Talking about the Energy Saving System Technology and Application of Gas Heating Boiler Room

Keywords: energy crisis, gas heating, energy saving, economic benefit

1 Introduction

There are four main ways of heating in Beijing: urban heating network heating, district boiler room heating (including coal, gas, fuel, electric boilers), clean energy household heating (natural gas boilers, electric heating) and Small stoves for heating. The main heating methods are coal, heat and gas heating. In order to ensure and improve the quality of the atmospheric environment, and vigorously promote and use clean energy, Beijing is changing the coal-fired boiler to a gas-fired boiler. Beijing coal-fired boilers have been heating for decades, and gas-fired boilers have been started since 1997 when natural gas entered Beijing. The actual operation is only a few years old, and there is no experience in design and operation. . Natural gas is a very valuable energy source. In particular, natural gas shortages occurred last year. Therefore, how to achieve energy saving for gas boiler heating has become a hot issue that people are paying close attention to.

In order to achieve energy-saving of gas-fired boiler systems, it is necessary to start from the design, construction and operation. The energy-saving system described in the following article can not only reduce the gas cost on the basis of ensuring the heating quality, prolong the service life of the boiler, ensure the safe and stable operation of the gas boiler, improve the equipment management level, and also solve the high gas consumption and boiler condensate. many.

The “GBC Gas Heating Energy Saving System” developed by Beijing Jinfang HVAC Energy Saving Technology Co., Ltd. has been applied to many heating districts such as Madian Nancun, Heping Street Xiyuan and Boya West Park, and more than 100 boiler houses total more than 10 million square meters. The rice heating district has passed the test of energy saving rate of more than 15% by Beijing Energy Conservation and Environmental Protection Center!

The company solved the problem of 120 million square meters of hydraulic imbalance in Beijing Wangjing Community, completed the energy-saving technical renovation project of the heating plant in Shangdi Information Industry Base in Beijing, and hundreds of projects in the “Eleventh Five-Year” heating plan in Changping District. Obvious economic and social benefits.

2. Gas heating energy-saving technology

2.1 Gas heating energy-saving technology 1: Climate compensation system

The heat consumption of buildings is constantly changing due to factors such as outdoor air temperature, solar radiation, air humidity, wind direction and wind speed. To ensure that the indoor temperature is constant (such as 18 ° C ± 2 ° C) or meet the user requirements under the above conditions, the supply and return water temperature of the heating system should be adjusted according to changes in outdoor meteorological conditions during the entire heating period. In order to make the heat output of the boiler and the heat dissipation of the heat dissipation equipment and the heat demand of the building consistent, the phenomenon that the room temperature is too low or too high is prevented in the user room. Through timely and effective operation and adjustment, it is possible to achieve a large amount of energy saving under the premise of ensuring the quality of heating. The change of outdoor temperature determines the amount of heat required by the building, which determines the energy consumption. The operating parameters must be adjusted every moment with the change of outdoor temperature, and the heat supply of the boiler room and the heat demand of the building are always guaranteed. Consistently, only in this way can we achieve a large amount of energy saving. Each boiler room should be operated according to its own running curve. This curve is the good running curve of the boiler room. The climate compensation system is a system that provides a good operating curve for the boiler room.

The system can save more than 5% energy by adding a climate compensation device.

2.2 Gas heating energy-saving technology II: flue gas condensation heat recovery system

By analyzing the flue gas components of various fuels, it was found that the proportion of water vapor volume in the flue gas components of various fuels is: natural gas 20%, oil 12%, coal 4%. Why is the ratio of the volume of water vapor in the flue gas component of natural gas large? Because the main component of natural gas is methane (CH4), it has a large amount of hydrogen, which combines with oxygen during combustion to produce a large amount of water vapor.

The heat carried by 1 kg of steam is 2400 KJ, and the 0.7 MW boiler produces 30-40 kg of steam per hour, which is roughly equivalent to taking 57 MW of heat for 25 to 33 hours. Therefore, the heat loss is very large, and this part of the heat must be recovered to improve the boiler thermal efficiency and reduce the gas consumption.

Foreign countries have long recognized the seriousness of this problem. At present, the exhaust gas temperature has generally dropped to 70 ° C, and the Zui is as low as 40 ° C. On the flyers of some foreign condensing boilers, the boiler efficiency can reach 104%, which is to make full use of this part of energy.

The dew point temperature of the flue gas is about 58 ° C. As long as it contacts the medium below the dew point temperature, it will condense into water and release a large amount of heat. The heat is composed of two parts: (1) Physical sensible heat: by reducing the temperature of the smoke, the exhaust gas temperature can be controlled at 70-80 °C. After testing, reducing the smoke temperature by 20 ~ 50 ° C, can improve the boiler thermal efficiency of 1 ~ 3%; (b) vaporization latent heat: through the phase change of water vapor condensation into water, after testing can improve the boiler thermal efficiency of 3 ~ 5%. The combination of the two can improve the thermal efficiency of the boiler by 3 to 8%.

The thermal efficiency of the gas boiler itself has reached 90%. If the boiler body is modified to improve the thermal efficiency, it will not be worth the effort. By adopting the flue gas condensation heat recovery system, without increasing the thermal efficiency of the boiler itself, the thermal efficiency of the boiler can be increased by 3 to 8%, which will be an energy-saving mode with low investment and large revenue.

2.3 gas heating energy-saving technology three: heating system hydraulic balance

The energy consumption of the heating system depends not only on the heat source, but also on the entire pipe network system. In the heating system, there is a common problem of hydraulic imbalance. The hydraulic imbalance causes the system to be unevenly heated and cold. Users who are close to the heat source have higher indoor temperatures, and the indoor temperature is far lower. In order to ensure the indoor temperature of the remote user, it is necessary to increase the water supply temperature of the pipe network and increase the circulating water volume, which is not only difficult to ensure the heating quality, but also causes huge waste.

Through actual tests, the traffic of the near-end user unit is often several times that of the remote user unit. To allow the remote user to reach 16 °C, the near-end user room temperature has exceeded 20 °C, and even opening the window causes energy waste. Therefore, through practice, after water balance adjustment, energy can be saved by about 10%.

2.4 gas heating energy-saving technology four: gas boiler room heating centralized control system:

The centralized heating control system for gas boiler room developed by Jinfang HVAC Co., Ltd. is a computer heating control system designed with a new concept based on the years of operation and management experience of heating companies and the use of fuzzy control theory. Through the calculation of various parameters of each boiler and the calculation of the parameters of the entire heating system, the theoretical boiler load is obtained, and the actual load of the boiler and the boiler are turned on according to it. The boiler is controlled by a microcomputer to make each boiler in the boiler room run cyclically, and each boiler is automatically and periodically switched according to the load rate of the system. Extend the service life of the boiler on the basis of ensuring energy saving. The centralized control system not only controls the boiler, but also controls the system equipment such as the climate compensator to achieve the purpose of controlling the entire system.

2.5 gas heating energy-saving technology five: time-sharing control:

By controlling the indoor temperature of the school and office area in a time-sharing manner and partitioning to achieve on-demand heating, energy can be saved very well. For district heating areas, office and school buildings should be heated as needed to reduce waste. We have achieved good energy savings by using it in the middle school of the Eighth Division.

3. Application examples of Beijing gas heating energy-saving system

The gas-fired boiler room energy-saving system has been applied in many projects in Beijing. Now we choose a few typical projects to introduce to you.

3.1 Heating system of Yanjing Temple boiler room in Chaoyang District, Beijing

Beijing Chaoyang Heating Co., Ltd. began gas modification of the Yanjing Temple coal-fired boiler room in June 2003. The boiler room has a heating area of ​​27,900 square meters and more than 560 heating households. Originally two sets of 2.8MW coal-fired hot water boilers. After the transformation, it is a 0.7WM and a 1.4WM gas hot water boiler. The modified waterway system adopts a secondary pump system with a water mixer. The condensing heat recovery device is installed on the smoke path system, and the climate compensator is used in the intelligent automatic control, thereby realizing the real-time adjustment of the user's heating according to the outdoor temperature change. The system supplies heat to achieve energy savings. At the same time, the boiler return water temperature is not lower than 55 degrees Celsius, which solves the boiler condensate problem, reduces boiler corrosion and prolongs the service life of the boiler.

Since its official operation on November 7, 2003, the system has been safe, stable, anti-interference ability, accurate measurement data, sensitive signal transmission, accurate adjustment, and no adverse effects on the system. No manual operation, all automatic control, the labor intensity of the furnace is greatly reduced, and all adjustments are completed by the climate compensator. The furnace worker laughed and said, "We have a 24-hour senior engineer in our boiler room."

The system has achieved significant energy savings as soon as it is invested. The following table shows the actual consumption of the gas meter:

name
Early cold period
Severe cold period


November 23
November 24th
November 25
December 9
December 10
December 11

Daily gas consumption (m3/day)
1704
1824
1776
1912
1901
1877

Average daily gas consumption (m3/day)
1768
1897

Estimating total winter air consumption (m3)
1768×30+1897×60+1768×45=246420

Note: The whole winter heating period in 2004 was 136 days from November 7, 2003 to March 21, 2004. The initial cold period was 39 days, the cold period was 62 days, and the end cold period was 35 days.

In order to more accurately test the energy-saving effect, it will provide reference for future energy-saving renovation and professional counterparts. We specially invite the Beijing Energy Conservation and Environmental Protection Service Center with testing qualification to conduct energy conservation testing. The Beijing Energy Conservation and Environmental Protection Service Center tested the system from December 11 to 14, 2003. Using the comparative test method, * 24 hours into the energy-saving system for testing, after removing the energy-saving system for one day, and then conducting the test without using the energy-saving system for 24 hours. The energy saving rate reached 10.89%.

Wenjing Temple boiler room full winter gas consumption statistics

name
Early cold period

November 7th to December 15th
Severe cold period

December 16th - February 15th
End cold period

February 16th to March 21st

Air consumption (m3)
68093
121695
42560

Average daily gas consumption ((m3/day)
1745.97
1962.82
1216

Actual air consumption in winter (m3)
232348

Whole winter unilateral air consumption and cost table

Name
Yanjing Temple

Heating area (m2)
27990.5

Single winter air consumption (m3/m2)
8.30

Full winter single gas fee (yuan/m2)
14.94

Save one-way gas consumption (m3/m2, according to the usual single-sided gas consumption of 10m3/m2)
1.7

Savings (yuan/m2, according to the usual single gas cost 18 yuan / m2)
3.06

Total cost for each heating season (yuan)
85650.93

Note: Usually the unilateral gas consumption is 10m3/m2: it is obtained according to the unit with higher management level (Haidian Heating, Fengtai Heating and Housing Management Company), and the social heating units are much higher than this value.

3.2 Beijing Badachu Middle School Boiler Room Heating System

In 2003, the Badachu Middle School boiler house was converted to a coal-to-gas project. After the transformation, the WNS1.4-1.0/95/70-Y (Q) and WNS0.7-1.0/95/70-Y (Q) hot water boilers produced by the Beijing Great Wall Boiler Plant were installed in the boiler room. The heating area is 18746.3m3 (including the teaching building area of ​​7829 square meters, and the teaching staff dormitory area of ​​10917.3 square meters). The gas heating boiler room is used to optimize the energy-saving system. The system adjusts the temperature of the system water supply according to the ambient temperature through the climate compensator, so that the boiler room can supply heat according to the heat demand of the user, thereby achieving the purpose of saving gas cost. According to the specific conditions of the school, the teaching area is controlled in a time-sharing manner. Under the premise of ensuring the quality of heating, Zui greatly saves energy, and also absorbs the heat of the flue gas through the LN-type flue gas condensation heat recovery device.

The Beijing Energy Conservation and Environmental Protection Service Center conducted a comparative test before and after putting into the energy-saving system of the Badachu Middle School boiler room in Shijingshan District, Beijing. According to the calculation and analysis, after the boiler room is put into the energy-saving system operation, under the premise of ensuring the heating quality, the gas saving rate is 19.78%.

3.3 Aerospace Architectural Design Institute

4 Conclusion

The gas energy situation in Beijing this winter has become so severe that it has become an urgent need to rationally save the use of existing energy. Through the two typical projects listed above, it can be seen that the heating quality after using the gas-fired boiler house energy-saving system is excellent, and the energy-saving effect is remarkable. If it can be used in the city's 68 million square meters gas heating energy-saving system, it will bring considerable economic and social benefits.