Dimethyl ether from Industrial Pellets as a rural smart fuel

Technischer Bericht, 2018

10 Seiten


Dimethyl ether from Industrial Pellets as a rural smart fuel

Johann Gruber-Schmidt


Wood Pellets are well known and a part of the global trading. But the main problems are the high costs, the energy needed, the high quality of wood, leads to a product, without any industrial application. For industrial application we need larger pellets up to 25 mm diameter and higher, with a very low ash production, with low limits in pollution like metals and organic compounds. Those industrial pellets can substitute fossil coal, and fossil crude oil. Beside the application of industrial pellets we are now in the position to recycle municipal waste and to produce pellets as secondary fuel or pellets as refused fuel. The classical pellets can be used in combustion chambers with attached boilers, this technology is well known. The industrial pellets can be used in gasifiers to produce a weak gas and charcoal. secondary fuel and RDF pellets can be used in advanced gasifiers to generate weak gas and charcoal. Again we have to recycle and separate the wood and waste wood and municipal waste into metals, plastics and biogenic waste. The biogenic waste has to be separated into used natural wood, used coated wood, in biogenic waste and in biogenic waste with plastic foils. Metals and plastics will be recycled in the industrial processes. With the separation and recycling process we now in the position to qualify the wood waste and to generate weak gas and charcoal or to generate a strong syngas for dimethyl ether production.

Biomass and Waste

Abbildung in dieser Leseprobe nicht enthalten

Table 1: Description quality of waste wood (Source, Johann Gruber-Schmidt, [ 1 ], 2018 )

Classical wood from the forestry converted to wood chips is well known. In common we are speaking from a product for the private consumer market, high quality core product with any bark. On the other side we have biogenic waste and municipal waste. Municipal waste separated leads to liquid biogenic waste, like food waste with a moisture of about 70%, and biogenic solid waste with a moisture of about 30%. Additional we have solid synthetic waste as plastic foils, plastic parts, in mots cases theses small particles cannot be separated from the biogenic waster. At the wend we have a biogenic liquid waste, and we have the solid biogenic waste mixed with solid synthetic particles. For the pellets we are focusing on the solid waste itself.

In the table 1 the two used wood qualities are shown. Under AI we understand used natural wood, like packages, palettes, offcuts, strips, furniture, wood for civil, or old cable drums. Under used wood we understand used painted and coated wood without (PVC), palettes, boxes, offcuts, windows, frames, ceilings, floors, and fixing plates in civil.

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Table 2: Measurement „ standard“ compared with „natural wood”

(Source, Johann Gruber-Schmidt, [ 1 ], 2018 )

An additional waste fuel are the secondary fuels or also called substitute fuels like RDF (refused derived fuel). If the municipal synthetic waste is not recycled, only separated from metals and waste food, we get a combination of biogenic and synthetic waste, shredded we call this high energetic waste a secondary fuel or refused derived fuel.

The limits for recycling wood for the pollution is shown in the table 2. The main interests are the metals and the poly cyclic aromatic carbon hydrates as a sum value. The main focus is lead to the substances Chlorine (Cl) and lead (Pb). Under “standard” the measurements of the industrial pellets are listed up, these measurements will be compared with the measurements of natural wood. The poly cyclic aromatic carbon hydrates are some mentioned with Lindan, Benzo(a)pyren and Pentachlorpheanol.

Refuse derived fuel (RDF) is produced from domestic and business waste, which includes biodegradable material as well as plastics. Non-combustible materials such as glass and metals are removed and the residual material is then shredded. Refuse derived fuel is used to generate energy at recovery facilities, many of them in Europe where they produce electricity and hot water for communal heating systems. With the bottom cycle and top cycle we are now able to convert RDF pellets into weak gas and charcoal.

Solid recovered fuel (SRF) is a high quality alternative to fossil fuel produced from mainly commercial waste including paper, card, wood, textiles and plastic. Solid recovered fuel has gone through additional processing to improve the quality and value. It has a higher calorific value than SRF and is used in facilities such as cement kilns. With the bottom cycle and top cycle we are now in the position to convert SRF pellets into weak gas and charcoal and to produce the needed for steam generation of biomass, biogas and charcoal to gain an high quality strong synthetic gas for dimethyl ether production.

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Table 3: Measurement of SRF Probes 01/02/03

(Source, Johann Gruber-Schmidt, [ 1 ], 2018 )

This is made difficult by the fact that that, in daily practice, many calorific wastes are referred to as refuse-derived fuel (RDF). But as there is no official definition of RDF, the content and quality of this may vary. Very often the compositional quality and the environmental parameters are not well described. This poses a risk for producers and users of these fuels as human health and equipment may suffer from certain, sometime hazardous, components in the fuel. As environmental impacts cannot be overseen, public acceptance and acceptance by competent authorities is generally low. So while an RDF, whatever that may be, might have a good calorific value and low chlorine content, clients can never be sure of its composition because it is not tested and evaluated in an appropriate and standardized way.

To make handling waste derived fuel easier, a common language has been made possible by European standards of CEN/TC 343 for ‘solid recovered fuel’ (SRF). SRF is a fuel produced from non-hazardous waste in compliance with the European standard EN 15359. Although this standard is not an obligation, the main requirement is that a producer specifies and classifies its SRF by detailing its net calorific value, and chlorine and mercury content of the fuel. Specification includes (as mandatory) several other properties, such as the content of all heavy metals mentioned in the Industrial Emissions Directive. Furthermore, a declaration of conformity has to be issued. Even though this standard means that there is an agreed upon definition of SRF, it is important to note that EN15359 and its underlying standards do not require any quality level. The required quality of SRF is therefore defined by the client, meaning that SRF quality can vary.

Dimethyl ether

Dimethyl ether is well known. It is the simplest ether consisting of two carbon atoms, one oxygen atom and six hydrogen atom, molar mass MZ~ 46 g/mol [ 11 ]. It is certificated by ISO 16 681: 2013 by the IDA. At a pressure of 6 bar Dimethyl ether is in liquid phase at an environment temperature of 25°C [ 11 ]. The simplest ether is synthetic and can produced with two pathways: the production in two steps in the first step over the intermediate product methanol ( methanol synthesis ) Abbildung in dieser Leseprobe nicht enthalten and in the second step over dehydration ( water removal ) Abbildung in dieser Leseprobe nicht enthalten, or in the direct synthesis in one step Abbildung in dieser Leseprobe nicht enthalten. The difference between both chemical processes is the energy (heat generated and needed) the resulting mass flows generated by the processes. The caloric heat value of dimethyl ether is given caloric combustion enthalpy Hc=1460 kJ/mol [ 11 ], the formation standard formation enthalpy Hf=184 kJ/mol [11]. The combustion of dimethyl ether in diesel engines leads to nearly no soot, dust, a reduction of carbon monoxide and nitrogen oxide [ 10 ].

Industrial Pellets

Because of the different shapes and structures of waste wood and biogenic waste we are searching for a common structure. Therefor we have to collect the biogenic mass and then we have to separate the metallic and plastic parts from the biogenic material. The biogenic material now will be shredded, in the next step dried to a moisture of 10%. After drying the biogenic mass is milled to particles diameter d~ 1mm up 5mm and pressed to larger pellets with a diameter d~15 mm up to 25mm and length l~30mm up to 50mm. The density of the pellets is given with 600 up to 650 kg/m³. We turn now to the content of the industrial pellets:


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Dimethyl ether from Industrial Pellets as a rural smart fuel
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Dr. techn. Johann Gruber-Schmidt (Autor), 2018, Dimethyl ether from Industrial Pellets as a rural smart fuel, München, GRIN Verlag, https://www.grin.com/document/434512


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