Oxford Dictionary of Chemical Engineering by Schaschke Flashcards
Another name for the *Weizmann process used for the production of acetone, butanol, and ethanol using the acid-resistant bacterium Clostridium acetobutylicum.
ABE fermentation
The removal of material by * erosion , * evaporation , or * chemical reaction . For short-term protection against high temperatures as a form of fire protection or fireproofing of process equipment, sacrificial materials are used such that during a fire there is resistance and protection to the equipment beneath for a sufficient period of time
ablation
The horizontal or x-coordinate in a two-dimensional Cartesian coordinate system such as a chart or graph. The * ordinate is the vertical or y-coordinate.
abscissa
Denoting a number or a measurement that does not rely on a standard reference value.
absolute
The mass per unit volume of a substance. It is the density of the actual substance and does not include any free space that may be between particles. The SI units are kg m –3 .
absolute density
The difference between a measured value and its true value.
absolute error
A type of filter used to remove all particles that may be present in the
flow of gas into or out of a process. Absolute filters are used for ensuring the sterile flow of
air or oxygen to biological reactors as well as for clean rooms and sterile cabinets used for
analytical work. Unlike an * air filter , the pore sizes are smaller than the expected particle
size. With a typical uniform pore size of 0.2 μm, the pressure drop is greater than that of air
filters made from fibrous materials.
absolute filter
The amount of water in air expressed as the mass of water vapour per unit mass of dry air for a particular temperature and pressure condition. The SI units are kg water kg air^–1
absolute humidity
The measurement of gas or air pressure relative to the pressure in a
total vacuum. In comparison, the * gauge pressure is measured above atmospheric pressure, which is variable.
absolute pressure
(Symbol ε) The roughness of a solid surface expressed as the average height of undulations and imperfections. It is measured using an instrument that draws stylus over the surface. The roughness of the inner surface of a pipe wall used to transport fluids with turbulent flow has the effect of increasing frictional pressure drop. Expressed as a ratio with internal pipe diameter, it is used in determining the friction factor of fluids flowing in pipes with turbulent flow. See relative roughness
absolute roughness
The lowest possible thermal energy state of a material. This corresponds to 0 K.
absolute zero
- A material that is capable of stopping ionizing radiation. * Alpha particles can be readily stopped by a sheet of paper whereas beta radiation can be resisted by a centimetre of aluminium. Gamma radiation is absorbed by materials with a high density, such as steel and concrete. Neutron absorbers include boron, hafnium, and cadmium and are used in the control rods in nuclear reactors.
- A shortened name for an * absorption tower
or column.
absorber
A mass transfer process in which one or more gases in a gaseous mixture is transferred into a liquid solvent or a solid. It is the most common form of separation of low molecular weight materials. Absorption is often used to remove gases from gas streams that may be harmful downstream or when released from the process. The absorption factor is used to determine the ease with which a component will absorb into the liquid phase and is based on liquid and vapour flow rates as well as the vapour liquid equilibrium for the component. For example, ammonia can be absorbed from a gas stream using water as the scrubbing liquid. Compare adsorption .
absorption
A tall vertical column containing a packing material in which a gas is absorbed by intimate contact with a liquid flowing downwards under the influence of gravity. The gas can be admitted either countercurrent or cocurrent to the flow of liquid in which one or more of the gaseous components are absorbed into the liquid. The minimum flow rate of scrubbing liquid required to achieve an absorption duty requires an infinite height of packing. In practice, a higher liquid rate is used to achieve a compromise between capital cost (i.e. height of column) and the operating cost (i.e. liquid flow rate). It is also known as a * scrubber.
absorption tower
The portion of radiant thermal energy falling on a surface which is converted to heat with the remainder being either reflected or transmitted. The absorptivity is dependent on the wavelength of the energy and the properties of the surface including colour. Compare reflectivity ; transmissivity .
absorptivity