A system for controlling gas leakage in a solids delivery system is provided. The system includes a bulk solids pump comprising an inlet for a particulate material and an outlet for discharge of said particulate material. The system also includes a buffer gas channel configured to impede backflow of process gas into the bulk solids pump, such as from a downstream system or process. The system further includes a pressure differential system configured to control a flow rate of the buffer gas and maintain a positive differential in pressure between the buffer gas and the process gas.