Hydrothermal processing of fermentation residues in a continuous multistage rig – Operational challenges for liquefaction,salt separation,and catalytic gasification

Fermentation residues are a waste stream of biomethane production containing substantial amounts of organic matter, and thus representing a primary energy source which is mostly unused. For the first time this feedstock was tested for catalytic gasification in supercritical water (T ≥ 374 °C, p ≥ 22 MPa) for methane production. The processing steps include hydrothermal liquefaction, salt separation, as well as catalytic gasification over a ruthenium catalyst in supercritical water.In continuous experiments at a feed rate of 1 kg h⁻¹ a partial liquefaction and carbonization of some of the solids was observed. Significant amounts of heavy tars were formed. Around 50% of the feed carbon remained in the rig. Furthermore, a homogeneous coke was formed, presumably originating from condensed tars. The mineralization of sulfur and its separation in the salt separator was insufficient, because most of the sulfur was still organically bound after liquefaction.Desalination was observed at a salt separator set point temperature of 450 °C and 28 MPa; however, some of the salts could not be withdrawn as a concentrated brine. At 430 °C no salt separation took place. Higher temperatures in the salt separator were found to promote tar and coke formation, resulting in conflicting process requirements for efficient biomass liquefaction and desalination. In the salt separator effluent, solid crystals identified as struvite (magnesium ammonium phosphate) were found. This is the first report of struvite formation from a supercritical water biomass conversion process and represents an important finding for producing a fertilizer from the separated salt brine.     

Catalytic effects of borax and iron(III) chloride on supercritical liquefaction of Anchusa azurea with methanol and isopropanol

Anchusa azurea is a lignocellulosic gramineous plant, and it has been selected as a renewable feedstock to be used in a liquefaction process to obtain biofuel. Milled Anchusa azurea stalks were converted to liquid products in methanol and isopropanol with (borax or iron(III) chloride) and without catalyst in an autoclave at temperatures of 260, 280, and 300°C. The liquefaction parameter effects such as catalyst, solvents, and temperature were investigated. The highest percentages of liquid yields from methanol and isopropanol conversions were 64.70% (with borax) and 29.20% (with borax) at 300°C in the catalytic runs, respectively. The highest conversion (73.80%) was obtained in methanol with borax catalyst at the same temperature. The obtained liquid products at 300°C were analyzed and characterized by elemental, Fourier transform infrared spectroscopy and gas chromatography–mass spectrometry (GC-MS). Seventy-three different compounds have been identified by GC-MS in the liquid products obtained in methanol at 300°C.     

Improved fuel properties of whole table olive stones via pyrolytic processing

This paper describes the thermochemical transformation of residual whole olive stones from the industrial production of pitted and stuffed table olives by using a rotary reactor. This experimental investigation describes the chemical, physical and fuel properties of the resulting solids and liquids obtained in the temperature range between 200 °C and 900 °C. Optimum torrefaction conditions, intended to maximize mass and energy yields, were obtained at 278 °C and resulted in a solid product with 68 wt% volatile matter, 29 wt% fixed carbon, 58 wt% elemental carbon, 0.55 O/C ratio, 23.4 MJ/kg of HHV, 11.25 GJ/m³ apparent energy density for an energy yield of 89%. The carbonized solids obtained at temperatures between 500 °C and 900 °C exhibited LHV and apparent energy density up to 57–66% higher than the original biomass. The carbonization process generates a condensable liquid that represents 50–53 wt% of the original biomass and contains between 57 and 61 wt% water and 39–43 wt% organic products. The carbon content (up to 25 wt%) and heating value (HHV and LHV up to 5.2 MJ/kg and 2.8 MJ/kg, respectively) of this liquid is limited. A model has been tested and a series of equations have been produced which allow us to predict the chemical and energy properties of the solid fraction derived from the torrefaction and carbonization process. This model has found linear correlations between the solid yield and elemental/proximate composition of the solids, and exponential correlations between solid and energy yields.     

Hydrogen transfer during co-liquefaction of Elbistan lignite and biomass: liquid product characterization approach

In this study, Elbistan lignite (EL) and manure were liquefied under catalytic conditions in an inert atmosphere. Red mud, tetralin, and distilled water were used as a catalyst and solvent, respectively. The liquefaction studies were carried out under catalytic conditions in the catalyst concentration of 9%, solvent/solid ratio of 3/1, reaction time of 60 min, waste/lignite ratio of 1/3, and at temperature of 400°C. Stirring speed and initial nitrogen pressure were kept constant at 400 rpm and 20 bar, respectively. At the end of liquefaction process, the soluble liquefaction products were separated by successive solvent extraction to preasphaltene, asphaltene, and oils. Oil products characterized by H-NMR to be able to differ hydrogen transfer from manure to EL surface. To obtain the hydrogen transfer way, liquefaction experiments conducted under inert atmosphere which does not related to hydrogen reaction, other above experimental conditions were kept same but only solvent type changed. The reason of using distilled water instead of tetraline is tetraline known as hydrogen donor but not water. Because water behaves supercritical conditions during the liquefaction stage. EL liquefied alone while using tetraline however EL liquefied with manure with using distilled water as a solvent. The obtained oil products form both experiments characterized by H-NMR. The radical groups diffraction and range values are not changed significantly shows that manure behaved as an hydrogen donor. So, EL with manure is the one great option to reduce cost of hydrogen source for direct coal liquefaction plant.     

Nitrogen-incorporated carbon nanotube derived from polystyrene and polypyrrole as hydrogen storage material

“Synthesis of nitrogen-doped carbon nanotubes from polymeric precursors (polystyrene and polypyrrole) by poly-condensation followed by carbonization under an inert atmosphere is reported. Three different carbonization temperatures (500 °C, 700 °C and 900 °C) were employed to synthesize three different carbon nanostructures with different morphologies. These were designated as NCNR-500 (nitrogen-doped carbon nanorods), NCBCT-700 (nitrogen-doped fused bead carbon nanotubes), and NCNT-900 (nitrogen-doped carbon nanotubes) according to morphology and carbonization temperature. Microstructure, morphology, porosity, and nitrogen content were characterized by several different techniques. The effects of carbonization temperature and the role of functional groups were also investigated. Total and excess hydrogen storage capacities of 2.0 wt% and 1.8 wt%, respectively, were measured at 298 K and 100 bar for the NCNT-900 material. This is higher than the capacities of the NCNR-500 and NCBCT-700 materials. NCNT-900 exhibited a porous structure with high specific surface area and total pore volume of 870 m/g and 0.62 cm³/g, respectively.     

Synthetic natural gas (SNG) liquefaction processes with hydrogen separation

The fact that synthetic natural gas (SNG) contains hydrogen has a great impact on its liquefaction process. Aiming to produce liquefied natural gas (LNG) from SNG, hydrogen separation from SNG through cryogenic processes is studied. A new separation method combining distillation and flash is developed, resulting in higher liquefaction rate than that of distillation under same operating parameters. Process simulations are performed by combining one liquefaction part (a nitrogen expansion process or a mixed refrigerant one) and one distillation part (direct flash, atmospheric distillation, pressurized distillation or the new separation method). Compared to direct flash, distillation can reduce the hydrogen content of products to a very low level, increasing the temperature of products by 8 °C and reducing the unit power consumption by 3%; and, compared to the other three separation ways, the new separation method reduces the unit power consumption by 7–10%. Both nitrogen expansion and SMR liquefaction processes can be integrated with hydrogen separation, but power consumptions for SMR processes are less than those for nitrogen expansion ones.     

Thermo-chemical conversion of waste rubber seed shell to produce fuel and value-added chemicals

Rubber seed shell (RSS), comprises of 96.67 wt% organic content and 38.6% crystallinity index, was used for the production of biofuel and value-added chemicals through semi-batch pyrolysis. Thermogravimetric analysis (TGA) of RSS at heating rate of 20 °C/min showed R50 value as 12.72%/min at 376.5 °C. The gaseous product evolved during the decomposition of RSS were analyzed through inline Fourier transform infrared (FT-IR) coupled with TGA instrument. The effects of pyrolysis temperatures (350°C-600 °C) and heating rates (10°C/min–40 °C/min) on the product distribution (liquid, gas and bio-char) were investigated. The maximum yield of liquid product (46.14 wt%) and the carbon-rich bio-char (31.92 wt%) were obtained at 550 °C temperature for heating rate of 30 °C/min. The fuel characteristics of produced bio-char such as higher calorific value (34.5 MJ/kg), higher fixed carbon (79.74 wt%), lower ash (1.87 wt%) and lower moisture content (2.11 wt%) suggested its potential to be used as solid fuel. Value-added organic compounds such as acetic acid, phenolic compounds, creosol, pilocarpine, benzene and levoglucosan were identified in the liquid product using gas chromatography. The pH values of liquid products (2.55–3.0) support the presence of organic acids and phenolic fraction. The presence of various functional groups was also identified using FT-IR spectroscopy. In depth analysis of physico-chemical-thermal properties of RSS and obtained products (liquid and bio-char) suggested that RSS can be considered as a suitable feedstock for the production of value added chemicals including fuel.     

Optimization and characterization of TiO2-based solar cell design using diverse plant pigments

The design of electrochemical solar cells (SCs), including those composed of biological pigments is an actively developing direction of obtaining alternative energy. SCs were studied under different temperatures, light intensities and spectral conditions. Furthermore, to understand processes occurring in the SCs, investigations characterizing the efficiency and stability with regard to environmental factors are also required. For this aim, novel instrumentation for the investigation of environmental effects on photocurrent generated by SCs has been designed and constructed. The system can be a model, which reflects conditions required for effective and stable functioning of the solar cells. Preliminary results are shown for two types of solar cells with two photosensitizers: thylakoid membrane preparations and anthocyanin-enriched raspberry extracts. It was shown that electrogenic activity decreased by a half at 40 °C and returned back to the initial value under gradual cooling. Maximum current obtained from the thylakoid-based SC was 0.46 μA, while maximum current generated by the anthocyanin-based SC was 1.75 μA. The goal of this investigation is to find new ways to increase efficiency and stability of bio-based SCs. In future, this measuring system can be used for investigation of solar cells based on long-wave forms of chlorophylls (Chls d and f) and components of the photosynthetic apparatus comprising these chlorophylls.     

Hydrothermal carbonization of unwanted biomass materials: Effect of process temperature and retention time on hydrochar and liquid fraction

Hydrothermal carbonization (HTC) was applied to examine the feasibility in converting coconut husk (CH) and rice husk (RH) to renewable fuel resource and valuable dissolved organic chemicals. HTC was conducted with varying process temperature (140–200 °C) and retention time (1–4 h). CH was a better feedstock to produce hydrochar as solid fuel than RH because of its compositions was significantly different. An increase in process temperature from 140 to 200 °C resulted in a decrease in hydrochar yield of CH from 77.1 to 67.8%, and corresponding decreases in O/C and H/C from 0.6 and 1.4 to 0.4 and 1.2, respectively, and this was associated to dehydration and decarboxylation reactions. Fuel ratio and HHV were in the range of 0.66–0.86 and 20.7–23.9 MJ/kg, respectively. Liquid fractions (LF) from both RH and CH were found to be abundant in dissolved organic chemicals which were regarded as valuable intermediate chemicals, including furfural, furfuryl alcohol, hydroxymethylfurfural (HMF), and low molecular-weight carboxylic acids (lactic acid, formic acid, acetic acid, levulinic acid, and propionic acid).     

Thermochemical liquefaction characteristics of Cyanobacteria in subcritical and supercritical ethanol–water mixture

The thermochemical liquefaction of Cyanobacteria in subcritical and supercritical ethanol–water mixture was studied with different reaction temperature, reaction time, solvent composition, and solid–liquid ratio. Highest bio‐oil yield of 42.5% containing mainly fatty acid ethyl esters, phenols, pyrrolidinones, and pyridinols was obtained in ethanol–water mixture (4/6, v/v) at temperature of 320°C for 30 min, with solid–liquid ratio of 1 g/15 mL. Both solvent composition and supercritical state had great influence on the liquefaction of Cyanobacteria, while the synergetic effects of water and ethanol in co‐solvents were again verified. Copyright © 2017 John Wiley & Sons, Ltd.