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•HTC is a promising process for production of hydrochar from orange pomace.•Spent liquor was used as feedstocks for biogas production.•No PAHs were detected in the hydrochars.•Heavy ...metal contents in hydrochars were found below limits.
In this study, the effect of the temperature and reaction time on hydrothermal carbonization (HTC) of orange pomace was investigated. In addition, a set of anaerobic batch tests were performed to determine the resulting biogas and methane potential of the spent liquor. Hydrochar yields followed a decreasing trend with the increasing temperature, whereas reaction time had no considerably effect on the yield. The evolution of the H/C and O/C atomic ratios from the raw material to the hydrochars suggested that dehydration reactions prevail during HTC. The hydrochars tended to become enriched in Ca, Mg and P minerals by increasing HTC temperature. The heavy metal contents in hydrochars were found below limits and no PAH compound was detected. Anaerobic digestion tests showed that the aqueous phase from HTC can be used as feedstocks for biogas production.
Hydrothermal carbonization (HTC) has become a promising technology for the production of hydrochar and carbon spheres. Several studies indicate a strong dependency of the reaction conditions on the ...sphere diameter. The usage of additives, such as salts, is one possibility to increase the size of the spheres. However, the growth mechanism which leads to larger particles is not fully understood. In this work, kinetic studies of HTC with fructose were performed with different salts as additives. The growth of the particles (the increase in size) has been compared to the formation rates (increase in yield) of hydrochar by using the reaction rate constants from the kinetic model. The results indicate that the acceleration of the growth rate is independent of the formation rate. It is therefore assumed that coagulation, as a growth mechanism, took place. With longer reaction times, the particles reached a stable particle size, independently from the added salts; therefore, it was assumed that the particles underwent some sort of solidification. The state of matter can therefore be described as an intermediate state between liquid and solid, similar to mesophase pitch. Experiments with a stirrer resulted in squashed particles, which supports the model, that the particles exhibit emulsion-like behavior.
In this study, utilization of a solid waste as raw material for activated carbon production was investigated. For this purpose, activated carbons were produced from chromium and vegetable tanned ...leather shaving wastes by physical and chemical activation methods. A detailed analysis of the surface properties of the activated carbons including acidity, total surface area, extent of microporosity and mesoporosity was presented. The activated carbon produced from vegetable tanned leather shaving waste produced has a higher surface area and micropore volume than the activated carbon produced from chromium tanned leather shaving waste. The potential application of activated carbons obtained from vegetable tanned shavings as adsorbent for removal of water pollutants have been checked for phenol, methylene blue, and Cr(VI). Adsorption capacities of activated carbons were found to be comparable to that of activated carbons derived from biomass.
In this study, the effect of the type of catalyst on hydrothermal gasification of three specifically chosen samples of natural biomass was investigated. Biomass feedstocks, including lignocellulosic ...materials (cotton stalk and corncob) and the tannery waste, were gasified in supercritical water by the addition of catalyst. The catalysts used were K
2CO
3, Trona (NaHCO
3·Na
2CO
3·2H
2O), red mud (Fe-oxide containing residue from Al-production) and Raney-Ni. The gasification experiments were performed in a batch autoclave at 500
°C. The amounts and compositions of the gases and the amounts of water soluble compounds from gasification were determined. The effect of catalysts on gasification varied with the type of biomass. The catalysts significantly increased the hydrogen yield by supporting the water–gas shift reaction and the methane reformation.
The gasification activity of Trona was similar to that of K
2CO
3. The results indicate that iron based catalysts can also be effective in gasification of biomass. In conclusion, the supercritical water gasification of biomass by addition of red mud and Trona is said to be promising method to produce H
2 from biomass efficiently similar to gasification with commercial alkali catalysts.
Sandpaper wastes were used as adsorbent after pyrolysis at 500 °C and calcination at 800 °C for the removal of brilliant green and malachite green cationic dye from an aqueous solution. The effects ...of the pH, the adsorbent dose, the contact time, and the initial dye concentration on the removal efficiencies were investigated. The isotherm studies were conducted by using the Langmuir, Freundlich, and Dubinin-Radushkevich models, and thermodynamic studies were also performed. The adsorption of the Brilliant green and malachite green were found to comply with the Langmuir isotherm model and the Freundlich isotherm model, respectively. The thermodynamic studies showed that the adsorption of dyes were endothermic. The E values obtained from the Dubinin-Radushkevich isotherm showed that the adsorption mechanism was chemical in nature. Furthermore, the three kinetic models (pseudo first-order, pseudo second-order, and intraparticle diffusion) were investigated. It was found that the pseudo second-order kinetic model fitted well for adsorption of dyes.
Activated carbons have been prepared from a lignocellulosic waste material by chemical activation. Phosphoric acid and zinc chloride have been used as activating agent. The influence of process ...variables on the carbons’ surface area was studied to optimize these parameters. The textural properties of active carbons were characterized by N
2 adsorption at 77
K and SEM analysis, while Boehm titration and Fourier transform infrared (FTIR) analysis were conducted to determine the surface groups of the activated carbons. Under optimum conditions, activated carbons with a maximum surface area of 1000 and 1152
m
2
g
−1 for the activating agent phosphoric acid and zinc chloride, respectively, were obtained. Zinc chloride produced the activated carbon having higher micropore volume compared to phosphoric acid activation. The results obtained showed that oak cups pulp is an economically promising material as a precursor in the activated carbon production, based on the combination of yield, surface area and raw material cost.
The application of activated carbons was studied by the aqueous adsorption tests using different kind of dyes (acidic and basic), phenol and Cr(VI) as adsorbates. The aqueous adsorption tests showed that the surface chemistry of the activated carbons also played important role in dye adsorptions as well as textural properties.
This study deals with pyrolysis of three agricultural wastes (corncob, straw and oreganum stalks) at 500 °C in a fluidized bed reactor. The yields of char, liquid and gas were quantified. Pyrolysis ...liquids produced were in two separate phases; aqueous phase and oil. Oil yields varied between 35 and 41%, depending on biomass type, whereas the yields of aqueous phases were almost similar, around 6%, for all feedstock. For characterization, oils were fractionated by water extraction into two fractions; water solubles and water unsolubles. Both aqueous phase and water-soluble fraction were analyzed by gas chromatography–mass spectrometry and high-performance liquid chromatography. In addition, water content and elemental analysis of the oils were determined. Chemical compositions of gas and char products relevant to fuel applications were determined.
In this study, different char based catalysts were evaluated in order to increase hydrogen production from the steam pyrolysis of olive pomace in two stage fixed bed reactor system. Biomass char, ...nickel loaded biomass char, coal char and nickel or iron loaded coal chars were used as catalyst. Acid washed biomass char was also tested to investigate the effect of inorganics in char on catalytic activity for hydrogen production. Catalysts were characterized by using Brunauer–Emmet–Teller (BET) method, X-ray diffraction (XRD) analyzer, X-ray fluorescence (XRF) and thermogravimetric analyzer (TGA). The results showed that the steam in absence of catalyst had no influence on hydrogen production. Increase in catalytic bed temperature (from 500 °C to 700 °C) enhanced hydrogen production in presence of Ni-impregnated and non-impregnated biomass char. Inherent inorganic content of char had great effect on hydrogen production. Ni based biomass char exhibited the highest catalytic activity in terms of hydrogen production. Besides, Ni and Fe based coal char had catalytic activity on H2 production. On the other hand, the results showed that biomass char was not thermally stable under steam pyrolysis conditions. Weight loss of catalyst during steam pyrolysis could be attributed to steam gasification of biomass char itself. In contrast, properties of coal char based catalysts after steam pyrolysis process remained nearly unchanged, leading to better thermal stability than biomass char.
•Char catalyst derived from coal was more stable than that from biomass.•H2 amount substantially depended on pretreatment and origin of chars to be used as catalyst.•Ni or Fe based coal char is a promising catalyst for steam reforming of bio-oil to enhance hydrogen production.
The main objective of the present study is to investigate the effect of the polymer types in scrap tires on the pyrolysis products. Two different types of scrap tires (passenger car tire, PCT and ...truck tire, TT) have been pyrolyzed in a fixed bed reactor at the temperatures of 550, 650 and 800
°C under N
2 atmosphere. Pyrolysis products (gas, oil and carbon black) obtained from PCT and TT were investigated comparatively. The gaseous products were analyzed by GC–TCD. The psychical and chemical properties of pyrolytic oils were characterized by means of GC–FID, GC–MS,
1H NMR. In addition, boiling point distributions of hydrocarbons in pyrolytic oils were determined by using simulated distillation curves in comparison with commercial diesel fuel. The production of activated carbon from pyrolytic carbon blacks (CBp) was also carried out. The composition of gaseous products from pyrolysis of PCT and TT were similar and they contained mainly hydrocarbons (C
1–C
4). Pyrolytic oils were found lighter than diesel but heavier than naphtha. The physical properties of pyrolytic oils from PCT and TT were similar at the same temperature. However, the composition of aromatic and sulphur content from pyrolysis of PCT was higher than that of TT. Furthermore, TT derived pyrolytic carbon black was found more suitable for the production of activated carbon due to its low ash content.
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