Waste pot discharge
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Waste boilers usually have two drainage points, one at a lower level and one at a higher level. What is controlled by the drainage point at the higher level? What is its function? Regarding the low point, is the position of the high-point design related to the level of the liquid under normal control?
The drainage at the high point on the drum is known as continuous drainage, and its main purpose is to remove the concentrated substances and foam on the surface of the liquid. The drainage from the bottom is periodic drainage, and its main purpose is to remove the deposited impurities.
I can’t remember where I copied this information from; I’m sharing it in the hope that it will be helpful to the original poster. The water supplied to the steam drum always contains a certain amount of salts. After chemical treatment is applied inside the boiler, the scaling substances in the boiler water turn into sludge. In addition, the corrosion of metals by the boiler water also produces various corrosion products. Therefore, the boiler water contains various soluble and insoluble impurities. During boiler operation, only a small portion of these impurities are carried away by the steam, while the majority remain in the boiler water. As the water in the boiler continues to evaporate, the concentration of these impurities gradually increases. An excessive concentration of impurities in the boiler water not only affects the quality of the steam but also can lead to scaling and corrosion on the heating surfaces, compromising the safe operation of the boiler. To control the quality of the boiler water, it is necessary to perform boiler blowdown in order to remove some of the water contaminated by salts and sludge, and to replenish it with clean feed water. Boiler blowdown is divided into continuous blowdown and periodic blowdown. The purpose of continuous blowdown is to remove the salts dissolved in the boiler water, in order to maintain a certain level of salt content and alkalinity in it. This type of blowdown is continuously discharged from the boiling surface where the salt concentration in the boiler water is highest; it is also known as surface blowdown. The purpose of regular slag discharge is to remove insoluble sludge from the boiler water, and therefore it is discharged from the water wall lower header where the most sediment accumulates. The drainage is carried out intermittently, with the interval between occurrences determined by chemists based on the requirements regarding the quality of the steam and water; the purpose of regular drainage is to remove the sludge at the bottom of the steam drum and waste boilers, thereby preventing this sludge from blocking the pipelines. Regular drainage can also remove some of the boiler water with a high concentration of dissolved solids from inside the furnace, thereby reducing the salt and alkali content in the boiler water and ensuring that its quality remains satisfactory. Periodic discharge is also known as intermittent discharge. The characteristic of periodic slag discharge is a short duration and high flow rate, so that the sediment can be carried away by the rapidly flowing boiler water. The interval and amount of regular blowdown depend on the dosage of chemicals added to the boiler water, the degree of turbidity of the boiler water and test results, as well as the quality of the feed water. Generally, the discharge volume does not exceed 5% of the water supply volume. It is best to carry this out when the steam load is low. Before discharge, the liquid level should be kept 30–50 mm above the normal level, and the accuracy of the level gauge should also be checked. During discharge, monitor the changes in the liquid level gauge while controlling the discharge. The regular sewage outlet is located at the lowest point of the boiler, where dissolved solids and sediments accumulate. The procedure for regular sewage discharge is as follows: first open the second valve, then slightly open the first valve for a while, and finally open the first valve fully. After the discharge is complete, close the first valve first, then the second valve. Note: Sludge discharge should be carried out at a high water level, and the amount of sludge discharged should be such that the quality of the boiler water remains satisfactory. Continuous discharge: Continuous discharge involves the continuous removal of boiler water with high salt and alkali concentrations from the boiler through surface discharge pipes located in the drum, thereby reducing the salt and alkali levels in the boiler water and ensuring the quality of the steam. Continuous discharge is also known as surface discharge. The drain pipe for continuous discharge is located about 80 mm below the steam-water interface in the drum; this is precisely the area where steam is released, and it is the spot with the highest salt concentration in the boiler water. By discharging a portion of this boiler water continuously from here, it is possible to keep the salt content in the boiler water as well as the salt content in the steam within specified limits
Are there any specific requirements regarding the amount of waste discharged? Is there a specified range? Is 3% too high?
The amount of waste discharged is determined based on daily analysis data; it depends on the requirements set by your organization, and you need to adjust it gradually so that it remains within the specified limits, while keeping the discharge volume at its minimum. Active participation