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)

Design & reasoning for measurment plate


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.



Requirement for the measurement plate design to success
-Stick with limit availability area, because of the I-beam located under the bin.

-The pivot point needs to be on the top left (above the I-beam), so we have the impact plate lay on the load-cell always.

-We need to cover the two edges to avoid falling of woodchips outside the throat.

-Load-cell arm need to be welded to bottom of the I-beam.

-There is a rubber will be added between the arm and the impact plate, for better readings.

-The supports will be attached to the top of the I-beam and the back of the impact plate.

Additional to the design
-We added a stud driver that goes the middle of the I-beam to the back of the impact plate. This driver will help to push the impact plate away in case we want to change or replace load-cell or the rubber band.



Electronics








Software and Code
-NI LabVIEW (2018)

-DAQ Assist takes load cell signals in so we can record them in LabVIEW

This system is calibrated to output a LBF signal.

=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.



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

=Project Schedule=

Gantt Chart
Summer 2018



Fall 2018



Meeting Minutes
[[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=