Controlled heating method of a process fluid through concentrating solar thermal plant and heat carrier system and apparatus thereof

Abstract

A controlled heating method of a process fluid through concentrating solar thermal plant and heat carrier system where the solar heat available from solar plant is transmitted to a heat carrier stream constituted by air and it is eventually integrated with post firing fuel stream; the heat carrier stream constituted by hot air and post-firing flue gas stream is circulated via a duct circuit through a heat exchanger with the process fluid to allow reaching final required process fluid temperature; the post-firing contribute is determined by an automatic control system which controls in continuous the process fluid temperature and adapt the firing contribute during the different operating phases of the concentrating solar plant.

1 . A controlled heating method of a process fluid through concentrating solar thermal plant and heat carrier system wherein:
 the solar heat available from solar plant is transmitted to a heat carrier stream constituted by air;   the variable heat supplied by solar thermal plant to heat carrier air stream is integrated with post-firing of a fuel stream;   the heat carrier stream constituted by hot air and post-firing flue gas stream is circulated via a duct circuit through a heat exchanger with the process fluid to allow reaching final required process fluid temperature;   the post-firing contribute being determined by an automatic control system which controls in continuous the process fluid temperature and adapt the firing contribute during the different operating phases of the concentrating solar plant.   
     
     
         2 . A controlled heating method of  claim 1  in which a first heat exchanger is transferring heat from molten salts to heat carrier stream during solar plant active phases (direct radiation and storage period). 
     
     
         3 . A controlled heating method of  claims 1  in which said post-firing contribute can vary from 0 to full duty requirement. 
     
     
         4 . A controlled heating method as per  claim 2  in which a second heat exchanger transfers heat from heat carrier to a process fluid up to a controlled final temperature. 
     
     
         5 . A controlled heating method as per  claim 1  in which process fluid is either a refinery fluid, a petrochemical process fluid, demineralized water, boiler feed water or steam. 
     
     
         6 . A controlled heating method as per  claim 1  in which fresh air flow rate in the duct circuit is determined by automatic control and admitted through relevant control valve via a fan. 
     
     
         7 . A controlled heating method as per  claim 1  in which a purge stream to stack is determined by automatic control and discharged to stack through relevant control valve. 
     
     
         8 . A controlled heating method as per  claim 1  in which the first heat exchanger between molten salts and heat carrier stream can work reversely as a heater of cold molten salt during solar plant inactive phase. 
     
     
         9 . A controlled heating method as per  claim 1  in which a heat carrier secondary stream is automatically sent through a control valve to molten salts heat exchanger to avoid cold molten salts solidification during solar plant inactive phase. 
     
     
         10 . A controlled heating apparatus of a process fluid through concentrating solar thermal plant and a heat carrier circuit, which comprises:
 a concentrating solar thermal plant ( 10 ) based on molten salts circulation;   a heat exchanger ( 20 ) to transfer heat from molten salts to a heat carrier fluid ( 201 ) during solar plant active phases;   a post-firing ( 30 ) to transfer heat to the heat carrier fluid ( 202 ) in output from exchanger ( 20 );   a heat exchanger ( 40 ) to transfer heat from the heat carrier fluid ( 203 ) in output from post-firing ( 30 ) to the process fluid ( 400 );   the post-firing contribute being calculated by an automatic control system ( 80 ) which controls the process fluid temperature in outlet ( 83 ) and adapts the firing contribute during the different operating phases of the solar plant ( 10 ).   
     
     
         11 . An apparatus according to  claim 10 , wherein the post-firing ( 30 ) is realized by duct burners located inside the air duct. 
     
     
         12 . An apparatus according to  claim 10 , further comprising a heat carrier circuit fan ( 50 ) capable to provide the pressure head necessary to the heat carrier fluid to win the circuit pressure drops. 
     
     
         13 . An apparatus according to  claim 10 , further comprising a fresh air fan ( 60 ) capable to admit the required fresh air flow ( 200 ) under automatic control via a flow control ( 85 ) into the heat carrier air-flue gas ( 201 ). 
     
     
         14 . An apparatus according to  claim 10 , further comprising a flow control loop ( 86 ) capable to control the purge gas stream to be sent to a stack ( 70 ). 
     
     
         15 . An apparatus according to  claim 10 , further comprising a control valve ( 88 ) which permits to derive a heat carrier by-pass stream ( 210 ) to allow temperature control of the cold molten salts circulating during CSP un-active phases.