Effective fuel burning in flameless burners with maintenance of a prescribed adiabatic combustion temperature

Abstract

Burners used traditionally for oxidizing hydrocarbons are considered. A method developed by FAST ENGINEERING is presented for effective fuel burning with thorough flue gas heat recuperation and stable maintenance of a prescribed adiabatic combustion temperature on the basis of using heat exchangers and flameless burners of a conceptually new design.A considerable part of extracted natural gas (NG) and other fuel is burnt in the furnaces of steam and water-heating boilers, gas turbine combustion chambers, and tubular furnaces for various branches of industry. The main requirements in burning fuel are provision of high effective utilization of the thermal energy obtained and minimum discharge of harmful components (CO, NO x , etc.) into the environment with flue gases [1,2].Technology for effective burning of fuel and also engineering facilities for accomplishing it developed at FAST ENGINEERING make it possible to resolve questions of saving energy and environmental protection to a considerable extent.Traditional Fuel Burning Technology. Flame burners are used extensively for burning fuel [1, 2], and heat exchangers are used for heat recuperation and utilization [2, 3] discharged with waste flue gases, and for a whole number of reasons it is impossible to resolve adequately urgent problems of energy saving and environmental protection.Existing flameless fuel combustion technology, for example, burning fuel in permeable matrices [4], and in a granular catalytic layer [5], have limitations with respect to application temperature and unit power of the burners used.Burning fuel in flame burners with an adiabatic combustion temperature above 1200°C leads to formation of considerable amounts of harmful components CO and NO x [2], discharged with waste flue gases into the environment. The higher the adiabatic combustion temperature, the greater the amount of CO and NO x formed.A dependence is shown in Fig. 1 for the amount of CO and NO x formed during burning of 1 nm 3 of NG in 10.5 nm 3 of air for different values of adiabatic combustion temperature with excess air coefficient α = 1. As may be seen from this, with an increase in adiabatic combustion temperature above 1200°C there is an increase in the amount of CO and NO x formed.For a whole number of thermal energy users, for example, gas turbines, there are limitations with respect to flue gas temperature (combustion products), entering heat utilization. As a rule, this is traditionally resolved by an increase in the supply of excess air in combustion or dilution products with cold air, and this leads to a reduction in unit efficiency.Normally, waste flue gas after different thermal energy uses has a temperature of 150-200°C and above [1][2][3]. As a result of the considerable amount of waste flue gas with a high temperature discharged into the environment, a great deal of thermal energy is lost.Normally, in order to heat air entering a burner as an oxidizing agent, shell-and-tube, plate, or other types of waste gas heat recuperator are used [2,3]. This equipment is i...