I actually heard of people doing this several years ago. Since I live in the Northland I don't have access to pecan trees or the hulls. I'm sure some of the other fellas on this sight might have experience using the hulls.
OK, I can weigh in on this. It is true you can use pecan hulls for smoke but you do not want them to be used in any great quantity. There is a whole lot of oil in the shells and you can overdo it if you get too shell happy. There is a pecan processor down in Troy where my daughter goes to school. I asked them what they charged for hulls and I ended up with a tote sack for free. When I am doing ribs or chicken I toss in a generous handfull each hour while I am adding the next set of logs. You can smell the pecan easy enough. Hope this helps.
If it can't be smoked .... try frying it. It that don't work, it's probably best just left alone