October 9, 2020: Battery recycling, lead recovery and water treatment company STC Italy has developed a paste desulfurization process which produces a by-product that can be used as fertilizer, the company told BESB at the virtual ELBC conference this September.
The process, called U4Lead, is based on using urea (CH4N2O) instead of sodium sulfate or ammonium carbonate, which are widely used in desulfurization. The end product is ammonium sulfate, which is widely used as an agricultural fertilizer and commands a ready price in international markets.
“The need to develop an alternative desulfurization process to the ones already available on the market arose about three years ago,” says Alberto Bergamaschini, commercial and marketing director at STC.
“We wanted to propose our lead paste desulfurization process via ammonium carbonate to one of our clients but we immediately realized that due to its high price, volatility and toxicity, it was necessary to look for other valid options.”
The firm had been looking for a more efficient desulfurization process starting from a cheaper amino compound, which was easier to find, treat and handle.
But that is not to say that the process will be a magic cure for one stage of the lead battery recycling process.
In a paper to have been presented at the LABAT conference in Bulgaria this summer (which was subsequently postponed due to the Covid crisis), STC demonstrated that the urea conversion needed would be energy intensive. The conversion rate needed to work is a temperature of 140°C-180°C and a pressure of between 5 bar and 12 bar.
“The U4Lead system is based on a well-defined and innovative STC process protected by patent and has been successfully installed and commissioned in the ULAB recycling plant realized by STC of our Nigerian client Green Recycling Industries based in Agbara, Ogun State,” says Bergamaschini.
A simplified reaction of the U4Lead process for dealing with the lead sulfate is:
CO(NH2) 2 + PbSO4+H2O = PbCO3 + (NH4) 2SO4
And this for neutralizing the sulfuric acid:
CO(NH2) 2 + H2SO4 + H2O = (NH4) 2SO4 + CO2
“Depending on local requirements, it can be concentrated in a simple evaporator and used directly in agriculture or alternatively crystallized to produce pure crystals,” says the firm.
STC says it offers turnkey plants, plug-and-play integrated technologies and a complete range of equipment mainly for the recovery of lead, polypropylene, PE and other materials from exhausted lead-acid batteries.
