Energy-saving retrofit measures for coal-fired and gas-fired boilers

First, commonly used in coal-fired boilers energy-saving transformation of the ten ways

In the low-carbon concept is increasingly popular today, energy saving and environmental protection will be more and more attention to the word, there are more than 500,000 industrial coal-fired boilers in China, the number of commercial and civilian coal-fired boilers is huge, although in recent times the country has introduced a series of coal-fired boiler phase-out policy, coal-fired boiler coal-to-gas conversion policy and other environmental protection policies, but due to the constraints of the energy structure and the cost of day-to-day operation of the problem, coal-fired boilers still occupy a dominant position. Boiler still occupies the mainstream position, so the coal-fired boiler energy-saving transformation of the relevant technology is still very practical, in reducing the cost of boiler use at the same time, but also to achieve a certain degree of environmental protection benefits, the following are specific about the existing ten coal-fired boiler energy-saving transformation technology.

1, coal-fired boiler flue gas recovery

Industrial coal-fired boiler flue gas emission temperature is generally as high as 180 ℃ or more, not only pollutes the environment, but also a waste of valuable flue gas resources. The use of heat pipe heat transfer technology, fluorine plastic heat exchanger, etc. can effectively recover this part of the polluted flue gas resources, used to preheat the boiler combustion air, preheat the boiler water supply, or direct production of hot water.

2、Coal-fired boiler coal transmission device modification

At present, layer-fired boilers are burning raw coal, which accounts for most of the positively rotating chain grate boilers, the original bucket-type coal feeding device, so that the lumps, the end of the coal mixture piled up on the grate, hindering the boiler air intake, affecting combustion. Bucket coal feeder will be transformed into stratified coal feed, the use of gravity sifter will be the original coal in the block, end of the coal from the bottom up loosely distributed in the grate, conducive to air intake, improve the combustion conditions, improve the combustion rate of coal, reduce the carbon content of ash, you can get 5% to 20% of the coal saving rate, energy saving effect depending on the furnace conditions before the change, the worse the furnace conditions, the better the effect. The project investment is very small, the energy-saving benefit is very good, and the recovery is very fast.

3, coal-fired boiler oxygen combustion technology

Generally in the boiler flame temperature is not enough, cinder carbon content is high, flue gas Ringelmann blackness level can not meet the standard, boiler combustion efficiency is not high, boiler output is not enough, you can consider the use of oxygen-enriched combustion technology, increase the content of oxygen in the combustion air, so that the fuel combustion is more fully and at the same time, reduce the air excess coefficient, reduce the combustion of flue gas emissions to improve the flame temperature and reduce the blackness of the exhaust smoke to achieve Energy saving of 5% to 15%, increase boiler output by more than 10%. Oxyfuel combustion technology, energy saving and environmental benefits are very good, the project's payback period of less than a year.

4, the use of automatic boiler ash technology

Boiler ash coking will seriously reduce the thermal efficiency, so ash removal is imperative. The use of shock wave generation technology, shock, impact and scrub boiler superheater, air preheater, economizer surface of the ash coking, so that it is broken off. Because of the good effect of ash cleaning, blowing thoroughly, leaving no dead ends, very low operating costs, high investment efficiency features, fully automatic and efficient surge sootblower is welcomed by users, is a coal-fired, oil-fired, gas-fired boilers and cellar furnace in addition to the ash of the best choice, will replace the other traditional sootblowing equipment, in the boiler sootblowing and energy saving has a broad prospect for development.

4, coal-fired steam boiler high temperature condensate recycling technology

In the past, the open recovery of condensate steam waste, condensate oxidation again, the heat recovery rate is not high, you can understand the heat load of the steam-using equipment under the premise of replacing advanced traps, balancing the recovery of pipeline pressure, the addition of steam injection heat pumps and GY condensate recovery device, you can realize the high-temperature condensate recovery of the closed, coal-fired boiler fuel savings of 15% to 30%, recovery of 95% pure condensate. 95% of pure condensate is recovered.

6、Coal-fired boiler combustion modification

From the coal-fired boiler into the appropriate location of the appropriate amount of pulverized coal sprayed into the appropriate location of the furnace, so that the grate layer combustion based on the increase in the appropriate amount of suspended combustion, you can get about 10% of the energy saving rate. It should be noted that the amount of pulverized coal sprayed into the amount, injection speed and location to control the appropriate, otherwise, it will increase the degree of exhaust smoke, affecting the energy-saving effect. For oil, gas and pulverized coal boilers, is a new energy-saving burner to replace the old, backward burner, the transformation effect is also related to the original equipment condition, the worse the original condition, the better the effect, generally up to 5% to 10%.

7, coal-fired boiler arch energy-saving transformation methods

Appropriate changes in the shape and location of the furnace arch, you can improve combustion conditions, improve combustion efficiency, reduce coal consumption, and now there are a variety of coal types applicable to the furnace arch configuration technology. This transformation can be about 10% of the energy-saving effect, the technical transformation investment can be recovered in about half a year.

8, coal-fired boiler auxiliary energy-saving transformation technology

Blower and induced draft fan operating parameters and coal-fired boiler thermal efficiency and energy consumption is directly related to the appropriate speed control technology, in accordance with the needs of the boiler load adjustment of the blower, induced draft air volume, to maintain the boiler running in the best condition, on the one hand, you can save boiler coal, but also to save the fan's power consumption, energy saving effect is very good.

9, regular cleaning of the boiler and coal economizer soot dirt can realize energy saving

General coal-fired boilers after a period of operation, tube bundles, smoke chamber and economizer inside and outside the wall will produce ash and scaling phenomenon, seriously affecting the boiler output and thermal efficiency, the establishment of a regular cleaning of the boiler ash, scaling system can reduce thermal resistance, increase the heat transfer effect, to ensure that the boiler operates in a good state, energy saving effect can be achieved.

10, coal-fired boiler control system transformation

Energy-saving industrial boiler control system can be realized energy-saving transformation of two types, one is in accordance with the requirements of the boiler load, real-time adjustment of the amount of coal, water, blower and induced draft, so that the boiler is often in a good state of operation. The original manual control or semi-automatic control into fully automatic control. This type of transformation, for the load changes in the magnitude of large and frequent changes in the boiler energy-saving effect is very good, generally up to about 10%; the second is for the heating boiler, the content is to maintain sufficient room temperature under the premise of real-time adjustment of the boiler's heat output according to the changes in the outdoor temperature, to achieve the purpose of comfort, energy saving, environmental protection. The realization of this type of automatic control can make the boiler save about 20% of coal burning. For oil-fired and gas-fired boilers, the energy-saving effect is the same, and their economic benefits are higher. Coal-fired boiler energy-saving renovation techniques and methods can not only achieve cost savings, improve thermal efficiency of the role of increasing the role of boiler life, but also to a certain extent fits the current technical requirements of the environmental aspects of the boiler, it can be said to be a one-two punch.

Second, the gas boiler energy saving and consumption reduction transformation program

1, today's gas boiler problems

(1) Insufficient gas combustion

Gas boiler in normal operation, the vast majority of the gas can be completely combusted, combustion losses are relatively small. Normally, the gas combustion rate in the gas boiler is between 99% and 99.5%, and the incomplete combustion rate is between 0.5% and 1%. As there is still some gas can not be burned, in the case of incomplete combustion, the heat loss rate of the gas boiler will be greatly increased. Gas boilers and traditional coal-fired boilers are different, gas boilers in the case of incomplete combustion will not appear black smoke, coupled with very few units equipped with flue gas analyzers, making it difficult to determine whether the gas boiler is completely combustion with the naked eye.

(2) Heat loss

The heat loss of the gas boiler mainly consists of two major aspects: one is the boiler equipment heat loss problem; the other is the boiler room other ancillary equipment or duct heat loss problem. Among them, the loss of the gas boiler itself is usually between 1% and 2%, and has been calculated in the boiler thermal efficiency. For these two cases, the heat dissipation loss of other equipment is smaller, and the air for combustion in small and medium-sized boilers is taken from inside the boiler, and the heat dissipation system is also able to increase the temperature of the air inside the boiler. At the same time, the boiler auxiliary equipment and piping heat dissipation can also play a role in assisting heating.

(3) Boiler exhaust heat loss

In the gas boiler operation, the main factors affecting the heat loss of exhaust smoke for the exhaust volume and exhaust temperature. Among them, the larger the exhaust volume, the higher the exhaust temperature, the greater the heat loss. When the exhaust temperature continues to rise, the functional efficiency of the boiler will gradually decrease. After relevant tests show that on the basis of today's gas boiler technology, every 18℃ rise in the exhaust smoke problem reduces the boiler's operational efficiency by 1%. Therefore, by spraying water and other measures to reduce the exhaust smoke temperature to improve the operating efficiency of the boiler.

(4) Gas boiler discharge heat loss

Usually, the larger the amount of discharge and the higher the internal pressure in a gas boiler, the higher the amount of heat loss will be. If there is no recovery device in the gas boiler, the heat loss in the gas boiler will be as high as between 3% and 5%. For every 1% increase in the discharge rate in a gas boiler, the natural gas consumption increases by 0.3% to 0.5%. It can be seen that the boiler effluent discharge has a direct relationship with the heat loss, which will cause excessive energy waste. Therefore, it is necessary to attract the attention of the relevant departments and attention, and through reasonable transformation for heat loss control. Among them, the hardness and content of dissolved solids, and gas boiler emissions have a direct relationship.

(5) condensate heat loss and make-up water heat loss

Water is an indispensable energy source for gas boiler operation. Due to heat network leakage, aging facilities can also cause heat loss, through the gas hot water boiler test, in different supply and return water temperatures, if the rate of water replenishment is reduced by 1%, the heat loss will be reduced between 1.8% and 4.5%. As for gas steam boilers, for every 10% reduction in the condensate ice recovery rate, the condensate heat loss rate will increase by about 1%. This shows that there is still a lot of room for maneuver in terms of condensate and make-up water heat loss.

2, strengthen the gas boiler energy saving and consumption reduction transformation of effective measures

(1) configuration burner

Smoke loss is the main reason affecting the operating efficiency of the boiler, mainly affected by the amount of smoke and excess air coefficient. By analyzing the principle of combustion can be found, the larger the excess air coefficient, the amount of smoke will be increased, and naturally will take away more heat. According to the relevant departments of the test report shows that when the gas boiler exhaust temperature at 250 ℃, the air excess coefficient will increase by 0.1%, the gas boiler operating efficiency will be reduced by 0.9%. Therefore, to protect the operating efficiency of gas boilers, to minimize the excess air coefficient in the gas boiler. In the actual use of the boiler, the unit should be configured with a reasonable burner, and debugging of the equipment. The burner can meet the operating characteristics of the boiler to match the characteristics of the fuel, to protect the flame combustion rate, to ensure that the flame is full of furnace chamber, so that the fuel can be fully combusted.

(2) reduce boiler piping system heat loss

Units need to focus on transforming the heat network pipe, the old rock wool wrapped in glass cloth form replaced by rock wool wrapped in the form of iron, thus reducing the heat loss rate of the pipe network, improve the efficiency of energy application. At the same time, strengthen the soft water tank insulation treatment, improve the soft water tank insulation function, reduce the boiler softened water heat loss.

(3) Reduce the amount of heat loss from the exhaust of gas boilers

Condensing boilers as an example. Condensing boiler is mainly from the gas boiler emissions in the flue gas, absorption of water vapor contained in the latent heat of vaporization of the boiler equipment. Conventional boilers transfer most of the heat energy to the water vapor (the principle of heat absorption by evaporation), increasing the amount of heat loss from the exhaust. However, in a condensing boiler, the exhaust smoke transfers heat energy to the water vapor and at the same time absorbs the heat energy from the condensation of the water vapor, thus reducing the amount of heat loss. There are many differences between condensing boilers and conventional boilers. Condenser boilers must have a condensing exchange heating surface, and the use of super-insulating sealing materials and insulation shell. By using low-temperature water for the boiler when exhausting smoke, it reduces the steam temperature to below the smoke condensing temperature, condensing the superheated water vapor into water, which in turn releases latent heat energy through vaporization, helping the boiler to absorb some of the heat energy. The overall operating efficiency of a condensing boiler is 10% to 17% higher than that of a conventional boiler, and it is also able to reduce the exhaust temperature to between 50% and 70%. Condensing boilers in operation, not only can reduce the amount of gas used, but also to dilute the harmful substances in the flue gas, recovery of steam water, with energy-saving, environmental protection, green, water-saving and other characteristics. Separate flue gas recovery device is usually divided into two kinds: one is direct contact heat exchanger; the second is indirect contact heat exchanger. Among them, the direct heat exchanger is mainly in direct contact with the exhaust smoke by spraying water, which in turn generates energy exchange (heat energy), improves the rate of heat recovery, and reduces the harmful gases in the exhaust smoke by drenching water. Although direct contact heat exchangers are used efficiently, there are many problems in recovery. The drench water is in direct contact with the harmful gases and absorbs some of them, which can make the water recovered from the heat exchanger acidic and corrode the boiler and related equipment. Therefore, if the wastewater is not properly treated it will pollute the environment, and it is difficult to be utilized twice in the boiler room. Therefore, direct heat exchanger has limitations in use.

(4) Reduction of electric power consumption of boiler room equipment

Gas boilers consume a lot of electricity in the operation process. In order to reduce the power consumption of the boiler room, it can be used to rationally configure the corresponding equipment and incorporate advanced technology. Require staff to do: first, to analyze the current situation of the boiler room operation, fully understand the characteristics and performance of each piece of equipment, calculate the pipe network under the pump, fan operation flow, power, efficiency, etc., through the rational configuration of the study to come up with the best program, to achieve a reasonable allocation of equipment; second, the introduction of frequency conversion technology, so that the contact is in the daily operation of a soft start state, which reduces the start-up current, to avoid excessive power consumption on the power grid. have an impact on the power grid due to excessive power consumption. The staff can use the frequency converter to reduce the frequency of the alternating current, adjust the speed and flow of the water pump, and improve the water leakage of the replenishment system in the operation of each link. Avoid operating the supplemental water pumps throughout the day to minimize power consumption. At the same time, fan inverters can also be added, such as using fan inverters to change the fan speed. Set the wind speed according to the demand of the boiler, and can make the boiler inside the composition of the closed-loop control system to realize constant energy and constant pressure, and then reduce the boiler energy consumption and improve the comprehensive efficiency.

(5) Reducing heat loss from sewage

The amount of heat loss can be reduced by using regular sewage discharge. At the same time, regular laboratory testing of softened water, check the water quality of the gas boiler, to ensure that the quality of the boiler water supply meets the standard. Grasp the gas boiler water alkalinity size and change rule, in the case of high vapor pressure, low load sewage. In addition, according to the salinity of the water at the liquid level in the boiler steam bag to adjust the sewage valve, so as to control the amount of sewage at the minimum, and then reduce the amount of sewage heat loss.

3, conclusion

From the above existing problems of gas boilers and consumption reduction program, the gas boiler consumption reduction and transformation must adopt a multifaceted energy-saving methods to reduce the amount of heat loss from all aspects of the boiler to improve the efficiency of the boiler operation, and then to achieve a good energy saving effect, to ensure that the economic and social benefits of heating and power supply enterprises.