U.S. patent application number 11/514139 was filed with the patent office on 2007-05-17 for compact heat exchanger made of ceramics having corrosion resistance at high temperature.
This patent application is currently assigned to Japan Atomic Energy Research Institute. Invention is credited to Shintaro Ishiyama, Shigeki Maruyama.
Application Number | 20070107888 11/514139 |
Document ID | / |
Family ID | 34269065 |
Filed Date | 2007-05-17 |
United States Patent
Application |
20070107888 |
Kind Code |
A1 |
Ishiyama; Shintaro ; et
al. |
May 17, 2007 |
Compact heat exchanger made of ceramics having corrosion resistance
at high temperature
Abstract
Ceramic materials that are highly resistant to strong acids such
as concentrated sulfuric acid and halides such as hydrogen iodide
are employed to make block elements through which a large number of
circular ingress channels extend in perpendicular directions and
which are joined and piled in the heat exchanging medium section to
provide a compact heat exchanger that excels not only in corrosion
resistance but also in high-temperature strength.
Inventors: |
Ishiyama; Shintaro;
(Ibaraki-ken, JP) ; Maruyama; Shigeki;
(Kanagawa-ken, JP) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700
1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
Japan Atomic Energy Research
Institute
Kashiwa-shi
JP
Kabushiki Kaisha Toshiba
Minato-ku
JP
|
Family ID: |
34269065 |
Appl. No.: |
11/514139 |
Filed: |
September 1, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10922153 |
Aug 20, 2004 |
7168481 |
|
|
11514139 |
Sep 1, 2006 |
|
|
|
Current U.S.
Class: |
165/165 ;
165/DIG.396 |
Current CPC
Class: |
F28F 7/02 20130101; F28F
21/04 20130101; Y02E 60/36 20130101 |
Class at
Publication: |
165/165 ;
165/DIG.396 |
International
Class: |
F28D 7/02 20060101
F28D007/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 20, 2003 |
JP |
2003-295841 |
Claims
1. A heat exchanger having corrosion resistance at high temperature
comprising a heat exchanging section, said heat exchanging section
comprising ceramic blocks made from silicon carbide or silicon
nitride having a first and a second group of channels opened in two
sides of each block, the blocks being stacked to fabricate a
ceramic pillar vaporizer, said first group of channels oriented
vertically to carry a corrosive solution of sulfuric acid or
hydrogen iodide upward, and said second group of channels oriented
horizontally to carry a hot helium gas laterally throughout the
horizontal channels, wherein the corrosive solution is supplied
from the bottom of the vaporizer, and a hot helium gas is
introduced laterally through the vaporizer; and the solution and
gas are respectively vertically and horizontally guided to the
channels through each of the ceramic blocks in the vaporizer, where
they undergo heat exchange until the corrosive solution is
gasified.
2. A heat exchanger of which the heat exchanging section comprises
ceramic blocks made from silicon carbide and silicon nitride.
3. A heat exchanger of which the heat exchanging section comprises
a bundle of pillar structures each consisting of ceramic blocks
joined together.
4. A heat exchanger for use in a chemical plant comprising a heat
exchange section, in which a corrosive solution of sulfuric acid or
hydrogen iodide near 600.degree. C. can be gasified by heating with
hot helium, SO2 and/or hydrogen iodide gas.
5. A corrosion-resistant heat exchanger comprising a heat exchange
section which permits heat exchange between a gas having a maximum
temperature of 1000.degree. C. and a maximum pressure of 6 MPa and
a gasified corrosive solution.
6. A compact heat exchanger comprising a heat exchange section
which enables the heat exchange of a primary helium coolant/a
secondary helium coolant near at 1000.degree. C. between a hot gas
furnace and a chemical plant.
7. A heat exchanger comprising a heat exchanger section which
enables heat exchange in the heat exchanging section through
perpendicular channels provided in ceramic blocks.
8. A heat exchanger according to claim 1, wherein a concentrated
sulfuric acid solution near 600.degree. C. can be gasified by
heating the hot helium gas.
9. A heat exchanger according to claim 1, which enables heat
exchange in the vaporizer through perpendicular channels provided
in ceramic blocks
10. A heat exchanger according to claim 8, which enables heat
exchange in the vaporizer through perpendicular channels provided
in ceramic blocks
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to heat exchangers that have the heat
exchanging section composed of ceramic blocks and which are
applicable to wide areas including the atomic industry, aerospace,
industries in general, and consumers use.
[0002] No corrosion-resistant materials have heretofore been
available that enable concentrated sulfuric acid solutions to be
vaporized and hydrogen iodide solutions to be vaporized and
decomposed under high-temperature (>1000.degree. C.) and
high-pressure (>6 MPa) conditions; heat exchangers for such
purposes have also been unavailable. To date, several ceramics
manufacturers have made attempts to fabricate heat exchangers for
high-temperature operation by using ceramic blocks but all failed
to make large enough equipment on account of inadequacy in the
strength of the blocks.
SUMMARY OF THE INVENTION
[0003] An object, therefore, of the present invention is to provide
a heat exchanger that withstands heat exchange in large capacities
ranging from several tens to a hundred megawatts in
high-temperature (>1000.degree. C.) and high-pressure (>6
MPa) environments of strong acids and halides in a solution as well
as a gaseous phase and which yet can be fabricated in a compact
configuration.
[0004] According to the present invention, ceramic materials that
are highly resistant to strong acids such as concentrated sulfuric
acid and halides such as hydrogen iodide are employed to make block
elements through which a large number of circular ingress channels
extend in perpendicular directions; by joining such block elements
and piling them in the heat exchanging medium section, the
invention provides a compact heat exchanger that excels not only in
corrosion resistance but also in high-temperature strength.
[0005] The compact heat exchanger of the invention which withstands
high temperature (-1000.degree. C.) and high pressure as well as
exhibiting high corrosion resistance can also be used as an
intermediate heat exchanger in hot gas furnaces.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 shows the concept of a nuclear thermochemical IS
plant;
[0007] FIG. 2 shows the design concept of a concentrated sulfuric
acid vaporizer in actual operation;
[0008] FIG. 3 shows the shapes of ceramic blocks and experimentally
fabricated ceramic pillars;
[0009] FIG. 4 shows a method of fabricating a ceramic pillar;
[0010] FIG. 5 shows individual ceramic blocks which are joined in a
plurality of pillars and then bundled together to form a heat
exchanging section;
[0011] FIG. 6 shows how ceramic pillars are eventually bundled
together and how they are combined with section plates and
partition plates to establish helium passageways;
[0012] FIG. 7 shows how section plates and partition plates are
assembled;
[0013] FIG. 8 shows ceramic flow rate regulating plates as attached
to the top and bottom of the fabricated heat exchanging
section;
[0014] FIG. 9 shows reinforcing rings as subsequently attached to
the fabricated heat exchanging section;
[0015] FIG. 10 shows the heat exchanging section as it is tightened
by means of tie rods;
[0016] FIG. 11 shows the installation of inner tubes;
[0017] FIG. 12 shows how a pressure vessel for accommodating the
heat exchanging section is assembled;
[0018] FIG. 13 shows how the heat exchanging section is installed
within the pressure vessel;
[0019] FIG. 14 shows earthquake-resistant structures as they are
fitted between the pressure vessel and the heat exchanging
section;
[0020] FIG. 15 shows how a top reflector and helium inlet bellows
are attached;
[0021] FIG. 16 shows a top cover as it is fitted on the pressure
vessel;
[0022] FIG. 17 shows a mechanical seal as it is fitted on the
pressure vessel;
[0023] FIG. 18 shows the autoclave employed in a high-temperature,
high-pressure corrosion test; and
[0024] FIG. 19 shows the results of the high-temperature,
high-pressure corrosion test conducted on various ceramics and
refractory alloys.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The invention provides a heat exchanger essential for
realizing commercialization of a nuclear thermochemical IS plant
that can produce large quantities of hydrogen and oxygen from the
water feed using nuclear heat with 950.degree. C. FIG. 1 shows the
concept of a nuclear thermochemical IS plant. Among the various
components shown, those which are operated under the most rigorous
conditions are the sulfuric acid vaporizer and the hydrogen iodide
decomposer.
[0026] FIG. 1 shows the concept of a nuclear thermochemical IS
plant; the reaction involved is such that using the hot thermal
energy of 850.degree. C. as supplied from the hot gas furnace,
water as the feed is decomposed into hydrogen and oxygen primarily
through the combination of a sulfuric acid decomposing and
regenerating cycle with a hydrogen iodide decomposing and
synthesizing cycle.
[0027] To be more specific, H.sub.2O as supplied into the Bunsen
reactor is decomposed under high-temperature, high-pressure
conditions in the presence of both H.sub.2SO.sub.4 and HI. After
the reaction, the liquid portion containing H.sub.2SO.sub.4 and HI
is supplied into the acid separator where it is separated into two
layers of H.sub.2SO.sub.4 and HI. The HI containing solution passes
through the purifier to be supplied into the distillation column;
the resulting HI vapor is decomposed in the HI decomposer and the
product H.sub.2 is recovered from the condenser. The distillation
residue in the distillation column and the condensate in the
condenser are returned to the reactor.
[0028] The H.sub.2SO.sub.4 containing solution coming from the acid
separator passes through the purifier to be supplied into the
concentrator and the concentrated H.sub.2SO.sub.4 solution is
subjected to vaporization in the H.sub.2SO.sub.4 vaporizer; the
resulting vapor is fed into the H.sub.2SO.sub.4 decomposer, where
it is decomposed into S02, H.sub.2O and O.sub.2, which then pass
through the condenser to return to the Bunsen reactor.
[0029] FIG. 2 shows the design concept of a concentrated sulfuric
acid vaporizer in actual operation. A concentrated sulfuric acid
solution is supplied from the furnace bottom of the vaporizer
toward the upper arm, whereas helium gas with 689.degree. C. is
introduced laterally through the upper arm of the vaporizer; the
two feeds are respectively guided to the perpendicular channels
through each of the ceramic blocks in the vaporizer, where they
undergo heat exchange until the concentrated sulfuric acid is
completely gasified.
[0030] FIG. 3 shows the shapes of ceramic blocks and experimentally
fabricated ceramic pillars. Individual blocks are piled up along
the four sides of the cross-shaped perforated section plate
provided through the center of the sulfuric acid vaporizer shown in
FIG. 2 and they are held in position as the sulfuric acid feed is
flowed upward through six or nine channels (holes) opened in two
sides of each block. The hot helium gas feed is flowed laterally
through four channels (holes) opened in a side of each block,
whereby the sulfuric acid is heated via each block. The two groups
of channels are formed in the block in such a way that they do not
communicate with each other.
[0031] FIG. 4 shows a method of fabricating a ceramic pillar by
stacking a plurality of ceramic blocks. As shown, a sufficient
number of blocks to form a pillar are vacuum sealed into a metal
vacuum chamber and heated from the outside, so that the blocks are
joined one on top of another by means of brazing sheets to form a
single pillar.
[0032] FIG. 5 shows individual ceramic blocks which are joined in a
plurality of pillars and then bundled together to form a heat
exchanging section.
[0033] FIG. 6 shows how ceramic pillars are eventually bundled
together and how they are combined with section plates and
partition plates to establish helium passageways.
[0034] FIG. 7 shows how section plates and partition plates are
assembled, with four ceramic blocks being inserted and fixed in the
center between adjacent partition plates.
[0035] FIG. 8 shows ceramic flow rate regulating plates as attached
to the top and bottom of the fabricated heat exchanging section and
FIG. 9 shows reinforcing rings as subsequently attached to the
fabricated heat exchanging section.
[0036] FIG. 10 shows the individual constituent elements of the
heat exchanging section as they are tightened by means of tie
rods.
[0037] FIG. 11 shows the installation of inner tubes on side walls
of the heat exchanging section that has been tightened by the tie
rods.
[0038] FIG. 12 shows that a pressure vessel for accommodating the
heat exchanging section is assembled as shown.
[0039] FIG. 13 shows how the heat exchanging section is installed
within the pressure vessel after it has been assembled as shown in
FIG. 12.
[0040] FIG. 14 shows earthquake-resistant structures as they are
fitted between the pressure vessel and the heat exchanging
section.
[0041] FIG. 15 shows how a top reflector and helium inlet bellows
are attached to the heat exchanging section as it has been mounted
in the pressure vessel with the aid of the earthquake-resistant
structures.
[0042] FIGS. 16 and 17 shows a top cover and a mechanical seal,
respectively, as they are fitted on the pressure vessel to complete
a heat exchanger for sulfuric acid.
EXAMPLE
(A) Design Concept of a Ceramic Compact Concentrated Sulfuric Acid
Vaporizer and Experimental Fabrication of Individual Elements
[0043] Table 1 shows the design specifications of a concentrated
sulfuric acid vaporizer for use in a nuclear thermochemical IS
plant in actual operation that can be connected to a hot gas
furnace of 200 MW. FIG. 2 shows the design concept of the
concentrated sulfuric acid vaporizer. TABLE-US-00001 TABLE 1
Specifications of Sulfuric Acid Vaporizer in Actual Operation
Hydrogen production rate 25,514 N.sup.3/h Heat load on vaporizer 63
MV Heating helium gas In/out temperature 689.degree. C./486.degree.
C. Flow rate 1.2 .times. 10.sup.8 Nm.sup.3/h Process In/out
temperature 455.degree. C./486.degree. C. Inlet H.sub.2O/(L/G)
363/816 kmol/h H.sub.2SO.sub.4 (L/G) 1552/408 kmol/h Total 3139
kmol/h Outlet H.sub.2O/(L/G) 0/1178 kmol/h H.sub.2SO.sub.4 (L/G)
0/1949 kmol/h Total 70,045 Nm.sup.3/h Heat exchange .DELTA.t1
203.degree. C. .DELTA.t2 31.degree. C. LMTD 92.degree. C. Heat
transfer coefficient 400 kcal/m.sup.2 .degree. C. (as assumed)
Pressure Helium inlet/H.sub.2SO.sub.4 inlet 3 MPa/2 MPa
[How to Assemble the Concentrated Sulfuric Vaporizer]
[0044] (i) Fabricate a plurality of ceramic blocks (see FIG. 3) in
each of which helium channels cross concentrated sulfuric acid
solution channels at right angles.
[0045] (ii) Fabricate a ceramic block pillar as shown in FIG. 4 by
vacuum sealing into a metallic vacuum chamber a sufficient number
of ceramic blocks to form a pillar and heating the blocks from the
outside.
[0046] (iii) Join individual ceramic blocks in a plurality of
pillars and bundle them together as shown in FIG. 5 to form a heat
exchanging section.
[0047] (iv) Eventually bundle ceramic pillars together and combine
them with section plates and partition plates to establish helium
passageways as shown in FIG. 6.
[0048] (v) Attach the ceramic heat exchanging section to the
assembled section plates and partition plates as shown in FIG.
7.
[0049] (vi) Attach ceramic flow rate regulating plates to the top
and bottom of the fabricated heat exchanging section as shown in
FIG. 8; subsequently attach reinforcing rings to the fabricated
heat exchanging section as shown in FIG. 9.
[0050] (vii) Tighten the heat exchanging section by means of tie
rods as shown in FIG. 10.
[0051] (viii) Install inner tubes as shown in FIG. 11.
[0052] (ix) In a separate step, assemble a pressure vessel for
accommodating the heat exchanging section as shown in FIG. 12.
[0053] (x) Install the heat exchanging section within the pressure
vessel as shown in FIG. 13.
[0054] (xi) Further, fit earthquake-resistant structures between
the pressure vessel and the heat exchanging section as shown in
FIG. 14.
[0055] (xii) Attach a top reflector and helium inlet bellows as
shown in FIG. 15.
[0056] (xiii) In the last step, fit a top cover and a mechanical
seal on the pressure vessel as shown in FIGS. 16 and 17,
respectively.
(B) Concentrated Sulfuric Acid Corrosion Test
[0057] The various ceramics and refractory alloys shown in Table 2
were filled into glass ampules together with concentrated sulfuric
acid and subjected to a high-temperature, high-pressure corrosion
test in an autoclave (see FIG. 18) under high-temperature
(460.degree. C.) high-pressure (2 MPa) conditions for 100 and 1000
hours. Test results are shown in Tables 3 and 4 and in FIG. 19. The
results for the 1000-h test are summarized in Table 5. Silicon
carbide and silicon nitride were found to have satisfactory
corrosion resistance. TABLE-US-00002 TABLE 2 Test Sections for
High-Pressure Boiling H.sub.2SO.sub.4 Corrosion Test (.times.100 h
and 1000 h) Description Ampule No. Designation Symbol
Classification Remarks 100 h test 1 SiC SiC-1 ceramic atmospheric
pressure sintering of 97 wt % SiC, 1 wt % B and 2 wt % C 2 Si--SiC
Si--SiC--N-1 atmospheric pressure sintering of 80 wt % SiC and 20
wt % Si (as silicon impregnated) 3 Si.sub.3N.sub.4
Si.sub.3N.sub.4-1 atmospheric pressure sintering of 1 wt % SrO, 4
wt % MgO and 5 wt % CeO.sub.2 4 Sx SX-2 H.sub.2SO.sub.4 resistant
steel preliminarily oxidized at 800.degree. C. .times. 90 h 5 FeSi
FS-1 high-Si ferrous alloy 14.8 Si--Fe 6 FS-2 19.7 Si--Fe 1000 h
test 1 SX SX-2/half H.sub.2SO.sub.4 resistant steel oxidized with
the atmosphere at 800.degree. C. .times. 90 h in half size 2
SX-2/small oxidized with the atmosphere at 800.degree. C. .times.
90 h in small size 3 SX SX-4/RT-1 H.sub.2SO.sub.4 resistant steel
oxidized with nitric acid in small size SX-4/70.1 oxidized with
nitric acid in small size 4 SiC SiC ceramic 5 Si--SiC Si--SiC--N-3
Si-impregnated silicon carbide ceramic 6 Si.sub.3N.sub.4
Si.sub.3N.sub.4 ceramic 7 FeSi FS-2/untreated high-Si ferrous alloy
19.7 Si--Fe FS-2/stress 19.7 Si--Fe, vacuum annealed at
1100.degree. C. .times. 100 h relieved
[0058] TABLE-US-00003 TABLE 3 Results of Size Measurements in
High-Pressure Boiling H.sub.2SO.sub.4 Corrosion Test (.times.100 h)
Length (mm) Width (mm) Thickness (mm) Ampule Before After Change
Before After Change Before After Change No. Designation Symbol test
test (%) test test (%) test test (%) 1 SX-2 SX-2/half 26.824 26.71
-0.42% 3.949 3.944 -0.13% 1.516 1.358 -10.42% 2 SX-2/small 1.798
1.789 -0.50% 3.988 4.1 2.81% 1.545 1.589 2.85% 3 SX-4 SX-4/RT-1
15.493 15.453 -0.26% 3.943 3.878 -1.65% 1.635 1.624 -0.67%
SX-4/70.1 15.071 15.063 -0.05% 3.937 3.903 -0.86% 1.627 1.744 7.19%
4 SiC SiC 39.727 39.71 -0.04% 4.035 4.034 -0.02% 2.993 2.991 -0.07%
5 Si--SiC Si--SiC 40.029 40.04 0.03% 4.061 4.06 -0.02% 3.077 3.080
0.10% 6 Si.sub.3N.sub.4 Si.sub.3N.sub.4 39.826 39.8 -0.07% 4.065
4.068 0.07% 3.013 3.021 0.27% 7 FeSi FS-2/untreated 19.083 19.101
0.09% 3.638 3.7 1.70% 3.595 3.638 1.20% FS-2/stress 19.585 20.055
2.40% 5.700 3.705 -35.00% 5.557 3.578 -35.61% relieved
[0059] TABLE-US-00004 TABLE 4 Results of Weight Measurements and
Corrosion Rate in High-Pressure Boiling H.sub.2SO.sub.4 Corrosion
Test (.times.100 h) Weight (g) Corrosion Ampule Before After Weight
change Area rate No. Designation Symbol test test (%) (mg)
(cm.sup.2) (g/m.sup.2 h) Remarks 1 SX-2 SX-2/half 1.2162 0.9816
19.29% -234.6 0.03052 0.961 Ampule broke in 800 h 2 SX-2/small
0.0772 0.0656 15.03% -11.6 0.00322 0.360 3 SX-4 SX-4/RT-1 0.7570
0.6738 10.99% -83.2 0.01857 1.244 Ampule broke in 360 h SX-4/70.1
0.7967 0.7198 9.65% -76.9 0.01805 1.183 Ampule broke in 360 h 4 SiC
SiC 1.4476 1.4487 -0.08% 1.1 0.05826 -0.002 5 Si--SiC Si--SiC
1.4823 1.4856 -0.22% 3.3 0.05964 -0.006 6 Si.sub.3N.sub.4
Si.sub.3N.sub.4 1.5611 1.5653 -0.27% 4.2 0.05883 -0.007 7 FeSi
FS-2/untreated 1.6720 1.6330 2.33% -39.0 0.03022 0.129 FS-2/stress
1.7425 1.7097 1.88% -32.8 0.05043 0.065 relieved
[0060] TABLE-US-00005 TABLE 5 Summary of 1000 h Test Cross section
Dimensional Corrosion observed at Overall Designation Symbol change
rate Appearance magnification Other rating SX-2 SX-2/half X X
.circleincircle. .circleincircle. -- X SX-2/small .largecircle.
.DELTA. .circleincircle. .circleincircle. -- .DELTA. SX-4 SX-4/RT-1
.DELTA. X .circleincircle. .circleincircle. -- X SX-4/70.1 .DELTA.
X .circleincircle. .circleincircle. -- X SiC SiC .circleincircle.
.circleincircle. .circleincircle. .circleincircle. .largecircle.
.largecircle. Si--SiC Si--SiC .circleincircle. .circleincircle.
.circleincircle. .circleincircle. .largecircle. .largecircle.
Si.sub.3N.sub.4 Si.sub.3N.sub.4 .circleincircle. .circleincircle.
.circleincircle. .circleincircle. .largecircle. .largecircle. FeSi
FS-2/untreated .circleincircle. .DELTA. X X -- X FS-2/stress
relieved X .DELTA. X X -- X
* * * * *