RU2179564C1 - Commercial carbon, method of its production and reactor for production of commercial carbon - Google Patents

Abstract

FIELD: commercial carbon used as filler of polymer materials. SUBSTANCE: proposed method consists in burning fuel gas, forming reaction zone due to separation of combustion products in multi-passage mixing nozzle into several flows, mixing hydrocarbon raw material with combustion products and cooling reaction products; rate of gas flow is maintained between 250 and 300 m/s at pressure differential at inlet and outlet of 0.02 to 0.04 MPa and distance not exceeding 2 to 5 diameter of passages; then flows are combined at abrupt deceleration and turbulent mixing; reaction products are cooled to 1100- 1200 C. Proposed method is performed in reactor having combustion chamber, chamber multipassage mixing nozzle and chamber for cooling the products; multipassage nozzle is made from refractory material at thermal conductivity of 1.5 to 4.8 W (m.K) and heat capacity of 0.7 to 1.08 kJ (kg. K); length of passage id equal to 2-5 its diameters; heat-insulating layer is laid around multi-passage mixing nozzle. Commercial carbon unit has the following sizes: mean diameter, 0.18 to 0.23 nm at standard deviation of ≥ 0,0881 nm, but ≤ 0,1617 nm; perimeter , 1.38 to 2.28 at standard deviation of ≥ 1,4703 nm, but ≤ 3,0334 nm; area of projection, 0.036 to 0.073 sq.nm at standard deviation of ≥ 0,0542 $\genfrac{}{}{0ex}{}{\text{2}}{\text{sq.nm.}}$ sq.nm, but ≤ 0,1363 sq.nm and area of pores 5.67 to 11.82 sq.nm at standard deviation of ≥ 19,8133 sq. nm, but ≤ 25,5591 sq. nm. EFFECT: enhanced stability of sizes; improved physico-mechanical properties of vulcanizers. 6 cl, 5 dwg, 6 tbl

Description

 The invention relates to a process for the production of carbon black from liquid raw materials, which is used as a filler for polymeric materials.

 The soot formation process includes several stages: dispersing liquid hydrocarbon feedstock in a stream of combustion gases, evaporating droplets formed, chemical decomposition of the vapor of the feedstock, the formation of soot particles from the pyrolysis products. The second stage, as the slowest one, limits the speed of the whole process as a whole and therefore can greatly affect the quality of the resulting product. Due to the high rate of the decomposition reaction, vapor pyrolysis proceeds in parallel and simultaneously with the evaporation of droplets, and if it occurs quickly, then after the formation of soot nuclei, the subsequent growth of all its particles occurs almost simultaneously. The result should be a product with a uniform particle size composition.

In the known methods for producing carbon black described, for example, in RU 2097398, RU 2083614, US 3477816, US 4360497 to produce carbon black with high activity, the temperature of the combustion gases is increased to 2000 ^° C and / or their velocity in the mixing zone is increased due to a decrease in diameter this zone.

 The first of these measures requires increasing the heat resistance of the refractory material of the reactor and significantly increases the cost of soot production. The second makes it necessary to increase the excess pressure when air is supplied to the reactor to 1.5 atm. At the same time, the costs of the blower are high.

 In addition, with a further increase in the load on the reactor and the creation of heavy-load reactors having large overall dimensions, it is difficult to obtain carbon black with high reinforcing properties.

 In the patent RU 2131766 (OJSC "Yaroslavl carbon black") 06/20/1999 describes a reactor and a method for producing carbon black with particle sizes of 110-600 angstroms with a degree of fusion of particles in the unit in the range of 0.03-0.09. It has a multichannel phase mixing zone in which the total total cross-section of the channels is approximately equal to the cross-section of the mixing zone in a conventional single-channel reactor. Distribution of the total feedstock consumption over several channels allows introducing it into each of them using one or two jet nozzles with a correspondingly smaller diameter of the outlet. This contributes to a finer primary atomization of the raw materials, faster evaporation of the droplets, greater uniformity of the carbon black particles in size, smaller average sizes of these particles and their greater activity. However, the number of inclusions and soot obtained in such a reactor is not uniform enough in the finished product.

 The present invention is aimed at further increasing the uniformity of the particles and providing a higher yield of highly active carbon black while reducing coke formation.

где n - количество исследованных агрегатов;
x_i - i-oe значение рассматриваемой величины;

среднее арифметическое рассматриваемой величины.The problem is solved in that the aggregates in carbon black have the following dimensions: average diameter 0.18-0.23 nm with a standard deviation ≥0.088 nm, but ≤0.161 nm, the perimeter 1.38-2.28 nm with a standard deviation ≥1 , 4703 nm, but ≤3.0334 nm, projection area 0.036-0.073 nm ² with standard deviation ≥0.0542 nm ² , but ≤0.1363 nm ² , pore area 5.67-11.82 nm ² with standard deviation ≥19.8133 nm ² , but ≤25.5591 nm ² . Under the standard (selective) deviation is understood as the positive square root of the sample variance and is determined by the formula:

where n is the number of investigated aggregates;
x _i - i-oe value of the considered quantity;

arithmetic mean of the considered value.

In the proposed method for producing carbon black, which includes burning fuel gas in a combustion zone, forming a reaction zone by dividing the total volume of combustion products into several streams of the same cross section, mixing hydrocarbon materials with combustion products in each stream and cooling the products of soot formation reaction in the reaction zone provide heat exchange between the above flows, evenly distribute the temperature field in the cross section of the multi-channel mixing nozzle throughout e length in the space surrounding the streams, provide the same temperature conditions for the soot formation reaction in each stream, while maintaining in the reaction zone a flow velocity of 250-300 m / s and a pressure drop at the inlet and outlet of 0.02-0.04 MPa then soot-gas flows are combined at a distance not exceeding 2-5 diameters of the channels, providing their sharp braking and turbulent mixing, then the products of the soot formation reaction are cooled to a temperature of 1100-1200 ^o C. The hydrocarbon feed enters the mixing zones through d at an angle of 90-135 ^o to the direction of the flow of combustion products, before being fed into the mixing zone, the hydrocarbon feed is heated to a temperature of 180-210 ^o C and fed under a pressure of 1.8-2 MPa, for heat exchange between the streams they are placed in a material with thermal conductivity about 1.2-4.8 W / (m • K) and a heat capacity of about 0.7-1.08 kJ / (kg • K), additionally cool the soot formation reaction products to a temperature of 750-800 ^o C.

In the reactor for producing carbon black, containing a sequentially installed combustion chamber with means for burning fuel with air, a multi-channel mixing nozzle with means for introducing raw materials, a chamber with means for cooling soot and gas products, a multi-channel nozzle is made of corundum or zirconium refractory with a thermal conductivity of about 1.2 -4.8 W / (m • K) and heat capacity of about 0.7-1.08 kJ / (kg • K), while the length of the channel of the mixing nozzle is not more than 2-5 diameters of the channel of the multi-channel mixing la, and around the multi-channel mixing nozzle is insulating layer. In addition, the means for introducing raw materials are configured to supply raw materials to the channels of the mixing nozzle at an angle of 90-135 ^o to the direction of flow, under the same pressure and with the same temperature.

 In FIG. 1 shows a reactor for the production of carbon black; in FIG. 2 - distribution of the average diameter of the projection of the unit; in FIG. 3 - distribution of the projection area of the unit; in FIG. 4 - distribution of the perimeter of the projection of the unit; in FIG. 5 - distribution of the projection area of the pores of the unit.

The best embodiments of the invention
Consider the processes that occur when receiving carbon black. A stream of liquid raw materials directed at an angle to the gas flow velocity in the mixing zone, as a result of pulsations, first breaks up into rather large droplets with sizes of 0.1-1 mm. At a gas velocity of 200-400 m / s, a further part of the droplets is crushed into smaller droplets up to several microns in size. The heat required for evaporation is supplied through the outer surface of the droplet in two ways: convective heat transfer of droplets with hot gas and thermal radiation from the walls of the reactor. Under ordinary conditions, convective heat transfer substantially prevails over thermal radiation. At a lower temperature of the combustion gases, the droplets do not have time to evaporate until they reach the boundary of the mixing zone and the reaction zone. In addition to direct participation in heat transfer from gas to droplets, the influence of thermal radiation on the soot formation process can also manifest itself as follows.

 The fact is that inside sufficiently large droplets there may exist vaporization nuclei — vapor-gas bubbles (or even solid particles) with micron sizes hundreds of times smaller than the average droplet size. When the liquid overheats, the thermal radiation penetrating into it, these nuclei can spontaneously grow, which leads to internal boiling of the drop, which ends with its “explosion” and crushing into smaller ones. The overheating of the droplets and the growth of steam bubbles in them go simultaneously. However, thermal radiation does not reach drops near the axis of the reactor immediately. At small distances from the nozzle, where the counted concentration of droplets is high, the radiation from the walls of the reactor is substantially shielded by other droplets that are far from the axis. As the droplets accelerate, the flow becomes more transparent, and the thermal radiation reaching them from the walls of the reactor increases, tending to the maximum value. In a channel of large diameter 2R> 0.3 m, the penetration of thermal radiation to droplets is hindered by the screening effect. Explosive secondary crushing of droplets, their complete evaporation does not have time to complete in the reaction zone, the evaporation process is delayed in time, which leads to an increase in the heterogeneity of the size of the obtained product, worsening its quality. On the contrary, if the diameter of the channel of the reaction zone is less than 0.3 m, for example, half, then the quality of carbon black obtained in such a reactor and the activity of soot are higher. In addition, the present invention achieves the spatiotemporal separation of the stages of evaporation of the feedstock, vapor pyrolysis and soot formation, which allows a wider range of variation in the process parameters of the carbon black production process and product properties.

 The process of soot formation in the claimed reactor provides for the following working areas.

Burning area. Designed for burning fuel (natural gas) using medium-pressure air (t = 480-510 ^o C and above, P _huts = 0.06-0.065 MPa) in order to obtain combustion products (N ₂ O, N ₂ , CO ₂ , О ₂ ) with a temperature of 1600-1700 ^o С. It effectively burns fuel (α = 1.1-1.5) with the development of the maximum allowable working temperatures of the combustion products with the presence of residual (active) oxygen necessary to replenish the heat balance of the process carbon black formation of active grades.

Reaction zone. Designed for mixing fuel combustion products with hydrocarbon raw materials (t _c = 180-210 ^o C, P _h = 1.8-2.0 MPa) and subsequent soot formation reactions (pyrolysis, decarbonization, condensation, graphitization) at a working temperature of 1580-1650 ^o C. In this zone, efficient mixing of high-temperature combustion products of fuel and hydrocarbon feeds is ensured by dividing the total volume of combustion products into several streams and proportional supply of hydrocarbon feed through the channels of the mixing nozzle. The uniform distribution of the temperature field, both along the radius of the cross section of each stream and along its length, is achieved by providing heat exchange between the flows. For this, the channels of the mixing nozzle are arranged axisymmetrically with respect to the longitudinal axis of the combustion chamber and are made of a material having high thermal conductivity and high heat capacity. For example, from corundum refractory having a thermal conductivity of about 4.8 W / (m • K) and a heat capacity of about 1.08 kJ / (kg • K), or a zirconium refractory with a thermal conductivity of about 1.2 W / (m • K) and heat capacity of about 0.7 kJ / (kg • K), which ensures uniform heating of the mixing nozzle and the same temperature conditions of operation of all reaction channels. The regulation and constant control of raw materials supplied to each channel are carried out. In the reaction channels the same working conditions are created t _slave = 1550-1560 ^o C and the pressure drop between the combustion zone and the reaction zone of 0.02-0.04 MPa. Using the above techniques, the evaporation of raw materials and the progress of further soot formation reactions are accelerated. At a distance not exceeding 2-5 of the diameter of the reaction channel, the soot-gas flows are output to the common channel of the reactor with a sharp increase in the diameter of the passage section. In this case, the motion of the general flow is inhibited and its turbulent mixing due to the formation of reverse vortex flows at the outlet of each reaction channel. This contributes to the growth and agglomeration of soot with the formation of aggregates with a developed structure.

Pre-hardening zone. The soot formation reaction is terminated by reducing the operating temperature to 1100-1200 ^o C. For this, chemically purified water under a pressure of 2.0-2.5 MPa is pre-heated to a temperature of 95-100 ^{o C.} To ensure the completeness of the decomposition of hydrocarbons of various quality, the place of water injection and the conditions for its dispersion (number and type of nozzles, temperature and pressure of water) are selected empirically.

Hardening zone. Further, in the cooling zone, the gas-black mixture is cooled to a temperature of 750-800 ^o C and is fed to a recuperative air heater to heat the process air entering the reactor for burning fuel.

The reactor for producing carbon black comprises a housing 1 in which a combustion chamber 2 is arranged in series, provided with an air chamber for supplying air 3 and a chamber for introducing fuel gas 4, a multi-channel mixing nozzle 5 consisting of two channels 6. The channels of the mixing nozzle are parallel to the axis of the reactor . Raw nozzles 7 are installed in each channel 7. A pre-cooling chamber 8 with water nozzles 9 for preliminary quenching and cooling of the gas-gas mixture and a cooling chamber 10 with a water nozzle 11 are located behind the mixing nozzle. The reactor can be equipped with a recuperative air heater that heats the process air to temperature 500 ^o C or more entering the reactor for burning fuel. The number of channels may be different, for example 3-6. The relatively small diameter of the channel ensures the distribution of the temperature field in it both along the radius of the channel section and throughout its length until it reaches the preliminary quenching zone of reaction gases. A multi-channel nozzle is made of a material with high heat capacity and thermal conductivity, for example, corundum or zirconium refractory, which ensures uniform heating of the mixing nozzle in cross section and the same temperature conditions for the operation of all reaction channels. The large inner surface of the reaction channels contributes to the fact that along with the existence of convective heat transfer, the radiant heat exchange between the hydrocarbon feed and the inner surface of the reaction channel is intensified. Distribution of the total consumption of raw materials over several, for example 2 ... 6 channels, allows you to enter the raw materials into each of them using one or two jet nozzles with a small diameter of the hole, giving a fine primary atomization of the raw material. Thermal insulation 12 around the mixing nozzle allows you to create isothermal operating conditions for the reaction channels and reduce heat loss from the reactor vessel in the installation zone of the mixing nozzle to 1-2%. The length of the mixing nozzle, not exceeding 2-5 the diameter of the reaction channel, allows for the most complete decomposition of the feedstock while reducing the possibility of formation of grit. In the reactor, the hydrocarbon feed rate can be achieved up to 5000 kg / h or more while reducing the time of soot formation reactions due to the intensification of their passage rate.

Studies of the obtained carbon black N220 were carried out on an electron microscope with an increase of x 1 • 10 ⁴ . For the study, 445 Cabot carbon aggregates (sample 1), 265 aggregates obtained using the proposed invention in a six-channel reactor (sample 2), and 602 units obtained in a four-channel reactor (sample 3) were taken. The results (physicochemical analyzes of carbon black samples are shown in Table 1. The sizes of the aggregates obtained and the size distribution of the aggregates are shown in Table 2-5.

 Analysis of the results of morphological studies of 3 samples of carbon black having similar physicochemical parameters showed that the improved carbon of the present invention has a significantly smaller aggregate size, a narrower aggregate size distribution and lower surface porosity, which allows to obtain vulcanizers with better physical -mechanical indicators (see tab. 6).

 In the proposed invention, the above separation of the soot formation process into zones and the provision of the best process parameters makes it possible to evenly distribute the hydrocarbon feed in the fuel combustion product streams and accelerate the hydrocarbon feed evaporation process, provide the necessary process time for the soot formation reaction during the passage of the carbon mixture in the closed volume of the reaction channel, provide the necessary technological time for the growth and agglomeration of soot due to the brake zheniya gas stream by combining particulate flows before cooling. Carbon black obtained by the claimed method in a multichannel reactor has improved reinforcing properties.

Claims (6)

1. Carbon black, characterized in that the aggregates have the following dimensions: average diameter 0.18-0.23 nm with a standard deviation of ≥0.0881 nm, but ≤0.1617 nm, the perimeter of 1.38-2.28 nm at standard deviation ≥1.4703 nm, but ≤3.0334 nm, projection area 0.036-0.073 nm ² with standard deviation ≥0.0542 nm ² , at ≤0.1363 nm ² , pore area 5.67-11.82 nm ² with a standard deviation of ≥19.8133 nm ² , but ≤25.5591 nm ² . 2. A method of producing carbon black, including burning fuel gas in a combustion zone, forming a reaction zone by dividing the total volume of combustion products in a multi-channel mixing nozzle into several streams of the same cross section, mixing hydrocarbon materials with combustion products in each stream and cooling the products of soot formation reaction , characterized in that in the reaction zone support the gas flow rate equal to 250-300 m / s with a pressure drop at the inlet and outlet of 0.02-0.04 MPa, while at a distance Phenomenon, not exceeding 2-5 diameters of the channels, combine soot-gas flows, while providing their sharp braking and turbulent mixing, cooling the reaction products lead to 1100-1200 ^o C. 3. The method according to p. 2, characterized in that the hydrocarbon feed is fed into the mixing zone at an angle of 90-135 ^o to the direction of flow of combustion products. 4. The method according to p. 2, characterized in that before being fed into the mixing zone, the hydrocarbon feed is heated to a temperature of 180-210 ^o C and served under a pressure of 1.8-2.0 MPa. 5. The method according to p. 2, characterized in that the soot formation reaction products are additionally cooled to 750-800 ^o C.  6. A reactor for producing carbon black, comprising a sequentially mounted combustion chamber with means for burning fuel with air, a multi-channel mixing nozzle with means for introducing raw materials, a chamber with means for cooling soot and gas products, characterized in that the multi-channel nozzle is made of refractory material with thermal conductivity 1.5-4.8 W / (m • K) and a heat capacity of 0.7-1.08 kJ / (kg • K), while the length of the channel is 2-5 of its diameters, and around the multi-channel mixing nozzle there is a thermal insulation onny layer.

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