OPTIMIZED REDUCTION OF NOx EMISSIONS FROM DIESEL ENGINES

Abstract

A system is provided for operating a diesel engine with reduced emissions of NOx. The system comprises a fuel tank adapted to directly or indirectly supply a first premixed fuel stream and a second premixed fuel stream, wherein each fuel stream comprises a primary fuel component and a reductant component. An engine is in fluid communication with the fuel tank, whereby the engine is configured to receive the first premixed fuel stream and create an exhaust stream. The system includes an emission treatment unit to treat the exhaust stream, and a separation unit configured to receive the second premixed fuel stream. The separation unit is also configured to separate the second premixed fuel stream into a first fraction stream and a second fraction stream, and supply the first fraction stream to the exhaust stream. The first fraction stream comprises a higher concentration of the reductant component than the second fraction stream. A temperature sensor measures the temperature of the exhaust stream, whereby the concentration of the reductant component in the exhaust stream is controlled based on the measured temperature of the exhaust stream. The invention further provides a method for operating a diesel engine with reduced emissions of NOx. The method includes supplying a first premixed fuel stream to an engine, wherein the engine is configured to create an exhaust stream. A second premixed fuel stream is supplied to a separation unit, wherein the first and second premixed fuel streams each comprise a reductant component and a primary fuel component. At least a portion of the second premixed fuel stream is separated into a first fraction stream and a second fraction stream via the separation unit, wherein the first fraction stream comprises a higher concentration of the reductant component than the second fraction stream. At least a portion of the first fraction stream is supplied to the exhaust stream. The temperature of the exhaust stream is measured, and the concentration of the reductant component in the exhaust stream is controlled based on the measured temperature. The selective catalytic reduction of NOx present in the exhaust stream is performed.

1 . A system for operating a diesel engine with reduced emissions of NOx comprising:
 a fuel tank adapted to directly or indirectly supply a first premixed fuel stream and a second premixed fuel stream, each fuel stream comprising a primary fuel component and a reductant component;   an engine in fluid communication with the fuel tank, wherein the engine is configured to receive the first premixed fuel stream and create an exhaust stream;   an emission treatment unit to treat the exhaust stream;   a separation unit configured to receive the second premixed fuel stream, the separation unit also configured to separate the second premixed fuel stream into a first fraction stream and a second fraction stream, and supply the first fraction stream to the exhaust stream, wherein the first fraction stream comprises a higher concentration of the reductant component than the second fraction stream; and   a temperature sensor to measure the temperature of the exhaust stream, whereby a concentration of the reductant component in the exhaust stream is controlled based on the measured temperature of the exhaust stream.   
   
   
       2 . The system according to  claim 1 , further comprising:
 a second premixed fuel controller that receives a signal from a sensor, the controller regulates the flow of the second premixed fuel stream into the separation unit in accordance with the received signal.   
   
   
       3 . The system according to  claim 2 , further comprising:
 a second fuel pump in communication with the second fuel controller to pump at least a portion of the second premixed fuel stream into the separation unit.   
   
   
       4 . The system according to  claim 2 , further comprising:
 a fuel slip stream off of the second premixed fuel stream, wherein the fuel slip stream is supplied to the exhaust stream; and   a three way valve in communication with the second fuel controller to adjust the flow of the second premixed fuel stream into the separation unit, and adjust the flow of the fuel slip stream into the exhaust stream.   
   
   
       5 . The system according to  claim 2 , wherein the signal received by the second premixed fuel controller represents the temperature of the exhaust stream measured by the temperature sensor. 
   
   
       6 . The system according to  claim 2 , further comprising:
 an NOx sensor to measure the concentration of NOx in the treated exhaust stream; and   wherein the signal received by the second premixed fuel controller represents the NOx concentration measured by the NOx sensor.   
   
   
       7 . The system according to  claim 1 , further comprising:
 a fuel slip stream off of the first premixed fuel stream, wherein the fuel slip stream is supplied to the exhaust stream; and   a third premixed fuel controller that receives a signal from a sensor, the controller regulates the flow of the fuel slip stream into the exhaust stream in accordance with the received signal.   
   
   
       8 . The system according to  claim 7 , further comprising:
 a third fuel pump to pump at least a portion of the fuel slip stream into the exhaust stream.   
   
   
       9 . The system according to  claim 7 , wherein the signal received by the third premixed fuel controller represents the temperature of the exhaust stream measured by the temperature sensor. 
   
   
       10 . The system according to  claim 7 , further comprising:
 an NOx sensor to measure the concentration of NOx in the treated exhaust stream; and   wherein the signal received by the third premixed fuel controller represents the NOx concentration measured by the NOx sensor.   
   
   
       11 . The system according to  claim 1 , further comprising:
 a first fraction controller that receives a signal from a sensor, the controller regulates the flow of the first fraction stream into the exhaust stream in accordance with the signal.   
   
   
       12 . The system according to  claim 11 , further comprising:
 a first fraction fuel pump in communication with the first fraction controller to pump at least a portion of the first fraction stream into the exhaust stream.   
   
   
       13 . The system according to  claim 11 , wherein the signal received by the first fraction controller represents the temperature of the exhaust stream measured by the temperature sensor. 
   
   
       14 . The system according to  claim 11 , further comprising:
 an NOx sensor to measure the concentration of NOx in the treated exhaust stream; and   wherein the signal received by the first fraction controller represents the NOx concentration measured by the NOx sensor.   
   
   
       15 . The system according to  claim 1 , further comprising:
 a condenser disposed in fluid communication with the separation unit for condensing at least a portion of the first fraction stream exiting the separation unit.   
   
   
       16 . The system according to  claim 15 , further comprising:
 a holding tank disposed in fluid communication with the condenser unit to store the first fraction stream exiting the condenser unit.   
   
   
       17 . The system according to  claim 1 , wherein the emission treatment unit is a selective catalytic reduction treatment unit. 
   
   
       18 . The system according to  claim 1 , wherein the separation unit is a membrane, distillation or flash separation unit. 
   
   
       19 . The system according to  claim 1 , wherein the reductant component comprises an alcohol, aldehyde, ketone, ether or ester or a combination thereof. 
   
   
       20 . The system according to  claim 19 , wherein the reductant component is ethanol. 
   
   
       21 . The system according to  claim 1 , wherein the premixed fuel comprises diesel fuel, biodiesel fuel, green diesel fuel, or Fischer-Tropsch fuel, or any combination thereof. 
   
   
       22 . The system according to  claim 21 , wherein the premixed fuel comprises biodiesel fuel. 
   
   
       23 . The system according to  claim 1 , wherein the engine is a liquid fueled engine, a compression ignition engine, or a gasoline engine, or any combination thereof. 
   
   
       24 . A method for operating a diesel engine with reduced emissions of NOx comprising:
 supplying a first premixed fuel stream to an engine, wherein the engine is configured to create an exhaust stream;   supplying a second premixed fuel stream to a separation unit, wherein the first and second premixed fuel streams each comprise a reductant component and a primary fuel component;   separating at least a portion of the second premixed fuel stream into a first fraction stream and a second fraction stream via the separation unit, wherein the first fraction stream comprises a higher concentration of the reductant component than the second fraction stream;   supplying at least a portion of the first fraction stream to the exhaust stream;   measuring a temperature of the exhaust stream;   controlling the concentration of the reductant component in the exhaust stream based on the measured temperature of the exhaust stream; and   performing a catalytic reduction of NOx present in the exhaust stream.   
   
   
       25 . The method according to  claim 24 , wherein the first and second premixed fuel streams are directly or indirectly supplied from a fuel tank, and the method further comprising:
 supplying the second fraction stream to the fuel tank.   
   
   
       26 . The method according to  claim 24 , wherein controlling the concentration of the reductant component comprises:
 regulating the flow of the second premixed fuel stream into the separation unit.   
   
   
       27 . The method according to  claim 26 , wherein controlling the concentration of the reductant component further comprises:
 regulating the flow of a fuel slip stream off of the second premixed fuel stream, wherein the fuel slip stream flows into the exhaust stream.   
   
   
       28 . The method according to  claim 27 , wherein the flow of the second premixed fuel stream and the fuel slip stream is regulated with a three way valve. 
   
   
       29 . The method according to  claim 24 , wherein controlling the concentration of the reductant component comprises:
 regulating the flow of a slip fuel stream off of the first premixed fuel stream, wherein the fuel slip stream flows into the exhaust stream.   
   
   
       30 . The method according to  claim 24 , wherein controlling the concentration of the reductant component comprises:
 regulating the flow of the first fraction stream into the exhaust stream.   
   
   
       31 . The method according to  claim 24 , further comprising:
 measuring a concentration of NOx in a treated exhaust stream exiting the emission treatment unit; and   regulating the flow of the second premixed fuel stream into the separation unit in accordance with the measured concentration.   
   
   
       32 . The method according to  claim 24 , further comprising:
 measuring a concentration of NOx in a treated exhaust stream exiting the emission treatment unit; and   regulating the flow of the first fraction stream into the exhaust stream in accordance with the measured concentration.   
   
   
       33 . The method according to  claim 24 , further comprising:
 condensing at least a portion of the first fraction stream exiting the separation unit.   
   
   
       34 . The method according to  claim 33 , further comprising:
 storing at least a portion of the condensed first fraction stream in a holding tank.   
   
   
       35 . The method according to  claim 24 , wherein at least a portion of the second premixed fuel stream is separated by membrane, distillation or flash separation or a combination thereof. 
   
   
       36 . The method according to  claim 24 , wherein the reductant component comprises an alcohol, aldehyde, ketone, ether or ester, or a combination thereof. 
   
   
       37 . The method according to  claim 36 , wherein the reductant component is ethanol. 
   
   
       38 . The method according to  claim 24 , wherein the premixed fuel comprises diesel fuel, biodiesel fuel, green diesel fuel, Fischer-Tropsch fuel, and any combination thereof. 
   
   
       39 . The method according to  claim 38 , wherein the premixed fuel comprises biodiesel. 
   
   
       40 . The method according to  claim 24 , wherein the concentration of the reductant component in the exhaust stream is maintained between approximately 1 ppm and approximately 20,000 ppm, when the measured temperature of the exhaust stream is between approximately 200° C. and approximately 600° C. 
   
   
       41 . The method according to  claim 24 , wherein the concentration of the reductant component in the exhaust stream is increased when the measured temperature of the exhaust stream is decreasing. 
   
   
       42 . The method according to  claim 24 , wherein the concentration of the reductant component in the exhaust stream is decreased when the measured temperature of the exhaust stream is increasing.