His youngest victim was an eight-year-old girl.
During a four-year investigation, detectives discovered nearly 10,000 illicit images of children on Andrews’ electronic devices and about 40 usernames he had used to pose online as a young boy.
Most of the offences relate to so-called catfishing, where a person pretends to be someone else online to deceive others, but some relate to the direct abuse of a vulnerable adult woman.
Andrews would pretend to be a boy aged 13 or 14 on Snapchat and Instagram before coercing victims into sending him nude photographs
Police have said it is clear his offending spread across the UK.
His crimes include attempted rape, causing or inciting a child under 13 to engage in sexual activity, sexual communication with a child, blackmail, attempting to pay for sexual services of a child, attempting to arrange or facilitate child prostitution or pornography and making and possessing indecent images of children.
Many of the offences took place between 2019 and 2020.
Delivering the sentence at Downpatrick Crown Court, Judge Geoffrey Miller KC said he would not detail Andrews’ offending in full as it was “too harrowing and vile to be repeated”.
The judge said: “In short form he deceived the children into engaging with him in the mistaken belief he too was a child.
“Having done this he then cynically and with clear pre-meditation, used threats to inveigle and coerce them to share images of themselves with him.
“The correspondence instigated by the defendant with each child victim is extremely graphic in content and gives an insight into his depraved thought processes which are deeply troubling.”
The judge said Andrews “exploited” his victims by “distributing the images he had obtained” and threatening “both they and their friends into providing still more material for his gratification”.
“Each time the circle of victims grew and throughout it all he took care to try to cover his tracks,” he added.
