The Viscoelastic Swirled Flow in the Confusor

A two-dimensional mathematical model for a steady viscoelastic laminar flow in a confusor was developed under the condition of swirled flow imposed at the inlet. Low density polyethylene was considered as a working fluid. Its behavior was described by a two-mode Giesekus model. The proposed mathematical model was tested by comparing it with some special cases presented in the literature. Additionally, we propose a system of equations to find the nonlinear parameters of the multimode Giesekus model (mobility factor) based on experimental measurement. The obtained numerical results showed that in a confusor with the contraction rate of 4:1, an increase in the swirl intensity at Wi < 5.1 affects only the circumferential velocity, while the axial and radial velocities remain constant. The distribution pattern of the first normal stress difference in the confusor is qualitatively similar to the one in a channel with abrupt contraction, i.e., as the viscoelastic fluid flows in the confusor, the value of N1 increases and reaches a maximum at the end of the confusor. Dimensionless damping coefficients of swirl are used to estimate the swirl intensity. The results show that the swirl intensity decreases exponentially

Production of soil amendment by utilization of the weed Amaranth

There is a possibility of using agricultural waste, in particular weeds, in innovative technologies for the restoration of disturbed land in order to increase fertility. Digestate, after anaerobic digestion of manure and weed plant Amaranthus retroflexus L. (AR), as well as solid carbonaceous residue after pyrolysis of AR. The combination of digestate, which contains high concentrations of total nitrogen, phosphorus, potassium, and solid carbonaceous residue, provides a new composite soil amendment. It has high potential as a source of nutrients because it contains a large amount of mineral components. The soil amendment does not contain toxic elements such as: lead, cadmium, mercury, arsenic and nickel, but the zinc and copper content exceeds the recommended values

An experimental study of sunflower husk pellets combustion

The thermogravimetric study of the sunflower husk pellets combustion was carried out at three heating rates: 5, 10, and 20 °C/min to increase the efficiency of agricultural waste disposal methods. The husk combustion process can be divided into several stages: the stage of moisture evaporation and the release of light fractions of volatile substances, the main stage of the release of volatiles and combustion, as well as the stage of the carbonaceous residue after-burning. The maximum mass loss was observed in the experiment with a heating rate of 10 °C/min, and it was equal to 91.99% of the total weight of organic matter. The average residual mass for all experiments was 3%. The higher heating value (HHV) of sunflower husk pellets was 19.2 MJ/kg. When implementing a biomass boiler with a capacity of 430 kW, the return period will be 3.43 years

A Comprehensive Study on the Combustion of Sunflower Husk Pellets by Thermogravimetric and Kinetic Analysis, Kriging Method

The combustion of sunflower husk pellets was investigated by kinetic analysis supplemented by the Kriging method. The nonisothermal thermogravimetric experiments in air were carried out at the temperatures from 20 to 700 °C and heating rates of 5, 10, and 20 °C/min. Kinetic analysis was carried out using the model-free OFW (Ozawa–Flynn–Wall) method and Coats–Redfern (CR) method. The activation energy values, calculated by the OFW method, ranged from 116.44 to 249.94 kJ/mol. These data were used to determine the combustion mechanism by the CR method. The kinetic triplet (Eα, A, g(α)) was determined in the conversion interval 0.2 to 0.8. The model of the chemical reaction F8 was recommended to describe the mechanism of the thermochemical conversion process. The relationship between the kinetic parameters was analyzed using the Kriging method. The patterns between the kinetic parameters were represented as three-dimensional surfaces and two-dimensional projections. The distribution’s surfaces were uniform; there were local extremes as well as linear regions. A new approach to the data analysis will allow predicting parameters of a thermochemical conversion of the various raw materials and contributes to a deeper understanding of the characteristics and mechanism of biomass combustion

Cavitation Reactor for Pretreatment of Liquid Agricultural Waste

One of the most well-known methods of intensifying the process of anaerobic digestion is the pretreatment of raw materials. For the first time, the use of a jet-driven Helmholtz oscillator for biomass pretreatment is proposed. The design of the device is optimal for creating hydraulic cavitation; however, in this case, acoustic oscillations are generated in the system and resonance occurs. In this study, the optimal design of this device was determined for the subsequent design of a cavitation reactor. The diameter of the resonant chamber was varied in the range from 28.3 to 47.5 mm, and its length from 6 to 14 mm; in addition, the diameter of the outlet was changed from 6.1 to 6.3 mm. Based on the experimental data obtained, it was found that the optimal ratio of the length of the resonator chamber to the diameter of the inlet nozzle is 1.73, and the inner diameter of the resonator chamber to the diameter of the inlet nozzle corresponds to 5.5. Improving the technology of agricultural waste disposal will ensure their maximum involvement in economic circulation, reduce the consumption of traditional fuel and energy resources, and improve the technological and machine-building base, which makes it possible to produce competitive cavitation reactors

Pyrolysis of Amaranth Inflorescence Wastes: Bioenergy Potential, Biochar and Hydrocarbon Rich Bio-Oil Production

Many agro-industrial companies grow amaranth for the subsequent production of amaranth oil, flour, cereals, flakes, and bran. After the grain is extracted, waste in the form of inflorescences remains, which can be used to obtain useful new products. This work investigated the use of pyrolysis to recycle amaranth inflorescence wastes (AIW). Thermochemical conversion experiments in an inert medium were carried out in a laboratory setup at 550 °C and a heating rate of 10 °C/min. It was found that the AIW pyrolysis produced 37.1 wt.% bio-oil, 35.8 wt.% pyrogas and 27.1 wt.% biochar. The oil fraction of the obtained bio-oil contains 41.8% of hydrocarbons. Thermogravimetric analysis of AIW was performed in the temperature range from 40 to 1000 °C at heating rates of 10, 15, and 20 °C/min in argon medium (75 mL/min). The kinetic parameters were determined by the model-free Friedman, Ozawa-Flynn-Wall, and Kissinger-Akahira-Sunose methods. The average activation energy values are in the range of 208.44–216.17 kJ/mol, and they were used to calculate the thermodynamic parameters. The results indicate that the pyrolysis application will allow efficient conversion of AIW into value-added products

Pyrolysis of Amaranth Inflorescence Wastes: Bioenergy Potential, Biochar and Hydrocarbon Rich Bio-Oil Production

Many agro-industrial companies grow amaranth for the subsequent production of amaranth oil, flour, cereals, flakes, and bran. After the grain is extracted, waste in the form of inflorescences remains, which can be used to obtain useful new products. This work investigated the use of pyrolysis to recycle amaranth inflorescence wastes (AIW). Thermochemical conversion experiments in an inert medium were carried out in a laboratory setup at 550 °C and a heating rate of 10 °C/min. It was found that the AIW pyrolysis produced 37.1 wt.% bio-oil, 35.8 wt.% pyrogas and 27.1 wt.% biochar. The oil fraction of the obtained bio-oil contains 41.8% of hydrocarbons. Thermogravimetric analysis of AIW was performed in the temperature range from 40 to 1000 °C at heating rates of 10, 15, and 20 °C/min in argon medium (75 mL/min). The kinetic parameters were determined by the model-free Friedman, Ozawa-Flynn-Wall, and Kissinger-Akahira-Sunose methods. The average activation energy values are in the range of 208.44–216.17 kJ/mol, and they were used to calculate the thermodynamic parameters. The results indicate that the pyrolysis application will allow efficient conversion of AIW into value-added products