Study on the Atomization and Dust-Reduction Performance of a New Type of External Pneumatic Vortex Fog Curtain Dust Removal Device in Fully Mechanized Excavation Face

Table 3

Sampling concentration of respirable dust.

Condition	Project
	Measurement point	Dwell time (min)	Flow (L·min^−1)	Filter weight (mg)	Filter weight gai (mg)	Net weight (mg)	Respirable dust concentration (mg·m^−3)
Condition 1	1	—	—	—	—	—	135.5
Condition 1	2	—	—	—	—	—	70.2
Condition 2 (1)	1	2	20	89.8	90.1	0.3	7.5
Condition 2 (2)	2	2	20	87.3	87.4	0.1	2.5
Condition 2 (1)	1	2	20	85.4	85.6	0.2	5
Condition 2 (2)	2	2	20	89.9	90.1	0.2	5
Condition 2 (1)	1	2	20	87.3	87.4	0.1	2.5
Condition 2 (2)	2	2	20	85.7	86.1	0.4	10