Apparatus and methods for incinerating sludge in a combustor

Abstract

A method of incinerating sludge in a combustor is disclosed including establishing at least one target performance characteristic of the combustor; introducing the sludge into the combustor as primary fuel; monitoring at least one performance parameter of the combustor; calculating an actual performance characteristic based on the performance parameter; and adjusting the quantity and/or quality of fuel introduced into the combustor in response to a monitored performance characteristic to substantially maintain the target performance characteristic. The apparatus for incinerating sludge includes a combustor adapted to receive sludge as fuel and incinerate the sludge; a sensor that monitors at least one performance parameter of the combustor; and a controller connected to the combustor and the sensor that 1) establishes at least one target performance characteristic of the combustor, 2) calculates an actual performance characteristic based on the performance parameter and 3) adjusts quantity and/or quality of fuel introduced into the combustor in response to a monitored performance characteristic to substantially maintain the target performance characteristic.

1 . A method of incinerating sludge in a combustor comprising:
 establishing at least one target performance characteristic of the combustor;   introducing the sludge into the combustor as primary fuel;   monitoring at least one performance parameter of the combustor;   calculating an actual performance characteristic based on the performance parameter; and   adjusting the quantity and/or quality of fuel introduced into the combustor in response to a monitored performance characteristic to substantially maintain the target performance characteristic.   
   
   
       2 . The method of  claim 1 , wherein the combustor is a fluidized bed combustor. 
   
   
       3 . The method of  claim 2 , wherein the performance parameter comprises freeboard temperature and/or bed temperature. 
   
   
       4 . The method of  claim 3 , wherein the target performance characteristic is the difference between a selected freeboard temperature and a selected bed temperature. 
   
   
       5 . The method of  claim 3 , wherein the selected temperature is about 1200-about 1400° F., the selected freeboard temperature is about 1550-1650° F. and the target performance characteristic is about 275-about 325° F. 
   
   
       6 . The method of  claim 1 , wherein the sludge is at least one selected from the group consisting of sludge generated in a wastewater treatment process and agricultural waste. 
   
   
       7 . The method of  claim 6 , wherein the sludge is from more than one source and blended. 
   
   
       8 . The method of  claim 7 , further comprising adjusting a blend ratio of sludge from influent sources in response to selected incinerator operating conditions. 
   
   
       9 . The method of  claim 1 , wherein adjusting the quality of fuel comprises increasing or decreasing a flow of a supplemental fuel into the combustor. 
   
   
       10 . The method of  claim 9 , wherein the supplemental fuel is oil or gas. 
   
   
       11 . The method of  claim 1 , wherein adjusting the quantity of fuel comprises increasing or decreasing a flow of the sludge into the combustor. 
   
   
       12 . The method of  claim 9 , wherein adjusting the quantity of fuel comprises controlling a ratio of the sludge to the supplemental fuel. 
   
   
       13 . The method of  claim 1 , wherein adjusting the quantity of fuel comprises controlling the moisture content of the sludge. 
   
   
       14 . The method of  claim 13 , wherein the moisture content is controlled by regulating polymer feed dose and/or regulating a centrifuge, dewatering belt, plate-frame press, screw press or vacuum press. 
   
   
       15 . The method of  claim 2 , wherein the performance parameter is at least one selected from the group consisting of fluidizing air flow, heat exchanger exit air temperature, auxiliary air flow, off gas temperature, off gas oxygen control, wind box temperature, sludge moisture content, centrate solids content, centrate flow rate and changes in the difference between freeboard and fluidized bed temperatures. 
   
   
       16 . The method of  claim 1 , further comprising adjusting one or more operating parameters in response to the monitored performance characteristic. 
   
   
       17 . The method of  claim 16 , wherein the operating parameter is at least one selected from the group consisting of cold air bypass flow, quench spray water flow, sludge feed rate, supplemental fuel feed rate and fluidizing air flow rate. 
   
   
       18 . Apparatus for incinerating sludge comprising:
 a combustor adapted to receive sludge as fuel and incinerate the sludge;   a sensor that monitors at least one performance parameter of the combustor; and   a controller connected to the combustor and the sensor that 1) establishes at least one target performance characteristic of the combustor, 2) calculates an actual performance characteristic based on the performance parameter and 3) adjusts quantity and/or quality of fuel introduced into the combustor in response to a monitored performance characteristic to substantially maintain the target performance characteristic.   
   
   
       19 . The apparatus of  claim 18 , wherein the combustor is a fluidized bed combustor. 
   
   
       20 . The apparatus of  claim 19 , wherein the performance parameter comprises freeboard temperature and/or bed temperature. 
   
   
       21 . The apparatus of  claim 20 , wherein the target performance characteristic is the difference between a selected freeboard temperature and a selected bed temperature. 
   
   
       22 . The apparatus of  claim 21 , wherein the selected temperature is about 1200-about 1400° F., the selected freeboard temperature is about 1550-about 1650° F. and the target performance characteristic is about 275-about 325° F. 
   
   
       23 . The apparatus of  claim 22 , wherein the sludge is generated in a wastewater treatment process. 
   
   
       24 . The apparatus of  claim 23 , wherein the sludge is from more than one source and blended. 
   
   
       25 . The apparatus of  claim 24 , wherein adjusting the quantity of fuel comprises increasing or decreasing a flow of a supplemental fuel into the combustor. 
   
   
       26 . The apparatus of  claim 25 , wherein the supplemental fuel is oil or gas. 
   
   
       27 . The apparatus of  claim 26 , wherein adjusting the quantity of fuel comprises increasing or decreasing a flow of the sludge into the combustor. 
   
   
       28 . The apparatus of  claim 27 , wherein adjusting the quantity of fuel comprises controlling a ratio of the sludge to the supplemental fuel. 
   
   
       29 . The apparatus of  claim 28 , wherein adjusting the quantity of fuel comprises controlling the moisture content of the sludge. 
   
   
       30 . The apparatus of  claim 29 , wherein the moisture content is controlled by regulating polymer feed dose and/or regulating a centrifuge, dewatering belt, plate-frame press, screw press or vacuum press. 
   
   
       31 . The apparatus of  claim 30 , wherein the performance parameter is at least one selected from the group consisting of fluidizing air flow, heat exchanger exit air temperature, auxiliary air flow, off gas temperature, off gas oxygen control, wind box temperature, sludge moisture content, centrate solids content, centrate flow rate. 
   
   
       32 . The apparatus of  claim 31 , further comprising adjusting one or more operating parameters in response to the monitored performance characteristic. 
   
   
       33 . The apparatus of  claim 32 , wherein the operating parameter is at least one selected from the group consisting of cold air bypass flow, quench spray water flow and fluidizing air flow rate. 
   
   
       34 . A method of controlling mass and heat loading of sludge feed into a fluidized bed combustor (FBC) controlled via regulation of a polymer dosage or a sludge feed rate comprising:
 continuously monitoring at least one performance characteristic of the FBC;   producing an input signal characteristic;   analyzing the input signal and determining a first rate of change of the characteristic;   generating an output signal based on the first rate of change to control addition of polymer to the FBC;   generating a second output signal to control addition of sludge feed to the FBC; and   determining a transition point between the addition of polymer and addition of sludge, which transition point is an upper limit of a first rate change to maintain flow so that the value of the characteristic is maintained proximate at the upper limit.   
   
   
       35 . The method of  claim 34 , wherein the characteristic is the difference between freeboard and bed temperatures ΔT. 
   
   
       36 . The method of  claim 34 , further comprising regulating operation of a centrifuge to provide a selected sludge quality. 
   
   
       37 . The method of  claim 34 , further comprising regulating at least one selected from the group consisting of operation a of a belt press via adjustment of belt speed or tension plate and frame press, screw press and vacuum press to provide a selected wastewater solids quality. 
   
   
       38 . The method of  claim 34 , wherein mass flow of solids to the FBC is regulated by blending influent sludge streams to control the ratio of primary and secondary sludge blends to a selected dry solids concentration based upon combustor performance. 
   
   
       39 . The method of  claim 34 , further comprising a suspended solids sensor selected from the group consisting of optical, microwave, ultrasound, vibrational frequency and zeta potential sensors that detect the moisture content of the sledge prior to entering the FBC. 
   
   
       40 . A method of controlling mass and heat loading of sludge feed into a thermal dryer controlled via regulation of a polymer dosage or a sludge feed rate comprising:
 continuously monitoring at least one performance characteristic of the thermal dryer;   producing an input signal characteristic;   analyzing the input signal and determining a first rate of change of the characteristic;   generating an output signal based on the first rate of change to control addition of polymer to the thermal dryer;   generating a second output signal to control addition of sludge feed to the thermal dryer; and   determining a transition point between the addition of polymer and addition of sludge, which transition point is an upper limit of a first rate change to maintain flow so that the value of the characteristic is maintained proximate at the upper limit.