Toxic Liquid Waste Incinerator - Essay Example

Toxic Liquid Waste Incinerator Incinerators burn waste, thereby destroying some waste materials and reducing the volume of others. Although manydifferent incineration technologies exist, nearly all incineration facilities share some common input and output streams. The primary inputs at most incineration facilities are the wastes to be treated, along with air and additional fuel to support combustion. Incineration occurs within combustion chambers, which destroys most organic material in waste, but in the process generates two general types of output streams: Air emissions and the residuals. Stack air emissions are gaseous, vapor, and particle-bound by-products of combustion. Facilities also have fugitive air emissions, which are releases to the air from process points other than stacks (e.g., equipment leaks, wind-blown dust). The design of an incinerator, including waste and residual handling, largely determines the amount of fugitive air emissions that might occur. Incineration facilities also generate solid and liquid residuals. These typically include wastewater from air pollution control devices and solid wastes, such as ash that remains in the combustion chamber and sludge that settles from wastewater treatment operations. In a waste liquid incinerator, the alkali waste liquids are recovered, the organic waste liquids are thermally decomposed and the hazardous waste liquid are made nonhazardous. All waste must be thoroughly characterized before they arrive at the incinerator and their contamination levels known before they can be treated. Liquid wastes are stored primarily in tanks which have passive vents to the atmosphere. All vapors released from tanks first pass through Adsorption filters that capture volatile chemicals which might otherwise enter the air. The liquid wastes are piped directly into the incinerator, either to the rotary kiln or to the afterburner. In the primary combustion chamber, the inside temperature is at least 1580°F (temperature varies depending on the type of waste treated). This process generates gases which pass into the secondary combustion chamber for further treatment. Incombustible material in the waste leaves the rotary kiln in the form of ash which drops into a water pool and enters into the residual management part of the process. In the secondary combustion chamber some liquid waste is sprayed directly into the afterburner for treatment purposes. The organic gases generated in the rotary kiln are destroyed when exposed to temperature of 2205°F for at least 4 seconds. In the incineration of different liquid wastes, some potentially harmful by-products form such as inorganic acids, dioxins and furans. Metals and radionuclides are not destroyed in the combustion chamber. Thus, effluent from these chambers contain a mixture of vapor products and particles that pass through a series of air pollution controls “to be cleaned” before being vented to the atmosphere. These controls are the quench chamber, the venturi scrubber, packed bed scrubber and 2 ionizing wet scrubbers. These controls efficiently remove numerous contaminants, including very fine particles that would otherwise escape to the air. After passing air pollution controls, processed gases are vented to the atmosphere. Sophisticated controls help ensure that the incinerator efficiently destroys waste without causing air emissions possibly harmful to health and the environment. Automated controls monitor waste handling operations, incineration and air pollution controls. Throughout incineration process, there are continuous readings of more than 30 different operating parameters. The controls ensure that the incinerator operates safely. All incinerators have air emissions. Stack air emissions are gaseous vapor, and particle bound products of combustion. Stack test are conducted regularly for the 8 groups of contaminants namely; particulate matter, volatile organic compounds, PCB’s, metals, acidic gases, dioxins and furans, polycyclic aromatic hydrocarbons, radio nuclides. In the continuous monitoring of the exiting stack gases, the extractive system is used. This system conveys a sample of gas from a stack to analyzers, usually located at some distance and housed in a sheltered environment for protection of instruments and personnel from the weather (Sutherland, 2003). In situ systems monitor the sample at the source and except for filtering to remove particulates, do not require conditioning and do not require transport (Earle, p. 2). Light Scattering technologies can be used for in situ, continuous stack sampling and / or ambient monitoring of Particulate Matter. Nephelometers measure the visual quality of local ambient air by measuring the scattering of light due to particles in continuous air samples in addition to the transmitted intensity. The measurement is directly related to the volume of Particulate Matter present, although in general it also depends on the PM size distribution and composition. The resultant volume measurement must then be related to mass by assuming a particular density. Stack gas emission analyzers use advanced dual sensor technology to measure the levels of up to seven (7) gases in a single compact unit. The unit is an extractive sampling, multi-gas analyzer system. The Chiller probe extracts and conditions the flue gas presenting a clean, dry and cool sample for transport to the analyzer. The analyzer accurately controls the flow rate and pressure of the gas prior to detection within the sensor module. The sensor is also supplied with air allowing continuous measurement of the sample with a repeating cycle of zero and span drift checks. Volatile organic compounds are collected on paired sets of Sorbent traps. Analysis of the trap is carried by thermal desorption purge-and-trap by gas chromatography / mass spectroscopy. Gas chromatography – mass spectroscopy (GC-MS) is one of the so-called hyphenated analytical techniques. It is actually two techniques that are combined to form a single method of analyzing mixtures of chemicals. GC separates the components of a mixture and mass spectroscopy characterizes each of the components individually. By combining the two techniques, a solution containing a number of chemicals can be evaluated both qualitatively and quantitatively. In all chromatography, separation occurs when the sample mixture is introduced (injected) into a “mobile phase”. In GC, the mobile phase is an inert gas such as helium. The “mobile phase” carries the sample mixture through what is referred to as “stationary phase”. The “stationary phase” is usually a chemical that can selectively attract components in a sample mixture. The “stationary phase” is usually contained in a tube of some sort. The mixture of compounds in the “mobile phase” interacts with the “stationary phase”. Each compound in the mixture interacts at a different rate. Those that interact the fastest will exit (elute from) the column first. Those that interact the lowest will exit the column last. By changing the characteristics of the “mobile phase” and the “stationary phase”, different mixtures of chemicals can be separated. As the compounds are separated, they elute from the column and enter a detector. The detector is capable of creating an electronic signal whenever the presence of a compound is detected. The greater is the concentration in the sample, the bigger the signal. The signal is then processed by a computer. The time from when the injection is made (time zero) to when elution occurs is referred to as the retention time (RT). As the individual compounds elute from the GC column, they enter the electron ionization (mass spectroscopy) detector. There they are bombarded with a stream of electrons causing them to break apart into fragments. These fragments can be large or small pieces of the original molecules. The fragments are actually charged ions with a certain mass. The mass of the fragment divided by the charge is called the mass to charge ratio (M/Z). A group of 4 electromagnets (quadruple) focuses each of the fragments through a slit and into the detector. They are programmed by the computer to direct only certain M/Z fragments through the slit. The rest bounce away. The computer has the quadruples cycle through different M/Z’s one at a time until a range of M/Z’s are covered. Each cycle is referred to as a “scan”. The computer records a graph for each scan. This graph is referred to as a mass spectrum. The mass spectrum produced by a given chemical compound is essentially the same every time. Therefore a mass spectrum is essentially a fingerprint for the molecule. When GC is combined with MS, a powerful analytical tool is created. An organic solution injected into the instrument, can be separated into individual components and the quantities of the components can be determined. Three GC detectors have been employed in the analysis of PCB’s in environmental samples: electron capture (Strachan), Hall Electrolytic Conductivity Detector (HECD) and Flame Ionization Detector (FID) (Lee, Paul, p.8). BIBLIOGRAPHY Advanced Dual Sensor Technology(ADST). Technical Bulletin. 2002 Land Instruments International. [Online] Available at http://www.landinst.com/comb/ Earle, John Sutherland. Rotary Kiln Incineration of Hazardous Wastes: Pilot Scale Studies at Louisiana University. December 2003, [Online] Available at http://etd.edu/docs/available.p. 2 Eiseman, Elisa. 1998, Monitoring for Fine Particulate Matter. Air Monitoring Technologies for Particulates. Appendix A. Gas Chromatography-Mass Spectroscopy Background. January 20, 1998. George Mason University Bioinstrumentation Class. [Online] Available at http://www.gmu.edu/department/SRIF/tutorial/gcd/gc-ms2.htmp. p.8 Lee, Paul, Lee, Jay, Sammis, Pat and Kasumovic, Anna. PolyChlorinated Biphenyls (PCB’s) in the Environment. University of Waterloo, Ontario, Canada. P.8 Method 5041A Analysis for Desorption of Sorbent Cartridges From Volatile Organic Sampling Train (VOST). (CD-ROM), December 1996, Air Toxics Laboratory Services [Online] Available at http://www.airtoxics.con/literature/download.html, pp. 1-12. On-Site Incineration: Overview of Superfund Operating Experience. United States Environmental Protection Agency. March 1998, [Online] Available at http://www.epa.gov.clu-in.com Public Health Assessment. TSCA Incinerator U.S. Department of Energy Oak Ridge Reservation. Agency for Toxic Substances and Disease Registry, Atlanta Georgia, March 1, 2005.[Online] Available at http://www.atsdr.cdc.gov, pp. 1-8. Air Monitoring in Road Tunnel Motor vehicles produce Carbon Monoxide, Nitric Oxide, Nitrogen Dioxide and fine particulate as part of their combustion process. Carbon monoxide is mostly unpleasant but at levels above 100 ppm it is harmful and at 4000ppm it is fatal. Nitric Oxide is mildly toxic but Nitrogen Dioxide is extremely toxic, levels of 60ppm are harmful and 150ppm is fatal. Fine dust particles (less than 10 micron in diameter) adhere to the lining of the lung and can cause respiratory infections and possibly cancer. Large amounts of particulate also impair a driver’s ability to see long distances. These are the pollutants that need to be monitored in a road tunnel. As the volume of traffic increases, the need to continuously monitor pollution levels is becoming increasingly important. A steady flow of air through the tunnel is needed to clear pollutants. Pollution sensors are used to operate road tunnel ventilation systems that clear pollutants from the tunnel and prevent a build up of harmful substances. In-situ monitors measure exhaust gases where they arise, thereby enabling effective monitoring and control of emissions, and ensuring that ventilation systems operate efficiently. Sensors for visibility, carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO2) and air / velocity monitoring are placed in strategic areas in a road tunnel to monitor the above mentioned pollutants and the air direction and velocity. Direction of the wind needs to be monitored in a road tunnel since high wind speeds pose danger to motorcyclists. Knowledge of the airflow is an important weapon in the event of a tunnel fire as it can be used to control the amount of air to the fire. NO2 is fast becoming the most important measurement in tunnels and will eventually replace NO as the key measurement. NO2 monitor uses both infrared and ultra violet light channels to detect the smallest concentration of gas in a sample. Transceiver projects infrared and ultraviolet light beams to a reflector with a stainless steel tube mounted 1m away. Sintered filters in the measurement chamber allow gases from the tunnel atmosphere to diffuse into the chamber while inhibiting the passage of particulates. The reflected light is received by the transceiver and the specific absorption is measured to determine the visibility dimming coefficient, carbon monoxide and nitric oxide concentration within a path of beams. The CO/NO analyzers consist of a transmitter head and a receiver head mounted 6m apart on the tunnel wall or roof. The transmitter emits an infrared (IR) beam for the CO/NO/NO2 measurement and a visible (green light) beam for the visibility measurement. Both beams make a single pass across the 6m open path between the transmitter and the receiver. The receiver collects both beams and calculates CO/NO using standard spectroscopy techniques. Visibility sensor measure atmospheric visibility (Meteorological Optical Range) by determining the amount of light scattered by particles (smoke, dust, haze, exhaust fumes) in the air that pass through the optical sample volume. A 42-degree forward scatter angle is used to ensure performance over a wide range of particle sizes. MOR is calculated by converting the received signal strength (extinction coefficient) using Koschmeider’s formula, MOR (km) = 3/G. For the air velocity and air direction monitoring, the measurement itself is made using ultrasound technology. An array of transceivers in the body of the instrument transmits a series of phased ultrasound clicks which are bounced off the instrument’s “roof” and then collected again by the transceivers in order. The time taken for the phased ultrasound signals to travel from one ultrasound to another is accurately measured to calculate the velocity in a single pass axis. This allows the instrument to determine speed and direction. BIBLIOGRAPHY Advanced Dual Sensor Technology(ADST). Technical Bulletin. 2002 Land Instruments International. [Online] Available at http://www.landinst.com/comb/ Introducing-Air Flow- Air Velocity and Direction monitors for Tunnels. Road Tunnel Atmosphere Monitoring. Emissions Monitoring and Combustion Control Services (EMACCS) Ltd. [Online] Available at http://www.tunnelsensors.co,uk/. p.1 Optical Sensors. NAL Research Corporation. 2008, [Online] Available at http://www.nalresearch.com/Optical Sensors.html/p.1 Sensors for Roads and Tunnels: Product Overview. SICK/MAIHAK Analyzers and Process Instrumentation. Jan., 2007. [Online] Available at http://www.sick-maihak.com, pp. 1-4 SVSI Sentry. Visibility Sensors: Road and Rail Tunnel Applications. PCB’s Environtech Tunnel Applications, March 2008, [Online} Available http://www.environtechsensors.com/ p.1-5 The Memorial Tunnel Fire Ventilation Program. Tunnel Research Projects: U.S. Department of Transportation Federal Highway Administration – Infrastructure Highway. July29, 2006.[Online] Available at http://www.thwa.dot.gov/bridge/tunnel/tunres2,htm,p.1 Transportation Accessories: Tunnel Photo Diode Sensors. PLC Multipoint Inc., 2008, [Online] Available at http://plc.multipoint.com/transportation/tranaccess.htm,p.1   Read More