Shanxi Coking Co., Ltd. Power Plant has three 35t/h pulverized coal boilers. The original design used 75t/h atmospheric deaerator. After the company's chemical fertilizer plant was put into production, in order to recover the high-temperature residual heat in the fertilizer production process, a preheating line was designed and installed. The soft water sent from the water treatment station was sent to the chemical fertilizer synthesis and purification plant through the preheating line, and the heat exchanger The endothermic heats up to about 100*C and is sent to the atmospheric deaerator.
During the operation of the preheating line, we found that the corrosion of the preheating line was very serious, and the iron ion content in the boiler feed water remained high. Leakage occurred in the preheating line, especially in the return line, after analysis and discussion on the workshop A set of 100 t/h vacuum deaerator 1 Vacuum deaeration process The vacuum deaeration process is as follows: The soft water from the water treatment station enters the vacuum deaerator tank, and under the effect of a three-stage steam ejector, the vacuum The deaerator generates a vacuum sufficient to make normal-temperature water boil. Under soft water, according to Henry's law, the partial pressure of water vapor is high and the partial pressure of oxygen is reduced, so that the dissolved oxygen overflows and is continuously extracted, and the effect of removing oxygen is passed through the steam. After the ejector work, in the first, second, and third condensers, after mixing and exchanging heat with 14*C fresh water, the condensate and cooling water are mixed and discharged into the trench.
2 Problems in operation 2.1 The condenser of the condenser is seriously blocked due to the mixed heat exchange between the waste steam and the cooling water in the condenser, the high-temperature steam and the low-temperature cooling water are in the process of heat exchange, the temperature of the cooling water is increased, and the fresh water is Temporarily, the hardness decreases, calcium and magnesium ions are precipitated and precipitated, and are gradually deposited on the water distribution plate and the outlet pipe wall of the condenser, so that the outlet flow area is reduced or even blocked, resulting in a decrease in the degree of vacuum in the deaerator, and the oxygen content in the effluent exceeds the standard. , can not be normal operation in the actual production every two or three months have to be a parking treatment, cleaning scaling 2.2 fresh water consumption Large condenser using fresh water cooling, the original design of the amount of cooling water condenser is 50t / h, The secondary level is 30 t/h and the tertiary level is 16 t/h. In actual operation, we have adopted a third-stage condenser that does not use fresh water, but the primary and secondary condensers still consume 250,000 tons of fresh water each year. "300,000 tons, the quality of the discharged cooling water is good, and the temperature is about 20C, causing huge waste. It is a pity.
闱 闱 韪 韪 韪 韪 韪 韪 从 从 从 从 从 , , , , , , , ,, Steam 400*, Loss of heating value approximately: / Say 0 2.3 Steam's residual heat does not use the steam condensation after the work done by the ejector after cooling water Discharged, equivalent to about 500 t standard coal per year.
3 transformation program Our reform idea is: First of all to completely solve the scaling problem of vacuum oxygen condensate system to prevent clogging of the sewage system; Second, it is best to use fresh water, to maximize the recovery of waste heat, reduce fresh water and steam The consumption design transformation plan is as follows: The parameters of the vacuum deoxidation operation are tested as follows: According to the actual situation of the workshop, the soft water flow in winter is generally 130t/h, the summer flow is about 70t/h or more, and the GS=70t/h is the cooling water. Calculate the usage water treatment station soft water outlet temperature of about 20 * C. 3.1-level secondary condenser to surface type heat exchanger, the use of string due to the level of condenser heat transfer than the secondary condenser, the test operation mode Cooling medium adopts soft water from the water treatment station. The soft water takes into account the convenience of making spare parts during operation. Therefore, the design of the condenser is sent to the vacuum deaerator after being heat-exchanged by the condenser.
The secondary condenser is a design object, and the first and second stages use the same change of steam condensate 3.2. The third stage condenser does not cast cooling water, and is the same as the current operation mode.
3.3 Design, production of new condenser, removal of the original hybrid condenser and all the fresh water pipeline transformation diagram such as the transformation of the original pipeline and equipment schematic heater.
According to the conditions, after design calculations and calibration calculations, the condensers are designed as follows: 4 Implementation of the transformation and calculation of economic benefits On July 15, 2003, equipment for the vacuum deaeration condenser was completed, and my workshop was actively organized and seriously reformed the equipment. The installation of the entire renovation work was completed on July 22.
The reformation only reconstructs the vacuum deaeration condensing system, and the principle and process of oxygen removal have not been changed. Therefore, we immediately organized a test run after the completion of the transformation. The vacuum deoxygenation was successful after a successful start, and the deaerator head pressure was a few minutes after driving. Within minutes, it reached 5.0kPa, the dissolved oxygen content quickly dropped to 50Pg/L. After several hours of operation, the dissolved oxygen content dropped to 30/g/L, and the oxygen removal pressure was 4.0kPa, after several months of trials. Operation, the current effluent oxygen content stabilized at 15g/L using the surface cooling method, due to changes in the cooling method, so that the heat exchanger heat exchanger efficiency has decreased, so the program is feasible or not, the key lies in whether or not The steam from the ejector and the steam extracted from the deaerator are condensed to achieve a certain degree of vacuum. After the condensing reform is implemented, the vacuum deaeration system completely disables the fresh water, and the water saving per hour can reach about 35 tons per year. Saving more than 250,000 tons of water by a shallow desalting water flow of 70 t/h, after flowing through the two-stage condenser, after calculation and field measurement, the water temperature can be increased by 5°C, and the heat recovery is 1.2X1, kj. The temperature will drop to the required absolute pressure Below the saturation temperature.
After checking the original vacuum vacuum deaerator thermal calculation book, the first condenser needs to condense 349.4 kg/h of steam, the absolute pressure in the condenser is 8.55 kPa, and the corresponding saturation temperature tm = 425*C, and the total gas volume = pumping Gas volume + working steam volume = 141+250 = 391kg/h The amount of steam to be condensed in the secondary condenser is 184. The absolute pressure in the condenser is 2 = 28.9kPa, the corresponding saturation temperature is 68*C, and the total gas volume = extraction volume +Working steam volume = 61. When fresh water for 600 t steam coal is calculated at 0.73 yuan/t, the annual water saving benefit can reach 228,800 yuan; thermal coal can be calculated at 150 yuan per ton, and the annual heat recovery benefit can reach 9 Ten thousand yuan; total annual economic benefit can reach more than 31 million yuan. 5. Conclusion The vacuum deoxidation and condensing system has achieved great success. Turn down page 79) (continued from page 62) (continued from page 67) The technical indicators of the project have reached the technical requirements of the original design, not only the economic benefits are significant, but also the social benefits are very significant.
First of all, after the vacuum deoxidation and condensing system was changed to soft water, the scaling problems of the condenser, the water pipeline, and the diffuser of the steam ejector were completely solved, the operation was stabilized, and the labor intensity of the inspection workers was reduced; secondly, the condensing system was changed to soft water. After the vacuum deoxidation process is also simplified, the amount of fresh water does not need to be adjusted, greatly reducing the operator's labor intensity; In addition, the recovery of steam waste heat, and the suspension of fresh water, reducing the large number of sewage and Waste heat pollution
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