Põllumajandusministeeriumi ja Maaelu ... - bioenergybaltic

problem-free only in fluidized bed boilers while the share of unknown biomass-based fuel
should not exceed 10% of the total fuel amount. In conditions of Estonia it would mean
agreements with the biomass-based CHP plants (Väo and Tartu) which are under
comnstruction or being designed and where the fluidized bed boilers have sufficient capacity
for the safe burning of small biomass batches. However, this kind of work may require also
building either of an additional fuel feeding unit, or in a less complicated case mixing small
amounts of additional fuel with the main fuel would be sufficient.
Up to now nobody has been engaged in designing special (small) boilers suitable for burning
herbaceous biomass either in Estonia or in other countries, because the amounts of herbaceous
biomass are small and the development would not be economically feasible. Thus we must
look for the most appropriate existing equipment for burning herbaceous biomass and give
preliminary recommendations for solving the possible problems related to the combustion
technology. As a rule, the most uncomfortable problem is the low melting temperature of
herbaceous biomass ash that may cause the ash becoming sticky and clogging the grate. The
stoker burner for pellet burning could be tested for checking the combustion conditions of
such fuels when the burner heads are cleaned after short intervals or mechanical ash removal
is applied. High Na and K content in the ash refers to the low ash melting temperature, but due
to the co-influence of many other components, this relationship cannot be pointed out. The
dangerously low melting temperature of ashes may occur in case of some fuel blends in spite
of the fact that the ash melting temperatures of both fuels are significantly higher.
Building of a special unit for upgrading various biomass types is not reasonable considering
the limited possibilities of Estonian market. It would be reasonable to select the equipment by
pilot production and based on the gained experience it may be expedient to adapt the press
slightly for a certain biomass type. Before starting wide-scale upgrading of herbaceous
biomass, the conditions necessary for burning the output must be checked and decision about
the expediency of making the products taken.
In Estonia the waste combustion is controlled with the regulation no 66 of the Minister of
Environment from June 4, 2004 “Requirements for Building, Use and Closing of Waste
Incineration Plant and Co-incineration Plant” (RTL, 21.06.2004, 83, 1316). The requirements
of the regulation are valid both for big and small incineration plants with over 50 t of waste a
year.
In the incineration plant of non-hazardous waste such a level of waste should be reached that
the total content of organic carbon (TOC) in the slag and bottom ash formed by incineration
remains below 3% or their heat loss is below 5% from the dry matter of the substance. The
temperature of flue gas derived from waste incineration must rise at least to 850 o C after the
last combustion air injection and remain at this temperature at least for 2 seconds. The content
of pollution components in the wastewater from cleaning the waste incineration flue gases
must not exceed the limit values of pollutants specified by the Waste Incineration Regulations.
A waste incineration plant must be equipped with a collection tank of sufficient volume for the
water from rainfall leaks and firefighting. At the wastewater outlet the pH, temperature and
rate of flow must be regularly measured. Once a day the content of floating matter in the
averaged sample proportional to the flow rate must be determined. The Hg, Cd, Tl, As,Pb, Cr,
Cu, Ni and Zn content must be established in the averaged sample proportional to the daily
flow rate at least once a month and the dioxyne and furane content must be measured at least
once in three months. The method of conducting more exact measurements is specified in the
Waste Incineration Regulations.
The technologies suitable for waste incineration are expensive due to strict environmental
requirements and problems related to the incineration techniques. Therefore, construction of
only big incinerators for over 200,000 tons of waste a year is considered economically
feasible. It is not expedient to build more than two or utmost three waste incineration plants in
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