Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ WO 94/21329 21 5 8 5 5 3 PCT/CA94/00152
SO~ WASTE CON~ERSION PROCESS AND APPAR~TUS
TECHNICAL FI}~LD
This invention relates to solid waste disposal and in particular a method
5 and appal~lus for the conversion of solid waste m~t~ri~l by destructive fli~till~tion of
waste m~teri~l and reacting of gaseous byproducts in a catalytic con-l~n~er.
BACKGROUND OF THE INVENTION
There is a growing col~cern reg~ding the disposal of waste in general
10 and in particular the disposal of biom~Aic~l and other ha_ardous wastes. Specifically,
with respect to biomYlic~l wastes there are not only all the problems associated with
waste disposal in general but also the problems of properly disposing of waste
cont~min~ted by bacteria and viruses. Accordingly there is a need to manage and
dispose of waste effectively and efficiently.
Various methods have been used for disposing of wastes including
incineration and l~nflfill. Some of the typical con~xrn.~ oci~ted with these methods
include finding environmlont~lly acceptable and politically acceptable landfill sites and
incineration sites, building smoke stacks for incineration that are tall enough so that
the gaseous waste is s-lfficiently diluted to meet the local standards, and transporting
the waste to the disposal site. With regard to biomY1ic~l waste cont~min~t~oA bybacteria and viruses, it is il,lpol~nt that the bacteria and viruses are stçrili7~1 as part
of the waste disposal process.
Disposing of waste through landfill is a very volatile political issue,
since no one wants a landfill site in their back yard and yet no one wants to pay the
high transportation costs ~ori~tPIi with transporting the waste to a remote site.
Further, the amount of waste that is generated and is filling our landfill sites is a
serious problem. With regard to biom~Ai~l waste cont~min~tPd by bacteria and
r viruses it is desirable to dispose of it either on site or as near thereto as possible so
that any conf~min~tion by bacteria and/or viruses is cont~in~d. Typically where
30 landfill is the method of disposal this is not always possible. In addition where the
waste is disposed of in a landfill site typically no steps are taken to stçrili7e the
bacteria and viruses.
WO 94/21329 PCT/CA94/00152
2i585~
Similarly disposing of waste through incineration is a volatile political
issue and no one wants an incin~r~tion site in their backyard. Incineration is
b~ ~lly burning the waste or converting it into ash and gas. Incineration has the
advantage of being adaptable to stt~rili7e the bacteria and viruses. However, after
5 incineration the ash still has to be disposed of, typically in a landfill site. Further, at
least some of the gases that are byproducts of incineration are harmful gases and
typically these are released into the atmosphere. More recentIy incineration also
incllldes scrubbers which process the gaseous byproducts of incineration. Although
the scrubber ~palen~ly "clean" the gaseous byproducts the invisible gases released
10 into the atmosphere may still be harmful. Spe~ific~lly, some of the gaseous
byproducts may be hydrocarbons which are known to be harmful if inh~led
More recently attempts have been made to use pyrolysis to destroy
waste. Pyrolysis overcomes many of the deficiencies of waste disposal through
landfill or incineration since it reduces the volume and mass of the waste. These
15 systems however are typically de~i~n~l for specific types of waste. In an attempt to
control the output, where the composition of the waste is varied, the process isadjusted by adding certain m~teri~l~ to the input. These systems are often impractical
for biom~Aic~l or m~nicir~l waste because it is difficult to analyze the waste
cor,lposilion prior to its disposal. In addition, pyrolysis typically has gaseous
20 hydroc~lJons as byproducts which, as tli~cn~ed above, are undesirable. Some of
these systems are used in combination with scrubbers. Spe~ifir~lly U.S. Patent
5,010,829 issued to P. Klllk~rni on April 20, 1991 and U.S. Patent 4,934,286 issued
to B.P. Fowler on June 19, 1990 show systems which destroy the waste through
pyrolysis and then remove chlorine by passing the cooled gaseous byproducts through
25 an NaOH tower.
Molten baths have been used in the past, as a step of a mamlf~st~lring
process, as a means for heating and/or vaporizing materi~l~. These baths, however,
were not used for solid waste or biom~Ai~l waste disposal because of the
helelogellous nature of the waste and its high water content since water, when
30 vaporized, in a molten bath would cause explosions.
More recently molten baths have been used in the treatment of sludge.
WO 94/2L329 PCT/CA94/00152
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Spe~ific~lly United States patent number 4,173,190 issued to Greenberg et al. shows a
coiled tube immersed in a molten salt bath. The sludge and hot air mixture is dried
and burned in the coiled tube. This system, however, is an oxygen based system and
the sludge is not submerged in the bath.
Until the present invention there has not been a method and a~pa-~Lus
for converting the gaseous byproducts of the waste into liquid hydrocarbons rather
than gaseous hydr~l,o"s.
DISCLOSURE OF INVENTION
The present invention provides for the combining of dissociated solid
waste with hydroxide ions to form liquid hydrocarbons. A hydroxide or carbonate
base solution is used to provide the hydroxide ions.
According to one aspect of the invention there is provided a solid waste
conversion process for converting solid waste having long carbon chains and hydrogen
groups and having by mass less than 80% water are disclosed. The solid waste
material is dissociated substantially in the absence of oxygen into unstable gaseous
byproducts and particulate matter and the bonds in the long carbon chains are broken.
In a con~ensPr system the unstable gaseous byproducts are conden~ed into a reacted
solution comprising liquid hydr~c~bons. The cond~n~er system utili7.in~ a hydroxide
or carbonate base solution, preferably a sodium hydroxide solution. Preferably the
liquid hydloc~bons are s~al~led from the reacted solution. According to
another aspect of the invention the condenser system includes the steps of spraying the
unstable gaseous byproducts with the solution to form reacted gases and cooling the
reacted gases.
.Al~e~ ely according to another aspect of the invention the con-len~er
system includes the steps of partially cooling the unstable gaseous byproducts and
g the unstable gaseous byproducts in their unstable form so that stable gases
- do not form and con-len~ing the partially cooled unstable gaseous byproducts in a
catalytic conden~er con~ g the solution.
According to a further aspect of the invention an apparatus is provided
for converting solid waste having long carbon chains. The appal~tus comprises a feed
wo 94/21329 2 iS~S PCT/CA94/00152
system for transporting the waste subst~nti~lly without introducing oxygen into the
system. A sealed reaction vessel is provided for receiving the waste from the feed
system. A heat source is provided to heat the waste subst~nti~lly in the absence of
oxygen to temperatures so that the solid waste dissociates into unstable gaseousS byproducts and particulate matter and so that the bonds in the long carbon chains are
broken. A condenser system is provided which is downstream of the heating sourceand in which the unstable gaseous byproducts is reacted with a solution chosen from
the group con~istin~; of hydroxide bases and carbonate bases to produce a reacted
solution comprising at least some liquid hydrocarbons.
According to a still further aspect of the invention the condenser system
comprises a sealed catalytic conversion chamber including a means for spraying the
unstable gaseous byproducts with the solution to form reacted gases and a means for
cooling the reacted gases.
Alt~rn~tively according to a still further aspect of the invention the
condenser system comprises a means for partially cooling the unstable gaseous
byproducts and m~int~ining the unstable gaseous byproducts in their unstable form so
that stable gases do not form and a catalytic condenser downstream of the partially
cooling means the catalytic condenser co~ ing the solution for con~en~ing the
partially cooled unstable gaseous byproducts.
Further features of the invention will be described or will become
a~nt in the course of the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be more clearly understood, the
plerell~d emborliment~ thereof will now be described in detail by way of example,
with reference to the accompanying drawings, in which:
Fig. 1 is a schematic view of the process used for the destructive
till~tion of solid waste material and the reacting of unstable gaseous byproducts
thereof in a con~ien~p~r system of the present invention;
Fig. 2 is a schematic view of the process used for the destructive
till~tion of solid waste material and the reacting of unstable gaseous byproducts
WO 94/2L329 PCT/CA94/00152
2158~3
thereof in a conden~er system of the present invention showing a condenser system in
more detail;
Fig. 3 is diagl;1"~",~l;c view of the a~p~dt.ls of the process shown in
Fig. 2;
Fig. 4 is a sçhpm~tic view of the process used for the destructive
till~tion of solid waste m~t~,ri~l and the reacting of unstable gaseous byproducts
thereof in a con~en~Pr system of the present invention showing an alternate con~len~,r
system in more detail;
Fig. 5 is diagr~mm~tic view of the a~ald~.ls of the process shown in
Fig. 4;
Fig. 6 is a vertical sectional view of a catalytic condenser shown in Fig.
5; and
Fig. 7 is a horizontal sectional view of a catalytic condenser shown in
Figs. 5 and 6.
MODES FOR CARRYING QUT THE INVENTION
In the following ~ c~ ion the term destructive ~ till~tion will be
understood to mean the çhemic~l deco",posiLion of matter into smaller and simpler
molecules. The reaction takes place by the application of energy in the absence of
oxygen so that no combustion takes place. The process is endothermic and therefore
there must be a constant application of energy to sustain the process. Destructive
till~tinn is also som~times referred to as pyrolysis but that term could also refer to
reactions which take place in the presence of oxygen and therefore to emphasis that
the process of the present invention takes place s--bs~ lly in the absence of oxygen
the term destructive ~ till~tion will be used.
The process for destructive rli~till~tiQn of solid waste material and the
reacting of the byproducts in a catalytic condenser will be liccl~seA generally first,
- followed by a ~ c~ ion of the a~a dlus of the plerelled embo~liment~.
Referring to the drawings, and in particular to Fig. 1, the process for
the conversion of solid waste material by destructive ~ till~tion and the reacting of
unstable gaseous byproducts in a catalytic condenser is shown generally at 10. The
wo 9412L~29 ~$~$ PCT/CA94/00152
main components of the system iriclude a feed system 12, a reaction vessel or reactor
14 and a conclçn.~-r system 16.
The waste material is fed into the reaction vessel through feed system
12. The feed system is adapted to minimi7P the amount of oxygen that enters the
5 reactor 14. It is important to minimi7e the amount of oxygen in the reactor 14 to
minimi7e and if possible e1imin~tt~ the amount of combustion that occurs.
In reactor 14 the waste is processed by destructive ~ till~tion reslllting
in unstable gaseous byproducts and particulate matter or solids 18. In order to
achieve destructive ~ till~tion of the waste, the waste products are heated to a10 tt;",peldture greater than the vaporization te"~ldL~Ire of the m~t~ . Further, the
ten,p~;ldture needs to be above the te",peldture at which the bonds in the long carbon
chains are broken. Typically a minimum temperature of 800C will be adequate formost species of hyd,o.;a,l,ons. Where the te",l.eldt~lre is above that at which the
bonds in the hydrogen groups are broken, simple hydrocarbons will be left. This will
15 typically occur at ~elll~GldlUlkS over 1100C. In some circllmst~nces it will be
desirable to break the waste m~t~qri~l down into simple hydrocarbons but it will be
appreciated that this will take more heat and therefore will be more costly.
It will be appreciated by someone skilled in the art that the destructive
distill~tion described above could also be described in terms of energy. That is,
20 enough energy is added to the reactor 14 so that the bonds in the long carbon chains
are broken. Typically the amount of energy that is required to break the long chain
carbons is 80 kcal/mole and to break the bonds in the hydrogen groups is
approximately 110 kcal/mole.
Further, it will be appreciated by someone skilled in the art that in the
25 above and following description the following definitions were used. The term long
carbon chains refers to molecules having more than two carbons in the molecule. The
bonds can be double or triple carbon bonds. Therefore when long carbon chains are
broken this means that carbon r~dicles are formed. The term hydrogen groups means
molecules having hydrogen as part of the molecule but it does not include hydrogen
30 on its own.
To break the long chain carbons, a variety of methods could be used in
WO 94/2L~29 215 8 5 5 3 PCTtCA94/00152
reactor 14 and the most a~l~,iate method can be chosen by someone skilled in theart. For eY~mple a plasma torch could be used as a heat or energy source.
Alternatively a sand bath or heat bath could be used as a heat or energy source.Similarly other material with a high heat capacity could be used as a heat source.
Condenser system 16 utilizes a hydroxide or carbonate base solution.
The hydroxide or carbonate base dissolves in water and s~a,d~s into ions.
Preferably sodium hydroxide is used since the sodium ion will combine with chloride
ions which are present and form sodium chloride, particulate matter. In the catalytic
condenser 16 the unstable gaseous byproducts react with the sodium, hydroxide, and
hydrogen in the sodium hydroxide solution to form liquid hydrocarbons, weak
alcohols or weak acids, water and salts. In Fig. 1 only liquid hydrocarbons 20, water
22 and particulates 24 are shown since these are the primary products of the process.
An embodiment of the system will now be described with reference to
Figs. 2 and 3. In this embodiment the condenser system includes a catalytic
conversion chamber 26, a first mist elimin~tor 28 and a second mist elimin~tor 30.
In the catalytic conversion chamber 26 the unstable gaseous byproduct
is reacted with sodium hydroxide solution to form converted gases. These converted
gases are processed in a first mist eli",i~ r 28 where the converted gases are cooled
to a tt;lllp~ld~lre of 100C. At this ~Illpeldtulc water 22 will condense. A second
mist elimin~tQr 30 cools the converted gas to below where liquid hydrocarbons 20 will
form a condense. Typically the gases will be cooled to standard te"~;,dture and
ples~iUl~. It will be appreciated by someone skilled in the art that multiple mist
eli"linAt-,ls could be used to remove specific liquid hydrocarbons since each liquid
hydrocarbons have a specific te"~ldLIlre at which it will change phase from gas to
liquid. For example methanol (methyl alcohol) changes phase at approximately 67C,
ethanol (ethyl alcohol) changes phase at 78C, benæne changes phase at 80.1C and
acetone changes phase at 56.5C
When the unstable gaseous byproducts react with sodium hydroxide
solution particulate matter 24, for example sodium chlori~l~, will also form.
Particulate matter 24 can be removed from the system wherever practicable by well
known methods and this is shown between catalytic conversion chamber 26 and first
Wo 94/21329 ~, lS ~ ~ S ~ PCT/CA94/00152
mist elimin~tor 28.
Fig. 3 shows a ~ r~mm~tic view of the apparatus for the system
shown in Fig. 2. Catalytic conversion chamber 26 has a plurality of spray nozzles or
atomizers for spraying the incoming unstable gaseous byproduct shown by arrow 32with sodium hydroxide solution. Catalytic conversion chamber 26 and the plurality of
nozzles are configured to ensure that the dwell time of the unstable gaseous byproduct
in the sodium hydroxide spray allows for the combination of the hydroxide ion with
the unstable gases. The concentration of sodium hydroxide in the solution which is
used is as high as practicable. As discussed above in the catalytic conversion chamber
26, in part, the hydroxide ion will combine with unstable gaseous byproducts to form
water and hydrocarbons, generally referred to as converted gases. As the converted
gases exit the catalytic conversion chamber 26 the converted gases are still gases and
need to be cooled to become liquids.
A conduit 34 between the catalytic conversion chamber 26 and a first
mist ~limin~tor 28, described below, is configured so that the velocity of the reacted
gases is re~uce i. This will allow particulates, shown by arrow 36 which have formed
in the catalytic conversion chamber 26 to be collected and removed or recycled. As
shown in Fig. 3, conduit 34 has an elbow and a reservoir 38 for collecting and
removing particulates. The particulates are predominantly sodium chloride when
sodium hydroxide solution is used as the spray. The particulates can be recycled back
through conduit 40 and used in the spray as catalytic conversion chamber 26. Theconc~ontr~tinn of the sodium hydroxide will be monitored. Periodically the reservoir
may be flushed as neerlecl
First mist eli",;n~tQl 28 cools the reacted gases to a temperature
between 100C and 85C at which temperature H2O will change phase, ch~nginp
from gas to liquid.
Second mist elimin~tor 30 cools the rem~ining reacted gases to a
temperature at which t~",pelature the liquid hydrocarbons will condense. Typically
the te"~eiature of second mist elimin~tor 30 will be between 80C and standard
temperature and pressure. ~ r~l~bly it will be at 55C.
Where there are some gases which pass through the system without
Wo 94/2L~29 215 8 5 5 ~ PCT/CA94/00152
comhining to form water, liquid hydrocarbons or particulate matter these gases are
routed back to the catalytic conversion chall,bel 26. Hydrogen is an example of a gas
which may do this.
An ~ltern~te con~en~ing system may be used, wherein rather than the
5 sodium hydroxide being sprayed on the unstable gas stream and then the reacted gases
are cooled to form liquids, as described above, the unstable gas stream is partially
cooled but l,,~ in~l in an unstable state and then bubbled through a sodium
hydroxide solution. This alternate system will now be ~ c~ Pd with reference to
Figs. 4-7.
The unstable gaseous byproducts are transported from the reactor 14 to
the catalytic conden~Pr S0. During transportation, the unstable gaseous byproducts
are cooled but no lower than the tem~l~tu~ at which the gases will recombine or at
which the gases become stable. For most appli~tion~ the gases will be cooled to
about 400C.
The catalytic condenser 50 utilizes a hydroxide or call,ollate base
solution. The hydro~ide or c~l.ona~e base dissolves in water and sel)andtes into ions.
Preferably sodium hydroxide is used since the sodium ion will combine with chloride
ions which are present and form sodium chloride a co,.,pou,ld which is highly soluble
in water. ~ltPrn~tively if a carbonate base is used ~ ilates will from which should
be removed before the solution enters the reverse osmosis unit.
In the catalytic condenser 50 cont~ lillg a sodium hydroxide solution,
the unstable gaseous byproducts react with the so~ m, hydroxide, and hydrogen toform liquid hydrocarbons, weak alcohols or weak acids and salts. The pH of the
solution is monitored to ~ i" a s~lfficient amount of sodium and hydroxide in the
system. The pH is ",~inl~ d between 9 and 12 and is preferably at 10. The
solution is m~int~ined at a lelllp~ Ltule below which the gases will recombine with the
sodium hydroxide solution. For most applications the conciçn~er will be kept below
65C and preferably at room ~e~"~ "c, approxim~tP-ly 25C.
In the sepa-~tor 52 the liquid hydrocarbons 20 are se~ from the
sodium hydroxide solution. This can be done by reverse osmosis. The liquid
hydrocarbons 20 can then be further separated into distinct hydrocarbons by
Wo 94/2L~29 ? i $ ~ S 5 3 PCT/CA94/00152
conventional methods.
The sodium hydroxide solution which has been se~ ~i from the
liquid hydrocarbons 20 is transported to the ~ till~tinn chamber 54 where it is
separated into water 22 having some carbonate and sodium chloride dissolved therein
S and salts, primarily sodium chloride. The salts are stored in reservoir 56 and are
available for recycling into the catalytic condenser as nP~etl.
Referring to Fig. 5, a conduit 58 is connecte~l between the reactor 14
and the catalytic condenser 50. In the conduit 58 the gases are cooled but no lower
than the lelnpe.ature at which they will recombine or become stable, for most
applications the gases will be cooled to about 400C. A bag house 60 is attached to
the conduit 58 to allow for the removal of particulate matter which is airborne in the
gases. A blower 62 is conn~ct~l to the conduit 58 between the bag house 60 and the
catalytic condenser 50 to ~ inli-in an e~uilibrium between the gas ~lCS:iULc in the
conduit 58 and the liquid p-cs~ule in the condenser 50.
The catalytic condenser 50 shown in Figs. 6 and 7 is a sealed vessel
filed with a hydroxide or c~b~ ate base solution 64, preferably sodium hydroxide.
An inlet pipe 66 is connçct~d a pair of spaced apart top 68 and bottom 70 spargeplates. The inlet pipe 66 is an exten~ion of the conduit 58. The peripheral edge 72 of
the sparge plates are ~tt~h~d together. The top sparge plate 68 has a plurality of
20 holes 74 as shown in detail in Fig. 7 formed therein through which the gas is released
into the solution as shown by arrows 76 in Fig. 6. The holes are as small as possible
so that no large bubbles are allowed to form in the solution and are preferably .0059"
in ~ met~r. A heat exchanger 78 (shown in Fig. 5) is attached to the con-içn~çr 50 at
port 80 to m~int~in the lelllpeldlule of the solution at less than 65C and preferably at
25 25C. A pH monitoring device (not shown) is ~tt~he~ to port 80 to measure the pH
of the solution and sodium hydroxide from reservoir 56 (shown in Fig. 5) is added to
the condenser 50 intermittçntly as needed. The pH of the condenser should be
m~int~ined in the range of 9 to 12 and is preferably at 10. The condenser 50 is sealed
so that all of the unstable gaseous byproduct is forced to go through the sodium30 hydroxide solution and there is no exhaust pipe for any gases to escape.
The reacted sodium hydroxide solution is drawn off at a predetermined
- 10-
i-- WO 94/2L~29 21 5 ~ 5 ~ ~ PCT/CA94/00152
rate through the outflow 82. The rate that the liquid is drawn off is equivalent to the
rate that liquid hydrocarbons are being produced in the condenser.
As shown in Fig. 4, the drawn off liquid is then processed by a reverse
o.~mo~i~ se~aldlol 84 which se~aldtes the liquid into liquid hydrocarbons and reacted
5 sodium hydroxide solution. The liquid hydrocarbons are then removed as shown by
arrow 86. Preferably the reverse osmosis se~)~r~or will be one which uses a cellulose
membrane. The liquid hydrocarbons which are sep~ d in the reverse osmosis
sep~dtor are then ready for reuse or separation by any conventional method.
The reacted sodium hydroxide solution is conducted to a ~ till~tion
10 chamber 54. Preferably the pipes 88 which conduct the reacted sodium hydroxide to
the ~ till~tion chamber 54 are wound around the conduit 58 so that the reacted
sodium hydroxide solution will cool the gases in conduit 58 while the gases will heat
up the reacted sodium hydroxide solution in pipes 88. The reacted sodium hydroxide
solution will be heated to less than its boiling point to minimi7e any precipitate
15 re~ ining in pipes 88. Preferably the reacted sodium hydroxide solution will be
heated to 65C in the pipes. In the rli~till~tion chamber 54 the reacted sodium
hydroxide solution is se~ ed into water having some carbonate and sodium chloride
dissolved therein and salts, primarily sodium hydroxide. The (~i~tilled water can then
be disposed of or used as required and it is removed as shown by arrow 90. The
20 salts, primarily sodium hydroxide, are stored in the reservoir 56 to be used as needed
In the plcfellc;d emb~iml~-nt for input waste of 50% water, 18%
plastics, 25% hydrocarbons and 7% glass and metals in general the following occurs.
In the reactor 14 the waste is dissociated into water vapour, carbon monoxide,
25 chloride ion, carbon dioxide, hydrogen gas, small chain hydrocarbons and/or simple
hydrocarbons, sulphur, nitrogen ions, carbon, char, glass and metals. In the catalytic
condçn~çr the sodium hydroxide ~ oci~teS in water into sodium ion and hydroxide
ion; the carbon dioxide dissolves in water; the chlorine ion combines with the sodium
ion to form sodium chloride, the carbon monoxide and the small chain hydrocarbons
30 and/or simple hydrocarbons combine with the hydrogen ion and the hydroxide ion to
form weak alcohols or weak acids and liquid hydrocarbons; the sulphur forms sulphur
wo 94~21329 2 i S 8 ~ 5 ~ PCTICA94/00152 ~l
based salts; the nil,ogen forms nitrogen based salts; and some of the sodium mayform sodium based salts. In the reverse osmosis sæ~ or the hydrocarbons are
removed from the saline solutiom In the ~i~till~tion chamber water with minor
amounts of weak hydloc~bons, carbonates and sodium chloride which were not
5 removed by the reverse osmosis unie is boiled off and then condensed; and a residue
of salts, primarily sodium hydroxide, is stored in the reservoir.
It will be appreciated that the above description related to the plc;rell~d
embodiment by way of example only. Many variations on the invention will be
obvious to those knowledgeable in the field, and such obvious variations are within
10 the scope of the invention as described and cl~imP~, whether or not expressly described.
The process is for solid waste m~teri~l having, by mass, less than 80%
water. The process is specifically designP~I for biome~ l waste material which has a
typical co,l,~osi~ion by mass of 50% water, 18% plastic, 25% hydrocarbons and 7%15 glass and metals. The process could also be used for the conversion of such things as
tires. Some mol1ifir~tions of the process may be needed to adapt the process to other
types of waste but these mo~lifir~tions are int~n-led to be within the scope of the
invention and would be obvious to someone skilled in the art.
For in~t~nce, it will be appl~iated by someone skilled in the art that
20 the feed tube system could be modified to allow for alternate methods of feeding the
waste material into the reactor and minimi7ing the amount of air that gets into the
cli~till~tinn vessel.
