Indirect counterflow heat recovery system of the regenerative type for steam generators, gas turbines, and furnaces and engines in general

• US 4,452,180 A
• Filed: 09/30/1982
• Issued: 06/05/1984
• Est. Priority Date: 09/30/1982
• Status: Expired due to Fees

• Current Assignee: Kamal-Eldin Hassan
• Original Assignee: Kamal-Eldin Hassan
• Inventors: Hassan, Kamal-Eldin
• Primary Examiner(s): Yuen, Henry C.
• Application Number:
  US06/430,281
• Time in Patent Office: 614 Days
• Field of Search: 110/254, 110/215, 122/1 A, 122/31 R, 165/104.31, 165/104.13
• US Class Current: 122/1.00A
• CPC Class Codes: F23L 15/045 using intermediate heat-transfer fluids
• CPC Class Codes: F24H 8/003 having means for moistening the combustion air with condensate from the combustion gases
• CPC Class Codes: Y02B 30/00 Energy efficient heating, ventilation or air conditioning [HVAC]
• CPC Class Codes: Y02E 20/34 Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery

Abstract

A heat regenerator indirectly utilizes the hot gases exhausted by a furnace or engine to heat the air supply to it, through the use of heat transfer fluids which function as an efficient heat transfer medium to implementation of the counterflow and direct contact heat transfer principles.

Claims

1. An indirect heat recovery system of regenerative type for use between an exhaust gases duct and an air intake duct, comprising:

a. at least one regenerative loop, provided in fluidly connecting relationship between said exhaust gases duct and said air intake duct, and disposed successively in said ducts, wherein each of said loop comprises;

i. a first recuperator disposed in the exhaust gases duct and a second recuperator disposed in the air intake duct;

ii. conduit means fluidly connecting said first recuperator to said second recuperator;

iii. at least one heat transfer media contained by said conduit means;

iv. circulating means for circulating said heat transfer media cyclically through said conduit means, through said first recuperator, such that said media enters said first recuperator at a point adjacent to the point of exit of exhaust gases in said exhaust duct, exiting said first recuperator at a point adjacent to the point of entrance of hot exhaust gases within said entrance duct, and said second recuperator, wherein said media enters said second recuperator at a point adjacent to the point of exit of said air intake flow within said air intake induct, and said media exit said second recuperator at a point adjacent to the point of entrance of said intake gases within said air intake duct, thereby causing within said first and within said second recuperator the temperature differential between said media and said gases to remain substantially maximized throughout the media flow path within said recuperators, thereby causing maxixum effective heat transfer from said exhaust gases duct to said first recuperator and from second recuperator to said air intake duct;

v. control means for controlling the rate of circulation of said heat transfer media cyclically through said conduit means, thereby controlling the amount of heat transferred from said exhaust gases duct to said first recuperator and from said said recuperator to said air intake duct;

wherein at least one of said regenerative loops comprises a first recuperator and a second recuperator of the open type, comprising, respectively, application means for introducing said heat transfer media into direct contact with the hot gases being exhausted through said gases duct, and the application means for introducing said air stream being conveyed through said air intake duct;

wherein each of said open type recuperator further comprises a plurality of banks each comprising a length of tubing, fluidly communication with each of said conduit means, disposed substantially in said ducts, wherein each of said banks comprises a plurality of orifices provided through the side of said tubing facing against the flow of said hot exhaust gases or said incoming air stream, fluidly communicating said tubing therewith, for thereby introducing said heat transfer media into direct contact therewith;

wherein said open type recuperator further comprises spray nozzle means fluidly communicating each bank with the flow of said hot exhaust gases of said incoming air stream, for spraying said heat transfer media into direction contact therewith;

wherein each said conduit means of each said loop further comprises a replacement reservoir for containing reserve supplies of heat transfer fluid for replenishing said loops;

wherein said conduit means of at least one of said regenerative loops further comprises filtering means for filtering all undesirable particulates and pollutants from said heat transfer fluids;

wherein said first recuperator and said second recuperator of each of said regenerative loops each comprises a collection means provided in fluid communication with said conduit means downstream of each of said application means, for collecting and conveying substantially all droplets of said heat transfer media which are suspended in said flow of hot exhaust gases or said stream of incoming air, through said conduit means for circulation of said heat transfer media by means of said circulation means, through said conduit means to one recuperator and back through said conduit means to the other recuperator;

wherein each of said collection means comprises a trough provided at the bottom of each of said duct beneath each of said application means, wherein each of said trough comprises a sump fluidly communicating with said conduit means;

wherein said first recuperator and said second recuperator of each of said loop each comprise separator means downstream of each of said bank and above each of said collector means for separating substantially all droplets of said heat transfer media which are suspended in said flow of hot exhaust gases and said incoming air stream therefrom, respectively, wherein each of said separation means is at least the length of each of said bank, and wherein said droplets of said heat transfer media are drained from each of said separation means into each of said collection means and conveyed through each of said sump thereof to said conduit means for circulation thereof;

wherein each said separation means comprises an array of baffles;

wherein said circulating means of each of said loop comprises throttling means for regulating the flow rate at which heat transfer media is circulated through each of said loop, thereby ultimately controlling the rate of heat exchange between said heat transfer media and said hot exhaust gases, said heat transfer media and said incoming air stream;

wherein at least two of said loops disposed successively within said exhaust gases duct and said air intake duct according to the temperature gradients in said ducts, comprise valving means for conveying said heat transfer media from the conduit means of the more downstream loop into the conduit means of the more upstream loop and vice versa, thereby indirectly implementing a parallel flow heat exchange principle to prevent undercooling of said hot exhaust gases when the temperature of said heat transfer media becomes lower than the dew-point of said gases, thereby preventing condensation of said gases on the outer surface of said first recuperator, thereby ultimately preventing corrosion thereof;

wherein it further comprises a water pump operatively associated with said highest temperature regenerative loop, said water pump comprising at least one bank, fluidly connected thereto, disposed substantially across said hot exhaust gas duct, wherein said bank(s) comprise(s) a plurality of passes provided integral to the side of said bank(s) facing against the flow of said hot exhaust gases, and wherein said water pump is actuatable upon the occurrence of the condition whereby the temperature of said hot exhaust gases exceeds a certain, preset value, to spray water through said passes of said bank(s) into said flow of hot exhaust gases, thereby cooling said exhaust gases to an acceptable temperature level.

2. The system of claim 1, wherein said valving means comprises temperature-sensing means for automatically actuating said valving means to indirectly implement the parallel flow heat exchange principle.

3. The system of claim 1, wherein said heat transfer media being circulated through said loop having recuperators of the open-type, comprise at least one liquid having a substantially low vapor pressure at the maximum operating temperature of said regenerative loops, to thereby minimize evaporation thereof and the amount of said reserve supplies of said heat transfer media.

4. The system of claim 3, wherein said liquid further has a flash point at least well above the maximum operating temperature of said regenerative loops, having recuperators of the open-type, thereby maximizing the safety of the operation of said heat recovery system.

5. The system of claim 3, wherein said liquid has vapors which are non-toxic to avoid polluting the exhaust gases released to the atmosphere through said hot exhaust gas duct.

6. The system of claim 3, wherein said liquid comprises polyphenyl ethers.

7. The system of claim 1, wherein said heat transfer media introduced through said application means of said open-type first recuperators, further acts to dissolve at least some of the gaseous pollutants and wash down any solid particles held in suspension by said exhaust gases, said heat transfer fluids of said open-type first recuperators thus acting as washers/scrubbers of said exhaust gases, thereby replacing at least some part of the pollution or emission-control equipment.