Hydrothermal Carbonization of Chemical and Biological Pulp Mill Sludges

A modern pulp mill generates a variety of different by-products and waste streams, some of these can be recycled, refined, sold, or used on-site for energy production. However, some, such as chemical and biological sludges produced in wastewater treatment cannot be reused or disposed of easily, mainly due to their high moisture content and poor drying characteristics. Tightening legislation regarding waste disposal as well as the growing need to increase the process efficiencies of pulp mills act as driving forces to find environmentally friendly and energy-efficient techniques for pulp mill sludge treatment. This study summarizes the current methods for pulp mill sludge handling and evaluates the potential of hydrothermal carbonization (HTC), a conversion process through which wet organic substrates can be transformed into a carbonaceous material (hydrochar). Depending on the process parameters, the material’s structure is modified, enabling hydrochar use in energy, soil conditioning and adsorption applications. The sludges were hydrothermally carbonized at 180, 200, 220 and 240 °C for 3 h. The hydrochar and liquid products’ main properties were analyzed. Their potential applications were also evaluated. The effective treatment of sludges from the pulp industry with HTC could transform energy-demanding waste into a value-added source of materials.

Non-Isothermal Pyrolysis Kinetic Studies of Kraft Pulp Mill Sludge and Its Blending with Coal Powder

Non-isothermal pyrolysis of kraft pulp mill sludge and coal has been investigated. Blending sludge with coal resulted time increase to complete the pyrolysis. This phenomenon indicated that volatile matter in coal was more difficult to be degraded. Sludge pyrolysis at 10, 15, and 20°C/min remained residual mass fraction of 64.6% w/w, 62.4% w/w, and 64.4% w/w, respectively. Coal addition into sludge had reduced char yield. Char yield decreasing was due to lower content of coal ash compared to sludge ash.Sludge lost most of its mass was between 200°C and 500°C, and its peak was at 280°C. -It was slow at >500°C. Wide range of coal degradation temperature indicated that coal may contain components having a wide range temperature degradation, such as lignin. Based on the curve of mass loss rate of reaction, there were three peaks which indicates three reaction mechanisms of sludge-coal pyrolysis. All peaks followed the mechanism of frst order reaction. First peak was likely to occur due to decomposition of hemicellulose and other highly volatile components. Second and third were associate with cellulose and lignin, respectively. The high thermal stability properties lead to a slow degradation of lignin, and its mass loss occurred in the a very wide of temperature range (160-900°C). Studi Kinetika Pirolisis Non-Isotermal Lumpur Industri Pulp Kraft dan Campurannya dengan Serbuk BatubaraPirolisis non-isotermal lumpur industri pulp kraft dan campurannya dengan serbuk batubara telah diselidiki. Pencampuran lumpur dengan batubara menghasilkan peningkatan waktu untuk menyelesaikan pirolisis. Fenomena ini menunjukkan bahwa zat volatil dalam batubara lebih sulit terdegradasi. Pirolisis lumpur pada 10, 15, dan 20°C/menit menghasilkan fraksi massa residu masing-masing 64,6% b/b, 62,4% b/b, dan 64,4% b/b. Penambahan batubara ke dalam lumpur mengurangi hasil arang. Penurunan hasil arang disebabkan oleh kandungan abu batubara yang lebih rendah dibandingkan dengan abu lumpur. Lumpur kehilangan sebagian besar massanya antara 200°C dan 500°C, dan mencapai puncaknya pada 280°C. Kehilangan massa melambat pada suhu >500°C. Rentang suhu yang lebar pada degradasi batubara menunjukkan bahwa batubara mengandung komponen yang memiliki suhu degradasi luas, seperti lignin. Berdasarkan kurva laju kehilangan massa, terdapat tiga puncak reaksi yang menunjukkan tiga mekanisme reaksi pirolisis lumpur-batubara. Semua puncak tersebut mengikuti mekanisme reaksi orde pertama. Puncak pertama kemungkinan terjadi karena dekomposisi hemiselulosa, dan komponen-komponen lain yang sangat mudah menguap. Puncak kedua dan ketiga masing-masing berhubungan dengan selulosa dan lignin. Sifat stabilitas termal yang tinggi menyebabkan degradasi lignin yang lambat, dan kehilangan massa terjadi dalam kisaran suhu yang sangat luas (160-900°C).

Wastes from pulp and paper mills - a review of generation and recycling alternatives

The production of pulp and paper is increasing worldwide, and wastes are therefore being generated in appreciable amounts. Various materials are generated in pulp and paper mills, such as ash, dregs, grits, lime mud and pulp mill sludge. Over the years, these wastes have typically been sent to landfills or incinerated. However, with increased environmental awareness new alternatives have been investigated, especially the valorization of these materials. In this review, the characteristics of the manufacturing process, generated wastes, main destinations and recycling alternatives are addressed. The state of the art indicates that dregs are useful in agriculture as soil amendments, while lime mud can be used in agriculture and in environmental technology, mainly in wastewater treatment. Grits are commonly employed in construction, and pulp mill sludge shows applications in agriculture, construction and energy processes. In conclusion, this review shows several successful cases of recycling wastes from pulp and paper mills.