CN109181782B - Air-cooling and water-cooling isothermal transformation process matched with coal water slurry gasification - Google Patents
Air-cooling and water-cooling isothermal transformation process matched with coal water slurry gasification Download PDFInfo
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- CN109181782B CN109181782B CN201811160904.5A CN201811160904A CN109181782B CN 109181782 B CN109181782 B CN 109181782B CN 201811160904 A CN201811160904 A CN 201811160904A CN 109181782 B CN109181782 B CN 109181782B
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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
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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
- C10J3/74—Construction of shells or jackets
- C10J3/76—Water jackets; Steam boiler-jackets
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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
Abstract
The invention relates to an air-cooling and water-cooling isothermal transformation process matched with coal water slurry gasification, which comprises a water-cooling reactor, wherein two groups of heat exchange tubes are arranged in the water-cooling reactor, crude synthesis gas is divided into two parts after liquid removal, heat exchange and detoxification, the two parts respectively enter the air-cooling reactor and the water-cooling reactor for primary transformation, transformed primary transformation gas flows in parallel and enters an adiabatic reactor for secondary transformation after heat exchange, the CO concentration in the secondary transformation gas is monitored, when the CO concentration is less than 0.4 v%, the two groups of heat exchange tubes work simultaneously, and when the CO concentration is more than 0.4 v%, the one group of heat exchange tubes are closed to ensure the requirement of the activity temperature of a catalyst in the water-cooling reactor, and simultaneously a steam pipe network and the yield are constant.
Description
Technical Field
The invention relates to the technical field of carbon monoxide conversion, in particular to an air-cooling and water-cooling isothermal conversion process matched with coal water slurry gasification.
Background
Based on the resource status quo of more coal and less oil and gas exhaust in China, in recent years, the chemical industry using coal as raw material is rapidly developed, and the coal is gasified at high temperature to prepare H2And CO, which is a suitable raw material for producing C1 chemical products and derivatives thereof. The coal water slurry pressure gasification technology has the characteristics of wide coal type application range, continuous and stable coal slurry conveying, high carbon conversion rate, low downstream gas compression energy consumption saving of pressure gasification, low equipment investment and the like, and is widely applied. The raw synthesis gas produced by adopting the coal water slurry gasification process comprises the main components of CO and CO2And 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 water-cooled reactor byproduct is unstable, and particularly, in the last-stage working condition, the isothermal shift reaction temperature needs to be increased along with the reduction of the activity of the catalyst to maintain the shift reaction conversion rate, so that the medium pressure steam pressure of the water-cooled reactor byproduct is fluctuated severely, 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 its equipment" disclosed in the chinese patent application with application number 200910056342.4, when the isothermal sulfur-tolerant shift is in the final stage, the medium-pressure steam pressure of the byproduct of the water-cooled reactor rises from the normal 6.5MPaG to about 10.0MPaG with the rise of the temperature of the synthesis gas entering the water-cooled reactor, which severely restricts the stable operation of the apparatus, and the severe fluctuation of the steam pressure also increases the investment of the equipment and pipelines such as steam drum; 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 an air-cooling and water-cooling isothermal transformation process matched with coal water slurry gasification, which can obviously reduce medium-pressure steam pressure fluctuation in a byproduct of a water-cooling reactor and simultaneously reduce the investment 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 air-cooling and water-cooling isothermal transformation process matched with coal water slurry gasification comprises a water-cooling reactor, wherein a plurality of heat exchange tubes are arranged in the water-cooling reactor, 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 areas of the cross sections of the inner cavities of the first heat exchange tubes is 15-60% of the sum of the areas 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;
raw synthesis gas from a coal water slurry gasification device at the temperature of 230-250 ℃ and the pressure of 6.0-6.5 MPaG, the dry content of CO is 40-50%, the molar ratio of water to gas is 1.3-1.5, after a liquid phase is separated, heat exchange is carried out to the temperature of 250-290 ℃, impurities are removed, and the raw synthesis gas is divided into two streams; wherein the first strand of crude synthesis gas accounts for 20-50 v% of the total amount of the crude synthesis gas;
the first strand of crude synthesis gas enters a gas-cooled reactor to carry out primary shift reaction, the reaction temperature of the gas-cooled reactor is controlled to be 330-380 ℃, and the content of CO dry basis in the primary shift gas discharged from the gas-cooled reactor is 2-6%;
the second strand of crude synthesis gas enters a water-cooled reactor to carry out primary shift reaction, boiler water in the steam drum simultaneously enters a first group of heat exchange tubes and a second group of heat exchange tubes to exchange heat with a catalyst bed layer, and generated medium-pressure saturated steam with the temperature of 252-300 ℃ and the pressure of 4.0-8.7 MPaG returns to the steam drum;
controlling the ratio (molar ratio) of the flow of the medium-pressure saturated steam byproduct in the water-cooled reactor to the flow of the crude synthesis gas entering the water-cooled reactor to be 1: 6-1: 10; the reaction temperature of the water-cooled reactor is 290-330 ℃; the content of CO dry basis in the first-stage conversion gas of the water-cooled reactor is 1-4%;
merging the primary shift gas of the outlet air-cooled reactor and the primary shift gas of the outlet water-cooled shift gas, and sending the merged gas into an adiabatic shift converter for secondary shift reaction after the heat exchange is carried out to 230-280 ℃; the temperature of the transformed gas discharged from the adiabatic shift converter is 240-290 ℃, the dry basis content of CO is less than 0.4 percent, and the transformed gas is sent to a downstream process after heat is recovered;
monitoring the content of CO dry basis in the secondary conversion gas discharged out of the heat-insulation shift converter (8), 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 0.4 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 pressure of 4.0-8.7 MPaG and the temperature of 250-300 ℃ in the steam pocket enters the second group of heat exchange tubes from the second boiler water pipeline, and medium-pressure saturated steam with the temperature of 250-300 ℃ and the pressure of 4.0-8.7 MPaG generated after heat exchange returns to the steam pocket.
Preferably, the first-stage shift gas discharged from the gas-cooled reactor enters a medium-pressure steam generator to be cooled to 270-310 ℃, then is mixed with the first-stage shift gas discharged from the water-cooled reactor, exchanges heat with the crude synthesis gas to be cooled to 260-310 ℃, enters a No. 1 low-pressure steam generator to further recover heat, and enters the heat-insulating shift converter after being cooled to 230-280 ℃. The scheme has good energy-saving and consumption-reducing effects.
Preferably, the secondary conversion gas out of the adiabatic converter sequentially enters a low-pressure steam superheater and a No. 2 low-pressure steam generator to recover heat, and is cooled to 200-220 ℃ and then sent to downstream processes for treatment;
and heating the low-pressure boiler water from the battery compartment by a No. 1 low-pressure steam generator and a No. 2 low-pressure steam generator to generate low-pressure saturated steam of 0.5-1.5 MPaG, entering the low-pressure steam superheater for superheating, and then sending the low-pressure saturated steam out of the battery compartment.
Preferably, the ratio (molar ratio) of the flow rate of the medium-pressure steam generated as a byproduct of the medium-pressure steam generator to the flow rate of the first-stage converted gas entering the medium-pressure steam generator is 1: 8-1: 12.
In each of the above schemes, preferably, each of the first heat exchange tubes is uniformly arranged in the catalyst bed layer of the water-cooled reactor, and each of the second heat exchange tubes is uniformly arranged in the catalyst bed layer of the water-cooled reactor.
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 pipeline and a second steam pipeline which are arranged in parallel;
and the outlet of each first heat exchange tube is connected with the first steam pipeline, and the outlet of each second heat exchange tube is connected with the second steam 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 transformation flow is introduced into the air-cooled reactor, so that the load of the water-cooled reactor can be reduced, and the aim of overheating and producing medium-pressure steam as a byproduct is fulfilled; the parallel connection of the gas-cooled reactor and the water-cooled reactor can effectively reduce the specification of the water-cooled reactor, and is beneficial to the large-scale device.
2. The medium pressure boiler feed water is sent into the water-cooled reactor through two independent collecting pipes, and the boiler feed water of one collecting pipe is closed through a control valve on a pipeline at the end of a shift reaction so as to reduce the number of effective heat exchange pipe bundles in the water-cooled reactor, remarkably reduce the pressure fluctuation of medium pressure steam as a byproduct and maintain the stable operation of the device.
3. Because the fluctuation of the byproduct steam pressure of the water-cooled reactor is small, the design pressure of equipment such as a steam drum and the like is reduced, and the reduction of equipment investment is facilitated.
4. The crude synthesis gas of high-concentration CO gas is firstly sent into a gas-cooled reactor and a water-cooled reactor, so that the process characteristic that the water-cooled reactor cannot overtemperature is fully exerted, the problem of overtemperature does not occur in the whole conversion process, the service life of the catalyst is long, the operation cost is low, and the operation of a conversion unit is stable;
5. the byproduct medium-pressure steam and the byproduct low-pressure steam are sent out of the device after being superheated by the steam superheater, and the byproduct steam is conveyed outwards.
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 embodiment of the present invention.
Fig. 3 is a transverse cross-sectional view of an embodiment of the present invention.
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 water-cooled reactor 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.
The first heat exchange tubes 41 are uniformly arranged in a cavity between the catalyst frame and the synthesis gas collecting tube, the second heat exchange tubes 42 are uniformly arranged around the first heat exchange tubes 41 and around the first heat exchange tubes, at least three second heat exchange tubes 42 are uniformly distributed around each first heat exchange tube 41, in the embodiment, six second heat exchange tubes 42 are arranged around each heat exchange tube 41, and the six second heat exchange tubes 42 are arranged on the same circumferential line L with the corresponding first heat exchange tubes as the circle center.
Each first heat exchange tube 41 and each second heat exchange tube 42 arranged therearound form a heat exchange tube pair, and a part of the second heat exchange tubes 42 is shared between adjacent heat exchange tube pairs, that is, the circumferential lines L where the second heat exchange tubes are located in the adjacent heat exchange tube pairs 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 15-60%, in this embodiment 35%, 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 and second boiler water pipes 91 and 92 are connected to a boiler water outlet of the steam drum 11 through a boiler water delivery 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 11 through a steam delivery line 97.
The raw synthesis gas inlet is arranged at the top of the furnace body 1'.
The raw synthesis gas from the coal water slurry gasification device with the temperature of 242 ℃ and the pressure of 6.3MPaG and the water-gas molar ratio of 1.42 is sent into a gas-liquid separator 1, a liquid phase condensed out due to pipeline transmission loss is separated out, the raw synthesis gas sent out from the top of the gas-liquid separator 1 enters a feeding-discharging heat exchanger 2 to exchange heat with primary conversion gas, and is sent into a detoxification tank 3 after being heated to 250 ℃ to 290 ℃, and impurities such as dust in the raw synthesis gas are removed.
The raw synthesis gas sent out from the detoxification tank 3 is divided into two streams, wherein the first stream of raw synthesis gas accounts for 20-50% of the total amount of the raw synthesis gas, and is sent into the gas-cooled reactor 5 for shift reaction, and the shift reaction heat is used for overheating medium-pressure saturated steam.
The temperature of the gas-cooled reactor 5 is controlled to be 330-380 ℃, the content of CO dry basis in the primary shift gas discharged from the gas-cooled reactor 5 is 2-6%, and the primary shift gas is cooled to 290-340 ℃ by the medium-pressure steam generator 6 and then is converged into the primary shift gas discharged from the water-cooled reactor 4.
The ratio (molar ratio) of the flow of the byproduct medium-pressure steam in the medium-pressure steam generator to the flow of the primary conversion gas entering the medium-pressure steam generator is controlled to be 1: 9-1: 11.
The second strand of crude synthesis gas is sent into the water-cooled reactor 4 for shift reaction, and the temperature of the water-cooled reactor 4 is controlled to be 290-310 ℃.
The medium-pressure boiler water in the steam pocket 11 enters each first heat exchange tube and each second heat exchange tube from the first boiler water pipeline 91 and the second boiler water pipeline 92 respectively, exchanges heat with heat generated by a conversion reaction in the water-cooled reactor to generate medium-pressure saturated steam with the pressure of 6.5MPaG and the temperature of 282 ℃, and returns to the steam pocket 11 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 constant in the water-cooled reactor.
The generated medium-pressure saturated steam returns to the steam drum 11 for gas-liquid separation, the temperature of the medium-pressure saturated steam from the steam drum 11 is about 288 ℃, the medium-pressure saturated steam is merged with the medium-pressure saturated steam sent by the medium-pressure steam generator 6, then the steam enters the gas-cooled reactor 5 for heat extraction, and the steam is sent out of a device boundary area after being overheated to about 350 ℃.
And controlling the ratio (molar ratio) of the flow of the byproduct medium-pressure steam in the water-cooled reactor to the flow of the crude synthesis gas entering the water-cooled reactor to be 1: 7-1: 9.
The dry basis content of CO in the primary shift gas discharged from the water-cooled reactor 4 is about 1-4%, the CO is converged with the primary shift gas discharged from the medium-pressure steam generator 6, then the gas enters the feeding and discharging heat exchanger 2 to exchange heat with the crude synthesis gas and cool to 260-310 ℃, and then enters the No. 1 low-pressure steam generator 7 to exchange heat with the low-pressure boiler water, further the heat is recovered, and the gas is cooled to 230-280 ℃ and then is sent to the adiabatic shift furnace 8 to carry out secondary shift reaction.
The temperature of the secondary shift gas which is discharged from the adiabatic shift converter 8 is 240-290 ℃, the dry basis content of CO is less than 0.4%, the secondary shift gas enters a low-pressure steam superheater 9 to exchange heat with low-pressure steam, and after the secondary shift gas is cooled to 235-285 ℃, the secondary shift gas enters a No. 2 low-pressure steam generator 10 to exchange heat with low-pressure boiler water, the heat is continuously recovered, and after the secondary shift gas is cooled to 200-220 ℃, the secondary shift gas is sent to downstream processes to be processed.
The temperature of 130 ℃ water of the medium-pressure boiler from the battery compartment is about 10MPaG, the water is divided into two parts, one part is sent into a steam drum 11, the other part is sent into a medium-pressure steam generator 6, and a byproduct of 6.5MPaG medium-pressure saturated steam enters a gas-cooled reactor 5 to be superheated and then is sent out from the battery compartment.
The low-pressure boiler water from the battery limits produces 1.0MPaG low-pressure saturated steam through the No. 1 low-pressure steam generator 7 and the No. 2 low-pressure steam generator 10, and is sent out of the battery limits after being superheated through the low-pressure steam superheater 9.
In the running process of the device, the CO dry basis content in the secondary conversion gas of the adiabatic conversion furnace 8 is detected by adopting online sampling analysis. When the dry basis content of CO in the secondary conversion gas is more than 0.4 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 to maintain the activity of the catalyst, the embodiment stops the work of the first heat exchange tube group by closing the valve on the first boiler water pipeline, and only the second heat exchange tube group works.
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.
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 comparative example is substantially the same as the process flow of the example, and the water-cooled reactor used in the comparative example is a conventional non-tunable isothermal transformation reactor, which specifically comprises:
the raw synthesis gas from the coal water slurry gasification device with the temperature of 242 ℃ and the pressure of 6.3MPaG has the water-gas ratio (water to dry gas, molar ratio) of about 1.42, is sent into a gas-liquid separator 1, a liquid phase condensed out due to pipeline conveying loss is separated out, the raw synthesis gas sent out from the top of the gas-liquid separator 1 is heated to 250-290 ℃ by a feeding and discharging heat exchanger 2, and then is sent into a detoxification tank 3, and impurities such as dust in the raw synthesis gas are removed.
The crude synthesis gas sent out from the detoxification tank 3 is divided into two streams, the first stream accounts for about 20-50% of the total amount of the crude synthesis gas, the two streams are sent into a gas-cooled reactor 5 for shift reaction, and the shift reaction heat is used for overheating medium-pressure saturated steam;
controlling the temperature of the gas-cooled reactor 5 to be 330-380 ℃, controlling the content of CO dry basis in the primary shift gas discharged from the gas-cooled reactor 5 to be about 2-6%, cooling the primary shift gas to 290-340 ℃ by the medium-pressure steam generator 6, and merging the primary shift gas sent out from the water-cooled reactor 4;
the ratio (molar ratio) of the flow of the byproduct medium-pressure steam in the medium-pressure steam generator to the flow of the primary conversion gas entering the medium-pressure steam generator is controlled to be 1: 9-1: 11.
The second strand of crude synthesis gas is sent into the water-cooled reactor 4 for shift reaction, and the generated heat is used for enriching 6.5MPaG medium-pressure saturated steam, and the specific arrangement is that medium-pressure boiler feed water in the steam drum 11 is pressurized by the boiler circulating water pump 12 and then is sent into the water-cooled reactor 4 for removing the heat generated by the shift reaction so as to maintain the reaction temperature of the water-cooled reactor to be basically constant. The generated medium-pressure saturated steam returns to the steam drum 11 for gas-liquid separation, the temperature of the medium-pressure saturated steam from the steam drum 11 is about 281 ℃, the medium-pressure saturated steam is merged with the medium-pressure saturated steam sent by the medium-pressure steam generator 6, and the steam is superheated to about 350 ℃ by the gas-cooled reactor 5 and then sent out of a device boundary region.
And controlling the ratio (molar ratio) of the flow of the byproduct medium-pressure steam in the water-cooled reactor to the flow of the crude synthesis gas entering the water-cooled reactor to be 1: 7-1: 9.
Controlling the temperature of the water-cooled reactor 4 to be 290-310 ℃, ensuring that the content of CO dry basis in primary shift gas discharged from the water-cooled reactor 4 is about 1-4%, merging the primary shift gas with primary shift gas from the gas-cooled reactor 5, sending the mixture into the discharge heat exchanger 2, exchanging heat with crude synthesis gas, cooling the mixture to 260-310 ℃, further recovering heat through a No. 1 low-pressure steam generator 7, cooling the mixture to 230-280 ℃, and sending the mixture into the adiabatic shift converter 8 for continuous shift reaction;
the temperature of the transformed gas discharged from the adiabatic shift converter 8 is 240-290 ℃, the dry basis content of CO is less than 0.4%, the transformed gas is cooled to 235-285 ℃ by a low-pressure steam superheater 9, and then the transformed gas is sent to a No. 2 low-pressure steam generator 10 to continuously recover heat, and is sent to downstream processes for treatment after being cooled to 200-220 ℃.
The temperature of 130 ℃ water of the medium-pressure boiler from the battery compartment is about 10MPaG, the pressure is divided into two parts, one part is sent into a steam drum 11, the other part is sent into a medium-pressure steam generator 6, and a byproduct of 6.5MPaG medium-pressure saturated steam is sent out of the battery compartment after being heated.
The low-pressure boiler water from the battery limits produces 1.0MPaG low-pressure saturated steam through a No. 2 low-pressure steam generator 7 and a No. 2 low-pressure steam generator 10, and is sent out of the battery limits after being superheated through a low-pressure steam superheater 9.
In 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 water-cooled reactor is increased to about 325 ℃, the byproduct steam pressure of the water-cooled reactor gradually increases to more than 10.0MPaG, 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 increased.
Taking a synthetic ammonia device adopting coal water slurry gasification gas making as an example, the effective gas (H2+ CO) entering the isothermal shift device is about 85000Nm3And h, comparing the main parameters of the air-cooling and water-cooling isothermal transformation process matched with the coal water slurry gasification under the standard, and showing in table 1.
TABLE 1
As can be seen from table 1, in the ammonia synthesis apparatus for coal water slurry gasification gas production, the gas cooling and water cooling isothermal transformation process adopted in the embodiment, the pressure fluctuation of the medium pressure steam in the byproduct of the water cooling reactor is obviously reduced, which is beneficial to the long-term stable operation of the steam pipe network and the apparatus, and meanwhile, the design pressure of the steam drum and the pipeline in the embodiment is obviously reduced, and the investment of the equipment and the pipeline is reduced by about 160 ten thousand yuan.
Claims (10)
1. An air-cooling and water-cooling isothermal transformation process matched with coal water slurry gasification comprises a water-cooling reactor (4), wherein a plurality of heat exchange tubes are arranged in the water-cooling reactor (4), inlets of the heat exchange tubes are connected with a boiler water outlet of a steam drum (11) through a boiler water pipeline, and outlets of the heat exchange tubes are connected with a steam inlet of the steam drum (11) through a steam recovery pipeline; the method is characterized in that:
the heat exchange tubes comprise a plurality of first heat exchange tubes (41) and a plurality of second heat exchange tubes (42), and each first heat exchange tube (41) forms a first group of heat exchange tubes; each second heat exchange tube (42) 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 15-60% 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);
raw synthesis gas from a coal water slurry gasification device at the temperature of 230-250 ℃ and the pressure of 6.0-6.5 MPaG, the dry content of CO is 40-50%, the molar ratio of water to gas is 1.3-1.5, after a liquid phase is separated, heat exchange is carried out to the temperature of 250-290 ℃, impurities are removed, and the raw synthesis gas is divided into two streams; wherein the first strand of crude synthesis gas accounts for 20-50 v% of the total amount of the crude synthesis gas;
the first strand of crude synthesis gas enters a gas-cooled reactor (5) for primary shift reaction, the reaction temperature of the gas-cooled reactor is controlled to be 330-380 ℃, and the content of CO dry basis in the primary shift gas discharged from the gas-cooled reactor is 2-6%;
the second strand of crude synthesis gas enters a water-cooled reactor (4) for primary shift reaction, boiler water in the steam drum (11) simultaneously enters a first group of heat exchange tubes and a second group of heat exchange tubes to exchange heat with a catalyst bed layer, and generated medium-pressure saturated steam with the temperature of 252-300 ℃ and the pressure of 4.0-8.7 MPaG returns to the steam drum (11);
controlling the ratio (molar ratio) of the flow of the medium-pressure saturated steam byproduct in the water-cooled reactor to the flow of the crude synthesis gas entering the water-cooled reactor to be 1: 6-1: 10; the reaction temperature of the water-cooled reactor is 290-330 ℃; the content of CO dry basis in the first-stage conversion gas of the water-cooled reactor is 1-4%;
the primary conversion gas of the outlet air-cooled reactor is merged with the primary conversion gas of the outlet water-cooled conversion gas, and the heat is exchanged to 230 to 280 ℃ and then sent into an adiabatic shift converter (8) for secondary conversion reaction;
the temperature of the transformed gas discharged from the adiabatic shift converter is 240-290 ℃, the dry basis content of CO is less than 0.4 percent, and the transformed gas is sent to a downstream process after heat is recovered;
monitoring the content of CO dry basis in the secondary conversion gas discharged from the heat-insulation shift converter (8), 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 0.4 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 pressure of 4.0-8.7 MPaG and the temperature of 250-300 ℃ in the steam pocket (11) enters the second group of heat exchange tubes from the second boiler water pipeline, medium-pressure saturated steam with the temperature of 250-300 ℃ and the pressure of 4.0-8.7 MPaG generated after heat exchange returns to the steam pocket (11).
2. The gas-cooled and water-cooled isothermal shift process matched with coal water slurry gasification according to claim 1, characterized in that the first-stage shift gas discharged from the gas-cooled reactor (5) enters a medium-pressure steam generator to be cooled to 270-310 ℃, then is mixed with the first-stage shift gas discharged from the water-cooled reactor, exchanges heat with crude synthesis gas to be cooled to 260-310 ℃, then enters a 1# low-pressure steam generator (7) to further recover heat, and enters the adiabatic shift furnace after being cooled to 230-280 ℃.
3. The air-cooled and water-cooled isothermal transformation process matched with coal water slurry gasification according to claim 1, wherein secondary transformation gas out of the heat insulation transformer (8) sequentially enters a low-pressure steam superheater (9) and a No. 2 low-pressure steam generator (10) to recover heat, and is cooled to 200-220 ℃ and then sent to downstream processes for treatment;
and low-pressure boiler water from the battery limits is heated by a No. 1 low-pressure steam generator (7) and a No. 2 low-pressure steam generator (10) to generate low-pressure saturated steam of 0.5-1.5 MPaG, enters the low-pressure steam superheater (9), is superheated and then is sent out of the battery limits.
4. The gas-cooled and water-cooled isothermal shift process matched with coal water slurry gasification according to claim 3, wherein the ratio (molar ratio) of the flow rate of the medium-pressure steam byproduct of the medium-pressure steam generator (6) to the flow rate of the primary shift gas entering the medium-pressure steam generator (6) is 1: 8-1: 12.
5. The air-cooled and water-cooled isothermal shift process matched with coal-water slurry gasification according to any one of claims 1 to 4, characterized in that each first heat exchange tube is uniformly arranged in the catalyst bed layer of the water-cooled reactor (4), and each second heat exchange tube is uniformly arranged in the catalyst bed layer of the water-cooled reactor (4).
6. The air-cooled and water-cooled isothermal transformation process matched with coal water slurry gasification according to 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 air-cooled and water-cooled isothermal transformation process matched with coal water slurry gasification according to claim 6, wherein 3-6 second heat exchange tubes are arranged around each first heat exchange tube.
8. The air-cooled and water-cooled isothermal transformation process matched with coal water slurry gasification according to 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 air-cooled and water-cooled isothermal transformation process matched with coal water slurry gasification according to claim 8, wherein a part of the second heat exchange tubes are shared between adjacent heat exchange tube pairs.
10. The gas-cooled and water-cooled isothermal shift process matched with coal-water slurry gasification according to claim 9, wherein the steam collecting pipeline comprises a first steam pipeline (93) and a second steam pipeline (94) which are arranged in parallel;
the outlet of each first heat exchange tube is connected with the first steam pipeline (93), and the outlet of each second heat exchange tube is connected with the second steam pipeline (94).
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| CN110921619B (en) * | 2019-10-24 | 2023-06-06 | 中石化宁波工程有限公司 | Multi-flow CO isothermal conversion process matched with pulverized coal gasification and isothermal conversion furnace |
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