Biomass Combustion Facilities
Energy utilisation of biomass is generally considered desirable and appropriate in terms of minimisation of the environmental burden. It also has its prospect within CEZ Group. It is expected that biomass co-firing in the production of the Hodonín, Poříčí and Dvůr Králové Power Plants will gradually increase. Besides, CEZ Group plans the construction of generators designed for combustion of pure biomass. CEZ Group is also active in acquisitions. In April 2009, it announced the purchase of combined power and heat generator using pure biomass combustion in Jindřichův Hradec. Starting from 31 December 2009, one unit of Hodonín Power Plant is designed solely to combust pure biomass.
How Power Production from Biomass Works
Combustion of biomass is the oldest thermo-chemical biomass conversion, in the process of which organic material is decomposed to flammable gases (and other substances), and in the subsequent oxidation the energy, carbon dioxide (CO2) and water are released. Unlike fossil fuel combustion, the biomass combustion results, in principle, in zero balance of CO2, which ranks among the so-called greenhouse gases. Production of CO2 from biomass combustion is neutral, since the amount of gas released in the air by combustion is approximately equal to the amount that is retroactively bound in plants in agricultural and forest greenery or at the so-called energy plantations. Also the content of released sulphur oxides is low (the content of sulphur in wood or straw is 0 to 0.1 % while brown coal sometimes contains even more than 2 %). The amount of produced NOx can be controlled e.g. by the adjustment of combustion temperature.
Biomass is very complex fuel, since the share of volatile combustible substance is very high (70 % for wood, 80 % for straw) and produced gases have different combustion temperatures. That is why only a part of fuel actually burns. Perfect combustion is pre-conditioned by high temperature, efficient mixing with air and sufficient space for all gases to burn properly at the designed place and not in the stack.
For energy utilisation, wood is chipped, sawdust is pressed to pellets and briquettes. Straw from both grain and oil crops, e.g. rape, is used; it is pressed or used to make briquettes and pellets. The list of permitted “energy plants” includes the whole range of annual, biennial as well as perennial species, e.g. amaranth, hemp, Chinese mallow, evening primrose, white melilot, cup plant, crown vetch or the most prospective in terms of energy utilisation – fodder sorrel. Also fast-growing aspen, willow, alder, acacia, plane-tree etc. can be used.
CEZ Biomass Combustion Power Plants
In 2014, CEZ Group produced nearly as much as 274 GWh of electric power from biomass in domestic power plants. The above-mentioned production would cover annual power consumption of approx. 80 thousand households. Regarding the output, Hodonín Power Plant is the number one in CEZ Group; in 2014, it produced more than 152 GWh from biomass.
Starting from 31 December 2009, one unit of Hodonín Power Plant is designed solely to combust pure biomass. The electric output of the facility is up to 30 MW and every day it requires 1,200 tonnes of biomass. In order to create the sufficient surplus necessary to cover weekend operation, the delivery of approx. 1,600 tonnes of biomass on weekdays is required.
Recently, the laboratory dealing with biomass analysis as well as biomass sorter and biomass pellet conveyor with haulage of 20 tonnes an hour have been put into operation there. In January, the automatic biomass sampler was put into operation.
Hodonín Power plant is also unique in Europe for its cross-border heat delivery. In 2014, it supplied approx. 90,000 GJ from the total heat production of 550,000 GJ to the Slovak town of Holíč.
CEZ Group is also active in acquisitions. In April 2009, it announced the purchase of combined power and heat generator using pure biomass combustion in Jindřichův Hradec. The produced heat is mainly supplied to the central distribution system of the town of Jindřichův Hradec. Every year, the generator produces over 30 thousand MWh of electric power by pure biomass combustion – such amount is an equivalent of the annual power consumption of 8,500 households.
In addition to Czech power plants, biomass is also successfully co-fired in Polish power plants of Skawina and ELCHO, which are a part of CEZ Group.