Flat bottom cryogenic vessels are designed to store large volumes of cryogenic air products (liquid nitrogen, oxygen, argon, liquefied natural gas) under atmospheric pressure.
A cryogenic tank makes it possible to accumulate and store cryogenic liquids in large volumes for their further gasification and supply to the consumer's network during peak consumption.
The tank is made of two vessels. Cryogenic liquid is stored in the inner vessel made of stainless steel. The outer vessel (casing) is made of carbon steel and acts as a protective casing. The inner vessel and casing are attached to the foundation by means of anchors connected to the reinforcing mesh of the foundation. Inner space is a heat-insulation between the inner vessel and the casing and is filled with heat-insulating material.
The tank is equipped with technological pipelines, globe, and safety valves, as well as instrumentation. For convenient operation, the cabinet with needed instrumentation is installed under the concrete base plate, where, as a rule, both cryogenic pumps and their control panels are located.
Liquid cryogenic product is supplied to the tank from an air separation unit through a cryogenic pipeline or from a tanker. The liquid enters through a pipeline to the upper part of the inner vessel into the funnel of the distributor manifold and from the lower perforated part enters the vessel. The liquid product is dispensed from the reservoir through the lower product delivery pipeline to the consumer. The product delivery pipe creates a gas seal when storing the product, which ensures minimal heat inflow to the delivery pipeline and virtually eliminates the formation of product bubbles in this pipeline.
Operating pressure in the inner vessel is automatically maintained at a set level by a boost circuit that includes a pressure build-up vaporizer under the tank, pressure sensors and a controlled pneumatic valves. The blowing of the heat-insulating space of the tank with gaseous nitrogen is carried out from an external source of nitrogen, and for storage tanks of liquid nitrogen. A supply of nitrogen from vessel’s gas discharge line is provided for tanks with liquid nitrogen. Excessive pressure maintenance in the heat-insulating space is ensured by automatic opening of a nitrogen supply valve when the pressure in the heat-insulating space is decreased.
|Pressure||from 0.1 to 0.3 bar|
|Volume||from 1 000 m³ to 30 000 m³ (liquefied natural gas), from 500 m³ to 10 000 m³ (low pressure liquified cryogenic gases)|
|Materials||inner vessel – stainless steel, outer vessel – carbon steel|
|Insulation type||perlite and foam glass|