Method of enhancing the quality of high-moisture materials using system heat sources

Abstract

The present invention harvests and utilizes fluidized bed drying technology and waste heat streams augmented by other available heat sources to dry feedstock or fuel. This method is useful in many industries, including coal-fired power plants. Coal is dried using the present invention before it goes to coal pulverizers and on to the furnace/boiler arrangement. Coal can be intercepted on current coal feed systems ahead of the pulverizers. Drying fuel, such as coal, is done to improve boiler efficiency and reduce emissions. A two-stage bed utilized in the process first “pre-dries and separates” the feed stream into desirable and undesirable feedstock. Then, it incrementally dries and segregates fluidizable and non-fluidizable material from the product stream. This is all completed in a low-temperature, open-air system. Elevation of fan room air temperature is also accomplished using waste heat, thereby making available to the plant system higher temperature media to enhance the feedstock drying process.

We claim: 
     
         1 . A method for thermally amplifying a gaseous stream for use within a manufacturing operation that produces at least one waste heat source, such method comprising:
 (a) providing a gaseous stream at a first temperature;   (b) providing heat from a waste heat source and a first heat exchanger, whereby the gaseous stream is delivered to the first heat exchanger and heat content contained within the waste heat source is delivered to the gaseous stream which exits the first heat exchanger at a second temperature that is higher than the first temperature; and   (c) providing heat from a waste heat source and a second heat exchanger, whereby the gaseous stream that exited the first heat exchanger is delivered to the second heat exchanger, and heat content contained within the waste heat source is delivered to the gaseous stream which exits the second heat exchanger at a third temperature that is higher than the second temperature.   
     
     
         2 . The method of  claim 1 , wherein the waste heat source delivered to the first heat exchanger and the second heat exchanger constitute the same waste heat source within the manufacturing operation. 
     
     
         3 . The method of  claim 1 , wherein the waste heat sources delivered to the first heat exchanger and the second heat exchanger constitute different types of waste heat sources within the manufacturing operation. 
     
     
         4 . The method of  claim 1 , wherein the waste heat sources are selected from the group consisting of hot condenser cooling water, hot stack gas, hot flue gas, spent process steam, and discarded heat from operating equipment. 
     
     
         5 . The method of  claim 1  further comprising the providing of at least one additional heat exchanger and associated source of heat, whereby the gaseous stream exits the additional heat exchanger at a temperature higher than the temperature at which it exited the previous heat exchanger. 
     
     
         6 . The method of  claim 5 , wherein the additional heat source constitutes a waste heat source. 
     
     
         7 . In an industrial plant operation having a fluid stream for performing work and producing at least one waste heat source, a system for utilizing the at least one waste heat source to thermally amplify the fluid stream in order to optimize plant efficiencies, such system including:
 (a) a first heat exchanger operatively connected to a first waste heat source and the fluid stream for transferring heat from the first waste heat source to the fluid stream to increase the temperature of the fluid stream; and   (b) a second heat exchanger operatively connected to a second waste heat source and the fluid stream exiting the first heat exchanger for transferring heat from the second waste heat source to the fluid stream to further increase the temperature of the fluid stream.   
     
     
         8 . The system of  claim 7 , wherein the waste heat sources delivered to the first heat exchanger constitute different types of waste heat sources within the industrial plant operation. 
     
     
         9 . The system of  claim 7  further comprising an additional heat exchanger operatively connected heat source for transferring heat from the additional heat source to the fluid stream exiting the second heat exchanger to further increase its temperature. 
     
     
         10 . The system of  claim 9 , wherein the additional heat source constitutes a waste heat source. 
     
     
         11 . The system of  claim 7  further including a dryer bed operatively connected to the fluid stream for receiving the fluid stream to treat particulate material contained within the dryer bed. 
     
     
         12 . The system of  claim 11 , wherein the dryer bed is a fixed-bed dryer. 
     
     
         13 . The system of  claim 7 , wherein the industrial plant operation is an electrical power plant having a condenser that produces hot condenser cooling water and a furnace that produces hot flue gas, wherein the first waste heat source constitutes the hot condenser cooling water and the second waste heat source constitutes the hot flue gas. 
     
     
         14 . The system of  claim 7 , wherein the industrial plant operation is an electrical power plant having a condenser that produces hot condenser cooling water, wherein the first waste heat source and the second waste heat source both constitute the hot condenser cooling water. 
     
     
         15 . The system of  claim 7 , wherein one of the heat exchangers is a bi-sector air preheater. 
     
     
         16 . The system of  claim 7 , wherein one of the heat exchangers is a tri-sector air preheater. 
     
     
         17 . A coal drying system incorporated into an industrial plant operation having at least two different types of waste heat, such system comprising:
 (a) a fluidized-bed dryer unit having an interior for receiving the coal, the dryer unit having a first drying stage in operative communication with a second drying stage wherein coal disposed in the dryer unit travels from the first dryer stage toward the second drying stage while being dried;   (b) an air pre-heater operatively disposed between the dryer unit and the two different waste heat sources to transfer heat from each of the waste heat sources to an air stream passing through the air pre-heater before it flows to and through the dryer unit, wherein the air stream fluidizes the coal particles contained within dryer unit; and   (c) a heat exchanger operatively connected to the dryer unit for transferring heat from at least one of the waste heat sources to the dryer unit for increasing the interior temperature of the dryer unit such that moisture within the coal is reduced.   
     
     
         18 . The system of  claim 17 , wherein the two different types of waste heat sources constitute hot condenser cooling water and hot flue gas produced within the industrial plant operation.