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AZERBAIJAN CHEMICAL JOURNAL № 4 2022 ISSN 2522-1841 (Online)
ISSN 0005-2531 (Print)
UDC 665.637.8
PRODUCTION OF THERMOSTABLE ROAD BITUMENS BY THE METHOD
OF "OXIDATION-COMPOUNDING"
1 12 2 N.G.Evdokimova1, A.R.Makhmutova\ N.T.Aliyeva2, E.A.Guseinova2
1Ufa State Petroleum Technical University, Institute of Oil Refining and Petrochemistry of the University in the City of Salavat, Salavat, Russian Federation Azerbaijan State Oil and Industry University
Received 11.04.2022
Accepted 27.05.2022
The paper proposes a technology for producing petroleum road bitumen by compounding deeply oxidized bitumen with tar, pre-oxidized to various temperatures, in order to produce binders stable to the processes of thermo-oxidative aging. The rate of technological and chemical aging of tar and bitumen has been studied. It was found that tar is most susceptible to technological, and bitumen to chemical aging. It is shown that the use of tar pre-oxidation technology is a promising direction in bitumen production in the production of standard grades of bitumen binders. The obtained compounded bitumens have high extensibility values at 250C and maximum tensile force, which characterizes their high cohesive properties, as well as high values of the needle penetration depth at 00C and low brittleness temperatures, which indicate good low-temperature properties of bitumen. It has been revealed that the use of oxidized tar with a softening point of 360C during compounding with deeply oxidized bitumen can achieve the minimum values of softening temperature change after aging and obtain standard bitumen grades BND 70/100 and BND 100/130 according to GOST 33133-2014. The resulting compounded bitumen is less susceptible to destructive and thermo-oxidative aging processes and can be effectively used for paving.
Keywords: tar, bitumen, compounding, pre-oxidation, aging, thermo-oxidative stability.
doi.org/10.32 73 7/0005-2531-2022-4-102-108 Introduction
Bitumen production is one of the multi-tonnages. Bitumen accounts for about 3% of the total volume of oil processed, but it also accounts for only 80% of what is needed. Petroleum bitumen is one of the key components in road and civil construction (85%), foundry and electrochemical production, medicine, paintwork and cable production, roofing materials, etc. [1, 2].
The bitumen market in 2022 is estimated at almost 100 million tons, with an average annual growth rate of more than 4%. In 2020, 374.73 thousand tons were produced in the Republic of Azerbaijan, which is 44.1% higher than the previous one [3]. In the Russian Federation, the production of petroleum bitumen in 2021 reached 8,366.7 thousand tons, which is 8.2% more than its production in 2020 [4]. Considering that the need for this type of product increases every year, the attention of researchers is predictably directed to solving problems related to improving the quality of bituminous mate-
rials, increasing its adhesive properties, resistance to temperature fluctuations, etc. [5-10].
One of the reasons for the appearance of cracks, shifts, peeling and potholes in the road surface is the aging of bitumen. Bitumen aging is understood as the totality of reversible and irreversible changes in its chemical composition and structural and mechanical properties that occur during its storage, technological processing and operation [1].
The analysis of scientific publications and studies of the authors [1-3] showed that it is most appropriate and logical to consider the thermal-oxidative stability of petroleum road bitumens as a single ability for high- and low-temperature oxidation at all stages of their production, storage and use.
It was shown in [4, 5] that the main factors under low-temperature oxidation conditions that affect the quality of bitumen in a thin layer on the surface of a mineral material are the presence of air oxygen, IR and UV radiation, water, and the catalytic surface of the mineral
material. As well as a high level of temperature fluctuations (up to 1000). According to the authors [6-8], the main processes causing irreversible changes in the composition and properties of bitumen are:
- evaporation of volatile components, occurring in the surface layer of bitumen of insignificant thickness and depending on the content of volatile components in bitumen, bitumen viscosity and temperature;
- polymerization associated with exposure to heat, even in the absence of oxygen;
- oxypolymerization of bitumen components, occurring mainly on the outer surface of the binder, which is directly exposed to light and ultraviolet rays;
- polycondensation, which occurs under the influence of oxygen and is the main process that changes the composition and structure of bitumen during aging.
Based on the results of studying the role of air oxygen and the effect of elevated temperature on bitumen in a thin film, the authors [4, 9-11] argue that the processes of irreversible structure formation in bitumen under these conditions proceed in three stages:
- formation of a coagulation network of as-phaltenes from the supramolecular structure of resins;
- development of a rigid spatial structural network of asphaltenes;
- destruction of the rigid spatial structural network of asphaltenes.
Thus, inseparably with a change in the group composition of bitumen, a change in their structure occurs, viscosity increases, heat resistance, elasticity, plasticity decreases, and, finally, bitumen becomes brittle.
Considering the aging of bitumen as a complex process that proceeds with the formation of free radicals that react with each other to form a network of high-molecular compounds, the presence of a large amount of as-phaltenes in the original bitumen leads to system heterogeneity and syneresis with the release of oils during oxidation.
There are two main stages in the aging process:
1) technological aging of bitumen at the stage of compounding, transportation, storage, preparation of bituminous binder and asphalt mixtures;
2) aging of bitumen during its operation in the road surface - chemical aging. During the technological aging of bitumen, the most intensive change in its properties occurs. Long-term heating of bitumen to high temperatures during its storage and preparation of the asphalt concrete mixture causes significant changes in its structure, there is a loss of binding properties or their significant deterioration.
During the operation of asphalt concrete pavements, the aging process of the bituminous binder is accelerated by the action of sunlight and atmospheric oxygen. As a result, an increase in the amount of hard brittle components reduces the adhesive and plastic properties of bitumen.
Petroleum bitumen is obtained in many countries of the world in several ways. Non-oxidized (residual) bitumen has a number of advantages over oxidized ones [11, 14, 16, 23, 24]. They are resistant to thermal oxidative aging processes and have better adhesion to mineral fillers, are less susceptible to qualitative changes over time and are more resistant to elevated temperatures. They contain natural inhibitors of oxidation processes. Consequently, such bits retain their original characteristics longer, and asphalt concrete pavements serve for a long time.
Oxidized road bitumens have insufficient resistance to thermal-oxidative aging processes and low adhesion to high-strength minerals [11, 12, 18, 23, 24]. This is due to the tendency of such bitumen to intense thermal-oxidative aging processes, which proceed by a radical mechanism with the formation of free radicals. At the end of the oxidation process, when the temperature drops and the air supply stops, the rate of transformations in bitumen slows down, but they continue due to the presence of free radicals in the product. Transformations continue during the period of transportation and storage of bitumen, during the preparation of asphalt concrete mixtures and during the operation of the mixture - on the road. As a result, bitumen
ages, becomes brittle, less plastic and prone to destructive processes.
Compounded bitumens obtained by mixing various oil residues with distillates and with oxidized or residual bitumen have increased resistance to thermal-oxidative aging processes, good adhesive characteristics, and high extensibility values [13, 16, 23, 24].
However, at present, at bitumen plants, when using the "oxidation-compounding" technology for the production of standard grades of road bitumen, due to the variability in the quality of raw materials, high-quality bitumen products are not always obtained due to its accelerated thermal-oxidative aging process. Currently, bitumen plants, due to the variability in the quality of raw materials, use the "oxidation-compounding" technology to produce standard grades of road bitumen. However, this technology does not always produce high-quality bituminous products due to its accelerated thermal-oxidative aging process. This process is largely
Table 1. Physical and chemical properties of the objects of study
Denomination Controlled indicators Meaning
Tar Viscosity conditional at 800C, sec. 87
Softening temperature on the ring and ball, 0C 29
Flash point in an open crucible, 0C 332
Change in softening temperature after aging according to GOST 18180-72, 0C 5,5
Softening temperature change after technological aging, 0C 15
Density at 15 0C, kg/m3 1007
Deeply oxidized bitumen Softening temperature on the ring and ball, 0C 63
Change in softening temperature after aging according to GOST 18180-72, 0C 23
Softening temperature change after technological aging, 0C 11
Penetration at 250C x 0.1 mm 38
affected by the unstable properties of both the deeply oxidized bitumen used for compounding and the thinner tar. Therefore, the development of technologies and technological solutions to improve the thermal-oxidative stability of bitumen is a very urgent task today.
The study of the possibility of improving the thermal stability of the compounded road bitumen obtained using the "oxidation-compounding" technology was the goal of the work.
Experimental part
As objects of research, we used tar and deeply oxidized bitumen obtained from a mixture of West Siberian oils, the physicochemical properties of which are presented in Table 1. Depending on the temperature softening along the ring and ball after aging according to GOST 18180-72 technological aging, which was carried out at a temperature of 1650C for 5 hours with continuous stirring.
Results and its discussion
Based on the dependences obtained, the rates of chemical (in a thin layer) (Figure 1) and technological (in volume) (Figure 2) aging were calculated.
Analysis of the results showed that the highest rate of change in the temperature of tar and bitumen occurs in the first hours of the aging process. Tar most intensively changes its properties during technological aging, and bitumen during chemical aging. As a result of the vacuum distillation of fuel oil in the tar, appa-
rently, there are unsaturated compounds that are most capable of polymerization and polycon-densation reactions even at fairly low temperatures. Thus, the thermal-oxidative properties of the finished product will be affected to the greatest extent by the rate of technological aging of tar during the process of compounding deeply oxidized bitumen with tar [12]. Therefore, it is proposed to change the traditional technological scheme for obtaining compounded bitumen (Figure 3) by including a tar pre-oxidation unit in its composition in order to stabilize it (Figure 4).
O
o
M C
"m
eö
<+H
O
O JD
"<5
>
12 10 8 6 4 2 0
1 2 3
aging time, h
Tar
Bitumen
Fig 1. The rate of chemical aging of tar and deeply oxidized bitumen
4,5 4
0 3,5 ^ 3
' £ 2,5
'S 2 ^ 1,5
1 1
"<5
> 0,5
0 1 2 3 4 5
aging time, h
—•— Tar —Bitumen Fig. 2. The rate of technological aging of tar and deeply oxidized bitumen
Tar deeply oxidized bitumen
Oxidat. compounding
j k
► BND
Fig. 3. Block diagram of the technological process for obtaining compounded oil road bitumen grades BND.
0
4
5
0
6
Tar
Tar
- BND
Fig. 4. Block diagram of the technological process for obtaining compounded oil road bitumen with a block for the pre-oxidation of BND grades
Softening temperature of oxidized tar , °C * BND 70/100 BND 100/130
Fig. 5. Dependence of the change in the softening temperature of bitumen samples after the aging process on the softening temperature of the tar that went for compounding.
Table 2. Physical and chemical properties of compounded bitumens
Nomination of indicators Softening temperature of oxidized tar, °C GOST 33133-2014
29 * 32 36 40 29* 32 36 40 BND 100/130 BND 70/100
Softening temperature for the ring and ball, 0C 45 45 45 45 47 47 47 47 Not less than 45 Not less than 47
Needle penetration depth at 250C, 0.1mm 108 101 102 94 90 123 94 127 100-130 70-100
Needle penetration depth at 00C, 0.1mm 34 29 31 29 37 28 34 29 Not less than 30 Not less than 21
Extensibility at 250C cm 150 150 112 118 92 98 135 77 Not less than 70 Not less than 62
Maximum tensile force, N 0.68 0.9 1.18 1.13 0.90 1.71 1.89 1.80 - -
Sample weight change after aging, % 0.0 0.0 0.5 1.0 0.05 0.00 0.00 0.07 No more 0.7 No more 0,6
Brittleness temperature, 0C -22.5 -21.1 -21.9 -21.3 -26.3 -19.9 -24.1 -20.2 No more -20 No more -18
Penetration index -0.5 -0.8 -0.7 -1.0 -0.5 0.4 -0.4 1.6 -1 to +1
Compliance with GOST 33133-2014 - ORB 100/130 ORB 100/130 - - ORB 100/130 ORB 70/100 - -
* - non-oxidized tar
The tar was oxidized at a temperature of 2500C with an air flow rate of 3.2 l/minkg to a softening point of 32, 36, and 400C. The temperature of the oxidation process was controlled by changing the voltage at the LATR. Deeply oxidized bitumen was compounded with tar and oxidized tar to obtain bitumen with ring and ball softening temperatures of 45 and 470C. Physico-chemical properties of the resulting bitumen are presented in Table 2.
Figure 5 shows the dependence of the change in the softening temperature of bitumen samples after the aging process, determined according to GOST 18180-72, on the softening temperature of the tar that went for compounding. It has been established that the obtained seconded bitumens have high values of extensibility at 250C and maximum tensile force, which characterizes their high cohesive properties. High values of the needle penetration depth at 00C and low brittleness temperatures make it possible to judge the good low-temperature properties of bitumen.
One of the most important indicators of the quality of oil road bitumen is the change in mass and softening temperature after aging, which characterize the stability of bitumen properties during the operation of asphalt concrete pavements. It is shown that when using non-oxidized tar, it is impossible to obtain compounded bitumen with the required values of the change in softening temperature after aging. The use of oxidized tar with a softening temperature of 360C when compounding with deeply oxidized bitumen can achieve the minimum values of softening temperature change after aging and obtain standard bitumen grades BND 70/100 and BND 100/130 according to GOST 33133-2014.
Thus, the use of tar pre-oxidation technology is a promising direction in bitumen production in the production of standard grades of bituminous binders. The resulting bitumen is less susceptible to destructive and thermal-oxidative aging processes and can significantly reduce the premature destruction of asphalt concrete pavements during their operation.
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"OKSIDLO§MO-KOMPAUNDLA§MA" ÜSULU ILO TERMOSTABIL YOL BITUMLARININ ALINMASI
N.G.Yevdokimova, A.R.Maxmutova, N.T.Oliyeva, E.A. Hüseynova
Maqalada darin oksidla§dirilmi;j bitumun qudronla kompaundla§ma üsulu asasinda neft yol bitumlann alinmasi texnologiyasi taklif edilib, hansilar termooksidla§dirici qocalma proseslara qar§i stabil alaqalandirici istehsal edilmak maqsad tutaraq öncadan müxtalif temperaturlara gadar oksidla§diriblar. Qudron va bitumun texnoloji va kimyavi qocalmasinin sürati öyranilmiijdir. Müayyan edilmi§dir ki, qudron texnoloji, bitum isa kimyavi qocalmaya an gox maruz qalirlar. Göstarilmi§dir ki, bitumlu alaqalandiricilarin standart markalannin istehsalinda bitum istehsalinda qudronun öncadan oksidla§masi texnologiyasindan istifadasi perspektivli istiqamatdir. Alinan kompaund bitumlar 25°C-da yüksak uzadilma qiymatlarina va onlann yüksak yapi§dinci xüsusiyyatlarini xarakteriza edan maksimum dartma gücüna, hamginin 0°C-da iyna batma darinliyinin yüksak dayarlari va a§agi kövraklik temperaturlan bitumun yax§i a§agi temperatur xüsusiyyatlari haqqinda fikir irali sürmaya imkan verir. Müayyan edilmi§dir ki, darin oksidla§mi§ bitumla qan§an zamani yum§alma temperatura 36 °C olan oksidla§mi§ qatranin istifadasi qocalmadan sonra yum§alma temperaturunun dayi§masinin minimum qiymatlarina nail olmaq va BND 70/100 va BND 100/130 standart bitum markalanni alda etmak imkan verir. Müayyan edilmi§dir ki, alda edilmi§ kompaund bitumlan destruktiv va termo-oksidla§dirici qocalma proseslarina daha az hassasdirlar va yol örtük salinmasinda effektiv istifada oluna bilar.
Agar sözlzr: qudron, bitum, kompaundla§ma, önc3d3n oksidh§ma, qocalma, termo-oksidh§dirici dayaniqliq.
ПОЛУЧЕНИЕ ТЕРМОСТАБИЛЬНЫХ ДОРОЖНЫХ БИТУМОВ МЕТОДОМ «ОКИСЛЕНИЕ-
КОМПАУНДИРОВАНИЕ»
Н.Г.Евдокимова, А.Р.Махмутова, Н.Т.Алиева, Э.А.Гусейнова
В работе предложена технология получения нефтяных дорожных битумов методом компаундирования глубокоокисленного битума с гудроном, предварительно окисленным до различных температур, с целью производства вяжущих стабильных к процессам термоокислительного старения. Изучена скорость технологического и химического старения гудрона и битума. Установлено, что гудрон в наибольшей степени подвержен технологическому, а битум химическому старению. Показано, что использование технологии предокисления гудрона является перспективным направлением в битумном производстве при производстве стандартных марок битумных вяжущих. Полученные компаундированные битумы имеют высокие значения растяжимости при 250С и максимального усилия при растяжении, что характеризует их высокие когезионные свойства, а также высокие значения глубины проникания иглы при 00С и низкие температуры хрупкости позволяют судить о хороших низкотемпературных свойствах битумов. Выявлено, что применение окисленного гудрона с температурой размягчения 360С при компаундировании с глубокоокисленным битумом можно достичь минимальных значений изменения температуры размягчения после старения и получить стандартные марки битумов БНД 70/100 и БНД 100/130 по ГОСТ 33133-2014. Установлено, что полученные командированные битумы в меньшей степени подвержены деструктивным и термоокислительным процессам старения и могут быть эффективно использованы для устройства дорожных покрытий.
Ключевые слова: гудрон, битум, компаундирование, предокисление, старение, термоокислительная стабильность.
