Method for treating non-condensable gas of crude methanol pre-rectifying tower

Abstract

The invention discloses a crude methanol pre-rectifying tower non-condensable gas treatment method which comprises the following steps: step 1, fully opening a non-condensable gas emptying valve, and fully closing a non-condensable gas recovery valve; 2, after starting of the pre-rectifying tower is stable, when a pressure transmitter detects that the pre-rectifying tower reaches a pressure value set by a pressure controller, the pressure controller controls a pressure regulating valve to be opened; and 3, after the flame detector detects that the incinerator of the sulfur recovery device is ignited and the temperature is increased to 1000 DEG C, the interlocking controller sends a signal to fully close the non-condensable gas emptying valve and fully open the non-condensable gas recovery valve, and non-condensable gas is fed into a hearth of the incinerator to be incinerated. According to the method, the non-condensable gas of the crude methanol pre-rectifying tower is conveyed to the incinerator of the sulfur recovery device for treatment, the practicability is high, the equipment investment and the compressor operation cost are saved, the environmental pollution is reduced, the energy consumption is reduced, the production cost is saved, and the incinerator is provided with a flame-out protection device, so that the safety is high, the operation is simple, and the automation degree is high.

Description

Technical Field

[0001] The invention relates to the field of crude methanol pre-distillation, and in particular to a method for treating non-condensable gas in a crude methanol pre-distillation tower. Background Art

[0002] In the methanol production device, the crude methanol produced by the methanol synthesis process contains not only water, but also dozens of trace organic impurities such as aldehydes, ketones, ethers, acid esters, alkanes, amines and carbonyl iron. It must be distilled to obtain qualified refined methanol products. When distilling crude methanol, the dissolved gases such as H2, CO, CO2, N2, CH4 and low-boiling impurities such as dimethyl ether and methyl formate contained in the crude methanol must be removed in the pre-distillation tower, and then enter the pressurized distillation tower and the atmospheric distillation tower to remove water and high-boiling impurities to obtain qualified refined methanol products. The gas discharged after treatment in the pre-distillation tower containing H2, CO, CO2, N2, CH4, dimethyl ether, methyl formate, methanol and other substances is called "non-condensable gas" and has the following characteristics: 1) The pressure is relatively low, about 30kPa; 2) It contains toxic and harmful substances such as H2, CO, CH4, dimethyl ether, methyl formate and combustible substances; 3) It contains methanol products.

[0003] In the prior art, there are mainly the following methods for treating the non-condensable gas in the crude methanol pre-distillation tower: the first method is to discharge the non-condensable gas directly into the atmosphere or to the flare, which has the disadvantages of polluting the environment and not recycling methanol and combustibles; the second method is to first wash the non-condensable gas with water to recover methanol, and then pressurize the non-condensable gas to send it to the fuel gas network for use as fuel. Although methanol and combustibles are recycled in this method, it increases equipment investment and power consumption during operation; the third method is to wash the non-condensable gas with water to recover methanol, and then send the non-condensable gas to the coal-fired boiler to recover the combustibles in the non-condensable gas, and send the non-condensable gas after washing to the secondary air inlet of the coal-fired boiler. Since the inlet pressure of the secondary air inlet of the boiler is negative pressure, the non-condensable gas is easily added to the coal-fired boiler. This method does not require the installation of a special compressor to increase the pressure of the non-condensable gas, saving equipment investment and power consumption during operation. However, this method is only applicable to factories with coal-fired boilers and the coal-fired boilers are close to the methanol distillation device. If the coal-fired boiler is far away from the methanol distillation device, a compressor is also required to increase the pressure of the non-condensable gas before it can be sent to the coal-fired boiler for treatment, which results in increased equipment investment and increased power consumption during operation. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a method for treating non-condensable gas in a crude methanol pre-distillation tower. A pressure transmitter is provided at the top of the pre-distillation tower, the pressure transmitter is connected to a pressure controller by signal, the pressure controller is electrically connected to a pressure regulating valve, the non-condensable gas outlet pipe of the pre-distillation tower is connected to the pressure regulating valve, the outlet of the pressure regulating valve is connected to a non-condensable gas vent pipe and a non-condensable gas recovery pipe, the non-condensable gas vent pipe is vented at a high point, the non-condensable gas recovery pipe is connected to an H2S-containing acid gas inlet pipe of an incinerator of a sulfur recovery device, the non-condensable gas vent pipe is provided with a non-condensable gas vent valve, the non-condensable gas recovery pipe is provided with a non-condensable gas recovery valve and a check valve, a flame detector is provided on the incinerator of the sulfur recovery device, the flame detector is connected to an interlock controller by signal, the interlock controller is electrically connected to the non-condensable gas vent valve and the non-condensable gas recovery valve, and the non-condensable gas treatment method based on the above device comprises the following steps: Step 1, fully open the non-condensable gas vent valve and fully close the non-condensable gas recovery valve; Step 2: After the pre-distillation tower is started and stabilized, when the pressure transmitter detects that the pressure of the pre-distillation tower reaches the pressure value set by the pressure controller, the pressure controller controls the pressure regulating valve to open; Step 3: After the flame detector detects that the sulfur recovery device incinerator is ignited and the temperature rises to 1000°C, the interlock controller sends a signal to fully close the non-condensable gas vent valve and fully open the non-condensable gas recovery valve to send the non-condensable gas into the furnace of the incinerator for incineration.

[0005] Furthermore, the following steps are included: Step 4, if the flame detector detects that the sulfur recovery device incinerator is extinguished, the interlock controller sends a signal to fully open the non-condensable gas vent valve, fully close the non-condensable gas recovery valve, send the non-condensable gas to a high point for venting, and stop entering the incinerator.

[0006] Furthermore, the pressure value set by the pre-distillation tower pressure controller is 30 kPa.

[0007] The present invention sends the non-condensable gas of the crude methanol pre-distillation tower after the methanol is recovered through cooling and water washing to the incinerator of the sulfur recovery device in the coal-to-methanol device for treating the H2S acid gas in the low-temperature methanol washing process, and carries out high-temperature incineration treatment. The sulfur recovery device is an environmental protection device that must be built in conjunction with the coal-to-methanol device, and the non-condensable gas of the crude methanol pre-distillation tower is sent to the incinerator of the sulfur recovery device for treatment, which is highly practical; the pressure of the incinerator of the sulfur recovery device is 5-10kPa, and the non-condensable gas with a pressure of about 30kPa does not need to be equipped with a compressor It can be sent to the incinerator for treatment, saving equipment investment and compressor operating costs; VOCs components such as dimethyl ether, methyl formate, methanol, etc. contained in the non-condensable gas are incinerated at high temperature in the incinerator, reducing environmental pollution; combustible substances such as H2, CO, CH4, dimethyl ether, methyl formate and methanol contained in the non-condensable gas are recovered to the incinerator for use as fuel, reducing the fuel gas consumption of the incinerator, reducing energy consumption and saving production costs; the incinerator is equipped with a flameout protection device, which is highly safe, simple to operate and highly automated. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a flow chart of a method for treating non-condensable gas in a crude methanol pre-distillation tower; Figure 2 It is a flow chart of a method for treating non-condensable gas in a crude methanol pre-distillation tower provided with flameout protection; Figure 3 It is a structural schematic diagram of a non-condensable gas treatment device in a crude methanol pre-distillation tower.

[0009] Reference numerals: 1: Pre-distillation tower; 2: Primary water cooler; 3: Secondary water cooler; 4: Reflux tank; 5: Reflux pump; 6: Separator; 7: Water scrubber; 8: Dilute methanol pump; 9: Sulfur recovery unit incinerator; 10: Water scrubber non-condensable gas inlet pipe; 11: Water scrubber non-condensable gas outlet pipe; 12: Non-condensable gas vent pipe; 13: Non-condensable gas recovery pipe; 14: Pressure regulating valve; 15: Non-condensable gas vent valve; 16: Non-condensable gas recovery valve; 17: Check valve; 18: Pressure transmitter; 19: Pressure controller; 20: Flame detector; 21: Interlock controller; 22: Non-condensable gas activation / disconnection button. DETAILED DESCRIPTION

[0010] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0011] like Figure 1As shown, a method for treating non-condensable gas in a crude methanol pre-distillation tower is provided. A pressure transmitter is provided at the top of the pre-distillation tower. The pressure transmitter is connected to a pressure controller by signal. The pressure controller is electrically connected to a pressure regulating valve. The non-condensable gas outlet pipe of the pre-distillation tower is connected to the pressure regulating valve. The outlet of the pressure regulating valve is connected to a non-condensable gas vent pipe and a non-condensable gas recovery pipe. The non-condensable gas vent pipe is vented at a high point. The non-condensable gas recovery pipe is connected to an H2S-containing acid gas inlet pipe of an incinerator of a sulfur recovery device. The non-condensable gas vent pipe is provided with a non-condensable gas vent valve. The non-condensable gas recovery pipe is provided with a non-condensable gas recovery valve and a check valve. A flame detector is provided on the incinerator of the sulfur recovery device. The flame detector is connected to an interlock controller by signal. The interlock controller is electrically connected to the non-condensable gas vent valve and the non-condensable gas recovery valve. The method for treating non-condensable gas based on the above device comprises the following steps: Step 1, fully open the non-condensable gas vent valve and fully close the non-condensable gas recovery valve; Step 2: After the pre-distillation tower is started and stabilized, when the pressure transmitter detects that the pressure of the pre-distillation tower reaches the pressure value set by the pressure controller, the pressure controller controls the pressure regulating valve to open; Step 3: After the flame detector detects that the sulfur recovery device incinerator is ignited and the temperature rises to 1000°C, the interlock controller sends a signal to fully close the non-condensable gas vent valve and fully open the non-condensable gas recovery valve to send the non-condensable gas into the furnace of the incinerator for incineration.

[0012] like Figure 2 As shown, the following steps are also included: Step 4, if the flame detector detects that the sulfur recovery device incinerator is out of flame, the interlock controller sends a signal to fully open the non-condensable gas vent valve, fully close the non-condensable gas recovery valve, send the non-condensable gas to a high point for venting, and stop entering the incinerator.

[0013] The pressure value set on the pre-distillation tower pressure controller is 30 kPa.

[0014] In a specific embodiment, if Figure 3The figure shows a crude methanol pre-distillation tower non-condensable gas treatment device, which is composed of a pre-distillation tower 1, a primary water cooler 2, a secondary water cooler 3, a reflux tank 4, a reflux pump 5, a separator 6, a water scrubber 7, a dilute methanol pump 8 and a sulfur recovery device incinerator 9; the top air outlet of the pre-distillation tower 1 is connected to the top air inlet of the primary water cooler 2, the top air outlet of the primary water cooler 2 is connected to the top air inlet of the secondary water cooler 3, and the bottom liquid outlet of the primary water cooler 2 is connected to the top of the reflux tank 4; the top air outlet of the secondary water cooler 3 is connected to the middle air inlet of the separator 6, and the bottom liquid outlet of the secondary water cooler 3 is connected to the top of the reflux tank 4; the bottom liquid outlet of the separator 6 is connected to the top of the reflux tank 4, and the top air outlet of the separator 6 is connected to the top of the reflux tank 4 through the bottom of the water scrubber. The non-condensable gas inlet pipe 10 is connected to the water washing tower 7; the bottom liquid outlet of the reflux tank 4 is connected to the top of the pre-distillation tower 1 through the reflux pump 5; the top of the water washing tower 7 is connected to the pressure regulating valve 14 through the water washing tower non-condensable gas outlet pipe 11, the top of the water washing tower 7 is connected to the desalted water pipe, and the bottom liquid outlet of the water washing tower 7 is connected to the crude methanol feed pipe of the pre-distillation tower 1 through the dilute methanol pump 8; the outlet of the pressure regulating valve 14 is connected to the non-condensable gas vent pipe 12 and the non-condensable gas recovery pipe 13, the non-condensable gas vent pipe 12 is vented to a high point, the non-condensable gas recovery pipe 13 is connected to the H2S-containing acid gas inlet pipe of the sulfur recovery device incinerator 9, the non-condensable gas vent pipe 12 is provided with a non-condensable gas vent valve 15, and the non-condensable gas recovery pipe 13 is provided with a non-condensable gas recovery valve 16 and a check valve 17.

[0015] A pressure transmitter 18 is provided at the top of the pre-distillation tower 1. The pressure transmitter 18 is signal-connected to a pressure controller 19. The pressure controller 19 is electrically connected to a pressure regulating valve 14. The pressure controller is used to control the pressure of the pre-distillation tower. The pressure controller detects the pressure through the pressure transmitter and opens the pressure regulating valve when the preset value is reached.

[0016] The non-condensable gas vent valve 15 and the non-condensable gas recovery valve 16 are both remote switch valves with solenoid valves, which are used to realize the rapid switching of the non-condensable gas vent valve and the non-condensable gas recovery valve.

[0017] The sulfur recovery unit incinerator 9 is equipped with a fuel gas pipe and an air pipe to provide fuel gas and oxygen for incinerating the non-condensable gas discharged from the pre-distillation tower 1 and the H2S-containing acid gas from the low-temperature methanol washing process.

[0018] The sulfur recovery device incinerator 9 is provided with a flame detector 20 , which is signal-connected to an interlocking controller 21 , and the interlocking controller 21 is electrically connected to the non-condensable gas vent valve 15 and the non-condensable gas recovery valve 16 .

[0019] The non-condensable gas treatment method comprises the following steps: Step 1, fully open the non-condensable gas vent valve 15 and fully close the non-condensable gas recovery valve 16; Step 2: After the pre-distillation tower is started and stabilized, when the pressure transmitter detects that the pre-distillation tower reaches the pressure value set by the pressure controller, the pressure controller controls the pressure regulating valve to open; the pre-distillation tower pressure controller 19 is set to "AUTO" (automatic), and the given value SP is input to 30kPa, and the pre-distillation tower pressure is automatically controlled by the DCS; Step 3: After the flame detector detects that the sulfur recovery device incinerator 9 is ignited and the temperature rises to 1000°C, it is confirmed that the flame detector 20 displays "fire", the interlock controller 21 is reset, and the "use non-condensable gas" soft button is clicked. The DCS sends a signal to fully close the non-condensable gas vent valve 15 and fully open the non-condensable gas recovery valve 16, and the non-condensable gas is sent into the furnace of the incinerator 9 for incineration treatment; Step 4, if the flame detector detects that the sulfur recovery device incinerator 9 is out of flame, the flame detector 20 displays "out of flame", the interlock controller 21 acts to "cut off non-condensable gas", and the DCS sends a signal to fully open the non-condensable gas vent valve 15 and fully close the non-condensable gas recovery valve 16, and the non-condensable gas is sent to a high point for venting, and stops entering the incinerator 9.

[0020] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

Claims

1. A method for treating non-condensable gas in a crude methanol pre-distillation tower, characterized in that: A pressure transmitter is provided at the top of the pre-distillation tower, the pressure transmitter is connected to the pressure controller signal, the pressure controller is electrically connected to the pressure regulating valve, the non-condensable gas outlet pipe of the pre-distillation tower is connected to the pressure regulating valve, the pressure regulating valve outlet is connected to the non-condensable gas vent pipe and the non-condensable gas recovery pipe, the non-condensable gas vent pipe is vented to a high point, the non-condensable gas recovery pipe is connected to the H2S acid gas inlet pipe of the sulfur recovery device incinerator, the non-condensable gas vent pipe is provided with a non-condensable gas vent valve, the non-condensable gas recovery pipe is provided with a non-condensable gas recovery valve and a check valve, a flame detector is provided on the sulfur recovery device incinerator, the flame detector is connected to the interlock controller signal, the interlock controller is electrically connected to the non-condensable gas vent valve and the non-condensable gas recovery valve, and the non-condensable gas treatment method based on the above device includes the following steps: Step 1, fully open the non-condensable gas vent valve and fully close the non-condensable gas recovery valve; Step 2: After the pre-distillation tower is started and stabilized, when the pressure transmitter detects that the pressure of the pre-distillation tower reaches the pressure value set by the pressure controller, the pressure controller controls the pressure regulating valve to open; Step 3: After the flame detector detects that the sulfur recovery device incinerator is ignited and the temperature rises to 1000°C, the interlock controller sends a signal to fully close the non-condensable gas vent valve and fully open the non-condensable gas recovery valve to send the non-condensable gas into the furnace of the incinerator for incineration.

2. The method for treating non-condensable gas in a crude methanol pre-distillation tower according to claim 1, characterized in that: The following steps are also included: Step 4: If the flame detector detects that the sulfur recovery unit incinerator is flameout, the interlock controller sends a signal to fully open the non-condensable gas vent valve, fully close the non-condensable gas recovery valve, send the non-condensable gas to a high point for venting, and stop entering the incinerator.

3. The method for treating non-condensable gas in a crude methanol pre-distillation tower according to claim 1, characterized in that: The pressure value set by the pre-distillation tower pressure controller is 30 kPa.

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