who we are
Clean Energy Holdings Pte Ltd is a technology company in Singapore that is focused in the Municipal Solid Waste (MSW) Waste-to-Energy (WTE) business. The company has more than 30 years of experience in research and development, and has invented a breakthrough patented “Cyclonic Combustion” technology, which is able to fully combust high moisture MSW with near zero need of auxiliary fuel, and at the same time producing energy to be exported to the grid, therefore contributing greatly to the environmental and economic benefit of our society.
Through this “Cyclonic Combustion” technology, the company has made several breakthrough achievements in the international market. In 1987, the technology was employed in Malaysia’s first WTE plant in the State of Terengganu, with a capacity of 100 tons per day (TPD) of MSW. The plant was in operation for more than 10 years and produced electricity of up to 1 MW, and had received the commendation from local state and technology ministry. So far, the technology is the only official recognized and approved technology for the incineration of MSW in Malaysia.
CEH’s has continued its R&D efforts to improve the technology. Our research partners include renowned researchers and professors from various international universities. In 2005, through the collaboration with a local Malaysia technological university, a research and demonstration plant was built especially for the R&D works of the technology. And as a result of such efforts and collaboration, the Malaysian government awarded the construction of 5 incinerator plants in the year 2008, all to be operated by means of this technology. The first of these incinerators have commenced operation since early 2012.
CEH has also entered into strategic alliances with various significant partners, in order to become the leader in its field, as it enters into the China, Middle East, and Asia Pacific WTE markets. In 2010, CEH & China Hubei Hongyuan Power Engineering Co Ltd entered an agreement and became CEH’s EPC contractor for both domestic &x` overseas markets. In the same year CEH & Chinese Research Academy of Environmental Science Environmental Technology Engineering Co Ltd also entered an agreement to became Strategic Alliance Partners, vowed to contribute and make our environment a cleaner and better place to live.
On 28th February 2014, CEH was declared as winner & received IAIR Awards 2014 for Best Company for Sustainability in Waste Management- Asia Pacific.
Cyclonic Combustion
Through various installations in South East Asia, CEH’s proprietary technology has proven itself to be able to combust municipal solid waste (MSW) with up to 60% moisture content with near zero requirement for auxiliary fuel, and is able to maintain a combustion temperature of 850 – 1200 C. Most all of the recent incinerator installations in China, be it the Stoker, or the Martin Drum, or fluidized bed type, require the addition of 15 – 20% auxiliary fuel to maintain the combustion of MSW in the incinerator. This patented technology is therefore a major breakthrough in the area of MSW incineration.
Technology Advantages
- Able to combust waste with moisture content of up to 60% at temperature of 850 – 1200C, with near zero requirement for auxiliary fuel. The Lower Calorific Value (LCV) of the waste can be as low as 4,600 kJ/kg.
- Bottom ash will have less than 3% Total Organic Compound (TOC), meeting the most stringent EU requirement for bottom ash. Bottom ash is 10 – 15% by weight and less than 10% by volume of the incoming waste.
- Dioxin/ Furan level is at 0.005 ng/Nm3, 20 times lower than EU regulated levels.
- Lower excess air requirement results in smaller air pollution control equipment capacity, and lower overall power consumption.
The technology uses a simple rotary kiln platform, which is lined with special heat and corrosion resistant refractory. Each end of the kiln serves as the feeding and discharge point of the MSW and bottom ash. The kiln is installed at a slight angle, such that when it rotates, MSW that is fed at the upper end will move slowly towards the lower ash discharge end.
An auxiliary burner is used for starting up, and for use in the event of any operational upset conditions. During operation, the rotation speed of the kiln is adjusted by a variable speed drive, to control the optimum time of combustion, and to ensure that the process of drying, pyrolysis, combustion, and ash cooling prior to discharge – the 4 basic steps of a successful combustion process – take place.
The proprietary and unique combustion air injection system differentiates CEH’s rotary kiln technology with other rotary kiln technologies. In a normal rotary kiln, combustion air from a forced draft fan enters the kiln longitudinally from the discharge end and exits the kiln at the waste inlet end, while MSW moves in the kiln at the other direction. The air delivery method of the normal rotary kiln causes the combustion air to be concentrated at the center of the kiln, and making minimum contact with the MSW at the bottom of the kiln. And due to inadequate mixing of air (oxygen) and solid waste, the combustion efficiency is lowered, and a higher level of excess air is required for complete combustion. On the other hand, a higher level of excess air will cause the combustion temperature to fall, and as a result, auxiliary fuel is needed to raise the temperature and assist in the combustion.
The combustion air for CEH’s rotary kiln system does not enter the kiln longitudinally, but instead is injected at an angle via the patented proprietary air injection system. While the air also enters the kiln at the ash discharge end and exits the kiln at the MSW inlet end, the air injection system causes air within the kiln to swirl like a cyclone in the opposite direction of the kiln rotation, thereby creating a double counter current effect of the contact between air (oxygen) and waste. Combustion air is no longer just concentrated at the center of the kiln, but is delivered downward toward the waste as it swirls within the kiln, and creates a high turbulence which is essential for effective combustion. Under such conditions, the mixture of waste and oxygen is optimized, and as a result, complete combustion can take place with near zero requirements for auxiliary fuel, at an excess air level of as low as 40%.
Technology Details
| Grate | Fluidized Bed | Rotary Kiln | Cyclonic Combustion |
|---|---|---|---|
| Major Mechanical Part | |||
| Grate | Sandbed | Kiln | Kiln |
| Furnace Movement | |||
| Stationary | Stationary | Rotating | Rotating |
| Garbage and Air Mixing | |||
| Very Good | Best | Very Good | Best |
| Garbage Calorific Value | |||
| Medium | Low | High | Low |
| Garbage Moisture Content Requirement | |||
| Medium | High | Low | High |
| Combustion Medium | |||
| None | Heated Sand | None | None |
| Secondary Combustion Chamber | |||
| Not necessary | Not necessary | Not necessary | Necessary |
| Flu Gas Temperature Without Aux. Fuel | |||
| Medium | Medium | Medium | High |
| Area of Operation | |||
| Large | Small | Medium | Medium |
| Unburned Material | |||
| < 3% | < 1% | < 5% | 0% |
| Operation Mode | |||
| Continuous | Batch | Continuous | Continuous |
| Furnace Volume | |||
| Very Large | Small | Large | Medium |
| Single Line Capacity | |||
| Large | Medium | Medium | Medium |
| Investment Capital Cost | |||
| High | Medium | Low | Low |
| Operational Cost | |||
| High | Very High | Low | Low |
| Maintenance | |||
| High | Low | Low | Low |
Why Cyclonic Combustion for your Waste to Energy project?
It is suitable for low calorific value, high moisture content waste. Normal Asian unsorted waste has very low calorific value and very high moisture content. By employing western technologies that are suited for western high calorific value waste, auxiliary fuel will be required to assist in the combustion.
With the rising cost of energy, the operational cost of a WTE plant will be greatly affected by employing western technologies. On the other hand, CEH’s technology has the capability to combust Asian waste without additional auxiliary fuel, and the same time, providing high-temperature, quick, stable, and complete combustion of the waste.
The rotary kiln platform is very versatile to be used for Asian unsorted MSW. Due to its seamless furnace bed and its ability to mix any incoming waste, the rotary kiln is able to receive all states of waste (solid, liquid, gas), with various calorific values, including hazardous and industrial wastes, hence the rotary kiln is known to be the “multi-waste furnace”.
The rotary kiln is suitable for waste with a wide range of calorific value, and a wide range of waste type, from sludge, to plastics, to rubber, to liquid waste oil, and all kinds of industrial waste.
The generated flue gas has a lower level of acidity. Due to the intense scrubbing caused by the cyclonic airflow, the flue gas is in constant contact and with the alkalic bottom ash. This results in overall lower flue gas pollutants such as NOx, HCl, and SOx, and lower requirement for air pollution control equipments.
Suitable single furnace capacity to be used for large scale incineration. While the maximum single furnace capacity is currently lower than the stoker type capacity at 250 tons per day, it is greater than many installed gasification technology, and is suitable to be used for a WTE plant.
A typical 1,000 tons per day WTE plant will have 5 furnaces, with 4 operational and 1 on standby. Such setup will ensure that any scheduled or unscheduled downtime does not greatly affect the operational capacity of the plant.
The Combustion Process
Process Flow Diagram
Waste is transported by waste trucks to the waste reception area, weighed, and then tipped into the waste raw bunker. Negative pressure is constantly maintained at the raw bunker to prevent the escape of any unwanted odor from the raw bunker. The first bunker is able to fit up to 3 – 5 days of incoming waste. Leachate that is collected at the bottom of the raw bunker is either sprayed into the furnace to be combusted, or channeled to the wastewater treatment plant for treatment.
From the raw bunker, waste is taken by a crane into the waste separation systems, where recyclables and incombustible are separated before entering the second bunker. Waste is segregated by size and type (plastics, metal, aluminum etc.), in order to maximize their economic and recycling value. The second bunker is also able to fit up to 3 – 5 days of waste, and will contain mostly segregated and combustible waste.
Rotary Kiln Furnace
The second bunker will be connected to various hoppers that lead to the opening of the rotary kiln furnaces. If the plant capacity is 1,000 tons per day, there will be 5 hopper openings, each leading to a rotary kiln with the capacity of 250 tons per day, with 4 in operation, and 1 on standby.
Overhead cranes will grab the waste from the second bunker and place them into the large hopper openings. Then waste will be transferred into the rotary kiln via a hydraulically operated ram feeder. The kiln is preheated during startup using auxiliary fuel for a short period before waste is charged into the kiln. Once waste in the kiln begins combustion, combustion air will be injected into the kiln to assist combustion, until combustion reaches an equilibrium and stable condition. Once combustion temperature reaches 850C, and is able to maintain the requirement of 2 seconds at the secondary chamber, then the burner is turned off, and the waste will serve as the fuel to sustain the combustion and temperature. Due to the breakthrough in air injection system, the excess air required for combustion is relatively low, and coupled with the cyclonic air flow that creates the required turbulence to sustain combustion, high temperature combustion ofwaste is able to take place without the need for additional auxiliary fuel.
The bottom ash is collected by a drag pan type conveyor that is fully submerged in water. Water not only cools the ash and prevents it from being airborne, but also provides a seal to prevent ambient air from entering the system, and disturbing the combustion process.
Steam Boiler
A high efficiency water-tube heat recovery steam boiler is situated after the secondary combustion chamber of the incinerator. The heat from the hot flue gas that enters the steam boiler will quickly convert water into high pressured superheated steam (30 bar pressure), and then cause the flue gas temperature to reduce quickly from 850 C to 200 C, prior to the flue gas being treated by the air pollution control equipments.
The heat exchanger tubes are made of special material in order to protect them from the corrosive flue gas. In addition, the boiler is fitted with sonic or mechanical soot remover, to remove any slag or fly ash that may attack the integrity of the boiler tubes.
High-pressured superheated steam that is produced in the steam boiler will be channeled to the steam turbine and generator.
Steam Turbine & Generator Set
Steam that is produced in the heat recovery steam boiler will be channeled to the multi-stage high efficiency fully condensing turbine and generator set. Steam enters the turbine at a pressure of 30 bar and exits the turbine at a pressure of less than 0.1 bar, thus ensuring that energy usage within the turbine is optimized. The generator will then produce electricity that is partly used for plant consumption, with the balance exported to the grid.
The low pressure steam exiting from the turbine is cooled and condensed back to liquid form with a cooling tower, and reused back at the steam boiler.
Air Pollution Control
Flue gas that exits the boiler at a temperature of approximately 200C, will contain various harmful pollutants, such as dust particulates, acidic compounds, nitrogen oxides (NOx), carbon monoxide, heavy metals and dioxin/furan, all of which will require “cleaning” prior to any discharge into the atmosphere.
The following methods are used for the flue gas cleaning:
Acidic Gas Cleaning
Flue gas exiting the boiler will enter the neutralization scrubber that uses a semi-dry process for the removal of acidic components such as HCl, H2SO4 and SO2 in the flue gas. The advantages of using the semi-dry system are:
- 1. Using Sodium Bicarbonate (NaHCO3), with the mixture of steam, ensures high efficiency of neutralization, without the need for prior mixture of water and powder to create any slurry mix. A semi-dry system will ensure ease of operation and low maintenance.
- 2. A semi-dry system is more efficient than a dry type system, and also eliminates the need for expensive wastewater treatment in wet scrubber systems.
- 3. As used in the reaction column and a controlled spray (steam) Synergist technique leverages the high reaction efficiency of ions, and improve the utilization and the neutralizing effect, reducing the water consumption.
- 4. The concentration of the neutralizing agent in the reaction column is significantly higher than other technology to improve the efficiency and effectiveness of the neutralizing agent thus reduces the volume and investment of the reaction tower.
A rotary valve is situated at the bottom of the scrubber to remove any fly ash and neutralization salt that is formed.
Dust Removal Baghouse Filter
From the semi-dry scrubber, flue gas enters the filter baghouse, where flue gas passes through multiple individual filter bags that acts to filter any micro> particulates such as the PM 2.5 particulate and various heavy metals. The filter bags are made of PTFE material, and can ensure a final flue gas particulate discharge of < 50mg/ Nm3, that meets the current regulation for dust particulate discharge. The lime (NaOH) coated filter bags will also act as a secondary neutralization for the flue gas, and remove any residue heavy metal and dioxin components inthe flue gas before the flue gas is released to the atmosphere.
A rotary valve is situated at the bottom of the baghouse to remove any fly ash that is collected at the bottom of the baghouse.
Flue Gas Discharge
From the baghouse, flue gas is the released to the atmosphere through a chimney via an induced draft (ID) fan. The ID fan is operated with a variable speed drive (VSD) and is controlled automatically by the set negative pressure in the system, to ensure optimum and stable operating pressure.
The chimney is lined with corrosion resistant refractory to extend the lifetime of the equipment.
CEH Incineration Advantages
- Sustainable & scalable system
- Unique air injection system- complete combustion
- No sorting of MSW is required
- No auxiliary fuel is required during incineration
- Able to handle high moisture (60%) MSW
- Able to handle low CV MSW (1300 kcal/kg)
- Meet EU emission standard/ Dioxin < 0.1ng/Nm3
- Final ash < 15% in weight & < 10% in volume
- 1000 TPD plant = 12-15 MW electricity
- Smaller land requirement for WTE plant (25%)
- Variable incinerator size: 25 – 300 Ton
our strategic partners
Chinese Research Academy of Environmental Science
Environmental Technology Engineering Co. Ltd.
China Central Research Institute of Environmental Technology Engineering Company Vice Chairman― Chen Xiao Ping ―
China Central Research Institute of Environmental Technology Engineering Company Vice Chairman― Chen Xiao Ping ―
China Central Research Institute of Environmental Technology Engineering Company ― Institute Building ―
Contact us
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Clean Energy Holdings
Pte Ltd
- 6 St George's Lane #08-209,
Singapore 320006 - [email protected]