Overview of Nauta Mixer^® and Introduction of Topics

Abstract

Introduction: The Nauta Mixer^® is a powder mixer developed in the 1940s in the Netherlands for mixing animal feed. The machine consists of a conical body with a mixing screw attached to a rotating arm. The Nauta Mixer has several favorable attributes, such as mixing swiftly with low energy consumption, minimal damage to the powder particles, ease of discharge with a low amount of residue, and ease of cleaning, making use of multiple products easier. The mixer has been widely adopted worldwide, with over 20,000 units sold across various industries.

Nauta Mixer^® principle and design: The Nauta Mixer utilizes the principle of convective mixing, where the powder undergoes upward, downward, and spiral motions within the casing due to the rotation of the screw. The mixer design follows a geometric similarity, with the casing angle remaining constant across different capacities, while only the height varies. As the capacity increases, the screw length also increases proportionally. This design approach ensures consistent mixing performance across different mixer sizes.

Nauta Mixer^® types and features: The Nauta Mixer is available in three main types: NX, DBX, and VN. The VN type, introduced in 1997, features a compact and sanitary design with improved drive-unit integration. Compared with the DBX type, the VN type offers a smaller footprint and improved cleanability while maintaining mixing performance.

Case study: low-floor VN mixer: A case study is presented where a low-floor 5000-L VN Mixer was replaced a horizontal mixer, addressing issues such as poor powder discharge and blocking by powder. The low-floor design was achieved by cutting the bottom section while ensuring adequate mixing performance through design modifications.

Research on mixing time: Research on estimating the mixing time for the Nauta Mixer is discussed, highlighting the correlation between mixing time and various parameters, such as screw diameter, length, rotational speed, and Froude number. While empirical equations show good agreement for smaller capacities, deviations are observed for larger mixers, likely due to more active convective mixing at higher powder levels.

Conclusions: The Nauta Mixer provides efficient convective mixing with minimal shear and temperature rise, making it suitable for various applications. Hosokawa Micron continues to innovate and provide tailored solutions to meet a variety of customer requirements and applications.