MXPA98010830A - Solvent resupply method for use with a carbon dioxide cleaning system - Google Patents

Abstract

A method (40) of replenishing liquid carbon dioxide solvent (12a) in a liquid carbon dioxide dry cleaning system (10) or other dense phase carbon dioxide cleaning system. The method uses dry-ice or solid carbon dioxide, as a replenishing stock, thus reducing transportation, storage and handling costs. The method disposes (42) solid carbon dioxide blocks in a cleaning chamber after a cleaning cycle. Liquid carbon dioxide solvent is boiled (45) and is used to melt (46) the solid carbon dioxide blocks. Liquid carbon dioxide solvent produced by melting the solid carbon dioxide blocks is pumped (47) from the cleaning chamber into a storage tank to replenish the liquid carbon dioxide solvent.

Description

SOLVENT REPAIR METHOD FOR USE WITH A CARBON DIOXIDE CLEANING SYSTEM BACKGROUND The present invention relates in general to a method for use in cleaning systems and more particularly to a method for replenishing solvent for use in cleaning systems using dense phase carbon dioxide as a solvent. All conventional organic solvents used for degreasing or cleaning present either safety or health risks or are environmentally harmful. For example 1, 1, 1-trichloroethane reduces the ozone layer, the perchlorethylene is suspected to be a carcinogen, while petroleum-based solvents are flammable and produce smog. Carbon dioxide is an unlimited and economical natural resource, which is non-toxic, non-flammable, does not produce smog or reduce the ozone layer. In its dense phase form (both liquid and supercritical), it exhibits solvation properties typical of hydrocarbon solvents. Carbon dioxide is a good solvent for fats and oils, does not damage fabrics or dissolves common patterns. As such, carbon dioxide is an environmentally friendly solvent that can be used efficiently either to degrease a common part / substrate or to clean fabrics and clothing. Several patents describing cleaning equipment or processes that use carbon dioxide in dense phase (liquid and supercritical) as a cleaning solvent have been issued for both cleaning and / or degreasing parts or for dry cleaning garments. Some of those patents are the following. Patent of E.U. No. 4,012,194, U.S. Patent. No. 5,267,455 and US patent. No. 5,467,492. All these patents describe the use of a liquid carbon dioxide as a cleaning medium for fabrics and garments. The U.S. Patent No.5, 339, 844, the U.S. Patent. No. 5,316,591 and the U.S. Patent. No. 5,456,759 are directed to the cleaning and / or degreasing of parts using liquid carbon dioxide as a cleaning medium. The U.S. Patent 5,013,366 and the U.S. Patent. No. 5,068,040 describes a cleaning process through a phase shift with dense phase carbon dioxide and cleaning and sterilizing with supercritical carbon dioxide. An example of a typical dry cleaning system for garments with liquid carbon dioxide is described in the U.S. Patent. 5,467,492, issued November 21, 1995, which was assigned to the assignee of the present invention. This dry cleaning system with liquid carbon dioxide comprises a fenced cleaning vessel with a perforated cleaning basket inside, containing the charge to be cleaned, a tank that supplies the liquid carbon dioxide to the cleaning vessel, an apparatus for stirring the liquid inside the fenced cleaning container, which agitates the load of garments inside the perforated basket. Temperature and pressure control means are provided in order to maintain the preset temperature and pressure process parameters, together with means for separating the dirt from the fluid and recovering the solvent after a cleaning cycle. However, none of the patents of the prior art emit the aforementioned address related to the cost of replenishing the carbon dioxide solvent. This is a major element of the operating cost of dense phase carbon dioxide cleaning systems, because the transportation, storage and handling of compressed gases is very expensive. Accordingly, it is an object of the present invention to provide an improved method of replenishing the liquid carbon dioxide solvent in these dense phase carbon dioxide cleaning systems.

SUMMARY OF THE INVENTION In order to fulfill the foregoing and other objects, the present invention provides a method for replenishing the liquid carbon dioxide solvent in a dense phase carbon dioxide cleaning system. The method can be used with a dense phase carbon dioxide cleaning system comprised of a cleaning chamber, a storage tank containing the liquid carbon dioxide solvent, a pump (or other means) for introducing the cleaning solvent into the cleaning chamber, a separator or even means for removing the dissolved or dispersed dirt from the cleaning, a refrigerator / condenser and a heater in the distiller that provides the pressure and temperature control and an optional gas recovery condenser to recover gaseous carbon dioxide. The method uses blocks of solid carbon dioxide (dry ice) that is placed in the cleaning chamber after a cleaning cycle. The cleaning chamber is closed as by closing a door and the cleaning chamber is vented to the atmosphere for a predetermined period of time. As the solid carbon dioxide is purified, the resulting gaseous carbon dioxide is expelled into the air from the cleaning chamber. Then the cleaning chamber opens to the distiller (which is connected to the storage tank on the liquid side through a replacement line.) The heater in the distiller ignites and boils the gaseous carbon dioxide. hot gaseous melts the solid carbon dioxide blocks (dry ice) and the temperature of the resulting liquid carbon dioxide slowly rises to a set point, at this time the heater in the distiller is turned off, the main pump and dioxide is activated Liquid carbon is pumped from the cleaning chamber back to the storage tank The gaseous carbon dioxide left in the chamber can also be recovered back to the storage tank using the gas compressor The method can be used to replenish the solvent of carbon dioxide lost in systems that use cleaning processes with carbon dioxide in den phase It's using dry ice. Replenishing dry ice may also contain optional additives such as surfactants, static dissipation compounds or deodorants where appropriate (such as in the dry cleaning of garments). The present replenishment method is advantageously economical because the transport of the solvent and the replenishment in its liquid form requires costly high-pressure steel vessels and cumbersome distribution systems. The method reduces the operating costs of dense phase carbon dioxide cleaning systems and processes in general and specifically reduces the cost of dry cleaning processes of garments with liquid carbon dioxide as described in the Patent. from EU do not. 5,467,492. The savings result from a reduction in the storage costs of the carbon dioxide solvent, in the costs of transportation of the solvent and in the costs of handling the solvent when using the present method. BRIEF DESCRIPTION OF THE DRAWINGS The various features and advantages of the present invention can be more readily understood with reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent similar structural elements and in which: Figure 1 illustrates a dry cleaning system with liquid carbon dioxide whose liquid carbon dioxide solvent can be replenished using the methods in accordance with the principles of the present invention; and Figure 2 is a flow chart illustrating a method for replenishing the solvent of liquid carbon dioxide, in accordance with the principles of the present invention. DETAILED DESCRIPTION Referring to the figures of the drawings, Figure 1 illustrates an exemplary closed cycle liquid carbon dioxide cleaning system 10, whose liquid carbon dioxide solvent can be replenished using the methods 40 (Figure 2), in accordance with the principles of the present invention. Figure 1 depicts one embodiment of a carbon dioxide cleaning system 10 that can utilize the present invention and is presented only to illustrate the replenishment method provided by this invention. Thus, the present invention is not limited to being used only with the specific system 10 shown in Figure 1. The dry cleaning system with exemplary liquid carbon dioxide 10 has a cleaning chamber 11 or a pressure vessel 11 with a door or lid (not shown) that houses a perforated basket containing a load of garments that are for cleaning. A storage tank 12 containing the liquid carbon dioxide solvent 12a is coupled by an inlet valve of the three-outlet pump 21 to a pump 13 which supplies the cleaning chamber 11 with the liquid carbon dioxide solvent 12a. An outlet of the pump 13 is coupled by means of a three-outlet valve 22 to an intake valve of the cleaning chamber 23 which joins a plurality of nozzles 11b in the cleaning chamber 11. A first outlet 11c of the The cleaning chamber 11 is coupled by means of a lint trap 14 to a first inlet of the lint manifold valve 24. A second outlet lid of the cleaning chamber 11 is coupled to a second inlet of the inlet valve of the pump 21. The valve outlet of the lint collector 24 is coupled to a filter 15 that filters the liquid carbon dioxide solvent 12a. The outlet of the filter 15 is coupled through a condenser 16 to the inlet of the valve of the pump 21. An outlet of the storage tank 12 is coupled to the inlet of the valve of the pump 21. A cooling system 17 is coupled to the condenser 16 and has a condensing valve 25 for controlling the amount of refrigerant coupled to the condenser 16. The cleaning chamber 11 is coupled by means of a compressor valve 26 to a gas recovery compressor 18 which is used to compress the solvent of gaseous carbon dioxide 12b in its liquid state and coupling the compressed gaseous carbon dioxide 12a through a check valve 35 to the condenser 16 and back to the storage tank 12. A gas flow valve 27 is used to decoupling the gaseous carbon dioxide 12b from the cleaning chamber 11 to the distiller 19. The gaseous carbon dioxide 12b coupled through the delivery valve of gas 27 is also coupled by means of a condensing valve 28 to the condenser 16. The liquid solvent 12a from the storage tank 12 is fed to the distiller 19 through a valve 31. A heater 19a in the distiller 19 is used to lift the temperature of the liquid carbon dioxide, which melts the solid blocks of dry ice of carbon dioxide placed in the cleaning chamber 11 used in the present method 40, as will be described below and with reference to Figure 2. A second valve drain 32 is coupled to distiller 19 and used to drain the dirt left after distillation. A vent valve 33 is coupled to the outlet of the cleaning chamber 11 and used to vent the cleaning chamber 11 to the atmosphere, as will be discussed below. During the cleaning and circulation cycles of the liquid, the valves of three outlets 21, 22, 24 are in the "a" position, as shown in Figure 1, while during the liquid drain cycles, the valves of three outputs 21, 22, 24 are in position "b". In a typical cleaning cycle, the laundry load is placed in the perforated basket in the cleaning chamber 11 and its door or lid is closed. The liquid carbon dioxide solvent 12a from the storage tank 12 is pumped into the cleaning chamber 11 using the pump 13. At this time, a recirculation cycle is established (illustrated by the black lines in Figure 1, with the valves 21, 22, 24 set to the "a" configuration) when properly closing and opening the valves selected. The garment twill is stirred, while the liquid carbon dioxide 12a is recirculated by the pump 13 through the cleaning chamber 11., the lint collector 14, the filter train 15 and returns to the cleaning chamber 11. At the end of the agitation cycle, the liquid phase of the carbon dioxide solvent 12a is recovered again in the storage tank 12 using the pump 13, with valves 21, 22, 24 set to configuration "b". At this time in the cleaning cycle, the cleaning chamber 11 contains the load of garments lia and the gaseous carbon dioxide solvent 12b at approximately 700 psi. The cleaning chamber is decompressed at atmospheric pressure when the gas compressor 18 again recovers the gaseous carbon dioxide solvent 12b in the storage tank 12. At this time, the door of the cleaning chamber 11 opens and the load of clean garments is removed from the cleaning chamber 11. A fraction of the liquid sarcoon dioxide solvent 12a is lost during a clean cleaning season. At a minimum, this frassion is equivalent to the weight of a cleaning chamber filled with gaseous carbon dioxide 12b at atmospheric pressure, plus any gaseous carbon dioxide solvent 12b absorbed by the load of garments lia. Therefore, the storage tank 12 must be replenished on a periodic basis with the liquid carbon dioxide solvent 12a to compensate for the loss of gaseous carbon dioxide solvent 12b. Commercially, the liquid carbon dioxide solvent 12a is handled and transported in pressurized cylinders. Except for bulky low-pressure storage containers, these cylinders do not become asylated and do not refrigerate. The liquid carbon dioxide solvent 12a contained in such cylinders, therefore, is at room temperature and is maintained at a relatively high pressure, typically about 850 psi. Bulky containers for storing the liquid sarcomonous dioxide 12a at low pressure (typically at or about 200-350 psi), are well insulated and equipped with a cooling medium to control and limit the internal pressures and temperatures within the containers bulky In both cases, the cost of the liquid carbon dioxide solvent 12a for a customer is a function of the cost of handling and storage of the pressurized containers and the shipping weight of the containers. In addition to this, the method for introducing the replenishing liquid carbon dioxide solvent 12a into the storage tank 12 requires an additional external pump (not shown), thus increasing the installation costs. Referring now to Figure 2, it is a flow diagram illustrating a method 40 according to the principles of the present invention for replenishing the liquid carbon dioxide solvent 12a in system 10. The present invention provides in 41 blocks or bricks of solid carbon dioxide (which may also contain for example, additives, such as surfactants, a static dissipation compound and / or deodorant), which are used to replenish or replenish the liquid carbon dioxide solvent 12a in the tank. Storage 12. Solid carbon dioxide blocks comprise solid dry ice that is at a temperature of -109.3 degrees Fahrenheit and that is transported and stored using thermal insulation, without containing pressure, thus reducing total costs and complexity of replenishment or replenishment . Solid dry carbon dioxide blocks of dry ice can be introduced into the cleaning system 10 in the manner described below and with reference to Figure 2. The blocks of solid carbon dioxide are placed in 42, in the perforated basket in the chamber of cleaning 11, for example, typically at the end of the working day and the door of the cleaning chamber 11 closes. The vent valve 33 is opened for a predetermined period of time and the air 43 is expelled from the cleaning chamber 11 by purifying the blocks of solid carbon dioxide, because carbon dioxide is heavier than air. The vent valve 33 is then closed and the gas flow valve 27 between the cleaning chamber 11 and the distiller 19 is opened at 44, towards the cleaning chamber 11. The heater 19a in the distiller 19 is turned on, which Boil in 45, the liquid carbon dioxide solvent 12a. The boiled liquid carbon dioxide is introduced at 46, into the cleaning chamber 11, which in turn heats the cleaning chamber 11 and the blocks of solid carbon dioxide.

The dry carbon solid carbon dioxide blocks are melted at 47 and converted from solid to liquid in the cleaning chamber 11 and the temperature of the resulting carbon dioxide rises until a predetermined temperature (54 degrees Fahrenheit) is reached. At this time, the valves 21, 22, 24 are switched to the "b" position, the pump 13 is turned on and the liquid carbon dioxide 12a produced by melting the blocks of solid carbon dioxide is pumped at 48, from the chamber of cleaning 11 to the storage tank 12. The heater 19a is then turned off. The compressor 18 is turned on and the gaseous carbon dioxide 12b is recondensed at 49, in the storage tank 12. The system 10 is now ready for the next cleaning cislo. The method 40 reduces the operating costs of the cleaning systems 10 which generally use dense phase carbon dioxide and specifically the operating cost of the liquid carbon dioxide jet cleaning system described for example in the U.S. Patent. No. 5,467,492, by reducing the cost of the solvent replenishment and replenishment process. In this way, a method for replenishing the solvent used in a dry cleaning system with liquid carbon dioxide has been described. It should be understood that the described embodiment is merely illustrative of some of the many specific embodiments that represent the applications of the principles of the present invention. Clearly, numerous and other facilities can be readily devised by those skilled in the art without departing from the scope of the invention.

Claims (12)

1. NOVELTY OF THE INVENTION Having described the present invention is considered as a novelty and therefore the content of the following claims is claimed as property. 1. A method for replenishing the solvent used in a liquid carbon dioxide cleaning system, which has a cleaning chamber, a storage tank containing the liquid carbon dioxide solvent, a pump for pumping the liquid solvent from the storage tank towards the cleaning chamber, a gas recovery compressor for compressing the gaseous solvent in its liquid state, a condenser for recondensing the gaseous carbon dioxide and a distiller containing a heater for heating the liquid solvent, said method characterized by the steps of: providing blocks of solid carbon dioxide, - placing blocks of solid carbon dioxide in the cleaning chamber; venting the cleaning chamber to the atmosphere for a predetermined period of time to expel the air from the cleaning chamber; ventilate the cleaning chamber towards the distiller; boiling the liquid solvent in the distiller to produce the boiling gaseous solvent; introduce the boiling gaseous solvent into the cleaning chamber; melt the blocks of solid carbon dioxide in the cleaning chamber, using the boiling gaseous solvent from the distiller; and pumping the molten carbon dioxide blocks from the cleaning chamber to the storage tank to replenish the liquid solvent.
2. 2. The method according to claim 1, characterized in that the blocks of solid carbon dioxide contain a static dissipation compound.
3. 3. The method according to claim 1, characterized in that the blocks of solid carbon dioxide contain a surfactant.
4. 4. The method according to claim 1, characterized in that the blocks of solid carbon dioxide contain a deodorant.
5. 5. The method according to claim 1, characterized in that the solid carbon dioxide blocks comprise solid dry ice.
6. 6. A method for replenishing the solvent used in a dense phase carbon dioxide cleaning system, which has a cleaning chamber, a storage tank containing the dense phase carbon dioxide solvent, a pump for pumping the solvent from the storage tank towards the cleaning chamber and a distiller containing a heater for heating the solvent, said method characterized by the steps of: placing the blocks of solid carbon dioxide in the cleaning chamber; boil the solvent in dense phase in the distiller to produce the boiling gaseous solvent; melt the blocks of solid carbon dioxide, using the boiling gaseous solvent from the distiller; and pumping the molten carbon dioxide blocks from the cleaning chamber into the storage tank to replenish the liquid solvent.
7. The method according to claim 6, further characterized by the steps of: before the boiling step, venting the cleaning chamber to the atmosphere for a predetermined period of time to expel air from the cleaning chamber; and ventilate the cleaning chamber towards the distiller.
8. 8. The method according to claim 6, characterized in that the blocks of solid carbon dioxide contain a static dissipation compound.
9. The method according to claim 6, characterized in that the blocks of solid carbon dioxide contain a surfactant.
10. The method according to claim 6, characterized in that the blocks of solid carbon dioxide contain a deodorant.
11. The method according to claim 6, characterized in that the solid carbon dioxide blocks comprise solid dry ice.
12. 12. A method to replenish the solvent used in a dense phase carbon dioxide processing system, which has a cleaning chamber, a storage tank containing the dense phase carbon dioxide solvent and a pump to pump the solvent from the storage tank towards the cleaning chamber, said method characterized by the steps of: placing the blocks of solid carbon dioxide in the chamber; boil the solvent in dense phase to produce the boiling gaseous solvent; melt the blocks of solid carbon dioxide, using the boiling gaseous solvent; and pumping the molten carbon dioxide blocks from the chamber to the storage tank to replenish the solvent therein.