I see the issue that you are having. You are building the field collection form, and then you are trying to build an additional field collection form, but the content is not being attached.
I think that instead, you want to use the following
module_load_include('inc', 'field_collection', 'field_collection.pages');
$field_collection_item = entity_create('field_collection_item', array('field_name' => 'field_collection_name'));
field_attach_form('field_collection_item', $field_collection_item, $form['participant'], $form_state);
That will allow you to attach numerous field collection items by changing the location in field_attach_form
module_load_include('inc', 'field_collection', 'field_collection.pages');
for ($i=0;$i<5;$i++) {
$field_collection_item = entity_create('field_collection_item', array('field_name' => 'field_collection_name'));
$form['category'][$i] = array();
field_attach_form('field_collection_item', $field_collection_item, $form['category'][$i], $form_state);
}
Make sure to set the #parent attribute on your original $form, otherwise your data will be joined together on submit