RU2426763C1 - Procedure for cleaning furnace coil from sedimentation of coke - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: pipes of furnace coil 1 are cleaned by break up of sedimentation of coke with scraper knives of moving scraper introduced by means of flow of oil product. At outlet from furnace the flow of oil product is simultaneously and continuously separated from the scraper and is divided into two not equal parts, bigger of which without the scraper is directed to reactor 9 for coking, while a smaller one with the scraper is directed to separator-catcher 36 for cleaning from coke sedimentation.

EFFECT: reduced capital and operational expenditures.

4 cl, 4 ex, 2 dwg

Description

The invention relates to methods for cleaning a furnace coil from coke deposits and can be used in the oil refining industry.

There is a method of mechanical cleaning of pipes of furnace coils from coke deposits, including the introduction of a plastic scraper into the pipes of the furnace, its transportation through pipes, reversal and withdrawal from the installation after cleaning (Journal of Chemistry and Technology of Fuels and Oils, No. 2, 2007, p. 16-17). Input and transportation of the scraper is carried out using a carrier - high-pressure water flow from autonomous pumps driven by diesel engines. When the scraper passes through the furnace coil, coke deposits are destroyed from the inner surface of the pipe and further removed by water flows.

The disadvantage of this method is the complexity and inefficiency, the process is difficult to manage, takes a long time, deformation and decrease in pipe strength are frequent, which leads to an increase in capital and operating costs due to frequent replacement of pipes and furnace stops for repair.

The closest in essential features is the method of mechanical cleaning of furnace coils from coke deposits with a scraper, in which an oil product is used as a carrier stream (Pat. RF No. 2358003, IPC C10G 9/16, op. 10.06.2009, BI No. 16) . The method includes introducing a scraper into the coil pipe of the furnace, actually cleaning the pipes by breaking coke deposits with scrapers of a moving scraper, removing the carrier stream with a scraper and coke particles from the furnace and feeding it through a four-way valve (pos. 72 of FIG. 12 of the prototype) for cleaning into the separator - a trap from where the scraper returns to the furnace coil cleaning process, and the oil product stream is sent to the reactor for coking.

The disadvantage of this method is that through a four-way valve into the separator trap is directed the entire flow of oil after the furnace, which determines the rigid technological parameters (high temperature, flow rate and flow rate) of the separator trap and creates increased requirements for safety and material design of this devices, which leads to an increase in capital and operating costs.

The technical result of the invention is to reduce the values of the technological parameters of the separator trap.

The specified technical result is achieved by a method of cleaning the furnace coil from coke deposits, including introducing a scraper into the furnace coil pipe using an oil product stream, actually cleaning the pipes by breaking coke deposits with scrapers of a moving scraper, removing the oil product stream with a scraper and coke particles, cleaning and feeding the scraper again into the cleaning process of the furnace coil, in which according to the invention, at the outlet of the furnace, the oil product stream is separated from the scraper and divided into two unequal parts, the larger of the cat The free ones, free from the scraper, are sent to the reactor for coking, and the smaller with the scraper - for its cleaning from coke deposits in the separator-trap, and the above-mentioned actions are carried out simultaneously and continuously.

Most of the split stream, free from scraper, can make up at least 80% of the total stream.

It is advisable to continuously separate the oil product stream from the scraper with the simultaneous separation of the stream into parts in a device consisting of a segment of a perforated chimney with oil input and output pipes with a scraper, enclosed in a closed chamber with water vapor input and oil output pipes.

It is advisable to cool a smaller part of the oil product stream with a scraper before feeding it to the separator-trap to a temperature of 180-220 ° C or to a temperature of 380-420 ° C, and then direct it to a raw material tank or reactor, respectively.

Separation of the scraper carrier oil product stream into two unequal parts - the larger one, free from the scraper, and the smaller one with the scraper, allows directing not more than 20% of the entire stream into the trap separator and thereby reduce its flow rate and speed.

The cooling of the flow before feeding it to the separator-trap can reduce the temperature parameters and increase the safety of operation during its operation.

Figure 1 shows the installation, and figure 2 is a flow separation device for implementing the proposed method.

The proposed installation is shown in combination with a delayed coking unit and includes a furnace 1 with a convection coil 2 and a radiation coil 3, a feed line 4, on which a valve 5 is installed, an output line for heat-treated raw materials 6 from the coil 3 of furnace 1, a device for separating the stream 7, a transfer line for introducing heat-treated raw materials 8 into reactor 9, a gate valve 10 (differential pressure regulator valve), a line for introducing water vapor 11 into the gate valve 10, a line for the output of coking vapors 12 from reactor 9 to a distillation column 13 with lines withdrawal of gas and gasoline 14, light gas oil 15, heavy gas oil 16 and bottom residue 17. To ensure the rectification process, the column provides return lines for chilled products: gasoline 18, light gas oil 19, bottom residue 20. A device for launching scrapers 21 is connected to furnace 1 with valves 22, 23, 24, 25. The valve 25 is connected by a perforated pipe to the annular chamber 26, which includes the supply line of the turbulator - water vapor (condensate) 27. The device for starting the scrapers 21 is connected by a line 28 through a four-way valve 29 with a loading device Property 30, equipped with valves 31, 32, 33, 34, 35, and a separator-trap 36, equipped with valves 37, 38, 39, 40, 41, 42 and 43. Four-way valve 29 is connected to the output device 44, equipped with valves 45 46, 47, 48. On the output line of low-coking oil product - gas oil 49, on the piping of the device for starting the scrapers 21 and on the piping of the separator-trap 36, valves 50, 51, 52, 53, 54, 55 are installed. The installation is equipped with a pump 56, differential pressure gauges 57 , 58 installed on the bypasses of the device for starting the scraper 21 and the separator-trap 36. To reduce the value of technological x parameters when receiving and scraping separation of oil and carbon deposit in the carrier flow path upstream of the separator 36 is introduced trap "cold stream" 61 - gasoil with temperature 120-180 ° C. Gas oil is supplied via line 59, then to a refrigerator 60, cooled by water, through a valve 43 through a cold jet line 61 to a cold jet tee-mixer 62 installed on the output line of the heat-treated raw material 6 from the coil 3 of furnace 1. Line 63 connects tee-mixer 62 with separator-trap 36.

The device for separating the stream 7 consists of a housing 64, in which a segment of a perforated chimney 65 is placed with input pipes 66 and an output 67 of the scraper forming an annular chamber 68 in the housing, which has a pipe 69 for outputting oil into the transfer line for input of heat-treated raw materials 8, a pipe 70 for introducing water vapor, which, in turn, enters the annular chamber 68. The annular chamber 68 is closed by the upper 72 and lower 73 bottoms through which the perforated chimney 65 passes. The upper 72 and lower 73 bottoms are fixed to the flanges 74 of the housing a bolting device 75.

The method is as follows (for example, the process of delayed coking).

The raw material is a mixture of tar and recirculate, fed through heat exchangers (not shown) through the feed line 4 to the convection 2 and radiation 3 coils of the furnace 1. To reduce the rate of coking of the coils, water vapor (condensate) 27 is supplied to the annular chamber 26. The heat-treated raw material leaves the coil along the output line of the heat-treated raw material 6, enters the device for separating the stream 7 with a perforated chimney 65, where it is divided into two parts. Most of the flow free from the scraper is directed through the valve 10 along the transfer line of the input of the heat-treated raw material 8 to the reactor 9, the smaller part with the scraper along the line 63, into the separator-trap 36, and then downward through the valves 40, 52, 53 upstream of reactor 9, and through a valve 54, into a feed tank (not shown). At the stage of pipe cleaning, the scraper, together with the oil product residue and coke residue from the coil 3 of the furnace 1, enters through the scraper inlet 66 into the section of the perforated pipe 65. The cracked products, together with the coke deposits and the turbulator, exit the perforated chimney 65 through the through holes 71 into the annular chamber 68 , there is introduced through the pipe 70 water vapor. All these components pass through the outlet pipe 69 for output of the oil product into the transfer line of the input of the heat-treated raw material 8, through the valve 10 and enter the reactor 9. The scraper, together with the carrier stream (oil product), leaves the perforated chimney 65 through the outlet pipe of the scraper 67 through the valve 55, the tee-mixer of the "cold stream" 62 and through line 63 enters the separator-trap 36. The products of the thermo-destructive process from the reactor 9 through the output lines of the coking vapors 12 are sent to the distillation column 13 for separation by compo tomers. From the top of the column, a mixture of gas, gasoline and water vapor is discharged through line 14, from the middle part - light gas oil through line 15, from the bottom - bottom residue along line 17. To ensure the rectification process, chilled products are returned to the column: gasoline, light gas oil, bottoms the balance on lines 18, 19, 20, respectively. To reduce the coking rate of the device for separating the stream 7 and the valve 10, water vapor 11 is supplied to them. If a pressure drop occurs on the coil (0.1-0.2 MPa), preventive pipe cleaning is performed without removing the furnace coil 1 from the feed stream ( go "). First, the device is charged for launching the scraper 21 with a scraper or using a loading device 30 or a separator-trap 36, which is prepared accordingly. Run the scraper into the coil 3 of furnace 1. To do this, open the valves 25, 23 and, covering the valve 5, create a pressure drop of 0.1-0.5 MPa on it, guided by the readings of the differential pressure gauge 57, while the feed stream begins to flow through the valve 23 into the device for launching the scraper 21, from where the scraper is carried out by the flow through the valve 25, the annular chamber 26, the coil 3 of the furnace 1, passing through which the scraper carries out the corresponding work of cleaning the pipe surface from coke deposits. Cracking products, a turbulizer, dust from coke deposits and a scraper pass through a heat-treated raw material outlet line 6 from a coil 3 of a furnace 1, a flow separation device 7, a valve 55, a tee-mixer 62 into a separator-trap 36. The first three participants in the movement through the valves 40 and one of the valves 52, 53, 54 fall into the reactor 9 or into a raw material tank (not shown), and the last one, a scraper, is delayed in the separator-trap 36. The flow rate, speed and temperature of the stream 63 at the inlet to the separator-trap 36 are regulated by the pressure drop at the valve 10 per show the differential pressure gauge 58 and the supply (flow, temperature) of the “cold stream” 61. After that, the separator-trap 36 and the device for starting the scrapers 21 are removed from the feed stream. Next, the valves 23, 55 are closed, the valves are fully open (differential pressure control valves) 5, 10. The device for starting 21 and the separator-trap 36, the scraper and the system from raw materials, cracking products and coke residue are washed with gas oil. To do this, open 22, 24, 50, 37, 38, 41. Pump 56 picks up fresh gas oil from the lines of light 15 and heavy 16 gas oil, pumps it throughout the transport system, the feeder scrapers 21 and the separator-trap 36 and through the valve 50 delivers into the still part of the distillation column 13. After this operation, the device 21 is loaded with a scraper from the separator-trap 36. To do this, open the valves 51, 42, close the valves 38, 37, open the valve 39. In this case, the scraper is transported by gas oil flow from the separator-trap 36 through the valve 39, four ANNUAL valve 29, valve 22 into the apparatus for running scrapers 21; Further, the carrier gas oil through the valves 24, 51 enters the intake of the pump 56, after which it is stopped. The device 21 is prepared for the launch of the scraper, and the separator-trap 36 - to receive it. In the first case, the operations on the corresponding valve switching are described above. When cleaning pipes of a furnace coil using a low-coking product - gas oil (gas oil is used instead of raw materials), the cleaning method does not differ from the above, as well as the cleaning technology and instrumentation of a parallel furnace coil.

In thermo-destructive processes, tar and gas oil are used as raw materials, the latter is also used as a diluent and recirculate and for washing raw lines.

Example 1

In the proposed method, the flow from the furnace 6 has the following indicators: oil flow rate (mixture of tar and gas oil) 50 t / h (100%), temperature 500 ° C, speed 50 m / s, pressure 0.8 MPa. The stream enters the device for separating stream 7, where it is divided into two parts: a large part, free from scraper, with a temperature of 500 ° C, an oil flow rate of 45 t / h (90%) and a speed of 45 m / s enters through the control valve 10, transfer 8 to reactor 9; the smaller part with a scraper - with an oil product flow rate of 5 t / h (10%), a temperature of 500 ° C and a speed of 10 m / s passes the tee-mixer 62, where it is diluted with a “cold stream” at a flow rate of 20 t / h, temperature 130 ° C and enters through line 63 to the separator-trap 36 with a flow rate of 25 t / h, temperature 200 ° C, where the separation of the scraper from the oil. The latter with a flow rate of 25 t / h and a temperature of 190 ° C is sent to the raw material tank.

Example 2

In the proposed method, the stream from the furnace and after separation into two parts has indicators similar to those shown in example 1, however, in the tee-mixer it is diluted with a cold stream with a flow rate of 2.3 t / h, temperature 130 ° C and enters through line 63 to the separator trap 36 with a flow rate of 7.3 t / h, temperature 420 ° C, where the separation of the scraper from the oil. The latter with a flow rate of 7.3 t / h, a temperature of 400 ° C, a pressure of 0.7 MPa is sent up or down the reactor.

Example 3

In the known method, the flow from the furnace 6 has the following indicators: oil flow rate 50 t / h (100%), temperature 500 ° C, speed 50 m / s, pressure 0.8 MPa; the flow enters through a four-way valve 7 during the cleaning operation of the furnace coil into a separator-trap 36 with a flow rate of 50 t / h, a temperature of 500 ° C, a speed of 50 m / s, a pressure of 0.8 MPa, and from there to a coking reactor . At the same time, bypass transfer of oil product from the furnace to the reactor is absent, i.e. flow rate is zero.

Example 4

In the known method, the flow from the furnace 6, having indicators similar to example 3, enters through a four-way valve 7 only after the operation of cleaning the coil of the furnace bypass transfer to the coking reactor, with approximately the same technological parameters: oil flow rate of 50 t / h ( 100%), temperature 485 ° С, speed 50 m / s, pressure 0.7 MPa. At the same time, the oil product is not supplied from the furnace to the separator-trap 36, i.e. flow rate is zero. It should be noted that at this time in the separator-trap 36 the scraper is flushed with gas oil, and then the launch device is loaded with a scraper.

The implementation of the cleaning pipe of the furnace coil of the proposed method allows to simplify the cleaning system and ease the operating conditions of the installation, reduce the value of the process parameters in the separator-trap 36: temperature 1.2-2.5 times, flow rate 10 times, speed 5 times, which is significantly reduces capital and operating costs, and also significantly facilitates the conditions of safe operation at the installation. In addition, the cleaning operation of the furnace coil does not interrupt the flow of heat-treated raw materials from the furnace coil into the reactor, does not reduce the specified value of the technological parameters of the coking process and, therefore, maintains the quality of coking products, in particular, the content of volatile substances in coke.

Claims (4)

1. A method of cleaning the furnace coil from coke deposits, including introducing a scraper into the furnace coil pipe using an oil product stream, actually cleaning the pipes by breaking coke deposits with scrapers of a moving scraper, removing the oil product stream with a scraper and coke particles, cleaning and feeding the scraper again into the cleaning process furnace coil, characterized in that at the outlet of the furnace the oil product stream is separated from the scraper and divided into two unequal parts, most of which, free from the scraper, are sent to the reactor ment and with smaller scraper - on its purification from carbon deposit in the trap separator, wherein the above steps are carried out simultaneously and continuously. 2. The method according to claim 1, characterized in that most of the split stream is at least 80% of the total stream. 3. The method according to claim 1, characterized in that the continuous separation of the oil product stream from the scraper with simultaneous separation of the stream into parts is carried out in a device consisting of a segment of a perforated chimney with oil input and output pipes with a scraper enclosed in a closed chamber with input pipes water vapor and oil product withdrawal. 4. The method according to claim 1, characterized in that a smaller part of the oil product stream with a scraper is cooled to a temperature of 180-220 ° C or to a temperature of 380-420 ° C before being fed to a separator trap, and then sent to a raw material tank or into the reactor.

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