## Mechanical process engineering

Process engineering is the engineering science of material transformation.

Mechanical process engineering involves the changes in material properties (e.g. particle size), and composition (concentration), due to mechanical effects.

Classification is a mechanical separation method for solid compounds. It utilises either, the geometric features (size) or the settling velocities of the individual particles for the separation process.

Sorting is a mechanical separation process in which a solid compound containing different material characteristics is divided into fractions with the same material characteristics.

Zigzag sifter to separate solid compounds

##### Learning objectives/experiments

- learning the fundamental principle of wind sifting (gas flow classification)
- sorting
- coarse material fraction
- fine material fraction

- dependent on solid mass flow rate and volumetric air flow rate

….

Sorting with a drum-type magnetic separator

##### Learning objectives/experiments

- learning the fundamental principle and the method of operation of a drum-type magnetic separator
- efficiency of separation process dependent on
- mass flow of feed material
- mixing ratio of feed material
- type of feed material

….

Mechanical process engineering in many cases utilises gravity to separate different phases. Gravity can be used to separate a solid phase off from a fluid.

Separation of suspensions

##### Learning objectives/experiments

- determination and comparison of the settling velocities of solids in suspensions dependent on the solid density and concentration and the liquid density and viscosity
- influence of coagulants on the settling velocity

Solid/liquid separation in a sedimentation tank, visualisation of flow conditions

##### Learning objectives/experiments

- basic principle for the separation of solids from suspensions in a sedimentation tank
- determine the hydraulic loading rate
- influence of the following parameters on the separation process:
- concentration of solids
- flow rate

….

Removal of solids from raw water using dissolved air flotation

##### Learning objectives/experiments

- functional principle of dissolved air flotation
- creation of a stable operating state
- effects of various parameters
- coagulant concentration
- flocculant concentration

….

As well as gravity, centrifugal force can also be used as the driving force for phase separation processes. The centrifugal force can be generated either by guiding the flow of the fluid, or by rotating vessels (centrifuges).

Continuous separation of emulsions

##### Learning objectives/experiments

- production of stable emulsions with different types of stirrer
- learning the fundamental principle of disc centrifuges
- influence of rotation speed and feed flow rate on separation result
- characteristic of concentration of the light phase in the stirred tank over time (with photometer)
- startup/shutdown and operation of a disc centrifuge

….

Solid separation from gases using a cyclone

##### Learning objectives/experiments

- influence of solid content and volumetric air flow rate on
- pressure loss at the cyclone
- separation efficiency
- separation function and separation size (with suitable analysis device)

- comparison of pressure loss and separation efficiency with theoretically calculated values

Separation of solids from liquids by using a centrifugal force

##### Learning objectives/experiments

- fundamental principle and the method of operation of a hydrocyclone
- solid mass flow rate in feed, overflow and underflow
- liquid mass flow rate in feed, overflow and underflow
- characteristic values for sharpness of separation
- pressure loss at the cyclone dependent on the feed flow rate

….

During filtration, solid particles are separated off by a filter medium from a flowing suspension. Suspensions contain insoluble solids finely distributed in a liquid. Usable filter media are sieves, cloths, papers or bulk solids.

Fundamentals of filtration: Darcy’s equation

##### Learning objectives/experiments

- fundamentals of filtration: Darcy’s equation
- depth filtration with different bulk solids and suspensions
- cake filtration with different suspensions
- identification of characteristic filtration values

Investigation of the properties of fixed and fluidised beds subjected to liquid flow

##### Learning objectives/experiments

- learning the fundamentals of flow through fixed beds and fluidised beds (Darcy)
- observation of the fluidisation process
- pressure loss dependent on the flow rate, type, particle size and height of the bulk solid
- determination of the fluidisation velocity and comparison with theoretically calculated values
- verification of Carman-Kozeny equation

Discontinuous cake filtration for separating solids out of suspensions

##### Learning objectives/experiments

- learning the fundamental principle and method of operation of a plate and frame filter press
- production of a suspension
- removal of the filter cake
- insertion of the filter cloth
- fundamentals of cake filtration

….

Continuous cake filtration for separating solids from suspensions

##### Learning objectives/experiments

- learning the basic principle and method of operation of a drum cell filter
- fundamentals of cake filtration
- variation in time of filtrate quantity, filter cake mass and thickness
- filter cake mass and thickness dependent on filtrate quantity, negative pressure and drum speed

Discontinuous cake filtration by negative pressure

##### Learning objectives/experiments

- basic principle and method of operation of a Nutsche vacuum filter
- fundamentals of cake filtration: Darcy’s equation
- mass and thickness of filter cake dependent on filtrate quantity

Discontinuous cake filtration by positive pressure

##### Learning objectives/experiments

- basic principle and method of operation of a Nutsche pressure filter
- fundamentals of cake filtration: Darcy’s equation
- mass and thickness of filter cake dependent on filtrate quantity

Filtration and backwash

##### Learning objectives/experiments

- pressure conditions in a filter
- factors influencing the pressure loss (Darcy’s law)
- flow rate
- height of the filter bed
- permeability of the filter bed

….

Comminution alters the particle size and shape and the surfaces of solids. Virtually all solids must be comminuted when being mined or processed.

Observation of the milling process: comminution of solids

##### Learning objectives/experiments

- cascade and cataract motion, critical speed
- theoretical and actual power demand
- degree of comminution dependent on milling time, rotation speed, ball diameter, ball filling, material to be milled

Mixing is the opposite of separating. The materials being mixed may be gaseous, liquid or solid.

Agglomeration is the opposite of comminution. The terms agglomeration, granulation and pelletisation designate the process of particle size enlargement of solids.

Visualization of flow fields when using various stirrer types

##### Learning objectives/experiments

- flow fields of various stirrer types
- power demand, mixing time, mix quality dependent on
- stirrer type
- speed
- materials used (density, viscosity)

….

Dish granulator with adjustable speed and angle of inclination

##### Learning objectives/experiments

- learning the basic principle and method of operation of an agglomeration unit
- agglomerate size and strength dependent on
- mass flow of solid feed material
- flow rate of liquid
- ratio of solid to liquid

….

The term “bulk solids” generally refers to materials in the form of collections of single or individual particles.

Influence of wall material and inclination of hopper walls on flow profile and outflow time

##### Learning objectives/experiments

- how wall material and inclination of the hopper walls affect the outflow time
- demonstrate typical discharge types in silos:
- mass flow
- funnel flow
- arching

….

Using a ring shear tester to record the shear force characteristics of bulk solids; basic principle of silo design

##### Learning objectives/experiments

- recording the shear force characteristics of bulk solids
- yield locus and wall yield locus design
- determination of flow properties
- compressive strength
- internal friction

….

A fluidised bed involves two phases: a solid and a fluid (gas or liquid).

Pneumatic conveyor systems transport powderous and granular bulk solids by means of a gas flow (mostly air) in pipelines.

Investigation of fluidised bed formation of solids in air and water

##### Learning objectives/experiments

- fundamentals of the fluidisation of bulk solids
- observation and comparison of the fluidisation process in water and air
- pressure loss dependent on flow velocity
- pressure loss dependent on the type and particle size of the bulk solid
- determination of the fluidisation velocity and comparison with theoretically calculated values (Ergun equation)

….

Pneumatic pressure-lifting of solids in a vertical transparent tube

##### Learning objectives/experiments

- learning the fundamental principle and method of operation of a pneumatic conveyor system
- observation of different transport states dependent on solid content and air velocity
- determination of the suspension velocity of the solid
- determination of the solid content of the flow
- pressure loss dependent on solid content and air velocity