1、 Overview

In recent years, our company has been committed to pollution control and environmental improvement in the power industry, steel industry, fertilizer industry, cement industry, and other industrial sectors. Our business areas involve flue gas purification, deep energy-saving transformation of boilers, sewage treatment, etc. We are an environmental engineering company with professional service capabilities in engineering design, construction, installation, commissioning, and after-sales. In terms of flue gas denitrification, dust removal and desulfurization, our company has SCR selective catalytic reduction denitrification technology, double alkali desulfurization technology, ammonia desulfurization technology, magnesium desulfurization technology and various dust removal technologies, and undertakes old engineering renovation projects.

2、 Boiler denitration, dust removal and desulfurization process flow

The design process of this scheme is as follows: flue gas → booster fan → waste heat recovery device (economizer) → heat exchanger → SCR catalytic denitrification system → primary dust removal → secondary dust removal → wet desulfurization system → heat exchanger → high-altitude emission. And it is equipped with a complete set of equipment including limestone slurry system, gypsum dewatering system, oxidation system, liquid ammonia storage and transportation system, industrial water system, anti-corrosion insulation and automatic control system.

3、 Characteristics of Selective Catalytic Reduction (SCR) Process

Among the currently applied boiler denitrification technologies in thermal power plants, the Selective Catalytic Reduction (SCR) process has been proven to be the most widely used and highly efficient mature denitrification technology, and is currently one of the advanced mainstream technologies for flue gas denitrification in thermal power plants worldwide. SCR method is a post combustion NOx control process, and the key technology includes injecting ammonia into the flue gas; Pass the flue gas containing NH3 (gas) through a reactor containing a dedicated catalyst; Under the action of the catalyst, NH3 (gas) reacts with NOx to convert NOx in the flue gas into H2O and N2, with a denitrification efficiency of ≥ 90%. At present, products utilizing this technology have a market share of up to 98%, ranking first in flue gas denitrification technology among developed countries in the world.

4、 Process principle

SCR technology is the selective reaction of reducing agents (NH3, urea) with NOx under the action of metal catalysts to generate N2 and H2O, rather than being oxidized by O2, hence it is called "selectivity". The main reactions are as follows:

4NH3+4NO＋O2→4N2+6H2O

4NH3+2NO2＋O2→6N2+6H2O

When using a catalyst to promote the reduction reaction of NH3 and NOx, the reaction temperature depends on the type of catalyst selected. In catalysts, TiO2 with rutile structure as the carrier and vanadium as the main active component are widely used in engineering, and their technological development is also mature. Its active temperature range is between 300-400 ℃. WO3 and/or MoO3 are usually added to such catalysts, whose main function is to increase the activity and thermal stability of the catalyst, prevent sintering of rutile and loss of specific surface area.

High denitrification efficiency, 90%;

5、 Characteristics of dust removal process

The commonly used dust collectors include ceramic multi tube cyclone dust collectors, bag filters, and electrostatic precipitators. Most projects use first level ceramic multi tube cyclone dust collectors and second level bag filters, which fully meet national emission standards.

A first level temperature resistant and wear-resistant ceramic multi tube cyclone dust collector can remove most of the dust without being limited by temperature and corrosion. The secondary bag filter has good dust removal effect, and the filtration mechanism of the bag filter determines that it is not affected by changes in the physical and chemical properties of the coal being burned, and has stable dust removal efficiency. Bag filters are more effective in capturing heavy metal particles and submicron dust particles that have a serious impact on the human body. Usually, the dust removal efficiency can reach over 99.99%, and the concentration of emitted smoke and dust can be stably below 50mg/Nm3, even up to 10 mg/Nm3 or below, achieving almost zero emissions.

6、 Characteristics of dual alkali desulfurization method

The dual alkali flue gas desulfurization technology overcomes the disadvantage of easy scaling in the limestone lime method. The traditional limestone/lime gypsum flue gas desulfurization process uses calcium based desulfurizers to absorb sulfur dioxide and generate calcium sulfite and calcium sulfate. Due to their low solubility, they are easily formed in the desulfurization tower and pipelinesScalingBlockage phenomenon. The problem of scaling and blockage seriously affects the normal operation of the desulfurization system, and even more seriously affects the normal operation of the boiler system. In order to avoid the adverse factors of using calcium based desulfurizers as much as possible, most calcium based desulfurization processes require corresponding forced oxidation systems (aeration systems), which increases initial investment and operating costs. Using inexpensive desulfurizers can easily lead toScalingThe problem of blockage arises from the contradiction between the high operating cost of using sodium based desulfurizers alone and the difficulty in treating desulfurization products. The dual alkali flue gas desulfurization process has emerged, which effectively solves the above-mentioned contradiction.

Compared with limestone or lime wet desulfurization processes, the double alkali method has the following advantages: 1. Using NaOH for desulfurization, the circulating water is basically an aqueous solution of NaOH, which has no corrosion or blockage to the water pump, pipeline, and equipment during the circulation process, making it easy for equipment operation and maintenance;
2. The regeneration of the absorbent and the precipitation of desulfurization slag occur outside the tower, which avoids blockage and wear inside the tower, improves operational reliability, and reduces operating costs; At the same time, efficient plate towers or packed towers can be used instead of empty towers to make the system more compact and improve desulfurization efficiency;
3. Sodium based absorption solution absorbs SO2 quickly, so a smaller liquid to gas ratio can be used to achieve higher desulfurization efficiency, generally above 90%;
4. For the integrated technology of desulfurization and dust removal, it can improve the utilization rate of lime.
The disadvantage is that Na2SO4, a byproduct of NaSO3 oxidation, is difficult to regenerate and requires continuous supplementation of NaOH or Na2CO3, which increases the consumption of alkali. In addition, the presence of Na2SO4 will also reduce the quality of gypsum.
The dual alkali desulfurization technology is a mature technology used both domestically and internationally, which is particularly suitable for flue gas desulfurization of small and medium-sized boilers and has broad market prospects.

7、 Characteristics of ammonia ammonium sulfate desulfurization process

The wet ammonia desulfurization process is currently a mature and industrialized desulfurization process. It uses ammonia absorbent to wash the flue gas containing sulfur dioxide, and the by-product ammonium sulfate can be used as agricultural fertilizer, which can better meet the needs of the development of flue gas desulfurization in China. Wet ammonia desulfurization has the following advantages:

1. Widely applicable, not limited by sulfur content or boiler capacity. The higher the sulfur content, the greater the production of ammonium sulfate.

2. The desulfurization efficiency is very high, easily reaching over 95%. The flue gas after desulfurization not only has a low concentration of sulfur dioxide, but also greatly reduces the dust content of the flue gas.

3. Absorbents are easy to purchase and can come in three forms: liquid ammonia, ammonia water, and ammonium bicarbonate.

4. The ammonia desulfurization device has strong adaptability to changes in unit load, and can adapt to fast start, cold start, warm start, hot start and other methods; Adapt to operating under a load range of 35% BMCR to 140% BMCR for the unit.

5. There are successful examples of operation both domestically and internationally, with good reliability and no scaling issues.

6. Ammonia is a good alkaline absorbent with a high utilization rate.

7. The by-product ammonium sulfate has high value, good economic benefits, and is integrated with fiberglass denitrification, dust removal, and desulfurization

Integrated design process for denitrification, dust removal, and desulfurization: flue gas → booster fan → waste heat recovery device (economizer) → heat exchanger → integrated tower for denitrification, dust removal, and desulfurization → heat exchanger → high-altitude discharge.

8、 Selection instructions for desulfurization and dust removal system

This system needs to be designed based on the boiler model, coal consumption, flue gas composition, flue gas flow rate, temperature, medium concentration and other indicators provided by the user, as well as user requirements. It can undertake all or part of the project. Our company has special calculation program software to ensure accurate and reasonable selection.

9、 Application area

This system is widely used in the control of flue gas pollution and environmental improvement in the power industry, steel industry, fertilizer industry, cement industry and other industrial enterprises. Its business areas involve flue gas denitrification, desulfurization and dust removal, sulfur dioxide waste gas reuse, deep energy-saving transformation of boilers, sewage treatment, etc.