Paliva (Fuels) is a scientific journal issued quarterly by the Faculty of Environmental Technology, ICT Prague. Fuels publishes papers on a broad range of topics covering exploitation, processing, upgrading, and utilization of various types of fuels, and power engineering.
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Testing of adsorbents for the storage of compressed natural gas in natural gas powered vehicles

Karel Ciahotný, Petr Lenkvík, Veronika Vrbová

The disadvantage of using compressed natural gas in gas powered vehicles is large volume of storage tanks and their great weight. Therefore, search one for new technical solutions that would eliminate these deficiencies. One of them is the use of appropriate adsorption materials filling in storage tanks for compressed natural gas, which under certain conditions lead to increase storage capacity. In the article is described the testing of three different commercially manufactured adsorbents based on activated carbon to increase the storage capacity of natural gas cylinders. There were obtained the results of the increasing storage capacity of pressure tanks for natural gas by their filling with the activated carbon AP4-60 (Calgon Carbon Corporation), activated carbon C46 (Silcarbon Aktivkohle) and BAC (KUREHA Corporation). Also decreasing of the storage capacity used adsorbents was monitored caused as the influence of irreversible sorption of higher hydrocarbons, odorants and other substances contained in natural gas in the pores of used adsorbents.

It was found that in the pressure range of up to 5 MPa usage all three adsorbents leads to increased storage capacity cylinders filled with adsorbent in comparison with a nonfilled pressure cylinder of the same volume. By the gas pressure of 5 MPa is the storage capacity of the tank in case of adsorbed natural gas increased by about 25 – 50 % of the storage capacity in case of compressed natural gas. At a pressure of 1 MPa makes this increase approx. 130 – 170 %.

The two best adsorbent (BAC and C46) were further tested using CNG in repeated cycles of adsorption-desorption in order to determine the decline its sorption capacity. The detected decrease in sorption capacity for methane and other adsorbed gases of CNG in the case of adsorbent C46 is about 0,6 % rel. and in the case of adsorbent BAC about 1 % rel. for every 10 adsorption/desorption cycles.
3/2016 - pages 78 - 83DOI: 10.35933/paliva.2016.03.01

The influence of storage time on the effectivity of addi-tives for improvement of diesel fuel low-te

Aleš Vráblík, Jana Hamerníková, Simona Waňousová, José M. Hidalgo, Radek Černý
The differences between the low-temperature properties of additived diesel fuel containing rapeseed oil methyl ester (RME) were identified with respect the time of storage. All the used samples were prepared in the laboratory scale. The RME was modified using antioxidant and diesel fuel was treated with depressants, WAFI type. The differences in the value of the cold filtration plugging point (CFPP) were observed depending on time of the depressants application. The biggest changes were measured in the first three hours after application. The most accurate results showed the sample which were 3 – 6 hours old. The value of CFPP was improved by up to 7 °C during the storage time. This finding could prevent the overdosing of the depressants for diesel fuel, especially on the commercial scale.
3/2016 - pages 84 - 89DOI: 10.35933/paliva.2016.03.02

Assessment of power industry facilities from the viewpoint of carbonate loop applicability

Marek Staf, Eva Krtková
The study deals with assessment whether the power plants and heating plants, currently operated in the Czech Republic, are eligible for installation of high temperature regenerative capture of carbon dioxide from flue gases by chemisorption on calcined natural limestone or analogous materials.
Based on several evaluating criteria selection of the above defined sources was performed. Method of high-temperature CO2 sorption onto limestones or calcium carbonate containing materials requires installation of relatively complicated system, consisting of a carbonator, in which sorption takes place, and a calciner for subsequent regeneration of the feedstock.
For this reason total annual CO2 emission from each assessed facility, amounting to 5.104 t, was proposed as the first elimination criterion. Other criteria included mainly the type of combusted fuel, the approximate planned life time of the combustion facility and the presence of steam, necessary for carrying out periodic reactivation of the sorbent.
The majority of technical parameters, like distribution of facilities according to the fuel type, distribution of facilities according to the design of combustors etc. were graphically expressed using pie charts.
After evaluating all available parameters 46 blocks of power plants and 32 heating plants were proposed as eligible for implementation of this method of carbon dioxide capture. In total, these sources emit over 39.5 million tons of carbon dioxide per year. If the above mentioned numbers are expressed in relative values installation of carbonate loop is feasible in 73% of the blocks of thermal power stations and 18% of heating plants due to hereby summarized reasons.
3/2016 - pages 90 - 100DOI: 10.35933/paliva.2016.03.03

Comparison of Limestone Adsorption Reactivity During Desulfurisation of Flue Gas From Co-Combustion

Petr Buryan

Research presented in this article proves that woodchips addition significantly negatively influences limestone-based flue gas desulfurization process. This work focuses on the reduction of the adsorption reactivity of two types of calcined limestone that were used for capturing sulfur dioxide from flue gases originating from woodchips and brown coal cocombustion in a fluidized-bed combustor.

3/2016 - pages 101 - 107DOI: 10.35933/paliva.2016.03.04

Thermo-acoustic experiments on drop tube flow

Petr Štěpánek, František Hrdlička, Vladimír Měchura

The mathematical formulation of time dependency of pulverized coal burnout is one of many CFD model parameters. The drop tube furnace is device used to obtain the time dependency of pulverized coal burnout. In order to solve the CFD model of pulverized coal combustion, it´s necessary to get knowledge of initial and boundary conditions of experimental measurement. These conditions can vary and one must know which variation can be neglected. This paper focus on the variation of conditions and it´s trying to calculate them. The sample of solid fuel is lignite of mine Libouš in north-western Bohemia.
There were demonstrated how to obtain the suite of lignite particles approaching to monodisperse. It´s obtained by air washing and separation of much finer particles.
There were presented simple experiment on particle dimensional analysis and calculation of particle sphericity (phi=0.8). Results of experiment were compared with Appalachian hard coal particles (phi=0.78).
In the end there is little discussion around combustion influence to changes of concentration O2 during thermokinetic measurements. The greatest decrement of O2 during thermokinetic measurement by 1200°C and at-mospheric pressure is 0,09% vol.
Method of thermokinetic measurements organized in Ostrava is comparable with methods of other laboratories. However there are differences in details, so before comparison the burnout characteristics must be calcu-lated influence of these differences. For example in Ostrava is used mixture of air and CO2 actually, but in another laboratory is used mixture of air and N2.
In paper [3] was found statement: increment of relative motion causes increment of fuel oxidation rate. There were also discussed similarity of conditions real boiler furnace and conditions of experimental apparat (drop tube furnace). During last two years there were done many experiments with synthetic jet which were focused on:
- Identification of flow character changes,
- Visual inspection of coal particle motion,
- Thermo-acoustic measurement,
- Thermo-kinetic measurement.
There weren`t identified difference: of flow character, visual inspection of coal particle motion, thermo-kinetic measurement during measurement with or without noise. Nevertheless thermo-acoustic measurement verify noise intensity inside reactor of drop tube furnace.
Explanation of these results were found in simple mathematical model of relative motion between elementary volume of reacting gas and small coal particle and shape of O2 concentration contours.
Experiments with synthetic jet on drop tube furnace reactor were absolved in order to approach the experiment conditions to conditions inside furnace of real steam boiler. Next potential step in approaching experiment conditions with conditions inside real furnace of modern steam boiler could lead to the application of air supplying in 2 levels (in 2 other levels of height).

3/2016 - pages 108 - 125DOI: 10.35933/paliva.2016.03.05

technical support editor-in-chief