DD289286A5 - METHOD FOR MICROBIAL CONVERSION OF ORGANIC SULFUR COMPOUNDS OF CARBON-CONTAINING MATERIALS - Google Patents

Abstract

The invention relates to a process for the microbial conversion of organic sulfur compounds from carbonaceous materials, in particular lignite. It can be used for the primary treatment of fossil fuels to reduce SO2 emissions when using briquetted coal. The object is achieved by using a new mixed thermophilic culture in an aerobic cultivation process in the presence of the materials to be desulfurized. The process can be carried out under unprotected conditions with long-term microbial stability {desulphurization; conversion; Cultivation methods; Bacteria; Mixed culture; Brown coal; fuels; Microbiology; IMET 11335}

Description

Field of application of the invention

The invention relates to a microbial process for the removal of organic sulfur compounds from materials such as hard and brown coal and petroleum and corresponding waste products. It can be used for the primary treatment of fossil fuels to reduce SO ₂ emissions when using briquetted coal.

Characteristic of the known state of the art

Fossil fuels contain, in addition to inorganic sulfur compounds, ζ. Β. Pyrite, organic sulfur compounds of different types and concentrations. While for the former, the reduction by chemical or microbial primary treatment methods is described relatively extensively, this applies to the organic compounds in only a very small extent.

Some organic sulfur compounds, such as mercaptans, aliphatic sulfates, disulfides or thiophenes, are chemically degradable, but the economics required are far from economical. Especially with lignite, the proportion of organic compounds in the total amount of sulfur predominates; it is 50 to 80%. The removal or reduction of these groups of substances is particularly important from an ecological as well as a material technical point of view, and since the beginning of the 1980s first positive results in microbial conversion processes have been reported. Within the framework of experimental research, a large number of microorganism species were investigated for the property of converting organic sulfur compounds into ecologically harmless components. These include strains of Pseudomonas, Arthrobacter, Alcaligenes, Bacillus, Desulfovibrio, Thiobacillus, Flavobacterium, Aoinetobacter, Sulfolobus, and others. Some of these microorganisms have the ability to decompose organic sulfur compounds. However, the number of specialized and patent publications in this field is very small. KOPAC (US 4,632,906) describes a process for reducing the sulfur content of carbonaceous materials such as coal and liquid hydrocarbons using Bacillus sulfasportare (ATCC 39909). The microbial treatment is carried out at 30 ° C to form sulfates.

The use of a mutant of Pseudomonas sp. (ATCC 39381) for removing organic sulfur from carbon suspensions is claimed by ISBISTER in US 4,562,156 (corresponding to EP 218734). The new mutant was obtained by adaptation of natural microorganisms to dibenzothiphene (DBT), selection for DBT oxidation and chemical mutagenesis of the selectants to increase the oxidation performance. The process is carried out under mesophilic conditions; Above 41 ⁰ C no microorganism growth takes place. For this purpose, it is contained in the most recent specialist literature that this Pseudomonas mutant is no longer available in the patent applicants' laboratories (JJ Kilbane, Tibtech, April 1989 Vol 7, with reference to Reed, L [1988], in: Proceedings of the 4th Department of Energy Preparation, Utilization and Environmental Control Contraetors Conference, DOE, Pittsburgh Energy Center, Pittsburgh, PA 15236 USA).

US 4,659,670 to STEVENS describes a process for microwave coal desulfurization using a mixed culture (ATCC 39327), which also operates in the mesophilic range. The mixed culture is composed of representatives of Pseudomonas, Acinetobacter, Azotobacter and Flavobacteria.

The described methods are all carried out in the mesophilic temperature range and contamination by foreign organisms is to be expected if unprotected conditions exist. Due to the exothermic reaction process also incur not inconsiderable cooling costs to maintain the necessary temperature regime.

Object of the invention

The object of the invention is to provide a microwave method for reducing organic sulfur compounds, in particular from brown coal, which can be realized under microbiological long-term stability.

Essence of the invention

The invention is based on the object bacteria with activity for the oxidation of organic sulfur compounds

select which can be used under unprotected conditions.

According to the invention the task by using bacteria of the new thermophilic mixed culture IMET is dissolved in an aerobic culture method 11335, which is carried out in the temperature range of 50 to 7O ⁰ C and in the pH range of 4 to 8 by the presence of the sulfur-containing materials. Particularly advantageous cultivation conditions are at 60 ° C and a pH of about 6.5 before.

The new thermophilic, aerobic, heterotrophic bacteria mix culture was deposited in the IMET culture collection for microorganisms of the Central Institute for Microbiology and Experimental Therapy Jena. It represents an enrichment culture, which under the conditions of cultivating conditions from Wostelbischer brown coal with the addition of dibenzothiophene

was won after 30 days.

The mixed culture can be characterized in the following way:

On peptone agar, colonies of 2-10 mm diameter are obtained after 16 hours with the following properties:

- no pigmentation

- cream colored

- smooth, shiny surface with increased mucus formation

- irregular, consistency not homogeneous

The mixed culture consists of three main components which can be distinguished as follows:

Component I: pleomorphic, slightly gram-negative, rod-shaped, inhomogeneous structure, size 0.3 ... 0.5 χ 2.3 ... 6.6 pm

Component II: Gram-positive, straight, forming central to subterminal spores, straight, rod-shaped. size

0.6 ... 1.3 x 1.5. "4.1 pm Component III: pleomorphic, gram-negative, terminal Spores forming, straight or curved, rod-shaped, size

0.6 ... 0.8x4.1 ... 6.5m

The proportion of the three main components in the mixed culture is at least 95% of the cell density.

The bacteria of this mixed culture are capable of organic sulfur compounds such. As thiophenes, thiols, sulfides or disulfides as pure substances as well as in carbonaceous materials, especially lignite, under thermophilcn conditions to oxidize sulfates.

This activity already possess the individual components, so that both the described mixed culture as well as combinations of the individual components or these can find their own use, wherein the sulfur-oxidizing activity of the mixed culture according to IMET 11335 is increased compared to the individual components contained. Using the deposited mixed culture, desulphurization of> 90% (relative to dibenzothiophene) was achieved in model studies, and combinations of 2 of the three major components still achieved 75-85%. In lignite-containing suspensions, the content of organic sulfur compounds was reduced by up to 70%.

The cultivation of the bacteria can be carried out batchwise or continuously in a step upstream of the actual sulfur conversion process under the culturing conditions claimed. However, it can be advantageously carried out so that the material to be desulphurised, e.g. the lignite is already fed to the fermenter during the growing process and then remains in the cultivation mixture for the required period of time, which varies with the composition and the amount of organic sulfur compounds present.

With the material to be treated by its nature, carbon compounds supplied to the cultivation medium, which can serve as a substrate for the microwave growth process. The same applies to inorganic salts that act as nutrient salts. In addition to the necessary balances are in stagnation of the microwave growth, if necessary, additionally easily utilizable C sources, such. As acetic acid or glucose, for which industrial waste waters are economically available.

The material to be desulphurised, when in solid form, must be made accessible to microwave treatment by comminution. Advantageously, it is z. B. crushed by ball mills and made ao aqueous slurry. The resulting suspension is then added to the fermentor.

During the microwave fermentation process, the organic sulfur compounds are oxidized to sulfates which, in the case of the treatment of lignite, are bound by the contained earth and alkali metals, mainly calcium. The decomposition temperatures of these sulfates are above 1200 ° C

 The process according to the invention is explained in more detail by the following examples.

embodiments

example 1

The mixed bacteria culture IMET11335 was used in a 1 l stirred reactor with a nutrient medium of the following composition

(NH) ₄ H ₂ PO ₄ 3.3 g / l KH ₂ PO ₄ 0.2 g / l MgCl ₂ χ δ H ₂ O 0.2 g / l NaCl 0.03 g / l CaCi ₂ 0.03 g / l

and chloride-containing trace saline cultured at 60 ° C and pH 6.5 under aerobic conditions (air flow 60 l / h).

As energy and carbon source, glucose (5 g / l) was added. The medium contained as organic sulfur compound Dibenzothiophene in a concentration of 300mg / l. After a fermentation period of 10 days, 90.5% of the organic sulfur bound in dibenzothiophene became Sulfates oxidized. In the control experiment without presence of microorganisms, no chemical oxidation

demonstrated.

In comparative experiments, the pH and the fermentation temperature was varied. It was found that a Functionality of the invention within the ranges pH4 to 8 and temperature 50 to 75 ° C is present. The Desulphurization rates at the range limits were approximately 30% for the given reaction times. Example 2

The bacterial mixed culture IMET 11335 was aerobically cultured in nutrient medium according to Example 1 at 60 ° C., pH 6.5, the air flow being 60 l / h.

However, the culture medium contained no dibenzothiophene but milled crude lignite in an amount of 200 g of coal per 1 suspension. The coal had a total sulfur content of 4.4% of which 55% was organically bound. After 3 days, growth stagnation occurred by wasting the utilizable components provided by the coal. There was a single addition of glucose in an amount of 10g / l culture medium. After a fermentation period of 12 days, the content of organically bound sulfur was reduced by 70%. In the control experiment without the presence of microorganisms, a chemical oxidation was detected.

Example 3 In a cultivation method analogous to Example 1 (cultivation temperature 60, pH 6.5, dibenzothiophene content 300 mg / l)

were as microorganisms components II and III of the deposited mixed culture IMET 11335 in a parity

Ratio of cell counts used. > After a treatment time of 10 days, dibenzothiophene degradation was 78%

reached.

Claims (3)

1. A process for the microwave conversion of organic sulfur compounds from carbonaceous materials, in particular brown coal, in a bacterial aerobic cultivation process, characterized in that the cultivation using bacteria of the new thermophilic mixed culture IMET11335, - in the temperature range from 50 to 75 ° C as well
- in the pH range of 4 to 8
is carried out. 2. The method according to claim 1, characterized in that the cultivation is carried out using one or more of the three main components is mixed culture. 3. The method according to claim 1 and 2, characterized in that substrates and nutrient salts are added to the culture medium in addition to the supplied by the material to be treated compounds.