OCR Text |
Show 2.02 Temperature of furnace chamber The temperature of furnace chamber can be changed between 800 and 1300°C The flame temperature can be even higher than the aforementioned ones The fibrous refractory material of lining is heat resistance to 1650°C The structure of furnace wall makes it possible to model the operational conditions of annealing furnaces working in the steel industry. The temperature of furnace chamber has significally changed along the axis. (The temperature map can be found in the first part of this paper read in Holland [4]) The data of experimental furnace in the course of experiments were the following: Volume of combustion chamber (without the calorimeter-chamber) 0 42 m3 Fuel natural gas Calorific value 34 MJ/m Temperature of gas 20 °C Temperature of furnace-chamber in axe at a distance of x = 2 0 5 m 900.1400 °C Air factor 1.05.1.10 Temperature of air 20... 2 5 °C Specific heat load: 227 MJ/m h 3.0 Description of experiments Identical factors were investigated during the experiments, where it became possible, as w e had done it in the course of our researches on oil-firing (see first part [3]), in order that the two research-series give results which can be compared with each other. The following effects were investigated: IV Effect of changing the temperature of combustion chamber, 2.1 NO-concentration in the length and cross section of flame, 3./Effect of air factor, 4/ Effect of steam-content on NO-development, 5,/ Effect of forced recirculation of flue gas. 3.01 Effect of changing the temperature of combustion chamber The maximum value of flame-temperature as well as the Nox emission increase by increasing the temperature of furnace chamber. Th effect of temperature of furnace chamber was investigated at a constant heat-load The temperature of chamber was changed by moving the cooling probes at the burner. Fig. S shows the effect of temperature on the NO-development as a function of the chamber-temperature. At the 0 sec experimental time the furnace chamber is not cooled. Then the 25, 50, 75 and 100% of the length of water cooled probes were pushed into the furnace chamber an later they were pulled out at their same lengths. The NO-analysis taken by means of "A" burner showed a characteristic fluctuation. 80 75 70 65- E 60S O 55Z 50 45 Fig 6 shows the NO-emission of "A" burner as a function of the temperature of furnace chamber: I I I I ' 4 0 8 8 8 8 8 8 8 8 8 8 8 § § i § § § § 8 § § §§ o - - time (J| > 70 E a 65 §60 55 50 "1 •'ABurer p. ?M^ f-j 0 »o V TenperiLre PQ Fig. 6: N O x emission by firing with "A" burner In the course of using the O R A , (swirl) burner ("B"), the N O emission is higher at each temperature (Fig 7) The faster the mixing is and the shorter the flame is, the greater is the N O x emission. Each burner is characterized by the feature, that the N O emission increases exponentially by increasing the temperature of chamber. & GO O z - • "B"- Bi mer Fig. 5: Effect of chamber-temperature on the NO-development 1100 1190 1300 Temperature PC] Fig. 7: N O x emission during firing with "B" burner In the cylindrical experimental chamber the NO emission can well be described as a function of temperature with second order polynomes: For 1 0 0 0 < » < 1350 °C In case of "A" burner: V = 8.6 10'5S2- 0.136S + 101, ppmv (6) In case of "B" burner V =9 10'5»2- 148S + 116 ppmv (7) where 3 = furnace temperature, °C. 3.02 NO-concentration in the cross section of flame A probe made of Al-oxide ceramics was introduced into the axis of "A" burner in order to investigate the place and concentration distribution of N O development. A bare Pt-PtRh thermal element was placed on the end of probe in order to measure the local temperature, and gas-sample was taken through the probe in order to determine the N O concentration. One of the NO-analyzers analyzed the sample taken through the probe, while the other one regist rated the NO-content of flue gas leaving the end of furnace. The distance from the burner can be seen on the horizontal axis of Fig. The probe was pushed into and pulled out of the axis of furnace by 10 m m steps during the check-measurements. |