Overview of temperature and pressure reducing device

1. Purpose of temperature and pressure reducing device

The desuperheating and pressure reducing device is an important device used to regulate the steam pressure and temperature. In the thermal power plant, the boiler generates superheated steam. If the boiler is not equipped with desuperheater, the steam temperature at the outlet of the boiler cannot be controlled within the required range, which will cause damage or major accidents to the boiler turbine and other equipment due to over temperature. At the same time, in the production process of chemical industry, light industry, medicine, food processing and so on, superheated steam as the generation of mechanical energy provides excellent energy. In many cases, saturated steam is more suitable for use. Due to the reasons of process and equipment, the control of pressure and temperature is also essential. Proper power steam can be obtained through temperature and pressure reduction device. For example, when the heat exchanger is used for process operation, the use of superheated steam reduces efficiency due to low heat transfer coefficient, and the use of saturated steam is more suitable. In addition, when the high-pressure dry saturated steam is reduced to low pressure, superheat will be generated at the downstream outlet. In this way, the superheated steam needs to be cooled to the required temperature close to saturation, which requires a desuperheater. In many cases, it is necessary to reduce the temperature and pressure of superheated steam at the same time. Desuperheating and reducing pressure device is an efficient energy-saving and environmental protection product. The temperature and pressure reduction device is equipped with corresponding industrial automation instruments (i.e. thermal control cabinet), which can reduce the primary (New) steam pressure P1 and temperature T1 transmitted from the power station or industrial boiler and thermal power plant, so as to make the secondary steam pressure P2 and temperature T2 meet the requirements of production process. Widely used in thermal power plant, central heating, food industry, petrochemical industry, textile industry, rubber industry, paper and pulp industry, tobacco industry, pharmaceutical industry and many other industries. In order to meet the process requirements of different equipment, our company provides different types of temperature and pressure reducers (temperature and pressure reducers), and realizes a full set of intelligent automatic control or DCS system networking.

According to the primary (New) steam pressure P1 and temperature T1, the temperature and pressure reducing device can be divided into high temperature and high pressure temperature and pressure reducing device, sub high pressure temperature and pressure reducing device, medium temperature and medium pressure temperature and pressure reducing device; the temperature and pressure reducing device can be divided into temperature reducing device, pressure reducing device and temperature and pressure reducing device according to the use.

The temperature and pressure reducing device is generally selected according to the parameters and consumption of primary steam (new steam) and secondary steam (steam after temperature and pressure reduction). Two sets of temperature and pressure reducing devices are generally set for regular operation, one of which is for standby; the temperature and pressure reducing device that is not frequently operated generally does not consider standby; the standby temperature and pressure reducing device shall be in hot standby state. During the design and calculation, the primary steam and desuperheating water quantity entering the desuperheating and pressure reducing device shall be determined according to the amount of secondary steam. The pressure and temperature of desuperheating water shall meet the requirements of water spray and atomization, and the water quality shall not be lower than the steam quality.

2. Model preparation
The model of the device is shown as follows:
Method 1:
 

Note 1: for the desuperheating device and pressure reducing device, the code is w or Y respectively.
Note 2: the pressure value related to the model shall be one decimal place.
For example: wy80-3.82/450-0.98/260-8.0/104 means the outlet steam flow is 80t / h; the inlet steam pressure is 3.82MPa, the temperature is 450 ℃; the outlet steam pressure is 0.98mpa, the temperature is 260 ℃; the temperature feed water pressure is 8.0MPa, and the feed water temperature is 104 ℃.

3. Executive standard
Standard of temperature and pressure reducing device: Nb / t47033-2013 temperature and pressure reducing device
Valve standard of power station: Nb / t47044-2014 valve of power station
Standard of temperature and pressure reducing valve: GB / 10868-2005 temperature and pressure reducing valve for power plant
Water supply regulating valve standard: power station regulating valve (GB / 10869-2008)
4. Classification method
A. classification by structure
1) integrated temperature and pressure reducing device; (WY type)
2) split type temperature and pressure reducing device; (y-w type)
3) desuperheating device (W type);
4) pressure reducing device (Y type);
B. classification according to steam parameters:
1) medium temperature and medium pressure desuperheating and reducing device; (P1 ≤ 3.82 MPa, temperature T1 ≤ 425 ℃);
2) sub high pressure temperature and pressure reducing device (P1 ≤ 5.4 MPa, temperature T1 ≤ 485 ℃);
3) high temperature and high pressure desuperheating and reducing device; (P1 ≤ 10 MPa, temperature T1 ≤ 540 ℃);

5. Main performance indexes
1) inlet steam pressure P1 and temperature T1
Medium temperature and medium pressure: P1 ≤ 3.82 MPa, temperature T1 ≤ 425 ℃.
Sub high temperature and high pressure: P1 ≤ 5.4 MPa, temperature T1 ≤ 485 ℃.
High temperature and high pressure: P1 ≤ 10 MPa, temperature T1 ≤ 540 ℃.
2) outlet steam flow Q
The outlet flow Q of the temperature and pressure reducing device varies from 10% Q to 120% Q, in which the regulation is ideal.
If there are special requirements, they can be negotiated with our company.
3) outlet steam pressure P2
The regulating accuracy of outlet steam pressure P2 shall not be lower than level 2.5. The error is not more than ± 0.04 MPa;
4) outlet steam temperature T2
The regulating accuracy of outlet steam temperature T2 shall not be lower than level 2.5. + 5 C;
5), noise
During normal operation of the device, the noise shall be measured one meter downstream of the temperature and pressure reducing valve and one meter away from the pipe wall, and the noise level shall not be greater than 85 dB.
6. Ordering instructions
Please provide:
1) outlet steam flow Q, inlet steam pressure P1, temperature T1, outlet steam pressure P2 and temperature T2;
2) pressure Pb and temperature TB of desuperheating water supply;
3) indicate the control mode; (instrument panel control, DCS control, DCS monitoring)
4) control category: electric, pneumatic and hydraulic;
When selecting pneumatic valve, it must also provide:
1) action form: air open or air closed; positive or negative action;
2) air source pressure;
3) description of other attachments: if the user has special requirements, it shall be noted after negotiation or a separate technical agreement shall be signed.
Note: 1 the outlet steam pressure P2 shall not be lower than the pressure value corresponding to the saturation temperature, or the outlet steam temperature T2 shall not be lower than the saturation temperature value corresponding to P2;
2 pairs of integrated structure of temperature and pressure reduction: the pressure Pb of desuperheating water supply is ≥ 0.6p1 + 0.8MPa; if the Pb value is too low, it will not be injected into the temperature and pressure reducing valve for temperature reduction.
(3) for the temperature and pressure reducing split structure: the pressure Pb of the temperature reducing water supply is ≥ P2 + 0.6MPa;
Attached table: basic order requirements

Note: unfilled pressure is gauge pressure

The scope of supply of temperature and pressure reducing device is within the mark, mainly including:
1. Pressure reducing system: temperature and pressure reducing valve or pressure reducing valve, throttle orifice, etc;
2. Desuperheating system: feed water regulating valve or adjustable nozzle, stop valve, throttle valve, etc.
3. Safety system: safety valve, check valve, etc;
4. Pipeline system: steam pipe, mixing pipe, transition pipe, desuperheating pipe, etc;
5. Supporting accessories: stop valve, bimetal thermometer and connecting pipe, pressure gauge and three-way valve, bend, joint, flange, gasket, bolt, nut, washer, etc.

The temperature and pressure reducing device produced by our company adopts unique pressure regulation and spray atomization device with adjustable ratio up to 1:25