CN-116972659-B - Control system and control method for reducing mercury emission by ash discharge of cement kiln dust collector

Abstract

The invention discloses a control system and a control method for reducing mercury emission by ash discharge of a dust collector of a cement kiln. When the mercury concentration in the flue gas is less than the environmental protection standard, the dust collector ash is not discharged, and when the mercury concentration in the flue gas is greater than the environmental protection standard, the computer controls related equipment to discharge the dust collector ash so as to reduce the mercury concentration of the chimney. The solid powder sampler is respectively arranged on the ash hopper of the bag type dust collector and the raw material lifting machine, samples are respectively taken according to a certain period and are sent to the solid mercury meter, and the solid mercury meter is used for conveying the mercury content of the dust collector ash and the mercury content of kiln-entering raw material to the computer. The computer calculates the external discharge capacity of the dust collector ash by comparing the input quantity and the output quantity of mercury, and the dust collector ash is conveyed to a temporary storage bin for temporary storage by controlling the bidirectional screw conveyor according to the calculated external discharge capacity, so that the emission concentration of the mercury in a chimney is reduced.

Inventors

• WANG YONGGANG
• CHENG ZHAOHUAN
• HUANG QING
• TANG XINYU

Assignees

• 天津中材工程研究中心有限公司
• 天津水泥工业设计研究院有限公司

Dates

Publication Date

20260505

Application Date

20230714

Claims (1)

1. 1. The control method for reducing mercury emission by ash discharge of the dust collector of the cement kiln is characterized by comprising the following steps of: (1) Solid sample sampling and testing Sampling kiln raw material and dust collector ash respectively, and testing mercury content by using a mercury tester, wherein the mercury content of the kiln raw material is A 1 , and the mercury content of the dust collector ash is A 2 ; (2) Gas sample sampling and testing The flue gas mercury analyzer tests the flue gas of the chimney, and the test result is A 3 ; (3) Dust discharge judgment of dust collector When A 3 ＜A 0 is carried out, the dust collector ash is not discharged, and when A 3 ≥A 0 is carried out, the dust collector ash is discharged; when the dust collector ash needs to be discharged, the discharge capacity is as follows: ① When a 1 ×M 1 ×1000＜ A 0 ×q: M 3 =K(A 3 -A 0 )×Q÷A 2 ÷1000 ② When a 1 ×M 1 ×1000 ≥A 0 ×q: M 3 =K(1000×A 1 ×M 1 -A 0 ×Q)÷ A 2 ÷1000 Wherein A 0 is the national standard of mercury emission limit, mg/m 3 A 1 Mercury content of kiln-entering raw material, mg/kg A 2 dust collector ash mercury content, mg/kg A 3 Mercury content in chimney mg/m 3 M 1 System charge, t/h M 2 total dust collection amount of dust collector, t/h M 3 dust collector ash discharge capacity, t/h Q, exhaust smoke amount, m 3 /h K, the safety coefficient is 1.1-1.3; The method adopts a control system for reducing mercury emission by ash discharge of a cement kiln dust collector, the control system comprises a preheater (1), a raw meal mill (2), a bag type dust collector (3), a chimney (7), a first belt conveyor (4), a raw meal elevator (6) and a raw meal warehouse (5), wherein a flue gas mercury analyzer (H-1) is arranged on the chimney (7), the flue gas mercury analyzer (H-1) tests the concentration of mercury in flue gas and transmits the mercury to a computer (H-5), a first solid powder sampler (H-2) is arranged below an ash hopper of the bag type dust collector (3), a second solid powder sampler (H-3) is arranged on the raw meal elevator (6), the first solid powder sampler (H-2) and the second solid powder sampler (H-3) are connected with the solid mercury meter (H-4), the solid mercury meter (H-4) conveys the mercury content of ash of the dust collector and the mercury content of the raw meal entering the kiln to the computer (H-5), a bidirectional screw conveyor (H-6) is arranged between the bag type dust collector (3) and the first belt conveyor (4), the computer (H-5) controls the bidirectional screw conveyor (H-6) to convey the dust collector ash to the first belt conveyor (4) or to convey the dust collector ash to the temporary storage bin (H-8) through the second belt conveyor (H-7).

Description

Control system and control method for reducing mercury emission by ash discharge of cement kiln dust collector Technical Field The invention relates to the field of cement kiln flue gas treatment, in particular to a control method and a control system for reducing mercury emission of a cement kiln. Background Mercury is input into the cement industry mainly from raw materials, coal dust and waste materials, while the output path mainly is exhaust emission, and a small amount of mercury enters cement products. After raw materials and fuel enter the preheater and the kiln, most mercury is volatilized into gaseous mercury and flows along with waste gas, then the gaseous mercury contacts with raw material powder in the preheater and is mostly absorbed, the raw material powder with the mercury absorbed enters the dust collector along with flue gas to be captured as return ash to be mixed into the raw material, most mercury enters the preheater system along with the raw material powder again to become a cycle, and a small amount of return ash enters the cement mill to be used as a mixed material. Gaseous mercury not captured by the dust collector is discharged into the atmosphere along with the tail gas of cement, so that the discharge of the atmospheric mercury is caused. As shown in fig. 1, which is a schematic diagram of a conventional ordinary cement production process, flue gas from a preheater 1 is recycled by waste heat and then enters a raw mill 2 to serve as a drying heat source for ground raw materials in the raw mill 2. The cooled flue gas is collected by the bag type dust collector 3 and then discharged through the chimney 7. The dust collector ash collected by the bag type dust collector 3 is sent to a raw material warehouse 5 for storage through a belt conveyor 4. Raw materials from the raw mill 2 subjected to grinding enter a raw material warehouse 5 for storage. The raw meal elevator 6 lifts cement raw meal from the raw meal reservoir 5 to the top of the preheater 1 and into the preheater 1. Tang Xinyu, the current state of mercury in the cement industry and the development of emission reduction technology (new century cement guide, no.4 2022) and other articles propose that the emission of mercury concentration can be effectively reduced because mercury can continuously increase concentration in the circulating enrichment process and the ash rich in mercury of the dust collector is discharged. The mercury content in the ash returned from the dust collector is about 10 times of the mercury content in the raw material, and the mercury content in partial areas can even reach hundreds of times of the mercury content in the raw material, so that the mercury is utilized for circulating enrichment and matched with the running interval of the raw material mill, and the ash returned with high mercury concentration is intermittently used as a mixed material to be added into cement products, thereby being a relatively promising technical direction. In Japanese patent application laid-open No. 2011-88770, in order to remove mercury and the like contained in cement kiln exhaust gas, dust collected by removing mercury and the like is reused in cement raw materials, and there is proposed a method of collecting cement kiln dust, heating exhaust gas using a clinker cooler, and recovering mercury volatilized by heating. However, the above documents and patents do not propose an effective method for controlling the discharge amount of dust collector ash, which causes waste and excessive energy consumption due to a large amount of discharged dust collector ash in practical application, or the discharged dust collector ash is too small to control the discharge of mercury, and the discharge of mercury in flue gas is still out of standard. Disclosure of Invention The invention aims to solve the technical problem of providing a control system and a control method for reducing mercury emission by discharging dust of a dust collector of a cement kiln, and the discharge of mercury in flue gas is reduced by testing and calculating how much dust of the dust collector is discharged. Is suitable for cement factories which are stable for a long time or have little fluctuation by using cement raw fuel, and is not suitable for cement factories which are used for cooperatively disposing waste with little high-concentration mercury-containing waste suddenly. In order to solve the technical problems, the invention adopts the technical scheme that the control method for reducing mercury emission by discharging ash outside a dust collector of a cement kiln comprises the following steps: (1) Solid sample sampling and testing Sampling kiln raw material and dust collector ash respectively, and testing mercury content by using a mercury tester, wherein the mercury content of the kiln raw material is A 1, and the mercury content of the dust collector ash is A 2; (2) Gas sample sampling and testing The flue gas mercury analyzer tests the fl