Method for Preparing Steam Using Waste Heat

Abstract

Provided is a method for preparing steam, comprising: making a process waste heat fluid supplied from a plurality of waste heat sources flow into each of refrigerant evaporators having numbers corresponding to plurality of waste heat sources to vaporize a refrigerant through heat exchange; joining vaporized refrigerant streams from each of refrigerant evaporators to one integrated pipe; compressing refrigerant stream joined to integrated pipe in a refrigerant compressor; heat exchanging compressed refrigerant stream with water in a refrigerant condenser to prepare a condensed refrigerant stream and steam; and decompressing the condensed refrigerant stream by passing condensed refrigerant stream through a refrigerant expansion valve, followed by branching and circulating the condensed refrigerant stream to each of plurality of refrigerant evaporators, and further including transferring and compressing steam flowing out of refrigerant condenser to a steam compressor, and a system for recovering waste heat.

1 . A method for preparing steam, comprising:
 making a process waste heat fluid supplied from a plurality of waste heat sources flow into each of refrigerant evaporators having numbers corresponding to the plurality of waste heat sources to vaporize a refrigerant through heat exchange to form a plurality of vaporized refrigerant streams;   joining the plurality of vaporized refrigerant streams from each of the refrigerant evaporators to one integrated pipe to form a joined stream;   compressing the joined stream in a refrigerant compressor to form a compressed refrigerant stream;   heat exchanging the compressed refrigerant stream with water in a refrigerant condenser to prepare a condensed refrigerant stream and steam; and   decompressing the condensed refrigerant stream by passing the condensed refrigerant stream through a refrigerant expansion valve, followed by branching and circulating the condensed refrigerant stream to each of the plurality of refrigerant evaporators, and   further including transferring and compressing the steam flowing out of the refrigerant condenser to a steam compressor.   
     
     
         2 . The method of  claim 1 , wherein the plurality of waste heat sources and refrigerant evaporators include of 2 to 10 units, respectively. 
     
     
         3 . The method of  claim 1 , wherein the process waste heat fluid flowing into each of the refrigerant evaporators has an initial temperature of 30 to 140° C. 
     
     
         4 . The method of  claim 1 , wherein the refrigerant flowing through each of the refrigerant evaporators has a pressure ranging from 1 to 30 bar and a temperature ranging from 10 to 120° C. 
     
     
         5 . The method of  claim 1 , wherein the refrigerant stream vaporized in each of the refrigerant evaporators has a temperature satisfying Equation 1:
   1° C.≤ T   WH   −T   G ≤20° C.  [Equation 1]
   wherein,   T WH  is a terminal temperature of the process waste heat fluid flowing into each of the refrigerant evaporator, and   T G  is a temperature of the vaporized refrigerant stream in each of the refrigerant evaporators.   
     
     
         6 . The method of  claim 1 , wherein the integrated pipe has a straight length of 5 m to 5,000 m and is controlled to maintain a flow rate of more than 5 m/s to 50 m/s. 
     
     
         7 . The method of  claim 1 , wherein the refrigerant compressor uses electrical energy to increase a pressure of the refrigerant stream by 1.2 to 5 times. 
     
     
         8 . The method of  claim 1 , wherein the compressed refrigerant stream has a temperature ranging from 90° C. to 200° C. 
     
     
         9 . The method of  claim 1 , wherein the refrigerant stream condensed by the heat exchange with the water in the refrigerant condenser has a temperature ranging from 85° C. to 170° C. 
     
     
         10 . The method of  claim 1 , wherein the refrigerant stream passing through the refrigerant expansion valve has a pressure ranging from 0.5 bar to 30 bar. 
     
     
         11 . The method of  claim 1 , wherein the steam prepared by the heat exchange between the refrigerant stream and the water in the refrigerant condenser has a pressure ranging from 1 bar to 16 bar. 
     
     
         12 . The method of  claim 1 , wherein the steam flowing out of the refrigerant condenser is compressed to 4 bar to 60 bar by supplying electrical energy from the steam compressor, converted into saturated steam by supplying water to the compressed steam, and is then used as a process heat source. 
     
     
         13 . A system for preparing steam, comprising:
 a plurality of waste heat sources and a heat pump device connected thereto,   wherein the heat pump device includes a refrigerant evaporator, a refrigerant compressor, a refrigerant condenser, and a refrigerant expansion valve connected through a pipe,   the refrigerant evaporator includes a plurality of refrigerant evaporators to communicate with each process waste heat fluid supplied from the plurality of waste heat sources,   refrigerant streams flowing out of the pipe connected to the plurality of refrigerant evaporators are joined through an integrated pipe and transferred to the refrigerant compressor,   the refrigerant stream passing through the refrigerant expansion valve is circulated to the plurality of refrigerant evaporators through a branched pipe, and   the refrigerant condenser is connected to an additional steam compressor.   
     
     
         14 . The system of  claim 13 , wherein the steam compressor compresses steam prepared by heat exchange between the refrigerant stream compressed in the refrigerant condenser and water and converts the compressed steam into saturated steam.