INDUSTRIAL AND ENGINEERING CHEMISTRY
154
formation of by-products. The correlating more effectually of small-scale tests with industrial practice has been advanced by giving a definite interpretation and usage to the term “carbonizing temperature”-namely, the temperature immediately at the surface of the carbonizing mass next to the hot wall of its container. The question of what constituents give the coking property, and how they do it, is by no means settled. It seems probable, in the author’s opinion (based on experiment), that by reason of the fluid quality of many good
Vol. 26, No. 2
coking coals, shown by their extrusion possibilities through very small orifices, a large proportion of a12 the organic constituents of coal softens more or less by heat. LITERATURE CITED (1) Rept. Fuel Research Board (Gr. Brit.) for year ended March 31, 1933, H.M.Stationery Office, London. (2) Sinatt, F. S., private communication, 1933. (3) Warner, A. W., U. S. Patents pending. RECEIVED September 8, 1933
Progress in Low-Rank Coals IRVIKLAVINE,TJniversity of North Dakota, Grand Forks, N. Dak. The importance of the low-rank coal reserres of this country becomes clearly evident when a comparison is made of the distribution and amount of coal in the fields of the LTnited States with the output of these mines. Such a study shows that, although the bulk of the coal in this country is low rank, the greatest output has been coming from the high-rank deposits. This discrepancy cannot CORtinue forever. The low-rank coals are characterized by a high moisture content, slacking upon exposure to the atmosphere, disintegration in the fire, and noncoking quality. The first attempt at eliminating some of these nondesirable qualities was the briquetting of these coals by the German process. It was soon found that the American fuels are not adaptable to this method, but that good briquets could be made from the carbonized residue obtained f r o m these coals.
T
HE low-rank coals of this country represent a vast tonnage of fuel of commercial value. For many
The low-runk coals are now burned in modern power plants with eficiencies that approach that obtained with high-rank f u e l . These fuels can be used successfully in the manufacture of producer gas. Microstructure and extraction studies haae provided valuable information as to the physical and chemical make-up of the low-rank fuels. The moisture in low-rank coals is held colloidally. Studies with lignite have indicated many of the properties of the moisture in these coals. They do not possess a n abnormally high tendency f o r self-heating owing, primarily, to the large proportion of water naturally contained which requires a large expenditure of energy to bring about its evaporation. Recent studies on the coking o j these coals have shown definite possibilities in this direction. Dehydration and the production of a n active carbon are other phases that offer possibilities.
Lignite is a noncoking and noncaking coal. Its destructive distillation leaves a noncoherent char in contradistinction years these fuels were given only little attention, but to the solid coherent coke obtained with certain bituminous their economic importance from a national point of view is coals. Jeffrey (34) has reported, however, that a coke can being discerned. The term “low-rank coal” will be applied be obtained from certain lignites, but unfortunately the to those coals that are lowest in the U. S. Geological Survey method for accomplishing this was not given. The term “sub-bituminous coal” has been adopted by the classification-namely, lignite and sub-bituminous coal (16). Lignite can be considered as the first stage in the trans- U. S. Geological Survey for the “black lignite” coals between formation of peat into coal. I n color lignite is brown or, in bituminous coal and brown woody lignite (16). A subthe better qualities, often deep black. The black variety bituminous coal can generally be distinguished from a lignite upon being dried and pulverized turns dark brown. The by its dense black color and its lack of a distinctly woody luster of lignite varies from dull to brilliant, depending on texture and structure. I n common with lignite, this coal the composition and structure. A woody specimen of freshly has a high moisture content, slacks freely on weathering, and is noncoking. These latter characteristics have heaped a mined lignite shows a dark dull luster. Some specimens of lignite upon being mined expose pitchy, national disgrace upon a natural resource which some day will jetlike, bright layers and inclusions which upon close ex- play an important role in our economic welfare. amination are found to be fragments of more or less rotted COALRESERVESIN THE UNITEDSTATES wood. These pieces may range in size from small slivers The United States is fortunately situated with respect t o to chunks of wood or parts of tree trunks. I n other speciabundant supplies of coal. Twenty-eight of the forty-eight mens the woody structure may be entirely obliterated. Lignite burns with both flame and smoke and often gives states, Blaska, and the Philippine Islands have a bountiful off a disagreeable odor in the process. Furthermore, in spite supply of coal; eight states possess only a small amount, and of its relatively high volatile content, lignite lacks the proper- twelve states and the Hawaiian Islands are absolutely void ties of fusing and coking in the fire that bituminous coals of coal. The total United States reserve represents nearly possess. I n consequence of this tendency to slack in the fire, 52 per cent of the world’s coal reserve (16). Table I gives the estimated tonnage of coal in the United special grate construction or firing methods are necessary to States and the reserves a t the end of 1930 according to data prevent excessive loss of unburned fuel in the ash pit.
L\DUSTKIAL
February, 1934 TABLE
I.
E ST I MiT E D ORIGlSXL
hXD
TOSSAGE OF
EYGINEERING CHEMISTRY RESERVES AT
cO.IL I N VNITED STATES AND THE
133 THE
ENDOF 1930
(In thousands of tons) LIGSITE
Alabama Arkansas Arizona California Colorado Georgia Idaho Illinois Indiana Iowa Kansas Kentucky Maryland Michigan Missouri Montana New Mexico North Carolina North Dakota Ohio Oklahoma Oregon Pennsylvania South Dakota Tennessee Texas Utah Virginia Washington West Virginia
...
SCB-BITUMINOCJ
BITUMINOUJ
1,141,000 16,000 104,175,000
67,583,000 170,000 10,000 27,000 2 13,071,000
90,000
SEMI-ANTHRACITE .&ND .$NTERACITE
F R O M E A R L I E S T RECORD TO END OF 1930
557,034 64,150
400,000
1,216,000
......
5,160R 348,705 10,747
100,000
93:~oon
100,000
....... , . . , ., . . . . .
2 ,‘1’02;374 613.575 283,679 2 11$7 5 924,711 228,423 40.266 186,089 97,135 94,768 1,011 24,606 1,190,506 119,052 2,380‘~ 9,095,888
6,536,000
........
62,985,000 172,906,000
315,474,000
. . . . . ...... 600,000,000
........
....... . . . . . .
. . .
93,967,000 46,951,000 3,000.000 102,574,000
7,000,000
........ 1.020,000 ........
8,000,000 2 1,000,000
9,574,000
......
219,568 51,918 110,317 279.003 L13.624 2,035,020 241,234 45.894
. . . . .
23,000,000
........
5,156,000
L9,900,000
590,’itio,ooo ,
.,.,
,
~-
939,584,000
900,000 23,000
400,000
52,442;OOO
. . . . . . Total
TOTAL PRODUCTION
SEMI-BITUXINOUJ
........
,
996,081,000
.......
. . . .
1,429,895,000
--
56,569.oon
~~
22,423,000
i9.798.612
Thousand tons Orieinal total reseryes: Lignite Sub-bituminous Bituminous Semi-hituminous Anthracite and seiu-anthracite Total reserves a t end of 1930 Total production Estimated loss in mining Through 1925.
939,584,000 996,081,000 1,429,895,000 56,569,000 22,423,000
furnished by the U. S. Geological Survey and the Bureau of Mines (16, 54).
RANKSOF COAL The U. S. Geological Survey uses the word (‘rank” to designate (‘those differences in coal that are due to the progressive change from lignite to anthracite, a change marked by the loss of moisture, of oxygen, and of volatile matter” (26). Obviously, the degree of metamorphism is not defined sharply, with the result that the classification of coal by rank has been a major problem of discussion. The Geological Survey recognizes the following ranks of coal: (1) lignite, (2) subbituminous, (3) bituminous, (4) semi-bituminous, ( 5 ) semianthracite, and (6) anthracite. All ranks of coal from the woody lignite of North Dakota to the highest rank of anthracite in the fields of eastern Pennsylvania are found within the boundarieb of the United States. Table I1 shows the average proximate and ultimate conipositions of peat and various coals. The low-rank coals of this country are found primarily in the western and southern coal areas. The northern Great Plains province, which includes all the coal fields in the Great Plains east of the front range of the Rocky Moun-
LI ) S I T E
PE.4T
28,207,612 3,416,344,388
Quantity available b Through 1920.
T.+BLE11.
3,444,552,000
19,798,612 8,409.000b
tains, contains the largest deposits of lignite and sub-bituminous eoal. The largest coal region in this province is the Fort Union which lies in North Dakota, South Dakota, Montana, and Wyoming. Throughout the western part of North Dakota, the northwestern part of South Dakota, and eastern Montana the coal is a brown woody lignite with a moisture content, as mined, of 30 to 45 per cent. However, in the vicinity of Miles City, Mont., the brown lignite begins to lose the woody structure and gradually assumes the black color and general appearance of a sub-bituminous coal. The sub-bituminous coal in southern Montana is not of high quality, but farther southwest it improves until it reaches its best development in the vicinity of Sheridan, Wyo., where it has been mined extensively for a number of years. The next field of any consequence in this province is found farther south in Colorado and is generally known as the Denver region. This extends from the Wyoming line southward as far as Colorado Springs. The sub-bituminous coal in this region is extensively mined northwest of Denver and to some extent at Colorado Springs, and finds a ready market in and about these two cities as a domestic fuel. Large fields of low-rank coal are found also in the Rocky Mountain province which includes the Yellowstone region in
. ~ . I L Y S E S OF
PEATAXD COALS SEMI-
SUBBITUXINOU4
~ITW\iINOUS
BITUXINOUI
SEMIANTAR\CITE
.iNTHR \CITE
PROXIMATE A N l L Y 3 E 3
Fixed carbon, % ’ Volatile matter, % Moisture, % Ash % Heiting value, B. t. u./lb. (Cal./kg.)
2.5 5.0 85.5 0.0 725 (403)
Carbon % Hydrogkn, % Oxygen, % Nitrogen, % Sulfur, %
55.0 6.0 36.5 1.5 1.0
30.0 27.0 36.0 7.0
6000-7000 (3334-3889)
45.0 32.0 15.0 8.0 10,500 (5834)
U L T I M A T E ANALYdEB ( M O I S T U R E -
68.0 5.5
24.5 1.0 1.0
73.0 5.5 18.5 1.5 1.5
50.0 35.0 5.0 10.0 14,000 (7778)
A N D ASH-FREE
85.0 5.0 7.0 1.4 1.6
72.3 16.5 3.5 7.5 13,500-14,000 (7500-7778)
i5.5 9.5 3.5 11.5 13,000-13,500 (7223-7500)
80.0 1.5 3.5 15.0 13,000-14,000 (7223-7778)
BASIS)
89.0 4.8 4.4 1.1 0.7
02.0 3.5 2.5 1.0 1.0
94.0 2.5 1.5 1.0 1.0
156
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
Montana; the Big Horn, Hams Fork, and Green River regions in Wyoming; the Uinta region of Utah and Colorado; the San Juan River region of Colorado and New Mexico; and the southwestern Utah region. This province contains a greater variety of coal than any other in the United States. The coal ranges from lignite to anthracite, though the prevailing ranks are sub-bituminous and low-grade bituminous. The coal is mined rather extensively, the greatest centers of development being Red Lodge, Mont., Rock Springs and Kemmerer, Wyo., Crested Butte and Durango, Colo., Castlegate and Sunnyside, Utah, and Gallup, N. Mex. Fields of low-rank coal are found also in the Pacific Coast province which includes California, Oregon, and Washington. California and Washington have small fields of lignite and sub-bituminous coal within their borders, but very little mining is done in these two states. However, considerable sub-bituminous coal is mined in Washington. Extensive lignite deposits are found in the southern Gulf province. These extend through parts of Texas, Louisiana, Mississippi, Arkansas, Alabama, and Tennessee. The presence of high-rank coal in the nearby fields of Arkansas, western Kentucky, and Alabama, as well as numerous oil and natural gas deposits throughout this province, has greatly handicapped the development of these lignite deposits. The deposits of lignite in the northern Great Plains province lie primarily in North Dakota where the reserve has been estimated a t 600 billion tons. Because of climatic conditions which make the use of fuel a necessity during the greater part of the year, the mining of lignite in North Dakota has received considerable attention. The state has always encouraged the development of the lignite mining industry and
and Texas. as follows:
Vol. 26, Yo. 3
Production data for these states in 1930 are
STATE
Tons 1,700,157 749,550 54,000 12,810 2,516,517
North Dakota Texas lfontana South Dakota
TABLE 111.
Value
$2,768,000 984,000 100,980 3 1,000 $3,883.980
;\SALYSES OF LOW-E.4NK C O A L S
VOLA- FIXED LOCATIOX OF COAL Aria.. Black Mesa Field Ark,.,’Cainden District Calif., Mount Deablo Dist. Calif. Ione County Colo. ’ Colo. Springs Field Colo.: North Park Field Idaho. Goose Creek Field Mont.’, Glendive-District Mont., Miles City District Mont.. Missoula Field N. Mex., Gallup District N. Dak. Ward County Ore. Cobs Bay Field S. D’ak., Harding County Texaa, Houston County Texas, Milam County Utah, Surnmet County Wash.. Kine Countv Wash.; ThGston County Wyo., Sheridan District Wyo., Big Horn Basin
TILE
CAR-
%
%
%
9.9 39.4 15.0 34.5 26.2 20.0 34.3 34.6 29.2 24.7 12.7 36.5 18.0 41.5 33.5 36.0 14.2 15.9 21.0 22.6 16.5
32.6 26.5 38.4 33.8 29.7 32.5 26.6 35.3 26.2 29.3 36.5 28.4 31.8 24.0 39.5 27.9 36.0 36.0 33.1 32.5 32.9
46.9 24.4 34.5 18.7 37.7 42.5 25.7 22.9 35.4 26.1 43.3 28.7 39.7 24.3 16.2 28.7 44.8 38.5 30.7 40.4 45.8
Ha0 MATTER B O N
(f 6)
CALORIFIC ASH SULFCRVALUE % % B.t . u./lb.
10.6 1.1 9.7 0.5 12.1 5.6 13.0 1.1 6.4 0.3 5.0 0.6 13.4 2.5 7.2 1.1 9.2 0.8 19.9 0.9 7.5 0.7 6.4 1.4 10.5 2.2 10.3 0.6 10.8 0.6 7.4 0.8 5.0 1.4 9.6 0.5 9.2 0.4 4.5 0.3 4.8 0.6
10,800 6,360 9,240 6,754 8,350 9,750 8,610 7,090 7,670 6,730 11,230 6.750 8,810 5,650 7,140 7,130 10,030 9,970 8,910 9,220 10,750
RESULTS O F BRIQUETTING TESTS
Mention has been made that the low-rank coals are characterized by a high moisture content. As a direct consequence, these coals have the undesirable property of slacking or crumbling upon exposure io the atmosphere. This may be attributed to physical strains set up within the lump. Thus, when a lump of lignite or sub-bituminous coal is allowed to dry rapidly, the outside layer loses moisture more rapidly than the inside. Consequently, the outside shrinks whereas the inside does not, and the outer layer splits and peels off. A new layer is exposed, and the process repeats itself until, finally, degradation is complete. Figure 2 illustrates this phenomenon. The possibility of concentrating these lowrank coals, particularly the lignites of low heat value, into a fuel of high heat efficiency which possesses weathering, handling, and burning qualities equal to the higher rank coals was considered as early as 1900. A satisfactory method had already been developed in Germany for the briquetting of brown coals. This consists in s u b j e c t i n g t h e p a r t l y dried and FIGURE1. LIGNITEBEDWITH OVERLYING CLAY AND S A K D powdered fuel to enormous p r e s s u r e s . No Ditch or bindine material is used except the inhas appropriated money annually for lignite investigations. herent tarry h a t t e r of t h e i o a l which is liberatid during This work has been carried on for the past thirty years a t the the compression. I n August, 1904, Holmes (33) shipped State University and as a result the beds of lignite in the samples of lignite from Lehigh, N. Dak., and Rockdale, northern field are much better known than are those in the Texas, to Madenburg, Germany, to be tested in a briquetting press. The first reports indicated that briquets of good southern field. There are approximately 124 thousand square miles of quality were made, but later it was shown that the American briquets did not possess good weathering or handling properlignite territory in the United States distributed as follows : ties. STATE STATE The U. S. Government began a series of briquetting inSq. miles SQ.miles vestigations in 1904 a t its fuel testing plant in St. Louis, 7.000 Montana Alabama 6,000 28,000 North Dakota 5,900 Arkansas Mo. The presses used were of English and American de4,000 South Dakota 1 California 1,000 sign (57). I n 1908 this work mas transferred to the Pitts500 Tennessee Kentucky 60,000 8,800 Texas Louisiana burgh fuel testing plant, where a complete briquetting plant, 3,000 .Mississippi 124,200 TotaI including a German press, was installed. Lignites from North Lignite production in this country is confined a t present Dakota, Montana, Texas, and California, and sub-bitumialmost entirely to North Dakota, South Dakota, Montana, nous coals from Wyoming, Washington, Utah, S e w Mexico,
I>
8:
Colurado, and CaliSorniu. were tested a t these two statiiins. The work showed definitely that briqiiets could be rnade from some OS the coals tested, hut, although tlie resistance to weatliering was increased, it was Couiid t.liat these hriquets did not siaiiri outside storage and disintegrated iii the
E AND SUB-BITUMINOUS C O A L A S A F U E l i I O N
POWER
The low-rank coals have been used for rriuiiy years for generating steam. Reports of tests on the use OS Dakota lignite for power purposes date from 1894, and doubtless fire. this :md tlic other low-rank fuels of this country were used igators iiext t,iirot:il their attention to the in t,iiis connection for some years previously. Phillips ani! irrattcr of using artificiil iiinderij in tlie lirirjoetting U S raw W,,rrcll (47) report also the early use of Texas lignite for pulverized liigli-moistnrt~ coals in tire attempt to iucrease steam raising purposes. the resistance to weathering arid t o ininirriiae tlic ilisiiiti:. One irf tlie early and rat,lier wniplete teats u i ligriite for gration in tire fire. Altlmngh it, \ w s Sound that tlic addition was iiiailc by liaiul:dl and Kreisinger (4% of pit,cli or asphalt for bioders does increase the wcatiiering 1)ak. They sliowcd at that time that stearn resistance of the iiriquet, t,lie proiliiatiun of a YatisfaCt
