Abstract
Tars from pyrolysis of brown coal can be refined to obtain compounds suitable for fuel production. However, it is problematic to refine the liquids from brown coal pyrolysis, because high molecular compounds are produced, and the sample solidifies. Therefore we decided to investigate the possibility of treating the product in the gas phase during pyrolysis, using a catalyst. A two-step process was investigated: thermal-catalytic refining. In the first step, alumina was used as the filling material, and in the second step a catalyst based on W-Ni was used. These materials were placed in two separate layers above the coal, so the volatile products passed through the alumina and catalyst layers. Pyrolysis tests showed that using the catalyst has no significant effect on the mass balance, but it improves the properties of the gas and the properties of the organic part of the liquid pyrolysis products, which will then be processed further.
Highlights
The pyrolysis products of brown coal are [1, 2]: (1.) a solid pyrolysis residue, referred to as coke or semi-coke, which is used as a fuel or as an adsorbent; (2.) a liquid product, which consists of an organic part and a water part and can be utilized as a fuel after refining; (3.) a gas, which is often used for heating a reactor
The analysis showed that the content of hydrogen, carbon monoxide and methane in the pyrolysis gas increased significantly when the catalyst was used
The use of alumina, or alumina with the catalyst, during pyrolysis of brown coal has no major effect on the mass balance, but it improves the gas properties and the properties of the organic part of the liquid pyrolysis products, which are further processed
Summary
(2.) a liquid product, which consists of an organic part and a water part and can be utilized as a fuel after refining;. The highest yields of liquid products can be achieved by fast pyrolysis, in which the products are rapidly removed from the pyrolysis reactor [3]. Increasing the residence time of the volatile product in the hot area leads to secondary reactions, such as thermal cracking, polymerization and condensation, which reduce theF yield of the liquid product [5, 6]. Substances containing sulphur, nitrogen and oxygen allow easier thermal decomposition, all of which leads to the formation of carbon dioxide, carbon monoxide, ammonia, hydrogen sulphide, pyrogenetic water and other products [1]
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