For many companies the cleaning of components such as powder coated & E-Dip hooks, floor grates, filters, spray nozzles, spinning plates and screws which are contaminated by paint, plastics, rubber or powder is a costly and time consuming process. Modern coatings and plastics bond very strongly to surfaces with a high degree of chemical resistance that renders customary cleaning and stripping methods ineffective. Manual chipping, parts burning, chemical stripping, blasting, high pressure water jet, and hammering are time consuming and inadequate. More stringent environmental regulations and the desire for better working conditions will result in close scrutiny or even discontinuation of many of these customary cleaning and stripping methods in future.
The fluid Clean fluidized bed installations are a practical, modern and environmentally-conscious alternative to outdated cleaning techniques.
- Cured or uncured paint removal from jigs, hangers, fixtures and gratings in paint shop.
- Powder removal from jigs & fixtures.
- Rubber denuding from metal.
- Aluminum de-coring from castings.
- Plastic removal from breaker plate, nozzles, polymer screws., etc.
Metal components contaminated by organic material (paints, powder, plastics and rubber) are stacked in a basket and immersed in the heated fluidized bed by an integrated lifting system. Organic substances are transformed from a solid to a gaseous form as a result of contact with the hot sand. The gases rise out of the fluidized bed, are combusted in the integral afterburner, then discharged and subsequently treated in an appropriate manner. After 30-60 minutes, the basket is lifted from the fluidized bed. The metal items are now cleaned. After cooling down, the clean items can be re-introduced into the industrial production process. In some cases the items may need a short post-treatment.
The next load of contaminated items can be placed in the bed immediately after the removal of the basket of cleaned items.
PRINCIPLE OF OPERATION
Fluid Clean is a direct heat process with integral thermal oxidation providing fast cleaning cycle times. A Fluidised bed insulated tank is filled with calibrated quartz sand that is fluidized by primary air blown into the bed at the bottom via air distribution system. Natural gas (or propane) is mixed into that air and as the mixture emerges from the sand, it is ignited by a pilot burner.
The low speed of the air through the sand mass causes a flame to spread over the complete surface of the fluidized bed. The contact of the flame with the fluidized sand provides excellent heat transfer. This action causes the fluidized sand to heat up to a controlled homogeneous temperature. The quartz sand temperature can be adjusted (315° – 537°C) using an automatic temperature regulator that controls the gas flow.
The phenomenon of fluidization makes it possible to totally immerse the parts to be cleaned in the hot quartz sand, where gasification of the organic impurities on the parts occurs. The released pyrolysis-gases are destroyed in the post-combustion chamber together with the combustion of the gas-air mixture. Additional or “secondary” air is injected tangentially into the post-combustion chamber ensuring better combustion of the pyrolysis-gases and gas-air mixture. The permanent gas flame on the surface of the bed guarantees the ignition of this mixture.
- Fluidized bed has long operating life
- Cold gas/air distribution system
- Direct combustion at the bed’s upper surface
- Compact construction
Fluidized Bed Filling
- Graded silica sand, Si02
- Original filling and reserve are included with machine shipment
Fluidized Bed Construction
- Outside casing in carbon steel
- Interior stainless steel
- Operating temperatures-300° to 550°C
- The fluidized bed employs an efficient direct gas heat process assuring short heat-up times and homogeneous temperatures throughout the fluidized bed. The direct heating method allows direct recovery of process-heat, which guarantees low energy-cost and eliminates the need to preheat incoming fluidization air. The installation employs its own air blower for the air-gas mixture pressure blown through the multi-tubular distributor system, which is embedded in a layer of mineral insulating material.
The fluidized bed is equipped with a high hood designed cover (ICV), which allows the basket to be set on top of the sand bed and the cover to be closed completely before the bed is fluidized and the parts sink in the hot sand. Opening and closing the cover is accomplished by pneumatic cylinders controlled via the control panel.
Post Combustion of the Flue Gases
Paint or plastic consist of organic components (polymers, solvents, etc.) and inorganic substances (pigments, fillers, etc.). In the hot fluidized bed, the organic components will be transformed into flue gases. These flue gases rise from the fluidized bed and are burned by a flame at the surface of the bed and are transformed into water vapor and CO2. Every installation is equipped with this system of direct combustion in the fluidized bed. All discharged process gases are immediately burned so that the transport of explosive gases is impossible (intrinsic safety). The combustion energy from these gases is immediately utilized to heat the sand mass (energy recovery).
Cyclone Battery (De-dusting of Flue Gases)
The fluid Clean flue gas cleaning consists of one or more integrated high performance cyclones. The flue gases that enter the cyclones are forced to undergo a number of turns due to the design of the cyclone, this combined with a downward flow at the outside, followed by an upward flow in the centre to the outlet. During these induced developments (vortex), the particles are forced to the wall of the cyclone by the centrifugal force and these then fall into the collector reservoir under the cyclone. In this way, the particulate matter is removed from the flue gas flow.
Purity of flue gases
For the combination of this basic machine (type B/ICV) and flue gas treatment (type- Cyclone Battery), the degree of purity of the flue gases that emerge from the exhaust fans should conform to Environmental Data Sheet. The emission needs to guarantee the normal operation of the installation and its correct regulation as well as appropriate maintenance and not exceeding the normal capacity.
For the standard combination offered, the noise level with normal operation at the operator’s position is lower than (the legislative) 85dBA.
For environments with specific requirements, additional noise insulation or shielding can always be provided.
Capacity: The capacity of installation is the quantity of organic material, which can be removed in one hour without overloading the machine. Capacity also depends on many factors such as nature of the organic material, calorific values, quantity of solvents, rate of gasification, layer thickness, amount of steel in the carrier, stacking pattern, treatment temperature, pre-treatment of the pieces and cycle duration.
The amount of paint depends on the calorific value of paint and it varies from one plant to the other. However, it can be referred to that wet paint which consists of more flammable liquid like thinner and solvent like those on paint booth grates will have a higher reaction rate and hence less amount can be put when compared to cured paint. An important part of the commissioning is to determine the calorific value of both cured and wet paint. As a result, we can have a more accurate calculation of paint quantity and number of parts to be cleaned to prevent overloading phenomenon.
Loading Basket: Hinged Front Doors for easier accessibility during loading or unloading of the basket.
Features: Grid type bottom; detachable and replaceable bottom and side panels; and swing aside crane hooks for easier accessibility during loading and unloading.
Hoisting System: For the safe operation and security of the operator, there is a three rail scissors hoisting system with single-hand electrical operation. The scissors system enables the loading basket to be constantly maintained in a fully horizontal position while being positioned in the fluidized bed. Manual contact with hot parts or basket is unnecessary. Columns anchored to the floor support the hoisting system and support structure. The advantages are accurate positioning of basket in the installation; no hand contact with hot parts; and basket remains fully horizontal.
Safety Equipment: Standard package includes safety equipment – Hard hat (1) with Plexiglas face screen; Pair (1) of heat-resistant gloves; and Leather apron (1).
Some advantages of thermal cleaning – Low operating cost due to short cycle times and low maintenance & reduced waste disposal; Easy operating system with minimum labour cost; No abrasive damage to parts being cleaned; Use of sand as medium ensures maintaining of precise temperatures and minimizing risk of annealing parts; Friction of sand in fluidized bed eliminates most ash on parts being cleaned; Redundant built-in safety checks and operator procedures assures safe environment; Durable and Reliable Machine suitable for operating 24hrs x 7 days/week; No health hazard; no toxic chemical involved and Negligible inventory of spare parts.Nitin Rathod, Divisional Manager-Projects Sales, Jost’s Engineering Company Ltd-Industrial Finishing Division (www.josts.com)