Search

Reduced volatile sulfur compounds emitted from e.g. livestock production and biogas production facilities contribute to general air pollution and local odour nuisance. Improved technologies are required to mitigate the emissions of both hydrogen sulfide and organic sulfur compounds. The present study examines the oxidative absorption of reduced sulfur compounds, i.e. hydrogen sulfide, methanethiol and dimethyl sulfide in a wet oxidation process with cupric chloride. It was found that this process efficiently removes both hydrogen sulfide and methanethiol with removal efficiencies >94% under all process conditions tested, while the removal of dimethyl sulfide was in the range 20–40%. The main products determined were dimethyl disulfide, dimethyl trisulfide and elemental sulfur. It was shown that the process was more efficient than the similar process with ferric ions and higher removal could be obtained with lower residence times. Furthermore, though employing cupric ion as metal catalysts results in the production of gaseous sulfur compounds, it is estimated that this process is efficient for deodorization due to the higher odour threshold values of the product compounds and the pH range is optimal for gas streams containing CO 2.

The dissolution of CuS particles with Fe3+ in acidic sulfate solutions was investigated in an oxygen-free environment. CuS particles, used in this study, were obtained from H2S removal operations from biogas with an acidic CuSO4 solution in a Vitrisol pilot absorber. The CuS particles were porous with an average diameter of 5.8 X 10(-6) m. Zero orders of reaction for both Fe3+ and H2SO4 were determined. Full conversion of CuS could be obtained independent of temperature. The activation energy was determined to be E-A = 22.0 kJ/mol. It seems plausible that the CuS dissolution reaction was affected by diffusion.

This paper deals with characterization of the oxyfuel combustion in a bubbling fluidized bed. The paper proposes a calculation procedure to evaluate gas flow streams, adiabatic flame temperature and concentrations of species in the flue gas. The second part describes a laboratory scale 30 kW oxyfuel BFB and presents results of experiments with various semi-oxyfuel and full oxyfuel modes. The results are compared with experimental results, the agreement is satisfactory with less than 10% relative difference. Sustaining of similar fluidization regime along all different cases resulted in decrease of the adiabatic flame temperature that had to be compensated by thermal volumetric load increase from 3.3 to 4.1 MW/m 3 .

Gas-dynamic perfection and intensity of heat exchange of intake systems determine the efficiency of the piston engine. The results of numerical simulation and experimental study of the heat transfer of gas streams in the intake system of engines having different configurations are presented in the article. Methods of modeling, experimental setup, geometric configuration of pipelines and measuring base are described in the paper. The investigations were carried out under steady-state air flow in the system. The results of mathematical modeling were verified using experimental studies. It is established that the use of profiled sections in the intake system leads to a decrease in the heat transfer rate up to 20 % at low air flow rates (up to 40 m/s) and an increase in the heat transfer rate up to 9 % at high speeds. © Published under licence by IOP Publishing Ltd. The work has been supported by the Russian Science Foundation (grant No. 18-79-10003).

A novel Fe-Mn-Zn-Ti-O mixed metal oxide has been developed for efficient low-temperature (25-50°C) removal of H2S from a gas mixture containing 600 ppm H2S, 25 vol% H2, 7.5 vol % CO 2, and 1-3 vol% H2O that simulates typical conditions experienced at the outlet of a bioreactor loaded with sulfate metal reducing bacteria (SMRB) that converts toxic Cr6+ and As5+ present in ground and surface waters and soils into nontoxic elements. During the latter conversion H2S gas is produced and has to be treated. In the present work it is demonstrated for the first time that by using the sol-gel synthesis route at given experimental conditions (e.g., metal precursor salts, solvent system, and solution pH), optimum structural properties for the Fe-Mn-Zn-Ti-O solid can be obtained for maximization of H2S uptake. In particular, at 25°C an H2S uptake (0.085 g H2S/g solid) larger by at least a factor of 3 compared to a commercial Ni-based H2S absorbent material was obtained. © 2009 American Chemical Society. 43 12 4367 4372 Cited By :14

In industrial applications CO2 is frequently removed from gas streams at elevated pressures by absorption and subsequent chemical reaction in carbonate/bicarbonate solutions (e.g. Benfield process). The criterion that determines whether or not this reaction can be regarded as pseudo-first order is given by Danckwerts and Sharma (1966), but its derivation has never been published. In the present study, a consistent set of equations and physico-chemical parameters is presented to describe the CO2 absorption/reaction process. It was found that the criterion was justified, but should be somewhat confined to reduce possible errors. Furthermore, the model was validated by experiments in a stirred cell reactor up to CO2 partial pressures of 16 bar.

Breakup of a planar liquid sheet in the presence of confining walls has been investigated using nonlinear stability analysis. The gas streams and the liquid sheet sandwiched between them are considered to be moving. Temporal stability analysis has been done for both sinuous and varicose modes of disturbance. The results show the clear influence of the proximity of confining walls on the stability and breakup of liquid sheets, particularly for the varicose mode where satellite drops are predicted for certain ranges of parameters. The presence of wall leads to shorter breakup lengths but larger drop sizes. � 2014 The Japan Society of Fluid Mechanics and IOP Publishing Ltd.

This review paper provides an overview of the use of hydrogen (H 2) gas towards the selective catalytic reduction of nitrogen oxides (NO x) under strongly oxidizing conditions found in many industrial flue gas streams and in the exhaust emissions of diesel-powered vehicles. Patenting activities in the last 15 years are discussed. The advantages in using the H 2-SCR of NO x control technology especially at low-temperatures as to the current NH 3-SCR technology are also discussed. Regarding the stationary NO x control applications, Pd-based catalysts exhibit NO x conversion and N 2-selectivity values in the 80-95% range, depending on the chemical promoter and support composition used have been reported. On the other hand, Pt-based catalysts present lower NO x conversion and N 2-selectivity values (Cited By :7

The purification of gas streams from phenol at low-temperatures (350-550 °C) was investigated by its reaction with steam over novel catalytic systems, namely 0.5 wt% Rh supported on Ce0.15Zr0.85O2, Ce0.15Zr0.83Mg0.02O2 and Ce0.14Zr0.81Mg0.05O2 mixed metal oxides. It was found that the rate of reforming reaction was largely influenced by the support chemical composition, where catalytic activity and selectivity towards H2 formation were increased with increasing support Mg content (0-5 atom%). The 0.5 wt% Rh/Ce0.14Zr0.81Mg0.05O2 catalyst showed the best activity in terms of phenol conversion and H2-yield, and the lowest CO/CO2 product ratio in the 350-550 °C range. In particular, at 450 °C a phenol conversion of about 80% and a H2-yield of about 85% were obtained for a feed containing 0.6 vol.% phenol and 40 vol.% H2O at a gas hourly space velocity of 54,000 h-1. The latter catalyst composition exhibited significantly better catalytic performance in the 350-450 °C range when compared to a commercial Ni-based catalyst used for tar steam reforming. In particular, at 450 °C the H2-yield was increased by 75% and the CO/CO2 product ratio decreased by a factor of eight compared to the commercial Ni-based catalyst. It was found that the catalytic behaviour of 0.5 wt% Rh/Ce0.14Zr0.81Mg0.05O2 correlates with the presence of a larger concentration of basic sites, a larger concentration of labile oxygen species, and of very small mean Rh particle size (∼1.3 nm) compared to the other supported-Rh catalysts investigated. The significantly lower CO/CO2 product ratio obtained in the Rh/Ce0.14Zr0.81Mg0.05O2 compared to the other supported-Rh catalysts was related to the presence of a large surface concentration of Rhn+ cationic sites which may promote the water-gas shift (WGS) reaction. The activity towards the WGS reaction was found to be promoted by the presence of Mg2+ in the support composition. In situ DRIFTS-WGS reaction studies revealed that the kinds and surface concentration of formate species formed, likely active reaction intermediates in the WGS reaction, depend on the chemical support composition. The Ce0.14Zr0.81Mg0.05O2 support when used to deposit the same amount of Rh metal (0.5 wt%) resulted in a larger concentration of formate species than the Ce0.15Zr0.85O2 support. This result could partly explain the significantly larger phenol steam reforming activity towards H2 and CO2 observed on the Rh/Ce0.14Zr0.81Mg0.05O2 than Rh/Ce0.15Zr0.85O2 catalyst. © 2010 Elsevier B.V. All rights reserved. 96 3-4 276 289 Cited By :37

In industrial applications CO2 is frequently removed from gas streams at elevated pressures by absorption and subsequent chemical reaction in carbonate/bicarbonate solutions (e.g. Benfield process). The criterion that determines whether or not this reaction can be regarded as pseudo-first order is given by Danckwerts and Sharma (1966), but its derivation has never been published. In the present study, a consistent set of equations and physico-chemical parameters is presented to describe the CO2 absorption/reaction process. It was found that the criterion was justified, but should be somewhat confined to reduce possible errors. Furthermore, the model was validated by experiments in a stirred cell reactor up to CO2 partial pressures of 16 bar.

Membrane gas absorption and desorption (MGA/MGD) for the removal of CO 2 in manned spacecraft or other enclosed environment is subject of study by Stork and TNO for many years. The system is based on the combination of membrane separation and gas absorption. Advantage of this technology is that the system not only can be used to remove the carbon dioxide but also to control the relative humidity and temperature. Absorption of moisture and heat is achieved by cooling the absorption liquid below the dewpoint temperature of the gas stream. From the start in 1995, the Crew Transfer Vehicle is used as a basis for the design (1,2). Compared to the planned air conditioning system, consisting of a condensing heat exchanger, LiOH cartridges and a water evaporator assembly, MGA/MGD shows advantage in volume, mass and power consumption. The absorption liquid circulates through the spacecraft thermal control loop, replacing the coolant water. The CO2 absorption capacity of the absorption liquid is restored in a desorption unit. This process is based on pervaporation. The absorption liquid is led through this membrane unit in which a reduced pressure is maintained using the space vacuum. Due to this pressure difference a driving force for water vapor and CO2 is created. The water evaporation and the CO2 desorption rate are controlled by a throttle valve in the venting duct to the vacuum source. Because the absorption liquid is used as coolant, temperature increases, a driving force for water vapor and CO2 mass transfer is created. Should additional heat rejection be required (off nominal case), it is established by dumping extra water, using the associated heat of vaporization. For the initial studies an existing laboratory set-up has been applied for the practical work. In 1999 a project started on the development of a dedicated breadboard. In this paper, the test results of this breadboard assembly will be presented. Copyright © 2003 SAE International.

Membrane gas absorption and desorption (MGA/MGD) for the removal of CO 2 in manned spacecraft or other enclosed environment is subject of study by Stork and TNO for many years. The system is based on the combination of membrane separation and gas absorption. Advantage of this technology is that the system not only can be used to remove the carbon dioxide but also to control the relative humidity and temperature. Absorption of moisture and heat is achieved by cooling the absorption liquid below the dewpoint temperature of the gas stream. From the start in 1995, the Crew Transfer Vehicle is used as a basis for the design (1,2). Compared to the planned air conditioning system, consisting of a condensing heat exchanger, LiOH cartridges and a water evaporator assembly, MGA/MGD shows advantage in volume, mass and power consumption. The absorption liquid circulates through the spacecraft thermal control loop, replacing the coolant water. The CO2 absorption capacity of the absorption liquid is restored in a desorption unit. This process is based on pervaporation. The absorption liquid is led through this membrane unit in which a reduced pressure is maintained using the space vacuum. Due to this pressure difference a driving force for water vapor and CO2 is created. The water evaporation and the CO2 desorption rate are controlled by a throttle valve in the venting duct to the vacuum source. Because the absorption liquid is used as coolant, temperature increases, a driving force for water vapor and CO2 mass transfer is created. Should additional heat rejection be required (off nominal case), it is established by dumping extra water, using the associated heat of vaporization. For the initial studies an existing laboratory set-up has been applied for the practical work. In 1999 a project started on the development of a dedicated breadboard. In this paper, the test results of this breadboard assembly will be presented. Copyright © 2003 SAE International.