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The traditional PDS desulfurization process for the removal of high-sulfur coke oven gas hydrogen sulfide, hydrogen cyanide, there are difficulties in sulfur bubble separation, desulfurization tower packing plugging, sulfur bubble difficult to dehydration and other issues affecting the system normal operation. In view of the fact that the content of hydrogen sulfide in coke oven gas is as high as 15g / m3, local power grids suffer frequent power outages, the production scale is small, the sulfur content in the existing desulfurization drybox is easy to catch fire, and some of the equipment is outdated, new process improvement solutions have been developed. As the project is a continuation of the project, the original design for the traditional tower desulfurization PDS process, the main equipment has been completed, the tower has entered the ring, crude benzene and other devices have been running, the construction of funds is limited. Therefore, the design can only be optimized under the traditional PDS desulfurization process. After repeated studies, in the rich liquid regeneration tower, sulfur bubble separation tank, desulfurization fluid accident tank, sulfur foam filter, vacuum pump made a bold and effective improvement.
1 release of sulfur foam tank, improve the separation efficiency
Although some studies suggest that an appropriate amount of sulfur particles are favorable for the absorption reaction, it is difficult to control the amount of sulfur in the conventional regeneration tower top ring shaped sulfur foam tank. If the process parameters are not properly controlled, a large amount of sulfur bubbles are often entrained in the desulfurization lean liquid for desulfurization Tower, resulting in desulfurization tower packing blockage. Heavy steel coking plant desulfurization tower put into operation less than six months, the import and export of tower pressure differential rose sharply, block tower obvious. Although there is a view that improper filler selection, and sulfur entrainment is one of many factors. Although the inner area of ​​the annular sulfur foam tank is generally designed to be 115 times the area of ​​the tower body, and there is no macroscopic rising velocity of the lean solution, since the tail gas pressure at this time is close to the atmospheric pressure, the volume expands and the airflow rises faster, Increasing the mixing intensity, liquid-solid separation less effective. In the study to improve the efficiency of sulfur bubble separation as the most important issue, the proposed release of annular sulfur bubble tank. After the separation tank is lowered, a concrete rectangular sulfur bubble separation tank (11m × 5m × 4m) is built on the ground. The effective separation depth is 215m, the protection height is 014m and the depth of accident fluid is 111m. The 112m section of the tank serves as the receiving lean liquid and the gas-liquid separation section. The 310m section of the tank serves as the auxiliary aeration separation section and the 618m section serves as the static separation section. In the middle of the tank, regeneration aeration and sulfur bubble particles are too large to replenish the aeration when they are floating up, otherwise aeration is not allowed, and the back part is left to stand for separation. In order to achieve the expansion of the sulfur bubble tank, improve the sulfur bubble separation effect, reduce the amount of elemental sulfur entrainment in the lean solution.
After the sulfur foam tank is decentralized, the height of the regeneration tower is reduced from 32m to 1415m as originally designed, which is 1015m lower than that of the 25m high desulfurization tower. The traditional tower regeneration, desulfurization tower contrast low contrast upside down. The gas, liquid and solid phases in the top of the regenerating tower are separated from each other by the tower process, and are separated into gas-liquid one separation and then liquid-solid secondary separation, which is beneficial to improve the liquid-solid separation efficiency and reduce the plugging factor. In actual operation, the lean solution after the separation tank is clear and transparent, and contains less elemental sulfur.
2 separation tank and accident tank merger
In the traditional design of wet desulfurization and cyanide removal process, a special accident tank is provided outside the main process for preparing desulfurization solution and accidental storage solution (the total volume of one regeneration tower) when starting the process. This approach is conducive to system maintenance, but the accident into the liquid and recovery of production back to pumping solution, the operation time is longer, and the operation is cumbersome. The power grid in the area where the plant is located is subject to frequent power outages due to lightning strikes, which will result in frequent downtime of accidents. In order to overcome this problem, the design breaks through the routine, leaving an accident capacity of 72m3 above the separation tank. When an accident such as shutdown or sudden power failure occurs, the desulfurization solution in the regeneration tower and the desulfurization tower can flow into the separation tank. Coupled with the tank with the return pipe, as long as the start poor, rich liquid pump can be completed within 1min solution circulation, to resume normal production. And on the poor, rich liquid pump does not start the order and interval
Between the strict operating requirements, reduce the workers operating intensity and the possibility of misuse, reducing the process links, storage tanks and covers an area, increased system accident handling speed.
3 using jet vacuum pump, secondary oxidation and energy saving
In order to ensure that the separation tank is lowered and the oxidative regeneration effect after the regeneration tower is reduced, a vacuum pump is injected after the regeneration tower, which is equivalent to replacing the ejector in the trough process, so that not only the air can be sucked back into the rich liquid again but also the belt vacuum Filter (hereinafter referred to as belt filter) of the vacuum pump, save 2 sets of 30kW SZ-3 water ring vacuum pump and a running power consumption.
According to the design parameters of the jet pump and the analysis of the oxidation process of the regeneration tower, the working pressure of the tower is designed to be in the range of 0105 ~ 0110MPa. The dissolved amount of air in the sulfur liquid at the top of the tower is 10 ~ 20mg / L, close to the oxidation regeneration of 30m regeneration tower effect. In actual operation, although the vacuum valve is shut down due to the frequent stoppage of the filter, completely relying on the rejuvenation tower to blow in the rejuvenation of the ballast gas, the content of hydrogen sulfide, hydrogen cyanide, the color of the desulfurizing liquid, the transparency, And the basic particle size unchanged. This shows that the regeneration tower to reduce the system capacity to reduce the oxidation regeneration time is reduced after the process performance did not decrease.
The recommended residence time in the tower regeneration tower should be 25-30 minutes in the design specification, while the residence time in the regeneration tank should be 6-10 minutes. Whether it is the pressure in the tower, or the injector in the trough process, the key is how to increase the diffusion rate of oxygen in the lean solution. From this it can be inferred that it is possible to replace the regeneration tower with a compact mixed-tube reactor. In order to verify this idea, a homemade tubular reactor (ê25 × 350mm) was used in the laboratory to inject about 280mL of desulfurization rich liquid first, then heated in a water bath and then compressed air of different pressure. Hydrogen sulfide pressure maximum range of 01042, the minimum time difference of 01008. This shows that the appropriate pressure (about 014MPa) is conducive to the conversion of hydrogen sulfide, and can shorten the reaction time. The amount of Na2S2O3 in the side reaction NaHS + 2O2 → Na2S2O3 + H2O is relatively less influenced by the time and the reaction time is short; the generation amount of CNS- is the most affected by the time, and the reaction time is also shortened to limit its generation . It can be seen from the perspective of improving the oxygen transmission rate, maintaining the appropriate pressure is conducive to the oxidative regeneration reaction, reducing the reactor volume. The design is not completely dependent on the jet pump instead of the jet for safety and reliability. Still using the tower tower has been designed to ê 212m × 1415m of the regeneration tower, you can once blowing compressed air (referred to as compressed gas) oxidation, but significantly reduced gas consumption. Due to the current gas processing capacity has not yet reached the design capacity, it is not certain that the design capacity of the gas pressure or rely entirely on the suction vacuum pump inspiratory oxidation.
4 with a vacuum filter belt to reduce sulfur cake liquid content
In the past often used drum-type vacuum (inside and outside) filter, frame filter press and so on the bubble filter liquid off. In recent years, some coking plants also adopt Gore membrane [6]. The filtered liquid of the filter is clear and transparent, but the sulfur liquid is much higher than the former (more than 50%), Secondary use and transportation adverse. Based on the good effect of the belt filter in the soot filtration of fertilizer plant, a 23m2 belt filter was used to replace the original three 40m2 drum vacuum Filter, so that the daily amount of sludge from the original less than 50t / d, increased to 80 ~ 90t / d. It can be seen in the fine particles and oily sludge dehydration have good performance. Therefore, the design for the first time selected the model filter sulfur bubble, filter area 7m2. In the vacuum of about 3kPa, you can scraping the cake of sulfur cream, liquid content is low, can be exported directly bagging. The machine has the functions of frequency control, filter cake cleaning, pressureless feeding, continuous work, secondary washing and other functions. It can reduce the liquid content of the sulfur cake and reduce the catalysis
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