Heat Exchanger Using Non-Pure Water for Steam Generation

Abstract

A process and a device are described for producing high purity and high temperature steam from non-pure water which may be used in a variety of industrial processes that involve high temperature heat applications. The process and device may be used with technologies that generate steam using a variety of heat sources, such as, for example industrial furnaces, petrochemical plants, and emissions from incinerators. Of particular interest is the application in a thermochemical hydrogen production cycle such as the Cu—Cl Cycle. Non-pure water is used as the feedstock in the thermochemical hydrogen production cycle, with no need to adopt additional and conventional water pre-treatment and purification processes. The non-pure water may be selected from brackish water, saline water, seawater, used water, effluent treated water, tailings water, and other forms of water that is generally believed to be unusable as a direct feedstock of industrial processes. The direct usage of this water can significantly reduce water supply costs.

1 . In a high temperature industrial process where heat recovery is desired, the improvement comprising transferring heat from a high temperature molten or gaseous material obtained in the high temperature industrial process, to generate high temperature steam from non-pure water, with the impurities in the water being reduced to a precipitate, a slurry or a concentrated aqueous solution, which can be disposed of, or subjected to further processing. 
     
     
         2 . The process as claimed in  claim 1 , comprising generating high temperature steam in a heat exchange process, wherein heat from molten material is supplied to non-pure water to produce high temperature steam, with the impurities in the water being reduced to a precipitate, a slurry or a concentrated aqueous solution, which can be disposed of, or subjected to further processing. 
     
     
         3 . The process as claimed in  claim 1 , comprising generating high temperature steam in a heat exchange process, wherein the steam is generated from a two-stage steam generation loop which comprises two heat exchanges, a first-stage heat exchange comprising transferring heat from molten material to a thermal fluid circulating to a second-stage heat exchange, and back again to the first-stage heat exchange; heat from the thermal fluid being transferred to non-pure water in the second-stage heat exchange to produce high temperature steam from which hydrogen gas is produced, and impurities in the water are reduced to a precipitate, a slurry or a concentrated aqueous solution, which can be disposed of, or subjected to further processing. 
     
     
         4 . The process as claimed in  claim 1 , wherein the industrial process is a thermochemical Cu—Cl cycle for producing hydrogen gas from water decomposition which comprises supplying heat to the non-pure water from molten CuCl to produce high temperature steam for the production of hydrogen gas, with the impurities in the water being reduced to a precipitate, a slurry or a concentrated aqueous solution, which can be disposed of, or subjected to further processing. 
     
     
         5 . The process as claimed in  claim 1 , wherein the industrial process is a thermochemical Cu—Cl cycle for producing hydrogen gas from water decomposition which comprises the generation of steam from non-pure water using a two-stage steam generation loop which comprises two heat exchanges, a first-stage heat exchange comprising transferring heat from molten CuCl to a thermal fluid circulating to a second-stage heat exchange, and back again to the first-stage heat exchange; heat from the thermal fluid being transferred to non-pure water in the second-stage heat exchange to produce high temperature steam from which hydrogen gas is produced, and impurities in the water are reduced to a precipitate, a slurry or a concentrated aqueous solution, which can be disposed of, or subjected to further processing. 
     
     
         6 . A device for use in a high temperature industrial process where heat recovery is required and high temperature steam is produced which comprises using a tube and shell heat exchanger, the tube is arranged to receive a high temperature molten or gaseous material obtained from the high temperature industrial process and the shell is arranged to receive non-pure water to which heat is transferred from the high temperature molten or gaseous material in the tube, which then generates high temperature steam from the non-pure water, with the impurities in the non-pure water being reduced to a precipitate, a slurry or a concentrated aqueous solution, which can be disposed of, or subjected to further processing. 
     
     
         7 . A device for use in a high temperature industrial process where heat recovery is desired and high temperature steam is produced, comprising a two-stage steam generation loop which comprises two heat exchangers, each having a central tube and surrounding shell, the first-stage heat exchanger arranged for high temperature molten or gaseous material to pass through its central tube and the surrounding shell is arranged to receive a secondary thermal fluid to circulate in the surrounding shell to absorb heat from the high temperature molten or gaseous material, the surrounding shell being in fluid communication with the shell in the second-stage heat exchanger to permit circulation of the heated thermal fluid from one shell to the other and back again to the shell in the first-stage heat exchanger; the central tube of the second stage heat exchanger arranged to receive non-pure water which absorbs heat from the thermal fluid to generate high temperature steam for use in the high temperature industrial process, and impurities in the water are reduced to a precipitate, a slurry or a concentrated aqueous solution, which can be disposed of, or subjected to further processing. 
     
     
         8 . The device as claimed in  claim 6 , wherein the industrial process is a thermochemical Cu—Cl cycle for the production of hydrogen from water decomposition and the molten material is CuCl salt, and the high temperature steam is used to produce the hydrogen gas from decomposition of water in the thermochemical Cu—Cl cycle. 
     
     
         9 . The device as claimed in  claim 8 , wherein the molten CuCl is received in the tube of the heat exchanger and passes therethrough with the assistance of at least one of gravity, a push-pull plate or a helical screw. 
     
     
         10 . The device as claimed in  claim 8 , wherein the molten CuCl passes through the tube of the heat exchanger at a rate that allows the production of high temperature steam at a temperature suitable for the production of hydrogen gas from the decomposition of water in the thermochemical Cu—Cl cycle. 
     
     
         11 . The device as claimed in  claim 8 , wherein the tube wall is treated with lubricant to assist passage of molten CuCl through the tube of the heat exchanger, in at least one of the following ways: in advance of the device being used, on a periodic basis and on a continuous basis during use of the device. 
     
     
         12 . The device as claimed in  claim 8 , wherein the shell walls are washed with water or water containing cleaners or both to remove any adhered impurities that foul the reactor, the washing taking place either when the device is in use or when the device is not in use. 
     
     
         13 . The device as claimed in  claim 9 , wherein a helical screw is used and assists the passage of molten CuCl through the tube as it passes from a molten state to a solid state, as well as the efficient heat transfer from the molten CuCl to the non-pure water.