UI Steam Plant Measurement Systems

The goal of the project is to measure and record the primary fuel variables for the wood fired boiler at the UI Energy Plant. The measurements can be used as inputs to automate the wood fired boiler combustion controls. Mass fuel flow of the wood chips, moisture of the wood chips, mass air flow, air temperature and air moisture flowing into the boiler are all necessary to optimize combustion.

=Problem Definition= The objective of our capstone project as Rolling Timber II is an extension of previous work with the intent of generating an operating lab prototype that can enable full-scale implementation in the UI Steam Plant.

Team Rolling Timber I (the previous team) was able to design and build a prototype sensor for mass fuel flow and fuel moisture content. These sensors will need to be refined and then a measurement and verification process can either prove or deny the design concept. Additionally, the measurement of mass air flow, temperature and moisture content will need to be developed.

Background
The University of Idaho Steam Plant produces steam for heating and campus buildings and sidewalks, as well as chilled water from a lithium bromide system. Steam is primarily produced in a boiler burning sawmill waste known as hog fuel.

The wood fired boiler at the University of Idaho is driven by the combustion of wood fuel and air. Mass fuel flow of the wood chips, moisture of the wood chips, mass air flow, air temperature and air moisture flowing into the boiler are all necessary to optimize combustion. Operation and control of biomass boilers has been primarily done by plant operators manually.

Although some of these measurements may seem easy to accomplish, the measurement of the fuel mas flow and the fuel moisture content in real time has been identified as the biggest challenge. To this end, Mr. Scott Smith sponsored our capstone team, Rolling Timber ll, to investigate and develop measurement systems for the mass flow rate of fuel and air into the firebox, as well as the moisture content of the fuel.

Deliverables
As of 2018, the woodchip boiler consumes approximately $ 1,000,000 per year in fuel. This is a significant savings over alternative fuels (e.g. natural gas), but could be further improved by implementation of a feedback control system to more efficiently supply fuel and combustion air.

Currently, excess fuel is supplied to the firebox of the boiler. Mr. Scott Smith, the Steam Plant Manager, estimates that approximately a 5-15 % reduction in fuel consumption could be achieved by implementation of a feedback control system, reducing operating costs and improving air quality in the City of Moscow. In addition to these tangible benefits, no other known wood-fired boiler has yet implemented comprehensive feedback control system, so implementation of this type of steam at the UI Steam Plant would be a breakthrough in biomass boiler technology.

Mass flow and moisture content measurement for wood chips is extremely hard since it requires a plant to implement mechanical system which perfectly fits the plant configuration, causing considerable design work and the plant’s down time. At the UI steam plant, the plant operators manually check how much wood chips going into the throat with lots of efforts and time. Hence, the task for Rolling Timber II is to design a system to measure and record wood chips mass flow rate and moisture content.

Functional Specifications
※It is fine to use modified unit such as lbs/min or lbs/s, however, lbs/hr is a unit which is usually used in the plant.

※Source of woodchips: Cedar, Pine, and Fir  (These are available in this area)

Mechanical Specifications
Spatial Requirements

Implementation of devices (our design) should be require little to no modification to the existing system in the plant.

•The available space within the throat is 9” wide × 84” long × 26” long. (for mass flow sensor of wood chips)

•Round duct – 24” diameter (for mass flow sensor of air)

•Rectangular duct – approximately the same cross-sectional area as the round duct (for mass flow sensor of air)

Materials for the prototype

Mild Steel is preferred by our client.

=Mass flow measurement=

How mass flow measurement works
Wood chips thrown from outside usually goes into a large bin. These wood chips stay there for a while and get smashed into smaller pieces by augers (rotational blades). These smashed wood chips flow into a throat and eventually get burned in a boiler after they pass the throat. The possible location to install mass flow sensor is the upper side of the throat since all the wood chips need to pass through the throat.



Idea behind the system
Impact plate: The possible design idea for the mass flow measurement system was impact plate since it can fit on the given throat dimensions and is mechanically simple. Whenever wood chips hit on the plate, it causes reaction force on the plate. Hence, this reaction force over time can be measured calibrated, which enables us to calculate mass flow rate [lbm/s] or [kg/s].

Design Concepts Considered
We have two major concepts for design.

1: Design for the prototype-scale testing

2: Design for the actual implementation in the plant (full-scale)

Now we are in the phase 1 as of July-9 in 2018, which is designing for the prototype-scale testing. By end of this summer 2018, we will start designing the full scale for the implementation in the plant.

Possible Designs for the implementation in the plant


Here are our first ideas of implementing the measurement plate for calculating the mass of the fuel and the reasons behind each design.

1-idea(1) is having a plate inside the throat. - less fabrication. - Free fall technique.

2-idea(2) is cutting a part of what is originally exist for and expanding the throat. - more space inside the throat to avoid clogging. - Free fall technique.

3-idea(3) cutting a small part at the corner of the bin and implement the measurement plate. - less fabrication - will tend to use alternative technique since free fall will not work for this design.



We combined idea (1 and 3) for # reasons: - less fabrication. - by adding the sliding plate in the top will increase the probability of falling the fuel above the measurement plate.

After meeting the client: idea (2) win. - easy for future maintenance. - safer place for the load cell, away from the heat. - easy to replace load cell if needed.
 * But we have a new challenge there is an I-Beam, part of the plant structure. We are limited to 5 inches in width.



=Moisture content measurement=

How mass measurement flow works
Moisture contents should be measured before wood chips go into the throat. (The reason for the target location for the moisture sensor installation, please refer to XXX). We assume that moisture content of the wood chips are all uniform for all the woodchips contained in the bin. Hence, moisture content measured from one specific location on the bottom of the bin can represent the moisture content of entire wood chips inside the bin.

Drier the wood chips, better they gets burn, which is related to the efficiency of the wood-fired boiler. Hence, it is important to keep on track how much moisture contents wood chips have all the time.



Idea behind the system
Moisture content can be calculated as [%]. WCMT-HGT: This sensor was from Schaller Messtechnik, which is a company in Austria. This can be installed stationary to measure the wood chips’ moisture, so we wouldn’t need major modification on the plant to install it. The nice thing about this moisture sensor is that the manufacture already provided the calibration table so that we can find moisture content [%] according to the output current we got.



=Testing=

Load Cell Testing
Our initial testing has been done with load cells we plan on using for measuring the mass flow rate of wood chips into the fire. For testing we are using a simple OpAmp circuit to boost the signal output by the load cells.

Basic Simulink Setup


We are running this boosted signal into Simulink for now just to see if the load cells are consistent enough and have the sensitivity we need for this application. Using this setup we conducted simple tests by placing mass on the load cells. With these basic tests we think the current load cells will be acceptable to continue testing.

Testing Equipment
Testing Equipment will be developed by our client, Mr. Smith Scott by July-9th (Mon). Testing of our prototype with circuits and software is planned in Week 5 (July-9 ~ July-13)



New Prototype






=Final Design=

Circuit and load cell
Highlights from the first half semester (From Jun 11 to July 9)

Previously, Team Rolling Timber ll spent most of time for figuring out what the previous team have done so far. More specifically, what Rolling Timber ll have done in the first half semester in summer 2018 were in the following:

•Identified client’s needs, constrains, specifications, and project schedule

•Initial load cell (LC302-25) testing

1. Understand the mechanism of load cell 2. Build our own circuits from scratch 3. Data acquisition with Matlab and Simulink 4. Test input sensitivity for load cell

• Initial preliminary design for wood chips mass flow sensor

1. Brainstorm initial mechanical designs for implementation (3 possible ideas, initially.) 2. Decide one possible idea for the implementation

In the latter half semester from (July 9 to Aug 3)

Our team progressed so much in term of mechanical design for our prototype and electrical components such as circuits and software for control system. We started testing the prototype (both wood chips mass flow sensor and moisture sensor) from the previous team in conjunction with our circuits and software screening. Our main job as Rolling Timber ll during summer 2018 is to deny or accept what the previous team had done so far by testing what they built. We actually denied their prototype of wood chips mass flow sensor and their circuits including Op-Amp (AD 524) that the previous team purchased by our testing. With the active discussion with our audiences in the design review on July 20th, we received lots of precious feedback and our plans for our mechanical designs and testing changed a lot. More specifically, what Rolling Timber ll have done in the latter half semester in summer 2018 were in the following:

•Software: LabVIEW 1.Learn how to use LabVIEW and build and refine our own code for testing

•Testing the previous prototype of wood chips mass flow sensor 1.Obtained the testing equipment with a real augur from our client

2.Data acquisition by using the testing equipment with real wood chips in conjunction with our circuits and LabVIEW

3.More load cell testing A.Obtain linearity between mass vs. output voltage B.Noise reduction for our signals C.Denied AD524 Op-Amp from the previous team

•Modifying and refining the mechanical design of wood chips mass flow sensor 1.Built the new prototype

•Testing the new prototype of wood chips mass flow sensor 1.Data acquisition by using the testing equipment with real wood chips in conjunction with our new circuits and LabVIEW program

•Testing the moisture sensor (WCMT-HGT) 1.Checked the current output from WCMT-HGT 2.Data acquisition by WCMT-HGT and LabVIEW •Modifying and refining the mechanical design of wood chips mass flow sensor 2.Built the new prototype

Mechanical design
-	The design is totally changed from previous team, the new design are

• more effective

• easy to install

• affordable

• easy to maintenance -	Previous team has the pivot pin below the plate, in our design we move it up to solve the shaking issue when the wood chips hit the plate. -	Pivot pins location will be chosen after some testing with the new prototype, as well as the arm length.

-	Previous team SW was helpful, especially parts drawing “augurs”.

-	We took care of the transferring the force from the plate to the load cell by designing arms between them.

-	Several ideas were introduces to the client, then we choose “1 load cell 3 arms”.

-	The dimensions restriction because of the I-beam which a part of the plant structure were taking care of, and the plate design would fit without any problem.

-	The problem because of the extra box in the right edge of the throat were taking care of by cutting the top of it.

-	Box for keeping the load cell in a safe place were designed.

-	Location for the load cell box will be underneath the I-beam.

-	All dimensions were checked twice.

=Team Members= {| width="80%" border="0"

=Project Schedule=

Gantt Chart
Summer 2018



Fall 2018



Meeting Minutes
Meeting Time (Summer 2018)

1- Group meeting every day (2 hours)

2- Meeting with clients and instructor every Tuesday at 11:00 am [[Media:Meeting Minutes for Week 1.pdf]]

[[Media:Week2. June 18-24.pdf]]

[[Media:Week3. June 25-29.pdf]]

[[Media:Week4. June 2-6.pdf]]

=Product Requirements=

[[Media:Product Requirements.pdf]]

=Value Proposition=

[[Media:Value Proposition.pdf]]

=Appendix=

Drawings package
=Document archive=