Apparatus and method for cleaning sterilizer exhaust gas

An apparatus for cleaning exhaust gas. The apparatus includes a housing having an upstream end configured to receive exhaust gas and a downstream end configured to release the exhaust gas. At least one coalescing filter layer and a catalyst filter layer are disposed within the housing. The catalyst filter layer includes molded sintered pellets formed from a porous material and a non-precious metal catalyst. The molded sintered pellets create a porous area for coalescing oil mist, and the catalyst hydrogen peroxide.

BACKGROUND

The present application relates generally to cleaning exhaust gas. In particular, the present application relates to the sterilization of objects using hydrogen peroxide vapor and for the decomposing of hydrogen peroxide vapor exhausted during the process. Systems are available for the sterilization of objects, such as medical instruments, utilizing hydrogen peroxide vapor to effect sterilization. In such systems, the objects are placed in a sterilization chamber and hydrogen peroxide vapor is pumped in. After the objects are sterilized, exhaust comprising hydrogen peroxide vapor is exhausted from the chamber. A need exists for reducing the concentration of hydrogen peroxide exhausted from the system.

SUMMARY OF THE INVENTION

Disclosed herein is a catalytic converter apparatus and method. The catalytic converter is comprised of different media to act as a sorb for oil mist and a catalyst for converting hydrogen peroxide into water and oxygen. The different media are disposed in a plurality of component layers within a housing through which exhaust comprising hydrogen peroxide vapor and possibly oil mist is passed prior to being emitted to the atmosphere. The component layers are not required to be coated with a precious metal catalyst.

DETAILED DESCRIPTION OF THE INVENTION

As shown inFIG. 1, a sterilization system10includes a sterilization chamber12. Exhaust from sterilization chamber12is pumped by a vacuum pump (not shown) into a catalytic converter14before being exhausted into the atmosphere. The exhaust may include hydrogen peroxide vapor from the sterilization process and oil mist from lubricating oil for the vacuum pump.

As shown inFIGS. 2 and 3, catalytic converter14comprises a plurality of component layers disposed within a housing16having an upstream end18and a downstream end20with respect to a direction of exhaust flow22. Housing16comprises a cylindrical outer portion24and an end cap26disposed at upstream end18. End cap26has an inlet28configured to allow exhaust from sterilization chamber12flow into and through the component layers disposed within housing16. As shown inFIG. 3, end cap26comprises a threaded joint30joining end cap26to housing16. The downstream end20of housing comprises an integral exhaust grate32. Housing16, end cap26and integral exhaust grate32are made from, for example, polyvinyl chloride (PVC) or other suitable materials.

In order, from the upstream end to the downstream end of housing, the component layers comprise one layer of each of the following components: a mesh layer34, a first foam layer36, a metal wool layer38, a filter layer40, and a second foam layer42.

Mesh layer34is of a suitable size, such as a 40×40 mesh, to screen any potential particle/debris backflow into the vacuum pump. The mesh layer34may be made of stainless steel or other suitable materials.

First foam layer36, metal wool layer38and second foam layer42act as coalescing filters to capture oil mist exhausting from the vacuum pump. The first and second foam layers36,42are preferably formed from reticulated foam having a dimensional latticework of interconnected ligaments forming a porous, open-celled sponge-like structure. Other suitable foam materials may also be used. First foam layer36also functions as a cushion between mesh layer34and metal wool layer38. Foam layer42also acts as the base foundation to support and cushion filter layer40. Metal wool layer38is preferably made from aluminum, but may also be made from other suitable materials such as stainless steel.

Filter layer40is made of sintered porous pellets40a(FIG. 4) of a porous material mixed with an inorganic, non-precious metal catalyst. The porous material may be a polyolefin such as ultra-high molecular weight polyethylene (UHMW-PE), but could be made from other suitable porous materials such as suitable metals, ceramics and glass. The inorganic, non-precious metal catalyst is preferably manganese dioxide but could also be other suitable inorganic, non-precious metal catalysts such as lead oxide, andiron (III) oxide. The pellets40aserve two functions: 1) the pellets40aare loosely assembled in random fashion inside housing16which creates a large porous surface area for coalescing oil mist, and 2) the inorganic, non-precious metal catalyst decomposes hydrogen peroxide by creating a chemical reaction when it comes in contact with hydrogen peroxide vapor. The chemical reaction caused by the inorganic, non-precious metal catalyst results in water and oxygen as the byproducts which are safe to exhaust into the environment.

As shown inFIGS. 2-4, the pellets40aare porous and cylindrically shaped. The pellets have a porosity in the range of, for example, 30-70% of void in the pellets, and more preferably 50-70% of void in the pellets. The pellets further have a filtration range of, for example, of 100-200 microns. When loosely assembled inside housing16, the cylindrical shape of the pellets40aprevents the pellets40afrom being tightly packed. This causes numerous spaces or pores to be present between the pellets40a. The porosity of the pellets40a, the large surface area of the numerous pellets40aand the numerous spaces in between the pellets40acreate an area allowing for coalescing oil mist and hydrogen peroxide vapor to pass through and decompose. In one embodiment, the pellets are approximately 0.25+/−0.005 inches in diameter by 0.25+/−0.005 inches long filling a space of approximately 15 cubic inches. Specifically, in this example, the volume of the housing where the pellets are contained between the second foam layer42and the metal wool layer38is 15.81 cubic inches. The total volume of the pellets40ais 9.225 cubic inches, leaving 6.585 cubic inches void. The pellets40amay have other suitable shapes and dimensions which prevent the pellets40afrom being tightly packed as long as they create a large porous surface area for coalescing oil mist.

The component layers are not required to be coated with a precious metal catalyst and precious metal is not required to be used in the construction of the components. Each component layer when assembled can be in contact with the components next to it and the inside diameter of the cylindrical portion24of housing16as shown inFIG. 2. The component layers do not require bores through them in order for gases and water to flow through them.

It will be appreciated by those of ordinary skill in the art that the disclosed apparatus may be comprised of a wide and equivalent range of apparatus and components and nothing herein is intended to limit the scope of the disclosed inventions or any embodiments thereof.