THERMAL OIL RECOVERY SYSTEM (THOR)

TECHNICAL SPECIFICATIONS

General

The skid mounted THOR System is capable of processing up to 3000 metric tons per month of diesel oil-based mud drill cuttings containing a maximum of 25% oil and 25% water and 50% solids by volume.  Processing of contaminated soils – production can be as high as 8000 to 10,000 metric tons per month depending on moisture content.  The processed solids will have less than 1% TPH when tested with the EPA 8015 protocol or similar. The system is designed for a maximum solids discharge of 700-800 degrees F., If needed.  The area needed for processing is approximately 100 ft x 90 ft not including space for raw storage or processed storage.

Feed system

The feed mix is introduced into the system through a vibrating grid to remove 4‑in and larger solids.  A feed hopper between the vibrating grid and the feed screw holds the feed mix and prevents the intrusion of air into the dryer drum.  Single 24-in variable-speed Feeder screw for slow rotation and precise feeding.  25 HP VFD controlled feeder screw drive utilizing a dual gearbox arrangement. 

All mounted on a separate Feeder skid attached to the dryer skid.
 

Dryer

Indirect fired with four (4) 5MM BTU/hr burners.  Furnace separated into two 10MM BTU/hr zones for better drying control. The Furnace length is 30 ft.  The drum is 7ft in diameter x 40ft long. It is made from a high-strength stainless steel alloy for extended service at elevated temperatures. 

Angular flights are used to get the material into the drum following the feeder screw. Chains are used to break up the solids and assist with heat conduction. Lifting plates are used in the hot section to roll the material for final drying. A center dam is used to add to retention time. Rock lifting devices are provided adjacent to the center and discharge dams.  40 HP VFD controlled electric motor coupled to a helical gearbox provide variable drum rotation from one (1) to six (6) RPM at full load.  An air/gear motor is provided so that drum rotation can be continued should a power failure occur.  Piping is provided that allows vapors to be pulled from either the feed end or discharge end of the dryer.  The firebox is built to withstand 2400°F and contains access panels, removable top, flame view ports to check flame trajectory and thermocouples to check firebox, stack and drum skin temperatures.  Dual combustion air fans and associated controls, one mounted on each end of the dryer unit, provide air and fuel to the four (4) 5MM BTU/hr burners. 

Triple layered stainless/composite leaf seals are used to seal each end of the furnace.  Triple layered stainless/composite leaf seal, with a water spray fire quench system, are used to make the drum end cover seal at the discharge end of the drum.  Furnace stacks are made from a high-strength stainless steel alloy for extended service at elevated temperatures.

Solids discharge and hydration

A 16-in screw conveyor is used to remove the solids from the discharge end. A thermocouple is mounted in the discharge end to check discharge dirt temperature.  The 16-in screw conveyor deposits the hot dirt into an 18-in screw conveyor for transfer to the rehydration skid.  The 18-in screw conveyor deposits the hot solids into dual 12-in double tipping valves on the rehydration skid to prevent air intrusion into the dryer.  From the double tipping valve the solids enter a dual-shafted pugmill, which mixes water with the solids to cool and rehydrate the solids.  All screw conveyors are oversized to prevent stoppages and designed for high- temperature operation.

Vapor recovery and condensation

A quench tank is used as the initial mechanism to cool the vapor stream and remove entrained solids from the produced gasses.  Cooling water is sprayed on the vapor stream in a specially designed quench tank where most of the hydrocarbon vapors are condensed along with some of the water vapor.  In addition the entrained solids are removed by the small water droplets produced by the spray system.  Recirculated water is pumped thru a series of spray nozzles to provide evaporative cooling in the quench tank and remove the solids.  Cooling water is brought to the quench spray system from the weir separator tank and from the recovered water tank after passing thru a plate and frame heat exchanger where the recirculated water is cooled by water from the cooling tower.  After passing through the quench tank, the uncondensed gasses move through the shell and tube heat exchanger where additional cooling takes place bringing the vapor stream to its dew point temperature and condensing more water vapor and uncondensed hydrocarbons.  The uncondensed vapors are directed to the oxidation system.  The condensed liquids from the quench system and from the condenser are directed to the water treatment system.  A cooling tower is used to remove the heat from the system.  The cooling tower, heat exchanger, and condenser system is capable of removing 12MM BTU/hr of heat from the system at maximum average dew point temperatures.  Normal heat removal requirement are approximately 6.5MM BTU/hr.  At 6.5MM BTU/hr heat removal the cooling tower consumes about 20 gpm of makeup water.  An Induced Draft Fan (IDF) moves the vapor and gasses through the system. 

Oxidation system
A 5MM BTU/hr max thermal oxidation system destroys any remaining uncondensed vapors. The thermal oxidizer unit burns only a small amount of fuel and greatly improves the safety of the system and reduces air emissions to meet local codes.  For safety, dual redundant flame arresters provide isolation between the thermal oxidizer and the other upstream systems.

Water treatment system

A simple weir tank is used to make the initial separation of the oily emulsion from the water and the unemulsified solids.  The oily emulsion and the unemulsified solids are directed to a high speed and high G force centrifuge where the solids are removed from the system.  The liquid faction is returned to the water treatment system.  A weir tank and a coalescing media oil/water separator are used to remove the recovered oil from the water.  The recovered oil is sent to a retention tank for final polishing and settling before it is sent to storage.  The water is recirculated back to the quench system after it is pumped through a plate and frame heat exchanger to remove the heat.   Excess water is directed to a recovered water tank where additional cooling takes place. This water is used to re-hydrate the processed solids.

Control system

The skid-mounted, climate-controlled control house is 33.5 ft long by 8.5 ft wide by 13.5 ft high. It has dual personnel doors, one on each side of the control house.  Controls furnished for 460-vac/60Hz/3‑phase power.  Multi-station motor control center provides control for all motors.   75KVA Delta-Wye transformer and distribution panel provides power for operator controls and lighting.  Variable frequency drives provided for the drum drive, feed augur, induced draft fan, and thermal oxidizer dilution air fan.  Large windows on one side and adjoining end for observing TDU plant operation.  Four data recorders providing 48 analog input channels for recording signals from thermocouples, flow meters, motor amp transmitters, and pressure sensors. Optional Ethernet connection for data transfer to PC is available.  Operator control panels for motor stop/start push buttons, VFD controls, burner controls, motion detectors, data recording, and valve control.   Emergency Stop buttons for motor control center and burner controls.

Utilities

Water – 25gpm maximum
Electrical power - 500 kW @ 0.8 P.F.
Air – 150 ACFM @ 100 psi minimum