PROCESS The pulp manufacturing process uses about 10,000 litres of water a minute. The wastewater treatment process begins at the AHD tanks – three glass-lined, 10,000-cubic metre tanks running parallel to each other. Bacteria of different varieties are present at various stages in the digesters. “There are different types of bacteria that all work together. It’s a step-by-step process. You have one type of bug that takes the organics and converts it to a simpler form that the next bug can use. And the final step is the bugs that create the methane that we can burn in our engines,” Boyce explains. The digesters create 600-900 cubic metres per hour of methane, which then flow to the 8x45-metre aerobic biological scrubbers. The scrubbers remove hydrogen sulphide from the gas and generate about 700-1,100 cubic metres of biogas each hour, which is sent to the GE Jennbacher engines equipped with power turbines. The entire process has the capacity to generate 6 MW of power, as well as three tonnes per hour of steam from Cain Industries heat recovery steam generators. The steam is used in the pulp drying process, which means less natural gas is burned at the dryers. ADDED BENEFITS FUTURE STEPS Sending the wastewater to the anaerobic digester process ahead of the mill’s existing aerobic effluent treatment system has further reduced the “organic loading” in the mill’s final effluent, as well as the volume of water discharged back into the Athabasca River, Shipton says. It has also reduced the mill’s fresh water intake and chemical consumption, and cut greenhouse gas emissions. On top of the environmental benefits, the increased capacity of the new treatment system has also eased a previous bottleneck at the mill. “We’ve been able to raise our pulp productivity by over 20,000 tonnes a year,” Shipton says. More capacity also means more flexibility in the pulp grades produced, he says. “That has allowed us to adapt to changing market requirements. We’re able to shift our focus and create different grades for different end users.” Now that the path has been forged to introduce AHD technology to the pulping process, the future is full of possibilities for Millar Western and other forest product companies. “We’re utilizing as much of each tree that we harvest as we can. This is the first step in terms of biofuels and the bioeconomy. We’re taking the waste stream and converting it into biogas, into methane. The next step for the forest sector is to look at higher-valued commodities – turning it into liquid biofuels, biopharmaceuticals or other bio-products,” Shipton says. For now, the Millar Western team continues to study methods to optimize the process and resulting biogas and power generation. “We generate a lot of data and making sense of it all is a lot of work. There’s a lot of sitting down and analyzing. It’s a work in progress, and we’re always looking for the next advancement,” Boyce says. • *With files from the Alberta Forest Products Association. YOUR CHOICE FOR ANY BIOMASS DRYING NEEDS WOOD FIBER • CELLULOSE • AGRICULTURAL • WOOD CHIP SAWDUST • WOOD BIO PRODUCT • WOOD POWDER Our Rotary Drying Systems are custom-built to produce a variety of fuels and products. We have been custom building equipment worldwide for over 30 years. BIOMASS Consultations are FREE. Please contact our Main Office in Greendale, WI ( 414 ) 529-0240 or Our Kansas Office in Neodesha, KS ( 620 ) 325-2269 PROUDLY GROWING IN GREENDALE, WI, USA • WWW.UZELACIND.COM 14 Canadian BIOMASS CBM_Uzelac _Summer19_CSA.indd 1 SUMMER 2019 2019-07-08 11:28 AM
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