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A Brief History of Energy Recovery from Municipal Solid Waste
Published in Ram K. Gupta, Tuan Anh Nguyen, Energy from Waste, 2022
Debra R. Reinhart, Aditi Podder, Stephanie C. Bolyard
Incineration chemically oxidizes waste to thermally convert MSW in the presence of either a stoichiometric or excess amount of air. The need for supplemental fuel will depend on the lower heating value of the waste, which is dictated by the overall composition. The primary characteristics that affect the need for supplemental fuel are heating value, moisture content, and ash content. The typical operating temperature range is 790 °C–980 °C. The primary end products of the incineration process are N2, CO2, water vapor, ash, and heat. Air pollution control is needed to capture dust, acid gases, volatile organic compounds, and nitrogen oxide. Particulates are captured as fly ash that is transported in the flue gases. Acid gases are generated from acids and acid precursors that can form sulfur dioxide, hydrochloric acid, and nitrogen oxides. Lastly, dioxins are generated and mercury in waste is volatilized through the combustion of MSW and needs to be controlled.
Treatment Considerations and Options
Published in Peter A. Reinhardt, Judith G. Gordon, Infectious and Medical Waste Management, 2018
Peter A. Reinhardt, Judith G. Gordon
With incineration, the most difficult (and expensive) requirement is meeting air pollution control standards that apply to infectious waste incinerators. The regulatory trend is toward emission controls for particulates, acid gases, and organic compounds.* If you are considering incineration as your treatment technology, you must obtain sufficient guarantees from the manufacturer and the contractor that your incinerator—once it is installed and operating—will meet all applicable regulatory requirements. (See Chapter 7 for a more detailed discussion of incineration, including this particular aspect.) If a wet scrubber is used to control emissions, the scrubber water is a potential problem. Even if it is recirculated, it will eventually be discharged to the sewer system and it must then meet the wastewater standards. A final consideration is the solid residue from incineration—bottom ash and flyash. There are concerns that this ash may be hazardous (i.e., by the extraction procedure [EP] toxicity test), which would necessitate its disposal in an RCRA-permitted hazardous waste landfill rather than in a sanitary landfill.
Feedstock Preparation
Published in James G. Speight, Handbook of Petrochemical Processes, 2019
Treatment of gas to remove the acid gas constituents (hydrogen sulfide and carbon dioxide) is most often accomplished by contact of the natural gas with an alkaline solution. The most commonly used treating solutions are aqueous solutions of the ethanolamine or alkali carbonates, although a considerable number of other treating agents have been developed in recent years (Mokhatab et al., 2006; Speight, 2007, 2014). Most of these newer treating agents rely upon physical absorption and chemical reaction. When only carbon dioxide is to be removed in large quantities or when only partial removal is necessary, a hot carbonate solution or one of the physical solvents is the most economical selection.
Thermodynamic modeling of ternary systems containing imidazolium-based ionic liquids and acid gases using SRK, Peng-Robinson, CPA and PC-SAFT equations of state
Published in Petroleum Science and Technology, 2019
Zargham Baramaki, Zahra Arab Aboosadi, Nadia Esfandiari
CO2 and H2S are the main impurities of natural gas that should be separated before usage. The presence of such sour impurities leads to low caloric value and corrosion of transportation pipeline and therefore removing acid gases is essential to avoid operational, economics and environmental problems. There are various industrial processes for gas sweetening such as physical or chemical sorption, gas membrane separation, molecular sieves and carbamation techniques. Several factors can be effective in the selection of process type like composition and pressure of natural gas, types and amounts of trace components and desired quality of natural gas for market. The common method for separating acid gases from gas stream mixture is by use of alkanolamine aqueous solutions in an absorber-stripper configuration. Using alkanolamines has some disadvantages including solvent regeneration, solvent loss, degradation and formation of corrosive by products, toxicity, high energy consumption during regeneration, transfer of water into the gas stream during desorption stage and insufficient CO2/H2S capture capacity which make the process economically expensive. In order to avoid these drawbacks, ionic liquids have been proposed as alternatives of alkanolamine aqueous solutions due to their negligible volatility, high thermal stability, non-flammability and higher absorption in comparison with alkanolamines (Afsharpour and Kheiri 2018).
Selective absorption of H2S from CO2 using sterically hindered amines at high pressure
Published in Petroleum Science and Technology, 2019
Hui Li, Lulu Li, Jilei Xu, Yuntao Li
The purification technologies for the removal of acid gas impurities from the gas streams include chemical and physical absorption, permeation through membranes, and chemical conversion (Wang et al. 2016). Absorption of acid gas into aqueous solutions of alkanolamines has been one preferred approach of the purification technologies in current industry due to highly reactive nature and low cost (Mandal, Biswas, and Bandyopadhya 2004).
Potential for helium recovery and purification in Australia through membrane gas separation
Published in Australian Journal of Multi-Disciplinary Engineering, 2020
Conventionally, helium is extracted from the off-gas of the nitrogen rejection unit (NRU) in a natural gas process. The primary purpose of this unit is to remove nitrogen from the natural gas and has the secondary effect of concentrating helium. Hence, helium recovery is primarily a process of separation from nitrogen (Rufford et al. 2014; Scholes and Ghosh 2016). Traditional helium recovery and purification is undertaken through liquefaction, where the NRU off-gas is cryogenically cooled to below the boiling temperature of nitrogen (−195°C or 77 K). Helium remains a gas and is separated from the liquid nitrogen. Further purification is achieved through pressure swing adsorption (PSA), which is able to purify the helium to >99.9% by removing trace amounts of oxygen and hydrogen. However, for low grade reservoirs where the helium concentration is very low, liquefaction separation is very energy intensive because of the amount of nitrogen that must be condensed. Hence, alternative technologies are required that can undertake helium recovery and purification. A potential technology is membrane gas separation, which is based on a semi-permeable membrane, generally a polymeric film, which enables selective gases to pass through while other gases and vapours experience the membrane as a barrier (Ho and Sirkar 1992). The main driving force for separation is the partial pressure difference across the membrane, and hence the technology lends itself to the high pressure gases associated with natural gas processing. The solution-diffusion mechanism that is used to explain gas permeation through non-porous membranes is not viable for helium, because the gas’s chemically inert state means that no chemical interactions with the polymeric membrane occurs; and hence mass transport is through diffusion alone (Scholes and Ghosh 2017). Membrane gas separation is currently commercialised in the natural gas industry for acidic gas removal and hydrocarbon vapour recovery (Baker 2002), and there is potential for membrane gas separation to also recovery and purify helium. Indeed, helium separation was one of the first applications proposed for membranes when the technology was first developed in the 1960s (Stern et al. 1965). However, to date membranes have been limited to small scale helium recycling processes in niche industries, such as recovering helium from air mixtures used in deep sea diving.