It was gearing up to be a heated debate, with plenty of fireworks.

Two scientists from Timminco’s metallurgical-silicon subsidiary, Becancour Silicon, are scheduled to speak Wednesday afternoon at the biennial Silicon for the Chemical and Solar Industry conference in Norway.

Short-seller advocate Manuel Asensio, who enjoys a good debate, was looking forward to it.

Timminco has so far kept quiet about the technology behind its claims that it has developed a process to make solar-grade silicon out of dirtier metallurgical-grade silicon at lower costs than its competitors. The company has drawn both enthusiastic support and skepticism from industry insiders amid speculation about whether it’s for real.

Asensio counts decidedly among the skeptics. He himself is a controversial figure, with whole Websites dedicated to both admiring and discounting him (see Asensio Exposed, Asensio Exposes, a Forbes story about Asensio and his record with the Financial Industry Regulatory Authority).

Asensio has released some 28 research notes on Timminco, that are all negative about the stock.

The presentation, “Process and apparatus for purifying silicon,” by Becancour Silicon CEO Rene Boisvert and another presenter only identified as D. Leblanc, could shed some light on the secret process.

And Asensio planned to be there with plenty of questions.

“I was invited,” he said. “I accepted the invitation. My acceptance was confirmed.”

Then, on Friday, he received an email from the conference chairman, Harald Øye, asking him not to attend.

The letter, forwarded from Asensio, purportedly ran as follows:

“I have been informed by Becancour Silicon Inc. that we have to make a choice between you attending the conference and Becancour Silicon Inc., GK Kropfmuhl and Q-Cells. As these companies have been long-time supporters of the conference, I have to inform you regretfully that you cannot attend the conference.”

In his response, Asensio wrote that the request was a move to “oppress the free exchange of ideas” and offered to provide questions in writing or appear by phone or teleconference.

“Timminco has gone to great lengths to appear to be open while refusing to provide the necessary support to substantiate [its] claims,” he wrote. “This I was looking forward to examining any new specifics in a forum where vague generalities should not be tolerated and where the claims’ veracity should be discussed.”

Neither Øye nor Boisvert responded to calls or emails about the matter.

But Robert Dietrich, chief financial officer and executive vice president for finance at Timminco, called Asensio’s attendance of the conference “a nonissue.”

“In the grand scheme of things, this won’t change the world,” he said.

Dietrich, who isn’t participating in the conference, was unable to confirm whether Becancour had asked for Asensio to be barred from the conference, as Øye’s letter states. But he said decisions about attendance were most likely to be up to the conference organizers, rather than the speakers.

Still, Timminco is clearly no fan of Asensio’s.

“We took grave exception to comments he made about our company,” Dietrich said. “It’s no secret that the interest of Manuel Asensio and the company are opposite. We have different interests – we are trying to run our business and he has an interest in being negative to our company. Why would we care too much about what he does or doesn’t do?”

In the last couple of months, the company had announced silicon supply agreements with Calisolar, Canadian Solar, Q-Cells and Solar Power Industries (see Timminco Shares Down Despite Deal With Canadian Solar).

In May, Timminco said that an independent review by Photon Consulting had verified its claims. Meanwhile, a story in the Globe and Mail that month suggested the stock could be overvalued.

Earlier this month, Timminco filed a lawsuit against a fund manager, Ravi Sood, and his firm, Lawrence Asset Management, for libel after Sood allegedly called the company “virtually worthless” (see Timminco Sues for Libel). And the Financial Post reported that two enforcement agencies, the Ontario Securities Commission and the Integrated Market Enforcement Team, are investigating trading in Timminco shares.