Flameless nitrogen skid unit

Abstract

A flameless nitrogen vaporizing unit includes a first internal combustion engine driving a nitrogen pump through a transmission. A second internal combustion engine drives three hydraulic oil pumps against a variable back pressure so that a variable load may be imposed upon the second engine. Liquid nitrogen is pumped from the nitrogen pump driven by the first engine into a first heat exchanger where heat is transferred from exhaust gases from the first and second internal combustion engines to the liquid nitrogen to cause the nitrogen to be transformed into a gaseous state. The gaseous nitrogen than flows into a second heat exchanger where it is superheated by an engine coolant fluid to heat the gaseous nitrogen to essentially an ambient temperature. The superheated nitrogen is then injected into the well. The engine coolant fluid flows in a coolant circulation system. Heat is transferred to the coolant fluid directly from the internal combustion engine. Heat is also provided to the coolant fluid from lubrication oil pumped by the three pumps attached to the second internal combustion engine. The coolant fluid circulating system includes a comingling chamber for comingling warmer coolant fluid flowing from the internal combustion engines to the second heat exchanger with cooler coolant fluids flowing from the second heat exchanger to the internal combustion engines. Methods of vaporizing nitrogen are also disclosed.