Abstract: For continuous combustion air control in a hazardous waste incinerator, two signals are generated which totalize the air required on a fuel supplied basis. One signal is responsive to measured totalized fuel flow and this total can include fuel flow signals which are limited to the fraction of available air which corresponds to the fuel flow. The other signal is responsive to the totalized fuel flow that is commanded for maintaining an incinerator condition. In use the signal which requires the greater air flow is selected as the actual control signal for combustion air, and this control signal is biased to increase the air flow to obtain complete combustion of the hazardous waste by a controller acting on the measured amount of oxygen in the flue gas. In this manner the combustion air is manipulated in parallel with the waste fuel and if the fuel flow is limited by the available air, the air flow is limited to match the limited fuel flow.

Abstract: The flow rate of multiple fuel streams supplied to an incinerator are controlled so as to provide maximum temperature and heat release conditions in the incinerator that will allow complete combustion of hazardous waste fuel. In addition, a minimum temperature for the incinerator is maintained by manipulating the flow rate of an auxiliary fuel such as natural gas, that is also supplied to the incinerator. In use, a control signal for manipulating a waste fuel flow is selected as the lowest signal of signals representative of a maximum temperature for the incinerator, a maximum heat release rate for the incinerator, a maximum heat release rate for a particular waste fuel, a maximum pressure for the incinerator, and the combustion air available.

Abstract: Boiler optimization is included in on-line control of parallel boilers by multiplying the total heat per unit time which must be supplied to all parallel boilers by the percentage of the total heat which should be supplied to each boiler in order to substantially maximize energy efficiency. The result of such multiplication is the heat per unit time which should be supplied to each boiler. The fuel and air supplied to each boiler is controlled so as to supply the thus determined heat per unit time which not only results in maintenance of a desired header pressure but also results in substantially maximizing energy efficiency of the parallel boilers.

Abstract: The flow of offgas from a common source as a fuel for multiple boilers is controlled so as to maintain a desired minimum pressure for the offgas supply unless the maintenance of such a desired minimum pressure would result in so much offgas being supplied to a boiler that a maximum offgas to fuel gas ratio is exceeded which impairs combustion. If the primary control would cause too much offgas to be supplied to a boiler, then the flow of offgas to such boiler is manipulated so as to prevent the maximum offgas to fuel gas ratio from being exceeded.

Abstract: A desired ratio of offgas to fuel gas is maintained for a fuel mixture supplied to the burners associated with a boiler by venting steam as required to insure than all offgas may be combusted while maintained the desired offgas to fuel gas ratio. The venting of steam causes the fuel gas control, which is based on steam pressure, to vary the flow rate of the fuel gas so as to maintain the desired offgas-fuel gas ratio. Control of the combustion process for the boiler in this manner results in total combustion of the offgas without violating process constraints.

Abstract: The control of the actual liquid level in a boiler is accomplished by using the flow rate of the fuel to the combustion system associated with the boiler to generate a signal which is utilized to bias a control signal generated in response to steam flow rate and the output from a conventional level controller in such a manner that swell and shrink caused by changes in fuel flow rate is compensated for and the desired liquid level is maintained in the boiler.

Abstract: A process and apparatus for minimizing breakage and stretching during the high speed production of plastic pipe is provided wherein a pipe is extruded at a first linear rate of speed, a slack segment is established and maintained between the extruder and a pipe winder, and the pipe is taken up on the winder at a second linear rate of speed which is the same as or different from the first rate, wherein the pipe is taken up on the winder responsive to the degree of slack in the slack segment.

Abstract: The rate of extrusion of an elongated article from a dynamic extruder is measured and a measurement signal representative thereof is established. The measurement signal is then compared with a setpoint signal representing the desired extrusion rate to produce a control signal which is responsive to the difference between the measurement signal and the setpoint signal. The rate of introduction of polymer particles into the plasticization section of the extruder is automatically manipulated responsive to the control signal to maintain the extrusion rate at least substantially constant at the desired rate. The control signal can be adjusted to take into account variations in the temperature of the molten polymer entering the long land cooling die of the extruder.

Abstract: A process and apparatus for minimizing breakage and stretching during the high speed production of plastic pipe is provided wherein a pipe is extruded at a first linear rate of speed, a slack segment is established and maintained between the extruder and a pipe winder, and the pipe is taken up on the winder at a second linear rate of speed which is the same as or different from the first rate, wherein the pipe is taken up on the winder responsive to the degree of slack in the slack segment.

Abstract: The rate of extrusion of an elongated article from a dynamic extruder is measured and a measurement signal representative thereof is established. The measurement signal is then compared with a setpoint signal representing the desired extrusion rate to produce a control signal which is responsive to the difference between the measurement signal and the setpoint signal. The rate of introduction of polymer particles into the plasticization section of the extruder is automatically manipulated responsive to the control signal to maintain the extrusion rate at least substantially constant at the desired rate. The control signal can be adjusted to take into account variations in the temperature of the molten polymer entering the long land cooling die of the extruder.

Abstract: In an extrusion system wherein a single source of molten extrudable material is utilized to provide feed to a plurality of extrusion lines, the rate of flow of extrudable material from the source thereof to the plurality of extrusion lines is controlled to provide a preselected total product output rate. The position of a flow control valve means associated with each extrusion line is controlled to maintain a preselected material supply pressure upstream of said plurality of extrusion lines and to provide a preselected relationship among the measured production rates of said plurality of extrusion lines. In a preferred embodiment, an extrusion system having two extrusion lines supplied by a single source of molten extrudable material is controlled to provide a preselected total production rate, a preselected molten material source pressure, and a preselected balance between the extrusion rates of the two extrusion lines.