除灰点较多而输送距离又较远时，可采用正负压联合气力除灰系统，或采用空气斜槽与正压式联合气力除灰系统。（)

A.正压浓项气力除灰

B.正压稀相气力除灰

C.负压稀项气力除灰

D.水力除灰

A.1000m

B.1200

C.800

D.1500

A.5%

B.8%

C.10%

D.12%

A.正压

B.微正压

C.负压

D.微负压

A.5%

B.6%

C.7%

D.8%