JP2016061485A - Powder heating type solar heat reduction furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder heating type solar heat reduction furnace which can evenly heat a great number of retorts.SOLUTION: Metallic oxide powder 5 having a high heat conductivity is heated by solar heat, and a plurality of retorts 20 are provided in the heated powder 5. Therefore, the plurality of retorts 20 are heated at the same time, and all of the retorts 20 are evenly heated. Consequently, efficient reduction of magnesium can be carried out.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a powder heating type solar thermal reduction furnace.

  Concentrates sunlight as clean energy that does not place a burden on the environment, and converts the collected sunlight into heat energy to create a very high temperature, which requires a high-temperature reaction environment There is known a solar thermal reactor in which a chemical reaction of the reactants proceeds.

  On the other hand, a magnesium battery using magnesium metal is known. It is a primary battery that generates electromotive force by immersing magnesium metal in an electrolyte as a negative electrode. In this magnesium battery, an insoluble oxide (magnesium hydroxide) is generated after use. It is desired to repeatedly use the insoluble oxide as a battery by reducing the insoluble oxide by solar heat and restoring it again to magnesium metal.

  A cylindrical steel container called retort is used for the reduction of the oxide. A magnesium oxide and a reducing material are put into this retort and reduced by heating to a high temperature (about 1200 ° C.), and only magnesium is vaporized and solidified and recovered in a cooling part at one end of the retort (for example, , See Patent Document 1).

JP-A-6-41654

  However, in such a related technique, when heating is performed by directly applying sunlight to the retort, many retorts cannot be heated at once. In other words, the back of the retort exposed to sunlight becomes a shadow, and the retort cannot be placed there. Further, depending on the light collection state, it may not be possible to uniformly heat a plurality of retorts.

  The present invention has been made paying attention to such related technology, and an object thereof is to provide a powder heating type solar thermal reduction furnace capable of uniformly heating a large number of retorts.

  According to the first aspect of the present invention, a heat-resistant transparent window for receiving sunlight collected by a beam-down condensing structure is formed at the upper portion, and metal oxide powder is accumulated therein. The tank body, the pipe means arranged in the powder, the heat conversion member that receives sunlight and converts light into heat and allows gas to pass through, and the high-temperature gas that has passed through the heat conversion member. A heat-resistant pump that circulates in the pipe means and a retort that can be installed in the powder of the tank body are provided.

  According to a second feature of the invention, the metal oxide is magnesium oxide or aluminum oxide.

  According to the third feature of the present invention, the powder heating type solar thermal reduction furnace is installed at a position higher than the ground and has a reflection surface on the lower surface, and a ground area around the center mirror. A plurality of heliostats that reflect sunlight toward the center mirror, and the sunlight reflected by the heliostat is focused on a ground position by a beam-down solar concentrator that reflects the center mirror downward. The center mirror has a curved surface whose cross section conforms to the spheroid and has a first focus and a second focus below, the lower opening is smaller than the upper opening and the inner surface is A cylindrical condenser mirror having a mirror surface is installed in the vicinity of the second focal point, a transparent window of the tank body is installed in the vicinity of a lower opening of the cylindrical condenser mirror, and the heliostat has reflected light as described above. First It is controlled so as to be directed to the point.

  According to the first aspect of the present invention, a metal oxide powder having a high thermal conductivity is heated by solar heat, and a plurality of retorts are installed in the heated powder. In addition, all retorts can be heated uniformly. Therefore, efficient reduction of magnesium can be performed.

  According to the second feature of the present invention, since the metal oxide is magnesium oxide or aluminum oxide, it is easily available and inexpensive.

  According to the third feature of the present invention, the condensing device is a beam-down type, the center mirror has a curved surface whose section matches an ellipse, and the sunlight reflected by the heliostat is reflected by the center mirror. If it passes through the first focal point, the sunlight is always focused on the second focal point geometrically. Therefore, the heliostat has only to be controlled so that the reflected light always goes to the first focal point, and the heliostat can be easily controlled. In addition, since the cylindrical condenser mirror is located around the second focal point, the sunlight that is out of the second focal point is also taken into the cylindrical condenser mirror and is reflected on the inner surface of the cylindrical condenser mirror to ensure that it is in the transparent window of the tank body. Can lead.

The perspective view which shows the powder heating type solar thermal reduction furnace and solar condensing structure which concern on embodiment of this invention. The top view which shows a powder heating type solar thermal reduction furnace and a solar condensing structure. The side view which shows a powder heating type solar thermal reduction furnace and a solar condensing structure. Explanatory drawing which shows the condensing state of sunlight. Sectional drawing of a powder heating type solar thermal reduction furnace. The perspective view which shows the structure in a sunlight introduction part. The top view of a powder heating type solar thermal reduction furnace.

  1 to 7 are views showing a preferred embodiment of the present invention.

  First, a beam-down solar concentrator for obtaining solar heat will be described. In this embodiment, a case of an area in the middle latitude of the northern hemisphere such as Japan will be described as an example.

  A center mirror 1 is supported by three towers 1a at the center of the beam-down solar concentrator. The center mirror 1 has a partial spheroid shape in which the opposite side to the direction in which the sun exists during the day is cut out. The center mirror 1 has a curved surface whose cross section coincides with an ellipse, and a first focal point A and a second focal point B exist below as shown in FIG.

  As shown in FIG. 2, the center mirror 1 is in a state of projecting by a predetermined angle range to the east side and the west side from the semicircle in a plan view. A plurality of heliostats 2 are radially arranged on the north side and the east and west sides of the center mirror 1.

  The heliostat 2 has a structure that changes its direction in conjunction with the movement of the sun by a sensor (not shown), and is always controlled to reflect the sunlight L toward the first focus A. The sunlight L that has passed through the first focal point A is reflected by the center mirror 1 and collected at the second focal point B.

  A cylindrical condenser mirror 3 is installed at the second condensing point B. The cylindrical condenser mirror 3 has a structure in which the lower opening is smaller than the upper opening and the inner surface is a mirror surface. The second focal point B is located near the center of the upper opening of the cylindrical condenser 3, and the sunlight L is further collected by being introduced into the cylindrical condenser 3 from the upper opening. The

  A powder heating type solar thermal reduction furnace 4 is installed below the cylindrical condenser mirror 3. The powder heating type solar thermal reduction furnace 4 includes a tank body 6 in which magnesium oxide powder 5 is accumulated as a heat storage material.

  The tank main body 6 is made of stainless steel, and includes a cylindrical sunlight introduction portion 7 located in the center and a powder storage portion 8 located in the periphery thereof. A transparent window 9 made of quartz glass is provided in the upper part of the sunlight introduction part 7.

  The sunlight introduction part 7 and the powder storage part 8 are partitioned through a partition wall 15. Magnesium oxide powder 5 is stored on the powder storage unit 8 side, and the powder storage unit 8 is provided with pipe means 10 penetrating through the powder 5. A plurality of retorts 20 for magnesium reduction are installed in the powder 5 in the powder storage unit 8.

  An upper space 11 and a lower space 12 are formed above and below the powder storage unit 8, and both ends of the pipe means 10 communicate with the upper space 11 and the lower space 12.

  The upper space 13 of the sunlight introduction unit 7 is partitioned from the upper space 11 of the powder storage unit 8 by the partition wall 15, but the lower space 14 of the sunlight introduction unit 7 is continuous with the lower space 12 of the powder storage unit 8. doing. All the spaces in the tank body 6 are filled with nitrogen gas as a heat medium.

  Four heat-resistant pumps 16 are provided in the circumferential direction at the upper part of the tank body 6, and nitrogen gas in the tank body 6 is passed between the solar light introduction part 7 and the powder storage part 8 through the pipe means 10. It can be circulated. This heat-resistant pump 16 has a structure using heat-resistant bearings, and can circulate high-temperature nitrogen gas.

  Inside the sunlight introduction part 7, a heat exchange member 18 attached to the upper end of the center pipe 17 and a ring-shaped auxiliary heat exchange member 19 along the cylindrical partition wall 15 of the sunlight introduction part 7 are vertically arranged in multiple stages. Is provided.

  The heat exchange member 18 has a black and multi-through hole structure made of a silicon carbide film (SiC) as a nonmetallic heat resistant material, and has a heat resistance of about 1000 ° C. or more. Due to the multi-through hole structure, gas can be passed vertically. The auxiliary heat exchange member 19 is made of the same metal as the partition wall 15 and is provided at a position close to the inside of the partition wall 15 of the solar light introduction unit 7.

  The position and size of the heat exchange member 18 correspond to the condensed spot of the sunlight L irradiated from the cylindrical condenser mirror 3. As shown in FIG. 4, the sunlight L irradiated from the lower side of the cylindrical collector mirror 3 once converges to the minimum spot S and then diffuses again, and is a roughly crescent shaped spot corresponding to the arrangement structure of the heliostat 2. Presents a shape. That is, as shown in FIG. 2, the arrangement of the heliostat 2 is not circular, but is arranged like a partial circle, so that it appears as a spot shape of the non-focal part.

  The heat exchange member 18 in this embodiment has a size that matches the minimum spot S in the condensed state of sunlight L, and the position also matches the same position as the minimum spot S.

  Thus, since the heat exchange member 18 is provided at a position where the energy of the sunlight L is most concentrated, the heat exchange member 18 can efficiently convert the sunlight L into heat energy. The nitrogen gas passing through the heat exchange member 18 can be efficiently heated.

  Further, the sunlight L irradiated from the lower part of the cylindrical condenser 3 not only converges toward the minimum spot S, but also includes sunlight L ′ that diffuses around. Such sunlight L ′ hits the auxiliary heat exchange member 19 before hitting the partition wall 15 of the sunlight introduction part 7, where it is converted into thermal energy, contributing to heating of the nitrogen gas in the sunlight introduction part 7.

  The sunlight L ′ that has hit the partition 15 without hitting the auxiliary heat exchange member 19 heats the partition 15 and heats the magnesium oxide powder 5 inside by heat transfer.

  Further, since the high-temperature nitrogen gas is circulated by the heat-resistant pump 16 through the pipe means 10 that vertically penetrates the powder 5, heat is transmitted to the powder 5 through the pipe means 10 to heat the powder 5. can do.

  Magnesium oxide has a thermal conductivity of 59 W / (m · K) (300 K), which is about 100 times that of molten salt. Therefore, the entire powder 5 is heated uniformly. Therefore, a plurality of retorts 20 installed in the powder 5 can be simultaneously and uniformly heated to perform efficient magnesium reduction.

  The price of magnesium oxide is about half that of molten salt. Therefore, it is advantageous in terms of cost. Further, since magnesium oxide has a high thermal conductivity, the heat conduction with the pipe means 10 is also good.

  Furthermore, because of the powder 5, it is easy to extract from the tank body 6, and maintenance of the pipe means 10 is easy.

  In the above description, magnesium oxide is taken as an example of the powder 5, but other metal oxides such as aluminum oxide may be used.

  Nitrogen gas is taken as an example of the circulating gas, but air may be used when the heat storage temperature is set low and there is no concern about oxidation of the metal in contact therewith.

  Further, it is possible to use a fluid (oil or the like) heated by another heat source without being heated by sunlight L. In that case, another heat pump 16 is used.

DESCRIPTION OF SYMBOLS 1 Center mirror 2 Heliostat 3 Cylindrical condensing mirror 4 Powder heating type solar thermal reduction furnace 5 Powder (magnesium oxide)
6 Tank body 7 Sunlight introduction part 8 Powder storage part 9 Transparent window 10 Pipe means 16 Heat-resistant pump 18 Heat exchange member 19 Auxiliary heat exchange member 20 Retort A 1st focus B 2nd focus L, L 'sunlight S Minimum spot

Claims (3)

A tank body in which a heat-resistant transparent window for receiving sunlight collected by a beam-down type condensing structure is formed at the upper part, and metal oxide powder is accumulated inside;
Pipe means arranged in the powder;
A heat converting member that receives sunlight and converts light into heat and allows gas to pass through;
A heat-resistant pump that circulates the high-temperature gas that has passed through the heat conversion member to the pipe means;
A powder heating solar reduction furnace comprising a retort that can be installed in the powder of the tank body.   2. The powder heating solar thermal reduction furnace according to claim 1, wherein the metal oxide is magnesium oxide or aluminum oxide. A center mirror installed at a position higher than the ground and having a reflecting surface on the lower surface, and a plurality of heliostats installed in a ground area around the center mirror and reflecting sunlight toward the center mirror, It is a structure that is focused on the ground position by a beam down type solar concentrator that reflects the sunlight reflected by the heliostat downward by the center mirror,
The center mirror has a curved surface whose cross section coincides with the spheroid and has a first focal point and a second focal point below, the lower opening is smaller than the upper opening, and the inner surface is a mirror surface. A cylindrical collector mirror is installed in the vicinity of the second focal point, a transparent window of the tank body is installed in the vicinity of a lower opening of the cylindrical collector mirror, and the heliostat reflects light to the first focal point. 3. The powder heating type solar thermal reduction furnace according to claim 1, wherein the powder heating type solar thermal reduction furnace is controlled so as to be directed.

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