Method for heating up or keeping warm the flow paths of a process plant

Abstract

The invention relates to a method for heating up or keeping warm the flow paths of a process plant, wherein a stream of fluid provided for heating up or keeping warm the flow paths is guided in a circuit which comprises a heating device ( 8 ) for warming up the stream of fluid. According to the invention, to equalize the pressure loss occurring in the circuit, the stream of fluid is supplied as a suction medium to a jet pump ( 5 ) arranged in the circuit and is exposed there to a pumping medium supplied at a higher pressure.

1 . A method of heating or keeping warm the flow passages of a process plant for the catalytic conversion of constituents of a process fluid outside the process operation during which the process fluid flows into the plant and there is subjected to a chemical or physical treatment or conversion, a fluid flow provided instead of the process fluid outside the process operation for heating or keeping warm the flow passages being guided in a closed loop containing a heater for warming up the fluid flow, wherein to compensate for the pressure loss occurring in the closed loop the fluid flow is fed as an inlet fluid to a jet pump in the closed loop and there is acted on with a motive fluid fed at a higher pressure. 
     
     
         2 . (canceled) 
     
     
         3 . The method according to  claim 1 , wherein flow passages of the process plant contain at least one apparatus holding bulk solids. 
     
     
         4 . The method according to  claim 1 , wherein a pressure within the entire closed loop is greater than 5 bar. 
     
     
         5 . The method according to  claim 1 , wherein the volumetric flow of the fluid flow provided for heating or keeping warm the flow is less than 15% of a nominal volumetric flow for which the process plant is designed with full work load in normal operation. 
     
     
         6 . The method according to  claim 1 , wherein an inert gas, preferably nitrogen or carbon dioxide, is fed to the jet pump as a motive fluid. 
     
     
         7 . The method according to  claim 1 , wherein a fluid containing gaseous constituents and water vapor is fed as motive fluid to the jet pump. 
     
     
         8 . The method according  claim 1 , wherein water vapor is fed as motive fluid to the jet pump. 
     
     
         9 . The method according to  claim 8 , wherein before return of the fluid flow to the jet pump, water is condensed out and removed from the fluid flow, the quantity of water condensed out of the fluid flow corresponding to the quantity of water fed to the jet pump as water vapor as motive fluid. 
     
     
         10 . The method according to  claim 1 , wherein part of the fluid guided in the closed loop is extracted. 
     
     
         11 . The method according to  claim 10 , wherein a volumetric flow of the extracted part corresponds to the volumetric flow of the fed-in motive fluid. 
     
     
         12 . The method according to  claim 10 , wherein the extracted part of the fluid is guided for heat recovery via a heat exchanger, the motive fluid being preheated with the recovered heat. 
     
     
         13 . The method according to  claim 1 , wherein a heat exchanger that is acted on with a heating medium is used as a heater for heating the fluid flow. 
     
     
         14 . The method according to  claim 1 , wherein an electrically operated heating element is used as a heater for heating the fluid flow. 
     
     
         15 . The method according to  claim 1 , wherein the motive fluid is held in a pressure tank. 
     
     
         16 . The method according to  claim 1 , wherein the process plant has at least two stages and that a flow splitter containing a flow controller is provided seen in the flow direction behind the jet pump, flow splitter renders possible a variable division of the fluid flow between the first stage and the second stage. 
     
     
         17 . A method of operating a process plant for the catalytic conversion of constituents of a process fluid where during normal operation of the plant the process fluid is fed into the plant, then passed through flow passages and flowed in a treatment stage over a bulk catalyst, and thereafter fed out of the plant, the method comprising, for heating or keeping warm the flow passages outside of normal operation, the steps of:
 providing a recovery line forming with the flow passages a closed loop passing through the treatment stage, through a heater, and from an inlet to an outlet of a jet pump having a motive-fluid nozzle; and   supplying a motive fluid under higher pressure than the process fluid in the closed loop to the nozzle so as to circulate the process fluid through the closed loop such that heat picked up from the heater is transferred to the flow passages and bulk material in the treatment stage.