氨合成塔中采取的双锥密封结构，属于（ ）结构。

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SQL Error: select id,body,options from ***_enewstiku where sourceid='24906' and id < 2125033 and id<>'2125033' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='24906' and id > 2125033 and id<>'2125033' order by id asc limit 5