firing heat consumption is an important index to judge whether the pre splitting system is advanced or not. but the pre decomposition system is a system, and its technological transformation is an innovative system engineering, which needs to be considered comprehensively and scientifically. by the way, the effect is remarkable, but not necessarily the best. this paper introduces the technical transformation of the sintering system of clinker production line of 5000t/d precalciner kiln in this plant, including the expansion of the capacity of the calciner, the modification of the three air pipe and the modification of the material dropping point.
abstract: heat consumption of sintering is an important index to judge whether the pre splitting system is advanced or not. but the pre decomposition system is a system, and its technological transformation is an innovative system engineering, which needs to be considered comprehensively and scientifically. by the way, the effect is remarkable, but not necessarily the best. this paper introduces the technical transformation of the sintering system of clinker production line of 5000t/d precalciner kiln in this plant, including the expansion of the capacity of the calciner, the modification of the three air pipe and the modification of the material dropping point. after revamping, the coal consumption, heat consumption and output of the system have been significantly improved.
0 introduction
the company rotary kiln predecomposition system decomposition system for the 5000t/d online pre design institute tianjin, dual 5 stage cyclone preheater dd calciner, supporting 4.8 * 72m rotary kiln and 119.3m2 cooler, design production capacity of 5000t/d, put into operation in october 2004. after 8 years' practice, production capacity far exceeds the design yield, actual yield 5900t/d, standard coal consumption more than 110kg/t-cl. the production and process data of the existing pre splitting system are shown in table 1 and table 2.
however, the design of the system also has some limitations due to the burning technology at that time. the basic operation condition and main problems of rotary kiln are as follows:
(1) the outlet temperature of c1 is 350~360 deg c, which is obviously higher, and the temperature gradient of cyclone at other levels is basically normal.
(2) the outlet temperature of the calciner is 890~910 degrees centigrade, and the outlet temperature of c5 cyclone is 910~920 degrees centigrade.
the above two groups of data are obviously higher, which is the main reason leading to high wind temperature at c1 outlet. analysis shows that the pulverized coal in calciner combustion is not sufficient, with gas and material into the c5 continue to burn heat, resulting in c5 and the outlet temperature of predecomposition system outlet temperature is high; decomposition furnace exports, exports and c5 tube temperature inversion.
(3) three winds are divided into two steps into the calciner. the air quantity is controlled by the high temperature gate valve. it can not be quantified quantitatively, resulting in the imbalance of distribution and the stability of the flow field in the calciner;
the horizontal pipe length of the three air duct in the frame is 34.4m, and there are 4 90 elbow, which cause the lining abrasion of the pipe lining and the inner ash in the tube;
the three air inlet is in the straight part of the decomposing furnace, and the feeding coal point is at the upper part of the air inlet, occupying the height of the straight cylinder about 3m, and reducing the effective volume of the decomposing furnace. the original three air pipe interface is positioned on the cone part of the decomposing furnace, and the straight cylinder occupying 2.3m height does not make full use of the effective volume of the calciner, and shortens the residence time of the three air in the decomposing furnace.
(4) the installation position of the spreading device on the wind pipe of the connecting pipe of each cyclone is higher, the moving distance of the material entering the heat exchange pipe is shorter, and the heat exchange time of the gas and the material is not enough.
when the output reaches 5900t/d, the capacity of the calciner is insufficient and the temperature inversion is more serious. the heat exchange function of the preheater is weakened, and the heat consumption of the clinker is increased.
1 technical transformation plan
1.1 decomposition furnace
the height of the vertical tube of the precalciner is only 22m, and it is occupied by about three 3m by the interface of the air pipe. the total volume is too small, and the capacity of the calciner must be expanded.
after the increase of the decomposition furnace to retain most of the shell, than the original decomposition furnace increased 12.5m, the original decomposition furnace straight cylinder part of the effective volume of 823m3, increased by 467m3 after the increase, than the original effective volume increased by 57%, to 1290m3.
when the clinker yield is 5900t/d, the residence time of the gas in the primary calciner is 2.2s, and the residence time of the gas is 3.6s after the decomposition furnace is increased.
1.2 adding calciner, -c5 cyclone tube
after raising the decomposition furnace outlet position of moving upward around 13m due to the beam limit, if the gooseneck is designed into a cylinder, the smaller cross-sectional area can not meet the requirements, can only be based on frame beam position of the gooseneck design into a cuboid, in order to obtain the maximum cross-sectional area.
cross section of the pipe main body goosenecks is 5.4 * 4.4m rectangular, the total height of 18m, the effective volume of 330m3. add the gooseneck, clinker production 5900t/d, pipe gas residence time is 1.0s.
after the modification, the effective volume decomposition furnace gooseneck reached 1620m3, increased by 97% than before. it can obviously improve the combustion of pulverized coal, the heat transfer of solid and gas, and the rate of caco3 decomposition. the gas temperature of the whole preheater decreases as a whole.
1.3 replace the c5 cyclone volute
the original decomposition furnace outlet and c5 cyclone through the flat pipe connected with the gooseneck must be carried out after the change to the c5 volute inlet direction. the original c5 cyclone volute is 270, three heart structure high cone, eccentric 450mm, this structure has not been adopted in the new production line. it is estimated that the original c5 cyclone inlet effective area is 8.1m2, the output of clinker 5900t/d, section wind is significantly larger than 22m/s. the new three core structure equiangular spiral adopted high cone, increasing inlet cross-sectional area, the section wind speed is less than 19m/s. the matching inner cylinder can also be adjusted accordingly.
replacing the larger volute and inner cylinder reduces the gas resistance of the c5 cyclone and reduces the gas resistance of the whole system.
1.4 reforming the calciner and the three air pipe interface
the three air pipe is changed into a single channel decomposing furnace, and the air quantity is regulated by 1 high temperature gate valves. the interface of the decomposing furnace is moved to the conical part of the decomposing furnace, and the eccentric side is turned into the furnace. burner position down 2m. the original c4 cyclone can be divided into two directions, the lower material location and the lower position.
the technological process is simplified after technical transformation, and the air quantity of the three air is easy to control. three wind pipe in the frame length is shortened to 8.2m, and no sharp, to reduce the level of ash length and gas resistance. reduce the surface heat dissipation and leakage point of the shell;
three wind pipe enters from the calciner cone side rotary parts, increase kiln gas and meet the necking decomposition furnace bottom spray combined with rotary flow, mixed gas and material, in favor of coal; air inlet position down to increase air in the furnace and the moving distance of material coal mixed heat time; position down c4 the feeding point and burner, increase the movement of material in the furnace coal distance also increases the effective height of the decomposition of 2m furnace.
1.5 partial modification of preheater
the air resistance of predecomposition system is mainly caused by the part of the preheater, calculation, after the transformation of preheater straight section wind speed to a maximum of 5.9m/s, levels of wind pipe section wind speed is the maximum value of 16.6m/s, while compared with the current design of the design institute are slightly larger, but as a technical innovation project within the normal range, do not have to do more changes the heater part, only in the local transformation.
(1) change the spreading box on the rising air pipe at all levels to reduce the position of the hopper
the bottom of the original sprinkling device is positioned at the 2m position of the air outlet of the cyclone cylinder, and is designed for preventing the short circuit of the material from falling into the air pipe and falling into the cyclone tube. the present output is 5900t/d, and the wind velocity in the rising air pipe is larger than the design value, the suspension capacity of the material increases, and the phenomenon of short circuit is ruled out. the technical transformation is only replaced by the new diffusion type spreading device, so that the material is dispersed more evenly and the heat exchange efficiency is improved.
when the inner cylinder is intact, the material is put into the air duct as much as possible, so that the residence time of the material in the heat exchange pipe can be increased.
(2) dealing with air leakage points and repairing all levels of air locking valves
as a result of years of production, repair doors, poke holes, connecting flanges, such as the existence of varying degrees of air leakage, in the technical transformation of the unified treatment. all levels of the air lock valve overhaul, the damaged valve plate all replaced.
1.6 burner of kiln head
according to the technical index and fuel characteristics to achieve the transformation, determine the kiln head to replace the existing multi-channel burner burner by hp strong vortex pattern of advanced performance, decomposing furnace by three channel two burner, with the transformation as follows:
(1) hp strong vortex flow type large thrust multi channel burner uses existing mobile walking device, existing coal feeding fan, replacing kiln head fan, replacing diesel ignition combustion supporting system.
(2) the calciner uses two three channel burners to replace the burner in use. two new fan burners for kiln burners are added, and the existing coal feeding fan is used.
2 operation of the system after technical transformation (see table 5)
3 project benefits
after more than half a year's production comparison, the kiln platform output has increased from the original 238.25t to the present 251.06t. the temperature of the five stage cylinder outlet and the lower tube is lower than the outlet of the decomposition furnace by about 10-20 deg c, and the outlet temperature of the first stage cylinder is lower by 20 to 30 deg c.
after the transformation, the average standard coal consumption of clinker kiln by more than 112kg/t-cl reduced to 108kg/t-cl tons of clinker, real coal consumption decreased from 147.61kg to 142.25kg, decreased 5.36kg, power consumption decreased 2.18 tons of clinker process, tons of clinker generating capacity of 2.87 degrees lower, the total real clinker coal consumption reduced 5.36 2.18-2.87=4.67kg, annual production of 1 million 700 thousand tons of clinker clinker calculation, year can save 170 tons of coal in *0.00467 =7752.
4 still existing problems
(1) the temperature of the first cylinder outlet is about 335 degrees, the temperature is higher, and the design requirements of 310 degrees, there is still some room for improvement.
(2) in the original design drawing, there is a corner of the interface between the three air pipe and the decomposing furnace, and the abrasion is greater in the actual production. the side air inlet has been straightened up at the time of stopping and is in good use at present.
(3) the actual standard coal consumption has been 108-111 kg since the first half of the production period, and there is a big gap from the design requirement of 106 kg.
(4) replacement of spare parts in the replacement plate valve leakage problems exist, the sealing effect is not good, in the future change.
5 conclusion
through the technical transformation of the firing system in hefei institute, the system output, coal consumption and heat consumption have been significantly improved, and the purpose of energy saving and consumption reduction has been achieved.
