Kill stuck imagemagick convert processes

gistfile1.txt

#!/usr/bin/env ruby
LIMIT=30 #limit on seconds
PROCESS="convert" #change to process u want to grep
COMMAND="ps -eo pid,cmd,etime"

process_list = `#{COMMAND} | grep #{PROCESS}`
process_list = process_list.split("\n") # make an array of process strings
process_list = process_list.select {|process| process !~ /grep/} # remove the grep process

process_list.each do |process|
  process_id = `echo #{process} | awk {'print $1'}`.to_i
  process_command = `echo #{process} | awk {'print $2'}`
  process_time = `echo #{process} | awk {'print $3'}`
  process_time_split = process_time.split(':')
  process_time_minutes, process_time_seconds = process_time_split[0].to_i, process_time_split[1].to_i

  process_started_ago_in_seconds = process_time_minutes * 60 + process_time_seconds

  if process_started_ago_in_seconds > LIMIT
    Process.kill 9, process_id
  end
end