Coal and Biomass Energy Laboratory
|Combustion and Emissions performance - Cofiring|
The overall goal of the program is to develop a technology for disposing of animal wastes through cofiring with coal using minimal modifications to existing coal fired units. The use of cattle manure (referred to as feedlot biomass, FB) as a fuel source has the potential to both solve waste disposal problems and reduce fossil fuel based CO2 emissions. A co-firing technology is proposed where FB is ground, mixed with coal, and then fired in existing, pulverized coal-fired boiler burner facilities.
An extensive research program was undertaken in order to determine,
i) fuel characteristics of coal, Feedlot Biomass ( cattle manure),Litter
Biomass (Chicken litter) ii) combustion characteristics of coal, 90:10
Wyoming Coal:Feedlot Biomass and Coal:Litter Biomass blends when fired
in a TAMU 30-kWt (100,000-BTU/hr.) boiler burner facility, and iii) combustion
and fouling characteristics when fired along with coal in a large pilot
scale 150-kWt (500,000-BTU/hr.) DOE-NETL boiler-burner facility
|Emission Control - Reburning|
|The N in NOx can come from both the N containing fuel compounds
(e.g. coal, biomass, animal waste) and from the N in the air. The NOx generated
from fuel N is called fuel NOx, and NOx formed from the air is called thermal
NOx. Typically, 75 % of NOx in boiler burners is from fuel N. The current
technologies developed for reducing NOx include: combustion controls (e.g.
staged combustion or low NOx burners LNB, reburn) and post combustion controls
(e.g. Selective Non-Catalytic Reduction, SNCR using urea, etc.). In reburning,
additional fuel (coal or natural or gas) is injected down stream from the
primary combustion zone to create a fuel rich zone where NOx is reduced
through reactions with hydrocarbons. The nitrogen in the reburn fuel then
recombines with oxygen to form NOx, or combines with N to form N2. After
the reburn zone, additional air is injected in the burnout zone to complete
the combustion process.
The current reburning experiments use a premixed propane burner along
with a small amounts of NH3 to simulate coal combustion gases, and to
test coal and feedlot biomass as reburn fuels in order to determine their
NOx reducing capability. The reburn fuel is fed from a dry solids feeder.
The reburn injection ports are located below the tip of the premixed
propane flame, after all of the NO has been formed in the primary zone.
An Enerac 3000E gas analyzer is then used to measure the concentration
of oxygen and NO in the final sampling port.
|In the U.S. alone, approximately 200 million tons of dry cattle waste is being produced annually. One of the processes for energy conversion of biomass fuels is thermochemical gasification. For the current study, a laboratory scale, 10 kWth, fixed-bed gasifier (reactor internal diameter 0.15 m, reactor height 0.30 m) facility was built at the Texas A&M University Boiler Burner Laboratory, and was fired with a) coal, b) feedlot biomass (FB), c) chicken litter biomass (LB), d) high ash feedlot biomass (HFB), e) coal: FB blend (CFB), f) coal: LB blend (CLB), g) coal: HFB blend (CHFB), and h) LB: HFB blend (LHFB). The temperature profiles, and the gas species profile in the bed are measured and the species analyzed for heat contribution. The parametric studies include the effect of fuel particle size (average particle used were 0.52 mm and 9.5 mm), and the air flow rate (45 and 60 SCFH) on the gasification characteristics of the fuels.|
A Thermogravimetric analyzer (TGA)is used for accurate determination of moisture, volatiles, ash, fixed carbon and loss of ignition in a large variety of materials, by measuring the change in mass as a function of temperature. The TGA can be used to analyze deabsorption and decomposition behavior, characterize oxidation behavior, set burnout or conditioning parameters (temperature/ramp rate/time), and determine chemical composition.
The Differential Scanning Calorimeter (DSC) is used to measure specific heat capacity and heats of transition as well as to detect the temperature of phase changes and melting points. DSC is based on measurement of the thermal response of an unknown specimen as compared with a standard when the two are heated uniformly at a constant rate.
|Objectives of this Project:
1. To study the flame structure (flame height and width, etc.) and flame stability (lift off and blow off) characteristics of laminar jet diffusion flames under interactive modes as a function of the flowrate through the burners, the spacing between the burners, the fuel properties, and the burner geometry.
2. To develop analytical expressions for the flame growth and the flame stability characteristics of single flames issuing from 2D and circular burners by solving the governing differential equations of mass, momentum, energy, and species.
3. To Extroplate the single flame model to include multiple burner effects
4. To Compare the experimental results and the analytical predictions
of flame structure and flame stability under interactive modes