820 MW Foster Wheeler Boiler

Background

BackgroundThe plant has two 820 MW Foster Wheeler balanced draft boilers. They have 32 steam-atomized burner guns, 8 burners on 4 burner decks and 2 rotating Ljungstrom pre heaters.

At the time of the testing, the unit burned 1.2 million tons of oil per year, and was using another product to keep the boiler tubes from being impacted by SO3 corrosion.  The two units were in generally good condition though they were having burner problems.

Bycosin was given an opportunity to see if they could duplicate the results seen in another of the company’s plants with 2 x 400 MW FW units (see case history).

The company also wanted to see if they could reduce emissions and opacity at the plant by using a new product developed specifically for that purpose. The testing was done on Unit 1 while Unit 2 continued to use the other product.

Fuel Analysis:

Heat value Btu/Lb: 18099 (MJ/kg 37.82)

Carbon: 87.73%

Hydrogen: 9.80%

Sulfur: 0.95%

Nitrogen: 0.26%

Water: 0.27%

Ash: 0.079%

Asphaltenes: 4.6%

API Gravity: 9.1@ 60°F

Vanadium: 38 ppm

Sodium: 27 ppm

Silicon: 79 ppm

 

Test Proposal

Before BycosinAfter BycosinBycosin would like the company to test two different products in one of their 820 MW boilers, in order to demonstrate that it is possible to improve overall performance by adding a second product.

It is suggested that the plant put Bycosin DP94001 into plant 1 and that plant 2 continue to use the competitor´s product.
Base line measurements will be taken and the two products will be tested separately and in combination.

Bycosin will supply two products to the recently cleaned Unit #1. The first will be Bycosin DP94001, an ash inhibitor and combustion catalyst containing oil soluble magnesium, iron and calcium.

This product is currently being used at a number of other plants owned by the company, one with a 400 Mw and 165 Mw and another with 2 x 400 Mw units. The product has been used for a number of years at the 2 x 400 Mw plant and has a proven record of keeping the furnace and back-end clean of deposits.

The second product is Bycosin DP99201, a fuel stabilizer and combustion catalyst containing an asphaltene dispersant along with oil soluble iron and calcium. DP99201 will improve combustion of the fuel, minimize stack solids and O₂ combustion levels, not contribute to ash loading of the air preheater and reduce NOx and SO₃

Injection System:
The DP94001 ash inhibitor and combustion catalyst will be injected into the fuel line using the existing system at the plant.

The DP99201 Fuel Stabilizer and Combustion Catalyst will require an injection system that is compatible with the existing injection system. The new system will be supplied and monitored by Bycosin during the trial.

Delivery Procedures:
Bycosin will deliver both products in ISO tanks that will be used as temporary storage tanks at the plant during the testing.

Test Procedures:
Bycosin will contract with Combustion Components Associates to monitor the conditions at the plant both before and during the trial. CCA will measure the product’s impact on the following areas: SO₃, ash pH, deposits , heat transfer, rate of corrosion and any other measurements that will help the company quantify the results of using the test products.

Dosing:
The DP94001 will be injected in advance of the DP99201’s arrival at the plant. The initial dosage will be 1:2000 in order to condition the plant, and will later be reduced to 1:4000 when the DP99201 is injected.

The DP99201’s dispersant will clean up any sludge in the fuel line and so testing should begin 24 hours after initial injection.
Bycosin will supply a technician who will be adjusting the injection of both products in order to maximize their benefits and results will be monitored by CCA.

The testing will take four to six weeks. At the estimated fuel consumption of 20,000 bbls per weekday and 10-15,000 bbls/day on weekends, two ISO containers of DP94001 ash modifier and combustion catalyst will be used and one ISO of DP99201.

It is expected that the testing will indicate that a “combination product” made up of the two test products, will provide the company one product for its fuel and operating conditions.

Company Concerns:
There is concern that the iron in the Bycosin products will result in increased SO₃ production.

Bycosin does not has never experienced this problem in any of their worldwide product applications. We will, however, monitor SO₃ production carefully during the trial.

The other concern is that the use of the products would result in fouling of the air preheater baskets. As mentioned above, the products will not increase ash loading at the plant.

 

Products

DP94001:
Bycosin DP 94001 is a slag inhibitor combined with a combustion catalyst that rapidly reduces existing slag deposits. It also reduces soot/stack solids and makes the remaining deposits soft, porous and easy to remove.

DP99201:
Bycosin DP99201 is a combustion catalyst designed to lower emissions of soot, SO₃, stack solids and CO. A secondary effect is to decrease deposits on tubes and walls.

BarrellsDP94001
• The organic Mg penetrates easy into the deposits and slag, due to the smaller size of our organic Mg, and makes the deposits soft and friable.
• DP94001 rapidly cleans tubes and walls throughout the whole system from furnace to air pre heater.
• The product raises the melting point of the ash compounds and prevents corrosion at both high and low temperatures.
• It is important to keep the furnace surfaces clean in order to get maximum heat transfer (heat radiation).

In most cases, a surface with deposits will reduce heat transfer to the water in the tubes and increase the temperature of the flue gases out the stack. This can result in more deposits and high temperature corrosion in the back end of the boiler._

DP99201:
Use of this product also reduces:
• SO₃, by reducing excess air.
• A lower O₂-level also increases plant efficiency and NOx

If Bycosin DP 99201 is added into the fuel storage tanks, the fuel will have a positive cleaning effect on the whole precombustion system: storage tanks, oil preheaters, filters, burners, and give better atomization.

 

Trial

TrialThe test was conducted over five days and was a cooperation between Bycosin, the power plant and two independent testing companies, CCA and EES.

The boiler was pre-treated for two weeks before the test with DP94001 to clean up existing deposits and, within two weeks, the boiler was almost clean.

Base line measurements were taken and then the two products, DP99201 and DP94001, were tested separately and then in combination. Dosage pump settings were made as directed by the plant engineer.

 

Trial DetailsFull boiler operations data was recorded by the power plant and include:

• NOx and “in stack” opacity readings that came from the plants emission equipment.
• The plant’s Stack Testing Crew performed particulate testing.
• EES tested the SO₃ levels at the air heater inlet (continuous emissions monitor).
• Fly Ash sample where taken by CCA at the air heater inlet for constituent analysis.
• CCA also tested the cooled plate deposition probe at the air heater inlet.
• The rate of build up was calculated based on total weight gain, exposure time and    the surface area of the plate.

The economizer outlet measurement of O₂, CO and NOx came from an existing 32-point test grid. These test where also made by CCA.

Results

Before BycosinAfter BycosinThe immediate benefits of using Bycosin DP 94001 and DP 99201 became clear in the test results:
- Reduction of stack particulates to 65 % below the allowable limit.
- Reduction of opacity from 36 % to 14 %.
- Reduction of SO₃ from 4.7 ppm to 3.1 ppm.
- Reduction of CO.

GrafReduced stack particulate and unburned carbon in fly ash:
The amount of stack particulate was reduced to 65% below the allowable limit. One test resulted in less than 4% unburned carbon.

Opacity:
A reduction was noticed in all combinations when the additives were used. A combination of the two additives resulted in opacity of 14%, a substantial improvement over the base line test of 32-36%.

SO₃ (Sulfur Trioxide):
Base line tests showed SO₃ concentration of 4.1 – 4.7 ppm. The combination of the Bycosin additives reduced the SO₃ to 3.1 ppm. Reduction of dew point temperature was: 2–3oC (4–6o F).

CO (Carbon monoxide):
The CO level was high in almost every test that was made. Later it was learned that there was damage to the primary burner air register. The combination of the combustion catalyst and the deposit inhibitor still reduced CO by 1500 ppm (25-30% reduction)

Reduction of stack particulate with Combustion Catalyst Bycosin DP 99201.
Reduction @ 1:3200: 47%.
Test made 990803 (* Baseline test #990803-1) at maximum load of the boiler, Unit #1.
** Variation in the air ratio (O₂ level) to the combustion.