Simultaneous carbon capture and nitrogen removal during supercritical water oxidation (original) (raw)
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Journal of Materials Science, 2008
This work investigated the destruction of N-containing hydrocarbons namely DBU (1,8-diazobicyclo[5.4.0]undec-7-ene) and DMF (dimethyl formamide) by supercritical water oxidation (SCWO), using hydrogen peroxide as oxidant. Reactions were conducted under temperatures of (400-650°C), pressures of (50-250 bars), oxidant stoichiometric ratio SR (0.9-12), initial concentrations of organics (0.1-8.4 mM) and residence time s (6-17 s). Reactions took place in a plug flow continuous reactor and the results were presented in terms of the % removal (of TOC and the organic compound), C-fraction and N-fraction; all plotted as function of the above system conditions. Also, GC-MS analysis for DMF was conducted. Percent removal increased with temperature and complete organic-and [90% TOC removal, was obtained at 500 and 600°C for DMF and DBU respectively. Conversion increased with the oxidant SR, residence time and initial organic concentration. Pressure affected conversion in the sub-and near-critical conditions but not in the supercritical region, yet an initial value of 150 bar was required to start the reaction. Pseudo first order-, integral power rate law-, and power law models successfully described the kinetic data; and the reaction constants for each model and energy of activation were evaluated.
Chemical Engineering Journal
This study investigates several commercial selective catalytic reduction (SCR) catalysts (A–E) for application in a high-temperature (approximately 525 ◦C) and high-concentration (5000 ppm NO) system in combination with CO2 capture. The suggested process for removing high concentrations of NOx seems plausible and autothermal operation is possible for very high NO concentrations. A key property of the catalyst in this system is its thermal stability. This was tested and modelled with the general power law model using second-order decay of the BET surface area with time. Most of the materials did not have very high thermal stability. The zeolite-based materials could likely be used, but they too need improved stability. The SCR activity and the possible formation of the by-product N2O were determined by measurement in a fixed-bed reactor at 300–525 ◦C. All materials displayed sufficiently high activity for a designed 96% conversion in the twin-bed SCR reactor system proposed. The amou...
Supercritical water oxidation of nitrogen compounds with multi-injection of oxygen
The Journal of Supercritical Fluids, 2013
A supercritical water oxidation (SCWO) process with oxidant multi-injection was studied in a continuous flow system in which the same amount of oxidant feed is split between two points -a first injection at the reactor inlet and a second injection at one of the three different positions along the reactor. Under the same operating conditions, this multi-injection configuration showed advantages over the system with a single oxidant entry. Moreover, oxidant dosage in a SCWO reactor is a key aspect in energy management.
Advances in Environmental Research, 2000
The catalytic behavior and some aspects of the development of novel catalysts for N O decomposition rhodium-2. Ž. on-zirconia based catalysts or selective reduction with propane FerZSM-5 type catalysts in the presence of the typical gas phase components of industrial emissions containing N O in concentrations below 0.1% are discussed. In 2 Ž. particular: i the possibility to improve the catalytic reactivity of rhodium-on-zirconia based catalysts by modification Ž. of the zirconia support with lanthanide ions or other dopants; ii the stability of the catalytic behavior of these Ž. samples in the presence or absence of SO ; and iii some characteristics and the stability behavior of FerZSM-5 2 catalysts in the presence of SO for the reduction of N O with propanerO are reported. The catalytic technologies 2 2 2 of decomposition and selective reduction of N O are compared in terms of economics of the processes and type of 2 emissions for which they are preferably suited.
Chemosphere, 2017
Supercritical water oxidation (SCWO) process of 14 N-containing compounds was investigated with residence time of 150 s, at a stable pressure of 24 MPa, temperatures of 350-500 o C and 500% excess oxygen, resulted in total nitrogen (TN) removal from 41-96%. The products of N-containing species were mainly N 2 , nitrate, ammonium, as well as hardly nitrite or NO X. The yield distributions of nitrate and ammonium were different: the main nitrate concentrations were obtained from the compounds containing nitro-group and diazonium, like nitrobenzene, 2-nitrophenol and eriochrome blue black R (EBBR); the predominant ammonium yields were achieved from amino-group and N-heterocyclic compounds, such as aniline, 5-chloro-2methylaniline, 3,4-dichloroaniline, 1-methylimidazole, 1,10-phenanthroline, cyanuric acid, indole and 2,3-indolinedione. It is interesting that 2-nitroaniline, possessing both nitro-and amino-group, would dominantly decompose into N 2. To explore the relationship between TN removal and molecular structural characteristics, density functional theory (DFT) method was used to calculate molecular descriptors of all 14 N-containing compounds. The correlation results showed that among all the fifteen molecular descriptors, q(C)-, q(C-H) + and F(0) x greatly affects temperature behavior of
The lean catalytic reduction of nitric oxide by solid carbonaceous materials
Applied Catalysis B: Environmental, 2001
The reactions of O 2 , NO x and soot from diesel exhaust over Cu containing catalysts can significantly reduce soot and NO x emissions while producing N 2 and CO 2 . We have evaluated the performance of Cu ion exchanged ZSM-5 and Cu adsorbed on granulated activated carbon (Cu-GAC) using GAC as a surrogate for soot in a packed bed reactor. CO, formed primarily by the oxidation of GAC with O 2 , appears to be a stable intermediate in the reduction of NO. With experimental parameters chosen to simulate diesel exhaust conditions, Cu-GAC is more effective than GAC mixed with Cu-ZSM-5, converting six times more NO x to N 2 at 500 • C at the representative gas hourly space velocity of 50,000. Both catalysts are poisoned by H 2 O and SO 2 . A mechanism is presented that is consistent with the experimental results.
Supercritical water oxidation for the treatment of various organic wastes: A review
The removal of complex organic and chemical industrial wastes is not accessible using conventional treatment methods. Incineration and hydrothermal oxidation under supercritical conditions are two options for dealing with a wide range of hazardous wastes. Incineration is an effective treatment for removing hazardous waste. The main disadvantages of incineration are a source of unwanted emissions and high operating costs. Supercritical water oxidation (SCWO) is considered a green technology for destroying organic waste with friendly environmental emissions. The removal efficiency reached 99.99% within a short residence time. In this review, the treatment of organic waste by SCWO is shown using cofuel and catalysts to enhance the performance of SCWO.
Fuel Processing Technology, 2011
This work presents a study of the effect of wet sulphuric acid treatment and gas-phase treatment with SO 2 + O 2 + H 2 O on the catalytic activity of a low-rank coal-based carbon for the nitric oxide reduction with ammonia. Carbons were characterized by N 2 adsorption, TPD, and FTIR in order to assess how the surface chemistry and the texture of carbons change after the treatments. A great amount of oxygenated functional groups both CO 2 and CO evolving ones are produced by liquid-phase sulphuric acid treatment. However, the amount of those groups after gas-phase treatment with SO 2 + O 2 + H 2 O is lower, in particular the CO 2 evolving groups. The catalytic activity of carbons was examined in a fixed bed reactor at 150°C in a gas flow containing NO, O 2 , N 2 and NH 3 , the effluent concentration being monitored continuously during the reaction. The obtained results indicate that an appropriate balance between the type of oxygen functional groups and surface area available to the reactant gas are required to reach high levels of NO conversion.