Treatment of organic products

May 11, 1937. c. J. merriam et al 2,080,179

TREATMENT OF ORGANIC PRODUCTS Filed July 10, 1936

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Patented May 11, 1937

2,080,179

UNITED STATES PATENT OFFICE

2,089,179 TREATMENT OF ORGANIC PRODUCTS Charles J. Merriam, Winnetka, and Russell Wiles, Chicago, Hl., assignors to Guardite Corporation, a corporation of Illinois

Application July 10, 1936, Serial No. 89,982

Claims.

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 prod5 ucts, tobacco or the like, to vacuilm 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 prod10 ucts 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 difficulty in completely removing the air. The air cannot be entirely re15 moved, and being incondensible, when another gas 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 incondensi25 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 prod30 uct 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 35 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 Sas 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 7, 8 and 9 (Cl. 21—58) and may be operated by any suitable means (not shown). The pump preferably has a capacity sufficient to evacuate the chamber I within a few minutes. The discharge end of the pump connects with an oil separator 10 from which 5 line II connects with an air vent 12, with line 9 and also with line 13. The line 13 connects with the pressure vessel 14 and the line i 5. Pressure vessel 14 is adapted to withstand a substantially complete vacuum and also pressures up to 10 100 pounds super-atmospheric and is sufficiently large to hold fumigating gas sufficient for the entire fumigating operation. Suitable heating means may be provided in this vessel, and are indicated in the drawing by steam coil inlet .16 15 and outlet 17. A supply tank of fumigant is indicated at 18. A plurality of supply tanks may be used, if desired.

A condenser 19 is provided on the intake side of the vacuum pump and on account of the for- ₂o mation 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. ₂5

A compressor 20 is provided, for example, on the line 9 and a separator 21 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. ₃θ

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 35 water at the prevailing temperature is reached. Thus at a room temperature of 20° C. the pressure 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 49 evacuating the tank, air is vented through line 12, other lines, of course, being closed. Appropriate valves' necessary to close all lines are, of course, provided and operated in any desired fashion. 45

When the desired pressure has been reached, water contained in the organic product will evaporate or boil. If there is not sufficient moisture present for this purpose, free moisture may be introduced either as steam or water. In some 50 instances it may prove desirable to steam the organic products before introduction in order that they may be moist enough to give off water vapor under the vacuum so that there may be a thorough washing out of gases held by the same by 55

3,080,178 the generated water vapor. In some instances it may prove desirable to introduce dry steam at atmospheric temperatures during the evacuating treatment. A steam boiler 30 connected to the manifold 3 is controlled by valve 31. 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 pumping operation the efficiency of the vacuum pump 6 is enormously increased by the use of the condenser 19 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 of 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 center of the bag or bale and diffusion of it therefrom is very slow. However, when water vapor is used in the chamber at atmospheric temperatures, 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 inflammability 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 19, if desired).

After the materials in the tank have been 5 thoroughly fumigated, the fumigant may be removed through the line 9 by the compressor 20 and stored in the tank 14. In order to remove the last traces of the fumigant, water vapor may again be employed, although in general It is pre- 10 ferred 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 15 from the condensers 19 and 21 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. 20

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 pre- 25 liminarily heat the products to some non-injurious point, which will, however, be well within the atmospheric range. A temperature of 100° F. will produce a vapor pressure of approximately 49 mm. compared to 19 at 70° F. A temperature 30 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 35 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 40 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 de- 45 sired 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 50 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 modem steam ejector 55 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 60 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 con- 65 tent 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 mols- 70 ture 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 fumi- 75

3,080,179 gant. 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 boll 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, 10 this procedure may be followed by steaming of the product, preferably at low temperatures and pressures.