Ammonia gas condensing and cooling method for ammonia still

Abstract

The invention discloses a method for condensing and cooling ammonia gas of an ammonia still, which comprises the following steps of: 1, replacing an existing tubular ammonia dephlegmator with a double-helix plate heat exchanger, and enabling the temperature of the ammonia gas passing through the ammonia dephlegmator to reach 92 DEG C or below; 2, replacing a shell and tube ammonia condensation cooler with a double-helix plate heat exchanger, and enabling the temperature of ammonia gas passing through the ammonia condensation cooler to reach 40 DEG C or below; step 3, installing a service valve behind the two ammonia dephlegmators, communicating a pipeline behind the valve to enter two ammonia condensation coolers which are connected in parallel, and enabling the ammonia condensation coolers to be standby for each other; and step 4, changing a strong ammonia water pipeline entering the desulfurizing tower from a phi 50 316L stainless steel pipe to a phi 65 TA2 pipeline, and ensuring a gradient of 1%, so that condensed strong ammonia water and non-condensable gas can smoothly enter the desulfurizing tower. The invention relates to the field of ammonia still ammonia gas treatment, in particular to an ammonia still ammonia gas condensing and cooling method.

Description

Technical Field

[0001] The invention relates to the field of ammonia treatment in an ammonia still, and in particular to a method for condensing and cooling ammonia in an ammonia still. Background Art

[0002] Each ammonia evaporation tower is equipped with an ammonia expander and an ammonia condenser cooler. Since the ammonia expander and the ammonia condenser cooler are both shell-and-tube heat exchangers, their heat exchange effect is poor, resulting in the concentrated ammonia vapor coming out of the top of the ammonia evaporation tower being almost not cooled, and entering the desulfurization pre-cooling tower from the non-condensable gas pipeline in a gas-liquid mixed state.

[0003] Under the above working conditions, the valves and pipelines after the ammonia splitter and the precooling tower are seriously corroded, posing a major safety and environmental hazard; and the ammonia gas is not completely liquefied before entering the desulfurization tower, resulting in only about 4.0g / L of volatile ammonia in the desulfurization liquid, which in turn affects the long-term stable operation of the desulfurization system. After the gas-liquid mixed evaporation enters the precooling tower and is absorbed by the spraying liquid, harmful substances such as NH3-N and cyanide return to the circulating ammonia system and continue to accumulate.

[0004] This process leads to severe corrosion of ammonia vapor transport equipment, enrichment of harmful substances in the ammonia water system, severe corrosion of ammonia water tanks, and increased ammonia vapor consumption, which in turn affects the operation of biological dephenolization. Summary of the invention

[0005] The technical problem to be solved by the present invention is that the ammonia vapor conveying equipment is seriously corroded, harmful substances in the ammonia water system are enriched, the ammonia water tank is seriously corroded, and the ammonia vapor consumption is increased, thereby affecting the operation of biological dephenolization.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows: The present invention is a method for condensing and cooling ammonia gas in an ammonia distillation tower, comprising the following steps: Step 1: Replace the existing shell-and-tube ammonia decompressor with a double-spiral plate heat exchanger to make the ammonia temperature after the ammonia decompressor reach below 92°C; Step 2: Replace the shell-and-tube ammonia condenser cooler with a double spiral plate heat exchanger to make the ammonia temperature after the ammonia condenser cooler reach below 40°C; Step 3: Install a maintenance valve after the two ammonia splitters, and then connect the pipeline after the valve to the two parallel ammonia condenser coolers, so that the ammonia condenser coolers can serve as backup for each other; Step 4: Change the concentrated ammonia water pipeline entering the desulfurization tower from a Φ50 316L stainless steel pipe to a Φ65 TA2 pipeline, and ensure a 1% slope so that the condensed concentrated ammonia water and non-condensable gas can smoothly enter the desulfurization tower; Step five: make an ammonia water distribution box made of TA1 material on the concentrated ammonia water pipeline before entering the desulfurization tower, so that the amount of concentrated ammonia water entering the desulfurization tower A and the desulfurization tower B can reach a flow ratio of 2:1, and install another spare concentrated ammonia water pipeline to enter the pre-cooling tower.

[0007] Furthermore, the step 1 needs to be performed in a standby state.

[0008] Furthermore, the step 2 needs to be performed under the condition of stopping production for maintenance.

[0009] Furthermore, the steps 3 and 4 need to be performed under maintenance.

[0010] Furthermore, the step five needs to be performed under the condition of stopping production for maintenance.

[0011] The beneficial effects achieved by the present invention using the above structure are as follows: 1. It can solve the most difficult to cure concentrated ammonia corrosion problem in the chemical product recovery system, and ensure the long-term safe operation of the desulfurization precooling tower, ammonia equipment and pipelines.

[0012] 2. The residual ammonia concentration can be reduced to 3500 mg / L, the steam consumption of the ammonia evaporation tower can be reduced by 1 t / h, and the direct economic benefit can reach 876,000 yuan / year.

[0013] 3. The volatile ammonia content in the desulfurization liquid can reach 8.0g / L, ensuring the long-term stable operation of the desulfurization system. DETAILED DESCRIPTION

[0014] The invention discloses a method for condensing and cooling ammonia gas in an ammonia distillation tower. Example

[0015] Step 1: First, in a standby state, replace the existing shell-and-tube ammonia decompressor with a double spiral plate heat exchanger to make the ammonia temperature after the ammonia decompressor reach 92°C; Step 2: When the production is stopped for maintenance, the existing shell-and-tube ammonia condenser cooler is replaced with a double spiral plate heat exchanger to make the ammonia temperature after the ammonia condenser cooler reach 40°C; Step 3: During the maintenance, install a maintenance valve behind the two ammonia splitters, and then connect the pipeline behind the valve to two parallel ammonia condenser coolers (one in operation and one in standby during actual operation), so as to improve the existing connection condition where the ammonia condenser coolers cannot serve as standby for each other; Step 4: Under maintenance, the existing concentrated ammonia water pipeline entering the desulfurization tower is changed from a Φ50 316L stainless steel pipe to a Φ65 TA2 pipe, and a 1% slope is ensured during installation so that the condensed concentrated ammonia water and non-condensable gas can smoothly enter the desulfurization tower; Step 5. When the production is stopped for maintenance, make an ammonia distribution box made of TA1 material on the concentrated ammonia pipeline before entering the desulfurization tower, so that the amount of concentrated ammonia entering the desulfurization tower A and the desulfurization tower B can reach a flow ratio of 2:1, and install a spare concentrated ammonia pipeline to enter the pre-cooling tower.

[0016] It should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for condensing and cooling ammonia in an ammonia distillation tower, It is characterized in that The steps include: Step 1: Replace the existing shell-and-tube ammonia decompressor with a double-spiral plate heat exchanger to make the ammonia temperature after the ammonia decompressor reach below 92°C; Step 2: Replace the shell-and-tube ammonia condenser cooler with a double spiral plate heat exchanger to make the ammonia temperature after the ammonia condenser cooler reach below 40°C; Step 3: Install a maintenance valve after the two ammonia splitters, and then connect the pipeline after the valve to the two parallel ammonia condenser coolers, so that the ammonia condenser coolers can serve as backup for each other; Step 4: Change the concentrated ammonia water pipeline entering the desulfurization tower from a Φ50 316L stainless steel pipe to a Φ65 TA2 pipeline, and ensure a 1% slope so that the condensed concentrated ammonia water and non-condensable gas can smoothly enter the desulfurization tower; Step five: make an ammonia water distribution box made of TA1 material on the concentrated ammonia water pipeline before entering the desulfurization tower, so that the amount of concentrated ammonia water entering the desulfurization tower A and the desulfurization tower B can reach a flow ratio of 2:1, and install another spare concentrated ammonia water pipeline to enter the pre-cooling tower.

2. The method for condensing and cooling ammonia in an ammonia still according to claim 1, Features: The step 1 needs to be performed in a standby state.

3. The method for condensing and cooling ammonia in an ammonia still according to claim 1, Features: The step 2 needs to be performed under the condition of stopping production for maintenance.

4. The method for condensing and cooling ammonia in an ammonia still according to claim 1, Features: The steps 3 and 4 need to be performed under maintenance.

5. The method for condensing and cooling ammonia in an ammonia still according to claim 1, Features: The step 5 needs to be performed under the state of stopping production for maintenance.