The conditions of stabilization of combustion of detached gas jets on the vertical surface of the range of nozzle diameters d0 = 1.6–3.0 mm are investigated. The mechanism of flame stabilization of a detached gas jet on a vertical surface is shown, which allows to increase the gas flow rate through one nozzle by 3 or more times with stable combustion, compared to diffusion combustion of a free gas jet, which is not stabilized. The optimal distance to the vertical refractory surface in the nozzle calibers for the creation of slot bottom burner devices has been established. The necessity of using the minimum angles of attack till failure of combustion, which were experimentally founded, for the construction of slot bottom burner devices, is substantiated. It is experimentally established that starting from the gas pressure in the collector-pipe near 500 mmwg and, accordingly, the speed of its flow through the nozzle is more than near 100 m/s at a distance to the vertical surface on which the flame is stabilized 15 < L/d0 <= 30, for the range of nozzle diameters d0 = 1.6–3.0 mm, dimensionless area base sg/s0 of the elliptical cylinder Eb, less than 2–2.5 times of the maximum observed at a distance L/d0 near 40. Bibl. 15, Fig. 6.

The installed capacity of boiler units in Ukraine significantly exceeds the needs for consumers was shown. The remarking of boiler units to lower capacity is the one of the least capital-intensive ways to increase their technical, economic, environmental indicators and the extension of their resource. To achieve EU norms it is necessary to reduce emissions of NOx by 50–80 % for boilers of LCP with an capacity a rated thermal input of 50 MW or more, which operate on natural gas has been established. An increase the concentration of recirculation gases in blow air of more than 25 % of all exhaust gases significantly reduces the concentration of oxygen in the mixture of air and exhaust gases. It’s can cause to: deterioration of combustion, the removal of a torch into the convective part, a significant increase electricity consumption and increase the temperature of the exhaust gases. The using of CO2 or N2 gases for balancing natural gas to reduce NOx emissions is economically impractical. The using of ballasting technology, which based on mixing exhaust gases with natural gas, requires special burners, due to the range of burner power control must be limited. To reduce NOx is advisable to combine several measures simultaneously. The plan an action to implement EU environmental directives by existing boiler units operating on natural gas with an increase their technical and economic indicators has been developed. There is one of the possible ways to implement the EU ecological directives by boiler units in Ukraine, it’s transferring the load from existing LCP with a rated thermal input of 50 MW or more to less powerful ones. For remove combustion plants from the requirements of the EU Directive 2010/75/EU, it is necessary to remark part of the boilers for a new nominal capacity for the purpose of obtaining combustion plants a rated thermal input of less than 50 MW. Bibl. 18, Fig. 6, Tab. 1.

The increases service life of gas hot water supply boilers with uniform heat supply along of the depth (width) of the combustion chamber for more than 40 years, by using of slot bottom burners was shown. While reducing nitrogen oxide emissions by using of dual-screens its can significantly increase the heat stress of the furnace, the volume of the furnace chamber and the temperature of the flue gases had left unchanged. The boilers with a capacity of 1–10 MW, with the above technical design solutions of the Gas Institute of the NAS of Ukraine, with a total heat capacity of more than 60 GW, continue to be operated and produce in Ukraine and the CIS countries. Installed boilers relatively nitrogen oxide emissions comply with new EU directive (EU) 2015/2193. The using of gas slot bottom burners can reduce nitrogen oxide emissions by approximately 15 % compared to the basic factory vortex types GMG or GMGB installed on many boilers was shown. A project for the reconstruction of boilers TVG-8 (TVG-8M) and KVG-7.56 with an increase in convective surface area by replacing the factory pipe 28x3 mm with 32x3 mm had developed. Using the improved slot bottom burners in particular equipped with calibrated nozzles for precise dosing of natural gas into the air was envisaged. As a result of a research test of the reconstructed boilers for 3-5 years these technical solutions could increase the energy efficiency of existing TVG and KVG boilers up to the current European level —94–95 at rated heat output was shown. Ref.18, Fig.4, Tab. 5.

The possibility of modernization of boilers TVH-8M, TVH-8 and NYYSTU-5, operated in Ukraine, with the increasing of their technical and economic indicators to the modern European level is shown. Projects of modernization of boilers have been developed, which consist in redesign of heating surfaces in convective shafts of existing boilers without increasing their overall dimensions with using convective part of pipes diameter 32 x 3 mm and replacement of burner devices by developed new type MPIG-3. It is shown that the results of industrial implementations achieved efficiency of boilers type TVH-8M (TVH-8) 94-96% in the operating range of their load and obtained the calculated efficiency for boilers NYYSTU-5 92-94%. It is experimentally proven that when installing special calibrated nozzle, instead of drilled holes in the collectors of gas burners, it is possible to keep the nozzle geometry (natural gas burner consumption depending on pressure) unchanged throughout the service life. The technical possibility of combustion of biogas and mixtures of natural gas and hydrogen in the slot bottom diffusion burners of the MPIG-3 type, when replacing only the nozzle apparatus is shown. Bibl. 17, Fig. 6, Table 1.

In the article discusses the features of constructive solutions accepted in the burner devices and chambers of boiler units, which were used both when converting solid fuel boilers to natural gas, and creating new designs of gas boiler units. The works to reduce nitrogen oxide emissions at the Gas Institute of the National Academy of Sciences of Ukraine began in the 1960s and by 1971 significant results had been achieved was shown. The main methods and technical solutions that are used to reduce emissions of nitrogen oxides during the combustion of natural gas in boilers of various capacities, including 300 MW power units, are considered. The principal design of a two-stage burner, which are operated in an amount of more than 2000 units in Ukraine and the CIS countries is presented. The installed two-stage burner devices for combustion of natural gas require immediate reconstruction with bringing their indicators to the calculated ones at the first stage. The modernization of the exist ing two-stage burners is possible to achieve the readings of the EU emissions directive 2010/75/EU was shown. The most promising technologies for further reducing the level of nitrogen oxide emissions less than 100 mg/Nm3 (3% O2, dry gases) when burning natural gas were shown. Bibl. 38, Fig.4, Tab. 1.