Table T. - Incrustations From Boilers. Heaters Used

Before

Heaters in use.

After Heaters in work.

(No. Soda.)

Calcic Carbonate

30.89

1.36

Calcic Sulphate ..

31.22

79.61

Ferric Oxide

2.96

112

Magnesic Carbonate .. ..

26.41

14.22

Soda Salts, etc. ..

0.48

0.46

Silica......

4.54

2.15

Organic Matter ..

2.66

0.85

Moisture

0.84

0.23

100.00

100.00

Thus the change in the composition of the water supply caused by the heaters is fully as well shown in the scale from the boilers. The calcic carbonate previously present in considerable quantity has almost disappeared. The magnesic carbonate is only about 1/2, whilst the ferric oxide, organic matter, and insoluble portion have been much diminished. Of course it must be remembered that this is not entirely due to the removal of the saline ingredients of the water supply, but is to a large extent traceable to the greatly increased supply of condensed water flowing from the heaters and sent to the boilers. This condensed water is much larger in proportion than would be the case in ordinary working, for it must be remembered that the heaters are being worked with steam direct from the boilers, instead of the waste cylinder supply. The sediment removed from the water by the heaters falls to the lower part of the apparatus, and is to some extent removed by a blowcock, which is to be used 4 times daily, but a larger amount remains in the apparatus, and is washed out once a month.

The analysis of this sediment shows: -

Table U. - Sediment From Heaters

Calcic Carbonate..

2.77

Calcic Sulphate ..

0.61

Ferric Oxide ......................

19-77

Ferrous Carbonate..

2.54

Magnesic Carbonate..

1.02

Soda Salts, etc...

0.46

Silica and Clay..

47.34

Organic Matter ..

25.49

100 00

These results show that whilst the calcic carbonate is removed by the blow-cock, the heavier oxide of iron falls to the lower part of the apparatus along with the sand and clay derived from the dirty water supply. The analysis of the liquid from the blowcock gives the following results: -

Table V. - Water From Blowcock Of Heaters

In Suspension:-

Per gal.

Saline Water..

..1.61

Organic Matter ••

.. 0.45

Solid Matter ••

2.06

Calcic Carbonate

.. 0 53

Calcic Sulphate

0.11

Ferric Oxide

0.28

Organic Matter

.. 0.45

Insoluble Matter

0.51

Suspended Matter: -

Per cent

Calcic Carbonate

.. 25.72

Calcic Sulphate

.. 5.34

Ferric Oxide ..

.. 13.59

Organic Matter

.. 21.84

Insoluble Matter

.. 2475

In Solution:-

Per gal.

12.72

Organic Matter

.. 2.96

Solid Matter..

.. 15.68

Calcic Carbonate...

3-68

Calcic Sulphate....

5 61

The simple heating of the feed water, before passing into the boiler, either by a direct fire or by the employment of waste steam, does good by removing much of the calcic carbonate, and settling out a considerable proportion of the suspended matter, whether such be of mineral or organic origin. As, however, the water is not under pressure, the calcic sulphate is practically undiminished in quantity. In one case, the waste steam is passed through copper pipes laid near the bottom of an iron cistern. The tank is 14 ft. long, 7 ft. deep, and 7 ft. broad, and has 24 pipes of 3 in. diameter laid within 6 in. of the bottom. Through these pipes the waste steam of a Lancashire boiler is passed, sufficient heat being obtained to raise 36,000 gal. water per week to a temperature ranging from 180° to 200° F. (82°-93° C). The steam and water condensed are then blown into another tank, and so utilized. The results of the analysis of the water before and after the heating are given in Table W: -

Table W. - Boiler Feed-Water Heated In Tank By Waste Steam To A Temperature Of 180&Deg; To 200&Deg; F. Per Gal

Before Heating.

After Heating.

Saline Matter ..

52.02

.. 4384

Organic Matter ..

7.04

.. 5.18

Total Solid Matter

59.06

.. 49.02

Calcic Carbonate

20.64

.. 9.92

Calcic Sulphate ..

11.36

.. 12.24

These results show that the heating throws down a very considerable proportion of the calcic carbonate, the actual amount being 10.72 gr. per gal. of water, or a little over a half of the whole present. The result of the operation will be more fully appreciated if the amount is calculated per week or per year: -

Table X. - Calcic Carbonate Removed From Boiler Feed-Water By Waste-Steam Heat

Per gallon

10.72 gr.

Per week

55.1714 lb.

Per year...

2868.9128 lb.

(1.2807 ton).

Besides the calcic carbonate, a proportion of the organic matter is deposited, the amount being: -

Table Y. - Organic Matter Removed From Boiler Feed-Water By Waste-Steam Heat

Per gal...

1.86 gr.

Per Week......

8.1371 lb.

Per year....

423.1292 lb.

These two ingredients added together give the following results: -

Table Z. - Calcic Carbonate And Organic Matter Removed Yearly From Boiler Feed-Water By Waste-Steam Heat

Calcic Carbonate

lb.

ton.

2868-9128

= 1.2807

Organic Matter

423.1292

= 0.1889

Total .. .,

3292.0420

= 1.4697

These figures do not represent the total matter removed, for they do not include magnesic carbonate, ferric oxide, nor a small proportion of calcic sulphate. The deposit formed is somewhat soft, but becomes very hard on drying. The analysis yielded the figures given below: -

Table Aa. - Sediment From Water Heated By Waste Steam

Calcic Carbonate

66.76

Calcic Sulphate

2.37

3.41

Magnesic Carbonate

17.42

Soda Salts, etc.......

0.24

Silicious Matter ..

0.52

Organic Matter .. ..

6.84

2.44

100.00

The amount of saline ingredients removed from a water by heat depends greatly upon the actual temperature to which the water is raised. A series of experiments was made with a tank heated by a direct fire to a temperature of 130° F. (54}° C). The results are: -

Table Bb - Boiler Feed-Water Heated To 130&Deg; F. By Direct Fire

Water before

Heating.

Water after

Heating.

Saline Matter ..

33.44

.. 28.56

Organic Matter ..

5.04

.. 3 92

Solid Matter

38.48

32.48

Calcic Carbonate

11.85

.. 7.52

Calcic Sulphate..

7.82

.. 8.56

Calculated to the gallon, week, and year, the following figures are obtained, 36,000 gal. water being heated per week: -

Table CC. - Calcic Carbonate Removed By Direct Heat (Temperature Of Water, 130&Deg; Fa

Per gallon

.. .. 4.33gr.

Per week...

.. .. 22.2685 lb.

Per year ..

.. „. 1157.962 lb.

Table Dd. - Organic Matter Removed By Direct Heat (Temperature Of Water, 130&Deg; Fa

Per gallon

1.12gr.

Per week..

..22.2685lb

Per year..

..1157.962lb

Table Ee. - Calcic Carbonate And Organic Matter Removed Per Year By Direct Heat (Temperature Of Water, 130&Deg; F.)

lb.

ton.

Calcic Carbonate

1157.962

= 0.517

Organic Matter ..

309.92

= 0.138

Total ..

1467.882

= 0.655

The incrustation formed was hard and tough, and had the following composition: -

Table Ff. - Incrustation Of Water Heated By Direct Fire To A Temperature Of 130&Deg; F

Calcic Carbonate

87.43

Calcic Sulphate...

1.42

Ferric Oxide...

2.68

Magnesic Carbonate ..

4.33

Soda Salts,&c

0.32

Insoluble Matter

0.72

Organic Matter...

1.56

Moisture...

1.54

100.00

Clarke's process, the addition of milk of lime, is suitable, but the space required for settling is against the general adoption of the method. This difficulty may, however, be got over by the employment of Porter's filtering cloth apparatus, with the careful adjustment of the quantity of milk of lime added. The process, however, is only of use in the case of temporary hard waters. Baron Nicolas de Derschau (Jl. Soc. Chem. Ind., No. 5, Vol. 1., May 1882, p. 176) employs Porter's principle, using, however, magnesia instead of lime. This process can be employed with sulphate of lime waters, magnesia sulphate being produced, and from its solubility remaining in solution. De Haen's process, the addition of baric chloride, is (as mentioned by Davis in the paper previously quoted) both costly and somewhat doubtful of action, even where lime water is afterwards added. Davis's "tripsa" (tribasic phosphate of soda) deserves a fair trial as a softening agent. The addition to the feed water of caustic soda, or still better of soda ash, and at the same time raising the temperature by utilizing waste steam or heat, would be beneficial in most cases, care being taken to afterwards settle or filter the water. Soda ash was first recommended in the columns of the.