SG177517A1 - Wastewater sludge processing system - Google Patents

Abstract

The Wastewater sludge processing system takes sludge directly from the municipal waste water treatment plant and processes it using a low-temperature, low pressure process that has no waste products. The process dries the sludge and separates it into oil that is turned into biodiesel feedstock, cellulose/minerals that are used for heating the process, and water that is reused in the process.

Description

Wastewater Sludge Processing System

GOVERNMENT INTEREST STATEMENT

[0001] None

BACKGROUND OF THE INVENTION

1. Field of invention {G002] The invention relates generally to a process for the treatment of wastewater sludge into desiralde products with no undesirable waste ef aver.

More specially the process relates to drying the sludge, and separaling the sludge into oil, water, and cellidose/minerals by the use of chemical and physical reactions. 2. Description of the Background 0003] Sewage is created by residences, institutions, hospitals and commercial and industrial establishments. Raw wifluent {sewage} includes household waste liquid from toilets, baths, showers, kitchens, sinks, and so forth that is disposed of via sewers, In Many areas, sewage also includes quid waste from industry and commerce. Municipal wastewater therefore includes residential, commaeraial, and industrial liquid waste discharges, and may include storm water runoff,

[0004] Conventional sewage freatment 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 nto a salid mass by using indigenous, water-borne micro-organisms. Finally, the hinlogical solids are neutralized then disposed of or re-used, and the treated water may be disinfected chemically or physically {for example by lagoons and microfitration}. The final efffuant can de discharged into a stream, river, bay, lagoon or wetland, or it oan be used for the irrigation of a golf course, green way or park. i it is sufficiently clean, it van also be used for groundwater recharge or agricultural purposes.

[0005] The sludges accumulated in a wastewater realment process must be freated and disposed of in a safe and effective manner. The purpose of digestion is to reduce the amount of erganic matter and the number of disease-causing mHoroorganisms present in the solids.

The most common treatment options include anaerobic digestion, asrchic digestion, and composting.

{G0D8] Choice of a wastewater sold treatment method depends an the amount of solids generated and other site-specific conditions.

However, in general, composting 1s most often applied io smaller-scale applications followed by aerchic digestion and then lastly anaerobic digestion for the larger-scale micipal applications.

{00077 SUMMARY OF THE INVENTION

{G00} It has now been found that wastewater sludge can be processed economically by virtue of using products of the freatment process as a fusd for one oF more healing steps in the process. | has further been found that wastewater sludge can be processed such that at the end of the process of the presant invention, all the useful matenials—ail, cellulose and minerals—have been captured.

Most important, it has still further been found that wastewster sludge can be processed such that there is nothing {eft 10 be incinerated, landfilled, or otherwise disposed of, making the system of the present invention a truly zero-waste process.

0008] In accordance with an embodiment of the invention, a zero-waste method of processing wastewater sludge ts provide such that al the end of the process of aif, cellulose, and minerals have bean captured and thers is substantially nothing laf to be incinerated, andfifled, or otherwise disposed of.

00010] In accordance with another embodiment of tha invention, a process is provide which comprises the steps of,

a- transferring solid wastewater sludge from a treatment plant 1 a wet studge holding bin, sad wastewater shudge containing from about 20 to 46% solids by wsight,

b- drying saw wastewater sludge to about 90% solids,

grinding the dried wastewater sludge an transfering the dried ground sludge fo a miner reactor, o- within the mixer reactor mixing the dried ground sludgs with a solvent and heating to produce viscous suspension of hydrocarbons or celitdoss and minerals in suspension, d= separating quids and solids, © heating the separated liquids © the boiling point of the soheent and the boing point of the residual water prior and collecting evaporated solvent and residual water,

I= transferring solventiree olf to a holding tank, g- condensing evaporated solvent and residual walsr and separating water from solvent, and h- iransfering separated solvent and residual walter to the mixer reactor of step {Cc}

[00011] Ih 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-minaral mixture from said filler press

IS drying sau celfulose-mineral mixture and removing and collecing solvent k- reusing collected solvent in the process at step {¢}, and + transferring dried cellidose/mineral miklure fo a fumace and using the heat from the furnace in of least one of steps bY, © and (8)

[00012] In arcordance with another embodiment of the vention the oll from step {f} is approximately 80% fatty acds, is approximately 85 weight % C18 and C18, and is substantially free of sulfur. [QO013] In accordance with stilt another embodiment of the vention the process extracts about 18% oil by weight from undigested sludge and 11% cif by weight fram digested sludge.

{G0014] In accordance with another embodiment of the invention the sfep of separating liguids and soluds produces a firate comprising extracted oll, residusi solvent, and races of water.

[00015] BRIEF DESCRIPTION OF THE DRAWINGS {0018} FIG 1 is part 1 of the process Sow diagram. [DO0171 FIG 2s part 2 of the process How diagram.

[00018] FIG 3 is part 3 of the process Sow diagram.

DETALED DESCRIPTION

{000191 His advantageous fo define cerlain farms before describing the invention. if should be appreciated that the following definitions are ussd throughout this application,

Definitions

[00020] The term “wastewater sludge” and “sludge” means sludge accumulated in a wastewater treatment process.

[00021] The term “solvent” means a substance capable of dissolving another substance.

[00022] The term "Hlirate” means a gud or gas that has been filtered. {00023} The term “sorew feeder” means a scraw feeder such as a wilumetiic screw feeder or gravimetne screw feeder, capable of metering materiglt ing production process. {00024] The term “filter ress” means a machine using filtering cloths and plates separate solids and liquids.

[00025] The term “biodiesel fepdstack” means organic material used in the production of biofuels. {00026] The terms “about” and “approximately” means a deviation of no greater than 15% from an absolute value,

[G0027] The term “substantially” means plus or minus 10%.

[00028] The term “holding tank” means any pisce of equipment that is used to store praduct.

[00028] The term "%", unless otherwise specified, refers to percent by weight.

[00030] The Wastewater sludge processing system takes sludge directly from the municipal waste water treatment plant, transforms it into usefid products, and lsaves no wastes behind, #15 g low-temperature, low prassurg process.

[00031] The municipal solid waste (101) is transferred from a treatment plant to 3 wet sludge holding bin (103). In the holding bin {103} the waste is 20-45% sohds by weight. The sludge is transferred by first screw feeder (105) to a dryer {107} where i is dried to 830% solids. During the drying, liquid is removed as steam {109}. The dried sludge is then ground in a grinder {111}. The dried ground siudge is transferred 0 a dried feed holding bin {203}. The dried ground sludge s transfered by a screw feeder (2058) slong the path (10014) to the path (10018 to the mixer reactor {113).

[00032] Solvent is added {o 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 andfor cellulose and minerals in suspension. The resulting solution is pumped by pump (218) info g filter press {117} where the filtrate and solids are separated, Tha filtrate which includes extracted ol, residual solvent, and traces of water, is sent to a holding tank (119).

The filtrate is pumped vig a second pump {2158} along the path (200088) to the path (20088) to the heat exchanger (121). The fillrate 1s heated to the balling point of the solver and the boating point of the residuat water prior to anlering the flash drum {123}. In the flash drum (123), the sohent and residual water are evaporated and removed vig the vacuum pump (125). The solvent-free oll 1s collected from the bottom of the Hash drum {123} and moved by third pump (315) © 8 holding tank (127) ready for shipping as biodiesel! feedsiock.

[00033] The solvent and residual water vapor from the vacuum pump (125) discharge and the vent lines from the upstream: process along the path (20034)

fo the path (J003R) are ooliscted and are routed {o the solvent recovery system indicated generally as {129} In the second heat exchanger (321) vapors are condensed back {o a liquid state. The liquid then travels along the path (20014) 0 the path (20018) {o the condsnseriseparator (131) which removes the water fram the solvent. The water and the solvent are both retined to be reused in the

Process. {000341 The cellulpse and minerals are moved from the condensarseparator {131} by a fourth pump (4158) into the make-up solvent tank (133). The vented vapor from the condenseriseparator (131) goes 10 an activated carbon canister (135) and then into the make-up solvent tank (133). Fresh solvent is also added {o the make-up solvent tank (133), Hot water (138) is also removed from the condenser/separator {131} for reuse.

[00035] Back al the filter press (117), the celluloseimineral mixiure is collecied and sant to a dryer (141) where the solvent is removed and recovered, The cellutosaiminaral mixture proceads to a holding tank (303). The third strew feadsr (309) lakes the cellulose/mineral mixture along the path (2007A) lo the path (20078) 10 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. [Q0036] Androgen tank {147} uses the fifth pump {518} {o move the nitrogen along the path (10014) {0 the path (10018) to the mixer reactor (113), the filtrate fank {119}, the dryer {141} and the dried cellulose bin (303). 000371 Preferably, the system does nol employ frther separation, but rather, the celiglose/mineral midure is used as fust 1 an sitamative fustHfumace {oo dry the incoming sludge. The oi has a 19.000 Blu/pound energy value and the celludoss/mineral mikdure has a 7000 Blwpound energy value, {000381 The ofl is considered {0 be a perfect feedstock for biodiesel. i is 80% fatty acids (85% C18 and C18), and has almost no sulfur. I also can be used as fusl aif without further processing. {GUS The process extracts 18% oll by weight from undigested sludge and 11% aif by weight from digested sludge. A bone dry pound of sludge yields 11-18% oil,

50-80% cellulose and 30% minerals hough the process need not separate the cellulose and minerals. {GU} The drying step of the process lakes ahout 45% of the energy oost of the process. i should be noted that because the process does not employ a washing step, drying costs arg minimized.

[00041] Atthe end of the process of the present invention, all the useful materials—ot, cellulose and minsrals—have been caplured. Mast important, there 5 nothing left © be incinerated, landfilled, or otherwise disposed of, making the system of the present uwention a fruly zero-waste process,

[00042] The following examples are Tor illustrative purposes and are not indicative of the limits of the present invention.

EXAMPLE

[00043] Process design Criteria and Assumptions

Hem Units Design

[00044] Municipal Solid Waste (MSW)

MEW Filter cake as feed to dryer bir 48

Moisture content % 75

Solids content Fs 25

Buk density of MSW ake thie £8

Temperature (avg) of MEW cake oF 85

[000458] Average Composition of Reactor Fead Solids

Dried MEW as feed to reactor fit 10

Solids content et ad

Maistre content % 10

Of {dry solids basis) Ya 10

Celhidase {dry sohds} % 50-60

Bulk density of cellulose Hoff” ih

Specific heat capacity BuibF 7850

Metal mades (MO), dry solids % 25.35 NT

Bulk density of MO hie 158

Sp. Gr. (average) of MO ~ 2.5

Specific haat capacity of MO Biufth~F $4.23

[00046] Average Composition of Mela! Oxides fron oxide Ha 10.0

Calcium oxide “a 8.25

Phosphorus oxide Ya 4.5

Aluminum oxide %o 2.25 {Other oxides % 20

[00047] Solvent Characteristics

Haptane (CMs)

Specific gravity ~ 0.684

Bulk density of CHa fit 42 B84

Baiting point of Cybis oF 208.1

Specific heat capacity of OMe Btuftb-F as

Latent haat of vaporization Btudlh 7845

Hom Units Design

Nitrogen Gas

Specific heat capacity of nitrogen Blthok 4.25

Density of nitragen ihe 4.073

[00048] Product Fuel Oi

Specific gravity of al - 0%

Bulk density of oil fh 58

Specific heat capacity of ui Biufb-F 18,000

[00049] Plant Operation

Length of shift hrid 164

Operating hows pear shift hrishiftd

Dried MSW fesd processed aft 10

Solvent addition

Pounds per pound of dry solids bib 4:1

Sobvant lossith of product oil Se 1.0 [GO0S0] MSW Feed to Dryer

Raw MSW filter cake bh 44

Solids content Ho 25

Moisture content % 75

Bulk density of dried MSW cake fa 21-31

Pilot Plant Operation Parameters

[00051] The Mixgr/Reackw was sized™ to process 20 ib of solids on a dry basis {22.2 tb of dried MSW containing S0% 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 oll. Approximately two {2} gallons of od at 895% recovery arg fo be produced during the 8 hours of operation each day.

Number of shits per day shiftsid 1

Duration of shift {total} hrishit10

Number of batches per shift batchesid 2

Reaction time per batch hribatch 3

Dried fend (80% solids) pay baich ih/batoh 23.3

Dry solids content of Reactor fesd ihibateh 20

Solvent addition rate ib/hatch 48

Solvent added {id 80 fem Units Design

[00052] Product Ol

Off in MSW feed solids % 10

Gil content of MSW feed solids ibid 2

Estimated ofl recovery % 85

Estimated oll recovery thd 14.25

Estimated oll recovery galid 1.8

[00083] MixeriReactor

Solids processed on a dry basis = 10 tbébatch

Solvent theplane) added per batch = 40 fvbaich

Mass of dried feed (80% salids) charged to Mixer/Reactor = {10 /batoh) {80% solids) = 11. ibibatch

Volume of driad feed charged to MixeriReactor = {11.1 tbatchi{21-31 ii) = (1.35. 52 f'hatch

Volume of solvent (heptane) added fo Mixer/Reactor = {40 n/batoh {21.3 bi’)

= 94 # batch

Total volume of faed to Mier/Readtor = 0.35- 52 8° dried MSW filter cake + 1.88 #° heptane = 1.29-1.46 f'bateh

Size of MixerReactor {0 = diameter = height} (mr) x (0%) = eee % {DY = 1.2841 46 4

Dw [{1.20-1.46) x (AY = 1.181.231,

The Mixer/Reactor is 1.5 ft, dia, x 2.8 ft. tall, which includes a freeboard altowance of 1.0 ft. and equipped with 1.0 hp motor with variable frequency drive (WFD). [4.42 #8

[00084] Broad Scope of the Invention

[00058] Although the present invention has been fully described in conjunction with several embodiments thereol with reference to the accompanying drawings, it is {o be understood that various changes and modifications may be apparent {0 those skilled in the ard. 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.

[00056] While Hustrative embodiments of the invention have been desoribed herein, the present invention is not limited to the various preferred embodiments described herain, bul includes any and all embodiments having sguivalent slements, modifications, omissions, combinations {e.g., of aspects across vanous embodiments), adapiations 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 daims and nat imited to examples describad in the present specification or during the prosacution of the application, which examples ars {© be construsd as non- exclusive.

For example, in the present disclosure, the term "prafarably” 1s non exclusive and means "preferably, bul 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 imitation: 8) "means for" or "slap for” 8 exprassly recited; b) a corresponding funchon is expressly recited; and ¢) structure, material or acts that support that structure are not recited.

In this disclose and during the prosecution of this application, the terminology "present vention” or “invention” may be used as a references to one or More aspect within the present disclosure.

The languages present invention or invention should not be improperly interpreted as an identification of griticality, should not be improperly interpreted gs applying across all aspects or embodiments {te # should be understood that the present invention has a number of aspects and ambodimenis} and should not be improperly interpreted as miting the scopes 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, alc. i some axamples, various embodiments may include overlapping features.

In this disclosure, the following abbreviated terminology may be employed™a.g” which means "or example”.

Claims (7)

1. What is claimed is Claim 1 A zera-waste method of processing wastewater sludge such that at the end of the process, oil, cellulose, and minsrals have been caplured and there is substantially nothing left to be incinerated, landfilled, or otherwise disposed of, comprising the steps of; a transferring solid wastewater sludge from a treatment plant to a wet sludge holding bin, said wastewater sludge containing from about 20 to 45% satids by weight, b- drying sad wastewater sludge to about 90% solids, grinding the dried wastewater sludge an transferring the dried ground sludge to a mixer reactor, Cr within the mixer reactor mixing the dried ground sludge with a solvent and heating 10 produce viscous suspension of hydrocarbons or cellulose and ginerals in suspension, a separating haquids and solids, a= heating the separated hguids to the bolting point of the solvent and the bofling point of the residual water prior and collecting evaporated solvent and residual water, fe transferring solvent-free olf fo a holding tank, g- condensing evaporated solvent and residual water and separating water from soba, and h- transferring separated solvent and residual water fo the mixer reactor of step {o).
2. Claim 2 The method of claim 1, further comprising saul step of separating lquids and solids is parfrmed in a filler press, i collecting cellulose-mineral midure from said filter press IS drying saw cellulose-mineral mixture and removing and collecting solvent k- reusing collected solvent in the process at slep (©), and iS transferring dried cellidoseimineral miklurs 0 8 furnace and using the heat from the furnace in at least one of steps {b), {¢) and {e}.
3. Claim 3 The method of claim 2, wherein the olf from step {f) is approximately 80% fatty acids.
4. Claim 4 The method of claim 3, wherein the oll from step (T) is approximately 85 weight % C18 and C18 Claim & The method of claim 3, wherein said oil is substantially ree of sulfur.
5. Clam The method of claim 1, wherein the process sxiracts about 18% oil by weight from undigested sludge and 11% oi by weight from digested sludge.
6. Claim
7. 7 The method of claim 1, wherein said step of separating liquids and solids produces a filtrate comprising extracted oll, residual solvent, and traces of water, Claim 8 Claim § A zero-wasts method of processing wastewater sludge such that at the end of the process, gif, cellulose, and minerals have been captured and there is substantially nothing left fo be incinerated, landfiled, or otherwise disposed of, comprising the steps of) a- transferring solid wastewater sludge from 8 trealment plant fo 8 wet shudge holding bin, said wastewater sludge containing from about 20 10 48% solids by weight, kee drying said wastewater sludge to about 80% solids,

   grinding the dried wastewater sludge an transfering the dried ground sludge fo a miner reactor, o- within the mixer reactor mixing the dried ground sludgs with a solvent and heating to produce viscous suspension of hydrocarbons or celitdoss and minerals in suspension, d= separating quids and solids, © heating the separated liquids © the boiling point of the soheent and the boing point of the residual water prior and collecting evaporated solvent and residual water, I= transferring solventiree olf to a holding tank, g- condensing evaporated solvent and residual walsr and separating water from solvent, h- iransfering separated solvent and residual walter to the mixer reactor of step {a}, i collecting cellulose-mineral mixture from step {d}, IS drying said cellidose-mingral mixture and removing and collecting solvent Ke reusing collected solvent in the process at step {¢), and I transferring dried celitdose/mineral mixlure {0 8 fumace and using the heat from the furnace in at least one of steps (bY, {&} and {8}, wherein the off fren step {) is approcimately 80% fatty acids and 65 weight % C18 and (18, and wherein said step of separating liquids and solids produces a filtrate comprising axtracted off, residus! sobvard, and traces of water,