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.
3. A composition of matter in the form of ash useful as a binding
agent or mineral filler in asphalt concrete, Portland Cement concrete
and gravel, wherein the ratio of spent water-softener lime to sewage
sludge solids is in the range of about 10:1 on the basis of wet
weight of sewage sludge solids and spent water-softener lime and
1:1 on the basis of dry weight.
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
 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.
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.