Pink Sky in the Morning, Should There Be a Warning?

Unexpected and unusual emissions from a large, mass-burn, waste-to-energy facility caused persistent and elevated opacity readings of the facility’s continuous opacity monitor (COM), and generated a visible pink-purple-tinted plume emanating from the exhaust stack. Non-radioactive iodine associated with medical wastes was determined to be responsible. As iodine is a known respiratory irritant, questions arose regarding potential short-term health risks to nearby residents. The rate of emission of the apparent release was estimated by two different methods, and then compared with facility-specific knowledge of waste composition. First, based on inverse, worst-case air dispersion modeling, the level of iodine emission that would be necessary to cause potential discomfort/mild irritation to people living near the facility was determined. Second, the level of iodine emission that would be necessary to account for elevations of in-stack opacity observed throughout the event was calculated. The level of iodine emissions necessary to cause mild health effects was found to be substantially greater than the actual release level as inferred from the opacity data. Moreover, based on descriptions of visual inspections of the waste stream and potential opacity interferences created by complex in-stack chemistry, it is likely that the opacity-based calculations overestimate the amount of iodine released. Accordingly, actual impacts are likely to have been smaller than those estimated herein. This paper discusses the process and procedures used to assess the health risk from this incident.

Numerical Analysis of the Size and Shape of New York City Municipal Solid Waste (NYCMSW) and Residues for Combustion Chamber Design

The size and shape of New York City municipal solid waste (NYCMSW) and combustion residues (ashes) are numerically analyzed in order to investigate the size reduction of particles on the grate of a waste-to-energy (WTE) combustion chamber. It is also necessary for designing a new combustion chamber, due to the heterogeneous MSW particles. About 360 MSW particles for this study were sampled in the black bags collected in residential areas at five boroughs of New York City. Also about 210 ash particles from a WTE combustion chamber were sampled. Length, breadth, perimeter and area of each MSW and ash particle are measured by means of image analysis that is more accurate than sieve analysis. Based on the image analysis, the particle size distributions (PSiD) and particle shape distributions (PShD) of MSW and residues were created. The mean size of NYCMSW was found to be 12.8cm and standard deviation of the MSW PSiD to be 6.4. Also mean size and standard deviation of the ash PSiD to be 2.4cm and 0.5889, respectively. Also Three types of shape factors (aspect ratio, roundness and sphericity) are used for creating 3 PShDs (aspect-ratio distributions, roundness distributions and sphericity distributions). Based on the similarity of the particle shapes quantified as these shape factors, the particles of MSW and residues are divided into 9 clusters by means of cluster analysis. This cluster analysis showed categorized characteristics of particle shapes that can be used for predicting surface areas of particles and mobility of particles in MSW bed on the traveling grate, both of which are major parameters for simulating combustion process in WTE systems.

Viable Production of Diesel From Non-Recyclable Waste Plastics

The art of refining liquid hydrocarbons (crude oil) into diesel, gasoline, and fuel oils was commercially scaled decades ago. Unfortunately, refineries are technologically limited to accepting only a very narrow range of liquid hydrocarbons with very specific properties and minimal contaminates. Unrecyclable, hydrocarbon-based waste is a significant environmental problem increasing every year. According to the Environmental Protection Agency’s 2010 Facts and Figures report, over 92% of waste plastic is not recycled and with a growth rate of approximately 8% per year, there exists a critical need for a viable and environmentally sound, general purpose hydrocarbon-based recycling process. Hydrocarbon streams that fall outside of accepted refinery standards have traditionally been landfilled or melted into products of low value. The barriers and challenges are so great that previous attempts to refine waste plastics into fuel resulted in unviable batch-based machines producing low-value, unstable mixed fuels. However, over the course of three years JBI, Inc. (“JBI”) has broken through these barriers and has designed and built a viable commercial-scale continuous refinery capable of processing a wide-range of hydrocarbon-based waste into ASTM specification fuels. Research and testing of scale-up through 1-gallon, 3000 gallon, multi-kiln, and 40 ton/day processors took place in a plant in Niagara Falls, NY. Technical challenges encountered and lessons learned during process development will be explained in detail. In 2009, our technology was “molecularly audited” by IsleChem, LLC (“IsleChem”) of Grand Island, NY and in 2012, the full-scale plant was viably validated by SAIC Energy, Environment & Infrastructure, LLC (“SAIC”). Numerous sources of waste plastic and users of the resulting fuel products conducted extensive audits of the technology, process, and plant. For the purpose of this paper, processing of waste plastics will be discussed in detail; however, this technology can be applied to other waste hydrocarbon-based materials such as contaminated monomers, waste oils, lubricants and other composite waste streams.

The Effect of SO2:HCl in Mixed Gas and Deposit Corrosion of Waste-to-Energy Boilers

High temperature corrosion via chlorine is a key factor in the degradation of boiler tubes in waste-to-energy (WTE) plants. Corrosion rates are particularly high in the superheater where material temperatures may exceed 450°C and where carbon or low alloy steels may be used. Although increasing sulfur, in the form of SO2, in WTE flue gas has been shown in previous works to have potential for decreasing the corrosion of these materials, the inhibitive effect is not well understood. This work investigated the corrosion of SA178A, a low carbon steel alloy (0.07 wt% C), and NSSER-4, a stainless steel (17.3Cr-13.1Ni-2.5 Si-Fe), via exposure under various well-defined environments, SO2:HCl ratios between 1:8 to 2:1 (HCl fixed at 800 ppm), 8% O2, 12% CO2, 0 and 15% H2O, N2 (balance) at 500°C in a horizontal tube furnace for 50 hours. Additional coupon testing was performed on NSSER-4 after application of 4 mg/cm2 ± 10% NaCl or Na2SO4 at 500 and 700°C for 24 hours to assess the impact of higher SO2 in the against both deposit and gaseous corrosion. Specimen preparation and corrosion assessment followed ASTM method G1-03. Experiments demonstrated little to no trends in corrosion rates at SO2:HCl ratios between 1:8–2:1 under mixed gas environment. However corrosion reduction was observed when SO2:HCl was increased from a reference condition of 1:8 to greater than 1.4:1 in tests with NaCl present, which was also not observed under dry conditions. These results suggest that one possible explanation for the reduction of boiler materials corrosion rate with higher concentrations of SO2 may be largely attributed to the conversion of metal chlorides to sulfates.

Innovative Concepts of Conversion and High Efficiency Using MARTIN Technology

Thermal treatment of waste using grate-based systems has gained world-wide acceptance as the preferred method for sustainable management of residual waste. However, in order to maintain this position and respond to new challenges and/or priorities, it is necessary to further develop innovative concepts that use safe process engineering technology in terms of climate and resource protection as well as reduction of environmental impacts. MARTIN, in collaboration with research institutes, successfully developed and optimized a multi-stage combustion process in the 1990s. Various pilot and full-scale studies and tests followed. Based on this knowledge, MARTIN and its cooperation partners COVANTA ENERGY (USA), CNIM (F) and Mitsubishi Heavy Industries (JP) developed the Very Low NOx (VLN) process as a large-scale primary measure for NOx reduction. MARTIN’s next step was to develop the Very Low NOx gasification mode (VLN-GM) process. This process has been implemented directly in continuous operation at an industrial-scale Energy-from-Waste (EfW) plant in Switzerland. In VLN-GM operation, the excess air rate in the gas above the grate is decreased from λ = 1.2 to about 0.8. The characteristics of municipal solid waste make it suitable for the generation of heat and power. While boiler concepts implemented in the past often focused on factors such as high availability, reduced downtimes and minimized maintenance costs, measures to increase the efficiency of the overall process are also growing in importance. Energy efficiency can be increased by optimizing boiler efficiency itself on the one hand, and on the other hand by improving peripheral plant devices, in particular by improving energy recovery through changes in the steam parameters. MARTIN has developed corrosion-protected wall and radiant superheater solutions, located in the upper furnace area, and installed these as prototypes in full-scale plants. As a result, steam can be heated about 35 °C (90 °F) in excess of the current state-of-the-art parameters without adversely affecting plant operation due to superheater corrosion. This paper documents that innovative concepts using MARTIN technology successfully provide solutions for a grate-based conversion technology (VLN-GM) as well as measures for increasing the energy efficiency of Energy-from-Waste plants.

Boiler Wall Protection With Rear Ventilated Refractory Tiles

The prevention of corrosion on boiler tube-walls has been a most difficult and cost intensive problem in WTE plants. This is specifically the case where the incineration boilers are operating with increased saturated steam temperatures and their corresponding pressures. In addition, variations in the garbage mixtures, with differing values of chemical content and varying waste composition give importance to the prevention of boiler tube corrosion. Several refractory lining systems and types have been installed over the previous 80 years and can be compared. In the early stages it began with simple concrete installations and only later was it developed to use heat resistant ceramic products, now essentially silicon carbide. 20 years ago cement or chemically bonded SiC monolithics (gunning, trowelling or casting materials) were usually installed to protect boiler walls, but today fabricated and fired SiC tiles, with their enhanced properties, are mainly used. A distinction is made between hanging and bolted tiles, as well as between oxide bonded and nitride bonded SiC material and between mortared, backfilled and rear ventilated tiles. All these systems were carefully examined and assessed. It proved possible to develop a revolutionary heat conduction and corrosion protection system utilising air. An air gap between the refractory SiC tiles and the boiler wall proved to be both simple and successful. By means of detailed and systematic documentation and monitoring, including J + G’ s “Air” tiling system, it has, for a few years, been possible to offer and recommend long lasting refractory linings with the aim of protecting boiler walls against corrosion, reducing operating costs and using the energy of the waste in an optimum manner.

A Proposed Method for Reliable Gasification Kinetics by Thermal Gravimetric Analysis

It has been shown in thermodynamic simulations of gasification that recycling up to 25% of carbon dioxide (CO2) into a reformer allows for a highly hydrogen (H2) concentrated syngas. While understanding thermodynamic limits is imperative, a kinetic analysis is desired to confirm applicability. Studies on thermal decomposition kinetics of polyethylene terephthalate (PET) in CO2 gasification atmosphere have been assessed. Using thermal gravimetric analysis, we can show that gasification may be modeled as a series of single step reactions and determine the activation energies, pre-exponential factors and reaction models of those reactions. The use of CO2/air atmosphere instead of air atmosphere results in better char conversion.

Managing Food Waste With Anaerobic Digesters: Is This a Greener Technology Than Conventional WTE

Recent attention in the North American market has focused on managing food waste biologically using anaerobic digestion (AD) technology, which produces a biogas that can be used to generate electricity and a digestate or residue that can be used as a fertilizer, or composted and used as a soil amendment. The increased focus on AD is driven by the desire to increase waste diversion rates and a perception that AD is a “greener” approach to managing food waste than landfilling or conventional waste-to-energy (WTE) technology. Policy makers in some cases have already concluded that AD of source separated organics is preferable to landfilling and WTE. While the environmental benefits of AD over landfilling are obvious, especially for landfill sites without active gas collection systems, the benefits are less clear when compared to conventional WTE technology since relatively little analysis has been performed to date. Two environmental considerations often associated with being a “green technology” are energy recovery potential and greenhouse gas generation. This paper examines the amount of energy that can be produced by treating food waste biologically using AD compared to treating the same material thermally using mass burn WTE, which is the most commonly used WTE technology. The impact on net greenhouse gas emissions, namely carbon dioxide generation, from each technology is also compared taking into account a variety of factors including differences in the percentage of the feedstock carbon converted to carbon dioxide, the amount of fossil fuel avoided as a result of power generation, and the amount of vehicle emissions associated with collection and transportation of source separated food waste. This paper also compares other important considerations such as capital and operating costs, residuals management, and odor control.

Effect of Number of Bars and Reciprocation Speed on Residence Time of Particles on a Moving Grate

The moving grate systems of waste-to-energy (WTE) mass-burn combustion chambers are designed for providing efficient flow and mixing of the municipal solid waste (MSW) over the length of the grade. This study presents results from a numerical analysis of the effect of number of reciprocating bars and reciprocation speed on the degree of mixing and residence time of MSW particles on the grate. A particle-based bed model of MSW and a physical model of reverse-acting grate were used in order to quantify the mixing diffusion coefficient of MSW particles. We analyzed the particle mixing with different parameters: particle size (d = 6–22cm diameter), reciprocation speed of moving bars (Rr = 0–90recip./h), and number of moving bars (Nb = 0 to 16 bars). This combination of mathematical modeling and experimental work has shown that: (1) different particle sizes result in different residence times, according to the Brazil Nut Effect (BNE) (2) The number of moving bars (from 0 to 16 bars) of a reverse-acting grate has the net effect of increasing the mean residence time of small and medium sized particles, while decreasing that of large particles. (3) The bar height, h, was found to be one of the major geometric parameters influencing mixing diffusion coefficient, D, and residence time.