Cupola program provides improved cost analysis.

The large number of variables involved in cupola operations, plus the inherent differences among cupolas, makes reaching optimal levels of cost and performance difficult. In addition, low cost charge materials often create secondary costs that outweigh their benefits. S. Katz Associates provides a new software-based service that provides the routes to achieve true costs savings.

CupolaMelt was developed over a 10-year period under contracts awarded to the American Foundry Society, Schaumburg, Ill., and S. Katz Associates, West Bloomfield, Mich., by the U.S. Department of Energy. The software is sensitive to both positive and negative factors affecting cupola operation as it moves from the charge door to the taphole. All the effects are integrated to provide an overall description of the cupola operation.

Savings generally are obtained as reductions in the amount of materials used or as substitution of materials. Representative, achievable cost savings obtained by reducing coke usage, silicon loss and oxygen are given in Table 1. The software generally indicates savings for more than one charge material, which increases the achievable benefits.

With the software, S. Katz Associates can provide three levels of service. At the first level, single issues are resolved, such as how to improve silicon recovery or coke usage. At the second level, the program provides a complete analysis that will reduce costs for the entire cupola operation. At the third level, the benefits of making physical changes to the cupola, such as adding/removing a refractory lining, altering the height of the tuyeres, increasing/decreasing the cupola diameter or changing to a hot blast operation, are determined.

Several of the improvements and solutions the software is able to analyze are relatively untried applications that offer great promise. One is low cost dehumidification of the blast air, which not only has been shown to reduce coke consumption in high humidity areas but also to increase iron temperature and carbon pickup. Clearly, metalcasting facilities have not been in a position to determine if the achievable savings from dehumidification are worth the costs of the investment and maintenance of the equipment. But, computer aided analyses can provide the savings information needed to make the decision.

An old metalcasting axiom says virtually no two cupolas are the same. This being the case, CupolaMelt must be provided with an accurate physical description of the cupola. Further accuracy is achieved if current operating data is provided. For the greatest accuracy and benefit, the program requires heat loss data. With the availability of these data, almost any situation can be simulated.

Improvements in cupola operation are developed through repeated interaction between the program and an expert in cupola operation. After a computer run is carried out, the examination of the output by the expert suggests new computer runs. Depending on the complexity of the issue, this process may be repeated many times. For example, finding the best operating conditions for the entire cupola operation likely requires dozens of computer runs.

Contact S. Katz Associates at 248/682-4131 for more information.

Areas of Cupola Operation Benefited by Computer Analysis

Solutions without major physical changes to the cupola

* Complete overall cost reduction

* Beneficial use of briquetted materials

* Cost/benefit selection of scrap

* Reduce coke and [O.sub.2] usage

* Improve carbon and silicon

* Increase iron temperature

* Energy loss assessment

Solutions requiring physical changes to the cupola

* Add or remove refractory lining

* Select optimum refractory

* Add/increase hot blast

* Alloy injection

* Blast dehumidification

* Change tuyere height

* Improve external desulfurization

Table 1. Estimated Annual Cost Savings for
Cupolas Melting 16 hours/day, 250 days/year

Melt Rate     Coke Change   Silicon Loss   Oxygen Change
(tons/hour)    10.5-10%        20-15%          2-1%

100            $400,000       $300,000       $200,000
80             $320,000       $240,000       $160,000
60             $240,000       $180,000       $120,000
40             $160,000       $120,000        $80,000
20              $80,000        $60,000        $40,000
10              $40,000        $30,000        $20,000