CN109054908B - Isothermal transformation process matched with pulverized coal gasification - Google Patents
Isothermal transformation process matched with pulverized coal gasification Download PDFInfo
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- CN109054908B CN109054908B CN201811160885.6A CN201811160885A CN109054908B CN 109054908 B CN109054908 B CN 109054908B CN 201811160885 A CN201811160885 A CN 201811160885A CN 109054908 B CN109054908 B CN 109054908B
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
- C10J3/00—Production of combustible gases containing carbon monoxide from solid carbonaceous fuels
- C10J3/72—Other features
- C10J3/82—Gas withdrawal means
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
- C10J3/00—Production of combustible gases containing carbon monoxide from solid carbonaceous fuels
- C10J3/46—Gasification of granular or pulverulent flues in suspension
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
- C10J2300/00—Details of gasification processes
- C10J2300/09—Details of the feed, e.g. feeding of spent catalyst, inert gas or halogens
- C10J2300/0913—Carbonaceous raw material
- C10J2300/093—Coal
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
- C10J2300/00—Details of gasification processes
- C10J2300/16—Integration of gasification processes with another plant or parts within the plant
- C10J2300/1603—Integration of gasification processes with another plant or parts within the plant with gas treatment
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
The invention relates to an isothermal transformation process matched with pulverized coal gasification, which comprises an isothermal transformation furnace and is characterized in that: two groups of heat exchange tubes are arranged in the isothermal converter; after the liquid phase of the crude synthesis gas is separated out, heat exchange is carried out, impurities are removed, and the crude synthesis gas is sent into the isothermal shift converter to carry out primary shift reaction; the medium-pressure boiler water in the steam pocket enters two groups of heat exchange tubes to exchange heat with a catalyst bed layer in the isothermal shift converter to generate steam, and primary shift gas discharged from the isothermal shift converter is sent to the adiabatic shift converter to carry out secondary shift reaction to obtain secondary shift gas; and monitoring the content of the CO dry basis in the secondary conversion gas out of the heat-insulation shift converter, closing one group of heat exchange tubes when the content of the CO dry basis in the secondary conversion gas is more than 1.2 v%, and operating the other group of heat exchange tubes to ensure the activity requirement and constant yield of the catalyst under the condition of not changing a steam pipe network.
Description
Technical Field
The invention relates to the technical field of carbon monoxide conversion, in particular to an isothermal conversion process matched with pulverized coal gasification.
Background
Based on the current resource situation of more coal and less oil and exhaust gas in China, the chemical industry taking coal as a raw material is rapidly developed in recent years, and pulverized coal gasification is widely applied due to the characteristics of wide coal variety application, high energy utilization rate, high gas production capacity of equipment units and the like. Coal is gasified at high temperature to produce H2And CO, which is a suitable raw material for producing C1 chemical products and derivatives thereof. The raw synthesis gas produced by adopting the pulverized coal gasification process mainly comprises CO, CO2 and H2And a CO conversion device is arranged in the follow-up of the synthesis gas to convert the over-high CO in the crude synthesis gas into CO2Simultaneously generating H2To adjust CO and H in the raw synthesis gas2The content of (b) meets the requirement of a downstream device on the hydrogen-carbon ratio in the synthesis gas.
Shift process, i.e. the CO and steam are reacted in the presence of a catalyst to form H2And CO2The process of (a) is applied to the synthetic ammonia industry at the earliest, and is subsequently applied to a plurality of industries such as hydrogen production, methanol synthesis, synthetic oil, coal-to-natural gas and the like. The CO shift reaction is a strongly exothermic reaction, and is classified into an adiabatic shift process and an isothermal shift process according to a heat transfer manner of reaction heat.
The isothermal conversion is realized by arranging heat exchange equipment in a conversion furnace, generally taking liquid water as a heat transfer medium, absorbing heat and then vaporizing the water into steam, so that the conversion reaction heat can be quickly absorbed, the temperature of a catalyst bed layer is kept stable, and the stable operation of a conversion device is further realized. Compared with the traditional adiabatic conversion technology, the isothermal conversion process has the characteristics of short flow, less equipment, low investment, high energy utilization rate, easy large-scale production and the like, and is paid more and more attention.
The fluctuation of the reaction temperature at the initial stage and the final stage of CO conversion in isothermal conversion can be transmitted to a heat exchange tube used for heat transfer in a reaction bed layer, so that the fluctuation of the temperature and the pressure of steam generated in the heat exchange tube is further caused, particularly, the amount of the steam rich in the steam is more and more along with the large-scale and multi-series of a CO conversion device, but the isothermal conversion reactor can not solve the problems of the fluctuation of the steam pressure and the increase of the investment of related equipment and pipeline engineering all the time. In the isothermal shift processes developed in recent years, the medium pressure steam pressure of the isothermal shift furnace byproduct is unstable, and particularly, when the reaction is in a final working condition, the isothermal shift reaction temperature needs to be increased along with the reduction of the activity of the catalyst so as to maintain the conversion rate of the shift reaction, the medium pressure steam pressure of the isothermal shift furnace byproduct is severely fluctuated, and the stable operation of a device and even a steam pipe network of a whole plant is seriously influenced.
For example, in the split-flow isothermal sulfur-tolerant shift process and equipment disclosed in the Chinese patent application with the application number of 200910056342.4, under the working condition of isothermal sulfur-tolerant shift at the end of reaction, the pressure of medium-pressure steam, which is a byproduct of the isothermal shift furnace, is rapidly increased from 4.0MPaG to about 6.5MPaG along with the increase of the temperature of synthesis gas entering the isothermal shift furnace, so that the stable operation of the device is seriously restricted, and the investment of equipment and pipelines such as a steam drum and the like is increased; according to the process, the crude synthesis gas from the gasification process is directly fed into a first shift converter, and the adiabatic reactor is used for carrying out first shift on high-concentration CO, so that the problem of over-temperature in the adiabatic reactor is easily caused, the catalyst in the adiabatic reactor is quickly deactivated and frequently replaced, and the operation cost is increased; meanwhile, in order to inhibit the over-temperature of the adiabatic shift converter, the molar ratio of water/dry gas at the inlet of the adiabatic shift converter in the process is up to 2.0, and the overhigh water-gas ratio can cause the catalyst to be reversely sulfurized, thereby shortening the service life of the shift catalyst.
Disclosure of Invention
The invention aims to solve the technical problem of providing the isothermal transformation process matched with pulverized coal gasification, which can obviously reduce the pressure fluctuation of medium-pressure steam as a byproduct of the isothermal transformation furnace and simultaneously reduce the investment and the operation cost of a device, aiming at the current situation of the prior art.
The technical scheme adopted by the invention for solving the technical problems is as follows: the isothermal conversion process matched with pulverized coal gasification comprises an isothermal conversion furnace, wherein a plurality of heat exchange tubes are arranged in the isothermal conversion furnace, inlets of the heat exchange tubes are connected with a boiler water outlet of a steam drum through a boiler water pipeline, and outlets of the heat exchange tubes are connected with a steam inlet of the steam drum through a steam recovery pipeline; the method is characterized in that:
the heat exchange tubes comprise a plurality of first heat exchange tubes and a plurality of second heat exchange tubes, and the first heat exchange tubes form a first group of heat exchange tubes; each second heat exchange tube forms a second group of heat exchange tubes; the sum of the cross sections of the inner cavities of the first heat exchange tubes is 15-35% of the sum of the cross sections of the inner cavities of the second heat exchange tubes;
correspondingly, two boiler water pipelines are arranged;
the inlet of each first heat exchange tube is connected with a first boiler water pipeline, and the inlet of each second heat exchange tube is connected with a second boiler water pipeline; a valve is arranged on the first boiler water pipeline;
separating liquid phase from crude synthesis gas with the temperature of 190-210 ℃, the pressure of 3.6-4.0 MPaG and the CO dry basis content of 55-75 v% from a pulverized coal gasification device, then carrying out heat exchange to 245-255 ℃, removing impurities in the crude synthesis gas, and sending the crude synthesis gas into the isothermal converter for carrying out primary conversion reaction;
controlling the ratio (molar ratio) of the flow of the medium-pressure steam byproduct of the isothermal converter to the flow of the crude synthesis gas entering the isothermal converter to be 1: 3-1: 4;
4.0-5.5 MPaG of medium-pressure boiler water with the temperature of 250-270 ℃ in the steam pocket respectively enters each first heat exchange tube and each second heat exchange tube from a first boiler water pipeline and a second boiler water pipeline, exchanges heat with heat generated by the transformation reaction in the isothermal transformation furnace to generate steam, returns to the steam pocket from a steam collecting pipeline for gas-liquid separation, and sends out medium-pressure saturated steam with the pressure of 4.0-5.5 MPaG and the temperature of 250-270 ℃ from the top of the steam pocket; controlling the temperature in the isothermal conversion furnace to be 275-315 ℃;
the content of CO dry basis in the primary shift gas discharged from the isothermal shift converter is 4-12 percent;
after the heat exchange of the primary shift gas is carried out to 220-235 ℃, supplementing medium-pressure steam and medium-pressure boiler feed water, adjusting the temperature to 215-225 ℃, and feeding the mixture into a heat-insulating shift converter to carry out secondary shift reaction after the water/dry gas molar ratio is 0.4-0.6;
the temperature of the secondary shift gas discharged from the adiabatic shift converter is 250-290 ℃, the content of CO dry basis is less than 1.2 percent, and the heat is recycled and then sent to the downstream;
monitoring the content of CO dry basis in the secondary conversion gas discharged out of the heat-insulation conversion furnace, and closing a valve on the first boiler water pipeline when the content of CO dry basis in the secondary conversion gas is more than 1.2 v%, wherein the first group of heat exchange tubes do not work, and only the second group of heat exchange tubes work; boiler water with the temperature of 250-270 ℃ and 4.0-5.5 MPaG in the steam pocket enters the second group of heat exchange tubes from the second boiler water pipeline, saturated steam with the pressure of 4.0-5.5 MPaG and the temperature of 250-270 ℃ is obtained after heat exchange, and the saturated steam returns to the steam pocket from the steam collecting pipeline.
Preferably, the primary shift gas out of the isothermal shift converter enters a low-pressure steam superheater to be cooled to 240-280 ℃, then exchanges heat with the crude synthesis gas to 220-235 ℃, and then is sent to the adiabatic shift converter.
Preferably, the secondary conversion gas of the adiabatic shift converter enters a low-pressure steam generator to be cooled to 195-205 ℃ and then is sent to downstream processes for treatment.
As an improvement, the medium-pressure steam discharged from the steam drum can be completely supplemented into the primary conversion gas;
in each of the above aspects, it is preferable that the first heat exchange tubes are uniformly arranged in the catalyst bed layer of the isothermal shift converter, and the second heat exchange tubes are uniformly arranged in the catalyst bed layer of the isothermal shift converter.
Preferably, at least three second heat exchange tubes are uniformly distributed around each first heat exchange tube; each first heat exchange tube and each second heat exchange tube arranged around the first heat exchange tube form a heat exchange tube pair.
And 3-6 second heat exchange tubes are arranged around each first heat exchange tube.
Furthermore, the second heat exchange tubes in each heat exchange tube pair are uniformly distributed on the same circumferential line with the center of the first heat exchange tube as the center of circle.
And a part of the second heat exchange tube is shared between adjacent heat exchange tube pairs. The structure ensures that the second heat exchange tubes are distributed more uniformly, the heat exchange effect is better, and the local temperature runaway of a catalyst bed layer is avoided.
Preferably, the steam collecting pipeline comprises a first steam collecting pipeline and a second steam collecting pipeline which are arranged in parallel;
the outlet of each first heat exchange tube is connected with the first steam collecting pipeline, and the outlet of each second heat exchange tube is connected with the second steam collecting pipeline. The structure can effectively avoid that steam is held back in the heat exchange pipes which are shut down when the first group of heat exchange pipes do not work.
Compared with the prior art, the invention has the following advantages:
1. the medium-pressure boiler feed water is fed into the isothermal conversion furnace through two groups of independent heat exchange tubes, and the boiler feed water of one of the collecting tubes is closed through a control valve on a pipeline when the working condition at the end stage of the catalyst is finished, so that the number of effective heat exchange tube bundles in the isothermal conversion furnace is reduced, the pressure fluctuation of medium-pressure steam as a byproduct can be remarkably reduced, and the stable operation of the device is facilitated.
2. Because the fluctuation of the steam pressure of the byproduct of the isothermal converter is small, the design pressure of equipment such as a steam drum and the like is reduced, and the investment of the equipment and pipelines is reduced.
3. The crude synthesis gas of high-concentration CO gas is firstly sent into an isothermal shift converter for conversion, so that the process characteristic that the isothermal shift converter does not generate overtemperature is fully exerted, the problem of overtemperature in the whole conversion process is avoided, the service life of the catalyst is long, the operation cost is low, and the operation of a conversion unit is stable;
4. by reasonably optimizing the conversion process, the medium-pressure steam produced in the conversion process is completely used for the conversion reaction, a medium-pressure steam superheater is omitted, and the equipment investment is reduced.
5. The by-product low-pressure steam is sent out of the device after being superheated by the low-pressure steam superheater, thereby being beneficial to outward conveying of the low-pressure steam.
Drawings
FIG. 1 is a schematic process flow diagram of an embodiment of the present invention.
FIG. 2 is a longitudinal sectional view of an isothermal shift converter in an embodiment of the present invention.
Fig. 3 is a transverse cross-sectional view of fig. 2.
Fig. 4 is a partially enlarged view of a portion a in fig. 2.
FIG. 5 is a schematic process flow diagram of a comparative example.
Detailed Description
The invention is described in further detail below with reference to the accompanying examples.
As shown in fig. 1 to 4, the isothermal converter used in the present embodiment includes:
the furnace body 1' is of a conventional structure and comprises an upper seal head 11, a lower seal head 12 and a cylinder body 13 connected between the upper seal head 11 and the lower seal head 12.
The catalyst frame 2' is used for filling a catalyst and is arranged in the cylinder 13; a plurality of air holes (not shown) are uniformly distributed on the side wall. The catalyst frame 2' can be any one of the prior art according to the requirement, and the embodiment is a radial reactor, and the raw synthesis gas enters the catalyst bed layer in the catalyst frame from each air hole for conversion.
The synthesis gas collecting pipe 3 'is arranged in the middle position in the cavity of the catalyst frame 2 and used for collecting synthesis gas, the upper port of the synthesis gas collecting pipe is closed, the lower port of the synthesis gas collecting pipe 33 is connected with the lower port of the synthesis gas collecting pipe, and primary conversion gas is sent out of the furnace body 1' through the synthesis gas pipeline 33.
The heat exchange tubes are arranged in the catalyst bed layer between the catalyst frame 2 'and the synthesis gas collecting tube 3' in a penetrating manner, and comprise a first heat exchange tube group consisting of a plurality of first heat exchange tubes 41 and a second heat exchange tube group consisting of a plurality of second heat exchange tubes 42.
For the sake of distinction, in fig. 4, each first heat exchange tube is represented by a solid circle, and each second heat exchange tube is represented by a hollow circle.
Wherein the first heat exchange tubes 41 are uniformly arranged in the cavity between the catalyst frame and the synthesis gas collection tube; the second heat exchange tubes 42 are uniformly arranged around the first heat exchange tubes 41; at least three second heat exchange tubes 42 are uniformly distributed around each first heat exchange tube 41; in the present embodiment, six second heat exchange tubes 42 are disposed around each heat exchange tube 41, and the six second heat exchange tubes 42 are disposed on the same circumferential line L with the corresponding first heat exchange tube as the center.
Each first heat exchange tube 41 and each second heat exchange tube 42 disposed therearound form a heat exchange tube pair; a part of the second heat exchange tubes 42 is shared between adjacent pairs of heat exchange tubes, i.e. the circumferential lines L of the second heat exchange tubes in adjacent pairs of heat exchange tubes are arranged crosswise.
The number of the second heat exchange tubes in each pair of heat exchange tubes may be designed in other numbers, for example, three, four, five or more, depending on the scale of the apparatus and the specification of the reactor.
The sum of the cross sections of the inner cavities of the first heat exchange tubes 41 is 15-35%, in this embodiment 25%, of the sum of the cross sections of the inner cavities of the second heat exchange tubes 42. The diameters of the first heat exchange tubes and the second heat exchange tubes can be equal or unequal, and in the embodiment, the cross sectional areas of the first heat exchange tubes and the second heat exchange tubes, namely the heat exchange areas corresponding to the first heat exchange tube sets and the second heat exchange tube sets, are controlled by controlling the number of the first heat exchange tubes and the number of the second heat exchange tubes.
The inlet of each first heat exchange pipe 41 is connected with a first boiler water pipe 91 through a first distributor 43, and a control valve 95 is arranged on the first boiler water pipe 91; the inlet of each second heat exchange pipe 42 is connected to the second boiler water pipe 92 through the second distributor 44. The first boiler water pipe 91 and the second boiler water pipe 92 are connected with a boiler water outlet of the steam drum 9 through a boiler water conveying pipe 96; the boiler water delivery pipe 96 is provided with a water pump 10.
The outlet of each first heat exchange tube 41 is connected with a first steam pipeline 93 through a first steam collection tube 45, and the outlet of each second heat exchange tube 42 is connected with a second steam pipeline 94 through a second steam collection tube 46. The first steam line 93 and the second steam line 94 are connected to the steam inlet of the steam drum 9 by a steam delivery line 97.
The raw synthesis gas inlet is arranged at the top of the furnace body 1'.
The crude synthesis gas from a pulverized coal gasification device with the temperature of 201 ℃ and the pressure of 3.8MPaG has the dry content of CO of 60-75 percent and is sent into a gas-liquid separator 1 to separate condensate generated by heat loss in the pipeline conveying process, the crude synthesis gas sent out from the top of the gas-liquid separator 1 is sent into a detoxification tank 3 after being heated to 245-255 ℃ by a feeding and discharging heat exchanger 2, and is sent into an isothermal converter 4 from the top after impurities such as dust in the crude synthesis gas are removed.
Carrying out shift reaction on the crude synthesis gas in an isothermal shift furnace 4; and controlling the temperature in the isothermal conversion furnace to be 275-295 ℃.
The medium pressure boiler water in the steam pocket 9 enters each first heat exchange pipe and each second heat exchange pipe from the first boiler water pipeline 91 and the second boiler water pipeline 92 respectively, exchanges heat with heat generated by the conversion reaction in the isothermal conversion furnace to generate medium pressure saturated steam with the pressure of 4.0MPaG and the temperature of 252 ℃, and returns to the steam pocket 9 from the first steam pipeline 93 and the second steam pipeline 94. To remove the heat generated by the shift reaction and maintain the reaction temperature in the isothermal shift furnace constant.
The generated medium-pressure saturated steam returns to the steam drum 9 for gas-liquid separation, medium-pressure saturated steam with the temperature of 252 ℃ is sent out from the top of the steam drum 9, and the medium-pressure saturated steam is totally incorporated into the primary conversion gas for humidification.
The content of CO dry basis in the primary shift gas out of the isothermal shift converter is 6-10%, the primary shift gas enters a low-pressure steam superheater 5 to exchange heat with low-pressure steam from a low-pressure steam generator 8, the heat is recovered, the primary shift gas is cooled to 240-280 ℃, the primary shift gas enters a feed-in and feed-out heat exchanger 2 to exchange heat with crude synthesis gas, the heat is continuously recovered, and the primary shift gas is cooled to 220-235 ℃; the steam is uniformly mixed with medium-pressure saturated steam from a steam drum 9 and medium-pressure boiler feed water from the outside with the temperature of 130 ℃ and the pressure of 4.0MPaG in a static mixer 6 to obtain primary shift gas with the temperature of 215-225 ℃ and the water/dry gas molar ratio of 0.4-0.6, and the primary shift gas is sent into an adiabatic shift converter 7 for secondary shift reaction.
The temperature of the secondary conversion gas which is discharged from the adiabatic shift converter 7 is 250-290 ℃, the dry basis content of CO is less than 1.2%, the secondary conversion gas enters a low-pressure steam generator 8 to recover heat, exchanges heat with low-pressure boiler water, and is sent to downstream processes for treatment after being cooled to 195-205 ℃.
Supplementing medium-pressure boiler water with the temperature of about 130 ℃ and the pressure of 4.0-6.0 MPaG to the steam drum 9; and controlling the ratio (molar ratio) of the total flow of the medium-pressure steam byproduct of the isothermal shift converter to the total flow of the crude synthesis gas entering the isothermal shift converter to be 1: 3-1: 4.
The low-pressure boiler water from the battery limits generates low-pressure saturated steam of 0.5-1.2 MPaG through a low-pressure steam generator 8, and is sent out of the battery limits after being superheated through a low-pressure steam superheater 5.
And in the running process of the device, the CO dry basis content in the secondary conversion gas of the adiabatic conversion furnace 7 is detected by adopting online sampling analysis. When the dry basis content of CO in the secondary conversion gas is more than 1.2 v%, the activity of the catalyst is reduced, and in order to keep the conversion rate of the reaction constant, the reaction temperature needs to be gradually increased, the activity of the catalyst needs to be maintained, and then a control valve on a boiler water supply pipeline connected with the first heat exchange tube group can be closed.
And the node for closing the first heat exchange pipe set can also be judged according to the activity decay period of the catalyst, and when the service time of the catalyst reaches the decay period, a control valve on a boiler water supply pipeline connected with the first heat exchange pipe set can be closed. The catalyst commonly used in the prior art is a cobalt-molybdenum catalyst, the activity degradation period of the catalyst is 3 years, and a control valve on a boiler water supply pipeline connected with a first heat exchange tube group can be closed after the device runs for three years.
And closing a control valve on the first boiler water pipeline, wherein the first group of heat exchange tubes does not work, and only the second group of heat exchange tubes works.
After the first heat exchange tube group is closed, compared with the two heat exchange tube groups which work simultaneously, the heat exchange area is reduced by 20%, the influence of the increase of the reaction temperature on the steam pressure of the isothermal shift byproduct at the last stage of the shift reaction is reduced by reducing the heat exchange area, and the stable operation of a steam pipe network and a device is ensured.
Therefore, in the application, the yield of the shift gas is constant in the whole process of the device operation, the pressure fluctuation of the byproduct medium-pressure steam is little or no fluctuation, and the device operation is stable.
Comparative example
As shown in FIG. 5, the process flow of the comparative example is substantially the same as that of the example, and the isothermal transformation furnace used in the comparative example is a conventional non-adjustable isothermal transformation furnace, and specifically comprises the following steps:
raw synthesis gas with the temperature of 201 ℃ and the pressure of 3.8MPaG from a pulverized coal gasification device, the dry content of CO is 60-75 percent, the raw synthesis gas is sent into a gas-liquid separator 1, condensate generated by heat loss in the pipeline conveying process is separated out, the raw synthesis gas sent out from the top of the gas-liquid separator 1 is sent into a detoxification tank 3 after being heated to 245-255 ℃ by a feeding and discharging heat exchanger 2, and is sent into an isothermal converter 4 after impurities such as dust in the raw synthesis gas are removed;
the raw synthesis gas is subjected to shift reaction in the isothermal shift converter 4, the generated heat is used for enriching medium-pressure saturated steam with the pressure of 4.0MPaG and the temperature of 252 ℃, and the specific arrangement is that the medium-pressure boiler feed water in the steam drum 9 is pressurized by the boiler circulating water pump 10 and then enters the isothermal shift converter for removing the heat generated by the shift reaction and maintaining the reaction temperature of the isothermal shift converter to be basically constant.
The generated medium-pressure saturated steam returns to the steam drum 9 for gas-liquid separation, and the medium-pressure saturated steam sent out from the top of the steam drum 9 is completely sent into the first-stage conversion gas for humidification.
Controlling the reaction temperature of isothermal transformation at 280 ℃, ensuring that the content of CO dry basis in primary transformation gas discharged from an isothermal transformation furnace 4 is about 4-12%, cooling to 240-280 ℃ through a low-pressure steam superheater 5, sending the primary transformation gas into a charging and discharging heat exchanger 2 to continuously recover heat, cooling to 220-235 ℃, finely adjusting the primary transformation gas through supplementing medium-pressure steam and medium-pressure boiler feed water which are byproducts of the isothermal transformation, controlling the temperature of the primary transformation gas to 215-225 ℃, and sending the primary transformation gas into an adiabatic transformation furnace 7 to continuously carry out transformation reaction after the water/dry gas molar ratio is 0.4-0.6.
The temperature of the transformed gas discharged from the adiabatic shift converter 7 is 250-290 ℃, the dry basis content of CO is less than 1.2%, the heat is recovered by a low-pressure steam generator 8, and the transformed gas is cooled to 195-205 ℃ and then sent to downstream processes for treatment.
The temperature of medium-pressure boiler water from a boundary area is about 130 ℃, the pressure is 4.0-8.0 MPaG, most of the medium-pressure boiler water is sent into a steam drum 9, 4.0MPaG medium-pressure saturated steam is produced through an isothermal shift furnace 4, and the rest part of the medium-pressure boiler water is used for adjusting the steam ratio and the temperature of primary shift gas.
The low-pressure boiler water from the battery limits generates low-pressure saturated steam of 1.0MPaG through the low-pressure steam generator 8, and is sent out of the battery limits after being superheated through the low-pressure steam superheater 5.
In the working condition at the last stage of the shift reaction, along with the reduction of the activity of the catalyst, the reaction temperature needs to be increased to maintain a constant conversion rate, the reaction temperature in the isothermal shift converter is increased to about 310 ℃, the byproduct steam pressure of the isothermal shift converter is gradually increased to more than 6.7MPaG, the steam pressure fluctuation is severe, the stable operation of a steam pipe network and a device is not facilitated, and meanwhile, the design pressure of equipment and pipelines such as a steam pocket and the like in the comparative example is greatly increased due to the fluctuation of the byproduct steam pressure, so that the investment of the equipment and the pipelines is.
Taking a synthetic ammonia device adopting pulverized coal gasification gas making as an example, the effective gas (H2+ CO) entering the isothermal conversion device is about 85000Nm3And h, comparing the main parameters of the isothermal transformation technology matched with pulverized coal gasification under the standard with the parameters shown in the table 1.
Table 1 (please confirm whether the supplement in Table 1 is correct)
As can be seen from table 1, for the ammonia synthesis device for gasification and gas production of pulverized coal, the isothermal shift technology adopted in this embodiment significantly reduces the pressure fluctuation of the medium-pressure steam as a byproduct of the isothermal shift furnace, which is beneficial to the long-term stable operation of the steam pipe network and the device, and meanwhile, the design pressure of the steam drum and the pipeline is significantly reduced, and the investment in equipment and the pipeline is reduced by about 120 ten thousand yuan.
Claims (10)
1. An isothermal conversion process matched with pulverized coal gasification comprises an isothermal conversion furnace (4), wherein a plurality of heat exchange tubes are arranged in the isothermal conversion furnace (4), inlets of the heat exchange tubes are connected with a boiler water outlet of a steam drum (9) through a boiler water pipeline, and outlets of the heat exchange tubes are connected with a steam inlet of the steam drum (9) through a steam recovery pipeline; the method is characterized in that:
the heat exchange tubes comprise a plurality of first heat exchange tubes and a plurality of second heat exchange tubes, and the first heat exchange tubes form a first group of heat exchange tubes; each second heat exchange tube forms a second group of heat exchange tubes; the sum of the areas of the cross sections of the inner cavities of the first heat exchange tubes (41) is 15-35% of the sum of the areas of the cross sections of the inner cavities of the second heat exchange tubes (42);
correspondingly, two boiler water pipelines are arranged;
the inlet of each first heat exchange pipe is connected with a first boiler water pipeline (91), and the inlet of each second heat exchange pipe is connected with a second boiler water pipeline (92); a valve is arranged on the first boiler water pipeline (91);
separating liquid phase from crude synthesis gas with the temperature of 190-210 ℃, the pressure of 3.6-4.0 MPaG and the CO dry basis content of 55-75 v% from a pulverized coal gasification device, then carrying out heat exchange to 245-255 ℃, removing impurities in the crude synthesis gas, and sending the crude synthesis gas into the isothermal converter for carrying out primary conversion reaction;
4.0-5.5 MPaG of medium-pressure boiler water with the temperature of 250-270 ℃ in the steam pocket (9) respectively enters each first heat exchange tube and each second heat exchange tube from a first boiler water pipeline (91) and a second boiler water pipeline (92) to exchange heat with heat generated by transformation reaction in the isothermal transformation furnace to generate saturated steam with the pressure of 4.0-5.5 MPaG and the temperature of 250-270 ℃, and the saturated steam returns to the steam pocket (9) from a steam collecting pipeline; controlling the temperature in the isothermal conversion furnace to be 275-315 ℃;
controlling the content of CO dry basis in the first-stage shift gas of the isothermal shift converter to be 4-12%;
after the primary shift gas exchanges heat to 220-235 ℃, supplementing medium-pressure steam and medium-pressure boiler feed water, adjusting the temperature to 215-225 ℃, and feeding the mixture into a heat-insulating shift furnace (7) for secondary shift reaction after the water/dry gas molar ratio is 0.4-0.6;
the temperature of the secondary conversion gas discharged from the adiabatic shift converter (7) is 250-290 ℃, the content of CO dry basis is less than 1.2 percent, and the heat is recycled and then sent to the downstream;
monitoring the content of CO dry basis in the secondary conversion gas discharged from the heat-insulation shift converter (7), and closing a valve on the first boiler water pipeline (91) when the content of CO dry basis in the secondary conversion gas is more than 1.2 v%, wherein the first group of heat exchange tubes do not work, and only the second group of heat exchange tubes work; boiler water with the temperature of 250-270 ℃ and 4.0-5.5 MPaG in the steam pocket (9) enters the second group of heat exchange tubes from the second boiler water pipeline, saturated steam with the pressure of 4.0-5.5 MPaG and the temperature of 250-270 ℃ is obtained after heat exchange, and the saturated steam returns to the steam pocket (9) from the second steam pipeline (94).
2. The isothermal shift conversion process matched with pulverized coal gasification according to claim 1, characterized in that the primary shift gas from the isothermal shift conversion furnace enters a low-pressure steam superheater (5) to be cooled to 240-280 ℃, then exchanges heat with the raw synthesis gas to 220-235 ℃, and then is sent to the adiabatic shift conversion furnace (7).
3. The isothermal shift process matched with pulverized coal gasification in claim 1, wherein the secondary shift gas from the adiabatic shift converter (7) enters a low-pressure steam generator (8) to be cooled to 195-205 ℃ and then is sent to downstream processes for treatment.
4. Isothermal shift process for gasification of pulverized coal as claimed in claim 1, characterized in that the medium pressure steam exiting the drum (9) is completely supplemented into the primary shift gas.
5. The isothermal shift process for supporting gasification of pulverized coal according to any one of claims 1 to 4, characterized in that each of the first heat exchange tubes is uniformly arranged in the catalyst bed of the isothermal shift furnace (4), and each of the second heat exchange tubes is uniformly arranged in the catalyst bed of the isothermal shift furnace (4).
6. The isothermal transformation process matched with pulverized coal gasification of claim 5, wherein at least three second heat exchange tubes are uniformly distributed around each first heat exchange tube; each first heat exchange tube and each second heat exchange tube arranged around the first heat exchange tube form a heat exchange tube pair.
7. The isothermal transformation process matched with pulverized coal gasification of claim 6, wherein 3-6 second heat exchange tubes are arranged around each first heat exchange tube.
8. The isothermal transformation process matched with pulverized coal gasification of claim 7, wherein the second heat exchange tubes in each heat exchange tube pair are uniformly distributed on the same circumferential line with the center of the first heat exchange tube as the center of a circle.
9. The isothermal transformation process matched with pulverized coal gasification in claim 8, wherein a part of the second heat exchange tubes is shared between adjacent heat exchange tube pairs.
10. The isothermal shift process for supporting gasification of pulverized coal as claimed in claim 9, wherein the steam collecting pipe comprises a first steam collecting pipe (93) and a second steam collecting pipe (94) arranged in parallel;
the outlet of each first heat exchange tube is connected with the first steam collecting pipeline (93), and the outlet of each second heat exchange tube is connected with the second steam collecting pipeline (94).
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