Breakthrough (adsorption)

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The breakthrough is a characteristic of adsorption . This denotes the increase in concentration of a selected component on the downstream side of an adsorber over an arbitrarily selected variable. The breakthrough behavior under various boundary conditions is described using breakthrough curves. These describe the course of the concentration of an adsorptive at the outlet of an adsorber plotted over time. Breakthrough curves can be symmetrical as well as asymmetrical.

Importance of the breakthrough

During the adsorptive separation of components of a fluid, individual molecules are attached to an adsorbent . In the case of spatially rigid adsorbers, such as fixed-bed adsorbers, it can then be observed that the loading of the adsorbent in the adsorber does not increase uniformly, but is highest in the inlet area of ​​the flow and decreases in the course of the adsorber. The adsorption capacity of the adsorbent also depends on the concentration of the adsorbent, i.e. the component to be deposited, so that the concentration of the adsorbent is in equilibrium with the adsorbent load. A breakthrough is used when the concentration of the component to be separated at the adsorber outlet exceeds an arbitrarily selected concentration.

The breakthrough is significant in areas such as exhaust gas purification , gas analysis and the purification of vehicle interior air. He is influenced by

  • the flow rate of the gas,
  • the respective heat and mass transfer coefficients,
  • the diffusion in the adsorbent,
  • the behavior of the sorption isotherm and
  • the heat of adsorption released.

Related and derived quantities

Breakthrough and degree of separation complement each other one hundred percent.

The breakthrough time is the period in which the concentration of the compound being investigated in the gas exiting the adsorber reaches a certain percentage of the concentration of the compound at the adsorber inlet. The breakthrough volume is the product of the gas volume flow and the breakthrough time.

literature

  • VDI 3674: 2013-04 Exhaust gas cleaning through adsorption; Process gas and waste gas cleaning (Waste gas cleaning by adsorption; Process gas and waste gas cleaning). Beuth Verlag, Berlin. ( Summary and table of contents online ).

Individual evidence

  1. ↑ a b Uta Sager, Eckhard Däuber, Christof Asbach, Dieter Bathen, Frank Schmidt, Claudia Weidenthaler, Jo-Chi Tseng, Wolfgang Schmidt: differences in the adsorption of NO 2 and NO on Modified Activated Carbon. In: Hazardous substances - cleanliness. Air . 74, No. 5, 2014, ISSN  0949-8036 , pp. 181-184.
  2. ↑ a b Werner Kast: Adsorption from the gas phase - engineering principles and technical processes. VCH, Weinheim 1988, ISBN 3-527-26719-0 , pp. 141-179.
  3. ↑ VDI 3674: 2013-04 Exhaust gas cleaning through adsorption; Process gas and waste gas cleaning (Waste gas cleaning by adsorption; Process gas and waste gas cleaning). Beuth Verlag, Berlin, p. 13.
  4. ↑ Harald Jüntgen: Basics of Adsorption . In: Dust - cleanliness. Air . 36, No. 7, 1976, ISSN  0949-8036 , pp. 281-288.
  5. ↑ VDI 3481 sheet 2: 1998-09 measurement of gaseous emissions; Determination of the organically bound carbon in exhaust gases that can be detected by adsorption on silica gel (Gaseous emission measurement; Determination of gaseous organic carbon in waste gases; Adsorption on silica gel). Beuth Verlag, Berlin, p. 5.
  6. ↑ VDI 2083 sheet 8.1: 2014-10 clean room technology; Air cleanliness chemical concentration (ACC) (Cleanroom technology; Air cleanliness chemical concentration (ACC)). Beuth Verlag, Berlin, p. 7.
  7. ↑ DIN ISO 16000-23: 2019-03 Indoor air pollution - Part 23: Performance test for assessing the reduction in the concentration of formaldehyde and other carbonyl compounds through sorbent building materials (ISO 16000-23: 2018). Beuth Verlag, Berlin, p. 9.
  8. ↑ VDI 2100 sheet 3: 2011-10 Measurement of gaseous compounds in the outside air; Measuring indoor air pollution; Gas chromatographic determination of organic compounds; Active sampling through enrichment on adsorbents; Thermal desorption (Determination of gaseous compounds in ambient air; Determination of indoor air pollutants; Gas chromatographic determination of organic compounds; Active sampling by accumulation on adsorbents; Thermal desorption). Beuth Verlag, Berlin, p. 11.