01 Introduction

A 4500t/d clinker cement production line of a company is equipped with a 9MW waste heat power station. The air ejector in the vacuum system of the steam turbine generator set is a water ejector, which mainly consists of 37kW water pump, 10.5kg/h air ejector and 12m³ water injection tank.

The role of water ejector is mainly two points: one is in the process of unit start and stop, the air in the condenser is pumped out, to establish a start-up vacuum; The other is that in the operation of the unit, the air leaking into the condenser and other non-condensing gases are continuously pumped out to maintain the vacuum in the condenser. During operation, the heat released by the mixture of gas, steam and water extracted by the ejector will heat the water of the ejector tank. In order not to affect the operation of the ejector, the water temperature of the ejector tank must be controlled below 38℃, which requires continuous cooling of industrial water, and the excess water is discharged from the overflow port of the ejector tank. The average daily water consumption is 270 ~ 300t, monthly water consumption is 8100 ~ 9000t, and annual water consumption is about 100000t.

02 Structure composition and principle of oil ring vacuum device

The oil-ring vacuum device is mainly composed of pre-heat exchanger, oil-ring vacuum pump, gas-liquid separator, working liquid cooling heat exchanger, oil-water separator and connecting pipes, valves and other components.

Working principle: the mixed gas such as uncondensed gas and water vapor in the condenser enters the pre-heat exchanger through the exhaust pipe. Most of the water vapor is cooled into condensate and then returns to the hot well of the condenser. The uncondensed gas and water vapor are sucked into the oil-ring vacuum pump and separated in the gas-liquid separator. The separated non-condensing gas is discharged into the atmosphere from the exhaust port, and the rest is fed into the working liquid cooling heat exchanger after the oil-water separator; After cooling and heat transfer, the working liquid enters the inlet of the oil-ring vacuum pump for circulation.

03 Economic Benefits

Zero supplementary water can be achieved in the operation of oil-ring vacuum device, and the operating power of the motor is reduced by about 26kW, and the effect of electricity saving and water saving is remarkable (see Table 1).

Table 1 Operating condition of oil ring vacuum device

items	The original water ejector	Oil ring vacuum device	Note
Operating vacuum	-0.090	-0.090	Remain unchanged
Operating power	37	11	/
Running current	54	14	Measured value
Annual consumption of electricity	216087	56022	Annual running 7 600h calculation
Annual electricity saving	160065		Annual running 7 600h calculation
Annual electricity saving	8.0		Calculated at 0.50 kWh
Annual water saving	100000		Straight line calculation
Annual saving of water charges	10		Calculated by 1 yuan /ton
Subtotal	18		Annual running 7 600h calculation

04 Operation and maintenance of oil ring vacuum device

4.1 Normal operation steps of oil ring vacuum device

(1) Confirm that the high vacuum cut-off valve of the original jet system pipe is closed.

(2) Confirm that the drain valve of the oil ring vacuum device is closed.

(3) All drainage valves of the separator are closed, the cooling water inlet valve of the working liquid cooling heat exchanger is opened, and the outlet valve is closed.

(4) The oil inlet valve of the vacuum pump is opened, the manual ball valve of the outlet is opened, and the oil discharge valve of the vacuum pump is closed.

(5) The manual valve at the inlet of the pre-cooler is opened, and the cooling water inlet and outlet valve is opened.

(6) Confirm the oil level at the normal oil level.

(7) The power station system is equipped with the condition of shock and start engine.

(8) Open the inlet and return water valve, air inlet valve and condensation backwater valve of the precooler; The central control closes the main valve of the condenser exhaust bus.

(9) Open the inlet and return water valve of the working liquid cooling heat exchanger of the vacuum system.

(10) Open the power supply control switch of the oil ring vacuum device body and confirm that the local \ remote control switch of the control panel is in the remote position; Confirm the vacuum pump inlet valve is open; Drainage valve closed, central control start machine.

(11) Put into the seal at the right time, and open the drainage valve after the vacuum degree reaches the working vacuum degree to check the operation of the system. When the outlet oil temperature of the vacuum pump reaches 54℃, the cooling water outlet valve of the working liquid cooling heat exchanger is fine-tuned to control the outlet oil temperature of the vacuum pump to operate stably between 50 ℃ and 60℃.

4.2 Operation steps for switching the oil-ring vacuum device to the original water ejector

(1) Start the original water ejector.

(2) Open the high vacuum cut-off valve of the main channel.

(3) Stop the vacuum pump after the steam engine vacuum degree is stable.

4.3 Operation steps of switching the original ejector to GS high efficiency vacuum system

(1) Start the vacuum pump.

(2) When the outlet electric valve of the vacuum pump is fully opened and the vacuum degree is stable, close the high vacuum cut-off valve.

(3) Stop the original water ejector.

4.4 Routine maintenance of oil ring vacuum device

(1) Due to the change of vacuum degree and exhaust temperature in summer and winter, it is necessary to adjust the circulating water outlet valve of plate heat exchanger in time to ensure that the outlet oil temperature is at the best working temperature (52 ~ 54℃).

(2) Make regular inspection to check whether there is blockage in the working liquid cooling heat exchanger, and judge by checking the inlet and return water pipe temperature of cooling circulating water or the oil temperature at the outlet of vacuum pump.

(3) If the cooling circulating water valve at the inlet and outlet of the plate heat exchanger is fully open, the temperature is still high, then close the valve before and after, clean up the Y-type filter.

(4) Timely observe whether there is oil emulsification phenomenon in the observation window of the oil-water separator at the bottom of the equipment.

(5) In the case of long-term shutdown (> for 2 months), the oil inlet valve of the vacuum pump should be closed, the vacuum pump body drain valve should be opened, and the residual liquid should be discharged. The working liquid in the separator can be stored for a long time (if the oil is not seriously deteriorated).

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