Disclosed are a solution preparation device, a solution replacement system and a solution replacement method. The solution preparation device comprises a liquid container, a powder container, an upper cover and a controller; the liquid container is provided with a detection element for detecting a specific parameter of a solution; the powder container is arranged above the liquid container, and the upper cover covers a top end of the powder container to form a material holding cavity for placing a powder, a bottom end of the powder container is provided with a material discharge port through which the powder in the material holding cavity enters the liquid container. The solution preparation device further comprises a stopper for blocking the material discharge port, the controller controls the stopper according to the specific parameter to realize opening and closing of the material discharge port.

The invention provides a fluid mixer with a fluid reservoir, a ring within the fluid reservoir, a stirrer rotatably coupled in the ring, and a motor to rotate the stirrer. The ring has a wall defining an inner and outer portion of the fluid reservoir, with wall cutouts that allow fluid to pass from the inner portion to the outer portion. The stirrer has a center and multiple paddles, and the rear surface of a first paddle and the front surface of a second paddle define a mixing space, and rotation of the paddles pushes a fluid from the mixing space through one of the cutouts into the outer portion. The invention also provides a method of mixing a fluid, including introducing liquid into a fluid reservoir and a powder into a powder dispenser, activating a stirrer, and dispensing the powder into the liquid while the stirrer is rotating.

Provided is a proportioner having one or more proportioner inlets to receive a common concentrated proppant fluid comprising a proppant, two or more flow lines fluidly connected to the one or more proportioner inlets, two or more proportioner outlets, each of the two or more proportioner outlets associated with one of the two or more flow lines, one or more fluid inlets, each of the one or more fluid inlets for introducing a proppant-free fluid to the proportioner, and a metering system associated with at least one of the two or more flow lines. Each metering system is positioned upstream of the proportioner outlet of the flow line with which it is associated and is fluidly connected with at least one of the one or more fluid inlets for proportioning one of the proppant-free fluids into the associated flow line at an injection point.