States that care about the health, well being and longevity of their people need to assess each such incinerator on a regular basis and offer research grants to develop a better method to capture and contain any Greenhouse Gas Emissions, but, more importantly emissions that cause harm or potential down wind infections. Not all medical waste, including bacteria or viruses, are killed in an incinerator.
3.2 Emissions And Controls 2,4,7-43 (click here)
Medical waste incinerators can emit significant quantities of pollutants to the atmosphere.
These pollutants include: (1) particulate matter (PM), (2) metals, (3) acid gases, (4) oxides of nitrogen
(NOx), (5) carbon monoxide (CO), (6) organics, and (7) various other materials present in medical
wastes, such as pathogens, cytotoxins, and radioactive diagnostic materials.
Particulate matter is emitted as a result of incomplete combustion of organics (i. e., soot) and
by the entrainment of noncombustible ash due to the turbulent movement of combustion gases.
Particulate matter may exit as a solid or an aerosol, and may contain heavy metals, acids, and/or trace
organics.
Uncontrolled particulate emission rates vary widely, depending on the type of incinerator,
composition of the waste, and the operating practices employed. Entrainment of PM in the incinerator
exhaust is primarily a function of the gas velocity within the combustion chamber containing the solid
waste. Controlled air incinerators have the lowest turbulence and, consequently, the lowest PM
emissions; rotary kiln incinerators have highly turbulent combustion, and thus have the highest PM
emissions.
The type and amount of trace metals in the flue gas are directly related to the metals contained
in the waste. Metal emissions are affected by the level of PM control and the flue gas temperature.
Most metals (except mercury) exhibit fine-particle enrichment and are removed by maximizing small
particle collection. Mercury, due to its high vapor pressure, does not show significant particle
enrichment, and removal is not a function of small particle collection in gas streams at temperatures
greater than 150°C (300°F).
Acid gas concentrations of hydrogen chloride (HCl) and sulfur dioxide (SO2) in MWI flue
gases are directly related to the chlorine and sulfur content of the waste. Most of the chlorine, which
is chemically bound within the waste in the form of polyvinyl chloride (PVC) and other chlorinated
compounds, will be converted to HCl. Sulfur is also chemically bound within the materials making up
medical waste and is oxidized during combustion to form SO2
Oxides of nitrogen (NOx) represent a mixture of mainly nitric oxide (NO) and nitrogen dioxide
(NO2). They are formed during combustion by: (1) oxidation of nitrogen chemically bound in the
waste, and (2) reaction between molecular nitrogen and oxygen in the combustion air. The formation
of NOx is dependent on the quantity of fuel-bound nitrogen compounds, flame temperature, and
air/fuel ratio.
Carbon monoxide is a product of incomplete combustion. Its presence can be related to
insufficient oxygen, combustion (residence) time, temperature, and turbulence (fuel/air mixing) in the
combustion zone.
Failure to achieve complete combustion of organic materials evolved from the waste can result
in emissions of a variety of organic compounds. The products of incomplete combustion (PICs) range
from low molecular weight hydrocarbon (e. g., methane or ethane) to high molecular weight
compounds (e. g., polychlorinated dibenzo-p-dioxins and dibenzofurans [CDD/CDF]). In general,
combustion conditions required for control of CO (i. e., adequate oxygen, temperature, residence time,
and turbulence) will also minimize emissions of most organics.
Emissions of CDDs/CDFs from MWIs may occur as either a vapor or as a fine particulate.
Many factors are believed to be involved in the formation of CDDs/CDFs and many theories exist concerning the formation of these compounds. In brief, the best supported theories involve four
mechanisms of formation.2 The first theory states that trace quantities of CDDs/CDFs present in the
refuse feed are carried over, unburned, to the exhaust. The second theory involves formation of
CDDs/CDFs from chlorinated precursors with similar structures. Conversion of precursor material to
CDDs/CDFs can potentially occur either in the combustor at relatively high temperatures or at lower
temperatures such as are present in wet scrubbing systems. The third theory involves synthesis of
CDDs/CDFs compounds from a variety of organics and a chlorine donor. The fourth mechanism
involves catalyzed reactions on fly ash particles at low temperatures....
