WO2011143067A2

WO2011143067A2 - Containment box

Info

Publication number: WO2011143067A2
Application number: PCT/US2011/035572
Authority: WO
Inventors: Leland Matthew Reineke
Original assignee: Americarb, Inc.
Priority date: 2010-05-10
Filing date: 2011-05-06
Publication date: 2011-11-17
Also published as: WO2011143067A3

Abstract

A containment box is provided, having four side walls, a bottom wall and a top opening. The containment box is operative to receive a Directional Solidification Silicon (DSS) container therein through the top opening. Such a container is operative to hold molten silicon therein for casting silicon ingots. Each of the walls of the containment box may be comprised of a carbon fiber woven material operative to have sufficient strength to contain a leak of silicon from the container.

Description

Title: Containment Box

BACKGROUND

Directional Solidification Silicon (DSS) ingot casting furnaces use a DSS fused silica container in which silicon is melted in a casting process that produces silicon ingots. Such fused silica containers typically rest on a graphite heat exchange block inside the furnace. Unfortunately, such containers may develop cracks during the casting process which may release molten silicon outside of the container.

Although DSS furnaces may have spill detection systems that shut down the furnace, silicon spills can still cause extensive damage to the graphite components and graphite insulation in the furnace. Further, if such spills are not detected and handled quickly, a catastrophic failure of the furnace system (such as an explosion) may occur.

Thus there exists a need for improvements to DSS furnaces. SUMMARY

The following is a brief summary of the subject matter that is described in greater detail herein. This summary is not intended to be limiting as to the scope of the claims.

Described herein are examples of a carbon composite melt containment box and example processes for producing a containment box, which box and processes are directed to overcoming one or more of the aforementioned problems with DSS furnaces. In example embodiments, a containment box may be made from a phenolic based carbon fiber pre-preg woven fabric and fiber wound materials. The box may also be constructed using a fiber winding technique only, or a combination of fiber winding or fabric layup techniques, to achieve the tensile strength needed to perform optimally for a given application.

The box may have a size and shape to receive therein a removable DSS container (e.g., a fused silica container / crucible) or other type of container that is operative for use with casting silicon ingots. If a crack in the fused silica container occurs, the described containment box is operative to accumulate spilled molten silicon therein and prevent the silicon from flowing onto other components in the DSS furnace.

In an example embodiment, the containment box is reusable. Thus after each ingot is cast, a fused silica crucible (which is usually damaged during the casting process) may be removed and replaced with a new fused silica crucible inside the existing containment box.

In a further embodiment, rather than using a fused silica crucible for melting the silicon metal therein, an example process may include assembling a modular lining for use inside the described containment box to cast a silicon ingot. In this example, the modular liner can be made from flat wall segments in the form of flat plates of fused silica.

In an example embodiment, the containment box may be relied on to support the wall segments of the modular liner. Thus the fused silica modular liner can be assembled from wall segments that are generally thinner than the walls of a prior art fused silica crucible. Such wall segments (in the form of flat plates) may be manufactured and shipped in a smaller and lighter package compared to the relatively heavier and larger fused silica crucibles. To assembled the described modular liner, the flat plates may be mounted into the shape of a box along the inside walls of the described containment liner. The seams of the box may be sealed with a silica cement to maintain the molten silica inside the modular liner. However, in the event that cracks develop in the modular liner, the described containment box is operative to hold the molten silica therein and prevent leakage of the silica into other portions of the DSS furnace.

As with prior art fused silica crucibles, the described modular liner may need to be replaced after each silicon ingot is cast. However, the lower weight and compact design (in an unassembled form) enable the described modular liner to be less expensive to manufacture and thus replace.

Other aspects will be appreciated upon reading and understanding the attached figures and description.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a block diagram of an example embodiment of a containment box for a DSS furnace.

Fig. 2 shows a cross-sectional view of an example embodiment of a containment box for a DSS furnace, having a DSS fused silica container therein.

Fig. 3 shows a cross-sectional view of an example embodiment of a containment box for a DSS furnace, having a fused silica modular liner therein.

Fig. 4 is flow diagram that illustrates an example methodology for using a containment box for a DSS furnace.

Fig. 5 is a flow diagram that illustrates an example process for using a modular liner with a containment box in a DSS furnace. Fig. 6 shows a perspective view of an example embodiment of a containment box.

Fig. 7 shows a perspective view of an example embodiment of a DSS fused silica container.

Fig. 8 shows a perspective view of an example embodiment of a DSS fused silica container mounted inside an example embodiment of a containment box.

Fig. 9 shows an exploded view of flat wall plates of an example embodiment of a fused silica modular liner.

Fig. 10 shows a perspective view of an example embodiment of an assembled fused silica modular liner.

Fig. 11 shows a perspective view of an example embodiment of a fused silica modular liner mounted inside an example embodiment of a containment box.

DETAILED DESCRIPTION

Various technologies pertaining to DSS furnaces and processes will now be described with reference to the drawings, where like reference numerals represent like elements throughout.

With reference to Figure 1 , a schematic diagram of an example embodiment

100 of a containment box 102 for a DSS furnace 104 is illustrated. It should be appreciated that example embodiments of the containment box described herein may be used with many different types and models of DSS silicon ingot furnaces, including those manufactured by GT Dolar, ALD/Holcroft, JYY, and Ferrotech.

Further it should be appreciated that the example embodiments of the containment box may be used with many different sizes of furnaces, such as furnaces capable of 240 KG to 1000 KG ingot production.

As shown in Figure 1, the containment box 102 may be placed on top of a heat exchange block 110 of the DSS furnace 104. The containment box 102 may have a sufficient interior size to receive a Directional Solidification Silicon (DSS) container 106 (e.g., a fused silica container / crucible) therein. For example, as illustrated in Figure 6, the containment box may include a five-walled box (four side walls 602, 604, 606, 608 and a bottom wall 610) with a top opening 612. An example of a container 106 is shown in Figure 7. As illustrated in Figure 9, the container 106 may be placed through the top opening and may be set on top of the bottom wall of the containment box.

In an example embodiment, the walls of the containment box 102 are comprised of a carbon fiber woven material and are constructed in manner which provides sufficient strength to contain a leak of silicon from the container 106. In an example embodiment, the container 106 is operative for use in casting a silicon ingot from molten silicon 108 held therein. Such a container may correspond to a fused silica crucible or any other type of container that is operative to be used to cast ingots from molten silicon. Also, as explained in more detail below, the container may correspond to a modular lining that is constructed at the location of the furnace.

Referring now to Figure 2, there is illustrated a cross-sectional view of an example embodiment 200 of a containment box 202. In Figure 2, the containment box is shown having a container 204 mounted therein including molten silicon 206. In an example embodiment, portions of the box 202 such as the bottom wall 210 and the inside portions 230, 232 of the side walls 212, 214 may be comprised of a carbon composite laminate. Also, outside portions 220, 222 of the side walls 212, 214 may be comprised of fiber wound composite or laminate. In an example embodiment, the walls of the box 202 may have thicknesses between .125 inches (3.175 mm) and 1 inch (about 25.4 mm), or other thicknesses depending on the particular model of DSS furnace and/or container for which the containment box is constructed.

In example embodiments, the box can be constructed completely out of carbon fiber pre-preg woven materials (e.g., 3k, 6k, 12k, fiber count; stretch broken in twill; plain weave; harness, and/or other types of carbon fiber fabric materials). The box may also be constructed using a fiber winding technique or a combination of fiber winding and fabric layup to achieve the desired tensile strength needed to perform optimally in a particular DSS furnace.

For example, as shown in Figure 2, in the described embodiment 200, a carbon fiber woven material 220, 222 may be wound around portions 230, 232 of the four side walls comprised of a carbon composite laminate. Also, it should be appreciated that the carbon fiber woven material wound around the four walls may not extend adjacent bottom edges of the side walls. Rather, portions 216, 218 of the four walls adjacent the bottom edges of the side walls 212, 214 may be comprised of a relatively thicker carbon composite laminate. The fiber wound composite 220, 222 may then be located relatively higher on the side walls above these lower thicker carbon composite laminate portions 216, 218 of side walls 212, 214. Also, it should be appreciated that alternative embodiments may use different techniques for forming the box out of a carbon composite laminate.

Referring now to Figure 3, there is illustrated a cross-sectional view of an example embodiment 300 of the previously described containment box 202. In Figure 3, the containment box is shown having a container 304 in the form of a modular liner. Here the modular liner includes four side wall segments 306, 308, 309 (only three shown) and one bottom wall segment 310 and a top opening 312. In this embodiment, the walls of the container may be comprised of generally flat fused silica plates or other materials that can withstand temperatures of 1,800 C in a vacuum atmosphere. In order to create a sealed container operative to hold molten silicon therein, the seams 320, 322 between adjacent edges of the flat plates may be sealed with a silica cement 324, 326.

Figure 9 illustrates an example embodiment of the five wall plates (side wall plates 902, 904, 906, 908 and bottom wall plate 910) of the modular liner 304 in an unassembled form. Figure 10 illustrates an example embodiment of the modular liner 304 in an assembled form. Figure 11 shows a perspective view of the modular liner 304 mounted in an example embodiment of a containment box 202

In example embodiments, the described flat fused silica plates may be shipped to a customer (operating the DSS furnace) in separate packages or in stacked relation, rather than in an assembled relation as shown in Figure 10. The customer may then assemble the plates together inside the containment box to form the desired container for casting a silicon ingot from molten silicon. The customer may assemble the plates outside the containment box and then place the assembled liner within the containment box.

Referring now to Figure 4, an example methodology (i.e., process) 400 of using the described containment box is illustrated. While the methodology is described as being a series of acts (i.e., steps) that are performed in a sequence, it is to be understood that the methodologies are not limited by the order of the sequence. For instance, some acts may occur in a different order than what is described herein. In addition, an act may occur concurrently with another act. Furthermore, in some instances, not all acts may be required to implement a methodology described herein.

As illustrated in Figure 4, the methodology 400 begins at 402, and at 404 includes a step of placing a containment box having four side walls, a bottom wall and a top opening in a Directional Solidification Silicon (DSS) furnace. As described previously, each of the walls of the containment box is comprised of a carbon fiber woven material.

Continuing at step 406, the method may include placing a DSS container into the containment box through the top opening, which container is operative to hold molten silicon therein. As discussed previously, the walls of the containment box have a sufficient strength to contain a leak of silicon from the container.

At step 408, the method may include operating the DSS furnace to cast a silicon ingot in the container. After the ingot is cast, the container may be damaged. However, the described containment box may be capable of being reused for many additional castings. Thus the method may include a step 410 of replacing the container with a further container placed in the same containment box in the DSS furnace, followed by a step 412 of operating the DSS furnace to cast a further silicon ingot in the further container. At 414 the described method may end.

Referring now to Figure 5, an example process 500 of using a modular liner in the described containment box is illustrated. Here the methodology 500 begins at 502, and at 504 includes a step of forming a container from five plates comprising a fused silica. The five plates may have sizes to enable all five plates to be placed adjacent respective inside surfaces of the bottom wall and the side walls of a containment box. At step 506, the method may include sealing seams between adjacent edges of the five plates with a silica cement, to enable the container to hold molten silicon therein. Also, at step 508, method may include operating a DSS furnace to cast a silicon ingot in the container positioned inside the containment box.

It is noted that several examples have been provided for purposes of explanation. These examples are not to be construed as limiting the hereto-appended claims. Additionally, it may be recognized that the examples provided herein may be permutated while still falling under the scope of the claims.

Claims

CLAIMS What is claimed is:

1. An apparatus comprising: a containment box having four side walls, a bottom wall and a top opening, wherein the containment box is operative to receive a Directional

Solidification Silicon (DSS) container therein through the top opening, which container is operative to hold molten silicon therein, wherein each of the walls of the containment box is comprised of a carbon fiber woven material, wherein the walls of the containment box have a sufficient strength to contain a leak of silicon from the container.

2. The apparatus according to claim 1 , wherein the four side walls and the bottom wall are comprised of a carbon composite laminate.

3. The apparatus according to claim 1, wherein the four side walls further comprise a carbon fiber woven material wound around portions of the four side walls comprised of carbon composite laminate.

4. The apparatus according to claim 1 , wherein the carbon fiber woven material wound around the four walls does not extend adjacent the bottom edges of the side walls, wherein portions of the four walls adjacent the bottom edges of the side walls are comprised of a carbon composite laminate that are relatively thicker than the portions of the four side walls around which the fiber woven material is wound.

5. The apparatus according to claim 1, wherein the carbon fiber woven material includes a phenolic based carbon fiber pre-preg woven material with a fiber count of 3k to 12k, and with at least one of a stretch broken in twill, plain weave, and harness fabric.

6. The apparatus according to claim 1 , wherein each of the walls has a thickness that is between about .125 inches (3.175 mm) and about 1 inch (25.4 mm) thick.

7. The apparatus according to claim 1, further comprising the container comprised of a fused silica.

8. The apparatus according to claim 1, wherein the container includes four side walls and one bottom wall and a top opening, wherein the walls of the container are comprised of generally flat fused silica plates, wherein seams between adjacent edges of the flat plates are sealed with a silica cement.

9. A method comprising: a) forming a containment box having four side walls, a bottom wall and a top opening, with a size sufficient to receive a Directional Solidification Silicon (DSS) container therein through the top opening, which container is operative to hold molten silicon therein, wherein each of the walls of containment box are formed using a carbon fiber woven material; and b) heating the containment box to cure the walls to produce a structure with sufficient strength to contain a leak of silicon from the container.

10. The method according to claim 9, wherein (a) includes constructing at least a portion of the side walls using a fiber winding technique.

11. The method according to claim 9, wherein (a) includes constructing at last a portion of the side walls using a combination of a fiber winding technique and fabric layup.

12. The method according to claim 9, further comprising: c) forming five plates comprising a fused silica, wherein the five plates have sizes to enable all five plates to be placed adjacent respective five inside surfaces of the bottom wall and the side walls of the containment box.

13. The method according to claim 9, further comprising: c) placing the containment box in a DSS furnace with the container therein; d) operating the furnace to cast a silicon ingot in the container; e) replacing the container with a further container placed in the same

containment box in the DSS furnace; and f) operating the furnace to cast a further silicon ingot in the further container.

14. A method comprising, a) placing a containment box having four side walls, a bottom wall and a top opening in a Directional Solidification Silicon (DSS) furnace, wherein each of the walls of the containment box is comprised of a carbon fiber woven material; b) prior to or after (a) placing a DSS container into the containment box through the top opening, which container is operative to hold molten silicon therein, wherein the walls of the containment box have a sufficient strength to contain a leak of silicon from the container; and c) operating the DSS furnace to cast a silicon ingot in the container.

15. The method according to claim 14, further comprising: d) replacing the container with a further container placed in the same

containment box in the DSS furnace; and e) operating the furnace to cast a further silicon ingot in the further container.

16. The method according to claim 14, further comprising: d) forming the container from five plates comprised of a fused silica, wherein the five plates have sizes to enable all five plates to be placed adjacent respective inside surfaces of the bottom wall and the side walls of the containment box; and e) sealing seams between adjacent edges of the five plates with a silica cement.