Control of range hood emissions

In a work station-serving system for collecting and processing an exhaust gas stream emanating from a process to be conducted at the work station in which an oily, greasy or fatty material is being heated,

• for removing potentially air-polluting mist and char from the exhaust gas stream when said exhaust gas stream is emanating into said system at an elevated temprature which lies above a known threshold temperature, before the exhaust gas stream is vented to the atmosphere,
• apparatus comprising:
• a mist eliminator fiber bed element having a capacity to filter substantial amounts of said potentially air-polluting mist and char from said exhaust gas stream when said exhaust gas stream is constrained to pass through said mist eliminator fiber bed element, provided said exhaust gas stream when coming into contact with said mist eliminator fiber bed element lies below said known threshold temperature;
• conduit means housing said mist eliminator element intermediate upstream and downstream ends of said conduit means;
• said conduit means having the upstream end thereof open for accepting said elevated temperature, above said known threshold temperature, exhaust gas stream;
• said conduit means having the downstream end thereof open for discharging to the atmosphere said exhaust gas stream after said exhaust gas stream has been cooled to below said known threshold temperature and has passed through said mist eliminator fiber bed element;
• wall means in and forming part of said conduit means for constraining all of the exhaust gas stream entering at said upstream end to pass through said mist eliminator fiber bed element before such exhaust gas stream is vented to the atmosphere;
• cooling water spray means having spray nozzle means thereof provided within said conduit means between said upstream end and said mist eliminator fiber bed element, for lowering the temperature of said exhaust gas stream by direct contact, adiabatic cooling thereof, to below said known threshold temperature, upstream of said mist eliminator fiber bed element;
• and
• suction blower means incorporated in said conduit means downstream of said mist eliminator fiber bed element, for maintaining when operating, enough of a pressure differential across said mist eliminator fiber bed element as to tend to draw said exhaust gas stream through said mist eliminator fiber bed element.

Pollution control apparatus for removing what otherwise would become visible emissions to the atmosphere from the ventilating system of a cooking area for fatty foods, comprising:

• a downwardly opening hood positioned above said cooking area;
• a ventilation duct means connected at one end to the hood and having an opposite end open to the atmosphere away from said cooking area;
• an aerosol particle coalescing filter enclosed within the ventilation duct means intermediate the ends thereof and a blower means interposed in said ventilation duct means downstream of said filter for drawing a hot, fat-containing gas stream resulting from cooking a fatty food in said cooking area, which gas stream has entered said hood, from the hood through the ventilation duct means, including through the aerosol particle coalescing filter and for discharging said gas stream to the atmosphere remotely of said cooking area after coalescing and removing from said gas stream aerosol particles including fatty aerosol particles by means of said filter;
• said filter being a hollow mist eliminator body having an inlet opening into an internal space thereof;
• said ventilation duct means including a filter housing in which said filter is mounted by mounting means which constrain all of said exhaust gas stream which enters said housing to pass into said internal space through said inlet opening, and then outwardly through the filter before said exhaust gas stream can pass out of said housing and become discharged to the atmosphere;
• means for collecting from the filter housing at least some of that which has been collected in said filter housing as a result of said coalescence and removal from said gas stream of aerosol particles including fatty aerosol particles by means of said filter;
• said collecting means including drain means from said housing, which drain means communicate with said housing so as to be in communication with said internal space of said filter relatively upstream of said filter;
• and
• means for cooling the gas stream after the gas stream enters the hood but before the gas stream is drawn outwardly of said internal space through the filter,
• (a) from a first, higher temperature at which, if the gas stream were to be drawn outwardly through the filter there would be at least one of
• (i) a first, higher tendency for a significant amount of small particles of that which would become visible emissions remaining in said gas stream downstream of said filter and unremoved from said gas stream by said filter, and
• (ii) a first, higher tendency for particles trapped from the gas stream by said filter to bake onto the filter,
• (b) to a second, lower temperature at which at least one respective said first, higher tendency is substantially reduced to a second, lower tendency.