Introduction of"YINENG TA-JNP "cleaning agents for environment-protection and coal-saving
China is the biggest coal production and consumption country in the world. Coal is the most widely distributed and most sufficient energy in our nation. Coal-based energy structure will not be changed until mid-century. Burning of coal will discharge huge amount of carbon dioxide and a lot of other pollutants which lead to pollution of our atmosphere, causing acid rain, greenhouse effect and water pollution. So developing the technology of cleaning burning of coal, deducing the emission of sulfur dioxide, oxynitride, carbon oxide, carbon dioxide and soot is an important part of realizing the sustainable development of coal chemical industry.
We work with college of chemistry and chemical engineering Xiamen university, and experts of electric power boiler together and successfully developed a "YINENG TA-JNP" cleaning agents for environment-protection and coal-saving. This product assembles coal- conserving, desulfurization, dust-cleaning, drag-elimination and energy-conservation in one.
1、The formation mechanism of sulfur oxide during coal burning
Sulfur in coal has four forms, which are: yellow iron sulphide(FeS2), sulfur in sulfate, organic sulfur and
elemental sulfur. Yellow iron sulphide, organic sulfur and elemental sulfur are flammable. And take about 90% of total
sulfur in coal. Sulfur in sulfate inflammable, and takes up about 5% to 10% of total sulfur in coal, which is main constituent part of coal ash. When coal is burning, all of the flammable sulfur will be released from coal because of heating, and be oxidized into
sulfur dioxide. When there exists oxygen atoms under high temperature or catalysis in the heating surface, some of sulfur dioxide will turn into sulfur trioxide. Water in the smog will react with sulfur trioxide to produce vitriol gas. When temperature goes down, vitriol gas become vitriol smog. Particles in the dust smog will absorb vitriol and become acid particles and then washed by rain to form acid rain. As we can see, sulfur oxide produced during the burning, such as SO2, SO3, vitriol smog, acid ashes, not only cause air pollution, but also corrosion to the coal-burning device.
Control of the SO2 emission can be divided into three categories: before
combustion,
during combustion and after combustion.
Desulfurization before combustion is to wash off the sulfur-containing substances through coal washing.
Desulfurization during combustion is to add some desulfurization agent during combustion and turn sulfur into solid and gone with the slag. Desulfurization after combustion is called
gas desulfurization, which focuses on desulfurization the after-burning gas and then purify it to reduce the content of the SO2. Gas desulfurization is now the most efficient way to control the SO2 emission, because the technology is mature and widely use and comprehensive utilization of flue gas, for example producing vitriol and fertilizer. But because there are so many disadvantages, such as: its devices are huge, the investment are huge, the operation is complicated, the cost of maintenance is huge, it can hardly be accepted in normal and middle sized boilers, which are the most widely spread and most widely used boiler in our nation. But desulfurization during combustion has so many advantages, its cost is small, the equipment is simple, cost of maintenance is low and desulfurization agent is cheap, so it can be easily accepted by middle and small sized companies.
2、The cause of coking and fouling and its harm.
Coking area in the heating surface of hot space in the hearth include grate, water screen, wall type reheater, sometimes radiant superheater and semi-radiant superheater. The mechanism of coking is that when the soot is under the softening point, it will be carried by the flue gas and adhered to the heating surface of hot space. It will conglutinate the soot in the hearth box and making the adhered ash zone become thicker and thicker. Clinker has high thermo-resistance, those who is near to the heating area is cooled by the actuating medium in the furnace tube and become stiff coking solid. The other side of the clinker zone is softened by the high temperature and keep conglutinate soot in the hearth box and become boiler fouling.
SO2 in the soot will react with oxygen in high temperature during combustion, and will definitely form some SO3. Alkali metal oxide(K2O and Na2O) in soot will volatile upon heating, and agglomerate with the SO3 in the flue gas at the cooler side of the heating surface to form K2SO4(lemery) and Na2SO4(sodium sulfate) which are easy to melt. The melting point of the mixture of K2SO4 and NaSO4 are even lower, which are usually below 335℃. At the same time, the dew point of flue gas will rise up because of coaction of the water and SO3. This let cooler side of heating surface become the hotbed of the dirt.
So at the end of heating surface area in boiler, including low-temp over heater, coal economizer or even air preheater, dust stratification will happen. Because the temperature of the flue gas in those heating area is low and cannot reach dirt’s softening temperature, it will not form a scorched state. Dust stratification at low temperature is determined by the content of the SO2,K2O,Na2O, the higher these contents are, the severer dust stratification will. Of course, unreasonable design of the flue gas’s through-flow at the end of heating surface area(low flow rate of the flue gas, existence of dead zone in flow field), no efficient use of slag-blowing equipment will also cause dust stratification which lead to severe coking of boiler.
Due to extremely low coefficient of heat conductivity of the coking, high temperature area of the combustion in the hearth box will become higher and thermal deviation between the two sides will rise and cause the flue gas temperature in the reheater and overheater and thermal deviation of tube wall, which are threats to the safety running of the furnace tube. Coking in the hearth box becomes thicker and thicker and will fall off when it reaches to a certain weight. The falling dregs will not only affect the running of taphole, break the hearth tube, but also bring unburnt carbon and spread to hearth box rapidly which may cause explosion and accident. For natural circulation boiler, because the decalescence of water screen become lower, circulation factor of boiler water will change and threats safety running of water screen. Coking will rise up the temperature of the flue gas, and at the circumstances of high sulfur content in coal, hot corrosion can easily happen, and affect the using age of both water screen, overheater and reheater, even explosion of boiler tube.
Coking and dust stratification will rise up the exhaust gas temperature, and thermal losses of exhaust gas will become greater, efficiency of the boiler will decrease. At normal situation, when the temperature of exhaust gas rise up about 8 to 15℃, the efficiency of the boiler will drop 1%. At the bottom of the dust there are always some SO3. When boiler is low-loaded or shut down, it will generate sulphuric acid and causes low-temperature corrosion at the heating surface area, affecting the safety and the using age of device. When there are too much dust stratification at the end, pressure difference between front and end become larger, the flow rate of the flue gas after heating surface area rises, abrasion is intensified and draught fan’s power consumption increases. So in conclusion, the hazard of coking and dust stratification to the boiler is self-evident.
3、Function of "YINENG TA-JNP" cleaning agents for environment-protection and coal-saving"
Towards the current problem of the boiler, both home and abroad have developed a series of desulfurizer, dust cleaner and slag-remover. But in the practical application, you have to use desulfurizer, dust cleaner and slag-remover at same time and the operation is complicated. The cost of production will rise up dramatically, so it is hard to apply widely in the medium and small sized company. "YINENG TA-JNP" cleaning agents for environment-protection and coal-saving, made by Xiamen Tongan chemical engineering Co.Ltd, not only have both the function of desulfurization, dust cleaning and slag cleaning spontaneously, but also energy saving and easy operation.
(1) Desulfurization
"YINENG TA-JNP" cleaning agents for environment-protection and coal-saving desulfurizes sulfur during the combustion. The constituent for sulfur fixation in the agent can turn the SO2 during combustion into sulfur-containing compound and fixed into clinker. The constituent for sulfur fixation is composed of high efficient desulfurizer additive. The purpose of additive is to stop sulfur-containing compound in the clinker from decomposing and thereby enhancing desulfurization effect. "YINENG TA-JNP" cleaning agents for environment-protection and coal-saving will have a more evident effect in CFB boiler, and will decrease the ratio of calcium and sulfur which the desulfurization efficiency of the limestone will increase greatly.
(2) Energy saving
"YINENG TA-JNP" cleaning agents for environment-protection and coal-saving can make all the combustive components in the coal interact with the effective chemistry elements in agent and result new flammable gas, and lower the kindling point of the coal, making the coal spread more even, accomplishing the purpose of extending combustion time, combustion-supporting, decreasing black smoke in the tail gas, decreasing the discharge amount of carbon oxide and saving coal. At the same time, it can make faulty coal which is hard to combust reach the same combusting effect as the high quality coal and using less high quality coal, hence more economical. CFB boiler usually use faulty coal, after adding "YINENG TA-JNP" cleaning agents for environment-protection and coal-saving to it, coal’s combustion will be more sufficient and stable. Also, because the agent has an effective sulfur fixation, bed temperature can be rose according to the quality of the coal and leading to a more efficient combustion.
(3) Dust cleaning and deslagging
"YINENG TA-JNP" cleaning agents for environment-protection and coal-saving cleans the clinker and coking that forming at the heating surface area in boiler, not only making metal remain its high efficient thermal conductivity, but also raises the thermal efficiency of boiler. At the same time, the agent can eliminate the corrosion caused by the temperature differences between coking surfaces and exposure surfaces and extent the lifespan of boiler. This agent is auto-added during running of mine coal. The vaporific agent particles that entered the high temperature combustion along with coal will fall on the heating surface area and cause chemical reactions with dregs, the reaction is especially evident at the crack. The agent will neutralize the acid combustive components of the gas, burnout the remaining of carbon powders and coal particles, forming low melting point eutectic complex salt and loosen the coking layer because of fluidization. Roaring flame air caused by this agent can scour, vibrate and fragment the slag layer.
4、Sphere of application
This suits the boilers that burn coal, such as fuel electric plant boiler, thermal power plant boiler, industrial boiler, heat input boiler, civilian use boiler. This agent can be widely applied in those boilers.
5、Using method
Choose the suitable filling machine (capacity ranging from 100 kilograms to 500 kilograms) according to user’s coal consumption. Measure the coal capacity per minute (or per hour), and convert that to the amount you should add this agent in. Adjust motor’s frequency of the filling machine in order to keep accurate about the agent’s amount added per minute (per hour). Check ratio between coal and agent to see if it is in accordance with standard proportion. If there is any mistake, fix it gradually. If filling machine is not used during the test run of boiler, use water ladle and add the agent to coal layer of the conveyer belt according to the right proportion.
For small sized boiler, manually feeding of "YINENG TA-JNP" cleaning agents for environment-protection and coal-saving should convert its amount based on one pot coal. After conversion, disperse the agent to the coal pot and poured into lift machines. Indurative pot should be used and mark the correct location at the inside wall for each use, or use a fixed-amount vessel as a feeding tool. Coal consumption per day and the number of feedings should be well known. Measure the time and amount of every feedings, and calculate the time consumed per ton. For example, coal is fed 2 minutes per ton, then the mixture should be well-distributed in two minutes and add the agent proportionally.
6、Dosage of this agent.
Under normal circumstances, dosage of this agent is 0.5-2.0‰ of mine run coal. First feeding dosage is about two times that of normal circumstances. If the coking is extremely severe, added more agent accordingly. Continuous feeding is best, don’t feed intermittently. Normally, you can see effects three to seven days later.
7、Properties of agent and matters that need attention
This series of product is particle and powder like solid, innocuity, flavor less, non-volatile, noninflammable, none explosive, pH value comes to neutral and no corrosion to boiler. Storage place of the agent should moisture proof. If the agent accidently get wet and agglomeration happens, please wobble it before using. It won’t affect the effect. But you shouldn’t dehydrate the agent by baking.
8、The key technical indexes and its economic benefit
"YINENG TA-JNP" cleaning agents for environment-protection and coal-saving can force the coal to oxide and burn, rise burn-off rate, decrease dash dust stratification and coking and basically eliminates dash attachment in air preheater, coal economizer, convection bank, water screen, boiler back-end, put an end to the breakdown of coking caused by high temperature dry coking and low temperature dry coking in the hearth box.
Coal can be saved by 6% to 15%, temperature of hearth box can be rose 80℃ to 150℃, temperature of the exhaust smoke can be lowered about 5 to 10℃,thermal efficiency can be rose more than 0.5 to 3%. Decreasing the discharge of oxysulfide(SOX), oxynitride(NOX), carbon oxide, hydrocarbon(CXHr) and soot. This can have a comprehensive benefit.
9、Packing standard
We use water proof plastic bags and each weight 25 kilograms for the purpose of transportation and storage.
Sinopec Jianghan Salt&Chemical Complex(JSCC) thermal power plant
Using of "YINENG TA-JNP" cleaning agents for environment-protection and coal-saving made by Xiamen TongAn chemical engineering corporation.
Analysis of energy-saving effect
1、Summary
In August 2010, Sinopec Jianghan Salt&Chemical Complex(JSCC) thermal power plant 1# boiler (35t/h circulation fluidized bed boiler) uses "YINENG TA-JNP" cleaning agents for environment-protection and coal-saving made by Xiamen TongAn chemical engineering corporation. During this time, dosage of agent added per hour is 10 to 12 kilograms per boiler and daily dosage is 250 to 300 kilograms per boiler.
This effect analysis uses the ratio between the mean rotate speed of the left and right coal feeders and the total steam flow (referred as rate of coal consumption in the below) as the quantized data of the energy saving effect. This analysis is based on the change of carbon content of the flying ash and slag which is detected by State Key Laboratory of Coal Combustion (Huazhong University of Science & Technology).
2、Using of environmental, coal-saving, dust cleaning agent
Mean rotate speed of the coal feeders and the total steam flow are given from data collected by the logsheet of thermal power plant 1# boiler.
(1) service condition of 1# boiler
From 15 to 17 of august 2008, agent was added discontinuously. Data before feeding is the mean value of 32 hours from august 12 at 1:00 to august 13 at 8:00. Data after feeding is the mean value of 32 hours from august 16 at 0:00 to august 17 at 7:00. The reason why we choose those time period is in the view of following:
1) average value of the steam flow rate does not change too much before and after adding of agent.
2) coal quality is almost the same before and after adding of agent.
3) Time period are both 32 hours
4) After adding data collects only the late stage of the feeding stage.
Table 1 boiler #1 rate of coal consumption before and after feeding
items | unit | Before feeding | After feeding | Data changes | Change rate(%) |
rotate speed of the left coal feeder | r/min | 10099.06 | 9670.37 | 428.69 | |
rotate speed of the right coal feeder | r/min | 10503.91 | 9797.79 | 706.12 | |
Steam flow rate | t/h | 23.06 | 23.75 | | |
rate of coal consumption per hour | rev/ton steam | 893.45 | 819.71 | 73.74 | 8.25 |
Table 2 boiler #1 the entropy change of steam before and after feeding
items | unit | Before feeding | After feeding | Data change |
Steam pressure | MPa | 2.0 | 2.1 | 0.1 |
Steam temperature | ℃ | 417.1 | 424.5 | 4.4 |
Entropy of steam | kJ/kg | 3284.28 | 3292.48 | 8.20 |
Table 3 carbon content change of the clinker before and after feeding
items | unit | Before feeding | After feeding | Percentage of decrease after feeding |
Carbon content of the flying ash | % | 15.12 | 12.37 | 2.75 |
Carbon content of the slag | % | 1.26 | 1.05 | 0.21 |
Notice: data of table 3 is based on the analysis of the change of carbon content of the flying ash and slag of the boiler #1 which is detected by State Key Laboratory of Coal Combustion (Huazhong University of Science & Technology).
3、effect analysis
The following analysis is only based on boiler #1. By using of "YINENG TA-JNP" cleaning agents for environment-protection and coal-saving made by Xiamen TongAn chemical engineering corporation, coal saving ratio of boiler is 8.2%.
Because the using of "YINENG TA-JNP" cleaning agents for environment-protection and coal-saving made by Xiamen TongAn chemical engineering corporation, working condition of combustion is improved. Boiler’s wind blowing volume can be lower, so the power consumption of the fan will drop. Decreasing of the coal consumption can also reduce the costs of coal transportation and treatment of slag.
So, The results of Sinopec Jianghan Salt&Chemical Complex(JSCC) thermal power plant show that the "YINENG TA-JNP" cleaning agents for environment-protection and coal-saving made by Xiamen TongAn chemical engineering corporation , which has a evident energy saving and carbon emission reduction effect.