Cement industry in the existing scenario can play an important role in processing of hazardous waste in its kiln when no other cost effective option is available. Milind Murumkar takes a stock of the situation.
Waste management is a growing concern for India. The Government of India is attempting to tackle this challenge through a number of initiatives, including the Clean India Mission. Cement industry can certainly play a key role in promoting better waste management practices & create a win-win situation by working with urban local bodies on waste segregation and management of municipal solid waste. Substantial fractions of industrial, commercial, domestic and other wastes contain materials that have the potential for use as an alternative raw material or as a supplementary fuel for energy recovery in cement kilns.
Co-processing is a proven sustainable development concept that reduces dependency on natural resources, reduces pollution and landfill space, thus contributing to reducing the environmental footprint. Co-processing is also based on the principles of industrial ecology, which considers the best features of the flow of information, materials, and energy of biological ecosystems, with the aim of improving the exchange of these essential resources in the industrial world.
This will be possible only when there will be appropriate will and proper facility in cement plants to process the non-homogeneous waste material into uniform quality AFR whether it is segregated municipal solid waste, waste from industrial sectors like-machinery parts making industry, forging industry, paint industry, FMCG, petrochemical, pharma industries, etc.
Cement industry in view of high temperature profiles that are available in their kiln system offers an excellent co-processing facility that can be utilised for management of any kind of waste. The best benefit of co-processing of different type of waste in the kiln system is a preferred option that helps in utilisation many waste materials without leaving any foot print on the environment and also on the product quality. There have been dramatic improvements in regulatory frame work and Pollution Control Authorities are also mandating for higher utilisation of waste in cement kilns. The waste generator are also satisfied with the facilities created by cement Plants for disposal of their waste in scientific and sustainable manner.
The concept of hand holding by the manufactures, waste generators and the authorities have greatly improved the waste utilisation in cement plants. Movement of waste from one state to other state, giving long term consents, authorising the transporters, etc. are some of the positive steps taken in this direction.On the other hand, the waste generators as well as the plant users are also gearing up by upgrading their facilities for improving the usage. All these steps will certainly help in avoiding land filling and shift to resource recovery in next two to three years through co-processing route.
The dream of the cement manufacturers is to raise their thermal substitution rate from present level of around 4 per cent to a level of 20 per cent in 2025, which is a very ambitious and the above initiatives can certainly help the industry. In order to have a step jump in utilisation the support of bodies like CII, CMA, etc. can boost the awareness and understanding in the waste generators and the community.In co-processing, the cement kiln in the cement manufacturing process has features that are suited for co-processing. These include:
Different feed points for AFR introduction in the cement process. Feed points can be via the main burner, secondary burners, pre-calciner burners, kiln inlet.
Alkaline conditions and intensive mixing in the kiln favours the absorption of volatile components from the gas phase. This results in low emissions of sulphur dioxide, hydrochloric acid (HCl) and most heavy metals.
The clinker reaction temperature at 1,450 degree Centigrade allows incorporation of ashes, in particular, the chemical binding of metals to the clinker
Cement kiln operates under negative pressure or draught, thus preventing the generation of fugitive emission.
With the large mass of clinker processed inside the cement kiln, there is a presence of a huge thermal inertia thereby eliminating the possibility of rapid swings in temperature
Carbon dioxide (CO2) emissions from cement manufacturing are generated by two mechanisms.
1.Combustion of fuels to generate process energy which releases good quantities of CO2.
2.Substantial quantities of CO2 are also generated through calcining of limestone or other calcareous material. This calcining process thermally decomposes CaCO3 to CaO and CO2
Emissions of metal compounds from cement grouped into three general classes: volatile metals, including mercury (Hg) and thallium (Tl); semi-volatile metals, including antimony (Sb), cadmium (Cd), lead (Pb), selenium (Se), zinc (Zn), potassium (K), and sodium (Na); and refractory or non-volatile metals, including barium (Ba),chromium (Cr), arsenic (As), nickel (Ni), vanadium (V), manganese (Mn), copper (Cu), and silver (Ag).
Although the partitioning of these metal groups is affected by kiln operating conditions, the refractory metals tend to concentrate in the clinker, while the volatile and semi-volatile metals tend to be discharged through the primary exhaust stack and the bypass stack, respectively.
Requirements for undertaking co-processing are: Best available technology for air pollution prevention and control with continuous emission monitoring
Exit gas conditioning/cooling and temperature less than 200 degree Celsius, in control devices to prevent dioxin formation. Adequate emergency and safety equipment and Procedure and regular training. Safe and sound receiving, storage, processing and feeding of hazardous wastes. The operator of the co-processing plant should develop a waste evaluation procedure to assess health and safety of workers and public, plant emissions, operations and market dynamics. Market information on waste availability is key for our service selling business. If parameters are not clearly defined, market surveys can be too vague. The objective of a market survey is to:
For cement kiln usage the following industrial segments have high-priority:
Moreover the following issues are looked at before selecting a waste stream,
Waste generators should provide information on characteristics, generating process, geographic availability, regulatory/legislative disposition, specific producers, volumes, prices, disposal alternative method and impacts/fits with the cement process per each waste type. Furthermore it should capture competitive information, the basic industry economics and the trends and events impacting the waste industry.
The waste generators requires a cement plant that can offer a Total service strategy (TSS) which means understanding the waste customer's problem and offering all required services to solve this problem, either through internal activities or in coordination with third-party-services (e.g. transport, chemical analysis, cleaning, etc.).
AFR quality control in a cement plant plays a vital role. The cement plant needs to address if it...
India is primarily a cement producer. Manufacturing of cement requires stable inputs of raw material of a certain composition to reach stable output qualities.Only certain waste types can be accepted and the timing of inputs must be aligned. An AFR Quality Control Scheme is absolutely necessary to minimise and control all possible risks associated with AFRs. The AFR Quality Control Scheme applies to waste materials prior to delivery, at time of delivery, during handling & storage phases and even through to feeding into the kiln.
As cement and AFR are very different, very different key success factors are present, too.These factors are industry specific, i.e. the cement industry as newcomer in the waste business needs to adapt to these key success factors.
ABOUT THE AUTHOR: Milind Murumkar is an Advisor & Consultant for AFR. He has been associated with Dalmia Group, Vicat Group, Orient Cement, Shree Digvijay Cement, Toshaly Cement Companies as an advisor and consultant. He can be contacted at: +919100960039 | +919004476333 or Email: milind.murumkar@gmail.com.
One needs to describe the waste, its form, characteristics, contaminants, legal status, additional storing and handling equipment, etc.... like