Granutools - Model GranuCharge -Granular Material Electric Charge Analyzer

Electrostatic charges appear in powders during a flow. The apparition of these electrostatic charges is due to the triboelectric effect, which is a charge exchange at the contact between two solids. During the flow of a powder inside a device (mixer, silo, conveyor, ...), the triboelectric effect takes place at the contact between the grains and at the contact between the grains and the device. Therefore, the characteristics of the powder and the nature of the material used to build the device are important parameters.

Unfortunately, the triboelectric effect is still poorly understood, even at the fundamental level, and most instruments that claim to measure electrostatics do it indirectly. Therefore, the approach to solving practical problems due to electrostatic is mostly empirical. Moreover, reproducible electrostatic measurements are difficult to perform.

The GranuCharge was developed to fill that gap in powder characterization instruments by measuring the electric charge density of a sample with a customized Faraday cup. 

GranuCharge measures automatically and precisely the quantity of electrostatic charges created in a powder during a flow in contact with a certain material. The powder sample flows inside a vibrating V-tube and falls into a Faraday cup connected to an electrometer. The electrometer measures the charge acquired by the powder during the flow inside the V-tube. To obtain reproducible results, a rotating or a vibrating feeder is used to feed the V-tube regularly.

The V-tube geometry has been selected to combine the different mechanisms leading to triboelectrification:

• friction between the grains
• friction between the grains and the wall
• impact of the grains on the wall at the connection between the two tubes.

Therefore, the V-tube charges the powder more in comparison to a single tube geometry and reproduces more accurately industrial processes.

• High precision (0.05 nC).
• High repeatability.
• Fast measurement: less than 5 minutes.
• Allows the determination of charge densities (in nC/g) of powders before and after a flow.
• Software-assisted measurement, for easy interpretation and comparison of results. Software uses secured user profiles, and allows for a fast and complete export of all
  data for reporting and post processing.
• Standard operating procedures (SOP) for high repeatability.
• Possibility to control the environmental conditions (humidity and gas).
• Designed to maximize uptime: modules can be swapped to avoid extensive diagnostics.
• Able to handle powders of various dimensions.
• Easy-to-clean parts.

• Design and principle fully patented and unique.
• Only instrument able to measure charge build-up after flow through pipes of different materials.
• Initialization protocol with automated feeders (vibrating tray or rotating beaker).
• Measurements of the charge density evolution through time.
• Vibrating feeder to allow the measurement of highly cohesive powders.
• Uniquely designed faraday cup easy to plug that allows fast measurements.
• Pipes and operators are grounded.
• Closed system for safety requirements

The GranuCharge is compatible with a large range of powders and used in many applications:

• Troubleshooting of processes where increases of cohesiveness are observed over time.
• Continuous Manufacturing: predictive test for supplies and formulations before filling the production line.
• Mimic electrostatic behavior of powder in mixers, silos, or conveyor systems.
• Additive Manufacturing and metallurgy: measurement of powder propensity to charge directly related to the particle surface properties. Ability to monitor powder performances with recycling and aging.
• Quantifying the effect of anti-static agents by allowing to measure the exact impact of the anti-static agent on the chargeability of the mix.
• Optimization of virgin/used blends.
• Selection of optimal tube materials combination.