CS262948B1 - Process for preparing natrium carbonate - Google Patents

Abstract

The solution consists in using ammonia waste water, preferably from pressure gasification of brown coal with a steam-oxygen mixture, as a partial or complete source of ammonia.

Description

BACKGROUND OF THE INVENTION The present invention relates to a process for the production of sodium carbonate by treating the sodium chloride with ammonia with carbon dioxide and water.

The present process for producing sodium carbonate consists in subjecting the purified sodium chloride solution to ammonia in an absorber, where the sodium chloride is saturated with ammonia. This ammonia is recovered in the recovery of mother liquors. Further, carbon dioxide from the carbonation columns is introduced into the absorber. This method requires the supply of compressed and pure ammonia from an external source, which is relatively expensive. Carbon dioxide is produced from calcium carbonate; its production is an integral part of the production of sodium carbonate and therefore requires appropriately sized machinery of o

One of the by-products of coal gasification is crude phenolic water, which, in addition to a number of substances such as mono- and dibasic phenols, fatty acids, hydrocarbons and ketones, also contains a large amount of ammonia "

At present, a number of methods are known for obtaining ammonia itself from these waters, possibly using ammonia water. »Raw phenol water is first deprived of phenols and the vast majority of organic substances and subsequently subjected to distillation. Here either ammonia water of varying concentration is obtained or pure ammonia of up to 99% purity can be recovered from this water by a multi-stage distillation. The ammonia thus obtained is fully equalized in many cases by synthetic ammonia made of hydrogen and nitrogen. Concentrated Wastewater is used to fertilize fields.

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The disadvantage of the current utilization of ammonia water treatment to pure ammonia is the high economic demands »Due to seasonality in field fertilization is not ensured then permanent ammonia water sales and thus limited time utilization of the dripping and ammonia operation is necessary to discharge often in concentrations exceeding permitted hygienic limits.

These drawbacks are overcome by the process for the production of sodium carbonate by treating ammonia with sodium chloride with the action of carbon dioxide and water according to the invention. It is based on the fact that ammonia effluent is preferably used as a partial or complete source of ammonia and carbon dioxide, preferably from the pressure gasification of brown coal with a vapor-oxygen mixture.

The main advantage of the process according to the invention is that the ammonia water from the gasification can be fed continuously into the production of sodium carbonate irrespective of the season, and thus a significantly better utilization of the gas stripping plant can be achieved. Therefore, the water discharged into the public watercourse is more suited to hygienic standards. Better ammonia utilization is achieved by better operation of the dewatering device. Since the ammonia water from the gasification of coal also contains carbon dioxide, dosing it will reduce the consumption of carbon dioxide produced from limestone. A further advantage of using ammonia water from gasification is that it also contains ammonium sulphide, which is used as an anticorrosive agent in the aforementioned soda production process. This will also limit its existing amount dosed into production. A further advantage in the ammonia water dosing is that it can also be used as a cooling medium for distillation in the currently operated technology.

The process according to the invention is described in more detail in the following example.

Example

Ammonia water from the pressure gasification of lignite is steamed into the mother liquor tank after filtration of the crude sodium bicarbonate after distillation of the ammonia to 16% by weight. Ammonia water is dosed at 20 liters per tonne of sodium carbonate produced. The mother liquor with added ammonia water is pumped into the distillation heat exchanger. In this apparatus, the distillation gases are cooled. the pre-heated liquor from the distillation passes through the following apparatus, where carbon dioxide is distilled off. The CO 2 distillation liquid is mixed with calcium hydroxide and passed on to distillation to remove the ammonia. The distillation solution contains 0.085 g / l of ammonia. Gases containing ammonia and carbon dioxide are recycled back. The contained ammonium sulfide in the ammonia water decomposes during distillation to form sulfane, which passivates the internal walls of the apparatus, thereby reducing the gland oxide content in the end product.

Claims (1)

A process for the production of sodium carbonate by treating ammonia with sodium carbonate with the aid of carbon dioxide and water, characterized in that ammonia effluent, preferably from pressure gasification of brown coal with a vapor-oxygen mixture, is used as a partial or complete source of ammonia.