In many industries, the blending of particulate material, for example, powders is often critical to the performance or desired characteristics of the resulting product, for example, the blending of powders to make concrete, the blending of pharmaceuticals, the blending of food ingredients, or the blending of ceramics, among other products. However, the blending equipment typically used to blend these and otherparticulate materials typically have the disadvantages of producing lack of uniform particle distribution in the product, sensitivity to particle size, and the excess generation and loss of fine particles in the product. This invention is directed to a device that is an extremely versatile fluid-particle contacting system that can be used to perform a wide variety of physical, chemical, and biodegradable operations (particlemixing, particle coating, water treatment, catalytic reactions, etc.). It consists of a pressure regulated riser, a particle separator and a downward moving packed bed. Particles can experience a single pass or be recycled as many times as required. A unique property of the device is its ability to simultaneously vary the particle velocity and the solids fraction (in the riser) to provide optimum processing conditions. The process combustion control system provides the means for the device to operate as many as three different operations in the unit. The device can be operated as a gas-solid, liquid-solid, or three phase contactor. Particles can be circulated or transported with low pressure drop.