Patent Description:
Ethylene oxide (ETO) is a highly reactive organic compound whose high reactivity makes it useful in many different applications. Due to the high reactivity of ETO, ETO may be used as a surface disinfectant, or sterilizing agent. ETO as a sterilizing agent is well known for its effectiveness to sterilize objects at certain gas concentrations. The objects for sterilization are placed in a hermitically sealed chamber. ETO vapor is then pumped into the chamber to sterilize the objects.

However, due to the high reactivity, ETO gas is extremely flammable, toxic, and explosive. Even in the absence of air, ETO must be used with extreme caution in high concentrations at low pressures for sterilization purposes. Presently, high concentration ETO gas is not recyclable and may be used only once. After use, the ETO gas is then discharged to an emission control device for destruction.

There are a few current approaches for addressing the problem of emission and disposal of the ETO toxic gas, which solves one problem in exchange for creating another problem. For example, if ETO is absorbed into water, then the problem then becomes the treatment and discharge of the toxic water. If one tries to dispose of ETO by combustion means, the problem then becomes how to prevent an explosion (e.g., prevent an explosive reaction).

One method for reusing ETO gas involves the use of a low concentration mixture of ETO and an inert gas at higher process pressures. High process pressures (e.g., up to <NUM> atmospheres) allow an increase in the ETO gas concentration to an acceptable milligram per liter value for effective sterilization. Mixtures having ratios of ETO to inert gas of <NUM>/<NUM> and <NUM>/<NUM> are generally used. These mixtures have sufficient ETO concentrations to sterilize objects regardless of the material being sterilized under normal temperature and at above atmospheric pressure conditions. Relative non-flammability of diluted ETO and inert gas mixtures allows for the recycling of these mixtures. However, these mixtures are not as effective as higher concentrations of ETO gas for sterilization.

In addition, the concentration of ETO decreases with continual use during the sterilization process since ETO is consumed in reacting with bacteria, water vapor, alcohol and the like during the sterilization process. Furthermore, the ETO gas concentration may be reduced to an unsatisfactory concentration level to provide a consistent sterilization effect. Thus, low concentration gas mixtures require processing using higher pressure rated vessels, which are more expensive. This process further involves processing the gases at above atmospheric pressures which carries the risk of fugitive and catastrophic leakage. Consequently, in the industry today, all large ETO sterilizer chambers are designed to operate using low pressure and high concentrations of ETO gas. Existing sterilizers in use in the industry are not rated for the higher pressures that are required to recycle the low concentration ETO gas sterilant.

Thus, it is desirable to provide a system and method for recycling sterilant gas mixtures to a high concentration of ETO gas to obtain maximum sterilization effectiveness while minimizing the complexity of the process and the cost of the sterilization equipment. It is desirable to provide a system that can be retrofitted to existing sterilization facilities, by the utilization of the existing sterilization process equipment and avoiding the expenses that are associated with complete system replacement.

Reference <CIT> discloses a method and an apparatus for recovering a sterilizing gas, in particular ethylene oxide (ETO), using a sterilizing chamber.

Reference <CIT> discloses a method and apparatus for recovering one or more components of a sterilizing gas, typically ethylene oxide mixed with a diluent.

Reference <CIT> discloses a vapor recovery apparatus which withdraws multicomponent vapor mixtures from a processing apparatus by condensation.

Reference <CIT> discloses a process and apparatus for sterilizing an object with a gaseous sterilizing agent which is recovered for reuse.

There is thus provided, in accordance with the present disclosure, a system for recovering a sterilization agent from a waste gaseous mixture including a pressure reducing throttling valve for reducing and maintaining a pressure of a waste gas from one or more sterilization chambers to a first predefined pressure of <NUM> bar. The waste gas includes a gaseous mixture of a sterilization agent, nitrogen gas, and water vapor. A first condenser is configured to receive the gaseous mixture via the pressure reducing valve, and to cool the gaseous mixture to a temperature below a boiling point temperature and above a freezing point temperature of the water vapor at the first predefined pressure. A first tank, coupled to the first condenser, stores the condensed water vapor separated from the gaseous mixture in the first condenser. A separation pump coupled to the first tank raises the pressure of the gaseous mixture to a second predefined pressure. A second condenser is configured to receive the gaseous mixture from the separation pump, to cool the gaseous mixture to a temperature below a boiling point temperature and above a freezing point temperature of the sterilization agent at the second predefined pressure causing the sterilization agent to condense into a liquid, and to discharge the nitrogen gas remaining in the gaseous mixture. A second tank, coupled to the second condenser, stores the sterilization agent separated from the gaseous mixture in the second condenser.

Furthermore, in accordance with the present disclosure, the sterilization agent is ethylene oxide (ETO).

Furthermore, in accordance with the present disclosure, the first predefined pressure is <NUM> bar (<NUM> pound per square inch) and the second predefined pressure is atmospheric pressure.

Furthermore, in accordance with some embodiments of the present disclosure, the boiling point temperature of the water vapor may be <NUM> deg C when the pressure of the gaseous mixture is <NUM> bar (<NUM> psi).

Furthermore, in accordance with some embodiments of the present disclosure, boiling point temperature of the ETO may be <NUM> deg C when the pressure of the gaseous mixture is atmospheric pressure.

Furthermore, in accordance with some embodiments not part of the present disclosure, the sterilization agent may be propylene oxide.

Furthermore, in accordance with some embodiments of the present disclosure, the system may include a chamber evacuation pump coupled to the pressure reducing valve for pumping the waste gas into the first condenser.

Furthermore, in accordance with some embodiments of the present disclosure, the system may include an exhaust warmer and a freezer economizer for recovering cooling energy in the system.

Furthermore, in accordance with some embodiments of the present disclosure, the system may include one or more H<NUM>O freezers coupled to the first condenser and the separation pump, and wherein each of the one or more H<NUM>O freezers may freeze H<NUM>O molecules in the water vapor to a freezer surface.

Furthermore, in accordance with some embodiments of the present disclosure, at least two H<NUM>O freezers from the one or more H<NUM>O freezers may be connected in parallel coupled between the first condenser and the separation pump.

Furthermore, in accordance with some embodiments of the present disclosure, the system may include an ETO freezer coupled to the second condenser for trapping residual vapors of the sterilization agent.

Furthermore, in accordance with some embodiments of the present disclosure, the system may include a waste gas holding tank coupled to the pressure reducing valve and to the one or more sterilization chambers for collecting the waste gas from the one or more sterilization chambers.

Furthermore, in accordance with some embodiments of the present disclosure, the system may include one or more ETO pre-condensers placed in series before the second condenser, wherein each of the one or more pre-condensers may have progressively lower temperatures above the temperature of the second condenser.

There is further provided, in accordance with the present disclosure, a method for recovering a sterilization agent from a waste gaseous mixture including receiving a waste gas from a sterilization chamber. The waste gas includes a gaseous mixture of a sterilization agent, nitrogen gas, and water vapor, A pressure of the gaseous mixture is reduced to a first predefined pressure so as to reduce a boiling point temperature of the sterilization agent to below the freezing point temperature of the water vapor in the gaseous mixture. The gaseous mixture with the pressure at the first predefined pressure is cooled to a temperature below a boiling point temperature and above the freezing point temperature of the water vapor. Condensed water vapor is removed from the gaseous mixture. The pressure of the gaseous mixture is raised to a second predefined pressure greater than the first predefined pressure so as to elevate a boiling point temperature of the sterilization agent in the gaseous mixture. The gaseous mixture at the second predefined pressure is cooled to a temperature below the boiling point temperature and above a freezing point temperature of the sterilization agent causing the sterilization agent to condense into a liquid. The liquid sterilization agent is separated from the gaseous mixture so as to recover the sterilization agent for reuse from the waste gas. The nitrogen gas remaining in the gaseous mixture is discharged.

Furthermore, in accordance with the present disclosure, the first predefined pressure is <NUM> bar (<NUM> pound per square inch (psi)) and the second predefined pressure is atmospheric pressure.

Furthermore, in accordance with some embodiments of the present disclosure, the boiling point temperature of the ETO may be <NUM> deg C when the pressure of the gaseous mixture is atmospheric pressure.

Furthermore, in accordance with some embodiments of the present disclosure, discharging the nitrogen gas may include discharging the nitrogen gas to the atmosphere or collecting the discharged nitrogen gas for reuse.

Furthermore, in accordance with some embodiments of the present disclosure, the method may include recovering cooling energy in the system by using an exhaust warmer and a freezer economizer.

Furthermore, in accordance with some embodiments of the present disclosure, the method may include freezing H<NUM>O molecules in the water vapor to a freezer surface of one or more H<NUM>O freezers.

Furthermore, in accordance with some embodiments of the present disclosure, at least two H<NUM>O freezers from the one or more H<NUM>O freezers may be connected in parallel, and the method may include defrosting at least one of the H<NUM>O freezers from the at least two parallel H<NUM>O freezers.

Furthermore, in accordance with some embodiments of the present disclosure, the method may include trapping residual vapors of the sterilization agent using one or more ETO freezers coupled to the second condenser.

Furthermore, in accordance with some embodiments of the present disclosure, at least two ETO freezers from the one or more H<NUM>O freezers may be connected in parallel, and the method may include defrosting at least one of the ETO freezers from the at least two parallel ETO freezers.

Furthermore, in accordance with some embodiments of the present disclosure, the method may include collecting the waste gas from the one or more sterilization chambers in a waste gas holding tank.

Furthermore, in accordance with some embodiments of the present disclosure, the method may include setting the temperatures of each of one or more ETO pre-condensers placed in series before the second condenser to progressively lower temperatures above the temperature of the second condenser.

In order for the embodiments of the present disclosure to be better understood and for its practical applications to be appreciated, the following Figures are provided and referenced hereafter. It should be noted that the Figures are given as examples only and in no way limit the scope of the embodiments of the present disclosure. Like components are denoted by like reference numerals.

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the disclosure. However, it will be understood by those of ordinary skill in the art that the embodiments of the disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, components, modules, units and/or circuits have not been described in detail so as not to obscure the embodiments of the disclosure.

Although embodiments of the disclosure are not limited in this regard, discussions utilizing terms such as, for example, "processing," "computing," "calculating," "determining," "establishing", "analyzing", "checking", or the like, may refer to operation(s) and/or process(es) of a computer, a computing platform, a computing system, or other electronic computing device, that manipulates and/or transforms data represented as physical (e.g., electronic) quantities within the computer's registers and/or memories into other data similarly represented as physical quantities within the computer's registers and/or memories or other information non-transitory storage medium (e.g., a memory) that may store instructions to perform operations and/or processes. Although embodiments of the disclosure are not limited in this regard, the terms "plurality" and "a plurality" as used herein may include, for example, "multiple" or "two or more". The terms "plurality" or "a plurality" may be used throughout the specification to describe two or more components, devices, elements, units, parameters, or the like. Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Additionally, some of the described method embodiments or elements thereof can occur or be performed simultaneously, at the same point in time, or concurrently. Unless otherwise indicated, use of the conjunction "or" as used herein is to be understood as inclusive (any or all of the stated options).

Embodiments of the present disclosure herein describe a method and a system for recovering a sterilization agent from a waste gaseous mixture. The sterilization agent as described herein may be, for example, ethylene oxide (ETO). The system may operate at pressure below and/or at atmospheric pressure and uses few moving parts. The energy efficient system may be configured to recover ETO that is clean and reusable while emitting an exhaust with a level of ETO at part-per-million (ppm) levels.

After the sterilization agent is used for sterilizing items and/or objects on a closed sealed sterilization chamber, the sterilization waste gas pumped out of the sterilization chamber may include a gaseous mixture of inert nitrogen gas, the sterilization agent, such as ethylene oxide gas, and water vapor. This system leverages the differences in the vapor pressures, and the boiling and freezing points of these three gases in order to separate them. As a result, clean nitrogen gas and liquid water may be safely isolated and disposed of, while the valuable ethylene oxide gas may be recollected at high purity, suitable to be reused after appropriate quality testing.

In the embodiments taught herein, the process for recovering a sterilization agent from a waste gaseous mixture may be achieved by lowering the gas pressure to a level where the freezing point of the two components are drastically different. The ethylene oxide molecules have sufficient energy to remain in the gas phase but does not covalently bind to water molecules that are being condensed and cooled from liquid phase, and removing the water from the mixture. In some embodiments, the mixture may be further cooled such that the water molecules may be frozen into the solid phase and the solid removed.

The pressure of the dry ethylene oxide gas may be then raised to normal atmospheric pressure so as to elevate its boiling point so as to condense the ETO into a liquid, which may be removed from the nitrogen gas component of the mixture. At the end of the process, pure, uncontaminated ethylene oxide liquid may be collected, ready to be inspected and reused. Clean waste water, safe and free from ethylene oxide contamination may be collected, tested and then discharged into the environment, for example. Similarly, the separated nitrogen gas, used in the sterilization process, may be discharged into an abatement system or into the atmosphere.

This is a "clean" process where the only waste products are nitrogen gas and water. No absorption materials or metal catalysts are needed, which would need to be disposed of periodically. This is also an intrinsically safe process the operation in that the waste gas from the sterilization chamber is maintained at or below atmospheric pressure, so that there is no ethylene oxide gas leakage out from the system. Furthermore, this 'cold' process may be carried out at near normal sterilization temperatures to cryogenic temperatures minimizing the risk of catastrophic explosions by staying well below ethylene oxide's autoignition temperature.

In the context of the present disclosure, two elements that are coupled together in the systems shown herein may refer to elements that may be physically connected together by tubes and pipes, for example, that may be thermally isolated to carry refrigerants, hermetic seals for preventing leaks, pressure valves, flanges, connectors and the like. The terms used herein such as waste gas, gaseous mixture, waste gaseous mixture, gas streams are all synonymous. They refer to a waste gas that is a gaseous mixture of chemical components emitted from a sterilization chamber that is progressively processed to remove, separate and/or purify the sterilization agent from the waste gas. These terms may refer to the original waste gas with all of its chemical components exiting the sterilization chamber, or the waste gas with any or part of its chemical components removed at any step of the process in recovering the sterilization agent.

<FIG> schematically illustrates a block diagram of a first embodiment of a system <NUM> for recovering a sterilization agent from a waste gaseous mixture, in accordance with some embodiments of the present disclosure. System <NUM> may include a sterilization chamber <NUM> coupled to a H<NUM>O condenser <NUM> (also known herein as a first condenser) and an ETO condenser <NUM> (also known herein as a second condenser). H<NUM>O condenser <NUM> may be coupled to H<NUM>O tank <NUM> (also known herein as a first tank), and ETO condenser <NUM> may be coupled to ETO tank <NUM> (also known herein as a second tank). H<NUM>O tank <NUM> and ETO tank <NUM> may be respectively used for storing the H<NUM>O liquid and ETO during their separation processes from the gaseous mixture. The gaseous mixture of waste gas from sterilization chamber <NUM> may be pumped into H<NUM>O condenser <NUM> via a pressure reducing valve <NUM> using a chamber evacuation pump <NUM>.

In some embodiments of the present disclosure, pressure reducing valve <NUM> may reduce the pressure of the gaseous mixture pumped into H<NUM>O condenser <NUM> to a first predefined value such as <NUM> bar (<NUM> psi) (e.g., pound per square inch), for example, or any suitable pressure valve, so as to reduce the boiling point temperature of the sterilization agent vapor component in the waste gas. The system elements operating at a reduced pressure are shown in reduced pressure region <NUM> (e.g., inside the dotted rectangle).

In some embodiments of the present disclosure, sterilization chamber <NUM> may include an enclosure with the objects and/or items to be sterilized, configured to withstand pressure variances. Sterilization chamber <NUM> may include inlet and/or outlet ports for removing air, injecting sterilization agent gases, and removing waste gases.

In some embodiments of the present disclosure, chamber evacuation pump <NUM> may include vacuum pumps of various types, capable of removing the waste gas from sterilization chamber <NUM>.

In some embodiments of the present disclosure, system <NUM> may include pressure reduction valve <NUM> which may be a throttling valve, capable of reducing and maintaining system pressure in reduced pressure region <NUM>.

In some embodiments of the present disclosure, H<NUM>O condenser <NUM> may include a shell-tube, plate or other type of heat exchanger, which may be cooled by chilled water or refrigerants. H<NUM>O condenser <NUM> may condense and trap water vaper and other contaminants, such as oil used by chamber evacuation pump <NUM>. H<NUM>O condenser <NUM> may also allow clean ETO gas, together with other inert gases, such as nitrogen (N<NUM>), to pass into ETO condenser <NUM>.

For a pressure of <NUM> bar (<NUM> psi), the boiling point of water may be reduced to <NUM> deg C, while the boiling point of ETO is -<NUM> deg C. H<NUM>O condenser <NUM> may be a heat exchanger that chills the gas mixture to about <NUM> deg C to condense the water vapor and contaminants from the sterilization process of the items and/or objects in sterilization chamber <NUM> such as oil, polymers formed by the sterilization agent, for example, that may be mixed into the water vapor.

An H<NUM>O discharge valve <NUM> may be used to discharge H<NUM>O and other contaminants stored in H<NUM>O tank <NUM>. Similarly, a vacuum release valve <NUM> may be used to release the vacuum inside reduced pressure region <NUM> so as to facilitate the discharge of material such as N<NUM> from H<NUM>O tank <NUM>.

In some embodiments of the present disclosure, the gaseous mixture with the water vapor removed in reduced pressure region <NUM> may be pumped into ETO condenser <NUM> by a separation pump <NUM> via a separation valve 4A, which separates reduced pressure region <NUM> in system <NUM> from normal pressure region <NUM> in system <NUM>. Separation valve 4A may allow the gaseous mixture with the water vapor removed to enter separation pump <NUM> which pumps the gaseous mixture into ETO condenser <NUM> while raising the pressure of the gaseous mixture to near atmospheric pressure.

In some embodiments of the present disclosure, separation pump <NUM> may include a vacuum pump capable of maintaining reduced pressures in reduced pressure region <NUM> (e.g., the region shown from pressure reduction valve <NUM> to separation pump <NUM>). Separation pump <NUM> may exhaust gases against atmospheric or near atmospheric pressure in a normal pressure region <NUM> from separation pump <NUM> to other abatement equipment/atmosphere as shown in <FIG>. Separation pump <NUM> may be a vacuum pump that is clean by design, namely that the vacuum pump does not introduce additional containments into the gaseous mixture. Separation pump <NUM> may include "dry" vacuum pumps, "oil-less" and "near-oil-less" vacuum pumps, and/or "diaphragm" vacuum pumps.

In some embodiments of the present disclosure, ETO condenser <NUM> may include a shell-tube, plate or other type of heat exchanger which may be cooled by coolant or refrigerant. ETO condenser <NUM> may condense and trap ETO vapors as well as other desirable dilutant such as CO<NUM>, while allowing non-condensable dilutant such as nitrogen (N<NUM>), to pass through to the other abatement equipment/atmosphere.

In some embodiments of the present disclosure, ETO condenser <NUM> may chill the gas mixture to a predefined temperature of about -<NUM> deg C (e.g., slightly higher than the ETO melting point temperature of -<NUM> deg C) for condensing the ETO into an ETO vapor. The ETO vapor may include CO<NUM>. ETO tank <NUM> may be used to store the condensed ETO (and CO<NUM> mixture, if any) until reuse. An ETO discharge valve <NUM> may be used to discharge ETO (and CO<NUM> mixture, if any) for reuse.

The following embodiments shown in <FIG> schematically illustrate modifications to the basic system configuration shown in <FIG> for improving the system energy efficiency and throughput while recovering a sterilization agent such as ETO from a waste gaseous mixture output from the sterilization chamber.

<FIG> schematically illustrates a block diagram of a second embodiment of a system <NUM> for recovering a sterilization agent from a waste gaseous mixture, in accordance with some embodiments of the present disclosure. System <NUM> may include the same elements of system <NUM> as shown in <FIG>. However, the difference between system <NUM> and system <NUM> is that system <NUM> may include an H<NUM>O freezer <NUM> after H<NUM>O condenser <NUM>, and an ETO freezer <NUM> after ETO condenser <NUM>. H<NUM>O freezer <NUM> and/or ETO freezer <NUM> are heat exchangers.

H<NUM>O Freezer <NUM> may be a shell-tube, plate or other type of heat exchanger, cooled by chilled water, a coolant, or a refrigerant, which may further trap residual water vapor in the gaseous mixture that may have passed through H<NUM>O condenser <NUM> by freezing the molecules to a surface of H<NUM>O Freezer <NUM>. H<NUM>O Freezer <NUM> may allow clean ETO gas, together with other inert gases, such as nitrogen, to pass through.

Similarly, ETO Freezer <NUM> may be shell-tube, plate or other types, cooled by a coolant, a compressed refrigerant, or liquid gas type refrigerant, such as liquid nitrogen, for example, which may further trap residual ETO vapor and condensable dilutants such as CO<NUM> vapors, that have passed through ETO condenser <NUM> by freezing the molecules to a surface of ETO Freezer <NUM>. ETO Freezer <NUM> may allow clean nitrogen gas to pass through an atmospheric exhaust valve <NUM> to the atmosphere.

<FIG> schematically illustrates a block diagram of a third embodiment of a system <NUM> for recovering a sterilization agent from a waste gaseous mixture, in accordance with some embodiments of the present disclosure. System <NUM> may include the same elements of system <NUM> as shown in <FIG>. However, the difference between system <NUM> and system <NUM> is that between separation pump <NUM> and ETO condenser <NUM>, system <NUM> may include an after cooler <NUM> coupled to separation pump <NUM> followed by an exhaust warmer <NUM> and an ETO pre-condenser 50a coupled to ETO condenser <NUM>. Similarly, an ETO freezer economizer <NUM> may be coupled between ETO condenser <NUM> and ETO Freezer <NUM>. Exhaust warmer <NUM> may also be coupled to ETO freezer economizer <NUM> and to atmospheric exhaust valve <NUM>.

After cooler <NUM> may be a heat exchanger that may be used to cool the hot compressed gas from separation pump <NUM> using cold water, for example. ETO Pre-condenser 50a may include one or more heat exchangers that may be placed before and coupled to ETO condenser <NUM> so as to provide progressive stages of cooling the gas mixture so as to reduce the heat loading on ETO condenser <NUM>.

ETO Freezer Economizer <NUM> may be a heat exchanger that pre-cools and pre-freezes the gaseous mixture entering ETO Freezer <NUM> using cooling energy from the exhaust gas of ETO Freezer <NUM>.

Exhaust warmer <NUM> may be a heat exchanger used for pre-cooling and pre-condensing the gaseous mixture entering the ETO pre-condensers using cooling energy from the exhaust gas of ETO Freezer Economizer <NUM> and pre-warms the exhaust gas to near ambient temperature before venting the gas to the atmosphere via atmospheric exhaust valve <NUM>.

<FIG> schematically illustrates a block diagram of a fourth embodiment of a system <NUM> for recovering a sterilization agent from a waste gaseous mixture, in accordance with some embodiments of the present disclosure. System <NUM> may include the same elements of system <NUM> as shown in <FIG>. However, system <NUM> may include one or more H<NUM>O freezers and one or more ETO freezers connected in parallel. This may be shown schematically in <FIG> as two H<NUM>O freezers <NUM> and <NUM>' and ETO Freezers <NUM> and <NUM>' connected in parallel.

In some embodiments of the present disclosure, one of the H<NUM>O freezers (e.g., H<NUM>O freezer <NUM>) may be performing the freezing operation, while the other H<NUM>O freezer (e.g., H<NUM>O freezer <NUM>') may be thawed out or defrosted in order to prevent a build-up of solid ice on any one of the H<NUM>O freezer surfaces, Similarly, one of the ETO freezers e.g., ETO freezer <NUM>) may be performing the freezing operation, while the other ETO freezer (e.g., ETO freezer <NUM>') may be thawed out in order to prevent a build-up of solid ETO on any one of the H<NUM>O freezer surfaces.

In some embodiments of the present disclosure, control and/or release valves may be placed before and/or after each of the two freezers that may be placed in parallel which may be used to control which freezer may route and cool the gaseous mixture while the other freezer is defrosting or de-thawing. In this manner, the entire process does not need to be halted so as to remove solid water ice and/or solid ETO by using the ETO and/or H<NUM>O parallel freezers.

<FIG> schematically illustrates a block diagram of a fifth embodiment of a system <NUM> for recovering a sterilization agent from a waste gaseous mixture, in accordance with some embodiments of the present disclosure. System <NUM> may include all of the elements of systems <NUM> and <NUM> shown in the previous <FIG> with additional elements for further improving the energy efficiency relative to the previous figures.

The following description uses the system embodiments shown in <FIG> for providing a summary of the processes highlighting the different steps for recovering a sterilization agent from a waste gaseous mixture from sterilization chamber <NUM> in accordance with some embodiments of the present disclosure. All or part of these steps described hereinbelow may be applicable to each of the figures described herein:.

The process for recovering and/or purifying a sterilization agent from a waste gas mixture as described hereinabove is not be way of limitation of the embodiments of the present disclosure. All or any steps of this process may be used in any of the <FIG> shown herein in any suitable combination or order. The sterilization agent is not limited herein to ETO but may include other sterilization agents such as propylene oxide. for example.

<FIG> schematically illustrates a block diagram of a sixth embodiment of a system <NUM> for recovering a sterilization agent from a waste gaseous mixture, in accordance with some embodiments of the present disclosure. System <NUM> may include elements of system <NUM>. However, the waste gaseous mixture processed by system <NUM> may be the waste gas from one or more sterilization chambers, denoted sterilization chamber <NUM>, sterilization chamber <NUM>', and sterilization chamber <NUM>". Each of the one or more sterilization chambers may include respective one or more evacuation pumps denoted chamber evacuation pump <NUM>, chamber evacuation pump <NUM>', and chamber evacuation pump <NUM>" and one or more respective chamber waste gas exhaust valves denoted chamber waste gas exhaust valve <NUM>, chamber waste gas exhaust valve <NUM>', and chamber waste gas exhaust valve <NUM>".

The waste gas from each of the one or more sterilization chambers may pass into a waste holding tank <NUM> and then coupled into the reduce pressure region <NUM> via pressure reducing valve <NUM> and normal pressure region <NUM> for recovering the ETO sterilization agent from the waste gas from the one or more sterilization chambers. Stated differently, the waste gases from the multiple sterilization chambers may be processed by a single sterilization agent recovery/process system as shown in <FIG>. Waste holding tank <NUM> may be of a variable volume so that pressure in the tank may be kept at atmospheric pressure, or a fixed volume type of tank.

<FIG> is a flowchart depicting a method <NUM> for recovering a sterilization agent from a waste gaseous mixture, in accordance with some embodiments of the present disclosure.

Method <NUM> may include receiving <NUM> a waste gas from a sterilization chamber. The waste gas may include a gaseous mixture of a sterilization agent, nitrogen gas, and water vapor.

Method <NUM> may include reducing <NUM> a pressure of the gaseous mixture to a first predefined pressure so as to reduce a boiling point temperature of the sterilization agent to below a freezing point temperature of the water vapor in the gaseous mixture.

Method <NUM> may include cooling <NUM> the gaseous mixture with the pressure at the first predefined pressure to a temperature below a boiling point temperature and above the freezing point temperature of the water vapor, and removing condensed water vapor from the gaseous mixture.

Method <NUM> may include raising <NUM> the pressure of the gaseous mixture to a second predefined pressure greater than the first predefined pressure so as to elevate a boiling point temperature of the sterilization agent in the gaseous mixture.

Method <NUM> may include cooling <NUM> the gaseous mixture at the second predefined pressure to a temperature below the boiling point temperature and above a freezing point temperature of the sterilization agent causing the sterilization agent to condense into a liquid.

Method <NUM> may include separating <NUM> the liquid sterilization agent from the gaseous mixture so as to recover the sterilization agent for reuse from the waste gas.

Method <NUM> may include discharging <NUM> the nitrogen gas remaining in the gaseous mixture to the atmosphere or collecting the nitrogen gas for reuse.

In the present disclosure, a system for recovering a sterilization agent from a waste gaseous mixture includes a pressure reducing valve for reducing and maintaining a pressure of a waste gas from one or more sterilization chambers to a first predefined pressure of <NUM> bar. The waste gas includes a gaseous mixture of a sterilization agent, nitrogen gas, and water vapor. A first condenser is configured to receive the gaseous mixture via the pressure reducing valve, and to cool the gaseous mixture to a temperature below a boiling point temperature and above a freezing point temperature of the water vapor at the first predefined pressure. A first tank, coupled to the first condenser, stores the condensed water vapor separated from the gaseous mixture in the first condenser. A separation pump coupled to the first tank raises the pressure of the gaseous mixture to a second predefined pressure. A second condenser is configured to receive the gaseous mixture from the separation pump, to cool the gaseous mixture to a temperature below a boiling point temperature and above a freezing point temperature of the sterilization agent at the second predefined pressure causing the sterilization agent to condense into a liquid, and to discharge the nitrogen gas remaining in the gaseous mixture. A second tank, coupled to the second condenser, stores the sterilization agent separated from the gaseous mixture in the second condenser.

Further, the sterilization agent comprises ethylene oxide (ETO).

In the present disclosure, the first predefined pressure is <NUM> bar (<NUM> pound per square inch) and the second predefined pressure is atmospheric pressure.

In some embodiments of the present disclosure, the boiling point temperature of the water vapor may be <NUM> deg C when the pressure of the gaseous mixture is <NUM> bar (<NUM> psi).

In some embodiments of the present disclosure, boiling point temperature of the ETO may be <NUM> deg C when the pressure of the gaseous mixture is atmospheric pressure.

In some embodiments not part of the present disclosure, the sterilization agent may be propylene oxide.

In some embodiments of the present disclosure, the system may include a chamber evacuation pump coupled to the pressure reducing valve for pumping the waste gas into the first condenser.

In some embodiments of the present disclosure, the system may include an exhaust warmer and a freezer economizer for recovering cooling energy in the system.

In some embodiments of the present disclosure, the system may include one or more H<NUM>O freezers coupled to the first condenser and the separation pump, and wherein each of the one or more H<NUM>O freezers may freeze H<NUM>O molecules in the water vapor to a freezer surface.

In some embodiments of the present disclosure, at least two H<NUM>O freezers from the one or more H<NUM>O freezers may be connected in parallel coupled between the first condenser and the separation pump.

In some embodiments of the present disclosure, the system may include an ETO freezer coupled to the second condenser for trapping residual vapors of the sterilization agent.

In some embodiments of the present disclosure, the system may include a waste gas holding tank coupled to the pressure reducing valve and to the one or more sterilization chambers for collecting the waste gas from the one or more sterilization chambers.

In some embodiments of the present disclosure, the system may include one or more ETO pre-condensers placed in series before the second condenser, wherein each of the one or more pre-condensers may have progressively lower temperatures above the temperature of the second condenser.

In the present disclosure, a method for recovering a sterilization agent from a waste gaseous mixture includes receiving a waste gas from a sterilization chamber. The waste gas includes a gaseous mixture of a sterilization agent, nitrogen gas, and water vapor, A pressure of the gaseous mixture is reduced to a first predefined pressure so as to reduce a boiling point temperature of the sterilization agent to below the freezing point temperature of the water vapor in the gaseous mixture. The gaseous mixture with the pressure at the first predefined pressure is cooled to a temperature below a boiling point temperature and above the freezing point temperature of the water vapor. Condensed water vapor is removed from the gaseous mixture. The pressure of the gaseous mixture is raised to a second predefined pressure greater than the first predefined pressure so as to elevate a boiling point temperature of the sterilization agent in the gaseous mixture. The gaseous mixture at the second predefined pressure is cooled to a temperature below the boiling point temperature and above a freezing point temperature of the sterilization agent causing the sterilization agent to condense into a liquid. The liquid sterilization agent is separated from the gaseous mixture so as to recover the sterilization agent for reuse from the waste gas. The nitrogen gas remaining in the gaseous mixture is discharged.

Further, the sterilization agent is ethylene oxide (ETO).

In the present disclosure, the first predefined pressure is <NUM> bar (<NUM> pound per square inch (psi)) and the second predefined pressure is atmospheric pressure.

In some embodiments of the present disclosure, the boiling point temperature of the ETO may be <NUM> deg C when the pressure of the gaseous mixture is atmospheric pressure.

In some embodiments of the present disclosure, discharging the nitrogen gas may include discharging the nitrogen gas to the atmosphere or collecting the discharged nitrogen gas for reuse.

In some embodiments of the present disclosure, the method may include recovering cooling energy in the system by using an exhaust warmer and a freezer economizer.

In some embodiments of the present disclosure, the method may include freezing H<NUM>O molecules in the water vapor to a freezer surface of one or more H<NUM>O freezers.

In some embodiments of the present disclosure, at least two H<NUM>O freezers from the one or more H<NUM>O freezers may be connected in parallel, and the method may include defrosting at least one of the H<NUM>O freezers from the at least two parallel H<NUM>O freezers.

In some embodiments of the present disclosure, the method may include trapping residual vapors of the sterilization agent using one or more ETO freezers coupled to the second condenser.

In some embodiments of the present disclosure, at least two ETO freezers from the one or more H<NUM>O freezers may be connected in parallel, and the method may include defrosting at least one of the ETO freezers from the at least two parallel ETO freezers.

In some embodiments of the present disclosure, the method may include collecting the waste gas from the one or more sterilization chambers in a waste gas holding tank.

In some embodiments of the present disclosure, the method may include setting the temperatures of each of one or more ETO pre-condensers placed in series before the second condenser to progressively lower temperatures above the temperature of the second condenser.

It should be understood with respect to any flowchart referenced herein that the division of the illustrated method into discrete operations represented by blocks of the flowchart has been selected for convenience and clarity only. Alternative division of the illustrated method into discrete operations is possible with equivalent results. Such alternative division of the illustrated method into discrete operations should be understood as representing other embodiments of the illustrated method.

Claim 1:
A system (<NUM>) for recovering a sterilization agent from a waste gaseous mixture, the system comprising:
a pressure reducing throttling valve (<NUM>) configured to reduce and maintain a pressure of a waste gas from one or more sterilization chambers (<NUM>, <NUM>', <NUM>") to a first predefined pressure of <NUM> bar, the waste gas comprising a gaseous mixture of a sterilization agent, nitrogen gas, and water vapor;
a first condenser (<NUM>) configured to receive the gaseous mixture via the pressure reducing valve, and to cool the gaseous mixture to a temperature below a boiling point temperature and above a freezing point temperature of the water vapor at the first predefined pressure;
a first tank (<NUM>), coupled to the first condenser (<NUM>), for storing the condensed water vapor separated from the gaseous mixture in the first condenser;
a separation pump (<NUM>) coupled to the first tank for raising the pressure of the gaseous mixture to a second predefined pressure equal to atmospheric pressure;
a second condenser (<NUM>), configured to receive the gaseous mixture from the separation pump (<NUM>), to cool the gaseous mixture to a temperature below a boiling point temperature and above a freezing point temperature of the sterilization agent at the second predefined pressure causing the sterilization agent to condense into a liquid, and to discharge the nitrogen gas remaining in the gaseous mixture; and
a second tank (<NUM>), coupled to the second condenser (<NUM>), for storing the sterilization agent separated from the gaseous mixture in the second condenser,
wherein the sterilization agent comprises ethylene oxide (ETO).