Apparatus for volumetrically controlling the flow of a gas and liquid mixture

Apparatus for volumetrically controlling a liquefied gas, such as agricultural ammonia, receives liquefied gas from a suitable pressure vessel through conventional hoses and fittings and removes the energy represented by vapor due to the pressure drop from the vessel to the metering means by either refrigeration or vapor stripping or both.

TECHNICAL FIELD 
This invention relates to systems handling liquefied gases where the 
presence of large quantities of vapor is detrimental to the desired 
operation of the system, and more particularly but without limitation, to 
liquid agricultural anhydrous ammonia systems. BACKGROUND ART 
The preferred environment of the present invention is described in my U.S. 
Pat. No. 4,364,409 issued Dec. 21, 1982, the disclosure of which is 
incorporated herein by reference. 
The field application rates of agricultural ammonia have drastically 
increased over the past few years with increased swath widths and larger 
tractors; however, the ability to volumetrically control the application 
of ammonia has deteriorated due to additional hardware required between 
the tank and the controlling apparatus. Ammonia is a vapor that is stored 
as a liquid in a pressure vessel due to its vapor pressure and is at its 
boiling point at normal ambient temperatures. During application, pressure 
in the vessel varies between 50 and 130 PSIG. Withdrawal from ammonia 
wagons is through a dip tube located at the top, and when the liquid 
reaches the withdrawal valve it is a superheated liquid and becomes more 
superheated as it passes through the required valves and hoses. The 
ammonia arrives at the control apparatus with an unidentifiable and 
variable vapor/liquid volume ratio, and the vaporeous component of the 
ammonia flow makes the volumetric control of the flow inaccurate and 
unpredictable. 
Therefore, there presently exists a need for an apparatus which separates 
the vapor and liquid components of ammonia prior to volumetric control of 
the liquid. The vapor content increases with system demand and decreases 
with ambient temperature, so it is essential that the flow of vapor from 
the apparatus be throttled in response to these factors. 
SUMMARY OF THE INVENTION 
This invention provides liquefied gas that is reasonably free of vapor 
prior to volumetric control. Energy is removed from the gas to lower the 
liquid temperature by either refrigeration or vapor stripping or both. 
Volumetric control means is arranged to provide ample system refrigeration 
at very low demands. The system pressure downstream from the volumetric 
control means is sensed to open vapor dump outlets at progressively higher 
downstream pressures and progressively reduce the dump pressures with 
increased ambient temperatures by using the vapor pressure acting to close 
the dump. 
The apparatus has in combination means to receive product, preferably but 
not necessarily ammonia, which may have a liquid volume as low as 20% of 
the total volume. The apparatus changes the flow path to circular where 
the liquid is separated from the vapor and continues its circular path 
maintaining much of its kinetic energy. The liquid spills over an edge 
formed by the lower inner portion of a circular receiver. Liquid flows 
down a main chamber inner wall that is conical in shape and has a helical 
floor that descends downward in the direction of flow into an exit. The 
exit is placed on a tangent to receive the liquid in such a way as to 
maintain as much kinetic energy as practical. 
The apparatus has means to remove and control the flow of vapor from the 
upper center portion of the main chamber and throttle it into dump 
chambers that surround the upper and lower portions of the circular 
receiver and the upper portion of the conical chamber, thereby 
refrigerating these surfaces. The apparatus has means to volumetrically 
control liquid flow which is placed in the lower portion of the apparatus. 
The refrigeration that results from metering at lower demand levels is 
ample to assure accurate volumetric control.

DETAILED DESCRIPTION 
Referring Initially to FIG. 1, apparatus 10 has an inlet 12, a liquid 
outlet 14, vapor dump outlets 16 and 18, metering control knob 20 and 
suitable hydraulic connections 22 and 24 to operate the apparatus. Inlet 
12 is adapted for connection to, for example, a source of ammonia such as 
a conventional towable pressure tank used in agricultural applications. 
Outlets 14, 16 and 18 are adapted for connection to, for example, 
conventional ammonia injection apparatus. 
Referring now to FIG. 2, apparatus 10 is shown closed to the flow of 
ammonia. The liquid leg of the apparatus, ending at liquid outlet 14, is 
closed by shutoff valve 30 in cooperation with spring 32 and the pressure 
across the shutoff valve 30. The vapor dump outlet 16 and dump outlet 18 
(not shown) are closed by dump valve 34 in cooperation with spring 36 and 
at dump leg control valve 38 in cooperation with spring 40. 
When ammonia is required, the operator opens a valve to pressurize the 
upper compartment of the shutoff cylinder 42 through hydraulic connection 
22 causing the piston 44 to move downward acting through pin 46 and fully 
open shutoff valve 30. This allows the ammonia in the lower shutoff 
chamber 48 to flow through liquid outlet 14 by way of valve 30. Ammonia 
flows across throttle control orifice 50 providing a pressure loss in 
throttle control chamber 52 and causing a pressure unbalance across 
throttle diaphragm 54 tilting open throttling valve 56. Throttle valve 56 
is offset from the center of the diaphragm 54 and is closed by spring 58 
and the pressure difference across it. With a pressure unbalance, 
diaphragm 54 is urged downward but is held in place under the valve 56 
causing diaphragm disc 60 and valve 56 to tilt using the outer portion 62 
of the valve seat as a fulcrum. This tilting continues with increased 
flows until the diaphragm disc 60 comes in contact with rib 64 which then 
becomes the fulcrum point causing the diaphragm disc 60 and valve 56 to 
tilt away from the seat to satisfy further demand increases. 
Referring now to FIGS. 2 and 3, the velocity of flow through the apparatus 
is read by the pressure difference across a metering point formed by the 
metering slot 66 of metering barrel 68 and metering port 70 and acting 
across throttle control diaphragm 72. The upstream or high pressure side 
of diaphragm 72 is read in lower control chamber 74 through passage 76, 
and the downstream pressure is read in chamber 78 by way of passage 80. 
Communication between chamber 78 and control chamber 52 through passage 82 
is closed by throttle control valve 84. Control valve 84 remains closed by 
spring 87 with ample force to allow throttling valve 56 to fully open so 
at all operating conditions throttling valve 56 can be considered normally 
open. Valve 56 continues to open until the velocity across the metering 
point formed with slot 66 and port 70 creates ample pressure difference 
across diaphragm 72 to overcome the force of spring 86, thereby opening 
control valve 84 to replenish the ammonia leaving control chamber 52 by 
way of orifice 50. Valve 84 has the capacity to allow valve 56 to close; 
therefore, valve 56 will function to allow a velocity across the metering 
port 70 that is a function of metering springs 86 and diaphragm 72 
regardless of the total demand of ammonia. The vapor dump valve 34 has the 
identical tilting action as the throttle valve 56 except it is normally 
closed by spring 36 and the system pressure across it. 
The metered liquid ammonia flows to the ground from the liquid outlet 14 
through conventional hoses, manifolds, and knives producing a back 
pressure at liquid outlet 14 that is related to the quantity of ammonia 
flowing. This back pressure is read by the dump control diaphragm 88 
through passage 90 between outlet 14 and the upper control chamber 92. 
Then the resistance to flow of ammonia at outlet 14 produces ample 
pressure in upper control chamber 92 by way of passage 90 acting on 
control diaphragm 88 to overcome spring 40 and the pressure closing 
control valve 38, to open a flow from vapor chamber 98 to the controlled 
pressure dump chamber 108 by way of orifice 100, passage 102, control 
chamber 104, passage 106, into chamber 94, by valve 38 into chamber 110 
and through passage 112. The resistance to flow through orifice 100 drops 
the pressure in control chamber 104 which opens the dump valve 34 allowing 
a flow from upper chamber 98 into chamber 108 by way of valve 34. The 
resistance to flow of orifice 114 is read in chamber 110 by way of passage 
112 to bring about a pressure balance of diaphragm 88, spring 40 and valve 
38. 
The system pressure is related to the ambient temperature and is read by 
the rather large control valve 38 which delays the initial opening of the 
dump valve 34, as well as reducing the pressure to the dump orifice 114, 
as the system pressure increases. The pressure in chamber 108 is related 
to the ambient temperature (read by valve 38) and to the metered ammonia 
flowing as read by diaphragm 88 and has a pressure function as follows: 
The downstream pressure of the metered ammonia, as read at liquid outlet 
14, multiplied by the area of dump control diaphragm 88, minus the area of 
the dump control valve 38, multiplied by the system pressure, plus the 
force of closing spring 40, divided by the area of diaphragm 88, minus the 
area of valve 38. 
A replaceable dump control orifice 114 is sized to set up the apparatus for 
different crops. The small grains such as wheat, rye, etc., use many more 
knives for a given swath width than the heavier grains such as corn and 
feed sorghums, but the heavier grains require more nitrogen per acre than 
the small grains. The use of restricting orifices at the manifolds for 
each knife to aid in the distribution of the ammonia is common practice 
for the small grains. These orifices increase the pressure at the liquid 
outlet 14 requiring a smaller dump control orifice 114 for a given output. 
When the pressure at liquid outlet 14 is sufficient to open dump control 
valve 38, which in turn opens vapor dump valve 34, suitable pressure will 
be in chamber 110 to provide a balanced force across the dump control 
means. 
The ammonia across dump valve 34 can be saturated or supersaturated vapor. 
The expansion across valve 34 will reduce the temperature of the ammonia 
in chamber 108 with another temperature drop with the expansion across 
orifice 114. The saturated ammonia across valve 34 represents the energy 
required to reduce the liquid temperature from the tank to the apparatus. 
The liquid particles accompanying the vapor will be used to lower the 
system's temperature as the vapor moves through the lower dump chamber 116 
that surrounds the lower section of receiver 118 and the upper conical 
portion 120 of main chamber 96. Vapor then flows up through riser 122 into 
upper dump chamber 124 that surrounds the upper portion of receiver 118 on 
its way to dump outlets 16 and 18. 
The ammonia entering the receiver 118 through inlet 12, which is on a 
tangent with the receiver 118, continually changes direction inwardly 
which separates the liquid from the vapor. The liquid continues its 
circular path around the inner vertical retaining wall 126 and the lower 
portion 128 with a continual liquid spill over spill edge 130. Liquid 
continues its circular downward path to the helical floor 132 that 
descends downward in the direction of liquid flow and enters the bore 136, 
shown in FIG. 3, of the metering barrel 68. The metering barrel 68 is 
positioned tangentially at the lower portion of the helical floor 132 to 
receive the liquid so as to maintain as much of the kinetic energy as is 
practical. 
The ammonia removed from the system through the vapor dumps 16 and 18 is 
fed into the ground through an appropriate number of larger outlets 
located at the rear of conventional knives. The pressure in riser 122 and 
chamber 124 is therefore related to the resistance through the dump legs 
and is usually under 10 PSIG, providing a temperature of -28.degree. F. to 
-8.degree. F. 
This reduced temperature refrigerates the walls separating the receiver 118 
and the main chamber 96 from the riser 122 and chamber 124. The ammonia 
vapor in the upper portion of main chamber 96 comes in contact with the 
colder surface 138. The vapor condenses and flows downward to lip 140, 
where it is joined with condensation from surfaces 142 and 144 of vapor 
chamber 98 and drips off the lip 140 to join the liquid in the lower 
portion of main chamber 96. 
The surface of the conical portion 120 of main chamber 96 is cooled by 
riser 122, supercooling the liquid ammonia as it moves downward and 
providing an ideal condition for absorbing any of the vapor that may come 
in contact with the liquid. At higher ambient temperatures and lower 
outputs, the dump leg of the apparatus will remain closed, depending 
entirely on the refrigeration due to metering to remove energy from the 
system. Expansion of liquid for metering takes place at valve 56 where 
there is an instant reduction of temperature to the dew point of ammonia 
at the vapor pressure in chambers 48 and 146 which refrigerates a lower 
portion of main chamber 96. 
Whereas the present invention has been described with respect to a specific 
embodiment and environment thereof, it will be understood that various 
changes, modifications and other uses of the invention will be suggested 
to one skilled in the art and that this invention encompasses such 
changes, modifications and additional uses of the invention as fall within 
the scope of the appended claims.