Thermal-Desorber system specification
Thermo desorption system can be supplied as mobile or stationary. Mobile system designed on two tracks and contains power generator which provide electric power required for system operation. System can be erected on site during 4-5 working days. Stationary unit will require power supply connection and building to set up system. All types of system are explosion and fire proof systems. Whole system consists of several units. Major units includes: material preparation unit, thermal extraction unit, environmental control unit and quench condensing scrubber.
Specification of system's main units
(Data provided for unit with throughput of 2 tons per hour. Depending of required throughput parameters of system can vary.)
| Material Preparation unit | Loading hopper with conveyor. Batch mixer. Chain transfer conveyor. |
|---|---|
| Feeding system | Live bottom feeder with two screws. Transporting screw conveyor and injecting screw conveyor. |
| Thermal extractor and combustion chamber | Combustion chamber - oxidizer. Indirect heated rotating kiln drum. Kiln plenum. Unloading hood. |
| Unloading and cooling system with environmental control | Thermal extractor water cooled unloading conveyor. Dust removal and collecting system. |
| Quench condensing scrubber | Direct contact quench condensing scrubber. Two mist eliminators. Two stage oil filtration system. |
| Scrubber cleaning tool | Hydraulic power pack. Hydraulic driven scrubber inlet pipe cleaning tool. |
| Main air blowers | Induced draft fan. Burner air blower. Quench air blower. |
| Emergency quench system | Nitrogen tank. Nitrogen supply lines. Monitoring systems and nitrogen flow control solenoid valves. |
| Emergency standby electric generator | Diesel power generator. Fuel tank. |
| Control system | Control system with graphic UI to monitor ant control system operation. |
Picture of mobile thermo desorption system
Material preparation unit
From loading hopper source material is transported to batch mixer by belt conveyor. Batch mixer (paddle type) mixes and averages source material to provide smooth system operation and facilitate material handling by feeding system. Chain conveyor transfer mixed material from mixer to live bottom feeder's hopper.
^TopUnloading and cooling system with environmental control
Unloading system is presented by inclined tubular screw conveyor with. Conveyor have water cooled jacket and tubular shaft. It is designed so that the ash forms a seal to prevent air from entering into the process.
Because processed material can contain fine particles, it is possible that air can be contaminated with dust when material is unloaded from system. To prevent air pollution system is equipped with air filter unit that collect dust by air filter from unloading zone through dust hood. Filter uses conical filter cartridges and has self-cleaning feature.
^ TopThermal extractor and combustion chamber
Proposed system is indirect heated thermal extractor unit. Source material is heated during contact with hot kiln shell which is heated by hot gases generated in combustion chamber.
Rotated kiln drum is equipped with mechanical system that prevents material build up inside kiln and it agglomeration. In addition it increases heat transfer and material mixing which provide better extraction of hydrocarbons from material. Material inside kiln in conveyed by means of drum rotation and slope. Processed material is unloaded at the unloading hood by a screw conveyor.
Because this is indirect firing kiln and special designed hoods and conveyors prevents air from entering inside kiln. By eliminating oxygen inside the kiln, the reaction is limited to the vaporization of the water and hydrocarbons. Kiln drum is insulated by high quality ceramic fiber that provides low system weight and high system mobility.
Part of gases extracted from source material and not condensed in scrubber are burned in combustion chamber lowering fuel consumption of the system. The process induced draft fan draws the products of combustion through the kiln combustion chamber. This heats the kiln and its contents and cools the gases. The cooled combustion gases are then sent to the atmosphere through the induced draft fan. The gases vaporized in the kiln are sent to the direct contact quench scrubber. The quench scrubber cools, condenses, and cleans the gases. The gases that condense below operating temperature of the quench scrubber are recovered in the scrubbing media (oil). The heavy hydrocarbons and the particulate are captured in the oil.
^ TopQuench condensing scrubber
The quench scrubber cools, condenses, and cleans the gases. The gases that condense below operating temperature of the quench scrubber are recovered in the scrubbing media (oil). The heavy hydrocarbons and the particulate are captured in the oil.
The scrubber consists of a vertical carbon steel vessel with multiple spray nozzles. The gas flow is counter-current to the oil flow. The oil is recirculated by a special low inlet head pump capable of handling hot oil. Dual parallel mist eliminators are provided to prevent liquid carry-over into the combustion chamber. A two stage filter system removes particulate from the oil. During system operation oil volume is constantly growing (depending of hydrocarbons content in source material).
Excess oil is flowing from the scrubber through loop seal to oil collection tank. From collection tank oil is pumped to centrifuge which removes particulate from the oil and adds clean oil to the scrubber. Part of gases extracted from source material and not condensed in scrubber are burned in combustion chamber lowering fuel consumption of the system. Dual parallel mist eliminators are provided to prevent liquid carry-over into the combustion chamber.
Main air blowers
An induced draft fan is located at the exit of the combustion chamber. It has sufficient volume and pressure to overcome the internal resistance of the combustion chamber, burner, piping and scrubber. A process controller and a pressure transmitter installed in the discharge hood will monitor and maintain kiln pressure.
Burner blower supply combustion chamber with air and provides additional air to limit combustion chamber temperature. It has two control valves to control air flow to the burner and combustion chamber. In addition to limiting combustion chamber temperature second air control valve is used to maintain minimal oxygen level in combustion gases.
Quench air blower provides air flow to the end of combustion chamber, this allow to control heat transfer to kiln drum and material inside kiln. Air flow control valve is installed in the quench air line, which allows controlling temperature of processed material and venting gases in the kiln.
^ TopEmergency quench system
In case of emergency (rapid temperature growth inside kiln or scrubber) nitrogen quench system is used. Nitrogen can be introduced inside kiln from the loading end and from unloading end. Nitrogen is feed automatically depending on process temperature using solenoid valves. For unloading end nitrogen is preheated in tubular heat exchanger at the end of the combustion chamber and is flow is controlled by float control valve and flow indicator.
Feeding system
Source material (cake after centrifuge, oil sludge or contaminated soil) is placed in the live bottom feeder. The live bottom feeder has a variable speed drive and a pair of counter-rotating screws that meter the material to the feed transfer conveyor. Live bottom feeder has adjustable speed.
The feed transfer conveyor is an inclined tubular screw conveyor that transfers the material from the live bottom feeder to the feed injection screw conveyor. The feed injection conveyor is a special tubular screw conveyor with a pair of external bearings and a cantilever drive shaft. It is designed so that the conveyed material forms a seal to keep air out of the process. The feed injection conveyor feeds the material into the indirect fired rotary kiln.
^ TopControl system
Control system provides operator control of process either in manual or automatic mode. Control system has graphic user friendly interface and provides alarm messages and indication. Control system based on Allen-Bradley SLC-500 controllers.
Control system monitors all process parameters, including:
- Combustion chamber temperature;
- Kiln plenum temperature;
- Combustion chamber oxygen level;
- Kiln vent gas temperature;
- Kiln material exit temperature;
- Scrubbers oil temperature;
- Scrubber vent gas exit temperature;
- Scrubber oil level;
- Oil level in oil collecting tank.
In addition control system provides:
- Automated system startup and burner startup;
- System warm up;
- Automated process control;
- Automated system shut down.
