CS255053B1 - Process for processing heavy tar sludge from coal gasification process - Google Patents

Abstract

A method of processing heavy tar sludge from a coal gasification process by separating it into a solid and liquid phase by distillation at a temperature of 180 to 360 °C. The immiscible components are separated from the distilled and condensed liquid phase on the basis of different specific weights. The distillation residue is used for energy by combustion.

Description

The invention relates to a method for processing heavy tar sludges from a coal gasification process containing a solid phase and a liquid phase with an aqueous and organic component.

During coal gasification, condensates are formed by cooling the raw gas, which are divided according to density into light tar, phenolic waters and heavy tar sludge.

Heavy tar sludge can be defined as a heterogeneous mixture of organic substances, a certain amount of mechanical impurities and water.

Heavy tar sludge is not currently used in practice. It settles at the bottom of the tanks, from where it is continuously or once transported to the sludge and waste landfill.

The construction of these landfills for heavy tar sludge is very expensive, their maintenance is complicated, and the work is harmful to the health of maintenance and operating personnel. After the landfill is filled, the construction of other landfills must be ensured. It is also necessary to take into account the negative impact on the environment in the vicinity of heavy tar sludge landfills, which is manifested by the permanent evaporation of harmful vapors of odorous substances.

Direct combustion of heavy tar sludges, or their return to the coal gasification technological facility, has not been fully proven in practice and is not known to be in permanent operation.

The above-mentioned invention relates to a method for processing heavy tar sludges, the essence of which lies in their distillation at a temperature of 180 to 360 ° C. During distillation, heavy tar sludges are separated into a solid phase with a distillation residue of organic substances and a vapor phase. The vapor phase is separated into an aqueous and organic component after subsequent cooling and condensation based on different specific weights.

The products obtained according to the above method can be used for energy purposes (bulk distillation residue), the organic components of the distillate can be used as raw materials in the chemical industry (possibility of processing as light tars of pressurized gas plants).

The water component of the distillate can be processed in the technological process of wastewater dephenolization, which is an essential part of every coal gasification operation.

Example of a specific use:

During pressure gasification of brown coal, the gas produced also contains water vapor, tar vapors and small particles of coal charge or ash. When the produced gas is subsequently cooled, condensate is formed, which is separated into individual components - tar, phenolic waters and heavy tar sludge.

Heavy tar sludge contains water, mechanical particles and industrially usable organic substances.

The composition of heavy tar sludge is given as an example in Table 1.

Table 1- Composition of heavy tar sludges /example from pressure gasification of brown coal/.

Mechanical impurities 19.4 % hm Asphaltenes 11.0 % hm Acid polymerizing oils 4.3 % hm Phenols 7.5 % hm Alkaline content of organic matter 0.9 % hm Neutral organic matter content 27.7 Water 29.2

Tar and phenolic waters are further processed, heavy tar sludge settles at the bottom of the tanks, from where it is continuously or once transported to the tar sludge landfill.

According to the method according to the invention, heavy tar sludges are distilled with constant stirring at a temperature of 180 to 360 °C in a simple distillation vessel without internal filling. Inside the distillation vessel there is a stirrer which also serves as a wall scraper.

The inclusion of a vapor outlet from the distillation vessel prevents the deposition of mechanical particles. The distillation vessel has an opening at the bottom for the solid phase outlet.

There is an opening in the upper part of the distillation vessel for the entry of heavy tar sludge.

The distilled vapor phase condenses in the cooler and is discharged to the condensate collector; where the content is divided into organic and aqueous phases according to specific weights, the phases are discharged separately for further use.

An overview of the composition of the distillate from pressure gasification of brown coal is given in Table 2 /atmospheric pressure, 250 °C/.

Table 2 - Composition of heavy tar sludge distillate /for example from pressure gasification of brown coal/.

Phenols 11.5 % hm Alkaline content of organic matter 1.4 % hm Neutral organic matter content 42.4 % hm Water 44.7 % hm

Composition of ^neutral^part^of^organic-substances:

Alkanes 11.2 % hm Non-condensed cycloalkanes 7.3 % hm Condensed cycloalkanes 13.9 % hm Alkylbenzenes 13.9 % hm Indans, tetralins 14.2 % hm Alkylnaphthalenes 22.1 % hm Acenaphthenes, diphenyls 13.6 % hm Benzothiophenes 3.8 % hm

The distillation residue /34.7% wt/ has a calorific value of 29.9 MJ/kg.

The entire device is adapted to allow cleaning of internal spaces with technological steam.

The organic component can be further processed energetically or by a technological process common for the use of light tars from pressure gasification of brown coal.

The proposed processing of heavy tar sludge has a major benefit in improving the environment and utilizing industrial and energy raw materials.

Claims (1)

Process for treating heavy tar sludge from a coal gasification process characterized in that the liquid phase of heavy tar sludge is distilled off at a temperature of 180 to 360 ° C and from the resulting distilled, condensed liquid phase the immiscible components are separated on the basis of different specific weights and by its combustion.