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Show High Efficiency, L o w Emission Marine Vapor Control System Callidus Technologies Inc. Callidus' solution to the problem is to create a combustion chamber with more pressure drop and a variable speed blower that provides quick and smooth response to both small transients and sudden step charges that are normally encountered in Marine Vapor Combustion service. Combustor Design As previously descussed, the key to destruction efficiency is a properly designed burner system and the key to high thermal efficiency is putting the air only where it is needed in the amount required. However, a properly designed combustion chamber is the glue that holds these other elements together and for sure, an improperly designed combustion chamber will adversely effect stability and can make a system intolerable. The authors have determined a volumetric heat release of 30,000 Btu/hr/ft3 provides sufficent margin to contain the visible flame without damaging low frequency rumbling. It has also been determined that a static vortice generator must be incorporated in the combustor design to assure that the products of combustion are not allowed to stratify after leaving the burner. Due to the cyclic nature of the use pattern of combustors in Marine service, ceramic fiber is generally the refractory system of choice due to its low heat capacitance and resistance to thermal shock. These units are routinely brought from ambient to 1500°F in less than 5 minutes. Control Design To successfully minimize the auxiliary fuel usage, the key goes back to the basic scheme of getting the fuel (hydrocarbon vapors) and the air together, properly with only just enough air. To take full advantage of the features designed in the Marine Vapor Combustor System, it is imperative the control system have the following features: Quick response to waste flow rates Quick response to combustor temperature changes The number of active burner stages is selected based on waste flow rate, while the amount of air for each burner stage varies with both flow and temperature. In all cases, special care is taken to operate each burner in the system within its optimum stability range. Auxiliary fuel control is kept "very tight" to avoid wasteful overshoots and excessively high setpoints to keep "swing minimums" above regulatory requirements. On the other hand, the quench air control is set at a higher setpoint than the auxiliary fuel and is tuned for much softer response since the acceptable operating range is 200°- 300° wide and the V F D is "slop" free. The quench control loop also has the ability to take preemptive control based on sudden change in vapor characteristics as sensed by the dock safety devices. 5 |