EURO-ECO 2009 Hanover 3 - 4 Dezember 2009	Environmental, Engineering - Economic and Legal Aspects for Sustainable Living
	European Academy of Natural Sciences, Hanover European Scientific Society, Hanover University of Bremen, Bremen

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Solution of the problem of air pollution in the areas of coke plants locations heavily depends on dust emission control success. Suspended solids in overall emission from organized sources (funnels, exhaust ducts, ventilation systems) of coke production make up from 30% with dry coke quenching to 70% - with wet quenching. Moreover, air pollution is also dramatically increased by unorganized sources such as dusting at open storage areas, batch charging, coke drawing and quenching, handling operations etc. These emissions rouse most censure due to their good visibility. Lately unorganized sources emissions control is carried on by conversion them to organized ones: indoor storage areas building, dust-free batch charging and drawing, building of aspiration systems with dust treatment of emissions an so on. This report covers some topical questions of increase of ecological and economical effectiveness of organized emission sources’ aspiration and treatment units.

Working on problems of dust emission control, the questions of treatment are emphasized. Dust collectors efficiency is the main measure of performance of rather big environmental investments. In this way, dust collectors with the cost and sizes comparable with that of the main technological equipment appear.

This approach provides reliable “internal task” solution – prevention of dust coming in workplace and working areas, but it complicates “external task” solution connected with air pollution. Industrial investigations results demonstrate that quantity of aspirated material particles is proportional to aspiration air flow rate raised to the third power; quantity of dust collected at treatment plant depends on the fractional performance of dust collector. Besides, speed rising under the shelters leads to increase of the size of the particles taken off by aspirated air. This, in turn, makes an impact to the rate of dust collectors’ and fans’ abrasion.

I must note that organized dust emission from high-capacity systems may exceed unorganized emission if without aspiration. It is likely connected with relatively low gas flow rates in aspiration absence. With aspiration increase dust concentration reduces, but overall emission increases. Therefore aspiration increase may lead to increase of emission to atmosphere even if high-efficiency dust collectors are used.

Obviously, dust emission effectiveness rise due to aspiration flow rate increase is expensive. The cost of aspiration systems’ building and maintenance rise sharply, as well as that of compensating input ventilation that intensifies facilities heating issues. In case of wet dust collection difficulties emerge connected with big sludge volumes formation that complicates the decision of general ecological issue. In practical conditions of electric power fast price increase and need of power reduction, high-capacity aspiration systems are stopped. Thus evidently, existing trend of dust control via high-capacity aspiration systems erection is a deadlock in this case.

We consider the following trend to be more advanced: required aspiration air exchange reduction by proper design of manufacturing equipment shelters. The shelters improvement methods (dust generation confinement) are diverse, and as a rule are aimed at the process energy characteristics use and dusted air flow development control under the shelters. At the same time both “internal” and “external” aspiration tasks are solved.

The most favorable way is connected with aspiration volumes optimization by dust generation sources total confinement. Main point of this optimization is determination of minimum aspirated volume when suspended dust particles emission via the shelter gaps stops. Optimization can be done both via calculations and via direct experiment on existing equipment. The effect of this procedure may be expressed by significant (from 30% up to 300%) reduction of designed aspiration volumes.

According to the foresaid, improvement of the shelters design should be recognized as one of the main trends of aspiration systems dust emission reduction for the nearest years. This way allows to reduce annual average aspiration costs, to avoid expensive duct collectors use, to prevent sludge forming and also to get collected dust as a ready saleable product.

Lowering of dust collector efficiency standards allows to use simple devices, such as dry cyclone. At the same time it is necessary to take into account coke dust abrasiveness.

The use of cone-cylindrical cyclones for abrasive dust collection is connected with quick wearing of construction unit and need of frequent repairs, that reduce their reliability. Cone-cylindrical cyclones are more abrasive wear-resistant, but their routine operation requires significant power consumption.

The research of dust collection process in high-performance cyclones on the basis of analysis of experimental dependencies of partial purification efficiency and aerodynamic resistance on performance, has shown that there are opportunities to reduce abrasive wear and power consumption without dust collection effectiveness decrease. This can be achieved by minor gas rates decrease as compared to those scheduled.

It is worth mentioning that cyclones the sizes of which are bigger than that recommended in the literature are successfully applied. Such cyclones provide good operating characteristics and are cheap to install and operate.

Purification efficiency and cyclone resistance calculation methods have been perfected during research and implementation work. For instance, variance analysis has been used to analyze dust and real gas flows with the help of impactors. This allows forecasting cyclones working parameters to a high accuracy on the base of standard calculation methods.

Actual effect of dust collectors’ installation depends not only on dust their performance factors but also on emission localization measures at escape places. Therefore the effect should be evaluated by ecological effect of air pollution elimination rather than by purification efficiency achieved.

Sometimes coke dumping and collected coke dust utilization are the factors restraining wide use of dry dust collection methods. Anyway the choice of coke dumping method is connected with coke dust utilization way and should be made on the base of marketing research.

Benchmark tests of coke dust collecting in different dust collectors (grain filters, electric filters, composite units) have been performed. The data for industrial devices calculation have been received. Electric filters for gas treatment at coke drawing form coke-ovens have been installed. Dust collection efficiency complies with calculated values.

 

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