Solar thermal process heat in fishmeal production: Prospects for two South African fishmeal factories

摘要

Fishmeal production may lend itself to integration of solar thermal heating due to favourable heating temperature requirements, high heat demand, and production plants being located in high solar irradiance areas for many countries, especially South Africa. Despite these potential compatibilities, and the potential to reduce fossil fuel consumption by switching to a renewable energy heating source, very little work has been done to determine the feasibility of solar thermal heat integration into existing fishmeal production plants. This study focuses on fishmeal production as a potential process for integrating industrial solar thermal heat, and aims to determine preliminary feasibility of solar thermal heat integration into two existing South African fishmeal plants. They differ according to scale of operation, production route, physical location, heating fuel, and the type of raw material processed. The studied factories are a good representation of the different locations and operating conditions that could be expected within the South African fishmeal industry: Factory A produces fishmeal from lean-fishprocessing by-products at a rate of 307 kg/h and requires 2988 MJ from heavy fuel oil per 1000 kg raw material, while Factory B produces fishmeal from pelagic fish species at a rate of 6276 kg/h and requires 1796 MJ from coal per 1000 kg raw material. The method followed identifies areas of heating inefficiency and opportunities for solar process heat integration, followed by preliminary economic analyses for possible implementations to determine economic viability. The study shows that in both factories, preheating the raw material stream to 70 degrees C is an attractive option that could utilise solar thermal heating and noticeably reduce fossil fuel consumption. For Factory A, the most attractive option is a solar thermal raw material preheating system with 384 m(2) flat-plate collector area, resulting in a solar fraction of 0.81 for this process. Factory A's relatively constant monthly heat demand and the high cost of heavy fuel oil being used were the greatest contributors to viability; indicated by a net present value of R 3.3 million for this particular system. For factory B, none of the investigated solar heating systems is found to be economically viable. This is due to the low cost of coal and the seasonal heat demand profile, with no demand from November to January and a maximum during winter months, when solar irradiation is at its lowest. The study concludes that fishmeal production processes have potential for solar thermal heat integration, but suitability and viability are greatly dependent on the specific framework conditions. (C) 2019 Elsevier Ltd. All rights reserved.