Passive injection of a chemical solution into a process stream

A continuous passive injection system for dispensing a chemical solution at a slow, controlled rate into a flowing process stream pressurized by a process stream pump, the system comprising:

• A bypass loop comprising:
• a bypass loop inlet fluidly coupled to the process stream downstream of said process stream pump, having a bypass loop inlet isolation valve;
• a bypass loop outlet fluidly coupled to the process stream downstream of the bypass loop inlet, having at least one bypass loop outlet isolation valve;
• and
• a pressure control valve located along the bypass loop between the bypass loop inlet isolation valve and the at least one bypass loop outlet isolation valve;
• wherein the fluid pressure in the process stream at the bypass loop outlet is lower than the fluid pressure in the process stream at the bypass loop inlet;
• a chemical injection branch comprising:
• a chemical injection branch inlet fluidly coupled to the bypass loop immediately downstream of the bypass loop inlet isolation valve;
• a chemical injection branch outlet fluidly coupled to the bypass loop downstream of the pressure control valve and upstream of the at least one bypass loop outlet isolation valve;
• a pressure vessel comprising at least one pressure vessel flange and a separator, the separator forming a movable seal within the pressure vessel between a pressurizing fluid portion and a chemical solution portion, the pressurizing fluid portion being fluidly connected to the chemical injection branch inlet and the chemical injection portion being fluidly connected to the chemical injection branch outlet;
• a pressure vessel vent line upstream of the pressure vessel, having a vent isolation valve
• a pressure vessel fill line downstream of the pressure vessel, having a fill isolation valve;
• and
• a capillary flow control tube located upstream of the pressure vessel vent line or downstream of the pressure vessel fill line and having a differential pressure gauge;
• wherein the rate of chemical injection is controlled by the pressure control valve, which adjusts a differential pressure across the capillary flow control tube, the differential pressure across the capillary flow control tube controlling a differential pressure across the separator, which causes the separator to inject the chemical solution from the chemical solution portion of the pressure vessel into the chemical injection branch outlet, the chemical solution then flows through the bypass loop outlet and into the process stream.