Improvements in Process of and Apparatus for Distilling Ammonia.
Year: 1897

page_text: Date of Application, 22nd July, 1897-Accepted, 13th Nov., 1897
COMPLETE SPECIFICATION.
Improvements in Process of and Apparatus for Distilling Ammonia.
I, HENRIK JOHANNES KREBS, of 806 Franklin Street Wilmington, in the County of
New Castle, in the State of Delaware, United States of America, Engineer,
do hereby declare the nature of this invention, and in what manner the same
is to be performed, to be particularly described and ascertained, in and by the
following statement:-
My invention relates to processes of and apparatus for distilling, condensing, and
purifying condensable gases under high pressures, and especially to such processes
and apparatus when applied to the manufacture of an anhydrous ammonia.
Heretofore anhydrous ammonia has been distilled from aqua-ammonia in low
pressure stills and the gaseous matter withdrawn therefrom and condensed by means
of pumps.
It has also been prepared by distillation under high pressure and after
cooling liquefied in a receiver by the pressure maintained in the still.
By the means generally employed heretofore it has been found to be very difficult
to free the ammonia completely from the water and other impurities, such as
hydrocarbon compounds, even when additional appliances were used, and except when
the residual water was used for reabsorption of ammonia, as may be done when the
operations are conducted in connection with absorption refrigerating apparatus and
in like situations, there is serious loss due to imperfect distillation of the ainmonia from
the water.
The special objects of my invention are processes and apparatus by which from
aqua ammonia may be produced a pure article of condensed anhydrous ammonia at a
minimum cost without material loss of ammonia in the residues and by which the
operations may be carried on continuously. The separation of the ammonia from the
water and from the impurities present is effected by a primary and a secondary or
refining distillation and condensation, the refining distillation being effected at a lower
temperature than the primary distillation, whereby the impurities remaining are
entirely separated. The loss of ammonia in the residues of these distillations is
prevented in the primary distillation by a return of the residue to the still in the
form of steam to effect the distillation and in the refining distillation loss is prevented
by a redistillation of the residue, the product of such redistillation being returned to the
body of the refining-still and the residue run off as waste. These operations may be
carried on in any suitable or preferred form of apparatus constructed and operated
upon either of the plans above referred to that is, distillation may be produced at
relatively low temperatures and pressures, the condensations being effected by means
of pumps, or the distillations may be and preferably will be carried on at a
temperature and pressure sufficient to effect the condensations of the ammonia.
In attaining the objects of my invention I have also devised certain improvements
in the construction and combinations of parts comprised in the apparatus, which will
be hereinafter fully described and claimed and which are also applicable to high or low
pressure stills.
The process in its entirety, considered apart from any apparatus which may be
employed, is as follows: The aqua-ammonia from which the ammonia is to be
separated free from impurities is gradually heated to a temperature at which, at the

page_text: pressure maintained, it will give off substantially all of its contained ammonia. The
residue is then vaporized and returned in that condition through the solution of
aqua-ammonia being treated, and by means of this vaporized water containing the
residual ammonia I raise the aqua-ammonia to the desired temperature and separate
the aminonia therefrom, the further separation of the aminonia from the watery vapor
being effected by cooling, and the reduction of the former to a liquid being effected
by cooling and pressure. The liquid thus produced is refined or further purified by
subjecting it to a much lower degree of heat, condensing the vapors so produced,
subjecting the residuum of this distillation to a further distillation, and cooling and
returning the vapors thus. produced to the mass of impure ammonia. The condensed
vapors forming the product of these distillations constitute a perfectly pure anhydrous
ammonia.
In the accompanying drawings, Figure 1 represents the entire plant in elevation.
Fig. 2 is a vertical section of the primary still. Fig. 3 is a horizontal section of the
same on line 3 3, Fig. 2. Fig. 4 is an elevation, partly broken a vay and in section,
of the refining still and rectifying column and the recovery trap connected there with.
In describing the construction and operation of the apparatus I will first point out
its preferred form in which high temperatures and pressures are maintained in the
stills and afterward point out the changes necessary to adjust to low pressures.
Referring to the drawings, 1 is a steam generator of any ordinary or preferred
construction and located in any convenient position and adapted to supply the
necessary quantity of steam to the several parts of the apparatus in which it may be
required, as hereinafter described, and to the various pumps and other engines which
may be employed about the building.
2 is the still, composed of a rectifying-column 3 and an analyzer 4. The analyzer
in general is of an ordinary construction, being formed of tubular sections 5, having
floors 6, forming chambers or compartments 7, these chambers communicating with
each other by vapor-pipes 8 extending from openings in the floors into the respective
chambers 7 above and covered by sealing-caps 9. Each chamber 7 is also provided
with an over-flow pipe 10, located at opposite sides in alternate chambers, and
extending from some distance above the floor of each chamber nearly to the bottom
of the chamber below.
At the bottom of the analyzer 4 is the usual chamber 11 for receiving the drainage
from the chambers above of the water freed as far as possible from ammonia and in
which the live-steam is admitted from pipe 12 in its floor for affecting the distillation
of the amnionia. This chamber 11 is also provided with an outlet or drain pipe 13
through its side wall above the floor, which is connected with a trapped receptacle 14,
which in turn is provided with a pipe connection with the boiler 1.
The pipe 13, leading into the receptacle 14, and the pipe leading from it, which in
the construction shown connects with the steam boiler 1, are each provided with a
cock or valve 141 and 142, connected together by a rod 143, carrying a sliding
float 144, so as to be operated, one to be open when the other is closed, by the rising
and falling of the water. The cock in the outlet pipe is closed when the receptacle
is empty, and it remains in that position until the receptacle becomes full, when a
reverse action takes place and the receptacle is permitted to discharge itself. The
receptacle 14, with its connected valved pipe, therefore constitutes a trapped
discharge from the drainage chamber 11.
As various devices of the same character are in common use for supplying feed
water to boilers, a particular description is unnecessary.
The uppermost section 15 of the analyzer 4 is of larger dimensions than those
below it, and is provided with a liquid gage 16, a pressure gage 17, and a ther-
mometer 18, and it receives the aqua-ammonia to be distilled from pipe 19 through
its side wall, said pipe 19 being shown as the continuation of another pipe 34 which
will be hereinafter described.
The rectifying-column 3, superposed upon the analyzer 4, consists of a series of 5
tubular sections 20, each having a floor 21, and a partition 22, thus forming, when
placed in position two chambers 23 and 24 in each section, the upper of the pairs of

page_text: chambers being collecting chambers for the condensed vapors and the lower being
cooling chambers for the circulation of a cooling medium around the pipes conveying
the ascending vapors.
The uppermost section 15 of the analyzer is connected with the collection
chamber 23 above it, and each collecting chamber 23 is connected with each
succeeding one by a series of vapor pipes 25 and by the usual overflow pipe 26:
The vapor pipes 25 pass through the intermediate cooling chambers 24, each being
tightly fitted in the floor and partition of the respective sections and extending a
short distance above the partition forming the floor of the collecting chamber into
a sealing-cap 27, supported therein. The aggregate area of the cross sections of
these pipes should be such as to render the current of vapor, slow through the
cooling chamber, and the size of each and their distance apart should be such that
the cooling medium circulating through. the chambers will effectually abstract the
heat. The pipes are shown to be seven in number, six being arranged in a circle
around a central pipe. In the drawings also, Figures 2 and 3, is shown a convenient
arrangement of the overflow pipe 26. These pipes in the rectifying-column 3, as in
the analyzer 4, are arranged at alternate sides of the alternate sections, and their
upper ends pass through and are tightly fitted in the corresponding sealing-cap 27,
and at a proper point to extend downward centrally through one of the vapor tubes
into the collecting chamber beneath, in which it is provided with a liquid seal. By
this construction the necessity of forming joints for the overflow pipe in the partition
and floor of each section is avoided, and at the same time the passage and cooling
of the ascending vapors are not interfered with. For the purpose of forming a liquid
seal for these overflow pipes the sealing-cap 27 are provided on their upper surface
with circular upwardly extending flanges 28, forming cups in which the lower ends.
of the overflow pipe dip.
The cooling chambers 24 above referred to are each provided with means for
admitting and discharging a cooling fluid, so as to maintain a constant circulation
through each during the time that the apparatus is in operation. For this purpose
I preferably provide the top cooling chamber near the bottom at one side with a
pipe 29, connected with a cold water supply, and at the opposite side, near the top
of the chamber with an outlet pipe 30. This pipe 30 extends downward and is
connected on the same side with the cooling chamber below near its bottom, the
outlet pipe for said chamber being connected near the top at the opposite side and is
carried to any suitable point in the building for discharge. The pair of cooling
chambers located next below are provided with inlet and outlet pipes 32, 33, and 34,
arranged in the manner above described; but as a cooling medium for these chambers
I preferably employ the aqua-ammonia to be treated, said chambers thereby acting,
as "fore-warmers." For this purpose the inlet pipe 32 of the upper one of the pair
of chambers is connected with the source of supply of the aqua-ammonia, which
after passing through and abstracting the heat from the ascending vapors in the
vapor pipe is conveyed to the chamber below through pipe 33. In this chamber the
aqua-ammonia is still further heated, and is then carried by pipe 34 and delivered
into pipe 19, through which it flows, as before described, into the uppermost chamber
of the analyzer, where it first meets the ascending steam and vapors and is permitted
to give off ammonia. By this construction and arrangement of pipes conducting the
aqua-ammonia through the cooling chambers and delivering it into the initial or
receiving chambers of the analyzer the use of an exterior forewarmer, and the
consequent use of heat derived from some other source, is avoided, and the incoming,
aqua-ammonia is applied to the cooling off of the vapors at the point at which it.
will be most effective and where it will absorb the greatest quantity of heat.
While it will be found to be generally sufficient to employ four sections in the
rectifying column a greater number may be employed, and in such cases the top and
bottom cooling chambers of the series using water will be provided with inlet and
discharge pipes corresponding to pipes 29 and 32, all the chambers being. connected*
by pipes corresponding to pipe 30. If more than two chambers are used, cooled by:
the aqua-ammonia, modifications will be made in the pipe similar to those above.

page_text: described. In other respect additional sections in the rectifying-column involve
multiplication of the parts described.
In the analyzer the sections, except the top and bottom, are all alike and may be
increased or reduced in number as may be deemed advisable.
From the domed top of the rectifying-column extends the pipe 35 for conveying
the gaseous ammonia to the coil 36 of a condenser 37 of any ordinary or preferred
construction, and from this condenser the ammonia is carried by a pipe 38 to the
receiver 39 for the liquefied ammonia.
The refining devices by which the impurities remaining in the liquid ammonia
contained in receiver 39 are removed consists of a distilling chamber 40 provided
with a steam or hot water coil 41 in its interior, liquid gage 42, and pressure gage 43
and surmounted by a rectifying column 44. To the bottom of this chamber is
connected a pipe 45 leading from the receiver 39 and provided with a stop
The rectifying column 44 is formed of tubular sections having the same
construction and parts as the rectifying column above described, the cooling chambers
thereof being provided with a similar arrangement of cold water circulating pipes 47,
cock 46.
48 and 49.
Adjacent to the still 40 and rectifying-column 44 and forming a material part of
the refining devices is the recovery trap 50.
This still 50 is a closed vessel surrounded
by a hot water-jacket 51, supplied by pipe 52 and dischargel by an over-flow or
siphon pipe 53. The still 50 is provided at its bottom with drainage-discharge
pipe 54, normally closed by stop-cock 55, and with the inlet pipe 56 provided with
a suitable valve or cock 57, and connected at its opposite end with the bottom of the
distilling chamber 40. This pipe 56 may be connected directly to the distilling
chamber, or it may be conveniently connected, as shown, with the pipe 45, the
desired communications, being maintained by opening and closing, the respective
valves in the pipes. The recovery still is also provided at its top with a vapor
pipe 58, leading to a coil 59 of a condenser 60, the discharge pipe 61 of said coil
communicating with the upper portion of the distilling chamber.
From the closed top of the rectifying column 44 a vapor conveying pipe 62
extends to the coil of a condenser 63 from which the purified ammonia is conducted
under pressure by pipe 64 to the final receiver 65 from which it may be drawn off in
a liquid condition for consumption.
In starting the apparatus steam is generated in boiler 1 and raised to a pressure
slightly in excess of that at which anhydrous ammonia will liquefy at the temperature
maintained in the condensers. Water is then turned on to the upper cooling
chambers 24 through the pipe 29 and on to the condensers. The aqua-aminonia is
then forced through the inlet pipe 32 into the lower cooling chambers 24 and passes
thence into the uppermost section of the analyzer 4 through pipe 34. This chamber
being filled above the mouth of the over-flow pipe, the aqua-ammonia descends
into the section below, which, being filled to the proper height, supplies the next
section, the chamber in each succeeding section being supplied in the same manner.
The forcing of the aqua-ammonia through pipe 32 is continued until the liquid
begins to be discharged through drain-pipe 13. At this time the over-flow through
the drain pipe is cut off by turning the cock therein, the inflow of the ammonia is
stopped, and steam from the boiler is admitted through pipe 12 to the drainage
chambers 11, which forces its way through the vapor pipes 8, beneath the sealing
cap 9, and through the aqua-ammonia contained in each chamber, being itself partially
condensed during its passage and gradually raising the temperature of the aqua-
ammonia in the superposed sections of the analyzer, setting free the ammonia from
the solution.
This operation continues until the thermometer shows a temperature of about 220°
Fahrenheit, when inflow of aqua-ammonia is again permitted. The still is now
in full operation, the aqua-ainmonia passing through the lower cooling chambers
of the rectifying column abstracting the heat from the ascending vapors, the
water and other condensable matters filling the collecting chambers to the

page_text: height of the over-flow pipe. At the same time the heat abstracted from the
ascending vapors warms up the aqua-ammonia nearly to the temperature maintained.
in the receiving chamber of the analyzer, so that it begins to give off the gaseous
ammonia immediately on its introduction therein. The ascending vapors are
further cooled in passing through the upper cooling chambers in which cold water'
circulates, and a further condensation takes place, the liquid filling the collecting
chambers and passing downward through the sealed overflow pipe into the chambers
beneath while the vapors, which are now nearly anhydrous ammonia, containing
only a small percentage of impurities, pass along the pipe 25 through condenser 37,-
and under the pressure maintained in the still collect in receiver 39 in the form of.
a liquid.
As soon as liquid appears in the gage 16 the valve in drain pipe 13 is opened,
permitting the liquid collected in the drainage chamber 11 to flow through it into
receptacle 14. As the entrance of the steam is into the bottom of this drainage
chamber, and as the steam passes through the liquid contained therein, constantly.
agitating it, the temperature at this point being higher than it is elsewhere in the
still, the temperature of the liquid gradually increasing from above downward, the
liquid passing through drainage pipe 13 will contain but little ammonia when the
still is operating effectively; but in order to avoid loss in this way the construction
above described is provided, by which this drainage liquid is forced from time to
time as feed water to the boiler. By this construction the ammonia contained in.
the drainage liquid is returned to the still in the form of vapor with the steam, and
it is also a matter of economy, since the boiler thereby is supplied with very hot
water. Means, of course, may be interposed between the receptacle 14 and the
steam generator to force the water into the generator below the water line.
The liquid passing through the drainage pipe consists not only of the water
condensed from the inflowing steam, but also of water contained in the aqua-ammonia *
and there will be therefore a greater amount of water passing through the drainage.
pipe than is represented by the incoming steam. The steam used elsewhere in the
building in driving pumps for other purposes, will, however, under ordinary.
circumstances consume this surplus, and in any event the quantity of ammonia lost is
reduced to a minimum. By forming a leak or telltale in the pipe 13 or other point
in the course of the drainage liquid the operator can by the odor determine whether
the still is operating properly.
A further advantage of the construction described, which is not dependent on the
delivery of the drainage liquid into the boiler, is that by the delivery of the drainage
through a trapped discharge the flow of the drainage liquid from the still may be
continuous instead of intermittent, as usual, and by the arrangement of the steam and.
drain pipe described there will not be under proper conditions a material
quantity of ammonia in the drainage.
excess of ammonia should be
contained in the drainage, its presence may be readily detected by smell and
the temperature, pressure, or quantity of aqua-ammonia supplied regulated
accordingly..
If an
The liquid ammonia contained in the receiver 39 contains a small percentage
of impurities, such as water, and when the ammonia is obtained, as usual, from
gas, liquor, hydrocarbon compounds. To eliminate these impurities, suitable
quantities of the liquid are delivered from time to time to the purifying portion
of the apparatus by means of the pipe 45. The liquid ammonia delivered by this
pipe is under a pressure such that it will liquefy at the temperature maintained
in the condensers. Being at that pressure when delivered to the distilling chamber,
raising the temperature slightly will volatilize the ammonia and cause it to distill
over through the rectifying column and condenser and when cooled therein liquefy
in the final receiver 65. For this reason I do not find it necessary to raise the
temperature in this still above one hundred degrees Fahrenheit, and it will operate
even at a lower temperature. The temperature in this distilling chamber as
compared with the pressure being so low the impurities contained in the liquid
delivered to it will not volatilize or if they do they will be condensed in passing..

page_text: through the chambers of the rectifying column and finally be returned to the:
bottom of the still from the collecting chambers. As the quantity of liquid contained
in the still becomes reduced an additional quantity of the liquid ammonia is
delivered to it from the receiver and the re-distillation continues. After this.
purification has been continued for some time, say about eight (8) hours, and
the still has been recharged several times some liquid impurities will have.
collected in the bottom of the still. This liquid will also contain ammonia,,
which should be recovered. To accomplish this recovery, the cock in pipe 56 is
opened, permitting the liquid to flow into the recovery still.
If the parts are arranged as shown, this flow will take place by gravity until the
level of the liquid in the two vessels is equal, and in such cases the cock in pipe 56
may remain open constantly except when the still is being charged through pipe 45,
and the flow of the liquid from the distilling chamber to the recovery still will be
constant. In this recovery still the liquid will be heated by the hot water jacket 51
to a temperature somewhat higher than is maintained in the adjacent still, (say.
130° or 140° Fahrenheit,) and the ammonia contained in the liquid will separate
in the form of a vapor, and pass through pipe 58; and through condenser 60, from
which it will pass in a liquid form into the upper portion of the distilling chamber
into the mass of liquid contained therein., By this arrangement if any of the
impurities are carried over with the ammonia, they will not pass into the purified
anhydrous ammonia, but will be returned to the unpurified portion, passing finally
back to the recovery still.
When the impurities are believed to be sufficiently concentrated, communication
through pipe 56 is shut off and the distillation in the recovery still continued for
a sufficient time to drive off the remaining ammonia, when the liquid is discharged
through pipe 64, and it is found that the residuam so discharged may be so
completely freed from the ammonia that it will not make frost.
If it should be found inconvenient to provide the distilling chamber with sufficient
heating surfaces, devices, such as a coil, may be provided for heating the ammonia
outside of the distilling chamber, and since the temperature in these vessels is not
high many of the ordinary means for heating may be conveniently employed.
In dotted lines in Fig. 1 of the drawings, have shown pumps interposed in
pipes 35, 62, and 58, and any one or all of these pumps may be employed if it is
deemed advisable to operate the still at lower temperatures and pressures than
have been specified herein. For instance, by the use of the pump in pipe 35 the
temperature and pressure maintained in the primary still may be reduced to any
degree found desirable. Also by the use of the pump in pipe 62 no additional
heat need be embodied to the contents of the refining still, or it may even be
cooled down below the temperature of a surrounding atmosphere, the volatilization
of the ammonia being effected by the reduction of the pressure. It will also be
obvious that by the use of the pump in pipe 58 there need not be a difference in
the pressures, but in that case free communication between the vessels through pipe
56 cannot be permitted.
In some apparatus I have found it advisable to connect the condensing coil 36
directly with the still 40 and the condensing coil 63 with a second still like 40 and
having also a rectifying column like 44, the pipe 56 in such case connecting
the bottom of the two stills and the like pipe from the second still connecting with
the still as 50.
Having now particularly described and ascertained the nature of my said invention,
and in what manner the same is to be performed, I declare that what I
claim is:
1. The process of separating ammonia from aqueous solutions carrying it, which.
consists in generating steam in a suitable steam boiler, discharging a current of
the steam into a still containing an aqueous solution of ammonia, conveying away
the ammonia-gas separated from the solution and returning the residual water from
which all or most of the ammonia has been driven off and the condensed steam back

page_text: to the steam boiler whereby the boiler will be fed with very hot water and
whatever ammonia is contained by the residual water in the still will be fed with it
into the boiler and return with the steam back to the still so that all loss will be
prevented.
2. The process of continuously producing anhydrous ammonia which consists in
continuously feeding an aqueous solution of ammonia into a suitable still, introducing
a current of high pressure steam into the solution, conveying away the gas driven
off therefrom cooling this gas to ensure the condensation of aqueous and other
impurities mixed therewith, producing thereby a more concentrated liquor, redis-
tilling this concentrated liquor at low temperatures, and without introducing steam into
the liquid collecting the unvaporized liquid in the bottom of this second still conducting
them to a third still wherein they are subjected to a temperature relatively higher
than that of the second still, and recovering the gas driven off therein by conveying
it back to the condensing apparatus appertaining to one of the other stills.
3. In an apparatus for making anhydrous ammonia, analyzer, a steam pipe opening
into or near the bottom thereof, a steam boiler for supplying steam to the analyzer,
a conduit through which an aqueous solution of ammonia is fed to the analyzer, an
out-let conduit for the gas and a conduit for conveying the condensed steam and
residual water from which most or all of the ammonia has been driven from the
analyzer to the boiler, all substantially as and for the purpose specified.
4. In an apparatus for making anhydrous ammonia, the combination with a
refining still of means for delivering liquid ammonia thereto, a recovery still, a
conduit leading from near the bottom of the refining still to the recovery still for
discharging the residuum from the refining still into the said recovery still, a
conduit pipe for the vapor driven off from the recovery still leading therefrom to a
condensing apparatus.
5. In an apparatus for making anhydrous ammonia the combination with a refining
still having a rectifying column connected therewith, and a conduit for delivering
ammonia thereto, of a recovery still, a conduit leading from near the bottom of the
refining still to the recovery still for discharging the residuum into the recovery still,
a conduit 58 for the vapor driven off from the recovery. still, a condenser for said
vapor into which the conduit 58 leads, a pipe for conducting the product resulting
from the condensation of the gas from the condenser into the main circuit, and
means for heating the contents of both stills.
6. In an apparatus for making ammonia the combination of a primary still and a
condenser for the gases discharged from the primary still with a refining still into
which the vapor partly or wholly condensed in the condenser is fed, a recovery still
and connections between the refining, the recovery stills and a condenser for the
gases discharged, from same.
7. The combination of a still having a drainage receiving chamber at the bottom,
a steam generator, a pipe connecting and transmitting steam from the generator into
the drainage chamber, and means connected with the drainage chamber and with the
steam generator for delivering the drainage from the former into the latter
substantially as described.
•
8. The combination with analyzer having a drainage chamber of a steam boiler 1,
a steam pipe leading from the boiler and opening into the drainage chamber near its
bottom, a drainage discharge pipe, a trap therein and a connection from the trap to
the steam boiler 1 substantially for the purpose specified.
Dated tuis Za 1 day of July 1031.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.