Recovery of titanium, tungsten, vanadium and molybdenum from spent denitrification catalysts in power plants: Turning waste into treasure and discovering gold in "urban mines".

Abstract: With the increasingly stringent environmental protection requirements, the number of spent denitrification catalysts (SCR) produced by coal-fired power plants and iron and steel mills has increased dramatically, which are classified as hazardous wastes with high disposal costs. However, these spent catalysts are rich in titanium, tungsten, vanadium, molybdenum and other scarce strategic metals, which is a huge "urban mine". In this paper, we analyze the process of recovering titanium, tungsten, vanadium, molybdenum from spent denitrification catalysts, and how to transform the environmental burden into considerable economic benefits, helping enterprises to realize green recycling and value-added resources.

Keywords: waste denitrification catalyst recycling, titanium, tungsten, vanadium, molybdenum recycling process, SCR catalyst resource utilization, hazardous waste disposal, rare metal recycling, green metallurgy

I. Imminent Challenges and Opportunities: Why is it Necessary to Recycle Spent SCR Catalysts?

Selective catalytic reduction (SCR) technology is currently the most effective way of flue gas denitrification, but its core component, the catalyst, has a service life of 2-3 years. The spent catalyst generated after expiration faces two core issues:

1. Environmental Risks and Disposal Pressure: Waste SCR catalysts are listed on the National Hazardous Waste List because they contain toxic vanadium pentoxide. The traditional landfill method is not only costly (disposal fees can reach thousands of dollars per ton), but also poses a long-term environmental risk of contaminating soil and groundwater with leaching of heavy metals.

2. Huge waste of resource value: Waste catalysts are not "waste", but are mainly composed of titanium dioxide (TiO₂) carriers, as well as tungsten (W), molybdenum (Mo), and vanadium (V₂O₅) as the active ingredients. These are high value strategic metals, with tungsten and vanadium being particularly scarce. Recycling them is an inevitable choice for resource recycling and supply chain security.

Therefore, the development of a highly efficient process for the recovery of titanium, tungsten, vanadium, molybdenum from spent denitrification catalysts has both environmental and economic benefits, and has a broad market prospect.

The core of the technology: efficient separation and purification of the joint process route

The recovery of spent SCR catalysts cannot be accomplished by a single technology, but requires a set of fine joint process. Currently, the mainstream and efficient process routes are as follows:

1. Pre-treatment and activation stage:

• Disassembly and crushing: The waste catalyst module is disassembled and crushed and ground to reach a suitable particle size to increase the reaction specific surface area.

• Roasting and activation: Roasting the material at high temperature, aiming at removing the attached toxic organic substances (such as arsenic, sulfur, etc.) and changing the physical structure, so that the subsequent valuable metals can be leached more easily.

2. Selective leaching of valuable metals:
This is the key link in the whole process. The goal is to leach as much tungsten, vanadium and molybdenum as possible into solution, while allowing titanium dioxide to remain in the slag as long as possible.

• Alkaline leaching (mainstream): Caustic soda (NaOH) or soda ash (Na₂CO₃) solution is used as the leaching agent. Under a specific temperature and pressure, tungsten, vanadium and molybdenum will enter into the solution in the form of soluble sodium salts (e.g., Na₂WO₄, NaVO₃, Na₂MO₄), whereas titanium dioxide is insoluble. The titanium dioxide is insoluble, forming "titanium slag".

• Acid leaching method: the use of acid solution, but this method may lead to the dissolution of titanium, increasing the difficulty of subsequent separation, so the application is relatively small.

3. Purification and separation of leach solution:
The alkaline leach solution obtained has a complex composition and requires fine separation to obtain a single metal product.

• Solvent extraction (preferred for high efficiency): This is currently the most advanced technology with the best separation effect. Utilizing the difference in the distribution ratio of different metal ions in the organic and aqueous phases, tungsten, vanadium and molybdenum can be efficiently and selectively separated and enriched for purification through multi-stage extraction and back-extraction.

• Ion exchange/chemical precipitation: can also be used for separation, but may not be as efficient or pure as solvent extraction when dealing with highly concentrated, complex solutions.

4. Product Preparation and Utilization of Titanium Slag:

• Preparation of metal compounds: the solution after separation and purification, through evaporation and crystallization, acid precipitation, calcination and other processes, to prepare high-purity ammonium paratungstate (APT), vanadium pentoxide (V₂O₅), ammonium molybdate and other products.

• Resourceization of titanium slag: The separated titanium-rich slag is of high purity and can be used as a high-quality raw material for titanium dioxide production or for manufacturing artificial rutile, so its value can be fully utilized.

Third, process advantages: why choose professional recycling technology?

Compared with simple landfill or low-level utilization, professional titanium, tungsten, vanadium, molybdenum recycling process has unparalleled advantages:

• High degree of resource utilization: It realizes the comprehensive recovery of titanium, tungsten, vanadium and molybdenum, and the comprehensive utilization rate of resources can reach more than 95%.

• Remarkable economic benefits: The high cost of hazardous waste disposal is transformed into income from the sale of high-value metal chemicals, with a high return on investment.

• Environmentally friendly: the whole process of hazardous waste "harmless, reduce, resource", completely eliminate environmental hazards, in line with the national circular economy and environmental policy.

• Strong technical barriers: Mature process packages and engineering experience constitute the core competitive advantage, and can produce stable output of high-purity products to meet market demand.

Investment Value: Strategic Transformation from Cost Center to Profit Center

For power generation groups, environmental protection companies or resource recycling enterprises, investing or cooperating in the construction of waste SCR catalyst recycling projects is an important strategic upgrade:

• Solve the disposal problem: fundamentally solve the "worries" of hazardous waste disposal and reduce the risk of environmental compliance.

• Open up the second track: From pure power production or environmental protection operation, we will enter the field of scarce resources recycling to create a new profit growth pole.

• Enhance ESG performance: The perfect resource recycling model greatly enhances the green image and social responsibility score of the enterprise, which is conducive to obtaining the favor of the policy and capital market.

V. Conclusion: Join hands with technology partners to win the future of green resources

Waste SCR catalysts are a "rich mine" that needs to be mined urgently. Successful recycling depends on reliable technology, mature processes and rich engineering experience.

We specialize in hazardous waste recycling and rare metal recycling technologies, providing a full range of solutions from waste catalyst composition analysis, process solution design, core equipment supply, to turnkey EPC and operation support. Our titanium, tungsten, vanadium and molybdenum recovery process for spent denitrification catalysts is designed to maximize environmental and economic benefits for our customers.

Contact us today for a customized technical and commercial feasibility study to turn your environmental responsibility into sustainable green wealth!