The analysis on bio-drying potential of sewage sludge in the North of China
This paper analyzes the overview of northern sewage sludge, focusing on the potential of bio-drying of sewage sludge in northern China by adopting the technology of biological drying to dispose the sewage sludge. Owning great development potential is the conclusion obtained by the experimental study of the northern sludge.
Emerging Biodrying Technology for the Drying of Pulp and Paper Mixed Sludges
Effective sludge management is increasingly critical for pulp and paper mills due to high landfill costs and complex regulatory frameworks for options such as sludge landspreading and composting. Sludge dewatering challenges are exacerbated at many mills due to improved in-plant fiber recovery coupled with increased production of secondary sludge, leading to a mixed sludge with a high proportion of biological matter that is difficult to dewater. Various drying technologies have emerged to address this challenge of sludge management, whose objective is to increase the dryness of mixed sludge to above critical levels (≈42% dryness) for efficient and economic combustion in the boiler for steam generation. The advantages and disadvantages of these technologies are reviewed in this article, and it is found that many have significant technical uncertainties and/or questionable economics. A biodrying process, enhanced by biological heat generation under forced aeration, is introduced that has significant promise. A techno-economic analysis of the batch biodrying process at a case study mill showed an annual operating cost savings of about $2 million, including the elimination of landfilling practices and supplemental fuel requirements in the boiler. It was shown that if a biodrying residence time of less than 4 days can be achieved, payback periods of 2 years or less can result in many mills. The potential for the development of a continuous biodrying reactor and the fundamentals of its mathematical modeling are thus presented. Compared to the batch reactor configuration, it is expected that the continuous process would result in improved process flexibility and controllability, lower investment and operating costs due to shorter residence times, and an improved potential to fit into the crowed pulp and paper mill site.
History, criminology and the ‘use’ of the past
This article considers why, despite an apparent congruence of subject matter and methodologies, the disciplines of sociological criminology and criminal justice history are not more closely aligned. It contends that intellectual traffic between the two fields is not usually limited by institutional barriers, nor is it a legacy of the disciplinary antipathy which existed between history and sociology in Britain during the mid-twentieth century. Rather, it is due to the different ‘purposes’ with which sociological criminologists and criminal justice historians imbue their work and to the differing disciplinary perceptions of the relationship between the past, present and future which result from this. These different ‘purposes’ are traced via a consideration of the paths of development of the two disciplines from the 1940s. The article concludes by proposing an arena for future collaboration between criminal justice historians and sociological criminologists.