Fuel Processing Technology (v.89, #10)

The total development trend in the world is towards continuously lower of sulfur content as a quality standard of diesel fuels. Integrating of an oxidative desulfurization unit with a conventional hydrotreating unit can bring benefits to producing low and/or ultra-low sulfur diesel fuels. Using the hydrotreated Middle East diesel fuel as a feedstock, four processes of the oxidative desulfurization have been studied: a hydrogen peroxide–acetic acid system and a Fenton's reagent system both without/with ultrasound. Results showed that the oxidative desulfurization reaction mechanics fitted apparent first-order kinetics. The addition of Fenton's reagent could enhance the oxidative desulfurization efficiency for diesel fuels and sono-oxidation treatment in combination with Fenton's reagent shows a good synergistic effect. Under our best operating condition for the oxidative desulfurization: temperature 313 K, ultrasonic power 200 W, ultrasonic frequency 28 kHz, Fe2+/H2O2 0.05 mol/mol, pH 2.10 in aqueous phase and reaction time 15 min, the sulfur content in the diesel fuels was decreased from 568.75 μg/g to 9.50 μg/g.
Keywords: Ultrasound; Diesel fuels; Oxidative desulfurization; Fenton's reagent; Synergistic effect;

Simultaneous removal of asphaltenes and water from a water-in-bitumen emulsion by adding light paraffinic solvents was investigated with a bench-scale unit. Asphaltene precipitation in bitumen, emulsion breaking, and phase separation were found to be largely dependent on solvency and temperature. Increasing temperature facilitated the precipitation of asphaltenes in bitumen, and accelerated the separation of the light deasphalting oil (DAO)/solvent phase and the heavy asphaltenes/water phase. The removal of 98 +% asphaltenes and 99.9 +% water from the emulsion was achieved with the n-pentane/bitumen volumetric ratio of 3.0 in temperature range of 423–453 K. The interaction between asphaltene particles and water droplets is actually beneficial to the removal process. For process design and optimization, the operation pathway including two-step solvent injections at different temperature, the supercritical recovery of solvent from DAO stream and the solidification of asphaltenes by depressurization, as well as other important issues have been addressed.
Keywords: Removal; Asphaltenes; Water-in-bitumen emulsion; Paraffinic solvent;

Application feasibility of the accelerated deasphaltening process for simultaneous removal of asphaltenes and water from a water-in-bitumen emulsion has been examined with a pilot plant having capacity of 1.590 m3/day. The solvent (n-pentane) was injected into the emulsion from three locations with progressively increasing temperature from 423 K. The first solvent injection precipitated the asphaltenes in bitumen, the second broke the emulsion and facilitated the phase separation, and the third extracted the oil that remained in heavy asphaltenes/water phase. The effects of operation parameters such as temperature, solvent/bitumen ratio, feed rate and feedstock composition on the quality of DAO (Deasphaltening oil) were investigated. The DAO with the yield of ~ 80 wt.% and asphaltene content of < 0.5 wt.% was produced under optimal operating conditions, and the residual product was a porous solids containing 38% sulfur, 47% nitrogen, 64% MCR, and 85% metals (nickel and vanadium) of the bitumen. For a real application in oil industry, other important aspects including energy efficiency, solvent recovery and water purification have been discussed.
Keywords: Removal; Asphaltenes; Water-in-bitumen emulsion; n-pentane; Pilot study;

An investigation of MSW gasification in a spout-fluid bed reactor by Maitri Thamavithya; Animesh Dutta (949-957).
This paper presents the experimental results of MSW gasification in a spout-fluid bed reactor. Municipal solid waste (MSW) modeled based on compositions of Bangkok waste transfer station “On-nuch” was used as the fuel. Three scenarios were investigated in this study. In the base case scenario, only primary air of equivalence ratios (ER) 0.35, 0.3, 0.25, 0.2, and 0.15 were used. The other two scenarios investigated the influence of secondary air in the free board, and the effect of the recirculation of carryover captured by the cyclone inside the reactor's free board at an ER of 0.25. In the base case, higher heating values of 2.40–5.05 MJ/Nm3 were obtained with the ER values of 0.35–0.15, respectively. However, opposite trend was observed for the tar content. At ER of 0.35, a value of 11.37 g/Nm3 was found compared to 20.76 g/Nm3 at ER of 0.15. The tar content in the producer gas was reduced from 14.47 to 10.98 g/Nm3 when secondary air was supplied in the freeboard due to an increase in temperature. The gasification efficiency was increased from the base case which was 35.78 to 38.99% with the recirculation of carryover. Higher heating value of producer gas was found to be 4.4–4.9 MJ/Nm3 in this case.
Keywords: MSW gasification; Spout-fluid bed; MSW-to-energy;

The influence of fuel bias in the primary air duct on the gas/particle flow characteristics near the swirl burner region by Zhichao Chen; Zhengqi Li; Jianping Jing; Fuqiang Wang; Lizhe Chen; Shaohua Wu (958-965).
A three-component particle-dynamics anemometer is used to measure, in the near-burner region, the influence of the particle bias in the primary air duct on the gas/particle flow characteristics for a centrally fuel rich swirl coal combustion burner, in conjunction with a gas/particle two-phase test facility. Velocities, particle volume flux profiles and normalized particle number concentrations were obtained. Compared with a common burner (a centrally fuel rich burner without a particle concentrator), the degree of penetration for the centrally fuel rich burner is higher, the residence time of particles in the central recirculation zone is longer and the central recirculation zone is larger. The particle volume flux and normalized particle number concentration for the centrally fuel rich burner are much larger near the chamber axis. The influence of gas/particle flow characteristics on combustion has been analyzed.
Keywords: Burner; Particle concentrator; Gas/particle flow; Coal combustion; Three-dimensional particle-dynamics anemometer;

Hydrogen was produced by hydrolysis of sodium borohydride (NaBH4) using nickel-boride–silica nanocomposite catalyst. The catalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectrometry (EDX). The Ni-B–silica nanocomposite catalyst was found to consist of amorphous Ni-B nanoparticles attached to the surface of amine-modified silica nanosphere. The kinetics of hydrolysis of NaBH4 by Ni-B–silica composite catalyst was investigated. The effects of temperature, NaBH4 concentration, and catalyst concentration on hydrogen generation were also investigated. A rate of hydrogen generation as high as 1916 ml H2/min/g Ni was achieved by catalytic hydrolysis of NaBH4. The stability of the composite catalyst was also explored.
Keywords: Hydrogen production; Nanocomposite catalyst; Nickel; NaBH4;

Effect of wax inhibitors on pour point and rheological properties of Iranian waxy crude oil by Jafari Behbahani Taraneh; Golpasha Rahmatollah; Akbarnia Hassan; Dahaghin Alireza (973-977).
A variety of techniques have been employed in order to reduce problems caused by the crystallization of paraffin during the production and/or transportation of waxy crude oil. Flow improvers are used extensively to increase the mobility of crude oil. In this study, the influence of the ethylene-vinyl acetate copolymer (EVA), as flow improver, with different ranges of molecular weight on the viscosity and pour point of five Iranian waxy crude oils was evaluated. Five types of Iranian waxy crude oil were selected based on their similar wax (> 10%) but different asphaltene contents. Also, the effect of asphaltene content on the performance of this flow improver was studied. The rheological behavior of these crude oils, with middle range API gravity, in the absence/presence of flow improver was studied. The rheological data cover the temperature range of 5 to 40 °C. The results indicated that the performance of flow improver was dependent on the molecular weight and the asphaltene content. For crude oil with low asphaltene, higher molecular weight flow improvers are the best additive and lower molecular weight flow improvers showed good efficiency for crude oil with high asphaltene content. Addition of small quantities of asphaltene solvents such as xylene (1 wt.%), alone or in combination with flow improver, can improve viscosity of crude oil with high asphaltene content.
Keywords: Waxy crude oil; Molecular weight of flow improver; Pour point; Asphaltene;

N-butylimidazole-derived dialkylphosphate ionic liquids (ILs) are demonstrated to be effective for extractive removal of aromatic sulfur compounds (S-compounds) from fuel oils, and show strong preferential extraction for aromatic S-compound versus toluene. Sulfur partition coefficients (K N ) between IL and fuel oil at 298.15 K are determined experimentally over a wide range of sulfur content. The results show that the sulfur removal selectivity for a specific IL is dependent on the molecular structure of the S-compounds and follows the order dibenzothiophene > benzothiophene > thiophene > 3-methylthiophene, and the efficiency of the ILs for removal of aromatic S-compounds is dependent on the size and structure of both cations and anions of the ILs. For the dialkylphosphate ILs studied with the same anion, the longer the alkyl substitute to the imidazolium ring is the higher the K N value for that IL, and a similar trend is found for the ILs with same cation.
Keywords: Extractive desulfurization; Fuel oil; Partition coefficient; Selectivity; Dialkylphosphate ionic liquids;

Effects of hydroprocessing on structure and properties of base oils using NMR by Brajendra K. Sharma; Atanu Adhvaryu; Joseph M. Perez; Sevim Z. Erhan (984-991).
The hydroprocessing technologies such as hydrocracking, hydrofinishing provide an opportunity to modify the chemistry of hydrocarbons to improve the properties of petroleum base oils. Quantitative 1H and 13C NMR data has been used to generate average structural profile for a variety of base oil samples and aromatic fractions. The average structural parameters were used to study the effect of hydroprocessing on structure and properties of paraffinic neutral base oils. In addition, the effect of severity of hydrogenation on structure and properties has been investigated on three aromatic extract fractions obtained from different degree of hydrogenation of catalytic cycle stock. A linear relationship was found between average structural parameters and properties such as viscosity index, volatility and refractive index. Thermo-oxidative stability of samples was measured using differential scanning calorimetry and thin film micro oxidation tests. Variation in oxidative stability of various samples was explained using structural parameters. The NMR data was found useful in explaining property changes as a result of hydroprocessing. The results suggest that deepest knowledge of chemical structure could help in selecting base oils to meet future product specifications.
Keywords: Structure-property relationships; Thermo-oxidative stability; Average-structural parameters; PDSC; TFMO;