Document OVdKmzKwb7gOwGxr70NYXpzL

HEATING VENTILATING AIR CONDITIONING GUIDE 1940 Table 9. Representative Properties of Gaseous Fuels, Based on Gas at 60 F and 30 in. He. --1---------- ;----------- Gas (Gross) . (Net) Specific Sravitt, roa Coubds- 1.00. (Co Ft) Products of Combustion Cubic Feet Total COi ff<0 with Ni Ulti- . ?lame TimHATE PESATUffiS, (DEO FAHB) Dry Baas Natural gas-- California . 1200 1087 0.67 11.26 T.24 2.24 12.4 12.2 3610 Natural gas--" J Mid-Conti nental , 967 873 0.57' .. .9.17' . o:97 1.92 IQ'-2, 11.7 3580 , Natural gas-- ^ Ohio 1130 1025 0^65 10,70 1.17 -2.16 11,8 12,1 . 3600 Natural gas-- Pennsylvania : Retort coal gas Coke oven gas .1232 575 588 1120 510 521 0.71; ; 11.70 0.42 5.00 0.42 5.19 1.30 0.50 0.51 2.29 1.21 1.25 12.9 .5,7 5.9 12.3 3620 11.2 ...3665.. 11.0 3660 Carbureted" water gas Blue water gas '536 308 496 0.65 281 0.53 4.37 2.26 0.74 0.75 0.46 0.51 5.0 17.2 2.8 22.3 3815 3800 Anthracite pro ducer gas 134 124 0.85 1.05 0.33 0.19 1.9 19.0 3000 Bituminous producer gas Oil gas 150 140 0.86 575 510 0.35 1.24 4.91 0.35 0.19 2.0 19.0 3160 0.47 1.21 5.6 10.7 3725 COMBUSTION OF GAS The majority of gas burners utilized in central domestic heating plants are: of the Bunsen type and operate with a non-luminous flame.. In this type of burner part of the air required for combustion is mixed with the gas as primary air, the air and gas mixture being fed to the burner ports. Additional secondary air is introduced around the flame by draft inspi ration. In the luminous flame burner, which is sometimes used, all of the air for combustion is brought in contact with the flame as secondary air. The importance of bringing the secondary air into intimate contact with the gas is noted. . Some makes of burners use radiants or refractories to convert some of the energy in the gas to -radiant heat by utilizing the principle of surface combustion. The radiants also serve as baffles in directing the flow of the products of combustion. Since one of the main functions of a gas burner is to properly proportion the air and gas, any marked change in the gas composition which affects the specific gravity necessitates a readjustment of the burner. It is necessary to supply a greater amount of air when the specific gravity of a gas is increased. 176. CHAPTER 9. COMBUSTION AND FUELS : The quantity of air given in Table 9 is that required for theoretical combustion, but with a properly designed.and installed burner the excess air can be kept low. The division of the air into primary and secondary is a matter of burner design and the pressure of gas available, and also of the type of flame desired. The air gas ratio has a decided effect upon flame propagation. It is necessary that the gas will flow out of the burner ports-fast enough so that the flame cannot travel back into the burner head, i.e. flash back, but the velocity must not be so high that it blows the flame away from the port. The maximum and minimum flow speeds from burner ports which may be permitted are known to be very close together when air-gas mixtures in theoretical proportions are being supplied to the burner. As the air-gas ratio is lowered, and the mixture becomes more gas rich, the limiting speeds become further apart, until with 100 per cent gas, in an all-yellow flame, flash back cannot occur and a much higher velocity is needed to klrtur rtff bVio fl-imnc The deposit of soot on the flue surfaces of a boiler or heater acts as an insulating layer over the surface and reduces the heat transmission to the water or air; the Bureau of Mines Report of Investigations No. 3272 shows that the loss of seasonal efficiency is not as great as has been believed and usually is not over 6 per cent because the greater part of the heat is transmitted through the combustion chamber surfaces. The soot accumulation clogs the passages and reduces the draft; the loss of effi ciency from this action may be considerably greater than from the reduction in heat transfer. REFERENCES Fuels and Their Combustion, Haslam and Russell (McGraw Hill Co., 1926). Principles of Combustion in the Steam Boiler Furnace, Arthur D. Pratt, (Babcock and Wilcox Co.). .uuuwng j enaencies in coats ot Various Rants h,, u T o a^riWApsi^E- Journal sTM .,, ,, Bureau of Mines Publications: Bulletin No. 97, Sampling and Analyzing Flue Gases, by Henry Kreisinger and F. K. Ovitz. Report of Investigations (R.I. 2980), Coke as a Domestic Heating Fuel, by P. Nicholls and B. A. Landry. Bulletin No. 276, Five Hundred Tests of Various Coals in House-heating Boilers, by P. Nicholls, S. B. Flagg and C. E. Augustine. Report of Investigations (R.I. 3283), Quality of Anthracite as Prepared at Breakers, 1935. Technical Paper No. 80, Hand Firing Soft Coal under Power-Plant Boilers, by Henry Kreisinger. Technical Paper ating Steam in F. C. Houghten. No. 303, Value a Low-pressure of Coke, Anthracite, Cast-iron Boiler, by and Bituminous Coal for GenerJohn Blizard, James Neil and