Getting refractive particle

Hello,

i've just read the other topics about it, but i didn't found an answer : i want to create a heat effect, so i made some tests, but i get to the same problem in every case




The particles seems to ignore each others on refraction, causing this "overlapping" issue. I tried to modify the blending option, to use a normal blend, but i always get those square masks. I know that my nodes are probably very bad, but is the system particle adapted to what i'm trying to do ?

Thank you