阅读说明：本技术 用于冷却合成气的方法和设备 (Method and apparatus for cooling syngas ) 是由 让-菲利普·塔迪耶洛 陈越 托马斯·文茨 于 2018-06-06 设计创作，主要内容包括：用于冷却由含烃进料气的催化蒸汽重整产生的合成气的方法和设备,该合成气已经通过与锅炉给水进行热交换而冷却,从而将锅炉给水转化为蒸汽,同时分离出形成的水性冷凝物,其中提供了进行进一步的冷却并且仅两个步骤,即将该设备加热以对锅炉给水进行脱气以及通过与周围空气进行热交换进行冷却,而进行进一步的冷却,由于所需的冷却步骤数量少,因此仅需要很小的结构高度。(Method and device for cooling synthesis gas produced by catalytic steam reforming of a hydrocarbon-containing feed gas, which synthesis gas has been cooled by heat exchange with boiler feed water, thereby converting the boiler feed water into steam, while separating off the aqueous condensate formed, wherein further cooling is provided and only two steps are provided, namely heating the device to degas the boiler feed water and cooling by heat exchange with ambient air, whereby further cooling is performed, which requires only a small constructional height due to the small number of cooling steps required.)

1. A process for cooling synthesis gas produced by catalytic steam reforming of a hydrocarbon-containing feed gas, the synthesis gas having been cooled by heat exchange with boiler feed water to convert the boiler feed water to steam, with separation of water condensate formed and treatment in an apparatus for the catalytic conversion of carbon monoxide to hydrogen and carbon dioxide by steam, the process comprising the treatment steps of:

(a) heat exchanging the synthesis gas with the hydrocarbon-containing feed gas,

(b) introducing the boiler feedwater into a degasser comprising a feedwater container, wherein the boiler feedwater is not preheated by heat exchange with the syngas prior to introduction into the degasser, the boiler feedwater flowing through a dome mounted on the feedwater container into the water container in counter-current flow with steam rising from the feedwater container to effect preliminary degassing of the boiler feedwater and discharging the steam from the degasser and process with gases absorbed from the feedwater and for further treatment,

(c) heat exchanging the synthesis gas with the boiler feed water that has been degassed in the degasser,

(d) at least a portion of the syngas is heat exchanged with boiler feed water present in a feed water vessel of the degasser,

(e) the synthesis gas is heat exchanged with ambient air,

(f) separating condensate from the synthesis gas and introducing the condensate into the degasser, wherein the condensate is caused to flow through a dome mounted on the feed water vessel in countercurrent to the water vapour rising from the feed water vessel into the feed water vessel for preliminary degassing and the water vapour is discharged from the degasser and process for further treatment together with the gas absorbed from the condensate,

(g) the synthesis gas is further sent out of the process for further processing.

2. The method of claim 1, wherein the boiler feed water and the condensate are each introduced into the feed water vessel of the degasser through separate domes.

3. An apparatus for cooling a synthesis gas produced by catalytic steam reforming of a hydrocarbon-containing feed gas, the synthesis gas having been cooled by heat exchange with boiler feed water to convert the boiler feed water to steam, with separation of water condensate formed, and being treated in a device for catalytic conversion of carbon monoxide to hydrogen and carbon dioxide by steam, the apparatus comprising the following components:

(a) a heat exchanger for exchanging heat between the synthesis gas and the hydrocarbon-containing feed gas,

(b) a heat exchanger for exchanging heat between the syngas and the degassed boiler feed water,

(c) apparatus for degassing boiler feed water, comprising a feed water vessel having a heat exchanger present therein for heat exchange between synthesis gas and the boiler feed water and having at least one dome, such as a bed of random packing elements or a bed of structured packing, mounted on the feed water vessel and having internals for gas-liquid mass transfer, through which the boiler feed water and/or condensate separated from the synthesis gas is introduced into the feed water vessel,

(d) a heat exchanger for exchanging heat between the synthesis gas and ambient air,

(e) a condensate separator for separating condensate from the synthesis gas,

(f) a pipe for supplying boiler feed water produced by the boiler feed water to the degasser (c), which pipe is not part of the apparatus, wherein the pipe is arranged in such a way that it opens into the dome for supplying the boiler feed water to be degassed into a feed water container of the degasser,

(g) piping for conveying the condensate from the condensate separator (e) to the degasser (c), wherein the piping is laid in such a way that it opens to the dome for supplying the condensate to the feedwater container.

Technical Field

The invention relates to a method and a device for cooling a synthesis gas produced by catalytic steam reforming of a hydrocarbon-containing feed gas, which synthesis gas has been cooled by heat exchange with boiler feed water in order to convert the boiler feed water into steam, while the water condensate formed is separated off and treated in a device for the catalytic conversion of carbon monoxide into hydrogen and carbon dioxide by means of steam.

Background

Processes for the production of synthesis gas comprising hydrogen and carbon monoxide by catalytic steam reforming of a hydrocarbon-containing feed gas are known and described, for example, in Ullmann's Encyclopedia of industrial chemistry, sixth edition, volume 15, natural gas production, chapter 2. Feed gases, i.e., hydrocarbon-containing gases such as natural gas and steam, are conveyed through externally heated catalyst-filled reactor tubes at elevated pressures (e.g., 20 to 35 bar) and elevated temperatures (e.g., 800 ℃ to 950 ℃). Here, the feed gas is converted into a synthesis gas rich in hydrogen and rich in carbon monoxide. This reactor is commonly referred to as the SMR and the process is referred to as the SMR process, an acronym for steam methane reformer. It is important in terms of process economics to exchange very efficiently between the syngas exiting the SMR and the feed gas.

After leaving the SMR, the resulting syngas is cooled by heat exchange with boiler feed water. Where the boiler feed water evaporates. Steam is used as feed steam for the SMR process and excess steam is vented as export steam for use outside of the SMR process. When syngas consisting of only hydrogen is to be produced as the final product of the SMR process, the syngas is then subsequently processed in a catalytic converter in which carbon monoxide is converted to hydrogen and carbon dioxide by steam. This transformation is described in ullman volume referenced above, page 382 and below.

The process of the present invention involves further cooling of the synthesis gas after the preceding steps.

Here, the synthesis gas is first further cooled by heat exchange with a hydrocarbon-containing feed gas. This is followed by further cooling by heat exchange with the degassed boiler feed water (which is then fed to the boiler), and then by heating the boiler feed water degasser and preheating fresh boiler feed water before it is introduced into the degasser. Degassing occurs purely as a result of boiler feed water heating. The water condensate formed in the synthesis gas up to this point is then separated as hot condensate from the synthesis gas stream. The synthesis gas is then further cooled to almost room temperature by an air cooler and the condensate formed, referred to as cold condensate, is separated from the synthesis gas by a further condensate separator. The hot and cold condensates that have been separated off are used in the process for generating process steam. Depending on the purity of the condensate and the purity requirements that the outlet steam has to meet, it is kept separate from the fresh boiler feed water and is evaporated in a separate boiler to form process steam, or it is introduced into the boiler feed water degasser and mixed with the fresh boiler feed water there.

A disadvantage of this method according to the prior art is the high outlay in terms of facilities, by means of which the boiler feed water is heated in two steps, as described above. Here, to accommodate the preheating of the boiler feed water, a bypass conduit of syngas around the heat exchanger is required. The division of the synthesis gas stream between the flow through the heat exchanger and the flow through the bypass conduit requires a three-way valve or two mechanically connected regulating valves as generally described in german first publication 1950055. The mechanical connection ensures that when one valve is closed, the other valve is opened to the same extent. These valves are very expensive. Furthermore, the piping of the boiler feed water must be secured by a safety valve to prevent overpressure due to the introduction of syngas through possible leaks in the preheat heat exchanger. The discharge conduit of the safety valve must be connected to the flare system of the steam reformer, but this may allow boiler feed water to enter the flare system and impair the function of the latter. The high outlay in terms of facilities also requires an additional structural height of the plant, since a fundamental problem with cooling the synthesis gas is that the pipes for the synthesis gas must be laid down smoothly, so that condensate gases formed in the synthesis can flow down. Thus, each cooling step results in additional height of the building and therefore higher building costs.

Disclosure of Invention

It is therefore an object of the present invention to provide a method and apparatus in which fewer cooling steps and therefore lower equipment and building costs are required.

This object is achieved by the invention according to the features of claims 1 and 3.

The method comprises the following steps:

a process for cooling synthesis gas produced by catalytic steam reforming of a hydrocarbon-containing feed gas, the synthesis gas having been cooled by heat exchange with boiler feed water to convert the boiler feed water to steam, with separation of water condensate formed and treatment in an apparatus for the catalytic conversion of carbon monoxide to hydrogen and carbon dioxide by steam, the process comprising the treatment steps of:

(a) heat exchanging the synthesis gas with the hydrocarbon-containing feed gas,

(b) introducing the boiler feedwater into a degasser comprising a feedwater container, wherein the boiler feedwater is not preheated by heat exchange with the syngas prior to introduction into the degasser, the boiler feedwater flowing through a dome mounted on the feedwater container into the water container in counter-current flow with steam rising from the feedwater container to effect preliminary degassing of the boiler feedwater and discharging the steam from the degasser and process with gases absorbed from the feedwater and for further treatment,

(c) heat exchanging the synthesis gas with the boiler feed water that has been degassed in the degasser,

(d) at least a portion of the syngas is heat exchanged with boiler feed water present in a feed water vessel of the degasser,

(e) the synthesis gas is heat exchanged with ambient air,

(f) separating condensate from the synthesis gas and introducing the condensate into the degasser, wherein the condensate is caused to flow through a dome mounted on the feed water vessel in countercurrent to the water vapour rising from the feed water vessel into the feed water vessel for preliminary degassing and the water vapour is discharged from the degasser and process for further treatment together with the gas absorbed from the condensate,

(g) the synthesis gas is further sent out of the process for further processing.

The apparatus of the present invention:

an apparatus for cooling a synthesis gas produced by catalytic steam reforming of a hydrocarbon-containing feed gas, the synthesis gas having been cooled by heat exchange with boiler feed water to convert the boiler feed water to steam, with separation of water condensate formed, and being treated in a device for catalytic conversion of carbon monoxide to hydrogen and carbon dioxide by steam, the apparatus comprising the following components:

(a) a heat exchanger for exchanging heat between the synthesis gas and the hydrocarbon-containing feed gas,

(b) a heat exchanger for exchanging heat between the syngas and the degassed boiler feed water,

(c) apparatus for degassing boiler feed water, comprising a feed water vessel having a heat exchanger present therein for heat exchange between synthesis gas and the boiler feed water and having at least one dome, such as a bed of random packing elements or a bed of structured packing, mounted on the feed water vessel and having internals for gas-liquid mass transfer, through which the boiler feed water and/or condensate separated from the synthesis gas is introduced into the feed water vessel,

(d) a heat exchanger for exchanging heat between the synthesis gas and ambient air,

(e) a condensate separator for separating condensate from the synthesis gas,

(f) a pipe for supplying boiler feed water produced by the boiler feed water to the degasser (c), which pipe is not part of the apparatus, wherein the pipe is arranged in such a way that it opens into the dome for supplying the boiler feed water to be degassed into a feed water container of the degasser,

(g) piping for conveying the condensate from the condensate separator (e) to the degasser (c), wherein the piping is laid in such a way that it opens to the dome for supplying the condensate to the feedwater container.

According to the invention, preheating of the boiler feed water by heat exchange with the synthesis gas before it enters the degasser is omitted, as is conventional according to the prior art. The elimination of heat exchangers required for this purpose has hitherto saved building height. Preheating of the boiler feed water is now carried out in the feed dome of the degasser by heat exchange with the water vapor rising from the feed water vessel. According to the prior art, this type of preheating is carried out only on the condensate which has been separated from the synthesis gas and recycled into the degassing device. In order to introduce the thermal energy now additionally required for the production of steam, the area of the heat exchanger installed in the feed water container is correspondingly increased. Furthermore, according to the present invention, a condensate separator for separating condensate from the syngas is not required after heat exchange between the syngas and boiler feed water. The omission of this condensate separator likewise saves building height. The subsequent air cooler, in which the synthesis gas is cooled to about 40 ℃ by heat exchange with the surrounding air, must therefore also cool the condensate remaining in the synthesis gas and must therefore be enlarged.

Detailed Description

A preferred embodiment of the invention is characterized in that the boiler feed water and the condensate separated from the synthesis gas are each introduced into the feed water vessel of the degasser via separate feed domes. The flux through each individual dome is thus smaller and preheating of the boiler feed water is improved.

Working examples

Further features, advantages and possible uses of the invention can be taken from the following description of working examples and the figures. All features described and/or depicted herein constitute the subject matter of the present invention by themselves or in any combination, irrespective of the way in which they are summarized in the claims or their back-references.

The process according to the invention is described below with the aid of FIGS. 1 and 2. The figures show:

figure 1 is a flow chart of the prior art,

FIG. 2 is a flow chart of an illustrative embodiment of the present invention.

FIG. 1:

the synthesis gas 1 is cooled to 360 ℃ by heat exchange and evaporation of boiler feed water to produce feed steam and outlet steam (not shown in fig. 1) and is introduced into heat exchanger 2. Where it transfers heat to natural gas stream 3 which is fed as feed gas to steam reforming (not shown). The synthesis gas 1 is then passed through a heat exchanger 4 and in this way heats the boiler feed water 6 which has been degassed in a degasser 5. Boiler feed water present in the feed water vessel 7 is heated by the syngas 1 through a heat exchanger 8. The performance of the heat exchanger 8 is regulated by a bypass 9 and a mechanically connected valve 10. Subsequently, fresh boiler feed water 12 is preheated by the syngas 1. The performance of the heat exchanger 11 is likewise regulated by a bypass 13 and a mechanically connected valve 14. In this way the syngas 1 is cooled to about 90 ℃. Since the syngas 1 is at elevated pressure, it may intrude into the boiler feedwater lines in the event of a leak in the heat exchanger 11, and therefore the boiler feedwater lines must be protected by a safety valve 16. The safety valve 16, when actuated, blows a gas/water mixture 17 into the flare system (not shown). The condensate 18 formed up to this point is separated in a separator 19. The synthesis gas 1 is further cooled to about 40 ℃ in an air cooler 20 and the condensate 22 is then removed in a separator 21. The syngas 1 is discharged for further processing outside the process.

Fresh boiler feed water 15 and condensates 18 and 22 are fed into degasser 5 through feed dome 23. The gas 24 discharged from the boiler feed water is discharged to the atmosphere.

FIG. 2

In this illustrated embodiment of the invention, a degassing device 5 with two feed domes 23a and b is used. The use of two domes, one for introducing fresh boiler feed water 12 and one for introducing condensate 22 separated from the syngas, makes it possible to create a larger contact area between the introduced liquid to be degassed and the steam coming from the feed water vessel in countercurrent to the liquid. According to the invention, the fresh boiler feed water 12 is not preheated by heat exchange with the synthesis gas 1 before being introduced into the degassing device 5. The heating of the synthesis gas takes place in the feed water vessel 7 only by means of the heat exchanger 8. The condensate formed here in the synthesis gas 1 is first retained in the gas and cooled together with the gas in the air cooler 20 and is then separated off and introduced into the degassing device 5. The omission of the heat exchanger 11 and the condensate separator 19 for preheating the fresh boiler feed water 12 results in a reduction in the structural height of the device for carrying out the synthesis gas cooling. In return, the heat exchanger 8 and the air cooler 20 of the degassing device 5 must be designed to have a higher performance.

Industrial applicability

The invention allows a smaller structural height and thus saves construction costs in further cooling the syngas process (as widely used in industry). Therefore, the present invention is industrially practical.

List of reference numerals

1 Synthesis gas

2 Heat exchanger

3 Natural gas

4 heat exchanger

5 degassing device

6 boiler feed water, de-aerated

7 water supply container

8 heat exchanger

9 by-pass

10 valves, mechanically connected

11 heat exchanger

12 boiler feed water, fresh

13 bypass

14 valves, mechanically connected

15 boiler feed water, fresh, preheated

16 safety valve

17 gas-water mixture

18 condensate

19 condensate separator

20 air cooler

21 condensate separator

22 condensate

23a, b feeder dome

24 exhaust gas