Distillation: apparatus – Apparatus – Systems
Reexamination Certificate
2000-10-11
2004-12-28
Tran, Hien (Department: 1764)
Distillation: apparatus
Apparatus
Systems
C202S155000, C202S172000, C202S173000, C202S182000, C202S202000, C203S005000, C203S023000, C203SDIG008, C203SDIG009, C203SDIG002, C203S078000
Reexamination Certificate
active
06835287
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for separation/enrichment of isotopes of a uniform compound, and to an apparatus and method for obtaining heavy oxygen water in which the oxygen isotopes
17
O and
18
O (referred to as heavy oxygen isotopes) within the water molecules have been enriched. More specifically, the present invention relates to a method of producing water enriched in the oxygen isotopes of
17
O and
18
O in which oxygen is enriched in
16
O
17
O,
16
O
18
O,
17
O
17
O,
17
O
18
O, and
18
O
18
O by cryogenic distillation of oxygen, and then converted to water, and to a method of producing water which is further enriched in the oxygen isotopes of
17
O and
18
O in which oxygen is enriched in
16
O
17
O,
16
O
18
O,
17
O
17
O,
17
O
18
O, and
18
O
18
O by cryogenic distillation of oxygen, and then converted to water which is then subject to water distillation.
2. Description of the Related Art
In the distillation operation in a system in which the relative vapor pressure (separation factor) is extremely small, as represented by the process of distillation separation/enrichment of isotopes, an extremely large theoretical number of plates is necessary.
In this case, generally, packed columns are used in order to suppress pressure loss within the column. However, it is not uncommon for the required packing height therefor to reach several hundred meters.
Consequently, actual apparatuses are constructed with a plurality of distillation columns connected by piping, the whole of which comprises a single distillation column group.
FIG. 18
shows an example of an apparatus provided with three distillation columns with each of the columns (first to third columns
61
,
62
, and
63
) connected.
In this apparatus, the liquid which accumulates in the bottom of the first distillation column
61
and the second distillation column
62
is supplied by means of pumps
61
a
and
62
a
to the tops of second distillation column
62
and third distillation column
63
respectively as reflux liquid. Vapor which is drawn off from the top of the second column
62
and the third column
63
is returned to the bottoms of the first column
61
and the second column
62
respectively as ascending vapor.
In this process, the supply of the process fluid from the first column
61
to the second column
62
and from the second column
62
to the third column
63
is carried out by liquid pumps
61
a
and
62
a
, but the return of the process liquid from the second column
62
to the first column
61
, and from the third column
63
to the second column
62
occurs due to the pressure differences in the vapor. Therefore, the pressure within the distillation columns must be successively higher from the first column
61
toward the third column
63
. In general, since the relative vapor pressure (separation factor) is smaller the higher the operating pressure of the distillation column, distillation efficiency is lower in the second column
62
than the first column
61
, and lower in the third column
63
than in the second column
62
.
In addition, in general, as in isotope separation processes, when the relative vapor pressure of the separation components is extremely small and the packing height is extremely large, the time (hereinafter referred to as the start-up time) from the start up of the apparatus until it becomes possible to collect the stipulated amount (the product amount extracted in accordance with the specifications, or the planned value) may take from several months to several years. Consequently, reduction of the start-up time has hitherto been an issue.
The start-up time is heavily dependent on the process liquid hold-up within the apparatus, and the greater the amount thereof, the longer the start-up time is.
FIG. 19
shows a distillation process having the same functions as the apparatus shown in
FIG. 18
, and each column
71
,
72
, and
73
is provided with condensers
5
,
7
and
9
, and reboiler
6
,
8
, and
10
. These are apparatuses which are generally used in processes comprising a plurality of distillation columns. The diameter of the distillation columns becomes smaller from the column
71
, to which the starting material is fed, to the column
73
, which is downstream from column
71
.
However, even when using this type of apparatus, since the pressure within the distillation column increases from the first column
71
to the third column
73
, in the same way as with the apparatus shown in
FIG. 18
, the distillation efficiency is lower in the second column
72
than in the first column
71
, and is lower in the third column
73
than in the second column
72
.
Thereby, it is possible to reduce the process liquid hold-up within the apparatus, and to shorten the start-up time.
Reductions in the distillation efficiency lead to increases in the necessary packing height of the distillation column and to increases in the process liquid hold up. Therefore, they are not desirable from the point of view of shortening the start-up time.
In addition, in conventional isotope distillation processes, columns packed using unstructured packing have been used. In general, unstructured packing has a larger specific surface area compared with structured packing. However, the liquid hold-up within the distillation column is 10 to 20% of the volume of the column, and in some cases exceeds 20%, and this is a cause of prolonged start-up time.
SUMMARY OF THE INVENTION
In consideration of the above-mentioned circumstances, the present invention has, as an object the provision of an apparatus comprising a plurality of distillation columns and with which the start-up time is shorter than with conventional apparatuses.
In order to overcome the above-mentioned problems, the apparatus of the present invention is an apparatus for separation of a vapor or liquid mixture comprising a plurality of distillation columns (a first column to an n
th
column) constructed in a cascade comprising introduction conduits which connect the bottom of a k
th
column (1≦k≦(n−1)) or an outlet of a reboiler provided in the vicinity of the bottom of the k
th
column to the t op of a (k+1)
th
column, an inlet of a condenser provided in the vicinity of the top of the (k+1)
th
column, or the middle section of the (k+1)
th
column, and return conduits which connect an outlet of the condenser of the (k+1)
th
column to an inlet of the reboiler provided in the vicinity of the bottom of the k
th
column, the bottom of the k
th
column, or the middle section of the k
th
column.
In addition, the apparatus of the present invention is an apparatus for separation on a vapor or liquid mixture comprising a plurality of components using a plurality of distillation columns (a first column to an n
th
column) constructed in a cascade comprising introduction conduits which connect the bottom of a k
th
column (1≦k≦(n−1)) or an outlet of a reboiler provided in the vicinity of the bottom of the k
th
column to the top of a (k+1)
th
column, an inlet of a condenser provided in the vicinity of the top of the (k+1)
th
column, or the middle section of the (k+1)
th
column, and return conduits which connect the top of the (k+1)
th
column, or the inlet of the condenser provided in the vicinity of the top of the (k+1)
th
column to the bottom of the k
th
column or the middle section of the k
th
column via a blower.
In addition in the apparatus of the present invention, at least one of the distillation columns is a packed column in which structured packing (promoting-fluid-dispersion type structured packing or non-promoting-fluid-dispersion type structured packing) is used, or a wetted wall column.
In addition, the apparatus of the present invention comprises an isotope scrambler, an extraction conduit which connects at least one section of said apparatus to an inlet of the isotope scrambler; and a return conduit which connects at least one section of said apparatus to an outlet of the isotope
Hayashida Shigeru
Kawakami Hiroshi
Kihara Hitoshi
Tachibana Hiroshi
Kolisch & Hartwell, P.C.
Leung Jennifer A.
Nippon Sanso Corporation
Tran Hien
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