Burner tunnel

Tunnel Test. The tunnel test is widely used to test the flame spread potential of building products such as electrical cable (15) and wall coverings (16). The test apparatus consists of a tunnel 7.62 x 0.445 m x 0.305 m ia cross section, one end of which contains two gas burners. The total heat suppHed by the burners is 5.3 MJ/min. The test specimen (7.62 m x 50.8 cm), attached to the ceiling, is exposed to the gas flames for 10 minutes while the maximum flame spread, temperature, and smoke evolved are measured. The use of this and other flame spread test methods has been reviewed (17). 

The burners at the reformer s top are in an enclosure called a penthouse. The flue gas is collected at the bottom in horizontal fire-brick ducts called tunnels. Flue gas exits horizontally into a waste heat recovery (WHR) unit. Combustion gas is drawn through the WHR unit by an induced-draft fan and then discharged to the atmosphere through a stack. 

Refractory tile TUNNEL BURNER (sealed-in burner)... 

FIG. 24-31 Aspirator (air-jet) mixer feeding a sealed-in large port premix tunnel burner. Blower air enters at lower left. Gas from an atmospheric regulator is pulled into the air stream from the annular space around the venturi throat in proportion to the air flow. Frcnn North American Combustion Handbook, 3d ed.. North American Manufacturing Company, Cleveland, 1996.)... 

Kilham, J. K., E. G. Jackson, and T. B. Smith. 1965. Oscillatory combustion in tunnel burners. 10th Symposium (International) on Combustion Proceedings. Pittsburgh, PA The Combustion Institute. 1231-40. 

FIGURE 14.11 ASTM E 84 Steiner tunnel test apparatus. Left insert Burner flame viewed from tunnel inlet. Right insert Initial flame tip location is 1.37m (4.5 ft) from the burner. (Photo courtesy of Southwest Research Institute, San Antonio, TX.)... 

The fire safety of mine conveyor belts is covered by the MSHA. The convoluted history of requirements is described by Verakis.93 The regulation mandates the exclusive use of flame-resistant conveyor belts, without details. The actual test used is a Bunsen burner-type test, based on ASTM D 635 (UF 94HB),94 which has been shown to be inappropriate for the associated fire hazard. Originally, large-scale tunnels were used to classify the flammability of the conveyor belts, but those tunnels have since been destroyed. There have been fire-testing research projects addressing the correlation of the various proposed tests with standard tests, but nothing has been implemented till date. 

The Steiner Tunnel test (ASTM E 84) is used to classify the fire-spread potential of products used in wall and ceiling linings [4], and is used to classify expanded polystyrene foam. In this method, specimens are placed on the ceiling of a 24 ft long tunnel. An 88 kW natural gas burner is placed at one end of the tunnel and a forced-air draft with a velocity of 1.22 m/s is introduced. The flame spread is recorded as a function of time and an arbitrary index is calculated from the measurements. 

This test has been criticized because it does not simulate actual building fire conditions [5,6], An additional problem with foamed samples is that the specimens either retract out of the reach of the flame or drip on to the floor of the tunnel. In Canada this has been addressed by using a downward-facing burner and mounting the specimens on the floor of the tunnel. Despite its limitations, the Steiner Tunnel method continues to be used to test and rate thermoplastic foams. 

The earlier plants operated at deficit, and needed an auxiliary boiler, which was integrated in the flue gas duct. Auxiliary burners in tunnels or flue gas duet were additionally used in some instances. This situation was partially caused by inadequate waste heat recovery and low efficiency in some energy consumers. Typically, the furnace flue gas was discharged in the stack at rather high temperature because there was no air preheating and too much of the reaction heat in the synthesis loop was rejected to the cooling media (water or air). In addition, efficiency of the mechanical drivers was low and the heat demand for regenerating the solvent from the C02 removal unit (at... 

This flame tunnel set-up was originally equipped with a modified oil burner RZ 3.3 from MAN, Germany, The burner was then fitted with a pilot burner for ignition of the bio-oil. A fuel pump delivers the fuel flow rate and pressure for load levels varying between 70 % and 100 % via electrically controlled valves. 

Figure 10 Photographs of the flame tunnel, with the control panel at the right hand side, and the flame tunnel in the middle. The burner is located at the top (not shown). At the flont side, the three injection nozzles for CEB material are visible. Through the opening in the mid e, the clear flame from diesel ts visible (right).

For the first preliminary experiments, a standard fuel oil burner system was purchased. Due to several reasons, however, a new pump and atomisation system was required, viz. a dedicated fuel punqp and a different spray nozzle. In this new set-up, primary air for a proper fiiel atomisation and secondary air for the combustion could be controlled separately. Furthermore, pumping and combustion of heavy fuel oil (sulphur content of 3.35 wt.% and a viscosity of 180 cP) was possible only, when mixed with diesel in a ratio of 60 40 (dicsehheavy firel oil). Besides, the flame tuimel had to be preheated to approx. TSO C using ordinary diesel or ethanol as a start-up fuel. When a steady state operation was observed (after approximately 10 minutes), the diesel flow to the flame tunnel could be replaced by a mixture of heavy fiiel oil and diesel (40 60), and the emissions of SOj are recorded (approx. 400 ppm). Then CEB is injected and subsequently the SO2 levels are recorded every 30 s. Usually, almost instantly a sharp decrease in the SOj concentration was observed, due to the reaction of the Ca wifti SO2. The experiments were carried out at various fiiel flow rates, ranging from 0.5 to 3 kg/hr, and at a CEB flow rate corresponding to Ca S ratios from 0 to 3. 

The products are usually fired in tunnel kilns heated with liquid fuel. The burners and lining have to be designed for temperatures of 1600 — 1800 °C,... 

Tunnel kilns are usually heated with gas or liquid fuels, and in some instances by means of electrically heated metal or SiC or M0S12 elements. The firing schedule can be controlled directly by burners and draught, and by adjusting the car speed. More uniform temperature distribution over the cross-section-is attained in small tunnel kilns which find application in the firing of special ware however, kilns with large cross-section arc used in normal ceramic operation. The functioning of a tunnel kiln is shown in Fig. I86. 

ASTM E 84 Steiner Tunnel Test. This test, which uses very large samples (20 ft x 20 1/4 in.) is referenced in all model building codes for evaluating flame spread and smoke emission of foam plastic insulation. The test apparatus consists of a chamber or tunnel 25 ft. long and 17 3/4 X 17 5/8 in. in cross section, one end of which contains two gas burners. The test specimen is exposed to the gas flame for ten minutes, while the maximum extent of the flame spread and the temperature down the tunnel are observed through windows. Smoke evolution can also be measured by use of a photoelectric cell. The flame spread and smoke evolution are reported in an arbitrary scale for which asbestos and red oak have values of 0 and 100, respectively. More highly fire-retardant materials have ratings of 0-25 by this method. 

Tunnel type. The tunnel or arch type of burner is shown in Figure 28. It consists of an accurately designed combustion chamber lined with a cement capable of withstanding over 3400° F. In this type of construe-... 

Diagram c in Fig. 114 gives the metal skin temperatures of the vertical tubes for a terrace wall furnace, as well as the temperatures reached by the wa s and supports. The top part of the figure shows the suspension of the coils by hangers, rod and counterweight Heating is provided in this case by combination burners running both on gas and fad oil atomized with steam, in the form of a line burner for the gas. and a tunnel burner for the fuel. 

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