Particulate matters, such as fly ash, play a crucial role in various applications like furnaces, gasifiers, power plants, and climate radiation, as they significantly impact heat transfer, particularly radiative heat transfer. The absorption and scattering properties of these matters affect the distribution of radiative energy, heat transfer rates, and temperature profiles. In the current study, we have examined the impact of anisotropic scattering by fly ash particles on radiative heat transfer. The spectral properties of fly ash particles has been calculated by lorenz-Mie theory for both uniform and non-uniform particle distributions. The finite angle method (FAM) is employed to solve the spectral radiation transfer equation (RTE) and the Line-by-line (LBL) method is used to account for the whole range of the thermal spectrum. Furthermore, to study the effect of particle size, three uniform particle clouds of different diameters are considered in this investigation. The radiative flux reduces drastically by not considering in-scattering. Moreover, the radiative flux is almost equal as particle size increases in the case of isotropic scattering. Furthermore, in the case of anisotropic scattering higher radiative heat flux is obtained for larger particles. The results show that anisotropic scattering and particle size can play an influential role in thermal radiation.