Application of Siemens PLC in waste incineration p

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Application of Siemens PLC in waste incineration power plant

this paper introduces the characteristics and treatment methods of waste treatment, and introduces in detail the characteristics of the control system of waste incineration power plant and the configuration, logic control and PID control loop of the corresponding control system

1 introduction

waste incineration technology, such as urban domestic waste, industrial waste, hospital sanitary waste, sludge and waste rubber tires, will be an important development direction of environmental protection technology in the future by using the waste heat of waste incineration to generate electricity and turn waste into treasure. The daily waste treatment capacity of this kind of waste incineration is 1 ~ 350t, the heat capacity of waste heat boiler is small, and the generator set is small, generally less than 20 MW. Therefore, the control system of waste incineration power plants is much simpler than that of large power plants. Generally speaking, the host control system of large power plants cannot be controlled by PLC, and only some auxiliary systems can use PLC. However, with the rapid development of fieldbus technology and microprocessor performance, high-end PLC distributed control system has been successfully applied in medium-sized and more complex control fields. For example, high-end PLC control system can be used in waste incineration power plants, which can greatly reduce the cost of control system

this paper will introduce the PLC control system of Nanhai waste incineration power plant in Guangdong Province. This control system was successfully developed by Zhuhai Guangdong Yafan Technology Co., Ltd. and successfully put into production at one time

2 introduction to the overall scheme of the control system

the distributed control system adopts Siemens s series PLC. Siemens s series PLC is a large model in the S7 Series launched in the 1990s. It has perfect functions and powerful communication ability. In particular, PROFIBUS, one of the international bus standards, is supported by many manufacturers, which is very conducive to the use of the distributed control system. The communication rate of PROFIBUS DP bus can reach 12mbps. The Profibus DP bus composed of SH dual computer hot standby system and et200m distributed i/o constitutes a switching structure to realize undisturbed automatic switching in case of failure, which can be used in control systems with high safety performance requirements. However, the cost of SH dual computer hot standby system is relatively expensive. In order to reduce hardware investment, software dual redundancy (dual computer hot standby with 416cpu), PROFIBUS DP field control bus with distributed i/o, osm/esm ring 100MB Industrial Ethernet optical communication between upper computer and PLC, and InTouch 7.1 configuration software for system configuration can be used for upper computer. The waste incineration process of the plant introduces the patented technology of American basic company and adopts four-stage pulse grate. All indicators meet the international environmental protection requirements. The daily incineration treatment of waste in phase I is 200t. This technology has practical application value in China

(1) working principle

garbage is sent to the drying bed of the incinerator for drying through the automatic feeding unit, and then sent to the grate. The grate is driven by the pulse aerodynamic device to throw the garbage. The garbage is mixed with the combustion supporting air ejected from the uniform pores on the grate, and the heat generated by combustion is recovered by the waste heat boiler. The high-temperature and high-pressure steam generated by the waste heat boiler drives the steam turbine to generate electricity. After burning out, it enters the ash pit and is discharged by the automatic slag removal device. The flue gas volatilized and cracked from the main combustion chamber enters the second and third stage combustion chambers for further combustion, so that the temperature of the flue gas is as high as 1000 ℃, and the flue gas stays here for no less than 2S, so that the toxic flue gas is rapidly decomposed, and then discharged into the atmosphere after being treated by the flue gas treatment equipment and dust removal equipment (electric dust removal, bag dust removal)

(2) main equipment of environmental protection power plant

① two incinerator boilers, and the main technical parameters of each are as follows:

garbage disposal capacity: 8.33t/h

steam generation capacity: 22.5t/h

superheated steam pressure: 4.0Mpa

superheated steam temperature: 400 ℃

furnace temperature: 980 ℃

feedwater temperature: 145 ℃

② a set of steam turbine generator unit, The main technical parameters are as follows:

main steam pressure: 3.9Mpa

main steam temperature: 390 ℃

③ the main technical parameters of the generator are as follows:

Power: 12000kW

outlet voltage: 10.5kv

frequency: 50Hz

rated speed: 3000r/min

power factor: 0.8

excitation mode: brushless excitation system

④ two sets of flue gas treatment system

the PLC distributed control system There are more than 3000 i/o points, including more than 300 analog quantities. The PLC distributed control system diagram of the whole plant is shown in the attached figure

attached figure PLC distributed control system diagram of the whole plant

3 upper computer monitoring system configuration

the system is equipped with 4 operator stations and 1 engineer station. Two operator stations are used for monitoring the equipment at the furnace side, including incinerator and boiler systems, flue gas desulfurization system and ash removal system; The other two operator stations are used for the monitoring of equipment at the turbine side, including steam turbine system, water supply system, wastewater treatment system, electrical and other parts. The two operator stations on the furnace side and the two operator stations on the machine side are both dual machine hot standby. The operator stations at the boiler side and the machine side have independent functions and cannot be interchanged. The engineer workstation is used for system software development configuration and alarm sequence event recording, and the engineer station will be able to complete relevant control and monitoring functions as any operator station. The engineer station, operator station and PLC are interconnected by osm/esm ring 100MB Industrial Ethernet light. The operating system adopts Chinese Windows NT window operating system

the upper computer adopts InTouch 7.1 configuration software for system configuration. The main design of man-machine interface includes the following contents:

(1) system process flow display: according to the system process flow chart provided by the Design Institute, it is divided according to the functional group area

(2) sequence control system operation guidance display: there is sequence control step display, that is, sequence control program step status display, as well as operation tips

(3) regulation system, regulation screen: loop manual operation station, centralized display of regulation parameters and parameter trend

(4) trend display of important parameters: there are two kinds of display: real-time trend and historical trend

(5) bar graph display of parameters such as turbine status

(6) global alarm display: the system is divided into several alarm groups according to functions. The alarm windows of each alarm group are distributed above the corresponding function display windows. The global alarm display provides the ability to view all the alarms of the system in a centralized way, or filter and view by priority and alarm group, and has global alarm confirmation

(7) report management: provide the function of monthly report printing. The printing methods include: regular printing, event driven printing, operator call printing, and provide the function of historical report data viewing

(8) PLC system status display: provide error detection and maintenance functions of system hardware network

(9) multi level map menu display

(10) definition of system security level

in order to ensure the safe operation of the system, three levels of permissions are designed: engineer level, senior operator level and operator level. The operator level user can operate the system normally. In addition to the operator level functions, the senior operator level user also has the functions of modifying adjustment parameters, modifying time, viewing historical reports, calling and printing. The engineer level has the highest permissions, It has all functions of senior operator level, and can also enter the development environment for configuration modification

4 PLC control system configuration

the whole system is divided into 1 × 2 × PLC master station. 1 # PLC master station controls 1 # and 2 # boiler incinerators respectively; 2. The PLC master station controls the steam turbine system, water supply system, wastewater treatment system, electrical and other parts respectively. Each PLC master station is composed of two cpudp (Order No.: 6es74162xl010ab0) dual computer hot standby, which realizes the undisturbed switching of the control system through real-time redundant software to ensure the safe and stable operation of the system. The two CPUs monitor each other and backup data through MPI interface, and each CPU communicates with the upper computer through CP Industrial Ethernet communication module. Siemens' 416cpu forms a dual computer hot standby, which can only be realized by software, so it is called soft redundancy. In principle, cpu315 or more CPUs can form soft redundancy. Users must write their own redundancy management program, put the data that need redundancy in a specific DB, and the main CPU will image the data in these specific DB to the slave CPU in each scanning cycle. Soft redundancy and hard redundancy have the advantage that developers can customize the redundant database, which can greatly shorten the image time of redundant data in each scanning cycle

The input/output of the

system signal is completed by the relevant et200m distributed i/o module, and the "proximity principle" is adopted to minimize the hard wiring on site. Each et200m has two IM communication modules, which are respectively hung on the DP bus to form a redundant DP bus. Et200m adopts Siemens 300 series distributed i/o module, which is cheap. Each et200m can be extended with 8 i/o modules, with a capacity of up to 128 word input/128 word output, and the maximum transmission rate is 12mbps

this control system is composed of Siemens 400 Series CPU for dual computer hot standby and data redundancy, and 300 series distributed i/o for dual redundant DP bus. It is a highly cost-effective distributed control system, which has great promotion value in the field of host control of various environmental protection power plants and auxiliary control of large generator sets in the future

cpu416 has extraordinary performance, and its binary instruction execution time is 0.08 μ S (cpu417h is 0.12 μ s) , the maximum digital IO or analog IO is as high as 65536 or 4096 points. The distributed control system has more than 8000 logic control statements and 30 PID control loops, including 2 loops with differential feedforward control, 10 loops with conditional switching output, 2 three impulse regulation loops and 26 single impulse regulation loops. The system requires high real-time reliability

in this distributed control system, PLC completes the logical sequence control of the whole plant and all PID loop control. Among them, the logic sequence control is divided into the following parts:

(1) level purging: its purpose is to ensure that the two main light bars are trapezoidal arranged to ensure that the relevant equipment of the air and smoke system of the level combustion chamber is normal and the channel is unblocked, which is one of the important operations required by the furnace protection; (2) Fan start; (3) Incinerator boiler purging: its purpose is to ensure that the relevant equipment of the whole incinerator boiler air and flue gas system is normal and the channel is unblocked, which is one of the important operations required by furnace protection; (4) Second stage preheating: its purpose is to increase the second stage temperature to reach the set value, which is the prerequisite for the first stage preheating and the first combustion chamber burner input; (5) First stage preheating: the purpose is to increase the first stage temperature to reach the set value; (6) Sequential shutdown; (7) Sequential ignition/shutdown of burner; (8) Automatic circulation of feeding system; (9) Automatic circulation of slag removal system; (10) Slag pit water level interlock control; (11) Sequence control of soot blowing system; (12) Boiler protection; (13) Main fuel trip; (14) Feed oil trip; (15) Normal power generation mode; (16) Isolated operation mode; (17) Turbine failure mode; (18) Chemical water treatment control; (19) Sewage treatment control

5 main PID control circuit

(1) furnace pressure regulation system

this system is a single impulse regulation circuit. According to the system process, the furnace should maintain a certain negative pressure value (pt101), so it is necessary to PI adjust the induced draft fan (pv101). In order to prevent the induced draft fan frequency converter from running too large or too small, resulting in boiler flameout, high and low limit modules are introduced into the regulation system

(2) drying grate temperature regulation system

this system is a single impulse regulation circuit. According to the system process, the garbage entering the 1 # grate of the first combustion chamber of the incinerator contains certain moisture, which directly affects the furnace temperature and increases the burden of the 1 #-2 # burner. Therefore, the mixed flue gas is introduced from the third combustion chamber for drying. Due to three

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