Note: Descriptions are shown in the official language in which they were submitted.
CA 02768176 2012-01-04
WO 2011/005883 PCT/US2010/041245
1
Wastewater Sludge Processing System
GOVERNMENT INTEREST STATEMENT
[P0011 None
BACKGROUND OF THE INVENTION
1. Field of Invention
10002] The invention relates generally to a process for the treatment of
wastewater sludge into desirable products with no undesirable waste left over.
More specially the. process relates to drying the sludger, and separating the
sludge into oil, water, and celluloseirninerals by the use of chemical and
physical
reactions,
2. Desscription of the Background
[0003] Sewage is created by residences, institutions, hospitals and commercial
and industrial establishments. Raw influent (sewage) includes household waste
liquid from toilets, dati :s, showers, kitchens, sinks, and so forth that is
disposed
of via sewers. In many areas, sewage also includes liquid waste from industry
and commerce. Municipal wastewater therefore includes residential, commercial,
and industrial liquid waste discharges, and may include storm water runoff,
[0004) Conventional sewage treatment involves three stages, called primary,
secondary and tertiary treatment. First, the solids are separated from the
wastewater stream, Then dissolved biological matter is progressively converted
into a solid mass by using indigenous, water-borne micro-organisms. Finally,
the
biological solids are neutralized then disposed of or re-used, and the treated
water may be disinfected chemically or physically (for example by lagoons and
microfÃltration)... The final effluent can be discharged into a stream,
ri'''ver, bay,
lagoon. or wetland, or it can be used for the irrigation of a golf course,
green way
or park. if it is sufficiently clean, it can also be used for groundwater
recharge or
agricultural purposes.
[0005] The sludges accumulated in a wastewater treatment process must be
treated and disposed of in a safe and effective manner. The purpose of
digestion
is to reduce the amount of organic matter and the number of disease.causing
CA 02768176 2012-01-04
WO 2011/005883 PCT/US2010/041245
2
microorganisms present in the solids. The most common treatment options
include anaerobic digestion, aerobic digestion, and composting,
10006] Choice of a wastewater solid treatment method depends on the amount of
solids generated and other site-specific conditions. Hovv~ever, in general,
composting is most often applied to smaller-scale applications followed by
aerobic digestion and then lastly anaerobic digestion for the larger-scale
municipal applications.
100071 SUMMARY THE INVENTION
1000$] It has now been found that wastewater sludge can be processed
economically by virtue of using products of the treatment process as a fuel
for
one or more heating steps in the process. It has further been found that
wastewater sludge can be processed such that at the end of the process of the
present invention, all. the useful materials-cil, cellulose and minerals-have
been captured. Most important, it has still further been found that wastewater
sludge can be processed such that there is nothing left to be incinerated,
landfilled, or otherwise disposed of, making the system of the present
invention a
truly zero-waste process.
['009] In accordance with an em odiment of the invention, a zero-waste method
of processing wastewater sludge is provide such that at the end of the process
of
oil, cellulose, and minerals have been captured and there is substantially
nothing
left to be incinerated. landfilied, or otherwise disposed of.
[00010] in accordance with another embodiment of the invention, a process is
provide which comprises the steps of;
a- transferring sod wastewater sludge from a treatment plant to a wet
sludge holding bin, said wastewater sludge containing from about 20 to 45%
solids by weight,
b- drying said wastewater sludge to about 90% solids,
CA 02768176 2012-01-04
WO 2011/005883 PCT/US2010/041245
3
grinding the dried wastewater sludge an transferring the dried ground sludge
to a
mixer rector,
c- within the mixer reactor mixing the dried ground sludge with a solvent and
heating to produce viscous suspension of hydà w.. arbons or cellulose and
minerals in suspension,
d- separating liquids and solids,
e- heating the separated liquids to the boiling point of the solvent and the
boiling point of the residual water prior and collecting evaporated solvent
and
residual water,
f- transferring solvent-free oil to a holding tank,
g- condensing evaporated solvent and residual water and separating water
from solvent, and
h- transferring separated solvent and residual water to the mixer reactor of
step (c),
00011 In accordance with a further embodiment of the invention the step of
separating liquids and solids is performed in a filter press, and further
comprises
the steps of;
i- collecting cellulose-mineral mixture from: said filter press
drying said cellulose-mineral mixture and removing and collecting solvent
1<- reusing collected solvent in the process at step (c), and
I- transferring dried cellulose/mineral mixture to a furnace and using the
heat
from the furnace in at least one of steps (b), (c) and ().
100012] In accordance with another embodiment of the invention the oil from
step
(f) is approximately 60% fatty acids, is approximately 65 weight % 1 and C18,
and is substantially free of sulfur,
[00013): In accordance with still another embodiment of the invention: the
process
extracts about 18% oil by weight from undigested sludge and 1'1% oil by weight
from digested sludge.
CA 02768176 2012-01-04
WO 2011/005883 PCT/US2010/041245
4
100 014) In accordance with another embodiment of the invention the step of
separating liquids and solids produces a filtrate comprising extracted oil,
residual
solvent, and traces of water,
f00015] BRIEF DESCRIPTION THE DRAWINGS
10001) FIG., I is part I of the process flow diagram.
[00017] FIG. 2 is part 2 of the process flow diagram.
[00018] FIG, 3 is part of the process flow diagram.
DETAILED DESCRIPTION
[00019] it is advantageous to define certain terms before describing the
invention.
It should be appreciated that the following definitions are used throughout
this
application.
Definitions
[00020] The term "wastewater sludge" and 'sludge." means sludge accumulated in
a wastewater treatment process.
1000211 The term "solvent means a substance capable of dissolving another
substance.
100022) The term "filtrate" means a liquid or gas that has been filtered.
(00023] The term "screw feeder" means a screw feeder such as a volumetric
screw feeder or gravimetric screw feeder, capable of metering material in a
production process,
[00024 The term "filter press" means a machine using filtering cloths and
plates to
separate solids and liquids.
1000251 The term "biodiesel feedstoc "` means organic material used in the
production of biofuels.
100026) The terms "about" and 'approximately" means a deviation of no greater
than 16% from an absolute value.
CA 02768176 2012-01-04
WO 2011/005883 PCT/US2010/041245
100027): The term "substantially" means plus or minus 10%.
[00025] The term ' holding tank" means any piece of equipment that i used to
store product,
[00029] The term "%", unless otherwise specified, refers to percent by weight,
f00030] The Wastewater sludge processing system takes sludge directly from the
municipal waste water treatment plant, transforms it into useful products, and
leaves no waste behind. It is a lowterr peratuÃre, low pressure process.
100031] The municipal solid waste (101) is transferred from treatment plant to
a
wet sludge holding bin (103). In the holding bin (103) the waste is 20-45%
solids
by weight, The sludge is transferred by first screw feeder (105) to a dryer
(107)
where it is dried to 90% solids. During the drying, liquid is removed as steam
(109). The dried sludge is then ground in a grinder (111), The dried ground
sludge is transferred to a dried feed holding bin (203), The dried ground
sludge is
transferred by a screw feeder 5) along the path (100 1 A) to the path 1001 B)
to
the mixer reactor (113).
[00032] Solvent is added to the sludge in the mixer reactor (113) via pump a
first
pump (115). Within the mixer reactor (113) the mixture is mixed and heated.
The
resulting material is viscous hydrocarbon and/or cellulose and minerals in
suspension, The resulting solution is pumped by pump 21) into a filter press
(117) where the filtrate and solids are separated. The filtrate which includes
extracted oil, residual solvent, and traces of water, is sent to a holding
tank (119).
The filtrate is pumped via a second pump (215 along the path (2005A.) to the
path (2005B) to the heat exchanger (121). The filtrate is heated to the
boiling
point of the solvent and the boiling point of the residual water prior to
entering the
flash drum (123). In the flash drum (123), the solvent and residual water are
evaporated and removed via the vacuum pump (125) The solvent-free oil Ãs
collected from the bottom of the flash: drum (123) and moved by third pump
(315)
to a holding tank (127) ready for shipping as biodiesel feedstock.
100033) The solvent and residual water vapor from the vacuum pump (125)
discharge and the vent lines from the upstream process along the path (2003A)
CA 02768176 2012-01-04
WO 2011/005883 PCT/US2010/041245
6
to the path (2003B) are collected and are routed to the solvent recovery
system
indicated generally as (129), In the second heat exchanger (221) vapors are
condensed back to a liquid state. The liquid then travels along the path (2001
A)
to the path (2001 B) to the condenser/separator (131) which removes the water
from the solvent. The water and the solvent are both returned to be reused in
the
process.
100034) The cellulose and minerals are moved from the condenser/separator
(131)
by a fourth pump (413) into the make-up solvent tank (133), The vented vapor
from the condenser/separator (131) goes to an activated carbon canister (135)
and then into the make-up solvent tank (133). Fresh solvent is also added to
the
make-up solvent tank (133). Hot water (13) is also removed from the
condenser/separator (1 1 for reuse.
[00035] Back at the filter press (117), the cellulose/mineral mixture is
collected and
sent to a dryer (141) where the solvent is removed and recovered, The
cellulose/mineral mixture proceeds to a holding tank (30$). The third screw
feeder (305) takes the cellulose/mineral mixture along the path (2007A) to the
path (200713) to a furnace (143) that provides heat for the process.
Optionally, the
ash that remains can be processed for further byproduct recovery (145) or
alternatively, it is used as a byproduct without further processing,
1000361 A nitrogen tank (147) uses the fifth pump (515) to move the nitrogen
along
the path (1001 A) to the path (10 113) to the mixer reactor (113), the
filtrate tank
(119), the dryer (141) and the dried cellulose bin (303).
('000,3 .? Preferably, the system does not employ further separation, but
rather, the
cellulose/mineral mixture is used as fuel in an alternative fuel furnace to
dry the
incoming sludge. The oil has a 19,000 enemy value and the
cellulose/mineral mixture has a 7000 Stu/pound energy value.
['00038] The oil is considered to be a perfect feedstock for biodiesel. It is
80% fatty,
acids (65% C16 and 018), and has almost no sulfur. It also can be used as fuel
oil without further processing.
(00030] The process extracts 18`%% oil by weight from undigested sludge and 11
%
oil by weight. from digested sludge. Abone dry pound of sludge yields 11--13%
oil,
CA 02768176 2012-01-04
WO 2011/005883 PCT/US2010/041245
7
50-60% cellulose and 30% minerals (though the process need not separate the
cellulose and minerals.
00O$0] The drying step of the process takes about 45% of the energy cost of
the
process, It should be rioted that because the process does not employ a
washing step, drying costs are minimized,
[00041] At the end of the process of the present invention, all the useful
à at rials ll; cellulose and à inerals 1 a been ma tured. Most important,
there is nothing left to be incinerated, landfill d, or otherwise disposed of,
making
the system of the present invention a truly zero-waste process.
[00042] The following examples are for illustrative purposes and are not
indicative
of the limits of the present invention.
EXAMPLE
100043] Process design Criteria and Assumptions
Item Units Pesi _rÃ
100044] Municipal Solid Waste MSW)
M SW Filter cake as feed to dryer Ib/hr 40
Moisture content % 75
Solids content % 25
Bulk density of MSW cake lb/ft' 85
Temperature (avg.) of NI SW cake 65
00045] Average Composition of Reactor Feed Solids
Dried M: SW as feed to reactor lb/hr 10
Solids content % 80
Moisture uonte % 10
i1 (dry solids basis) % 10
Cellulose (dry solids) % 50-
CA 02768176 2012-01-04
WO 2011/005883 PCT/US2010/041245
8
Bulk density of cellulose lbrft 11
Specific heat capacity Btu'lb--, 7550
Metal oxides (MO), . dry solids % 25-35 NT
Bulk density of MO lb/ft 156
. Gr. (average) of MO - 2.
Specific heat capacity of MO Btu/lb-+ 0.23
L000461 Average Composition of Metal Oxides
iron oxide r 10.0
Calcium oxide % 6.25
Phosphorus oxide fz, 4.5
Aluminum oxide 2.25
Other oxides % 2.0
[000471 Solvent Characteristics
l e t ne (C7H.16)
Specific gravity 0-684
Bulk density of Ctft lb ft'
42.64
Boiling point of 0; H,i 209.1
Specific heat capacity of C7H,6 t `lb-.,F 0.5
Latent heat. of vaporization Btullb 76.45
Item Unit Din
Nitrogen Gas
Specific heat capacity of nitrogen Btu</lb_+ 0.25
Density of nitrogen WW' 0.073
1000481 Product Fuel Oil
CA 02768176 2012-01-04
WO 2011/005883 PCT/US2010/041245
9
Specific gravity of oil - 0,9
Bulk density of oil Ili/W' 5
Specific heat capacity of oil Btu/ll - . 18,000
[000491 Plant Operation
Length of shift hr/d 10
Operating hours per shift ter./shifts
Dried MW feed processed Id/hr 10
Solvent addition
Pounds per pound of dry solids lb/lb 41
Solvent loss/lb of product oil % 1.0
100050] MSW Feed to Dryer
Raw MSW filter cake Ib/hr 40
Solids content % 25
Moisture content % 75
bulk. density of dried MSW cake ib ft' 21-31
Pilot Plant Operation Parameters
100051] The fixer/Reactor was si: ed * to process lb of solids on a dry basis
(22.2 lb of dried MSW containing 90% solids) per batch of 3 hours duration.
Forty (40) pounds of dry solids processed during a shift contain an estimated
37.5% or 15 pounds of oil>. Approximately two (2) gallons of oil at 95%
recovery
are to be produced during the hours of operation each day.
Number of shifts per day sh fts/d I
Duration of shift (total) hr/shiftlO
CA 02768176 2012-01-04
WO 2011/005883 PCT/US2010/041245
Number of batches per shift bate es:id 2
Reaction time per batch: hr/batch 3
Dried teed (90% solids) per batch I / batch 22.2
Dry solids content of Reactor feed Ib/batch 20
Solvent addition rate lb/batch 40
Solvent added lb/d' 80
Item Units Design
[000521 Product Oil
Oil in MW feed solids % 10
Oil content of MSW feed solids Ib d2
Estimated oil recovery % 95
Estimated oil recovery lb /d 14.25
Estimated oil recovery ai/ 1.9
100053] Mixer,/Reactor
Solids processed on a dry basis 10 1b/batch
Solvent (heptane) added per batch = 40 lb/batch
Mass of dried feed (90% solids) charged to Mixer/Reactor
(10 l / at h) (9 % solids)
111 lb batch
Volume of dried feed charged to Mixer,'Reactor
(11.I lb/bat ch)f(21-31 lb/ft)
0.35-.5 ft batch
Volume of solvent (heptane.) added to Mixer/Reactor
(40 lb/"batch)+(2'l. lb/ t )
CA 02768176 2012-01-04
WO 2011/005883 PCT/US2010/041245
11
.94 ft"/!batch
Total volume of feed to Mixer/Reactor
= 0.35-,52 ft" dried MS W filter c k + 1.88 "' heptane
= 1,29-1 .46 ft`rbatch
Size of Mixer/Reactor (D = diameter . height)
()x(D2)
x (D) 1,29-1,46 ft':
4
D w 1(1.29-1.46) x (4 /tiff] >" - 1.1 -1.23 ft.
The Mixer/Reactor is I,5 ft. dia. x 2. ft. tall, which includes a freeboard
allowance of 1.0 ft. and equipped with 1.0 h.p motor with variable frequency
drive
(FD). [4.42 ft$'
1000541 Broad Scope of the Invention
1,00055] Although the present invention has been fully described in
conjunction
with several embodiments thereof with reference to the accompanying drawings,
it is to be understood that various changes and modifications may be apparent
to
those skilled in the art. Such changes and modifications are to be understood
as
included within the scope of the present invention as defined by the appended
claims, unless they depart therefrom.
1000561 While illustrative embodiments of the invention have been described
herein, the present invention is not limited to the various preferred
embodiments
described herein, but includes any and all embodiments having equivalent
elements, modifications, omissions, combinations (e.g., of aspects across
various embodiments), adaptations and/or alterations as would be appreciated
by those in the art based on the present disclosure. The limitations in the
claims
are to be interpreted broadly based on the language employed in the claims and
CA 02768176 2012-01-04
WO 2011/005883 PCT/US2010/041245
12
not limited to examples described in the present specification or during the
prosecution of the application, which examples are to be construed as non-
exclusive. For example, in the present disclosure, the term "preferably2z is
non-
exclusive and means "preferably, but not limited to." in this disclosure and
during
the prosecution of this application, means-plus-function or step plus-function
limitations will only be employed where for a specific claim limitation all of
the
following conditions are present in that limitation,, a) "means for" or "step
for" is
expressly recited; b) a corresponding: function is expressly recited; and c)
structure, material or acts that support that structure are not recited. In
this
disclosure and during the prosecution of this application, the terminology
"present
invention" or "invention" may be used as a reference to one or more aspect
within the present disclosure,. The language present invention or invention
should
not be improperly interpreted as an identification of criticality, should not
be
improperly interpreted as applying across all aspects or embodiments (i.e., it
should be understood that the present invention has a number of aspects, and
embodiments) and should not be, improperly interpreted as limiting the scope
of
the application or claims. In this disclosure and during: the prosecution of
this
application, the terminology "embodiment" can be used, to describe any aspect,
feature, process or step, any combination thereof, and/or any portion thereof,
etc.
In some examples, various embodiments may include overlapping features. In
this disclosure, the following abbreviated terminology may be employed:' e.
.~t
which means for example".
