U.S. patent application number 12/454627 was filed with the patent office on 2010-01-21 for organic recycling with a pipe-cross or tubular reactor.
Invention is credited to Gary L. Dahms, Gary D. Greer.
Application Number | 20100011823 12/454627 |
Document ID | / |
Family ID | 32593034 |
Filed Date | 2010-01-21 |
United States Patent
Application |
20100011823 |
Kind Code |
A1 |
Dahms; Gary L. ; et
al. |
January 21, 2010 |
Organic recycling with a pipe-cross or tubular reactor
Abstract
The invention is directed to a process for enhancing the plant
nutrient value of relatively low analysis organic waste material
(e.g. sewage sludge) involves treating the waste material with an
acid and base in a pipe-cross,reactor or tubular to form a melt;
spraying the melt onto a recycling bed of fines in a granulator and
flashing off the water contained in the melt as steam; rolling the
melt onto recycled fine particles in a granulator to form
granulated particles; and drying these granulated particles in a to
form an enhanced plant nutrient value composition (e.g. a
fertilizer or soil conditioner having a greater NPK value than the
original relatively low analysis organic waste material). The
process further includes drawing off the fumes from the granulator,
passing them through a dryer with the granulated particles, and
subsequently oxidizing the fumes to eliminate volatile organic
compounds and/or gaseous hydrocarbon pollutants be converting such
into carbon dioxide and water vapor.
Inventors: |
Dahms; Gary L.; (Soda
Springs, ID) ; Greer; Gary D.; (Pocatello,
ID) |
Correspondence
Address: |
DRINKER BIDDLE & REATH;ATTN: INTELLECTUAL PROPERTY GROUP
ONE LOGAN SQUARE, 18TH AND CHERRY STREETS
PHILADELPHIA
PA
19103-6996
US
|
Family ID: |
32593034 |
Appl. No.: |
12/454627 |
Filed: |
May 19, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11522083 |
Sep 15, 2006 |
7534281 |
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12454627 |
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10322802 |
Dec 19, 2002 |
7128880 |
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11522083 |
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Current U.S.
Class: |
71/12 ;
422/244 |
Current CPC
Class: |
C05B 7/00 20130101; Y02A
40/213 20180101; C05F 7/00 20130101; Y02A 40/20 20180101; C05B 7/00
20130101; C05B 19/00 20130101; C05C 3/00 20130101; C05F 7/00
20130101; C05G 5/12 20200201; C05F 7/00 20130101; C05G 5/12
20200201; C05B 7/00 20130101; C05B 19/00 20130101; C05C 3/00
20130101; C05F 7/00 20130101; C05G 5/12 20200201; C05F 7/00
20130101; C05G 5/12 20200201 |
Class at
Publication: |
71/12 ;
422/244 |
International
Class: |
C05F 3/04 20060101
C05F003/04; C05F 3/06 20060101 C05F003/06 |
Claims
1. A method of treating an organic waste material to form a
nutritional composition for plants comprising: mixing said organic
waste material with scrubber water to form a slurry capable of
being pumped; pumping said slurry to a reactor selected from the
group consisting of a pipe-cross reactor and a tubular reactor for
reaction with a base and acid to form a melt; spraying said melt
onto a recycling bed of fines in a granulator, and flashing off
water contained in said melt as steam; rolling said melt onto fine
particles in said granulator to form granulated particles; further
reacting the melt with ammonia in the granulator to complete
product formation reaction; drawing fumes from said granulator;
oxidizing said fumes to reduce any noxious odor associated
therewith; and drying said granulated particles in said dryer to
reduce the moisture content thereof to form dried granulated
particles comprising an enhanced plant nutrient value
composition.
2. The method of claim 1 wherein the organic waste material
comprises relatively low analysis organic waste material.
3. The method of claim 1 wherein the reactor is a pipe-cross
reactor.
4. The method of claim 1 which does not exhaust significant amounts
of noxious odors.
5. A process for preparing a composition that is capable of
providing nutrition to plants from a waste material comprising:
pumping a slurry form of the waste material through a pipe reactor
for reaction with at least one base or acid to form a high
temperature melt; spraying the melt from the pipe reactor directly
onto a recycling bed of fines in a granulator, and flashing off
water contained in the melt as steam; rolling the melt onto
particles in the granulator to form granulated particles; and
drying the granulated particles to reduce the moisture content
thereof to form dried granulated particles.
6. The process of claim 5 wherein the pipe reactor is located
within the granulator.
7. The process of claim 6 wherein the granulator is a rotating
cylinder.
8. The process of claim 5 wherein the pipe reactor comprises two
cross pipes.
9. The process of claim 8 wherein two acids are introduced via the
two cross pipes.
10. The process of claim 9 wherein the two acids are sulfuric acid
and phosphoric acid.
11. The process of claim 5 wherein the temperature is maintained at
less than 149 degrees centigrade.
12. The process of claim 5 further comprising adding water to the
waste material to form a slurry prior to pumping.
13. A system of exothermically mixing a pipe fed sludge slurry with
one or more fluid reagents introduced by one or more cross pipes to
produce a high temperature mixture, wherein the temperature is
controlled by a feedback system that adjusts turbulence introduced
by a protuberance.
14. The device of claim 13 wherein the protuberance is selected
from the group consisting of a bump in the plumbing, at least two
bumps in the plumbing, an orifice plate and two or more orifice
plates.
15. The system of claim 13 wherein the turbulence is adjusted by at
least one action selected from the group consisting of moving the
protuberance, altering the penetration of the protuberance into the
plumbing, switching of cross pipe reactors, adjusting the flow rate
of the sludge, and adjusting the flow rate of one or more of the
fluid reagents.
Description
RELATED APPLICATIONS
[0001] The present application is a continuation of co-pending
application Ser. No. 11/522,083, which is a divisional of
application Ser. No. 10/322,802.
BACKGROUND
[0002] 1. Field of the Invention
[0003] This invention is directed to systems, devices and methods
for converting organic material into fertilizer. More specifically,
the invention relates to pipe-cross or tubular reactors that
produce an enhanced plant nutrient value composition.
[0004] 2. Description of the Background
[0005] The disposal of sewage sludge is a significant world-wide
problem. Current methods of disposing of sewage sludge include
incineration, direct land or ocean application, heating and drying
the sludge for sterilization and then applying it to land,
depositing it in a landfill, or granulating the sludge with a
standard rotary granulator with heating and drying being provided
by exogenous heat sources (e.g. by burning purchased fuel). While
some of these methods result in a fertilizer, such fertilizers are
of relatively low analysis with regard to their plant nutrient
value.
[0006] Methods of expressing a fertilizer's plant nutrient value
involve identifying the fertilizer's NPK value, wherein N relates
to the amount of nitrogen, P relates to the amount of phosphorus
(expressed as P.sub.2O.sub.5), and K relates to the amount of
potassium (expressed as K.sub.2O). Thus, as reported in U.S. Pat.
No. 3,050,383, sewage sludge with a 2.5/2.5/0 value contains two
and a half percent nitrogen, two and a half percent phosphorous as
P.sub.2O.sub.5, and zero percent potassium as K.sub.2O. Except as
otherwise indicated by usage, all percentage values herein are
weight-based percentages (i.e. w/w).
[0007] Fortunately, methods exist for enhancing the nutrient value
of relatively low analysis organic waste material. For instance, in
the aforementioned Wilson patent (the contents of which are
entirely incorporated herein by reference), a method is disclosed
for treating dried animal manure and sewage sludge with controlled
amounts of an acid, such as sulfuric acid, phosphoric acid (or an
equivalent phosphorous compound, the strength of which is expressed
as phosphoric acid), or mixtures thereof, and an aqueous ammoniacal
solution, such as aqueous ammonia or ammoniacal nitrogen
salt-containing solutions and tumbling the resulting reaction mass
to form fertilizer granules having an upgraded or enhanced plant
nutrient value.
[0008] Other methods of enhancing the plant nutrient value of
relatively low analysis organic waste material with acids, bases,
or mixtures thereof have also been described (e.g. U.S. Pat. No.
4,743,287, U.S. Defensive Publication T955,002, Norton et al. (Feb.
1, 1977), U.S. Pat. No. 5,466,273, U.S. Pat. No. 5,125,951, U.S.
Pat. No. 5,118,337, U.S. Pat. No. 5,393,317, and U.S. Pat. No.
5,422,015.
[0009] Tubular reactors are known in the art for producing ammonia
salts (e.g. U.S. Pat. No. 6,117,406, U.S. Pat. No. 2,902,342, U.S.
Pat. No. 2,755,176, and U.S. Pat. No. 2,568,901, the contents of
which are hereby incorporated by reference). Exothermic reactions
are carried out in the tubular reactors by reacting a base with an
acid in the reactor tube. European Patent Publication 770,586A1
also discloses that tubular reactors may be used for the treatment
of relatively low analysis organic waste material. This European
Patent Publication generally describes a process of treating such
organic waste by introducing the organic waste, ammonia, and an
acid into a tubular reactor, carrying out an exothermic reaction,
separating vapor from sludge, and then further processing the
sludge.
[0010] A component typically associated with tubular reactors is a
preneutralizer. The preneutralizer is typically used in conjunction
with tubular reactors to effect partial neutralization of the acid
prior to its introduction into the reactor. However, the use of a
preneutralizer poses various disadvantages including difficulty in
obtaining accurate control of flow rates. Additionally, operating
and equipment costs associated with the use of a preneutralizer
often represent a significant expense.
[0011] A reactor similar to the tubular reactor is the pipe-cross
reactor. Pipe-cross reactors similarly allow for an exothermic
reaction to take place, but typically involve the introduction of
one or two different acid solutions for reaction with a base in a
method to thoroughly mix the reagents. This is an important feature
of pipe-cross reactors as it eliminates the need for a
preneutralizer. At the first stage of the cross pipe reactor, the
base and/or scrubber water and organic material solution are
premixed. At the second step, pipe-cross reactors are formed with
up to two acid inlets configured such that the acid solutions are
introduced perpendicular to the pipe cross reactor as substantially
opposing streams. The perpendicular entry and opposing streams
allow for thorough mixing of the acids within the reactor, thus
eliminating the need for extraneous equipment such as a
preneutralizer.
[0012] Pipe-cross reactors are well-known and have been used in the
past to produce granular NPKS fertilizers from liquid chemicals
(e.g. Energy Efficient Fertilizer Production with the Pipe-Cross
Reactor (U.S. Dept. of Energy, 1982) (a pipe-cross reactor fit into
the granulator drum of a conventional ammoniation-granulation
system); Achom et al., "Optimizing Use of Energy in the Production
of Granular Ammonium Phosphate Fertilizer" (1982 Technical
Conference of ISMA, Pallini Beach, Greece); British Sulfur Corp.
Ltd., "TVA modifies its pipe reactor for increased versatility",
Phosphorus & Potassium, No. 90, pp. 25-30 (1977); Achom et al.,
"Efficient Use of Energy in Production of Granular and Fluid
Ammonium Phosphate Fertilizers" (1982 Fertilization Association of
India Seminar, New Dehli, India), Salladay et al.
"Commercialization of the TVA Pipe-Cross Reactor in Regional NPKS
and DAP Granulation Plants in the United States" (1980
Fertilization Association of India Seminar, New Dehli, India); U.S.
Pat. No. 4,619,684; U.S. Pat. No. 4,377,406; U.S. Pat. No.
4,134,750; U.S. Defensive Publication T969,002 (Apr. 4, 1978) to
Norton et al.; and Salladay et al., "Status of NPKS
Ammmoniation-Granulation Plants and TVA Pipe-Cross Reactor" (1980
Fertilizer Industry Round Table, Atlanta, Ga., US)). More recently,
pipe-cross reactors have been successfully used to enhance the
plant nutrient value of relatively low analysis organic waste
material (e.g. U.S. Pat. Nos. 5,984,992 and 6,159,263, the entirety
of both of which is incorporated by reference herein).
[0013] One potential drawback of exothermically treating relatively
low analysis organic waste material with reactors, such as a pipe
cross reactor or tubular reactor, is the potential for exhausting
noxious odors during the process. The use of cross-pipe reactors
for treating such waste has helped to reduce the odors typically
associated with the treatment thereof. However, a need exists to
provide greater assurance that such potential odors are eliminated,
or at least reduced beyond current emission levels.
[0014] Additionally, a continued desire exists to improve the
efficiency of sludge treatment, both in terms of capital
expenditure as well as in operating costs.
[0015] There is a need in the art for relatively simple and
efficient processes for processing relatively low analysis organic
waste material to an enhanced plant nutrient value composition
without substantial emission of noxious odors. Preferably, such
processes would produce products that were sized and shaped to be
spread by commercially available commercial spreaders.
SUMMARY OF THE INVENTION
[0016] The present invention surprisingly overcomes the problems
and disadvantages associated with current strategies and designs,
and provides improved systems and methods for treating organic
material, namely sludge.
[0017] One embodiment of the invention is directed to methods for
treating relatively low analysis organic waste material having a
solids content of at least approximately five percent or greater to
form an enhanced plant nutrient value composition. These methods
comprise mixing the relatively low analysis organic waste material
with scrubber water to form a slurry which is capable of being
pumped. The slurry is pumped into a pipe-cross reactor or tubular
reactor for reaction with a base and acid, to form a melt. The melt
is sprayed onto a recycling bed of fines in a granulator and liquid
is flashed off of the melt in the form of steam. The melt is rolled
onto fine particles in the granulator to form granulated particles
further reacted with a base to complete the product formation, and
subsequently dried in a dryer to reduce the moisture content of the
granulated particles. Fumes created during the process, such as the
flashed off steam, which may also contain particulates and ammonia,
are oxidized to destroy gaseous hydrocarbon pollutants contained
therein.
[0018] Another embodiment of the invention is directed to devices
and systems for treating relatively low analysis organic waste
material having a solids content of at least approximately five
percent in forming an enhanced plant nutrient value composition.
The system comprises a pipe-cross reactor or tubular reactor which
is configured to receive a slurry, a base, and an acid therein. The
reactor is configured to give thorough mixing and retention time so
as to allow substantial completion of a reaction between the
components introduced therein and form a melt from such components
while flowing through the reactor. Substantial completion means
that substantially most of the heat of mixing is generated by the
mixing step. Preferably at least 50%, 60%, 75%, 85%, 90% or even
95% of the total mixing heat produced by the exothermic step is
generated. A granulator, positioned to receive the melt from an
outlet of the reactor, is configured to further react the melt with
the base reagent to complete product formation and to mix fine
particles with the melt to form granulated particles. A dryer
receives the granulated particles from the granulator and reduces
the moisture content thereof resulting in substantially dried
granulated particles. A granule separator receives the dried
granulated particles and separates them into fines, product, and
oversized particles. The system may also comprise an oxidizer that
receives fumes formed during the reaction, granulation, and drying
processes. The oxidizer removes gaseous hydrocarbon pollutants from
the fumes prior to their exhaust.
[0019] Another embodiment of the invention is directed to methods
for treating relatively low analysis organic waste having a solids
content of at least approximately five percent to form an enhanced
plant nutrient value composition. These methods comprise mixing the
relatively low analysis organic waste material with scrubber water
to form a slurry which is capable of being pumped. The slurry is
pumped into a pipe-cross reactor or reactor for reaction with a
base, and acids to form a melt. The melt is sprayed onto a
recycling be of fines in a granulator and liquid is flashed off of
the melt in to form of steam. The melt is rolled onto fine
(smaller) particles in the granulator to form granulated (larger)
particles and then further reacted with the base reagent to
complete product formation and subsequently dried in a dryer to
reduce the moisture content thereof, resulting in an enhanced plant
nutrient valued composition in the form of dried granulated
particles. The granulated particles are conveyed to a dryer along
with the steam flashed off during the reaction and granulating
processes. The granulated particles are then dried to reduce the
moisture content thereof to form dried granulated particles which
comprise an enhanced plant nutrient value composition.
[0020] Another embodiment of the invention is directed to systems
for treating relatively low analysis organic waste material having
a solids content of at least approximately five percent in forming
an enhanced plant nutrient value composition. The system comprises
a pipe-cross reactor or tubular reactor for receiving a slurry, a
base, and an acid therein. The reactor is configured to give
thorough mixing and adequate retention time so as to allow
substantial completion of a reaction between the components
introduced therein and form a melt from such components while
flowing through the pipe-cross reactor. A granulator, positioned to
receive the melt from an outlet of the reactor, is configured to
further react the melt with the base reagent to complete product
formation and to mix fine particles with the melt to form
granulated particles. A dryer receives the granulated particles
from the granulator and reduces the moisture content thereof
resulting in substantially dried granulated particles. The dryer
also receives the flashed-off steam and fumes formed during the
reaction and granulation processes. A granule separator receives
the dried granulated particles and separates them into fines,
product, and oversized particles.
[0021] Other embodiments and advantages of the invention are set
forth, in part, in the following description and, in part, may be
obvious from this description, or may be learned from the practice
of the invention.
DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1--A process flow diagram of one embodiment of the
invention.
[0023] FIG. 2--A stylized view of a pipe-cross reactor.
[0024] FIG. 3--A partially cut away, perspective view of a
pipe-cross reactor in a rotary ammoniator-granulator.
[0025] FIG. 4--A stylized end view of a rotating bed of material in
a granulator.
[0026] FIG. 5--A side view of an orifice plate utilized with a
pipe-cross reactor.
DESCRIPTION OF THE INVENTION
[0027] As embodied and broadly described herein, the present
invention is directed to systems and methods for treating organic
material. More specifically, the present invention relates to
systems and methods for treating sludge and converting sludge into
fertilizer.
[0028] As depicted in FIG. 1, a process for enhancing the plant
nutrient value of organic waste material generally involves mixing
the organic waste material with water in an agitation tank or
sludge slurry tank 10 to form a slurry. The water used in making
the slurry may desirably include scrubber Water from the
hereinafter described scrubber 38, which may comprise waste acid.
The slurry is mixed at a sufficient concentration and consistency
such that it will, preferably, process the organic waste material
as quickly as possible, but will not clog or block a reactor during
operation. A preferred reactor is a pipe-cross reactor 12, but a
tubular reactor might alternatively be used, or even used, in a
system, in conjunction with a pipe cross reactor. The particular
slurry concentrations and consistencies will depend, to some
extent, on the size and amount of insoluble particulate material
contained in the particular organic waste material and the size and
length of the reactor components. However, as delivered to the
pipe-cross reactor, the slurry generally has a solids content of at
least about five percent and possibly as high as about 35%.
Preferably, the solids content of the slurry is from about 10% to
27%.
[0029] As depicted in FIG. 1, the slurry is pumped from the
agitation tank 10 to a pipe-cross reactor 12 for an exothermic
reaction with, for example, a base such as ammonia and an acid or
acids such as sulfuric acid, phosphoric acid, and mixtures thereof,
with or without extra water to form a melt.
[0030] Amounts of acid and base used in the exothermic process can
be determined by one of skill in the art. However, for guidance in
the neutralization of ammonia, approximately one mole of sulfuric
acid, or two moles of phosphoric compounds expressed as phosphoric
acid, is used for each two moles of ammonia. Concerning the
concentration of phosphoric acid, typical molar ratios of N:P in
the pipe-cross reactor are between 0.4:1 to 0.7:1, preferably 0.55
to 0.65:1, concerning the concentration of sulfuric acid, typical
molar ratios of N:S in the pipe cross reactor are between 0.5:1 and
0.8:1 preferably 0:65:1 to 0.72:1. The molar amount of nitrogen
should take into consideration not only the amount of ammonia being
added but the typical amount of ammoniacal nitrogen contained in
the particular organic waste material.
[0031] Other acids which may be used with the invention comprise
nitric acid, acetic acid, citric acid and mixtures thereof, all of
which are well know to those skilled in the art (e.g, nitric acid
and an ammonia compound which might form ammonium nitrate in the
presence of organic materials which is explosive). Whatever the
acid or acids chosen, the strength of one of the acids used in the
process will preferably be equivalent to 90% sulfuric acid (e.g. 93
to 100 percent sulfuric acid).
[0032] As depicted in FIG. 2, the pipe-cross reactor 12 is
preferably provided with two cross pipes 26, 28 to receive sulfuric
acid (at a rate of about 17.2 to 25.8 gpm) and phosphoric acid (at
a rate of from about 5.2 to 7.8 gpm). A third pipe 30 incorporates
the ammonia into the center of the reactor. The length of this pipe
30 is desirably at least twenty to thirty inches to ensure adequate
mixing. A third cross pipe 32 incorporates the slurry and
additional water into the mixing chamber. Positioned between the
third cross pipe 32 and the first and second cross pipes 26 and 28
is an orifice plate 33 which is utilized to introduce turbulence
into the flow of the slurry ensuring even greater mixing.
[0033] A typical pipe-cross reactor for use with the invention has
a diameter of about three to ten inches, is from about seven to
about fifty feet long, and terminates in, for example, a two to
eight inch discharge pipe (or a slot of equivalent cross-sectional
area), preferably with a stainless steel insert or TEFLON.TM.
lining. The discharge pipe preferably discharges into a standard
rotating drum granulator 14, and is preferably made of a steel pipe
(e.g. HASTELLOY C-276 or 316L stainless steel (with HASTELLOY C or
B for the reaction tube)). A TEFLON.TM., ceramic, or other
corrosion-resistant lining may also be used in the pipe-cross
reactor. The temperature is preferably maintained below 204.degree.
C. (400.degree. F.).
[0034] The orifice plate 33, as shown in FIG. 5, includes a plate
formed from a material similar to the pipe-cross reactor 12 and
includes an orifice 35 or aperture which exhibits a smaller
diameter than that of the pipe-cross reactor 12. Thus, for example,
a pipe-cross reactor having a (6) inch diameter would employ an
orifice plate 33 having an orifice 35 which exhibited a diameter
less than inches, for example inches. In determining the size of
the orifice 35, various parameters may be considered including flow
rates of the slurry, acids and base, as well as the solid content
of the slurry. Thus, the size of the orifice 35 may be changed for
a given pipe-cross reactor 12 if the any process parameters are
altered.
[0035] Although FIG. 5 shows use of a circular orifice plate, it
was surprisingly discovered that adding a protuberance generally to
increase turbulence upstream of the two pipe cross reactor provides
greater heat recovery. In other embodiments, the turbulence is
created through use of a protuberance, such as a bump, multiple
bumps in series or parallel with respect to the flow stream, one or
more wires, input of pressurized gas such as air, use of a sonic
vibrator or vibrating wall at this position. For example, two,
three, four, five, six, seven, eight or more equally spaced bumps
that each protrude into the space towards the lumen middle, by, for
example, 0.02, 0.05, 0.1, 0.2, or 0.3 times the diameter at that
point may be used to create turbulence. In an embodiment a bump is
an annular thickening that forms a constriction within the pipe. A
sonic vibrator (for example such as that offered by Advanced
Sonics, also may be used. A restriction, as shown in FIGS. 2 and 5,
does not have to be round but can be another cross sectional shape,
such as oval, square or irregular. An oval share is desirable,
particularly with the narrow ends pointed to the cross pipes such
that the larger oval axis extends across a line connecting the two
cross pipe openings. In another embodiment the short axis of the
oval extends across a line connecting the two cross pipes. The oval
shape with long matching axis provides a turbulence that more
closely matches the incoming flows from the perpendicular cross
reactors and is particularly desired when perpendicular cross pipe
reactors as shown in FIG. 2 are used.
[0036] The optimum placement of the protuberance(s) in many
embodiments is between 0.1 to 3 flow stream diameters upstream of
the average position of the cross reactor outlets (i.e. mean of the
cross reactor outlets, which may be staggered down the length of
the flow stream). More preferably the protuberances are located
between 0.3 to 1.5 diameters ahead of the cross pipe reactors.
Optimum placement will vary depending on the flow rate. For a very
high flow rate the protuberance(s) should be set further away or
the degree of protuberance into the flow path should be limited.
This embodiment may be carried out by an adjustable annular ring or
adjustable bumps that provide the ability to control the distance
away and the degree of flow path entry of the protuberance. An
annular ring may be adjusted for opening size and may be mounted at
alternative locations, for example. Multiple sonic vibrators, if
used may be placed at different locations and individually switched
to accommodate slower (vibrate closer to the cross pipes) or faster
(further away location) flow rate and/or lowered viscosity.
[0037] Adjustment of the cross pipe reactor itself may be optimized
for a given viscosity and flow rate. In many embodiments the cross
reactor pipes advantageously are exactly opposite each other, as
shown in FIG. 2. This placement is desirable when adding comparable
viscosity fluids at comparable flow rates. Also desirable, is the
use of multiple (3 or 4, or more) cross pipes. For example, a four
way (four perpendicular pipes) that administers two materials each
through two opposing sides, may be used if the viscosity is low
enough. Multiple cross reactor pipes may be switched to accommodate
changes in viscosity and/or flow rate. For example a less viscous
material or higher flow rate system may benefit by using one or
more cross reactor inlets that are further away (more downstream)
with respect to the protuberance(s) and that can be opened and
closed. Other combinations may be optimized upon routine
calibration, by changing the flow, and/or type of sludge material
and/or a reagent and then monitoring for heat recovery by measuring
temperature downstream at one or more points. By providing
adjustable protuberance(s), and/or cross pipe placements, and/or
flow rates optimized heat recovery may be obtained.
[0038] Yet another embodiment provides an automatic system that
constantly monitors temperature of mixed material at some point
downstream of the cross pipe reactor and adjusts protuberance
positioning, flow rate of sludge, flow rate of base, flow rate of
added water, flow rate of one or more acids, and switching of cross
reactor outlets for optimum effect. In a desirable embodiment flow
rate of base, and/or dilution water and/or an acid and/or a second
acid and/or sludge is adjusted up or down to obtain a higher
temperature. In another embodiment a switch selects between two or
more cross pipes to obtain a more desirable temperature. In yet
another embodiment some of the released heat is transferred in a
controllable way back to an input stream to obtain a more desirable
viscosity for adequate mixing. A control system may adjust heat
transfer up or down depending on the heat recovered, or depending
on another monitored variable, such as back pressure to the sludge
pump(s) or back pressure measured at a pipe-cross reactor
gauge.
[0039] Without wishing to be bound by any one theory of this
embodiment of the invention, it is thought that the use of a
protuberance such as an orifice plate allows greater mixing of the
slurry by inducing a zone of turbulence downstream of the orifice
plate 33 and generally in the vicinity of the first and second
cross pipes 26 and 28. The increased turbulence generated in many
cases increases heat production as measured as a higher melt
temperature. The temperature also can be measured at or downstream
of the last cross pipe addition of reagent, such as for example, 1
or 2 pipe diameters further downstream of the last cross pipe. It
has been observed that use of an orifice plate has effected an
increase of heat recovery, as much as approximately 30%, over
similar pipe-cross reactors lacking an orifice plate. An orifice
plate 33 may be changed for another orifice plate exhibiting a
different diameter orifice 35 if desired.
[0040] Referring to FIG. 2, ammonia is introduced into the
representative system depicted here at a rate of from about 4.3
gpm. Organic waste material (e.g. sewage sludge) and water are
incorporated at a rate of from about 30 to about 40 gpm of slurry.
The pipe-cross reactor shown here typically operates at a gage
pressure of between fifteen and sixty psig.
[0041] A hot melt discharges from the pipe-cross reactor 12 into
the granulator 14, while water flashes from the reactor product as
it issues into the granulator 14. Steam is generated by the
exothermic reaction conducted within the pipe-cross reactor 12.
[0042] A preferred granulator (e.g. an ammoniator-granulator),
depicted in FIGS. 3 and 4, is a two to four meter diameter rotating
drum granulator having a length of from about five to about nine
meters. As shown in FIG. 3, the pipe-cross reactor 12 is oriented
vertically and includes a number of 90 transitions or bends prior
to entering the granulator 14. The shown position of the pipe-cross
reactor 12 is preferred as it provides greater mixing capabilities.
However, satisfactory results may be achieved with the pipe-cross
reactor 12 oriented horizontally without any transitions or bends
(e.g. U.S. Pat. Nos. 5,984,992 and 6,159,263).
[0043] In the depicted process, the granulator 14 includes an
ammonia sparger 20 operably positioned within the granulator 14 for
the addition of ammonia to the melt to complete the reaction of
acid and base for the final product. The melt is rolled onto
recycled fine particles within the granulator 14 to form granulated
particles, thus causing the granulated particles to grow to a
desired size. Afterwards, as depicted in FIG. 1, these granulated
particles are passed into a rotary dryer 16 for a sufficient amount
of time to reduce their moisture content, thus forming a fertilizer
having an enhanced plant nutrient value. The vapors formed during
the reaction of the slurry with the acid and base (e.g. the flashed
off steam) are also collected and conveyed into the rotary dryer 16
for increasing the dew point vapors so as not to condense in the
plant equipment.
[0044] Passing such vapors directly into the dryer 16 is an
alternative process as compared to that of U.S. Pat. Nos. 5,984,992
and 6,159,263. Previous processes associated with pipe-cross
reactors have typically separated the granulated particles from the
vapor for independent processing prior to the drying of the
granulated particles. The presently depicted process eliminates the
need for additional particulate separation equipment and processing
of the air and ultimately results in a simpler and more efficient
process.
[0045] A preferred dryer for use with the invention is a two to
four meter diameter rotating drum dryer having a length of from
about seventeen to about thirty three meters, and having a heating
capacity of 30 to 70 million BTU/hour, with a lump crusher at the
discharge end.
[0046] The process further includes passing the dried granulated
particles to a granule separation apparatus, such as a screen 18,
and separating the dried granulated material into fines, product
and oversized material. Oversized material is reduced in size to be
incorporated, as a fine, back into the process. The fines are
returned to the granulator 14 (along with potash or any
micronutrients required for the desired final product analysis) for
incorporation into the process.
[0047] During the process, fumes, which may contain ammonia,
particulates, and water vapor above its dew point, are collected
from the dryer 16 and passed through particulate separating
equipment, such as a dust cyclone 34. The dust cyclone 34 removes a
portion of the particulates from the air and recycles these
particulates (e.g. dust) with the fines and ground material. The
resultant fumes leave the dust cyclone 34 and are processed through
additional particulate separating equipment, such as a baghouse
filter 36. The baghouse filter serves to remove an additional
amount of particulates, particularly particulates which exhibit a
smaller size than those removed by the dust cyclone 34.
Particulates removed from the baghouse filter 36 are similarly
recycled with the fines and ground material for use in the
granulator 14.
[0048] The fumes leaving the baghouse filter 36 are subsequently
processed through a scrubber 38, such as a venturi scrubber or
packed bed scrubber, which includes water separation chambers for
collecting ammonia fumes and small dust particles. The invention
uses low pH water in the scrubber 38 to collect unreacted ammonia
vapors escaping the granulator 14. In one embodiment, small amounts
of sulfuric or phosphoric acid are added to the scrubber 38 to
maintain a low pH (e.g. 2 to 3) for proper ammonia vapor
scrubbing.
[0049] The process further includes oxidizing the air exiting the
scrubber, such as in a regenerative thermal oxidizer (RTO) 40. The
RTO 40 is used to destroy volatile organic compounds (VOCs) and
other gaseous hydrocarbon pollutants that would otherwise be
released into the atmosphere. The RTO 40 destroys such VOCs and
hydrocarbon fumes through a process of high temperature thermal
oxidation, converting the VOCs and fumes to carbon dioxide and
water vapor. The oxidation of the air further serves to
substantially eliminate any noxious odors that would otherwise be
exhausted into the atmosphere. Energy released from the oxidation
process is recycled to reduce operating costs.
[0050] Air is drawn from the RTO 40 and exhausted into the
atmosphere through a stack 42. The process may advantageously
include using heat from the exhaust in the stack 42 to preheat the
base (e.g. ammonia) prior to its introduction into the pipe-cross
reactor 12 and/or the granulator 14 via the sparger 20.
[0051] Another aspect of the ventilation for the depicted process
includes collecting air from the screens 18. The process
contemplates two options, both of which involve particulate removal
and recycling of both particulates and air. The first option
includes processing the air through a dust cyclone 34 and recycling
both the particulates and the air back to the granulator 14. The
second option includes utilizing the dust cyclone 34, but further
includes processing the air through a baghouse filter 36, again
collecting the particulates for recycling in the granulator. The
air leaving the baghouse filter 36 is advanced to the dryer 16
instead of the granulator 14.
[0052] Other aspects of a ventilation system for use with the
invention preferably include fans for moving the air to and from
the various processing stages described above herein. Volume of air
moved is determined by the amount of moisture to be removed (above
dew point) and the melting point or disassociation temperature of
the fertilizer product.
[0053] NPK fertilizers preferably include the micronutrients iron
and zinc. In a preferred embodiment, spent acid from a hot dip
galvanizing or steel pickling process is used to maintain the low
pH of the scrubber water. These spent acids commonly are sulfuric
acid of five to ten percent strength, containing three to eight
percent iron. Galvanizing spent acid contains three to eight
percent zinc along with iron. The iron and zinc are fed with the
ammonia-laden scrubber water from scrubbing to the sludge slurry
tank and on to the pipe-cross reactor for incorporation as iron and
zinc micronutrients in the final NPK fertilizer. In the case of
spent sulfuric acid, the sulfur also becomes a nutrient in the
resulting fertilizer, since it reacts in the pipe-cross reactor to
form ammonium sulfate.
[0054] Other micronutrients or additional ingredients may be
incorporated into the resulting fertilizer by adding them with a
weigh feeder as a dry solid to the fines recycle stream.
Micronutrients or additional ingredients include lime, dolomite,
calcite, hydrobiotite, gypsum, phosphates (e.g. rock phosphate or
ammonium phosphate), potash, urea, soil clays, calcium peroxide,
ammonium nitrate, vermiculite, humic acid, and trace minerals such
as iron, manganese, magnesium, boron, copper, and zinc.
[0055] Although the invention has been most particularly described
for the processing of municipal sewage sludge, the inventive
process may also be used to enhance the plant nutrient value of
other relatively low analysis organic waste material such as
poultry manure, food processing wastes, wastes from paper
manufacturing, swine manure sludge, mixtures thereof, and the like.
In such a case, the particular relatively low analysis organic
waste material is substituted for the sewage sludge in the process,
and the process parameters are accordingly modified.
[0056] The following examples are offered to illustrate embodiments
of the present invention, but should not be viewed as limiting the
scope of the invention.
Examples
Example 1
[0057] In an agitation tank, 6700 kilograms/hour (7.4 tons/hour) of
sewage sludge were mixed with 37 liters per minute (ten
gallons/minute (gpm)) of scrubber water to form a slurry. The
slurry was of such a consistency (a solids content varying between
10% and 27%) that it can be pumped-with a positive displacement
pump or other suitable pump to a pipe-cross reactor equipped to
receive ammonia, sulfuric acid, phosphoric acid, sewage sludge, and
water. The pipe-cross reactor had a diameter of approximately four
inches and was forty feet long. The pipe-cross reactor terminated
in a rotating drum granulator. The rotating drum granulator was six
feet in diameter and twenty feet long.
[0058] The slurry was added to the pipe-cross reactor and reacted
with 8.6 gpm 99.5% ammonia, 8.6 gpm sulfuric acid (93%), and 2.6
gpm phosphoric acid (54% P.sub.2O.sub.5). The temperature of the
pipe-cross reactor (due to the exothermic reaction between the acid
and the base) was maintained at about 149.degree. C. (300.degree.
F.) with moisture in the sludge. This temperature (above minimum
sterilization temperature) acts to kill Salmonella, E. coli, and
other pathogens which may be found in the slurry. This temperature
also acts to deodorize the material somewhat.
[0059] The resulting melt from the pipe-cross reactor is sprayed
onto a recycling bed of fines, along with 2000 pounds of added
potassium chloride (60% K.sub.2O) while the water contained in the
melt flashed off as steam. An ammonia sparger is provided in the
granulator to add small amounts of ammonia to the granulation
mixture for reaction completion and final hardening of
granules.
[0060] Operating the pipe-cross reactor in such a manner
incorporated approximately 14.8 tons per hour of 20% solid sewage
sludge at a ten ton per hour production rate.
[0061] Granulated material exits the granulator at about 93.degree.
C. (200.degree. F.) and at about a five to fifteen percent moisture
content into a rotary dryer. The rotary dryer was approximately two
meters in diameter and has a length of about twenty meters. It has
a heating capacity of 30 million BTU/hour and is associated with a
lump crusher or lump breaker at the discharge end. The moisture in
the material was reduced to less than three percent by heated
forced air in the dryer.
[0062] Materials exiting the rotary dryer were run through the lump
crusher to reduce oversized material to less than one inch in
size.
[0063] Screens are used to separate the material into (a) fines,
(b) product and (c) oversized material. Fines are returned to the
granulator. Product went to a two meter diameter, twenty meter long
cooler and then on to storage, while the oversized material is
passed through a grinding mill and reduced to fines for recycling
to the granulator. About two tons (1800 kg) of fine material per
ton of product were required in the recycle stream.
[0064] Fumes from the granulator containing steam, ammonia and
particulate were collected by maintaining a negative pressure
inside the granulator with a fan pulling the fumes into the rotary
dryer to reduce the moisture content thereof. The air was drawn
from the granulator at a rate of 20,000 cubic feet per minute (cfm)
at a temperature of 92.degree. C. (198.degree. F.) and at 100%
relative humidity. This is roughly equivalent to conveying 34,200
pounds per hour (lbs/hr) of water and 296 pounds per minute
(lbs/min) of dry air.
[0065] The air from the rotary dryer was directed to a dust
cyclone, a baghouse filter, and then a scrubber. Air was drawn from
the dryer at a rate of 70,000 cfm at 45% relative humidity. The air
leaving the dryer had a dry bulb temperature of approximately
93.degree. C. (200.degree. F.) and a wet bulb temperature of
74.degree. C. (165.degree. F.). This is roughly equivalent of
conveying 56,100 lbs/hr water and 2,711 lbs/min of dry air. Air
entering the scrubber is scrubbed with low pH water (water at a pH
lowered by the addition of spent acid from a hot dip galvanizing
process). If galvanizing acid is unavailable, the pH may be
controlled with phosphoric or sulfuric acid. The low pH water
collects ammonia vapor present in the fumes, as well as dust
particles.
[0066] Air was directed from the scrubber to a regenerative thermal
oxidizer at a rate of 67,100 cfm at a temperature of 165.degree. F.
and at 100% relative humidity. Oxidized air was then drawn from the
regenerative thermal oxidizer and is exhausted through a stack
approximately one hundred (100) feet tall at a temperature of
93.degree. C. (200.degree. F.).
[0067] Dust-laden air is collected from the grinding mills and
screens by a fan maintaining negative pressure on the equipment.
The air is pulled through a cyclone system that removes about 97%
of the dust. From the cyclones, the air was passed back to the
rotary granulator and the dust added to the recycled fines.
[0068] The resulting fertilizer had an NPK value of 12-3-6 (12%
nitrogen, 3% phosphate, and 6% potash). It was also homogenous and
properly sized for standard application equipment.
Example 2
[0069] The process of Example I is repeated in a tubular reactor
rather than a pipe cross reactor. In an agitation tank, 6700
kilograms/hour (7.4 tons/hour) of sewage sludge are mixed with 37
liters per minute (ten gallons/minute (gpm)) of scrubber water to
form a slurry. The slurry is of such a consistency that it can be
pumped with a positive displacement pump or other suitable pump to
a tubular reactor equipped to receive ammonia, sulfuric acid,
phosphoric acid, sewage sludge, and water. The tubular reactor
preferably has a diameter of approximately 1.5 to 30 cm and a
length of 2 to 10 meters, preferably 5 to 8 meters. The reactor
terminates in a rotating drum granulator. The rotating drum
granulator is six feet in diameter and twenty feet long.
[0070] The slurry is added to the reactor and reacted with 8.6 gpm
99.5% ammonia, and an acid solution containing 8.6 gpm sulfuric
acid (93%) and 2.6 gpm phosphoric acid (54% P.sub.2O.sub.5). The
temperature of the reactor (due to the exothermic reaction between
the acid solution and the base) is maintained at about 149.degree.
C. (300.degree. F.) with moisture in the sludge.
[0071] The resulting melt from the reactor is sprayed onto a
recycling bed of fines, along with 2000 pounds of added potassium
chloride (60% K.sub.2O) while the water contained in the melt
flashes off as steam. An ammonia sparger is provided in the
granulator to add small amounts of ammonia to the granulation
mixture for reaction completion and final hardening of the
granules.
[0072] Granulated material exits the granulator at about with a
moisture content into a rotary dryer. The rotary dryer is
approximately two meters in diameter and has a length of about
twenty meters. It has a heating capacity of 30 million BTU/hour and
is associated with a lump crusher or lump breaker at the discharge
end. The moisture in the material is reduced to less than three
percent by heated forced air in the dryer.
[0073] Materials exiting the rotary dryer are run through the lump
crusher to reduce oversized material to less than one inch in
size.
[0074] Screens are used to separate the material into (a) fines,
(b) product and (c) oversized material. Fines are returned to the
granulator. Product goes to a two meter diameter, twenty meter long
cooler and then on to storage, while the oversized material is
passed through a grinding mill and reduced to fines for recycling
to the granulator. About two tons (1800 kg) of fine material per
ton of product are required in the recycle stream.
[0075] Fumes from the granulator containing steam, ammonia and
particulate are collected by maintaining a negative pressure inside
the granulator with a fan pulling the fumes into the rotary dryer
to reduce the moisture content thereof. Air is drawn from the
granulator at a rate of 20,000 cubic feet per minute (cfm) at a
temperature of 92.degree. C. (198.degree. F.) and at 100% relative
humidity. This is roughly equivalent of conveying 34,200 pounds per
hour (lbs/hr) of water and 296 pounds per minute (lbs/min) of dry
air.
[0076] The air from the rotary dryer is conveyed to a dust cyclone,
a baghouse filter, and then a scrubber. Air is drawn from the dryer
at a rate of 70,000 cfm at 45% relative humidity. The air leaving
the dryer has a dry bulb temperature of 93.degree. C. (200.degree.
F.) and a wet bulb temperature of 74.degree. C. (165.degree. F.).
This is roughly equivalent of conveying 56,100 lbs/hr water and
2,711 lbs/min of dry air. Air entering the scrubber is scrubbed
with low pH water. The low pH water collects ammonia vapor present
in the fumes, as well as dust particles.
[0077] Air is conveyed from the scrubber to a regenerative thermal
oxidizer at a rate of 67,100 cfm at a temperature of (165.degree.
F.) and at 100% relative humidity. Oxidized air is then drawn from
the regenerative thermal oxidizer and is exhausted through a stack
approximately one hundred feet tall at a temperature of 93.degree.
C. (200.degree. F).
[0078] Dust-laden air is collected from the grinding mills and
screens by a fan maintaining negative pressure on the equipment.
The air is pulled through a cyclone system that removes about 97%
of the dust. From the cyclones, the air is passed back to the
rotary granulator and the dust is added to the recycled fines. The
resulting fertilizer is determined to have an NPK value.
[0079] Other embodiments and uses of the invention will be apparent
to those skilled in the art from consideration of the specification
and practice of the invention disclosed herein. All references
cited herein, including all U.S. and foreign patents and patent
applications, including U.S. patent application Ser. Nos.
08/852,663, 09/735,768 and 09/416,370, are specifically and
entirely incorporated herein by reference. It is intended that the
specification and examples be considered exemplary only, with the
true scope and spirit of the invention indicated by the following
claims.
* * * * *