US2080179A - Treatment of organic products - Google Patents

Description

May 11, 1937. c. J. MERRIAM ET AL 2,080,179

TREATMENT OF ORGANIC PRODUCTS Filed July 10, 1936 .Ezven Patented May 1 1', 1937 UNITED STATES PATENT OFFICE TREATMENT OF ORGANIC PRODUCTS Application July 10, 1936, Serial No. 89,982

17 Claim.

This invention relates to the treatment of organic products and more particularly to the treatment of such products with steam.

It is frequently desirable to subject food products, tobacco or the like, to vacuum treatment as a preliminary to further treatment such as fumigation, or as a step in some other process. Where it is desired to replace the air which permeates the interstices and cells of organic prod- 1o nets with some other gas, which may be a fumigating gas such as ethylene oxide, carbon dioxide and mixtures, hot steam or water vapor, there has heretofore been great difliculty in completely removing the air. The air cannot be entirely rer5 moved, and being incondensible, when another as is added to the chamber the residual air packs into the center of the cells or into the center of the packages of material. Moreover, if attempts are made to remove substantially all of 20 the air by ordinary evacuating processes, the moisture content of the products is frequently disturbed.

By means of the present invention it is not only possible to remove air or other incondensi- 25 ble gas completely from organic products as a preliminary to other treatment, but it is possible to prevent packing of any residual gas by the introduction of a gas at higher pressure and at the same time the moisture content of the product in question may be readily adjusted to the most desirable point.

The invention is illustrated diagrammatically in the drawing in connection with a fumigating apparatus, but it is to be understood that the 5 invention is by no means limited to the use of such an apparatus but may be applied wherever it is desired to remove a non-condensible gas or to adjust the water content of a product. By incondensible gas as used herein is meant a 40 as whose vapor pressure at the temperature involved (generally atmospheric) is not substantially less than atmospheric pressure.

As illustrated diagrammatically in the drawing, I represents a closed chamber adapted to 45 withstand the full pressure of the atmosphere,

which is provided with a door 2, closely fitted to avoid any leakage of oxygen. The tank may be of any desired shape or size, but for normal commercial practice it generally has a capacity of .50 at least one thousand cubic feet. The tank may be provided with a manifold 3 having a plurality of inlet pipes 4 and is supplied with fumigant through the line 5.

A two-stage vacuum pump 6 is connected with 55 the treating tank through the lines I, 8 and 9 and may be operated by any suitable means (not shown). The pump preferably has a capacity suflicient to evacuate the chamber I within a few minutes. The discharge end of the pump connects with an oil separator III from which line II connects with an air vent I2, with line 9 and also with line I3. The line I3 connects with the pressure vessel [4 and the line I5. Pressure vessel I4 is adapted to withstand a substantially complete vacuum and also pressures up to 10 100 pounds super-atmospheric and is suiliciently large to hold fumigating gas sufiicient for the entire fun-ligating operation. Suitable heating means may be provided in this vessel, and are indicated in the drawing by steam coil inlet I6 and outlet I 7. A supply tank of fumigant is indicated at l8. A plurality of supply tanks may be used, if desired.

A condenser I9 is provided on the intake side of the vacuum pump and on account of the formation of ice at low temperatures, it is preferably maintained at about the freezing point. If greater removal of water is desired, a brine tank,.or other means for preventing freezing, may be provided.

A compressor 20 is provided, for example, on the line 9 and a separator 2| may also be provided, on the outlet side thereof, for the separation of condensed water, and oil, if desired. A by-pass 22 is provided around the compressor.

In carrying out the operation, an organic product such as furs, wool, tobacco, food products, or the like, is placed within the tank I and the door 2 closed. The tank is then evacuated until an absolute pressure below the vapor pressure of water at the prevailing temperature is reached. Thus at a room temperature of 20 C. the pres sure is reduced to 15 mm. and preferably below 15 mm., say to 13 mm., the vapor pressure of water at this temperature being 17.5 mm. In evacuating the tank, air is vented through line I2, other lines, of course, being closed. Appropriate valves necessary to close all lines are, of course, provided and operated in any desired fashion.

When the desired pressure has been reached, water contained in the organic product will evapcrate or boil. If there is not sufficient moisture present for this purpose, free moisture may be introduced either as steam or water. In some instances it may prove desirable to steam the organic products before introduction in order that they may be moist enough to give oif water vapor under the vacuum so that there may be a thorough washing out of gases held by the same by the generated water vapor. In some instances it may prove desirable to introduce dry steam at atmospheric temperatures during the evacuatin treatment. A steam boiler 30 connected to the manifold 3 is controlled by valve 3|. It is preferred that such introduction should be in a manner to wash through products in the chamber, as for example by admission through a large number of openings beneath the products. Similar results may also be obtained by introducing steam at the top of the chamber and drawing off air at the bottom, preferably beneath the products. The operation of the pump and the evacuation is continued until tests indicate the substantial or complete elimination of oxygen from the tank.

In many instances, it is desirable to evacuate the tank to a pressure below the vapor pressure of water at the prevailing temperature and then to introduce water vapor at the maximum, or about the maximum pressure of water at the prevailing temperature. This operation may be repeated several times.

During this pumpingoperation the efliciency of the vacuum pump 6 is enormously increased by the use of the condenser l9 which at 15 mm. pressure and a temperature of 33 will condense approximately two-thirds by volume of the outgoing water vapor. By lowering the temperature, another ten or eleven degrees centigrade, approximately 60% of the remaining water may be condensed.

;The introduction of water vapor. steam or water may, of course, be controlled so as to adjust the moisture content of the products concerned to the desired point.

The complete elimination of air from the chamber results in the prevention of packing of air within the interstices of the product upon introduction oi. other gas at higher pressure. Thus, in ordinary fumigation .or in steaming of the products for fumigating or other purposes, when there is air left in the organic products as, for example, within a bag of rice or a bale of tobacco, or the --like, upon the introduction of gas at a higher pressure the air is driven toward the 1 center of the bag or bale and diffusion of it therefrom is very slow. However, when water vapor atures, this packing of vapor can result only in the condensation'of water vapor in excess of its vapor pressure at the current temperature and there can never be an excess of condensible gas in the interstices of the product.

When oxygen has been eliminated to the desired point, fumigant may be introduced. A preferable fumigant is ethylene oxide, one part of which is generally combined with nine parts of carbon dioxide. The use of such a high ratio of carbon dioxide is partially for the purpose of reducing the infiammability of the gas, however, and in the present operation, due to the absence of oxygen, such precautions are unnecessary and higher percentages of ethylene oxide may be used or the carbon dioxide may be eliminated entirely. The invention is, of course, applicable with all other gaseous fumigants, such as methyl formate, methyl bromide, hydrogen cyanide, or the like, or mixtures of such gases with other gases.

It is preferred to introduce large amounts of these gases, the pressure within the tank I frequently being raised above atmospheric. Such pressure not only results in complete fumigation much more rapidly than with pressures now in use, but prevents contamination of the gases by leakage of air into the chamber.

After the fumigant has been introduced, or during its introduction, if desired, it may be recirculated by operation of the pump 6 (by-pass the condenser I 9, if desired).

After the materials in the tank have been thoroughly fumigated, the fumigant may be removed through the line 9 by the compressor 20 and stored in the tank H. In order to remove the last traces of the fumigant, water vapor may again be employed, although in general it is preferred to leave a little of the fumigating material in the products. It is therefore preferred to have a compressor of large capacity and remove the fumigant with great rapidity.

When using a water soluble fumigant, water from the condensers l9 and 2| may, if desired, be treated to recover the fumigant.

The fumigating gas may likewise be treated with an oxygen remover to remove traces of oxygen picked up during recycling.

Heat losses may be made up by conduction through the walls of the chamber, these walls normally being of steel, or heating coils, or other heating means may be used if desired. Where time is of importance, it may be desirable to preliminarily heat the products to some non-injurious point, which will, however, be well within the atmospheric range. A temperature of F. will produce a vapor pressure of approximately 49 mm. compared to 19 at 70 F. A temperature of 122 F. will produce a vapor pressure of 92 mm.

Air, sterilized air, or an inert gas, such as carbon dioxide may then be introduced to the chamber, after which the products are removed.

The process may also be employed for adjusting the water content of the food or organic products being treated either in combination with fumigation or separately. Thus, where food products or organic products are too dry before introduction into the chamber, the steaming may be so controlled and extended that the moisture content thereof will be adjusted to the desired point. On the other hand, when the products are too wet the pressure may be lowered enough to cause evaporation, and continued until the desired amount shall have evaporated. The pressure and temperatures required for this purpose depend upon the vapor pressure of water in connection with the particular product undergoing treatment and the temperature. In many instances, it would be necessary, in order to evaporate moisture from the products, to go to pressures as low as .1 to .4 inch of mercury absolute. In order to reach such pressures it is of course desirable to use modern steam ejector apparatus. In many cases the steam may be introduced at considerably higher temperatures and pressures.

This treatment is particularly advantageous in connection with tobacco, cereal products, such as rice and wheat and dried fruits.

Surprisingly little variation in pressure may be used to produce considerable changes in moisture content of food products. For example, in connection with rice which had a moisture content of 8.52% initially the vessel was evacuated to 13 mm. pressure and then the pressure was raised with water vapor to 23 mm. with the resulting rise in water content to 8.87%. Of course, where larger or more rapid adjustments in moisture content are desired, higher water vapor pressures may be employed.

In certain instances it is desirable, as hereinbefore explained, to use a condensible gas, preferably water vapor or steam, to remove the fumigant. This may be accomplished by again lowering the pressure below the vapor pressure of the water in the products and either permitting the water therein to boil or by washing fumigant out with introduced water vapor or steam. In some cases the boiling of water vapor from the product may result in undesirable lowering of the moisture content thereof and in such cases or in cases where the moisture content is undesirably low,

this procedure may be followed by steaming of the product, preferably at low temperatures and pressures.

We claim:

1. The method of preventing packing of noncondensible gases in the interstices of a bulk product upon subjection to an increased gas pressure, which comprises boning a condensible gas of low vapor pressure within the product at a high vacuum and at substantially atmospheric temperatures and continuing the boiling until substantially all non-condensible gases are washed from the interstices and replaced by the condensible gas. and then introducing gas at substantially higher pressure.

2. The method as set forth in claim 1, in which the last gas is condensible.

3. The method of adjusting the moisture content of an organic product in a chamber, which comprises subjecting such product to an absolute pressure below the vapor pressure of water therein at substantially atmospheric temperature whereby water vapor within the product is boiled, continuing the boiling until substantially all air has been washed from the interstices thereof and then introducing water vapor at substantially higher pressure.

4. The method as set forth in claim 3 in which the product is a cereal product.

5. The method as set forth in claim 3 in which 40 the product is tobacco.

6. The method as set forth in claim 3 in which the product is a dried fruit.

7. The method as set forth in claim 3, in which substantially dry steam is introduced during the boiling at a pressure substantially higher than the pressure in the chamber.

8. The method as set forth in claim 3, in which steam is introduced during the evacuation of the chamber in a plurality of openings beneath the organic products.

9. The method which comprises subjecting an organic product to an absolute pressure below the vapor pressure of water in the product at atmospheric temperature in the presence of available water and continuing the removal of gas until substantially all gas has been. replaced by water vapor, introducing a fumigant gas at higher pressure, again lowering the pressure below the vapor pressure of water in the product in the presence of water to remove fumigant gas, and introducing steam at higher pressure in amounts to substantially modify the moisture content of the product undergoing treatment.

10. The method as set forth in claim 1 in which the process is repeated, using a different gas to raise the pressure.

11. A method of preventing packing of noncondensible gases in the interstices of a bulk product which comprises boiling a condensible gas of low vapor pressure within the product at substantially atmospheric temperatures at a high vacuum and continuing the boiling until substantially all non-condensible gases are washed from the interstices of the product and replaced by the condensible gas, and then introducing an impregnatingfluid. at substantially higher pressure.

12. The method of fumigating a moisture-containing product in bulk, which comprises subjecting the product at substantially atmospheric temperatures in a closed chamber to a high vacuum to produce boiling of contained moisture within the product and continuing the boiling until the interstices of the product have been substantially freed from oxygen and replaced by water vapor, and introducing a fumigating gas to the chamber at substantially higherpressure.

13. The method as set forth in claim 12, in which the fumigant is introduced to produce a super-atmospheric pressure in the chamber.

14. The method of preventing packing of noncondensible gas in the interstices of a plurality of articles in bulk contained in a chamber which comprises boiling a condensible gas of low vapor pressure within the articles by the imposition of a high vacuum at substantially atmospheric temperature, and maintaining the vacuum and boiling until substantially all non-condensible gas has been washed from the interstices of the articles by the boiled condensible gas, and then introducing a fumigating gas to the chamber at a substantially higher pressure.

15. The method as set forth' in claim 12, in which liquid water is added to the product prior to the boiling operation to provide available water for the boiling operation.

16. The method asset forth in claim 12, in which fumigant is retained in the chamber until fumigation is complete, and is then rapidly removedby the imposition of a high vacuum.

17. The methoid as-set forth in claim 12, in which dry steam is introduced at substantially higher pressure during the boiling operation.

' CHARLES J.MERRIAM.

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