Patent Application
20230174403
This application claims priority to provisional application Ser. No. 63/285,508 filed on Dec. 3, 2021 titled Systems and Methods for Mechanically Removing Liquid from Material, the entire content of which is incorporated herein by reference.
The disclosed inventions relate to novel systems, apparatuses, and methods to remove liquid from material. In most applications, the material comprises biosolids, e.g., the solid, semi-solid, or liquid residue generated during the biological wastewater treatment process. In other applications, the material comprises organic or inorganic material such as feed additives. The term “material” is used collectively to include biosolids and other organic or inorganic compositions.
The disclosed inventions may operate independently to mechanically dewater material. Alternatively, the disclosed inventions may supplement existing systems or methods used to generate class A fertilizer from biosolids as described in U.S. letters Pat. Nos. 9,751,813 and 10,259,755 and pending application Ser. No. 17/220,994, all of which are owned by the instant applicant, and the entire disclosures of which are incorporated herein by reference.
The disclosed inventions process material (e.g., sludge) that may have been dewatered with a belt press, centrifuge, screw press, or other type of dewatering device. The inventions mechanically compress the material (sludge) to remove water from the material that cannot be extracted through conventional means. Material such as sludge starts out as a liquid and can be dewatered by adding polymer. Adding polymer removes water from the material to increase the percent solids of the material. The dewatered material may then be fed into the double drum dryer to remove additional water to increase the percent solids to a concentration of about 90%.
The disclosed inventions apply high pressure forces to the material. A belt transports material on a woven mesh belt to a compression zone. Hydraulically actuated plates exert high pressure forces on the material to press additional water out of the material. This process increases the solids percentage from 15-25% to about 30-45%. The reduction in water content reduces the volume of material. When used in conjunction with existing systems (e.g., a double drum dryer) the disclosed inventions materially increase the throughput (i.e., the end product) because less water remains in the material before being exposed to a thermal drying system.
The disclosed inventions may also allow liquid sludge to be delivered directly into the system with or without first adding a polymer to the sludge. One of the existing challenges in the industry is to dewater material as much as possible mechanically. Mechanical dewatering includes any system or process that does not use heat or thermal energy; therefore, mechanical dewatering costs less than heat or thermal drying. In one embodiment, a polymer is added to the sludge, the sludge is then processed through a centrifuge, belt press, or screw press. In this embodiment, the cost is about $0.01-$0.02 per gallon to remove a gallon of water from of a material.
Thermal drying costs about $0.10-$0.20 per gallon to remove a gallon of water. The disclosed inventions reduce the cost to about 10% of the cost of thermal systems. Plants, such as municipal wastewater treatment facilities, that have moderate to low disposal costs focus on mechanical dewatering. Larger volume plants that have higher disposal costs and want to achieve a Class A fertilizer end product will use mechanical dewatering and thermal energy dewatering.
In one example for one city in Indiana, the sludge averages 15% solids (85% moisture or water). Using a prototype of the invention disclosed herein, the system was able to achieve 30% solids (70% moisture) at less than $0.01 per gallon. Mechanical dewatering also reduces the volume and weight of material to be transported by about half, thereby providing additional cost savings during transportation.
This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. Further embodiments, forms, objects, features, advantages, aspects, and benefits shall become apparent from the following description and drawings.
The following detailed description provides contemplated modes of carrying out embodiments of the invention. The description is not limiting, rather it illustrates the general principles of the inventions.
Most biosolids from wastewater treatment plants comprise a liquid similar in consistency to skim or whole milk. The concentration typically ranges from 1-8% solids (92-99% moisture). Wastewater that is received in a typical wastewater plant will generally consist of a water content and smaller solids content. Typically, 99% of what comes into a wastewater plant is water. This water is usually treated biologically and discharged into a nearby stream or water body. The remaining 1% that consists of solids is separated and treated independently. The remaining solids are dewatered to 15-25% solids meaning the material still has 75-85% moisture in it.
The inventions combine the use of pre-screening, chemical flocculation dewatering, non-chemical dewatering, conditioning, and/or leveling with high pressure compression and filtration to remove water and thereby reduce the volume of material. Material may be screened and dewatered with a centrifuge, belt press, screw press, or similar devices. Optionally, a polymer may be added to the material before dewatering to flock the liquid. The dewatering process thickens the material to approximately 15-30% solids (70-85% moisture) by weight. After this first thickening step, the material can be conveyed into the disclosed system.
The disclosed inventions process the material that has about 75-85% moisture and reduces the moisture content to 55-75%. This dewatering substantially reduces the transportation and disposal cost. When this technology is used in conjunction with other thermal drying processes, it improves the economics and increases throughput by removing additional moisture that does not need to be removed thermally. By reducing the amount of water in the material, thermal dewatering may be avoided or minimized that reduces the effective cost of dewatering the material.
Referring to
Referring to
During the pumping process, one or more polymers 140 (not shown) may be injected into the material 60. The polymer 140 causes the material 60 to “flock”. Flocking aids in the separation of the solids 80 from the water in the material 60. In the case of a centrifuge 110, the specific gravity is magnified once the material 60 enters the centrifuge 110 which causes some water to separate from the material 60, and the material 60 exits the centrifuge 110 at about 20-30% solids (70-80% moisture). The centrate 150 (i.e., water extracted from the centrifuge 110), is discharged back into the wastewater plant. The material 60 may then be deposited into the slitter hopper 160 for further dewatering. In one embodiment, the mechanical dewatering apparatus 10 comprises two conveyor belts 100 that operate in parallel. One skilled in the art will realize that any combination of one or more belts 100 may be used without deviating from the claimed inventions.
Referring to
Hydraulic cylinders 190 are operably connected with compression plates 180 to articulate plates 180 toward and away from belt 100. The hydraulic cylinders 190 activate and move the compression plates 180 toward the conveyor belt 100 and onto the material 60 positioned on the conveyor belt 100. In a preferred embodiment, mechanical dewatering apparatus 10 comprises sets of five compression plates 180 serially positioned above each of two conveyor belts 100. Any number of compression plates 180 may be used without departing from the scope of inventions disclosed and claimed.
Each compression plate 180 has a seal 200 (
Referring to
Conveyor belt 100 comprises a woven cloth 220 (not shown). Conveyor belt 100 carries the material 60 into position under the compression plates 180 and is supported by a wedge wire 230. The hydraulic cylinders 190 cause the compression plates 180 to impart substantial force onto the material 60 and the conveying belt 100. The wedge wire 230 is exposed to substantial pressure to support the impact and force being applied. Wedge wire 230 is preferably composed of carbon or stainless steel. In a preferred embodiment, the wedge wire 230 has a width of about ¼ inch and a height of about 5/16 inch. Positioned underneath wedge wire 230 are secondary and tertiary support structures, respectively 240, 250 that bear the weight of the compression until the final force is applied to a floor 260. Secondary and tertiary support structures 240, 250 are preferably comprised of carbon or stainless steel. Floor 260 may be concrete or other suitable composite. The secondary and tertiary support structures 240, 250 may comprise one or more drain pans 270 (not shown) to capture water that has been compressed out of the material 60 through the filter belt 100. The drain pans 270 connect to one or more pipes 280 (not shown) that allow the removed water to flow out of the system 10 for disposal or reuse.
A Programmable Logic Control (PLC) 290 (not shown) controls the compression rate and force. The PLC 290 allows the compression rate and force of the compression plates 180 to be programmed as desired depending on the material 60 being compressed. Multiple operating parameters may be programmed, including without limitation the amount of force exerted on the material 60, the frequency of compression cycles, speed of compression plates 180, speed of belt 100, and others that may be known to a person of ordinary skill in the art.
The cycle time is operator dependent and can be as little as 45 seconds or as long as the operator desires depending on throughput and desired dryness. For example, the longer the cycle time, e.g., the time that the compression plates 180 engage the material 60, more water will be removed, the post-compression material 60 will contain less water, but the volume of material 60 processed over time will be reduced. Preferably, the cycle time for sludge is in the range of about 45 seconds to about 90 seconds.
Once the programmed cycle completes, the hydraulic actuators 190 move compression plates 180 away from the material 60 and the conveyor belt 100. The belt 100 may then rotate forward to convey the material 60 out of the compression chamber 90. At or about the same time, one or more knives 300 (
The material 60 is then conveyed off belts 100 and deposited into a screw auger 340 or second belt conveyor (not shown) for transport to a truck and/or holding chamber 350 (not shown). After the material 60 is removed from conveyor belt 100, the conveyor belt 100 continues back to the slitter 170 to receive new material 60 to repeat the compression process. The material 60 processed as described above can be reduced in volume by as much as 50-75% depending on the original moisture content and material 60.
Referring to
The discs 370 may have apertures 380 positioned and sized to accept shaft 390. In one embodiment, shaft 390 has a substantially hexagonal cross section. The shaft 390 has a first end 400 and a second end 410. The shaft 390 may include threaded portions 420 proximate first and second ends 400, 410. The threaded portions 420 receive a locking nut 430 to be positioned to hold the discs 370 to shaft 390 with a desired distance separating individual discs 370. If the operator desires larger or smaller material 60 strips, the discs 370 may be sized accordingly and the distance between individual discs 370 may be adjusted accordingly as would be recognized by a person of ordinary skill in the art.
The slitter 170 may be controlled by a variable frequency drive (VFD) (not shown) as known in the art. The VFD allows the operator to adjust the rate and/or volume of material 60 discharged out of the slitter 170 to the speed of the belt 100 on to which the material 60 is discharged. The width of the slitter 170 can be varied to the width of the belts 100. The width of the slitter 170 may be adjusted by adding or removing discs 370. Once the material 60 exits the slitter 170, a self-leveling adjustable plate 450 (not shown) positioned proximate belt 100 substantially evenly distributes material 60 across the belt 100. A belt control 460 (not shown) may be used to set and alter the movement of the belt 100 to convey the material 60 from the slitter 170 to the compression chamber 90 underneath the compression plates 180. The belt control 460 may be manually adjusted or controlled by a VFD as would be known to one skilled in the art.
The slitter 170 can be programmed to start and stop as needed to control the volume of material 60 discharged so as to avoid positioning material 60 on the belt 100 corresponding to areas between the compression plates 180 where no compression occurs. These systems can consist of a single, dual, triple, or multiple lines of compression plates 180. In the case of a plurality of lines, a divider 470 (not shown) such as a V blade, may be used to deflect material 60 to a desired belt 100.
Referring to
The seals 200 may be comprised of rubber or other suitable compositions. The compression plates 170 have recesses 500. In preferred embodiments, the recess 500 may be either about ½″ or about ¾″ wide by ½″ or ¾″ deep. The recesses 500 extend continuously proximate the four outside edges 510, 520, 530, 540 of the compression plates 180. In one embodiment, the seal 200 comprises Urethane material. The seal 200 has a durometer range from about 40 to about 45. The depth of the recesses 500 on the compression plates 170 allow the seals 200 to retract during the compression cycle. The seals 200 absorb shock and compress into the compression plates 180 while still maintaining a seal around the material 60 . As shown in
The seals 200 may comprise a durometer that is strong enough to handle the pressure forces created when the plates 170 compress against the conveyor belt 100 but yet flexible enough to compress inward and recess back up into the extrusion 210. The seals 200 preferably have a memory characteristic to allow them to return to original shape once the compression cycle is finished.
The compression rate and force are adjustable based on parameters set by the operator. The compression cycle may be held for any desired duration and at any desired pressure up to a maximum of about 223 psi. In one embodiment, the compression cycle starts at about 1 psi and increases to about 223 psi over about 60 seconds. A person skilled in the art will appreciate that the amount of force and duration of compression can be varied depending on the material being compressed, the desired water content, the desired volume of throughput or any combination thereof.
Once the compression cycle is complete, the hydraulic cylinders 190 articulate the compression plates 180 away from the conveyor belt 100. In one embodiment, the retraction rate is about 0.25 to 2.0 seconds per inch depending on the operator's throughput variables. The conveyor belt 100 may start to convey forward while moving blades 300, with a minimum air pressure applied against compression plates 180 of about 80 psi, counter to the direction of travel of the belt 100. Alternatively, the blades 300 may move in the same direction as the belt 100 to remove material 60 that may have stuck on the compression plate 180. Alternatively, a pulsating air knife delivery system can be used to reduce the volume of compressed air. The belt 100 continues rotating around and begins the cycle over again at the slitter 170. Depending on the material 60, a high pressure water pump 550 (not shown) and spray bar 560 (not shown) may be used to wash the material 60 off of the belt 100.
During the compression cycle, a hopper 570 positioned above the slitter 170 stores material 60. Once a compression cycle is complete, the hopper 570 deposits material 60 through the slitter 170 onto belt 100 and the compression cycle repeats. This allows the dewatering device (centrifuge, belt press, screw press, etc.) to operate continuously as desired by the volume of material 60 to be dewatered.
An additional feature of this invention is the ability to provide a one-step dewatering and compression cycle instead of using an optional centrifuge, belt press, screw press, or the like. With this option, the operator may optionally add polymer 580 (not shown) to material 60. If polymer 580 is used, the material 60 throughput will be higher. With this option, the operator may bypass the slitter 170 and pump material 60 into the inlet pipe 590 (
Once the compression zone 90 is substantially filled with material 60, the pump 50 is turned off and the compression cycle begins. The compression plates 180 engage material 60 and belt 100 at a predetermined speed to extrude water from material 60. A check valve (not shown) prevents material 60 from backfilling inlet pipe 590. The compression cycles continue based on the predetermined cycle times. When finished, the compression plates i80 retract upward and the belt 100 unloading cycle commences as described above and the cycle repeats. The pressure exerted on the material 60 forces water out of the material 60, through the conveyor belt 100, and into drain pans 270.
The compression plates 180 may exert up to about 223 psi on material 60. A belt press or screw press may exert up to about 10-15 psi. Support steel capable of supporting approximately, 200,000 lbs. of pressure is required to keep the deflection rates to a minimum for each 30″×30″ compression plate.
The disclosed inventions my work in conjunction with devices like a double drum dryer or other thermal drying technologies. The disclosed inventions may be adapted to work in conjunction with existing dewatering technologies like a centrifuge, belt press, screw press, and the like. The disclosed inventions may include a screw press 30o positioned above the slitter machine 170 to first dewater the material 60, move the material 60 to the slitter machine 170, and expose the material 60 in the high pressure press 10 making the entire operation a complete replacement for the traditional dewatering machines.
In another embodiment, the material may comprise of animal feed like a product such as Okra. The Okra may be about 10% solids (90% water). Okra may be added to cattle and hog feed for nutrient value. Byproducts such as Okra may be processed using the inventions disclosed herein to arrive at about 30% solids (70% water). Thus, one may dry the byproduct without adding heat that would adversely impact the nutrient value to be added to the cattle feed. Dewatering reduces weight and volume of the material and thereby reduces transportation expenses by about 70%.
| Number | Date | Country | |
|---|---|---|---|
| 63285508 | Dec 2021 | US |
