I found a very good example on retrieving the Vocabulary object by name.

/**
 * This function will return a vocabulary object which matches the
 * given name. Will return null if no such vocabulary exists.
 *
 * @param String $vocabulary_name
 *   This is the name of the section which is required
 * @return Object
 *   This is the vocabulary object with the name
 *   or null if no such vocabulary exists
 */
function _get_vocabulary_by_name($vocabulary_name) {
  $vocabs = taxonomy_get_vocabularies(NULL);
  foreach ($vocabs as $vocab_object) {
    if ($vocab_object->name == $vocabulary_name) {
      return $vocab_object;
    }
  }
  return NULL;
}

Example

$vocab_object = _get_vocabulary_by_name("<vocabulary name>");
$vocab_id = $vocab_object->vid;

Done =)

Reference: StackOverflow – get vocabulary id by name