Opportunities for solar process heat integration and heat recovery in the South African fishmeal industry

Oosthuizen, Dewald (2018-03)

Thesis (MEng)--Stellenbosch University, 2018.

Thesis

ENGLISH SUMMARY: Solar thermal renewable energy is a promising alternative heat source capable of providing a large portion of the South African industrial heat demand. The major energy demand within the energy intensive South African industrial sector is process heat, furthermore, industrial process heat constitutes approximately 30% of the national annual energy consumption. Most of this heat is currently supplied by fossil fuels, which is a challenge to the future sustainability of the industrial sector since the cost of fossil fuels is expected to increase indefinitely, and their use impacts negatively on the environment. Two South African fishmeal factories were studied with the aim of determining the feasibility of integrating solar thermal heat into existing production processes within the industrial sector. The fishmeal production process is energy intensive as it requires the evaporation of large amounts of water. Base case processes were established, based on actual production data collected from the factories, in order to determine the energy and fuel requirements of the factories. Opportunities for heat recovery and solar heat integration were identified, and their effects on the energy demand quantified. The total potential for solar heat (in terms of total collector area) was established and two systems proposed: 1) with an area that minimised the difference between solar heat demand and supply, and 2) with an area that resulted in no excess heat production. A preliminary economic analysis was performed to quantify the economic viability of the proposed systems. Factory A produces fishmeal from lean-fish processing by-products using a single dryer, with heavy fuel oil as fuel source. Preheating of the raw material stream presented an opportunity for both solar heat integration and heat recovery. A 384 m2 solar heat system was the most profitable option investigated with a net present value of R 3.3 million and levelized cost of heat of R 0.79. Heat recovery from the condensate stream exiting the dryer was also economically viable, however, it was less profitable and resulted in lower fuel savings. Factory B produces fishmeal and fish oil from pelagic fish species using the wet-pressing method, with coal as fuel source. Solar thermal heat could be used to preheat the entering raw material and boiler make-up water streams and to heat the stickwater concentrate prior to drying. Heat recovery from the fish oil stream could only supply a very small fraction of the heat required. Due to the large capital costs of the solar thermal systems and the low cost of coal, none of the proposed systems were economically viable. The cost of the fuel being replaced and the heat demand throughout the year were found to be major factors affecting the economic viability of the solar thermal heat systems. It is recommended that the energy requirements and production schedules determined in this study, be used to simulate the solar heat systems and obtain more accurate values of the solar thermal system efficiency and output. This will aid the specific factories to obtain implementable solutions.

AFRIKAANSE OPSOMMING: Hernubare sonverhittings energie is ʼn belowende alternatiewe hitte bron wat ʼn groot gedeelte van die Suid-Afrikaanse industriële hitte vraag kan voorsien. Die grootste vraag vir energie in die energie intensiewe Suid-Afrikaanse industriële sektor is vir proses hitte, verder maak industriële proses hitte ongeveer 30% van die nasionale jaarlikse energie verbruik uit. Die meeste van die hitte word tans deur fossiel brandstowwe voorsien, wat ʼn uitdaging is vir die toekomstige volhoubaarheid van die industriële sektor, siende dat die koste van fossiel brandstowwe verwag word om onbepaald toe te neem, en die gebruik daarvan ʼn negatiewe impak op die omgewing het. Twee Suid-Afrikaanse vismeel fabrieke was bestudeer met die doel om die lewensvatbaarheid van die insluiting van sonverhitting in bestaande produksie prosesse binne die industriële sektor te bepaal. Die vismeel produksie proses is energie intensief weens die feit dat dit die verdamping van groot hoeveelhede water vereis. Basis geval prosesse was gestig, gebaseer op werklike produksie data wat by die fabrieke ingesamel was, om die energie vereistes en brandstof verbruik van die fabrieke te bepaal. Geleenthede vir hitte herwinning en die insluiting van sonverhitting was geïdentifiseer en die effekte daarvan op die energie vraag gekwantifiseer. Die totale potensiaal vir sonverhitting (in terme van die totale versamelaar area) was bepaal en twee sisteme voorgestel: 1) met ʼn area wat die verskil tussen die hitte vraag en aanbod minimeer het, en 2) met ʼn area wat geen ongebruikte hitte tot gevolg gehad het nie. ʼn Voorlopige ekonomiese analise was uitgevoer om die ekonomiese lewensvatbaarheid van die voorgestelde sisteme te bepaal. Fabriek A produseer vismeel vanaf maer-vis prosessering byprodukte met ʼn enkele droër, met swaar olie as brandstof. Voorafverhitting van die rou materiaal stroom het ʼn geleentheid gebied vir beide sonverhitting en hitte herwinning. ʼn 384 m2 sonverhittingstelsel was die mees winsgewende opsie wat ondersoek was, met ʼn netto huidige waarde van R 3.3 miljoen en ʼn genormaliseerde hitte koste van R 0.79. Hitte herwinning vanaf die kondensaat stroom wat die droër verlaat was ook ekonomies lewensvatbaar, dit was egter minder winsgewend en het minder brandstof besparings tot gevolg gehad. Fabriek B produseer vismeel en vis olie vanaf pelagiese vis spesies met die nat-druk metode, met steenkool as brandstof. Sonverhitting kan gebruik word om die rou materiaal stroom, die addisionele ketel water, en die konsentraat te verhit. Hitte herwinning vanaf die vis olie stroom kon slegs ʼn baie klein gedeelte van die vereiste hitte voorsien. Weens die groot kapitaal koste van die sonverhittingstelsels en die lae koste van steenkool, was geen van die voorgestelde stelsels vir Fabriek B ekonomies lewensvatbaar nie. Die koste van die brandstof wat vervang word en die hitte vraag deur die loop van die jaar het die grootste effek op die ekonomiese lewensvatbaarheid van die sonverhittingstelsels gehad. Dit word aanbeveel dat die hitte vereistes en produksie skedules wat in die studie bepaal was, gebruik word om die sonverhittingstelsels te simuleer en sodoende meer akkurate waardes van die sisteem doeltreffendheid en uitset te kry. Dit sal die spesifieke fabrieke help om ʼn implementeerbare oplossing te vind.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/103640
This item appears in the following collections: