Development of double screw press and method of controlling the parameters of the briquetting process

Paper is focused on development of new patented construction of screw briquetting machine for compacting biomass into the solid biofuel. Developed machine design is based on achieved results of comprehensive research of the complicated process of biomass densification. Patented construction provides two main goals: the elimination of axial forces, which causes increasing of bearings lifetime, and a new modular design of pressing chamber and tools with geometry based on application of the mathematical model. Research of the biomass densification pointed to the need for modular design of densification machine, where it is possible to control all significant parameters of the densification process. The goal of this paper is to present a new patented design of screw press, which satisfies all requirements for modularity and control of the parameters. It allows optimizing this process for different types of raw materials and achieving high quality production. Results of experimental research of densification process then allow the engineering design of the production machine tailor-made to the customer, while being able to minimize investment, energy and operating costs. The developed design of screw press is unique in its modularity and high reliability.

Valorization of Vine Tendrils Resulted from Pruning as Densified Solid Biomass Fuel (Briquettes)

Concerns over the past few decades have focused, more than ever, on finding and implementing efficient, handy, and renewable sources to reduce pollution. Biomass, in general, and biomass from annual vine cuttings, are renewable sources that can be used by a large amount of the population. Biomass densification in the form of briquettes is an efficient method of obtaining a biofuel with the same characteristics as wood. The production of densified material as a briquette consists of sampling, drying naturally, chopping, grinding and briquetting the vine cuttings. The obtained results showed that the size of the briquettes met the requirements imposed by the standard, with a length between 185 mm and 400 mm and a diameter of 58 ± 0.75 mm, the humidity of the briquettes varying between 5.42%, at Sauvignon Blanc and 7.98% for Pinot Noir, while the durability of the briquettes registered minimum values of 98.17% for Muscat Ottonel and a maximum of 99.14% for Feteasca Neagra, and a unit density with values between 1227 kg/m3 for Feteasca Alba and 1389 kg/m3 for Pinot Noir. The conclusions of these experiments are promising, showing that the densification of biomass from vines cuttings qualifies within the standard requirements for obtaining a valuable biofuel.

A Method of Adding Binder by High-Pressure Spraying to Improve the Biomass Densification

In order to cut down the usage amount of binder, mix it more evenly with the biomass raw materials and improve the quality of pellets in the densification process, this study explored the feasibility of promoting the densification of biomass by using a high-pressure spraying method to add liquid binder. In the study, a high-pressure sprayer was used to spray saturated brown sugar water into sawdust for densification tests. A three-factor orthogonal experiment was designed to analyze the physical characteristics of the pellets under different variables. Through analysis of range and multiple linear regression, the effect curve was drawn to analyze the impact of the high-pressure spraying method on densification. The results showed that under low compaction pressure of 14.9 MPa, the raw materials with adding 6% saturated brown sugar water can be densified into pellets, while the raw materials without binder cannot. Moreover, compared with the method of adding binder by stirring, the high-pressure spraying method obtained the pellets with fewer cracks on the surface and increased the relaxation density of pellets by 8.65%. Under high compaction pressure (75, 100, 124 and 149 MPa), the high-pressure spraying method has a significant effect on increasing the relaxation density, not only on the compressive strength.

Research on the mechanical behavior of the biomass densification process based on a thick-walled cylinder

The mechanical behavior of the biomass densification process has noticeable influences on energy consumption and pellet quality. In the authors’ previous work, a method was proposed to determine the inner pressure by testing the circumferential strain of the outer die wall. Based on this method, a device was developed with strain gauges in the form of a single pellet unit. With this device, experiments were conducted with wood shavings, rice straw, and wheat straw under different levels of particle size, compression rate, and moisture content. The effects of these factors on the inner pressure were analyzed. The relationships among the inner pressure, pellet density, and specific energy consumption were obtained. Results showed that the pressure ratio increased linearly and then decreased and became constant during the relaxation period. The pressure change during the relaxation period was isotropic. The results could provide mechanical explanations for the phenomena in biomass densification processes.