2、 Development status of flue gas denitrification process for gas generators

At present, the commonly used ways to control NOX emissions can be roughly divided into two categories:

1. Combustion control is an internal purification technology centered on improving the combustion process of internal combustion engines, represented by lean combustion technology and low emission combustion technology such as exhaust gas recirculation;

2. End of pipe treatment refers to the emission post-treatment technology that uses chemical or physical methods to purify NOx in the exhaust system. The main technologies include selective catalytic reduction (SCR) and selective non catalytic reduction (SNCR).

Among them, Selective Catalytic Reduction (SCR) is currently the mainstream international technology route for efficiently removing nitrogen oxides from exhaust gas: mainly targeting NOx in exhaust gas, the catalyst decomposes NOx into harmless nitrogen gas (N2) and water (H2O) within a certain temperature range (generally 350 ℃ -600 ℃).

3、 Characteristics of Kaineng Technology Gas Generator Exhaust SCR Denitrification System

1. Kaineng Technology's gas generator exhaust SCR denitrification system products are widely used in exhaust treatment of diesel generators, gas internal combustion engines, and gas turbines. Kaineng Technology has been committed to flue gas waste heat recovery and SCR denitrification products for 20 years. It can design and manufacture flue gas waste heat utilization products and SCR flue gas denitrification products, as well as plan and match waste heat utilization and SCR denitrification systems to ensure that the system and equipment are in good working condition.

2. Kaineng Technology has equipped more than a thousand sets of waste heat boilers for gas generators, and is very familiar with the structure of waste heat boilers for gas internal combustion engines. It arranges SCR system equipment more reasonably to ensure the rationality and uniformity of the flue gas velocity field and NH3 concentration field.

3. Kaineng Technology uses high-efficiency imported catalysts to ensure the SCR denitrification effect of gas generator exhaust.

1. The integrated design of SCR denitrification equipment and flue gas waste heat recovery enables the denitrification system to adapt to the start stop and load changes of the boiler, and has good adaptability.

2. The debugging, start stop, and operation of SCR denitrification equipment do not affect the normal operation of the internal combustion engine.

3. Minor modifications to the original unit and low renovation costs.

4. The NOx conversion rate exceeds 90% and can still ensure a high conversion rate even in a large temperature range;

5. Using urea as a reducing agent is safe and reliable.

6. Low back pressure design has minimal impact on engine efficiency.

7. Capable of adapting to any load between 40% BMCR and 100% BMCR conditions of the boiler.

5、 Principle of Kaineng Technology's SCR Denitrification Technology

SCR, also known as selective catalytic reduction system, works by spraying a certain amount of urea aqueous solution into the engine exhaust pipe in a mist form. The urea droplets undergo hydrolysis and pyrolysis reactions at high temperatures, generating the required reducing agent ammonia gas (NH3). Under the action of a catalyst, ammonia selectively reduces nitrogen oxides (NOx) in flue gas to nitrogen (N2) and water (H2O), thereby reducing the concentration of NOx in flue gas.

Under the control of the electronic control unit, the urea pump extracts urea from the urea tank, pressurizes and filters it, and sends it to the metering injection unit. Compressed air is also sent to the metering injection unit after being regulated by the control unit. After the quantitative injection valve is opened, urea is injected under the injection of compressed air, mixed with compressed air, and sprayed into the exhaust pipe through the nozzle. The electronic control unit accurately calculates the required urea injection amount based on the exhaust gas flow rate, catalyst temperature, and nitrogen oxide content, and sends corresponding pulse width modulation signals to the quantitative injection valve. The injection valve measures the urea according to the signal to ensure the accuracy of the urea injection amount.

Decomposition reaction of urea aqueous solution:

(NH2)CO+H2O=2NH3+CO2

NOx reduction reaction:

Standard reaction: 4NH3+4NO+O2 → 4N2+6H2O

Slow reaction: 6NO2+8NH3 → 7N2+12H2O

Quick response: NO+NO2+2NH3 → 2N2+3H2O

6、 Composition and Characteristics of Kaineng Technology's SCR Denitrification System

1. Characteristics of SCR denitration system

a. The SCR denitrification device has a simple structure, no by-products, easy operation, high reliability, high denitrification efficiency, and relatively low initial investment;

b. The reduced nitrogen is directly discharged into the atmosphere without secondary pollution;

c. Small equipment size, low operating costs, high degree of automation, and good reliability;

d. Low resistance to system operation;

e. The device has simple and fast connection, strong corrosion resistance, and excellent overall performance.

2. Composition of SCR denitration system

a. SCR reactor assembly

b. SCR catalyst assembly

c. SCR control system

d. Urea solution metering and injection system

e. Urea solution storage system

The Kaineng SCR reaction zone consists of three parts: the first part is the urea injection mixing section, the second part is the diversion section, and the third part is the SCR reaction section. The internal components are installed on both sides of each section, which is more conducive to the installation and maintenance of the internal components.

Temperature sensors and NOx sensors are installed at the front and back ends of the SCR reaction section to detect the temperature and NOx concentration of the flue gas before and after the reaction.

The middle part of the reaction section is the catalyst carrier section, which is detachable and can be installed with different numbers and models of catalyst carriers according to different requirements to be applied to equipment of different powers.

1. Selection of catalyst

In terms of catalyst selection, a medium temperature vanadium based coating catalyst is chosen with a temperature window of 350-400 ℃. The catalyst has high removal efficiency (the NOx concentration in the treated exhaust can be less than 100mg/m3, and the NOx concentration in the treated exhaust can be less than 10mg/m3 at the optimal activity temperature of around 350 ℃), with a denitrification efficiency of over 98%. It has many advantages such as good selectivity and low ammonia leakage rate, making it a particularly suitable catalyst for the treatment of nitrogen oxides in gas engine exhaust. And the pressure drop is lower when the airflow passes through the catalyst. The geometric surface area is large, the unit processing capacity is strong, and the efficiency is high.

The catalyst of this project adopts a multi-layer layout, with one layer as a backup layer. The catalyst adopts a modular pull-out design, which is easy to install and replace in the future.

2. Performance characteristics of catalyst support

◇The catalyst carrier has good compressive and wear-resistant strength and can withstand long-term erosion;

◇Catalyst support is resistant to alkali metals and toxic substances such as arsenic and mercury;

◇The catalyst carrier has high selectivity and can inhibit the generation of sulfur trioxide, reducing catalyst poisoning;

◇By using section hardening technology, the mechanical properties of the catalyst support have been enhanced and the service life has been extended.

1. The control system of the exhaust denitrification device includes: SCR flue gas monitoring system, urea injection system, reducing agent supply system, remote control system, and remote display.

2. Key technical design of exhaust denitrification device control system: integrated computer PLC control device, high-precision sensor, SCR denitrification device control cabinet design.