Sampling and sub-sampling of granular waste: size of a representative sample in terms of number of particles

This paper elucidates the theoretical principles behind the calculation of the size of a representative sample of granular solid waste. The key concept is the number of particles that must be present in a sub-portion of matter to be representative of a larger portion of matter. This depends on the fraction of particles in the waste batch showing the properties of interest, which shall be measured. A representative sample must include a fraction of particles of interest reliably similar to that of the waste batch to be characterized, with a controlled variability. In this context, it is demonstrated that the number of particles of interest that must be collected in a representative sample is 100. From this requirement, the mass of a representative sample can be calculated based on the knowledge of the frequency of particles of interest of the waste lot to be characterized. Data on particles concentrations in different samples of WEEE plastic scraps exemplifies how the presence in the sample of enough rare particles showing the property of interest is key to ensure reliable measurements. Further, the assumptions made on the controlled degree of variability to determine the minimum number of particles are discussed based on data on achievable intra- and inter-laboratory variability of analytical standards for waste characterization. Accordingly, the mass of laboratory samples and test portions recommended in published sampling plans or analytical standards are assessed for the occurring number of particles.

Use of Taguchi Methods for Hierarchy of Influence Factors in the Application of Carbonitration in a Fluidized Bed Steel for 41Cr4 Steel

The work is based on carbonitriding in a fluidized layer with methane and ammonia gas applied to 41Cr4 steel samples. To achieve the best possible results, other factors must be taken into account, than those specific to carbonitring. It was necessary to use a partially factorial working procedure due to the increase in the number of factors. An A18 matrix has been used, with 18 lines of experiments in which three levels have been modified for 6 factors. The objective function was fixed at the final hardness after carbonitriding, hardening and tempering. The carbonitriding was performed in fluidized bed with granular solid ground and sorted to 0.1- to 0.16mm, and brought to fluidization with a mixture of methane and ammonia. The hardening has been done directly after carbonitriding in the fluidized bed. The experiments have been performed according to Taguchi Methods and the results indicate an optimal regime and the influence of the factors considered on the hardness after the thermo-chemical treatment and the thermal treatment. Metallographic analysis has been performed on the carbonitrided layer.

ROCKET ENGINE ON GRANULAR SOLID FUEL

The paper is devoted to the development of a rocket engine on granular solid fuel (REGSF). The paper shows the main advantages and disadvantages of widely used propulsion systems (such as a solid-propellant rocket engine, liquid-propellant rocket engine, gas turbine engine). The proposed hybrid power plant borrows the strengths of well-known engines, such as the ability to control thrust in a wide range, multiple on and off, the ability to work in high temperatures and low oxygen content. The fuel in a REGSF is granules, the constituent components of which are both oxidizing agent and combustible. Possible propulsion systems based on REGSF, applicable for different types of tasks (can be used both for spacecraft and for ground unmanned aerial vehicles used at different altitudes with different flight speeds), are proposed and considered. As a prototype of the granular solid fuel supply system (GSFSS) the powder metal fuels supply system (PMFSS) is chosen. The flow rate and speed characteristics of the GSFSS are similar to the same characteristics of the PMFSS, they are also presented in this paper. Based on the available data on the supply system for powdered metal fuels and powdered aluminum (which is used as a fuel in a similar propulsion power plant), the requirements that granular fuel must satisfy in order to efficiently feed and ignite it are formulated and given. Requirements: dry, hydrophobic material, which must have high flowability, have a dispersion in the specified range, the type of particles must be spherical.

A heavy intruder in a locally-shaken granular solid

We experimentally investigate the gravitational-driven motion of a heavy object inside a vertical 2D assembly of identical, plastic cylinders arranged in a regular, triangular lattice.

An Energetic Model for Detonation of Granulated Solid Propellants

Unexpected detonation of granular solid energetic materials is a key safety issue in the propellants manufacturing industry. In this work, a model developed for the characterization of the early stages of the detonation process of granular solid energetic materials is presented. The model relies on a two-phase approach which considers the conservation equations of mass, momentum, and energy and constitutive relations for mass generation, gas-solid particle interaction, interphase heat transfer, and particle-particle stress. The work considers an extension of approximated Riemann solvers and Total Variation Diminishing (TVD) schemes to the solid phase for the numerical integration of the problem. The results obtained with this model show a good agreement with data available in the literature and confirm the potential of the numerical schemes applied to this type of model. The results also permit to assess the effectiveness of different numerical schemes to predict the early stages of this transient combustion process.