17 research outputs found
Rheological Study of a Direct Liquefaction Feed Slurry
A rheological study was made of a liquefaction startup- feed slurry. The slurry consisted of North Dakota lignite sized to 70% less then 200 mesh and a carrier solvent of an thracene oil. The rheological behavior of the slurries, o with coal concentrations of 0 to 40% at 40 C, was shown to be Newtonian, allowing Bernoulli\u27s equation to be used for direct calculation of pressure drop. Calculated values pre dicted the measured data within 10% for the test conditions.
The investigation used an experimental slurry loop, con sisting of a bank of pipes with nominal sizes ranging from 1 inch (2.54 cm) to 3/8 inch (0.95 cm), to determine the actu al pressure drops for the slurries. The pressure drops were found to range from 0.064 psi (4.43xlOJ dynes/cm ) for an thracene oil pumped through the 2.54 cm pipe to 11.71 psi (8.07xl05 dynes/cm2) for the 40% coal slurry pumped through a 0.95 cm pipe.
A Brookfield Rheolog viscometer was used to determine viscous behavior of samples taken from the runs. Using lin ear regression analysis, a straight line through zero was obtained for torque vs. angular velocity for each sample with correlation coefficients greater then 0.98. Viscosities of the samples ranged from 23.3 centipoise for anthra cene oil to 286.6 centipoise for the 40% coal slurry. A statistical comparision indicated that calculated and exper imentally measured pressure drops were not significantly different at the 95% confidence level
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Evaluation of Alternatives to the Ontario Hydro Method as a Reference Method for CAMR
In June 2005, the U.S. Environmental Protection Agency (EPA) finalized the Clean Air Mercury Rule (CAMR). As part of the rule, all coal-fired power plants will be required to do continuous mercury measurements. To complete the required relative accuracy test assessment (RATA), the only reference methods allowed are the wet-chemistry methods: the Ontario Hydro (OH) mercury speciation method (ASTM International D6784-02) and EPA Method 29. Either method will be a challenge and expensive. It would be much more desirable to use an instrumental reference method (IRM) or use sorbent traps as a reference method so that the results can be obtained quickly and cheaply. This report presents the results from testing at Reliant Energy, Inc.'s, Portland Station. The project was designed to compare mercury concentrations measured using sorbent traps to those obtained using the OH method. The tests were done using a RATA scenario and at three different conditions. In addition, as part of the project, limited IRM testing was also completed. The results from the testing show that the sorbent traps compared very well with the OH method and, therefore, must be considered as a potential reference method. Although the IRM testing using manual injection of elemental and oxidized mercury for dynamic spiking showed some promise, it was clear that additional testing was needed. However, this method of dynamic spiking may not be acceptable to EPA, as it does not consider vapor pressure curves for elemental mercury a National Institute of Standards Technology traceable standard
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Bench- and pilot-scale evaluation of mercury speciation measurement methods
The 1990 Clean Air Act Amendments require the US Environmental Protection Agency (EPA) to assess the health risks associated with mercury. Since the rate of mercury deposition and the type of control strategies used may depend on the type of mercury species emitted, a proven sampling method that can reliably and accurately speciate mercury at the very low concentrations found in coal combustion flue gas is necessary. A number of mercury speciation methods have been proposed, including wet-chemistry methods, such as EPA Method 29, the Ontario Hydro method, and the tris-buffer method, as well as dry methods such as the Mercury Speciation Absorption method (MESA). In addition, a number of companies are developing continuous emissions monitors to speciate mercury by difference. Bench- and pilot-scale tests, sponsored by the Electric Power Research Institute (EPRI) and the US Department of Energy (DOE), are currently under way at the Energy and Environmental Research Center (EERC) to determine the most accurate and precise mercury speciation method available. The overall objective of the test program is to determine whether EPA Method 29 or other sampling methods can reliably quantify and speciate mercury in flue gas from coal-fired boilers at both the inlet and outlet of a particulate control device such as a pulse-jet baghouse. A specific goal of the project is to determine the precision and bias of the various mercury speciation methods as a function of process variables
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PILOT-SCALE EVALUATION OF THE IMPACT OF SELECTIVE CATALYTIC REDUCTION FOR NOx ON MERCURY SPECIATION
Full-scale tests in Europe and bench-scale tests in the United States have indicated that the catalyst, normally vanadium/titanium metal oxide, used in the selective catalytic reduction (SCR) of NO{sub x}, may promote the formation of Hg{sup 2+} and/or particulate-bound mercury (Hg{sub p}). To investigate the impact of SCR on mercury speciation, pilot-scale screening tests were conducted at the Energy & Environmental Research Center. The primary research goal was to determine whether the catalyst or the injection of ammonia in a representative SCR system promotes the conversion of Hg{sup 0} to Hg{sup 2+} and/or Hg{sub p} and, if so, which coal types and parameters (e.g., rank and chemical composition) affect the degree of conversion. Four different coals, three eastern bituminous coals and a Powder River Basin (PRB) subbituminous coal, were tested. Three tests were conducted for each coal: (1) baseline, (2) NH{sub 3} injection, and (3) SCR of NO{sub x}. Speciated mercury, ammonia slip, SO{sub 3}, and chloride measurements were made to determine the effect the SCR reactor had on mercury speciation. It appears that the impact of SCR of NO{sub x} on mercury speciation is coal-dependent. Although there were several confounding factors such as temperature and ammonia concentrations in the flue gas, two of the eastern bituminous coals showed substantial increases in Hg{sub p} at the inlet to the ESP after passing through an SCR reactor. The PRB coal showed little if any change due to the presence of the SCR. Apparently, the effects of the SCR reactor are related to the chloride, sulfur and, possibly, the calcium content of the coal. It is clear that additional work needs to be done at the full-scale level
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Mercury Information Clearinghouse
The Canadian Electricity Association (CEA) identified a need and contracted the Energy & Environmental Research Center (EERC) to create and maintain an information clearinghouse on global research and development activities related to mercury emissions from coal-fired electric utilities. With the support of CEA, the Center for Air Toxic Metals{reg_sign} (CATM{reg_sign}) Affiliates, and the U.S. Department of Energy (DOE), the EERC developed comprehensive quarterly information updates that provide a detailed assessment of developments in the various areas of mercury monitoring, control, policy, and research. A total of eight topical reports were completed and are summarized and updated in this final CEA quarterly report. The original quarterly reports can be viewed at the CEA Web site (www.ceamercuryprogram.ca). In addition to a comprehensive update of previous mercury-related topics, a review of results from the CEA Mercury Program is provided. Members of Canada's coal-fired electricity generation sector (ATCO Power, EPCOR, Manitoba Hydro, New Brunswick Power, Nova Scotia Power Inc., Ontario Power Generation, SaskPower, and TransAlta) and CEA, have compiled an extensive database of information from stack-, coal-, and ash-sampling activities. Data from this effort are also available at the CEA Web site and have provided critical information for establishing and reviewing a mercury standard for Canada that is protective of environment and public health and is cost-effective. Specific goals outlined for the CEA mercury program included the following: (1) Improve emission inventories and develop management options through an intensive 2-year coal-, ash-, and stack-sampling program; (2) Promote effective stack testing through the development of guidance material and the support of on-site training on the Ontario Hydro method for employees, government representatives, and contractors on an as-needed basis; (3) Strengthen laboratory analytical capabilities through analysis and quality assurance programs; and (4) Create and maintain an information clearinghouse to ensure that all parties can keep informed on global mercury research and development activities
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INVESTIGATION OF THE FATE OF MERCURY IN A COAL COMBUSTION PLUME USING A STATIC PLUME DILUTION CHAMBER
The overall goal of the project was to further develop and then verify SPDC's ability to determine the physical and chemical transformations of mercury in combustion stack plumes. Specific objectives of the project were to perform controlled tests at the pilot scale using dynamic spiking of known mercury compounds (i.e., Hg{sup 0} and HgCl{sub 2}) to prove the ability of the SPDC to determine the following: whether mercury condenses onto particulate matter in a cooling plume; whether there is reduction of Hg{sup 2+} to Hg{sup 0} occurring in hygroscopic aerosols; whether condensed Hg{sup 2+} on particles is photochemically reduced to Hg{sup 0}; and whether or not the Solid Ontario Hydro mercury speciation method (SOH) provides the same results as the Ontario Hydro (OH) mercury speciation method
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EVALUATION OF AEROSOL EMISSIONS DOWNSTREAM OF AN AMMONIA-BASED SO2 SCRUBBER
Depending on the size and type of boiler, the 1990 Clean Air Act Amendments required specific reductions in SO{sub 2} emissions from coal-fired electric utilities. To meet these requirements, SO{sub 2} reduction strategies have included installing scrubbing technology, switching to a more expensive low-sulfur coal, or purchasing SO{sub 2} allowances. It is expected that over the next 10 years there will be an increase in the price of low-sulfur coals, but that higher-sulfur coal costs will remain the same. Technologies must be strongly considered that allow the use of high-sulfur fuels while at the same time meeting current and future SO{sub 2} emission limits. One such technology is the ammonia based flue gas desulfurization (FGD) (NH{sub 3}-based FGD) system manufactured by Marsulex Environmental Technologies (MET). The MET scrubber is a patented NH{sub 3}-based FGD process that efficiently converts SO{sub 2} (>95%) into a fertilizer product, ammonium sulfate ([NH{sub 4}]{sub 2}SO{sub 4}). A point of concern for the MET technology, as well as other FGD systems, is the emission of sulfuric acid/SO{sub 3} aerosols that could result in increased opacity at the stack. This is a direct result of firing high-sulfur fuels that naturally generate more SO{sub 3} than do low-sulfur coals. SO{sub 3} is formed during the coal combustion process. SO{sub 3} is converted to gaseous H{sub 2}SO{sub 4} by homogeneous condensation, leading to a submicron acid fume that is very difficult to capture in a dry electrostatic precipitator (ESP). The condensed acid can also combine with the fly ash in the duct and scale the duct wall, potentially resulting in corrosion of both metallic and nonmetallic surfaces. Therefore, SO{sub 3} in flue gas can have a significant impact on the performance of coal-fired utility boilers, air heaters, and ESPs. In addition to corrosion problems, excess SO{sub 3} emissions can result in plume opacity problems. Thus the Energy & Environmental Research Center (EERC) was contracted by MET and the U.S. Department of Energy (DOE) to evaluate the potential of a wet ESP for reducing SO{sub 3} emissions. The work consisted of pilot-scale tests using the EERC's slagging furnace system (SFS) to determine the effectiveness of a wet ESP to control SO{sub 3}/H{sub 2}SO{sub 4} aerosol emissions in conjunction with a dry ESP and MET's NH{sub 3}-based FGD. Because these compounds are in the form of fine particles, it is speculated that a relatively small, highly efficient wet ESP following the MET scrubber would remove these fine aerosol particles. The performance target for the wet ESP was a particulate mass collection efficiency of >90%; this level of performance would likely ensure a stack opacity of <10%
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DEVELOPMENT OF AN IN SITU INSTRUMENT FOR MEASURING MERCURY IN A GAS STREAM
As part of its overall Environmental Management Program, the U.S. Department of Energy (DOE) has developed thermal and incineration processes for treating hazardous mixed wastes. These mixed wastes often contain mercury that is released into the atmosphere during the incineration process. The U.S. Environmental Protection Agency (EPA), as well as many states, clearly views mercury emissions from incinerators and combustion systems as a potential human health problem (1). Although validated batch measurement methods such as EPA Method 29, the Ontario Hydro mercury speciation method, and EPA Method 101A exist for total and speciated mercury, they are difficult and costly to perform. In addition, the data are not available for use until several days later. Continuous emission monitors (CEMs) are a very attractive option because the data are in near real-time, allowing the data to be used as feedback control for mercury control strategies. Also, a properly designed analyzer should require minimal operator input. However, based on the current state of the art, mercury CEMs are not without problems, as demonstrated in recent field tests (2). In addition, they are often bulky and costly to purchase. Sensor Research and Development Corporation (SRD) was contracted by DOE's National Energy Technology Laboratory (formerly the Federal Energy Technology Center [FETC]) to develop a prototype instrument for thermal treatment process continuous emission monitoring applications. The work by SRD for DOE on the mercury CEM was conducted under two different contracts. Work under the first contract began October 1, 1997, and ended June 2000, with a second contract continuing until June 2001. The SRD process has the potential to be the basis for a very low-cost mercury CEM. The initial cost estimates provided by SRD are an order of magnitude lower than any other proposed mercury CEM. Although the instrument will be low-cost, it still has the potential to detect low limits of mercury and, therefore, has a wide range of possible uses. In addition, the instrument will be very portable
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CHARACTERIZATION AND MODELING OF THE FORMS OF MERCURY FROM COAL-FIRED POWER PLANTS
The 1990 Clean Air Act Amendments (CAAAs) required the U.S. Environmental Protection Agency (EPA) to determine whether the presence of mercury in the stack emissions from fossil fuel-fired electric utility power plants poses an unacceptable public health risk. EPA's conclusions and recommendations were presented in the Mercury Study Report to Congress (1) and the Utility Air Toxics Report to Congress (1). The first report addressed both the human health and environmental effects of anthropogenic mercury emissions, while the second addressed the risk to public health posed by the emission of mercury and other hazardous air pollutants from steam-electric generating units. Given the current state of the art, these reports did not state that mercury controls on coal-fired electric power stations would be required. However, they did indicate that EPA views mercury as a potential threat to human health. In fact, in December 2000, the EPA issued an intent to regulate for mercury from coal-fired boilers. However, it is clear that additional research needs to be done in order to develop economical and effective mercury control strategies. To accomplish this objective, it is necessary to understand mercury behavior in coal-fired power plants. The markedly different chemical and physical properties of the different mercury forms generated during coal combustion appear to impact the effectiveness of various mercury control strategies. The original Characterization and Modeling of the Forms of Mercury from Coal-Fired Power Plants project had two tasks. The first was to collect enough data such that mercury speciation could be predicted based on relatively simple inputs such as coal analyses and plant configuration. The second was to field-validate the Ontario Hydro mercury speciation method (at the time, it had only been validated at the pilot-scale level). However, after sampling at two power plants (the Ontario Hydro method was validated at one of them), the EPA issued an information collection request (ICR). The ICR required all coal-fired utilities to submit the mercury concentrations in their coal for one year quarterly, and 80 coal-fired power plants were selected to do mercury flue gas analysis. It was decided by EPRI and the U.S. Department of Energy (DOE) that this project would be suspended until the results of the ICR were known. This report presents the results that were obtained at the two power plants referred to as Sites 111 and E-29. The EERC teamed with Radian International (now URS Corp.) to do the sampling and analysis at these two power plants
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MERCURY AND LEAD SAMPLING AT MINNESOTA POWER'S BOSWELL ENERGY CENTER
At the request of the Minnesota Power, Inc., the Energy & Environmental Research Center (EERC) sampled for lead at the stack (or duct directly leading to the stack) for three units at the Boswell Energy Center. All sampling was done in triplicate using U.S. Environmental Protection Agency (EPA) Method 12, with sampling procedures following EPA Methods 1 through 4. During the test program, lead sampling was done using EPA Method 12 in the duct at the outlet of the baghouse serving Unit 2 and the duct at the outlet of the wet particulate scrubber serving Unit 3. For Unit 4, lead sampling was done at the stack. The specific objective for the project was to determine the concentration of lead in the flue gas being emitted into the atmosphere from the Boswell Energy Center. The test program was performed during the period of May 8 through 11, 2000. This report presents the test data, sample calculations, and results, and a discussion of the lead sampling performed at the Boswell Energy Center. The detailed test data and test results, raw test data, process data, laboratory reports, and equipment calibration records are provided in Appendices A, B, and C