The capital cost for production facilities is the third largest item in a
glass melter's budget, following raw materials and energy. The investment
requirement for emission control of fuel melters can be of the same general magnitude
as is the investment for melting facilities alone.
In addition, operating costs associated with the emission control equipment (utilities, operating labor, chemicals) add another 10 to 20 percent to the annual costs associated with the investment in emission control equipment.
Thus, the Clean Air Act favors electric melting and the use of oxygen gas rather than air in combustion. The advantage of oxygen is the reduction in nitrous oxides and the increased furnace efficiency, but the cost of oxygen and the required capital to use it make this a significant capital expenditure. Electric utilities may wish to become joint venture partners with glass makers since the production of oxygen, either on-site or in neighboring air separation plants is extremely electric energy intensive.
Electric boosting can also be used to incrementally increase output and reduce emissions per unit of output without the need for new facilities. Furnaces already equipped for electric boosting can be increasingly electrified to replace part, or if the furnace design permits, all of the fuel overfiring.
The initial capital costs for direct resistance glass melting equipment vary with the application. The costs of electric boosting for existing furnaces can be roughly estimated at $3,000-$5,000 per ton of increased glass production per day.
Capital costs for all-electric melting furnaces and comparable fuel-fired furnaces also vary widely. Electric melters require electrical power supplies and control equipment while fuel-fired furnaces do not. Fuel-fired furnaces, however, require equipment such as burners and blowers and fans. Most importantly, fuel-fired furnaces can require extensive pollution control equipment. This equipment can cost nearly as much as the furnace itself.
When costs of pollution control equipment are included, direct resistance melters are typically less costly than fuel-fired furnaces, particularly those of smaller capacities. Larger fuel-fired furnaces (200 tons per day) can be less costly than a comparable electric melters because the pollution control equipment is a smaller percentage of the total system cost.
Capital costs for direct resistance electric glass melters can range from $15,000 to $20,000 per ton per day of capacity. Fuel-fired furnaces including pollution controls can run as much as twice the initial costs of electric melters. This is why boosting has such popularity for incremental increases in production.
