METHOD AND DEVICE FOR COOLING A SYNTHESIS GAS STREAM

The invention relates to a method for carrying out a process with at least one heat-consuming process step, a first fluid containing acid gases and water vapor occurring in the process being cooled indirectly against a second fluid with the formation of an acid condensate.

The invention also relates to a device for performing the

method according to the invention.

The fact that one fluid is cooled indirectly against another fluid is to be understood in such a way that heat is transferred between the two fluids via a heat-conducting wall, which separates the two fluids from one another and prevents a mass transfer.

Methods and devices of the generic type are used, for example, in the thermochemical generation of synthesis gas or hydrogen. Here, an insert containing carbon or hydrocarbons is used for example

Steam reforming or partial oxidation as well as water gas shift converted to a hot synthesis gas containing water vapor and acid gases, which is then cooled to condense water and enable the acid gases to be separated off in a subsequent gas scrubbing process. Since some of the acid gases dissolve in the condensed water and form an acid together with it, the apparatus used for cooling the crude synthesis gas must be made from an acid-resistant material, which is correspondingly expensive.

In order to use the heat contained in the raw synthesis gas economically, it is used according to the state of the art to generate clean steam, which is typically given off to an external consumer at a pressure of 5-100 bar as so-called export steam for credit. For this purpose, demineralized water (hereinafter DMW for short) is degassed and then at a pressure between 30 and 120 bar in a heat exchanger called a KSW preheater, indirectly against the raw synthesis gas to be cooled from approx. 100 ° C to just below it

Warmed to boiling temperature. After heating, the degassed DMW evaporates

the expert knows as boiler feed water (KSW for short) in a steam drum to export steam.

To degas the DMW, a degasser is used with one above one

Includes separating column arranged in the bottom space. The DMW to be degassed, which is fed in at the top of the separating column operated with a slight overpressure, is brought into intensive contact on its way downwards with the stripping steam which is led in countercurrent and which is a relaxed part of the clean steam produced for export. While the degassed DMW collects in the bottom space of the degasser, the stripping steam loaded in particular with oxygen, but also with other gases separated from the DMW, is drawn off at the top of the column and disposed of into the atmosphere. The part of the clean steam diverted as stripping steam is thus lost and can no longer be used economically as export steam.

Usually at least one additional heat exchanger is arranged downstream of the KSW preheater in order to use low-temperature heat of the crude synthesis gas economically, for example by making it available to a heat-consuming step within the process. The disadvantage here, however, is the increased pressure loss in the flow path of the crude synthesis gas. Because the additional heat exchanger, like the KSW preheater, comes into contact with acidic condensate, it too has to be made from a material such as stainless steel that is sufficiently acid-resistant under operating conditions. Around

To avoid incorrect distribution of the crude synthesis gas on the exchange surfaces, the additional heat exchanger is either located at a lower level than the KSW preheater, so that sufficient pressure is available to distribute the condensate in a controlled manner, or it is between the KSW preheater and a condensate separator arranged on the additional heat exchanger, which ensures that only one gas phase flows onto the exchange surfaces. In both variants, long and expensive stainless steel lines are required, which

Impair the profitability of the synthesis gas or hydrogen generation.

The object of the present invention is therefore to provide methods and devices of the generic type which are suitable for overcoming one or more of the disadvantages of the prior art.

In terms of the method, this object is achieved according to the invention in that the first fluid is cooled in at least two successive steps, between which the second fluid indirectly receives heat for use in the

heat-consuming process step is withdrawn.

With the method according to the invention, a larger part of the heat contained in the first fluid than in the prior art can be used economically without an additional heat exchanger having to be integrated into the flow path of the first fluid.

A particularly advantageous variant of the method according to the invention provides for a chemically neutral second fluid to be used and the heat intended for use in the heat-consuming process step to be transferred to a likewise chemically neutral medium. A substance should be considered chemically neutral if, under the operating conditions of the process, it is neither acidic nor alkaline or at least significantly less aggressive than the acidic condensate formed from the first fluid. Under these conditions, a heat exchanger can be used for the transfer of heat between the two media, which is inexpensively manufactured from a material that does not need to be acid or alkali-resistant.

The process carried out according to the invention is preferably a synthesis gas generation in which a carbon-containing insert is involved

is thermochemically converted to an acid gas and as an intermediate

To obtain hot raw synthesis gas containing water vapor as the first fluid, which is cooled to obtain clean export steam against DMW as the second fluid.

The DMW is particularly preferred between the two steps of

Raw synthesis gas cooling removes heat in order to use it to generate stripping steam, which is used for degassing DMW. For this purpose, heat is expediently withdrawn from the heated DMW via a heat exchanger, which is arranged in the sump chamber of a degasser operated with only a slight excess pressure and is referred to as an intercooler, and indirectly to the already degassed and in the sump chamber

transferred collected DMW, which evaporates in the process and rises as stripping steam in a separating column (DMW separating column) of the degasser arranged above the sump. At the top of the column, the DMW to be degassed is fed in and the stripping steam laden with separated gases is released into the atmosphere, while degassed DMW is withdrawn from the bottom space, pressurized and used to cool the crude synthesis gas.

According to the invention, the DMW can either be degassed before it is against

Raw synthesis gas is heated or only after heat has been withdrawn from it to generate the stripping steam used for DMW degassing.

In the case of thermochemical synthesis gas generation, so-called process steam is generated from the condensate occurring in the process (process condensate), which, due to its low purity, cannot be passed on to an external consumer and is therefore used within the process. Like the DMW, the process condensate must also be degassed before it is evaporated, for which purpose it is treated with stripping steam at a slight excess pressure in a separate separation column (PK separation column), which, according to the state of the art, is also a relaxed part of the clean, for the export of steam produced.

Developing the method according to the invention, however, it is proposed to remove heat from the DMW between the two steps for cooling the crude synthesis gas in order to use it to generate stripping steam which is used in the

Degassing of the process condensate intended for process steam generation is used. For this purpose, heat is particularly preferably withdrawn from the DMW via the intercooler arranged in the sump space assigned to the DMW separating column and transferred indirectly to DMW collected there and already degassed, which is evaporated and transferred as stripping steam to the PK separating column.

The invention further relates to a device for carrying out a process with at least one heat-consuming process step, having a

Cooling device with which a first fluid, which occurs in the process and contains acid gases and water vapor, can be cooled indirectly against a second fluid with the formation of an acid condensate.

In terms of the device, the object is achieved according to the invention in that the cooling device comprises two serially arranged cooling stages through which the two fluids can each flow, between which a heat exchanger called an intercooler is arranged, via which heat can be extracted indirectly from the second fluid and fed to the heat-consuming process step .

Preferably, the device according to the invention for performing a

Synthesis gas generation is suitable, in which a carbon-containing feed can be thermochemically converted in order to obtain as an intermediate a hot synthesis gas containing hydrogen, carbon monoxide, acid gases and water vapor as the first fluid, which can be cooled in the cooling device to obtain clean export steam against DMW as the second fluid .

The cooling device particularly preferably comprises the device according to the invention

Device a degasser for degassing DMW intended for export steam production. The degasser comprises a separating column (DMW separating column) arranged above a sump space, the intermediate cooler being arranged in the sump space of the degasser so that degassed DMW that collects in the sump space can be converted into stripping steam for the degassing of DMW against the DMW to be cooled in the intermediate cooler .

The degassing device is expediently arranged in the flow path of the DMW in such a way that the degassing of the DMW can be carried out upstream of the cooling device. However, an arrangement is also possible in which the DMW after heating in the first

Cooling stage downstream of the intercooler and upstream of the second cooling stage can be degassed.

The device according to the invention can also have a further degasser with which condensate occurring in the process can be degassed with the aid of stripping steam before it is further processed into process steam. In this case, an expedient development of the invention provides a fluidic connection between the two degassers, so that DMW steam generated according to the invention can be introduced as stripping steam into the separating column (PK separating column) of the condensate degasser in the bottom space of the DMW degasser. The two degassers can each be designed as independent devices with a separating column and sump chamber and only be connected by a stripping steam line. A construction is also conceivable in which the two degassers are arranged above a jointly usable sump space, the PK separation column having one at its lower end

Has chimney bottom, which prevents the entry of degassed, but not suitable for the generation of clean export steam condensate in the sump space, but allows the passage of stripping steam from the sump space. The respective

Column internals can be arranged in separate housings or directly next to one another and only separated from one another by a flat wall in a common housing. It is also conceivable to arrange the internals of the PK separating column in a common housing directly above those of the DMW separating column, with a chimney tray also closing off the PK separating column at the bottom in this variant.

In the following, the invention will be explained in more detail with reference to three exemplary embodiments shown schematically in FIGS.

FIG. 1 shows a process with a heat-consuming process step in which a hot first fluid is cooled according to the invention.

FIGS. 2 and 3 each show a section from a synthesis gas production in which hot synthesis gas, which occurs as an intermediate product, is cooled according to the invention while generating stripping steam. In the two figures, the same parts of the plant and process streams are identified by the same reference numbers.

A feedstock is fed to the process P in FIG. 1 via line 1, from which a first fluid 2 containing acid gases and water vapor is obtained as an intermediate product in process step A. To condense out water and then

To be able to separate acid gases, the first fluid 2 is fed to the cooling device B, where it is indirectly cooled in a first cooling step in the heat exchanger E1 against a second fluid 3. While the second fluid leaves the heat exchanger E1 warmed up via line 4 and is processed into a product 5, for example, in process step C, the cooled first fluid 6 is transferred to the

Heat exchanger E2 passed on, where it is cooled down to below the water dew point against the cold first fluid supplied from the outside via line 7. Some of the acid gases dissolve in the resulting condensate, so that an acidic two-phase mixture of substances leaves the heat exchanger E2 via line 8, which is passed on to process step D, where the product 9 is obtained in particular by separating water and acid gases. The one in the heat exchanger E2

Heated second fluid 10 is withdrawn in the intercooler E3, which heat is used in the heat-consuming process step F. For renewed heating, the second fluid cooled in the intercooler E3 is demineralized via line 3

Heat exchanger E1 supplied.

In FIG. 2, hot synthesis gas comprising water and acid gases at a temperature between 370 and 150 ° C. is fed via line 11 to a first heat exchanger E1 1, where in a first step it is indirectly against degassed DMW 12 to between 300 and 120 ° C lying temperature is cooled. While the degassed DMW 13 exits the heat exchanger E1 1 at a temperature just below its boiling point, in order to be subsequently evaporated into export steam in a steam drum (not shown), the crude synthesis gas 14, which was cooled in the first step, is also counteracted in a second heat exchanger E12 degassed DMW 15 further withdrawn energy, with water condensing out and a two-phase mixture 16 is formed, which in the

Separation device D into a largely anhydrous synthesis gas 17 and acid

Process condensate 18 is separated. The degassed DMW 19, which has been warmed up against the raw synthesis gas 14 in the second heat exchanger E12, emits part of its heat again via the intercooler E13 before it is transferred to the first via line 12

Heat exchanger E1 1 is supplied. The intercooler E13, designed as an evaporator, is in the sump space S1 of the DMW degasser, which is operated with a slight overpressure

G1 arranged and surrounded by already degassed DMW 20, from which stripping steam is produced by the supplied heat. Part 21 of the stripping steam rises in the separating column T1 of the DMW degasser G1 arranged above the bottom space S1 and is brought into intensive contact with the DMW 22 supplied at the top of the DMW separating column T1, which is degassed in the process. The stripping steam loaded with the gases separated from the DMW 22 is withdrawn from the top of the DMW separation column T1 and fed to a disposal (not shown), while the degassed DMW is withdrawn via line 24 from the sump S1 of the DMW degasser and after increasing the pressure in the pump P is fed to the second heat exchanger E12 as coolant 15.

The process condensate 18 is also degassed, for which it is fed via the top of the separating column T2 of the PK degasser G2, in which it flows downwards and is brought into intensive contact with the stripping steam supplied via line 25 from the sump S1 of the DMW degasser G1 . While with those from the

Stripping steam 26 laden with process condensate 18 is withdrawn from the top of the PK separating column T2 for its disposal, the degassed condensate 27 can be withdrawn from the bottom S2 of the PK degasser G2 and subsequently converted to process steam (not shown).

In FIG. 3, DMW 22 is first warmed in heat exchanger E12 against the crude synthesis gas 14, which has already been cooled in a first step in heat exchanger E11, before it is fed to intermediate cooler E13 via line 28 to give off heat. The intercooler E13, designed as an evaporator, is arranged in the sump space S of the degasser G operated with a slight excess pressure and is surrounded by degassed DMW 20, from which stripping steam is produced by the heat supplied via the DMW 28. A first part 21 of the stripping steam rises in the DMW separating column T1 arranged above the sump space S, at the top of which the im

Intercooler E13 cooled DMW 29 is fed to be degassed on its way down with the help of stripping steam 21. The stripping steam 21 loaded with the gases separated off from the DMW 29 is drawn off from the top of the DMW separating column T1 and fed to a disposal (not shown).

For its degassing, the process condensate 18 is fed via the top of the PK separating column T2 ', which is also arranged above the bottom space S of the degasser G.

On the way down, the process condensate is brought into intensive contact with stripping steam 25, which flows up through the chimney bottom K from the sump space S. While the stripping steam loaded with the gases separated from the process condensate 18 is discharged from the top of the PK separating column T2 'for disposal, the degassed condensate 27 can be withdrawn from the chimney tray K and subsequently converted into process steam (not shown).

Claims

1 . Method for carrying out a process (P) with at least one

heat-consuming process step (F), wherein a first fluid (2) occurring in the process and containing acid gases and water vapor is cooled indirectly with the formation of an acid condensate against a second fluid (7), characterized in that the first fluid (2) is divided into at least two

successive steps (E1, E2) is cooled, between which heat is indirectly withdrawn from the second fluid (10) for use in the heat-consuming process step (V).

2. The method according to claim 1, characterized in that a chemically

neutral second fluid (7) used and for use in the

heat-consuming process step (F), certain heat is transferred to a likewise chemically neutral medium.

3. The method according to any one of claims 1 or 2, characterized in that the process (P) is a synthesis gas generation in which a carbon-containing insert (1) is thermochemically converted to a hot synthesis gas containing water and acid gases ( 11) as the first fluid to be obtained, which is used to obtain clean export steam against

demineralized water (DMW) (22) is cooled as the second fluid.

4. The method according to claim 3, characterized in that heat is withdrawn from the DMW between the two steps of raw synthesis gas cooling in order to use it to generate stripping steam (21) which is used for degassing DMW (22).

5. The method according to any one of claims 3 or 4, characterized in that the DMW between the two steps for cooling the crude synthesis gas

Heat is withdrawn in order to use it to generate stripping steam (25), which is used in the degassing of process condensate (18).

6. Device for carrying out a process (P) with at least one

heat-consuming process step (F), comprising a cooling device (B) with which a first fluid (2) containing acid gases and water vapor occurring in the process can be cooled indirectly against a second fluid (7) with the formation of an acid condensate, characterized in that the Cooling device (B) two serially arranged, each through which the two fluids can flow

Cooling stages (E1, E2), between which a heat exchanger (E3) called an intercooler is arranged, via which heat can be extracted indirectly from the second fluid (10) and fed to the heat-consuming process step (F).

7. The device according to claim 6, characterized in that it is suitable for carrying out a synthesis gas production in which a carbon-containing insert (1) can be thermochemically converted in order to obtain a hot synthesis gas (11) containing acid gases and water vapor as the first fluid, which can be cooled in the cooling device (B ', B “) to obtain clean export steam against DMW (22) as the second fluid.

8. The device according to claim 7, characterized in that the

Cooling device (B ', B ") comprises a degasser (G1, G) for degassing DMW (22) intended for export steam production, the

Intercooler (E13) is arranged in the sump space (S1, S) of the degasser (G1, G) so that degassed DMW that collects in the sump space (S1, S) against the DMW (19, 28) to be cooled in the intercooler (E13) Stripping steam (21) for degassing DMW (22) can be implemented.

9. Device according to one of claims 7 or 8, characterized in that they have a PK separation column (T2, T2 '), with the process condensate (18) occurring during the cooling of the crude synthesis gas (1 1) with the aid of

Stripping steam (25) can be degassed before it is further processed into process steam, the PK separating column (T2, T2 ') in terms of flow with the

Bottom space (S1, S) of the degasser (G1, G) is connected, so that DMW steam generated there from degassed DMW (20) can be introduced as stripping steam (25) into the PK separating column (T2, T2 ').