JPH0444619Y2 - - Google Patents

Description

[Detailed explanation of the idea]

(Field of Industrial Application) This invention relates to a heat insulating sheet for an electrolytic cell used for refining non-ferrous metals. (Prior art) In electrolytic operations that are carried out at temperatures higher than room temperature, such as electrolytic refining of non-ferrous metals such as aluminum and copper, an electrolytic solution is heated in a storage tank and circulated between the electrolytic tank and the electrolytic solution. In order to prevent a large amount of heat from being taken away by the steam evaporating from the electrolytic cell and from generating mist in the atmosphere, the upper part of the electrolytic cell is covered with a sheet-like material. For example, Japanese Utility Model Publication No. 55-7564 discloses that the top surface of an electrolytic cell is covered with an acid-resistant filter cloth having an air flow rate of 10,000 to 22,000 cm ³ /min/cm ² in a water column with a pressure difference of 12.7 mm. In addition, in Utility Model Application Publication No. 57-44178, air permeability
It is disclosed that a sheet of 9000 ml/min/cm ² or less is used to cover multiple tanks. (Problem that the invention attempts to solve) However, the ventilation volume is 10,000 to 22,000 cm ³ /
min/cm ² acid-resistant filter cloth had an insufficient heat-retaining effect because the ventilation rate was too large and steam, that is, mist, passed through the acid-resistant filter cloth. Also, the air permeability
For sheets of 9000 ml/min/cm ² or less, the lower the air permeability, the less steam passes through and the heat retention effect improves, but on the other hand, steam condenses on the bottom side of the sheet.
This condensed liquid falls into the electrolytic cell through the support portion of the sheet and contaminates the electrolyte, and to prevent this, it is necessary to frequently replace the sheet. This invention provides a heat-insulating sheet for an electrolytic cell that has an excellent heat-insulating effect and prevents condensate from falling. (Means for solving the problem) This sheet consists of a sheet that covers the top surface of the electrolytic cell, and this sheet is obtained by piercing a synthetic fiber web laminated in multiple layers with a barbed needle to entangle the fibers three-dimensionally. It is a non-woven fabric with a basis weight of 300~
It is characterized by having an apparent density of 1200 g/m ² and 0.1 to 0.3 g/cm ³ . The synthetic fiber used in this invention can be any synthetic fiber as long as it has acid resistance, preferably fibers made of polyester, polypropylene, polyacrylonitrile, etc. Synthetic fibers can be used. The fibers may be in the form of staples or filaments, and have a fineness of 1
~10 denier is preferred. The above-mentioned nonwoven fabric made of synthetic fibers is produced by laminating thin carded webs made of synthetic fiber staples or filament webs obtained by the spunbond method to a desired area weight, and intermittently layering this soft cotton-like laminated web. Needling is performed in the vertical direction on the laminated web using multiple barbed needles while the web is being fed forward and stationary.
This is called a needled nonwoven fabric or needle punched nonwoven fabric, in which the fibers are three-dimensionally intertwined and tightened and hardened by pushing a portion of the synthetic fibers in the thickness direction many times.
Depending on the number of laminated sheets of the above-mentioned web, the basis weight of the non-woven fabric is 300 to 1200 g/ ^m2 , and the apparent density of the non-woven fabric is 0.1-1200 g/m2 depending on the needle penetration density of the above-mentioned needling.
Each is set at 0.3g/ ^cm3 . In addition, the above nonwoven fabric uses a coarse woven fabric as the base fabric, and by stacking the above laminated web on one or both sides of this base fabric and performing the above needling, the fibers of the web are bonded to each other. At the same time as they are entangled, the fibers of the web are entangled with the warp and weft of the base fabric, thereby making it possible to manufacture the base fabric and the fibers in an integrated manner. (Function) Inside the nonwoven fabric, many thin synthetic fibers cross each other and are tightened by needling to form many fine voids. That is,
The porosity is high and the individual voids are finely formed. Therefore, as a heat insulating sheet that covers the electrolytic cell, it has extremely high water retention properties, blocking the steam rising from the electrolytic cell, and allowing the condensed liquid generated at that time to enter the minute voids above without letting it fall. Hold. However, if the basis weight is less than 300g/ ^m2 ,
If the apparent density is less than 0.1g/ ^cm3 , the air permeability will be too high and the heat retention will be insufficient.
On the other hand, when the basis weight exceeds 1200g/ ^m2 , the weight increases, but the effectiveness does not increase and the apparent density decreases.
When it exceeds 0.3g/ ^cm3 , the porosity decreases,
Water retention decreases. In particular, when synthetic fibers of 1 to 10 deniers are used, the voids are formed to a desirable size and good water retention is achieved. However, if the fineness is less than 1 denier, the porosity will be small and the water retention will be reduced, whereas if it exceeds 10 denier, the pores will be too large and breathability will increase, increasing the passage of steam and making the heat retention effect insufficient. Become. Furthermore, when a water-absorbing synthetic fiber is used, the water-absorbing property of the fiber itself is added to the water-retaining property due to the fine voids, and the water-holding property of the nonwoven fabric is further improved. (Example) In Fig. 1, 1 is an electrolytic tank, 2 is an electrolytic solution, and 3
is an electrode plate, and a large number of electrode plates 3 are arranged at appropriate intervals in the direction perpendicular to the plane of the paper, and each is inserted vertically into the electrolytic solution 2. A heat insulating sheet 4 made of non-woven fabric is placed. This heat insulation sheet 4
As shown in the figure, it is a non-woven fabric in which synthetic fiber webs 4b are laminated on both the upper and lower surfaces of a base fabric 4a and integrated by needling. In addition, the above electrolytic cell 1 is
It is connected by two pipes to a liquid storage tank (not shown) equipped with a heating device, so that the electrolytic solution 2 heated in the liquid storage tank is circulated between it and the electrolytic tank 1. As shown in Table 1 below, Examples made of nonwoven fabrics with the structure shown in Figure 2, Comparative Example 1 made of woven fabrics, and
A total of three types of heat insulation sheets of Comparative Example 2 made of corrugated FRP (fiber-reinforced plastic) sheets were prepared.

【table】

[Table] Using a manganese sulfate solution as the electrolytic solution, manganese dioxide was deposited on the anode plate, and the performance of the above three types of heat insulation sheets was compared, and the results shown in Table 2 were obtained. However, the temperature of the electrolyte was set at 90°C, and the test time was 7 days. Further, the steam usage rate in the table is expressed with the total steam usage rate of Comparative Example 2 as 100%.

【table】

[Table] As is clear from Table 2 above, the embodiment of this invention has the least impurities in the electrolyte and the product, and the largest amount of condensate, which is 5 times that of Comparative Example 1. The steam usage rate was the lowest, and could be reduced by 15% and 20% compared to Comparative Examples 1 and 2, respectively. (Effects of the invention) The heat insulating sheet of this invention is made of a nonwoven fabric with a high porosity and a density of 300 to 1200 g/m ² and an apparent density of 0.1 to 0.3 g cm ³ with many fine voids. It has excellent heat retention properties because less steam passes through it, and it also has excellent water retention properties and can hold a large amount of condensate, thereby saving energy consumption and reducing the production of impurities.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the electrolytic cell, and FIG. 2 is a cross-sectional view of the heat-insulating sheet. 1... Electrolytic tank, 2... Electrolyte, 3... Electrode plate,
4... Heat retention sheet made of nonwoven fabric, 4a... Base fabric, 4
b...Synthetic fiber web.

Claims (1)

[Scope of claims for utility model registration] [1] Consisting of a sheet covering the top surface of the electrolytic cell,
This sheet is a nonwoven fabric obtained by piercing a multi-layered synthetic fiber web with a barbed needle to entangle the fibers three-dimensionally, and has a basis weight of 300 to 1200 g/m ² and an apparent density. 0.1~0.3
A heat insulating sheet for an electrolytic cell, characterized by a temperature of g/cm ³ . [2] A coarse nonwoven fabric is used as the base fabric, and a synthetic fiber web is laminated on at least one side of the base fabric,
A heat insulating sheet for an electrolytic cell according to claim 1, which is a utility model registration sheet, which is formed by integrating the base fabric and the web by piercing with barbed needles.