STUDY OF BITUMENS FROM BROWN COALS OF THE YARSKOYE DEPOSIT IN TOMSK OBLAST

I. V. GEBLER and K. K. STRAMKOVSKAYA

Brown coals constitute a fairly significant part of the enormous coal resources of our country. Although the USSR possesses very large quantities of hard coals, which in most cases find broader application for economic purposes than brown coals, the role of brown-coal resources is nevertheless enormous. Brown-coal basins and deposits are, first and foremost, local coal bases. The use of brown coals may be carried out not only by burning them, but also as a chemical raw material for gasification, low-temperature carbonization, the production of liquid fuel, and a number of valuable chemical products (if the properties of the coal permit this).

One of the valuable products that can be obtained from brown coals is montan wax, or mineral wax, which belongs to the class of valuable fossil waxes. It finds wide application in a whole series of branches of industry, among which the following may be mentioned: electrical engineering—for insulating purposes; printing—in the production of technical papers and typewriter ribbons; the leather and footwear industry—for creams and dressings; and the production of consistent lubricants—for the manufacture of ointments and heavy lubricants for rolling mills.

Montan wax is obtained by extracting bituminous brown coals. The bitumen obtained by extracting brown coal with benzene or with an alcohol–benzene mixture, or crude montan wax, is a black or black-brown brittle mass with a shiny surface and conchoidal fracture.

We studied 6 samples of brown coal from the Yarskoye deposit. One of the samples was taken from the first drift that had been driven and had lain in the laboratory for approximately 1.5 years (hereafter it will appear under the designation “oxidized”). Five samples were fresh, taken from various places of the seam along its strike. The results of technical and elemental analyses for the oxidized sample are given in Table 1.

Table 1

For the fresh samples only a technical analysis was carried out, and it is presented in Table 2.

The industrial value of brown coal depends to a significant degree on its bitumen content, for the latter determines the amount of tar obtained from brown coal in the process of low-

Table 2

coking, and also resolves the question of the use of brown coals for obtaining montan wax, or mineral wax.

Extraction was carried out by us in a Soxhlet apparatus. The sample was first brought to an air-dry state and ground to the fineness required for analysis. As solvent, alcohol-benzene (1:1) was taken, giving the highest yield of extract. Extraction was carried out for each sample until the liquid in the siphon of the Soxhlet was already only faintly colored. Alcohol-benzene was distilled off from the extract obtained, and the remaining mass was dried, until all traces of solvent had been completely removed, in a vacuum drying oven at a temperature of 50°C and a vacuum of 600 mm of mercury to constant weight. The crude mineral wax obtained in this way is a black, lustrous mass with a conchoidal fracture, easily ground in a mortar.

At present it has been established that crude brown-coal bitumen consists of montan wax and montan resin. From the chemical point of view, bitumen is not a homogeneous substance, but is a mixture of various substances, chiefly high-molecular fatty acids and their esters with high-molecular alcohols, which constitute the wax proper, accompanied by resinous and sulfur-containing substances. Waxes belong to compounds of the fatty series, while resins belong to hydroaromatic compounds. The most rapid separation of bitumens into waxes and resins is achieved by treating the crude bitumen with ether [3]. A weighed portion of well-ground bitumen was moistened with approximately five times its weight of ether, shaken at room temperature, and filtered after first allowing it to settle. The undissolved wax was washed on the filter with ether until the solvent became colorless; after distilling off the ether, the resins were dried in a vacuum drying oven under the above-mentioned conditions, and the montan resin obtained was purified from the wax that passed into solution by dissolving it in boiling alcohol and subsequently precipitating the wax fraction from the cold solution in the form of a precipitate. But the part of the wax obtained in this way has the same softening temperature as the resins; therefore this part was assigned to the resins.

The content of montan wax was determined as the difference of 100% minus the percentage of resins. The softening temperature was determined by the Kremer-Sarnow method. In addition to the softening temperature, the acid, esterification, saponification, and iodine numbers were determined for the crude bitumen, montan wax, and montan resins.

The chemical characteristics of the bitumen from brown coal of the Yarskoye deposit, oxidized sample, are presented in Table 3.

Table 3

The yield of bitumen from fresh samples of Yarskoye brown coal is presented in Table 4.

Table 4

If these brown coals are compared with other brown coals of the USSR, they are closest to the Aleksandriyskoye coals [1]. The bituminousness of bed samples of Aleksandriyskoye brown coal is given in Table 5.

Table 5

The composition of the crude bitumen of Yarskoye brown coal from fresh samples is, on average: montan wax—41.03%; montan resin 58.97%. Hence the yield of montan wax on the dry mass of coal averages about 4.5%.

The determination of the characteristic numbers and of the yield of resins and waxes, in view of the small amount of bitumen, was carried out after the bitumen extracted from the various samples had been mixed. The results are presented in Table 6.

Table 6

The montan wax of the Aleksandriyskoye brown coals, containing 6.74% resins, has the following characteristics [2]:

Softening temperature according to Kramer-Sarnow . . 84°C
Acid number . . . . . . . . . . . . . . . . . . . . 16.8
Ester number . . . . . . . . . . . . . . . . . . . 56.9
Saponification number . . . . . . . . . . . . . . . 73.7

The debituminized coal has the following characteristics.

Sample No. 4

Analytical moisture \(W^a = 4.3\%\)
Ash on dry mass \(A^c = 25.2\%\)
Volatiles on combustible mass \(V^r = 59.6\%\).

It follows from this that the volatiles in the coal lost as a result of extraction amount to

\[ 63.4 - 59.6 = 3.8\%. \]

Such coal briquettes quite well.

According to the results obtained, Yarskoye brown coal has a significant bitumen content. This makes it possible to assume that the Yarskoye brown coals merit attention from the standpoint of using them as a material for the industrial production of montan wax.

LITERATURE

1. Burov M. N.—Chemical processing of brown coals of the USSR. Collection of articles. Publishing House, 1938.

2. Burov M. N.—Chemical processing of fuels in the USSR. Collection of articles. Publishing House, 1936.

3. Ed. Grefe—A guide to the study of products of the brown-coal industry.