Mixing apparatus and method for operating a mixing apparatus

A mixing apparatus for mixing a fluid and/or a solid, comprising:

• a mixing container comprising a container wall defining an interior and configured to contain the fluid and/or the solid;
• a feed-through passage_extending through the container wall;
• a stirring element arranged at least partly in the interior of the mixing container;
• a drive shaft extending through the feed-through passage and configured to drive the stirring element to mix the fluid and/or the solid contained in the mixing container, wherein the drive shaft comprises a drive-side shaft end configured to couple a drive arranged outside of the mixing container to the drive shaft;
• a radial shaft seal arranged in the feed-through passage and resting in a sealing manner against the drive shaft;
• a housing arranged at the feed-through passage and defining an interior, wherein the drive shaft is movably mounted in the interior of the housing;
• an adjustable seal that produces a first sealing effect with respect to the feed-through passage in a first sealing operation state and produces a second sealing effect with respect to the feed-through passage that differs from the first sealing effect in a second sealing operation state, wherein the adjustable seal annularly surrounds the drive shaft, and the housing annularly surrounds the adjustable seal;
• a setting apparatus that annularly surrounds the drive shaft for switching the adjustable seal between the first sealing operation state and the second sealing operation state;
• and
• a particle separator arranged in the feed-through passage,
• wherein the adjustable seal is arranged between the drive shaft and the housing,
• wherein the adjustable seal contacts the housing and extends radially from the housing to the drive shaft in the first sealing operation state,
• wherein the adjustable seal contacts the housing and extends radially from the housing to the setting apparatus in the second sealing operation state,
• wherein the adjustable seal contacts the housing and extends radially from the wherein the feed-through passage comprises a container-side feed-through end, and
• wherein the particle separator is arranged at the container-side feed-through end and provides a barrier against entry of abrasive particles into the interior of the mixing container resulting from rotational movement generated between the radial shaft seal and the drive shaft and contact of the abrasive particles with the fluid and/or the solid contained in the mixing container.