Water softener abstract
A method and apparatus are disclosed for mixing sewage sludge with
spent water-softener lime in a ratio of approximately 10:1 on a
wet basis. The mixture is introduced to a rotary pre-dryer kiln
and a rotary combuster kiln to kill pathogens. An ash by-product
and gases are thereby produced. The ash by-product can be disposed
of at much less cost or can be incorporated in a variety of applications
such as an aggregate substitute.
Water softener claims
What is claimed is:
1. A method for recycling sewage sludge comprising the steps of:
a. Blending sewage sludge with spent water softener lime in a feed
hopper to produce a mixture; b. Introducing said mixture into a
pre-dryer kiln wherein said pre-dryer kiln maintains a temperature
sufficient to evaporate water from said mixture; c. Subjecting said
mixture to a refractory-lined combuster rotary kiln, said rotary
kiln being maintained at a temperature of at least 1500 degrees
Fahrenheit resulting in an ash by-product and gases of combustion;
d. Removing said ash by-product to a storage area; e. Introducing
said gases of combustion to a thermal oxidizer maintained at a temperature
of between 1500 degrees Fahrenheit to 1700 degrees Fahrenheit resulting
in an ash by-product and heated gases; f. Removing said ash by-product
from said thermal oxidizer to said storage area; g. Transferring
said heated gases to said pre-dryer kiln; h. Delivering spent exhaust
gases from said pre-dryer kiln to a cooling tower maintained at
between 300-450 degrees Fahrenheit to quench said spent exhaust
gases; i. Passing said cooled spent exhaust gases to a baghouse
controller; j. Extracting ash from said baghouse controller and
storing it with said ash by-products from said thermal oxidizer
and said combuster kiln and exhausting the baghouse controller.
2. A method for the preparation of ash by-product consisting essentially
of sewage sludge solids and spent water-softener lime which comprises
(a) mixing sewage sludge with spent water-softener lime wherein
the ratio on a wet basis is approximately 10:1; and (b) pre-drying
the resulting mixture in a rotary kiln; and (c) combusting the resulting
mixture producing solid ash by-product and gases of combustion with
entrained ash; and (d) thermally oxidizing said gases of combustion
wherein they are subjected to a temperature in the range of 1700
degrees Fahrenheit producing additional solid ash by-product and
heated gases with entrained ash; and (e) cooling said heated gases
in a cooling tower wherein they are reduced to a temperature in
the range of 300-450 degrees Fahrenheit; and (f) filtering said
cooled gases in a baghouse controller wherein additional ash by-product
is removed; and (g) exhausting all remaining gases; and (h) collecting
said ash by-products in storage; and (i) recycling heat from said
combusting and thermal oxidizing to said pre-dryer kiln to increase
said kiln's efficiency.
Water softener description
BACKGROUND OF THE INVENTION
The present invention involves an apparatus and process for recycling
sewage sludge. In particular, the invention involves the blending
and reduction of spent water-softener lime and sewage sludge to
produce sludge ash which is reduced by approximately 90 percent
and which can be either disposed in an approved landfill or can
be incorporated as a binding agent or mineral filler in asphalt
concrete, Portland cement concrete and gravel.
Recycling of waste products is a problem which has received considerable
attention in an effort to protect the environment. Sewage sludge
is a waste product which is typically treated and then either spread
on land or is disposed in an approved landfill. Sewage sludge typically
has high levels of heavy metals and pathogens. Consequently, where
land spreading is practiced, the land can become unacceptably contaminated.
Where sewage sludge is disposed of in approved landfills, transportation
costs and dumping fees are incurred and the presence of heavy metals
and pathogens in the waste product requires an accounting of each
load by the landfill operator prior to dumping. Sewage sludge holds
large quantities of water which increases the weight and volume
of the sludge as well as the cost to dispose of it since dumping
fees are typically charged based upon weight. Accordingly, it would
be desirous to provide apparatus and a process by which sewage sludge
is recycled in a way which reduces the water content of the waste,
which removes pathogens from it and which creates a by-product that
either can be incorporated into construction materials such as concrete
and cement or land spread with less chance of soil contamination.
The present invention satisfies these needs by providing an alternative
treatment for sewage sludge by blending it with spent water softener
lime. Spent lime, after its use by water softening plants, is presently
either being land spread or landfilled itself. Combining spent lime
with sewage sludge and subjecting it to the steps of the present
invention kills the pathogens in the sewage sludge, reduces the
sludge ash by approximately 90 percent and renders a by-product
which can be utilized as an aggregate substitute in the production
of asphalt concrete, Portland Cement concrete or as a backfilling
material for ditches or trenches. The by-product can also be used
as a base stabilizer for wet soil during construction. Moreover,
the recycled by-product can itself be land spread or deposited in
an approved landfill at much less cost and with less danger to the
environment because it weighs less and it has less potential for
soil contamination.
It is an object of this invention to reduce the possibility of
disease bearing air-borne bacteria and reduce the possibility of
water contamination associated with sewage sludge.
It is a further object of the invention to reduce heavy metal contamination
of the earth caused by disposal of sewage sludge.
Another object of the invention is to reduce unpleasant odors associated
with land spreading and land-filling of sewage sludge.
A further object of the invention is reducing the cost including
landfill tipping fees of sewage waste disposal.
It is an object of the invention to reduce the burden of record
keeping due to elimination of pathogens from sewage waste.
It is an object of the invention to treat sewage sludge so as to
provide a resultant material that can be used as an element of construction
materials such as a mineral filler, binding agent, an aggregate
substitute or aggregate equivalent.
Another object is to provide a valuable use for spent water softener
lime which would otherwise need to be disposed, such as in a landfill
or land spreading.
A further object of the invention is to provide a process by which
spent water softener lime is recycled.
Another object is to treat sewage sludge so as to provide a binding
agent for the concrete/cement block industry, asphalt industry and
the construction industry.
Moreover, it is an object of the invention to provide a process
by which for every ten tons of waste processed, one ton of ash is
created.
SUMMARY AND OBJECT OF THE INVENTION
The present invention provides a method and apparatus for recycling
sewage sludge. Sewage sludge first is blended with spent water softener
lime and is followed by subjecting the mixture then to a pre-dry
rotary kiln and then a combuster rotary kiln. The material is thereafter
subjected to a thermal oxidizer which produces an ash that is carried
to a storage bin. Non-ash by-products are sent to a cooling tower,
then to a baghouse controller which entraps residual ash which has
precipitated. Resultant gases are exhausted by a fan while the ash
is transported from the baghouse controller to a storage bin after
which the ash can be transferred to a truck for ultimate use or
disposal.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic illustration of the instant invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIG. 1 sewage sludge is conveyed from line 5 and
spent water-softener lime is supplied from line 6 to a divided feed
hopper 7. Regulating gates well known in the art are provided within
the feed hopper for mixing sewage sludge and spent water-softener
lime: the preferred ratio being ten tons of sludge to one ton of
lime on a wet basis. The resultant mixture is next fed via an auger
through line 8 to a pre-dryer kiln 9. The lime and sludge mixture
continue to blend as it is subjected to a rotary motion of approximately
eight rpm within the pre-dryer kiln. The kiln has an annular chamber
surrounding the dryer for receiving gas generated in the process
as will be explained later. During this step of the process the
moisture content is reduced to at least 15 percent. Next the blend
is transferred by either belt feed or auger feed through line 10
to a combuster/rotary kiln 11. Kiln 11 has approximately 9 inches
of refractory lining and rotates at about one and one-half rpm.
The action of said kiln 11 creates both an ash by-product and gases
of combustion. This step in the process also destroys pathogens.
The ash produced is conveyed from the combuster/rotary kiln 11 to
an ash receiver or bin 13 through line 12. Gases from the combuster/rotary
kiln 11 travel by tube 14 to thermal oxidizer 15. The gases of combustion
produced in the combuster/rotary kiln are subjected to a temperature
between 1500 degrees Fahrenheit to 1700 degrees Fahrenheit in the
thermal oxidizer. Some additional ash will precipitate and is then
transferred through line 16 to ash receiver 13. Heated gases from
the thermal oxidizer 15 are sent to the annulus of pre-dryer kiln
9. Heat transfer occurs within the pre-dryer kiln 9 which helps
to maintain the temperature within the dryer chamber of the kiln
thus increasing the efficiency of the process. The waste gases from
which heat has transferred are then drawn through line 17 to a cooling
tower 18 where their temperature is reduced to a range of 350 degrees
Fahrenheit to 500 degrees Fahrenheit. From the cooling tower the
gases are drawn to the baghouse controller 19 where additional ash
is retrieved and forwarded to the storage bins 13 via pipe 21. Exhaust
gases from the baghouse controller are removed by induced draft
fan 22 which is in communication therewith and which draws all gases
generated in the system toward the baghouse controller. An optional
wet scrubber 23 may be provided between the baghouse controller
and the induced draft fan to provide additional cleansing of the
gases before they are released to the atmosphere. Fan Induced draft
fan 22 is pneumatically in communication with the combuster/rotary
kiln, the thermal oxidizer, the cooling tower and the baghouse controller.
It creates a negative pressure which draws the gases produced at
each of the stages through the process and ultimately exhausts the
gases from the baghouse controller.
The thermal oxidizer 13 is a well known piece of equipment to those
ordinary skilled in the art and is equipped with baffles which create
multiple pathways for the gases of combustion of the instant process.
The purpose of the thermal oxidizer is to further cleanse the gases
to meet regulations of environmental protection agencies, specifically,
functions to reduce the odor and hydrocarbons. Thermal oxidizers
contemplated by the present invention are manufactured by Texas
Incinerator.
The cooling tower is likewise well known in the art and is manufactured
by Texas Incinerator. Essentially, it comprises a tank in which
a fine mist of high pressure water is introduced to the waste gases.
Finally, the baghouse controller is an item commercially available
through either Texas Incinerator or Barber Green, for example. The
air flume that results from all of these steps and which is exhausted
by induced draft fan 22 meets all requirements of environmental
regulations.
The ash by-product collected in the storage bins can be used as
an aggregate substitute in the production of asphalt concrete, Portland
Concrete or as a backfilling material for ditches or trenches. The
ash by-product may also be used as a base stabilizer for wet soil
during construction. Also, the ash by-product can be lawn spread
or deposited in an approved landfill at much less cost and with
less danger to the environment because its weight is much less than
the combined wet weight of the unprocessed sludge and lime and because
the pathogens have been destroyed. |