S C I E N C E F O R T H E G L A S S I N D U S T R Y

CORRECTION OF IRON OXIDE CONTENT IN FLAT GLASS

M. I. Manusovich, L. Ya. Levitin, and N. A. Pankova

UDC 666.151:666.124.2

One of the important requirements for stabilizing convection flow in molten glass in tank furnace is stability in the permeability of the glass melt toward infrared radiation. This is especially important in the production of flat glass.

Better stabilization of infrared permeability of glass melts is attained by controlling the iron oxide content by addition of iron oxide-containing materials.

The usefulness and, in some cases, the need to enforce stability in the iron oxide con- tent in glass is convincingly demonstrated by experience with a series of flat glasses.

As with any adjustment of glass chemical content, correction of iron oxide content should first rest on information concerning fluctuations in chemical composition of the raw mate- rials (assuming reliable sampling), and secondly, on data about the tendency of the glass composition to change as shown by the 3 last analyses with 5-7 day intervals.

It is recommended to adjust the iron oxide content when the Fe203 content in the batch components fluctuates by more than 0.01%* (of total glass composition), and also when the iron oxide content in the glass decreases continuously over 15-20 days.

In Table 1 is a sample calculation of the amount of iron-containing component necessary to adjust the iron oxide content in a glass composition to a preassigned quantity.

If the difference in calculated iron oxide content between formulas No. 1 and No. 2 equals--0.0100% it is not necessary to increase the iron oxide content, since following change of their calculated content by formula No. 3 involves increase of iron oxide content practically up to the quantity corresponding with formula No. i. When there is a change of calculated iron oxide content in glass between formulas of No. i, 2, and 4, in the latter case correction should be carried out.

The size of the correction is determined by the fluctuations of calculated iron oxide content in each batch formula and by the difference between the first of the three most re- cent analyses of iron oxide content in the glass and the mean of the two succeeding analyses over 15-20 days.

An example of change in iron oxide content in glass according to chemical analyses at 5-7 day intervals is shown below.

Analysis number Iron oxide content, % 1 0.16 2 0.14 3 1.12

In this case the quantity of iron oxide in pigment added to correct the iron oxide con- tent is

0 . 1 4 + 0 . 1 2 O. 16 ~ = 0.03%.

2

The preassigned level of iron oxide in glass should be accepted as 10% below the maximum value for the preceding calendar year that was obtained in no less than five analyses.

*Here and further, mass contents are indicated.

State Institute of Glass. Translated from Steklo i Keramika, No. i, pp. i0-ii, January, 1986.

0361-7610/86/0102-0009512.50 �9 Plenum Publishing Corporation 9

TABLE 1

Indicator

Dose per 100 kg glass, kg: formula No. I (before correc- tion of FeOs content) formula No, 2

" No. 3 " No. 4

Iron oxides content, % formula No. I

" No. 2 " No. 3 " No. 4

Calculated iron oxide content

sand

67.32

68.00 68.00 68.00

in glass, %: formula No. i

" No. 2

" No. 3 " No. 4

Difference of calculated iron oxide content in glass be- tween formulas, %; No. i and 2 (total-0.0100) No. 2 and 3 (total +0.0372) No. 4 and 2 (total-0.0120)

0.08 0.05 0.09 0.05

0.0539 0.0340 0.0612 0.0340

Batch components

-0.0199 +0.0272

0

dolomite

19.81

19.62 19.72 23.50

0.17 0.12 0.15 0.i0

0.0337 0.0235 0.0296 0.0235

--0.0101 +0.0061

0

limestone

1.20

1.32 1.39 1.39

0.18 0.17 0.18 0.18

0.0021 0.0022 0.0025 0.0025

0 +0.0003 +0.0003

feldspar

7.53

7.21 7.68 7.02

0.50 0.80 0.80 0.62

0.0377 0.0577 0.0614 0.0455

+0.0200 +0.0037 --0.0122

In order to evaluate the appropriateness of the choice of preassigned level it is ne- cessary to calculate the maximum possible iron oxide content in the glass by summing the maximum contributions from each batch component. This should be compared with the real maxi- mum iron oxide content in glass as determined by analysis.

In the maximum possible iron oxide content in glass exceeds the real content by not more than 0.005%, then the preassigned level of iron oxide should be accepted as equal to the maxi- mum real content. If the maximum possible content in glass exceeds the real content by more than 0.005%, then the preassigned level should by accepted as 0.003% lower than the maximum possible content.

It is recommended that iron oxide content in glass be corrected by first adding only part of the iron oxide pigment necessary to attain the calculated preassigned level.

This initial addition of iron oxide should suffice to raise the iron oxide in the glass not more than 0.01% for 7 days.

When it is necessary to use a portion of a return cullet with an iron content different from that required at the time, the difference in iron oxide content in the current portion of the culler and the succedlng portions should each be considered separately when making the adjustment.

As added iron oxide one can use polishing powder, katrel dust, and iron oxide pigment. In some eases it is permissible to use small additions of sand or dolomite containing in- creased quantities of iron oxides. The material should come from one supplier to ensure a constant chemical composition which does not contain toxic impurities or substances that color molten glass. This material should be mixed, carefully sampled and analyzed.

We will examine sample calculations of the required amounts of added iron oxide pigment under the following conditions: FesOs content in iron oxide pigment, 0.96%; preassigned FeO2Os quantity in glass, 0.16%; Fe=Os quantity needed for adjustment by glass analysis + 0.030%.

i0

If the change of calculated iron oxide content of the glass introduced in the batch components equals --0.0100% (see Table i), the Fe203 content in the glass falls short of the preassigned level by %:

-0.0100-0.03 =-0.040.

The quantity of iron oxide pigment dose will be equal to (%)

0.040:0.96 = 0.0417.

If the change of calculated iron oxides in glass introduced in the batch components equals + 0.0372% (see Table I) the quantity of Fe203 is below the preassigned level by (%)

-0.0300+0.0372 = +0.0072.

In this case the adjustment is not made.

The principles for stabilization of iron oxides content in flat glass should constitute a basis for batch correction with iron oxide-containing materials with consideration of the individual conditions at each plant.

RESERVES FOR ECONOMIZING IN FUEL FOR GLASS-MELTING FURNACES

M. B. Usvitskii and M. A. Zezin UDC 666.1.031~2: 662.75.003.18

The use of automated dosing systems which by 1977 were utilized in 75% of the glass furnaces at the plants under the Ministry of Structural Materials of the USSR has made it possible to lower the costs of natural fuel.

At the present time the glass furnaces fueled by Mazut make use of automated dosing sys- tems through nozzles [i, 2], using special NSh-40I gear pumps which are designed to supply solutions to synthetic-fiber machines. The pumps are driven by thyristor-controlled d.c. motors. Here we are concerned only with increasing the effectiveness of their use.

With the aim of achieving accurate dosing and reliable operation beyond the pumps, it is necessary to carry out systematic observation of the pumps, above all, to make adjustments in good time, and to change the packing in the pumps themselves and in the other mechanisms which are part of the operation of the whole system. It is sensible to replace the packing rings without waiting for leaks to appear. If these measures are not carried out there will be unjustified loss of fuel and a deterioration in the working of the system. However, the cost of making sure of hermetic sealing will soon be compensated by savings in fuelo

The packing rings must be made from polychlorvinyl or Teflon-4. It is necessary in this case to ensure that the finishing is accurate and that the necessary quality is achieved of the bearing surfaces. When a grease-resistant rubber is used it is essential to avoid drawing out of the packing since this will cause rapid wear of the details.

When the rotation rate is increased, the accuracy of the dosing is lowered and therefore for the specified maximum productivity of the pumping equipment, the number of pumps that are switched on must be such that their rotation rate is maintained within the limits of 50 rev/min| The useful life of the pumps is limited only by their mechanical wear and is 4-5 years on average.

The accuracy of the operation and the durability of the equipment depends on the degree to which mazut has been freed from inclusion and therefore it is necessary systematically to attend to the state of the filters used in the mazut-preparation lines and in the dosing equipment (Fig. i). When the mesh filters (2, 3) mounted on the input of the equipment be- came clogged, the pressure in the pipe line is reduced by comparison with the pressure in the main line after the filter (i) and this can be used as a sign that the filters should be cleaned. The extent of the clogging of the filters can be judged from the indication on the

State Scientific-Research Institute of Glass. Planning and Design Bureau of the State Scientific-Research Institute of Glass. Translated from Steklo i Keramika, No. I, pp. 11-13, January, 1986.

0361-7610/8610102-0011512.50 �9 Plenum Publishing Corporation ii