700 TPD700 TPDNitric Acid PlantNitric Acid Plant

700 TPDNitric Acid Plant

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General Overview

Capacity: 700 ton per dayTechnology: UhdeProduct: Nitric Acid (53% HNO3)

General Overview

Nitric acid is produced through distilling (burning) ammonia with oxygen from the air and absorption in water. Aside from producing nitric acid, a large quantity of heat is produced which, as much as possible, is converted into steam. This steam is used as a source of energy elsewhere on site. The SZF 4 is a so-called medium-pressure installation with a capacity of 775 ton a day 100% HNO³.

Process Overview

Ammonia is delivered by General Supplies. Refuse condensate from the Calcium Ammonia Nitric Acid Factory is used as process-water for production acid.

Ignition gas for the distiller (burner), consisting of a mixture of three (3) parts hydrogen gas and one (1) part nitrogen, is supplied by General Supplies.

Demineralized water is delivered from the existing demi-installation and is used for the boiler feeding-water, supplemented by the clean cool-water system.

The brackish water for the condensor is supplied from the Havenwater pump-station.

Oil is used as grease- and regulation-oil for the compressorset.

The acid produced (approximately 54% HNO³) is removed to either the production acid-tanks and/or the sales acid-tanks.

Raw Materials and End Products

Ammonia

• Boiling point at 1 bar is -33°C.

• Minimal ignition-temp. detonationdetonation blend (16-25%

vol. %) is 650°C (in air).

• MAC-value 20 ppm

General OverviewMaterial Data

Nitrogen Monoxide

• Boiling point at 1 bar is -152°C.

• MAC-value 25 ppm

Nitrogen Dioxide

• Boiling point at 1 bar is 21°C.

• MAC-value 2 ppm

• MAC TGG-15 min. 4 ppm

Oil (compressors)

• Congealing point -2°C

• Ignition point ± 240°C

Ignition Gas

• Mixture N2 and H2 (1:3)

• Detonation Limits 5.5 – 72%

Nitric Acid

• Concentration 54%

• MAC-value 2 ppm

• Boilingpoint at 1 bar 118°C

General OverviewPreparation of Air and Compression

The air, necessary for the distillation (burning) of ammonia is drawn from the atmosphere through an air compressor.

Before the air gets into the compressor, the air passes through an air-filter.

The drawn-in air is compressed to 3.8 bar. Thereafter, the entire air-stream is divided in two parts. The larger part, approximately 80%, called the primary-air is used for the distillation (burning) of ammonia. The remaining 20% of the air volume is called secondary-air. The secondary-air is cooled in a cooler and used for the degassing of the acid produced.

Liquid ammonia is evaporated in an evaporator using 20 bar steam. The gasiform ammonia moves to the mixer through a preheater and drop-separator and is blended into the right composition with the primary-air stream. The ammonia/air blend with an ammonia concentration of 10 – 10.5%, is then delivered to the distillers (burners) in the distillation (burning) drums.

Ammonia/Air Bending

General OverviewPreparation of Air and CompressionThe ammonia/air blend is delivered to the distillation (burning) drums and flows by way of a separation-sheet to the networks.

The distillation (burning) of ammonia takes place on platina-/rhodiumnets at a temperature of approximately 880 °C, following the reaction:

4NH³ + 5O² → 4NO + 6H²O + heat

and then is partly deoxided through:

2NO + O² → 2NO² + heat

The heat is used to generate 20 bar steam and the reheating of the endgas.

After distilling (burning) the ammonia/air blend on the nets, the resulting nitrous gases are cooled through sequentially the Pt-recycle cooler, the excess-heater, the evaporator-spirals and the economizer.

The temperature of the nitrous gases when exiting the economizer is approximately 320 °C. Further cooling of the nitrous gases takes place in the endgas pre-heaters, in the drum feeding water pre-heater and the gas cooler. The larger part of the water-vapor in the nitrous gases will condensate through the cooling of the gas in the gas-cooler. This results in the production of weak nitric acid of approximately 33%.

The weak acid from the gas coolers flows to absorption-tower C-402.

General OverviewAbsorption

Two reactions find place in the absorption towers C-401 through C-404:

2NO + O² → 2NO² + heat

3NO² + H²O→ 2HNO ³ + NO + heat

Both reactions find place in all towers. In the towers there are packs with ceramic Rashig-rings over which the acid circulates. The reaction heat is removed by way of sheet-coolers.

Process-water is delivered to tower C-404, and at C-401 54%-like nitric acid is removed. The acid is pumped by way of the production-acid tank to the acid degassing. Nitrous gas from the gas-cooler enters the absorption at C-401 and leaves it at C-404.

General OverviewAcid Degassing

The production-acid pump presses the acid using a sprinkler at the top of the acid degassing tower, which is filled with stainless steel Rashig-rings. The production-acid is degassed in the degassing tower in counter-flow with secondairy air. This air originating from the secondairy air-cooler, is delivered at the bottom of the tower. The blend of air and nitrous gas is delivered to absorptiontower C-401. The production-acid is delivered from the bottom of the tower to the production-acid storage tanks and the sales-acid tanks.

Leaked acid and acid drained from the entire gas-cooling, oxidation and absorption is gathered and delivered to the leaked-acid tank which is provided with a leaked-acid pump. The pump moves the acid through the suction-pipes to the acid-ciculation and returns it to the absorption.

General OverviewReduction Installation

The endgas which leaves the absorption towers is heated in endgas preheaters in order to meet the necessary temperature (approximately 270 °C) for the endgas reactor.

After it passes through the last preheater and immediately before the NH³-endgas mixer, ammonia is injected in the endgas. The quantity of ammonia injected is determined based on the level of NO³ in the endgas. After the DENOX installation, NO³-content is checked with the use of ammonia. The necessary concentration is monitored using an NO³-meter. Conversion of the nitrous gases takes place in the DENOX-installation with the use of a selective katalysator (vanadium pentoxide).

NO + NO² + 2NH³ → 3H²O + 2N² + heat.

General OverviewThe Expansion Turbine

Gas from the DENOX installation then flows to the expansion turbine. The endgas expands in the expansion turbine to near atmospheric pressure whilst expelling energy which is used to propel the air compressor. The endgas is blown off through the chimney at a height of 110 m.

Steam Supply

The reaction heat which is released on the Pt/Rh-nets in the distillation(burning) cauldron is used to produce excess-heated steam of 20 bar and 330 °C.

The steam system consists of a feedingwater degasser cauldron, a steamdrum, and on top of each distilling (burning) cauldron an economiser, a vaporizer-spiral, a platina-recoup cooler and an excess-heater.

In the degasser condensate is delivered from the steam-users, such as the steam turbine 01T, the NH³ preheater and the endgas preheater.

General OverviewSteam Supply continued

Shortage is supplemented with demineralized water. In the degasser water is heated through means of an LD-steam injection to a temperature of 105 °C. The water from the cauldron feeding-water degasser is pumped through the economizer to the steam cauldron to the cauldron feeding water pump.

Before the cauldron feeding water enters the economizer, it is first heated from 105 °C to 120 °C through heat exchange in the steam drum.

From the steam drum the water is pumped through evaporators by means of a cauldron water circulation pump.

The saturated steam, which is developed in these evaporators, leaves the steam drum at the top and is then heated to approximately 330 °C in the excess heater.

Part of the approximately 60% of the produced excess heated steam is then delivered to the steam-turbine to propel the air-compressor.The remainder of the excess heated steam is delivered to the so-called 20 bar net.

General OverviewProcess

Mono, medium pressure plant (4.5 bar) with 3 burners and an absorption system of 4 packed columns.

Equipped with a steam driven Parson compressor train with a Curtis-wheel and a DeNOx installation to reduce NOx emissions to 200 ppm

Steam system operates @ 20 bar and is integrated with site steam production grid.

Process Flow

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Contact Information

MICHAEL JOACHIMDIRECTOR, PLANTS DEPT.

Tele: 609-838-5930 (direct)Mobile: 609-516-9107

MichaelJ@ippe.com

SANJEEV REGEVP GLOBAL PLANT SALES

Tele: 609-838-5938 (direct)Mobile: 609-510-2616

SanjeevR@ippe.com