SO₂ Emissions

• SO₂ Control by Limestones in FBC
• SO₂ Control by Limestones in WFGD Systems
• SO₂ Control by Sorbent Injection

SO₂ Control by Limestones in FBC

SO₂ Control by Limestones in WFGD Systems

Twenty-five well-characterized limestones were evaluated as reagents in a pilot-scale, forced-oxidation wet flue gas desulfurization (WFGD) test facility. Limestone performance was determined as the extent and rate of sulfur capture as a function of time and the dissolved carbonate/sulfur capture molar ratio. A data base was generated of the relative performance of the limestones, which represented a range of stratigraphic intervals with diverse chemical compositions, and geologic histories.

The study suggests that limestones with as little as 82 wt. % calcium carbonate are suitable reagents based on the defined performance parameters. Relative performance was not predictable solely from the calcium carbonate content. The effect on limestone performance of operating parameters, i.e. liquid-to-gas ratio, gas-liquid contact time, residence time in the reaction tank, pH, and SO₂ concentration, and slurry characteristics, i.e., solids loading and particle size distribution, was also investigated.

Results of the program include:

• There is no obvious relationship between the calcium carbonate content of a limestone and utilization as defined in the study.
• There was little correlation between the dissolution rate, rate of sulfur capture, and percent of sulfur capture with time.

SO₂ Control by Sorbent Injection

Energy Institute personnel have experience in sorbent (limestone, lime, hydrated lime, and sodium-based compoungds) injection into coal-fired boilers for SO₂ control. This includes in-furnace and duct injection technologies for pulverized and micronized coal-fired boilers. Recently The Energy Institute evaluated sodium bicarbonate duct injection into the flue gas from a micronized coal-fired industrial boiler to achieve 90% SO₂ emissions, and to reduce SO₃ emissions to minimize ammonium bisulfate deposition during NO_x reduction from a SCR system. Penn State's demonstration boiler system was used for this demonstration.

NO_x Emissions

• Cofiring CWSF and Pulverized Coal
• Low NO_x Burners
• Selective Catalytic Reduction
  

Cofiring CWSF and Pulverized Coal

Low NO_x Burners

The Energy Institute is actively involved in the development and evaluation of low-NO_x burners for industrial boilers. This includes burner and boiler modeling, burner performance evaluation, and new burner development. Low-NO_x burner evaluation and development activities have been conducted in conjunction with ABB Combustion Engineering (High Efficiency Advanced Coal Combustor and Radially Stratified Fuel Core burner), Energy and Environmental Research Corporation (FlamemastEERTM burner), and Foster Wheeler Development Corporation, using the demonstration boiler.

Selective Catalytic Reduction

A NO_x reduction catalyst was evaluated at the Energy Institute, in conjunction with Corning Inc. and Englehard Corporation, that is compatible with the typical operating conditions and the economic constraints of industrial boilers. The optimum temperature for SCR catalysts currently being used is ~700^oF. The objective of the low-temperature catalyst work is to operate a SCR system at typical baghouse temperatures (~350-400^oF). This work has progressed from a bench-scale laboratory reactor to the pilot scale (100 acfm) and is being scaled up to the demonstration boiler (8,150 acfm). The catalyst was developed as a coating on a ceramic filter.

Hazardous Air Pollutants (HAPs)

• Fine Particulate Matter
• Trace Metals
• Volatile Organic Compounds (VOCs)
• Dioxin/ Furan TEQs

Fine Particulate Matter

The Energy Institute, in conjunction with Corning Incorporated, and the U.S. Department of Energy evaluatedceramic membrane filters for fine particulate control. Of particular interest is the viability of using these filters, due to their compactness, as a retrofit technology for industrial boilers. The technical issues addressed included: filter performance and regeneration, fine particulate and condensable particulate emissions, multi-element composition and mercury speciation of the emissions, comparison of particulate emissions between a ceramic filter chamber and a conventional fabric filter baghouse, and the effect of fuel form (micronized coal and coal-water slurry fuel) on particulate emissions.

The Energy Institute is demonstrating this technology by operating a ceramic filtering device in parallel with the fabric filter baghouse on the demonstration boiler. The system was operated for more than 2,000 hours and exhibited better capture of finer ash particles, mercury, and condensable particulate matter than the conventional baghouse filters. EPA Methods 5, 201A (modified to include PM_2.5), 202, and 29 were used. In addition, the Ontario Hydro Method and the PSU Method (described in the trace elements section) were also used.

Trace Metals

The Energy Institute is studying the occurrence of trace elements, with an emphasis on mercury, in flue gas from both pilot- and demonstration-scale facilities. The emphasis of the work is on mercury emissions from coal-fired boilers as a consequence of Title III of the Clean Air Act Amendments of 1990, which designates 188 hazardous air pollutants (HAPs). Included in this list are the following inorganic elements: arsenic, beryllium, cadmium, cobalt, manganese, nickel, lead, antimony, selenium and mercury. Mercury has been of primary concern given its significant negative health effects on humans and wildlife.

Examples (not inclusive) of activities includes: under the direction of the U.S. Department of Energy, the Energy Institute developed a sample train and methodology capable of simultaneously sampling and measuring the above trace elements and mercury species. The advantage of this method is that it enables trace elements and mercury species to be sampled simultaneously. This reduces the time required to change out sampling trains and obtain and recover samples, as well as allow for a complete suite of data to be collected during one continuous run. A rigorous statistical analysis was performed assessing the PSU Method. The study demonstrated that the PSU Method is capable of simultaneously sampling mercury species and all inorganic trace elements listed as HAPs. Data sets generated by the PSU Method are statistically indistinguishable from data produced by Method 29 for multielements and the Ontario Hydro Method for mercury species.

Tests were conducted, using EPA Method 29, to determine the emissions of trace elements from ceramic membrane filters and fabric filters when firing micronized coal. Mercury emissions from the ceramic filter were 79% lower than from the baghouse. The ceramic filter captured more of the fine particulate and it was determined that the mercury was associated with the fine particles.

The effect of coal cleaning and fuel form (pulverized or coal-water slurry fuel) on toxic emissions were investigated using several coals provided by CQ, Inc. and Cyprus-AMAX Research & Development Center (cleaned under DOE’s Premium Fuel Program).

Metals emissions when cofiring sewage sludge and waste coal in a circulating fluidized-bed combustor were determined for the Illinois State Geological Survey.

Volatile Organic Compounds (VOCs)

Volatile organic compounds (VOCs) are routinely performed during combustion testing. This includes determining total hydrocarbon emissions using EPA Method 25A (Flame Ionization Detection for Total Hydrocarbons with GC Analysis of Bag Samples for Methane and Ethane) and polycyclic aromatic hydrocarbons (PAHs) using EPA Method 8270C (Semivolatile Organic Compounds by Gas Chromatography/Mass Spectrometry). The PAHs of interest include naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, fluoranthene, pyrene, chrysene, benz[a]anthracene, benzo[b]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, benzo[ghi]perylene, and dibenz[ah]anthracene, which have been specified by EPA as priority pollutants.

Dioxin/Furan TEQs

Dioxin/Furan TEQs are determined using EPA Method 23 (Determination of Polychlorinated Dibenzo(p)dioxins and Polychlorinated Dibenzofurans from Stationary Sources) and Cape Technologies Method IN-DF1 (High Performance Dioxin/Furan Immunoasay Analysis of PCDD/Fs in Prepared Sample Extracts). There are 75 polychlorodibenzodioxin (PCDD) congeners and 135 polychlorodibenzofuran (PCDF) congeners. Of these, 17 are considered to be toxic. The EPA, based on a variety of toxicity tests, has assigned Toxic Equivalency Factors (TEFs) of 1.0 to 0.0001 (relative to 2,3,7,8-tetrachlorodibenzo-p-dioxin) to these 17 compounds. In any given sample, the concentrations of each of these compounds can be determined, and, when their individual TEFs are factored in, the total Toxic Equivalency (TEQ) of a sample can be determined. This TEQ is generally considered the data most revealing about a sample’s dioxin-like toxicity. These Methods have been extensively used when assessing the combustion/ emissions performance of agricultural plastics cofired with coal.