Co-processing of Plastic Waste in Cement Kilns

Co-processing is a more environmentally friendly and sustainable method of waste disposal as compared to land filling and incineration because of reduced emissions and no residue after the treatment. Co-processing refers to the use of waste materials in industrial processes as alternative fuels or raw material (AFR) to recover energy and material from them. Due to the high temperature in cement kiln, different types of wastes can be effectively disposed without harmful emissions. As per the Basal Convention, variety of wastes including hazardous wastes, get disposed in an environmentally safe and sound manner through the technology of co-processing in cement kiln. Disposal of different categories of plastic wastes through co-processing is practiced in many countries as a regular method for their environmentally sound disposal.

Evaluation of Co-processing in cement kilns as an option for management of Plastic Wastes

Co-processing of plastic wastes in cement kiln is practiced substantially in different countries as an environmentally sound option for management of plastic wastes. In cement kiln, different kinds of hazardous and non-hazardous wastes including plastic wastes get utilized as Alternative Fuel and Raw materials (AFRs). During the usage of plastic wastes in cement kiln as AFRs, the material and energy value present in them gets fully utilized in the cement kiln as replacement to the fossil raw materials and fossil fuels that are conventionally utilized in the kiln. The performance evaluation of co-processing of plastic waste was carried out in ACC Limited, Kymore, Madhya Pradesh, in collaboration with Indian Centre for Plastic in Environment (ICPE) and Madhya Pradesh Pollution Control Board (MPPCB). The various trial parameters such as raw material & product testing and emission monitoring was carried out by SGS Limited, which is a CPCB approved testing laboratory. Based on the results of trials - that included chemical & thermal parameters of raw materials, clinker product, plastic wastes & coal and the emission monitoring during and after feeding of plastics waste in the cement kiln as AFR. Based on their evaluation, MPPCB forwarded the same to CPCB along with their recommendations. CPCB after reviewing the trial report approved the results of the trial and declared co-processing of plastic waste in cement kiln as a successful method for its environmentally sound management. Based on this suggestion, several SPCBs have provided consent to various cement plants and plastic waste generators to implement co-processing of plastic wastes. Various cement plants are currently managing plastic wastes as AFRs in their kilns. A list of cement plants having co-processing facility as shown at Annexure-I.

Infrastructural Requirement for Plastics Co-processing:

Every cement plant will have to have a separate feeding arrangement for undertaking coprocessing of AFRs. In case it already has one on the calciner or kiln inlet, then the same can be utised for plastics as well. However, if it does not have any on the calciner or kin inlet, then the same needs to be set up. This feeding facility will consists of proper covered storage along with conveying mechanism to move plastic waste from storage area to kiln. This can be manual or can be automatic. The manual one consists of winch and hopper arrangement and conveyor belts arrangements. At the feed point, it is desired that equipment such double flap valves, shut off gates etc. are implemented to ensure uniform feed and safety in operation. The feeding facility shall also be equipped with a lab to carry out the calorific value, ash content, moisture content and chloride content.

Feeding of plastic waste material for co-processing:

Different feed points that can be used to feed the plastic waste materials into the cement production process are given below. • The main burner at the rotary kiln outlet end • The rotary kiln inlet end • The pre-calciner • The mid kiln (for long dry and wet kilns) Appropriate feed points amongst the above will have to be selected for the environmentally sound co-processing of the plastic waste. Usually, plastic wastes, that are contaminated with toxic components such as pesticides etc, should be fed to the main burner to ensure its complete combustion in the high temperature and long retention time. For this, the plastics may need to be shredded to less than 20 mm size. The non-recyclable plastic wastes, that is not contaminated with toxic components, can be fed at the other feed points such as calciner, kiln inlet or mid kiln depending upon its size. Process flow diagram for co-processing of plastic waste in cement kilns along with the points of feeding of plastic waste

Operating Conditions: