Contaminant control system in an evaporative water treating system
A contaminant control system for an evaporative water purification process as deployed in a steam assisted gravity drainage process facility for in situ heavy oil recovery, The contaminant control system is specifically designed to simultaneously control silica, hardness and oil contaminant present in the evaporator feed water to prevent fouling of heat exchange surfaces and improve system reliability and can be applied to many evaporator designs available on the market.
1. A closed loop contaminant control system for an evaporative water purification process in an SAGD (Steam Assisted Gravity Drainage) system for a heavy oil recovery facility, the system comprising:
an evaporator including a tube side for producing steam and a shell side for producing distilled water, a bottom, a water inlet, at least one distilled water discharge and at least one oil and brine water discharge, a sump provided at the bottom proximate said at least one oil and brine water discharge thereof, an oil skimming weir dividing the sump into a main sump and a blowdown sump, said at least one oil and brine water discharge being located proximate said blowdown sump;
a distillate tank for receiving distilled water from said evaporator and for discharging distilled water where said distillate tank has a level controller for controlling 1) the energy supplied to the evaporator and 2) distilled water production;
a plurality of controllers comprising:
a distilled water flow meter located proximate the at least one distilled water discharge of said evaporator,
a blowdown flow meter measuring a flow from the main sump to the blowdown sump,
a cycle controller calculating a ratio between a distilled water flow and a blowdown flow;
a total flow controller for adjusting a flow of make-up water into said evaporator;
a hardness controller for providing a set point of the cycle controller affecting the flow of the make-up water into said evaporator; and
a pH controller for adjusting a flow of a caustic to the evaporator sump; wherein a set point for the pH controller is determined by silica concentration in the make-up water.
2. The system of claim 1 wherein the evaporator has three modes of operation:
1) a normal mode wherein the evaporator receives water from the evaporative water purification process, the blowdown sump discharges waste oil and brine, and the distillate tank discharges distilled water.
2) an idle mode wherein there is no flow in or out of the evaporator; and
3) a recycle mode wherein the distilled water is recycled into the water inlet of the evaporator.
3. The system of claim 1 wherein the weir separating the main sump and the blowdown sump further comprises a top and a bottom, said weir further comprising a v-notch located proximate the top.
4. The system of claim 3 wherein said weir is located in said sump such that any oil floating on top of the water in the main sump is continuously removed from the evaporator with the brine water.
5. A closed loop contaminant control system for an evaporative water purification process in an SAGD (Steam Assisted Gravity Drainage) system for a heavy oil recovery facility, the system comprising:
an evaporator including a tube side for producing steam and a shell side for producing distilled water, a bottom, a water inlet, at least one distilled water discharge and at least one oil and brine water discharge, a sump provided at the bottom proximate said at least one oil and brine water discharge thereof, an oil skimming weir dividing the sump into a main sump and a blowdown sump, said at least one oil and brine water discharge being located proximate said blowdown sump;
a distillate tank for receiving distilled water from said evaporator and for discharging distilled water where said distillate tank has a level controller for controlling 1) the energy supplied to the evaporator and 2) distilled water production;
wherein the weir comprises a v-notch cutout proximate an upper edge of the weir; and
a plurality of controllers for the system, wherein the plurality of controllers comprises:
a distilled water flow meter located proximate the at least one distilled water discharge of said evaporator,
a blowdown flow meter measuring a flow from the main sump to the blowdown sump,
a cycle controller calculating a ratio between a distilled water flow and a blowdown flow;
a total flow controller adapted to adjust a flow of make-up water into said evaporator;
a hardness controller for providing a set point of the cycle controller affecting the flow of the make-up water into said evaporator; and
a pH controller for adjusting a flow of a caustic to the evaporator sump; wherein a set point for the pH controller is determined by silica concentration in the make-up water.
6. The system of claim 5 wherein said weir is located in said sump such that any oil floating on top of the water in the main sump is continuously removed from the evaporator via the weir so as to retard foaming events in the evaporator.