METHOD FOR OPERATING A REACTOR FACILITY

Abstract

A method for operating a reactor facility for equilibrium-limited reactions, includes: converting starting materials to a product in a reaction chamber under a pressure p1, wherein an absorbent is loaded with the product and absorbs starting materials; discharging the loaded absorbent from the reaction chamber; lowering the pressure of the absorbent to a pressure p2 which is lower than pressure p1 and the product and starting materials are discharged in the gaseous state from the liquid absorbent; separating the gaseous products by condensation from the gaseous starting materials at the same time as a pressure p3 higher than pressure p1 is applied to the liquid absorbent, under pressure p3 into a liquid jet gas compressor in which the gaseous starting materials separated from the products are aspirated and dissolved in the liquid absorbent; and then introduced under pressure p4, which is lower than pressure p3, into the reaction chamber.

Claims

1. A method for operating a reactor system for carrying out equilibrium-limited reactions, comprising: converting starting materials into a product in a reaction chamber under a pressure p1, wherein an absorbent is laden with the product and thereby also absorbs starting materials, a) discharging the laden absorbent from the reaction chamber, and b) lowering the pressure of the absorbent to a pressure p2, wherein the pressure p2 is lower than the pressure p1, and wherein the product and starting materials are discharged in a gaseous state from the liquid absorbent and c) the gaseous products are separated from the gaseous starting materials by condensation, d) while a pressure p3 is applied to the liquid absorbent, the pressure p3 being higher than the pressure p1, and e) the liquid absorbent is conducted under the pressure p3 into a liquid-jet gas compressor, in which the gaseous starting materials separated from the products are aspirated and dissolved in the liquid absorbent and f) are then introduced into the reaction chamber under the pressure p4, which is lower than the pressure p3.

2. The method according to claim 1, wherein the pressure of the absorbent is lowered from the pressure p1 to the pressure p2 over a pressure stage p11 and method steps c) and e) are also carried out analogously for the pressure p11.

3. The method according to claim 1, wherein the pressure p1 lies between 20 bar and 250 bar.

4. The method according to claim 1, wherein the pressure p2 lies between 1 bar and 50 bar.

5. The method according to claim 2, wherein the pressure p11 is between 3 bar and 10 bar lower than the pressure p1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In the figures

[0022] FIG. 1 shows a reactor system with one-stage pressure relief,

[0023] FIG. 2 shows a reactor system with multi-stage pressure relief, and

[0024] FIG. 3 shows a cross-section through a liquid-jet gas compressor.

DETAILED DESCRIPTION OF INVENTION

[0025] FIG. 1 first shows schematically a reactor system 2 which can be operated, for example, on the basis of a reactor bundle 14. A possible mode of functioning of such a reactor system, in particular for carrying out equilibrium-limited reactions, will be discussed briefly hereinbelow. Equilibrium-limited reactions, for example the reaction of carbon dioxide and hydrogen to methanol according to the equation

CO.sub.2+3H.sub.2.fwdarw.CH.sub.3OH+H.sub.2O

[0026] have the property, determined by the system because of the energy balance, that the chemical equilibrium lies more on the left side than on the right side of the reaction equation. In the described equation, the equilibrium lies approximately 20% on the right side and 80% on the left side. This has the result that, for a successful implementation of the described equation, the resulting product, or the products methanol and water, should if possible be removed from the equilibrium between the starting materials and the products. By removing the products, the prevailing equilibrium is disturbed, with the result that the system strives to achieve the equilibrium state again and to that end products are formed.

[0027] The products are advantageously transported away by an absorbent, for example by an ionic liquid. This absorbent, continuously in through-flow by suitable process management, is also continuously laden with the products formed and discharged from the reaction zone. The absorbent 10 in the reactor system 2 thereby has the prevailing process pressure p1, wherein in the described reaction an advantageous process pressure p1 is about 80 bar. However, in addition to the products methanol and water already described, traces of starting materials, that is to say of carbon dioxide and hydrogen, also dissolve in an undesirable manner in the absorbent 10. Both are useful substances in pure form. Although the solution of the starting materials in the absorbent lies only between 2% and 5%, depending on the process management in the continuous range, this portion of the cost-intensive starting materials introduced is lost if they are not fed back to the process again. Therefore, in the further described method, a possibility is provided of feeding these starting materials 4 undesirably dissolved in the absorbent 10 to the reactor system again with a comparatively low energy outlay, and thus of recycling them.

[0028] The absorbent 10 laden as described is discharged from the reaction chamber 8 via a valve 16. If, as shown in FIG. 1, there is a reactor bundle 14, the laden absorbent 10 is discharged from each individual reaction chamber 8 of the reactor bundle 14 via a corresponding valve 16 and optionally guided via a common line to a pressure chamber 18, wherein further valves 16 can be arranged in that path. In the pressure chamber 18, the pressure p1 of the absorbent, which in the laden state is provided with the reference numeral 10′, is relieved, that is to say the pressure p1 is lowered to a pressure p2. Depending on the load state and the process management, the pressure p2 is significantly lower than the pressure p1. If the pressure p1 lies in the region of approximately 80 bar, then the pressure p2 is closer to atmospheric pressure between 1 bar and 5 bar, generally not more than 10 bar. As a result of the pressure relief of the absorbent 10′, it loses the ability to absorb products and starting materials, which thereby dissolve out of the absorbent 10′ and escape in gaseous form. The absorbent 10 so unloaded is optionally cooled in a heat exchange device or cooling device 22, and pressure is applied thereto again by a pump 24. This pressure is denoted p3, wherein p3 is higher than p2 and, as will be explained, should be higher than p1 in this embodiment. For the pressure p3, a pressure that lies in the region of 100 bar is optionally to be chosen.

[0029] In a parallel process step, the product 6 which has escaped in the form of a gas, and which is present in gaseous form still mixed with the starting material 4 also discharged from the absorbent 10, is cooled in a condensation device 20, wherein the substances water and methanol, which in this case constitute the products 6, condense in the cooling device. The starting materials 4, that is to say the carbon dioxide and the hydrogen, do not condense in conventional condensation devices and remain in the gaseous phase. This is a suitable separating method for separating the undesired starting materials present and the products 6 of value.

[0030] In the absence of the attempt to make the production process as cost-effective as possible, the starting materials 4 could then be discharged into the environment, but it would also be possible to compress them by means of a compressor to such an extent that they could be fed under the process pressure p1 to the reaction chamber 8 again. However, since the starting materials 4 separated from the condensation device 20 are gases, a very large amount of energy would have to be introduced in order to compress these gases to the pressure of about 80 bar, that is to say the pressure p1, again. The outlay in terms of energy which would be required therefor would correspond approximately, depending on the price level of the raw materials, to the value which the raw materials in any case already have, so that it would also be similarly economical or uneconomical to freely release the starting materials 4 from the condensation device 20 into the environment.

[0031] It is provided in the present method to supply a so-called liquid-jet gas compressor 12 to the absorbent 10, which now has the pressure p3. Such a liquid-jet gas compressor functions similarly to a water-jet pump in the form that a liquid is conducted at high pressure through a nozzle and thereby aspirates a gas via a further supply line. A liquid-jet gas compressor 12 is shown schematically in FIG. 3. This gas compressor has substantially three openings, one of the openings is denoted V.sub.F, which stands for a volume flow rate V of the absorbent 10. The absorbent 10 has a pressure p3 on entering the gas compressor 12 and a pressure p4 at the exit, which is shown on the right-hand side. At the exit, the absorbent 10 has the reference numeral 10″, the volume flow rate is denoted V at this point. The pressure p4 is lower than the pressure p3. Through a third opening, gas with the volume flow rate V.sub.G (G for gas) is introduced under a pressure pG into the gas compressor 12. This gas contains or consists substantially of the separated starting materials 4. The pressure pG is not substantially higher than atmospheric pressure, which has the result that the pressure p3 is reduced to the pressure p4 when the gas in the form of the starting materials 4 is mixed with the absorbent 10 in the gas compressor 12.

[0032] The pressure p4 is then, as already mentioned, correspondingly lower than the pressure p3, wherein the system is correspondingly so designed that the pressure p4 is close to the pressure p1, so that the absorbent 10″ laden with the starting materials can if possible be fed into the reaction chamber 8 under the pressure p1 again without a complex pressure correction.

[0033] The advantage of the described method is that the discharged starting material 4 or the starting materials 4 are present in gaseous form, and under the pressure pG, which lies close to atmospheric pressure, do not require substantial working up and can be mixed with the absorbent 10 again. An appreciable energy input for the starting material gas 4 is thus not necessary. Only an energy input for increasing the absorbent 10 to a pressure p3, which is slightly higher than the process pressure p1, is required. The additional energy outlay accordingly consists merely in applying the pressure difference Δp between p3 and p4 (Δp=p3−p4). Since the absorbent 10 is a liquid, the energy input for a pressure difference between, for example, 80 bar and 90 bar or 100 bar is comparatively small. The energy input into the absorbent 10 for producing Δp is at least significantly smaller than the energy input which would be necessary to increase the starting material 4 in gaseous form from atmospheric pressure to the pressure p1. This saved energy outlay is ultimately the contribution which allows the system to become more economical compared with the prior art.

[0034] If the pressure difference between p3 and p4 in the liquid-jet gas compressor 12 were to be reduced, the gas compressor 12 could be designed more simply, which likewise means a cost saving. In other words, a smaller Δp leads to a more advantageous form of the gas compressor 12. This results in the form shown according to FIG. 2. This consists in lowering the pressure p1 of the absorbent 10 or 10′ gradually, stepwise via one or more cascades to the pressure p2. These intermediate pressures, which each require a separate pressure chamber 18 or 118, 218, 318 and 418, lie between p1 and p2, and these intermediate pressures are denoted p11, p12, p13 and p14. The pressure drop between the respective pressure chambers 18 or 118 or 218 etc. is advantageously approximately 5 bar, so that a portion of the products 6 or also of the starting materials 4 is discharged from the absorbent 10′ in each pressure chamber 18, 118, 218, etc. Complete discharge of the absorbent 10′ does not take place in any of the mentioned pressure chambers 18, merely partial discharge. Only in the last pressure chamber, according to this nomenclature 418, is the absorbent 10′ lowered to the final pressure and relief pressure p2 and discharged completely there.

[0035] The process steps already described of condensing the products 6 in a condensation device 20 and feeding the uncondensed starting materials 4 into the respective liquid-jet gas compressor takes place in an analogous manner, as already described in FIG. 1. In principle, correspondingly more individual components are required in this cascaded arrangement than in the representation according to FIG. 1, but, on the other hand, the liquid-jet gas compressor 12 and the pump 24 can be configured significantly more advantageously than the gas compressor 12 and the pump 24 according to FIG. 1. Which method is ultimately the more economical depends to a very large extent on the process management and on the individual costs of the individual process components.

LIST OF REFERENCE SIGNS

[0036] 2 reactor system [0037] 4 starting materials [0038] 6 products [0039] 8 reaction chamber [0040] 10 absorbent [0041] 10′ laden absorbent [0042] 10″ absorbent [0043] 12 liquid-jet compressor [0044] 14 reactor bundle [0045] 16 valves [0046] 18 pressure chamber 118, 218, 318, 418 [0047] 20 condensation means [0048] 22 cooling device [0049] 24 pump [0050] V.sub.F volume flow rate absorbent inlet [0051] V.sub.G volume flow rate gases [0052] V volume flow rate mixture [0053] p1 pressure [0054] p2 pressure [0055] p3 pressure [0056] p4 pressure [0057] p11 pressure