PROCEEDINGS
OF THE TOMSK POLYTECHNIC INSTITUTE NAMED AFTER S. M. KIROV,
ORDER OF THE OCTOBER REVOLUTION AND ORDER OF THE RED BANNER OF LABOR

Volume 195 1974

DEVELOPMENT OF THE FOUNDATIONS OF A METHOD FOR THE CHEMICAL-METALLURGICAL USE OF PEAT

S. I. SMOLYANINOV

1. Prospects for the Use of Peat in the Metallurgy of Western Siberia

Western Siberia is now beginning to play an outstanding role in the development of the material and spiritual culture of the Soviet Union, in the creation of the material and technical base of communist society. The economic power of the country is increasingly based on Siberian sources of energy and industrial and agricultural raw materials. The concentration of colossal and diverse natural resources, as well as the geographical position of Western Siberia, create exceptionally favorable opportunities for the growth of its economic potential. Fuel and energy resources of this region must have an altogether special significance for the development of Western Siberia and of the whole country as a whole.

The broad involvement of the fuel and energy resources of the eastern regions of the USSR in the national economy is closely connected with the general task of rationalizing the entire fuel economy of the country; this determines the rational location of industry over the territory of the USSR in the direction of concentrating the further construction and development of energy-intensive production in the East.

The specific nature of the economics of energy-intensive production consists in the high share of energy costs: they account for 35–60% of all production and operating expenses, while the accompanying (associated) capital costs in the fuel and energy bases serving them amount to 50–100% of the capital investments in the main production. In terms of the magnitude of fuel and energy resources, as well as the degree to which Western Siberia is supplied with them, it ranks third in the USSR after Eastern Siberia and the Far East. The fuel and energy resources of the region, in absolute magnitude, exceed those of the European part of the country.

In recent years, colossal oil and gas deposits have been discovered in the West Siberian Lowland. Thus, the potential reserves of natural gas amount to 16.5 trillion \(m^3\). In the future, oil production may be raised to 150 million \(t\), and gas production to 200 billion \(m^3\) [1].

The West Siberian Lowland is also the largest peat region and possesses peat resources estimated at almost 95 billion \(t\), constituting more than 60% of the all-Union peat reserves [2]. The scale of the resources of this type of combustible mineral can be understood if it is pointed out that the reserves of coal suitable for open-pit mining in the Kuznetsk Basin amount to 7 billion \(t\), and bu-

...of the Itat deposit—one of the most promising in our country for open-pit mining—20 billion tons [1].

Increasing the efficiency of fuel utilization may be regarded as one of the most urgent tasks of science and practice. A realistic path in this direction is the comprehensive use of fuel with the maximum extraction of chemical products before its combustion. Among the possible methods of comprehensive processing, the economically most advantageous are those in which the solid residue finds the most qualified application, i.e., above all as a metallurgical fuel. In this respect peat has a number of advantages. With a high yield of chemical pyrolysis products, the blast-furnace process on peat can produce high-quality pig iron, such as that obtained, for example, with charcoal, which is still used for smelting high-grade steel.

These questions are of special interest for the Vasyugan-Tym territorial complex of natural resources, which occupies the central part of Tomsk Oblast. Within this territory are concentrated world reserves of iron ores, as well as oil, natural gas, peat, and timber [3]. The presence here of colossal resources of iron ore and peat raises the problem of the comprehensive use of peat and metallurgy.

Peat can find varied applications in metallurgy. Peat semicoke and coke are suitable for use as a lean component of the burden and for the agglomeration of iron ores. Coke from peat, or the latter in an air-dry state in the form of pieces with specified physical properties, can serve as blast-furnace fuel and as fuel for foundry purposes. Owing to its high reactivity, peat is a good reducing agent for iron.

Experiments on the use of peat coke were begun in Russia in 1897 at the Kulebaki ironworks. In 1930 work in this direction was carried out by a special commission under the leadership of Academician M. A. Pavlov at the Vyksa and then at the Kosogorsk works. At about the same time attempts were made to use peat coke for foundry purposes. Air-dry noncoked peat was also successfully used as a blast-furnace fuel. The latter experiments were conducted by P. M. Vavilov at the Kulebaki and Vyksa works in 1913 and later, in 1922–1923. In 1932 an experimental smelting was carried out by a commission that included Academicians M. A. Pavlov and E. V. Britske, Prof. N. P. Chizhevsky, and others, at the Kosogorsk works in a furnace with a volume of 348 m³. In 1933, at the Chernorechensk chemical combine, the Nitrogen Institute conducted experiments on the use in a blast furnace of air-dry peat with an oxygen-enriched blast.

Experiments with air-dry peat showed that in this case the blast furnace is transformed into an integrated unit that produces three times as much gas as in the process using coal coke, with a significantly higher calorific value. In addition, from 5 to 10% of the weight of the peat tar is obtained. A consequence of this was the advancement of the idea of a comprehensive chemical-metallurgical process, which found support among leading scientists up to the most recent time [4–8].

In recent decades, work on various directions in the use of peat in metallurgy has been carried out by VNIITP, Giprotorf, the A. A. Baikov Institute of Metallurgy of the Academy of Sciences of the USSR, the Voronezh Civil Engineering Institute, and the Moscow Mining Institute [9–12].

For the blast-furnace process, lump fuel of definite physical and physicochemical properties is required above all. Lump fuel is obtained directly by various methods of producing machine-formed peat.

However, coking of machine-formed peat obtained on modern excavator-type equipment yields a product of low mechanical strength; therefore, the primary task in this area is to study the factors that improve the strength properties of the final product.

The production of strong lump fuel on the basis of products from the progressive milling method of peat extraction is possible by the method of thermobriquetting, i.e., pressing peat that has been preliminarily heated to a certain stage of thermal decomposition under a comparatively low pressure (in comparison with ordinary briquetting).

At the Tomsk Polytechnic Institute, research has been conducted for a number of years on developing the scientific foundations of a comprehensive chemical-metallurgical process based on peat. The first stages of the research are the development of methods for obtaining metallurgical fuel and fuel-smelting materials based on machine-formed and milled peat.

2. Fuel-smelting materials based on machine-formed peat

The task of improving the quality of metallurgical fuel from machine-formed peat was addressed by us comprehensively through the creation of so-called fuel-smelting materials, i.e., materials containing in their composition fuel, iron ore, and fluxes in the ratios necessary for the blast-furnace process. This corresponds to one of the main directions of progress in ferrous metallurgy—intensification of the blast-furnace process through improvement of the aerodynamic properties of burden materials by creating “monoburdens” based on finely ground concentrate, a product of iron-ore beneficiation.

In the problem laboratory, the influence of the initial and final moisture content of peat, the intensity of its processing, the forming pressure, the degree of grinding of ore and fluxes and their quantity, the coking regime, and other factors on the strength of fuel-smelting materials was investigated. For a number of promising peat deposits in Tomsk Oblast, preliminary technical specifications have been determined for the regime of preparing fuel-smelting materials. The materials obtained are distinguished by high mechanical strength [13—24, 81, 82, 84, 94, 96—100, 106].

The development of technology for producing fuel-smelting materials is based on the study of structure-forming processes in peat colloidal systems according to the principles of the physicochemical mechanics of disperse structures and materials—a new independent field of science developed by the school of Academician P. A. Rehbinder—and also on the theoretical laws of drying capillary-porous colloidal bodies developed by Academician A. V. Lykov and, in application to peat, investigated by M. P. Volarovich, N. V. Churaev, and others [25—51].

Peat must be regarded as a disperse multiphase system. The presence in peat of hydrophilic and hydrophobic organomineral colloids, solutions, and dispersions of low- and high-molecular compounds leads to the formation of various associates of the solid phase.

In the process of producing fuel from peat, two tasks are solved: removal of the excess amount of water and formation of a strong structure of the peat. Knowledge of the properties of this material as a disperse system, and study of the mechanism of drying and of structure-formation processes, make it possible to exert the necessary action on peat in the course of technological operations in order to obtain the desired result.

Academician P. A. Rehbinder notes that the problem of the formation of spatial structures of various kinds in disperse systems, and of control over the processes of structure formation and over the properties of disperse structures, above all their principal mechanical properties (deformational and strength properties), should be regarded as one of the most important problems of modern colloid chemistry.

In a number of its external properties, peat represents a typical model of capillary-porous bodies, and it is precisely these properties that exert a substantial influence on the formation of a strong structure of a solid body [28, 29, 52].

As Academician P. A. Rehbinder points out, many disperse structures are unstable with respect to removal of the disperse medium by drying. As the liquid evaporates in the pores of the structure, micromenisci—concave liquid/air interfaces—are formed, and in view of this there arises a jump in hydrostatic pressure, the so-called capillary pressure, determined by the Laplace equation.

\[ P_{\sigma}=\frac{2\sigma}{r}, \]

where

\[ P_{\sigma} \]

— capillary pressure;

\[ \sigma \]

— surface tension of the liquid at the liquid/vapor boundary;

\[ r \]

— radius of the capillary.

Thus, in the process of drying capillary-porous colloidal bodies, as a result of the change in the free energy of the surface, forces arise that lead to a decrease in the volume of the system. Drying of various materials with fibrous-porous, disperse, and gel structures proceeds under a complex mechanical interaction of a number of forces, the ratio of which changes successively according to the stages of removal of the liquid phase [54]. In the cited work an attempt is made to estimate the shrinkage stress as the resultant of a number of components, which can be expressed by the following equality:

\[ F_{\sigma}=\frac{\sigma L+F_{\sigma 0}-F_s+F_k}{S_0}, \]

where

\[ \frac{\sigma L}{S_0} \]

— compressive stress due only to the surface tension \((\sigma)\) of the liquid along the perimeter \((L)\) of the cross section of the specimen being tested;

\[ \frac{F_{\sigma 0}}{S_0} \]

— stress of the forces of capillary contraction as the sum of elementary capillary forces acting in the plane of the cross section along the line of intersection of all menisci encountered;

\[ \frac{F_s}{S_0} \]

— stress of the elastic resistance of the structure;

\[ \frac{F_k}{S_0} \]

— stress of cohesive and adhesive interaction

at the points of secondary contacts arising when structural elements come closer together during the drying process.

The change in the magnitude of the shrinkage stress during drying, \(F_{\sigma 0}=f(\tau)\), is shown in Fig. 1 [53].

The dashed branch of the end of the curve shows a possible decrease in \(F_{\sigma 0}\) upon complete removal of the liquid phase and subsequent relaxation processes in the structure. This is possible when \(F_k < F_s\). The same figure shows hypothetical curves for the development of the stress components, on the basis of which the entire process may be divided into 4 characteristic stages:

1. In the maximally moistened body, with a minimum of the total potential energy of internal and surface stresses in the structure:

\[ F_{\sigma}^{\mathrm{I}}=\frac{\sigma L}{S_0}. \]

1. At the second stage, capillary contraction forces \((F_{\sigma 0})\) arise and develop at an accelerated rate up to the end of this stage, together with the elastic resistance forces of the structure \((F_s)\) opposing them. In this case water is removed not only from capillaries of large diameter, but also from very narrow micropores and from part of the liquid interparticle bridges. This stage apparently covers the 1st and a certain share of the 2nd segment of the falling drying rate. For this period

\[ F_{\sigma}^{\mathrm{II}}=\frac{F_{\sigma 0}-F_s}{S_0}. \]

1. For the third period

\[ F_{\sigma}^{\mathrm{III}}=\frac{F_{\sigma 0}-F_s+F_k}{S_0}. \]

1. In the fourth period, with the disappearance of the capillary contraction forces, the compensating stresses of cohesive-adhesive bonds \((F_k)\) at the points of secondary contacts, formed earlier under the compressive action of capillary forces, come into effect:

\[ F_{\sigma}^{\mathrm{IV}}=\frac{F_k-F_s}{S_0}. \]

Numerous works [53–56 et al.], carried out mainly by M. S. Ostrikov and co-workers, on the study of the mechanism of structure-forming processes using the example of many porous materials and disperse structures from the standpoint of the principles considered of physicochemical mechanics, have revealed the predominant importance of capillary contraction forces in the formation of disperse structures. A definite importance is also attached to certain other factors [57, 58].

With respect to peat, the separation of the second stage of structure-forming processes for independent consideration may also be supported by technological considerations, since in most industrial methods of peat extraction the final product in the drying process is brought to a moisture content of 30–40%, i.e., in this case one does not have to deal with the removal of sorption water from peat. Thus, the task of studying the mechanism of structure-forming processes at this stage should be to examine the change over time, and under the influence of individual factors, of the forces of capillary contraction, the elastic resistance of the structure, and, finally, the resultant of these two forces.

It should be said that the role of capillary phenomena in the mechanical properties of peat was noted as early as the 1930s. By Tertsagi and N. M. Gersevanov

[52] introduced the concept of capillary pressure in soils (including peat soil) and noted its role in the settlement of soils when water evaporates from them, as well as the analogy between compression of soil under the action of a load and settlement due to evaporation.

To solve the indicated problems, various experimental methods had previously been used: measurements of the total force arising during drying of bodies while preventing settlement in the direction of the action of the forces being determined [53], the capillary potentiometer of S. S. Korchunov [38, 45], direct determination of the settlement stress in a mass of drying peat [36], etc.

Fig. 1. Development of shrinkage stress during the drying of disperse structures as the resultant of its constituent quantities: \(F_{\sigma_0}\) — stress of capillary contraction; \(F_s\) — stress of structural resistance; \(F_k\) — stresses of cohesive and adhesive interaction at points of secondary contacts; \(F_\sigma\) — shrinkage stress; I—IV — drying periods

We determined, by calculation, the capillary pressure and certain structural characteristics of peat systems. In studying structure-forming processes occurring during the drying of capillary-porous colloidal bodies, in accordance with the principles of the physicochemical mechanics of disperse structures, in our opinion, one of the characteristics of peat structures proposed by M. P. Volarovich and N. V. Churaev [30] may be of definite interest—the hydraulic pore radius (\(\delta\)), calculated as the ratio of the active porosity to the value of the kinetic specific surface and characterizing the average sizes of water-conducting pores. In all probability, the hydraulic pore radius as an averaged characteristic of peat capillaries can be used in estimating the capillary-pressure forces in the Laplace equation or in the expression for capillary potential [27, 28, 29].

In a state of equilibrium the capillary potential of a body at any point is equal to the potential of the force of gravity [28, 29]. Since the latter acts as an external force, it is apparently possible to establish a relation between the capillary potential and any external force tending to change it.

Modern experimental methods do not make it possible to trace the change in the porous structure of peat over a wide range of its moisture content. However, we have shown that one of the main parameters of capillary-porous colloidal bodies—the hydraulic pore radius (\(\delta\)), characterizing the average sizes of water-conducting pores—can be obtained by calculation.

For this purpose we shall use the equation of S. S. Korchunov [45]:

\[ \lg \varphi = \lg \varphi_0 - 3{,}10 \frac{W}{W_{\mathrm{n}}}, \]

where \(\varphi\) is the capillary potential, \(g/\mathrm{cm}^2\);

\(\varphi_0\) is a constant;

\(W\) is moisture content, \(g/g\);

\(W_{\mathrm{n}}\) is the full moisture capacity, \(g/g\).

Based on the Laplace equation, we write:

\[ \varphi = \frac{a}{\delta}. \]

Here \(a\) is a quantity reflecting \(2\sigma \cdot \cos \alpha\), which we have conventionally taken to be constant. This can be done because it is known that \(\sigma\) changes little with a change in pore radius, while the hydrophilicity of the surface of the solid phase of peat in the drying process remains practically the same, as can be judged from the unchanged amount of physicochemically bound moisture. It may also be thought that, as peat dries, \(\sigma\) will decrease owing to an increase in the concentration of natural surface-active substances, but since at the same time the concentration of electrolytes acting on \(\sigma\) in the opposite direction also increases, the total effect may prove to be insignificant.

Thus:

\[ \lg \delta = 3{,}10 \frac{W}{W_{\mathrm{п}}} + \lg a - \lg \varphi_0. \]

It can be shown that

\[ \lg a - \lg \varphi_0 = \lg \delta_m, \]

where \(\delta_m\) is the minimum (limiting) hydraulic pore radius at \(W \to 0\).

The numerical value of this quantity can be found by using the published data of M. P. Volarovich and N. V. Churaev [30], A. A. Golovach and N. V. Churaev [39], and L. S. Amaryan [40] on the determination of the hydraulic pore radius of various peats as a function of external pressure and moisture content by the compression-filtration method. The graph constructed by us from the indicated experimental data showed that, for all peats, with the exception of complex raised bog peat with a degree of decomposition \((R)\) equal to \(0—5.0\%\), the experimental points fit well on a straight line described by the equation

\[ \lg \delta = 3{,}10 \frac{W}{W_{\mathrm{п}}} - 6{,}5, \]

i.e. \(\lg \delta_m = -6{,}5\) and \(\delta_m = 3{,}16 \cdot 10^{-7}\ \text{cm}\), whereas for peat \((R = 0 \div 5.0\%)\) \(\lg \delta_m = -5{,}8\) and \(\delta_m = 1{,}59 \cdot 10^{-6}\ \text{cm}\). It is possible that the latter value of \(\delta_m\) is generally characteristic of peats with a low degree of decomposition (up to 10%). A basis for such a conclusion may be the different behavior of peats with low and high degrees of decomposition during filtration as a function of the pressure gradient, as noted by A. A. Golovach and N. V. Churaev [39] and explained by them as compression of the easily deformable large pores of plant residues. It is interesting to note that, using the relationship found, one can find the value of \(a\) and then determine \(\varphi\) for the corresponding values of \(\delta\).

The energies of the bonds of moisture with peat calculated in this way obey well the above-mentioned equation of S. S. Korchunov.

Using the formula found, it proved possible to test the assumption of N. A. Gal’bin, N. K. Rabotnov, and E. P. Semensko-go [43] concerning equality of pore sizes at the critical points for various peats. For this purpose, from experimental data of compression tests, the quantities \(W_{\mathrm{п}}\) and \(W_{\mathrm{k}}\) for the first and second points were determined for peat and its mixtures with different amounts of iron ore. The calculation of the hydraulic pore radius for the first case gave \(0.053—0.055\) microns at moisture content \(W_{\mathrm{k}}^{\prime} = 3{,}10—3{,}65\ \text{g/g}\) (for

mixtures with ore, recalculated to the peat component) and for the second \(0.26—0.028\) micron at a moisture content of \(2.30—2.80\) g/g \((W_k^*)\).

Using the present formula, we calculated the change in the hydraulic radius of pores during the drying of peat and peat–ore moldings (Figs. 4 and 5). As was to be expected, throughout the entire drying period the peat–ore moldings are characterized by pores of smaller size than pure peat.

It is also interesting to note the characteristic points on the curves where their parameters change, which indicates a change in the mechanism of shrinkage and is in full agreement with our other experiments, including compression tests, and, in particular, confirms the analogy between mechanical compression and shrinkage during the drying of peat.

In the course of natural drying of samples of molded peat passed three times through a meat grinder and of a mixture of it (fuel–flux material) with iron ore (magnetite concentrate in the ratio \(100:6\)), we determined the change in moisture content. The total moisture content of the peat was \(12.50\) g/g, and that of the mixture of peat with ore (TFM) was \(10.8\) g/g.

For analysis of drying processes, the construction of drying-rate curves according to V. V. Lykov is of great importance; these curves have a characteristic appearance with four clearly distinguishable drying periods and critical points determined by different mechanisms of mass and heat transfer.

As can be seen from Fig. 2, the drying-rate curves of peat and TFM have a characteristic appearance. It should be noted, however, that the period of constant

Fig. 2. Dependence of the intensity of moisture evaporation in samples of peat (curve 1) and fuel–flux materials (curve 2) on moisture content during natural drying.

drying rate is shown by us conditionally, since the experimental data do not provide sufficient grounds for this.

The periods of increasing and decreasing drying rates are clearly separated, and the latter can also be divided into two stages. An initial period of falling drying rate was detected, amounting in time to one third of the total duration of the experiment. Taking into account that the samples of peat and TFM were placed for drying

immediately after formation, it may be assumed that this portion must be characteristic of all disperse systems capable of forming coagulation structures with immobilization of moisture. As our experiments on the kinetics of the development of coagulation structures in a raw peat mass (without drying) have shown, it is precisely during this time that they reach their maximum development.

According to A. V. Lykov, an increasing drying rate is observed at the initial moment and corresponds to the heating of the material. In our case, the stage of increasing drying rate obviously cannot be explained from these positions.

Proceeding from the properties of the liquid in capillaries, N. A. Nasedkin [52] assumes that the amount of free water is directly proportional to the dispersity and compressibility of peat. Evaporation of water from the surface leads to an increase in the curvature of the meniscus, which increases the evaporation surface and, consequently, at the initial stage a portion of increasing drying rate is observed.

The explanation of the increase in the drying rate of peat at this stage by an increase in the evaporation surface is, in all probability, correct. However, in our opinion, this phenomenon must be explained not by an increase in the curvature of the menisci, but by a decrease in the radius of the capillaries with a simultaneous increase in their number. The latter conclusion follows directly from the works of M. M. Volarovich and N. V. Churaev [30], which show that when peat is compressed its active porosity and kinetic specific surface increase, the average sizes of water-conducting pores decrease, but their number increases, which should cause an increase in the specific evaporation surface.

What has been said will be valid in the case when the rate of shrinkage corresponds to the rate of moisture loss, and if this condition is observed, the considered drying stage will, apparently, be typical for the drying of all capillary-porous colloidal bodies.

In this case the increase in drying rate should cease at the moment when, on the surface of the materials, a moisture content corresponding to the complete loss of capillary moisture is reached. In the cited work of M. P. Volarovich and N. V. Churaev, on the basis of a generalization of the material from the works of other researchers, the value of the moisture content corresponding to the indicated point is given as equal to 0.5 g/g or about 33.3% relative.

Analysis of our experimental data on the distribution of moisture in the concentric layers of cylindrical specimens fully confirms this proposition. And, finally, a sharp decrease in the drying rate begins after the loss of capillary moisture by the entire mass of the specimen. Fig. 2 testifies in favor of this. From the same figure it is evident that the increase in drying rate ceases for peat upon reaching a moisture content of about 55%, and for TPM, 50%. From the standpoint of the mechanism analyzed, this difference is easily explained. Fig. 3 presents the results of calculating the average moisture gradient along the radius of peat and TPM specimens at different drying times. The average moisture gradient is calculated as the ratio, at each given moment of time, of the difference in the moisture content of the material at the center and at the surface to the radius of the specimen. Hence it is clear that the noted difference in the moments of completion of the period of increasing drying is due to the difference in the moisture gradient of the peat and TPM specimens.

Thus, analysis of the experimental material makes it possible to draw the following conclusion regarding the drying of fuel-molding materials in comparison with pure peat. Drying of TPM over the greater part of the complete cycle proceeds more intensively than drying of specimens of pure-

of peat. At the maximum value, the drying rate of TPM samples (mg/cm²·h) is 1.5 times higher than that of samples of pure peat; however, at a moisture content below 30%, the drying rate of both materials is the same. The peculiarity of TPM drying, as well as the drying periods characteristic in both cases, are logically explained from the standpoint of developing views on the mechanism of structure-forming processes in the drying of disperse systems.

Fig. 3. Dependence of the moisture gradient along the radius of cylindrical samples of peat (curve 1) and fuel-smelting materials (curve 2) on moisture content in the process of natural drying. The moisture content of TPM has been recalculated to peat

During the drying of TPM, smaller moisture gradients are observed throughout the entire period than in peat, which leads to less cracking of the fuel-smelting materials.

Judging from the changes we determined in the content of bound water and in the limiting shear stress, the introduction of finely ground iron ore changes the character of the course of structure-forming processes toward acceleration of the processes of compact coagulation and a reduction in the mean radius of capillaries in the peat system; moreover, shrinkage phenomena are not only not hindered by the presence of the mineral filler, but, on the contrary, the rate of shrinkage increases noticeably. Altogether, this has a positive effect on the quality of the final product.

In Figs. 4 and 5 we present the capillary-pressure values calculated by us according to the equation of S. S. Korchunov. As can be seen, the curves of this indicator over time have a characteristic S-shaped form, which fully corresponds to the regularities established earlier.

The hydraulic pore radii calculated according to the equation proposed above (Figs. 4 and 5) change during drying: for peat, from 0.362 to 0.015 micron as the moisture content changes from 5.80 to 0.20 g/g, and for TPM, from 0.240 to 0.014 micron as the moisture content decreases from 4.38 to 0.15 g/g. The values obtained correspond well to the values of this indicator obtained earlier by another method [30],

and the general regularities of drying of capillary-porous colloidal bodies [28, 29], which testifies in favor of the applicability of the indicated equation.

It is interesting to note that throughout the entire drying period the capillary pressure in the TTM samples is higher, while the hydraulic radius of the pores is correspondingly smaller, than in peat samples. Thus, the addition of finely ground iron ore to the raw peat mass leads to the formation of more compact coagulation structures, and this effect is noticeable at all stages of the structure-forming processes occurring during drying.

A comparison of the change in capillary pressure and ultimate shear stress (Figs. 4 and 5) can give an idea of the dynamics

Fig. 4. Change in capillary pressure (curve 1), ultimate shear stress (curve 2—Rebinder method, 3—conical plastometer), and hydraulic pore radius (curve 4) during natural drying of peat

and the character of the forces causing shrinkage at individual stages of drying. One of the methods for producing machine-formed fuel may be placed at the basis of the technology.

In 1963, at the Ayat peat enterprise, industrial tests were carried out on a method for producing fuel-smelting materials. In March 1966, IMET of the Academy of Sciences of the USSR conducted an experimental blast-furnace smelting, which showed the fundamental possibility of using

In 1963, at the Ayat peat enterprise, tests were also carried out on an experimental installation of the Tomsk Polytechnic Institute. Unlike the furnace of IMET of the Academy of Sciences of the USSR, the TPI installation

has a system for capturing chemical products, which made it possible to evaluate the material balance for these products of blast-furnace smelting on air-dry peat. In May 1968, the first pig iron from Bakchar iron ore was obtained in the TPI experimental blast furnace.

The iron ore contained about 38% total iron, 24% silicon oxide, 0.64% calcium oxide, 5% aluminum oxide, and 1.17% phosphorus pentoxide. The pig iron obtained contained 1.1% silicon, 0.06% vanadium, 0.5% phosphorus, and 0.21% manganese. The slag contained: silicon oxide—43.82%, calcium oxide—30.36%, aluminum oxide

Fig. 5. Change in capillary pressure (curve 1), ultimate shear stress (curve 2—Rebinder method, 3—conical plastometer), and hydraulic pore radius (curve 4) during the natural drying of fuel-smelting materials.

—15.85%, ferrous oxide—2.94, phosphorus pentoxide—0.11%, vanadium—0.06%, magnesium oxide—2.11%.

3. Thermal Briquetting of Peat

The prospects for thermal briquettes as blast-furnace fuel were confirmed at a number of conferences [9, 10, et al.].

Studies carried out at different times made it possible to identify a number of basic factors in the regularities governing the production of strong thermal briquettes and to give the first positive assessment of their practical significance [60—67]. However, there still remained a whole series of unresolved questions, above all connected with the assessment of thermal briquettes

as metallurgical fuel, little attention was paid to elucidating the mechanism of thermal briquetting, which hindered the scientific substantiation of the technological regime. At the Tomsk Polytechnic Institute, beginning in 1959, systematic studies were carried out in the field of thermal briquetting of peat. The influence of various factors was investigated (the temperature of peat heating before pressure was applied under slow and high-speed heating, the briquetting pressure, the holding time of the peat before pressure was applied and during pressing, and the degree of peat grinding) on the mechanical properties of thermobriquettes and of the solid residues from their pyrolysis at different final heating temperatures. The distinctive features of thermal-briquetting technology using high-speed heating were revealed [68—70, 81, 82, 85, 89, 93, 98, 103, 106].

The possibilities of obtaining fuel-smelting materials from milled peat by the method of thermal briquetting, using ore and fluxes as a solid heat carrier, were demonstrated [71]. On the basis of studying the influence of various factors on the process, technological regimes of thermal briquetting were recommended for peats of different types and, in particular, for a number of peats of the Vasyugan peat massif. Laboratory studies of the physical and physicochemical properties of thermobriquettes and of the coke obtained from them make it possible to conclude that this type of fuel can be used as a combustible material for metallurgical purposes both directly and after coking.

The study of the mechanism of formation of the strong structure of a thermobriquette plays, besides a theoretical role, an important practical role, since the thermal destruction of the organic matter of peat and the changes in physicochemical and physical properties associated with this process apparently determine the success of thermal briquetting. Studies of the yield of products of the thermal decomposition of peat and of its constituent parts, the yield of pyrobitumens, changes in the content of functional groups and paramagnetic centers in the temperature range of thermal briquetting, as well as study of changes in the group composition of peat during the process and a number of other experiments (change in the specific surface area of peat during thermal briquetting, production of thermobriquettes from debituminized peat, etc.) made it possible to give an approximate assessment of a number of individual factors in the formation of the strong structure of a thermobriquette.

The special role of kinetic factors in the process of thermal briquetting should be emphasized. Analysis of the experimental data indicates the decisive importance of intermediate products of the reaction of thermal decomposition of the organic matter of peat. This is evidenced by the presence of pronounced maxima in the temperature dependence of thermobriquette strength, the yield of pyrobitumens, the formation of paramagnetic centers, and the manifestation of plastic properties. Still more convincing are the dependence of thermobriquette strength on holding time under high-speed heating and the kinetic curves for the formation of paramagnetic centers.

Thus, we have shown that in the mechanism of formation of the strong structure of a thermobriquette, reactions leading to the appearance of chemically active substances, realized under pressure, play a role, while the mechanical properties of the thermobriquette are ensured both by dispersion structures of coalescence of the cohesive and adhesive molecular and mechanical types, and by condensation structures formed by the action of the forces of the principal valences. The formulated foundations of the mechanism of thermal briquetting made it possible to give a scientific interpretation of the influence of the main technological factors on the quality of the thermobriquette [88, 109].

In addition to the above, in the peat problem laboratory of TPI, research is being conducted on the effect of iron-ore additives on the yields of chemical products of the thermal decomposition of peat over a broad temperature range of pyrolysis. Experiments have been carried out with a whole series of peats from deposits of Tomsk Oblast in the presence of Bakchar iron ore and magnetite. The experiments showed that significant yields of pyrolysis products can be obtained under various conditions. This testifies to the high chemical potential of the complex chemical-metallurgical process [72, 73, 87, 95].

Close contact between the reducing agent and the ore in peat briquettes, as well as the high yield of volatiles from peat, favorably affect the reduction of iron ore. It has been shown that the rate of reduction of magnetite and brown iron ores in the presence of peat is higher than with other solid reducing agents. This circumstance makes it possible to substantially shorten the process time and lower its temperature.

All this opens favorable prospects for the use of fuel-smelting materials prepared by the method of the peat problem laboratory for the direct (out-of-blast-furnace) production of iron or for other metallurgical processes in which a highly reactive reducing agent is needed [74, 75, 80, 86, 105, 107, 108].

The complex chemical-metallurgical (blast-furnace) process is based on the use, as blast-furnace fuel, of air-dry lump peat or “monoshikhty” that have not undergone preliminary coking, or of thermobriquettes. In this case the blast furnace combines the process of smelting pig iron with the process of coking peat and, along with pig iron, yields a high-calorific gas and other chemical products of peat pyrolysis: peat tar and gas gasoline.

On the basis of carbon monoxide, which is the predominant component of blast-furnace gas, and water vapor, when these components are passed through a catalyst at a temperature of 220–280°C, a broad range of hydrocarbons and organic oxygen-containing compounds can be obtained. The gas can be used economically for the generation of electric power or for the synthesis of ammonia. In the peat problem laboratory, a number of studies have been carried out in the field of synthesis from carbon monoxide and water vapor [76–79, 83, 90–92, 101, 102, 109–111].

Conclusions

1. The prospects for the comprehensive use of peat in the metallurgy of Western Siberia have been demonstrated.

2. A method has been developed for producing fuel-smelting materials based on machine-formed peat.

3. Structure-forming processes in capillary-porous colloidal bodies have been investigated. The role of iron-ore additives in the formation of a strong structure of a peat-ore briquette has been shown.

4. The influence of various factors on the process of obtaining metallurgical fuel by the thermobriquetting method has been studied.

5. Some questions of the mechanism of thermobriquetting have been studied. The role of chemical and physicochemical processes in the formation of the structure of a thermobriquette has been established.

6. Experimental smelts have been carried out in an enlarged laboratory blast furnace using peat fuel-smelting materials; the yields and composition of the chemical products of pyrolysis have been determined. The fundamental possibility of using FSM in metallurgy has been shown.

7. Some questions of the kinetics and mechanism of iron reduction by peat and of the pyrolysis of FSM have been investigated. The high chemical activity of FSM has been shown.

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1. S. I. Smolyaninov, V. M. Mironov, A. V. Kravtsov. “Chemistry and Technology of Fuels and Oils,” No. 8, pp. 12—16, 1962.

2. S. I. Smolyaninov, V. M. Mironov. Izv. TPI, vol. 136, pp. 58—60, 1965.

3. S. I. Smolyaninov, A. V. Kravtsov. Izv. TPI, vol. 167, pp. 101—108, 1967.

4. V. M. Mironov, A. V. Kravtsov, S. I. Smolyaninov. Coll. “Chemistry of Kuzbass over 50 Years of Soviet Power and Prospects for Its Development,” pp. 120—126, Kemerovo, 1967.

5. O. P. Lobas, S. I. Smolyaninov. Coll. “High-Temperature Endothermic Processes in a Boiling Bed,” pp. 466—469, publ. “Metallurgiya,” Moscow, 1968.

6. S. I. Smolyaninov, S. G. Maslov, G. G. Krinitsyn. Izv. TPI, vol. 196, pp. 143—149, 1969.

7. S. I. Smolyaninov, N. M. Smolyaninova, K. K. Stramkovskaya, N. F. Tyumentsev, S. G. Maslov, G. G. Krinitsyn. Coll. “Proceedings of the First Scientific Conference of the Tomsk Branch of the D. I. Mendeleev All-Union Chemical Society,” TGU Publishing House, Tomsk, pp. 248—251, 1969.

8. S. I. Smolyaninov, A. V. Kravtsov. Ibid., pp. 99—102.

9. S. I. Smolyaninov, G. G. Krinitsyn. Coll. “Prospects for the Use of Peat in Metallurgy,” VNIITP Publishing House, Leningrad, pp. 64—66, 1970.

10. S. I. Smolyaninov, S. G. Maslov. Ibid., pp. 67—68.

11. S. I. Smolyaninov, V. I. Lozbin, O. P. Lobas. Ibid., pp. 69—72.

12. S. I. Smolyaninov, K. K. Stramkovskaya, G. I. Kravtsova. Ibid., pp. 113—115.

13. S. I. Smolyaninov, S. G. Maslov, N. M. Smolyaninova, I. A. Oshchepkov. Izv. TPI, vol. 175, pp. 102—104, 1971.

14. S. I. Smolyaninov, S. G. Maslov, V. G. Teteryak, G. F. Kraskov. Ibid., pp. 98—101.

15. S. I. Smolyaninov, V. M. Mironov, A. V. Kravtsov. Ibid., pp. 88—93.

16. S. I. Smolyaninov, V. M. Mironov, V. A. Kornyakov. Ibid., pp. 83—87.

17. S. I. Smolyaninov, V. M. Mironov. Ibid., pp. 79—82.

18. S. G. Maslov, S. I. Smolyaninov. Coll. “Proceedings of the 1st Conference of Young Scientists of the City of Tomsk,” pp. 214—215, publ. TGU, Tomsk, 1970.

19. V. N. Ponomarev, S. I. Smolyaninov. Ibid., pp. 220—222.

20. S. I. Smolyaninov, G. I. Kravtsova. Izv. TPI, vol. 185, pp. 100—105, 1970.

21. S. I. Smolyaninov, V. N. Ponomarev, M. I. Fomchenkov. Izv. TPI, vol. 163, pp. 78—81, 1970.

22. S. I. Smolyaninov, V. N. Ponomarev, Yu. N. Vasil’ev. Ibid., pp. 82—84.

23. S. I. Smolyaninov, G. G. Krinitsyn, S. G. Maslov. Ibid., pp. 85—90.

24. S. I. Smolyaninov, G. G. Krinitsyn. Ibid., pp. 91—93.

25. S. I. Smolyaninov, G. G. Krinitsyn. Ibid., pp. 94—97.

26. S. I. Smolyaninov, A. V. Kravtsov. Ibid., pp. 112—116.

27. S. I. Smolyaninov, A. V. Kravtsov, V. M. Mironov. Ibid., pp. 117—123.

28. S. I. Smolyaninov, S. G. Maslov. Ibid., pp. 109—111.

29. S. I. Smolyaninov, S. G. Maslov. Chemistry of Solid Fuel, No. 4, pp. 76—82, 1971.

30. S. I. Smolyaninov, V. I. Lozbin, Ya. A. Belikhmasr, V. M. Ikrin. Coll. “Second Republican Scientific Conference on the Extraction and Use of Coals of Kirghizia,” pp. 65—66, publ. Kirghiz. INTI, Frunze, 1971.

31. S. I. Smolyaninov, G. G. Krinitsyn, S. G. Maslov, V. S. Arkhipov. Ibid., pp. 102—104.

32. S. I. Smolyaninov, V. I. Lozbin, V. M. Ikrin, Ya. A. Belikhmasr. Coll. “Application of Modern Physicochemical and Mathematical Methods of Research to Processes and Products of Solid Fossil Fuels,” pp. 22—24, Novokuznetsk, 1971.

33. S. I. Smolyaninov, V. I. Lozbin. Ibid., pp. 36—37.

34. S. I. Smolyaninov, A. V. Kravtsov, V. M. Mironov. Izv. TPI, vol. 216, pp. 83—89, 1971.

35. S. I. Smolyaninov, A. V. Kravtsov. Ibid., pp. 90—92.

36. S. I. Smolyaninov, A. V. Kravtsov, V. N. Yatsko. Ibid., pp. 93—98.