FCC CATALYST FINDS THREE SAFE REUSE OUTLETS IN EUROPE

Rodolphe Schmitt
European Cracking Catalyst Producers Association
Brussels

Three usages in the area of construction materials offer a potential outlet for the reuse of spent fluid catalytic cracking (FCC) catalyst that far exceeds the supply from European refineries.

The proximity of the spent catalyst source to the point-of-use is critical because this determines the transportation cost-the major element in the cost of disposal/reuse. This is why a balanced geographical spread of reuse outlets throughout Europe is sought.

In 1990, about 350,000 metric tons of FCC catalyst were used worldwide, including 180,000 tons in the U.S., and some 60,000 tons in the 60 refineries with FCC units (FCCUS) in Western Europe.

Western Europe in this article is defined as all countries comprising the European Community (EC), plus Norway, Sweden, Finland, Switzerland, and Austria.

SPENT CATALYST

Two types of catalyst waste are generated by Western European FCCUS:

Catalyst fines-6,000 tons/year
Spent FCC catalyst-25,000 tons/year.

Under the auspices of the European Chemical Industry Council, or Cefic, the European FCC catalyst manufacturers formed the European Cracking Catalyst Producers Association (Eccpa) in 1988.

The primary objective of Eccpa is to study and promote viable and environmentally safe disposal or reuse options for spent FCC catalyst and catalyst fines.

Of the 60,000 tons of fresh catalyst purchased annually by European refiners, only about 5% is either reused in-house or sold to other refineries as equilibrium catalyst (E-cat). Ultimately, some 30,000 tons needs to be disposed of in a safe and environmentally acceptable fashion.

Spent catalyst, i.e., a catalyst not suited for further (E cat) use, is a silica/alumina zeolite-containing material with concentrations of heavy metal contaminants usually exceeding 2,000 ppm total nickel and vanadium.

Antimony is the other major potential metal contaminant. It is used in 10-20% of FCCUs as a nickel passivator. Other contaminants are generally present only in trace quantities,

Nickel, vanadium, and antimony are elements that may render waste hazardous under the conditions of the latest EC regulations-in particular, the proposed council directive on hazardous waste (4008/91, Jan. 9, 1991).

EC LEGISLATION

With tightening legislation, landfilling will become increasingly difficult and costly, with possible associated liabilities.

A new EC directive on landfilling is under preparation and will supersede less-stringent national legislation, thus constituting the minimum requirement in all EC member states.

For the purpose of landfilling, waste acceptance criteria and procedures will apply. The requirements for contaminant concentrations in the eluate from leaching tests are set out in Annex 3 of the draft directive (COM[91] 102 final SYN 335, May 22, 1991). These proposed EC assignment values for contaminants are notably lower than those of the present U.S. regulations.

These stringent future requirements may not be met in some cases and treatment prior to landfilling may be necessary. Such treatment will surely increase the cost of landfilling.

WASTE SHIPMENT

Another piece of legislation of relevance is the proposed EC council regulation on the supervision and control of shipments of waste within, into, and out of the EC (OJEC No. C289, 17.11.1990).

In this text, the concept of "waste intended for further use"-what industry calls secondary raw materials-is introduced. Simplified procedures are foreseen for the movement of these types of goods, with a system of notification to the appropriate local authorities.

CIVIL LIABILITY

In 1989 the Commission of the European Communities (CEC) submitted a proposal for a council directive on civil liability for damage caused by waste (OJEC No. C251, 4.10.89). The draft introduces a system of strict liability for producers of waste in relation to:

The damage caused by the waste to persons or property
Injury to the environment.

According to the CEC's proposal, the producer of the waste-in the case of spent catalyst, the refiner-is responsible until the waste is given to an authorized disposal facility. Thus the producer could be held liable for the damage caused by a third party, such as the transporter of the waste.

The definition of waste does not distinguish between wastes, as such, and secondary raw materials.

The CEC's proposal has been under discussion by the European Parliament (EP) Committee on Legal Affairs and Citizen's Rights for the past 15 months. The EP has made several amendments to the proposal. One links civil liability to operational control.

In an amended proposal (COM[91] 219-SYN 217, June 27, 1991), the commission has taken parts of the EP's opinion into account. However, the producer will continue to be liable, even if he has no operational control over the waste, as long as the waste has not been given to a licensed disposal site or storage facility.

ASSESSMENT OF REUSES

The area of construction work-a traditional outlet for industrial residues-has been investigated as an outlet for the reuse of spent catalyst. Potential reuses identified include:

Road surfacing-As a filling agent for asphalt
Housing-In the manufacture of bricks and cement.

These uses were scrutinized from two angles:

Technical acceptability-Meaning that the physical and textural properties of the end products should not be impaired
Environmental acceptability-Meaning that no adverse environmental effects, i.e., leaching of metal ions into the soil and groundwater, should occur under use conditions throughout the life cycle of the products.

Checking these two criteria involves performing production test runs and leachability studies. Such work was undertaken by Eccpa in conjunction with a series of potential users in the various fields of application.

Technical acceptability was studied primarily by the potential user.

It is an absolute prerequisite to reuse.

The following discussion examines the reuse of spent catalyst in the previously listed outlets, with emphasis on environmental acceptability testing, which ultimately decides the product's commercial acceptability and use.

ASPHALT FILLER

In The Netherlands, for example, a standard composition of asphalt is as follows: gravel and sand, 90%; bitumen, 5%; filler, 5%.

The filler is required to have a specific particle-size distribution, typically as follows: fraction above 90 m, < 5%; fraction above 63 m, < 15%. Furthermore, the fraction below 10 m must be kept to a minimum to prevent blockage of the bitumen pores.

This means that spent catalyst must be milled to this particle-size distribution in order to be used as a filler. Also, small quantities of calcium hydroxide and calcium carbonate are usually added to improve the adhesive properties of the filler.

To date, spent catalyst is used commercially by two manufacturers of asphalt filler in Europe-one in Germany and one in The Netherlands. And one Italian company is considering its use.

A manufacturer will reuse spent catalyst only after leaching tests have been performed, both in-house and at outside laboratories.

A comprehensive study, commissioned by an asphalt manufacturer, was performed at Ruhr University in Bochum, Germany, under Professor Dr. Ing. K. Krass. The various technical and environmental aspects of using spent catalyst as asphalt filler were evaluated. Leaching tests were conducted according to method DIN 38414, Part 4.

Although the experimental results have not been published, the study by Ruhr University concluded that up to 5% spent catalyst can be used as a filler, when antimony is present at a concentration not greater than 600 PPM.

At higher antimony concentrations, the proportion of spent catalyst is not to exceed 3%.

CEMENT

From a technical, economic, and environmental point of view, the use of spent FCC catalyst as a raw material in cement is considered an acceptable alternative, and is now being adopted in France and Germany. FCC catalyst can account for up to 6% of cement raw material, the bulk being chalk (75%) and clay (19%).

The manufacture of cement involves a calcination step at 2,000 C., during which metals are vaporized in the kiln and subsequently scrubbed from the vent. Leaching tests on the clinker, according to method DIN 38414, Part 4, demonstrate levels well within acceptability limits.

On the basis of these tests, the use of spent FCC catalyst in cement received approval from the authorities in Germany.

RED BRICKS

A third large-volume outlet that has been investigated is the manufacture of red bricks.

Extensive production trials and leaching tests have been performed, particularly in The Netherlands. With 5% spent catalyst incorporated, the quality of the resulting bricks was found to be fully satisfactory.

Two different types of leaching tests were performed on red bricks:

Leaching tests on crushed bricks
Leaching tests on whole bricks.

The eluates were analyzed using graphite furnace atomic absorption spectrophotometry. Test conditions and eluate analysis results are shown in Table 1.

The experimental results from both forms of red brick show that red bricks are an environmentally acceptable reuse outlet for spent catalyst.

A third experiment was performed on the bricks to determine the fate of the metals during manufacture, i.e., the retention of these metals during firing.

This consisted of a volatility test carried out at 1,080 C. for 55 hr.

The results, shown in Table 2, indicate that the three metals of concern (Ni, V, and Sb) are retained in the bricks during firing. (Bismuth is not widely used in Europe, but is expected to be environmentally acceptable.)

Although this reuse outlet features full environmental acceptability, it has not yet found an industrial application because brick manufacturers could not be guaranteed a continual long-term supply of large volumes of spent FCC catalyst.

Each of the uses described and assessed requires the approval of the appropriate national authorities.

A number of other applications are under development-all in the area of construction materials-and their environmental acceptability is being investigated.