Koch Engineering Press Release
By Robert W. Bly



Contact: Bob Bly (212) 682-5755


The Dry FGD System now in operation at the Strathmore Paper, Woronoco, Massachusetts, plant of the Hammermill Paper Company has by a wide margin exceeded the rigorous sulfur dioxide (S02) and particulate control requirements of the Massachusetts Department of Environmental Quality; has provided unusual reliability (onstream 98% of the time); and has substantially cut the company's fuel costs. According to John G. Gallup, president of Strathmore, the system is expected to save the company around 30% of its annual fuel bill, a savings expected to total more than one million dollars per year.

In most recent compliance tests, performed by Mostardi-Platt Associates, Inc. in March 1981, the Dry FGD System performed with an average efficiency of 92.4%. The boiler burned coal with a sulfur level of 3.95% (on a dry basis). Particulate emissions were 15% of the allowable limit, and S02 emissions 37% of the allowable limit. This is equivalent to the Federal New Source Performance Standards. Tests were observed by the Massachusetts Department of Environmental Quality.

The Dry FGD System at Strathmore, in operation since July 1979, collects fly ash and neutralizes the sulfur oxide emissions from a pulverized coal-fired, field-erected power boiler with a capacity of 65,000 lbs. of steam per hour. The cogeneration boiler operates 24 hours a day, seven days a week, providing steam for power, process, and heat.

MikroPul supplied and installed the entire system on a turnkey basis with Koch Engineering responsible for the spray dryer. The system was guaranteed to remove 77% of S02 from 3% sulfur coal. In the actual tests over 90% of the S02 was removed.

In the dry scrubbing operation, pollutants are collected as a dry powder that is much easier to handle than the wet sludges produced by wet scrubbing systems. Strathmore directly disposes ©f the collected material as landfill. As demonstrated at Strathmore, dry scrubbers require less maintenance, consume less energy and water, and are less costly to operate than wet systems. Initial investment for installation of a dry system is lower as well. Payback period at Strathmore is estimated to be less than 18 months. This includes the capital cost and costs of operation, reactants, etc.

Koch and MikroPul: The Dry Scrubbing Experts

The Strathmore FGD System is a natural extension of the combined experience of MikroPul and Koch in industrial air pollution control.

MikroPul has to date supplied, and in many cases installed, some 125,000 dust collectors over the past 25 years. A significant number are operating with spray dryers. Koch Engineering has experience and expertise in large industrial spray dryers and wet scrubbing systems.

Development work on Dry FGD Systems began in MikroPul's R&D laboratory in Summit, New Jersey in early 1973, and was complemented by Koch's work at its Abcor Research Center in Wilmington, Massachusetts. Abcor test facilities include a dry scrubbing pilot plant equipped with a pulverized coal-fired boiler dedicated to evaluation of customer coal and chemicals. Scale-up criteria from pilot plant data were verified at semi-works located at Koch's Commercial Development Laboratories in Wichita, Kansas. The semi-works consist of a 40 foot tall, 8 foot diameter spray dryer equipped with a lime slaking system and sophisticated instrumentation.

How the System Works

In the Dry FGD System, offered by Koch and MikroPul, dry lime reactant is gravimetrically conveyed from a storage silo to the slurry preparation tank where it is slaked to calcium hydroxide. The calcium hydroxide is then transferred to the slurry holding tank, which controls the concentration and flow rate of the slurry as it is pumped through two fluid nozzles into the spray dryer reactor.

The nozzles generate a fine mist made up of millions of droplets of calcium hydroxide slurry. When this mist comes in contact with hot flue gas from the boiler, the S02 reacts with the alkali to form calcium sulfite and sulfate. The heat of the flue gas evaporates the tiny droplets, leaving a dry powder consisting of sulfite, sulfate, fly ash, and excess alkali. Some of this powder drops out in the spray dryer where it is collected in bins or by a solids conveying system. Any suspended matter remaining in the flue gas is filtered out in the fabric filter, and the clean gas is then exhausted through a stack to the atmosphere.

Two Fluid Nozzle for High Reliability, Low Maintenance

The two fluid nozzle has proven itself at Strathmore to be the most effective and practical technique to atomize the alkali slurry.

In an external mix nozzle, the calcium hydroxide slurry (one of the fluids) and compressed air (the other fluid) meet about 1 inch from the tip of the nozzle. The compressed air breaks up the alkali slurry into droplets of appropriate size to provide optimum surface for the reaction with the S02 in the spray dryer.

This nozzle design has no moving parts that wear and have to be replaced. With four nozzles in the Strathmore dryer, one or more can be inspected or serviced while the System continues in compliance. Dry FGD Systems using multiple nozzles are more reliable and easier to service than systems with a rotary atomizer.

Flexibility for Optimum Operation

The Dry FGD System is easily adjusted for change in both flue gas rate and variations in sulfur dioxide concentration.

The outlet temperature controls the flow of slurry to the spray dryer. As the outlet temperature increases, more slurry is delivered to the dryer and when the temperature decreases the amount of slurry is decreased.

Variations in sulfur dioxide concentration are handled by adjusting the flow of slurry to the spray dryer and concentration of the lime in the slurry.

High Efficiency Pulsaire Collects Solids

Three 289 bag pulse-jet fabric filter dust collectors collect the solids coming from the spray dryer. The bags are 10 feet long and are of Draylon-T.

The Mikro-Pulsaire is 99+% efficient. With no moving parts, maintenance is reduced to a minimum. The collected fly ash and sulfates are removed from the bags by a high pressure jet of compressed air directed through the bags at timed intervals. The unreacted lime, sulfates and fly ash (which is alkaline) can be recycled to the slurry tank, thus reducing lime requirements.

Bob Bly
Copywriter, Consultant and Seminar Leader
22 East Quackenbush Avenue, 3rd Floor, Dumont, NJ 07628
Phone (201) 385-1220, Fax (201) 385-1138

email: rwbly@bly.com