Compact heat exchanger made of ceramics having corrosion resistance at high temperature
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.
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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.
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° 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 INVENTIONAn 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° 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.
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.
The compact heat exchanger of the invention which withstands high temperature (−1000° 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
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° C.
To be more specific, H2O as supplied into the Bunsen reactor is decomposed under high-temperature, high-pressure conditions in the presence of both H2SO4 and HI. After the reaction, the liquid portion containing H2SO4 and HI is supplied into the acid separator where it is separated into two layers of H2SO4 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 H2 is recovered from the condenser. The distillation residue in the distillation column and the condensate in the condenser are returned to the reactor.
The H2SO4 containing solution coming from the acid separator passes through the purifier to be supplied into the concentrator and the concentrated H2SO4 solution is subjected to vaporization in the H2SO4 vaporizer; the resulting vapor is fed into the H2SO4 decomposer, where it is decomposed into S02, H2O and O2, which then pass through the condenser to return to the Bunsen reactor.
(A) Design Concept of a Ceramic Compact Concentrated Sulfuric Acid Vaporizer and Experimental Fabrication of Individual Elements
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.
[How to Assemble the Concentrated Sulfuric Vaporizer]
(i) Fabricate a plurality of ceramic blocks (see
(ii) Fabricate a ceramic block pillar as shown in
(iii) Join individual ceramic blocks in a plurality of pillars and bundle them together as shown in
(iv) Eventually bundle ceramic pillars together and combine them with section plates and partition plates to establish helium passageways as shown in
(v) Attach the ceramic heat exchanging section to the assembled section plates and partition plates as shown in
(vi) Attach ceramic flow rate regulating plates to the top and bottom of the fabricated heat exchanging section as shown in
(vii) Tighten the heat exchanging section by means of tie rods as shown in
(viii) Install inner tubes as shown in
(ix) In a separate step, assemble a pressure vessel for accommodating the heat exchanging section as shown in
(x) Install the heat exchanging section within the pressure vessel as shown in
(xi) Further, fit earthquake-resistant structures between the pressure vessel and the heat exchanging section as shown in
(xii) Attach a top reflector and helium inlet bellows as shown in
(xiii) In the last step, fit a top cover and a mechanical seal on the pressure vessel as shown in
(B) Concentrated Sulfuric Acid Corrosion Test
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
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° 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° 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° 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° 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
Type: Application
Filed: Sep 1, 2006
Publication Date: May 17, 2007
Applicants: Japan Atomic Energy Research Institute (Kashiwa-shi), Kabushiki Kaisha Toshiba (Minato-ku)
Inventors: Shintaro Ishiyama (Ibaraki-ken), Shigeki Maruyama (Kanagawa-ken)
Application Number: 11/514,139
International Classification: F28D 7/02 (20060101);