Method for cooling a process flow

Abstract

A method of cooling a process stream with an auxiliary stream is described, wherein the exchange of heat between the process stream and the auxiliary stream is effected in a first heat exchanger and a second heat exchanger connected downstream thereof.

Claims

1. A method of cooling a process stream with an auxiliary stream, wherein an exchange of heat between the process stream and the auxiliary stream is affected in a first heat exchanger and a second heat exchanger connected downstream of the first heat exchanger, said process comprising: a) dividing the process stream into a first substream, a second substream, and optionally one or more further substreams, b) regulating the individual flow rate of each substream by a valve associated therewith, c) cooling said first substream by heat exchange with the auxiliary stream in both the first exchanger and the second heat exchanger, to form a cooled first substream, d) mixing the second substream with the cooled first substream to form a combined substream and cooling the combined substream in the second heat exchanger to form a cooled combined substream, and e) if said process stream is divided into said one or more further substreams, mixing each of said further substreams with said cooled combined substream and cooling the resultant combined substream in the second heat exchanger after each further substream has been mixed in, wherein the flow rates of the substreams are regulated such that the temperatures of the substreams to be cooled in the second heat exchanger, on entry into the second heat exchanger, differ from one another by not more than 10 K, and wherein at least one of the valves that regulate the flow rates of the substreams is fully opened.

2. The method as claimed in claim 1, wherein the flow rates of the substreams are regulated such that the temperatures of the substreams to be cooled in the second heat exchanger, on entry into the second heat exchanger, differ from one another by not more than 5 K.

3. The method as claimed in claim 1, wherein the first heat exchanger and/or the second heat exchanger is/are plate heat exchangers.

4. The method as claimed in claim 1, wherein the process stream to be cooled is a hydrogen-rich gas, a helium-rich gas, or a neon-rich gas.

5. The method as claimed claim 1, wherein the auxiliary stream is a nitrogen-rich liquid or a nitrogen-rich gas.

6. The method as claimed in claim 2, wherein the temperatures of the substreams to be cooled in the second heat exchanger, on entry into the second heat exchanger, differ from one another by not more than 2 K.

7. The method as claimed claim 1, wherein, prior to heat exchange in the first heat exchanger and the second heat exchanger, the auxiliary stream is separated in a separator into a liquid fraction and a gas fraction, the liquid fraction is subjected to heat exchange in the second heat exchanger and then mixed with the gas fraction to form a combined auxiliary stream, and the combined auxiliary stream is then subjected to heat exchange with the first substream in the first heat exchanger.

8. A method of cooling a process stream with an auxiliary stream, wherein an exchange of heat between the process stream and the auxiliary stream is affected in a first heat exchanger and a second heat exchanger connected downstream of the first heat exchanger, said process comprising: a) dividing the process stream into at least a first substream and a second substream, b) regulating the flow rate of the first substream by a first valve, and regulating the flow rate of the second substream by a second valve, c) cooling said first substream by heat exchange with the auxiliary stream in both the first exchanger and the second heat exchanger, to form a cooled first substream, d) mixing the second substream with the cooled first substream to form a combined substream and cooling the combined substream in the second heat exchanger to form a cooled combined substream, and wherein the flow rates of the first and second substreams are regulated such that the temperatures of the substreams to be cooled in the second heat exchanger, on entry into the second heat exchanger, differ from one another by not more than 10 K, and wherein at least one of the first valve and the second valve that regulate the flow rates of the first and second substreams is fully opened.

9. A method of cooling a process stream with an auxiliary stream, wherein an exchange of heat between the process stream and the auxiliary stream is affected in a first heat exchanger and a second heat exchanger connected downstream of the first heat exchanger, said process comprising: a) dividing the process stream at least a first substream, a second substream, and a third substream, b) regulating the flow rates of said first, second and third substreams by a first valve, a second valve, and a third valve, respectively c) cooling said first substream by heat exchange with the auxiliary stream in both the first exchanger and the second heat exchanger, to form a cooled first substream, d) mixing the second substream with the cooled first substream to form a combined substream and cooling the combined substream in the second heat exchanger to form a cooled combined substream, and e) mixing the third substream with the cooled combined substream to form a further combined substream and cooling the further combined substream in the second heat exchanger to form a cooled further combined substream, wherein the flow rates of the first, second, and third substreams are regulated such that the temperatures of the substreams to be cooled in the second heat exchanger, on entry into the second heat exchanger, differ from one another by not more than 10 K, and wherein at least one of said first, second, and third valves is fully opened.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The method of the invention for cooling a process stream with an auxiliary stream and further advantageous configurations thereof will be elucidated in detail hereinafter with reference to the working examples shown in the FIGURE.

DETAILED DESCRIPTION OF THE INVENTION

(2) What are shown are two embodiments of the method of the invention for cooling a process stream with an auxiliary stream, as implementable, for example, in cryogenic helium and neon refrigeration systems, hydrogen and helium liquefiers, etc. The process stream to be cooled shall be helium hereinafter, while the auxiliary stream is a nitrogen-rich stream.

(3) The helium process stream 1 to be cooled, in accordance with a first embodiment shown in the FIGURE, is divided into two substreams 2 and 2a. The valves a and b serve to regulate the flow rates of the two substreams. The first and largest substream 2 is cooled in the heat exchangers E1 and E2 down to a temperature of about 1 K above the temperature of the auxiliary stream or liquefied nitrogen 9.

(4) A refrigeratively expanded, nitrogen-rich stream 8 is separated in the separator D into a liquid fraction 9 and a gas fraction 10. Only the liquid fraction 9 is guided through the heat exchanger E2 in countercurrent to the above-described helium substream 2 to be cooled in the heat exchanger E2 and mixed with the gas fraction 10, and the combined nitrogen-rich substream 11 is then guided through the heat exchanger E1 in countercurrent to the helium substream 2 to be cooled, before it is drawn off via conduit 12 and fed back to a circulation compressor not shown in the FIGURE.

(5) Then the second helium substream 2a is mixed into the helium substream 3 cooled down in heat exchangers E1 and E2. The helium process stream 4 formed in this way is cooled in the heat exchanger E2; the cooled helium process steam 5 is then fed to the load to be cooled and/or to at least one expansion apparatus.

(6) If there are to be at least two mixing-in operations of helium substreams into the helium substream 2 to be cooled in the heat exchangers E1 and E2, separation of the helium process stream 1 into three substreams 2, 2a and 2b is required. This variant is shown in the FIGURE by the conduit sections 2b, 5, 6 and 7 shown by dotted lines and the control valve c shown by dotted lines. In this embodiment of the method of the invention, the helium process stream 5 cooled in the heat exchanger E2 after the helium substream 2a has been mixed in is not drawn off via conduit 5. Instead, the third helium substream 2b is mixed into it and the helium process stream 6 thus formed is cooled in the heat exchanger E2 before being drawn off via conduit 7.

(7) Irrespective of whether the helium process stream 1 to be cooled is divided into two, three or more than three helium substreams 2, 2a, 2b, . . . , the flow rates of the helium substreams 2, 2a and 2b should be regulated by means of the control valves a, b and c such that the temperatures of the process streams 2, 4 and 6 to be cooled in the second heat exchanger differ from one another by not more than 10 K, preferably by not more than 5 K, especially by not more than 2 K.

(8) If control/regulation valves that are required only during particular operating states, for example in sustained operation, are provided within a refrigeration system or liquefaction plant, these may assume the function(s) of one of the above-described control valves a, b and c. By means of this embodiment, the additional outlay on required fittings or valves can be reduced.