Nakamura, Kenji

Shimomura, Akira

English

Kyoto University Research Information Repository

RIGHT:URL:CITATION:AUTHOR(S):ISSUE DATE:TITLE:On the Relative IgnitionTemperatures of Solid FuelsNakamura, Kenji; Shimomura, AkiraNakamura, Kenji ...[et al]. On the Relative Ignition Temperatures of Solid Fuels. Memoirs ofthe College of Science, Kyoto Imperial University. Series A 1926, 10(2): 89-941926-11-05http://hdl.handle.net/2433/256784On the Relative Ignition Temperatures of Solid Fuels. By Kenji Nakamura and Akira Shimomura. (Received March 31, 1926) ABSTRACT. Twenty-two kinds of solid fuels, including lignites, bitumiI1ou, as well a, anthracitic coals of oriental origin, scmi-cokP, metallurgical coke and wood-charcoal were tc,ted for their relative ignition temperatures in the sense of Wheeler's defiI1ition. A special form of heating tube with a paraffin-bath fn,ed in was used, and wa, found to give more uniform heating than the ordinary tube snch a, Wheeler used. \Vheeler's general conclmion that the higher the oxygen content of the coal, the lower the relative ignition temperature ha, been confirmed with mmt of the coals we examined. We found, moreover, that the volatile matter and ash-content, of the fuel h:we a decided influence on their relative ignition temperature,, that is, generally a high volatile or a low a,h-content gives a low ignition temperature, provided the other condi-tions remain equal. In connection with the spontaneous combustion of coal and its com-bustibility, the ignition temperature of coal has been studied by many in-vestigators under various conditions, among whom Wheeler\ Arms2, Sin-natt, Moore and Slater have recently published interesting results relating thereto. None of the methods proposed, however, is entirely satisfactory for the determination of the i1;nitz'on temperature of the solid fuel, the definition of which itself is by no means absolute at the present. In the circumstances, we experimented in the light of Wheeler's method (l. c.) which we thought very practical and easy to copy. He declares that I J. Chem. Soc., 113, 945 (1918); Fuel, 3, 366 (1924). 2 Bull. 128, Univ. IlliI1ois (1922). 3 J. Soc. Chem. Indust. 39, 72T (1920); Fuel, 2, 211 (1923); 4, 194 (1925). I<clljz" Nalamura and /lktra S!ttiilOlltUra. " from a practical as well as from a theoretical point of view, it is suffi-cient to know at what temperatures, under standard conditions, different coals begin to react with oxygen so rapidly that the ultimate appearance of flame is assured," and proposes a method to heat the coal powder by means of a sand-bath under specified coaditions, and note the rise of temperatures of both the coal and the bath, the latter always higher than the former at the beginning of the experiment The temperature of the coal rising more rapidly than that of the bath, reaches the same tempera-ture as the latter in due course, and finally exceeds it. The point at which b'.)th the coal and the sand-bath assume the same temperature is taken to be the ignition temperature of the coal relative to other coals tested in the same way. Descnptz'rm o.f tlzc Apparatus and tl1c .lvfdlzod qf Opcratz'on :-Taking into consideration all the governing experimental factors, such as degree of fineness of the coal powder, the rate of the air current, the height of the coal column, the diameter of the heating tube, the position of the thermometer bulbs and the influence of the heating medium, we resorted to the following method. Twenty grams of powdered coal (50-80 mesh) were put into a Flow meter Ca.C(2.-tube 2_5c.,,_ Gloss wool --+-+---;;;;,g Coa.l Pn, .. ~p,. bath C,los~ wool -+7...'--_-_-_-_-:._ii---~ Fig. 1. To $UC tfnri pump E:mpty bottle On the Relative Ignz'tz'on Temperatures o./ Solz'd Fuels. 9 t glass tube as shown in Fig. 1, which is a mobified form of Wheeler's original tube. It was found to offer the advantage of more uniform heating owing to the presence of a paraffin-bath secondarily heated by the electrically heated sand-bath. While a current of dry air was passed at a constant rate of 1 1 oo C· c per minute, the temperature of the sand-bath was slowly raised as uniformly as possible in each experiment, and simultaneous readings of two thermometers, one in the coal column, and the other in the paraffin-bath, were taken at frequent intervals. In this manner two time-temperature curves are obtained, one show-ing the rate of rise of temperature of the paraffin-bath, and the other that of the fuel. These two curves usually cross at a definite point, or the relative ignition temperature, characteristic of the fuel. Fig. 2. Na.n1,w Ro9a.ty• Hon<Jhi> l243'l • .-1233•, a-· . • . , • • 0 a ' (lo6.s•, ,~o 0 0 • 0 • • • 0 0 . • 0 • -0 . 0 • • 0 0 . • . S 6 I 12 IS ra 21 24 21 3 & .a ,, IS ,, 21 24 2f Time in minuteE> Fig. 2 shows the general form of the curves with three typical coals, Nansu (bituminous, vol. matter 30·84 % ) Rogatyi (semi-anthracitic, vol. matter I g• r 7 fo) and Hong he ( anthracitic, vol. matter Io oo % ). Generally bituminous coal, when it reaches its ignition temperature, shows so sudden a rise of temperature that often the hard glass tube may be fused in a few minutes, - in other words, the crossing of the two curves is very sharp. As for the anthracitic coal, not only is the relative ignition tem-perature very high, but the rate of self-heating of the coal is very much slower in comparison to other types of coal,- or the two curves do not cut each other as sharply as in the case of bituminous coals. There are, of course, intermediate forms between them. Twenty-two kinds of solid fuels, including various types of coal, semi-coke, metallurgical coke and wood-charcoal ,vere tested for their relative ignition temperatures and the results are summarised in the following table, together with the analyses of the fuels showing their percentage of volatile 92 I(m/i Nakamura and .Akim S!ttillomura. matter, ash and oxygen contents. Analyses Volatile- Ash Oxygen Relative No. Solid fuel matter (dry basis) (dry, ashlcs; basis) ignition temp. (dry basis) % % 100-(C+H+N)% oc -- -·--·-- -·---, I Ten-tan 32,73 II•53 21•03 215 2 Mgach 3ft 35·7° 2·34 23•77 221 3 Yubari No. 1 pit 43,39 10,69 II,74 216 4 Koyaki 38,88 8,78 J0,85 22i 5 Sakito 37·23 12•I4 IJ,63 22I 6 Namu 30•8} 3·73 13,16 206,5 7 Hashima 33·7+ 6-75 9•27 225 8 Matsushima 33·57 12,63 12·93 218 9 Besshu 32,81 II•70 6°56 228 IO Sasa 30,80 13,99 8-92 222 II Kaiping 27,47 13-43 13,22 213 12 Dui 24,69 5·03 u,46 221 13 Pmhan 20•02 11·27 5·4° 24i 14 Rogatyi 19-17 9-56 5-64 233 15 Honghe l0•00 12,83 3·42 243 16 Tsun-chin 8-75 II 0 85 5-83 241 17 Kin t,hou 7-68 13·95 3-21 231 18 Mallien 3·5 2 16,61 2•74 347 19 Semi-coke 14,87 II•04 9·94 223 (Yubari No. I pit) 20 Coke J,70 15-29 0•27 too high to (Yubari No. I pit) measure 21 Charcoal (soft) 16,46 0-85 8-34 208 22 Charcoal (hard) 5,ro 3,41 5°01 230 ----It is known that coals that most readily self-heat are those containing the highest proportion of oxygen. As ~hown in Fig. 3a, this was found true with most of the fuels we examined, with occasional exceptions. So far as we have examined, this rule does not seem to hold with lig-nitcs, the oxygen content of which exceeds 2o~{J. Although not so distinct as the oxygen content, the volatile matter Fig. 3a. Fig. 3b. Fig 3c. t34'7° t 347' 347"1' C) . @ @ ® ;t 0 LI') ~ CII "' ® @ @ @ @ ~ @ "' 0 ~ 0 @ ® @ ~ <at C,I ".'1. "' " ® ~ .. ® ® ;::: :, +>. ® @lj) €) ~-O 0 @ @ "' .. t') <::)' .. C\I ® ® ® ,:: CL E ®© ® ® ;;:-3 ~ @ @ © @ " . @)@12(IDS ®2Cll)s @) ;::: @ @ ® @ @ ~ c:o "' O Cl ~ .,.:e1 ® ® ® C: @ (1 ®<D ~ "' © © a ., 0 @ @ @ .::. 0 ~ +- -~ CJ @ ® @ ~ " ® ® @ 0::: I ~ :;:._; . ~ 0 0 Cl 10 15 20% 10 20 30 40% s 10 rs% ;;; 5 ~ Oxy9en.-content Vo la.tile Matter Ash-coni:ent. C (.,J gi 1Vaka111ura and Shr"momum. On thr: Rdatzi1e fgmlton Temp. de, and ash contents of the fuel were found abo to exert a decided influence on its relative ignition temperature as shown diagrammatically in Figs 3b and 3c, contrary to \Vheeler's conclusion that "no relationship exists h::tween the ignition temperature now recorded and other (than oxygen content) analytical data." 1 Hence, in general, the greater the oxygen content or volatile matter, or the less ash content tends to lower the relative ignition temperature of the solid fuel if other factors remain constant. On closer examination, it will be found that those the ignition temperatures of which deviate from the general trend have always a more prominent effect of other factors than th::: one in question. Prof. J. Yonez::iwa of the Osaka lligher Technical School examined the relationship between the relative ignitiori temperatures and the amount of pyridine extract with several Hokkaido coals and Hokoku coals (unpub-lished), and came to the conclusion that the coals that yield less extract generally show lower ignition temp:cratures. \Ve wish to take this op-pnrtunity to thank Prof. Y oneza wa for kindly giving us his data on this subject. In conclusion we offer our cordial thanks to Prof. M. Chikashige for his interest in this work. I J. Chem. Soc., 113, 95.3 ~1918). 

On the Relative Ignition Temperatures of Solid Fuels

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On the Relative Ignition Temperatures of Solid Fuels

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