GB2094127A - Straw/fodder conversion apparatus - Google Patents

Abstract

Straw/fodder conversion apparatus comprising a sealable bin (10) which can receive straw to be heated in an ammonia laden atmosphere, wherein the ammonia atmosphere is fed to the bin from an expansion tank (18) external to the bin, into which ammonia from a liquefied source is allowed to expand and boil as it warms under the influence of the environmental temperature, generating an ammonia atmosphere which expands naturally through a connecting duct (24) into the bin interior. Heating is preferably provided by a fluid circulating system (28) which includes a duct (38) passing through the expansion tank (18) to enable supplementary heating of the ammonia in the tank in cold weather conditions. <IMAGE>

Description

SPECIFICATION Improvements in straw/fodder conversion This invention relates to a method and apparatus for straw/fodder conversion.

It is known that straw, i.e. the waste from cereal crops, can be converted into useful fodder for livestock by treating the straw in a heated ammonia laden atmosphere. The ammonia attacks the straw, breaking down the fibrous content and simultaneously substantially increasing the protein content.

Farmers keeping livestock frequently have straw available, but usually burn it as waste, while at the same time growing grass for hay for use as fodder.

The hay would often be unnecessary if the straw was converted to fodder instead of being burnt.

In a known conversion apparatus, liquefied ammonia supplied from a pressurised source, i.e. a commercially available sealed cylinder or holder thereof, is directly connected to the bin containing the straw to be converted. The liquefied ammonia is allowed to expand directly into the interior of the bin from one or more nozzles in the roof thereof, cooling on expansion through the nozzle or nozzles and falling directly on to the straw in the bin effectively to freeze at least the upper layer thereof.

This is extremely disadvantageous, since heating is necessary to effect the required conversion, and initially a considerable consumption of the energy from the heating source must be utilised simply to raise the temperature of the straw back to its original level.

It is a primary object of this invention to provide apparatus for straw/fodder conversion wherein this disadvantage is substantially overcome.

According to the present invention, apparatus for straw/fodder conversion comprises a bin which can be opened for insertion of straw and then sealed closed, means for maintaining an ammonia laden atmosphere in the closed bin, and means for heating the ammonia laden atmosphere in the bin, wherein ammonia under pressure from a source of liquefied ammonia is fed to an expansion tank external of the bin, the ammonia being cooled on initial expansion into the tank and being allowed or caused to boil in said tank to produce an ammonia atmosphere which expands through a supply duct which communicates through the wall of the bin to the interior thereof.

In accordance with the invention, the liquefied ammonia can be allowed to warm up naturally in the expansion tank, under the infuence of the environmental temperature, thus producing an ammonia atmosphere in the tank which expands naturally into the bin interior.

Liquid ammonia boils at about -26 degrees Centigrade. so that normally the atmospheric air temperature around the expansion tank, which is external of the bin, will suffice for warming the tank.

However, heating assistance may occasionally be desired in very cold weather conditions. Thus, according to further feature of the invention, heating of the bin is effected by means of a fan-assisted air circulatory system, which includes a warm air duct passing through the expansion tank.

Heating of the air in the circulatory system, which includes a duct opening into the top of the bin and a duct communicating with the interior of the bin at the bottom, can be effected by means of electric heating elements. Preferably, however, an option will be provided for breaking into the air circulatory system in order to take the air through a heat exchanger at which the air is heated by heat exchange with a second fluid, e.g. air or water, which second fluid is heated in a fuel burner, conveniently a straw burner. A straw burner coupled with a heat exchanger provides an extremely economical method of carrying out the straw/fodder conversion; however the use of the electric heaters in the path of the circulatory airflow demands less initial capital outlay.

At the end of the conversion process, it is necessary to provide a facility for venting the circulatory system to the atmosphere in order to enable the bin to cool and be cleared of the ammonia vapour, and a further feature of the invention concerns a control valve provided for this purpose, as will be apparent hereinafter.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic illustration of straw/ fodder conversion apparatus in accordance with the invention, and Figure2 illustrates a control valve employed in the apparatus.

In Figure 1,the reference 10 denotes a bin supported on feet 12 and having an access door 14 at the front enabling bales of straw to be inserted for conversion to fodder. The illustrated bin is rectangular, but the bin could instead be cylindrical. Furthermore, the bin can be available in a range of sizes to enable larger or smaller amounts of straw to he converted in a single operational process.

Conversion is effected by subjecting the straw in the bin to heat in the presence of an ammonia laden atmosphere. For enabling this, the door 14 closes against seals, diagrammatically indicated at 16, effectively to seal the loaded bin.

In accordance with the invention, ammonia from a liquefied source 17 thereof, e.g. a commercially available cylinder or canister or other holder thereof, is supplied to an expansion tank 18. This tank 18 is, as shown, located externally of the bin 10, being mounted on the outside of the bin by suitable brackets or like supports.

Ammonia under pressure from the source reaches the tank 18 through connecting pipe 20, into which it has expanded through an orifice plate 22 at the outlet from the pressurised source 17. The ammonia cools on expansion through the orifice plate 22 and, after entering the tank 18 from the connecting pipe 20, which latter is not pressurised owing to the presence of the orifice plate, tends to condense on the roof of the tank 18, thence to run down the side walls. The tank 18 tends to cool, but warms up under the infuence of the external environmental atmosphere, which typically will be of the order of 10 to 20 degrees Centigrade, well above the boiling point of ammonia at -26 degrees Centrigrade. Gradually, therefore, and in a continuous manner, the ammonia in the tank 18 vapourises, creating an ammonia atmosphere in the tank.This ammonia atmosphere naturally tends to expand as fresh liquefied ammonia from the source expands into the tank, and the ammonia vapour is thereby communicated to the interior of the bin 10 buy a connecting duct 24. In the illustrated embodiment, the duct 24 enters the bin 10 along the roof wall, and has two outlets 26 into the bin interior from the roof thereof. However, the number of outlets, and possibly also the number of ducts supplying ammonia vapour to said outlets, will depend on the size of the bin 10.

It can be advantageous for the expansion tank 18 to have a shallow covering of water at the bottom, so that a uniform vapour saturated atmopshere is maintaned in the tank. It can be arranged that such a layer of water naturally tends to be maintained in the bottom of the tank 18 due to infiltration of moisture from the outside environmental atmosphere.

Heating of the bin 10 is carried out by means of a hot air circulatory system, generally referenced 28.

This system, which is somewhat simplified in the illustration of Figure 1, incudes a duct 29 which, in the direction of air flow, opens into the top of the bin 10, and a duct 30 which opens into the bottom of the tank for return air flow. Outside the bin 10, the system includes a fan 32, a control valve 34 and one or more electric heaters 36. It will also be noted that the system includes a portion of hot air duct 38 which extends through the expansion tank 18.

In operation, heated air is circulated through the interior of the sealed bin 10 resulting in a hot, ammonia laden internal atmosphere therein, with continuous recirculation of the air past the heater assembly 36 being maintained bythefan assembly 32. In a large sized bin 10, a plurality of air inlet and outlet ducts may communicate with the bin, possibly in association with separate fans and/or heaters, one for each circulatory path.

In order to avoid undue loss of heat, the walls and door of the bin 10 will preferably be made, as indicated atthe bottom left-hand corner of the illustration, with an internal heat insulating layer 40 covered on the inside by a heat reflective foil or like layer 42.

The purpose of the duct 38 extending through the expansion tank 18 is to assist in vapourising the ammonia in the tank, more especially in very cold weather. If, for example, the outside air temperature is as low as -10 degrees Centigrade, the ammonia in the tank would naturally tend to boil only relatively slowly, possibly not fast enough to maintain an adequate supply to the bin 10. The supplementary heat radiated by the duct 38 within the tank 18 provides a solution to this possible problem.

Figure 1 also serves to show an optional alternative heating means which may be employed to heat the air flowing in the circulatory system 28. The alternative heating means, generally referenced 44, may be connected into the circulatory system at 46, downstream of the fan 32, to extend the circulatory system through a heat exchanger 48. The heat exchanger, which can be of any convenient type employing heat transfer plates or coils, is supplied with hot air or water from a fuel burner 50. This fuel burner can conveniently be a straw burner, which generates sufficient heat to enable use of the electric heater assembly 36 to be discontinued, or a least used only on a very low power to provide supplementary heat to the air flowing in the system.

The process of converting straw to foddertakes a predetermined number of hours and, at the end of the operational period, it is necessary to stop the circulation of hot air in order to enable the interior of the bin 10 to be cleared of ammonia vapour and other fumes, which is assisted by venting the bin.

Thus, at the end of the operational period, when the electric heaters 36 are switched off, the control valve 34 is provided to vent the circulatory system 28.

This control valve 34 is shown in Figure 2 and comprises a valve casing 52 having respective, longitudinally spaced ports 54,56,58, connecting to the heater assembly 36, the fan assembly 32 and outside atmosphere, through which casing extends a spring loaded piston rod 60 having a latch releasable by a solenoid 62 and carrying two spaced pistons 64 and 66. This piston rod 60 is releasable in one direction by the solenoid 62, and can be manually reset by a handle (not shown) on a protruding end of the piston rod.

In the latched position of the piston rod 60, the respective pistons, which are mounted with a degree of free play on the rod and backed by biassing springs 68, are urged tightly aganst special rubberised seals 70 mounted on the interior of the valve casing 52, whereby the fan assembly 32 is communicated to the heaters 36 and the vent port 58 is sealed off. In the released position of the piston rod 60, the fan assembly 32 is communicated to the vent port 58. References 64A, 66A denote the positions of the pistons in the released condition of the piston rod 60.

The above-described embodiment may be modified in various ways within the scope of the invention as defined in the appended claims. For example, heating of the bin can be effected in various other ways, which may or may nor comprise of fluid circulatory system, and in this case the above-described control valve may or may not be required. An advantage of the fluid circulatory system is that it readily enables substitution of one source of heating energy for another, such as substitution of a straw burner for at least part of the electric heater assembly, which latter can then be used as and when necessary only to provide supplementary heat. A fluid circulatory system also facilitates the application of supplementary heat in the expansion tank.

Claims (16)

1. Apparatus for straw/fodder conversion comprising a bin which can be opened for insertion of straw and then sealed closed, means for maintaining an ammonia laden atmosphere in the closed bin, and means for heating the ammonia laden atmosphere in the bin, wherein ammonia under pressure from a source of liquefied ammonia is fed to an expansion tank external of the bin, the ammonia being cooled on initial expasion into the tank and being allowed or caused to boil in said tank to produce an ammonia atmosphere which expands through a supply duct which communicates through the wall of the bin to the interior thereof.

2. Apparatus according to claim 1, wherein the heating means is a fluid circulatory system.

3. Apparatus according to claim 2, wherein the circulatory fluid is air.

4. Apparatus according to claim 2 or claim 3, wherein the circulatory system includes an inlet duct opening into the bin and an outlet duct exiting from the bin at a point remote from the inlet duct entrance.

5. Apparatus according to claim 4, wherein the said inlet opens into the bin through the top wall thereof and the outlet emerges through the bottom wall of the bin.

6. Apparatus according to any of claims 2 to 5, wherein the fluid circulatory system includes a duct passing through the expansion tank.

7. Apparatus according to any of claims 2 to 6, wherein the heating means includes or comprises one or more electric heating elements in the path of fluid flow in the circulatory system.

8. Apparatus according to any of claims 2 to 7, wherein the heating means includes or comprises a heat exchanger at which the circulatory fluid is heated by heat exchange with a heated second fluid.

9. Apparatus according to claim 8, wherein the second fluid is heated at a straw burner.

10. Apparatus according to claim 8 or claim 9 when appendant claim 7, wherein the heat exchanger and straw burner constitute an optional heating system which can be connected to the circulatory system to supplement or replace the one or more electric heating elements.

11. Apparatus according to claim 3 or any of claims 4 to 10 when appendantto claim 3, wherein the fluid circulatory system includes a fan and a control valve downstream of the fan, which control valve is operable either to connect the fan outlet to the bin interior or to connect the fan outlet to an atmospheric vent.

12. Apparatus according to claim 11, wherein the control valve is latched and releasable by a solenoid.

13. Apparatus according to claim 11 or claim 12, wherein the control valve comprises a piston rod carrying two pistons which slide in a valve casing having three longitudinally spaced parts, the two pistons being alternatively positionable one between the intermediate part and one end part and the other beyond said one end part, or vice versa.

14. Apparatus according to claim 13, wherein, in the position in which the fan outlet is connected to heat the bin interior, the pistons seat against respective rubberised seals carried by the interior wall of the valve casing.

15. Apparatus according to claim 14,wherein the pistons are mounted on the piston rod with free play so as to be urged towards the said seals by respective biassing springs also mounted on the piston rod.

16. Apparatus for straw/fodder conversion substantiallv as hereinbefore described with reference to the accompanying drawings.