Note: Descriptions are shown in the official language in which they were submitted.
1~398~9
VERTICAL EVAPORATOR FOR THE PRODUCTION OF MAPLE SYRUP
BACKGROUND OF THE INVENTION
Field of the invention
The invention is directed to a process and an
apparatus for producing maple syrup and more particularly for
a vertical evaporator adapted to save energy and to improve the
quality of the syrup produced.
Prior Art
The evaporation of sap in the production of maple
syrup is usually made in horizontal pans provided with
partitions and heated with wood logs. The vapor produced is
usually lost in the atmosphere. Some attempts have been made to
use the heat lost by the vapor which rises over the flat
horizontal pans.
The applicant has also been informed that water has
been extracted from sap by a process referred to by the
reversed osmoses process.
SU~MARY OF T~ INVENTION
The present invention is particularly directed to a
new type of concentrator for sap adapted to evaporate water
from sap and to collect maple syrup. The sap is sprayed into
fine drops, in a vertical housing and a flow of upwardly
projected air is circulated through the fine drops to pick up
a percentage of the water contained in the drops. The
humidified air is ejected out of the housing and the partially
concentrated sap is recirculated in the housing until it is
concentrate according to the predetermined characteristic of
the maple syrup. The new concentrator is generally used in
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combination with a conventional evaporator for sap. The heat
from the vapor of the evaporator is used to additionally heat
the sap before it enters the housing and is also used to heat
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enters the housing. The use of the heat from the vapor
throughout the concentration cycle constitutes an energy
saving means. The boiling and the dehydrating stages can
alternately be used to vary the characteristics of the
resulting maple syrup.
More particularly, the invention provides a con-
centrator for use in the production of maple syrup, the
concentrator comprising:
- a vertical housing;
- intake means connected to the housing for intro-
ducing heated sap containing water to be evaporated to
produce maple syrup into the housing;
- spraying means in the housing connected to the
intake means for spraying the heated sap in the form of
droplets throughout this housing;
- ventilation means connected to the housing below
the spraying means for introducing an upward flow of air
into the housing and throughout the sprayed sap for
dehumidifying this sap in part;
- venting means mounted at the top of the housing
for allowing the flow of air to exit the housing in a water
saturated condition free of droplets;
- tray means disposed in the lower part of the
housing for collecting the dehumidified sap;
- pumping means for returning at least part of
the dehumidified sap collected in the tray means through
the intake means into the vertical housing for addi-
tionally dehumidifying this sap,
and
- first heating means for heating this partially
dehumidified sap before it enters the intake means and
returns into the vertical housing, the first heating means
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comprlsing a condenser having an enclosure, a winding
tubular member in the enclosure through which the sap may
circulate, means for circulating heated humid air around this
tubular member and within the enclosure, and receptacle
means for collecting a condensate from said humid
air, whereby the sap, in the winding tubular member, is
heated by the humid air.
BRIEF DESCRIPTION OF THE DRAWINGS:
Figure 1 is a schematic representation of a
process for producing maple syrup, according to the
invention,
Figures 2 and 3 are perspective views of a
vertical housing for concentrating sap,
Figure 4 is a perspective view of an evaporator
for producing maple syrup according to the process
represented in figure 1, and
Figures 5 and 6 are two schematic representations
of alternative processes to the one represented in figure 1.
DETAILED DESCRITPION OF THE INVENTION:
The process according to the invention is illus-
trated in figure 1. The conventional sap evaporator 10 when
heated produces vapor through the chimney 12 which is sent
in the condenser 14. The heated sap which comes out of
the evaporator 10 is directed to the coil 16 in the
condenser 14 at a temperature which is close to the boiling
temperature. The heated sap is directed towards the upper
part of a vertical housing 18 in which the sap is sprayed
during its fall towards the bottom of the verticla housing
18. A ventilator 20 produceds a flow of air which is
directed towards the lower part of the vertical housing 18
and projected through the sprayed sap, i.e. through the
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- 2b -
droplets of sap falling in the vertical housing 18. The
upward flow of air has a very small pressure but sufficient
to pass through hte droplets of sap. The incoming flow of
air is relatively
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dry but picks up humidity from the droplets of sap before it
reaches the venting outlet 22. The relative speed and
temperture of the droplets of the sap and of the air in the
vertical housing 18 is such that the air reaching the venting
outlet 22 will reach a humidity saturation of about 100%. The
speed of the air flow from the ventilator 20 is controled at 24
and is heated in the condenser 26 before it reaches the intake
28 of the vertical housing 18. The condenser 26 consists of an
enclosure through which the air from the ventilator flows and
contains a radiator element such as a car radiator through
which the condensate collected in the tray 32 passes through.
The condensate is formed in the tray 32 from the vapor received
from the chimney 12 and which is cooled by the coil 16. The
condensate flows freely from the tray 32 through the radiator
30 and is expelled through an exit 34. A tray 36 is disposed
below the vertical housing 18 to receive the partially
concentrated sap from the housing 18 and is returned to the
coil 16 to be heated and to the top of the housing 18 to be
sprayed for further concentration of the sap. A portion of the
sap from the tray 36 can leave through the conduit 38 to return
to the conventional evaporator 10 to be directed to the housing
18 in a manner explained above.
The novel aspect of this process is particularly
characterized by the vertical housing 18. One embodiment of the
vertical housing is illustrated in figure 2 which comprises a
vertical housing 40 containing a continuous piping system 42
receiving the sap from the condensor 14 (fig. 1). The piping
system 41-42 is provided with a plurality of nozzles 44 adapted
to spray sap throughout the vertical housing 40. The intake 46
of the air flow has a cover 48 to protect it and prevent the
sap from entering the intake 46. The air from the ventilator
passes through the radiator or heat exchanger 50 to reach the
air duct 52 before it reaches the air intake 46. A tray 54
mounted at the bottom of the housing 40 is adapted to collect
the sap in a partially concentrated condition and corresponds
to the tray 36 shown in figure 1. A roof 56 covers the housing
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40 and is spaced from it to allow the humid air to flow out of
the housing 40. A venting system such as louvers are disposed
below the roof 56 to control the exit of the humid air. The
housing 40 operates at its maximum efficiency when the humidity
of the air coming out at the top of the housing is 100~.
Figure 3 illustrates an installation similar to one
shown in figure 2 including a condenser 60 corresponding to the
condenser 14 shown in figure 1 and a tray 62 corresponding to
the tray 32 for the condensate shown in figure 1. The air from
the conventional evaporator 10 enters the condensor 60 through
the holes 64 at about the boiling point of the water and leaves
through the exhaust hole 66 after having passed through a
winding tube 68. The amount of vapor which condensates during
its passage in the condenser 60 falls in the tray 62 to produce
a condensate which is directed through the tube 70 towards the
heat exchanger 50. The condensate being hot water is adapted,
as explained in figure 1, to heat the air coming from the
ventilator and to direct it towards the air inlet 46 and
through the housing 40. The sap which as been partially
concentrated in the housing 40 and which has reached the tray
54 is redirected towards the condenser 60 through the tubes 72
and 74. The partially concentrated sap which has reached the
tube 74 at a temperature of about 130~F, passes through the
winding coil 68 to be reheated by the vapor in the condenser
60. The sap coming out of the condenser 60, through the tube
76, reaches a temperature of about 200~F. The sap leaving the
tube 76 is redirected towards a spreading channel 41 (fig. 2)
which directs the partially concentrated sap towards the
feeding lines 42 and the nozzles 44. The temperature of the sap
downwardly flowing through the housing 40 and the temperature
and the speed of the air upwardly flowing through it, is
optimized by maintaining a complete water saturation of the air
leaving through the vents 55. The air pressure coming from the
air intake 46 is maintained at a relatively low level and
usually at a pressure of less than 2 inches of water.
As shown in figure 1, the addition of new partially
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concentrated sap may be introduced into the condenser 14 for
maintaining a continuous circulation of sap through the system.
The maple syryp, when it has reached the desired concentration,
is collected from the tray 36 or 54. The fully concentrated sap
may also be returned to the conventional evaporator as
explained later.
Figure 4 shows an embodiment of the invention in
combination with the conventional evaporator 80. The hot air
which is produced by the evaporator and rejected through the
chimney 82, instead of being wasted in the atmosphere, is
directed towards the condenser 84. The sap going through the
coil of the condensor 84 is directed through the tube 86 into
the vertical housing 88, collected by the tray 90 and returned
to the condenser 84 by a circulating pump 92. The obtained by
the condenser 84, is directed to the heat exchanger 9 6 as a hot
liquid and expelled through the tube 100 as a cool liquid. The
air from the ventilator 94 is projected at surrounding
temperature into the air exchanger 96 and reaches the tube 102
as hot air which is then blown into the vertical housing 88
through the sprayed sap as explained above. The sap, which has
reached a satisfactory high degree of concentration in the tray
sO is directed to a terminal tray 93 of the evaporator 80
through a conducting line 94 and collected through a tap 96. In
this embodiment, the vapor which reaches the condenser 84 from
the chimney 82 iS at about 212~F. The sap which enters the
condenser 84 at about 120~F leaves the condenser at about 195~F
before it enters the vertical housing 88. The condensate which
is formed from the condenser 84 passes through the heat
exchanger 96 and warms up the air coming from the ventilator to
a temperature between room temperature and the atmospheric air
to reach a temperature of about 105~F. The hot dry air flowing
upwardly through the vertical housing 88 and in particular
through the vaporized sap flows outside the housing 88 through
a venting system which is schematically illustrated by a
chimney 100.
The use of the vapor from the chimney 82 of the
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conventional evaporator of the sap and the condensat,e from the
condenser such as 14, is designed to save energy while the use
of the vertical housing such as 18 can produce a higher quality
of maple syrup particularly due to the fact that the sap and
the partially concentrated sap are not exposed to high
temperatures during any long length of time. High temperatures
over extended periods of time cause the maple syrup to be dark
while clear maple syrup is considered to be of a higher
quality.
The procedure for saving energy can be modified while
maintaining the above-described process and all its essential
parts. In figure 5, the air from the ventilator 102 is not
heated before it reaches the bottom of the vertical housing
104. However, the speed of the air flow is modified by a flow
controlling device 106 while the condensate 108 from the
condensor 110 is used to warm up an inflow of sap which is fed
to the tray 112 disposed below the vertical housing 104. The
system as described in figure 5 is substantially similar to the
one described in figure 1 except that the conventional
evaporator is fed by the tray 112 which is constantly fed by an
inflow of sap from a conduit 114. Before entering the tray 112,
the sap is preheated in a condenser 116 which receives the
condensate 108. One of the main differences with the procedure
described in figure 5, consists in that the air from the
ventilator 102 is not heated before it enters the vertical
housing 104. This modification affects the temperature of the
air reaching the venting system 118. This procedure may be
preferred depending on the quantity of water which needs to be
extracted from the sap.
Another alternative process is schematically
illustrated in figure 6. The process makes use of two vertical
housing 120 and 122. The part of the process surrounded by the
dotted line 124 corresponds essentially to the one described in
figure 5. However, the ventilator 126 projects an upward flow
of air through both vertical housings 120 and 122 while
controling the speed of the air through flow control devices
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121 and 123 respectively. The condenser 128 has a double
winding coil so as to supply both vertical housings 120 and
122. The partially concentrated sap, leaving line 133 is
returned to the conventional evaporator. The tray 130 is
constantly fed through the feed line 132. The partially
concentrated sap flowing with the direction of the condenser
128 from the tray 134 is heated, while passing through the
double condenser 128 and further concentrated through the
vertical housing 120 before returning to the tray 134 where the
fully concentrated maple syrup will be picked up through line
136. It is pointed out that the tray 134 is also constantly fed
through the line 135 and may also be heated to increase its
efficiency in a similar manner as tray 130.
In one of the specific embodiments made from the
present invention, the vertical housing has a rectangular
horizontal cross-section of about 50 inches by 25 inches and
about 165 inches high. The nozzles 44 are disposed in three
vertical columns mounted on a plurality of horizontally
superposed pipes 42 projecting 45 gallons of sap per minute.
The pipes 42 are spaced by about 4 inches and are spread over
a height of about 52 inches. The temperature of the sap and of
the surrounding air as well as a plurality of other factors are
generally adjusted so that the humidity leaving the top the
vertical housing is about 100~. It should be reminded that the
quantity of water that can be contained in the exhausted
substantially varies with the temperature of the latter. Air at
a temperature of 140~F may contain 2.2 times more water than
the same quantity of air at 115~F.
The flow of air is accordingly computed in relation
with the mass of water which needs to be absorbed and the
available heat from the condensate. The air pressure needed to
maintain an acceptable flow of air through the liquid droplets
in the vertical housing is usually less than half an inch of
water.
One preferred embodiment of the condenser 60 such as
shown in figure 3 consists essentially of a continuous tubular
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winding 68 disposed in a horizontal fashion and extending
throughout the enclosure of the condenser 60. The heat
exchanger such as 26 in figure 1, was made with a pair of car
radiator connected in series through which the condensate was
flowing. For a flow of 170 gallons per hour of condensate,
entering at 200~F the temperature of the condensate at the exit
was 75~F. Such an arrangement could use a maximum flow of air
of 600 feet per minute.
