Sulfur-tolerant shift system for producing hydrogen or hydrogen-rich gas

Abstract

Disclosed in the present utility model is a sulfur-tolerant shift system for producing hydrogen or a hydrogen-rich gas, comprising: a raw material main pipe, a raw material gas preheater, a shift reactor set, a medium-pressure steam superheater and a medium-pressure waste heat boiler. The shift reactor set comprises two or more shift reactors; the raw material main pipe is divided into two branch pipes; the first branch pipe is connected to a tube side of the raw material gas preheater and then is connected to the inlet of a first shift reactor, and the outlet of the first shift reactor is connected to a shell side of the raw material gas preheater; the second branch pipe is combined with a line at the outlet of a shell side of the raw material gas preheater and then connected to the inlet of a second shift reactor; the outlet of the second shift reactor is sequentially connected to a tube side of the medium-pressure steam superheater and a tube side of the medium-pressure waste heat boiler and then enters a subsequent shift reactor; a medium-pressure boiler water supply line is connected to the inlet of a shell side of the medium-pressure waste heat boiler; the outlet of the shell side of the medium-pressure waste heat boiler is divided into two paths, one path is connected to the inlet of the first shift reactor, and the other path enters a shell side of the medium-pressure steam superheater. According to the present utility model, the temperature of a catalyst bed of the first shift reactor is controlled by means of chemical balance, thereby thoroughly solving the over-temperature problem of catalyst beds, and prolonging the service life of catalysts. Only part of a raw material gas passes through the first shift reactor, and steam consumption of devices is reduced by adjusting loads of the first shift reactor and the second shift reactor.

Description

A sulfur-tolerant conversion system for producing hydrogen or hydrogen-rich gas Technical Field

[0001] The utility model belongs to the field of hydrogen and synthesis gas preparation, and particularly relates to a system for producing hydrogen or hydrogen-rich gas through sulfur-resistant conversion. Background Art

[0002] Sulfur-tolerant shift reaction is a crucial component of coal chemical plants. Through the carbon monoxide shift reaction, it converts CO in raw coal gas into H2 to meet the H2 / CO ratio requirements for different syngases. Raw coal gas produced by dry pulverized coal gasification can contain as much as 60-75% CO, with a water-gas ratio of approximately 0.15-1.1. Directly subjecting this type of raw coal gas to the shift reaction would result in catalyst bed temperatures exceeding 500°C in the reactor. Current shift catalysts cannot withstand these high temperatures, severely impacting the catalyst's service life and the plant's safe and stable production. Furthermore, severe methanation side reactions can occur, resulting in effective gas loss.

[0003] To address the shift reaction overheating problem, patent WO 2013072659A1 discloses a method for controlling the reaction temperature by increasing the catalyst space velocity. However, this method has a short catalyst life and cannot meet the requirements of long-term operation. At the same time, during startup and low-load conditions, the space velocity does not reach the design value, and the catalyst bed will still overheat. U.S. Patent US 20140252277A1 discloses a method for controlling the temperature of the catalyst bed by arranging a heat exchange tube bundle in the reactor to remove the reaction heat through gas cooling and steam production. This method has a complex reactor structure and high investment. At the same time, due to corrosion and stress problems, the heat exchange tube bundle in the reactor has the risk of leakage, affecting the safe and stable operation of the device. U.S. Patent US 10549991B2 discloses a process for controlling the temperature of the catalyst bed by adding steam to the feed gas and circulating part of the reaction gas. This method not only consumes a large amount of steam and has high energy consumption, but also the circulation of the reaction gas increases the investment in the device.

[0004] Utility Model Content

[0005] The purpose of the utility model is to provide a sulfur-resistant conversion system for producing hydrogen or hydrogen-rich gas in response to the deficiencies in the prior art.

[0006] In order to achieve the above-mentioned object, the present invention adopts the following technical solution: a sulfur-resistant shift conversion system for producing hydrogen or hydrogen-rich gas, comprising: a raw material main pipe, a raw gas preheater, a shift conversion reactor group, a medium-pressure steam superheater and a medium-pressure waste heat boiler;

[0007] wherein the shift reactor group comprises two or more shift reactors;

[0008] The raw material main pipe is divided into two branches, the first branch pipe is connected to the tube side of the raw gas preheater and then connected to the inlet of the first shift reactor, and the outlet of the first shift reactor is connected to the shell side of the raw gas preheater;

[0009] The second branch pipe is connected to the outlet of the shell side of the raw gas preheater and then connected to the inlet of the second shift reactor. The outlet of the second shift reactor is connected to the medium-pressure steam superheater tube side and the medium-pressure waste heat boiler tube side in sequence and then enters the subsequent shift reactor.

[0010] The medium-pressure boiler feed water pipeline is connected to the shell-side inlet of the medium-pressure waste heat boiler. The shell-side outlet of the medium-pressure waste heat boiler is divided into two paths, one is connected to the inlet of the first shift reactor, and the other enters the shell-side of the medium-pressure steam superheater.

[0011] Furthermore, the shift reactor group further includes a third shift reactor and a fourth shift reactor, which are sequentially connected to the outlet pipeline of the medium-pressure waste heat boiler tube side.

[0012] Furthermore, the sulfur-tolerant shift system further includes a waste heat recovery unit, which is connected to the outlet of the fourth shift reactor.

[0013] Furthermore, the sulfur-tolerant shift conversion system further comprises a condensate stripping unit, the inlet of the condensate stripping unit is connected to the waste heat recovery unit, and the condensate outlet is respectively connected to the inlets of the second, third and fourth shift reactors and the outside.

[0014] Furthermore, the raw gas in the first branch accounts for 0.2 to 0.6 of the total volume of the raw gas.

[0015] Furthermore, the ratio of water vapor to dry gas in the inlet gas of the first shift reactor is 1.5 to 2.0.

[0016] Furthermore, the CO dry molar concentration in the gas at the inlet of the second shift reactor is 43% to 48%.

[0017] Compared with the prior art, the utility model has the following advantages:

[0018] (1) Using chemical equilibrium to control the catalyst bed temperature in the first shift reactor can completely solve the problem of catalyst bed overheating and extend the service life of the catalyst.

[0019] (2) Only a portion of the raw gas passes through the first shift reactor. By adjusting the load of the first shift reactor and the second shift reactor, the steam consumption of the device is reduced.

[0020] (3) All steam consumed comes from within the system, and no external steam is required. At the same time, high-grade medium-pressure superheated steam can be produced as a by-product. This serves as motive steam to drive the compressor.

[0021] (4) The conversion gas is directly quenched and cooled using the condensate produced inside the system. This is not only simple to operate and easy to control, but also reduces the amount of wastewater discharged and improves the overall conversion rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG1 is a schematic diagram of the process flow of a sulfur-tolerant conversion system for producing hydrogen or hydrogen-rich gas in an embodiment.

[0023] Figure markings: 101-raw gas preheater; 102-first shift reactor; 103-second shift reactor; 104-medium-pressure steam superheater; 105-medium-pressure waste heat boiler; 106-third shift reactor; 107-fourth shift reactor; 108-waste heat recovery unit; 109-condensate stripping unit; 111~114-raw gas; 115~122-shift gas; 131~136-condensate; 141-medium-pressure boiler feed water; 142~143-medium-pressure saturated steam; 144-medium-pressure superheated steam. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0025] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products or apparatuses.

[0026] The raw gas from the upstream device is divided into two streams. The first stream of raw gas is sent to the raw gas preheater tube for heating. The heated raw gas is fed with the medium-pressure saturated steam produced by the system and then enters the first conversion reactor for conversion reaction.

[0027] a. The conversion gas at the outlet of the first conversion reactor first enters the shell side of the raw gas preheater to heat the raw gas in the tube side, then mixes with the second raw gas, and finally adds condensate to cool it down before being sent to the second conversion reactor to continue the conversion reaction.

[0028] b. The shift gas at the outlet of the second shift reactor passes through the medium-pressure steam superheater and the medium-pressure waste heat boiler, recovering heat before being fed with condensate to cool the gas. The gas then enters the third shift reactor for further shift reaction. Boiler feedwater enters the medium-pressure waste heat boiler, absorbing heat to produce medium-pressure saturated steam. The medium-pressure saturated steam leaving the medium-pressure waste heat boiler is split into two streams. One stream is mixed with the first feed gas at the outlet of the feed gas preheater, while the second stream is fed to the medium-pressure steam superheater for heating to produce medium-pressure superheated steam.

[0029] c. The conversion gas at the outlet of the third conversion reactor is fed with condensate to cool it down and then enters the fourth conversion reactor for the final conversion reaction.

[0030] d. The shift gas at the outlet of the fourth shift reactor enters the waste heat recovery unit to recover heat and separate the condensate. The shift gas is cooled to approximately 40°C before being sent to downstream equipment. The separated condensate is sent to the condensate stripping unit for processing. A portion of the treated condensate is used as quench water at the inlets of the second, third, and fourth shift reactors, and the remaining condensate is discharged.

[0031] In the present invention, the feed gas has a dry-basis molar content of CO of 40% to 75%, a dry-basis molar content of H2S of 0.01% to 5%, a water vapor to dry gas ratio (water-gas ratio) of 0.15 to 1.2, a feed gas temperature of 160 to 240°C, and a pressure of 3.0 to 9.0 MPa. The feed gas entering the system is divided into two streams. The first stream, which accounts for approximately 0.2 to 0.6 of the total feed gas, first enters the feed gas preheater tube side, is heated to 260 to 350°C, and then is supplemented with medium-pressure steam to adjust the water-gas ratio before being delivered to the first shift reactor.

[0032] The gas temperature at the inlet of the first shift reactor is controlled between 230 and 300°C, the water-gas ratio is controlled between 1.5 and 2.0, the gas temperature at the outlet of the first shift reactor is controlled between 400 and 475°C, and the CO dry basis concentration is controlled between 6% and 12%.

[0033] The inlet gas temperature of the second shift reactor is controlled between 230 and 300°C, the water-gas ratio is controlled between 0.4 and 1.2, the outlet gas temperature of the second shift reactor is controlled between 400 and 475°C, and the CO dry basis concentration is controlled between 8% and 20%.

[0034] The CO dry basis concentration of the gas at the inlet of the second shift reactor is controlled between 40% and 50%. Preferably, the CO dry basis concentration of the gas at the inlet of the second shift reactor is controlled between 43% and 48%.

[0035] The inlet gas temperature of the third shift reactor is controlled between 200-240°C, the water-gas ratio is controlled between 0.2-0.5, the outlet gas temperature of the third shift reactor is controlled between 260-320°C, and the CO dry basis concentration is controlled between 1.6%-5%.

[0036] The inlet gas temperature of the fourth shift reactor is controlled between 180 and 220°C, the water-gas ratio is controlled between 0.2 and 0.5. The outlet gas temperature of the fourth shift reactor is controlled between 200 and 250°C, and the CO dry basis concentration is controlled between 0.4% and 1.5%.

[0037] The waste heat recovery unit first recovers the heat of the conversion gas by heating boiler feed water, desalting water, etc., and then cools the conversion gas to 40℃ through circulating water cooling or air cooling.

[0038] The condensate stripping unit directly or indirectly strips the condensate using low-pressure steam. The NH3 content in the condensate treated by the condensate stripping unit is 0-100ppm, and the H2S content is 0-20ppm.

[0039] The temperature of the medium-pressure superheated steam after being heated by the medium-pressure steam superheater is 380~420℃.

[0040] The main active components of the catalysts loaded in all the shift reactors are cobalt and molybdenum, and the catalysts loaded in the third shift reactor and the fourth shift reactor also contain alkali metals.

[0041] Example

[0042] Figure 1 shows a sulfur-tolerant shift system for producing hydrogen or hydrogen-rich gas. The feed gas temperature is 208.5°C, the pressure is 3.75 MPa, and the molar flow rate is 11,000 kmol / h. The molar composition is shown in Table 1.

[0043] Table 1

[0044] The feed gas has a CO dry molar content of 68.73% and a water-gas ratio of 0.96. The feed gas 111 entering the system is first split into two streams. The first stream, comprising approximately 26% of the total feed gas, 112 enters the feed gas preheater 101 tube side, where it is heated to 267°C. It is then fed with system-generated medium-pressure saturated steam 143 and sent to the first shift reactor for a shift reaction. The shifted gas 115 exiting the first shift reactor has a temperature of 457°C and first enters the feed gas preheater 101 shell side for heat exchange with the feed gas. It is then mixed with the second stream of feed gas 113 and condensate 135 before being sent to the second shift reactor for a shift reaction. The shifted gas 117 exiting the second shift reactor has a temperature of 454°C and passes through the medium-pressure steam superheater 104 tube side and the medium-pressure waste heat boiler 105 tube side to recover heat. It is then mixed with condensate 134 and sent to the third shift reactor 106 for a shift reaction. The shift gas 120 at the outlet of the third shift reactor has a temperature of 276°C. After mixing with the condensate 133 and cooling, it is sent to the fourth shift reactor 107 for the final shift reaction. The shift gas 121 at the outlet of the fourth shift reactor has a temperature of 218°C. After cooling in the waste heat recovery unit 108 and separation of the condensate, the product shift gas is obtained at a temperature of 40°C.

[0045] The medium-pressure boiler feed water 141 from the pipeline network first enters the shell side of the medium-pressure waste heat boiler 105, absorbs the heat of the conversion gas 118 to generate medium-pressure saturated steam 142. Part of the generated medium-pressure saturated steam is mixed with the raw gas 114, and the remaining part is sent to the shell side of the medium-pressure steam superheater 104 to obtain medium-pressure superheated steam 144 with a temperature of 380°C and a pressure of 4.0 MPa.

[0046] The condensate 131 from the waste heat recovery unit is sent to the condensate stripping unit 109, where low-pressure steam stripping is used to remove NH3 and H2S in the condensate. Part of the condensate 132 after stripping is used as quenching water for the conversion gas to cool the conversion gas, and the remaining condensate 136 is sent out of the boundary.

[0047] The operating parameters and compositions of the inlet and outlet of the four shift reactors are shown in Table 2.

[0048] Table 2

[0049] The product temperature was 40°C, the pressure was 3.25 MPa, and the molar flow rate was 9434 kmol / h. The molar composition is shown in Table 3.

[0050] Table 3

[0051] By using the system and method of the present invention, the conversion rate of CO in the raw gas is 98.80%, and the produced shift gas can be used to produce hydrogen or synthetic ammonia.

[0052] The above embodiment is used to produce hydrogen or ammonia synthesis gas. It only needs to be slightly modified based on this embodiment to eliminate the third and fourth conversion reactors, and it can be used to produce synthesis gas for synthesizing chemicals such as natural gas, methanol or oil products.

[0053] The above is a further detailed description of the present invention and should not be considered as a limitation on the specific implementation of the present invention. For those skilled in the art of the present invention, simple deductions or substitutions that do not depart from the concept of the present invention are within the scope of protection of the present invention.

Claims

1. A sulfur-tolerant conversion system for producing hydrogen or hydrogen-rich gas, characterized in that include: Raw material main, raw gas preheater, shift reactor group, medium-pressure steam superheater and medium-pressure waste heat boiler; wherein the shift reactor group comprises two or more shift reactors; The raw material main pipe is divided into two branches, the first branch pipe is connected to the tube side of the raw gas preheater and then connected to the inlet of the first shift reactor, and the outlet of the first shift reactor is connected to the shell side of the raw gas preheater; The second branch pipe is connected to the outlet of the shell side of the raw gas preheater and then connected to the inlet of the second shift reactor. The outlet of the second shift reactor is connected to the medium-pressure steam superheater tube side and the medium-pressure waste heat boiler tube side in sequence and then enters the subsequent shift reactor. The medium-pressure boiler feed water pipeline is connected to the shell-side inlet of the medium-pressure waste heat boiler. The shell-side outlet of the medium-pressure waste heat boiler is divided into two paths, one is connected to the inlet of the first shift reactor, and the other enters the shell-side of the medium-pressure steam superheater.

2. The sulfur-tolerant shift conversion system for producing hydrogen or hydrogen-rich gas according to claim 1, characterized in that: The shift reactor group further includes a third shift reactor and a fourth shift reactor, which are sequentially connected to the outlet pipeline of the medium-pressure waste heat boiler tube side.

3. The sulfur-tolerant shift conversion system for producing hydrogen or hydrogen-rich gas according to claim 2, characterized in that: The sulfur-tolerant shift system further includes a waste heat recovery unit connected to the outlet of the fourth shift reactor.

4. The sulfur-tolerant shift conversion system for producing hydrogen or hydrogen-rich gas according to claim 3, characterized in that: The sulfur-resistant conversion system further comprises a condensate stripping unit, the inlet of the condensate stripping unit is connected to the waste heat recovery unit, and the condensate outlet is respectively connected to the inlets of the second, third and fourth conversion reactors and the outside.

5. The sulfur-tolerant shift conversion system for producing hydrogen or hydrogen-rich gas according to claim 1, characterized in that: The raw gas in the first branch accounts for 0.2 to 0.6 of the total volume of the raw gas.

6. The sulfur-tolerant shift conversion system for producing hydrogen or hydrogen-rich gas according to claim 1, characterized in that: The ratio of water vapor to dry gas in the inlet gas of the first shift reactor is 1.5 to 2.

0.

7. The sulfur-tolerant shift conversion system for producing hydrogen or hydrogen-rich gas according to claim 1, characterized in that: The CO dry molar concentration in the inlet gas of the second shift reactor is 43% to 48%.

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