Slogan of ultra-low emission

1 project overview

This project is an ultra-low emission project of 2×35 t/h+ 1×75 t/h boiler in power plant. After the project is completed, the final emission concentration of smoke and dust in boiler flue gas is less than 5 mg/nm3, the final emission concentration of SO2 is less than 35 mg/Nm3, and the final emission concentration of nitrogen oxides is less than 50 mg/Nm3, which meets the requirements of ultra-low emission index. 2. Compilation basis

(1) secondary standard of Ambient Air Quality Standard (GB3095-20 12); (2) Emission Standard of Air Pollutants for Thermal Power Plants in Shandong Province (DB37/664-2013); (3) Shandong Provincial Environmental Protection Department's Guiding Opinions on Accelerating the Ultra-low Emission of Coal-fired Units (Boilers) (Lu Huanfa [2015] No.98);

(4) Relevant national laws, regulations, guidelines, industrial policies and investment policies; (5) Relevant basic information provided by the construction unit. 3, the preparation principle

(1) Project construction must comply with national policies, regulations and decrees, conform to national industrial policies, investment directions and industry development plans, and implement relevant standards and norms. Focus on meeting the social benefits of environmental protection and energy conservation and emission reduction, and give consideration to the rationality of investment cost and economic benefits.

(2) Prepare in strict accordance with the scope and content requirements of the construction project, and abide by the basic construction procedures. Pay attention to saving investment and rationally arranging the general layout of the device in the design. On the basis of fully analyzing the factors such as traffic, raw material supply, water source conditions and facilities that the power plant can rely on, make full use of the existing public works (water, electricity and steam) of the power plant and the formed traffic and other favorable conditions, reasonably select the general layout of the device, save the construction investment as much as possible and minimize the project cost.

(3) The adopted technology is an environmentally friendly, energy-saving and technologically advanced process route actively recommended and advocated by the national industrial policy. The design is based on the basic principle of "mature technology, reliable device and reasonable economic operation", making full use of the existing facilities of the enterprise, occupying less land, saving investment and using funds reasonably.

(4) Conscientiously implement the national laws and regulations on labor safety, industrial hygiene and environmental protection, realize the "three simultaneities" of three wastes treatment, and improve the comprehensive treatment level; Carry out the policy of "safety first, prevention first" to ensure that the project meets the occupational safety and health requirements after it is put into production, and ensure the safety and health of workers in the production process.

Chapter II Basic Information

1, boiler technical parameters

Boiler type: circulating fluidized bed boiler model and specification: 1#, 2 # yg-35/3.82-m13.3 # TG-75/3.82-m3 Rated evaporation: 1#, 2 # 35t/h boiler outlet. 180000 m3/h flue gas concentration at the outlet of electric bag filter: 20 mg/Nm3 flue gas outlet temperature: 150℃ 2. Boiler fuel.

(1) Coal slime+gangue washing+washing mixture, in which: coal slime accounts for 92%; (2) The average calorific value of fuel is13800kJ/kg; (3) The water content of coal slime is 32%; The technical parameters of induced draft fan are (1) 1 # and 2#.

4. Present situation and basic data of desulfurization, denitrification and dust removal system

Each boiler in the power plant is designed with an electric bag dust collector, the dust removal efficiency is greater than 99.99%, and the outlet dust can be controlled at 20 mg/nm3; ; 20 10 boiler is put into operation for wet desulfurization by ammonia method, and ammonia water with a concentration of about 20% is used, ammonia water with a spraying concentration of about 5% is used, and 2×35t/h boiler desulfurization tower 1 seat, 1×75t/h boiler desulfurization tower 1 seat, * * desulfurization. There is no denitration system in the power plant.

The initial emission concentration of SO2 is1100 ~1500mg/nm3, the smoke concentration (at the outlet of electric bag dust collector) is 20 mg/Nm3, and the initial emission concentration of NOX is 220~260 mg/Nm3.

Chapter II: Ultra-low Emission System

Continuous monitoring system for ultra-low emission flue gas (CEMS)

Equipment name: continuous flue gas monitoring system (CEMS). Installation location: dust collector outlet. Number of mounting tables (sets): 2 sets

Monitoring items: SO2, nitrogen oxides, O2 concentration, smoke concentration, temperature, pressure, smoke flow and humidity, and requirements of gaseous pollutants monitoring system.

Brand requirements: imported brands such as Siemens, ABB, SICK and Shimadzu are selected as analytical instruments. ※

Scope requirements: ※:

The instrument provided by the bidder shall have dual-range switching function, and its minimum range shall meet the requirements of this project and the national ultra-low emission.

SO2: 0 ~ 100 ~ 500mg/nm3 (the measuring range can be set at will) NO: 0 ~ 100 ~ 500mg/nm3 (the measuring range can be set at will) O2: 0 ~ 5 ~ 25 vol%.

Calibration method: The gas analyzer provided by the bidder shall have the function of automatic calibration with air, and can save the measurement data during calibration. . span deviation: ※:

Working temperature: 5-45℃ (it can work safely in the range of 0-45℃). Sample flow rate: 2L/ min.

The measured data of the analyzer should be automatically converted into dry basis concentration value to meet the relevant requirements of national environmental protection.

Technical performance requirements of smoke and dust continuous monitoring system

This project is an ultra-low emission project, and the dust measurement system provided by the bidder should ensure accurate and stable measurement in harsh environments such as high humidity and low concentration.

Brand requirements: German ABB, German Siemens, German SICK, American Hot or equivalent brand imported products. ※

Measurement method: dilution extraction type+laser forward scattering probe: heating type, length not less than 1500mm. ※

Measurement range: 0~5~ 15mg/Nm3. Measurement accuracy: no more than 2% of full scale.

Correction method: timing automatic zero and range correction of flue gas humidity: 100% RH (including liquid water) flue gas temperature:

Probe material: 3 16Ti stainless steel, optional Hastelloy nickel-gold anticorrosion grade: IP65.

Working power supply: 220 V AC /380 V AC/50 Hz, 4 KVA.

In addition to meeting the above technical requirements, the dust removal measurement system provided by the bidder shall also have the following certificates:

Certificate of measuring instruments and certificate of national environmental protection product certification.

Product practicability certificate issued by the quality supervision and inspection center of environmental monitoring instruments of the Ministry of Environmental Protection.

Monitoring report

Note: The name and model of the instrument must be consistent with the above certificate and within the validity period.

On-line flue gas monitoring system (CEMS) at the inlet of desulfurization tower

The bidder shall provide two sets of continuous flue gas monitoring systems (CEMS). CEMS adopts direct extraction method, and the monitoring items before desulfurization system are: nitrogen oxides, SO2, O2, flue gas temperature, flue gas pressure, flue gas humidity, flue gas quantity and NH3 (in situ).

The CEMS system provided by the bidder shall have the applicability test report issued by the Environmental Monitoring Instrument Quality Supervision and Inspection Center of the State Environmental Protection Administration, and the model shall be consistent with the report. 4.3 Monitoring (testing) items and parameters:

Note: In the above table, in order to check the actual values of various process parameters under the working condition of 100% BMCR of coal, the bidder is requested to consider sufficient margin and select the appropriate range in combination with the actual optional range of the flue gas analyzer.

The bidder can optimize the configuration of the provided CEMS system to ensure the reliable operation of the whole system and the approval of the local environmental protection department, and explain it in the tender.

Chapter III: Ultra-low Emission (Data Processing) -3

The first part is an overview of ultra-low emission.

The concept of ultra-low emission

At present, there is no strict official definition of "ultra-low emission" of air pollutants in coal-fired power plants at home and abroad, and there are many expressions such as "ultra-low emission", "near zero emission" and "ultra-net emission" in practical application. The control indexes of soot, sulfur dioxide and nitrogen oxides in "ultra-low emission" are also not uniform. Most documents or engineering cases respectively adopt the emission limits of gas turbine set specified in Emission Standard of Air Pollutants for Thermal Power Plants (GB11223-201,hereinafter referred to as the "standard"): 5 mg/m3 and 5mg/m3. There is no convincing scientific basis for the determination of the above indicators and their differences.

It is worth noting that the reference oxygen content after conversion of the standard limit value of gas turbine specified in the standard is 15%, while that of coal-fired units is 6%. If converted into comparable conditions, the standard value of gas should be 2.5 times that of coal, that is, when the oxygen content is 6%, the emission limits of "ultra-low emission" soot, SO2 and nitrogen oxides are 12.5mg/m3 and 87.5 respectively. Generally speaking, the implementation of "ultra-low emission" for coal-fired units is looser than the implementation of special emission limits. In fact, the "ultra-low emission" of coal-fired units is based on the condition that the benchmark oxygen content of coal is 6% and the emission limit of gas-fired units is the control index.

It can be seen that the current "ultra-low emission" is mainly at the emission level within the standard limit of coal-fired power plants, but there is no specific control index. Only the emission level within the standard and below the limit is widely called ultra-low emission.

Present situation of ultra-low emission

1. Technical analysis

Under the existing technical level, ultra-low emission can be achieved by increasing the input of environmental protection equipment and raw materials, optimizing the system, transforming auxiliary machines, controlling coal quality and other means, but there are still some problems:

First of all, theoretically, flue gas denitrification can achieve high efficiency, but in order to control very low nitrogen oxides, more NH3 must be injected, the leaked NH3 will increase accordingly, the corrosion and blockage of the boiler tail and the pressure difference of the air preheater will increase.

Secondly, WESP lacks operating experience and operating index data. WESP is imported from Japan and has been used in metallurgical and chemical industries in China for many years. It always has some shortcomings, such as equipment corrosion, unstable flue gas flow field and difficult wastewater treatment. It is much more complicated than ESP in operation and maintenance, and it is worrying whether it can reach the gas standard value stably for a long time.

Third, it is difficult for some coal to achieve "ultra-low emission". Burning coal with low sulfur, low ash and high calorific value is the basic premise to realize ultra-low emission. At present, most coal in China contains sulfur and other impurities, so it is difficult to reach special emission limits, let alone ultra-low emissions. For example, the low calorific value of coal is 4000kca/kg and the ash content is 35%. Before dust removal, the smoke concentration in flue gas is about 53.8 g/m3. Even if the total dust removal efficiency is as high as 99.99%, the smoke emission concentration is still higher than the ultra-low emission requirement of 5mg/m3. Another example is that the SO2 concentration in the flue gas generated by coal with sulfur content of 3% is about 6900mg/m3. Even if the desulfurization efficiency of the desulfurization system reaches 99% for a long time, its emission concentration is still as high as 69mg/m3, which cannot meet the ultra-low emission requirement of 35mg/m3. In fact, the concentration of SO2 in flue gas of most power plants in southwest China is as high as 10000mg/m3.

2. Economic analysis

It is reported that ultra-low emission and special emission limits will be implemented for new coal-fired units.

Compared with the numerical value, the emission of pollutants decreased by 30% ~ 50% (an average decrease of 45%), but the one-time investment and operating expenses of environmental protection increased by about 30%. The greater the installed capacity, the lower the investment per kilowatt of environmental protection transformation of coal-fired generating units without flue gas denitration SCR device, and the more remarkable the transformation benefit. For example, 600MW and above active coal-fired generating units will achieve ultra-low emissions, with an investment of 345 ~ 439 yuan per kilowatt for environmental protection transformation. In addition, according to the calculation of environmental protection transformation and operation cost of some coal-fired power units, the additional cost of 1000MW unit is 0.96 cents/kwh from special emission limit to ultra-low emission; For 600MW units, the additional cost is1.43 min/kwh; For a 300 MW unit, the additional cost is 1.87 minutes/kWh.

It can be seen that "ultra-low emission" brings great pressure to the stable operation of enterprises and the economy. Since 2004, every round of emission standard improvement means that all desulfurization facilities in thermal power plants must be upgraded. After careful calculation, in order to meet the emission standards, a thermal power plant with an installed capacity of/kloc-0.0 million kilowatts will only spend 6,543.8+billion yuan on desulfurization.

According to a recent research report by the Environmental Planning Institute of the Ministry of Environmental Protection, although the thermal power industry claims that the cost of gas-fired power generation is one kilowatt-hour in 0.8 yuan and that of ultra-low emission power generation is only one kilowatt-hour in 0.4 yuan, this advantage will no longer exist after the external cost of coal is included.

3. Environmental benefits

Experts pointed out that compared with the special restrictions on emissions, the three pollutants can be removed by 0.47 percentage points. The implementation of ultra-low emission of coal-fired generator sets has little effect on reducing conventional pollutants in the ambient air, but it has a significant effect on reducing PM2.5, because the contribution of gaseous pollutants emitted by thermal power industry to PM2.5 in the ambient air accounts for about 88% of its total contribution, and the contribution of soot emissions to PM2.5 in the ambient air accounts for about 12% of its total contribution. Therefore, one-sided pursuit of ultra-low emission of soot from coal-fired generating units has no obvious effect, whether it is total emission reduction or environmental quality improvement, and it belongs to "inefficient emission reduction". For example, the relevant data of "ultra-low emission" implemented by units with special emission limits are shown in the following table.

Moreover, the existing continuous flue gas monitoring technology is difficult to support the accuracy of ultra-low emission monitoring data. At present, there is no such precision instrument in China that can accurately measure dust below 20 mg, and the monitoring data of ultra-low emission is not reliable.

According to the standard, the emission concentration of coal-fired power plants is already very low. How to transform it to achieve "ultra-low emission" has not improved much, but the cost has greatly increased. Therefore, after technical, economic and environmental evaluation, "ultra-low emission" can be tried out in some power plants in some areas, but it is not suitable to be popularized nationwide at this stage.

The second part, typical technology and equipment.

First, efficient desulfurization technology

The efficiency of limestone-gypsum wet desulfurization is usually between 95% and 98%. When the desulfurization efficiency exceeds 95%, it is necessary to take coordinated measures: multi-spray technology, double-cycle technology and double-disk technology.

1, single tower multi-spray technology (conventional technology)

Its basic principle is to increase the number of spray layers or increase the spray circulation, so as to improve the liquid-gas ratio of the absorption tower, increase the contact time between flue gas and desulfurizer and the mass transfer driving force, and then improve the desulfurization efficiency.

Technical characteristics: increasing the number of spray layers requires increasing the height of absorption tower, increasing the volume of slurry pool and increasing the investment cost; Increasing the cycle requires more power consumption, and at the same time, it needs to increase the pressure head required by the oxidation fan, which increases the operating cost. Generally, increasing to 5~6 floors is the upper limit, and the total efficiency can reach 98.5%. Although single-tower multi-layer spraying saves floor space, it has some shortcomings such as low utilization rate of desulfurizer and unstable oxidation rate of calcium sulfite.

2. Single tower and double pallet technology (Wuhan Katie introduced the technology of American B&W company)

The basic principle of plate tower technology refers to adding one or more trays with perforated plates on the basis of countercurrent spraying, and arranging the trays on the cross section of the whole absorption tower. After the flue gas with higher flow rate enters the absorption tower, the gas-liquid two-phase and the liquid film on the tray are homogenized, so that the gas and the slurry can achieve the best contact above the whole height of the absorption zone. Because the tray can keep a certain liquid film height, the residence time of flue gas in the absorption tower is increased and the absorption is more sufficient. Sometimes, a spray layer is set below the tray to pre-saturate the flue gas.