Atmospheric and pressurized bubbling and circulating fluidized-bed combustion test facilities are available for the development of technology using conventional solid and alternative fuels.

Available Services

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• Characterization of candidate fuels and sorbents
• Development of design data
• Evaluation of emission control requirements and equipment (including air toxics)
• Evaluation of corrosion, erosion, and deposition
• Evaluation of ash disposal and reuse options
• Materials selection
• Performance optimization
• Consultation services
• Refinement of heat-transfer correlations
• Evaluation of bed material agglomeration
• Evaluation of hot-gas cleanup technologies

18- × 18-in. Bubbling Atmospheric Fluidized-Bed Combustor (AFBC) Test Unit
The 2.25-ft² test unit is a fully instrumented pilot plant system that was constructed in 1979 and has been in operation since 1980. This combustor operates in the bubbling mode of fluidization and has been used primarily for the generation of environmental and operational data for the fluidized-bed combustion of western coals. The unit has overbed and underbed feed capabilities, a primary cyclone with fly ash reinjection capabilities, and a baghouse for fine particulate control.

The unit is fully instrumented with computer-controlled data acquisition system capabilities to collect and display detailed operating information, including temperatures and pressures throughout the system and flue gas concentrations. Additionally, critical operational parameters like excess air, superficial gas velocity, and fuel feed rate are continuously calculated and displayed. Flue gas analyzers measure concentrations of oxygen, carbon dioxide, carbon monoxide, nitrous oxides, sulfur dioxide, and total hydrocarbons.

20-in.-diameter Circulating Fluidized-Bed Combustor (CFBC) Test Unit
The 42-ft-tall pilot-scale CFBC was completed in 1990. The unit was designed as an independent test facility to be used by the energy industry to perform evaluations on operating conditions, fuel characteristics, and sorbent characteristics on combustion and emission performance. Several such tests have been performed to provide emission data and ash stream samples to facilitate permitting of a full-scale CFB. A wide variety of fuels have been tested in the CFBC, including high- and low-rank coals, petroleum cokes, and dried municipal sewage sludge. The pilot plant is capable of operating over the range of conditions currently offered by most boiler vendors.

To quantify the effect of CFBC design and operating parameters and the effects of fuel and sorbent properties, the EERC measures a number of important performance variables and relates them to design and operating conditions, fuel, and sorbent properties. Environmental performance is evaluated by measuring sorbent addition and utilization to achieve the desired SO₂ control; NO_x, N₂O, CO, and hydrocarbon emissions; particulate collectibility; and waste characterization and disposal. Evaluation of thermal performance is accomplished through measurement of combustion efficiency (carbon burnout), heat transfer, sorbent thermal losses, and fouling in the convective pass. Operational performance can be qualitatively assessed by examining for fouling and deposition on heat-transfer surfaces, agglomeration or sintering of the ash or bed materials, changes in coal or ash particle size, and evidence of erosion or corrosion.

3-in.-diameter Pressurized Fluidized-Bed Reactor (PFBR)
The 55-in.-tall, 3-in.-diameter PFBR was built in 1992 to investigate pressurized fluidized-bed combustion sorbent utilization, emissions, alkali gettering, hot-gas cleanup, and agglomeration over a wide range of operating conditions. An alkali-sampling probe can be inserted through the top of the hot cyclone. A data acquisition/control system is used to monitor/record all critical temperatures, pressures, flow rates, and emissions and to remotely control the numerous valves distributed throughout the system. A solids-sampling port is located at the top of the cyclone, and flue gas is sampled after the pressure letdown valve. The system is designed to operate at pressures up to 300 psi and temperatures up to 2000°F at ambient pressure. Either dry or slurry fuel can be used. Air or nitrogen or any combination of both gases is used for fluidizing gas. External heaters are used for preheating and assisting in maintaining operational temperatures at specified conditions.

8-in.-diameter Circulating Cold-Flow Model
An 8-in.-i.d. by 20-ft-tall cold-flow model was constructed in 1988. This system is being utilized for the development of heat-transfer correlations between the circulating fluidized bed and the containing walls and between horizontal and vertical surfaces suspended in the bed. Variables that can be studied include particle size and distribution, gas velocity, solids loading, and vertical and radial position. Additional studies include the investigation of the fluid dynamic characteristics of circulating fluidized beds as a function of radial and axial position in the bed and sealing laws.

4-in.-diameter Bubbling Cold-Flow Model
The 4-in.-i.d. cold-flow model constructed out of plexiglas material has an overall height of 8 ft. It operates in the bubbling mode and has been used for cold-flow heat-transfer investigations. Air or water can be used as the fluidizing media.

Small-Scale Fluidized-Bed Reactor (FBR)
An FBR has been constructed to simulate the bed chemistry, ash interactions, and emissions from an FBC under closely controlled conditions. This reactor is used for sorbent characterization, gaseous emissions including trace elements, agglomeration, and hot-gas cleanup testing in a cost-effective manner over a wide range of operational conditions. The 55-in.-tall reactor is constructed of 3-in. Schedule 80 pipe and is externally heated with three ceramic heaters. A hot cyclone collects the ash and bed material carried out of the reactor. The preheated fluidizing gas can be a mixture of air and nitrogen or just air, and one additional gas such as carbon dioxide, carbon monoxide, sulfur dioxide, or a nitrogen oxide can be added to result in a flue gas similar to that generated in a full-scale FBC. Preheated gas at temperatures of up to 1400°F is supplied at the bottom of the reactor through a 1-in. Schedule 40 pipe. The fluidizing gas is supplied at sufficiently high velocities to prevent the sized bed material from dropping out during operation.

The fluidizing gas enters into the 3-in. Schedule 80 main section of the reactor through a conical transition designed without a distributor plate to allow quick removal and quench of the bed material after test completion. Bed material can be sampled or collected using a lock hopper system located at the bottom of the reactor.

The use of electric heaters provides the capability to match the fuel feed rate to the amount of bed material in the reactor. External heaters are used for heating and maintaining the reactor and hot cyclone at temperatures up to 2000°F. The external ceramic heaters on the gas preheater and the reactor itself are rated at 10.8 and 10.05 kW, respectively, with an upper temperature limit of 1200°F. In a full-scale system, the bed is deep relative to that in the FBR. Therefore, to keep the coal feed rate-to-bed inventory similar between bench- and full-scale systems, the coal feed rate in the FBR is kept low relative to full-scale systems, compared on a fuel feed rate per bed cross-sectional area basis. Therefore, additional heat is required to maintain the desired temperature. The high heat losses through the reactor walls inherent to small-scale systems also require either good insulation or reactor heating. This type of heating system provides very good control of the reactor temperature. The use of both air and nitrogen as fluidizing gas allows excess air quantities and gas velocity to be matched to any design condition.

Dry coal is metered with a small auger that feeds into a water-cooled auger which, in turn, carries the material into the reactor. A bed material hopper empties directly into the water-cooled auger. Each hopper is kept at a pressure slightly higher than that in the combustor during operation. The hoppers can be refilled during a test.

A data acquisition and control system is used to monitor and record all critical pressures, temperatures, flow rates, and emissions and to remotely control the numerous valves distributed throughout the system. These critical data include the gas flow rates, bed static and differential pressures across the bed and cyclone, eight internal reactor temperatures, and coal feed rate, as well as information monitored from other operating conditions. Continuous emission sampling of the flue gas measures and records the levels of O₂, SO₂, NO_x, CO, and CO₂. Ports for an alkali-sampling probe and solid-sampling or gas-sampling probes are located at the top of the reactor and the top of the cyclone.