The work concerns an important in our times problem related to different areas as ecology, economy and proper use of energy resources: reduction of NOx by rebuming process. The main goal of the work was to develop the technology of NOx reduction during zone combustion of coal and mine gas with process optimal conditions determination in power boilers in aspect of environmental protection. In the work was presented: investigation of numeric model of zone combustion of coal and mine gas; aplied combustion research of the boiler OCG-64 produce on RAFAKO.

The article presents the procedure for how to establish a mathematical model of nitrogen oxides formation based on the theory of dimensional analysis. The model is based on selected physical quantities (parameters) measurable during regular operation of a heat generation plant. The objective of using dimensional analysis to describe nitrogen oxides formation is to show that between operating parameters of the combustion equipment and the NOx formation there is a significant correlation.

The obtained results, which are further described in this article, have proved this fact. The obtained formula expressing nitrogen oxides formation, based on dimensional analysis, applies universally to any boiler fuelled by coal, gas or biomass. However, it is necessary to find C, m, n constants for the formula by experiment, individually for each type of boiler and used fuel. The experiment is based on on-line measurements of selected operational parameters for a given boiler, combusting a certain type of fuel with its actual moisture content and calorific value. The methodology, described in this article, helps to find relationships between the operational parameters and the formation of NOx emissions for a particular furnace. The developed mathematical model has been validated with boilers fuelled by black coal and biomass. Both the results obtained from direct measurements of NOx in both types of boilers, and the results obtained by calculation using equation based on the dimensional analysis, are in a very good accord. When burning coal, the variation between NOx expression from the model and the on-line measurements ranges between -12.23 % and + 9.92 %, and for burning biomass between -0.54 % and 0.48 %.

The intention of the authors is to inform the professional community about the suitability of the dimensional analysis to describe any phenomena for which there is currently no exact mathematical formulation based on differential equations or empirical formulas. Many other examples of dimensional analysis applications in practice may be found in the work of Čarnogurská and Příhoda (2011).

In the paper, a numerical simulation of the co-combustion process of sewage sludge gasifi cation syngas in a hard coal-fi red boiler was done. Two different syngases (SS1 and SS2) were taken in consideration. Additional (reburning) fuel was injected into the combustion chamber, which was modeled as a plug fl ow reactor (PFR). The molar fl ow rates ratio of reburning fuel is assumed to be 5.0%, 7.5%, 10.0%, 12.5% and 15.0% of the whole exhaust. The simulations were conducted for constant pressure equal to 1atm for temperatures range from 600 to 1400 K. It was assumed that a fl ue gases which enters the reburning zone contains 300 ppm of NO and that during combustion only NO is formed without other NOx. Results show that that gas from sewage sludge gasifi cation gives reburning effi ciency of up to 90%. Calculation shows also an optimum value of temperature reburning for gas from sewage sludge gasifi cation which is equal to 1200 K. The type of the sewage sludge has no strong infl uence on the NO reduction.

ln laboratory electrically heated entrained flow reactor with quasi one-dimensional laminar flow the influence of fuel properties on the nitrogen oxide emission for 23 coals of various rank from brown coal, bituminous coal to anthracites has been examined. For one brown coal type twofold increase of nitrogen content resulted in NO, emissions increase of about 30%. Increasing rank from brown coal to bituminous coal increases NO emissions and next a fall in the anthracites range. With nitrogen content increase NO - emission grows a~d the ratio of fuel nitrogen conversion to nitrogen oxide decreases. Experiments results and their statistical analysis were used to determine relationships describing NO, emissions and conversion ratio of fuel nitrogen to nitrogen oxide as functions of two variables. describing coal properties, i.e. nitrogen content and fuel ratio (fixed carbon to volatile matter ratio).

The subject of this work was the investigation of zeolite as a sorbent of toxic gases. In Nizny Hrabovec in the Slovak republic, two layers of zeolite with the active component clinoptilolite can be found. The study presented here investigated the ability of this natural zeolite to reduce polycyclic aromatic hydrocarbons (PAH) and NO emissions from engine exhaust. Exhaust gases from combustion engines include toxic components such as carbon monoxide, nitrogen oxides and hydrocarbons. Polycyclic aromatic hydrocarbons (PAH) are a component of hydrocarbons causing harmful influence on life forms. The experiments focused on the potential reduction of these toxic gases based on the sorption and catalytic properties of natural zeolite. Also observed was the influence of chemical adjustment including incorporation of certain metal elements. Chemical analysis by mutually independent technologies served to observe the sorption of PAH with carcinogenic properties on the natural zeolite tested. The experiments showed that chemical modification improved the sorption and catalytic properties of natural zeolite. The PAH were analysed in an extract of the contaminated, thermally-activated natural zeolite and modified zeolite after washing with ammonium chloride, cobalt chloride and copper sulphate. The study also presents results of NO measurements obtained by testing the filter-sorptive automobile system.