Production of leather under the influence of compressed carbon dioxide
Special Symposium - EPIC-1: European Process Intensification Conference - 1
EPIC-1: Intensified Plants & Process Integration (IPPI)
Keywords: tannery co2 high pressure chrome
The central focus of the leather producing industry is the transformation of untreated hides that may rot under wet conditions and are brittle under dry conditions into durable, imperishable leather by processes which incorporate tanning agents into the hides. The traditional processes comprise a multitude of different steps (up to 70) and are time-consuming and water intensive. A consumption of 20 to 40 t of wastewater per tonne of hides is typical. About 75% of the wastewater contain less critical compounds like salts and tensides, while 25% of the wastewater may contain metal cations and/or organic tanning agents.
In order to intensify the processes a new method of high-pressure-impregnation was developed. The impregnation steps are carried out in aqueous systems in the presence of pressurized carbon dioxide, which may be either in its liquid, gaseous or supercritical state. The processes are considerably accelerated. Tanning for instance is achieved already after a few hours if the process is operated at elevated pressure between 30 and 100 bar, while the traditional process may take some ten hours. Similar acceleration was found for other steps like washing, pickling or defattening of the treated hides. The water consumption can be reduced to about one fourth of the traditional method.
In the presentation, the process principle will be described and the acceleration is demonstrated for the tanning process. A quantitative analytical method for monitoring the tanning success via the ion content in the tanning liquid has been developed. On this account traditionally tanned hides were produced. With a comparable experimental approach, the time dependency of the ion content in the tanning liquid was measured when the tanning was performed in the presence of CO2. The Comparison of the measured dependencies does not only quantify the acceleration, but is also the basis for developing models to understand the beneficial role of CO2 in the process. First ideas on such physical models will be presented.
Presented Wednesday 19, 15:20 to 15:40, in session EPIC-1: Intensified Plants & Process Integration (IPPI).
