US3589025A

US3589025A - All weather gas generation controlled environment storage

Info

Publication number: US3589025A
Application number: US836063A
Authority: US
Inventors: Frank D Hamerski
Original assignee: AO Smith Corp
Current assignee: AO Smith Corp
Priority date: 1969-06-24
Filing date: 1969-06-24
Publication date: 1971-06-29
Anticipated expiration: 1988-06-29

Abstract

The disclosure is of an all weather gas supply unit for delivering generally inert gas to a sealed storage structure for atmosphere control. In the system, a gas generator combustion chamber exhausts generally oxygen-free gas to a condenser and thence to an icing arrester, the condenser being cooled by ambient air in a cooling shroud system enveloping the condenser and combustion chamber, and the icing arrester serving to collect ice from the gas exhaust when the arrester is in a freezing ambient. The condenser and arrester have water collecting and draining assemblies which are kept from freezing by a heating system such as scavenger air shrouds extending from the cooling shroud. A heating system in the cooling air shroud intake keeps the exhaust in the condenser to temperatures above freezing.

Description

United States Patent {72] lnventor Frank D. llamerski Milwaukee, Wis. [21] Appl. No. 836,063 [22] Filed June 24, 1969 [45] Patented June 29, 1971 [73] Assignee A. 0. Smith Corporation Milwaukee, Wis.

[54] ALL WEATHER GAS GENERATION CONTROLLED ENVIRONMENT STORAGE 12 Claims, 4 Drawing Figs.

[52] US. Cl 34/32 [51] Int. Cl F26b 3/06 [50] Field of Search 34/32, 72-76; 23/281 [56] References Cited UNITED STATES PATENTS 2,746,245 5/1956 Geisler et al 23/281 X 2,756,215 7/1956 Burgess 23/281 X 2,787,530 4/1957 Staiger 23/281 2,876,069 3/1959 Geisler 23/281 3,205,049 9/1965 Lannert 23/281 3,348,922 10/1967 Bose et a1. 23/281 Primary Examiner- Edward J. Michael Attorney-Andrus, Sceales, Starke & Sawall ABSTRACT: The disclosure is of an all weather gas supply unit for delivering generally inert gas to a sealed storage structure for atmosphere control. In the system, a gas generator combustion chamber exhausts generally oxygen-free gas to a condenser and thence to an icing arrester, the condenser PATENTEUJUHZQISYI 3,589,025

SHEET 1 [IF 2 FIG ll WM WW 21 M FUEL F J CONOEN ER j I PREMIX COMBUSTION FLOW I I 17 T16) 22 POWER CONTROL I F I I I3 L l l \23 FUEL VALVES FIG 2 24f I 12 FUEL I ICING L g3 2 O 1O ARRESTER TO STORAGE I STRUCTURE E INVENTOR. FRANK D. HAMERSKI Attorneys PATENTED JUH29 I97! SHEET 2 OF 2 INVENTOR. RANK D. HAMERSKI Attorneys ALL WEATHER GAS GENERATION CONTROLLED ENVIRONMENT STORAGE BACKGROUND OF THE INVENTION This invention relates to a controlled environment storage system and more particularly to a gas supply unit for supplying gas having minimal water vapor and minimal oxygen content to sealed storage structures in varying weather conditions.

Perishable materials, such as animal feeds like silage, are often stored in airtight silos or other sealed storage structures in order to minimize contact between the material and oxygen from the ambient air. Accessory systems have been developed to protect the sealed structures and the stored material. For instance, protection is needed for sealed structures against pressuredifferentials with the ambient, which are due in part to temperature differences with the ambient. Since a pressure differential can cause undue stress and leakage problems, breather systems and pressure control systems having breather valves are commonly employed in the unit. Often, flexible breather bags are used, which being located in the head space of the silo, and being internally in communication with the ambient atmosphere, will expand and contract in accordance with the pressure differential to balance the differential.

In this way, entry of air from the atmosphere to the silo is restricted and oxygen content of the storage atmosphere is minimized. Breather bag systems provide advantage, but improved results can be obtained by purging the sealed storage structure with a gas which is largely devoid of oxygen that is free to react. Gas burners or generators will provide a gas with a high percentage of CO and N and a low percentage of CO and near zero percentage of In theory then, it would be expected that gas generators could be used to further control the atmosphere in a sealed storage unit.

As a practical matter, however, gas generators cannot simply be connected to a storage structure and operate satisfactorily. One problem is that heat is also an undesired product of the combustion gas generator process and an ap preciable temperature difference between the silo and the ambient can arise when the heated generator gas is supplied. This temperature difference can aggravate the normal pressure differentials between the silo and ambient, thus hampering the otherwise adequate operation of a breather system.

The gas-generating process also generates water vapor, another undesirable element in the storage unit. Moisture can increase spoilage and excess moisture can actually create standing water problems in a silo.

Moisture creates problems in the generator and gas line also, particularly in freezing winter conditions. The moisture collects and freezes within pipes and other components through which the gas passes to the silo. The operation of a gas generator can be stopped by such freezeups, making the generators usable only in favorable climate.

Another problem is presented in that the usual gas drying equipment, as condensers or other heat exchangers, generally operate by expanding and cooling the gas. But in a sealed storage structure system, the temperature of the gas is a key consideration and the removal of the water vapor by the usual condensers would not cooperate satisfactorily with a breather system pressure control.

The conventional equipment is also inadequate to provide for the varied dew point conditions which would exist in the storage atmosphere. For example, a generator gas which would be adequately dry under one temperature in the storage structure may have an excess of water vapor under a lower temperature and a lower dew point. No simple combination of presently available equipment can provide a system with satisfactory cooperation between the various components in order to obtain dry gas at the proper temperature for the variety of conditions in the storage structure.

As a further difficulty in employinga gas generator at mosphere control, the designer is always restricted by con siderations of economy and space. The expense of preserving the stored materials should not surpass the expense of spoilage. Further, bulky systems are a disadvantage, especially when the generator unit is to be employed in working areas, such as near silos where space is already at a premium.

SUMMARY OF THE INVENTION The invention is directed to the solution of the above problems and has further advantages as described.

The structure of the invention provides a controlled atmosphere storage structure with an all-weather gas supply unit for supplying generally inert gas to the sealed storage structure. The gas supply unit is operable in any climate, including freezing winter conditions. The gas is delivered with a water vapor content which will not endanger storage conditions, even when very dry gas is needed due to low dew point conditions existing in the storage structure.

At the same time, the invention delivers the gas at a temperature near whatever temperature the ambient is at any moment. Thus, pressure control within the storage structure is not hampered by the gas supply unit and the unit cooperates with the breather system to obtain the desired pressure equalization in the sealed storage unit.

Low ambient temperature operation is made possible by the provision of antifreczeup equipment for parts subject to icing. The antifreezeup assembly is designed. to cooperate with the desired feature of gas temperature control.

The system which provides this sophisticated operation in cludes a gas generator having a combustion chamber which burns fuel and air and exhausts inert gas, meaning here: gas having no more than a trace of oxygen available for oxidation. The exhaust gas is passed through a condenser which is a heat exchanger between the ambient air and the exhausted gas. Water vapor is condensed and removed as liquid and the gas is cooled to near the ambient temperature by the condenser. The gas is then passed through a defrostable icing arrester, which is disposed in the ambient air and operates to collect ice and remove water vapor in a freezing ambient.

Advantageous cost saving and compactness is served by accessory equipment for the gas supply unit. An integral cooling air shroud and scavenger duct system provide the ambient air for cooling the condenser and for cooling the combustion chamber, and also provides the warming air for the parts subject to icing.

In freezing weather operation, a heating element or air tempering system, which can be supplied with warm air by a feedback duct from the cooling air shroud, keeps the ambient air in the shroud above a minimum temperature to protect the condenser and other elements from freezing. In winter operation of the invention, the gas is cooled to near the ambient temperature by the defrostable ice arrester after the gas has been partially cooled and dried by the condenser.

Thus, the gas supply unit provides an all weather system which has components cooperating to provide an oxygendepleted gas, at a favorable temperature and vapor condition to preserve the stone material and also to cooperate with the breather system of a sealed storage unit.

The figures illustrate the best embodiment and modifications of the invention presently contemplated by the inventor.

FIG. I is a side elevation of the invention with parts broken away to reveal the inside structure of the storage unit;

FIG. 2 is a flow diagram showing the: essential features and operation of the invention;

FIG. 3 is a side elevational view of the gas generator with parts of the cabinet broken away to reveal the inside structure, and having certain parts shown generally in block diagram; and

FIG. 4 is a perspective view of part of a modified generator having a feedback air tempering assembly.

DESCRIPTION In the illustrated example, a sealed silo l is adapted to store silage 2 and is exposed to the ambient environment. Above silage 2 A headspace 3 exists wherein a flexible breather bag 4 of a well-known construction is suspended in any suitable fashion from the roof of silo 1.

Breather bag 4 is exposed internally to the ambient pressure by a breather tube 5 connected to the bag and extending through the silo roof to vent 6. Thus, bag 4 will expand and contract in response to the pressure differentials across the walls of silo l and act to balance such differential.

For excess pressure differentials, a relief valve 7 on the silo roof will permit controlled ingress or egress of air to headspace 3. Valve 7 is of a well-known construction and may be set to open for pressure differentials in the range of L5 to +3.5 inches of water.

A gas supply unit 8 is provided for storage atmosphere control in accordance with the invention and includes an exother mic gas generator 9, a defrostable ice arrester l0 and gas conduit 11. Unit 8 is disposed near silo 1 and defines a gas supply passageway ultimately reaching headspace 3 through conduit 1 1 which is connected to silo 1.

The essential features and operation of the invention are shown diagrammatically in the flow diagram of FIG. 2. A supply of fuel, such as propane, is contained in a fuel tank 12 and passes through a fuel flow rate control 13 to a premix chamber 14 where the fuel is mixed with air supplied from the ambient through an air volume flow rate control 15.

The fuel mixture passes to a combustion chamber 16 where an ignition device 17 fires to initiate the combustion. After combustion is initiated, the process is self-sustaining and provides a heated exhaust gas comprised largely of N CO and H 0. This exhaust gas passes through a condenser 18, to a water separator and trap assembly 19, and then out of the generator 9 to defrostable icing arrester 10, having a water trap 20 and ultimately to the storage structure.

To cool condenser 18 and combustion chamber 16, a cooling air shroud 21 provides space for ambient air to flow past the condenser and combustion chamber. Blower 22 provides the air flow for shroud 21.

Protection from freezing is provided for various elements including water separator and trap 19, trap 20 and condenser 18. This is indicated diagrammatically by heaters 23, which in the most advantageous structure is supplied by scavenger ducts from shroud 21 as indicated by ducts 24.

The gas supply unit 8 includes a power supply and control device which is manually or automatically operated to start and stop the unit and its various parts. The power and control unit is shown schematically as connected to the appropriate electrically operated components.

Having enumerated the various parts which make up gas supply unit 9 and together define a gas flow path to the silo, the various parts will now be described in accordance with a particular illustrative example of the invention.

Referring particularly to FIG. 3, gas generator 9 is disposed in an upright cabinet 25 which may be metallic and of any suitable construction. Several parts are numbered the same as their generalized versions shown in the flow diagram in FIG. 2. Shown generally in block diagram, a fuel supply assembly 26 represents the fuel control 13, mixing chamber 14, air volume control 15 and various other elements which are well known and are required to provide air and fuel for combustion chamber 16. These elements may be located in various places within cabinet 25 in the actual design. Air is supplied to the device through a louvered vent 27 in cabinet 25, and propane fuel is supplied from a fuel tank via a gas line 28.

To provide the inert gas at the proper temperature and vapor condition, combustion chamber 16 and condenser 18 are disposed in cooling air shroud 21. Combustion chamber 16 is attached by suitable means, such as suspending rod 29 depending from the top of cabinet 25 and extending through shroud 21 to attachment at the top of the combustion chamber 16. Chamber 16 is thus in a vertical position.

Combustion chamber 16 has an elongated cylindrical wall 30 with top and bottom walls 31 defining a tubular combustion chamber. A strong, heat resistant, metallic material,

such as carbon steel, is desirable for use in constructing

walls

30 and 31. Adequate cooling of the walls is provided by a plurality of integral fins 32 extending the length of cylindrical wall 30 and extending radially outward therefrom in the flow path of cooling air.

The fuel mixture is passed to chamber 16 through fuel line 33 extending from fuel supply assembly 26 through shroud 21 and to chamber 16 where it connects with a fuel orifice admitting the fuel-air premix into the chamber such as by spraying the premix to obtain proper combustion.

lgnition unit 35, shown diagrammatically, provides a means of initiating combustion. Although it may be a pilot light device, it is shown as an electrical ignition and is shown schematically as being electrically connected to a suitable control and power supply box 36. Control box 36 may also contain suitable switches and motors for controlling the operation of fuel supply assembly 26.

After ignition, the heat from combustion should sustain the reaction until fuel is cut off. It is contemplated that control box 36 could have a programmer for that purpose, so that the generator operates periodically in accordance with a desired schedule or varying conditions in the field.

Combustion of fuel will produce an exhaust gas comprised mainly of CO N and H 0. This exhaust will exit chamber 16 through chamber exhaust opening 37 to pipe 38 which extends downwardly to condenser 18 where it connects to inlet opening 39 in a header 40 of the condenser.

Condenser 18 serves to reduce the gas temperature and water content. For this purpose it has a series of interconnected metal tubes 41 joined together to provide a cooling passage for the gas. Fins 42 are welded to the tubes and give more air-metal interface for heat exchange. At the end of bottom tube 41 an exhaust opening 43 is provided so that tubes 41 and openings 39 and 43 define a gas passageway which is interconnected into the supply passageway of unit 8. The gas will pass into the condenser and come in contact with the tube walls which are cooled by means described below. Water vapor will condense and collect on the walls of the tubes and on the walls of parts connected down the line. The condenser is disposed at an angle to facilitate drainage.

Gas conduit 44 is connected to exhaust opening 43 and extends to water separator and trap assembly 19. The water separator is of a well-known construction and has a collector bulb 45 disposed beneath the level of conduit 44 and an end bell 46 on top of bulb 45. Bulb 45 and bell 46 together define a closed chamber. On one side of end bell 46 there is a gas inlet opening 47 to which conduit 44 opens and on the opposite side there is an outlet opening 48. Gas will thus pass through end bell 46 from condenser 18 via conduit 44.

Condensate will drain from condenser 18 and conduit 44 to collector bulb 45, where it will collect for purposes of drain ing. A drain pipe 49 is connected to bulb 45, opening into the bottom of the bulb, and extends to water trap 50, which is also of a well-known construction and will not be described in detail here.

Trap 50 is subjected to the gas pressure by means of gas line 51 connected between conduit 44 and the trap. A suitable water drain is connected to the bottom of trap 50, extends through cabinet 25, and provides a drain passageway for the water in trap 50.

To exhaust the gas from generator 9 on down the gas supply unit 8, gas conduit 52 is connected to outlet opening 48 of end bell 46 and extends through cabinet 25 to icing arrester 10 where it is connected to an arrester pipe 53.

The icing arrester 10 serves to further cool the gas and in freezing or winter ambients will operate to condense out the water vapor in the form of ice. For this purpose, arrester 10 has a defrostable chamber defined by a cylindrical sidewall 54, and end walls 55. These walls are constructed of good heat conducting material, such as aluminum. The gas entrance is provided by an opening 56 in the forward end wall 55, which opening is in communication with arrester pipe 53. An arrester exhaust opening 57 is in sidewall 54, and gas exhausted from generator 9 via conduit 52 will pass through the chamber of icing arrester and contact sidewall 54. in near freezing or freezing ambients, water vapor freezes on wall 54 due to exposure to the ambient temperatures.

The defrostable feature of arrester 10 may be provided by a heating rod 58 which extends the length of the chamber along the axis ofcylindrical sidewall 54. Rod 58 is an electrical conductor, having electrical resistance sufficient to serve as a heating source. Connected electrically to terminals on opposite ends of rod 58, are leads 59 which extend through a control 60 to any suitable power source, thus completing a normally open circuit. Control 60 can be any type of switch which can be set to periodically close the heating rod circuit for purposes of defrosting as needed.

When the heating rod 58 is operating, the ice collected in the chamber of icing arrester 10 will defrost and the resulting water will drain out arrester pipe 53 and flow to an arrester water trap 61 to which the pipe 53 connects. Trap 61 is a wellknown device and will not be described in detail here. Trap 6] has a water drain 62 at its bottom, and is subject to gasline pressure via line 63 connected between trap 61 and arrester pipe 53 at a point above conduit 52. Trap 61 thus operates to drain water, but to restrict appreciable gas leakage from the system.

in accordance with the invention, gas supply unit 8 includes accessory equipment that cooperates with the various elements which provide the gas passageway to silo 1, resulting in the desired all-weather operation, and the additional advantages in cooperation with breather bag 4.

Generator 9 has a cooling air shroud 21 which serves a number of functions in combination with the other elements of the generator. Shroud 21 has a cylindrical sidewall 64 of diameter to encompass finned combustion chamber 16 so as to leave a substantial annular cooling air space. Sidewall 64 is disposed approximately coaxially with chamber 16 and at con denser 18 the shroud assumes the shape of a box and extends vertically from below the condenser to above the chamber to fully envelope them. The bottom of shroud 21 has an air inlet 65. At the top of the shroud, cooling air exit is permitted by an air outlet 66 which comprises a series of bias cuts around the circumference of sidewall 64. Top wall 67 completes the structure of shroud 21, while brackets 68 are bolted to wall 64 and cabinet 25 to secure the shroud in position. The materials used in the shroud structure may be any inexpensive thin metal.

Cooling air is supplied to shroud 21 by a blower 69 con nected to shroud 21 at air inlet 65. An inlet louvered vent 70 in the bottom of cabinet 25 permits air entry for blower 69 and an exit louvered vent 71 in cabinet 25 at the top permits air exhaust from air outlet 66.

The motor of blower 69 is electrically connected to control box 36 for operation when generator 9 is in service. The blower has an inlet 72 at the end opposite shroud 21 and adjacent vent 70.

When generator 9 is operating, blower 69 causes ambient air to flow through shroud 21 and around condenser 18 and combustion chamber 16. The air flow cools the bottom tube 41 to within a few degrees of the ambient temperature and still provides cooling for the upper tubes and combustion chamber 16.

In freezing ambient conditions, condenser 18 and other parts may collect ice due to air flow. For this reason, air heater 73 is provided and for the overall operation of the system can be any heater such as an electrical resistance element as shown. Heater 73 is disposed at air inlet 72 for blower 69 and is electrically connected to control box 36 for operation with the generator 9. The operation of heater 73 is controlled by thermostat 74 on shroud 21 to heat the inrushing air only to maintain the condensate abow il'CCZll'lg temperatures, thus avoiding freezeup. Thermostat 74 shuts heater 73 down when the shroud air is at a temperature such as +25 F. which will keep the temperature in the gas passageway components above freezing. Housing 75 connecting to cabinet 25 and to blower 69 includes a cylindrical sidewall for enclosing heater 73, and for defining an air passageway from vent 70 to blower inlet 72.

When the cooling air is heated in operation of heater 73, condenser 18 may not cool the gas to near the ambient temperature. However, the gas will be cooled considerably from its high temperature achieved in combustion chamber 16. in the case of such operation in a freezing ambient, further cooling of the gas is provided by icing arrester 10, and the gas will be ultimately supplied to the silo at near the ambient temperature even in winter weather. This manner of operation avoids freezeup of the delivery line and still provides low dew point, inert gas delivery to the storage structure.

Also, for operation in freezing winter ambient temperature, a scavenger duct 76 and warming hood 77 are provided for water separator bulb 45 and trap 50. lDuct 76 is a hollow conduit connecting hood 77 to shroud 21 for communication with the warmed air from the shroud. For this purpose, duct 76 is attached to an appropriate opening in shroud 21 which opening is disposed near the top or above combustion chamber 16. Thus, chamber 16 will warm the air when the generator is operating and part of the warm air will be used to maintain bulb 45 and trap 50 from freezeup.

Hood 77 and duct 76 may be made of any suitable material, as metal. To enclose separator bulb 45 and trap 50, hood 77 has top and sidewalls and is attached to cabinet 25 to define a closed box. Warm air circulation may be assisted by cutting a hood vent 78 in one of the sidewalls of the hood and the cabinet. it is contemplated that an electrical heating element may be substituted for the scavenger system shown without hampering the overall operation of the system of the invention. However, the scavenger system is advantageously efficient and an added feature of the invention.

A similar antifreezeup device is provided for arrester water trap 61. Warming hood 79 envelopes trap 61, has an end wall, two sidewalls, and top and bottom walls and is connected on one end to cabinet 25 to define a closed box enveloping arrester pipe 53 and trap 61, leaving appropriate holes for extension of the various pipes and conduits. Where cabinet 25 is connected to hood 79, an appropriate hole is cut for communication with a second scavenger duct 80 which is a hollow conduit member extending to the top of shroud 21.

FIG. 4 illustrates a modified form of the invention in which a modified heating system for the inrush of air to shroud 21 is provided by an air tempering system. The other components of generator 9 are the same and numbered identically in this embodiment as in the first embodiment. The air tempering system has a feedback duct 81 extending from an appropriate opening near the top of shroud 21 to a tempering hood 82 disposed at the bottom of cabinet 25 between blower 69 and cabinet 25. Hood 82 is a metal box having two chambers, a plenum chamber 83 and a lower chamber 84. The

chambers

83 and 84 are defined by the hood walls and a partition 85 extending horizontally across the center of hood 82. One lower chamber wall of the hood is attached to blower 69 at its inlet 72, which opens into lower chamber 84.

Feedback duct 81, which can be constructed similarly to the other ducts, provides a passageway for air warmed by combustion chamber 16 to an opening through hood 82 into plenum chamber 83.

Lower chamber 84 is adapted to conduct cooling air introduced through ambient air inlet 86 disposed at vent 70 in cabinet 25, and discharged through the opening on the opposite side of hood 82, complementing and in communication with blower inlet 72.

Air tempering is provided by a cooperating pair ofdampers, a warm air damper 87 which is normally closed and is disposed to fit in'a complementary opening 88 in partition 85, and an ambient air damper 89 fitted in lower chamber ambient air inlet 86, damper 89 being normally open. A common linkage 90, having an elongated metal strip link 91 or other thermostatic control in contact with the ambient air, operates the dampers. As part of linkage 90, each

damper

87 and 89 has an offset rod 92 clamped to the respective dampers and positioned horizontally across the center thereof. Rods 92 each have an offset portion at an end where they are attached to opposite ends of strip link 91 to complete linkage 90. The linkage may be secured in place for operation by providing opening frames 93 around the periphery of the respective damper openings and then extending rods therethrough for a mounting arrangement permitting rotation of the rods.

Control 91 will contract and expand according to the temperature, and the offsets in rods 92 are adapted to translate such change in dimension into rotation of

dampers

87 and 89. For instance, contraction of strip 91 will tend to close damper 89, and simultaneously to open damper 88. In that case, warm air from plenum chamber 83 will enter lower chamber 84 and will ultimately pass back through the cooling air shroud 21. The dimensions and temperature expansion and contraction characteristics of strip 91 are chosen so as to keep warm air damper 88 closed until near freezing ambient temperatures; but for lower temperatures the strip should contract an amount to open damper 88 an amount permitting enough feedbackair to mix with inrushing ambient air to keep the resultant mixture at the proper temperature in shroud 2]. These parameters can only be determined in relation to the particular dimension and materials used in the unit.

OVERALL OPERATION The structure of the invention provides an atmosphere control for a storage structure which operates in all weather conditions and cooperates with pressure control in the storage -unit.

Operating in a warm ambient, for one situation, control device 36 can be set to periodically switch on, simultaneously, the various operating parts of generator 9. Combustion chamber 16 then begins supplying the oxygen depleted gas which will ultimately reach silo 1. The gas passes through the various elements as described relative to the flow diagram of FIG. 2.

At the same time, blower 69 is switched on and cooling air shroud 21 is supplied with ambient air. The air is originally at the ambient temperature, as air heater 73 and thermostat 74 have been set to close the electrical heating circuit only near freezing ambient temperatures. in the embodiment of FIG. 4, the

dampers

87 and 89 are in their normal positions and feedback duct 81 is closed off from lower chamber 84 so that the inrushing ambient air is not being mixed with warm air.

Thus, the products of combustion from chamber 16 are cooled by contact with the walls of tubes 41 of condenser 18. Water will condense out in tubes 41 and further down the line in conduit 44, to be collected by bulb 4S and ultimately drained from the system. The extent of cooling is limited byL.

the temperature of the ambient air in shroud 21 and therefore even during warm ambient operation, the gas will not be cooled below the ambient temperature. As the gas eventually reaches hcadspace 3 of silo 1, no appreciable temperature differential with the ambient will be caused and breather bag 4 will operate generally independently of gas unit 8. Further. the moisture content of the gas will have been reduced to a level whereat even for the warm ambients, moisture will not condense out when the gas reaches hcadspace 3. As conditions change in the silo or ambient air, the described operation of condenser 18 and cooling air shroud 21 will tend to stabilize the situation, since gas unit 8 supplies gas generally at the conditions of the ambient, and purges the atmosphere in silo 1 of gas therein which may have been at a different condition.

I Arrcster 10 and the various heating arrangements for water separator bulb 45, trap 50 and trap 61 have no vital operation in a warm ambient. As the climate approaches freezing weather, however, these parts play an important role. First, the setting of eitherthermostst 74 for heater 73 or strip link 91 and damper linkage 90 for the feedback air tempering system are such as to operate their respective systems to warm the air in shroud 21, maintaining the condenser temperature above freezing. in that case, the condition of the vapor leaving condenser 18 and generator 9 will not be cooledj and at the proper dew point so as to match the conditions in'rheadspace 3, since the condenser has not cooled it to near the ambient temperature. Freezeup, of course, has been avoided in condenser 18 and conduit 44.

lcing arrester 10, however, is in contact with thefreezing ambient air, mainly by wall 54. There the gas is cooled to near the ambient temperature, and moisture is largely removed by collecting as ice on the walls of arrester 10. Control 60 being set to periodically close the circuit in heating rod 58, the ice is melted at such times to defrost the'unit and keep it operable. The gas is thus conditioned by arrester 10 in winter situations, so as to generally correspond to the condition of the ambient, and the oxygen-depleted and vapor-depleted atmosphere in silo l is maintained without causing difficulties with pressure differentials.

Freezeup of other vital parts is prevented by the scavenger ducts 76 and and their respective warming hoods 77 and 79. These scavenge air from shroud 2|, which air has been warmed by cooling combustion ehamber'l6, and very efficiently prevent l'rcezcup of separator 19 with trap 50 and the defrost trap 20. These warming systems do not appreciably interfere with the temperature control of the gas vapor. Thus, all weather operation is provided for generator 9 and ice arrester unit 10.

The invention described provides an atmosphere control system for a storage structure, which system operates in all weather conditions to provide a gas that is proper for varying storage conditions and cooperates with pressure differential control in the storage structure.

The embodiments described are the best examples ofthe invention which are presently contemplated.

The following claims define the scope of the invention.

1. A gas supply unit for a storage structure adapted to store perishable materials and disposed in the ambient air, comprising a gas passage line connected to the storage structure unit, a gas generator connected to said line for discharge of an oxygen-depletcd gas into said line, and a defrostable icing arrester connected into said line between the generator and the storage structure, the arrester defining a gas passage chamber connected with said line, the arrester chamber providing an ice collecting surface in contact with said gas passing through the arrester, the surface being a heat exchanger with the ambient, the arrester having defrosting means for melting ice col: lecting on said collecting surface, and the arrester having a water drain to drain water from the defrosted ice, whereby the gas supply unit avoids gas at near ambient temperatures even in freezing ambient.

2. The assembly of claim 1, wherein the defrostable icing arrester is comprised of:

an outside heat conducting wall assembly defining said arrester chamber and exposed to the ambient, the wall as sembly having an inlet in gas communication with the combustion chamber, further having an arrester exhaust outlet in gas communication with said gas passage line and the storage structure, the wall assembly and its openings thereby defining a gas passage which brings the gas in contact with the outside will for heat exchange with the ambient; and

the defrosting means being an electrical heating element disposed in the arrester chamber and having a resistance circuit with a control switch means for closing the circuit at preselected times in accordance with the amount of ice collection in the chamber in freezing ambient operation.

3. The structure defined by claim 1, wherein: the gas generator has an integral condenser connected betweer the combustion chamber and the icing arrester for gas communication, said condenser being a heat exchanger between said gas and a cooling fluid having a temperature above a minimum temperature to avoid freezing of condensate in the generator.

4. The structure ofclaim 1, wherein the arrester has a water separator assembly in fluid communication with said arrester chamber drain opening to drain water therefrom; and the gas unit includes a heater member disposed at the drain and separator assembly.

5. The structure of claim 6, wherein the generator includes a cooling air shroud enveloping the combustion chamber and providing a space for airflow past the combustion chamber the generator further includes a blower member which supplies a cooling airflow in said shroud, and said drain heater member comprises a warming hood enveloping the drain and separator assembly, and a scavenger duct connected between the hood and the shroud, the duct being a conduit connected through said shroud at a position to accept airflow after it has flowed past at least part of the combustion chamber, the duct defining an airflow passage from the shroud to the hood.

6. In a storage unit having a sealed storage structure for storing a perishable material, a gas generator disposed in the ambient air for supplying gas to the atmosphere of the storage structure, the generator comprising:

a carbonaceous fuel burner having a combustion chamber with an exhaust end having an exhaust opening through which products of combustion of a carbonaceous fuel are expelled;

a condenser disposed adjacent the combustion chamber at the exhaust end and having a condenser inlet opening communicating with said combustion exhaust opening to define a gas passage from said exhaust opening to said inlet, the condenser providing a gas passageway from the inlet to a condenser outlet, which outlet is connected for gas communication with the storage structure, and the condenser having a heat exchanger wall with one surface in contact with the atmosphere surrounding said condenser and the opposite surface in contact with gas passing through said condenser;

a shroud having a wall assembly enveloping the combustion chamber and condenser and defining an air space around said chamber and condenser, the shroud having an air inlet opening at the condenser and an air outlet opening at a chamber end opposite the exhaust end of the chamber;

a blower disposed at one ofthe shroud openings, the blower having operable structure which draws ambient air in and causes said air to flow in said inlet through the shroud air space and out said outlet;

the shroud having a duct opening disposed near the combustion chamber end opposite the exhaust end;

a water separator assembly connected by conduit between the condenser outlet and the storage structure, said separator assembly having water collecting and draining structure;

a warming hood having wall structure enveloping said water collecting and draining structure and defining an air space around said collecting and draining structure, the hood having a duct opening in its wall structure; and

a scavenger duct connected between the shroud and hood duct openings, said scavenger duct providing an air passageway from the shroud to the hood,

7. In a storage unit having a sealed storage structure for storing a perishable material, a gas generator disposed in the ambient air for supplying gas to the atmosphere ofthe storage structure, the generator comprising:

a condenser disposed adjacent the combustion chamber at the exhaust end and having a condenser inlet opening communicating with said combustion exhaust opening to define a gas passage from said exhaust opening to said inlet, the condenser providing u gas passageway from the inlet to a condenser outlet, which outlet is connected for gas communication with the storage structure, and the condenser having a heat exchanger wall with one surface in contact with the atmosphere surrounding said condenser and the opposite surface in contact with gas passing through said condenser;

a blower disposed at one of the shroud openings, the blower having operable structure which draws ambient air in and causes said air to flow in said inlet through the shroud air space and out said outlet;

the shroud having a duct opening at. a position near the combustion chamber end opposite the exhaust end of the chamber;

a tempering hood disposed at the shroud inlet, the hood having a wall structure defining an air chamber which is divided by a partition into a plenum chamber and another chamber, a hole being through the partition, said other chamber having a hood inlet opening and a hood outlet opening which is in gas communication with the shroud inlet, said plenum chamber having an opening through the wall structure;

a feedback duct connected between the plenum chamber opening and the shroud duct opening thus defining an air passageway between the insides of said chamber and shroud operation;

a pair of dampers, one each disposed in said hole in the partition and the hood inlet opening; and

a thermostatic control means for opening and closing said dampers to mix air from said plenum chamber and said other chamber in a manner which maintains condensate in said condenser above freezing.

8. The structure defined by claim 9, wherein the thermostatic control mcans is a linkage assembly comprising:

a pair of offset rods, each connected on one end to a damper, offset portions being on another end of each rod and the offsets being opposite in direction,

a heat expansiblc link connected between the offset ends of the rods, the link being exposed to the ambient temperature, said link having an above freezing temperature dimension such as to close the damper in the partition closed and to open the damper in the hood inlet, and the link having below freezing dimensions such as to contract and draw the offset portions toward each other thus to partially open the partition opening damper and partially close the hood inlet damper.

9. In a sealed storage structure adapted to store perishable materials in a controlled atmosphere, the storage structure having a breather assembly adapted to pressurize the interior of the storage structure to generally match the pressure of the ambient; a gas supply unit having in combination:

a gas generator having parts interconnected such that together they provide a gas passage leading to an exhaust conduit member at an exhaust end of the passage, said interconnected parts including: a burner at the end of the passage opposite the exhaust end, which burner exhausts products of combustion of carbonaceous fuels; a condenser connected in the passage after the burner, the condcnser having a surface which is a heat exchanger between the burner exhaust and the ambient air; a water separator connected in the passage after the condenser and having a water collecting and drain assembly;

an icing arrester connected for gas communication to the generator via said exhaust conduit, said arrester having an arrester outlet and defining a gas passageway for the generator exhaust from the exhaust conduit to said arrester outlet, the arrester providing a heat exchanger surface in said passageway, which surface exposes the generator exhaust to the temperature of the ambient, and having a water drain assembly;

defrosting means for melting ice in the icing arrester; and

an elongated conduit connected to the arrester at the ar rester outlet and providing a gas passageway to the interior of the storage structure from said arrester outlet.

10. The combination of claim 9 and including:

a heater disposed at the water separator; and

a heater disposed at the arrester drain assembly.

11. The structure defined by claim 9, and including a combination:

an air shroud in said generator, the shroud having wall structure which envelops the condenser and provides an air space around said condenser, the shroud having an inlet and an outlet which with said wall structure define an air flow path therebetwecn;

a blower in said generator, which blower has structure adapted to propel ambient air into the shroud inlet; and an air heater in the generator, the heater being disposed at said shroud inlet and having a thermostatic means for maintaining the gasflow in the condenser at above freezing temperatures. 12. The method of controlling the atmosphere in a sealed storage structure disposed in the ambient air, the method comprising:

generating at predetermined times gaseous products of combustion ofa carbonaceous fuel by burning the fuel;

cooling said products of combustion by heat exchange with the ambient air;

heating the ambient air which cools said products when the ambient is at freezing temperatures so as to maintain said gaseous products above freezing;

separating water from the products of combustion after said products have been cooled;

then after said cooling and water separation, passing said products through a second cooling device wherein the products are cooled by heat exchange with a wall surface exposing the products to ambient temperatures including freezing temperatures;

then passing the products of combustion into the storage structure; and

defrosting the second cooling device at selected times to maintain said device open to gas passage.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,589,025 Dated June 29, 1971 Inventor(s) Frank Hamerski It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 12, after "of" insert a minus sign before the "1.5"

Column 9, line 4, cancel "6" and substitute therefor (in claim 5 Signed and sealed this 21 at day of December 1 971 (SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Acting Commissioner of Patents FORM PO-1050 (10 69) USCOMM-DC 60376-P6D fi LIS GOVERNMENT PRINTING OFFOCI: "Q9 O3I6-3ll

Claims

2. The assembly of claim 1, wherein the defrostable icing arrester is comprised of: an outside heat conducting wall assembly defining said arrester chamber and exposed to the ambient, the wall assembly having an inlet in gas communication with the combustion chamber, further having an arrester exhaust outlet in gas communication with said gas passage line and the storage structure, the wall assembly and its openings thereby defining a gas passage which brings the gas in contact with the outside will for heat exchange with the ambient; and the defrosting means being an electrical heating element disposed in the arrester chamber and having a resistance circuit with a control switch means for closing the circuit at preselected times in accordance with the amount of ice collection in the chamber in freezing ambient operation.
3. The structure defined by claim 1, wherein: the gas generator has an integral condenser connected between the combustion chamber and the icing arrester for gas communication, said condenser being a heat exchanger between said gas and a cooling fluid having a temperature above a minimum temperature to avoid freezing of condensate in the generator.
4. The structure of claim 1, wherein the arrester has a water separator assembly in fluid communication with said arrester chamber drain opening to drain water therefrom; and the gas unit includes a heater member disposed at the drain and separator assembly.
5. The structure of claim 6, wherein the generator includes a cooling air shroud enveloping the combustion chamber and providing a space for airflow past the combustion chamber the generator further includes a blower member which supplies a cooling airflow in said shroud, and said drain heater member comprises a warming hood enveloping the drain and separator assembly, and a scavenger duct connected between the hood and the shroud, the duct being a conduit connected through said shroud at a position to accept airflow after it has flowed past at least part of the combustion chamber, the duct defining an airflow passage from the shroud to the hood.
6. In a storage unit having a sealed storage structure for storing a perishable material, a gas generator disposed in the ambient air for supplying gas to the atmosphere of the storage structure, the generator comprising: a carbonaceous fuel burner having a combustion chamber with an exhaust end having an exhaust opening through which products of combustion of a carbonaceous fuel are expelled; a condenser disposed adjacent the combustion chamber at the exhaust end and having a condenser inlet opening communicating with said combustion exhaust opening to define a gas passage from said exhaust opening to said inlet, the condenser providing a gas passageway from the inlet to a condenser outlet, which outlet is connected for gas communication with the storage structure, and the condenser haviNg a heat exchanger wall with one surface in contact with the atmosphere surrounding said condenser and the opposite surface in contact with gas passing through said condenser; a shroud having a wall assembly enveloping the combustion chamber and condenser and defining an air space around said chamber and condenser, the shroud having an air inlet opening at the condenser and an air outlet opening at a chamber end opposite the exhaust end of the chamber; a blower disposed at one of the shroud openings, the blower having operable structure which draws ambient air in and causes said air to flow in said inlet through the shroud air space and out said outlet; the shroud having a duct opening disposed near the combustion chamber end opposite the exhaust end; a water separator assembly connected by conduit between the condenser outlet and the storage structure, said separator assembly having water collecting and draining structure; a warming hood having wall structure enveloping said water collecting and draining structure and defining an air space around said collecting and draining structure, the hood having a duct opening in its wall structure; and a scavenger duct connected between the shroud and hood duct openings, said scavenger duct providing an air passageway from the shroud to the hood.
7. In a storage unit having a sealed storage structure for storing a perishable material, a gas generator disposed in the ambient air for supplying gas to the atmosphere of the storage structure, the generator comprising: a carbonaceous fuel burner having a combustion chamber with an exhaust end having an exhaust opening through which products of combustion of a carbonaceous fuel are expelled; a condenser disposed adjacent the combustion chamber at the exhaust end and having a condenser inlet opening communicating with said combustion exhaust opening to define a gas passage from said exhaust opening to said inlet, the condenser providing a gas passageway from the inlet to a condenser outlet, which outlet is connected for gas communication with the storage structure, and the condenser having a heat exchanger wall with one surface in contact with the atmosphere surrounding said condenser and the opposite surface in contact with gas passing through said condenser; a shroud having a wall assembly enveloping the combustion chamber and condenser and defining an air space around said chamber and condenser, the shroud having an air inlet opening at the condenser and an air outlet opening at a chamber end opposite the exhaust end of the chamber; a blower disposed at one of the shroud openings, the blower having operable structure which draws ambient air in and causes said air to flow in said inlet through the shroud air space and out said outlet; the shroud having a duct opening at a position near the combustion chamber end opposite the exhaust end of the chamber; a tempering hood disposed at the shroud inlet, the hood having a wall structure defining an air chamber which is divided by a partition into a plenum chamber and another chamber, a hole being through the partition, said other chamber having a hood inlet opening and a hood outlet opening which is in gas communication with the shroud inlet, said plenum chamber having an opening through the wall structure; a feedback duct connected between the plenum chamber opening and the shroud duct opening thus defining an air passageway between the insides of said chamber and shroud operation; a pair of dampers, one each disposed in said hole in the partition and the hood inlet opening; and a thermostatic control means for opening and closing said dampers to mix air from said plenum chamber and said other chamber in a manner which maintains condensate in said condenser above freezing.
8. The structure defined by claim 9, wherein the thermostatic control means is a linkage assembly comprising: a pair of offset rods, each connected on one end to a damper, offset portions being oN another end of each rod and the offsets being opposite in direction, a heat expansible link connected between the offset ends of the rods, the link being exposed to the ambient temperature, said link having an above freezing temperature dimension such as to close the damper in the partition closed and to open the damper in the hood inlet, and the link having below freezing dimensions such as to contract and draw the offset portions toward each other thus to partially open the partition opening damper and partially close the hood inlet damper.
9. In a sealed storage structure adapted to store perishable materials in a controlled atmosphere, the storage structure having a breather assembly adapted to pressurize the interior of the storage structure to generally match the pressure of the ambient; a gas supply unit having in combination: a gas generator having parts interconnected such that together they provide a gas passage leading to an exhaust conduit member at an exhaust end of the passage, said interconnected parts including: a burner at the end of the passage opposite the exhaust end, which burner exhausts products of combustion of carbonaceous fuels; a condenser connected in the passage after the burner, the condenser having a surface which is a heat exchanger between the burner exhaust and the ambient air; a water separator connected in the passage after the condenser and having a water collecting and drain assembly; an icing arrester connected for gas communication to the generator via said exhaust conduit, said arrester having an arrester outlet and defining a gas passageway for the generator exhaust from the exhaust conduit to said arrester outlet, the arrester providing a heat exchanger surface in said passageway, which surface exposes the generator exhaust to the temperature of the ambient, and having a water drain assembly; defrosting means for melting ice in the icing arrester; and an elongated conduit connected to the arrester at the arrester outlet and providing a gas passageway to the interior of the storage structure from said arrester outlet.
10. The combination of claim 9 and including: a heater disposed at the water separator; and a heater disposed at the arrester drain assembly.
11. The structure defined by claim 9, and including a combination: an air shroud in said generator, the shroud having wall structure which envelops the condenser and provides an air space around said condenser, the shroud having an inlet and an outlet which with said wall structure define an air flow path therebetween; a blower in said generator, which blower has structure adapted to propel ambient air into the shroud inlet; and an air heater in the generator, the heater being disposed at said shroud inlet and having a thermostatic means for maintaining the gasflow in the condenser at above freezing temperatures.
12. The method of controlling the atmosphere in a sealed storage structure disposed in the ambient air, the method comprising: generating at predetermined times gaseous products of combustion of a carbonaceous fuel by burning the fuel; cooling said products of combustion by heat exchange with the ambient air; heating the ambient air which cools said products when the ambient is at freezing temperatures so as to maintain said gaseous products above freezing; separating water from the products of combustion after said products have been cooled; then after said cooling and water separation, passing said products through a second cooling device wherein the products are cooled by heat exchange with a wall surface exposing the products to ambient temperatures including freezing temperatures; then passing the products of combustion into the storage structure; and defrosting the second cooling device at selected times to maintain said device open to gas passage.