LAS CUALIDADES FEBRÍFUGAS DE LA

The subject matter of this paper is part of the urban area, e.g. consumption in certain defined area, composed of public facilities (primary and secondary schools, kindergartens, dormitories, ad- ministrative buildings, libraries, etc.), objects of public interest (ambulance, post office, banks, gyms, etc.), other major facilities (hotels, restau- rants, administrative buildings of private compa- nies, etc.), commercial entities and residential buildings (individual and collective). The buildings are mostly of solid construction, especially larger facilities, collective residential buildings and a large part of individual residential buildings. Most of the examined area is connected to the central heating system while the lower part, mostly house- holds, have individual heating systems, mostly are using boilers that are powered by electricity, heat- ing fuel oil (EL), firewood and coal fraction, while rest of residents the heating of homes have settled with solid fuel stoves and electricity panels. An installation for heating by applying modern eco- nomical heating system is negligible.

According to the existing regulations in RM the heating season begins when the temperature of the outside air at 21 p.m, three consecutive days will fall under 12oС, and ends when the outside air temperature under the same circumstances rise above 12o_{С. Thus usually the heating season starts}

on October 15th and ends on April 15 next year, with an average outdoor temperature during the heating of 6o_{С, with a daily average of 15 hours}

warming and theoretical duration of the heating season of 182 days.

In the examined area there is district heating system with plant comprised with three hot water boilers in block construction. Two boilers are with a capacity of 6 MW (with consumption of 1000 kg/h heavy oil or 1155 Nm3_{/h natural gas), and one}

boiler with capacity of 16.3 MW (with consump- tion of 1659 kg/h heavy oil or 1900 Nm3_{/h natural}

gas), or a total plant capacity of 28.3 MW. Plants originally worked with heavy oil, but after per- formed adaptation an old heavy oil burners of the two smaller boilers was replaced with new burners for combustion of natural gas only, while in the larger capacity boiler with appropriate reconstruc- tion was inserted two combined burners with the possibility of using fuel gas / heavy oil alterna- tively.

In order to improve the quality and efficiency of heating, there is set up different modes of op- eration of the plant, where qualitative delivery of heat is directly dependent on the outside air tem- perature. During their daily work, the plant oper- ates in two modes: daily regimen and reduced mode. With the introduction of these two modes will allow improvement of the quality of heating facilities in particular exerted energy on a daily basis. The Figure 1 is represented delivery of heat for each day of the heating season, while the share given from each boiler at same production is re- spectively shown. The energy deposited by the plant provides uniform heating of all facilities and maintenance of stable parameters throughout the day.

When analyzing the emissions of the com- bustion products from the operation of the plant there are considered three scenarios of operation of boilers depending on the plant used fuel: only heavy oil, combined heavy oil / natural gas and natural gas only, under the same external tem- perature terms and heating needs. From the at- tached diagrams is evident that emissions of harm- ful substances SO2, NOx, suspended particles are

far more for production, transmission and distribu- tion of heat energy per unit with using heavy oil as fuel compared with emissions of harmful sub- stances in the production of the same amount of heat energy while using natural gas.

While emissions of CO are inversely propor- tional in terms of SO2, NOx, suspended particles,

emissions are higher when using natural gas than

the combined use of fuel oil / natural gas. You can see that work only with fuel oil as fuel is worst in terms of emissions of harmful substances and it is justified tendency to use natural gas as fuel.

SO2 (kT/yearly)

NOx (kT/yearly)

CO (kT/yearly)

MMVOC (kT/yearly)

Fig. 1. Comparison of total emissions in kT for the period

2003–2010, with an upper limit on pollutants respectively (data from reports of Ministry for Environment of RM)

0 100 200 300 400 500 600 10/10/2005 10/20/2005 10/30/2005 11/9/2005 11/19/2005 11/29/2005 12/9/2005 12/19/2005 12/29/2005 1/8/2006 1/18/2006 1/28/2006 2/7/2006 2/17/2006 2/27/2006 3/9/2006 3/19/2006 3/29/2006 4/8/2006

Amount of heat produced from boiler K1 in 24h  Amount of heat produced from boiler K2 in 24h  Amount of heat produced from boiler K3/1 in 24h  Amount of heat produced from boiler K3/2 in 24h 

Fig. 2. Daily plant production of heat from each boiler in heating season (MW/24 h)

0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 10/10/2005 10/20/2005 10/30/2005 11/9/2005 11/19/2005 11/29/2005 12/9/2005 12/19/2005 12/29/2005 1/8/2006 1/18/2006 1/28/2006 2/7/2006 2/17/2006 2/27/2006 3/9/2006 3/19/2006 3/29/2006 4/8/2006

Total sulfur oxides SO2 in 24h ‐heavy oil Total sulfur oxides SO2 in 24h‐ heavy oil/natural gas Total sulfur oxides SO2 in 24h‐ natural gas Fig. 3. Total emissions of SO2 (t/24h) for every day of the heating season

0 50 100 150 200 250 300 350 400 0/10/2005 10/20/2005 10/30/2005 11/9/2005 11/19/2005 11/29/2005 12/9/2005 12/19/2005 12/29/2005 1/8/2006 1/18/2006 1/28/2006 2/7/2006 2/17/2006 2/27/2006 3/9/2006 3/19/2006 3/29/2006 4/8/2006

Total nitrogen oxides NOx in 24h‐ heavy oil Total nitrogen oxides NOx in 24h‐ heavy oil/natural gas Total nitrogen oxides NOx in 24h‐ natural gas Fig. 4. Total emissions of NOx [t/24h] for every day of the heating season

0 100 200 300 400 500 600 0/10/2005 10/20/2005 10/30/2005 11/9/2005 11/19/2005 11/29/2005 12/9/2005 12/19/2005 12/29/2005 1/8/2006 1/18/2006 1/28/2006 2/7/2006 2/17/2006 2/27/2006 3/9/2006 3/19/2006 3/29/2006 4/8/2006

Total carbon monoxide CO in 24h‐ heavy oil Total carbon monoxide CO in 24h‐ heavy oil / natural gas Total carbon monoxide CO in 24h‐ natural gas Fig. 5. Total emissions of CO [kg/24h] for every day of the heating season

For boilers of older production, often energy from fuel is underused since the temperature of the exhaust gas is relatively high and it is discharged into the environment. In recent years many im- provements have been made and necessary changes to the central heating system, with the sole aim to improve the utilization of thermal energy supplied to final consumers, and thereby reduce emissions of greenhouse gases and the environ- mental impact.

6. OPPORTUNITIES FOR APPLICATION