provides air directly to the top of the burner where the feed is split into secondary and tertiary line internally within the burner. The overfire line can be flexibly connected to different points in the rig vessel to provide additional control over the combustion process.
Exhaust gas:  Flue gases discharge from the bottom of the rig and are fed through a water cooled flue gas section to a dedicated heat exchanger. A bypass system allows simple control of the flue gas temperature before it is fed to filter to remove fly ash. Filter fan pulls the flue gases through the system and the speed of the fan is automatically adjusted by a pressure sensor on the combustion vessel.  Filtered flue gases are vented through the facility stack. A tee connection before the stack provides a link to the Solvent-based Carbon Capture Plant (SCCP) for Post Combustion Capture research. The SCCP is equipped with an integrated flue gas scrubbing facility.
 

150kW Air Combustion plant, from left, burner and upper sections of the combustion rig, flue gas duct and heat exchanger

Candle filter for 150kW Air/Oxyfuel Combustion Plant

 

Analytical capability

The rig sections and flue gas pipework are fitted with thermocouples and a pressure sensor enabling full system temperature and pressure monitoring. The rig vessel is additionally equipped with sampling and injection ports for gas sampling, pyrometer and heat flux probes and visualisation ports for state of the art 3D Laser Diagnostics and Thermal Imaging facility enabling detailed combustion research and modelling. The system has a dedicated gas analysis systems enabling continuous online monitoring of the flue gas. There are also provisions for gas injections,  ash deposition, and slagging and fouling studies.

Associated analytical facilities include: