How to get rid of a burned coal smell that's coming to my flat?
In terms of plant answers,  mother in law tongue is one of 15 plants recommended by NASA for air purification. Plus this plant releases oxygen at night as well as during that daytime(good plant to keep near your bed). I have this plant in my dorm room, works wonders. 

Additionally this site will give a basic outline of a few others that work well. 

In case you need more evidence, this is a CAM plant which means the plant separates the two photosynthesis pathways and performs all light dependent reactions during the day and stores the products up for use at night when the light dependent reactions take place, called Calvin's cycle. Ergo, this plant is awesome.

*Verdict, get some mother in law tongue plants, they look good, NASA proven, they can take some neglect, and they don't rack up your electric bill.