Chemistry: molecular biology and microbiology – Process of utilizing an enzyme or micro-organism to destroy... – Petroleum oil or shale oil treating
Patent
1996-03-15
1997-11-25
Beisner, William H.
Chemistry: molecular biology and microbiology
Process of utilizing an enzyme or micro-organism to destroy...
Petroleum oil or shale oil treating
435266, 4352991, C12M 114, C12S 500
Patent
active
056911920
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a biological filter for the removal of volatile, hydrophobic compounds from gas emissions, whereby the gas emission is passed through the filter, in which those compounds are broken down with the aid of a fungus (fungi) which is (are) present on a bearer material.
BACKGROUND OF THE INVENTION
In industrial gas emissions such compounds often occur; they are polluting for the environment and are not permitted on the grounds of national environmental laws, or are only permitted in very limited quantities. They must therefore be removed from the gas emission and broken down. For example, the toxic styrene occurs in concentrations of up to approximately 1 gr/m.sup.3 in gas emissions of factories which manufacture (poly)styrene and reinforced plastic.
A known technique for catching and breaking down such compounds is with the aid of biological filters, filled with compost. Micro-organisms are present on the compost particles, which achieve the desired breakdown.
It turns out that such compost filters only work with a pH of between 5 and 9 and in the event of a high water capacity, corresponding with a water content of 40 to 60%. Further the demands were made of the filters that the drop in pressure across the filter is slight, that the gas is distributed homogeneously across the filter, whereby there is no case of channel-forming, and that the bearer material for the micro-organisms holds water well and absorbs the volatile compounds.
Problems in the use of the compost filters are, that during use the pH and the water capacity/the water content must be continuously checked and kept at the right level. Furthermore, it appears that the filter is unstable when used for the said hydrophobic compounds: it only works during a relatively short time--several weeks. And the mass transport of the gas to the water phase is small, so that the filter has a low volumetric elimination capacity.
A solution could be to achieve the breaking down of the compounds especially with the aid of fungi which break down those compounds. For example, in the case of the breaking down of styrene, with the aid of "Exophiala jeanselmei" as described in Appl. Microbiol. Biotechnol (1993) 39:372-376. Such fungi also work at a relatively low pH, for example pH=3, and with a relatively low water capacity. Furthermore, the active surface of the fungi mycelia in the gas phase is large and, as a result of the fact that a low water content is possible, the mass transport of the hydrophobic compounds can be higher. The fungi can be cultivated, for example, on compost; see, for example, the patent publication DE 3807033.
However, it appears that on the grounds of further essential qualities for such a filter (the pressure drop across the filter, the homogeneity of the distribution of the gas across the filter, the capacity to hold water to a sufficient degree and the absorption effect) such a filter also only works sufficiently during a very limited time.
SUMMARY OF THE INVENTION
The latter is solved according to the invention by choosing a bearer material which consists of particles of an inert, inorganic or an organic material, which holds water well. Especially good representatives of such materials are: perlite and vermiculite.
The use of perlite in order to cultivate micro-organisms is as such known from the Japanese patent publication J 61141917--however, not in a filter and in combination with a fungus as referred to here.
DETAILED DESCRIPTION OF THE INVENTION
With a filter according to the invention, in which perlite acted as the bearer material, the following results were achieved when removing styrene from a gas emission: the gas emission contained 800 mg styrene/m.sup.3. A quantity of 120 m.sup.3 per m.sup.3 filter per hour was passed for 70 days through the filter, which was moistened regularly and whose pH had dropped to 3 after 15 days, and this value remained during the rest of the time. The elimination capacity amounted to 80 gr. styrene per m.sup.3 filter per hour. This is 1.5 tim
REFERENCES:
patent: 3216905 (1965-11-01), Baptist
patent: 4734111 (1988-03-01), Hoffmann et al.
patent: 4806148 (1989-02-01), Ottengraf
Cox et al. "Growth of the black yeast Exophiala jeanselmei on styrene and styrene-related compounds." Applied Microbiology and Biotechnology. vol. 39 (Jun. 1993), pp. 372-376.
Cox et al. "Enrichment of Fungi and Degradation of Styrene in Biofilters." Biotechnology Letters. vol. 15 (Jul. 1993), pp. 737-742.
Cox Hubertus Henricus Jacobus
Doddema Harmannus Johannes
Beisner William H.
Nederlandse Organisatie voor Toegepast Natuurwetenschappelijk On
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