Systems of phasic staged combustion of fuel focused on reduction of NOx emission

Technology of phasic staged combustion of pulverized coal in low-emission straight-flow burners allows providing extremely low NOx emission. That burner’s technology and design are advised for pulverized combustion of black and brown coals in boiler plants of thermal power plants and in big boiler plants.

That technology and burners’ design have been introduced in the following boiler plants:

  • P-57 (500 MW power generating unit) at Ekibastuz State District Power Plant-2 (SDPP-2),
  • PK-401 (200 MW power generating unit) at Tom’-Usinsk and Belovo State District Power Plants (SDPPs),
  • OP-140 and WP-120 at thermal power plants (TPP) “Poznan” and “Lublin” in Poland.

Technology of phasic staged combustion  allows the following:

  • Reducing NOx emissions to the level of 350-400 mg/nm³ (reduction by 1.5 – 2 times);
  • Providing high efficiency and stability of combustion at a low level of CO emissions;
  • Reducing the level of slagging and corrosion of furnace screens.

The three-stage combustion system has resulted from cooperation of experts of the group of companies SibEnergoGroup and engineering company “ZIOMAR”. It is one of the products delivered in the development of low-emission combustion technology. This system is designed to arrange three zones in a combustion space (see Figure 1). In the lower zone, 70…85% of the total fuel is burnt with excess air close to one or even lower. The remaining fuel (15…30%), with excess air considerably lower than one, is supplied to the area, which is above that zone. And even higher above that zone, the leftover air (15…25%) is supplied to that third zone with the purpose of afterburning of products of chemical and mechanical underburning that have formed in the previous zones.

The system of three-stage combustion with coal reducing agent in combination with pulverized coal feed and combustion of the highly concentrated dust under pressure (HDCp) was initially implemented in re-conditioned boiler E-210-98 (OR-210M) at TPP Skavina (Poland) (see Figure 2). In this boiler, a part of pulverized coal with the finest particles that had not been collected by dust systems’ cyclones was used as deoxidizing fuel at the second stage.

Under conditions of shortage of oxygen at combustion of additional fuel, deoxidizing gaseous medium is generated, and a part of NO (coming from the first area) is decomposed in it with next generation of N2.

Development and introduction of the system with deoxidizing gaseous stage into the TPE-214 boiler plant (200 MW power generating unit), installed at Novosibirsk cogeneration plant-5, has resulted from cooperation of experts of the SibEnergoGroup and SibTekhEnergo companies and the Taganrog factory “Krasny kotelshchik”. The proposed method of three-stage combustion with the gaseous deoxidizing fuel provides diminishing NOx emissions to the level even below 300 mg/nm³, which is three times less than at combusting similar coals.