The Utilization of Alternative Fuels

Presented at CIBO Energy Options For the 1990’s

Washington, D.C.
June 14-16, 1991

Thomas E. deHaan (Director of Marketing), Coen Company, Inc.

INTRODUCTION:

In the early 80’s, we saw incredible interest in alternative fuel use spurred on by high fossil fuel cost and a multitude of legislative tax and investment incentives. With the drop in oil prices and repeal of most tax incentives, we saw a sharp decline in alternative fuels in the latter half of the decade. Today’s alternative fuel user must rely on pure economic plus environmental factors. A good example is Pulp & Paper industry waste sludge. The cost of landfill and environmental concerns make this a good choice as a fuel for use in power boilers.

LEGISLATIVE ACTS:

During the late 1970’s and early 1980’s, there was a steep rise in the price of oil and other fossil fuels. To counteract this rise and reduce our dependence on foreign oil, there were several legislative incentives passed on federal and state levels to provide incentives to promote the utilization of alternative fuels. The following is a sample of some of those incentives:

  • Fuel Use Act (1978)
  • PURPA
  • Investment Tax Credit
  • Accelerated Depreciation
  • Biomass Tax Credits
  • D.O.E. R&D Funds
  • Producer Gas Tax Credits
ALTERNATE FUELS:

These legislative incentives plus a rise in the price of oil to $35 per barrel spurred on an interest in several alternate fuel type projects and industries. Examples of the types of fuels that were being promoted at the time are:

  • Micro-Fine Coal
  • Coal Water Slurry
  • Food Processing Waste
  • Agricultural Waste
  • Producer Gas
  • Petroleum Coke
  • Woodwaste/Pellets

Many of the projects utilizing these alternative type fuels were very profitable. If you combined a tax incentive, with a biomass type of alternative fuel, in a cogeneration type facility,and got a good power contract, it would be virtually impossible not to be profitable. Several industries took advantage of these opportunities to burn their waste products as a boiler fuel. Other industries purchased alternative fuels to replace the high cost of gas and oil.

During this period there were a dozen suppliers of micro-fine coal and coal water slurry. These fuels were designed to replace oil and gas in industrial boilers. Considerable sums of money were poured into promotion, R&D, and demonstration sites by industrial concerns as well as the D.O.E.

Food processing waste was an especially good alternate fuel during this time. Many food waste were sent to landfill which entailed transport and tipping fees. Utilizing waste heat from a boiler exhaust to dry this waste and then burning it in suspension proved to be very profitable when replacing oil at $35 per barrel.

Petroleum coke, while not suitable for boilers because of its’ sulfur content, was a very sought after fuel in the Pulp & Paper industry for their rotary lime kilns. Virtually every Pulp mill in North America converted or had plans to convert to this abundant and low cost fuel.

Woodwaste was a very popular fuel and most forest product firms converted from gas or oil to burning their own wastes. Several companies were formed to purchase excess woodwaste and convert it to pellets or dust for sale as a boiler fuel.

WHAT HAPPENED!!

Most of these projects and fuel suppliers disappeared during the mid-1980’s due to three key factors. First, the price of oil dropped in the second quarter of 1986 from $32 to $13 per barrel. During the following 5 years, it varied from $15 to $21 per barrel. Second, most of the legislative tax incentives were repealed or modified to a point where they lost their original purpose. Third, government sponsorship of R&D efforts has been reduced. Funding for all renewable energy research and development has declined by almost 90% from 1981 to 1990. A tremendous amount of money had been spent in developing technology to make and burn all these alternate type fuels, but by the end of the 80’s, virtually all of them were out of business.

TOMORROW’S ALTERNATE FUELS:

With all the tax incentives gone and the price of oil staying low, one wonders what types of alternate fuels would be feasible in today’s market. One area that seems justifiable is biomass type waste products that are generate by many industries. These wastes are usually high in moisture content and are normally disposed of by hauling to a landfill disposal site or simply stored on site in a large pile creating odor and possible environmental problems. With the cost of landfill use going up because of fewer sites, longer hauling distances, and environmental concerns; alternative methods of disposal for many biomass type waste must be found.

There are three alternatives to landfilling these waste: recycling, incineration, and utilization of the waste as a fuel. If the waste can can be utilized as a boiler fuel, it has the advantage of displacing oil or gas and reducing the waste to a small quantity of ash.

PULP MILL SLUDGE:

Pulp and paper mill sludge, a waste product formed in the paper making process, is a perfect example of the type of waste that can be profitably used as a boiler fuel. Typically, this waste was either landfilled or stored on site. Landfill cost is skyrocketing and there is environmental pressure against open storage, so these options are no longer acceptable as a long range solution.

Nearly 8000 tons (dry basis) of sludge is produced each day by the North American pulp and paper industry. A typical mill can produce 40 to 80 tons per day of this waste. This sludge is very high in water content, and even after mechanically de-watering, the moisture content can still be as high as 60% to 80%. If a mill wished to dispose of this high moisture sludge on their grate boiler with bark and wood waste, it could create a number of problems including high excess air, high sensible heat lost, erratic firing, and increased combustibles out the stack.

A better way to improve the combustion of sludge is to dry it with waste heat from the boiler stack. Utilizing a rotary or flash type dryer, the moisture content can be reduced down to as low as 35% for course particles and 10% for fine particles depending on the temperature of the flue gas. Using this dry course material on the grate will substantially improve the efficiency and operation of the boiler.

SUSPENSION BURNING:

Further gains can be realized by burning the fine material in suspension over the grate. These fines can easily be mechanically separated from the course material and metered separately to a suspension burner. As long as the material is less than 1/16″ in size and around 10% moisture content, it will burn is suspension quite satisfactorily. Bark fines can be added to the sludge fines and burned in combination. Suspension burning can be as efficient, flexible, and easy as burning oil or gas. There are many benefits to suspension burning including:

  • Eliminates fines carryover from grate
  • Lower excess air
  • Increased capacity
  • Higher turndown
  • Displaces oil and gas
  • Improves load response time

Figure 1, DAZ Scroll Burner

A burner such as the one shown in (fig. 1) can burn sludge, bark fines, gas or oil in combination or individually. Typically, the turndown on sludge would be three or five to one. The response to load changes would be instantaneous just like on gas or oil.

IN CONCLUSION:

While the incentives for utilizing alternative type fuels have disappeared, there are still many areas where landfilling and environmental cost can make the use of alternative fuels not only a necessity but even profitable. High moisture waste that contain biomass materials can be dried with waste heat from the boiler flue gas and utilized as a fuel in most boilers either on the grate or burned in suspension. Look to the Pulp & Paper industry as a leader in this technology to dispose of their paper mill sludge.