Pyrolysis plastic oil production and optimisation followed by maximum possible replacement of diesel with bio-oil/methanol blends in a CRDI engine

The primary focus of this study was to effectively extract the available energy from plastic wastes and provide maximum possible replacement of diesel fuel. After careful optimisation of reaction time, reaction temperature and the catalyst percentage, low-density polyethylene (LDPE) plastic wastes were converted into fuel by catalytic pyrolysis process. The plastic oil was then used to operate a single-cylinder common rail direct injection diesel engine. The operating parameters such as compression ratio, injection timing and injection pressure of the test engine were optimised by the Taguchi method. The test engine's performance, combustion, and emission values at 800 bar injection pressure with an advanced injection timing (27° bTDC) were analysed for different brake mean effective pressure values. It was clear that the increase in plastic oil concentration affected the combustion process, and a significant reduction in the performance factors were noticed, especially above 40% addition. Methanol and diethyl ether (DEE) were added to the P40 blend at different ratios to counteract the reductions. These additions showed a significant improvement producing 31.25% of brake thermal efficiency and reducing hydrocarbon, nitrogen oxides, carbon monoxide levels to 2.3, 20.28, 34.61 g/h and smoke to 44% at full load condition. The results proved that diesel fuel could be replaced partially by plastic oil up to a maximum of 40%, and the adverse effects of using plastic oil can be eliminated with the usage of methanol fuel and diethyl ether additive. [Display omitted] •(79%) than thermal pyrolysis process (62.5%)Low-density polyethylene plastics produced better yield in catalytic pyrolysis (79%) than thermal pyrolysis process (62.5%).•A quaternary blend containing plastic oil, methanol, diethyl ether and diesel is used.•65% substitution for diesel is made possible by blending 40% plastic oil, 20% methanol, 5% diethyl ether with diesel fuel.•6.838% improvement in BTE is achieved with a 13.643% NOx reduction.•The price of the best blend is 106.26 INR/litre, costing 23.98 INR/kW at full load.