Browsing by Subject "Hydrothermal carbonization"

Now showing 1 - 3 of 3
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    Industrial symbiosis: corn ethanol fermentation, hydrothermal carbonization, and anaerobic digestion
    (2012-12) Wood, Brandon M.
    The production of dry-grind corn ethanol results in the generation of intermediate products, thin and whole stillage, which require energy-intensive downstream processing for conversion into commercial co-products. Alternative treatment methods, specifically hydrothermal carbonization of thin and whole stillage coupled with anaerobic digestion were investigated to determine if they provide an opportunity to recover some of this value. By substantially eliminating evaporation of water, reductions in downstream energy consumption from 65-73% were achieved, while hydrochar, fatty acids, treated process water, and biogas co-products were generated, providing new opportunities for the industry. Processing whole stillage in this manner produced the four co-products, eliminated centrifugation and evaporation, and substantially reduced drying. With thin stillage, all co-products were again produced, as well as a high quality animal feed. Anaerobic digestion of the undiluted aqueous product stream from thin stillage hydrothermal carbonization reduced chemical oxygen demand (COD) in this product stream by more than 90% and converted 83% the initial COD to methane. Internal use of this biogas could entirely fuel the HTC process and reduce natural gas overall usage.
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    Use of Improved Densification Conditions for Producing High Fuel Content Products from Biomass Processed by Torrefaction, Hydrothermal Carbonization, and Various Densification Methodologies: Final Report
    (University of Minnesota Duluth, 2018-03-31) Fosnacht, Donald R; Hagen, Timothy S; Young, Matthew; Carden, Kendall; Kiesel, Richard F
    The Natural Resources Research Institute is engaged in work to develop demonstration-level production of solid biofuel densified products that can be stored outside, have high bulk densities for ease of logistical transport, have good handling characteristics that minimize dust generation, possess grindability that is like coal used in power plants, and have fuel contents that match or exceed sub-bituminous coal levels. During the work, two pretreatment technologies have been investigated for concentrating the energy content of raw biomass. These include: torrefaction using an indirectly fired rotary kiln process at the demonstration level and hydrothermal carbonization at the bench and pilot scale. The Institute has also collaborated with Syngas technologies on a pilot-scale moving bed, directly heated steam-based process at the pilot scale and next year will install this technology at the demonstration scale. A key factor in showing the full technical feasibility of using the pretreated materials is to demonstrate that the produced particulate fuel products can be densified to a level that allows good logistical and handling practices to be routinely attained. It has been found that hydrothermally carbonized processed materials can be agglomerated using a variety of densification devices including pelleting and briquetting in a repeatable and practical manner using commercial densification equipment with and without the use of binders. However, torrefied materials have proven to be much more difficult to densify using a variety of densification equipment, especially as the degree of torrefaction increases. Uniformly torrefied materials at high energy level appear to be especially difficult to densify but have the attributes of high fuel value and good grindability, with very little residual fiber content compared to less-torrefied material or steam-exploded biomass. Therefore, the work undertaken and explained in the following discussion has been conducted and shows that highly torrefied materials can be satisfactorily densified to produce high-energy-content products that have good physical properties, possess acceptable moisture resistance, low ash, sulfur and mercury content, and have bulk densities that can lead to improved logistics. The densification practices involve optimizing overall process conditions on an integrated systems basis and include moisture level, densification pressure, mix preparation pressure, and the use of appropriate binders when required. The densification system that seems to show the greatest promise for the highly torrefied materials is briquetting. Work will continue in examining other densification options and in improving the conditions used and discussed in this report.
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    Utilization of aqueous product generated by hydrothermal carbonization of waste biomass
    (2014-10) Vozhdayev, Georgiy Vladimirovich
    Hydrothermal carbonization (HTC) is a thermochemical treatment process that allows for the conversion of relatively dilute biomass slurries into value added products which are hydrochar and filtrate. This investigation focuses on the potential for utilization of the filtrate (aqueous by-product) created via HTC. A majority of the research to date has focused on the solid HTC product (hydrochar), however little attention has been paid to the utilization of the HTC filtrate, which makes up the larger mass fraction. Finding value added products is key to making the process a viable treatment option for waste biomass and other organic by-products. The option of using HTC filtrate as a fertilizer replacement for agricultural crop production was evaluated through studies of soil microbial effects and impacts on seed germination and early plant growth. These studies confirmed bio-toxicity effects of HTC filtrate on agricultural soil microbes at high application rates. On the other hand, lower rates of application induced biodegradation of the phytotoxic components of the filtrate and released additional plant nutrients through N-mineralization. These effects are dependent on filtrate type, concentration, and post-treatment of the applied filtrate. Phytotoxicity effects on seed germination and seedling growth of corn (Zea mays L.) also showed a dependence on HTC filtrate source and concentration. Similar to the impacts observed on the soil microbes, high concentration typically inhibited seed germination and growth, but lower concentrations stimulated early corn growth. Characterization of the filtrates via a 2-dimensional gas chromatography (GC) time-of-flight mass spectrometry confirmed a very complex chemical fingerprint of the filtrates. Chemical speciation in the filtrate appeared to be a function of the feedstock. More importantly, the simple storage of filtrate in an open container for 90 days drastically alters the chemical species composition and correspondingly the observed impact on soil microbes and plant growth, leading to the conclusion that there could be chemical inhibitors present in the filtrate that are responsible for the observed effects that are eliminated though simple volatilization or microbial mineralization during storage. This work shows great promise for utilization of HTC filtrates as an agricultural fertilizer and the recycling of critical plant nutrients. Additional work is needed to fully characterize the chemical diversity present in these filtrates prior to the implementation of this renewable and sustainable source of agricultural fertilizers.