Method and apparatus for ash cooling

Abstract

Systems and methods for step-wise cooling high pressure and high temperature ash discharged from the gasifier used for gasification of carboneous materials, wherein a high pressure cooler cools the ash under the operating pressure of the gasifier, which may be followed by a depressurizer which brings the cooled ash to safe-handling temperature. A low temperature ash cooler may also be optionally used. Also provided is a system where a wet scrubber is used to clean the syngas from the gasifier, the waste water blow down from the scrubber is used to cool the hot ash either in the high temperature ash cooler, or the low temperature ash cooler. Steam generated in the ash coolers is supplied back to the gasifier to reduce steam consumption.

What is claimed is: 
     
         1 . A gasification system comprising:
 a fluidized bed gasifier into which a carbonaceous feed material is fed, and out of which a product gas stream and a flowable ash is discharged, wherein the gasifier is operated at a temperature just under a melting point of the ash, and under a pressure not less than 6 bar gauge, and   a high temperature ash cooler connected to the gasifier and into which the hot ash under pressure is discharged, wherein the high temperature ash cooler comprises a water-supplying apparatus that provides water for cooling the flowable ash, wherein the flowable ash is cooled to a temperature suitable for the ash to be handled with conventional carbon steel equipment.   
     
     
         2 . The gasification system of  claim 1 , wherein the water supplying apparatus supplies the cooling water to the high temperature ash cooler to be in direct contact with the flowable ash, and wherein the system further comprises a controller to control the water supplying apparatus wherein the water is vaporized upon direct contact with the ash to generate steam, the flowability of the ash is maintained, and the flowable ash is cooled to a temperature not lower than the pre-determined threshold temperature. 
     
     
         3 . The gasification system of  claim 1 , wherein the cooling water is supplied to the high temperature ash cooler and cools the ash via indirect heat transfer. 
     
     
         4 . The gasification system of  claim 3 , wherein the high temperature ash cooler comprises a cooling jacket, or cooling coils, or a cooling panel through which the cooling water flows and absorbs heat indirectly from the hot ash. 
     
     
         5 . The gasification system of  claim 1 , wherein a portion of the cooling water is supplied to the high temperature ash cooler in direct contact with the flowable ash, and wherein the system further comprises a controller to control the water supplying apparatus so that the water is vaporized upon direct contact with the ash to generate steam, and the flowability of the ash is maintained; and a portion of the cooling water is supplied to the high temperature ash cooler where the cooling water cools the ash via indirect heat transfer; and wherein the flowable ash is cooled to a temperature not lower than the pre-determined threshold temperature. 
     
     
         6 . The gasification system of  claim 1 , further comprising a connection between the high temperature ash cooler and the gasifier, wherein steam generated from the water supplied to the high temperature ash cooler is supplied to the gasifier. 
     
     
         7 . The gasification system of  claim 1 , further comprising:
 a depressurizing device which is connected to the high temperature ash cooler to receive the cooled high pressure ash from the high temperature ash cooler, and which is able to reduce the pressure of the ash to ambient pressure.   
     
     
         8 . The gasification system of  claim 7 , wherein the depressurizing device comprises a double sealed lock hopper. 
     
     
         9 . The gasification system of  claim 1 , further comprising:
 a second ash cooler device which is connected to the high temperature ash cooler to receive the cooled high pressure ash from the high temperature ash cooler, and which is able to further lower the temperature of the ash to ambient temperature.   
     
     
         10 . The gasification system of  claim 7 , further comprising:
 a second ash cooler device which is connected to the depressurizing device to receive the ash from the high temperature ash cooler, and which is able to further lower the temperature of the ash to ambient temperature.   
     
     
         11 . The gasification system of  claim 9 , further comprising:
 a depressurizing device which is connected to the second ash cooling device to receive the ash from the second ash cooling device, and which is able to reduce the pressure of the ash to ambient pressure.   
     
     
         12 . The gasification system of  claim 2 , wherein the high temperature ash cooler comprises a fluidized bed or a moving bed wherein the high pressure ash makes direct contact with the water from the water supplying apparatus. 
     
     
         13 . The gasification system of  claim 2 , wherein the water supply apparatus comprises means to disperse the liquid into the ash such as spray nozzles, atomizing spray nozzles, microporous pipes. 
     
     
         14 . A gasification system comprising:
 a fluidized bed gasifier into which a carbonaceous feed material is fed, and out of which a product gas stream and a flowable ash are discharged, wherein the gasifier is operated at a temperature just under a melting point of the ash, and under a pressure not less than 6 bar gauge, and wherein the product gas stream comprises gaseous and particulate pollutants,   a wet scrubber for removing the pollutants from the product gas stream and producing a waste water stream,   an ash cooler connected with the gasifier to receive hot ash from the gasifier; and   a connection to deliver at least a portion of the waste water stream to the ash cooler, wherein the waste water stream is converted into steam.   
     
     
         15 . The gasification system of  claim 14 , wherein the ash cooler comprises a high temperature ash cooler connected directly with the gasifier. 
     
     
         16 . The gasification system of  claim 15 , wherein the ash cooler further comprises a low temperature ash cooler, and wherein at least a portion of the waste water is delivered to the low temperature ash cooler. 
     
     
         17 . The gasification system according to  claims 15 , wherein the waste water makes direct contact with the ash and steam generated from the contact is delivered to the gasifier. 
     
     
         18 . A method for cooling ash discharged from a fluidized bed gasifier, wherein a fluidized bed gasifier is fed with a carbonaceous feed material, and a product gas stream and a flowable ash is discharged out of the gasifier, wherein the gasifier is operated at a temperature just under a melting point of the ash, and under a pressure not less than 6 bar gauge, the method comprising:
 cooling the flowable ash to a temperature suitable for the ash to be handled with conventional carbon steel equipment in a high temperature ash cooler which is connected to the gasifier and into which the hot ash under pressure is discharged, wherein the high temperature ash cooler comprises a water-supplying apparatus that provides water for cooling the flowable ash.   
     
     
         19 . The method according to  claim 18 , wherein the water supplying apparatus supplies the cooling water to the high temperature ash cooler to be in direct contact with the flowable ash, and the method further comprises controlling the water supplying apparatus so that the water is vaporized upon direct contact with the ash to generate steam, and the flowability of the ash is maintained, and the flowable ash is cooled to a temperature not lower than the pre-determined threshold temperature. 
     
     
         20 . The method according to  claim 18 , further comprising:
 receiving the cooled high pressure ash from the high temperature ash cooler, and reducing the pressure of the ash to ambient pressure with a depressurizing device which is connected to the high temperature ash cooler.   
     
     
         21 . The method according to  claim 20 , further comprising:
 receiving the cooled ambient pressure ash from the a depressurizing device, and further lowering the temperature of the ash to ambient temperature with a second ash cooler device which is connected to the depressurizing device.   
     
     
         22 . A method for cooling ash discharged from a fluidized bed gasifier, wherein a fluidized bed gasifier is fed with a carbonaceous feed material, and a product gas stream and a flowable ash are discharged out of the gasifier, wherein the gasifier is operated at a temperature just under a melting point of the ash, and under a pressure not less than  6  bar gauge, and wherein the product gas stream comprises gaseous and particulate pollutants, the method comprising:
 removing the pollutants from the product gas stream and producing a waste water stream with a wet scrubber, 
 delivering at least a portion of the waste water stream from the wet scrubber to a ash cooler connected with the gasifier which receives hot ash from the gasifier, wherein the waste water stream is converted into steam. 
 
     
     
         23 . The method according to  claim 22 , wherein the ash cooler comprises a high temperature ash cooler connected directly with the gasifier. 
     
     
         24 . The method according to  claim 23 , wherein the ash cooler further comprises a low temperature ash cooler, and wherein at least a portion of the waste water is delivered to the low temperature ash cooler. 
     
     
         25 . The method according to  claims 23 , wherein the waste water makes direct contact with the ash and steam generated from the contact is delivered to the gasifier.