Targets & Objectives

Concentrated catalytic oxidation system will be installed to remove VOCs from the paint spraying process exhaust gas using a combination of wet scrubbing, overspray filter, activated carbon concentrator system and catalytic oxidation technologies. Organic-rich gas from paint spraying process will pass through wet scrubbers, overspray fabric filters and then into the activated carbon adsorption treatment system. A concentrator, consisting of several activated carbon adsorption beds which operate alternately in adsorption/desorption (or regeneration) mode, is used as a pre-treatment to effectively concentrate the mass of VOC originally contained within the original stream. Large volume exhaust air with diluted VOC levels is adsorbed with concentrator, and then the adsorbed VOC is desorbed/regenerated with high-temperature blast. This much smaller stream with concentrated VOC levels is then treated efficiently and economically using a small catalytic oxidiser. Furthermore, the temperature produced in the oxidiser is reused to heat the desorption air, contributing considerably to the reduction in the energy demand. As VOCs will be removed or degraded in the course of air flow and the amount of VOC emissions can be reduced.

Automatic screen printing machine with automatic alignment are installed to replace existing manual traditional screen printing machine to save ink/solvent and reduce VOC emissions The machine adopts programmable logic controller (PLC) and human-machine interface (HMI) as control system. The positioning method adopts servo motor and control to ensure high printing accuracy and production efficiency resulting in reduction of ink/solvent and electricity consumption. With enclosed chamber, solvents cannot evaporate and the condition of ink is more stable, which ensures a high quality products could be printed over extended periods. 

Exhaust air treatment system adopting chemical scrubbing will be installed to treat exhaust collected from paint spraying process to reduce VOC emissions. Organic-rich gas from spraying process is currently extracted by the exhaust fans and exhausted to the open air. To enhance VOC removal efficiency, the exhausted air will be treated by chemical scrubber. Inside the scrubber chamber, scrubber solution which can absorb VOC due to “like-dissolve-like” effect will be sprayed from the top. Two layers of small plastic balls were located below the sprinklers to increase surface area for VOC absorption. VOC-laden exhaust air will be driven into chemical scrubber chamber from below, comes into contact with the scrubber solution and VOC will be absorbed. The exhaust is then passed through a filter layer which retains liquid scrubber solution and released to open air. Scrubber solution will be collected in the recycling tank below, filtered then reused for scrubbing. The scrubber solution can be reused for few months, then collected and transferred to authorise contractor for further treatment.

Low-temperature plasma + UV photocatalytic treatment system will be installed to remove VOCs from exhaust air stream of printing process. Low-temperature plasma, which has a much lower energy requirement when compared to other oxidation technologies, is used to generate gas-phase active species and free radicals at near-ambient pressures and temperatures which can then degrade complex organic molecules into simpler, less hazardous organic molecules or even water and CO2. For better system performance and power/cost efficiency design, using special high-energy ultraviolet light beam irradiation malodorous gases, the organic or inorganic polymer molecular chain malodorous compounds are degraded into low molecular weight compounds, such as CO2, H2O, etc. The composite treatment systems using low-temperature plasma + UV photocatalytic technology is adopted to ensure that residual organics are captured prior to final discharge to ambient air and minimise consumed power for operation.

Selective Non-Catalytic Reduction (SNCR) system will be installed to existing thernal oil boilers to reduce NOx emission. SNCR is a low-cost but efficient post-combustion NOx reduction method, it reduces NOx through a cotrolled injection of aqueous ammonia or urea solution into the combustion flue gas at a temperature between 850 to 1,050 degree Celsius without the aid of catalyst. The solution then react with the nitrogen oxides formed in the combustion process to produce harmless water vapour and nitrogen gas.

UV photo-catalytic oxidation technology system will be installed to remove VOCs from exhaust air stream of injection moulding and soldering of plastic products manufacturing process. VOC-laden flue gas will be firstly treated by water scrubber and drying filtration to remove dust and impurities. Then the exhaust gas will be transferred into UV photo-catalytic oxidation chamber. UV radiation itself and ozone from oxygen generated by UV light will both degrade complex organic molecules into simpler, less hazardous organic molecules or even water and CO2. As organics will be removed or degraded in the course of air flow, the amount of VOC emissions can be reduced.

Exhaust air treatment system adopting UV photo-catalytic oxidation technology will be installed to remove VOCs from plastic package printing process. UV radiation itself and ozone from oxygen generated by UV light will both degrade complex organic molecules into simpler, less hazardous organic molecules or even water and CO2. As organics will be removed or degraded in the course of air flow, the amount of VOC emissions can be reduced.

Composite treatment system adopting UV photocatalytic oxidation + activated carbon technologies will be installed to remove VOCs from injection moulding process. The exhausted air will be treated by UV photocatalytic oxidation + activated carbon adsorption treatment. Exhaust air will first be collected and driven into a UV- photocatalytic oxidation system, in which UV photocatalytic oxidation (with Titanium Oxide as catalyst) reaction and ozone from oxygen generated by UV light will both degrade complex organic molecules into simpler, less hazardous organic molecules or even water and CO2. For better system performance, air stream leaving UV photocatalytic oxidation treatment will be further polished by an activated carbon filter, in which to capture the residual organics prior to final discharge to ambient air.

Composite exhaust air treatment systems using water scrubbing and UV-degradation technology will be installed to reduce VOC emissions from printing process of plastic products. To facilitate the overall system removal efficiency, organic-rich air will first be driven into water scrubber to remove dust and impurities. UV-degradation device assists in removing organic molecules in exhaust air. UV radiation itself and ozone from oxygen generated by UV light will both degrade complex organic molecules into simpler, less hazardous organic molecules or even water and CO2. As organics will be removed or degraded in the course of air flow, the amount of VOC emissions can be reduced.

UV-degradation treatment systems will be installed to remove VOCs from exhaust air stream emitted from plastic melting, extruding and cooling processing of plastic manufacturing process. VOC-laden flue gas will be firstly treated by wet scrubbing to remove dust and impurities. Then the water vapor and dust in organic air pass thought the oil mist centrifugal separator and parts of oil mist will be trapped by the oil mist and dust catcher. After that, the water vapor and organic air will be dehumidified before getting into UV-degradation chamber. UV radiation itself and ozone from oxygen generated by UV light will both degrade complex organic molecules into simpler, less hazardous organic molecules or even water and CO2. As organics will be removed or degraded in the course of air flow, the amount of VOC emissions can be reduced.

Composite treatment systems UV-degradation and activated carbon adsorption technologies to reduce VOC emissions from printing and screen printing process is installed. VOC-laden air will first be collected by extraction hoods and extracted into the UV-degradation system. Filter bed equipped at the inlet of the UV-degradation device assists in removing particulates in exhaust air. UV radiation itself and ozone from oxygen generated by UV light will both degrade complex organic molecules into simpler, less hazardous organic molecules or even water and CO2. For better system performance, air stream leaving UV-degradation device will be further polished by an activated carbon bed to capture residual organics prior to final discharge to ambient air.

Exhaust air treatment systems adopting zeolite adsorption and bag filter technology will be installed to remove VOCs from printing process. The raw material of artificial zeolite is paddy shell and each metric ton of artificial zeolite can adsorb 0.75-1 metric tons of VOC. In the adsorption chamber, the air is extracted by exhaust fan and negative pressure is generated inside pulsed bag filter. Due to small size, the zeolite will adhere to the outer surface of high density bag and form a filter layer with thickness 0.5~2mm. When VOC-laden gas are forced into adsorption chamber, VOC will be removed by adsorption of zeolite filters. There are several layers of zeolite filters in the chamber and VOC will be removed further. Depending on the VOC concentration, the bag filter shall be cleaned periodically to remove the saturated zeolite which will be collected at the bottom of chamber. New layers of zeolite filters will be formed after cleaning.

Organic-rich air will first be driven into the UV photocatalytic oxidation system. UV radiation itself and ozone from oxygen generated by UV light will both degrade complex organic molecules into simpler, less hazardous organic molecules or even water and CO₂. After leaving the UV photocatalytic oxidation system, the exhaust gas will be driven into the chemical scrubber to remove the particles and reduce the VOC concentration. With the use of high-efficiency paint-removal solution, the paint mist will coagulate with inorganic base to form non-sticky particles. The scrubber solution will then be treated by passing through water recycling tank with addition of polymer, which interacts with the particles to form large floc, so as to allow better collection and separation of paint mist. The VOC-laden exhaust will be further treated by deodorant by series of chemical reactions. As organics will be removed or degraded in the course of air flow, large amount of VOC emissions can be reduced.

In these projects, the composite VOC treatment system using wet-scrubbing and biofiltration technology are installed to treat exhaust collected from painting and winding process to reduce VOC emissions.  Emission gas from paint manufacturing will be collected and treated by wet-scrubbing and biofiltration system, in which the VOC-laden exhaust passes through a wetted biotrickling filters with synthetic media, which supports a biomass of bacteria that adsorb and metabolize pollutants prior to final discharge to ambient air. With the use of advanced synthetic media, the system can degrade VOC compound and thereby reduce VOC emissions from paint manufacturing more efficiently.

In these projects, the UV printing and curing machine is installed to replace conventional printing machine using solvent-based ink to save ink/solvent and reduce VOC emissions. The new equipment uses environmentally friendly inks, namely UV inks, which are solvent-free inks. Compared with traditional printing machines, the nozzles use thin ink layer technology and can reduce ink consumption. The LED-UV inkjet printer adopts instant curing technology, equipped with digital automatic control which ensure high production efficiency resulting in reduction of ink/solvent. Compared with traditional inkjet printers, there is a significant increase VOC emission reduction benefits.

In this project, composite system adopting UV-degradation and activated carbon adsorption technologies will be installed to remove VOCs from paint spraying process.  VOC-laden exhaust air will be firstly treated by UV-degradation device. UV radiation itself and ozone from oxygen generated by UV light will both degrade complex organic molecules into simpler, less hazardous organic molecules or even water and CO2. For better system performance, air stream leaving UV-degradation device will be further polished by an activated carbon bed to capture residual organics prior to final discharge to ambient air.

In this project, the concentrated catalytic oxidation system will use the activated carbon concentrator and catalytic oxidation technologies to remove VOC from the printing process exhaust gas. Organic-rich gas from printing process is currently treated by water scrubbing and activated carbon adsorption treatment system. The current system will be replaced by the composite treatment system equipped with activated carbon concentrator and a catalytic oxidation system. With the new system, the VOC-laden exhaust from printing process is first passed through an overspray fiber filter and then an activated carbon concentrator. The concentrator consists of five activated carbon adsorption beds, which operate alternatively in adsorption/desorption (or regeneration) mode, as a pre-treatment step to effectively concentrate the mass of VOC originally contained within the original stream. Large volume of exhaust air with diluted VOC level is adsorbed with the concentrator, and then the adsorbed VOC is desorbed/regenerated with high-temperature blast. This much smaller air stream with concentrated VOC levels is then treated efficiently and economically using a small catalytic oxidiser.  Furthermore, the temperature produced in the oxidizer is reused to heat the desorption air, contributing considerably to the reduction in the energy demand.  As VOC will be removed or degraded in the course of air flow and the amount of VOC emissions can be reduced. 

In these projects, the electrostatic precipitator will be installed to remove VOC in gas stream from dye fixation via electrostatic precipitation. Apart from VOC emissions reduction, particulate matters (with a removal efficiency of 90%) will also be reduced. 

In this project, the low NOx burner with metal fibre surface combustion technology will be retrofitted to existing natural gas-fired steam boilers to reduce NOx emissions.   
Metal fibre surface combustion is a technology that combines premixed gas and air together and burns on the surface of metal fibre. The combustion medium used in metal fibre burner is usually made of high temperature resistant metal fibre. Under all operating conditions, the metal fibre burner can achieve uniform combustion. When the burner is running in a closed environment, the surface temperature is higher and the radiation power increases. Due to the uniform air gap and air permeability on the surface of the metal fibre, the direction and length of the flame are evenly distributed. In turn, the radiation efficiency would be greatly improved, the exhaust air temperature can be reduced.  Thus, less thermal NOx will be formed during the combustion process.

In this project, a set of exhaust air treatment system adopting zeolite rotor concentrator and catalytic oxidation technologies will be installed to remove VOC from the printing process.For exhaust air stream with large volume flow and low VOC concentration, a zeolite rotor concentrator can be used for capturing and concentrating the VOC to facilitate subsequent VOC destruction in catalytic oxidation process.  In the adsorption section of the zeolite rotor concentrator, VOC is captured and removed from the exhaust air stream with honey-comb structured zeolite adsorbent.  In the desorption section of the zeolite rotor concentrator, hot air at around 120ºC will pass through the concentrator to desorb and release the VOC captured in the zeolite adsorbent.  The highly concentrated VOC released from the concentrator is then delivered to the catalytic oxidiser where it will be decomposed into carbon dioxide and water at 200-300ºC with the help of catalyst. Heat will be recovered from the catalytic oxidiser to produce hot air used in the desorption process, with a heat exchanger to reduce energy consumption. 

A centralised cooling system with variable speed drive technology and automatic control will be installed to replace existing standalone cooling systems to achieve optimal efficiency and save energy. The COP of centralised cooling system is higher than that of standalone cooling system. Under the centralised system, chillers and chiller pumps are controlled to match the load demand for achieving optimal efficiency of cooling system.

A centralised vacuum system with VSD will be installed to replace standalone vacuum pumps to achieve optimal efficiency and save energy. The central controllers keep the compressed air network running within a narrow, predefined pressure band. This ensure the vacuum system matches the demand and increases the stability of the process, optimizes overall energy consumption. With energy-efficient screw vacuum pumps, the rated power will be decreased. Furthermore, the system features central controller and variable speed drive so that it can accurately monitor system pressure and vary the speed of the drive motor to match the load demand over a wide range. Therefore, typical energy waste during partial load is avoided, leading to energy savings.

A centralized compressed air network with central controller and variable speed drive will be installed to replace existing standalone cooling systems to achieve optimal efficiency and save energy. Under the centralized network, seven rotary screw compressors are controlled to match the load demand for achieving optimal efficiency of compressed air system. With energy-efficient air compressors, the power consumption will be decreased. Furthermore, the system features central controller and variable speed drive so that it can accurately monitor system pressure and vary the speed of the drive motor to match the load demand over a wide range. Therefore, typical energy waste during partial load is avoided, leading to energy savings.

Several energy optimisation systems will be installed in air conditioners with water cooled condensers to save energy. The system mainly employs two temperature sensors:1) to measure the room/space temperature 2) to measure the evaporator coil temperature. The evaporator coil temperature sensor is used to determine when the hydraulic work of compressor is completed, i.e. the refrigerant gas is fully compressed. The compressor will be temporarily turned off until the evaporator coil temperature is above the predetermined temperature. Thus, the operational run-time of the compressor could be controlled and optimised. It also eliminates the problem of dripping and icing up of evaporator fin.

A heat recovery system will be installed to save energy. Hot waste water is drawn from the waste water tank to a heat exchanger where heat is transferred from waste water to fresh water. Wasted heat recovered from effluent can preheat the fresh water and reduce the steam consumption. Moreover, the wastewater treatment process, especially biochemical treatment process, is very sensitive to the temperature. The temperature of wastewater is usually over 50°C, the bacteria cannot survive in high temperature, thus affecting the effectiveness of wastewater treatment. Lower the temperature will improve the wastewater treatment and lower the operating cost.

Non-invasive electromagnetic scale control systems will be installed to heat transfer efficiency of cooling tower of centralised air-conditioning system. The primary energy savings from non-invasive electromagnetic scale control system result from decrease in energy consumption in cooling associated with the prevention of scale built-up on a heat exchange surface when even a thin film of 1mm can increase energy consumption by nearly 12%. Secondary energy savings can be attributed to reducing system pressure required to pump water through a scale-free and unrestricted piping system. Other benefits include: eliminate or greatly reduce the need for scale and hardness control chemicals and their costs; process downtime, chemical usage and labor requirements are reduced due to less periodic descaling of the heat exchange equipment; reductions in heat exchanger tube replacement due to failure from scale formation.

Non-invasive electromagnetic scale control systems will be installed to enhance heat transfer performance of the cooling systems of plastic injection moulding machines. Currently, process cooling is achieved by both chiller (for cooling plastic mould) and hydraulic oil heat exchanger (for cooling working hydraulic oil) with cooling tower rejecting waste heat. The primary energy savings from non-invasive electromagnetic scale control system result from decrease in energy consumption in cooling associated with the prevention of scale built-up on a heat exchange surface when even a thin film of 1mm can increase energy consumption by nearly 12%. Secondary energy savings can be attributed to reducing system pressure required to pump water through a scale-free and unrestricted piping system. Other benefits include: eliminate or greatly reduce the need for scale and hardness control chemicals and their costs; process downtime, chemical usage and labor requirements are reduced due to less periodic descaling of the heat exchange equipment; reductions in heat exchanger tube replacement due to failure from scale formation.

Non-invasive electromagnetic scale control systems will be installed in the same steam system to prevent limescale formation and enhance heat transfer efficiency of steam boilers. In steam boilers, water is rapidly heated to high temperature and evaporated, causing the water to become supersaturated and form limescale. The electromagnetic devices adopt non-invasive design (i.e. devices are completely external to the pipe). It generates magnetic field which facilitates the formation of aragonite crystals (a softer and less adhesive form of calcium carbonate) in suspension rather than hard scale (calcite, a harder form of calcium carbonate) on heating surfaces, which would otherwise reduce the ability of the heat-exchanger to transfer heat. By inhibiting scale effectively, non-invasive electromagnetic scale control system can improve the overall performance of steam boiler system. Although electromagnetic scale control system can inhibit the formation of hard limescale deposits on heating surface, suspended crystals produced will still build up and thus regular blow-down of the boiler is still essential.

The oil-free magnetic-bearing centrifugal blowers offer economic, energy and environmental benefits, including increased energy efficiency, the elimination of oil, and considerably less noise and vibration. It mainly comprises integrated variable speed drive (VSD)-controlled magnetic bearing centrifugal blowers and electronic expansion valve. Instead of using conventional oil-lubricated bearings, the newly-developed oil-free blower uses magnetic bearing, which eliminates high friction losses, mechanical wear and high-maintenance oil management system. The integrated VSD provides good flow rate control, allowing the system to run at high speed (because there is no friction in the motor), and also enhances the overall efficiency of the blower because the system can operate efficiently at low/partial loads matching the actual demand.

Energy efficient rotary screw air compressors with permanent magnet motor and built-in variable speed drive feature will be installed to save energy of compressed air system. The compressor employs a highly efficient design of rotor that integrates embedded high-performance permanent magnets made from rare-earth metals, in place of a squirrel-cage rotor. This design significantly reduces copper loss or heat losses from the rotor and increases total efficiency by 10% or more. Furthermore, the system features variable speed drive (VSD) technology so that it can accurately monitor system pressure and vary the speed of the drive motor as well as cooling fan motor to provide only the required amount of air delivery to match the load demand over a wide range. Therefore, typical energy waste during partial load is avoided, leading to energy savings. These improvements translate into a lower total cost of ownership, a reduction in CO2 emissions, and on-going savings that can help to counter future increases in energy costs.

Energy efficient two-stage rotary screw air compressor will be installed to save energy of compressed air system. The two-stage compressor intrinsically consumes less energy over equivalent size single-stage compressor due to the divided compression cycles with much lower compression ratio resulting in compressor’s power savings and reducing internal leakage losses. Furthermore, the system features variable speed drive (VSD) technology so that it can accurately monitor system pressure and vary the speed of the drive motor as well as cooling fan motor to provide only the required amount of air delivery to match the load demand over a wide range. Therefore, typical energy waste during partial load is avoided, leading to energy savings

Energy efficient UV-LED powered exposure machine will be installed to replace conventional PCB exposure machine with high-pressure mercury lighting source to save energy. UV-LEDs are known to have a longer life, lower power consumption, and easier maintenance compared to conventional mercury lamps light source. Other benefits of UV-LED include: instant on/off to eliminate standby power loss; no infrared to avoid the film expansion and contraction for stable image transfer quality; mercury and ozone free; lower heat generated to reduce necessary cooling load. Lower energy demand for the light source as well as the demand for cooling contributes to a reduction in energy consumption during PCB manufacturing.

Heat recovery units will be retrofitted to existing air compressors in a compressed air system to recover rejected heat from air compressors and produce hot water for industrial process.

Oil-free magnetic-bearing compressor will be installed in this project. The oil-free magnetic-bearing compressor offer economic, energy and environmental benefits, including increased energy efficiency, the elimination of oil, and considerably less noise and vibration. It mainly comprises integrated variable speed drive (VSD)-controlled magnetic bearing compressors and electronic expansion valve. Instead of using conventional oil-lubricated bearings, the newly-developed oil-free compressor uses magnetic bearing, which eliminates high friction losses, mechanical wear and high-maintenance oil management system.Furthermore, the oil-free design eliminates some typical operating problems associated with oil flooded compressors, for example, some oil will travel through the refrigeration loop to the compressor causing a decrease in heat transfer

Existing hot blast oven will be retrofitted with heat recovery devices to save energy.  Passive air preheaters (i.e. gas-to-gas heat recovery devices for low- to medium-temperature applications where cross contamination between gas streams must be prevented) will be used to cool the outgoing air and uses the recovered heat energy to preheat fresh air feeding back into the oven, resulting in energy saving. 

Central control and monitoring system (CCMS) equipped with chiller with variable speed drive (VSD) feature and chilled water pumps with VSD feature will be installed to enhance the operation efficiency of the centralised air-conditioning system and thus save energy. By implementing CCMS, the energy efficiency of the centralised air-conditioning system can be optimised through:
•    Optimisation of the operation of chillers by dynamic monitoring on actual cooling load demand;
•    Optimisation of the operation of chilled water pumps by dynamic monitoring on actual water flow demand 

An alternative way to VSD/servo control is adopted for enhance energy efficiency of rubber mixing machines, by using dynamic voltage regulation on induction motor. The motor power phase angles are continuously detected to monitor the motor load and efficiency.  A digital micro-processor with built-in control logic is then used to dynamically adjust the input voltage and power of the motor to match the required motor load and optimize the motor efficiency.  In this way, the electromagnetic loss is reduced and the power consumption can be reduced without the need to change motor speed. Controlled by a closed-loop feedback system, the sensing circuit compares the voltage and current waveforms in the motor at a very fast detection rate. This high detection rate enables a very fast response in voltage regulation, thereby optimizing the motor efficiency.  It has also soft start function to eliminate mechanical shock and large starting current to extend equipment lifetime.  This technology has the following advantage compared to VSD and servo control:
-    Production speed can be higher since no motor speed change is needed
-    Control is very dynamic that can closely synchronise with the change in demand
-    No unwanted harmonic distortions are introduced to power supply

In this project, 46 plastic injection moulding machines will be retrofitted with infrared heater systems to save energy.  Infrared heating coils are employed to melt plastic material for plastic injection moulding.  This energy saving technology is applicable to different types of injection moulding machines and can replace traditional electric heating coil directly.  Infrared heaters are preferred to electric heaters for a variety of reasons: (i) lower cost for heating as radiated infrared can be easily directed and concentrated to reduce energy wastage; and (ii) efficient operation to fit production conditions.  The anticipated saving in electricity consumption is 30%.