Method for Removing Foulants from a Heat Exchanger through Coolant Flow Control

Abstract

A method for removing a foulant from a heat exchanger is disclosed. A process fluid, comprising a process liquid and a fouling component, are provided to a process side of the heat exchanger. A flow of a coolant to the coolant side is provided by opening an inlet to the coolant side. The process fluid is cooled, a portion of the fouling component desublimating, crystallizing, freezing, condensing coupled with solidifying, or a combination thereof as a first portion of the foulant onto an outer surface of the coolant side. The inlet to the coolant side is periodically closed such that the flow of the coolant slows or stops, warming the process side, and causing the first portion of the foulant to sublimate, melt, absorb, or a combination thereof off the outer surface of the coolant side. The process then returns to the providing the flow of the coolant step.

1 . A method for removing a foulant from a heat exchanger comprising:
 providing the heat exchanger comprising a process side and a coolant side;   providing a process fluid, comprising a process liquid and a fouling component, to the process side;   providing a flow of a coolant to the coolant side by opening an inlet to the coolant side;   cooling the process fluid, a portion of the fouling component desublimating, crystallizing, freezing, condensing coupled with solidifying, or a combination thereof as a first portion of the foulant onto an outer surface of the coolant side;   periodically closing the inlet to the coolant side such that the flow of the coolant slows or stops, warming the process side, and causing the first portion of the foulant to sublimate, melt, absorb, or a combination thereof off the outer surface of the coolant side; and,   returning to the providing the flow of the coolant step;   
       whereby the foulant is removed from the heat exchanger. 
     
     
         2 . The method of  claim 1 , wherein cooling the process fluid further crystallizes, freezes, solidifies, or a combination thereof a portion of the process liquid onto the outer surface of the coolant side such that the portion of the process liquid forms a second portion of the foulant. 
     
     
         3 . The method of  claim 2 , providing the heat exchanger further comprising a shell and tube style exchanger, plate style exchanger, plate and frame style exchanger, plate and shell style exchanger, spiral style exchanger, plate fin style exchanger, or combinations thereof. 
     
     
         4 . The method of  claim 3 , wherein the inlet to the coolant side comprises a valve or a pump. 
     
     
         5 . The method of  claim 4 , further comprising removing the coolant from the coolant side through an outlet from the coolant side when the inlet to the coolant side is closed. 
     
     
         6 . The method of  claim 5 , wherein the removing the coolant step is accomplished by pumping the coolant as a liquid from the heat exchanger. 
     
     
         7 . The method of  claim 5 , wherein the removing the coolant step is accomplished by boiling the coolant out of the heat exchanger. 
     
     
         8 . The method of  claim 7 , wherein the removing the coolant step is further accomplished by providing vacuum to the outlet of the coolant side. 
     
     
         9 . The method of  claim 5 , wherein the heat exchanger further comprises instruments, the instruments comprising a flow meter on an inlet of the process side, a temperature sensor on the process side, a pressure sensor on the process side, or a combination thereof. 
     
     
         10 . The method of  claim 9 , further comprising providing a controller that receives signals from the instruments and uses the signals to control the inlet of the coolant side. 
     
     
         11 . The method of  claim 10 , wherein a change in pressure on the process side indicates a change in the amount of the foulant, an increase in the pressure above a threshold triggers the controller to completely close the inlet to the coolant side, and the pressure returning below the threshold triggers the controller to completely open the inlet to the coolant side. 
     
     
         12 . The method of  claim 10 , wherein a change in pressure on the process side indicates a change in the amount of the foulant, and an increase in the pressure above a threshold triggers the controller to close the inlet to the coolant side in proportion to how far above the threshold the pressure climbs, with the inlet to the coolant side fully open with the pressure below the first threshold, and the inlet to the coolant side fully closed above a high pressure limit. 
     
     
         13 . The method of  claim 10 , wherein an increase in temperature on the process side indicates an change in the amount of the foulant, and an increase in the temperature above a threshold triggers the controller to close the inlet to the coolant side in proportion to how far above the threshold the temperature climbs, with the inlet to the coolant side fully open with the temperature below the first threshold, and the inlet to the coolant side fully closed above a high temperature limit. 
     
     
         14 . The method of  claim 1 , providing the fouling component further comprising carbon dioxide, nitrogen oxide, sulfur dioxide, nitrogen dioxide, sulfur trioxide, hydrogen sulfide, hydrogen cyanide, water, condensed hydrocarbons, or combinations thereof. 
     
     
         15 . The method of  claim 1 , providing the fouling component further comprising a solid portion comprising particulates, mercury, other heavy metals, condensed organics, soot, inorganic ash components, biomass, salts, water ice, other impurities common to a vitiated flow, producer gases, or other industrial flows, or combinations thereof. 
     
     
         16 . The method of  claim 1 , providing the process liquid comprising any compound or mixture of compounds with a freezing point below the temperature at which the fouling component solidifies. 
     
     
         17 . The method of  claim 1 , providing the contact liquid stream comprising water, brine, hydrocarbons, liquid ammonia, liquid carbon dioxide, other cryogenic liquids, and combinations thereof. 
     
     
         18 . The method of  claim 1 , providing the contact liquid stream comprising 1,1,3-trimethylcyclopentane, 1,4-pentadiene, 1,5-hexadiene, 1-butene, 1-methyl-1-ethylcyclopentane, 1-pentene, 3,3,3,3-tetrafluoropropene, 3,3-dimethyl-1-butene, 3-chloro-1,1,1,2-tetrafluoroethane, 3-methylpentane, 3-methyl-1,4-pentadiene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-methylpentane, 5-methyl-1-hexene, 5-methyl-1-pentene, 5-methylcyclopentene, 5-methyl-trans-2-pentene, bromochlorodifluoromethane, bromodifluoromethane, bromotrifluoroethylene, chlorotrifluoroethylene, cis 3-hexene, cis-1,3-pentadiene, cis-2-hexene, cis-2-pentene, dichlorodifluoromethane, difluoromethyl ether, trifluoromethyl ether, dimethyl ether, ethyl fluoride, ethyl mercaptan, hexafluoropropylene, isobutane, isobutene, isobutyl mercaptan, isopentane, isoprene, methyl isopropyl ether, methylcyclohexane, methylcyclopentane, methylcyclopropane, n,n-diethylmethylamine, octafluoropropane, pentafluoroethyl trifluorovinyl ether, propane, sec-butyl mercaptan, trans-2-pentene, trifluoromethyl trifluorovinyl ether, vinyl chloride, bromotrifluoromethane, chlorodifluoromethane, dimethyl silane, ketene, methyl silane, perchloryl fluoride, propylene, vinyl fluoride, or combinations thereof. 
     
     
         19 . The method of  claim 1 , providing the coolant comprising liquid nitrogen, ethane, methane, propane, or other refrigerants. 
     
     
         20 . A method for removing a foulant from a heat exchanger comprising:
 providing the heat exchanger comprising instruments, a process side and a coolant side, the heat exchanger further comprising a shell and tube style exchanger, plate style exchanger, plate and frame style exchanger, plate and shell style exchanger, spiral style exchanger, plate fin style exchanger, or combinations thereof, and the instruments comprising a flow meter on an inlet of the process side, a temperature sensor on an outlet of the process side, and a pressure sensor on the process side;   providing a process fluid, comprising a process liquid and a fouling component, to the process side, the process liquid comprising any compound or mixture of compounds with a freezing point below the temperature at which the fouling component solidifies, and the fouling component comprising carbon dioxide, nitrogen oxide, sulfur dioxide, nitrogen dioxide, sulfur trioxide, hydrogen sulfide, hydrogen cyanide, water, condensed hydrocarbons, or combinations thereof;   providing a flow of a coolant to the coolant side by opening an inlet to the coolant side, the inlet to the coolant side comprising a valve or a pump;   cooling the process fluid, a portion of the fouling component and a portion of the process liquid desublimating, crystallizing, freezing, condensing coupled with solidifying, or a combination thereof as the foulant onto an outer surface of the coolant side;   receiving signals from the instruments indicating pressure, temperature, and flow, an increase in the pressure, a decrease in the flow, or an increase in the temperature indicating an increase in the amount of the foulant;   periodically closing the inlet to the coolant side when the pressure goes above a pressure threshold, the temperature goes above a temperature threshold, or the flow goes below a process flow threshold, such that the flow of the coolant slows or stops, removing the coolant through an outlet of the coolant side by providing vacuum such that the coolant boils from the coolant side and leaves through the outlet of the coolant side, warming the process side, and causing the foulant to sublimate, melt, absorb, or a combination thereof off the outer surface of the coolant side; and,   returning to the providing the flow of the coolant step;   
       whereby the foulant is removed from the heat exchanger.