Filling process for recovering coal pillars by filling goaf with paste

The invention provides a filling process for recovering coal pillars by filling a goaf with paste. The filling process comprises three parts: preparing filling paste; conveying the paste via a pipe; and filling the goaf with the paste. The adopted filling paste comprises the following raw materials in percentage by weight: 40%-70% of aeolian sand, 10%-25% of coal ash, 3%-10% of cementing materials, 0.4%-1% of additive and 10%-30% of water. In the filling process, the goaf filling part comprises the procedures of primary filling and secondary filling, wherein, the coal pillars are recovered after primary filling; the whole goaf is fully filled after secondary filling; and roof-contacted supplementary filling is carried out in each filling procedure. The filling process has the advantages that the problems of filling the goaf formed after pillar-support mining and recovering the coal pillars are solved, the mining area environment can be protected more effectively, the increasingly exhausted coal resources are saved, and the filling cost is lowered.