RU2317308C2 - Technical carbon production process and a system for recuperative heating of process air - Google Patents

Abstract

FIELD: carbon materials.

SUBSTANCE: invention provides process of producing technical carbon from liquid hydrocarbon stock. Process comprises preliminary heating of liquid hydrocarbon stock and process air to 150-200°C, heating in shell-and-tube heat exchanger to temperature higher than fuel inflammation temperature. Combustion of fuel with process air is conducted at temperature exceeding hydrocarbon stock decomposition temperature by 200-300°C to produce smoke gas with specified content of residual active oxygen calculated in dependence on mark of obtained technical carbon. First section of recuperative heating system represents shell-and-tube heat exchanger with spirally finned tubes having winding pitch 5 to 15 mm, finning being made in discontinuous manner and, in intersection partitions, tubes are sealed with cylindrical plugs. Second section represents annular tube heat exchanger in cylindrical shell with two annular grooves. In the first annular groove, spiral turbulizing tapes are placed and second annular groove has special ribbing to provide tangential movement of air in countercurrent to movement of hot heat carrier.

EFFECT: optimized expenses on power resources ensuring adequacy of process parameters and required quality of technical carbon.

3 cl, 2 dwg, 1 tbl

Description

The invention relates to the field of production of carbon black from liquid hydrocarbon materials by thermo-oxidative decomposition (pyrolysis) and to a system for the regenerative heating of process air, which is an oxidizing agent that provides a thermo-oxidative process.

State of the art

It is known that, in order to obtain the required parameters of carbon black, it is important that the flue gases from fuel combustion entering the hydrocarbon pyrolysis zone have the required temperature and the required composition of the “residual active” oxygen, which ensures complete decomposition of the hydrocarbon raw material (V.Yu. Orlov , A. Komarov, L. A. Lyapina “Production and use of carbon black for rubbers”, Yaroslavl, A. Rutman publishing house, 2002, pp. 165-167). As a result of chain reactions of the decomposition of hydrocarbon molecules, the formation of radical nuclei of soot particles (carbon black aerosol) occurs, which, as a result of condensation growth, reach the normalized sizes of primary particles and aggregates in accordance with parameters according to ASTM D1765 or GOST 7885-86. For this purpose, a modern reactor is an apparatus functionally consisting of several working zones in which the process steps occur and partially overlap:

1) the combustion zone, which is used for efficient combustion of fuel pre-mixed with process air;

2) the mixing zone, where the spraying of liquid raw materials occurs, its intensive mixing with the combustion gases of the fuel leaving the combustion chamber, and the evaporation of the raw materials;

3) a reaction zone that provides thermo-oxidative vapor decomposition of hydrocarbons in a high-temperature gas stream with the formation of carbon black particles;

4) the cooling zone of the carbon black aerosol leaving the reactor to the temperature necessary for the operation of recuperative heat exchangers.

It is known that to ensure an effective technological process (in the temperature range 1300-1600 ° C), which excludes the distortion of the parameters of the obtained carbon black, it is necessary to carry out:

- processes of preheating of all material flows entering the reactor to temperatures ensuring complete combustion of the fuel;

- rapid evaporation of hydrocarbons and its pyrolysis,

- effective cooling of carbon black aerosol (VF Surovikin “Study of the kinetics and mechanism of the formation of dispersed carbon during the decomposition of liquid hydrocarbons”, Scientific works of VNIISP, issue 1. West Siberian Book Publishing House, 1972, pp. 9-30).

There are various methods of intensification of the technological process. So in the patent RU 2179564 (publ. 2002.02.20) in order to accelerate the evaporation processes and the passage of soot formation reactions, the reaction chamber for mixing flue gases with hydrocarbon feed is divided into many cylindrical channels. In patent RU 1329158 (publ. 1997.09.20), hydrocarbon feed is fed into the reactor after a 2-stage cavitation treatment, which ensures the creation of a homogenized working mixture, which is fed into a swirling flow of fuel combustion gases, which contributes to a uniform distribution of the feed in the working volume and accelerates the evaporation processes and soot formation. In another patent RU 2205195 (publ. 2003.05.27), dispersions of hydrocarbon feedstock in flue gases of fuel combustion are improved by adding 1.5-12 wt.% Water to the hydrocarbon feedstock, which ensures efficient crushing of drops of liquid feedstock during bubble evaporation of water.

However, all these methods of intensification of the technological process for producing carbon black affect only some stages of its passage, which do not affect the factors of increasing efficiency in terms of reactor productivity and finished product yield.

Of all the known techniques, the most important for the intensification of the technological process and ensuring the required parameters of the obtained carbon black is the preliminary heating of the process air, which allows not only to reduce the flow of fuel supplied, but also to increase the flow of hydrocarbon feed to the reactor at the same air flow (Gregory J. Homoki, “Using Secondary Energy in the Production of Carbon Black,” Proceedings of the International Conference on Carbon Black, Houston Texas, USA, pp. 18-21). This is directly related both to reactor productivity and to an increase in the yield of carbon black, since in this case the content of residual “active” oxygen in flue gases increases, which allows increasing the supply of hydrocarbon raw materials and thereby increasing the reactor productivity while maintaining the volume of process air supplied . At the same time, this provides an increase in the yield of finished products due to the limitation of the amount of air entering the combustion chamber. It should be borne in mind that each brand of carbon black requires its own technological parameters of the process in the reaction zone (temperature, time, gas velocity), which will correspond to the optimal performance of the reactor for hydrocarbon raw materials and the maximum achievable finished product yield. In this direction, preheating of process air is one of the main stabilizing factors providing the necessary parameters of the process for producing carbon black.

Given the high energy potential of the carbon black coming out of the aerosol reactor with a temperature of more than 800 ° C, it is natural to consider its use as a heating medium for heating process air. The main reason that impedes the efficient heat exchange of the carbon black aerosol with the process air is the deposition of carbon black on the heat transfer surfaces and, as a result, the decrease in the temperature of heating the air, as a result of which the operating parameters of the technological process for producing carbon black are distorted.

Closest to the method claimed according to claim 1, is a method for producing carbon black from liquid hydrocarbon raw materials by thermooxidative decomposition, including preheating liquid hydrocarbon raw materials and process air through regenerative heat exchange with carbon black aerosol first in a pipe-in-pipe heat exchanger "Enclosed in a cylindrical shell, and then in a shell-and-tube heat exchanger, mixing fuel with heated process air and burning it for radiation of flue gas with residual active oxygen, intensive mixing of liquid hydrocarbon feedstock in the flue gas stream, evaporation of hydrocarbon feedstock, its thermo-oxidative decomposition with the formation of carbon black aerosol and its subsequent cooling (Orlov V.Yu. et al., Production and use of carbon black for rubber, Yaroslavl, Alexander Rutman, 2002, S. p. 156-170, 218-224, p. 131, Fig. 4.4).

However, the prototype method does not allow to optimize the technological parameters of the process for obtaining various grades of carbon black and has a significant energy consumption of the technological process.

The objective of the present invention is the ability to implement a differentiated approach to the organization of the technological process for obtaining various grades of carbon black while reducing energy intensity, increasing the efficiency of the process by reducing the specific consumption of fuel and hydrocarbons, achieving optimal reactor performance and maximum yield of finished products.

Disclosure of invention

To solve this problem, a method for producing carbon black from liquid hydrocarbon raw materials by thermooxidative decomposition, including preheating liquid hydrocarbon raw materials and process air by regenerative heat exchange with a carbon black aerosol first in a pipe-in-tube heat exchanger enclosed in a cylindrical shell, is proposed. and then in a shell-and-tube heat exchanger, mixing fuel with heated process air and burning it to produce smoke gas with residual active oxygen, intensive mixing of liquid hydrocarbon raw materials in the flue gas stream, evaporation of hydrocarbon raw materials, its thermo-oxidative decomposition with the formation of carbon black aerosol and its subsequent cooling, which consists in the fact that the preliminary heating of the process air is carried out to a temperature of 150-200 ° C, and heating in a shell-and-tube heat exchanger - to a temperature exceeding the temperature of self-ignition of the fuel, burning fuel with process air is carried out by and a temperature exceeding the decomposition temperature of the hydrocarbon feedstock to 200-300 ° C, and the amount of residual active oxygen content in the flue gas is calculated from the condition of complete combustion by the number of residual air for 1 kg of hydrocarbon feedstock, wherein:

upon receipt of inactive carbon black, the amount of residual air is chosen equal to 0.4-0.7 nm ³ / kg of hydrocarbon feed;

upon receipt of semi-active carbon black, the amount of residual air is chosen equal to 0.7-1.0 nm ³ / kg of hydrocarbon feed;

upon receipt of highly active carbon black, the amount of residual air is chosen equal to 1.0-1.4 nm ³ / kg of hydrocarbon feed.

The “active oxygen” contained in the residual air oxidizes part of the hydrocarbon feedstock, which ensures temperature stabilization in the endothermic pyrolysis process of the main part of the hydrocarbon feedstock, which corresponds to the required parameters of carbon black (specific external surface and adsorption surface according to DBP).

The efficiency factor of the reactor process is determined from the following formula:

where Q _VSD is the flow rate of process air of medium pressure, nm ³ / h;

Q _t - fuel consumption (natural gas), nm ³ / h;

Q _VVD - high pressure air flow rate, nm ³ / h;

G _{raw materials} - the consumption of hydrocarbons, kg / h

Periodic technological control of the parameters of carbon black is carried out around the clock after 4 hours, which allows you to quickly provide the necessary adjustment of the technological regime, and, first of all, according to the correspondence of the flow of process air to the accepted load of hydrocarbon raw materials. Failure to achieve the required quality parameters of carbon black leads to the need to increase the consumption of residual air, which reduces the efficiency of the reactor process. Exceeding the required quality parameters of carbon black can reduce the consumption of residual process air, which, accordingly, contributes to an increase in the efficiency of the reactor process. In practical terms, the initial installation of operational technological parameters on each brand of carbon black is carried out on the basis of operational maps, which are developed depending on the quality of the prepared hydrocarbon feed (density, degree of aromatization according to the IR correlation index). After receiving the first analyzes of the physicochemical properties of carbon black and comparing them with the specification of the parameters in accordance with the requirements of GOST or ASTM D1765, a decision is made on the need to adjust the technological regime for further technological process.

Process description

The technological process (Fig. 1) in the reactor (1) begins with the combustion zone, where, in limited volumes of the combustion chamber, the fuel is completely burned to prevent its pyrolysis, for which the process air is pre-heated sequentially in a pipe-in-pipe heat exchanger enclosed into a cylindrical shell (2), to a temperature of 150-200 ° C and then in a shell-and-tube heat exchanger (3) to a temperature higher than the auto-ignition temperature of the fuel, for example, in the case of natural gas, up to 650-700 ° C. Next, flue gases enter the mixing zone, where liquid hydrocarbon feed is introduced, where it is intensively evaporated and mixed with flue gases containing residual active oxygen. The resulting working mixture enters the reaction zone for thermo-oxidative pyrolysis with the formation of particles and aggregates of carbon black. Given the endothermic nature of the chain reactions of the pyrolysis of hydrocarbons, the temperature of the flue gas leaving the combustion zone is maintained at 200-300 ° C above the reaction temperature upon receipt of a given grade of carbon black. Maintaining a stable temperature in the reaction zone is carried out by oxidizing part of the hydrocarbon feed when it is burned in residual active oxygen. At the outlet of the reactor, the carbon black aerosol is cooled to a temperature of 850 ° C, which ensures reliable operation of the process air recuperative heating system. After cooling the aerosol in a tube-in-tube heat exchanger enclosed in a cylindrical shell (2) and a shell-and-tube heat exchanger (3) to a temperature of 450-550 ° C, the carbon black aerosol in the cooler-sprinkler (4) is additionally cooled by adding chemically purified water to temperature 260-280 ° C. After that, the carbon black aerosol is fed to the bag filter (5) for its capture. The cleaned off-gas is then sent for disposal.

The present invention considers 3 groups of carbon black, produced in accordance with the international standard ASTM D1763-2003, which are most common in tire and rubber products and differ in specific surface area and organization of the reactor process:

- Group I - low-active carbon black with a specific external surface of 19 to 30 m ² / g.

- Group II - semi-active carbon black with a specific external surface of 35 to 45 m ² / g.

- Group III - medium and high carbon black with a specific external surface of 75 to 140 m ² / g.

All of the above groups of carbon black are produced at reactors of different technological designs, because the process parameters are significantly different, and it is not possible to combine them in a universal reactor. As an example, we cite the characteristic differences that exist in the production of inactive and highly active carbon black.

Type of carbon black Specific external surface, m ² / g The temperature in the reaction zone, ° C Time spent in the reaction zone, s The velocity of the reaction gases, m / s Group I - P803 (GOST 7885-86) twenty 1260-1280 2-3 0.5-1.5 Group III - N220 (ASTM D1765) 110 1570-1590 10 ^-2 -10 ^-3 300-350

To stabilize the properties of the obtained carbon black of a certain brand in the quenching zone of the reactor, a sharp cooling of the carbon black aerosol to a temperature of 1100 ÷ 1200 ° C is carried out.

The best option for implementing the method according to the invention

1. For the production of inactive carbon black.

The implementation of the method is performed on a vertical reactor unit operating under overpressure. The operation of the reactor is organized taking into account the use of natural gas as fuel. As process air, low pressure air of 0.04 MPa, preheated to a temperature of 650 ° C, is used.

In accordance with the required process parameters (temperature, time, gas velocity in the reaction zone), the following mode was implemented:

No pp Parameter Name Units rev. Qty one. Fuel consumption nm ³ / h 320 2. Low pressure air flow nm ³ / h 5000 3. Hydrocarbon consumption kg / h 3500 four. High pressure air consumption for spraying raw materials nm ³ / h 600 5. Temperature in the combustion zone ° C 1540 6. The temperature in the reaction zone ° C 1280 7. Carbon black aerosol temperature in the quench zone ° C 750 8. Air heating temperature after gas cooler ° C 150 9. Air heating temperature after heat exchanger ° C 625 10. Specific consumption of residual air per 1 kg of hydrocarbon feed nm ³ / h 0.57 eleven. The output of carbon black relative to hydrocarbons % 69 12. Parameters of carbon black (1 group) according to GOST 7885-86 - iodine adsorption mg / g 21 - specific external surface m ² / g eighteen - adsorption of DBP ml / 100 g 95

The implementation of the process according to the invention provides the required purity of carbon black from residues of undecomposed raw materials with a simultaneous increase in the basic productivity of the reactor (by 500 kg / h) and an increase in the yield of carbon black up to 69% while ensuring quality that meets GOST 7885-86.

2. For the production of semi-active carbon black.

Implementation of the invention is carried out on a heavy-load reactor unit with a hydrocarbon production rate of up to 5000 kg / h or more with the following process conditions:

- stable heating of medium-pressure technological air to a temperature of 650 ° C.

- operating temperature in the combustion zone is 1650-1700 ° C.

- radial entry of hydrocarbon feed into the reaction zone with a working temperature of 1360-1380 ° C.

To obtain semi-active carbon black of type N550, the following technological regime is established:

No. Parameter Name Units rev. Qty one. Raw material consumption kg / h 4200 2. Natural gas consumption nm ³ / h 700 3. Process air consumption nm ³ / h 10 800 four. High pressure air consumption for spraying raw materials nm ³ / h 1420 5. Temperature in the combustion zone ° C 1700 6. The temperature in the reaction zone ° C 1330 7. Tempering zone temperature ° C 750 8. Air temperature after gas cooler ° C 195 9. The temperature of the air entering the reactor ° C 645 10. Specific consumption of residual air per 1 kg of hydrocarbon feed nm ³ / h 0.75 eleven. Carbon black yield % 67 12. Parameters of carbon black type N550 according to ASTM 1765 (group II) - iodine adsorption mg / g 43 - specific external surface according to CTAB m ² / g 41 - adsorption of DBP ml / 100 g 120

The need to supply high pressure air is caused by the relatively low speeds of the flue gases from the combustion chamber to 100 m / s.

The main advantage of the technological regime for the production of semi-active carbon black is the achievement of stable parameters of the resulting products and a decrease in the likelihood of grit formation. In addition, the example implementation of the invention shows that, provided that the conditions for preheating the process air and the required amount of residual air of 0.75 nm ³ / kg are ensured, the efficiency of the reactor increases as the productivity of hydrocarbons increases (from 3500 kg / h to 4200 kg / h), and the finished product yield up to 67%. At the same time, the quality of carbon black meets the requirements of the international specification ASTM D1765.

3. For the production of active carbon black.

The main problem of obtaining active carbon black of type N220 according to ASTM D1765 (group III) is a decrease in the profitability of the process due to a decrease in the productivity of the reactor for hydrocarbons and a decrease in the yield of carbon black.

When implementing the invention, associated with an increase in the temperature of heating of process air to 750-800 ° C and a decrease in the specific consumption of process air per 1 kg of hydrocarbon feedstock, this trend disappears due to an increase in the fraction of heat of flue gases entering the reaction chamber with a temperature of up to 1800 ° FROM. At the same time, the hydrocarbon productivity of the reactor and the maximum allowable yield corresponding to the quality of the prepared hydrocarbon feed are kept at a cost-effective level.

To obtain active carbon black of type N220, the following technological regime is established:

Npp Parameter Name Units rev. Qty one. Raw material consumption kg / h 4300 2. Natural gas consumption nm ³ / h 1180 3. Process air consumption nm ³ / h 17200 four. Temperature in the combustion zone ° C 1780 5. The temperature in the reaction zone ° C 1565 6. Aerosol temperature at the device inlet ° C 850 7. Air temperature after gas cooler ° C 260 8. The temperature of the air entering the reactor ° C 780 9. Specific consumption of residual air per 1 kg of hydrocarbon feed nm ³ / h 1.21 10. Carbon black yield % 59 12. Parameters of carbon black type N220 according to ASTM 1765 - iodine adsorption mg / g 121.0 - specific external surface according to CTAB m ² / g 110 - adsorption of DBP ml / 100 g 114

The results obtained allow us to state that a high yield of finished products is ensured - 59 wt.% (At 51-52 wt.% According to the basic version of the technology). At the same time, a sufficiently high reactor productivity is maintained, which ensures the profitability of the process stream.

Achievable technical result

The advantage of the proposed method is the ability to obtain various grades of carbon black while reducing energy intensity. The technological process for producing carbon black, proposed according to the invention, allows optimizing technological costs in terms of energy resources, ensuring the sufficiency of the process parameters while ensuring the required quality of carbon black.

Description of the prior art for the device

In domestic factories for the production of carbon black, the most common are regenerative shell-and-tube air heaters operating at an inlet temperature of the carbon black aerosol of 750-800 ° С. Moreover, the heat transfer surface is developed using highly alloyed pipes (10X23N18) with a diameter of 42 × 3 (3.5) mm with a total heat transfer surface of 85 m ² to 240 m ² . Temperature compensation from the difference in temperature changes of the pipes and the casing is provided due to the preliminary deformation of the pipes with the formation of an angle of rotation of 90 °. With an increase in the productivity of reactors from 2-3 t / h to 4-5 t / h and more, air heaters basically did not change, but increased only in overall dimensions (length, diameter, weight) by 1.5-2 times (V.I. Ivanovsky "Carbon black. Processes and apparatus", Omsk, OJSC "Carbon black, 2004, p. 228). This led to the fact that the existing problematic issues regarding the efficient operation of air heaters (stable heating temperature, service life, etc.) remained unresolved, and in the production of semi-active and inactive carbon black these problems were especially aggravated.

The main problem of the effective operation of air heaters is the presence of a high dust content of aerosol technical carbon, which leaves the reactor as a heating medium for heating process air. Fundamental decisions inherent in the above air heaters do not ensure their effective operation for stable air heating due to the high rate of clogging of pipes with carbon black and increased hydraulic resistance along the carbon black aerosol path. Ultimately, this leads either to a decrease in reactor productivity, or to the necessity of shutting down the reactor for repair in order to forcibly clean the pipes of the tube bundle of the air heater clogged with carbon black. Changes in the thermal and hydraulic mode of operation of the air heater negatively affect the stability of the reactor parameters, which is directly reflected in the stability of the quality parameters of the finished product.

It is known that to reduce the likelihood of carbon black entering the heat exchange surface, it is necessary to carry out aerosol transportation of carbon black through the pipes of the heat exchanger at a speed of at least 70-80 m / s (R. Busroyd "Gas flow with suspended particles", M .: Mir, 1975 ., p. 373). In this case, the permissible hydraulic resistance of the air heater and, first of all, along the carbon black aerosol path due to the limitation of the pressure of the process air entering the device (not more than 0.06-0.07 MPa) is of decisive importance. The total hydraulic resistance of the 2-phase system can be considered due to the gas and solid phases. In this case, the hydraulic resistance from the contact of solid carbon black particles moving with the gas flow velocity with the stationary inner surface of the pipes will increase with decreasing pipe cross-section, as well as with increasing particle size of carbon black due to agglomeration associated with collisions of carbon black aggregates with the formation of more large agglomerates in conditions of a limited volume of pipe space and significant concentrations of dusting particles technically of carbon flow in a vertical pipe exchanger.

The second problem associated with the possibility of deposition of carbon black on the heat exchange surface is the presence in the gas part of the aerosol of carbon black up to 30-35 vol.% Water vapor due to the supply of cooling water to the reaction gases to achieve the required parameters of carbon black. This process is most pronounced on the “cold” side of the heat exchanger, which includes a coolant with a temperature below the dew point for water vapor (+ 120 ÷ 140 ° C), which is part of the carbon black aerosol. In the event that droplet moisture appears in the aerosol of carbon black, the process of deposition of carbon black on the heat exchange surface becomes irreversible even with an increase in the speed of movement of the carbon black aerosol through pipes above 70-80 m / s.

The above technological problems of using carbon black aerosol as a heating medium for heating air are supplemented by high fire hazard and corrosiveness of the gaseous medium due to its content of hydrogen (15-17 vol.%) And carbon monoxide (12-14 vol.%). Particularly quickly occur corrosion processes at the level of intergranular corrosion (MCC) at a temperature of the reducing medium above 850 ° C. As a result, air heater designs must meet the requirements for long-term strength and operational reliability. The implementation of these measures, taking into account the operation of the heater under high temperature loads with a carbon black aerosol temperature above 800-850 ° C, requires the use of high alloy steels and alloys, effective protective refractories and other solutions that significantly increase its cost.

To solve the problem of creating a reliable and efficient heat exchange device that works with limiting the temperature of the hot coolant (not more than 850 ° C), in conditions of lowering the speeds of the heated air (not more than 20 m / s), it is necessary to compensate for these limitations by developing a heat exchange surface, contacting with heated air, and to minimize heat loss due to effective design solutions that allow you to bring the temperature of the heated air closer to the temperature of the heating gas by entering the device.

In the RF patent for utility model No. 37818 (publication 05/10/2004, Bulletin of Inventions No. 13), a heating system for process air is proposed, which is currently implemented in domestic carbon black plants. The heating system consists of a main recuperator and an additional section installed sequentially along the carbon black aerosol.

The disadvantage of this heating system is the high hydraulic resistance along the aerosol path of carbon black, arising from the limited caliber of the heating pipes (not more than 42 mm) of the main recuperator and the clogging of the tube bundle tubes of the additional section (item 7 of figure 1 to the description of utility model No. 37818 ) due to the intake of cold air after cooling the direct-flow section of the main recuperator (item 1). Another technological drawback of this heating system is the need to maintain a high temperature (940-970 ° C) of a carbon black aerosol at the entrance to the main recuperator (item 1). This leads to the need to develop special measures to protect the tube plate and tube bundle of the main recuperator from intergranular corrosion, which is intensified in a reducing environment at a gas temperature of more than 850 ° C. The use of higher alloy steels and alloys leads to an increase in the cost of equipment. The above disadvantages make it difficult to use this heating system for all types of produced furnace carbon black.

The disadvantages of the method used in the analog of compensation for temperature deformations of heating pipes due to the rotation of the tube bundle by 90 ° are:

- the lack of technological cleaning of clogged pipes with gases of complete combustion of fuel, which leads to the need to reduce the load on the reactor using hydrocarbon raw materials or installing a bypass line with the supply of additional cold air to the reactor;

- limiting the possibility of increasing the caliber of the heating pipes (not more than 42 mm);

- incomplete compensation of temperature deformations of the central pipes in the tube bundle, perceiving the main carbon black aerosol flow during the clogging of the peripheral pipes, which practically leads to an increase in the level of thermal stresses in the welded joints of the central pipes in the hot tube plate and is the cause of the failure of the main recuperator.

The prototype of the present invention is a system for the regenerative heating of process air, structurally made of two sections arranged sequentially along the hot aerosol of carbon black (Orlov V.Yu. et al., Production and use of carbon black for rubbers, Yaroslavl, Alexander Rutman, 2002, p. 233-228, fig. 5.35, 5.38). Air pre-heating is provided in a section consisting of a pipe-in-pipe heat exchanger enclosed in a cylindrical shell by cooling the carbon black aerosol during countercurrent movement. The carbon black aerosol passes in the annular space formed by the inner and outer tubes of the pipe-in-pipe heat exchanger. Air passes through the inner pipe and in the annular space formed by the outer tube of the heat exchanger and the cylindrical shell. Heated air is sent to the first section of the regenerative heating system, which is a shell-and-tube heat exchanger with cross and countercurrent flow of heat carriers. The heat exchanger has a cylindrical body containing a bunch of vertical pipes passing through the entire height of the heat exchanger, separated by partitions and resting on the lower base plate, where they are rigidly fixed in the lower tube sheet, which is cooled by part of the flow of cold air entering the internal cavity of the base plate. The fastening of vertical pipes in the upper tube sheet is carried out with the help of compensators, which make it possible to compensate for the thermal deformations of each pipe of the tube bundle both during thermal expansion and during compression during a change in the temperature regime. High-temperature carbon black aerosol flow passes through the pipes, and heated air passes through the annulus, the direction of movement of which is determined by the location of the partitions.

The main disadvantages of the prototype include the possibility of the formation of carbon black deposits in the annular space between the inner and outer tubes of the pipe-in-pipe heat exchanger due to the presence of cold air (in winter conditions), which is sucked out of the atmosphere through the inner pipe. Under these conditions, the temperature of the wall of the inner tube in contact with the aerosol reaches the dew point temperature, which contributes to the deposition of carbon black. This reduces the efficiency of heat transfer and leads to an increase in hydraulic resistance, which reduces the throughput of the apparatus and reduces the performance of the reactor with a load of hydrocarbon raw materials. In addition, the well-known system of regenerative heating of process air is very complex, responsible and expensive.

The objective of the present invention is to provide a system of recuperative heating of process air of optimal metal consumption and dimensions, which allows for a differentiated approach to the organization of the process upon receipt of various grades of carbon black, increasing the efficiency of the process by reducing the specific consumption of fuel and hydrocarbons, achieving optimal reactor performance and maximum yield finished products while ensuring the required quality technically th carbon.

Disclosure of invention

To solve this problem, a system for the regenerative heating of technological air is proposed, structurally made of 2 sections arranged sequentially in the direction of movement of a hot carbon black aerosol (Fig. 2), the first section being a shell-and-tube heat exchanger (3) with cross and countercurrent flow of heat carriers, having a cylindrical body, a tube bundle extending to the entire height of the heat exchanger, separated by partitions (6) with a gap providing free movement pipes (7) during heating or cooling, resting in the lower part on a support plate (8), and in the upper part fixed in the tube sheet (9) using bellows devices (10) installed on each pipe, providing mobility pipes, both during their thermal expansion and during compression of the pipes in the process of changing the temperature regime of the heat exchanger, and the second section, providing pre-heating of the process air by cooling the carbon black aerosol during their countercurrent movement, It is drawn from a pipe-in-pipe heat exchanger enclosed in a cylindrical shell (2) and has two annular channels, the first annular channel (11) intended for aerosol movement of carbon black formed by the outer surface of the inner pipe (12) and the inner surface the outer pipe (13) of the heat exchanger, and the second annular channel (14), designed to move the heated air, is formed by the outer surface of the outer pipe (13) and the inner surface of the cylindrical shell (15), namely, that the pipe ( 7) a shell-and-tube heat exchanger (3) is installed in the partitions (9) with a seal by means of cylindrical bushings (16) with a height of 100-120 mm with a gap of up to 1 mm, ensuring their mobility, the outer surface of the pipes (7) is developed by spiral intermittent finning (17), the step is from 5 to 15 mm, and the base plate (8) of this heat exchanger is made double, and the second section is made with the possibility of heating the process air to 150-200 ° C due to the fact that on the outer surface of the inner pipe (12) is installed spiral the tape (18) with a winding pitch of 1.5-2.5 m, and the outer surface of the outer pipe (13) has a ribbing made in uniform sections using plates (19) with an inclination of up to 30 degrees with respect to the generatrix, which allows tangential air movement.

The principal differences of the proposed heating system is the following:

special design of the 1st section - a regenerative shell-and-tube heat exchanger (3) with a developed heat exchange surface along the heated air, achieved by spiral finning (17) of the outer surface of the pipes (7). An important element in the performance of spiral finning is the winding pitch, which is set from 5 to 15 mm. The differentiated approach to spiral finning of heating pipes is explained by the need to achieve maximum effect during heat transfer between the heating surface and the heated process air. For this purpose, the kinetic characteristics of the coolants (speed, heat transfer time, hydraulic resistance, etc.) are optimized by technological calculations, allowing to achieve the maximum heating temperature of the process air in the process of obtaining various grades of carbon black (Table 1). To obtain low-active carbon black, the step of winding spiral-shaped finning on the outer surface of the shell-and-tube heat exchanger tubes is set to 10-15 mm, to obtain semi-active carbon black 8-10 mm, to obtain highly active carbon black 5-8 mm. To reduce air flow along the step of the spiral finning (17), it is planned to intermittently perform it at the intersection of the pipes (7) and the partition (6). In these places, the seal of the gap between the partition (6) and the pipe (7) is achieved by installing a cylindrical sleeve (16). Partitions (6) are installed with the minimum allowable pitch over the entire height of the heat exchanger. The difference from the prototype is also that in the double base plate (8), the heating pipes are fixed by special welding after preliminary expansion of the pipes in the lower tube plate, which excludes the transmission of vibration from the vertical beam to the welds of the pipe seal in the tube plate. These differences, supplemented by effective thermal insulation, make it possible to increase the efficiency of heat transfer through the air path and thereby bring the temperature of the heated process air closer to the temperature of the carbon black that enters the heat exchanger.

The proposed system for the regenerative heating of process air required the development of new designs of the 2nd section, designed for preheating of process air to a temperature of at least 150-200 ° C, i.e. above the dew point of a carbon black aerosol (120-130 ° С depending on the concentration of sulfur compounds). A tube-in-pipe type heat exchanger is proposed, enclosed in a cylindrical shell (2) and having two annular channels (11, 14), while spiral turbulent ribbons (18) are installed in the first annular channel (11) and the second annular channel (14 ) has a special finning with the help of plates (19), which makes it possible to ensure tangential air movement countercurrent to the movement of hot heat carrier.

These differences can reduce the possibility of clogging of the heating pipes with carbon black in the 1st section of the heating system and intensify heat transfer.

Achievable technical result

1. Creation of a system for recuperative heating of process air of optimum metal consumption and dimensions.

2. Achieving optimal reactor productivity and maximum yield of finished products while ensuring the required quality of carbon black.

3. Improving the efficiency of the process by reducing the specific consumption of fuel and hydrocarbons.

4. Improving the efficiency of heat transfer and heating of process air.

5. The ability to implement a differentiated approach to the organization of the technological process upon receipt of various grades of carbon black.

6. Reducing the volume of binding steel structures and the volume of foundations, which reduces costs during construction and installation works.

Claims (3)

1. A method of producing carbon black from liquid hydrocarbon raw materials by thermo-oxidative decomposition, including preheating liquid hydrocarbon raw materials and process air through recuperative heat exchange with a carbon black aerosol first in a pipe-in-pipe heat exchanger enclosed in a cylindrical shell, and then in a shell-and-tube heat exchanger, mixing fuel with heated process air and burning it to produce flue gas with residual active oxygen ohm, intensive mixing of liquid hydrocarbon raw materials in a flue gas stream, evaporation of hydrocarbon raw materials, its thermo-oxidative decomposition with the formation of carbon black aerosol and its subsequent cooling, characterized in that the process air is preheated to a temperature of 150-200 ° C, and shell-and-tube heating heat exchanger - up to a temperature exceeding the auto-ignition temperature of the fuel, the fuel is burned with process air at a temperature higher than the temperature Proposition hydrocarbons at 200-300 ° C, and the amount of residual active oxygen content in the flue gas is calculated from the condition of complete fuel combustion by the number of residual air for 1 kg of hydrocarbon feed, wherein upon receipt of inactive carbon black, the amount of residual air is chosen equal to 0.4-0.7 nm ³ / kg of hydrocarbon feed; upon receipt of semi-active carbon black, the amount of residual air is chosen equal to 0.7-1.0 nm ³ / kg of hydrocarbon feed; upon receipt of highly active carbon black, the amount of residual air is chosen equal to 1.0-1.4 nm ³ / kg of hydrocarbon feed. 2. A system for recuperative heating of process air, structurally made of two sections arranged sequentially along the hot aerosol of carbon black, the first section being a shell-and-tube heat exchanger with cross and countercurrent movement of heat carriers, having a cylindrical body and a tube bundle passing through the entire height of the heat exchanger divided by partitions, resting on the base plate in the lower part, and fixed in the middle of the tube sheet in the upper part the number of bellows installed on each pipe, providing the mobility of the pipes both during thermal expansion and during compression during the change in the temperature regime of the heat exchanger, and the second section, which provides preheating of the process air by cooling the carbon black aerosol during their countercurrent movement from a tube-in-pipe heat exchanger enclosed in a cylindrical shell and has two annular channels, the first annular channel designed for movement carbon black aerosol is formed by the outer surface of the inner tube and the inner surface of the outer tube of the heat exchanger, and the second annular channel for moving heated air is formed by the outer surface of the outer tube and the inner surface of the cylindrical shell, characterized in that the shell-and-tube heat exchanger tubes are installed in the walls with a seal by means of cylindrical bushings with a height of 100-120 mm with a gap of up to 1 mm, ensuring their mobility, the outer surface pipes is developed by spiral intermittent finning, the step of which is from 5 to 15 mm, and the base plate of this heat exchanger is double, and the second section is made with the possibility of heating the process air to 150-200 ° C due to the fact that on the outer surface of the inner pipe a spiral tape with a winding pitch of 1.5-2.5 m, and the outer surface of the outer pipe has a ribbing made in uniform sections using plates with an inclination of up to 30 ° with respect to the generatrix, which ensures that potential air movement. 3. The system of recuperative heating of process air according to claim 2, characterized in that the step of winding spiral fins on the outer surface of the shell-and-tube heat exchanger tubes to produce low-active carbon black is 10-15 mm, to obtain semi-active carbon black 8-10 mm, to obtain highly active carbon black carbon 5-8 mm.

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