The volume of gas-fired boiler is much smaller than coal-fired boiler, and it can be more easily controlled automatically. Gas fired boiler has a broader prospect in application. At present, China is in the stage of energy structure adjustment. The development and utilization of natural gas has become an important issue in energy use and decision-making. It can be seen that the application and development of gas-fired boiler has entered a new stage of development. The development of gas-fired boiler control system has also experienced the process from simple to complex and gradually to automatic control.

Gas fired boiler system is applied more and more in practice. In practical application, the operation and application of gas filter system not only has low investment and application cost, but also has the advantages of high automation, outstanding operation and application efficiency, energy saving and environmental protection. Therefore, gas boiler has great application value in practical application. In the process of gas-fired boiler operation, the main support for the combustion operation of the combustion control system of gas-fired boiler is the electric control circuit of gas-fired boiler, which is also an important part of the realization of gas-fired boiler operation control.

Operation control points of gas fired boiler

1. Optimal control of gas fired boiler

The amount of air (dry air) required for the complete combustion of 1m3 gas fuel under the air coefficient standard state according to the combustion reaction metering equation is called the theoretical air amount of gas fuel (m3 / m3), which can be expressed by V0 and can be calculated according to the composition of gas fuel. The actual air quantity V (m3 / m3, gas fuel) into the boiler is called the actual air quantity, which is expressed by V, and its value is generally greater than the theoretical air quantity. The part of air more than the theoretical air volume is called excess air. So the actual air quantity is the sum of theoretical air quantity and excess air quantity. The ratio of actual air volume to gas volume is called air / fuel ratio, which is equal to the actual air volume. The ratio of actual air volume to theoretical air volume is called excess air coefficient α I.e α= v/v0。 Excess air coefficient α It is a very important index that affects boiler combustion condition and operation economy. α When the temperature is too low, the incomplete combustion loss increases; α When it is too large, the heat loss of boiler exhaust gas increases. Therefore, controlling the optimal excess air coefficient is one of the most important means.

2. Water temperature control of gas boiler

In the combustion process of gas-fired boiler, the working condition will change from time to time. Therefore, according to the change of total heat required, appropriate adjustment of gas and air intake can make the boiler operate more economically and effectively. The company uses a low nitrogen burner with electronic proportional regulation. For the proportional regulation burner, the outlet water temperature control is a single loop PID control. According to the difference between the set value of outlet water temperature and the actual detection value of outlet water temperature, the fuel valve opening is adjusted, and the air distribution is automatically matched by the mechanical connecting rod. In order to achieve the best combustion effect, the oxygen content of flue gas can be introduced as the adjustment parameter index of blast volume.

In addition, the combustion control algorithm with manual guidance function, the user can set the time from ignition to full load. Therefore, under different temperature conditions, once the operator inputs the time requirement of start-up to full load, the combustion control software will control the load according to the actual outlet water temperature, and adopt full open combustion in case of large temperature difference; When approaching the full load state, the intelligent software adjusts the combustion damper according to the dynamic PID parameters to ensure the smooth arrival of the full load state and reduce the overshoot, so as to achieve the best control effect and fully meet the operation requirements from start-up to full load under different temperature states.

3. Gas fired boiler

The closed-loop control of oxygen content in flue gas during combustion process a control loop of oxygen content in flue gas is added to the combustion control of gas-fired boiler. This is a variable ratio control system of combustion flow and air flow, also known as the closed-loop control system of flue gas oxygen content. This control system can ensure the most economical combustion of boiler. In order to ensure the most economical combustion in the whole production process, the optimal ratio of fuel and air flow must be ensured. It can ensure the ratio of fuel and air, but it can not guarantee the complete combustion control of fuel. Firstly, the optimal ratio of two flows is different under different loads; Second, the composition of fuel (such as water content, methane, etc.) may change; Third, the flow measurement is not accurate. These factors will affect the incomplete combustion of fuel or excessive air in varying degrees, resulting in the decrease of thermal effect of boiler, which is the disadvantage of fixed ratio of combustion flow and air flow. In order to improve this situation, the simplest method is to have an index to close the ratio of two flows. At present, the most commonly used is the oxygen content in flue gas.

With the increasing application of gas-fired boiler in practice, the analysis of gas-fired boiler control principle and control points is not only conducive to guarantee the safe and reliable performance of gas-fired boiler system operation, but also conducive to improving the utilization time of gas-fired boiler, so as to reduce the investment cost of enterprises and promote the application of gas-fired boiler in practice.