Volatile organic compounds (VOCs) are detrimental to human health, and are also among the most important causes of secondary particulate formation and ozone pollution. The combined method of adsorption and non-thermal plasma has been attracting increasing interest due to its efficient energy consumption. This study aims to explore a new approach for removing gaseous toluene using electrically conductive charcoal (ECC) as an adsorbent and to trigger discharge. ECC was prepared from biomass and had a low electrical conductivity of 0.354 Ω cm and an abundant porous structure with a surface area of 717 m2 g−1. After toluene adsorption (53–217 mg g−1), adsorbent particles were fluidized with oxygen-containing gas and subjected to high voltages (17.4–26.3 W). Micro-arcs formed between the fluidized ECC particles, which led to toluene desorption and decomposition while the ECC was regenerated. The desorption was facilitated compared to thermal desorption. The adsorbed toluene was almost completely desorbed, and 59.23% of toluene was decomposed at one time. Almost no ozone or nitrogen oxides were found in the gas produced from decomposed toluene. Higher adsorption and discharge power were beneficial for decomposition capacity, but the former was limited by short residence time. The adsorption capacity of ECC increased by 16.4% after four cycles. A design was presented for continuous treatment of VOC pollutant without the emission of VOCs.

The efficiency of electricity production in biomass-fired circulating fluidized bed (CFB) boilers needs to be enhanced, which may increase the risks of high-temperature corrosion (HTC) as a side effect derived from the higher steam temperature. In this study, coal bottom ash (CBA) obtained from a pulverized coal-fired power plant was used to replace all the regular bed materials (quartz sand) in a biomass-fired CFB boiler, attempting to solve its HTC problem. Two kinds of mature deposits on the high-temperature superheater with regular bed materials and with CBA as a bed material were obtained and analyzed in detail. The deposit formation mechanisms with regular bed materials were discussed. Our results show that CBA can capture 22% of potassium during biomass combustion in the CFB boiler. However, CBA cannot effectively decrease the deposition of potassium chloride on high-temperature superheater, therefore leaving a serious HTC problem. The low effect of CBA for potassium capture may derive from its low chemical reactivity.

•An acoustic wave can change the trajectories of the fine particles.•The effectiveness of sound on the improvement of particle removal diminishes as the voltage increases.•There exists an optimal frequency and SPL for a given discharge voltage.•A long residence time is favorable for fine particle removal.•It is not always positive for a high concentration.Traditional electrostatic precipitation has a relatively low collection efficiency of fine particles emitted from coal combustion due to insufficient particle charging. This paper establishes an experimental system combining travelling sound waves with wire-duct electrostatic precipitation in order to measure the separated and simultaneous effects of an electric and acoustic field on fine particle penetration efficiency. The ranges of the main physical parameters are as follows: discharge voltage, V = 8–12 kV; acoustic frequency, ƒ = 800–2400 Hz; sound pressure level (SPL), SPL = 130–148 dB; residence time, t = 2–6 s; initial fine particle concentration, N0 = 6.5 × 105–4.99 × 106/cm3. The application of acoustic waves in an electric field is proven as an advisable method to remove fine particles with the lowest total penetration efficiency of 4.4%. Although the sound does not change the current–voltage curves of negative corona, it can distort the motion trajectory of the particles leading to a positive result for fine particle removal. The effectiveness of sound on the improvement of fine particle removal diminishes as the voltage increases. For a given discharge voltage, there exists an optimal frequency and SPL. The optimal frequency slightly increases, while the optimal SPL decreases as the applied voltage increases. The influence of residence time and initial fine particle concentration in combined fields are also studied.This paper establishes an experimental system combining travelling sound waves with wire-duct electrostatic precipitation in order to measure the separated and simultaneous effects of an electric and acoustic field on fine particle penetration efficiency.Download full-size image

The effects of reaction conditions, including the initial hydrogen pressures (0.5 MPa, 2.0 MPa), the mass ratios of ethanol to bio-oil (5:1, 3:1, 2:1, 1:1) and reaction temperatures (260 °C, 280 °C, 300 °C) on catalytic upgrading of fast pyrolysis bio-oil were investigated in this work. Experiments were carried out in supercritical ethanol with bifunctional 5%Pt/SO42-/ZrO2/SBA-15 catalyst. The physical properties and organic compounds of upgraded bio-oil were compared and the mass and energy balance of certain upgrading processes were studied. The results showed that higher initial hydrogen pressure (2.0 MPa) could inhibit coke formation effectively. Increasing mass ratio of ethanol to bio-oil (5:1, 3:1) was helpful for desired products formation and heating value improvement as well as lower coke yield. With the rising temperature, the heating value of upgraded bio-oil increased, but the amount of desired products reduced and the formation of coke became much more serious.Highlights• The effects of reaction conditions on bio-oil upgrading were studied. • The physical properties and chemical compounds of upgraded bio-oil were analyzed. • Higher initial hydrogen pressures can inhibit coke formation effectively. • Rising mass ratio of bio-oil to ethanol is helpful for desired products formation. • Rising temperature will increase the heating value of upgraded bio-oil.

In this paper, bio-oil from fast pyrolysis of Pinus sylvestris L. was upgraded over supported noble metal catalysts in supercritical monoalcohols under a hydrogen atmosphere. Esterification, cracking (both alcoholysis and hydrolysis), hydrogenation, along with acetalization, isomerization, and other reactions were combined during the upgrading process. The product analysis showed that processing in ethanol over Pt/SO42–/ZrO2/SBA-15 had a good upgrading performance. The removal of acids and aldehydes and the decrease of ketones, phenols, sugars, and polycyclic aromatic hydrocarbons were achieved. Meanwhile, esters became dominant in upgraded oil. The effects of solvents, noble metal catalysts, and catalyst supports had been briefly discussed. Pretreatment tests suggested that the presented upgrading process can be applied to the whole bio-oil without fractionation. As a result, an effective solvent recovery and a post-water-removal process will be required for the application of upgraded oil.

In this work, the effects of nanoparticle size, particle volume fraction and pH on the viscosity of silicon dioxide nanocolloidal dispersions are investigated. Both size and pH are found to significantly affect nanocolloid viscosity. Two models are used to study the effect of aggregate structure on the viscosity of the nanocolloidal dispersion. The fractal concept is introduced to describe the irregular and dynamic aggregate structure. The structure of aggregates, which is considered to play an important role in viscosity, is affected by both intermolecular and electrostatic forces. The particle interaction is primarily affected by particle distance and becomes stronger with decreasing particle size and increasing volume fraction. The aggregate structure is also affected by the pH of the solution. Studying the relationship between pH and zeta-potential shows that with the neutralization of charges on the particle surface and decreasing electrical repulsion force, the particle interaction becomes dominated by attractive forces and the aggregates form a more compact structure.

This paper presents the experimental results of CaO sorption enhanced anaerobic gasification of biomass in a self-design bubbling fluidized bed reactor, aiming to investigate the influences of operation variables such as CaO to carbon mole ratio (CaO/C), H2O to carbon mole ratio (H2O/C) and reaction temperature (T) on hydrogen (H2) production. Results showed that, over the ranges examined in this study (CaO/C: 0–2; H2O/C: 1.2–2.18, T: 489–740 °C), the increase of CaO/C, H2O/C and T were all favorable for promoting the H2 production. The investigated operation variables presented different influences on the H2 production under fluidized bed conditions from those obtained in thermodynamic equilibrium analysis or fixed bed experiments. The comparison with previous studies on fluidized bed biomass gasification reveals that this method has the advantage of being capable to produce a syngas with high H2 concentration and low CO2 concentration.