By B.H. THWAITE.

In order to approximately ascertain the relative reducing action of water gas, carbon monoxide, and superheated steam on iron ore, the author decided to have carried out the following experiments, which were conducted by Mr. Carl J. Sandahl, of Stockholm, who also carried out the analyses. The ore used was from Bilbao, and known as the Ruby Mine, and was a good average hematite. The carbonaceous material was the Trimsaran South Wales anthracite, and contained about 90 per cent. of carbon.

A small experimental furnace was constructed of the form shown by illustration, about 4 ft. 6 in. high and 2 ft. 3 in. wide at the base, and gradually swelling to 2 ft. 9 in. at the top, built entirely of fireclay bricks. Two refractory tubes, 2 in. square internally, and the height of the furnace, were used for the double purpose of producing the gas and reducing the ore.

The end of the lower tube rested on a fireclay ladle nozzle, and was properly jointed with fireclay; through this nozzle the steam or air was supplied to the inside of the refractory tubes. In each experiment the ore and fuel were raised to the temperature "of from 1,800 to 2,200 deg. Fahr." by means of an external fire of anthracite. Great care was taken to prevent the contact of the solid carbonaceous fuel with the ore. In each experiment in which steam was used, the latter was supplied at a temperature equivalent to 35 lb. to the square inch.

The air for producing the carbon monoxide (CO) gas was used at the temperature of the atmosphere. As near as possible, the same conditions were obtained in each experiment, and the equivalent weight of air was sent through the carbon to generate the same weight of CO as that generated when steam was used for the production of water gas.

Water Gas The Relative Value Of Water Gas And Othe 531 11a

First Experiment, Steam (Per Se)

Both tubes, A and B, were filled with ore broken to the size of nuts. The tube, A, was heated to about 2,000 deg. Fahr., the upper one to about 1,500 deg.

Note

In this experiment, part of the steam was dissociated in passing through the turned-up end of the steam supply pipe, which became very hot, and the steam would form with the iron the magnetic oxide (FeO). The reduction would doubtless be due to this dissociation. The pieces of ore found on lowest end of the tube, A, were dark colored and semi-fused; part of one of these pieces was crushed fine, and tested; see column I. The remainder of these black pieces was mixed with the rest of the ore contained in tube, A, and ground and tested; see column II. The ore in upper tube was all broken up together and tested; see column III. When finely crushed, the color of No. I. was bluish black; No. II., a shade darker red; No. III., a little darker than the natural color of the ore. The analyses gave:

 -----------------------------+---------+---------+---------

| I. | II. | III.

+---------+---------+---------

|per cent.|per cent.|per cent.

Ferric oxide (Fe_{2}O_{3}). | 68.55 | 76.47 | 84.81

Ferrous oxide (FeO). | 16.20 | 9.50 | 1.50

+---------+---------+---------

Total. | 84.75 | 85.97 | 86.31

+---------+---------+---------

Calculated: | | |

Ferric oxide (Fe_{2}O_{3}). | 32.55 | 55.36 | 81.47

Magnetic oxide (Fe_{3}O_{4}).| 52.20 | 30.61 | 4.84

Ferrous oxide (FeO). | | |

+---------+---------+---------

Total. | 84.75 | 85.97 | 86.31

+---------+---------+---------

Percentage of total

oxygen reduced. | 6.93 | 4.02 | 1.07

Metallic iron. | 60.59 | 60.92 | 60.54

-----------------------------+---------+---------+--------- 

Second Experiment, Water Gas

The tube, A, was filled with small pieces of anthracite, and heated until all the volatile matter had been expelled. The tube, B, was then placed in tube, A, the joint being made with fireclay, and to prevent the steam from carrying small particles of solid carbon into ore in the upper tube, the anthracite was divided from the ore by means of a piece of fine wire gauze. The steam at a pressure of about 35 lb. to the square inch was passed through the anthracite. The tube, A, was heated to white heat, the tube, B, at its lower end to bright red, the top to cherry red.

 ------------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+

Experiment. | 1st. | 2d. | 3d. |

------------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+

Number. | I. | II. | III.| I. | II. | III.| IV. | I. | II. | III.|

------------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+

Total Iron. |60.59|60.92|60.54|65.24|61.71|61.93|57.23|59.73|57.93|55.54|

------------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+ 
Iron occurring as ------------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+ FeO. |12.60| 7.39| 1.17|46.98|18.59| 4.03| 0.84|29.45| 2.69| 1.12 Fe_{2}O_{3} |47.99|53.33|59.37|18.26|43.12|57.90|56.39|30.28|55.24|54.42 ------------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
Per cent. of Oxides. | ------------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+ FeO. |16.20| 9.50| 1.50|60.40|23.90| 5.18| 1.08|37.86| 3.46| 1.44 Fe_{2}O_{3}. |68.55|76.47|84.81|26.08|61.60|82.71|80.55|43.26|78.91|77.74 Total. |84.75|85.97|86.31|86.48|85.50|87.89|81.63|81.12|82.37|79.18 ------------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
Oxygen in Ore. ------------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+ Before experiment.|25.97|26.10|26.05|27.96|26.45|26.54|24.52|25.60|24.81|23.80 After experiment. |24.16|25.05|25.77|21.24|23.79|25.96|24.40|21.39|24.44|23.64 Difference. | 1.81| 1.05| 0.28| 6.72| 2.66| 0.58| 0.12| 4.21| 0.37| 0.16 ------------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
Per cent. of oxygen reduced. ------------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+ oxygen reduced. | 6.93| 4.02| 1.07|24.03|10.02| 2.18| 0.49|16.44| 1.49| 0.42 ------------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
Degree of Oxidation of the Ore after the Experiment. ------------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+ FeO. | ... | ... | ... |84.66| ... | ... | ... |18.40| ... | ... | Fe_{3}O_{4}. |52.20|30.61| 4.84|37.82|77.01|28.12| 3.88|62.72|11.14| 4.64| Fe_{2}O_{3}. |32.55|55.36|81.47| ... | 8.49|59.77|77.75| ... |71.23|74.54| Total. |84.75|85.97|85.97|85.97|85.97|85.97|85.97|85.97|85.97|85.97| ------------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
------------------+-----------------+-----------------------+-----------------+ The ore having | | | | been exposed to | Steam. | Water gas. | Carbon monoxide.| ------------------+-----------------+-----------------------+-----------------+

Four Samples Were Tested

I. The bottom layer, 1¼ in. thick; the color of ore quite black, with small particles of reduced spongy metallic iron. II. Layer above I., 4¼ in. thick; the color was also black, but showed a little purple tint. III. Layer above II., 5 in. thick; purple red color. IV. Layer above III., ore a red color. The analyses gave:

 -----------------------------+---------+---------+---------+---------

| I. | II. | III. | IV.

+---------+---------+---------+---------

|per cent.|per cent.|per cent.|per cent.

Ferric oxide (Fe_{2}O_{3}). | 26.08 | 61.60 | 82.71 | 80.55

Ferrous oxide (FeO). | 60.40 | 23.90 | 5.18 | 1.08

+---------+---------+---------+---------

Total. | 86.48 | 85.50 | 87.89 | 81.63

+---------+---------+---------+---------

Calculated: | | | |

Ferric oxide (Fe_{2}O_{3}). | ... | 8.49 | 59.77 | 77.75

Magnetic oxide (Fe_{3}O_{4}).| 37.82 | 77.01 | 28.12 | 3.88

Ferrous oxide (FeO). | 48.66 | | |

+---------+---------+---------+---------

Total. | 86.48 | 85.41 | 87.89 | 81.63

+---------+---------+---------+---------

Percentage of total

oxygen reduced. | 24.03 | 10.02 | 2.26 | 0.49

Metallic iron. | 65.24 | 61.71 | 61.93 | 57.23

-----------------------------+---------+---------+---------+--------- 

Note

All the carbon dioxide (CO) occurring in the ore as calcic carbonate was expelled.

Third Experiment, Carbon Monoxide (Co)

The tube A was filled with anthracite in the manner described for the second experiment, and heated to drive off the volatile matter, before the ore was placed in the upper tube, B, and the anthracite was divided from the ore by means of a piece of fine wire gauze. The lower tube, A, was heated to the temperature of white heat, the upper one, B, to a temperature of bright red. I. Layer, 1 in. thick from the bottom; ore dark brownish colored. II. Layer 4 in. thick above I.; ore reddish brown. III. Layer 11 in. thick above II.; ore red color. The analyses gave:

 -----------------------------+---------+---------+---------

| I. | II. | III.

+---------+---------+---------

|per cent.|per cent.|per cent.

Ferric oxide (Fe_{2}O_{3}). | 43.26 | 78.91 | 77.74

Ferrous oxide (FeO). | 37.86 | 3.46 | 1.44

+---------+---------+---------

Total. | 81.12 | 82.37 | 79.18

+---------+---------+---------

Calculated: | | |

Ferric oxide (Fe_{2}O_{3}). | ... | 71.23 | 74.54

Magnetic oxide (Fe_{3}O_{4}).| 62.72 | 11.14 | 4.64

Ferrous oxide (FeO). | 18.40 | |

+---------+---------+---------

Total. | 81.12 | 82.37 | 79.18

+---------+---------+---------

Percentage of total

oxygen reduced. | 16.44 | 1.49 | 0.42

Metallic iron. | 59.73 | 57.93 | 55.54

-----------------------------+---------+---------+--------- 

Note

The carbon monoxide (CO) had failed to remove from the ore the carbon dioxide existing as calcic carbonate. The summary of experiments in the following table appears to show that the water gas is a more powerful reducing agent than CO in proportion to the ratio of as

 4.21 x 100

4.21 : 6.72, or ------------ = 52 per cent.

72 

Mr. B.D. Healey, Assoc. M. Inst. C.E., and the author are just now constructing large experimental plant in which water gas will be used as the reducing agent. This plant would have been at work before this but for some defects in the valvular arrangements, which will be entirely removed in the new modifications of the plant.