Date of Award

Fall 12-16-2022

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science in Chemical Engineering (MSChE)

Department

Chemical Engineering

Advisor

Peter van Walsum

Second Committee Member

Adriaan R. P. van Heiningen

Third Committee Member

Jennifer J. Perry

Abstract

Seaweed (macroalgae) is a marine resource that has a high economic value. Seaweeds are important commodities as raw material for food or additives and as a source of biomass. One popular species of seaweed is Sugar kelp (Saccharina latissima) – a brown algae that is native to the Maine coast and also a commonly farmed species. It is a rich source of fibers, vitamins, minerals, and antioxidants. Seaweeds are highly perishable due to their high moisture content and will spoil quickly if not preserved, therefore a common practice is to dry the product to prolong storage life and to minimize the cost for transportation. A drying method using warm (not hot) air will extend seaweed shelf life and also retain many of the valuable bioactive components that are heat and/or UV sensitive. Thus, a controlled drying environment can best retain product and nutritional value and prevent degradation of the food quality. A first of a kind drying system with controlled temperature, air flow and exit humidity has been developed and assembled in the advanced manufacturing center (AMC) at the University of Maine. The drying system is built within a 40-foot-long shipping container. vi Inside the container, the seaweed is suspended from an oval shaped overhead conveyor system, where it slowly rotates around the length of the chamber. A utility room at one end of the container houses two parallel propane powered heaters with integral blowers, an exhaust fan and a control system. My project is looking at examining the drying time, the temperature and humidity within the drying process, the drying rate, and energy efficiency of the process. Several experiments were run during early and late springtime 2020 using wet towels or fresh Sugar kelp in the dryer. The drying system is equipped with five temperature and humidity sensors which logged data every 0.5 seconds. Examination of the drying runs shows that as air passes through the drying chamber it decreases in temperature and gains humidity, as expected. It became apparent that partial recycling of the air was important for achieving high exit humidity and lower energy cost. In early runs, the data showed that air was short circuiting through the dryer and circumventing the hanging material being dried. This flaw was partly resolved by adding some sheeting at the top of the conveyor and partially blocking two ventilation ports. We also noted that the temperature measurement of the incoming air was being affected by the level of recycle and furnace activity. It can also be seen that through the duration of the drying work, the exiting air shows a steady trend of rising temperature and decreasing RH. Analysis of the energy dynamics for the system shows that more data are needed to consistently close the energy balance, particularly with respect to metering the propane used, determining the temperatures of different surfaces of the dryer, the rate of air flow into and out of the system, as well as weather conditions, insolation rate and orientation to the sun. Estimated values for these variables suggest that insulating the walls of the container, except on bright sunny days, will likely be cost effective.

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