The cyclone is a simple device, which causes the centrifugal separation of materials in a fluid stream. These materials may be particles of solid, bubbles of gas or immiscible liquids. Cyclone separator, due to relative simplicity to fabricate, low cost to operate, and well adaptability to extremely harsh conditions has become one of the most important particle removal devices. Especially, nowadays because of stringent environmental regulations cyclone is becoming the best alternative for gas scrubbers and this has opened a wide application for this equipment. Many industries could then use this low investment and operating cost equipment with the required efficiency to avoid having to resort to equipments with much higher capital, operating, or maintenance costs, such as venturis, scrubbers and bag filters.

The cyclone utilizes the energy obtained from fluid pressure to create rotational fluid motion. This rotational motion causes the materials suspended in the fluid to separate from one another or from the fluid quickly due to the centrifugal force. The rotation is produced by the tangential or involuted introduction of fluid into the vessel.

There are many design and operation parameters that affect separation efficiency such as cyclone geometry, fluid velocity and stagnation velocity. The most important trade-off in cyclone design is that high efficiency separation results in high pressure drop and hence high operational costs. Based on fluid throughput when a single cyclone does not provide the required efficiency, one or multi cyclones are arranged to meet the separation requirements. In this study we did a mixed integer nonlinear programming to solve the cyclone problem in order to find the optimal multicyclone geometry and operational specifications in order to reach the desired separation requirement while having the minimum pressure drop.