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Comprehensive Improvement Technology of Boiler

Circulating fluidized bed boiler furnace for the central high-temperature cyclone separator, π-type layout of the furnace, the original fuel for the coal, is the mainstream of market. Improve the load, thermal efficiency, change the type of fuel, save environmental costs, reduce resistance, reduce the boiler exhaust temperature and other aspects of technical introduction.

1, low nitrogen capacity and furnace to increase the heating surface transformation:

At present, national energy policy and environmental policy are becoming more and more stringent on coal and electricity projects. Combined with the market is small and medium-sized circulating fluidized bed boiler more than the lack of load capacity and NOx average initial emissions in the 300 ~ 400mg / Nm3 or so, for the circulating fluidized bed boiler combustion characteristics, through the implementation of a number of projects , our company summed up the development of unique combination of low nitrogen capacity transformation technology. The low nitrogen capacity of this technology is very obvious, from the demonstration project point of view, its nitrogen efficiency at least 55% or more, can achieve the vast majority of circulating fluidized bed boiler NOx emissions below 150 ~ 200 mg / Nm3, boiler load Increase by 10% -20%.

Main technical features:

1-1, reasonable classification of air supply. According to the coal design a reasonable second-class wind ratio, a wind to ensure that the material temperature and bed temperature, secondary air to ensure that the amount of oxygen load. Secondary air rate increase, graded combustion to improve the burning rate, effectively slow down the furnace wear, without reducing the thermal efficiency.

1-2, the furnace increased heating surface. In the furnace to increase the shape of water-cooled heating surface, a reasonable heating surface size on the one hand to ensure that the boiler load to improve, on the one hand to adjust the material temperature, including bed temperature, furnace outlet temperature and separator temperature, making the material temperature to low nitrogen required temperature window.

2, transform the separator, improve the separation efficiency:

High temperature cyclone separator is a key component of circulating fluidized bed boiler, its main role is to separate a large number of high temperature solid material from the air flow back to the furnace to maintain the rapid flow of the furnace run to ensure that fuel and desulfurization agent multiple cycles,providing conditions for the extension of the residence time of the coke particles and the desulfurizer. Therefore, the separation efficiency of the separator has a direct effect on the operation of the circulating fluidized bed boiler. If the separation efficiency is low, the particles will not be effectively separated from the flue gas, which will cause a large number of particles to pass through the furnace without being recycled into the tail heating surface,  which will cause the boiler load capacity is poor, low combustion efficiency and low desulfurization efficiency.

Normal transformation program:

2-1, transform the upper part of the flue gas outlet part of the separator, select a reasonable diameter and insert the depth, deviate center design, control reasonable resistance, improve the ability to capture particles, control export flue gas flow rate of 25m / s or so. 

2-2, the separator cylinder to do volute transformation, improve the separation efficiency.

2-3, the furnace outlet through the transformation of castable material thickness to a reasonable outlet size, control the outlet of flue gas flow rate of 15m / s or so.

Through the selection of reasonable flue gas flow rate, the flue gas resistance of the separator is controlled at about 1500pa, the separation efficiency is more than 99% and the circulation rate is between 15 and 20, thus reducing the power consumption of the induced draft fan and increasing the boiler load.

3, steam boiler's superheater adjustment.

Mainly in the following areas:

3-1, through a small R to bend, the appropriate compression maintenance space, increase the vertical or horizontal direction of the tube row number, etc., in the original space to increase the superheater heating surface.

3-2, in the fuel type conversion, the original furnace design defects, etc., replace old superheater for new.

3-3, into a superheater covered, change superheater at the heavy furnace to  wall light wall, reduce the comprehensive investment operating costs.

4, the transformation of economizer, reduce the boiler exhaust temperature, free SCR denitrification transformation space:

Due the aging of economizer heating surface, the worse effect of heat transfer will cause exhaust gas temperature to rise. In a limited space, change the original light pipe, spiral finned tube and other economizer structure to H-finned tube. Its characteristics are as follows:

4-1, Increase the heat transfer area, reduce the number of pipe arrangement, thereby increasing the smoke flow cross section, so that the smoke speed is low, reduce wear. Since the wear rate of the pipe is proportional to the 3.33 th power of the flue gas flow rate, the wear rate will be reduced to 43% if the flue gas velocity is reduced from 9 m / s to 7 m / s. At the same time, the experiment shows that the finned tube itself has the effect of concentrating the fly ash to the tube row, so the finned tube economizer has the effect of reducing the wear on the structure.

4-2, H-type finned tube can be made into double-tube "double H" type finned tube, its structure is with good rigidity, can be applied to the longer row of the occasion.

4-3, H-type finned tube economizer with row arrangement, H-fin fins divided the space into several small areas, the current sharing flow, so that greatly reduce the wear and tear.

4-4, Both sides of h fin tube form a straight channel to get a best soot effect.

4-5, compact space, the overall weight greatly reduced, reducing the cost. If the SCR on the denitrification equipment, H-finned tube is more likely to free up the flue gas leads back to the space, the vertical height of about 3 meters. Even in some of the space on the boiler, the direct release of more space, the SCR denitrification equipment directly on the boiler tail flue, greatly reducing the user environmental protection equipment investment.

4-6, simple operation and maintenance; save labor: the overall assembly of the economizer factory, moving parts less knot 4-7, simple structure, easy to install. High level of automation, simple operation and maintenance , can reduce the operating staff.

5, the end of the air preheater into enamel pipe material, to extend the service life, reduce maintenance costs.

Boiler end air preheater working environment is bad, facing serious problems of low temperature corrosion. Enamel tube air preheater is the device that  in the air pre-tube wall to do enamel treatment, with the following characteristics:

5-1, super strong corrosion resistance, wear resistance, erosion resistance. The acidity of the enamel tube is several hundred times higher than that of the metal tube. According to the relevant information, enamel glaze layer Vickers hardness HV = 652, and metal Q235A steel Vickers hardness HV = 114, showing that the wear resistance of enamel is much larger than the metal Q235A steel.

5-2, the surface is smooth, not easy to fouling, reduce congestion, easier to clean. According to the relevant information, enamel tube surface roughness of 0.005mm, and Q235A steel pipe surface roughness of 0.2mm, 40 times of the enamel tube. Therefore, the enamel pipe surface finish is good, hard to sticky ash, flue gas flow resistance is small, small ash heat resistance, heat transfer coefficient, thereby reducing the exhaust temperature and improve operating efficiency.

6, the overall transformation of the boiler.

Our circulating fluidized bed boiler has a rich technical resources, can be engaged in major changes, expansion, replacement of coal, the replacement of biomass fuels, by the transformation of the new furnace and other aspects of the overall boiler transformation.

7, Shandong Hengtao Energy Saving and Environmental Protection Co., Ltd., boiler comprehensive transformation efficiency part of the performance profile:

Jilin white town of Zhonghe public biomass power plant No. 1 furnace, for the sub-high temperature sub-high-pressure coal-fired circulating fluidized bed boiler, converted into pure burning biomass furnace. Due to the great changes in fuel, coal biomass, our company do a comprehensive improvement of this furnace.

7-1, the furnace increased 7 water cooling screen, the down tube and the rising tube to do a new layout to increase the evaporation surface.

7-2, the lower part of the water wall from the tube structure into a film-type water wall structure, enhance the sealing performance. In the middle and lower water wall at the junction, the design of double R to bend, with castable, to avoid wear and tear here.

7-3, redesign the feed port to accommodate the geometric characteristics of the biomass fuel.

7-4, re-arranged secondary air, to meet the combustion characteristics of biomass fuels.

7-5, the central tube into eccentric structure, improve the separation efficiency of high temperature cyclone separator.

7-6, the feeder into a self-balanced non-mechanical structure, design return to the hood, to promote smooth return.

7-7, replace superheater with new structure, increase the spacing between the pipe system to reduce the high temperature of biomass fuel flue gas corrosion. Increase the number of superheater tubes in the vertical direction to increase the heat transfer area to ensure the load.

7-8, The end of the air preheater tube designed to enamel tube structure, reduce low temperature corrosion, reduce fouling avoid clogging, to extend equipment life, to avoid high exhaust temperature.

After the above measures to complete the transformation, the boiler load can reach 90% or so of the original pure coal which is a more ideal data.