Solid Pyrolysis Products Research Articles

Biochar Amendment Enhances Water Retention in a Tropical Sandy Soil

The use of biochar, which is the solid product of biomass pyrolysis, in agricultural soils, has been shown as a strategic solution for building soil carbon stocks and mitigating greenhouse gas emissions. However, biochar amendment might also benefit other key soil processes and services, such as those that are related to water retention, particularly in sandy soils. Here, we conducted an experiment to investigate the potential of biochar to enhance pore size distribution and water retention properties in a tropical sandy soil. Three biochar rates were incorporated (equivalent to 6.25, 12.5, and 25 Mg ha−1) into plastic pots containing a sandy Oxisol sampled from a sugarcane field in Brazil. Undisturbed samples of the mixture were collected at two evaluation times (50 and 150 days) and used to determine water retention curves and other soil physical properties. The results showed that biochar amendment decreased soil bulk density and increased water retention capacity, micropore volume, and available water content. Higher soil water retention in amended soil is associated with the inherent characteristics of biochar (e.g., internal porosity) and potential improvements in soil structure. Microporosity and water retention were enhanced with intermediate biochar rate (12.5 Mg ha−1), instead of the highest rate (25 Mg ha−1) tested. Further studies are needed to validate these results under field conditions.

Experimental Investigation of the Process of Cooling Waste Tire Pyrolysis Products

Waste tire disposal, being currently a topical problem, can be implemented by low-temperature pyrolysis in continuous units used to obtain commercial products: liquid fraction and solid coke residue. In creating such units, cooling the discharged coke residue may become a factor limiting the entire technological process. The process of cooling a bed of solid pyrolysis products in the open air has been investigated in this work. The development of heat generation has been established experimentally in bulk coke residue at a surface layer temperature of 608°C or higher. A procedure has been developed which makes it possible to detect this effect for the process of pyrolysis of other carbon-containing materials.

Моделирование и исследование процесса охлаждения твердых продуктов пиролиза отработанных шин

Every year, 1.5 billion tires are produced around the world, and each of them eventually falls into the waste stream. The growing volume of waste tires and limited possibilities for their disposal generate the need to develop methods for recycling them. A review of papers addressing the waste tire recycling problem with the use of proposed mechanical and thermochemical processing methods is presented. It is shown that researchers take interest in pyrolysis as a technology for thermochemical conversion of waste tire to produce valuable products: a solid fraction represented by coke residue (carbon black), a liquid hydrocarbon fraction (pyrolysis oil), and non-condensing gaseous fraction (pyrolysis gas). In a number of published papers, focus is placed on improving the consumer properties of each fraction. Conditions under which the coke residue quality can be improved to the level of activated carbon are, and methods for implementing this are developed. The cooling of solid pyrolysis products can be a limiting factor for the pyrolysis plant operation. Unloading of the coke residue at increased temperatures with outdoor cooling can lead to its burning out. To develop an efficient coke residue cooling heat exchanger, it is necessary to know the physical properties of this substance. A method for determining the thermal conductivity of fine coke residue based on the use of physical and mathematical modeling of the cooling process has been developed and implemented. Experiments on studying the coke residue bed cooling process in air in the temperature range from 500 °C to the ambient temperature were carried out. The time dependences of temperature at several points of the bed layer are obtained. A measuring chamber mathematical model reproducing the experimental conditions is developed. By studying the model, it is possible to determine the coke residue thermal conductivity, which approximates the calculated cooling process temperature curves to those obtained in the experiment with satisfactory accuracy. Based on the analysis of experimental data, two temperature ranges are identified, and a linear dependence of the bed thermal conductivity on the temperature is found in each of them. The coefficients of these functions are determined by minimizing the response function using the Box--Wilson method. The obtained results are used for the development of industrial thermal power engineering facilities.

Исследование кинетики термодеструкции сшитого полиэтилена

This paper presents a study of the process of thermal degradation of crosslinked polyethylene. The kinetics of polymer decomposition was studied by thermogravimetry. Crosslinked polyethylene showed high heat resistance to temperatures of 400 °C. The temperature range of 430–500 °C was determined for the loss of the bulk of the sample. According to thermogravimetric data, the decomposition process proceeds in a single stage and includes a large number of fracture, cyclization, dehydrogenation, and other reactions. The process of pyrolysis of a crosslinked polymer in a stationary-bed metal reactor was investigated. The influence of the process temperature on the yield of solid, liquid, and gaseous pyrolysis products was investigated. The optimum process temperature was 500 °C. At this temperature, the yield of liquid and gaseous products was 85.0 and 12.5% (mass.), Respectively. Samples of crosslinked polyester decomposed almost completely. The amount of carbon–containing residue was 3.5% by weight of the feedstock. With increasing temperature, the yield of liquid products decreased slightly and the yield of gaseous products increased, but their total yield did not increase. For gaseous products, a qualitative and quantitative composition was determined. The main components of the pyrolysis gas were hydrocarbons C1–C4. The calorific value of pyrolysis gas obtained at a temperature of 500 °C was 17 MJ/m3. Thus, the pyrolysis process can be used to process crosslinked polyethylene wastes to produce liquid hydrocarbons and combustible gases.

Behaviour of waste polypropylene pyrolysis char-based epoxy composite materials.

In this study, polypropylene (PP) plastic wastes were pyrolysed. Solid pyrolysis product (char) was used as filler material for the preparation of epoxy composite. 300, 400, 500, 600 and 700°C were selected as final pyrolysis temperatures. Solid pyrolysis product (char) was analysed by elemental, FTIR, SEM, BET and TGA analysis. The epoxy composite samples were prepared with char obtained from pyrolysis. Mechanical properties of composites were analysed by hardness, tensile strength, elongation at break, electrical conductivity tests to explain the effects of pyrolysis temperature and char doses over composite properties. Thermogravimetric properties of composites were determined by TGA analyses. The water absorption behaviour of composite samples was determined by water adsorption test. Epoxy composite produced from PP char obtained under 300°C showed the most ideal behaviour.

Free radicals formation on thermally decomposed biomass

Pyrolysis provides an attractive alternative for the upgrading of agro-wastes to energy and chemicals. However, consistent quality of the final products is still a goal to be achieved at industrial level. The present study aims at complementing existing results recently published by the authors and investigating the physico-chemical evolution and oxidative reactivity of solid products of pyrolysis of citrus waste. Chars derived from slow pyrolysis (50 °C min−1, 200–650 °C peak temperature) of orange and lemon pulp (OP and LP) in a horizontal batch reactor were characterized by means of Thermo-Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Electron Paramagnetic Resonance (EPR) and Raman spectroscopy. Results show how the onset of breaking of covalent bonds in matrix is triggered by reaching pyrolysis temperatures of 330–350 °C. Around those temperatures, the population of free-radicals significantly increases on solids and chars become more reactive, thereby favoring retrogressive, recombination and secondary solid-vapor reactions. Results also show that the higher content of lignin on LP may facilitate the formation of aromatic networks via lignin fragmentation and condensation above 500 °C. This trend is also confirmed by DSC patterns in which, above 500 °C, significantly more endothermic reactions occur in LP as a comparison to OP. This conclusion is further corroborated by more pronounced G-band Raman shifts shown for LP as a comparison to OP. The present results shed new light on the thermochemical breakdown of solid agro-wastes and provide insights for development of slow pyrolysis technology toward the production of valuable renewable carbonaceous materials.

Characterization of the products obtained by pyrolysis of oil sludge with steel slag in a continuous pyrolysis-magnetic separation reactor

In this study, a strategy of combining oil sludge with steel slag to improve the quality of tar resulting from oil sludge pyrolysis and steel slag recycling is proposed. Oil sludge pyrolysis with the addition of different amounts of steel slag at different temperatures was conducted by employing a continuous pyrolysis-magnetic separation (CPM) process. The characteristics of oil pyrolysis were characterized by thermogravimetric analysis (TG), the compositions of the non-condensable gas and tar were characterized by gas chromatography (GC) and gas chromatography-mass spectrometry (GC–MS). The effect of steel slag on the tar composition and char surface morphology was analysed. The recovered steel slag concentrate was measured by a magnetic separation method. The results indicated that steel slag addition caused the weight loss rate of oil sludge to increase. The yield of tar reached a maximum of 10.63% at 550 °C, and the increase in temperature intensified the secondary thermal cracking of the volatile fraction and decreased the tar yield. The gas composition analysis indicated that steel slag could act as a catalyst in improving the H2 content during the pyrolysis process of oil sludge. The addition of steel slag significantly increased the content of short alkanes and increased the C5 ∼ C10 fraction by improving the decomposition of the C15 ∼ C20 fraction. The recovery of steel slag from the solid pyrolysis products of oil sludge containing steel slag was conducted in a magnetic separator, and the maximum recovery rate could reach 55.03%. It was concluded that the integration of oil sludge pyrolysis with steel slag and the recovery of steel slag from the solid pyrolysis products of oil sludge containing steel slag could be feasible.

Oxidative Pyrolysis of the Mixtures of Oil and Plant Raw Materials

The influence of the composition of the mixtures of petroleum (fuel oil) and vegetable raw materials on the yield and composition of products formed upon the pyrolysis of the mixtures was investigated. Data on the pyrolytic transformations of the mixtures in a temperature range of 140–700°C are given. It was established experimentally that the yield of solid pyrolysis products decreases and the yield of gas and tar increases with the fuel oil content of the mixture. The yield of pyrolysis products also depends on the concentration of emulsified water in the mixtures.

The influence of temperature on the physicochemical properties of products of pyrolysis of leather-tannery waste

The present paper examines the pyrolysis of waste from leather tanneries at 300–500 °C. These studies are important because of difficulties in the utilisation of this type of waste as well as its energy potential as fuel. The pyrolysis of tannery waste and data from the relevant literature showed that thermal degradation can be explained using tanned collagen as a reference. Moreover, the experimental results indicated that this process is highly non-linear, due to various mechanisms of heat transport which cause temperature differences in a laboratory pyrolysis reactor. Thermogravimetric analysis has shown that the greater part of mass loss is observed between 80 and 500 °C and that the most significant mass release occurs at 325 °C. Moreover, the proportions of CO2 and CO decrease along with increasing temperatures. The paper presents characteristics of the composition of solid, liquid, and gaseous products of leather-waste pyrolysis at various temperatures. The maximum heating value of gaseous products at 500 °C was 9.54 MJ/Nm3. An increase from 300 to 500 °C results in the dominant position of condensation polymerisation; the maximum value of the liquid phase yield is reached at 400 °C (42%). HHV analysis of the resulting char showed a maximum value of 21.18 MJ/kg at 450 °C. The results of oxidised component analysis showed that the major oxidised component of char was chromium oxide (Cr2O3), with a content of approximately 8.5% at all pyrolysis temperatures.

1D Modeling of the Microwave Discharge in Liquid n-Heptane Including Production of Carbonaceous Particles

Microwave plasma in the liquid is initiated inside a gas bubble formed at the end of the electrode-antenna, through which microwave energy is introduced into the liquid. A 1D model a set of gas phase kinetic reactions describes the evolution processes of ionization, heat transfer and formation of gas and solid products inside the plasma bubble. The code is based on joint solution of the Boltzmann equation for free electrons of the plasma, a simplified equation for the microwave field, the heat conduction equation, the balance equation for the electron density and the balance equations for the weight fraction for all gas and solid products of n-heptane pyrolysis. The Joule heat released in the plasma is expended on the evaporation of liquid n-heptane into the bubble and the decomposition of the n-heptane molecules. The model includes both the description of gas phase processes and formation of solid carbon-containing particles. The growth mechanism for generation of solid particles describes simultaneous processes of the initial nucleation, surface growth and coagulation of soot particles. The results of calculations are compared with known experimental results.

Effect of Metal Chlorides on the Pyrolysis of Wheat Straw

In this paper, the results of the study on the influence of the addition of 10 wt.% of FeCl3, CoCl2, NiCl2, ZnCl2, SnCl2, and CuCl2 on the wheat straw pyrolysis process are presented. The studied chlorides were found to affect the pyrolysis process; however, the highest activity was observed while using CuCl2. The presence of the copper chloride led to the decrease in the temperature of the initial destruction of hemicellulose fraction of wheat straw by 64°С. Besides, the use of CuCl2 allowed increasing the yield of liquid and solid pyrolysis products as well as decreasing the molecular weight distribution of the volatiles. Moreover, the increase in the hydrogen and decrease in carbon dioxide concentration were also observed in the presence of copper chloride. The analysis of the solid residue obtained in the wheat straw pyrolysis in the presence of CuCl2 showed the increase in the specific surface area of the carbon residue from 24 up to 63.5 m2/g in comparison with that obtained for the noncatalytic process.

Effect of the Kinetic Model of Pyrolysis on Prognostic Estimates of Ignition Characteristics of Wood Particles

The effect of the kinetic model of the thermal decomposition of wood on the results of prognostic modeling of the ignition of wood particles was analyzed. The results of mathematical modeling were verified by experimental studies of the ignition of wood particles in a high-temperature environment. Comparative analysis of theoretical and experimental ignition delays shows that they are in good agreement. The prognostic potential of three substantially different kinetic models of wood pyrolysis was analyzed. The model of one-step pyrolysis involving the formation of gaseous reaction products adequately describes thermal decomposition during thermal preparation in the whole range of heating conditions (the deviation from the times obtained using the three-step pyrolysis model does not exceed 5%). Numerical simulation results show that accounting for the thermal decomposition reactions of the second and third levels with the formation of intermediate (liquid and solid) pyrolysis products does not have a significant influence on the characteristics and conditions of ignition of wood particles in a high-temperature gas environment.

Physicochemical Transformations of Mixed Fuels Based on Typical Coals and Wood upon Heating

The thermal decomposition of the mixtures of two types of dispersed coals and shredded wood in a temperature range until the complete pyrolysis of the organic matter of both components at different concentrations was experimentally studied in order to evaluate the prospects of using these fuels as composite fuels for large- and small-scale power plants (combustion in the furnaces of steam and hot-water boilers). It was established that the joint thermal decomposition of a mixture of coal and wood particles leads to a significant change in the pyrolysis temperature range and the release of anthropogenic gases (sulfur and nitrogen oxides) in the case of the high-temperature heating of such a mixture based on lean coal. A similar effect, but on a much smaller scale, was detected for a mixture based on long-flame coal. A hypothesis on the mechanism of sequestering sulfur and nitrogen oxides on the thermal decomposition of a mixture of lean coal and wood particles as a result of the interaction of intermediate gaseous and solid products of coal and wood pyrolysis in a temperature range to 1000°C was formulated. The possibility of using a mixture of crushed coal and wood as fuel for steam and hot water boilers was substantiated. With a certain decrease in the energy characteristics of such fuels compared to homogeneous coals, the environmental and economic characteristics of fuel burning processes were significantly improved. It was shown that a significant synergistic effect of co-combustion of particles of coal and wood is achieved only in certain coals.

Термохимическая переработка лузги подсолнечника

The article discusses the study of the process of thermochemical processing of sunflower husk into liquid, solid and gaseous products. According to the statistics provided by Rosstat, sunflower is the traditional largest agricultural oil crop in Russia. To date, the gross seed collection of about 12 million tons per year. In the process of industrial production of sunflower oil during the entire production cycle, a large amount of plant waste, including husk seeds. Currently, there are many areas for the use of sunflower husk, the main of which is the production of feed additives for cattle. However, the presented areas of industrial application do not allow to fully process this valuable resource into cost-effective products, which leads to its accumulation. Analysis of the physical properties of sunflower husk showed a high calorific value of this biomass due to the high lignin content. Sunflower husk has a low ash content. These facts indicate the possibility of effectively using the husks as raw materials for the production of coal briquettes, liquid biofuels and gaseous products by the thermochemical method. Using standard techniques, the properties and chemical composition of selected samples of sunflower husk were determined. In order to identify the optimal parameters for the maximum yield of liquid and solid products of pyrolysis of sunflower husk, the experimental ways were determined dependences of the yield of products on the temperature of thermal decomposition. The study of the thermal decomposition of sunflower husk was carried out in isothermal conditions at temperatures of 450, 500, 550 and 600 ° C. The experiments were carried out in a periodic pyrolysis reactor of plant biomass. The results of studies on the yield of process products from the temperature of thermal decomposition of sunflower husk showed that the maximum yield of liquid product up to 43% occurs at a temperature of 550 ° C, and that of a solid product up to 35% at a temperature of 450 ° C. A further increase in the temperature of the pyrolysis process leads to an increase in the yield of the gaseous product.

Investigation of heavy metals emission from pyrolysis product of rubber wastes treated with ashing

Aim: In this paper, the emission of heavy metal ions from potential sorption materials is investigated. Samples were obtained by low‑temperature pyrolysis from rubber waste (used car tires) and treated with dry ashing. The use of a solid pyrolysis product after ashing involves the purification of wastewater from contaminants. Methods: The content of heavy metal ions in aqueous extraction and extraction with an acetate‑ammonium buffer of a solid product of pyrolysis of rubber waste was determined by means of atomic emission spectrometry. Of decreasing mass concentration, the heavy metal ions in the aqueous extract of the solid pyrolysis product after treatment with ashing are arranged in the following order: Zn, Si, Mn, Sr, Co, Ba, Mo, Ni, and Sb. In the acetate‑ammonium extract of the test sample, the heavy metals are arranged in the following order in the order of decreasing values: Zn, Mn, Co, Fe, Sr, Cu, Al, Ni, B, V, Pb, Cr, Ba, Se, Pb, and Sb. Results: The obtained results show that the aqueous extract of the solid pyrolysis product of rubber waste after treatment with “dry” ashing does not exceed the normative indices for sewage by the content of heavy metals. According to the values of the concentration coefficient relative to the permissible concentration of pollutants in the wastewater admitted to discharge into the centralized system of wastewater disposal, the excess of the norm takes place according to Zn. Conclusions: It has been established that the solid pyrolysis product of rubber waste treated with ashing does not pollute the wastewater. This implies the possibility of using the processed pyrolysis product from environmental positions with limiting the discharge of wash water directly into fishery water reservoirs.

Influence of wood component on physical and chemical transformations during high temperature heating of composite fuel based on bituminous coal

Experimental studies of ignition delay time for mixtures of dispersed hard coal of two types and milled wood over a wide temperature range have been performed. Time of total completion of organic part pyrolysis of both components at different concentrations have been established in order to assess the prospects for such fuels application in large- and small-scale power engineering (combustion in boiler furnaces of different capacities). It has been established that simultaneous thermal decomposition of mixture of coal and wood particles leads to a significant change of pyrolysis temperature range and release of anthropogenic gases (sulfur and nitrogen oxides) in case of high-temperature heating of the mixture based on lean coal. The same effect, but in much smaller scale, has been recorded for a mixture based on long-flame coal. A hypothesis has been formulated on the mechanism of sulfur and nitrogen oxides precipitation during thermal decomposition of the mixture of lean coal and wood particles as a result of interaction between transitory gaseous and solid pyrolysis products of coal and wood in the temperature range up to 1000°C. Prospects of applying the milled coal and wood mixtures as fuel for steam and hot water boilers have been substantiated. With a small decrease of energy characteristics of such fuels, compared to homogeneous coals, significant improvement of ecological and economic characteristics of the fuel combustion processes can be achieved. It has been shown that vital synergistic effect of co-combustion of coal and wood particles is achieved only with certain coals.

Slow pyrolysis of walnut shells in nitrogen and carbon dioxide

Previous studies have shown that increased carbon dioxide concentration upon heat up affects the products of coal pyrolysis and in particular that chars prepared under carbon dioxide rich atmospheres are less reactive than chars prepared in nitrogen, and consistently tars are more aromatic. In the present work, this issue is investigated with reference to a biomass, namely walnut shells (WS), where the lignin component prevails over cellulose and hemicellulose.Preliminary experiments of thermal degradation have been carried out using a thermogravimetric (TG) apparatus, under constant heating rate conditions, in flows of either nitrogen or carbon dioxide. Derivative thermogravimetric (DTG) curves reveal the existence of multiple peaks, which are typically associated with the degradation of different ligno-cellulosic components. A multiple parallel reaction scheme has therefore been used to fit the experimental data and kinetic parameters have been obtained.Walnut shells were also pyrolyzed in a fixed bed reactor at 600 °C in either nitrogen or carbon dioxide so as to collect pyrolysis products in amounts sufficient for further analysis. Char and tar samples have been characterized using different techniques (e.g. GC–MS, elemental analysis, TGA, SEM) revealing limited differences. Combustion rates of the chars have been measured by means of non-isothermal thermogravimetric experiments in air and again small differences have been observed between the samples prepared under carbon dioxide and nitrogen.It has been concluded that under the low heating rate conditions typical of the thermogravimetric apparatus and fixed bed reactor used in the work, the effects of carbon dioxide on liquid and solid products of biomass pyrolysis exist but are less important than for coal.The work is complementary to another paper, which addresses the effect of carbon dioxide on biomass pyrolysis under high temperature and fast heating rate conditions in a drop tube reactor.

A comparison of CO2, N2, and Ar to maximize plant nutrient retention in biochar

Nutrient-rich biochar improves soil significantly; however, the nutrients nitrogen (N), phosphorous (P), and potassium (K) can be easily lost during the pyrolysis of straw feedstock. To resolve this problem, the mechanism for retaining the biochar nutrient elements in the solid, liquid, and gas products of pyrolysis under different atmospheric conditions and at different temperatures was studied systematically so that the best method for the preparation of the biochar could be determined. The observations are as follows: (1) the CO2 atmosphere was more favourable than the N2 atmosphere for biochar preparation; (2) at 400 °C, the carbon in the biochar was mainly in the form of conjugated aromatic carbon; (3) when the temperature increased from 300 to 600 °C, the nitrogen content in the biochar decreased from 88.42 to 39.02%; (4) most of the phosphorus and potassium were mainly retained in the biochar; (5) the lower pyrolysis temperature (400 °C) under a CO2 atmosphere is the best biochar preparation conditions for promoting lettuce growth.

Biochar as an adsorbent for inorganic nitrogen and phosphorus removal from water: a review.

Biochar is the solid product of biomass pyrolysis that can be used for carbon sequestration, soil amendment, and pollution remediation. The use of biochar as an adsorbent for the removal of water contaminants has elicited increasing interest due to the multifunctional properties of this material. The application of biochar in the adsorption of inorganic nutrients from eutrophic water has not been reviewed. This review focuses on recent research on the use of biochar for the adsorption of inorganic nitrogen (ammonium and nitrate) and phosphorus (phosphate) from water, especially for the main influence factors and mechanisms for nitrogen and phosphorus adsorption on biochar.

Adsorption of copper from waste printed circuit boards with modified orange peels

Copper adsorption from waste printed circuit boards (PCBs) was studied using biosorbents derived from waste orange peels (OP). The orange peels were modified by different methods including saponification with NaOH (OP-S), crosslinking with sodium trimetaphosphate and sodium tripolyphosphate (OP-C), hydroxypropylation with propylene oxide (OP-H), and acidification with citric acid (OP-A) to increase the adsorption capacity of orange peels. Adsorption tests on the copper (Cu) model solutions were performed by using native and modified orange peels at three different temperatures (25 °C, 40 °C, and 60 °C) to determine the optimum adsorption conditions. The PCB was pyrolyzed in a fixed bed stainless steel reactor to obtain a solid product that contained only inorganic material. Metals were then leached from the solid product, and adsorption studies were realized on the leach solution under optimum adsorption conditions. According to the analyses results, the best adsorption efficiency for the Cu model solution was obtained with OP-S at 25 C for 30 min. Under these conditions, the Cu adsorption efficiency from pyrolysis solid product was approximately 86%.