Chilling economizer

Abstract

Chilling is produced from heat that is normally wasted in the economizer section of a steam boiler. A thermally-activated ammonia-water absorption chiller is powered by a heat recovery unit. The heat recovery unit supplies boiler exhaust heat to desorb the working fluid of the chiller. That can be directly, such that the heat recovery unit is a heat recovery vapor generator that can be colocated with an economizer, in parallel or series. The exhaust heat can alternatively be supplied to the AARC indirectly, via a heat transfer loop and a separate generator. The desorbed ammonia vapor is rectified, condensed, and then used to produce the chilling. The heat released in the chiller when low pressure ammonia vapor is re-absorbed is used to preheat the boiler feedwater.

1 . An apparatus for producing chilling comprised of:
 a. A steam boiler;   b. An economizer in the exhaust from said steam boiler;   c. A thermally-activated chiller;   d. A heat recovery vapor generator (HRVG) for said chiller that is colocated with said economizer in said exhaust stream; and   e. A thermal heating load that receives reject heat from the absorber of said chiller.   
     
     
         2 . The apparatus according to  claim 1  wherein said thermally-activated chiller is an ammonia-water absorption refrigeration cycle (AARC), and wherein said thermal heating load is a preheater for the feedwater supplied to said economizer. 
     
     
         3 . The apparatus according to  claim 2  wherein said economizer is comprised of at least two sections, with a section of HRVG between adjoining economizer sections. 
     
     
         4 . The apparatus according to  claim 2  wherein said economizer and said HRVG are in parallel with respect to the exhaust flow direction. 
     
     
         5 . The apparatus according to  claim 2  additionally comprised of a gas turbine that discharges combustion exhaust to heat said boiler, and a turbine inlet chilling coil that is supplied chilling from said AARC. 
     
     
         6 . The apparatus according to  claim 5  wherein said AARC is adapted to supply heating to said chilling coil in cold ambient conditions. 
     
     
         7 . The apparatus according to  claim 5  additionally comprised of a second generator for said AARC that is supplied steam from said boiler. 
     
     
         8 . The apparatus according to  claim 2  wherein working fluid from said AARC is supplied directly to said HRVG and has countercurrent flowpath to said exhaust flow. 
     
     
         9 . The apparatus according to  claim 2  wherein a manufactured product is heated by steam from said boiler and is chilled by said chiller. 
     
     
         10 . The apparatus according to  claim 2  wherein a conditioned space is heated by steam from said boiler and cooled by said chilling. 
     
     
         11 . The apparatus according to  claim 2  wherein said feedwater preheater is the absorber in said AARC. 
     
     
         12 . The apparatus according to  claim 11  additionally comprised of a second absorber for said AARC that is cooled by heat rejection to ambient, e.g. via cooling water. 
     
     
         13 . An apparatus for heating boiler feedwater and for producing chilling comprised of:
 a. A steam boiler;   b. A thermally-activated chiller that includes a rectifier;   c. A heat recovery unit (HRU) for said chiller that is located in the exhaust stream of said boiler, and that transfers exhaust heat to said chiller; and   d. An absorber in said chiller that transfers reject heat to said feedwater such that the feedwater is heated to at least about 140° F.   
     
     
         14 . The apparatus according to  claim 13  wherein the chiller working fluid is an ammonia-water mixture and wherein the feedwater is also heated by the condenser of said chiller. 
     
     
         15 . The apparatus according to  claim 14  wherein said HRU supplies heat to the generator in said AARC. 
     
     
         16 . An ammonia-water absorption refrigeration cycle (AARC) that is powered by waste heat associated with the exhaust of a steam boiler, comprised of:
 a. A solution pump and solution heat exchanger (SHX);   b. A rectifier;   c. A heat recovery unit that:
 i. Supplies heat to the generator of said AARC, 
 ii. Wherein said generator is supplied pumped solution after heating in said SHX; and 
 iii. Said generator supplies partially desorbed solution to said rectifier; 
   d. At least one low pressure absorber that supplies heat to a heat load; and   e. An evaporator that supplies chilling.   
     
     
         17 . The apparatus according to  claim 16  wherein at least part of said heat load is preheating of the feedwater and/or makeup water for said economizer. 
     
     
         18 . The apparatus according to  claim 16  additionally comprised of an intermediate pressure absorber and an intermediate pressure generator that supplies it vapor. 
     
     
         19 . The apparatus according to  claim 17  additionally comprised of a gas turbine combined cycle that includes said boiler, and an inlet air chilling coil for said turbine that utilizes said chilling, and wherein said AARC is adapted to provide heating to said inlet air coil when needed. 
     
     
         20 . The apparatus according to  claim 16  additionally comprised of an ammonia expansion turbine that produces work from high pressure ammonia vapor by expanding it to low pressure. 
     
     
         21 . A method for producing chilling and feedwater heating from steam boiler exhaust comprising:
 a. Providing an AARC;   b. Transferring boiler exhaust heat to said AARC;   c. Desorbing pumped AARC liquid with said heat;   d. Rectifying the desorbed vapor;   e. Condensing the rectified vapor;   f. Evaporating the condensed vapor to produce said chilling; and   g. Preheating boiler feedwater to at least 140° F. with heat rejected from the absorber of the AARC.   
     
     
         22 . The method according to  claim 21  additionally comprising using a three-pressure AARC to cool the steam boiler exhaust to below 190° F.