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WO-2026093433-A1 - A PROCESS FOR DEGASSING WATER

WO2026093433A1WO 2026093433 A1WO2026093433 A1WO 2026093433A1WO-2026093433-A1

Abstract

The invention relates to a process for degassing water used in steam production, the process comprising: (a) heating a feed water stream (9) to a temperature in a range from 60 to 95 °C in a first heat exchanger (11) and feeding the heated feed water stream (9) into a degassing apparatus (13), which is operated at a pressure of 0.15 to 0.8 bar(abs), so that a part of the feed water stream evaporates due to expansion when entering the degassing apparatus or feeding a feed water stream (9) into a degassing apparatus (13), which is operated at a pressure of 0.15 to 0.8 bar(abs) and in which the feed water is heated to a temperature in a range from 60 to 95 °C, so that a part of the water evaporates; (b) withdrawing a gas stream (15) and a degassed water stream (21) from the degassing apparatus (13); (c) optionally compressing the degassed water stream (21) to a pressure in a range from 0.25 to 30 bar(abs).

Inventors

  • RHEINFURTH, Martin

Assignees

  • BASF SE

Dates

Publication Date
20260507
Application Date
20251030
Priority Date
20241030

Claims (15)

  1. 1 . A process for degassing water used in steam production, the process comprising: (a) heating a feed water stream (9) to a temperature in a range from 60 to 95 °C in a first heat exchanger (11) and feeding the heated feed water stream (9) into a degassing apparatus (13), which is operated at a pressure of 0.15 to 0.8 bar(abs), so that a part of the feed water stream evaporates due to expansion when entering the degassing apparatus or feeding a feed water stream (9) into a degassing apparatus (13), which is operated at a pressure of 0.15 to 0.8 bar(abs) and in which the feed water is heated to a temperature in a range from 60 to 95 °C, so that a part of the water evaporates; (b) withdrawing a gas stream (15) and a degassed water stream (21) from the degassing apparatus (13); (c) optionally compressing the degassed water stream (21) to a pressure in a range from 0.25 to 30 bar(abs).
  2. 2. The process according to claim 1 , wherein the gas stream (15) is cooled in a condenser (3), in which water condenses from the gas stream (15), the condensed water (7) is separated from the gas stream (15) and mixed with fresh water (1) to obtain the feed water stream (9).
  3. 3. The process according to claim 2, wherein the fresh water (1) is preheated in the condenser (3) by heat transfer from the gas stream (15) and the preheated fresh water (5) is mixed with the condensed water (7) upstream the first heat exchanger (11) to obtain the feed water stream (9).
  4. 4. The process according to claim 3, wherein the gas stream (15) is cooled to a temperature in a range from 20 to 40 °C by heat exchange with the fresh water (1).
  5. 5. The process according to claim 1 , wherein the gas stream (15) is cooled in a condenser (3) to a temperature in a range from 50 to 80 °C to condense water, and the condensed water (7) is combined with the feed water stream (9) downstream the first heat exchanger (11).
  6. 6. The process according to any of claims 1 to 5, wherein 0.05 to 2.0 wt% of the feed water stream (9) are evaporated in the degassing apparatus (13).
  7. 7. The process according to any of claims 1 to 6, wherein gases being removed from the feed water stream (9) comprise at least one of nitrogen, oxygen, carbon dioxide, argon, and ammonia. 240138W001 14
  8. 8. The process according to any of claims 1 to 7, wherein the feed water stream (9) comprises demineralized water.
  9. 9. A process for producing steam, comprising: (I) degassing water in a process according to any of claims 1 to 8; (ii) feeding the compressed degassed water stream (21) obtained in step (d) into a flash apparatus (23), in which the degassed water stream (21) is expanded to a pressure in a range from 0.1 to 0.4 bar(abs), so that a part of the water evaporates to form steam (31) or evaporating the degassed water stream obtained in step (c) in an evaporator (47) to obtain steam (31); (ill) compressing the steam (31) in at least one compressor (33, 35).
  10. 10. The process according to claim 9 wherein a liquid water stream (25) is withdrawn from the flash apparatus (23), heated to a temperature in a range from 60 to 95 °C and compressed to a pressure in a range from 0.25 to 30 bar(abs) and the thus obtained heated liquid water stream (29) is returned into the flash apparatus (23).
  11. 11 . The process according to claim 10, wherein the heated liquid water stream (29) is combined with the degassed water stream (21) before being fed into the flash apparatus (23).
  12. 12. The process according to any of claims 9 to 11, wherein the feed water stream (9) is heated in the first heat exchanger (11) by heat transfer from a heating medium (41), wherein after having passed the first heat exchanger (11), the heating medium (41) flows through a second heat exchanger (27), in which the liquid water stream (25) is heated by heat transfer from the heating medium (41).
  13. 13. The process according to claim 11 or 12, wherein the liquid water stream (25) is preheated in the condenser (3) by heat transfer from the gas stream (15), before being fed into the second heat exchanger (27).
  14. 14. The process according to any of claims 11 to 13, wherein the heating medium (41) is water or a condensable gas.
  15. 15. The process according to any of claims 9 to 14, wherein the degassed water stream (21) and the liquid water stream (25) are compressed to a pressure in a range from 0.25 to 30 bar(abs) before being combined.

Description

240138W001 A process for degassing water Description The invention relates to a process for degassing water used in steam production and a process for producing steam using the degassed water. Steam is a major thermal energy carrier in industry, for example in chemical industry. Conventional fossil steam production comes along with significant carbon dioxide emissions. Heat pumps are considered to minimize the carbon dioxide emissions with reduced demand of renewable power compared to electric boilers. Besides energy, the main utility for steam production is demineralized and degassed water. Widely used thermal degassing at slightly above 100 °C and 1 bar deploys steam. Using steam from the open loop heat pump for thermal degassing reduces the system's efficiency. Membrane degassing with sweep gas like nitrogen leaves inert gas in the steam, which can affect the functionality of equipment like heat exchangers. The water temperature needs to be below 50 °C because of membrane degrading. Conventional vacuum degassing at temperatures below 25 °C uses steam to reach pressures below 40 mbar(abs). Due to the very low pressure, the equipment choice is limited, its size is large and/or expensive. An open loop lithium bromide heat pump system with a degassing apparatus is shown in CN-A 109028644 or in CN- U 208588109. Further degassing processes are described in Hans Gunter Heitmann, "Praxis der Kraftwerk-Chemie”, Vulkan-Verlag Essen, 2nd edition, 1997, pages 462 to 468. Therefore, it was an object of the present invention to provide a process for degassing water used in steam production and a process for producing steam, which are more energy efficient and in which an equipment having a smaller size and being less expensive can be used. This object is achieved by a process for degassing water used in steam production, the process comprising: (a) heating a feed water stream to a temperature in a range from 60 to 95 °C in a first heat exchanger and feeding the feed water stream into a degassing apparatus, which is operated at a pressure of 0.15 to 0.8 bar(abs), so that a part of the feed water stream evaporates due to expansion when entering the degassing apparatus or feeding a feed water stream into a degassing apparatus, which is operated at a pressure of 0.15 to 0.8 bar(abs) and in which the feed water is heated to a temperature in a range from 60 to 95 °C, so that a part of the water evaporates; (b) withdrawing a gas stream and a degassed water stream from the degassing apparatus; 240138W001 2 (c) optionally compressing the degassed water stream to a pressure in a range from 0.25 to 30 bar(abs). Heating the feed water stream for degassing to a temperature in a range from 60 to 95 °C needs less energy than heating to a temperature above 100 °C. Compared to cold degassing, a pressure in a range from 0.15 to 0.8 bar(abs) is sufficient for degassing at a temperature in this range. Hence, less compression energy and smaller and, thus, less expensive equipment can be used for setting the pressure and degassing. Degassing at a temperature in the range from 60 to 95 °C has the additional advantage that no steam is used which has to be generated with high energy consumption. Depending on the origin of the water to be used and to be degassed, gases that may be contained in the water are at least one of nitrogen, oxygen, argon, and ammonia. Nitrogen, oxygen, and argon generally originate from air that is solved in the water. While ammonia is used for conditioning of the feed water to prevent corrosion of the steel equipment. The ammonia will partially remain in the degassed water because it is chemically dissolved. This is beneficial for the steam production. In a first embodiment, the water is heated to a temperature in a range from 60 to 95 °C, more preferred to a temperature in a range from 65 to 90 °C and particularly to a temperature in a range from 70 to 85 °C in a first heat exchanger and after heating the feed water stream in the first heat exchanger, the feed water stream is fed into the degassing apparatus, which is operated at a pressure in a range from 0.15 to 0.8 bar(abs), more preferred in a range from 0.2 to 0.6 bar(abs) and particularly in a range from 0.25 to 0.5 bar(abs). The first heat exchanger may be any heat exchanger suitable for heating water, known to a skilled person. Suitable heat exchangers for example are heat exchangers, in which the water is heated by indirect heat transfer from a heating medium. Preferably, the heat exchanger is a heat exchanger in which the water is heated by indirect heat transfer, for example a tube-and-shell heat exchangers, plate heat exchangers, spiral heat exchangers. Arrangements with counter current flow, which preferably can be archived in a plate heat exchanger, are best suited to reach highest temperature of the feed water while exploiting the heat source to lowest temperatures. With this, the volume flow from the heat source for pre-heating of the feed water ca