A comparative techno-economic analysis of combined oil and power production from pyrolysis and co-pyrolysis plants utilizing rice straw and scrap rubber tires

Abstract

In this study, three pyrolysis and co-pyrolysis plants processing rice straw (RS) and scrap rubber tire (SRT) to produce oil and power (i.e., electricity) at 30 t/hr capacity are simulated using SuperPro Designer software. The objective of the study is to comparatively evaluate the techno-economic performance of hypothetical (co-)pyrolysis plants at commercial scale. The RS production is estimated in 36 districts of Punjab, Pakistan through GIS mapping and the location and capacity of the plants are selected accordingly. The RS plant has the lowest capital and annual operating costs of $53.70 million and $43.70 million, respectively however, it is not economically feasible under current conditions due to its low quantity and quality of the produced oil. The base cases of SRT and co-feed (RS and SRT) plants are found to be viable with capital costs of $66.90 million and $68.30 million, and annual operating costs of $77.20 million and $70.30 million respectively. The co-pyrolysis plant produces the highest oil (main product) yield of 74 kilotons annually and power of 4801 KWe with the lowest unit production cost of $950/tonne. Consequently, the co-pyrolysis plant offers the highest economic performance with $35.55 million of net present value (NPV) estimated at a discount rate of 15% over 20 years of plant life. The payback period (PBT), internal rate of return (IRR) and gross margin (GM) are 5.08 years, 34.67% and 21.35% respectively. Sensitivity analysis suggests that the NPV is sensitive to the oil selling price, feedstock cost, and capital investment for all plants. Moreover, economy of scale analysis quantified the effects of different processing capacities on the economic metrics such as NPV, PBT, capital cost, and operating cost.