I have been doing some research on black liquor and can't seem to find any thermal properties. The only thing I've come across is the vicosity (3 CP @ 185 F). Is there a website to use for reference when the thermal properties of a substance is needed?
I just skimmed the recovery boiler section of the B&W steam book and there is qutie a bit of info there.
I saw one figure of ~6,000 btu/lb of the solids. I'm not sure how useful that number itself is to you but I'd look at the book anyway. The book itself is fairly cheap and can be bought through their webpage.
For what percent solids are you looking for that information? My B&W steam that I have here at home is over 40 years old (can that be right?) and back when it was written they didn't go much above 65% solids. Last I heard the concentrators added to the evap trains were getting it above 80%. I would think the thermal properties would have to have changed due to that.
That sounds about like the concentration that would come off of the brown stock washers. At that point unless you needed to be super sophisticated for some reason, I'd treat that as water and use water thermal properties-maybe muddy water.