Leszek Czepirski

Fitting of different models for water vapour sorption on potato starch granules

Abstract Water vapour adsorption isotherms for native and modified potato starch were investigated. To obtain the best fit for the experimental data several models based on the BET approach were evaluated. The hypothesis that water is adsorbed on the starch granules at the primary and secondary adsorption sites as well as a concept considering the adsorbent fractality were also tested. It was found, that the equilibrium adsorption points in the examined range of relative humidity (0.03–0.90) were most accurately predicted by using a three-parameter model proposed by Kats and Kutarov.

Adsorption Characteristics of Powders of Nanometric Gallium Nitride and Aluminium Nitride

The results of studies on new precursors for the preparation of gallium nitride and aluminium nitride were presented. The samples obtained were characterised by argon adsorption at 77 K. The variation of the porous structure parameters with the pyrolysis temperature was discussed. The adsorption of water vapour and the selectivity of adsorption with respect to some gases at 298 K were also investigated.

Improvement of Methane Storage Capacity for Active Carbons

A method for increasing storage capacity by working of the commercial active carbons in a spouted bed is proposed. By abrasion of external layers of grain active carbons with better adsorptive properties, smaller voids of bed and improved attrition strength was obtained. Investigations of methane storage capacity for active carbon NORIT R2 with different degrees of external layers removed, were carried out. Experiments indicate that methane storage capacity can be increased up to 15–20% over commercial carbon.

Improvement of Commercial Active Carbon for Use in an Adsorption Cooling System

Of the various gas/solid adsorption processes, the adsorption of methanol on active carbon seems to be most interesting for use in thermodynamic systems such as heat pumps and transformers, as well as in cooling systems. The porous structures of two series of active carbons modified by the successive removal of the external layers from the particle surface, one by abrasion in a spouted bed and the other by subsequent demineralization of the abraded particles, were evaluated on the basis of nitrogen and methanol adsorption data. The porous structure parameters for these two sorbate series agreed reasonably well and allowed the D–R approach to be usefully applied for the characterization of these systems. The methods for calculating the heat effects associated with methanol adsorption over wide ranges of temperature and pressure are discussed.

Optimization of Adsorptive Storage Systems for Natural Gas

It is concluded from experimental data that is is possible to increase the storage density of natural gas in active carbon — containing storage systems. Adsorptional and densimetric characteristics determine the usability of active carbons for adsorption storage. Useful parameters for the most favourable sorbent and the methods of storage capacity improvement are proposed. Model for estimation of oprating parameters in non-isothermal conditions is developed.

Adsorption of Water Vapours in Natural and Modified Zeolites

Abstract The adsorption equilibria as well as kinetics of adsorption of water vapours in temperature range 323 - 473K and relative pressures range 0.00025 - 0.33 were studied for natural zeolites-formed with organic binder. Temperature and pressure dependence of diffusivities was analysed. System of secondary (transport) pores is a factor limiting the rate of adsorption process. The diffusion for systems under study is a thermally activated process.