Molecular sieve catalyst regeneration scorching method for moving bed light hydrocarbon conversion device

Abstract

The invention discloses a method for regenerating and scorching a molecular sieve catalyst of a moving bed light hydrocarbon conversion device. The method comprises the following steps: a to-be-regenerated molecular sieve catalyst reacted by a moving bed light hydrocarbon conversion device enters a regenerator by virtue of gravity for catalyst scorching, regeneration scorching is divided into three sections, namely a first-section scorching section, a second-section scorching section and an axial scorching section, and the three sections are in contact with oxygen-containing regeneration gas in sequence to burn carbon deposit on the catalyst; the coke-burning regeneration process of the spent molecular sieve catalyst is completed, and the regenerated catalyst is recycled; the charred regeneration gas is led out from the upper part of the regenerator, is divided into three paths after being subjected to heat exchange, cooling, drying and compression, and enters the regenerator for catalyst regeneration charring after being respectively supplemented with air and heated. The method provided by the invention can effectively control the temperature of the catalyst bed, ensure the burning effect of the catalyst and prolong the service life of the catalyst.

Description

Technical Field

[0001] The invention belongs to the field of petrochemical industry and relates to catalyst regeneration and coking, and specifically to a molecular sieve catalyst regeneration and coking method for a moving bed light hydrocarbon conversion device. Background Art

[0002] Light hydrocarbons mainly include C2 to C7 components produced from refineries. C2 components are mainly found in dry gas products produced from catalytic cracking, delayed coking and other units. They contain some olefins such as ethylene and can be used as raw materials for light hydrocarbon conversion to produce aromatics. C3 and C4 components are mainly found in liquefied petroleum gas products produced from refineries and are the main processing raw materials for existing light hydrocarbon conversion technologies. Moreover, with the development of my country's natural gas industry, the market for urban civil liquefied gas is gradually shrinking. The use of light hydrocarbon conversion technology to convert this relatively surplus liquefied gas resource into high value-added products has important practical significance and good economic efficiency.

[0003] Light hydrocarbon conversion technology originated in the early 1970s. The catalyst is a modified ZSM-5 molecular sieve catalyst. The catalyst can be used to convert light hydrocarbon components from C2 to C5 into aromatics and produce hydrogen as a by-product. It has the advantages of wide raw material adaptability, high product value, simple process flow, and low construction cost. It has developed rapidly in recent years. Representative technologies include UOP's Cyclar process, MOBIL's M2-Forming process, Japan's SANYO's Alpha process, Japan's Mitsubishi Oil (MITSUBISHI) and Chiyoda Corporation (CHIYODA) jointly developed Z-Forming process, France IFP and Australia SALUTEC jointly developed Aroforming process, etc.

[0004] Most light hydrocarbon conversion units use fixed-bed technology, which is characterized by low investment and quick results, but its disadvantages are also obvious: due to the use of two reactors for switching regeneration, the operation is cumbersome and the investment in catalysts is also large (the fixed bed catalyst capacity is about doubled that of the moving bed); there are also changes in product distribution, especially in the later stage, the dry gas yield in the product increases significantly, and the hydrogen yield produced is unstable, which affects subsequent units.

[0005] The moving bed catalyst regeneration and coking technology realizes the continuous coking and regeneration of the catalyst in the regenerator, so that the average activity of the catalyst is always maintained at a high level, avoiding cumbersome switching operations, maintaining plug flow of catalyst particles, strengthening mass transfer and heat transfer, and improving product yield and quality. Since the hydrogen-containing coke on the surface of the catalyst will generate water vapor during the combustion process, that is, the catalyst coking process is carried out in a high temperature and water-containing environment, the regeneration and coking process of the catalyst is a key link affecting the life of the catalyst. The amount of carbon deposits, coking temperature, and oxygen partial pressure of the catalyst are the main factors affecting the catalyst coking rate. Increasing the coking temperature under the same coking conditions can accelerate the coking rate, but too high a coking temperature will cause the catalyst bed to overheat, the catalyst to sinter, and the equipment to be damaged. The proper coking temperature must be controlled. Under the same coking temperature and gas-agent ratio, appropriately increasing the oxygen partial pressure in the coking medium can also accelerate the coking rate and shorten the coking time. Different oxygen contents can be controlled at different coking stages according to actual conditions.

[0006] In the dry regeneration process provided by USP5,304,117, CN1045411A and CN102869447A, mainly for precious metal catalysts, the regenerator charring zone is a two-stage charring structure. The catalyst bed in the charring zone is divided into two sections, and the catalyst is transported from top to bottom through the material legs. The two sections of the bed have the same structural dimensions and different regeneration gas inlet conditions. The entire charring is mainly concentrated in the upper section of the bed. The inlet temperature of the regeneration gas of the lower section of the bed is higher than that of the upper section of the bed. The regeneration gas inlet of the lower section of the bed is supplemented with air to adjust the oxygen content of the regeneration gas, and the regeneration gas enters from the top and exits from the bottom. A drying system is set in the regeneration gas circulation loop, so the water content of the regeneration circulation gas is low, and the mass flux of the bed gas is large, so the temperature rise of the overall bed is lower than that of the single-stage charring. However, the measure of bed segmentation increases the complexity of the charring structure, increases the manufacturing difficulty and investment cost, and increases the burden of operation and maintenance.

[0007] CN101658799B discloses a continuous catalyst regeneration method, which discloses that the reactor system does not have a spare reactor, and the reactor uses a spherical particle catalyst containing an active molecular sieve. During the reaction, the coke-containing catalyst is continuously removed from the reactor and regenerated in a regenerator. The regenerated regenerator enters the reactor system and continues to participate in the catalytic reaction. After the gas in the regenerator completes the catalyst coke regeneration, it enters the purification system for purification, and is matched with a certain amount of air. After pressurized heat exchange and heating, it enters the regenerator as regeneration gas again; air matching the gas from the regeneration gas purification system is injected from the downstream of the regeneration gas purification system. In this method, the regenerator is coked in one stage and oxygen is injected once, and there is no effective means to control the temperature of the coke bed of the regenerator.

[0008] CN105879927A discloses a moving bed light hydrocarbon to aromatics catalyst regeneration and charring method, which discloses that the charring area is divided into two sections, namely, an upper charring section and a lower charring section. The catalyst charred in the upper charring section and the lower charring section of the charring area enters the drying area under the action of gravity, completing the charring and regeneration process of the molecular sieve catalyst to be regenerated, and the regenerated catalyst is recycled. We have improved and optimized it on this basis, and modified the original drying area into an axial charring section to further ensure the charring effect of the catalyst. Summary of the invention

[0009] Aiming at the problem that the core of the regenerated molecular sieve catalyst of the light hydrocarbon conversion device is not easy to burn, resulting in a black core of the catalyst, the present invention provides a moving bed light hydrocarbon conversion device molecular sieve catalyst regeneration and burning method to solve the problem of uneven distribution of the device reaction products due to incomplete burning of the catalyst.

[0010] The present invention provides a method for regenerating and burning a molecular sieve catalyst in a moving bed light hydrocarbon conversion device, which is characterized by comprising the following steps:

[0011] 1) After the reaction in the moving bed light hydrocarbon conversion unit, the regenerated molecular sieve catalyst enters the regenerator through the catalyst feed leg for catalyst burning. The catalyst burning is divided into three sections, namely, the first burning section, the second burning section and the axial burning section. In the regenerator, the regenerated molecular sieve catalyst passes through the first burning section, the second burning section and the axial burning section in sequence by gravity, and contacts with the oxygen-containing regeneration gas in the first burning section, the second burning section and the axial burning section in sequence to burn the carbon deposits on the catalyst, completing the regeneration and burning process of the regenerated molecular sieve catalyst. The regenerated catalyst comes out from the bottom of the regenerator and is recycled;

[0012] 2) The regeneration gas in the first burning section and the second burning section are distributed circumferentially in the regenerator space surrounded by the outer screen and the regenerator cylinder, and pass through the catalyst bed radially and centripetally to burn the carbon deposits on the catalyst. After the regeneration gas in the axial burning section completes the charring of the residual carbon deposits in the core of the molecular sieve catalyst along the axial direction, it is collected with the regeneration gas in the first burning section and the second burning section that have completed the charring in the space surrounded by the screen in the regenerator, and is led out from the regeneration gas outlet, and is successively cooled by heat exchange in the regeneration gas heat exchanger tube, cooled by the regeneration gas cooler, dried by the regeneration gas drying system, and then regenerated by the regeneration gas inlet. After the pressure stabilization of the pressure-stabilizing tank, the pressure boosting of the regeneration gas circulation compressor and the heat exchange and temperature raising of the shell side of the regeneration gas heat exchanger, the circulating regeneration gas is divided into three routes. One route is supplemented with air and heated to 410-480°C by a first-stage heating device, and then enters the first-stage coking section through the first-stage coking section regeneration gas inlet; the other route is supplemented with air and heated to 415-495°C by a second-stage heating device, and then enters the second-stage coking section through the second-stage coking section regeneration gas inlet; the last route is supplemented with air and heated to 420-510°C by an axial section heating device, and then enters the axial coking section through the axial coking section regeneration gas inlet;

[0013] The operating pressure of the regenerator is 0.35-1.40 MPa, the catalyst bed temperature of the regenerator is 440-600°C, and the catalyst residence time in the regenerator is 6-20 hours;

[0014] The mass ratio of the regeneration gas flow rate entering the first coking section to the regeneration gas flow rate entering the second coking section and the regeneration gas flow rate entering the axial coking section is (3:7:1) to (4:10:1).

[0015] The light hydrocarbon conversion unit of the present invention is preferably a light hydrocarbon aromatization unit or a light hydrocarbon to propane unit.

[0016] The method for regenerating and coking molecular sieve catalysts in a moving bed light hydrocarbon conversion device of the present invention has further technical characteristics in that the oxygen content of the regeneration gas entering the first coking section is 1.0-4.0% by volume, the oxygen content of the regeneration gas entering the second coking section is 1.2-4.2% by volume, and the oxygen content of the regeneration gas entering the axial coking section is 1.5-4.5% by volume.

[0017] The method for regenerating and burning molecular sieve catalysts in a moving bed light hydrocarbon conversion device of the present invention has a further technical feature that the regenerated gas is dried by a regenerated gas drying system until the water content is no more than 20 ppm.

[0018] The present invention provides a molecular sieve catalyst regeneration and coking method for a moving bed light hydrocarbon conversion device, and its further technical feature is that the catalyst regeneration cycle has a period of 60 to 180 hours.

[0019] The method for regenerating and coking molecular sieve catalyst in a moving bed light hydrocarbon conversion device of the present invention has further technical characteristics in that the number of pipe openings of the first coking section regeneration gas inlet, the second coking section regeneration gas inlet and the axial coking section regeneration gas inlet are all 1 to 4.

[0020] The molecular sieve catalyst regeneration and coking method of the moving bed light hydrocarbon conversion device of the present invention has a further technical feature that an air compressor is arranged on the supplementary air pipeline.

[0021] The method for regenerating and burning molecular sieve catalysts in a moving bed light hydrocarbon conversion device of the present invention has a further technical feature that the regeneration gas cooler is preferably an air cooler or a water cooler.

[0022] The method for regenerating and burning molecular sieve catalysts in a moving bed light hydrocarbon conversion device of the present invention has a further technical feature that the regeneration gas heat exchanger is preferably a plate heat exchanger or a wound tube heat exchanger.

[0023] The method for regenerating and burning molecular sieve catalysts in a moving bed light hydrocarbon conversion device of the present invention has a further technical feature that the heating device is preferably an electric heater or a heating furnace.

[0024] The method for regenerating and burning molecular sieve catalysts in a moving bed light hydrocarbon conversion device of the present invention has the following beneficial effects compared with the prior art:

[0025] 1) In the prior art, after the molecular sieve catalyst is charred in the first and second charring sections, carbon deposits still remain in the core, resulting in a black core of the molecular sieve catalyst. The present invention provides an axial charring section in the regenerator, and a heating device is provided at the regeneration gas inlet of the axial charring section, and supplementary air is used to adjust the oxygen content. In this way, charring can be performed by adjusting the inlet temperature and oxygen content to prevent incomplete combustion of the core coke, thereby better ensuring the catalyst charring effect and ensuring the distribution of the reaction products of the device.

[0026] 2) The charring zone in the regenerator of the present invention is divided into three sections. The regeneration gas inlets of the first charring section, the second charring section and the axial charring section are respectively supplemented with air to adjust the oxygen content of the regeneration gas to meet the requirements of the charring regeneration of the molecular sieve catalyst to be regenerated. In addition, the temperature of the charring bed of the regenerator can be prevented from flying over by controlling the outlet temperature of the heating device, which not only protects the service life of the catalyst, but also prevents the damage of the regenerator caused by the flying over temperature of the bed. A thermocouple is provided in the regenerator to monitor the catalyst bed temperature at any time.

[0027] 3) The regeneration gas entering the first coking section, the second coking section and the axial coking section of the present invention is the regeneration gas dried by the drying regeneration system, and has a low water content, which is beneficial to protecting the catalyst and thus prolonging its service life.

[0028] The present invention will be further described in detail below with the accompanying drawings and specific embodiments, but the scope of the present invention is not limited thereto. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a schematic flow diagram of a molecular sieve catalyst regeneration and coking method in a moving bed light hydrocarbon conversion device.

[0030] The reference numerals shown in the figures are:

[0031] 1 molecular sieve catalyst to be regenerated, 2 regenerator buffer, 3 first stage charred section, 4 second stage charred section, 5 axial charred section, 6 first stage electric heater, 7 second stage electric heater, 8 axial stage electric heater, 9 regeneration gas heat exchanger, 10 regeneration gas cooler, 11 regeneration gas drying system, 12 regeneration gas inlet pressure-stabilizing tank, 13 regeneration gas circulation compressor, 14 air, 15 catalyst feed leg, 16 inner screen, 17 outer screen, 18 regenerator space surrounded by outer screen and regenerator cylinder, 19 space surrounded by inner screen of regenerator, 20 regeneration gas outlet, 21 first stage charred section regeneration gas inlet, 22 second stage charred section regeneration gas inlet, 23 axial charred section regeneration gas inlet, 24 regenerator, 25 thermocouple. DETAILED DESCRIPTION

[0032] Combination Figure 1 The process of the present invention is described as follows:

[0033] The catalyst bed of the regenerator coking section is composed of a cylindrical inner screen 16 and an outer screen 17. The regenerator coking zone is located below the regenerator buffer zone 2 and is connected by a catalyst feed leg 15. The heating device is an electric heater.

[0034] The regenerated molecular sieve catalyst 1 after the reaction of the light hydrocarbon conversion unit enters the regenerator buffer zone 2, and enters the regenerator 24 through the catalyst feed leg 15 for charring. The charring is divided into three sections, namely the first charring section 3, the second charring section 4 and the axial charring section 5. The regenerated molecular sieve catalyst passes through the first charring section 3, the second charring section 4 and the axial charring section 5 in sequence by gravity, and contacts with the oxygen-containing regeneration gas to burn the carbon deposits on the catalyst, completing the charring regeneration process of the regenerated molecular sieve catalyst. The regenerated catalyst comes out from the bottom of the regenerator 24 and is recycled.

[0035] The charred regeneration gas comes out from the regeneration gas outlet 20, and after heat exchange and temperature reduction in the tube side of the regeneration gas heat exchanger 9, it is cooled to 45-50°C in the regeneration gas cooler 10, enters the regeneration gas drying system 11, and after drying to a water content of no more than 20ppm (volume), it enters the regeneration gas inlet pressure-stabilizing tank 12. The pressure-stabilized regeneration gas is compressed by the regeneration gas circulation compressor 13, enters the shell side of the regeneration gas heat exchanger 9 for heat exchange and temperature increase, and is divided into three paths as the circulating regeneration gas. One of the paths is supplemented with air 14 through the supplementary air pipeline. The first-stage electric heater 6 is used to heat to 410-480°C, and enters the first-stage coking section 3 through the first-stage coking section regeneration gas inlet 21; the other route is supplemented with air 14 through the supplementary air pipeline, and then heated to 415-495°C by the second-stage electric heater 7, and enters the second-stage coking section 4 through the second-stage coking section regeneration gas inlet 22; the third route is supplemented with air 14 through the supplementary air pipeline, and then heated to 420-510°C by the axial-stage electric heater 8, and enters the axial-stage coking section 5 through the axial-stage coking section regeneration gas inlet 23.

[0036] The regeneration gas in the first charring section 3 and the regeneration gas in the second charring section 4 are circumferentially distributed in the regenerator space 18 surrounded by the outer screen and the regenerator cylinder, and radially and centripetally pass through the catalyst bed and burn the carbon deposits on the catalyst. After the regeneration gas in the axial charring section 5 is charred in the axial direction, it is collected with the regeneration gas that has been charred in the first charring section 3 and the second charring section 4 in the space 19 surrounded by the screen in the regenerator, and is led out from the regeneration gas outlet 20 at the top of the regenerator 24. The charring temperature of the entire bed in the regenerator 24 can be detected and observed by a thermocouple 25. The thermocouple 25 is a flexible thermocouple that can run through the entire regenerator.

[0037] The catalyst regeneration cycle generally has a period of 60 to 180 hours.

[0038] The regeneration gas cooler is preferably an air cooler or a water cooler.

[0039] The above description is only a typical embodiment of the present invention, and does not impose any form of limitation on the present invention. Any changes or modifications made by any technician familiar with the profession, without departing from the scope of the technical solution of the present invention, using the above content should be regarded as equivalent examples of equivalent changes. Any equivalent changes made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are within the scope of the technical solution of the present invention.

Claims

1. A method for regenerating and burning molecular sieve catalysts in a moving bed light hydrocarbon conversion device, characterized in that The following steps are involved: 1) After the reaction in the moving bed light hydrocarbon conversion unit, the regenerated molecular sieve catalyst enters the regenerator through the catalyst feed leg for catalyst burning. The catalyst burning is divided into three sections, namely, the first burning section, the second burning section and the axial burning section. In the regenerator, the regenerated molecular sieve catalyst passes through the first burning section, the second burning section and the axial burning section in sequence by gravity, and contacts with the oxygen-containing regeneration gas in the first burning section, the second burning section and the axial burning section in sequence to burn the carbon deposits on the catalyst, completing the regeneration and burning process of the regenerated molecular sieve catalyst. The regenerated catalyst comes out from the bottom of the regenerator and is recycled; 2) The regeneration gas in the first burning section and the second burning section are distributed circumferentially in the regenerator space surrounded by the outer screen and the regenerator cylinder, and pass through the catalyst bed radially and centripetally to burn the carbon deposits on the catalyst. After the regeneration gas in the axial burning section completes the charring of the residual carbon deposits in the core of the molecular sieve catalyst along the axial direction, it is collected with the regeneration gas in the first burning section and the second burning section that have completed the charring in the space surrounded by the screen in the regenerator, and is led out from the regeneration gas outlet, and is successively cooled by heat exchange in the regeneration gas heat exchanger tube, cooled by the regeneration gas cooler, dried by the regeneration gas drying system, and then regenerated by the regeneration gas inlet. After the pressure stabilization of the pressure-stabilizing tank, the pressure boosting of the regeneration gas circulation compressor and the heat exchange and temperature raising of the shell side of the regeneration gas heat exchanger, the circulating regeneration gas is divided into three routes. One route is supplemented with air and heated to 410-480°C by a first-stage heating device, and then enters the first-stage coking section through the first-stage coking section regeneration gas inlet; the other route is supplemented with air and heated to 415-495°C by a second-stage heating device, and then enters the second-stage coking section through the second-stage coking section regeneration gas inlet; the last route is supplemented with air and heated to 420-510°C by an axial section heating device, and then enters the axial coking section through the axial coking section regeneration gas inlet; The operating pressure of the regenerator is 0.35-1.40 MPa, the catalyst bed temperature of the regenerator is 440-600°C, and the catalyst residence time in the regenerator is 6-20 hours; The mass ratio of the regeneration gas flow rate entering the first coking section to the regeneration gas flow rate entering the second coking section and the regeneration gas flow rate entering the axial coking section is (3:7:1) to (4:10:1).

2. The method for regenerating and burning molecular sieve catalysts in a moving bed light hydrocarbon conversion unit according to claim 1, characterized in that: The light hydrocarbon conversion unit is a light hydrocarbon aromatization unit or a light hydrocarbon to propane unit.

3. The method for regenerating and burning molecular sieve catalysts in a moving bed light hydrocarbon conversion unit according to claim 1, characterized in that: The oxygen content of the regeneration gas entering the first coking section is 1.0-4.0% by volume, the oxygen content of the regeneration gas entering the second coking section is 1.2-4.2% by volume, and the oxygen content of the regeneration gas entering the axial coking section is 1.5-4.5% by volume.

4. The method for regenerating and burning molecular sieve catalysts in a moving bed light hydrocarbon conversion unit according to claim 1, characterized in that: The regeneration gas is dried by a regeneration gas drying system until the water content is no more than 20 ppm.

5. The method for regenerating and burning molecular sieve catalysts in a moving bed light hydrocarbon conversion unit according to claim 1, characterized in that: The catalyst regeneration cycle has a period of 60 to 180 hours.

6. The method for regenerating and burning molecular sieve catalysts in a moving bed light hydrocarbon conversion unit according to claim 1, characterized in that: The number of the pipe openings of the first-stage coking section regeneration gas inlet, the second-stage coking section regeneration gas inlet and the axial coking section regeneration gas inlet are all 1 to 4.

7. The method for regenerating and burning molecular sieve catalysts in a moving bed light hydrocarbon conversion unit according to claim 1, characterized in that: An air compressor is provided on the make-up air line.

8. The method for regenerating and burning molecular sieve catalysts in a moving bed light hydrocarbon conversion unit according to claim 1, characterized in that: The regeneration gas cooler is an air cooler or a water cooler.

9. The method for regenerating and burning molecular sieve catalysts in a moving bed light hydrocarbon conversion unit according to claim 1, characterized in that: The regeneration gas heat exchanger is a plate heat exchanger or a wound tube heat exchanger.

10. The method for regenerating and burning molecular sieve catalysts in a moving bed light hydrocarbon conversion unit according to claim 1, characterized in that: The heating device is an electric heater or a heating furnace.

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