Title of Invention

PROCESS OF HEAT INTERCHANGE OF PREGANANT LIQUOR

Abstract

The present invention discloses a process of heat interchange of a pregnant liquor, when using a plate type heat interchanger to heat interchange a pregnant liquor (a hot fluid), directly feeding the pregnant liquor (the hot fluid) to be cooled into the plate type heat interchanger, directly feeding a secondary wash liquor and a precipitation spent liquor from alumina process or only the precipitation spent liquor as a cold fluid into the plate type heat interchanger to interchange heat with the pregnant liquor (the hot fluid), and then using recycling cooling water as a cold fluid to interchange heat with the pregnant liquor (the hot fluid) whose temperature is already reduced. According to the present invention, the secondary wash liquor or precipitation spent liquor from alumina process as a cold fluid and the pregnant liquor (the hot fluid) to be cooled are both directly fed into the plate type heat interchanger for heat interchange. So, the costly and hard-to-manufacture reversing valve is omitted, thus evading the difficulty in manufacturing the reversing valve, the process becomes simpler, the pipeline is saved, arrangement/layout is simplified and maintenance is rendered easier and more convenient.

Full Text

Process of Heat Interchange of Pregnant Liquor Technical Field The present invention relates to a process of heat interchange of pregnant liquor (sodium aluminate solution in alumina process), particularly to a process of heat interchange of pregnant liquor without using a reversing valve. Background Art At present, in the prior art, heat of pregnant liquor of a hot fluid is generally interchanged by using a cold fluid with help of a plate type heat interchanger and a reversing valve. However, there is a high technology requirement for manufacture of the reversing valve so that it is very difficult to manufacture the reversing valve, which not only makes the current processes hard to fulfil but also causes many problems such as a high production cost and a high operation cost, a complicated pipe structure and difficult maintenance. Summary of the Invention The purpose of the present invention is to provide a process of heat interchange of pregnant liquor that does not employ a reversing valve, requires a less production and operation cost and is easy to fulfil, so as to overcome the above-mentioned drawbacks in the prior art. The present invention is fulfilled as follows: a plate type heat interchanger is used for heat interchange of the pregnant liquor of a hot fluid, wherein the pregnant liquor (the hot fluid) to be cooled is directly fed into the plate type heat interchanger, a secondary wash liquor and a precipitation spent liquor from alumina process or only the precipitation spent liquor are or is directly fed as a cold fluid into the plate type heat interchanger to interchange heat with the pregnant liquor (the hot fluid), and then recycling cooling water is used as a cold fluid to interchange heat with the pregnant liquor (the hot fluid) whose temperature is already reduced. Three-stage four-set plate type heat interchangers can be used for heat interchange of the pregnant liquor as follows: first, directly feeding pregnant liquor (the hot fluid) into a first stage plate type heat interchanger (1), directly feeding a secondary wash liquor (a cold fluid) from alumina process into said first stage plate type heat interchanger (1) to interchange heat with the pregnant liquor (the hot fluid), then allowing the pregnant liquor to enter a second-stage first-set plate type heat interchanger (2) and a second-stage second-set plate type heat interchanger (3), allowing the precipitation spent liquor (the cold fluid) from alumina process to directly enter said second-stage second-set plate type heat interchanger (3) and interchange heat with the pregnant liquor via said second-stage first-set plate type heat interchanger (2), if temperature of the pregnant liquor (the hot fluid) reaches the process requirement, it enters next workshop through a bypass (5) provided beside a third stage heat interchanger; if the temperature of the pregnant liquor (the hot fluid) is higher than a temperature required by the process, it enters a third stage plate type heat interchanger (4) and interchanges heat with the recycling water (the cold fluid) and then enters the next workshop. Two-stage three-set plate type heat interchangers can be used for heat interchange of the pregnant liquor (the hot fluid) as follows: first, directly feeding pregnant liquor (the hot fluid) into a first-stage first-set plate type heat interchanger (6) and a first-stage second-set plate type heat interchanger (7), allowing the precipitation spent liquor (the cold fluid) from alumina process to directly enter said first-stage second-set plate type heat interchanger (7) and interchange heat with the pregnant liquor via said first-stage first-set plate type heat interchanger (6), if the pregnant liquor (the hot fluid) reaches the process requirement, it enters next workshop through a bypass (9) provided beside a second stage heat interchanger; if the temperature of the pregnant liquor (the hot fluid) is higher than a temperature required by the process, it enters a second stage plate type heat interchanger (8) and interchanges heat with the recycling water (the cold fluid) and then enters the next workshop after reaching the requirement. According to the above technical solutions of the present invention, the secondary wash liquor and precipitation spent liquor from alumina process or only the precipitation spent liquor and the pregnant liquor (the hot fluid) to be cooled are all directly fed into the plate type heat interchanger for heat interchange. So, the costly and hard-to-manufacture reversing valve is omitted in the heat interchange process of the present invention, thus evading the difficulty in manufacturing the reversing valve, the process becomes simpler, the pipeline is saved, arrangement/layout is simplified and maintenance is rendered easier and more convenient. Therefore, as compared with the prior art, the present invention has advantages such as a simpler process, easy implementation and saving of investment as well as lower production cost and operation cost and easy maintenance. Brief Introduction of Drawings Fig. 1 is a schematic drawing/sketch showing the process of heat interchange of pregnant liquor by using three-stage four-set plate type heat interchangers according to the present invention. Fig.2 is a schematic drawing/sketch showing the process of heat interchange of pregnant liquor by using two-stage three-set plate type heat interchangers according to the present invention. Preferred Embodiments According to the embodiments of the present invention, conventional plate type heat interchangers in the prior art and recycling cooling water as a cold fluid are used for heat interchange of the pregnant liquor (the hot fluid): the pregnant liquor (the hot fluid) to be cooled is directly fed into the plate type heat interchanger, a secondary wash liquor or a precipitation spent liquor from alumina process is directly fed as a cold fluid into the plate type heat interchanger to interchange heat with pregnant liquor (the hot fluid), and then recycling cooling water is used as a cold fluid to interchange heat with pregnant liquor (the hot fluid) whose temperature is already reduced. To reach a better heat interchange effect, when a secondary wash liquor and a precipitation spent liquor are used as cold fluid for heat interchange of the pregnant liquor (the hot fluid), three-stage four-set plate type heat interchangers can be used for heat interchange of the pregnant liquor as follows: as shown in Fig.l, first, directly feeding pregnant liquor (the hot fluid) into a first stage plate type heat interchanger (1), directly feeding a secondary wash liquor (a cold fluid) from alumina process into said first stage plate type heat interchanger (1) to interchange heat with the pregnant liquor, then allowing the pregnant liquor to enter a second-stage first-set plate type heat interchanger (2) and a second-stage second-set plate type heat interchanger (3), allowing the precipitation spent liquor (the cold fluid) from alumina process to directly enter said second-stage second-set plate type heat interchanger (3) and interchange heat with the pregnant liquor via said second-stage first-set plate type heat interchanger (2), if the pregnant liquor (the hot fluid) reaches the process requirement, it enters next workshop through a bypass (5) provided beside a third stage heat interchanger; if the temperature of the pregnant liquor (the hot fluid) is higher than a temperature required by the process, it enters a third stage plate type heat interchanger (4) and interchanges heat with the recycling water (the cold fluid) and then enters the next workshop. To obtain a further simplified process, when only a precipitation spent liquor is used as cold fluid for heat interchange of the pregnant liquor (the hot fluid), two-stage three-set plate type heat interchangers can be used for heat interchange of the pregnant liquor as follows: as shown in Fig.2, first, directly feeding pregnant liquor (the hot fluid) into a first-stage first-set plate type heat interchanger (6) and a first-stage second-set plate type heat interchanger (7), allowing the precipitation spent liquor (the cold fluid) from alumina process to directly enter said first-stage second-set plate type heat interchanger (7) and interchange heat with the pregnant liquor via said first-stage first-set plate type heat interchanger (6), if the pregnant liquor (the hot fluid) reaches the process requirement, it enters next workshop through a bypass (9) provided beside a second stage heat interchanger; if the temperature of the pregnant liquor (the hot fluid) is higher than a temperature required by the process, it enters a second stage plate type heat interchanger (8) and interchanges heat with the recycling water (the cold fluid) and then enters the next workshop after reaching the requirement. Claims 1. A process of heat interchange of a pregnant liquor, comprising of heat interchange of a pregnant liquor (a hot fluid) by using a plate type heat interchanger, wherein when using a plate type heat interchanger to heat interchange the pregnant liquor (the hot fluid), directly feeding the pregnant liquor (the hot fluid) to be cooled into the plate type heat interchanger, directly feeding a secondary wash liquor and a precipitation spent liquor from alumina process or only the precipitation spent liquor as a cold fluid into the plate type heat interchanger to interchange heat with the pregnant liquor (the hot fluid), and then using recycling cooling water as a cold fluid to interchange heat with the pregnant liquor (the hot fluid) whose temperature is already reduced. 2. A process of heat interchange of a pregnant liquor as claimed in claim 1, wherein when using a plate type heat interchanger to heat interchange a pregnant liquor (a hot fluid), using three-stage four-set plate type heat interchangers for heat interchange of the pregnant liquor, i.e. first, directly feeding the pregnant liquor (the hot fluid) into a first stage plate type heat interchanger (1), directly feeding a secondary wash liquor as a cold fluid from alumina process into said first stage plate type heat interchanger (1) to interchange heat with the pregnant liquor (the hot fluid), then allowing the pregnant liquor to enter a second-stage first-set plate type heat interchanger (2) and a second-stage second-set plate type heat interchanger (3), allowing the precipitation spent liquor (the cold fluid) from alumina process to directly enter said second-stage second-set plate type heat interchanger (3) and interchange heat with the pregnant liquor via said second-stage first-set plate type heat interchanger (2), if the pregnant liquor (the hot fluid) reaches the process requirement, it enters next workshop through a bypass (5) provided beside a third stage heat interchanger; if the temperature of the pregnant liquor (the hot fluid) is higher than a temperature required by the process, it enters a third stage plate type heat interchanger (4) and interchanges heat with the recycling water (the cold fluid) and then enters the next workshop. 3. A process of heat interchange of a pregnant liquor as claimed in claim 1, wherein when using a plate type heat interchanger to heat interchange a pregnant liquor (a hot fluid), using two-stage three-set plate type heat interchangers for heat interchange of the pregnant liquor, i.e., first, directly feeding the pregnant liquor (the hot fluid) into a first-stage first-set plate type heat interchanger (6) and a first-stage second-set plate type heat interchanger (7), allowing the precipitation spent liquor (the cold fluid) from alumina process to directly enter said first-stage second-set plate type heat interchanger (7) and interchange heat with the pregnant liquor via said first-stage first-set plate type heat interchanger (6), if the pregnant liquor (the hot fluid) reaches the process requirement, it enters next workshop through a bypass (9) provided beside a second stage heat interchanger; if the temperature of the pregnant liquor (the hot fluid) is higher than a temperature required by the process, it enters a second stage plate type heat interchanger (8) and interchanges heat with the recycling water (the cold fluid) and then enters the next workshop after reaching the requirement.

Documents:

1965-CHE-2005 CORRESPONDENCE OTHERS 13-12-2011.pdf

1965-CHE-2005 EXAMINATION REPORT REPLY RECEIVED 03-10-2012.pdf

1965-CHE-2005 CORRESPONDENCE OTHERS 05-06-2012.pdf

1965-CHE-2005 EXAMINATION REPORT REPLY RECEIVED 16-07-2012.pdf

1965-CHE-2005 FORM-3 16-07-2012.pdf

1965-CHE-2005 POWER OF ATTORNEY 05-06-2012.pdf

1965-che-2005-abstract.pdf

1965-che-2005-claims.pdf

1965-che-2005-correspondnece-others.pdf

1965-che-2005-description(complete).pdf

1965-che-2005-drawings.pdf

1965-che-2005-form 1.pdf

1965-che-2005-form 3.pdf

1965-che-2005-form 5.pdf

1965-che-2005-other document.pdf