Embodiments of the present invention include a method and system for blending multi-component granular compositions such as proppant used in hydraulic fracturing in well drilling. The system includes the control and management of an on-site storage system for each of the components, regulating the delivery of specified quantities of each component to a blender, and coordinating the flow of materials into and out of the blender.

A mixing apparatus includes a material supply line, a mixing tank, a stirring device, and a transportation line. The material supply line supplies two or more kinds of materials including a liquid. The mixing tank accommodates the two or more kinds of materials that have been supplied. The stirring device stirs a mixed solution of the two or more kinds of materials inside the mixing tank. The transportation line transports the mixed solution inside the mixing tank to an outside of the mixing tank. The mixing apparatus maintains a liquid level height of the mixed solution inside the mixing tank at a level falling within a predetermined range by controlling at least one of a supply amount of the two or more kinds of materials to be supplied into the mixing tank and a transportation amount of the mixed solution to be transported to the outside of the mixing tank.

Proposed is a fluid metering device including a mixer receiving fluid in a storage tank, a metering tank metering and supplying the fluid to the mixer, a first transfer device transferring the fluid from the storage tank to the metering tank, a second transfer device transferring an input of the metered fluid to the mixer, a sensor measuring a fluid mass in the metering tank, and a controller stopping the first transfer device and activating the second transfer device with the initial remaining fluid greater than the input, and allowing the second transfer device to transfer the amount of input from the metering tank to the mixer, based on the fluid mass from the sensor and preset first and second metering set values, so that it is possible to quickly input a desired amount of fluid step by step, and to precisely adjust a fluid input into a final process.