Refining Report Catalyst handling, disposal become more important in environmental era

Gulf Chemical and Metallurgical Corp.'s state-of-the-art drying and pyrometallurgical facility at Freeport, Tex., recovers nonprecious metals from spent catalysts sent to Freeport from refineries around the world.

In today's operating climate of increased attentiveness toward environmental and safety issues, catalyst management options have become an important consideration for refiners.

The U.S. Environmental Protection Agency (EPA), for example, is in the process of reevaluating the designation of spent hydroprocessing catalysts as a nonhazardous waste. Industry sources say the outcome likely will reduce the options available to refiners for catalyst disposal and increase shipping and disposal costs.

After a refining catalyst is manufactured, its so-called cradle-to-grave cycle entails a number of key steps, including: unit loading and unloading, transport, regeneration, reuse, reclamation, and disposal. These steps were discussed by a number of catalyst industry specialists at Oil & Gas Journal's International Catalyst Conference Feb. 1-2 in Houston.

A review of catalyst management procedures will provide a reference for some of the options available to refiners at each juncture in a catalyst's life cycle.

Loading

Daniel P. Helfrich of Catalyst Technology Inc., Buckner, Ky., recommends what he calls "preloading." In this process, the catalyst drums are lifted hydraulically and screened, then stored in the loading bag or bin.

"Transient chips and fines fall through the sized screen while an air or nitrogen purge flows up through the catalyst," says Helfrich. The smaller particles are trapped in the hood of the hopper and a dust collector removes and collects the dust.

Many refiners prefer to have their catalyst delivered in loading bags. This reduces handling, but does not eliminate the formation of catalyst fines and chips. Catalyst from loading bags can be loaded into a special hopper on top of the reactor and screened.

Sock loading is the simplest way to load a reactor, but care should be taken to minimize catalyst breakage. Helfrich recommends using a non-free-fall technique.

For this technique, says Helfrich, "The loading hose should remain full, and the technician in the reactor should ensure the catalyst discharge from the flexible sock is from no higher than 2 ft off the catalyst bed. The catalyst should be distributed evently throughout the reactor, and weight-distribution shoes must be worn by anyone standing on the catalyst bed."

The dense-loading technique uses particle-movement principles to achieve improved catalyst orientation. This method takes advantage of the tendency of catalyst particles to orient themselves horizontally when allowed to fall individually. The result is tighter packing of particles.

In the dense-loading technique, the catalyst is distributed radially at a controlled rate, producing a "rain" of catalyst. The process maintains a level bed surface and results in horizontal particle orientation, uniform void spaces, and near-maximum bed density.

Catalyst Technology offers an improved dense loader, says Helfrich. This system discharges catalyst from three stages in concentric circles. Each stage has its own regulator for air or nitrogen.

Helfrich says the technology increases loading rates, relative to conventional single-stage loaders.

Unloading

Spent catalysts contain metals in a highly reactive, sulfided state. This problem is compounded during reactor unloading by the presence of pyrophoric iron sulfide and coke or carbon desposits.

When these materials are exposed to oxygen in the form of air, they react, often spontaneously igniting. This creates a fire hazard and can release highly toxic sulfur dioxide.

The solution to this problem is to remove catalyst under a nitrogen atmosphere. By eliminating the presence of air, the catalyst can be unloaded safely, packed in sealed containers, and sent off site for regeneration, reclamation, or disposal.

But it is dangerous to enter a reactor using life-support apparatus, as is necessary in a nitrogen atmosphere. And, in instances requiring inert entry, every step in the unloading process takes longer.

For a typical vacuum unloading of a hydrocracker under nitrogen, for example, 30% of the costs are attributable to working in an inert atmosphere, says Helfrich.

The simplest way to unload spent catalyst from reactor vessels is by gravity dumping under a nitrogen purge stream. The catalyst is collected in drums or bins, then shipped for regeneration or reclamation.

The catalyst can be screened when it is dumped to remove the catalyst support balls. Screening reduces costs because the support does not have to be shipped or removed by the regenerator or reclaimer.

Catalyst Technology uses a Rapid Support Separator to increase screening rates, and dust-containment devices to reduce particulate emissions. In addition, Helfrich says his company offers a filtration system that is 100% effective for particles as small as 5 m, after exposure to 300 g of dust.

Spent catalyst also can be removed under nitrogen using a vacuum system, cyclone separator, and dust filter. Using this system, says Helfrich, the catalyst can be separated according to particle size and immediately prepared for reloading.

Another method of unloading involves flooding the reactor with a solution of soda ash in water, temporarily rendering the catalyst nonreactive. But this does not guarantee that the catalyst can be classified as nonhazardous. In fact, says Helfrich, catalyst treated in this manner fails the self-heating test used by the U.S. Department of Transportation (DOT). In addition, the aqueous residue is a disposal problem for the refiner, and vessel cleanup is difficult.

Other catalyst passivation methods use organic passivators rather than an aqueous solution. One such technology is Nikko Engineering Co.'s passivation process for removing catalyst from heavy resid hydrotreaters. This process was developed in the 1970s, says Merlin Hoiseth, Reactor Services Inc. of Alvin, Tex.

Safety is the primary emphasis of refinery management and an important consideration for catalyst handlers, says Hoiseth. The Occupational Safety and Health Administration's Rule 1910.119, for example, places heavy requirements on both refiners and catalyst handlers.

"Mandated rules now require the typical worker to spend as many as 110 hr a year viewing training films and taking tests," says Hoiseth. "Workers for catalyst service contractors, who travel to many different plants, must carry a card that identifies the type of orientation training received from each safety council in whose jurisdiction they work."

Hoiseth suggests that safety councils and industry owners cooperate to develop standardized training requirements and plant procedures. "This would permit a more intensive and effective training program that would provide certification in all jurisdictions," said Hoiseth.

Transport

Once spent catalyst has been removed from the reactor, it must be transported to a regenerator, reclaimer, or disposal site. In the U.S., pyrophoric catalysts must be classified as hazardous because they meet DOT criteria for flammability. This entails special permitting and placarding, and increases transportation costs and liabilities.

EPA considers spent hydrotreating and hydrorefining catalysts a hazardous waste only if they exhibit certain hazardous characteristics, such as pyroforicity, or fail the Toxicity Characteristic Leachate Procedure (TCLP). Catalysts that fail the TCLP test usually do so because of arsenic or benzene.

The EPA, however, is in the process of deciding whether to classify all hydrotreating and hydrorefining catalysts as a listed hazardous waste, regardless of their characteristics. This decision is the result of a lawsuit filed against EPA by the Environmental Defense Fund (EDF), says Jay S. Jaffe, Gulf Chemical & Metallurgical Corp. (GCMC), Houston.

The proposed rule was published in the Federal Register on Nov. 20, 1995. The comment period has been extended to Mar. 21. At press time, the final rule had not been published, but it is likely to be effective Oct. 31, 1996, says Jaffe.

Gulf Chemical & Metallurgical met with EPA during the rule-making process. Gulf asked EPA to grant the catalyst a "conditional exclusion" from the hazardous classification, provided that the catalyst was handled according to specific management standards and shipped to a recycler. Gulf's position was that the catalyst should be considered a listed waste only when it is disposed of in a landfill.

"It appears that the position of GCMC, the API, and the Metal Catalyst Producers Panel went unheeded," said Jaffe, "and that EPA will list the catalysts as hazardous waste.

"The listing affects all of us," added Jaffe. "It will mean major capital expenditures, not only for the refineries, but also for catalyst handlers, regenerators, and reclaimers."

Regeneration/reuse

James J. Barry of CRI International Inc., Houston, says a catalyst's deactivation mechanism determines how it can be handled after it is discharged from the processing unit.

The three basic deactivation mechanisms for refining catalyst are:

Coke or carbon formation (plugging of pores, coverage of ative sites)
Aging (metal agglomeration)
Poisoning (feed contaminants).

In most cases, catalyst deactivated by coking is suitable for regeneration and reuse.

As mentioned previously, the regeneration of catalyst in situ releases SO2 and other pollutants to the atmosphere. With the ex situ regeneration processes commonly used today, these regeneration products are scrubbed and emissions eliminated.

Other advantages of ex situ regeneration include close temperature control, reduced unit downtime, and consistent activity recovery. Barry says ex situ regeneration has been used on:

Hydrotreating catalysts (NiMo, CoMo, and NiW)
Hydrocracking catalysts
Molecular sieves
Reforming catalysts
Petrochemical catalysts
Alumina.

Often, regenerated catalysts can be reloaded into the same unit. "In severe-duty units," says Barry, "only fresh catalyst will give the desired performance and the regenerated can be cascaded to less severe service."

A recent development in the regeneration and reuse of catalysts is what CRI calls management of regenerated catalysts for groups of refiners.

"A pool of regenerated catalyst is maintained and available to all refiners," says Barry. "The pool can be used in emergencies or for routine changeouts.

"Most companies have a catalyst coordinator who evaluates catalyst for regeneration and reuse," continues Barry. "The coordinator also works with the individual refinery units to determine their catalyst needs and the most economical way to meet them."

CRI also operates a catalyst resale program that serves as an outlet for refiners with a surplus of regenerable catalyst, and as a source of regenerated catalyst for refiners seeking to use it for economic reasons.

CRI acquires the catalyst either on consignment, or as a direct purchase. Barry says the refiner receives more money if the catalyst is consigned (Table 1 [16502 bytes]).

Reclamation

The type of catalyst and its condition (whether it is considered hazardous or nonhazardous) often determines the disposal route selected. Precious-metals catalysts, for example, should be sent for metals recovery.

Gemini Industries, Santa Ana, Calif., is a reclaimer of precious metals from catalysts. Reforming and isomerization catalysts, for example, contain platinum as an active ingredient.

Gemini's J.P. Rosso says refiners should pay strict attention to materials handling and record keeping when recycling precious-metals catalysts. An error of 0.5% when weighing a catalyst shipment, for example, can equate to $32,500, given current metals prices.

Put another way, says Rosso, a single drum of spent catalyst containing precious metals is worth about $7,500. Rosso recommends care be taken during every phase of catalyst handling:

Accurate records should be kept regarding the type and quantity of catalyst loaded in a reformer. Records should include operating upsets and other factors that may affect the catalyst during its life.
Service companies should be supervised when dumping a reactor. In one case, says Rosso, use of the wrong screen resulted in 20,000 lb of support material being shipped as precious-metal catalyst, causing the refiner's economic projections for the shipment to be off by 1,020 oz. of platinum, or $400,000.
Refiners should institute inventory procedures to track every pound of catalyst purchased, used, dumped, and shipped. The system should include purchase orders, metals assays, shipping manifests, drum counts, and weights. Because of mislabeling, says Rosso, one refiner accidentally loaded 150,000 lb of platinum/rhenium catalyst onto trucks for use as roadbed material. The result was a $3.25 million roadbed, which later had to be excavated.
Drums should be eqipped with locking rings and numbered seals, and the catalyst should be stored in a secured warehouse, clearly marked and segregated from other catalysts.
Warehouse control should include a double-signature system for materials entry and exit.
Catalyst should be shipped via a large, reputable freight carrier. Rosso strongly encourages the use of enclosed vans.
The catalyst shipment should be insured for the full, estimated value of the platinum. A large, financially sound company should be used.

Rosso also recommends having precious-metals catalyst regenerated before it is sent to a reclaimer. Catalyst contaminated with wet hydrocarbon presents a serious safety and handling problem. In addition, contaminated catalyst cannot be sampled and tested properly.

Regeneration can occur on site or off site, depending on circumstances and economics. In either case, clean catalyst means maximum metals recovery.

Metals recovery

In recent years, a select number of refiners have been shipping a greater portion of their spent hydrotreating catalysts to landfills. The refiners all have their own reasons, but this practice has come under the watch of the EPA as a result of a questionnaire trefiners were required to fill out and return.

The results of this questionaire indicated that this practice was becoming more prevalent and that less catalyst was being recycled. This was one of the reasons for the newly proposed listing.

When EPA restricts a hazardous waste from disposal in landfills, it must set methods or levels of treatment. In the case of hydrotreating catalysts, this means high-temperature metals recovery, followed by stabilization.

Because of the self-heating and leaching problems associated with spent hydrotreating catalyst, Jaffe recommends that refiners ship their spent catalysts to what he calls a "true recycler." Such a company should:

Be a low-cost processor
Offer a process that is environmentally superior to alternative options
Offer maximum price for each metal recovered
Hold a Resource Conservation & Recovery Act Part B permit
Form strategic alliances with smelters and other users of reclaimed materials
Refrain from dealing with traders or speculators.

The costs of dealing with irreputable companies can be astronomical. In fact, says Jaffe, EPA is now considering for Superfund status a site only a mile from downtown Houston where spent catalyst was dumped.