Powder flow criteria for design of vertical silo walls

Corrêa

et al. 2022

Braz. J. Food Technol.

Flowability of agricultural products is an important factor to be considered at post-harvest, thus impacting directly on number of operations and the design of machinery. This study aimed to evaluate and determine the K coefficient and flow properties as a function of different levels of roasting, grain size, temperature and storage. Coffee beans were roasted at medium light and moderately dark, then ground at fine, medium and coarse sizes. An additional coffee lot was not ground. Samples were stored at 10 ºC and 30 ºC and analyzed during storage (0, 30, 60, 120 and 180 days), regarding internal and external friction coefficients, angle of internal friction, effective angle of internal friction, wall friction angle (concrete, rough steel and wood) and lateral pressure coefficient (K coefficient). Angle of internal friction varied significantly due to particle size and roast degree. Moderately dark roast with fine particle size led to higher values (about 29.5 º) of wall friction angle. The wood sample was the material with the highest values of wall friction angle, followed by the concrete and steel samples, when compared at the same storage temperature, roast degree and particle size. Whole coffee was classified as free-flowing. Fine particle size leads to cohesive flow characteristic, according to the flow function. Coffee roasted at medium light, kept whole requires storage facilities with higher pressure support, accordingly to the K coefficient values.

Section: Introductionmentioning

confidence: 99%

Arabica coffee flow properties assessed using different roasts and particle sizes during storage

Corrêa

et al. 2022

Braz. J. Food Technol.

Mechanical properties of grain in silos for simulation designs

et al. 2016

Self Cite

For the calculation of silos structures it has been used new methods and computational tools that require mechanical properties knowledge that are still unknown for most storable materials, especially grains. In this context, we aimed to determine the mechanical properties of rice and beans grains with moisture contents of 10, 12, and 14% by applying four compressive loads (5, 10, 15 and 20). The determined mechanical properties were Poisson's ratio (ν), Modulus of Elasticity (E), and the dilatancy angle (ψ). The procedure consisted in the application of the load in compression cell, adapted from MOLENDA & STASIAK, aiming to simulate loading and unloading of silos. We observed that the Poisson's ratio calculated for both loading and unloading, presented higher values than the experimental values, with the increase of their moisture content; the experimental elastic modulus presented higher values than the calculated ones, and both increased their values with the increase of their moisture content; the dilatancy angle decreased with the increase of moisture content and compressive loads.

Flow Properties and Pattern Flow Prediction of Food Industrial Powders

2017

Self Cite

More and more industries are faced with new products that need to be stored in silos which, in general, require knowledge of their physical properties and, above all, flow. Food industries are among those using powders as raw materials likely to develop functional problems. Thus, the aim of the present study was to investigate the flow properties of six food powders using equipment called Powder Flow Tester, and the results were compared with those recommended by the Eurocode 1 Part 4 international standard. Wide range of variation in the flow properties responses was observed, suggesting that their expression through a single average value may not be suitable for vertical silos. It was concluded that only the bulk density of products is in accordance with the standard. In relation to flow, only flaked corn is able to flow without possibility of obstruction in the discharge with higher discharge outlet dimensions, being also recommended for flaked oat.