阅读说明：本技术 一种甲烷化镍基催化剂的钝化回收再利用方法 (Passivation recycling method of methanation nickel-based catalyst ) 是由 何伏牛 李慧鹏 于 2020-05-14 设计创作，主要内容包括：本发明公开了一种甲烷化镍基催化剂的钝化回收再利用方法。甲烷化系统停车后切断原料气,控制甲烷化反应器的床层降温,引入高压氮气吹扫、置换；床层温度降至200～220℃时停用电加热器,床层温度降至70～90℃,停用循环压缩机；将钝化的反应器和系统换热设备泄压,加装盲板安全隔离,停车流程倒为钝化流程,系统充入0.35～0.50MPa的氮气；启用循环机,在反应器中缓慢通入空气,逐渐提升氮气与空气混合气中的含氧量；当床层反应完全穿透时,检测进塔气和出塔气中的氧含量一致,催化剂钝化结束。本发明经过钝化能够使部分有催化活性或催化活性良好的镍基催化剂得以回收再利用。(The invention discloses a passivation recycling method of a methanation nickel-based catalyst. Cutting off the raw material gas after the methanation system stops, controlling the bed layer of the methanation reactor to cool, and introducing high-pressure nitrogen for blowing and replacing; stopping the electric heater when the temperature of the bed layer is reduced to 200-220 ℃, and stopping the circulating compressor when the temperature of the bed layer is reduced to 70-90 ℃; releasing pressure of a passivated reactor and system heat exchange equipment, additionally installing a blind plate for safety isolation, turning a shutdown process into a passivation process, and filling nitrogen of 0.35-0.50 MPa into the system; starting a circulator, slowly introducing air into the reactor, and gradually increasing the oxygen content in the mixed gas of nitrogen and air; and when the bed layer reaction is completely penetrated, detecting that the oxygen content in the tower inlet gas and the tower outlet gas is consistent, and finishing the catalyst passivation. The invention can recycle and reuse part of nickel-based catalyst with catalytic activity or good catalytic activity through passivation.)

1. The passivation recycling method for the methanation nickel-based catalyst is characterized by comprising the following steps of:

a. after the methanation system stops working, cutting off the raw material gas, starting an electric heater to control the bed temperature of the methanation reactor to cool, and controlling the cooling rate to be 30-50 ℃/h; introducing high-pressure nitrogen into a methanation device, and purging and replacing a methanation system;

b. carrying out primary constant-temperature drying when the temperature of a bed layer of the methanation reactor is reduced to 300-320 ℃, detecting after drying, and finishing system replacement when the content of nitrogen in a detection system is more than 99.9%;

c. continuously controlling the cooling rate of the bed layer temperature of the methanation reactor, carrying out secondary constant-temperature drying when the bed layer temperature of the methanation reactor is reduced to 200-220 ℃, stopping the electric heater after drying is finished, and circularly reducing the bed layer temperature;

d. continuously controlling the cooling and pressure reduction rate to reduce the pressure of the methanation system at a rate of less than or equal to 0.1MPa/min, controlling the pressure of the system to be reduced to 0.2-0.5 MPa, finally reducing the bed temperature of the methanation reactor to 70-90 ℃, and at the moment, stopping the circulating compressor;

e. releasing pressure of a reactor to be passivated and system heat exchange equipment, and adding a blind plate for isolation; after system isolation is confirmed, nitrogen is filled into the methanation system, and the pressure is increased to 0.35-0.50 MPa;

f. turning the shutdown process of the methanation system into a passivation process, starting a circulating compressor when the temperature of a catalyst bed is stabilized at 70-90 ℃, slowly introducing air into the methanation reactor, controlling the introduction amount of the air on the basis that the temperature rise rate of the catalyst bed is less than 0.5 ℃/min, and controlling the bed temperature to be less than 100 ℃;

g. analyzing and detecting the percentage content of the air introduced into the methanation system, controlling the oxygen content in the mixed gas of the nitrogen and the air to be 1-2V/V%, and gradually increasing the oxygen content in the mixed gas of the nitrogen and the air to be 2-3V/V%;

h. according to the temperature rise condition of the catalyst bed, gradually increasing the oxygen content in the mixed gas of nitrogen and air, and finally increasing the oxygen content to 9-10V/V%; when the bed layer reaction is completely penetrated, the oxygen content in the tower inlet gas and the tower outlet gas is analyzed and detected, and when the oxygen content of the tower inlet gas and the oxygen content of the tower outlet gas are consistent, the catalyst passivation is finished.

2. The passivation recycling method of the methanation nickel-based catalyst according to claim 1, characterized in that: and the time for the first constant-temperature drying in the step b is 2-4 h.

3. The passivation recycling method of the methanation nickel-based catalyst according to claim 1, characterized in that: and in the step b, the high-pressure nitrogen is normal-temperature nitrogen, and the pressure is 3.5-4.0 MPa.

4. The passivation recycling method of the methanation nickel-based catalyst according to claim 1, characterized in that: and c, the cooling rate in the step c is 20-40 ℃/h.

5. The passivation recycling method of the methanation nickel-based catalyst according to claim 1, characterized in that: and c, drying for the second time at constant temperature for 5-8 hours.

6. The passivation recycling method of the methanation nickel-based catalyst according to claim 1, characterized in that: and d, the cooling rate in the step d is 15-25 ℃/h.

The technical field is as follows:

the invention relates to the technical field of coal-based natural gas, in particular to a method for passivating, screening, recycling and reusing a methanation nickel-based catalyst.

Secondly, background art:

the methanation catalyst generally adopts aluminum oxide as a carrier, nickel is used as an active component, when the used catalyst loses activity, nitrogen or steam needs to be filled into a reactor, and the catalyst can be discharged from the methanation reactor under the nitrogen environment, and the catalyst is discharged under the condition of losing activity after the steam is filled, otherwise, the nickel in the catalyst is contacted with air to cause severe temperature rise and spontaneous combustion, so that equipment damage and safety accidents are caused.

At present, in the aspect of the methanation catalyst passivation technology, steam or air is introduced into a reactor for passivation and scrapping replacement after the nickel-based catalyst is used and activated at the end stage, but the nickel-based catalyst cannot be continuously used after being passivated although the nickel-based catalyst is also passivated, so that the purpose is to only discharge and replace the nickel-based catalyst, and the recycling and the reutilization of the nickel-based catalyst are not considered.

At present, the catalyst used in the technical field of coal-to-natural gas in China is not made into a home at present (a small part of methanation catalysts independently developed by Datang International chemical technology research institute Co., Ltd just runs through an industrial online device), and the catalyst completely depends on foreign import and is expensive in purchase price.

The domestic coal-to-natural gas (SNG) process adopts foreign Topyuo process, David process and the like, the main methanation reactor adopts casting material-high temperature resistant and heat insulating double-layer casting material, the reactor is put into use after cast-in-place construction and drying, the reactor not only needs to carry out high-temperature reaction, but also needs to meet the requirement of carrying out heat insulation control on the wall temperature of equipment, the use of the casting material is very strict, the occurrence of flaws is difficult to avoid, the high-temperature resistant casting material can insulate heat and partially high temperature or overtemperature of a large area in operation, the system can not normally operate and stop, the discharging of the catalyst and the inspection and repair of the casting material are carried out, the casting material is dismounted and replaced when the system is serious, the construction period is as long as 3-4 months, the catalyst is discharged and stored, serious potential safety hazards exist, the catalyst supply period is as long as 6-7 months after the catalyst is reordered, and enterprises are often in a difficult place.

In addition, when the catalyst is used, carbon precipitation, defect leakage of heat exchange equipment of a methanation device and the like are caused by side reaction in the catalytic reaction process, so that the using process condition of the catalyst is deviated, the inlet temperature of a catalyst bed layer is lower due to reasons of sudden change of process gas components, improper operation and the like, the resistance of the reactor bed layer is increased, the high-load production stable operation of a system is influenced, and the safe cost and the economic cost of operation are increased.

The existing passivation method for the methanation catalyst aims to scrap, discharge and replace the catalyst, and does not solve the problem of recycling the catalyst still having catalytic activity or good catalytic activity. By combining the technical problems, the active catalyst is passivated, screened, recycled and reused, and economic benefits are created, which is a difficult problem to be solved urgently in the industry.

Thirdly, the invention content:

the technical problem to be solved by the invention is as follows: aiming at the defects existing in the methanation catalyst passivation technology (namely the technical problem of the passivation of the catalyst with good catalytic activity or good catalytic activity), the invention provides a method for passivating, screening, recycling and reusing the methanation nickel-based catalyst. By utilizing the technical scheme of the invention, the catalyst with good catalytic activity or good catalytic activity after the methanation nickel-based catalyst is unloaded due to equipment replacement (equipment castable removal and inspection and the like) and the like is treated, so that the part of the nickel-based catalyst with good catalytic activity or good catalytic activity can be recycled.

In order to solve the problems, the invention adopts the technical scheme that:

the invention provides a passivation recycling method of a methanation nickel-based catalyst, which comprises the following steps of:

a. after the methanation system stops working, cutting off the raw material gas, starting an electric heater to control the bed temperature of the methanation reactor to cool, and controlling the cooling rate to be 30-50 ℃/h; introducing high-pressure nitrogen into a methanation device, and purging and replacing a methanation system;

b. carrying out primary constant-temperature drying when the temperature of a bed layer of the methanation reactor is reduced to 300-320 ℃, detecting after drying, and finishing system replacement when the content of nitrogen in a detection system is more than 99.9%;

c. continuously controlling the cooling rate of the bed temperature of the methanation reactor (so that the bed temperature of the methanation reactor is stably reduced), when the bed temperature of the methanation reactor is reduced to 200-220 ℃, carrying out secondary constant-temperature drying (when no water is collected in a separator, a catalyst bed is fully dried), stopping an electric heater after drying is finished, and circularly reducing the bed temperature;

d. continuously controlling the cooling and pressure reduction rate to reduce the pressure of the methanation system at a rate of less than or equal to 0.1MPa/min, controlling the pressure of the system to be reduced to 0.2-0.5 MPa, finally reducing the bed temperature of the methanation reactor to 70-90 ℃, and at the moment, stopping the circulating compressor;

e. releasing pressure of a reactor to be passivated and system heat exchange equipment, and adding a blind plate for isolation; after system isolation is confirmed, nitrogen is filled into the methanation system, and the pressure is increased to 0.35-0.50 MPa;

f. turning a process of stopping a methanation system into a passivation process, starting a circulating compressor when the temperature of a catalyst bed is stabilized to be 70-90 ℃, slowly introducing air into a methanation reactor, controlling the introduction amount of the air (at the moment, the oxygen content in a mixed gas of nitrogen and air is controlled to be 0.5-1V/V%) by taking the temperature rise rate of the catalyst bed to be less than 0.5 ℃/min as a reference, and controlling the bed temperature to be less than 100 ℃ (gradually increasing the oxygen content in the mixed gas of nitrogen and air, and properly reducing the air supplement amount when the temperature is excessively fast until the air supplement is cut off);

g. analyzing and detecting the percentage content of air introduced into the methanation system, controlling the oxygen content in the mixed gas of nitrogen and air to be 1-2V/V%, and gradually increasing the oxygen content in the mixed gas of nitrogen and air to be 2-3V/V% (when the temperature rise is too fast, the operation is properly reduced or stabilized, and the severe reaction is strictly controlled to cause the temperature of a bed layer to fly, so that the catalyst is scrapped);

h. according to the temperature rise condition of the catalyst bed, gradually increasing the oxygen content in the mixed gas of nitrogen and air, and finally increasing the oxygen content to 9-10V/V%; when the bed reaction is completely penetrated (at the moment, the bed temperature gradually shows a descending trend), the oxygen content in the tower inlet gas and the tower outlet gas is analyzed and detected, and when the oxygen content of the tower inlet gas and the tower outlet gas is consistent, the catalyst passivation is finished.

According to the passivation recycling method of the methanation nickel-based catalyst, the first constant-temperature drying time in the step b is 2-4 hours.

According to the passivation recycling method of the methanation nickel-based catalyst, the high-pressure nitrogen in the step b is normal-temperature nitrogen, and the pressure is 3.5-4.0 MPa.

According to the passivation recycling method of the methanation nickel-based catalyst, the cooling rate in the step c is 20-40 ℃/h.

According to the passivation recycling method of the methanation nickel-based catalyst, the time of the second constant-temperature drying in the step c is 5-8 hours.

According to the passivation recycling method of the methanation nickel-based catalyst, the cooling rate in the step d is 15-25 ℃/h.

In order to ensure that the catalyst has good effect on recycling and reusing and reduce the breakage rate, the catalyst needs to be manually drawn out in an oxygen-free environment in the tower after being passivated, and the mechanical equipment is strictly prohibited to be drawn out! And (4) vibrating and screening the catalyst taken out manually, then placing the catalyst into a closed container, filling nitrogen for keeping, and carrying out reloading and recycling when reloading conditions are met.

The invention has the following positive beneficial effects:

1. the existing method for passivating the methanation catalyst can only effectively avoid the severe temperature rise or spontaneous combustion after the methanation reactor is opened due to the fact that the catalyst is not passivated, so that equipment damage or safety accidents caused by temperature runaway are avoided, the purpose is to scrap, discharge and replace the catalyst, and the problem of recycling the catalyst still having catalytic activity or good catalytic activity cannot be solved; the technical scheme of the invention can recycle part of the nickel-based catalyst with catalytic activity or good catalytic activity.

2. In order to ensure the catalytic activity of the catalyst, the invention ensures that the oxygen content in nitrogen carrier gas is less than 10 v% during passivation, belongs to superficial passivation and strictly prohibits deep passivation.

3. The passivation method is realized on a methanation process device of a David company in England of coal chemical industry, Inc. of Gentle coal celebration in coal-based natural gas project, when the first methanation reactors (R61802 and R61803) are put into trial production for 6 months (2016, 12 and 23 days), more than 10 super-temperature points appear at the annular filling position of a catalyst with the diameter of 1200mm below the upper manhole, the super-temperature area is gradually enlarged, the maximum wall temperatures of the R61802 and R61803 reactors are respectively increased to 295 ℃ and 300 ℃ (the index is less than or equal to 150 ℃), and the system is forced to carry out emergency stop treatment.After parking, through analysis of an invitation expert, the conditions are consistently considered as follows: the high-temperature resistant casting material of the first methanation reactor has defects of a poured heat insulation layer due to poor quality in the cast-in-place construction process, the heat insulation effect of the high-temperature resistant casting material cannot meet the requirement, the methanation catalyst must be discharged for inspection, and local repair treatment is carried out or casting is carried out again after old materials are dismantled according to circumstances. But the use effect is not good after the repairing treatment, the operation period is short, and the hidden trouble of overtemperature also exists; if the pouring construction is performed again, the old material is removed, the material is prepared, and the construction period is 3-4 months long; more importantly, the methanation catalyst with activity is predicted to be scrapped without controlling contact oxidation with air in the discharging process, the methanation catalyst used in the system is an imported catalyst of Dyvier company in England, the price is high, the production period is 6-7 months, and the methanation catalyst cannot be purchased in domestic markets in a short time. Therefore, the technical scheme of the invention is adopted to carry out passivation and screening recovery treatment on the methanation nickel-based catalyst, after the recovery treatment is finished, the methanation catalyst is reloaded, and the raw material gas 40000m is introduced into the methanation device in 2017, 6 months and 2 days according to a normal driving program³The catalyst is heated and reduced with the lowest load, the temperature of a catalyst bed layer rises rapidly, the temperature rises to the index upper limit (575 +/-10) DEG C within about 15min, and the performance of the catalyst recovers rapidly; in order to prevent the catalyst bed from being over-heated, the loading operation is gradually tried, and CH is contained in the product gas₄The content is stable and finally reaches the index (CH)₄The content is more than or equal to 95.5 percent) is operated; after the stable operation is carried out for about 12 hours, the system is recovered to the load before the shutdown, and various operation data are stable, which indicates that the high nickel catalyst can be reused after being passivated. The catalyst is replaced when the catalyst is operated to overhaul, and is stopped for overhaul until 2020, 4, 15 and 15 days, the use time of the passivated catalyst is as long as 3 years, and about 500 million yuan is saved for a company. Therefore, the technical scheme of the invention has remarkable social benefit and economic benefit.

Fourthly, the specific implementation mode:

the passivation process of the methanation nickel-based catalyst adopts closed gas circulation, the circulating gas compressor provides gas circulation power, the electric heater is used as a heat source supplement point, instrument air is introduced into a circulation system and mixed with nitrogenThe obtained product is sent to main methanation reactors R61802 and R61803 through a recycle gas compressor, and undergoes oxidation reaction (2Ni + O) with a catalyst in a reduction state in the main methanation reactor₂→2NiO；ΔH_θ-480 kJ/mol); the heat evolved during passivation is considerable and therefore oxidation proceeds under controlled and closely monitored conditions.