Automated Biochar Injection System
|Mean Clean Water Machine Team|
|Sponsors||Gregory Möller [UI Clean Water Machine]|
|Team Name||Mean Clean Water Machine|
|Duration||Fall 2018 - Spring 2019|
The goal of the project is to design a mobile BioChar (BC) injection system that will accept and inject BC into pressurized water lines in an accurate, controlled, and recorded manner in tandem with existing systems on the UIdaho Clean Water Machine with minimal adaptation of current systems.
- 1 Problem Definition
- 2 Design Considerations
- 3 Project Learning
- 4 Final Design
- 5 Validation
- 6 Team Members
- 7 Additional Documentation
Extensive algal blooms and phosphorous resource limitations are current problems faced by communities globally, primarily regarding agricultural fertilization and waste products. The University of Idaho Capstone teams in the past have partnered with Nexom and other entities to create the Clean Water Machine, an upward-circulating sand filtration system, to address the algae growth and purify the agricultural wastewater. Current research is being conducted by pumping BioChar (Bio-mass charcoal, created by burning wood products and other organic materials) into the system in an effort to absorb more chemicals (namely phosphorous) from the wastewater. The BioChar is ideally then filtered out, collected, and mixed into the soil in an attempt to recycle some of the lost phosphorous and create a way to fertilize crops without needing to mine a limited resource. Our goal as a team is to create a system that integrates cohesively with the current Clean Water Machine and automates the process of dosing the BioChar into the wastewater flow, so that more experiments and research may be conducted efficiently and effectively in the future. The completed project will be a mobile unit that accepts and injects BioChar into the pressurized water lines in an accurate, controlled, and recorded manner in tandem with the existing Clean Water Machine system with minimal adaptations. Our system will be completed by May 2019 as a fully functional product ready to be integrated into the Clean Water Machine's operations.
All three of the following design include three common areas: BC storage, conditioning, and metering. The hopper will include an auger to transport the BC into the conditioning system. The design will also include a dryer, dehumidifier, and mixer. It must produce the same conditions regardless of external environment.
Our first design is consistent with typical powder dosing system at a wastewater facility. The metering doses into a conical container, creating mixing of the BC with water. Spray nozzles above the funnel provide access points if the operator needed to dose other types of chemicals simultaneously. The progressive cavity displacement pump also assists with mixing the BC.
However, these type of pumps are generally very expensive and difficult to find one appropriate for this scale of treatment. The numerous components introduce many moving parts that could malfunction from abrasion. The size and space requirements of this design are also unlikely to fit within the given constraints while remaining accessible for repair.
In our second design, the BC is metered into a sloped container and washed out using water from the influent piping. A ball valve opens, allowing the water from the influent to flow through after the BC has been metered. This valve then closes and a check valve opens simultaneously with an air compressor pushing the water-BC slurry back into the influent pipe.
This is more simple and condense, has fewer moving parts, and is lower cost than the initial design. However, timing between the two valves is critical, and malfunction or clogging would completely disrupt the flow. It is also a design without much mixing of the BC into the water, which may cause the BC to clump or be left behind on the container. Another significant issue is the introduction of compressed air into the system, which could interfere with the rest of the treatment process.
The final version of the third design was the team's suggested prototype. Two parallel sloped floor containers receive BC from the metering system and intermittently dose into the influent pipes to creates a more continuous dosing. This system is also directly in line with the influent water. The BC is dropped into the chamber when both three-way valves are closed. One three-way valve switches the incoming water between the two chambers, and the other three-way valve alternates which chamber is emptied back in line with the pipes. A constant pressure tank and pressure regulator is supplied so that the influent pipe pressure is not altered. An air release valve is included for when the machine is first started, since the pipes will not have any water in them when not in use.
Clean Water Machine System
Currently, the biochar is dosed into the Clean Water Machine in batches in the ratio of 6kg per 50 gallons of influent water. This requires an operator to pour the biochar into the tanks, and manually stir. This is inefficient and does not produce consistent dosing. The flow diagram to the right was provided by our client to describe how the biochar can be monitored, dosed systematically, integrated into the current Clean Water Machine design.
Our clients identified the pumping mechanism as a significant challenge in moving biochar. Because it is a granular material which does not dissolve in water, it often clogged pumps and the small particles cause pump parts to wear quickly or malfunction. The team toured the Water Reclamation and Reuse Facility in Moscow, ID, to see how this treatment process dosed powder polymer. This facility used large positive displacement pumps, which could be scaled down for our project. Progressive cavity positive displacement pumps are effective with viscous fluids, can produce a constant flow, and has few moving parts that the BC could damage.
A venturi nozzle operates based on a change in liquid pressure when it flows through a constricted space. This type of metering provides continuous flow and can be easily adjusted to vary the output. Another consideration when using the venturi nozzle is that it will need to start and stop as it moves between the two different BC containers. Our preliminary BC experiments showed that the BC does not stay suspended in any constant concentration, so metering volumetrically would be a concern with this nozzle. However, it may be used at a different location in the system to overcome the back pressure from the transport between atmospheric pressure and pressurized pipes.
An auger is a simple, inexpensive form of dosing BC. Although there are few parts involved, the motion against the dry BC could quickly damage the surface of the equipment. Most significantly, although an auger is continuous, it is not an accurate dosage, and any differences in BC properties could impact the dose rate.
A simple method of dosing is a scale and cup set up. BC would be dosed gravimetrically into the cup, which would be very accurate and eliminate areas for BC clogging. However, this would be challenging in our application since it would be noncontinuous and must be completely separated from the external environment.
The following electrical components were researched for the project related to sensors and controls:
|Requirement||Test||Test subject||Target Date||Result||recommendation|
|Operating at less than 60dB at full capacity||Use a sound sensor to record a full cycle of the system, and verify signal remains below maximum sound level||Functional prototype||1/18/2019||N/A||N/A|
|15% accuracy dosing||Have BC dump into separate receptical and weigh on a scale to verify accuracy of dosage dispenser||Functional prototype||1/18/2019||N/A||N/A|
|Must account for variability in BC moisture content||Use a high-accuracy moisture sensor to detect moisture of several batches of BC after processing through system, and compare discrepancies||Functional prototype||1/18/2019||N/A||N/A|
|Must account for variability in BC consistency and texture||Manually, visually inspect BC for clumping and inconsistencies in texture; should be no particles larger than 0.25 inches||Functional prototype||1/18/2019||N/A||N/A|
|Must account for variability in BC dose-rate||Run system through 5 different dose rates, have BC dump into separate receptical, and weigh on a scale to verify accuracy of dosage dispenser||Functional prototype||1/18/2019||N/A||N/A|
|Must account for variability in BC temperature||Use a high-accuracy temperature sensor to detect temperature of several batches of BC after processing through system, and compare discrepancies||Functional prototype||1/18/2019||N/A||N/A|
|Dosage must withstand pressure of 20 psig||Use pressure gauge on output pipe to verify it expels BC mixture at desired pressure||Functional prototype||1/18/2019||N/A||N/A|
|Touch-screen must last 24-hours without recharging||Unplug touchscreen and wait 24-hours; intermittently activate screen (once every 8 hours) to simulate use; after total time period, activate screen and verify use||Functional prototype||1/18/2019||N/A||N/A|
|Must operate within conditions ranging from 20-90% Humidity||Design tests in sealed containers or rooms where humidity level can be adjusted and run system to verify function||Functional prototype||1/18/2019||N/A||N/A|
|Refill no more than once every 3-days||Run system for 72 hours straight with maximum dose-rate and verify that the BC supply will last||Functional prototype||1/18/2019||N/A||N/A|
Major: Mechanical Engineering
Major: Biological Engineering
Major: Biological Engineering
Major: Electrical Engineering