Optimisation of fuel usage and steam availability in the power and steam plant of a paper mill

This paper presents the results of a project aimed at minimising fuel usage while maximising steam availability in the power and steam plant of a large newsprint mill. The approach taken was to utilise the better regulation and plant wide optimisation capabilities of Advanced Process Control, especially Model Predictive Control (MPC) techniques. These have recently made their appearance in the pulp and paper industry but are better known in the oil and petrochemical industry where they have been used for nearly 30 years. The issue in the power and steam plant is to ensure that sufficient steam is available when the paper machines require it and yet not to have to waste too much steam when one or more of the machines suffers an outage. This is a problem for which MPC is well suited. It allows variables to be kept within declared constraint ranges, a feature which has been used, effectively, to increase the steam storage capacity of the existing plant. This has resulted in less steam being condensed when it is not required and in significant reductions in the need for supplementary firing. The incidence of steam being dump-condensed while also supplementary firing the Combined Heat & Power (CHP) plant has been reduced by 95% and the overall use of supplementary firing is less than 30% of what it was. In addition the plant runs more smoothly and requires less operator time. The yearly benefit provided by the control system is greater than £200,000, measured in terms of 2005 gas prices.

Zero carbon manufacturing facility - Towards integrating material, energy, and waste process flows

The increasing pressure on material availability, energy prices, as well as emerging environmental legislation is leading manufacturers to adopt solutions to reduce their material and energy consumption as well as their carbon footprint, thereby becoming more sustainable. Ultimately manufacturers could potentially become zero carbon by having zero net energy demand and zero waste across the supply chain. The literature on zero carbon manufacturing and the technologies that underpin it are growing, but there is little available on how a manufacturer undertakes the transition. Additionally, the work in this area is fragmented and clustered around technologies rather than around processes that link the technologies together. There is a need to better understand material, energy, and waste process flows in a manufacturing facility from a holistic viewpoint. With knowledge of the potential flows, design methodologies can be developed to enable zero carbon manufacturing facility creation. This paper explores the challenges faced when attempting to design a zero carbon manufacturing facility. A broad scope is adopted from legislation to technology and from low waste to consuming waste. A generic material, energy, and waste flow model is developed and presented to show the material, energy, and waste inputs and outputs for the manufacturing system and the supporting facility and, importantly, how they can potentially interact. Finally the application of the flow model in industrial applications is demonstrated to select appropriate technologies and configure them in an integrated way. © 2009 IMechE.

Centrifuge modelling and dynamic testing of municipal solid waste (MSW) landfills

An investigation into the seismic behaviour of municipal solidwaste (MSW) landfills by dynamic centrifuge testing was undertaken. This paper presents physical modelling of MSW landfills for dynamic centrifuge testing, with regard to the following research areas: 1. amplification characteristics of municipal solid waste; 2. tension induced in geomembranes placed on landfill slopes due to earthquake loading; 3. damage to landfill liners due to liquefaction of foundation soil. A model waste, that has engineering properties similar to MSW, is presented. A model geomembrane that can be used in centrifuge tests is also presented. Results of dynamic centrifuge tests with the model geomembrane showed that an earthquake loading induces additional permanent tension (∼25%) in the geomembrane. © 2006 Taylor & Francis Group, London.

Development of low-pH cements for immobilisation of intermediate level radioactive waste: Achievements and challenges

Although cementation is a widely recognized solidification/ stabilization process for immobilisation of Intermediate Level Radioactive Waste (ILRW), the low resistance to hyperalkaline pore waters compromises the effectiveness of the process when Portland Cement (PC) is employed. Moreover the manufacture of PC is responsible for significant CO2 emissions. In this context, low pH cements are environmentally more suitable and have emerged as a potential alternative for obtaining secure waste forms. This paper summarises the achievements on development of low-pH cements and the challenges of using these new materials for the ILRW immobilisation. The performance of waste forms is also discussed in terms of radionuclides release. Reactive magnesium oxide and magnesium phosphate cements are emphasised as they feature important advantages such as consumption of available constituents for controlling acid-base reactions, reduced permeability and higher density. Additionally, in order to identify new opportunities for study, the long-term modelling approach is also briefly discussed. Copyright © 2013 by ASME.

Current status and perspectives of accelerated carbonation processes on municipal waste combustion residues

The increasing volumes of municipal solid waste produced worldwide are encouraging the development of processes to reduce the environmental impact of this waste stream. Combustion technology can facilitate volume reduction of up to 90%, with the inorganic contaminants being captured in furnace bottom ash, and fly ash/APC residues. The disposal or reuse of these residues is however governed by the potential release of constituent contaminants into the environment. Accelerated carbonation has been shown to have a potential for improving the chemical stability and leaching behaviour of both bottom ash and fly ash/APC residues. However, the efficacy of carbonation depends on whether the method of gas application is direct or indirect. Also important are the mineralogy, chemistry and physical properties of the fresh ash, the carbonation reaction conditions such as temperature, contact time, CO2 partial pressure and relative humidity. This paper reviews the main issues pertaining to the application of accelerated carbonation to municipal waste combustion residues to elucidate the potential benefits on the stabilization of such residues and for reducing CO2 emissions. In particular, the modification of ash properties that occur upon carbonation and the CO2 sequestration potential possible under different conditions are discussed. Although accelerated carbonation is a developing technology, it could be introduced in new incinerator facilities as a "finishing step" for both ash treatment and reduction of CO2 emissions.

Waste management companies in Europe 2009

This paper examines the ownership, employment and finances of the major waste companies in Europe, and recent developments in ownership.

Waste management in Europe: framework, trends and issues

This paper reviews major factors affecting the waste managment sector in Europe, including EU legislation, ECJ rulings, the economic crisis, outsourcing and municipalisation, and employment, including disputes and pay and conditions.

Bioremediation of waste under ocean acidification: Reviewing the role of Mytilus edulis

Waste bioremediation is a key regulating ecosystem service, removing wastes from ecosystems through storage, burial and recycling. The bivalve Mytilus edulis is an important contributor to this service, and is used in managing eutrophic waters. Studies show that they are affected by changes in pH due to ocean acidification, reducing their growth. This is forecasted to lead to reductions in M. edulis biomass of up to 50% by 2100. Growth reduction will negatively affect the filtering capacity of each individual, potentially leading to a decrease in bioremediation of waste. This paper critically reviews the current state of knowledge of bioremediation of waste carried out by M. edulis, and the current knowledge of the resultant effect of ocean acidification on this key service. We show that the effects of ocean acidification on waste bioremediation could be a major issue and pave the way for empirical studies of the topic.

Reuse of construction waste: performance under repeated loading

The use of recycled aggregates has increased greatly over the last decade owing to enhanced environmental sensitivities. The level of performance required by such materials is dependent upon the applications for which they are used. Many recycled construction wastes have adequate shear strength in relation to various geotechnical applications. However, a possible drawback of these materials is the risk of crushing during repeated loading. The work reported in this paper examined two waste materials: crushed concrete and building debris, both regarded as construction wastes. Tests were also performed on traditionally used crushed rock, in this case basalt. The materials were subjected to repeated loading in a large direct shear apparatus. The amount of crushing was quantified by performing particle size analysis of the tested material. The results have shown that both recycled construction wastes were susceptible to particle crushing. The amount of crushing was influenced by both the vertical pressure and the number of loading cycles. This leads to a marked decrease in peak friction angle

Activation of waste MDF sawdust charcoal and its reactive dye adsorption characteristics

This paper reports an experimental investigation of converting waste medium density fibreboard (MDF) sawdust into chars and activated carbon using chemical activation and thermal carbonisation processes. The MDF sawdust generated during the production of architectural mouldings was characterised and found to have unique properties in terms of fine particle size and high particle density. It also has a high content of urea formaldehyde resin used as a binder in the manufacturing of MDF board. Direct thermal carbonisation and chemical activation of the sawdust by metal impregnation and acid (phosphoric acid) treatment prior to pyrolysis treatment were carried out. The surface morphology of the raw dust, its chars and activated carbon were examined using scanning electron microscopy (SEM). Adsorptive properties and total pore volume of the materials were also analysed using the BET nitrogen adsorption method. Liquid adsorption of a reactive dye (Levafix Brilliant red E-4BA) by the derived sawdust carbon was investigated in batch isothermal adsorption process and the results compared to adsorption on to a commercial activated carbon (Filtrasorb F400). The MDF sawdust carbon exhibited in general a very low adsorption capacity towards the reactive dye, and physical characterisation of the carbon revealed that the conventional chemical activation and thermal carbonisation process were ineffective in developing a microporous structure in the dust particles. The small size of the powdery dust, the high particle density, and the presence of the urea formaldehyde resin all contributed to the difficulty of developing a proper porous structure during the thermal and chemical activation process. Finally, activation of the dust material in a consolidated form (cylindrical pellet) only achieved very limited improvement in the dye adsorption capacity. This original study, reporting some unexpected outcomes, may serve as a stepping-stone for future investigations of recycle and reuse of the waste MDF sawdust which is becoming an increasing environmental and cost liability. (C) 2004 Elsevier Ltd. All rights reserved.