Method and a system for drying sludge

Apparatus for dehydrating sludge comprising:

• an elongate drying chamber having an inlet opening and a discharge opening at respective opposite ends thereof;
• an endless traveling grate disposed within said drying chamber arranged for transporting sludge to be dried from the inlet opening to the discharge opening of said drying chamber;
• extruder means spaced above the inlet opening end of said traveling grate for feeding sludge in the form of one or more elongate strings onto the inlet end of said grate at a rate substantially equal to the rate of travel of said traveling grate such that said one or more strings remain intact during transport through said drying chamber, said extruder means including heating means in heat-exchanging relationship therewith for preheating the extruded sludge to a temperature in the range between 80.degree. C. and 100.degree. C.;
• means for supplying heat to said drying chamber at a temperature sufficiently high as to cause water contained in the sludge to boil substantially immediately upon entry of a string into the drying chamber whereby to form steam in the immediate vicinity of the string of sludge for preventing the sludge from sticking to said traveling grate and to further dry said sludge as it is transported through said drying chamber;
• and
• means arranged in the discharge opening of said drying chamber for dividing the dried string or strings of sludge into smaller pieces and removing same from said drying chamber.

Apparatus for partially or completely dehydrating sludge which originates from sewage, for example, said apparatus comprising:

• a drying chamber having an inlet opening and a discharge opening arranged at respective opposite ends thereof;
• an endless travelling grate arranged in said drying chamber for transporting sludge to be dried from the inlet opening to the discharge opening of said drying chamber with simultaneous addition of heat from one or more heat releasing means;
• extruder means having a mouthpiece relatively closely spaced above the feed end of said travelling grate for feeding sludge onto said travelling grate;
• and
• one or more heat releasing means arranged around said extruder means and/or its transport means adapted to cause the sludge to leave the mouthpiece of said extruder with a temperature which is in the range between 80.degree. C. and 100.degree. C.

Apparatus for dehydrating sludge comprising:

• an elongate drying chamber having an inlet opening and a discharge opening at opposite ends thereof;
• an endless traveling grate arranged within said drying chamber for transporting sludge to be dried from the inlet opening to the discharge opening of said drying chamber;
• extruder means disposed above the inlet end of said traveling grate for feeding sludge in the form of one or more elongate strings onto the inlet end of said grate at a rate substantially equal to the rate of travel of said traveling grate;
• means for supplying heat to said drying chamber at a temperature sufficiently high as to cause water contained in the sludge to begin to boil substantially immediately upon entry of a string into the drying chamber whereby to form steam in the immediate vicinity of the string of sludge for preventing the sludge from sticking to said traveling grate and to further dry said string as it is transported through said drying chamber.

A method of partially or completely dehydrating sludge which originates from sewage, for example, comprising the steps of:

• feeding said sludge in one or more strings by means of an extruder to a drying chamber;
• transporting said one or more strings on a traveling grate from an inlet to a discharge opening in said drying chamber with addition of heat with such an intensity that the water in the sludge immediately begins to boil and that a zone of preferably saturated water steam is formed at any rate in the immediate vicinity of the sludge;
• and
• discharging completely dehydrated or partially dehydrated sludge through the discharge opening of said drying chamber.