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Sludge Dryer FAQ’s

  1. How does a sludge dryer work? 
  2. Do I need a filter press in order to use a sludge dryer? 
  3. What is typical drying time? 
  4. Do I need a scrubber with my dryer? 
  5. What if I don’t have a lot of space available? 
  6. Can a dryer be used on oily sludge? 
  7. What types of heat sources are available? 
  8. How can I be sure a sludge dryer is the right answer for my application? 

 

    1. How does a sludge dryer work? 

      A Met-Chem sludge dryer will use an indirect heat source (Gas, Steam/Hot water, or electrically heated) to heat a stainless steel surface, (Trough) holding the sludge to be dried.  This heated surface will drive off water like a frying pan on a stove top.  The trough also has one or two augers, depending on the size of the dryer, to stir the sludge on the heated surface, much like the spatula in the frying pan.  The heated moist air inside the dryer is then drawn out of the unit typically with a wet scrubber and exhausted out of the building.

    2. Do I need a filter press in order to use a sludge dryer? 

      Typically a Met-Chem filter press will be the most efficient way to feed the sludge dryer.  The sludge dryer is not designed to be a water tight vessel; it is intended to receive sludge that has been dewatered to about 30-35% solids (similar to the constancy of a sand castle).  This is the expected output from a filter press.

    3. What is typical drying time? 

      The drying time will vary depending on the solid content of the incoming sludge, and the desired dryness of the sludge.  Other factors will include the temperature setting and capability of the sludge dyer heat source.  Gas and electric Met-Chem sludge dyers can be set to a high enough temperature to dry as fast as the sludge can shed the evaporating water, while steam or hot water may be a limiting factor depending on the independent supply to the sludge dryer.  The expected drying time usually ranges from 4-6 hours.

    4. Do I need a scrubber with my dryer? 

      The sludge dyer is basically a hot box with water being evaporated from sludge and making the air in the box humid.  This humid air must be removed before the air becomes saturated and allows the water to condense out of the air and fall back into the sludge.  Air must be pulled from this box and vented outside to allow the sludge to dry.  In the early stages of the drying cycle, the sludge is like mud with little or no dust, but as the drying continues, the fringes of the sludge will dry rapidly and start to form dust, and this will become more prevalent as the cycle continues to the end.  This dust will be entrained in the humid air stream and should not be allowed to be vented outside. A Met-Chem sludge dryer is always offered with an optional Wet Scrubber as the Wet Scrubber will be required to accommodate the needs described above, but some facilities already have a Wet Scrubber in the area with enough unused CFM to also accommodate the needs of the sludge dryer.

    5. What if I don’t have a lot of space available? 

      Met-Chem batch style sludge dryers can be mounted under you filter press in place of a sludge dumpster or it can be located in a remote area of the shop.

    6.  Can a dryer be used on oily sludge? 

      No!  Met-Chem sludge dryers are not made to handle oily waste. 

    7. What types of heat sources are available? 

      Heat sources for Met-Chem sludge dryers are:  gas, electric, steam and hot water.

    8. How can I be sure a sludge dryer is the right answer for my application? 

      Met-Chem can test your filter cake sample to let you know if, in fact, a sludge dryer will bring your desired results.  Testing also assists in determining the amount of drying time that will be required.