License to Kiln

Project undertaken in course year 2022-23 with the Stanford Woods Institute for the Environment

Project Goal

Reduce harmful carbon emissions from brick kilns in Bangladesh through implementation of an automatic coal feeder.

Our year's challenge was to improve on the automatic coal feeder designs of previous ME170 teams to account for coal clogging in the device when the coal is damp.

Top of kiln, showing coal feeding locations.

Project Motivation

According to the World Health Organization, it is estimated that around 37,000 Bangladeshis die each year due to air pollution.
Many of these deaths can be attributed to the rapidly expanding brick industry, which accounted for half of the total air pollution in Bangladesh’s capital, Dhaka, in 2018.
Despite health issues, brick production is a widespread practice that is not slowing down. About 23 billion bricks are produced per year at some 7,000 kilns across the country as the need for infrastructure continues to rise.

In the current process of coal dispersal, workers shovel large clumps of coal into the kiln as fuel.
- As a result of the large quantity, the first layers of coal are smothered by the previous layers. This limits oxidation, leading to incomplete combustion, which emits black soot (black carbon) and carbon monoxide into the air.

Background

Previous teams designed a device that is successfully able to feed dry coal into a kiln autonomously at a specified feed rate.

However, in situations on kilns, coal is often damp from rain or to reduce particulates in the air. In these instances, the device clogs immediately

High Priority Requirements

Use common parts that do not require special ordering in Bangladesh
Deliver coal feed rate of 0.5 g/s to 2.0 g/s, within a tolerance of 15% of expected rate
Device will have enough power to sustain at least 6 hours of running
Device does not clog or need additional maintenance to run for 6 hours
Device shall withstand temperatures of 200C

Ethical Considerations

Maintaining firemen's ownership over their product.

Firemen sometimes receive benefits for creating higher quality bricks.
With their specialized skill set and training, the firemen know best what feed rate will produce the highest quality bricks.
Affirms the importance of allowing for variable speed control with our automatic coal feeder.

Working with the kiln owners to lower harmful emissions.

Kiln owners will likely continue using coal because of its low cost.
However, their families are similarly affected by pollution.
Making our product as cheap as possible will help them to lower emissions while lowering any financial burden.

Solution

We designed an internal fan that rotates with the previous teams' feed wheel, which is able to disturb the coal and remove both columned and domed clogs.

System assembly

Entire system with funnel where coal is placed, and feeder mechanism suspended on bricks

Fan geometry

The fan is attached to the feeder rotor inside the funnel, spinning through the coal to keep it agitated and mixing. The coal falls through the single hole just above the fan and into the feeder.

Fan moving coal

Coal being agitated so it continues to fall through the feed hole without clogging

Coal output over rotations

We ran the device over 20 rotations, and found that the output was consistent over that period of time. We did this test with two different starting masses of coal in the funnel (900g and 3600g) and achieved similar results