The blast furnance

FRANKLIN INITIATE VOL.

MAY,

CXXI.

TIIE

FRANKLIN

and opinions

INSTITUTE

advanced

The

RCAST

No.

responsible

5.

for the statements

to the JOURNAL.

FURNACE.

delivererl

process

of

divided into three (I .> Deoxidizing (2.)

is not

by contributors

Tl1E

[A ‘!h-trrre

I 886.

Carbonizing

parts : the ore. the

deoxidized

ore.

(3.) Liquefying All

the deoxidized ore. iron ores are essentially oxides, and may be divided

species : (I.) Protoxide

of iron, in which

the

atomic

into five

ratio

of oxygen

to

ratio

of o_xygen

to

iron is one to one, as in fayalite. (2 .) Magnetic

oxide

iron is one and one-third (3,) Sesquioxide one and one-half

of iron,

in which

the

to one, as in magnetite.

of iron. in which

the ratio

of oxygen

to iron is

to one, as in hematite.

in which the ratio of oxygen, iron, (4.) Hydrated sesquioxide, anal\vater is one and one-half to one, to three-fourths, as in limonite. \Y~tote No. Var.. CXXT.-_(TI~IRI>

SERIES, 1’01. xci.)

?I

322

iY~~r?~t??zrr?t . Carbonate

(3.)

oxygen, In mill

of 1)rotoxide

iron and carbonic addition

cinder,

to the

from

in composition

in facility

(I .) Siderite

Magnetite

(5.)

Fayalite

The

magnetic

for reduction,

or

magnetic

or silicate oxide

In some

abstracted,

as a pasty

silicate

the surface

of the ore which

The

abstracting

Substantially, but are always

difficulty

from

of protoxide, Magnetite netic oxide, Hematite

is formed

from

about

cinder giving

fiftyT-eight

magnetite or rolling-

the oxygen

temperature,

is over

and prevents

as pure oxides

one or more

to sixty-nine

from

forty

from

the

sulphur,

per

cent.

fol-

phos-

of

prot-

per cent. of iron.

fifty-two

to sixty-seven

to fifty-two

fifty-five

of iron,

of the

per cent.

per cent. of iron.

to ninety-three per

cent of mag-

giving about forty to sixty-eight per cent. of iron. L varies from fifty-seven to ninety-seven per cent.’ of about

Limonite

varies

from

about

its

Knob

with

manganese,

to fifty-four

varies

about

varies

with

magnesia,

f@-ty-five

giving

Siderite

at a low

retains Pilot

fayalite

before

ores exist

in combination

sesquioxide, giving

:

the oxygen.

found

varies

fusing

seals up the oxygen

: silica, alumina, lime, water, carbonic acid. giving

as follows

and

that

in reducing

from

none of the these

Rolling-mill

The

compound

cases as with

the siiicate

giving

rank

ore is so dense and hard, that it is classed

Fayalite

corresponds

of iron.

is a firm stable

tenaciously.

is to keep

oxide,

which

oxide.

mill cinder

oxide,

and

ore or rolling-

these ores

of protoxide

reduction.

lowing

is the artificial

is extracted,

for difficult

phorus,

of

or sesquioxide.

(4.)

CO from

ratio

or hydrate

(3 .) Hematite

hematite

the

or carbonate.

Limnnite

oxygen

which

is one to one to one, as in siderite. there

iron

in

to fayalite.

Practically, (2.)

which

of iron,

acid

above,

[J. F. I.,

about varies

from

remainder

above

ores,

mentioned,

which

the ore occurs

to

to fifty-six

forty-two

is composed

to

IOO per of

in varying

one

eighty

sixty

per

cent.

of

sesqui-

per

cent.

cent. by weight or

of protoxide,

per cent. of iron. more

proportions.

are called

per cent. of iron.

per cent. of iron.

to forty-seven

to make

before

to sixty-eight

fifty-seven

forty

thirty-five

forty

the gangue.

of any

of the

of the nine substances The

earthy

matters

in

‘\[A> ,

I

T/L

XS(>. 1

The

oxygen

of

the

ore

Rl
/‘i’il~l.:~fc-

is scInrntcct

j3j

I>rincipaIly

11~7 carbonic

oxide generated from the fuel The fuel may be divided into tour species : lvhich is obtainrtl 1~) i.lrivi;lE tjff 13~’heat, tilt‘ (1 ..l C:harcoal, \\xter and volatile matter from wood, leaving a residue containing tivo untI one-half hydrogen, one about eighty-six per cent. carbon, and one-half oxygen, seven water, three-tenths ash. (2 ) Cc)ke, tvhich is obtained by driving ol‘f by heat the volatile a x.esidue containing about matter of bituminous coal, leaving eighty-sis per cent. carbon, two per cent. volatile matter, one per cent. sulphur, eleven per cent. ash. (3,) Hlock coal, containing about fifty-s:s and one-half per cent. &bon, thirty-two and one-half volatile matter, eight and one-half water, two and one-half ash. (4,) Anthracite, containing about eighty-eight per cent. carbon, three and one-half volatile matter, two-tenths per cent. sulphur, eight per cent. ash. Charcoal is a porous, bulky material that will fire at Qoo”, burns a\vay quickly, and causes a furnace charge to settle rapidly. Coke is porous, less bulky, fires at LOO’, burns moderately quick, and causes a furnace charge to settle rapidly; used with ant’hracite, it eases up the pressure and Ijermits more air to pass through the furnace. Anthracite is dense, hard, bright, gives off’ carbonic oxide slowIy, and at a high heat is pasty and has a tendency to stick together. It burns slowly, and having no pores like coke, it burns on the surface only, requiring a large surface of contact to carburize a cubic foot of air per minute. In the blast furnace, it requires care to work alone, but with twelve to twenty-five per cent. of coke, good restilts are obtained. When properly handled, a pound of anthracite wiI1 do the same work as a pound of coke, but it takes more bIast pressure and stronger blowing engines. The gangue, or foreign acid elements of the ore, are liquefied by the base or bases obtained from hmestone or oyster shells. Limestone may be divided into two species: (I’.) Calcite, containing from fifty-four per cent. lime, forty-two per cent. carbonic acid, four per cent. silica, alumina and iron, to fifty per cent. lime, forty per cent. carbonic acid, and ten per cent. silica, alumina and iron. (2.)

Magnesian

limestone,

containing

about thirty

per cent. lime,

324 twenty

[J. F. I.,

HcrYt?!mzn:

per cent. magnesia,

forty-six

per

cent.

carbonic

acid, and

four per cent. silica, alumina and iron, to forty-four per cent. lime, five per cent. magnesia, forty-one per cent. carbonic acid, ten per cent. silica, alumina and iron. A ton of coke or anthracite carbon

and two

per

cent.

teen per cent.

ash is worth

containing

twelve

forty

only $2.39.

An

ninety-three

per cent.

ash, is worth to the iron master, say, seventy-five per cent. carbon and fourforty only ,$.2.74. An ore containing

$3.68, while that containing per cent. iron,

containing

per

cent.

silica,

is worth,

per cent. iron and thirty ore containing

sixty

cent. silica is worth, say, $6.58. cent. iron and ten per cent. silica

per

per

cent. silica is worth

cent

An ore is worth

say, $3.71 ; one iron and four

per

containing sixty pear $6.12. A limestone

containing one per cent. of silica is worth, say, fifty-four cents; a stone containing fifteen per cent. of silica is onIy worth fourteen A furnace using forty per cent. ores with twelve per cent. cents. of silica will make, say, 820 tons per week, but with forty fier cent. ores and thirty per cent. silica will make only 500 tons. ‘The same furnace, with sixty per cent. ores and four per cent. silica will make I ,ZI I tons, and with sixty per cent. ores and ten per cent. Furnace plants are in ruin silica will make 1,039 tons. that have neglected to go over these matters carefully. ’ Oyster shells are practically use is limited to a few furnaces The

fuel

twenty-three

is oxidized

by

pure carbonate of on the sea coasts.

the

per cent. oxygen Such are the materiaIs

nitrogen. iron, and sound judgment a commercial success.

blast or air which and used

to-day

lime, but their is composed

of

seventy-seven per cent. in the production of pig

must be used in their selection

to make

1 The iron master having secured his supplies, selects a site for the blast furnace plant, the general arrangement of which is exhibited in PZ&P I; In making this selection, the following points have to be considered. (I .) Transportation

of the raw material

(2.)

Transportation

of the pig iron to market.

(3.)

If poss i bl e, a site on competing water

furL!e

A

dra(Ll?

.

supply

of,

say, 750

eve1 plot of, say, four ’

to the furnace.

lines of railroad. gallons

acres abo

1

per minute

e high

water,

for each and well

(6.)

A cinder dump of thirty-five

acres of rough land.

The size of the furnace will be governed by the fuel. As a maximum for charcoal, say, bosh of twelve feet. As a maximum for coke, say, bosh of twenty feet. As a maximum for anthracite, say, bosh of seventeen feet Larger bashes are used but are not giving the results of smaller boshes. The heights will be determined ; as sufficient time must be allowed

by the reductibility of the ores, for their exposure to deoxidize

them. With

siderite

quired. With With

limonite or hydrates seventeen hours exposure hematite or sesquioxide twenty hours.

or carbonates

fifteen

hours exposure

will be reis wanted.

With magnetite or magnetic oxide twenty-four hours. With fayalite or rolling-mill cinder thirty hours. These are average figures, but shorter time can b$ used by For instance, the Mount Hope Furnace made using more fuel. No. I charcoal

pig with only

excess of charcoal.

The

ore

seven hours exposure,

but it used an

was a fine disintegrated

hematite.

In another instance, a furnace 13 x65 feet, working with another 20x80 feet, on same stock, it was found the small furnace carried the same burden as the large but with refractory ores the

one when using easily reduced ores, higher furnace carried more’burden.

To determine the size of a coke furnace, the volume of air must Say 24,000 feet per minute is used. This be first determined. must have a crucible

of sufficient

size to use it which will be eleven

feet diameter, and allowing four and one-half feet for angle of bosh on each side will give twenty feet of bosh. This crucible will consume 17,880 pounds per hour of an eighty-six per cent. carbon coke, which, with its proper burden of, say, hematite ore and lime! stone will take up 1,217 cubic feet of space per hour,whioh, multi: plied by twenty

hours time required

for reduction,

gives a furnace

of 24,340 cubic feet contents, or ninety feet high. For an anthracite furnace using, say, 18,000 feet air per minute, the crucible

would be ten feet diameter, allowing for angle of bosh This crucible will lvould give bosh seventeen feet diameter. consume I I;5 14 pounds per hour of an anthracite containing eighty-eight per cent. carbon, which, with its proper burden of, say,

Hnrtmnn

326 magnetic

ore and stone,

will

take

:

[J. F. I.,

up 410 cubic feet, which,

plied by twenty-four hours required for reduction, contents, or a furnace seventy-five feet high.

gives

multi-

9,840 feet

The tuyere nozzles for the twenty-foot coke furnace eight of six inches diameter, giving a velocity of ~,OOO

would be feet per

minute. Tuyere eight

nozzles

for seventeen

to four and one-half

feet

inches

anthracite

diameter,

furnace

giving

would

a velocity

be

of 20,-

feet per minute.

000

The The

angle of bosh should be 75O. diameter of bell equals one-half

general

diameter

of

bosh,

rule.

The

stock

line at top under

two feet less in diameter bosh.

the

be11 can vary

from

than the bosh, according

one foot to

to heights

above

The foundation of the furnace is built of stone, leaving centre an opening five feet deep, which is filled with fire-brick ing the hkarth columns, mantel. hearth,

or bottom.

about To

extending below offset

On the foundation,

twenty-four

this

mantel

from

thence

is pIaced

feet high,

on which

is attached

a heavy

to

a cast

tcp

iron

of

crucible

below

to

off

draw

the

the

tuyeres,

iron.

This

jacket

through

which

water

circulates

burning

of the

walls.

Suitable

from

hearths

to centre

is cooled

by a water

coil

for tuyeres

a heavy

jacket,

bottom,

at

inch

has aa to the

hearth

coils

cool

level

cast

and

in it,

prevent

are

left in the jacket

and

one 3

top

\vrought

of this

six

feet g inches

crucible

jacket

iron bosh jacket

i&side of it, in event

or

18 inches

This jacket thicker walls

them

openings

a cast iron

plate

the

opening

keep

the

is bolted boiler

in the form-

cast iron

extending

has one

to

From

up for the cinder notch. up to the mantel, is placed

jacket hearth. to give

and has an

are placed

On

fukace.

the hearth and 8 feet above iti it just below the tuyere

crucible

feet

as a

of a scaffold,

which localiz-

ing the heat. The

crucible

at the thick, bosh inches

tuyeres,

walls

below

and to

and are supported to

top of furnace, long,

for expansion

and

back

of the

tuyere

top of bosh

are twenty-seven the

walls

by_ the bosh jacket. there

is a single

of it is piaced

brick.

On

the

two

inches

thick

are eighteen inches From the top of the

thickness

of brick

inches

of mineral

top of the

furnace

thirty wool

is placed

May,

I

The

886.1

the wheeling

plates

a flue leads

to

it from

boilers

steam

rous pockets,

which

the stoves. are generally

work

run with

a maximum

at furnaces

and they

per square

inch

55 feet

long

The stoves on blast

when

top, On

are sprung. erators,

crossing

g x g inches courses

Across

angles

these each

Gothic other

through

of gas and

of the stoves,

extend

On

blast.

to

leaving within

valve,

two

valves

are to let on and

gas valves valves

walls

and

The

valves,

dome

small

valve,

tering

the

flue.

P&e one shell Inside,

Gothic

arches

called

regen-

openings

is lined with from

two

of this

5 x 5 inches

and

blow-off

under

from

escapes The

to

blow-off $9

of hot

the valves, a small

These

them

first valve,

the

air, valves

blast

are

hot

back

blast The

which

into

the flues.

is slightly open

preventing relieve

TWO

the

it pushes to

the

hot-blast

furnace.

destroys

thereby

The at

the stoves.

valve

the

right

bottom.

The

the

and

wall,

at

in them.

valves.

the blast

is placed

passes

division

thick,

of the

piers

the bottom

wall to turn the

inches

distance

any leakage burns

two valves

If any blast and

stoves,

are ptaced a water-cooled,

two

cut off

side 2%

openings a short

and

fires the gas,

these

weighted.

each.

leaving

is a division

other

on girders

are used to prevent

Between

built

are to let on and cut off the gas from

flues which

heaters

three

air-tight

which

and extending

the

On the front of stoves gas

or

with fire-brick.

angles,

regenerators

thin walls are supported bottom.

3o-inch

heavy

over

are

of the dome,

called

to each other,

openings

pounds cylinders

are used alternately,

of a

them.

plain

regenerative

chamber

at right

of blowing

brick.

the centre

walls

with

Their

twenty

are

of two

They

arches

three

sets

consist

a combustion

to

but They

minute.

long,

in

are fire-brick They

per

boilers

70 feet

engines,

to blow

and are lined throughout

vertically

placed

nume-

are required.

of steam

arranged

up to the bottom

current

gas to them

pressure

enough The

say,

them,

of nine-inch

of stove

of two

required.

on gas.

is placed

the

flue contains

engines

three for each furnace.

with a d!!&

This

of 300 feet

be strong

diameter,

and two

at front,

speed

to heat the blast

14 requiring

the top of furnace,

convey

high

condensing

be in ratio

under

to

blast.

vertical

piston

should

about 40 inches

are

and heating

engines

piston area should

From

stoves

catch the dust and dirt in the gas and prevents

for good

piston,

and

reaching

The

337

F74rmzct~.

and bell and hopper.

the

for generating

Bhst

the

this

it

en-

stove

[J. F. I., from

pressure

when they are changed

from

blast

to gas.

They

are piston valves operated by blast pressure. On turning four-way cock attached to them, they fly open, relieving

the the

internal pressure of the stoves, and at the same time sweeping out the dust that has been deposited in the regenerators, keeping them clean and in good

order.

The

gas ashes or dust has the

affinity for the part of the stove that is the hottest,which is the Gothic

arches.

when the blow-off after it is formed. burn the gas.

As

valves

all the blast are opened,

These

The

valves

sweeps

strongest

in this stove

quickly

over them.

the dust is removed

each time

are then left open to admit

combination

of the pockets

(before

air to

mentioned)

in the flue and these blow-off valves at the bottom oi the combustion chamber has resulted in keeping the stoves clean for two years up to the present the end of the

time.

blast,

When

a crane

On the back of the stoves

the stoves swinging

are placed

require

under

the

to be cleaned

the

chimney

dome valve

at

is used. and

cold

blast valve. With

one

is no danger

substantial

gas pass direct more division heating

with

walls are

used.

These

skeleton

operate

these

stove as occurs where

division

walls give

top for stoves,

but one opening

walls

at

top

stoves,

in the

where

there

and leave the but

the best part of the stove.

These skeleton walls are used. stoppages and annoyances. To

the whole

and most substantial

wall requires

of stove

the wall by cracking

traversing

surface and occupy

the

wall in the centre

through

without

is the strongest division

division

of leakage

and

top, which

a number

continuahy

by

dome

with

way, the

one

dispenses

of openings

giving

gas is admitted

little

The

are

causing

gas valves,

burned in the combustion chamber in contact with massive walls, escapes up through the nine-inch openings of the first regenerator into the space under the dome, thence it turns over the division wall, down valve

through

at bottom

combustion

the

to

chamber

five-inch

openings,

Any

chimney. is finished

escaping

imperfect

through

combustion

in the second

combustion

the

in the cham-

Gas in combustion expands and ber, or space under dome. ascends, after combustion there is no further expansion, and, as its heat is absorbed, erator,

it

contracts

there is combustion

regenerator,

absorption

and

descends.

and an upward and

a

descending

In

the first

regen-

current ; in the second current

working

in

329 accordance

with

natural laws, and requiring

less height

of chimney.

After gas has burned through a stove for four hours, the gas valves are closed, the bottom blow valves are closed, the chimney valve is closed, the cold blast valve opened, which leaves the blast into tlie stove. The hot blast valve is then opened, leaving the blast pass through the stove to the furnace. The next stove is then cut off from the furnace and put on gas to be heated up again. Using three stoves, gives two on gas heating up, with one on the furnace. The blast, sweeping by the fire-brick

through

walls

This when required. time it will lose about

into

the stove, the

is maintained 50~

if

carries

furnace,

the

for

two

stoves

escaping gas should never pass off over Stoves with five square feet of surface

the

heating

hours,

are large

heat absorbed 1,500~ which The enough.

the blast

during

350~. in the combined

regenera-

tors to each cubic foot of air per minute will be found ample. Unless large surfaces are used, the walls glaze and lose their efficiency. ,411 the valves are placed at the bottom of the stove, where they cari always be under the eye of the stove tender, and are made

so that they

By burning more regulated at will.

can be instantly

taken

apart

and

repaired.

or less gas through them, the temperature can be The brickwork at the bottom of the combustion

is massive, which retains the heat and fires the gas immediately on This avoids the explosions which hereits entrance to the stove. Fire-brick stoves cannot be tofDre shattered the brickwork. destroyed, they last longer, cost less for repairs, and use less gas to heat I ,600~ than pipe stoves to heat goo”. In practice, it is found that taking iron pipe stoves at their ordinary limit %f goo”, and replacing them saving of fifteen

with brick stoves using 1,400”, that there is a per cent. in the fuel, and an increase in the make

of iron amounting to twenty per cent. iZir o’r steam hoists are used to elevate the stock to the top of The stock house is an iron building furnace from the stock house. with two or four railroad tracks through it, which are elevated, say, sixteen to eighteen feet above the floor. It is divided off into bins for the storage of stock of different kinds, which is dumped into the bins from the cars overhead. In the stock house, at the bottom of the hoist, are placed suitable scales to weigh all the material that goes in the furnace. Strict attention has to be paid to this, as the whole operation

depends

on

the

proportions,

by

weight,

of fuel,

Hnrtmnn

330 ore and stone.

Iron

barrows

are

the bins to the scales, where and the contents

dumped

bins have been stock

tried,

in barrows

to dispense far, have In

composition containing oxide

but

the

barrows

over

of iron, two

sent

up the hoist,

Skip

hoists,

to the top, have been tried,

cheapest

and

best.

but, so

the old arrangements the first thing

cinder

one-half

the stock from

convey

Various devices of draw arrangement of shovelling the

old

the

going

a furnace

of the

to

are balanced,

in the hopper.

not superseded

starting

[J, F. I..

used

they

has proved

with

.

shall be.

sulphur

of barrows.

is to determine

A good

cinder

what the

with

will be silica, thirty-eight

per cent. ;

oxide

alumina, ten per cent. ; magnesia,

of manganese,

ores not per cent.;

five per

cent. ;

per cent. ; sulphur, twotenths per cent. ; lime, twenty-eight When there is much per cent. sulphur in the stock more lime must be used. A cinder of the following formula replace extent.

is good,

the The

substances arating nate.

it.

two

is

atoms

in selecting of silica

pose the stone

RO,

(2

cent.

then

added

limestome

in the stone used

of lime

Si 0,).

Lime

can

alumina replace either to a limited the cinder is made by getting all the

of base to

and limestone,

to get

requires

contains

more

from

pounds

acids,

silica,

limestone,

as every

of lime to saturate

per cent. of silica, the

of lime

silica

in the

coal,

Sup-

then thirty

to saturate more

giving

care is neces-

per cent. of lime.

to saturate

per cent.

the

Great

it free two

fifteen

is required

saturate

but fifty-six

then on sep-

that the acids predomi-

one of acid.

to

contains

leaving only twenty-six the ore. This requires cinder

-t

in per cent. in the fuel, ore

A pure limestone

per

and for

calculation

Limestone

pound

3 Si 0,)

the acids and bases, it will be found

generally sary

(2 R,O,,

magnesia,

seventeen

stone,

the silica in makes

more

and less iron.

is used in the sizes that it comes from the kiln, coke Anthracite should be the same, averaging, say, five-inch cubes. used in sizes not exceeding four-inch cubes, and ores should not Charcoal

exceed

three-inch

will break tegrate

before

if uniform

doing

charging

nace before

it.

it dries.

This

by the

crushers

cubes

to disin-

than to depend

irregular

iron.

on The

can be used by wetting

it to get well

denser

Ore crushers

and cheaper

and producing

will allow

The larger,

is wanted.

better

to three-inch

it chemically,

and fine ore made

work

; it is much

the ore mechanically

the furnace dust

cubes

the ore cheaply

lumps

down

it

in the fur-

of ore get through

\I

1y,

The RZast Furrznce.

1886.~

the zone of fusion

with

greater

33’

part of their oxygen,

and

if not

reduced by solid carbon before reaching the zone of combustion cinder that annoys a furnace they melt, making a black scouring man. Lumps of magnetite have been found at the tuyeres with their surfaces reduced in for a quarter of an inch, while the balance Large ore can be used, was magnetic oxide as put in at the top. but it is done at the expense of fuel: irregular quality, and less output of iron. Limestone should also be broken, that it may part -with its carbonic acid in the upper part of the furnace before reaching a high temperature. In the first filling of a furnace small channels are formed by These channels lead to the loosely laid red brick on the hearth. The crucible is front and supply fresh air to the burning wood. then filled with short dry wood up to the off-set or starting of the bosh, and from that point up for about two-thirds the height of Then follows a burden the bosh is filled with coke to form a bed. composed of one of coke to one-quarter of ore, and the proper amount of limestone to top of bosh, then I

I I I

of coke to ‘I ‘,

1;; of ore, etc., for IO feet up, then I‘ !,$ 41 I( I’3 “

“

“

I

‘I

.‘

Ix

IL

‘L

,‘

I.

Ij

“

the balance

‘6

to top.

The wood is then fired, leaving the tuyeres and iron notch open, water is turned through the tuyeres and breasts, and after six or seven hours burning the wood will be gone and cinder found trickling down the walls. The tuyere pipes are then put up, and blast heated about 500~ turned on, say, about one-half the volume to be regularly used. The gas at top will fire after the wood is fired say five hours, and must be ignited to prevent an explosion. Soon as blast is turned on the bell at top is closed and the gas passes down the flue to the boilers and stoves, where it is burned for purposes already described. After blast is on the furnace for eight or ten hours cinder will be up to the cinder notch. The iron notch is then opened and the cinder drawn off at the hearth level. This is repeated for three flushes, which cleans the hearth of the ashes and mucky cinder, heating it up and preparing it to hold a large volume of iron. The iron that flows out with these three flushes is skimmed off and sent back to the top of furnace to be re-melted. After

332

Hartmm

the third flush the cinder is and, if cinder is made rapid

[J. F. I.,

.

drawn

off

at

the

cinder

notch,

enough, the notch is allowed After to flow constantly until next casting time, when it is closed. eighteen to twenty hours, iron enough will have accumulated in The water the hearth to make a cast, when it is run out into pigs, turned

is now

through

as the cinder

will

flow, and the ore with grade

The

the jacket.

admit,

which

blast

is judged

its limestone

of iron ; that is, the hotter

is increased

of by

its

is increased,

judging

the iron the more

heat in the blast is held in reserve

as fast

limpidity

or

by

the

burden

can be

to increase

or de-

used.

The

crease

the heat in the furnace as may be required.

After bIast is put on, there should be no stoppage for thirty-six The burhours at least, when the furnace ivill be out of danger. den, volume

of blast, and heat in bIast, must be increased

so that

in six days the furnace will be up to her full capacity, as the and hearth will be fully saturated with heat by that time. The

furnace

ant matter

having

started

of burdening

successfully,

her to make

walls

then comes the import-

a given

grade

of iron

with

The fuel unit having been fixed at, say, z,ooo, 3,000, the least fuel. or 4,000 pounds per charge, is never varied, but the ore and stone For to suit circumstances. say, fuel contains eighty-eight

are varied cautiously), pounds

fuel are required

and for each pound with

r,zooO

for

reduction

of cinder

to 1,300~ hot

per cent. of sulphur

or manganese

of iron No.

soft

iron, containing

combined

carbon,

about

92.40

(but

and carbonization not

use 1,400

of ores,

fuel

is required,

which,

over

five-tenths

of one

in the burden

less of the fuel will be required.

rule

pe.r cent. carbon,

31aa 1 pounds

blast, and

be made, and for each grade

a general

below

No.

No.

I iron should

I three

per

cent.

I is a dark, large, open grain

iron, 3.50

graphitic

carbon,

-13

2.40 silicon,

the balance being alumina, sulphur, No. 2 is not so dark, finer grain, a phosphorus, manganese, etc. little harder, tougher, and contains 93.00 iron, 3.20 graphitic carNo. bon, -48 combined carbon, 2-30 silicon, balance alumina, etc. 3 is gray color, line grain, hard, and of high tensile strength, con taining 93-66 iron, 232 graphitic carbon, 1.23 combined carbon, 1.94 silicon, gray rather

balance

spots, is. harder brittle,

combined

alumina, than

containing

carbon,

etc.

No. 4 is white

No. 3, of higher 94.25

iron, 2.10

I ‘30 silicon, balance

tensile graphitic

alumina, etc.

mottled

with

strength

and

carbon,

1.36

No. 5 is white

iron, no grain, per cent.

extremely

iron,

hard

and

-36 graphitic

brittle,

carbon,

value increases existence, being

with their purity, simply a brown powder

it is what gives change

its character

sulphur

and

etc.

The

its strength

but makes

Some

furnace

The

Silicon

somewhat. harden

make iron fluid or easy melting its fluidity

carbon,

‘50

that will burn off to oxide

small percentage

and value.

manganese

combined

2.80

with al1 other metals their pure iron has no commercial

alumina,

to the air.

ninety-five

While

silicon, balance

of iron if exposed

containing

and

elements

softens

pig

Silicon

it.

of carbon with

other

weak,

in it

iron, while

and

phosphorus

while

sulphur

grades,

which

retards

it stronger.

men sub-divide

the above

confuses

If iron will not pass strictly for a certain number put the market. it in the grade below, which gives the iron a better standmg in the market and retains customers in dull times. Nos. I and z are foundry irons for castings. No. 3 is used for both castings and wrought iron. Nos. 4 and 5 are forge irons for making wrought iron. Nos.

I,

and

2,

make Bessemer An

important

portions

3, when

not

over

phosphorus,

-20

are

used

to

steel. subject

is the proper All

of the furnace.

of fuel and improve

efforts

the working

temperature to

decrease

in the different the consumption

of the furnace must be based upon

it. Tracing

the thermic

the bottom

conditions

of a blast furnace

from below

(PCzte f11),

of 2,900 0 F., which increases In the immediate below the tuyeres. temperature is somewhat lower, owing

perature

a short distance

above

the

blast has been converted

tuyeres,

to a point

vicinity to the

a little

of the tuyeres entering

all

acid,

we have at

No. 3 iron, a tem-

slightly

where

into carbonic

upwards,

making

the

the

the

blast ; but

oxygen

highest

of the tempcra-

This carbonic acid is, however, ture in the furnace is attained. almost as soon as formed, converted by the glowing coal into carbonic oxide, and provides

a process which absorbs heat, reduces the temperature, the active agent for the reduction of the iron ores. In

its ascent, the

hot

carbonic

first fusing the descending down

to

the

hearth

fusion is rather sharply

oxide

gradually

iron and earthy

of the

furnace.

defined,

and

materials,

The thd

parts limit

with its heat, which

oi this

temperature

trickle zone

of

in this zone

334

Hfzl-t7nn?t

suddenly

decreases Passing

fusion.

part of the

of the

that escapes with

reduction

which

at

furnace

the

top,

is working

resented

CO by

absorption These

well.

without

the direction

the, thermic

involved

conditions

limestone, three heated

per

hour

(if the

at the expense

of the

ture

of about

570~

their

oxygen

under

quantity

is

750”,

somewhat

the

if the

are

rep-

in Rate

llln

and trace

at the rate of about properly),

become

gas.

At a temperato be reduced, or to lose

of the

in deoxidizing

carbonic

the

carbonic

oxide.

ores being acid,

The less than

an increase

in

result.

Further down, at a temperature of begins to part with its carbonic acid, a

the limestone

higher

hot

the gas

F.,

of the coal, ore and

is driven

ascending

of

further

finally 250~

of temperature

descending

influence

of heat

its

of the investigation,

furnace

by the formation

temperature

about

to actual values,

the ores begin

the

of heat absorbed

that developed about

F.,

of

in the descent

we find that the charges

feet

In

acid from the limestone,

changes

regard

by dotted lines’ a, b. If, now, we reverse

a loss

C02.

of heat, and

at a temperature_

graphically,

to

The by contact

reduced

and causing

CO

the greater

acid, increasing

to a sponge.

is then

CO,

F. I.,

latent by the

gas absorbs carbonic

off the carbonic

causes an additional

escapes

by

reduction

ascent, the hot gas drives

oxide

made

the iron reduced

or fuel forming the

and

ores, forming

and leaving

with solid carbon, compared

absorbed

on up, the carbonic

oxygen

the temperature, oxide

by the heat

1 J.

:

temperature

being

necessary

where

dolomite

is

Still descending, the point is reached where the earthy used. matters are fused together as cinder, and the iron separates from From this fusion limit downward to a point about three them. feet above the tuyeres, an atmosphere of carbonic oxide exists, which reduces

prevents

zone of fusion. six

the

oxidation

any fugitive

inches

exists.

below

pieces

This space is called

nace, or the volume

the

falling

which

shots

may

have

the zone of combustion,

that the

of entering

of the furnace

with glowing

of ore

of iron,

and

escaped

the

From about three feet above the tuyeres to about them, an atmosphere of mostly carbonic acid

the area of this region or bottom

of

rapidity

blast, depends,

to the zone of fusion,

coal, although

occasionally

ore or stone will be found here, which

and it is upon

of the driving From

of the furthe hearth,

the furnace

is filled

a stray piece of refractory is reduced

by contact

with

May,

ir/te BZC?.st i;l/?Ylznce.

1886.1

solid carbon generating carbonic oxide iron not being thoroughly carbonized

335

This with a loss of heat. mixes with the iron in the

hearth and lowers its grade, by decreasing the graphitic carbon in the iron already in the hearth. This bed of glowing coal acts as a-filter or screen to take up all oxygen or carbonic acid before reaching the zone of fusion, and thereby to maintain a powerful reducing atmosphere immediately below and in the zone of fusion, as well as above it for some distance. The deoxidized ores as a sponge entering the zone of fusion with its intense heat have such a strong affinity for oxygen that they will split up any carbonic acid which may have escaped reduction in the bed of glowing coal, rob it of one atom of oxygen, the sponge burning to oxide of iron, which escapes and shows at the chimney top in a peculiar brownish-red stnoke. The heat in the hearth of a blast furnace is the result of the combustion of the fuel by the blast, to which is added, in the case of hot blast, the heat brought in with the air, and the heat brought It is evident that if the blast be down by the descending stock. cold a correspondingly larger amount of fuel must be employed to maintain the same amount of heat in the hearth than when hot A temperature of blast of 2300~ F. is needed to blast is used. ignite charcoal, of goo” to ignite coke, and fully 1,300~ to ignite The convenience and advantage of contributing to the anthracite. heat of the hearth by heating the blast is now fully understood. Running on a burden of one pound of coal to one pound of ore, more heat is developed than is required. The descending stock cannot absorb the large volume of heat coming up, and consequently the furnace becomes hot to the top, as shown by PZ&C I?? This excess of heat is partly absorbed by the decomposition of some of the carbonic acid in the gas by the glowing coal at the top, carbonic oxide being formed. As this amount of coal is lost to the furnace, it is wasted. This waste, however, acts advantageously by causing less coal to reach the hearth, and thus hindering the make of iron high in silicon.* This evil exists more widely than is generally supposed, as it is, to a certain extent, self-corrective. If the burden is increased, say two pounds of ore to one of ~~_-..-__ * Before the coal gets to burning at the top, in this case, iron high in silicon is always

made.

in the fuel.

The

excess

of fuel heat on long

exposure

reduces

the silica

Havtman :

336 coal, and the same volume hour to the

hearth

[J. F. 1..

of blast used, then the heat returned

from the

ore and stone

will be double.

per This

heat, in. combination with a higher temperature of the blast, replaces the pound of coal which it saves, and at the same time doubles the yield of iron. Concentration

of heat at the

of the first aims for successful only by large

hearths,

by using a large the furnace

hot blast, heavy

volume

collects

tuyeres

and

in the hearth

furnace work.

of hot

blast.

the heat from

is one

This can be obtained

burden, The

and

rapid

descending

the ascending

driving stock

in

gas and carries it

down to the hearth again, increasing the intensity of combustion an important matter, when it is considered that at the tuyeresthe intensity of combustion heating the hearth determines the grade of iron. The

iron arriving

at the hearth

contains

combined

carbon

but

no graphitic carbon. The intense heat of the hearth changes the greater part of the combined carbon to graphitic carbon, and as the hearth is more or less hot so will the iron be grayer or whiter Buckshot by the change. quent,sticky cinder which allow

them

to separate.

iron is due to colder

hearths

and conse-

entangles the shots of iron and will not It invariably accompanies sulphur, either

in the ore or fuel, which requires a heavy lime cinder to take up The more limy the cinder the the sulphur and avoid white iron. higher is the heat required to fuse it. The rapidity

descent

of stock

of combustion

is the number the greater

of tons

in the furnace at the tuyeres. of fuel consumed

the proportion

of ore

is governed

entirely

by the

A true test of the furnace in twenty-four

in the burden,

hours, and

the larger

will be

In the yield oi iron if the furnace process is ‘properly managed. Hate 114 it will be noticed the zone of reduction (colored red) is low This prevents the down in the furnace compared with Rate IV. CO2 of the limestone being driven off in the presence of a high heat and combining with the fuel to waste it by forming CO near the top ofthe

furnace as in Hate IV, and giving the CO no time to

act on the ore. The stock entering the furnace, PCate II& is gradually heated, the ores well reduced at a low temperature, and there being but little excess of heat to reduce silica to silicon the rcsulting

pig

iron

is low

furnace being driven

in silicon,

strong

and

dark

in color.

rapidly, and the heat development

The

and heat

\I.I~,

TEP

r886.1

Bhst

337

LTw’~lilcL’.

requirements being well balanced, the hearth is kept hot and the turnace works well. The heat that is conducted off through the tbundations, crucible, bosh, shell of furnace and by waste tuyeres water is a constant sum, no matter whether the furnace makes a !arge or small yield. The faster the furnace is driven the hotter the hearth becomes, as the loss from the above cause is decreased in ratio to the amount of fuel cinder and iron arriving at the tuyeres and in the hearth. This allows more burden to be carried and at the same time this extra burden robs the escaping gas of more heat which is returned to the hearth, making it hotter and allowing a still further increase of burden. This cold top working favors the accumulation of cyanides, which is another economical factor to be explained hereafter. With a furnace in normal working, it requires about one-sixth of the fuel to supply the heat lost through foundations, etc., as above explained. Taking advantage of all the little points above mentioned, and working them together as a whole, the highest type of furnace economy is attained. A cold top and hot bottom is economy, large product and good quality. A hot top and cold bottom is waste of fuel., small product and poor quality. P&e IV, as before stated, shows the effects of a light burden in The amount of heat generated is in the interior of the furnace. excess of its requirements and the heat gradually works up to the top. This partially corrects itself by burning off to waste part of In this case, the ores arriving the fuel at the top as before explained. in the high heat quickly, only the outside of the lumps are deoxidized when the oxide fuses with the gangue and covers the lump with a pasty coating that prevents the CO from reaching the oxygen in the interior. This ore then passes down until it reaches a heat sufficient to melt it when it is reduced by trickling down over the surface of the glowing coal, which reduces the oxygen by contact with solid fuel, forming CO with a loss of heat and making an iron high in silicon, as the more fuel the more silica there is per ton of iron in the fuel, from which the silicon is mostly derived. To prevent.this reduction of silica as much as possible with a light burden the heat in the blast has to be lowered. Iron from a light burden is light colored, small grain, weak, but runs fluid and makes good stove castings, but costing more than WHOLE

No.

VOL.

CXXI.-(THIRD

SERIES

VOL.

xi.)

22

Hm-tmn n :

338 it is Garth, better

the founder

and cheaper

When worked

tries to get on a heavy

has

dotted lines on drawing, at a point just above short distance the original

been

P&e

them,

upward above

in blast

it

full capacity,

that from there

will

III.

the

they are

denly

disappear, line between

nearly

This

burning

are

the smooth

the furnace

per minute.

air entering

per minute

divided

of

from

to

The

number

paring

it with the air entering

and, for all practical Heretofore

furnaces

limits

the volume

of air

to

blown

built

and

the

the limit of volume

of

feet of

tuyeres

These

for

figures

oi and com-

in a number

of furnaces,

correct.

with

the

sud-

for coke, and

the area spoken

On starting

intense

walls

of cubic

for anthracite.

it will be found

have been

walls and 80~ to 85O boshes.

down

per minute

purposes,

a

the cubic contents

the cubic contents

by measuring

the

by the

limit

the cubic contents

and

the wear of stock.

of the zone from the top of fusion by three,

by

a point

the

charcoal;

have been determined

given back,

surface marks

by five will give

by four, will give

has been

until

is due

is determined

air entering

and shape

burned

surface

and rough

the zone of fusion, and its height

divided

make

when the walls are found

away

fretted

the

uniform,

and the walls are smooth

divided

and

from the tuyeres, we find,

walls

the bosh is reached,

thickness.

This

a month,

assume

Starting

that

At this point, the rough,

heat.

burden

iron.

a furnace up to

[J. F. I.,

small

hearths,

thick

up, the size of the hearth zone

of

fusion

is found

part way up on the bosh. If sufficient

heat gets above

the fusion limit

of a blast

furnace

to paste the stock and yet not fuse it, this stock jams

on the bosh,

as per Plate

cannot push

Vforming

a ring which, if the stock above

it down

to the fusion Iimit, becomes permanently set and obstructs If the materials in the stock passed abruptly the flow of stock. from the solid to the fluid state, as ice does to water, thiscondition of affairs could not arise, but we may rather compare the stock to wax, which, when the heat is just insufficient to melt it, becomes pasty and can then be moulded of a furnace of twenty cumference

below

stock immediately about central

thirty

at the fusion limit on the

inches thick,

portion

and compressed.

feet bosh is sixty-three

travels

bosh

and

.while

the

independently

The circumference feet,

while

is about

forty-four

sliding

down

balance and

as a

of the

much more

the

feet. stock

cirThe

whole

is

in the

rapidly.

A

May,

2%

JX86.3

compression

or squeezing

Bzlrst

339

Fw’irclCL’.

together

of 63 -44

=

I 9 feet has to take

If the place in the stock travelling down the slope of the bosh. stock is pasty, it squeezes together and jams as above described. This ring or “ skew-back ” lodges the stock above it up to the top The stock descending through the of the furnace (see PZ’ntc V). middle

of the furnace

a vertical reducing yield

making a dry wall area of the furnace and proves

of a furnace

The

by its side thrust retains this lodged stock in This cuts off the of it.

position,

founder

shows its working would

hearth by allowing This cuts away

the circular

from fuel blanks

back

his tuyeres.

with

a larger

ring or scaffold

When

the

charged

enlarge

volume

and allows

there was ample

previously

law-that

area.

draw

it to cut away

down to the tuyeres. fold

then

Cochran’s

it to

fuel below

to meet

the

of blast. come

the scaf-

it, the furnace

would pull through all right, but, if the coal were burned away, the scaffold would chill the zone of combustion and the furnace would have to be shovelled Instances

out.

have been found where

a furnace

IG-foot

bosh, 65 feet

high, had a vertical well perfectly round, 6 feet diameter, extending The sides of the well from 7 feet above the tuyeres to the top. were about

12

stone partly

fused together.

inches

thick,

composed of the fuel ore and limeBetween this wall and the in-walls of

the furnace the stock laid loose and in good condition. When this lodgment or scaffold occurs, the lodged part collects heat at the bottom,

which accumulates

the top of the furnace.

The

stock

and works

lodged

against

up throughit the

walls

to

under

the bell becomes red hot, while the moving stock in the centre is cold. This has led to the idea that a furnace sometimes works up its walls, while the reverse is the case. If a furnace has been in this condition for some time, the attrition of the stock and an increase of temperature sufficient to partly melt off the skew-back, slowly, and the scaffold

sometimes causes the latter to give way gradually slides downward in the furnace

leaving a ring adhering to the bosh. While the furnace is melting and burning up the lodged part, it becomes extremely llot, as the work

of reduction

has been

stored up in the part of the scaffold oxygen or CO2 can reach it. The the burden

and drives

the furnace.

done

thoroughly

above

and

carbon

is

the skew-back,

where

no

founder in this case increases As soon as this 1odAecl part is

Hartman

340 worked

out, the furnace

reserve

heat in the hot blast.

condition

is bIown

down

[J. F. I.,

turns on white When

iron, unless the founder a furnace

down, the dry wall around When

no trace of it can be found. blown

:

the

to the bosh and finds

the

founder

no scaffold,

first time slack blast is used, the skew-back putting

on full blast

the

trouble

shows itself.

From

seen that the difficulty or skew-back

enough about

the

furnace but

the

white

iron

and

explanations,

is that he did not blow

it down

the

old

it wiH be to this ring

the tuyeres, to supply

that the engine

blast

to fill

this

and hot

space,

white

iron

results.

other.

As

The

furnace

blast

and

are

the bIast

it to work

the heat must

cannot then

be

out and a new bosh put in.

The

difficulties

adopting proper

volume

bosh.

of the old form

the form shown

fusion limit Any

of air, and placing

to avoid

the danger

pastiness

tuyere

section. during

charging

of stock

the bosh far

and

occur

apparatus

on the bell and change the stock is high

the

blast

below

vertical

equalized, a hopper

the walls,

across

the

to hold

the

so long

as the

the stock evenly. the founder will often lay the blame

it, thinking

a smaller

bell will do better,

on the walls, but he has not discovered

causing

by

of the stock on the

its shape will be immaterial

can distribute

be avoided

enough

between

As the upper part is simply

reduction,

may

using a large hearth, with the

of the jamming will

If the furnace works irregular,

scaffold

of furnace

in Plate III,

the heat will be concentrated

a ring

gets

he refills;

from side to side of the furnace, causing

be concentrated,

stock

sides falls in and

builds up again and on

foregoing

hot first on one side and then on the blown

has

scaffolded

built the old shape, as per J%z&es 5 and 6, cut out so

much at and above shuffles

makes

the

this

*

Furnaces not large

furnace

in

the furnace

to work

up through -

as

the fact of the centre,

* The fuel, ore and limestone above the fused part of the ring scaffold disintegrate to a gravel and dust, which, when the ring gives way, (more or less) roll down to the tuyeres and smother the coal in the zone of combustion. The fine fuel would burn readily if the blast could penetrate it. In some few cases where the engines could blow twenty pounds to the inch pressure, they succeeded in blowing through the gravel and dust. The better plan is to take out the tuyeres and shovel it out before it fuses, sets and chills the hearth. Fifteen cart loads have been taken from a single furnace before the bright fresh coal got down to the tuyeres. A vigorous pohcy in blowing will stop this trouble.

me- h’lflst

1886.j

May,

and not

on the sides.

one-half

the

bosh

Pyrometers the bosh furnace

one

may To

and take zones

A

heat, a burden grade

of iron

blast

to

of

Furnaces cooled, volumes mean

an

of

tribution

they

works

up the walls, to form

pipe,

and

as

If

too by

the

stock

occurs,

above

There

the

success stock

must

penetrate allowing

tuyeres

with

travelling

that

the

the furnace and

fuel is

of

the

volume

of hot

too

the

cinder

runs to

used,

back

the

dis-

the

in

blaht in

the

front

the

cinder

notch. on

To each

the

walls

a skew-back

scaffold.

of

tuyerr

under

stock

a

to

the in

placed

forms

forming

and

and

the stock pockets

now

eventually

back,

large,

leaving forms

are

blast

be proportioned

are

and

large hearths

penetration

then

water

with

Large

must

passage

bound,

tuyeres.

they

are

while

When

this

in yield.

the

furnace

evenly

on

on

column

to settle it

of the

iron

blown

proper

them

be no skew-backs

from scaffolds, admit

of

and

held

of

a given

heat

heat,

the

loss

for

the

walls. well

proper

notches

falls off

of

to one

any

upon

and

bronze the

nozzles

is

correct

of

blast

blast

small

bosh

hearths

When

air.

the friction

the furnace

Perfect and

nozzles

cinder

to

work

its shape

relation

as by varying

the

has no free

small

the by

is the

contents

a fixed

excess

above of

or decrease

retain

as the

bear

get

destroying

cinder

slow

tuyere.

have

The

will

stoves

their

short To

a core.

this,

settles

the

furnace

produced.

large

on slacking

the

about

working

equilibrium

biast,

or

with

must

of entering

centre

prevent

built

through

blast,

the volume

is

is disturbed

determined

deficiency

distributed.

of

tuyeres

any

emergency,

blast,

it well

it

by any excess

will be

the

equilibrium

of

no changing,

can be always

business,

have

as

the

described

in the

then

of

that

this

as

volume

can

now

the

reduction

needs

up

are

for

long

sides

flue,

maintain

power

ore

that

quality

as

on another

built

uniform reserve

make

required

and

and

in the

case

zone

furnace

a certain With

alone

escaping in

establish

of combustion

another.

the

of one

future.

bell

be placed

in

be controlled

the encroachment of the

the

341

in diameter.

should

and

of heat.

Let

l’?li’/Ztzit?.

the will

evenly.

rare

to

depends the

on clean

walls

bosh, burn But

and

bosh

iri the

and the blast across few

find a founder

walls, centre.

must

so

at the tuyeres,

furnaces who

are

free

is willing

to

he has one.

Again,

if the nozzles

up on one side,

are too

all the blast

will

large pass

and the up

that

furnace side,

should checking

ease tile

Eff7rtrlznlz:

342 descent fusion.

of the stock r)n the opposite

rJ. F. I.,

side at and above

the zone of

If this is not corrected. the stock will fasten to the walls and form a side scaffold, as per R%UV VI, which will show at the top by the stock settling on one side. ‘These are the most annoying and troublesome scaffolds, and they can be often detected by their making one side of the furnace shell lrot, and on going out of blast a large space will be found cut in the inwalls where the gases were forced past the edge of the scaffold, as in FGte VI. A differential blast is entering

gauge attached to each tayere pipe shows whether all the tuyeres evenly. The heat under a scaffold

gradually works up through it, melting out the iron and leaving behind the fuel and lime cemented together by the cinder in a compact mass. This is difficult to burn and fuse, as the blast cannot zet at the fuel in it until the cinder and lime disappear. When the volume of blast is increased so that the under side of the scaffbld is attacked, the skew-back will loosen more or less, and leave it down to the action of the blast, when, if there is not ample fuel before the tuyere to work it up, the zone of combustion is chilled and the furnace goes out. The

iron and cinder

melting

out of ;;’ scaffold

is caught

by the

slope of the bosh, and grooves are worn in it by this running iron and cinder, If one of these grooves directs the iron and cinder on the nose of a tuyere. it destroys it, leaving water in the crucible and destroyill g-the heat just at the time it is most wanted. The quickest way to get rid of these scaffolds is to have a series of holes in the bosh and side walls where they are likely to form. and crack them off with giant powder, but the precaution must be taken to have some extra fuel down to the hearth to melt them up and prevent chilling. When any trouble occurs with a scaffold, thehearth generally fiils up with mucky cinder, coal and iron. lhe iron notch should then be used exclusively to take off the cinder and iron, and if this does not clear the hearth then cut another iron notch in the crucible at hearth line opposite the regular iron the cinder and iron flow out there. This will heat notch, leaving up hearth and keep tuyeres clear of cinder. clear or the furnace goes out. Heretofore,

there. has been a horror

Tuyeres

or dread

must be kept

of cutting

a hole

in the furnace, but this must not stand in the way of helping the A furnace with the cinder notch placed opposite the iron furnace. notch alw.ays lvorks more evenly than with both on the same side.

Mny,

1886.j

The Bfast

Fi~nac~.

343

When a furnace works irregularly, some tuyeres are bright, some are dark; if the belly pipe is cold no blast is entering at that tuyere and it must be opened at once by the pricker rod, or by a small cartridge exploded just beyond the tuyere, circulation must be had at once. A bright tuyere and cold belly pipe shows but little circulation. The differential gauges are the best things to A constant half hourly inspection of the rely on in this case. tuyeres must be continually made to see that no water gets in the hearth. With a large hearth and the proper time for reduction, the faster a furnace is driven the hotter she becomes, more burden is carried, more iron made, and more steady is her working, until the limit of the volume of blast for the hearth is reached, when no further advance can be made without cooling the hearth, as the With a rate of combustion is limited by the size of the hearth. given hearth, more blast can be used at 1,4000 than at gOO”. A serious evil with furnaces is a stoppage, as it always gives For each more or less trouble by forming incipient scaffolds. minute that blast is off, a furnace making 700 tons per week, 156 pounds of iron are lost. Leakage of blast is another evil to be carefully guarded against. Even with a new plant, well built, there is a loss of twenty-five per cent. of the volume when blowing The volume of air that passes the ten pounds to the square inch. tuyeres is what does the work, and not the volume that is blown Instances have been found where the engine runby the engine. ni!lg twenty-four revolutions, on blanking all the tuyeres tight, the engine run sixteen revolutions on the leaks. In addition to the difficulties mentioned of the running of the furnace. the superintendent has to be continually on the guard against changes in the character and quality of his stock, in neglect or carelessness of his men, especially at night, and in stormy weather to see that the stock is well supplied and kept dry; that freshets do not interfere with the tuyere water, and that the machinery, boilers, stoves, pumps, etc., are ke.pt in good order. When his furnace is carrying a good burden and a damp spell comes on, he must add fuel to the furnace to keep up his heat, as each 10,000 feet of air per minute will require a ton of coal in twenty-four hours to maintain the equilibrium of heat in the furGood analysis of all stock should be going on constantly nace.

Hnrtmnn

344 and avoid

the stumbling

in the

.

dark

[f. and

the

blundering

F. I.,

of the

past. Having given a general description of furnaces, let us the Franklin Furnace of New York, as shown by P&e 3, workings for one week. Hearth g feet, bosh 14 feet, height 70 feet, stock line bell 6 feet 6 inches; bosh walls 18 inches thick on slope, inches above

the slope,

and

the

mantel

placed

above

Fuel per ton pig coke, Ore

sixty-three

thirty-six

per ton

Volume

and

.

.

.

.

of blast,

Temperature

of escaping

Iron,

.

blast per minute

.

.

.

.

.

.

.

.

contents

.

.

.

.

of furnace

Air per minute, feet, Ratio

.

.

per

.

of escaping

Grade

ofiron,

.

. .

cubic

.

gas

.

.

342 tons No.

ore,

44‘00

:.

Cinder,

sizien

.

. _

Al.U>?Zi?Z&.

12’20

. .

. . . . . . . . . feet, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . of

.

.

co2 ~__ CO

2,538

contents

.

.

.

.

.

.

in

.

.

OF

CINDER.

ORE

AND MagmGz.

6.30

11’80

Cnv6onic

Acid.

Water.

6.20

4’10

.~uz~/zuv.

Oxide

3’30 6-38

43’67

pounds.

. 5,091 “ “ . 1,426 . 13,514 “ . I,IooO ZIOO . 614 tons. . . 2,474 ‘I . 6,731

2, 12 tons No. 3.

Lilne.

top of bound

cent.

anthracite,

I, 260 tons No.

5’04

35’98

per

cent.

feet

.

by weight

ANALYSES

rron

. . . .

in feet,

1,000

.

.

gas,

per ton of pig iron,

Cubic

one-half

in cubic

feet, 14

WORK.

per

fossiliferous,

Temperature

Cinder

and

one-half

hematite

Limestone,

WEEK’S

I I

and

the Bosh

Crucible bound with cast iron water jacket. bosh. Fire brick stoves. with heavy boiler plate jacket. ONE

take up and its

I’12

Oxypn. 18.86 of

Iron.

I ‘or2

The ore is composed principally of small grains or shots of hematite, resembling shad eggs. This rapidly disintegrates in the furnace, leaving the CO act quickly, and as the ore contains some CO2 this is easily expelled, leaving the ore absorb carbon quickly. IIEAT Total ‘,

heat generated ‘I absorbed

Loss by radiation etc.,

.

_ .

per

ton

of iron, -8‘

I‘ water,

tuyere

.

CALCULATIONS.

.

.

.

.

.

.

.

.

.

.

.

gas at top, blowing

.

.

.

.

.

.

.

.

Calories. 18,051,8 r9

.

.

15,661,716

out,

.

.

2.39o.ro3

TLk- Blcrnst Fzf uztzrr.

May, 1X86.1

345

NO allowance is made for loss in expansion of blast, fallacy in the English calculations of Bell. A pound of cannot lose ing does not lose weight and consequently it does work. It has simply changed its quality quantity. The above loss is 13.2 per cent., a gain of

as this is a air expandheat unless but not its twenty-two

per cent. in calculations of heat loss in the best English furnaces. The rapid rate of driving with heavy burden leaves the escaping gas go off at a remarkably low temperature, and prevents any burning off of the fuel at the top of the furnace by the carbonic acid of the limestone attacking the fuel and forming carbonic oxide. This low temperature of escaping gas favors the accumulation of alkaline cyanides in the furnace, which under the influence of high heat at the bottom of the absorb oxygen rapidly, and then escape upward where they part with their oxygen, are condensed on the cold down coming stock and carried down to the bosh to perform again their office of reduction, and save fuel. The&z cyanides are formed from minute traces of potash and soda occurring in the coke or coal, and which, being set free in the zone of fusion, escape up, are condensed on the cold stock, and returned down again. This accumulation goes on until a large volume is collected. With charcoal, there is always plenty of potash and soda. When a furnace begins to scaffold below, the stock at top If gas washers gets hot, leaving the cyanides escape into the flue. are used the waste water from washer will give off the fumes that This simple are noticeable by their smell when the tops get hot. test tells beforehand

that trouble

is coming.

co2 by weight is much higher than has been hereThe ratio CO tofore found. Gas analyses are troublesome and rarely accurate as the furnace does not constantly give off a uniform volume of gas. Taking gas temperatures at the tunnel head they will vary on four points in an hour ZOO”. In the flue where the gas samples are taken for analyses the heavier gas, carbonic acid, flows along the’bottom while the carbonic oxide flows along the top an d it is impossible

to get an uniform

sample.

This

CO2 . IS CO gas is ex-

ratio of

an index or guide to show furnace men how near the hausted of its reducing power. To absorb the last atoms of oxygen from the ores requires a with hard, clnseigrained ores difficult to high heat, especially

H~tYt?Uz?z :

346 reduce.

If

they

were

hot iron sponge back

to

the

reduced

would

split

oxide.

*

[ J. F. I.,

by CO forming

CO2 the

intensely

up the CO2 and burn part of the iron

This

fact

requires

that

the

last

atoms

oxygen must be removed by solid fuel which forms CO. According to the degree with which reduction is carried solid

fuel

If

perfect

would

ratio

reduction

on by

co2 -I _ vary. co

could

be

made

with

CO

the

ratio -E{

be 1-22.

The the

so will the

OF

nearer

ore

reduced

CO2 generates forming

we approach by

that figure,

solid

The

fuel.

the less oxygen

calorie 5 while oxygen The but 1,855 calories.

by CO the more

is the heat produced

oxygen

absorbed

and the heavier

of

by CO to

absorbed by more oxygen

4,205

CO gives

is the

solid fuel absorbed

is the burden

that can be carried. The

less fuel burned

to CO by the oxygen

fuel escapes

to the tuyere

allows

burden

more

With pensed

analyses

to make

CO

and heat which

with by making book

stone,

the following

gas

analyses

in fuel CO

(less

carbon

to reduce

say

data

:

CO2. in pig) . say,

ore,

can be dis-

Taking

calculations.

of any furnace for one week,

CO. Carbon say,. Deduct

in its turn

to be carried.

of fuel, ore and

from the charge

of the ores, the more

.

‘7hzs. to CO., . . . j,og‘+ 1,680

.

. . . -co = 3.414 3,1’S co2 = 3.4’4

Mr. Bell gives

l !

CO2 in stone, say, . . . . . 0 in ore reduced to CO2, say, CO reduced by ore to COS, say,

at

.

. . . .

.

Tars. 560 960

1,680

cw = 3,zwj ‘935.

CO.

the best English

have been been found

.

workings

The

-76.

best

at ‘70, and instances American

practice

pre-

vious to this has been ‘72. No carbon, as

except

that in the pig, can escape the furnace except

CO or CO2 ; if fuel

leaving

is the same bottom.

in the

Much

have

off

calcined furnaces,

gas

in

the

has been said

than a ton of fuel higher

burns

at the

top,

it goes

that much less to burn to CO at bottom,

to

a ton

carbonates, and a coke

flues

about

of iron. with that

part

whether English While of the

contains

six

off as CO,

so that the result it burns

at top or

workings using less this is true, yet they work per

already

done,

cent. more car-

&lay, 1885.1

.

Thf

BZast

~~‘jfYPztzC‘

bon than ours, and which will carry twelve

.

347

per cent. more burden.

Our ores are more siliceous and require more limestone, whose carbonic acid weakens the action of the carbonic oxide in reducing the ores, which, in its turn, to make proper reduction, requires more fuel. At the present time, at Woodside Furnaces, in England, they are calcining the limestone, using it direct from the kilns, and tind a good saving in fuel in the furnace, as the carbonic acid driven off in the kiins does not dilute the reducing gas. By the use of rich sixty-three and but 608 pounds

limestone

per cent. ores, high heat in blast, to the

ton

of iron, American

naces have got their fuel down to 2,020 pounds, with

E$?

fur-

-73, and

escaping gas, 4SOO. -l-he limit of heat fixed by Mr. Bell in English escaping gases has been lowered by our workings beyond his expectations. Returning to the lines of the Franklin Furnace, it will be seen that the zone of fusion is above the bosh and the bosh is below the mantel. This prevents any partly fused material touching the bosh, as all the ore and stone disappear above it, leaving nothing but the fuel to slide down the bosh, thereby preventing any accumulation on the bosh, and keeping the bosh walls perfectly clean. No water has so far been used on the bosh jacket and no signs of heat are exhibited about it. The ores are oolitic fossiliferous hematite, that disintegrate and reduce readily. This is one reason why this furnace will use so much more air per 1,000 cubic feet ofcontents than is usually found. Since making the 614 tons here noted, the furnace has made 6pz tons per week on the same mixture, using 14,000 feet of air per minute. Twelve years ago this furnace ten feet lower, made 156 tons per week, using the same ores-stone and fuel, but by the addition of powerful engines, boilers, and large fire-brick stoves, with an active, intelligent management, their present success has been obtained and will continue. Turning to the Isabella Furnaces at Pittsburg, it will be found eleven )-ears ago they averaged 578 tons per week on 7 feet 6 inch hearth, 20 feet bosh 75 feet high, to-day, with more engines and large fire-brick stoves, they are averaging 1,200 tons, while at the Lucy Furnaces 1,825 tons were made in one week on a spurt.

Hurtman.

348 Heretofore,

young

[J. F. I.

??

men have kept out

furnace business,

of

as it is

a dusty, dirty, hard, brain-working trade, requiring twenty-four hours a day of constant care, 365 days a year, and as a blast usually lasts about 1,000 days, he has but little chance for a genuine holiday. Much is yet to be learned to always operate a furnace successfully, but the day is coming when it will be run with all the precision of a Bessemer converter, NOTE.---Mr. James Gayley, Supt. of Furnaces at Edgar Thomson Steel Works, writes, “ Our furnace 4 D ’ for week ending April 3. 1886, made 1,529 tons of No. I Bessemer iron, using x:993 pounds of coke (including waste) with 65 per cent. ores limestone per ton of iron.” .- -~--_ THE known

NEW to

discovery first upon observation

for

have

since,

proved

their

lines,

have

and The

no doubt,

to attempt

powers

one is already

sun

in size or

structure.

brightness

within

the course

the increase

and

subsequent

have

with

bodies

coohng. but

The

that

some

inadmissable, Nova

appreciable briIliancy

only

intervening Since,

parallax so high,

shown

borne the not

which

some

nature,

deductions

it

screen

has

been

our

resume

temporarily

in view of the spectroscopic

then, has

the

distance

not been

of

obtained

we are compeIled

in it, but it is

widely

extending an

indefinitely

system

larger

of

small

or in the rings

of Saturn.-

The

scale,

one

resembling

sun

be

The

to

Obscr-~olnuy,

” our

suddenly

its former

scale

suddenness

of of

that we of rapid its lustre,

withdrawn-seems of T. of

Coronet

them)

for a compact bodies-a

out-

“ temporary

stars is so great

for any

to substitute

but

history

these

transremain

from the present

months.

or

this has

Its be before it. It is premature,

that these of

dis-

others

without

stars

may simpIy employed.”

in mind

and

compose

1.500

ago,

those

stars,

a gaseous

radiations

of a few weeks

scattered, corona

of

is continuous,

possibly

character,

on

among

be stars in the least

Could

it could

now

one, the

writer has

decrease of light prove unmistakably and therefore capable relatively minute, that the star has not really altered alternative-

especially

Cygni.

have

fading-cannot

a thousandfold,

of

substances

be clearly

increased

do

to be

stars belong to it ; they according to the power

always

clusters

spectrum

the

astronomical

Whilst,

into

to draw any very definite

burst ; but it should stars-this

Its

nebuke only

we were two centuries

nebula.

constitution

consequently

a recent than

resolved

mysterious.

highest

as

immense

of

is the

of the telescope. It was also the and it has now been a subject of

advanced

been

chemical

and

not certain that these shape alters strangely

to

in Andromeda

Yet,

more

of this

some

silent

unknown.

own

all the thousands

Nebula

30~1 years.

are hardly

explanation

remained versal

the Great

nearly

“ We

the

covered

IN ANDROMEDA.-of

of which preceded the invention which the telescope was turned,

remarked, as to

STAR

astronomers,

and 851 pounds

and

(as yet an and

their

sun a loosely

system

that which

we

October,

~88~.

similar see

in

in the