RU2555678C1 - Bulk stock ignition prevention process - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: prevention of ignition of bulk stock carried in enclosed cargo compartment consists in air replacement therein with inert gas. Air is replaced with inert gas in space between bulk stock particles by feed of said gas under bulk stick pile at overpressure, Inert gas concentration reached, cargo compartment of sealed.

EFFECT: higher reliability due to ruled out oxidation, hence, probability of spontaneous ignition.

2 dwg

Description

The invention relates to the carriage of goods by sea and can be used to prevent the ignition of bulk cargo, which is prone to fire, carried in a closed cargo area, for example, direct reduced iron.

Some types of bulk cargo have a tendency to self-heating and spontaneous combustion. The process of spontaneous combustion develops in dispersed materials at relatively low temperatures for a long time. Under such conditions, to maintain the process of spontaneous combustion, there is not enough heat released during oxidation by the external surface. A prerequisite is the involvement of the entire mass of material in the oxidation or decomposition reaction. And the larger the mass, the easier it is to develop processes of self-heating and self-ignition in it. Such cargoes include direct reduction iron. Direct reduction iron is a gray metallic colloidal substance, which is a compacted iron obtained by the direct reduction method (DRI iron). In the process of transporting this cargo, its strong heating, fire and explosion are possible, because when interacting with air and fresh or salt water, it releases hydrogen and heat.

According to the requirements of the International Code for the Carriage of Bulk Cargo by Sea, at the end of loading, the cargo area must be immediately closed and sealed. Then inert gas should be supplied to this room in an amount sufficient to reduce the oxygen content in its entire atmosphere to less than 5%.

Known methods of supplying inert gas to extinguish fires that occur in enclosed spaces (see Russian patent No. RU 2317835, publ. 02/27/2008; Russian patent No. RU 2362600, publ. 07/27/2009; Russian patent No. RU 2468844, publ. 10.12. 2012). These solutions use inert gas to prevent fire. A known method of producing inert gas according to US patent No. 20060278359.

The closest analogue is the Inertization Method for extinguishing a fire indoors under the patent of the Russian Federation No. 2317835, which mentions the use of inert gas to prevent re-ignition. Inert gas in a known solution is fed through nozzles into a closed room, thereby displacing (replacing) oxygen.

However, when using such a scheme on marine vessels, inert gas is supplied to cargo rooms over a stack of cargo. In this case, the oxygen located between the particles of the bulk cargo, contributes to the oxidation of the cargo, its heating and, as a consequence, its ignition. Thus, the known method is not reliable enough when used to prevent the ignition of bulk cargo, prone to spontaneous combustion.

The technical result achieved by the present invention is to increase the reliability of preventing the ignition of bulk cargo by reducing the oxygen concentration in the cargo stack, which leads to the termination of the oxidation process and reduces the likelihood of spontaneous combustion of the cargo.

To achieve the desired result, as in the closest analogue, it is proposed to prevent the ignition of bulk cargo transported in a closed cargo room by replacing the air in the cargo room with inert gas.

The difference is that air is additionally replaced with inert gas in the space between the particles of the bulk cargo by supplying inert gas under the stack of the bulk cargo under excess pressure, and upon reaching the required concentration of inert gas, the cargo room is sealed.

The specified result is achieved by the fact that the inert gas supplied from below, passing through a stack of cargo, displaces the air contained between the particles from it. The passage of inert gas through the cargo stack is facilitated by its overpressure in the supply pipelines, as well as a lower specific gravity, in comparison with oxygen.

In FIG. 1, an embodiment of a piping system for supplying inert gas to a cargo room (three-dimensional image) is proposed, in FIG. 2 is a diagram of an inert gas advancement in a stack of bulk cargo during purging. The figures show 1 — cargo room (hold), 2 — inert gas supply pipelines, 3 — perforation on pipelines 2 for inert gas outlet, 4 — source of inert gas. A uniform arrangement of pipelines 2 over cargo room 3 is desirable. Nitrogen is most often used as an inert gas, which is obtained from the air with the help of a special installation, which should be equipped with vessels for transporting self-igniting bulk cargoes.

The method is as follows. Before loading on the deck deck 1 horizontally lay the perforated inert gas supply lines 2. To ensure uniform distribution of inert gas throughout the entire volume of the hold, it is advisable to arrange the pipes at a distance of about 1-1.5 m from each other. Horizontal pipelines are connected to a common vertical supply pipe.

After loading the hold with bulk cargo and performing work on sealing the covers of the holds, the hold is purged with inert gas. During the entire purge time, pressure relief must be ensured through a special pipeline in communication with the atmosphere or a regular ventilation system. Purge ends after the oxygen concentration in the hold, according to the readings of the sensors located in it, reaches a predetermined limit. Upon completion of the purge, the hold is completely sealed.

After unloading the hold, the dispensing pipelines are dismantled and they are checked for reuse.

Claims (1)

A method for preventing the ignition of bulk cargo carried in a closed cargo room by replacing air in the cargo room with inert gas, characterized in that it additionally replaces air with inert gas in the space between the particles of the bulk cargo by supplying an inert gas under the stack of bulk cargo under excess pressure, and, upon reaching the required concentration of inert gas, the cargo room is sealed.

Images