Mike, I also feel prosoco would be the choice. 12 years ago I worked with a masonry Co. before starting my pressure washing biz. We cleaned 6 very larged brick buildings on the Capital Green here in Dover, De. We used a hot pressure washer and prosoco restoration cleaner. The job came out great. The buildings were very old and were covered with mildew and black pollution stains from close by industrial plants. We wet the walls applied cleaner with stiff bristled brushes then hot water rinsed at 3000 psi and the buildings came out great. The cleaner looked like milk but it is pretty nasty if it gets on your skin. We wore rubber gloves, rainsuits and goggles. I think you can find what your looking for at www.prosoco.com. Good luck and Im not a salesman just telling you what worked for us and what may work for you. I would imagine that it will work through a chemical injector and allow to dwell a few mins but i would still talk to one of their reps and do some testing.
Mike, you may want to talk to Jim Dietrich at Dietrich Chemicals. They sell similar restoration products and are very good at working with you one-on-one over the phone or by email - more so than Prosoco. I really can't tell by the picture what the main problem is - soot or whatever. That affects significantly the type of chemical to use. In most cases you will want to test 2-4 materials and see what it will take to get the cleaning accomplished.
I have been looking at doing restoration work, and if you can give me any tips on how to find this type of business they would be appreciated. Bill