Efficiency Diagram for District Heating System with Gas Condensing Unit

AbstractThe integration of a flue gas condensing unit in a district heating (DH) system source increases the efficiency of the DH system due to the partial recovery of flue gas heat. A multi-regression equation obtained linking the gas condensing unit efficiency indicator with several statistically significant independent variable parameters based on the statistical analysis of the DH system data in Ludza, Latvia, is discussed in this paper. Parameters related to the interaction between the gas condensing unit and the DH system, boiler capacity and the influence of the DH network return temperature on the efficiency of the gas condensing unit is discussed in more detail. To assess the efficiency of the gas condensing unit and to show the distribution of the boiler house heat load between the boiler and the gas condensing unit during the heating season, a diagram is proposed. As a result of the installation of a gas condensing unit after the boiler, the primary energy savings during the heating season is 11.8%

Analysis of Energy Consumption for Biomass Drying Process

This study is dedicated to the analysis of the drying process energy consumption. In order to evaluate the main energetic processes that consume the most energy, the energy consumption of each individual drying process with and without air recirculation was modelled. The model shows that drying agent (air) recirculation is not an energy-saving operation, since it increases the total electricity and heat consumption. Recirculation of the drying agent increases the moisture content of the drying agent at the dryer entrance, which increases the need for fresh air in the dryer so that it can absorb the evaporating moisture from the dried material. An increased flow of the drying agent in the dryer increases the heat and electricity consumption

Co-Firing of Natural Gas with Wood Dust Experimental Test Runs

Co-Firing biomass in the form of wood dust or sawdust with natural gas is a new concept, which was performed in a specialized burner from the Riga Technical University. In order to test the burner, primary experimental test runs were performed to get an overview of flue gas behaviour. The addition of sawdust increased CO values but O2 values remained very low in the flue gases. This was due to technical problems with the fuel. Co-Firing has the potential to reduce CO2 emissions of energy production and wood dust is an abundant by-product of forestry, therefore the potential has to be explored in future research

Modelling of Technological Solutions to 4th Generation DH Systems

Flue gas evaporation and condensing processes are investigated in a direct contact heat exchanger - condensing unit, which is installed after a furnace. By using equations describing processes of heat and mass transfer, as well as correlation coherences for determining wet gas parameters, a model is formed to create a no-filling, direct contact heat exchanger. Results of heating equipment modelling and experimental research on the gas condensing unit show, that the capacity of the heat exchanger increases, when return temperature of the district heating network decreases. In order to explain these alterations in capacity, the character of the changes in water vapour partial pressure, in the propelling force of mass transfer, in gas and water temperatures and in the determining parameters of heat transfer are used in this article. The positive impact on the direct contact heat exchanger by the decreased district heating (DH) network return temperature shows that introduction of the 4th generation DH system increases the energy efficiency of the heat exchanger. In order to make an assessment, the methodology suggested in the paper can be used in each particular situation

Multi-Criteria Analysis to Select Renewable Energy Solution for District Heating System

The research paper is focused on how to choose the most suitable renewable energy solution using multi-criteria analysis for a district heating system. Making choices is based on indicators – economic, environmental and social. In this case, the study used five indicators: resources costs, totals investments, reduction of greenhouse gas emissions, specific weight of renewable energy resources and impact on utilized land. Three situations have been compared – current situation: gas boiler, planned: solar collectors 21 595 m2 + accumulation tank 8000 m3 and alternatives: solar PV panels 5504 m2 – heat pump COP 3 are used in the estimation. The multi-criteria decision-making analysis shows that solar collectors 21 595 m2 + accumulation tank 8000 m3 are considered as the best alternative. The methodology is based on choosing a solution for a district heating company in Latvia