TECHNOLOGY OF EXTRACTION OF CUBIC RESIDUES BY THERMAL OXIDATION OF OIL SLUDGE

ABSTRACT

This article describes the process of oil sludge preparation in detail. The technological scheme of the thermooxidation of oil sludge and the sequence of its description are clearly presented. Physico-mechanical characteristics of the samples of cube residues obtained by thermooxidation of oil sludge were presented. The resulting cube residues allowed to use as a secondary bitumen to replace construction and road bitumen.

АННОТАЦИЯ

В данной статье подробно описан процесс подготовки нефтешламов. Наглядно представлена технологическая схема термоокисления нефтешламов и последовательность ее описания. Приведены физико-механические характеристики образцов кубовых остатков, полученных термоокислением нефтешламов. Полученные кубовые остатки позволили использовать в качестве вторичных битумов для замены строительных и дорожных битумов.

Keywords: Oil sludge, cube residue, secondary bitumen, construction bitumen, road bitumen, disposal, thermal oxidation, absorber.

Ключевые слова: Нефтешлам, кубовый остаток, вторичный битум, строительный битум, дорожный битум, утилизация, термическое окисление, поглотитель.

Introduction. The share of oil bitumen in the total volume of oil refining products in the world is 3-4%. At the moment, about 110 million tons of bitumen are produced annually in more than 70 countries of the world. According to analysts, the global annual demand for bitumen in 2021 will exceed 120 million tons, which is 59%. In 2010, the USA (29.22%), China (9.38%) and Japan (6.59%) were among the top three consumers of petroleum bitumen [1,2].

In the years of independence, the consumption of petroleum bitumen in Uzbekistan has increased significantly, which is due to the implementation of large projects for the construction of new highways, a sharp increase in the reconstruction and repair of highways. highways leading to cities are no exception [3].

It should be noted that there is an increasing trend in oil bitumen production in the countries of Central, South and East Asia. Production of bitumen products in the joint venture of "Fergana Oil Refinery" LLC and "Jharkurgan Oil Refinery" in our republic. Based on the needs of our Republic, these enterprises produce road, construction, roofing bituminous products and special brands of bitumen[4].

Research method. In order to study the possibility of obtaining commercial oil products on the basis of NSh, a pilot experimental laboratory device for the processing of oil sludge was developed and prepared (Fig. 1).

One of the main problems encountered during the experiment is foaming of the oil slurry during dewatering. This foaming occurs under the layer of viscous oil product due to the fact that water is at a temperature of 107-125 ^oС in the lower part of the apparatus [5].

In order to minimize foaming, oil slurries are supplied with air using a compressor. In the device, first of all, it is necessary to dewater the samples of oil sludge one after another, that is, it is aimed at extracting the water contained in the oil sludge as much as possible. Depending on the amount of water in the composition, oil sludge samples differ from each other.

A periodic experimental device consists of:

• oxidation cube;
• air supply and control system to the oxidation cube;
• system for cleaning gaseous substances (absorbers).

1- motor-reducer; 2- holding place; 3- bearing support; 4- mixer shaft; 5, 9, 13- faucet; 6- air pipe; 7- shell containing an electric coil; 8- cube holding support; 10- nozzle for receiving cube residue; 11- mixer; 12th body; 14, 15- absorbers; 16- hatch; 17- shaft hardener; 18- clutch. I- sending air using a compressor; II- sending light components to the gas meter; III- taking samples of the finished product, i.e. finished cube residue

Figure 1. Experimental device for thermal oxidation of oil sludge

The amount of substances required for the use of the experimental device [9]:

1) To get a 60 gram cube: Raw material (Oil sludge) - 100 g; Diesel fuel (for 1 absorber device) – 40 g; Air consumption - 8 l/min.

2) To get 100 grams of secondary road bitumen: Cube residue (CR) – 73 g; Technical sulfur (TS) – 15 g; Soapstock - 12 g; Air consumption - 8 l/min.

3) To get 100 grams of secondary construction bitumen: Cube residue (CR) – 88 g;

Technical sulfur (TS) – 4 g; Soapstock - 8 g; Air consumption - 8 l/min.

To process oil sludge at atmospheric pressure, they are heated in a cube to the temperature of azeotropic water distillation: 107-125 °C (depending on the composition of the oil sludge), then separation of the light components of the separated oil waste begins at 150-178 °C [6].

Research results and discussion. In order to test the residual cubes, whose physical and mechanical properties meet the requirements of GOST 33133-2014, which can replace road construction bitumen, samples were sent to the Central Laboratory of the Fergana Oil Refinery and the parameters listed in Table 1 were obtained [7].

Table 1.

Physico-mechanical characteristics of the samples of cubic residues obtained from thermal oxidation of oil sludge

As seen in Table 1, samples 7 and 8 CR gave good performance. But based on the above table 1, we selected the 7th CR sample. Because sample 8 contains less petroleum hydrocarbons and asphaltenes in the middle layers, we recommend preparation of high-quality asphalt concrete mixture as sample 7 corresponds to the physical and mechanical properties of road bitumen.

Based on the indicators of the 3rd and 6th CR samples, it can be concluded as follows. These samples meet the standard requirements of GOST 6617-2021 on the physical and mechanical properties of construction bitumen and were recommended for use in construction works [10-11].

Oil sludge thermal oxidation process is carried out as follows [8]:

1-oxidizing cube; 2,3-screw pumps; 4-compressor; 5.6-refrigerator condenser; 7,8,9,10,14,15,16 valves; 11-electric heater; 12-water condensate collection capacity; 13. Sludge light fraction collection capacity.I-raw materials (oil slurry); II-water; Fractions separated from III-slurry composition (125-360 ºС); IV gases; Sending the V-thermoxidized cube residue to the modification reactor; Air delivery to the VI-modification reactor

Figure 2. Scheme of domestic oil sludge thermal oxidation technology

Thermooxidation process of oil sludge. In the thermooxidation cube shown in Fig. 2, the oil slurry is first dried by evaporation from residual moisture, the clear fractions of oil are separated, and it is intended for thermooxidation. It is intended to accelerate the separation of residual moisture and volatile components by increasing the temperature and blowing air. The oxidation cube is a hollow cylindrical vessel made of steel St3 with a diameter of 2.5 m, a height of 8 m and a volume of 20 m3. for vaporization, an electric heater is installed inside the oxidation cube to provide the necessary temperature for thermooxidation. Oxidation cube is loaded in the amount specified in 1, i.e., 850 (3500 for secondary road bitumen) kg of oil slurry at 107-125ºС and light fractions (360ºС) in order to obtain secondary construction bitumen. In this case, according to the composition of the raw materials, it is desirable that the level of the slurry loaded into the oxidation cube occupies 1⁄3 to 1⁄2 of the total height of the oxidation cube. To remove the residual moisture in the slurry and hydrate it, the oil slurry is first heated to a temperature of 107-125ºС through a 1.5 kW heater installed inside the oxidation cube. In this case, as a result of heating up to 125ºС, the residual moisture in the form of water vapor is cooled to a temperature of 25-30 0С from the top of the oxidizing cube through the valve 7 - condenser - condenser 5, and the water condensate collection capacity 12 is collected. The period of sending the aqueous condensate of the separated vapors to the collection capacity lasts up to 2-3 hours, depending on the experimental data, depending on the type of sludge being processed. During the drying process of raw materials, when it is visible from the observation hatch that water vapor has formed foam on the surface of the heated slurry, in order to eliminate it and to ensure the maximum separation of the components separating at 107-125ºС, through the air nozzles located at the bottom of the thermooxidation cube, using compressor 4, through the valve 16 - 10 minutes every half hour during which air is pumped. The temperature is heated up to 360 ºС using an electric heater 11 in order to extract the components of light fractions of oil in the dehydrated oil slurry. In the process of heating, valve 7 is closed, and continuous air blowing with the help of compressor 4 begins to accelerate the boiling of heavy hydrocarbons and to carry out partial thermal oxidation. Due to the high temperature (150-178 ºС), vaporized hydrocarbons from the upper part of the oxidation cube 8 - through the valve - cooler - condenser 6 are cooled to 45-50 ºС and are collected in the capacity for collecting the light fraction of sludge 13. Condensed droplets are captured through shutters located in the collection capacity of the light fraction of the slurry, and the light components, i.e. gaseous substances, are sent to the gas collection system IV. Evaporation of heavy hydrocarbons and partial evaporation of raw materials takes up to 5-6 hours at 360 ºС depending on the type of slurry. Condensate separated from the slurry, consisting mainly of hydrocarbons that make up the solar fraction, is collected in the capacity of collecting the light fraction of the slurry 13. 12 and 13 are released from the valves 14 and 15 in the lower parts of the collecting tanks, so that the excess amount of the mixture is at the required level in the tank. The partially oxidized sludge, dewatered and cleaned of heavy hydrocarbon vapors in the oxidation cube 1, is kept for another 15 hours, in order to continue the thermooxidation with the air supplied by the compressor 4. Then, from the cubic part of the oxidation cube 1, through the valve 10, the thermally oxidized oil sludge, that is, the cube residue, is sent to the modification reactor 25 by means of the pump 3.

Summary. Based on the results obtained in the thermal oxidation pilot plant of oil sludge, 35-40% loss was separated as light components. The physico-mechanical properties of the samples of cubic residues obtained by thermal oxidation of oil sludge were compared with the requirements of GOST, and the samples of cubic residues 3,6,7,8 were obtained and gave good indicators. The resulting cube residues allowed to use as a secondary bitumen to replace construction and road bitumen.

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