Abstract: A two-stage starved air furnace system is controlled to simultaneously achieve desired temperatures and percent stoichiometric air operation in the primary stage by modulating transformation relay functions acting upon measured temperature deviations to change both primary combustion air and primary auxiliary burner operation. At the set-point value of percent stoichiometric air, the relay functions are modulated in reverse direction to satisfy changing heat demands.

Abstract: The present invention relates to a method for efficiently incinerating waste material, particularly dewatered sludge, in a multiple hearth furnace by controlling the temperature of the individual hearths of the furnace within certain prescribed limits by modulating the amount of combustion air, and controlling the temperature of the after-burner or combustion hearths to within certain prescribed limits by splitting the feed sludge between the first two upper waste material handling hearths.

Abstract: A method for controlling two-stage combustion furnaces having a first stage operated with sub-stoichiometric airflow and a second stage operated with excess air, whereby the first stage airflow is controlled such that the ratio of first stage airflow to total airflow is maintained less than ##EQU1## where N lies between zero and unity.

Abstract: The present invention relates to a method and apparatus for controlling the operation of a multiple hearth furnace system for efficiently incinerating combustible materials, such as sludge in which the air of combustion is essentially all introduced at the bottom of the furnace to incinerate solid materials. This control involves the following essential steps:scanning the temperature of two or more combustion hearths to determine which is the hottest hearth;controlling the temperature of the thus-determined hottest hearth at a predetermined temperature set point value;controlling the oxygen content of the system exhaust gas at least as high as the predetermined set point value; andmaintaining the system exhaust temperature at least as high as the predetermined set point value.

Abstract: The present invention relates to a method for efficiently incinerating waste material, particularly dewatered sludge, in a multiple hearth furnace by controlling the temperature of the individual hearths of the furnace within certain prescribed limits by modulating the amount of combustion air, and controlling the temperature of the afterburner or combustion hearths to within certain prescribed limits by splitting the feed sludge between the first two upper waste material handling hearths.

Abstract: A process is disclosed in which any off-gas generated in a wastewater treatment plant, which off-gas has a low calorific (or BTU) value about one-tenth of that of natural gas, and usually even less, may be profitably burned in a multiple hearth furnace if the off-gas is first wet-scrubbed to a temperature below about 90.degree. F., then pre-heated by passing it through the center shaft of a multiple hearth furnace, before the pre-heated gas is burned. Such cooling of the off-gas by wet-scrubbing has the effect of lowering the moisture content of the wet-scrubbed gas sufficiently so that it may be advantageously pre-heated in the center shaft of the furnace and recycled to the hearths to assist in the combustion of sludge. In addition to providing desirable savings in auxiliary fuel usage, wet-scrubbed off-gas is unexpectedly cleansed of a sufficient amount of its corrosive components so as to permit ducting the wet-scrubbed gas in mild steel or cast iron equipment.

Abstract: The present invention relates to a method for efficiently incinerating waste material, particularly dewatered sludge, in a multiple hearth furnace by controlling the temperature of the individual hearths of the furnace within certain prescribed limits by modulating the amount of combustion air, and controlling the temperature of the afterburner or combustion hearths to within certain prescribed limits by splitting the feed sludge between the first two upper waste material handling hearths.

Abstract: A process for making an aural communications receiving device of formed-in-place elastomeric composition constructed especially to provide a smooth, tight seal over the mouth of the ear canal when stretched and including a formed-in-place sound transmitting passageway acoustically coupled to an integral connecting means for securing a communications component or to an embedded speaker at an outwardly presented surface.

Abstract: A locking ring for a castellated nut threadably connected to a bolt having a transversely extending aperture has a diametrically extending section located in the aperture with opposite end portions engageably located in opposing castellations formed on the nut. One of the end portions of the diametrically extending section overlies and springily cooperates with an annular shaped section located about the outer periphery of the castellated formation to lockingly secure the ring to the nut and preclude inadvertent removal. In one form of the invention, an end portion of the arcuately shaped section is folded radially inwardly to cooperatively engage one of the castellations and in another form the diametrically extending portion is centrally bowed so as to engage the inner periphery of the aperture and thereby minimize relative movement between the locking ring and the bolt.