燃烧理论之燃烧及热化学.ppt

* * Gas-Gas Heat Exchanger * 烧嘴A 烧嘴B 交替切换 steel Nox emission fuel fuel 陶瓷球型蓄热体 gas air gas 切换阀 (1620 K) Preheated air (1270 K) 分散式余热回收方式 出处：NKK公司（日本）：“蓄热式烧嘴加热炉概要及其在钢铁设备上的应用” Basic conception * 25-30% 以往的水平 预热前窑炉出口排烟温度(℃) 1400 1200 1000 800 600 400 50-60% 70 60 50 40 30 20 10 0 0 200 400 600 800 1000 1200 1400 预热空气温度 燃料节约率 % ℃ 出处：NFK公司（日本)：产品目录 节能潜力 * 例 2.8 图2.16所示的一个对流换热式回热器，用于天然气加热的热处理炉上. 炉在常压下工作，当量比为 0.9. 燃料气的入口温度为298K, 空气被预热 A.求当空气预热温度从298K到1000K时对绝热火焰温度的影响. B. 空气温从298K 升到600K时的节能有多少?假设不管是预热还是不预热空气，炉子的出口(进入换热器前）烟气温度1700K。 * 解(Part A) Fortran program HPFLAME, which incorporates the Olikara and Borman equilibrium routine, to solve the first-law problem, Hreac=Hprod. The input file for the program requires the definition of the fuel by providing the number of carbon, hydrogen, oxygen, and nitrogen atoms constituting the fuel molecule, the equivalence ratio, a guess for the adiabatic flame temperature, the pressure, and the reactants’ enthalpy. * The input file for this example, treating natural gas as methane, is shown below: Adiabatic Flame Calculation for Specified Fuel, Phi, P, Reactant Enthalpy Using Olikara Borman Equilibrium Routines * Problem Title: Example 2.8 Air Preheat at 1000K 01 /Carbon Atoms in fuel 04 /Hydrogen atoms in fuel 00 /Oxygen atoms in fuel 00 /Nitrogen atoms in fuel 0.900/Equivalence ratio 2000./Temperature(K)(Initail Guess) 101325.0 /pressure(Pa) 155037.0 /Enthalpy of reactants per kmol fuel(kJ/kmol-fuel) * The only quantity requiring calculation is the reactants’ enthalpy, expressed as kJ/kmol of fuel. To find the number of moles of O2 and N2 supplied per mole of fuel, we write our combustion equation as * Where Thus, The reactants’ enthalpy(per mole of fuel) is then * The above expression can be evaluated for various temperatures * 空气温度增加100K，烟气温度增加50K，原因： 1、分解？ 2、烟气比热比空气大？ 事实：烟气量比空气量大 * * Solution (part B) To determine the