Located outside St. Louis, AmerenUE’s four-unit 865 MW Meramec plant switched to 100% Powder River Basin (PRB) coal in 2001. Approximately three million tons of PRB coal—2 inch (50 mm) minus in size—is moved from the plant’s unit train unloading facility through the coal handling system and into the powerhouse bunkers without additional crushing.
The coal-reclaim system at the Meramec plant was designed to operate with a capacity of 1000 tons per hour. All conveyors in the system are 42 inch (1062 mm) wide with a belt speed of 630 fpm (3.2 m/sec), with a design flow rate of 1000 tons per hour. But at any rate of operation, the chutes wouldspill coal and create dust.
At present, the plant operates without any “baghouse” dust collection system, and plant officials hope to keep it that way. So Meramec Plant’s management team and Ameren’s Corporate Engineering Department looked for ways to improve coal handling and reduce dust and spillage.
The most troublesome points in the plant were the conveyor transfers 4A to 5A and 4B to 5B. These nearly identical 90° transfer points drop coal approximately 12 feet (3.7 m) onto the tripper conveyors that feed the storage bunkers.
Engineered Chutes Offer Improvement
After evaluating a number of proposals for engineered chute engineering and construction, AmerenUE turned to the engineered transfer chute system available from Martin Engineering, Neponset, Illinois.
MARTIN® INERTIAL FLOW™ Transfer Technology combines a set of proven components into engineered system to reduce fugitive dust and spillage at conveyor transfer points. The chute is custom engineered and modeled in 3-D to provide the correct design for the material and flow rate required.
Inside the chute, a "clamshell” or “hood” controls the flow of material from the discharging conveyor, maintaining a coherent material stream and minimizing induced air. A "smoothline" transfer loading chute or “spoon” directs the stream of material onto the belt at the proper speed and angle and without impact, to minimize material degradation, belt abrasion, and the expulsion of airborne dust. By controlling the flow of material, the engineered chute eliminates blockages, shapes the load, and minimizes the creation of dust.
Control of spillage and dusting—and the resultant reduction in labor costs for cleanup, as well as the reduced probability of an emergency outage due to a plant fire—were the key justifications in the decision to go ahead with the project.
Martin Engineering was confident of dust control performance of its engineered chutes. In fact, Martin Engineering guaranteed to reduce the amount of total amount of material lost as dust and spillage from the Meramec system by 98 percent. To evaluate the success of the engineered chutes in dust control, Martin Engineering and AMEREN UE Meramec arranged a testing program.
Comparative Testing
The first step was to establish a baseline for evaluation of the performance of the new system. In this program, dust is collected over a three-day, 24-hour-per-day period. A pan and bucket system was used to collect spillage and heavy dust; this is the method approved for testing to achieve Best Available Control Technology (BACT) status. In this system, pans placed around the perimeter of the installation, alongside the conveyor and around the exterior walls (inside the building) collect spilled coal and heavy dust. In a couple of locations—such as near the conveyors’ tail pulleys—larger collecting pans (buckets) were needed to hold the full material sample.
By carefully collecting and weighing the material, plant officials could assess the amount of material lost from the coal handling system before and after the MARTIN® INERTIAL FLOW™ Chutes were installed.
To establish a baseline, measurements were taken over three days of operation using the old chutes. These results shows that during average daily run of 4297 tons the 4A to 5A and 4B to 5B conveyors would lose over 7614.637 grams (16.75 pounds). This represents an average loss of 1.810 grams lost per ton conveyed.
Testing Shows 98% Dust Reduction
A similar three-day test was conducted after the new chutes were installed. The collecting pans were placed in the same locations, and the samples gathered and weighed on a daily basis.
Following the installation of the engineered chutes, the testing showed the loss of material was reduced to 0.022 grams per ton, which represents a reduction of 98.77% in the amount of material lost per ton. These results indicate that the project was successful in achieving the specified (and guaranteed) dust control performance.
Satisfaction with the results of the installation at Meramec Plant has led Ameren to install engineered chutes from Martin Engineering at other company plants.
Table 1
Material Collection Test Results
AmerenUE Meramec
GRAMS OF MATERIAL LOST PER TON OF COAL CONVEYED
BEFORE
TONS CONVEYED DAILY GRAMS GRAMS
DATE PER DAY COLLECTED PER TON
12/17/2003 5,792.00 9,929.05 1.714
12/18/2003 3,997.00 6,175.21 1.545
12/19/2003 3,103.00 6,739.65 2.172
TOTALS 12,892.00 22843.91 5.431
DAILY AVERAGE 4,297.33 7,614.63 1.810
AFTER
TONS DAILY GRAMS GRAMS
DATE PER DAY COLLECTED PER TON
2/25/2003 5,724.00 148.74 0.026
2/26/2003 8,808.00 189.37 0.021
2/27/2003 7,537.00 143.92 0.019
TOTALS 22,069.00 482.03 0.067
DAILY AVERAGE 7,356.33 160.677 0.022
Average Material Lost Per Ton of Material Conveyed
Before 1.810 Grams
After 0.022 Grams
ANALYSIS
A 98% reduction from the original average of 1.810 grams per ton equals a maximum loss of 0.0362 grams per ton.
With the new transfer technology installed, the loss of material was 0.022 grams per ton, which represents a reduction of 98.77% in the amount of material lost per ton.
This reduction was accomplished despite increasing the overall volume of material by more than 70%.
Dust collection test in process at AmerenUE Meramec
Table 2
Dust Suppression System Results
AmerenUE Meramec
DUST SUPPRESSION APPLICATION RATE AVERAGE
BEFORE INSTALLATION
DATE COAL TONS WATER/ CHEMICAL APPLICATION
PER DAY CHEMICAL RATE
SOLUTION
APPLIED
(Tons) (Gallons) (Gallons) (Gallons Per Ton)
12/17/2003 5,792.00 9,388.00 67.6 1.62
12/18/2003 3,997.00 6,838.00 53.4 1.71
12/19/2003 3,103.00 5,700.00 44.7 1.84
TOTALS 12,892.00 21,926.00 165.7 5.17
DAILY AVERAGE 4,297.333 7,309.00 55.2 1.72
4A to 5A Transfer at AmerenUE Meramec following installation
MARTIN® INERTIAL FLOW™ Engineered Chute.
AFTER INSTALLATION
2/25/2003 5,724.00 4,843.00 34.4 0.85
2/26/2003 8,808.00 2,274.00 16.2 0.26
2/27/2003 7,537.00 9,532.00 70.7 1.26
TOTALS 22,069.00 16,649.00 121.3 2.37
DAILY AVERAGE 7,356.33 5,549.67 40.4 0.79
Average Mixture Used Gallons Per Ton used
Before 1.72
After 0.79
Reduction of 54.17%
Analysis
After the installation of the MARTIN® INERTIAL FLOW™ Transfer Technology, the Meramec Plant was able to reduce the amount of dust suppressant solution (moisture) applied to the coal by 54% from 1.72 gallons per ton to 0.79 gallons per ton. This should reduce consumption of dust suppressant chemicals at the plant in half, providing an annual cost savings of roughly $100,000.
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