United States
                     Environmental Protection
Municipal Environmental Research ^
Cincinnati OH 45268
                     Research and Development
EPA-600/S2-84-010  Jan. 1984
&ERA          Project  Summary
                     Conversion  of Sewage Sludge to
                     Oil  by  Hydroliquefaction
                     Wilmer L. Kranich and Atal E. Eralp
                       A study was undertaken to determine
                     the feasibility of converting municipal
                     wastewater  sludges into  oil  under
                     hydrogen  pressure.  In a  laboratory
                     autoclave,  raw and digested sludges
                     were subjected to 14 MPa (2000 psig)
                     total  pressure for 20 to 90 minutes.
                     Aqueous suspensions were treated at
                     about 300C, and predried sludge sus-
                     pended in an oil carrier was reacted at
                     about 425C. When the predried sludge
                     solids were suspended in an oil carrier,
                     50 percent of the organic  content of
                     sludge  was converted  into pentane-
                     soluble oil; but significant amounts of
                     oil were not produced under the condi-
                     tions studied when the sludge  solids
                     were slurried in  water.  A commercial
                     plant  using  the  oil carrier  process
                     scheme would be complex with high
                     capital  and operating costs. Conse-
                     quently, further development work on
                     hydro-liquefaction of sewage sludge is
                     not recommended.
                       This Project Summary was developed
                     by EPA's  Municipal Environmental
                     Research Laboratory, Cincinnati. OH.
                     to announce key findings of the research
                     project that is fully documented in a
                     separate report of the same title (see
                     Project Report ordering information at

                       This study was undertaken to assess
                     the feasibility of  converting municipal
                     wastewater sludge to liquid and gaseous
                     fuels through reactions with hydrogen at
                     high pressure and temperature. The work
                     was based on earlier experiments carried
                     out in the Resource Recovery Laboratory
                     at the Worcester Polytechnic Institute. In
                     the  earlier studies  ft-cellulose  and
                     powdered newspaper were used to model
the behavior of combustible municipal
solid waste (J. A.  Kaufman and A. H.
Weiss; 1975; Solid Wastes Conversion:
Cellulose Liquefaction; NTIS Report PB
235-509, National Technical Information
Service,  Springfield,  Virginia  22161).
These studies involved the hydrolique-
faction and hydrogasification over nickel
catalysts of cellulosic substances slurried
in paraffin oil at temperatures of 350 to
450C under hydrogen pressure in the
range of 3 to 8 MPa (1150 psig). Under
such  conditions, up  to 90 percent of
cellulosic substances can beconvertedto
gaseous and liquid fuels. The background,
techniques, and experimental equipment
associated with the cellulose and lignite
liquefaction studies have been applied in
the present investigation to the hydro-
liquefaction and gasification of sewage

Experimental Procedures
  For  this study,  raw and  digested
sludges were collected from the Deer
Island Sewage Treatment Plant in Mas-
sachusetts. These samples were used in
experiments either as aqueous suspen-
sions as received or as suspensions of
dried sludge solids slurried in anthracene
or paraffin oil.
  Experiments were carried out in  an
autoclave under hydrogen pressure. The
principal  apparatus  consisted  of  a
magnetically  stirred  batch autoclave.
Maximum safe pressure that could  be
applied to this autoclave was 14 MPa
(2000  psig). Auxiliary  equipment
included  a  hydrogen-feed  system, a
slurry-feed  device,  pressure and
temperature recorder-controllers, a wet-
test meter for measuring the off-gas, and
analytical equipment for determining the
mass and composition of the liquid and

   gaseous  products.  Conditions for
   experiments are listed in Table 1.
   Table 1.    Conditions for the Oil and Water
             Slurry Experiments
Oil slurry
Water slurry
Initial H2 Operating
pressure tempera-
(MPa) ture (C)
8.3 (1200 psig) 425
3,5 (500 psig) 300
   With the total pressure limited to 14 MPa
   (2000 psig), it was necessary to use lower
   initial  hydrogen  pressures  and
   temperatures for the water slurry experi-
   ments because of the vapor pressure
   generated by the water. The  conversion
   nearly reached its maximum  after about
   20 min  at  reaction temperature;  little
   further conversion was observed after 30
     Results are evaluated in terms of the
   total fractional conversion of the toluene-
   insoluble organic feed into oils (pentane-
   soluble  substancesjand into  other
   substances. These are calculated by the
   following relationships:

   Conversion to Pentane-Soluble Oil, XQ =
   (weight of oils in
    product slurry)
  (weight of oils in
- sewage sludge and
  carrier oil)       x 100
   (weight of organic toluene-insolubles in
             sewage sludge)

  Conversion of Toluene-insolubles, XT! =

   (weight of organic   (weight of organic
   toluene-insolubles  - toluene-insolubles
   in sewage sludge)   in product slurry) x 100
   (weight of organic  toluene-insolubles
           in sewage sludge)
  Thus Xo represents the net oil yield per
unit  of insoluble  organic material  in
sewage sludge,  and XTI represents the
conversion  of   the  insoluble  organic
material in sewage sludge to all liquidand
gaseous products.

Results and Conclusions
  1.  Raw  sewage  sludge and  sludge
     settled  in digesters can be largely
     converted  to  liquid  and gaseous
     products by heating the water slurry
     to  about 300C  under  its vapor
     pressure. Conversion of  up to 90
     percent  of the  toluene-insoluble
     organic  feed  can   be  achieved
     with  or without added  hydrogen.
     Neither sodium carbonate, sodium
     molybdate,  nor  nickel  carbonate
     catalyst  significantly  alters   the

  2.  Significant  amounts  of  pentane-
     soluble oils were not produced from
     the water-slurried sludge under any
     of the conditions studied

  3.  If raw or settled digester sludge, or
     the final effluent  sludge from the
    digesters  is dried,  ground,  and"
    slurried in a carrier oil, up to 90
    percent of  the toluene-insoluble
    organic content can be converted in
    20 min in the presence of hydrogen
    at a total initial pressure of 8.3 MPa
    (1200 psig) and a temperature  of
    about 425C.

 4. Under  these conditions, up to 50
    percent of the material so converted
    may  be  recovered  as  pentane-
    soluble oils or asphaltenes.

 5. Great complexity and high projected
    investment and operating costs of a
    commercial  plant are indicated  by
    the results obtained  here for dried
    sludge slurried with  oil. These re-
    sults  do  not  encourage  further
    development work on  hydrolique-
    faction of sewage sludge.

  The full report was submitted in fulfill-
ment of  Cooperative  Agreement  No.
80739001  by   Worcester   Polytechnic
Institute,  Worcester,  MA,  under  the
sponsorship of the  U.S.  Environmental
Protection Agency.
   Wilmer L. Kranich is with Worcester Polytechnic Institute, Worcester, MA 01609.
   Atal E. Eralp is the EPA Project Officer (see below).
   The complete report, entitled "Conversion of Sewage Sludge to OilbyHydrolique-
    faction." (Order No. PB 84-133 768; Cost: $8.50. subject to change) will be
    available only from:
           National Technical Information Service
           5285 Port Royal Road
           Springfield, VA 22161
           Telephone: 703-487-4650
   The EPA Project Officer can be contacted at:
           Municipal Environmental Research Laboratory
           U.S. Environmental Protection Agency
           Cincinnati, OH 45268
                                                                                            irUS GOVERNMENT PRINTING OFFICE 1984-759-015/7302
United States
Environmental Protection
                  Center for Environmental Research
                  Cincinnati OH 45268
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