ER.MOHAMMAD ASHRAF FAZILI
Right from ancient times, citizens were concerned about the accumulation of waste contaminating their city. This problem remained unsolved in human settlements for centuries together. The problem became more acute in modern industrial society, as there was no appropriate method for handling the daily growing quantities of refuse. Waste continued to be dumped in giant landfill sites. This storage continued creating ecological time bombs. In addition, methane gas was released: a greenhouse gas over 20 times more harmful to the climate than carbon dioxide. In some countries steps have been taken by disallowing the deposition of untreated organic waste anywhere. But in many more countries a great proportion of waste still goes to landfill. Hence, we are faced with a challenge of how to treat refuse in a sustainable, environmentally compatible, economically sound way.
While attending the WORLD FUTURE ENERGY SUMMIT at Abu Dhabi UAE on 15-18 January, 2018, besides other international companies, I came across the Germany-based Steinmuller Babcock Environment (SBEng) – a name that stands for cutting-edge technology in thermal waste treatment and flue gas cleaning. Their technology could be a solution to our waste disposal besides adding to our much-needed power supply and avoiding encroachments on wetlands by landfills.
“Waste incineration not only serves the purpose of environmentally sound waste disposal but also generates significant amounts of energy in the form of electricity and heat. In this way, it contributes to climate protection and helps preserve natural resources.”
(Study by the German Federal Ministry for the Environment, Berlin, 2005)
Reduce, Reuse, Recycle
Waste prevention is the highest priority, followed by reuse and where not possible, to be recycled. The non-recyclable quantities of waste still contain energy that can be harnessed through thermal treatment. Only those substances that remain after thermal treatment and cannot be used any further go to landfill.
There is considerable reduction in the volume of waste by thermal treatment. On average every citizen produces 500 kgs of refuse every year. Incineration reduces the waste volume by around 90%. This way there is a lasting reduction in the quantity of waste sent to harmful landfill sites. Besides, the residual substances remaining after thermal treatment are completely sanitised, free of hazardous and pathogenic substances.
With the modern cutting-edge technology in the field of flue gas cleaning, the flue gas that leave a modern waste incineration plant is clean and poses no danger to man or the environment. Thus, the thermal waste treatment offers a proven and safe way to reduce quantities of waste while adhering to all environmental considerations.
Energy from Waste
Thermal treatment uses the energy contained in the waste to produce power and heat, which is another step towards reducing the burden on the environment. Thus, the harmful fossil fuels such as natural gas, oil, and coal can be replaced with a clean alternative. Hence the modern thermal treatment systems guarantee eco-friendly, energy efficient and future-oriented treatment of our residual waste.
“Before 1990, pollutants with a toxicity equivalent to that of 188 tonnes of arsenic were distributed in the air; today, at least 3 tonnes are withdrawn from the air. Admittedly, this concept takes some getting used to. But this reduction results from the power and heat produced by incinerating household refuse. If this energy was produced in traditional power stations, there would be 3 tonnes more toxins in the air.”
(Study by the German Federal Ministry for the Environment, Berlin, 2005)
Process of Waste Incineration: Clean and Safe
The stages through which the waste has to pass is Waste Bunker, Moving Grate, Slag Extractor, Slag Bunker, Boiler, Evaporator. The process leads the live steam to the turbine to turn the rotor of the turbine, using the energy released in the attached generator to produce electricity to be fed to the public grid. The condensate is collected in the feed water tank and finally returned to the boiler. Alternatively, part of the energy can be fed to local or district heat networks or used as process steam (combined heat and power production).
The other equipment used are Spray Absorber, Fabric filter, ID-fan, Stack: The cleaned flue gas leaves by the process to the atmosphere via the stack. The process ensures optimal burnout, high versatility, high availability-assured long service life, and economical solution.
“Cautious estimations assume that using waste to produce energy now saves on average, a quantity of fossil fuels corresponding to the needs of around 700,000 citizens. Incineration of around 2kg of household refuse with a calorific value of around 8,000 kj/kg can produce 1kwh of power. This can light a bulb for some 24 hours. The amount of energy in a well-filled 60-litre household bin can run the light bulb for almost entire week.”
(Study by the German Federal Environment Agency, Dessau, 2008)
The German company Steinmuller Babcock Environment uses modern and environmentally friendly process for handling residual materials with tailored solutions at every step. In Germany, the Federal Immission Control Act specifies that flue gases must reach a temperature of 850 degrees for at least two seconds. This ensures that pollutants, in particular dioxins, are destroyed.
“Given the limited supply of fossil primary energy sources, the globally rising energy demand cannot be met in the current form over the long run. In parallel with intensive efforts to boost energy efficiency and realize energy savings, it is imperative to make use of all available energy sources that help conserve limited resources, are environmentally benign and contribute to climate protection. This also applies to high-calorific waste streams… the waste sector is already making relevant contribution to energy supply…”
(Study by the German Federal Environment Agency, Dessau, 2008)
“The reduction in fossil fuel usage through waste recycling are eight times higher today than in 1990. Standards are being set by developments in climate protection by using the energy and by avoiding greenhouse gas emissions from landfill sites.”
(Waste Management in Germany, 2011, published by the German Federal Ministry for the Environment, Nature Conservation and Reactor Safety)
Hazardous Waste
This is a legal term for which the European Union’s list of refuse includes around 400 types of waste. These include among others:
Residues from production processes in the chemical industry
Laboratory chemicals
Used pesticides
Hospital waste, infectious materials
Highly polluted industrial waste
This hazardous waste may not be incinerated together with normal household and residual waste. It belongs in systems that allow high temperature incineration. This is because in the thermal treatment of hazardous waste at temperature of 1100 degrees must be reached for at least two seconds to prevent the release of emissions that are harmful to health and to the environment. The high temperature ensures the destruction of all organic substances. Further, this type of waste treatment makes it possible to obtain energy in the form of steam and power from polluted, contaminated, and mixed waste. This technology therefore currently represents the only proven procedure for the economically sound treatment of large quantities of hazardous waste.
“Thanks to stringent emission control standards, dioxin, dust and heavy metals emissions from waste incineration are no longer an issue, a fact that is all the more impressive as the waste incineration capacity has more than doubled since 1985.”
(Study by the German Federal Environment Agency, Dessau, 2008)
The cleaning systems use cutting-edge technology developed based on decades of research and practical experience. The problem is well known only if the pollutants in the gases are safely removed, the strictest emission requirements can be met as a result.
“Without waste incinerators, ambient air pollutants levels would be much higher than with waste incinerators. After all, electricity and heat generated in MSWIs substitute fossil energy sources in conventional (heat and) power plants which typically release higher specific pollutant levels than waste incinerators.”
(Study by the German Federal Environment Agency, Dessau, 2008)
Core Technologies of Flue Gas Cleaning
Dedusting
Fabric filter
Electrostatic precipitator
Wet electrostatic precipitator\Separation of acidic gaseous pollutants
Combined scrubbing systems based on lime products of sodium hydroxide
Spray absorption with slaked lime
Dry scrubbing with sodium bicarbonate
Combined scrubbing process Removal of heavy metals and organic compounds
Injection of activated carbon
Activated carbon fixed-bed adsorber
Catalytic dioxin removal
Denitrification
SCR process for catalytic reduction in NOx emissions, as both “High Dust” configurations
SNCR process for non-catalytic reduction in NOx emissions using ammonia or urea solutions
Energy recovery systems
Downstream economizer
Heat transfer systems for preheating of combustion air
Flue gas condensation, e.g., for district heating use (optionally with heat pump)
Heat transfer systems within the flue gas cleaning for optimizing energy efficiency.
Er. Mohammad Ashraf Fazili is a Former Chief Engineer.
