Reduced blowdown makes Clayton generator more efficient steam source

 All  boilers  require  blowdown  for  proper maintenance.  However,  blowdown  losses  for Clayton  Steam  Generators  are  generally  less  than for  fire-tube  boilers  due  to  Clayton’s  significantly higher  tolerance  for  dissolved  solids.  Lower blowdown rates translate to savings in three areas: less  total  water  is  used,  less  water  treatment  is required and less heat is wasted. The latter results in large fuel savings in total boiler operation. Figure 8A  dramatically  demonstrates  the  difference  in blowdown  flow  rates  of  the  Clayton  Steam Generator versus the fire-tube boiler.

Clayton  Steam  Generators  can  tolerate  up  to  11 times  more  dissolved  solids  than  fire-tube  boilers (40,000  ppm  as  opposed  to  3,500  ppm)  without affecting  moisture  carryover.  This  is  due  to  the method  of  steam-water  separation.  The  Clayton design  incorporates  a  high  velocity  centrifugal separator  whose  function  is  totally  unaffected  by high concentration of dissolved solids. In this design, water is quickly and forcibly removed from the steam flow path. With fire-tube boilers, on the other hand, dissolved  solids  are  critical  due  to  the  tendency  of the  water  surface  in  the  steam  drum  to  foam  and surge over as solids concentration increases.

There  is  about  a  four  to  one  concentration  of dissolved solids from the coil inlet to the coil exit due to the generation of steam in the coil. Thus, if water entering  the  coil  has  a  concentration  of  5000  parts per million, it will contain 20,000 parts per million at the  core  exit.  For  simplicity  of  monitoring  and control,  we  refer  to  the  concentration  of  the feedwater entering the coil.

In  addition  to  affecting  moisture  carry-over,  the amount  of  dissolved  solids  in  the  system  affects scale  formation  on  the  heating  surface.  Due  to  the forced flow of  water  in the Clayton  design,  a much higher concentration of dissolved solids is tolerated without increasing scale build-up.

The  Clayton  standard  design  incorporates  a continuous,  proportional,  automatic  blowdown system.  Water  that  is  drained  during  blowdown  is replaced  by  feedwater  that  contains  a  much  lower level  of  dissolved  solids.  In  this  manner,  an acceptable  dissolved  solids  concentration  is maintained  while  the  steam  generator  is  in operation. Blowdown  water is drawn from the zone of  highest  concentration  of  dissolved  solids,  the steam separator.

Rys. 1 - Zrzut wody w funkcji stężenia soli rozpuszczalnych