While the lead ISASMELT 5 t/h pilot plant was being designed in 1982–1983, MIM continued to use the 120 kg/h test rig to develop other processes, including the dross treatment process previously mentioned, and the treatment of lead-acid battery paste for lead recycling.
The MIM Holdings Board of Directors approved the construction of an ISASMELT plant at Britannia Refined Metals, the company's lead refinery at Northfleet in the United Kingdom, for commercial recovery of lead from battery paste to supplement the existing plant, which used a short rotary furnace to produce 10,000 t/y of lead. The new plant increased annual production to 30,000 t/y of recycled lead, and was commissioned in 1991. The ISASMELT furnace was used to produce low-antimony lead bullion from the battery paste and an antimony-rich slag that contained 55–65% lead oxide. While it was possible to recover the lead from the slag in the ISASMELT furnace by a reduction step, the total throughput of the plant was increased by treating the slag in the short rotary furnace when sufficient quantities of the slag had been generated. The plant was designed to treat 7.7 t/h of battery paste, but routinely treated 12 t/h. The plant was shut down in 2004 when Xstrata Zinc, which took over the MIM Holdings lead operations, decided to leave the lead recycling business.
A second lead ISASMELT plant for recovering lead from recycled batteries was commissioned in 2000 in Malaysia at Metal Reclamation Industries’ Pulau Indah plant. This ISASMELT plant has a design capacity of 40,000 t/y of lead bullion.